Implantable Glucose Telemetry

Glucose Poster Abstracts

• Continuous Glucose Monitoring During Pregnancy in Healthy Mice - February 2021

  Caroline Wuyts 1 2, Caroline Simoens 1 2 3, Silvia Pinto 1 2, Koenraad Philippaert 1 2, Rudi Vennekens 4 5
  During pregnancy, metabolic adaptations occur to maintain the balance between maternal and foetal growth, including increased insulin secretion and decreased insulin sensitivity. When the body fails to adjust, gestational diabetes mellitus develops. To gain insight in the pregnancy-induced adaptations, we applied continuous glucose monitoring via telemetric transmitters. We show that continuous glucose monitoring in conscious, non-stressed, freely moving mice throughout the full pregnancy is feasible, accurate and safe. We show that healthy mice during a full pregnancy develop adaptations in glucose homeostasis reminiscent of those in pregnant women. Furthermore, continuous glucose monitoring allows the complete analysis of all aspects of glucose excursions associated with spontaneous feeding episodes, and the thorough analysis of glycaemic variability. In conclusion, continuous glucose monitoring allows a detailed description of the glycaemic status during pregnancy, which will help to unravel specific mechanisms for gestational diabetes mellitus.
  https://pubmed.ncbi.nlm.nih.gov/33627830/
  

• Contrasting effects of afferent and efferent vagal nerve stimulation on insulin secretion and blood glucose regulation

  Erin E. Meyers, Ana Kronemberger, Vitor Lira, Kamal Rahmouni, Harald M. Stauss

  Physiol Rep, 4 (4), 2016, e12718, doi: 10.14814/phy2.12718

  Parasympathetic activation reduces hepatic glucose release and increases pancreatic insulin secretion in hyperglycemic conditions. Thus, vagal nerve stimulation (VNS) may potentially be effective in treating type II diabetes. To investigate this possibility, we hypothesized that VNS reduces blood glucose concentration [Glu] via insulin secretion. [Glu] together with insulin and glucagon serum concentrations were determined in anesthetized rats during baseline conditions and 120 min of cervical VNS with the nerve left intact for combined afferent and efferent VNS (n = 9) or the nerve sectioned proximal or distal from the stimulation electrode for selective efferent (n = 8) or afferent (n = 7) VNS, respectively. Afferent VNS caused a strong and sustained increase in [Glu] (+108.9 +/- 20.9% or +77.6 +/- 15.4%, after 120 min of combined afferent and efferent VNS or selective afferent VNS) that was not accompanied by an increase in serum insulin concentration. However, serum insulin levels increased significantly with selective efferent VNS (+71.2 +/- 27.0% after 120 min of VNS) that increased [Glu] only temporarily (+28.8 +/- 11.7% at 30 min of VNS). Efferent VNS initially increased serum glucagon concentration which remained elevated for 120 min when efferent VNS was combined with afferent VNS, but returned to baseline with selective efferent VNS. These findings demonstrate that afferent VNS causes a marked and sustained increase in [Glu] that is partly mediated by suppression of pancreatic insulin secretion. In contrast, efferent VNS stimulates pancreatic glucagon secretion that appears to be antagonized by insulin secretion in the case of selective efferent VNS. Selective efferent VNS may potentially be effective in treating type II diabetes.

• Afferent vs. efferent cervical vagal nerve stimulation: effects on blood glucose, insulin, and glucagon concentrations in rats

  Meyers, Erin Elizabeth

  MS (Master of Science) thesis, University of Iowa, 2016. https://ir.uiowa.edu/etd/3144

  Glucose uptake into the cells is impaired in type II diabetes, leading to elevated blood glucose levels. The hormone insulin lowers blood glucose levels by increasing cellular glucose uptake. The hormone glucagon increases blood glucose levels through increased glucose release from the liver. Nerves in the body send signals about glucose homeostasis from the peripheral organs to the brain, where these signals are processed and then returned to peripheral organs to maintain glucose homeostasis. We investigated the potentially differential effects of selectively activating nerve fibers traveling from the peripheral organs to the brain vs. nerve fibers traveling from the brain to the peripheral organs on glucose homeostasis. Therefore, we electrically stimulated either the central or peripheral end of the cut vagus nerve in anesthetized rats and measured glucose, insulin, and glucagon blood concentrations.

  Stimulating fibers running from the periphery to the brain strongly increased blood glucose concentration. Interestingly, this was not associated with an increase in insulin that would normally be seen when glucose levels increase, suggesting that insulin secretion is suppressed in this condition. Stimulating fibers traveling from the brain to the periphery transiently increased blood glucose concentration before returning to or below baseline levels. This response was associated with a strong increase in insulin secretion. These findings are important because they may potentially lead to novel treatment strategies for type II diabetes based on electrical stimulation of nerve fibers traveling in the vagus nerve from the brain to the periphery.

• Sustained effect of glucagon on body weight and blood glucose: Assessed by continuous glucose monitoring in diabetic rats

  Pedersen C, Porsgaard T, Thomsen M, Rosenkilde MM, Roed NK

  PLoS ONE 13(3): e0194468. doi: 10.1371/journal.pone.0194468

  Insulin is a vital part of diabetes treatment, whereas glucagon is primarily used to treat insulin-induced hypoglycemia. However, glucagon is suggested to have a central role in the regulation of body weight, which would be beneficial for diabetic patients. Since the glucagon effect on blood glucose is known to be transient, it is relevant to investigate the pharmacodynamics of glucagon after repeated dosing. In the present study, we used telemetry to continuously measure blood glucose in streptozotocin induced diabetic Sprague-Dawley rats. This allowed for a more detailed analysis of glucose regulation compared to intermittent blood sampling. In particular, we evaluated the blood glucose-lowering effect of different insulin doses alone, and in combination with a long acting glucagon analog (LAG). We showed how the effect of the LAG accumulated and persisted over time. Furthermore, we found that addition of the LAG decreased body weight without affecting food intake.

  In a subsequent study, we focused on the glucagon effect on body weight and food intake during equal glycemic control. In order to obtain comparable maximum blood glucose lowering effect to insulin alone, the insulin dose had to be increased four times in combination with 1 nmol/kg of the LAG. In this set-up the LAG prevented further increase in body weight despite the four times higher insulin-dose. However, the body composition was changed. The insulin group increased both lean and fat mass, whereas the group receiving four times insulin in combination with the LAG only significantly increased the fat mass. No differences were observed in food intake, suggesting a direct effect on energy expenditure by glucagon. Surprisingly, we observed decreased levels of FGF21 in plasma compared to insulin treatment alone. With the combination of insulin and the LAG the blood glucose-lowering effect of insulin was prolonged, which could potentially be beneficial in diabetes treatment.

• Continuous Blood Glucose Monitoring Reveals Enormous Circadian Variations in Pregnant Diabetic Rats

  Golic M, Kräker K, Fischer C, Alenina N, Haase N, Herse F, Schütte T, Henrich W, Müller DN, Busjahn A, Bader M and Dechend R

  Front. Endocrinol. 9:271. doi: 10.3389/fendo.2018.00271

  Aim: Diabetes in pregnancy is a major burden with acute and long-term consequences. Its treatment requires adequate diagnosis and monitoring of therapy. Many experimental research on diabetes during pregnancy has been performed in rats. Recently, continuous blood glucose monitoring of non-pregnant diabetic rats revealed an increased circadian variability of blood glucose that made a single blood glucose measurement per day inappropriate to reflect glycemic status. Continuous blood glucose measurement has never been performed in pregnant rats. We wanted to perform continuous blood glucose monitoring in pregnant rats to decipher the influence of pregnancy on blood glucose in diabetic and normoglycemic status.

  Methods: We used the transgenic Tet29 diabetes rat model with an inducible knock down of the insulin receptor via RNA interference upon application of doxycycline (DOX) leading to insulin resistant type II diabetes. All Tet29 rats received a HD-XG telemetry implant (Data Sciences International, USA) that measured blood glucose and activity continuously. Rats were divided into four groups and blood glucose was monitored until end of pregnancy or the corresponding period: Tet29 + DOX (diabetic) non-pregnant, Tet29 + DOX (diabetic) pregnant, Tet29 (normoglycemic) non-pregnant, Tet29 (normoglycemic) pregnant.

  Results: All analyzed rats displayed a circadian variation in blood glucose concentration. Circadian variability was much more pronounced in pregnant diabetic rats than in normoglycemic pregnant rats. Pregnancy ameliorated variation in blood glucose in diabetic situation. Pregnancy continuously decreased blood glucose during normoglycemic pregnancy. Diabetic rats were less active than normoglycemic rats. We performed a calculation showing that application of continuous blood glucose measurement reduces animal numbers needed to detect a given effect in experimental setting by decreasing variability and SD.

  Interpretation: Continuous blood glucose monitoring via a telemetry device in pregnant rats provides a more informative picture of the glycemic situation in comparison to single measurements. This could improve diagnosis and therapy of diabetes, decrease animal numbers within experimental settings, and add another physiological parameter (activity) to the analysis that could be helpful in testing therapeutic concepts targeting blood glucose levels and peripheral muscle function. We propose continuous glucose monitoring as a new tool for the evaluation of pregnant diabetic rats.

• From Mouse to Monkey: Revolutionizing Research via Preclinical Continuous Glucose Telemetry

  Stephanie Simonds, Megan Fine

  Webinar retrieved from https://insidescientific.com/webinar/mouse-to-monkey-preclinical-continuous-glucose-telemetry-DSI, October 30, 2018

  The most commonly used method for measuring glucose in preclinical research remains intermittent blood sampling. However, continuous glucose monitoring via implantable telemetry offers numerous benefits over periodic measurements, including larger sample counts, improved animal welfare and higher data quality, to name a few. When appropriate for the study, monitoring physiological events with telemetry allows for continuous data collection from fewer animals who are conscious, freely moving, and under minimal stress from handling. The simultaneous acquisition of a continuous glucose profile with physiologic telemetry measurements will arm researchers with unique scientific information sure to advance scientific discovery, improve our understanding of disease and in turn help develop effective treatments.

  During this webinar sponsored by Data Sciences International (DSI), Stephanie Simonds, PhD shares novel research conducted using implantable glucose telemetry for basic analysis and combination studies investigating the effects of drugs and hormones in mice. Specifically, she discusses research case studies involving Designer Receptors Exclusively Activated by Designer Drugs (DREADDs) and adeno-associated virus neuronal knockdown models, and speaks to the importance of collecting continuous glucose data simultaneously with physiologic telemetry measurements.

  In addition, Dr. Megan Fine from DSI’s Surgical Services team presents the surgical techniques and best practices that her team has developed for use with glucose telemetry. She discusses the use of this technology in a variety of animal models, including recommendations for surgery and techniques to help ensure successful calibrations. Finally, Megan highlights the concurrent collection of multiple endpoints, such as glucose and cardiovascular data, in the same subject.

• Use Of Real-Time Glucose Monitoring In Rats To Investigate Changes In Glucose Excursions And Hypoglycemia After Bariatric Surgery

  TA LUTZ, S SENN, CN BOYLE

  Poster 74, Society for the Study of Ingestive Behavior Annual Meeting, Bonita Springs, FL, July 17-21, 2018

  Bariatric surgery, and specifically Roux-en-Y gastric bypass (RYGB), currently the most successful treatment of obesity, can also eliminate the need to treat type-2 diabetes. Unfortunately, RYGB patients also exhibit increased glycemic variability, spending more time in hyper- and hypoglycemic states, and are at increased risk of postprandial hypoglycemia, which can be fatal in the most severe cases. As the incidence of postprandial hypoglycemia increases, so does the importance of understanding this disabling complication and finding ways to control it. Our previous work showed that Zucker diabetic fatty (ZDF) rats undergoing RYGB were also prone to severe hypoglycemia, and even non-diabetic rats exhibit increased glycemic variability after RYGB. We therefore performed real-time glucose monitoring in ZDF rats following RYGB surgery. Food intake was also continuously monitored, allowing us to investigate the relationship between spontaneous meals and hypoglycemia. Because the pancreatic hormone amylin controls the rate of glucose appearance following a meal, we tested whether amylin or its agonist, salmon calcitonin (sCT), could minimize the initial postprandial glucose peak in an effort to reduce the ensuing hypoglycemia. Pre-prandial treatment with amylin or sCT appears to stabilize postprandial glucose, reducing glycemic variability. However, higher doses also promote hyperglycemia. Thus, amylin and its analogues represent potential candidates to treat postprandial hypoglycemia after RYGB, however additional studies are needed to understand appropriate dosing strategies and the precise mechanism through which amylin exerts these actions.

• Non-insulin determinant pathways maintain glucose homeostasis upon metabolic surgery

  Zongshi Lu, Xiao Wei, Fang Sun, Hexuan Zhang, Peng Gao, Yunfei Pu, Anlong Wang, Jing Chen, Weidong Tong, Qiang Li, Xunmei Zhou, Zhencheng Yan, Hongting Zheng, Gangyi Yang, Yu Huang, Daoyan Liu, Zhiming Zhu

  Cell Discovery 2018 4:58. doi:10.1038/s41421-018-0062-x

  Insulin is critical for glucose homeostasis, and insulin deficiency or resistance leads to the development of diabetes. Recent evidence suggests that diabetes can be remitted independent of insulin. However, the underlying mechanism remains largely elusive. In this study, we utilized metabolic surgery as a tool to identify the non-insulin determinant mechanism. Here, we report that the most common metabolic surgery, Roux-en-Y gastric bypass (RYGB), reduced insulin production but persistently maintained euglycemia in healthy Sprague-Dawley (SD) rats and C57 mice. This reduction in insulin production was associated with RYGB-mediated inhibition of pancreatic preproinsulin and polypyrimidine tract-binding protein 1. In addition, RYGB also weakened insulin sensitivity that was evaluated by hyperinsulinemic-euglycemic clamp test and downregulated signaling pathways in insulin-sensitive tissues. The mechanistic evidence suggests that RYGB predominately shifted the metabolic profile from glucose utilization to fatty acid oxidation, enhanced the energy expenditure and activated multiple metabolic pathways through reducing gut energy uptake. Importantly, the unique effect of RYGB was extended to rats with islet disruption and patients with type 2 diabetes. These results demonstrate that compulsory rearrangement of the gastrointestinal tract can initiate non-insulin determinant pathways to maintain glucose homeostasis. Based on the principle of RYGB action, the development of a noninvasive intervention of the gastrointestinal tract is a promising therapeutic route to combat disorders characterized by energy metabolism dysregulation.

• Continuous Glucose Monitoring Reduces Stress and Improves Metabolic Data Quality in Mice

  TS Nielsen, JT Treebak

  Platform Session PS14, AALAS 69th National Meeting, Baltimore, MD, October 28-November 1, 2018

  Glucose homeostasis is a primary readout used to assess effects of pharmacological, environmental, or genetic manipulations in most metabolic studies. In mice, it is widely accepted that blood glucose (BG) values are obtained on a background of stress caused by handling, restraint, and sample collection. However, the potential confounding effect of stress can be difficult to assess and is often either trivialized or ignored in the literature. Mice are usually fasted prior to metabolic tests like glucose or insulin tolerance tests (GTTs and ITTs) to avoid interference from postprandial glucose and hormone excursions. Fasting durations vary, but 4-6 h or overnight (16-20 h) are commonly used. Using continuous glucose monitoring (CGM) by radio telemetry, which continuously measures arterial BG, body temperature, and physical activity in mice for up to 6-8 wk, we studied 6 female C57BL/6JBomTac mice, to investigate the responses to common experimental conditions. Overall, we found that BG levels were exceptionally sensitive to acute stress, and activities, like weighing, changing cages, or measuring BG from the tail, caused it to increase by 25-50% and stay elevated for up to 1 hr. Notably, we measured BG from the tail at standard intervals during a GTT, and found that this caused a significant increase in BG throughout the test, compared to a GTT with no tail sampling. However, the most dramatic effects were the response to an overnight fast. BG declined gradually, reaching clinical hypoglycemia (3.9 mM) after 11 h, and dropping further to 2.7±0.5 mM at 14 h of fasting. Mean body temperature was normal for 11 h, followed by 7 h of hypothermia, with an overall temperature drop of 6.2±1 C, suggesting that the mice were in torpor for several hours. We conclude that stress-induced glucose excursions can be a major confounder in metabolic studies, and that they can be either avoided or accounted for by using CGM. Furthermore, fasting beyond 7-8 h in mice is a severe metabolic stress and should only be considered as a direct metabolic challenge. In terms of blood glucose levels, fasting for 4-6 h appears to provide the most physiologically relevant baseline for further metabolic testing.

• Changes in blood glucose as a function of body temperature in laboratory mice: implications for daily torpor

  Viviana Lo Martire, Alice Valli, Mark J Bingaman, Giovanna Zoccoli, Alessandro Silvani, and Steven J. Swoap

  American Journal of Physiology-Endocrinology and Metabolism 2018 315:4, E662-E670. doi: 10.1152/ajpendo.00201.2018

  Many small mammals, such as the laboratory mouse, utilize the hypometabolic state of torpor in response to caloric restriction. The signals that relay the lack of fuel to initiate a bout of torpor are not known. Because the mouse will only enter a torpid state when calorically challenged, it may be that one of the inputs for initiation into a bout of torpor is the lack of the primary fuel (glucose) used to power brain metabolism in the mouse. Using glucose telemetry in mice, we tested the hypotheses that 1) circulating glucose (GLC), core body temperature (Tb), and activity are significantly interrelated; and 2) that the level of GLC at the onset of torpor differs from both GLC during arousal from torpor and during feeding when there is no torpor. To test these hypotheses, six C57Bl/6J mice were implanted with glucose telemeters and exposed to different feeding conditions (ad libitum, fasting, limited food intake, and refeeding) to create different levels of GLC and Tb. We found a strong positive and linear correlation between GLC and Tb during ad libitum feeding. Furthermore, mice that were calorically restricted entered torpor bouts readily. `precipitously as Tb did at the onset of a torpor bout. GLC significantly increased during arousal from torpor, indicating the presence of endogenous glucose production. While low GLC itself was not predictive of a bout of torpor, hyperactivity and low GLC preceded the onset of torpor, suggesting that this may be involved in triggering torpor.

• High Fat Diet Induced Hypertension is Associated with a Pro-Inflammatory T Cell Profile in Male and Female Dahl Salt Sensitive Rats

  Lia E Taylor, Ellen E Gillis, Jacqueline B Musall, Babak Baban, Jennifer C. Sullivan

  American Journal of Physiology-Heart and Circulatory Physiology 21 Sep 2018 doi: 10.1152/ajpheart.00389.2018

  Evidence supports a sex difference in the impact of a high fat diet (HFD) on cardiovascular outcomes, with male experimental animals exhibiting greater increases in blood pressure (BP) than females. The immune system has been implicated in HFD-induced increases in BP, and there is a sex difference in T cell activation in hypertension. The goal of this study was to determine the impact of HFD on BP, aortic and renal T cell profiles in male and female Dahl salt-sensitive rats (DSS). We hypothesize that male DSS will have greater increases in BP and T cells with a HFD compared to females. BP was measured by tail-cuff plethysmography, and aortic and renal T cells were assessed by flow cytomety in male and female DSS on a normal fat diet (NFD) or HFD from 12 to 16 weeks of age. A HFD increased BP in male and female DSS to a similar degree. Increases in BP were accompanied by increased percentages of CD4+ T cells and Th17 cells in both sexes, although males have more pro-inflammatory T cells. Percentages of renal CD3+ and CD4+ T cells and Th17 cells were increased in both sexes by a HFD, although the increase in CD3+ T cells was greater in males. HFD decreased the percentage of aortic and renal Tregs in both sexes, although females maintained more Tregs than males regardless of diet. In conclusion, both male and female DSS exhibit BP sensitivity to a HFD.

• Improved glucose homeostasis in male obese Zucker rats coincides with enhanced baroreflexes and activation of the nucleus tractus solitarius

  Parul Chaudhary and Ann M. Schreihofer

  American Journal of Physiology-Regulatory, Integrative and Comparative Physiology. 26 Sep 2018. doi: 10.1152/ajpregu.00195.2018

  Young adult male obese Zucker rats (OZR) develop insulin resistance and hypertension with impaired baroreflex-mediated bradycardia and activation of nucleus tractus solitarius (NTS). Because type 1 diabetic rats also develop impaired baroreflex-mediated NTS activation, we hypothesized that improving glycemic control in OZR would enhance compromised baroreflexes and NTS activation. Fasting blood glucose measured by telemetry was comparable in OZR and LZR at 12-17 weeks. However, with access to food, OZR were chronically hyperglycemic throughout this age range. By 15-17 weeks of age, tail samples yielded higher glucose values than those measured by telemetry in OZR but not LZR, consistent with reports of exaggerated stress responses in OZR. Injection of glucose (1g/kg, i.p.) produced larger rises in glucose and areas under the curve in OZR than LZR. Treatment with metformin (300 mg/kg/day) or pioglitazone (5 mg/kg/day) in drinking water for 2-3 weeks normalized fed glucose levels in OZR with no effect in LZR. After metformin treatment, area under the curve for blood glucose after glucose injection was reduced in OZR and comparable to LZR. Hyperinsulinemia was slightly reduced by each treatment in OZR, but insulin was still greatly elevated compared to LZR. Neither treatment reduced hypertension in OZR, but both treatments significantly improved the blunted phenylephrine-induced bradycardia and NTS c-Fos expression in OZR with no effect in LZR. These data suggest that restoring glycemic control in OZR enhances baroreflex control of heart rate by improving the response of the NTS to raising AP even in the presence of hyperinsulinemia and hypertension.

• Glucagon receptor agonists

  Jorge Alsina-Fernandez, Tamer Coskun

  US Patent Grant US9764004B2

• Dosage regimen for a phosphatidylinositol 3-kinase inhibitor

  Christian Schnell, Christine Fritsch, Emmanuelle di Tomaso, Cristian Massacesi, Lars Blumenstein

  US Patent Application US20180280370A1

• Continuous glucose and food intake monitoring in the male ZDSD rat: Comparison of normal and high-fat diets - EB 2014

  Charles V. Jackson¹, Richard G. Peterson¹, Douglas Compton², Edward Ulman², Scott Tiesma³, Robert Brockway³
  _{1. PreClinOmics, Indianapolis, IN 2. Research Diets, New Brunswick, NJ, 3. Data Sciences International, St. Paul, MN}

  Poster B-168, Experimental Biology Annual Meeting, San Diego, CA, April 2014

  The effect of a high-fat diet on glucose and food intake (FI) in pre-diabetic ZDSD male rats was assessed using continuous glucose (CG) telemetry (DSI, model HD-XG) and the BioDAQ FI monitoring system (Research Diets). Ten male rats, 14 weeks old, were housed singly for 3 days prior to aseptic surgery to acclimate them to the FI system on control diet (Purina #5008). All rats under isofluorane anesthesia were implanted with a glucose sensor in the abdominal aorta and transmitter in the peritoneum. The animals were maintained on 5008 for 2 weeks at which time an OGTT was performed. Animals were then switched to a high-fat diet (Research Diets #D12468) for an additional 2 weeks at which time another OGTT was performed. OGTT AUC was significantly larger in the presence of D12468 when compared to 5008 (35.5x10³±1.4; 30.1x10³±0.9 mg/dl x 180 min, respectively). CG monitoring allowed for visualization of the circadian pattern that was not seen with FI and would not have been detected using twice daily sampling.

  There was a significant elevation in glucose during the PM while FI was the same. When rats were switched to D12468 their glucose excursion was significantly greater, even though their FI was similar to 5008.

• Long-term blood glucose monitoring with implanted telemetry device in conscious and stress-free cynomolgus monkeys - JEI 2017

  Wang B, Sun G, Qiao W, Liu Y,Qiao J, Ye W, Wang H, Wang X, Lindquist R, Wang Y, Xiao YF

  J Endocrinol Invest (2017). https://doi.org/10.1007/s40618-017-0651-9

  Aims
  Continuous blood glucose monitoring, especially long-term and remote, in diabetic patients orresearch is very challenging. Nonhuman primate (NHP) is an excellent model for metabolic research,because NHPs can naturally develop Type 2 diabetes mellitus (T2DM) similarly to humans. This study was to investigate blood glucose changes in conscious, moving-free cynomolgus monkeys (Macaca fascicularis) during circadian, meal, stress and drug exposure.

  Materials and methods
  Blood glucose, body temperature and physical activities were continuously and simultaneously recorded by implanted HD-XG telemetry device for up to 10 weeks.

  Results and discussion
  Blood glucose circadian changes in normoglycemic monkeys significantly differed from that in diabetic animals. Postprandial glucose increase was more obvious after afternoon feeding. Moving a monkey from its housing cage to monkey chair increased blood glucose by 30% in both normoglycemic and diabetic monkeys. Such increase in blood glucose declined to the pre-procedure level in 30 min in normoglycemic animals and >2 h in diabetic monkeys. Oral gavage procedure alone caused hyperglycemia in both normoglycemic and diabetic monkeys. Intravenous injection with the stress hormones, angiotensin II (2 μg/kg) or norepinephrine (0.4 μg/kg), also increased blood glucose level by 30%. The glucose levels measured by the telemetry system correlated significantly well with glucometer readings during glucose tolerance tests (ivGTT or oGTT), insulin tolerance test (ITT), graded glucose infusion (GGI) and clamp.

  Conclusion
  Our data demonstrate that the real-time telemetry method is reliable for monitoring blood glucose remotely and continuously in conscious, stress-free, and moving-free NHPs with the advantages highly valuable to diabetes research and drug discovery.

• Letter to the Editor: Diabetes in rats is cured by islet transplantation… but only during daytime - CT 2016

  Aileen King, Amazon Austin, Manasi Nandi, James Bowe

  Cell Transplantation. August 5, 2016. CT-1633. doi: 10.3727/096368916x692258.

  Rats and mice are commonly used as animal models in diabetes research with blood glucose concentrations often used as endpoints of the study. Most islet transplantation studies assess blood glucose levels during the day, primarily for practical reasons. However, blood glucose concentrations can vary depending on food intake and activity, both of which peak during the night in these nocturnal animals (1,2). Indeed, it has been shown that blood glucose concentrations in normal nondiabetic rats peak during the night (3). Most studies carried out in diabetic animals do not report the time of day at which blood glucose is measured and whether this is kept constant throughout the study. We here present evidence obtained using continuous glucose monitoring in rat islet graft recipients which suggests that the perceived outcome of the islet transplantation may depend upon the timing of the monitoring of glycemic control.

• Accuracy of Continuous Glucose Telemetry throughout a Stepped Hyperinsulinemic-Euglycemic-Hypoglycemic Clamp in Rats - ADA 2017

  Tiesma S, Wang P, Zhu W, Chan O

  Poster 911-P, American Diabetes Association Annual Meeting, San Diego, CA, June 2017

  Introduction: Continuous Glucose Telemetry (CGT) is a relatively new technology available to researchers for monitoring blood glucose (BG) in laboratory rodents in real-time. Utility of CGT during glucose clamp studies has not previously been documented. In this experiment, CGT was recorded during the performance of a stepped hyperinsulinemic-euglycemic-hypoglycemic clamp and compared to values obtained with a plasma glucose analyzer.

  Methods: Seven clamps, with glucose measurements approximately every 5 minutes, were performed in well- and poorly-controlled insulin-treated streptozotocin diabetic rats that were implanted with CGT devices. Subsequent to the clamps, all glucose measurements were used to calibrate each CGT device and the resulting measurements were compared with the BG reference value. Accuracy was assessed via Trueness as represented by the mean difference of all paired measurements, Mean Relative Difference (MRD), and Mean Absolute Relative Difference (MARD). These three parameters were assessed both throughout the entire clamp and also only during the period when the hypoglycemic target level was achieved.

  Results: Throughout the entire clamp and across 7 rats the trueness was -0.2 ± 0.5 mg/dl, MRD was 1.7 ± 1.6%, and MARD was 10.1 ± 2.8%. At target hypoglycemic levels the trueness was -0.1 ± 3.3 mg/dl, MRD was 0.3 ± 6.2%, and MARD was 9.3 ± 4.7%.

  Discussion: The ability to monitor BG changes in real-time during a clamp may provide significant benefits including, but not limited to, animal welfare (reduced blood draws for assessing glucose levels during the clamp), improved accuracy/predictability in adjusting GIR, improved clamp stability and the potential to automate.

  Conclusions: CGT has the ability to accurately present BG values to the extent that a clamp can be performed accurately without using the traditional (frequent) blood draws for glucose measurements.

• The Effect of Blood Glucose Telemeter Implantation on Oral Glucose Tolerance Testing and Glucose Monitoring in Diet-Induced Obese Mouse - AALAS 2016

  GJ DeMarco, X Chen, C Salatto, S Tiesma

  Poster 219, American Association for Laboratory Animal Science National Meeting, Charlotte, NC, October 2016

  Oral glucose tolerance testing (OGTT) and serial blood glucose (SBG) monitoring are important tools in basic diabetes research and the preclinical development of new treatments for diabetes. Although mouse models are critical to diabetes research, their small blood volume and marked stress response to restraint presents significant challenges to generating reliable and consistent OGTT and SBG data. Since telemetric technology can often mitigate the challenges of physiologic data collection in mouse, the purpose of this study was to evaluate the effects of an implantable telemetric glucose sensor designed for mouse on OGTT and SBG in the diet-induced obese mouse model (DIO) of diabetes. Male C57BL/6J mice fed a high-fat diet to induce and maintain diabetes (DIO), divided into 3 groups were used. Groups consisted of animals implanted with a glucose sensing telemeter (HD-XG, DSI™) placed in the carotid artery, sham surgery, and nonsurgical controls. Excepting weight loss, no significant postoperative complications were noted in telemeterized and sham surgery animals. Telemeterized animals lost 15.6 percent and sham surgery animals 5.2 percent of pre-surgical body weight postoperatively which returned to baseline values at 42 and 18 days respectively. Results from OGTT tests, including the effects of a sodium-glucose co-transporter 2 (SGLT-2) inhibitor, were similar between all groups and data captured by telemetry was not different from that obtained with a glucometer. Data from 11 out of 12 telemeterized animals was well correlated (R2 > 0.75), and 1 animal poorly correlated (R2= 0.34) with glucometer results. Bland-Altman plots suggested individual variation in agreement between glucometer and telemeter blood glucose values. Continuous blood glucose measurements from the telemeters were possible for 70 days postdevice implantation. These data suggest the HD-XG telemeter can be used in mouse and that implantation of the device does not significantly impact the DIO phenotype. Data from the telemeter correlates well with glucometer results although significant individual variation can occur.

• Continuous Blood Glucose Monitoring in a Rat Model of Islet Transplantation - EASD 2016

  Aileen King, Amazon Austin, Manasi Nandi, James Bowe

  Poster 403, European Association for the Study of Diabetes Annual Meeting, Munich, Germany, September 2016

  Background and aims
  Rodent models of diabetes are often used in pre-clinical islet transplantation studies.  In most studies, blood glucose is measured daily and often the time-point is not reported. The aim of this study was to measure blood glucose continuously in a rat model of islet transplantation to assess blood glucose excursions in the night when the rats are active and are feeding.

  Materials and methods
  Three male Lewis rats were implanted intraperitoneally with continuous glucose telemetry devices with blood glucose measured in the descending aorta in accordance with manufacturer’s instructions. Following complete recovery from surgery blood glucose monitoring started, with recordings taken every 10 seconds. After five days of baseline measurements the rats were injected with 65mg/kg streptozotocin (STZ) to induce diabetes. Five days later, 2000-3000 Lewis rat islets were implanted under the kidney capsule and animals were maintained for a further 14 days. Each rat generated 207355 individual blood glucose measurements, and as such for purposes of statistical analysis mean blood glucose concentrations for each day (7am-7pm) and night cycle (7pm-7am) were calculated. 

  Results
  In the non-diabetic state, the mean difference in blood glucose concentrations between day and night was minimal (day: 6.9±0.6 mmol/l vs night: 7.2±0.7 mmol/l, p=0.764, t-test. Mean day-night difference: 0.42±0.1mM). After STZ injection, rats became hyperglycaemic (>20 mmol/l) within 13-22h and day to night blood glucose excursions increased (day: 24.7±2.8 mmol/l vs night: 33.0±4.8 mmol/l; mean excursion: 8.3±1.2 mmol/l, p<0.0001 vs pre-STZ, t-test. Data within 5 hours of an insulin injection were excluded). After transplantation, two rats showed improved blood glucose concentrations but day vs night glucose excursions were still significant (day time mean of 10.5 mmol/l and 11.0 mmol/l vs night mean of 14.6 mmol/l and 14.8 mmol/l respectively, p<0.0001 vs respective mean day glucose concentrations, t-test. Mean excursion: 3.8 mmol/l and 4.2 mmol/l respectively). The graph below shows the trace of one of these rats. The third rat remained hyperglycaemic and showed substantial day vs night glucose excursions, similar to that seen after STZ-treatment (mean day blood glucose: 25.2 mmol/l vs night blood glucose 38.1 mmol/l, p<0.0001, t-test. Mean excursion 12.0 mmol/l).

  Conclusion
  During basal conditions, differences in mean blood glucose concentrations between the night and day are minimal in Lewis rats. In an islet transplantation model, blood glucose excursions during the night are significantly pronounced after STZ administration. Despite the improvement in glycaemic control following transplantation, the significant night time glucose excursions persist. This may lead to an over-estimation of the efficacy of an intervention, as most researchers measure blood glucose during the day. The data also highlights the importance of consistent glucose monitoring time-points both within a study and when comparing studies.

• Artificial Intelligence Based Artificial Pancreas System In an Animal Model of Stress Induced Hyperglycemia - ADA 2016

  Leon DeJournett, Jeremy DeJournett, Heather DeLoid, Justin Prater

  Poster 999-P, American Diabetes Association Annual Meeting, New Orleans, LA, June 2016

  Artificial Intelligence (AI) based glucose controllers can be patterned after the lines of reasoning of a human expert, or after the workings of the native pancreas/liver system. These AI based controllers can mimic the pancreas with regards to timing of insulin release (every 3-7 minutes), and be capable of rapid changes of insulin output (up to 600% within a 20 minute interval). In addition, they can match or exceed the liver’s ability to release glucose in hypoglycemic states. We have developed a working AI based artificial pancreas (AP) system and successfully tested it in a novel swine model of stress induced hyperglycemia. These successful test results will allow us to proceed with clinical testing of this AI based glucose controller, with the eventual goal of creating an artificial pancreas system for use in the Intensive Care Unit (ICU) setting.

• Continuous Glucose Measurements Using Telemetry in Male and Female Dahl Salt-Sensitive Rats on a High-Fat Diet - EB 2016

  E. Gillis, E. Ralph, S. Tiesma, R. Lindquist, J.Sullivan

  Poster B175, Experimental Biology Annual Meeting, San Diego, CA, April 2-6, 2016

  The HD-XG glucose telemetry implant from DSI provides the ability to obtain continuous, real-time, blood glucose measurements in rodents. The goal of the current study was to compare spot blood glucose measurements with values obtained using telemetry in male and female DSS. Male and female rats were implanted with glucose telemeters at 11 weeks of age, and allowed 1 week to recover before being placed on receivers. Rats were maintained on a normal-salt, normal-fat (NF; 16% caloric intake from fat) diet for 1 week and then were switched to a high-fat diet (HF; 65% caloric intake from fat) for 4 weeks (n=4-5/group sex). Additional rats without telemeter implants were maintained on normal-salt, normal-fat diet for the duration of the experiment. All rats gained weight over the 4 week treatment period, however, rats of both sexes on a HF diet exhibited a significantly greater increase in body weight compared to rats on NF (males: 15±1% on NF vs. 22±2% on HF, p<0.05; females: 12±1% on NF vs. 18±2% on HF, p<0.05). There was not a sex difference in weight gain in response to HF diet. Mean absolute relative differences in blood glucose as measured by the HD-XG compared to spot glucose ranged from 0.1% up to 4.8% in males and 0.7% up to 8.9% in females, indicating that the 2 measurements were always within 10% of one another. Baseline blood glucose levels in male and female DSS measured by HD-XG were comparable (109±2 vs. 111±2 mg/dL, respectively). HF diet for 4 weeks did not significantly alter blood glucose levels in either sex (male: 106±3 mg/dL; female: 104±4 mg/dL). Additionally, average weekly glucose for both sexes were statistically identical whether analyzed over 24 hour periods or limited to only the light or dark periods. From this study we can conclude the following: 1) glucose telemeters are a reliable methods to obtain continuous measurements of blood glucose in male and female rats, 2) there are no sex differences in blood glucose following a 4 week HF diet in DSS, and 3) DSS are able to tolerate a HF diet with minimal alterations in body weight or blood glucose.

• Unlocking a More Comprehensive Assessment of Diet with Continuous, Chronic Blood Glucose and Complete Hemodynamic Monitoring in Rodents - EB 2016

  B. Main, K. Holliday-White, H. Bogie, K.E. Lillegard, R. Lindquist

  Poster LB655, Experimental Biology Annual Meeting, San Diego, CA, April 2-6, 2016

  New technology was employed in a novel way to monitor the effect of diet change on continuous blood glucose in addition to standard hemodynamic parameters. A new telemetry implant (HD-S11-F2, DSI) enables researchers to collect and transmit data at a different radio-frequency (18MHz) than the traditional 455KHz implants. While a second frequency allows for social housing and tighter density of research subjects, in this experiment the 18MHz device was paired with a continuous glucose telemetry implant (HD-XG, DSI) in the same animal. Implantation of two devices in a single animal allowed us to measure blood pressure, ECG, arterial blood glucose, body temperature and activity in a single rat. Six male Sprague Dawley rats were implanted with 2 telemetry implants that each required an arterial site for sensor placement. The HD-XG sensor was placed in the descending abdominal aorta and the device body was located IP. The HD-S11-F2 was inserted in the femoral artery and the catheter tip was advanced to the abdominal aorta (just cranial to the iliac bifurcation), not overlapping the glucose sensor. The HD-S11- F2 implant body was placed subcutaneously on the flank. After recovery from surgery, animals were enrolled in a cross-over designed study to compare the physiologic effects of offering high carbohydrate or low carbohydrate treats after a 12 hour fast. Blood pressure, heart rate and blood glucose values are presented. Marshmallows and mangos were offered as high carbohydrate treats while cheese cubes were offered as the low carbohydrate treat. Approximately 1 hour after the treat offering, the standard rat chow was restored to the cage feeders. The excitement from the technician opening the cage was evident in HR and BP changes associated with that activity. Blood glucose levels from 9-12 hours post-fast were approximately 92 mg/dl in both groups. Eating marshmallows and mango caused a rapid rise to ~103 mg/dl in ~30 minutes. Eating cheese resulted in a modest rise in blood glucose (~96 mg/dl). These experiments demonstrate a successful surgical approach using two implants to get a more comprehensive picture of whole animal cardiovascular and metabolic physiology.

• Blood Glucose Fluctuations during Daily Activities and Stress Procedures in Cynomolgus Monkeys Monitored By Implanted Telemetry Device - ENDO 2016

  Bingdi Wang, Guofeng Sun, Yongqiang Liu, Wei Qiao, Jiqiu Qiao, Weiwei Ye, Hui Wang, Xiaoli Wang, Yixin (Jim) Wang, and Yong-Fu Xiao

  Poster SUN720, Annual Meeting of the Endocrine Society, Boston, MA, April 1-4, 2016

  Insulin-resistant diabetes (Type 2 diabetes mellitus, T2DM) is the most common form of diabetes. Nonhuman primates (NHPs) can naturally develop to insulin resistance and diabetes in a way similar to the progression and onset of T2DM in humans, which makes them as an excellent model for diabetes research. The conventional tests of blood glucose are by handheld glucometer, clinical chemistry analyzer or Analox analyzer. These methods require sampling blood periodically and may miss some critical information during monitoring. This study investigated the changes of blood glucose during circadian, meal, stress procedure and drug exposure monitored continuously by implanted HD-XG transmitter device (Data Sciences International, Inc) in conscious Macaca fascicularis. The glucose sensor was implanted into the femoral artery and its reference electrode plus the device body was implanted subcutaneously nearby. A small receiver/amplifier was carried in the monkey jacket for remote signal collection from outside cage. Blood glucose, body temperature and physical activity were simultaneously monitored wirelessly and recorded continuously for more than 6 weeks. The blood glucose levels were in the range of 60-80 mg/dL in the selected normal monkeys (n=4) and 100-130 mg/dL in the selected diabetic monkeys (n=2). Their blood glucose levels showed circadian oscillations and kept at low levels during 12 am to 9 am (housing light circle = 7pm off to 7am on). There was no obvious postprandial hyperglycemia after morning feeding, but blood glucose increased by 20 to 30% after afternoon feeding. Grabbing out a monkey from its housing cage for sitting in a monkey chair caused a transient increase in blood glucose by 30 to 40% in both normoglycemic and diabetic monkeys, but took 30 min for returning to its baseline in normoglycemic animals and almost 2 hrs in diabetic monkeys. The stress-induced hyperglycemia by oral gavage was similar to grabbing monkey from hosing cage. To mimic stress-induced hyperglycemia, Angiotensin II (2 μg/kg, iv bolus injection, conscious) and norepinephrine (0.4 μg/kg/min, iv infusion, anesthetized with 10 mg/kg ketamine, im) induced the increase in blood glucose by 30%. However, intravenous injection of acetylcholine (1 μg/kg) had no obvious effect on blood glucose level. The results demonstrate that compared with nighttime, blood glucose during daytime is higher in the experimental monkeys. It is interesting that housed monkeys only showed afternoon post-prandial hyperglycemia after feeding. Operation-induced stress can increase blood glucose transiently. Stress-related hormones, such as norepinephrine and angiotensin, can also cause hyperglycemia. Therefore, remote and continuous monitor of blood glucose via telemetry device in conscious NHPs may provide a sophisticated approach to investigate neurological regulation of blood glucose due to behavior and hormonal changes.

• Changes in Blood Glucose, Blood Pressure, Heart Rate and Temperature in Rats Challenged with Either Low Carbohydrate, or High Carbohydrate Treats Following a 12 Hour Fast: Changes Tracked Using Dual Telemetry Implants - ENDO 2016

  Scott Tiesma, Kimberly L Holliday-White, Heather M Bogie, Kathryn E Lillegard, Ryan Lindquist, and Bradley W Main

  Poster LBSat-47, Annual Meeting of the Endocrine Society, Boston, MA, April 1-4, 2016

  Six male Sprague Dawley rats were simultaneously implanted with a telemetry device measuring continuous arterial blood glucose (HD-XG) transmitting at 455KHz, and an second telemetry device measuring arterial blood pressure and a biopotential (ECG) operating at 18MHz (HD-S11-F2). The HD-XG sensor was placed in the descending abdominal aorta and the device body was located IP. The HD-S11-F2 catheter was inserted in the femoral artery and routed to the abdominal aorta (just proximal to the iliac bifurcation and distal to the glucose sensor. The HD-S11-F2 transmitter body was placed subcutaneously on the flank. After recovery from surgery, data were collected for several days to observe changes in normal circadian rhythm. To demonstrate rapid changes in blood glucose while monitoring blood pressure and heart rate, animals were enrolled in a simple cross-over designed study to compare the response to high carbohydrate (marshmallows and fruit) with low carbohydrate treats (cheese cubes) after a 12 hour fast. Blood pressure, heart rate and blood glucose values are presented in this poster. Monitoring hemodynamic parameters in addition to blood glucose allowed us to separate excitement responses due to room entry or offering food, and actual changes in blood glucose due to the composition of the food. Room entry had minimal effect on the blood pressure and heart rate following the 12 hour fast, and no observed effect on blood glucose. Addition of a food offering caused an immediate increase in blood glucose that was related to the carbohydrate load offered by the food. Animals offered marshmallows and fruit had an immediate increase in blood glucose while those offered cheese had a blunted glucose response. However, 1 hour after the treats were offered, the normal rat chow was restored to the feeders. When the normal rat chow was restored, the rats in the marshmallow and fruit group showed little additional increase in blood glucose, while the cheese group had an immediate increase in blood glucose that was even greater than the group that had received the marshmallows and fruit. Blood pressure and heart rate were clearly elevated by adding food to the animals. These experiments demonstrate the value of using two implants to get a more complete picture of whole animal metabolic and cardiovascular physiology.

• Continuous Glucose Monitoring for Diabetes, Obesity, and Metabolism Research in Rodents - Webinar 2015

  R. Dechend, C. Schnell
  _{Max Delbruck Center for Molecular Medicine, Novartis Institutes for Biomedical Research}

  Webinar retrieved from https://insidescientific.com/webinar/continuous-glucose-monitoring-diabetes-obesity-metabolic-research-rodents-data-sciences/, November 18, 2015

  Available on demand at the URL listed above.

  Historically, diabetes, obesity and metabolism research has focused on acute metabolic testing characterized by infrequent sampling methods. This research contributes critical information regarding glucose metabolism and homeostasis; however, the acute approach and low sampling frequency leaves critical gaps in glucose metabolism research findings.

  In this exclusive webinar sponsored by Data Sciences International, we present a new method of continuously monitoring blood glucose via implantable telemetry. Using case studies, we explore how a complete glucose profile can be observed while also reducing animal stress and associated labor for the scientist. Dr. Ralf Dechend (Max Delbruck Center for Molecular Medicine) presents a method of glucose monitoring in a novel pregnant rat model of type 2 diabetes and shares realized advantages pertaining to this new continuous approach. In addition, Christian Schnell (Novartis) discusses the value of continuous glucose data in the application of pharmacokinetics and pharmacodynamics while testing an oncology compound.

• Impact of a High-Fat Diet on Blood Glucose and Blood Pressure in Female and Male Dahl Salt-Sensitive Rats - APS 2015

  Jennifer C. Sullivan, Erica Ralph, P. Thomas Menk, Eric J. Belin de Chantemèle
  _{Department of Physiology, Georgia Regents University, Augusta, GA 30912}

  Poster 28, APS Conference: Cardiovascular, Renal and Metabolic Diseases: Physiology and Gender, Annapolis, MD, November 17-20, 2015

  There are numerous sex differences in metabolic parameters and blood pressure (BP), although many fewer studies have examined the molecular mechanisms driving high-fat (HF)-induced increases in BP and metabolic disorders in males vs. females.

  Obesity and a HF diet are risk factors for hypertension, and male Dahl salt-sensitive rats (DSS) exhibit an increase in free fatty acids and BP in response to a HF diet; nothing is known in females.

• Fully Implantable Arterial Blood Glucose Device for Metabolic Research Applications in Rats for Two Months - JDST 2015

  Robert Brockway¹, Scott Tiesma¹, Heather Bogie¹, Kimberly White¹, Megan Fine¹, Libbey O’Farrell², Mervyn Michael², Amy Cox², and Tamer Coskun²
  _{1. Data Sciences International, Inc.  2.  Eli Lilly, Inc.}

  J Diabetes Sci Technol. 2015 Jul;9(4):771-81. doi: 10.1177/1932296815586424.

  Background: Chronic continuous glucose monitoring options for animal research have been very limited due to various technical and biological challenges. We provide an evaluation of a novel telemetry device for continuous monitoring of temperature, activity, and plasma glucose levels in the arterial blood of rats for up to 2 months.

  Methods: In vivo testing in rats including oral glucose tolerance tests (OGTTs) and intraperitoneal glucose tolerance tests (IPGTTs) and ex vivo waterbath testing were performed to evaluate acute and chronic sensor performance. Animal studies were in accordance with the guidelines for the care and use of laboratory animals and approved by the corresponding animal care and use committees (Data Sciences International, Eli Lilly).

  Results: Results demonstrated the ability to record continuous measurements for 75 days or longer. Bench testing demonstrated a high degree of linearity over a range of 20-850 mg/dL with R2 = .998 for linear fit and .999 for second order fit (n = 8 sensors). Evaluation of 6 rats over 28 days with 52 daily and OGTT test strip measurements each resulted in mean error of 3.8% and mean absolute relative difference of 16.6%.

  Conclusions: This device provides significant advantages in the quality and quantity of data that can be obtained relative to existing alternatives such as intermittent blood sampling. These devices provide the opportunity to expand the understanding of both glucose metabolism and homeostasis and to work toward improved therapies and cures for diabetes.

• Long-term Continuous Glucose Monitoring in Conscious Stressfree Nonhuman Primates with Implanted Telemetry Device - ADA 2015

  Bingdi Wang, Guofeng Sun, Xiaoli Wang, Xunhua Ding, Weimin Tang, Yi-Xin (Jim) Wang, Yong-Fu Xiao
  _{Crown Biosciences, Inc}

  Poster 972-P, American Diabetes Association Annual Meeting, Boston, MA, June 5-9, 2015

  Diabetes becomes a global epidemic issue. Aging nonhuman primates (NHPs) develop insulin resistance and high blood glucose in a way similar to the progression and onset of type 2 diabetes in humans, which makes them an excellent model for diabetes research. The conventional tests of blood glucose are by handheld glucometer, clinical chemistry analyzer or analox analyzer. These methods require periodical blood sampling with potential subject stress and ethical volume limitation, especially during research. This study investigated HD-XG transmitter, a Data Sciences International implantable device, for continuous monitoring of blood glucose in conscious NHPs. The glucose sensor was implanted into a femoral artery and the reference electrode plus its device body was implanted subcutaneously nearby. A small receiver/amplifier was carried in the monkey jacket for remote signal collection from outside cage. Blood glucose, body temperature and physical activity were monitored wirelessly and recorded continuously for over a month. Many classical diabetes assays, such as ivGTT, oGTT, ITT, clamp, were tested with this remote method and compared with the conventional glucometer assay (Fig. 1). Our data demonstrate the 1st success of remote, continuous monitoring of blood glucose in conscious, stress-free NHPs and its potential advantages bringing to diabetes research and drug discovery.

• Telemetry for Continuous Glucose Monitoring in Rats - AALAS 2015

  Xiaoli Ping¹; Zuliang Yao²; Andrea Nawrocki²; Bernard Doerning¹; Colena Johnson¹; Xiaolan Shen¹
  _{Departments of 1 Laboratory Animal Resources, 2 In Vivo Pharmacology, Merck Research Laboratories (Kenilworth, NJ), Merck & Co., Inc., Kenilworth, NJ, USA}

  Poster P296, AALAS 67^th National Meeting, Charlotte, NC, October 30-November 3, 2015

  Metabolic syndrome is a cluster of abnormalities often associated with obesity and diabetes. The hallmark of diabetes is insulin resistance, an impairment of insulin action within tissues at the level of the insulin receptor and subsequent cellular events. Type 2 diabetes arises from a combination of insulin resistance and a relative impairment of insulin secretion in response to meal ingestion. The glucose tolerance test (GTT) is vital for the characterization of metabolic syndrome, the natural progression of type 2 diabetes. In metabolic syndrome research, routine glucose measurements, including GTT, are often accomplished using glucometers and test strips. This method has significant limitations, as it is inaccurate, is timeconsuming, requires frequent sampling, and induces animal stress. However, with newly developed implantable continuous glucose telemetry, we now are able to obtain continuous, real-time, blood glucose measurements in conscious laboratory animals without disturbing them. The present study evaluates the use and the performance of this system in hyperglycemic Goto-Kakizaki (GK) rats and Zucker Diabetic Fatty (ZDF) rats. Glucose telemetry was implanted in the abdominal aorta and the transmitter body in the peritoneum via an aseptic surgery. The system enabled monitoring of disease progression over time as well as repeatedly glucose tolerance test on same animal. Two weeks after postsurgical recovery, detectable differences of treatment effects on prandial and fasting blood glucose levels were evident. Telemetry glucose monitoring data, in parallel with measurements of food intake, body weight, and locomotor activity validated this platform technology as a refinement in aiding our understanding of anti-diabetic therapeutic agents.

• Continuous Glucose Monitoring via Telemetry in Rats - MTS 2015

  Zuliang Yao¹, Xiaoli Ping², Maria Trujillo¹, Andrea Nawrocki¹, Xiaolan Shen², Margaret Van Heek¹
  _{1. Department of in Vivo pharmacology, 2. SALAR, Merck Research Laboratories, Merck and Co., Inc.}

  Poster presented at Merck Technology Symposium, Somerset, NJ, June 2-3, 2015

  Continuous glucose monitoring (CGM) systems are becoming more prevalent providing real-time measures of blood glucose in humans but may also prove invaluable in diabetes research. Routine glucose measurements in a typical preclinical study use glucometers and test strips, a method that entails some limitations such as accuracy, stress due to handling of animals and frequency of sampling.  Glucose telemetry implants offer preclinical diabetes and metabolic disease scientists a novel tool to obtain continuous, real-time, blood glucose measurements in laboratory animals. Data Sciences International (DSI) rolled out a novel telemetry device HD-XG, an implantable glucose sensor for acute and chronic glucose measurements in the arterial blood of rats in 2014.  The present study evaluates the use and the performance of this system in hyperglycemic Goto-Kakizaki (GK) rats and male, diabetic ZDF rats, representative for diabetic disease models. The system allows monitoring disease progression over time, in parallel with measurements of food intake, body weight and locomotor activity.  Moreover, this system facilitates testing of antidiabetic treatment effects on both prandial and fasting blood glucose levels compared to placebo treatment over a natural feeding cycle. These data validate this platform technology against standard methods of glucose monitoring and demonstrate the utility of this technology in drug discovery and diabetes research.

• Assessment of the hyperglycemia profile of NVP-BYL719, a selective inhibitor of the class Ia PI3K isoform alpha using real-time continuous glucose monitoring via radio-telemetry in rats - AACR-NCI-EORTC 2015

  C. R. Schnell, T. Ferrat, C. Fritsch and M.R. Jensen
  _{Oncology Research , Novartis Institutes for Biomedical Research, 4002 Basel, Switzerland}
  

  Poster B108 AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics, November 5-9, 2015

  The gene encoding for the catalytic subunit of the phosphatidylinositol-3-kinase (PI3K), p110a (PIK3CA) is the most frequently mutated kinase in cancer. This discovery triggered the development of small molecule anti-PI3K inhibitors, such as NVP-BYL719. However, the PI3K / Akt signaling pathway plays not only an important role in promoting cell growth, proliferation and survival but also in regulating glucose homeostasis by directly mediating insulin-stimulated glucose uptake into insulin sensitive tissues (adipocytes and muscles). Hyperglycemia has been reported to be one of the most frequent adverse events in clinical trials for PI3K inhibitors.  Therefore, NVP-BYL719, a selective inhibitor of the class Ia PI3K isoform-alpha, can impair glucose metabolism.

  However until now, continuous glucose monitoring options have been very limited in biomedical research. Investigators have used periodic sampling of blood glucose using a glucometer and test strips approach to provide a snap-shot assessment of the effect of PI3K inhibitors to glucose metabolism. Thus, ‘around the clock’ real-time measurements of blood glucose in unstressed, freely moving animals are needed to better assess pharmacokinetic (PK: drug levels in plasma) and pharmacodynamics (PD: glucose levels in blood) relationship in pre-clinical models.

  The present study evaluates the use of a new radio-telemetry device (HD-XG, Data Sciences International) incorporating an implantable glucose sensor (Nova Biomedical, Waltham, MA) for chronic continuous (every minute) glucose measurements in the arterial blood of brown Norway (BN) rats. We evaluate the day-and-night profile of glucose blood levels as well as the PK/PD relationship of NVP-BYL719 following daily oral treatment at efficacious anti-tumor doses.

• Continuous recording of blood glucose reveals that taste modulates the blood glucose response to a gavaged glucose load - SSIB 2015

  Rachel L. Poole, Hillary T. Ellis, and Michael G. Tordoff. 
  _{Monell Chemical Senses Center, Philadelphia}

  Poster P26, Society for the Study of Ingestive Behavior Annual Meeting, Denver, CO, July 7-11, 2015

  Bitter taste decreases gastric emptying after an intragastric fat load and decreases blood triglycerides (e.g., Saitou, PlosOne 9: e90717, 2014). To assess whether bitter taste also decreases blood glucose after a glucose load, we took advantage of a new technology that continuously monitors changes in blood glucose – the DSI HD-XG glucose sensor. The HD-XG sensor was inserted into the abdominal aorta of a Sprague Dawley rat and a telemetry transponder was implanted into the peritoneal cavity. After several days to recover from surgery, the rat was gavaged every 1-2 days with 5 mL of 6 g/kg glucose and then it immediately tasted 1 mL of water, 0.125% saccharin (a sweet taste) or 0.15% quinine hydrochloride (a bitter taste). The rat was then returned to its home cage and remained undisturbed while blood glucose levels were monitored every 10 sec for several hours. The rise, peak, and duration of the elevation in blood glucose produced by the glucose load were similar after the rat tasted water or saccharin. However, tasting quinine significantly delayed the return of blood glucose concentrations to their nadir. Thus, stimulation of bitter taste receptors can influence blood glucose levels after a glucose load. This work highlights the advantages of the HD-XG glucose sensor, which allows monitoring of blood glucose with 10-sec temporal resolution without the stress of repeated blood draws.

• Modulation of Blood Glucose Concentration by Vagal Nerve Stimulation - EB 2015

  Harald M. Stauss¹, Erin E. Meyers¹, Taylor J. Glab¹, and Kamal Rahmouni²
  _{1. Department of Health and Human Physiology and 2. Department of Pharmacology, The University of Iowa, Iowa City, IA}

  Poster B447, Experimental Biology Annual Meeting, Boston, MA, March 28-April 1, 2015

  Chronic cervical vagal nerve stimulation (VNS) causes weight loss in obese patients and in experimental animal models of obesity. Furthermore, parasympathetic activity directed to the liver has been demonstrated to reduce hepatic glucose release. Thus, chronic cervical VNS may be particularly beneficial in obese type 2 diabetic patients. Here we tested the hypothesis that acute cervical VNS reduces blood glucose concentration in anesthetized rats. Sprague Dawley rats were instrumented with catheters in the left carotid artery, bipolar electrodes on the right cervical vagus nerve, and a novel telemetric glucose sensor (HD-XG, DSI) in the abdominal aorta, that allows for continuous monitoring of blood glucose concentration. Once stable mean blood pressure (106±14 mmHg), heart rate (322±25 bpm), and blood glucose concentration (157±21 mg/dL) was obtained (usually after 30-60 min) VNS (rectangular impulses, 3 V, 1 ms pulse width, 5 Hz) was initiated. The stimulator was turned on and off every 30 min for five complete on/off cycles. During the “on cycles” heart rate and mean blood pressure decreased (-79±5 bpm and -9±3 mmHg) while blood glucose concentration increased (+116±66 mg/dL). During the “off cycles” heart rate, mean blood pressure, and blood glucose concentration returned to baseline levels. A similar increase in blood glucose concentration was observed with efferent VNS after sectioning the vagus nerve cranial to the stimulation electrode. In summary, acute cervical VNS at an intensity that reduces heart rate elicits a glucogenic effect in anesthetized rats. Further studies are needed to understand the mechanisms by which acute and potentially also chronic cervical VNS may increase blood glucose.

• 28-day Continuous Glucose Profiles Via Implantable Telemetry in Mice - ENDO 2015

  Robert Brockway¹, Justin Van Hee¹, Kimberly Holliday-White¹, Heather Bogie¹, Kathryn Lillegard¹
  _{1. Data Sciences International, Inc.}

  Poster LBF-097, Annual Meeting of the Endocrine Society, San Diego, CA,  March 5-8, 2015

  A fully implantable telemetry device is evaluated for continuous monitoring of blood glucose, temperature and locomotor activity in C57BL/6 male mice.  A surgical procedure has been established based on previous success with continuous blood pressure monitoring in mice.  The sensor is surgically placed through the carotid artery to the aortic arch with the device housing placed sub-cutaneously on the side.  A calibration method is established using an intraperitoneal glucose tolerance test (IPGTT) with reference samples collected from the tail.  Sensors were evaluated by observing the continuous signal for expected variations with feeding, activity and circadian variations.  IPGTT was also used periodically to assess sensor response over a range of glucose.  Using this device we recorded 10-second averages in over 25 mice for durations ranging from a few days to 37 days.  The chronic data demonstrates a high degree of physiologic variability both during light and dark periods, with minimal overall circadian baseline variations.  These patterns are distinctly different from previous experience with continuous glucose measurements in rats.  The sensors respond as expected to IPGTT with peak amplitudes approaching 500mg/dL and time from dose to peak of 11-15 minutes.  The IPGTT also provides highly detailed morphology, low sample variability (noise), and a good basis for calculating parameters such as AUC.  These new telemetry sensors will provide a basis for enhanced understanding of glucose metabolism in mice and will contribute to advancements in therapies for diabetes in humans.

• Continuous Glucose Correlation with Food Intake in the Male C57BL Mouse - SWCIB 2015

  Scott Tiesma¹, Robert Brockway¹
  _{1. Data Sciences International}

  Presentation at the Swiss Winter Conference on Ingestive Behavior, Saint Moritz, Switzerland, February 28-March 5, 2015

  Food intake is known to result in acute excursions in blood plasma glucose levels.  In order to observe and characterize this relationship, continuous glucose (CG) and food intake (FI) were recorded simultaneously in the male C57BL mouse.  Ingestive behavior and basic glucose homeostasis evaluations were also performed.

  In a pilot evaluation of the HD-XG telemetry (DSI) device for mice, one mouse, 14.6 weeks old, was surgically instrumented with the glucose sensor in the aortic arch through a carotid artery cannulation and transmitter body placement in the right flank.  This device provides continuous measurements of blood glucose, temperature and locomotor activity.  Surgical recovery occurred in parallel with FI system acclimation which consisted of individually housing the mice and providing ad libitum access to food and water via both the standard cage top and the FI perimeter mounted hoppers. 3 weeks following surgery the cage top food was removed.  In vivo calibration of the glucose sensor occurred on days 7 and 28.  Data was evaluated by assessing 4 days of CG and FI data to characterize night/day differences and correlation between FI and CG.  Data during the calibration on day 28 was omitted from analysis.

  CG and FI meal data were found to be strongly correlated with the preponderance of glucose excursions associated with a meal.  Over the course of 4 days, the mouse ate 82% ± 15% of food volume during the dark period through both increased meal occurrence (69% ± 14% of total meals) and increased meal volume (~0.30 ± 0.11 grams/meal versus 0.14 ± 0.04 grams/meal during the light).

  During the period when FI was monitored the mouse had an average daily glucose of 116 ± 16 mg/dL and daily range between 82 and 182 mg/dL.  Light versus dark period average glucose values were 112 ± 16 and 120 ± 15 mg/dL respectively.  Light versus dark period range of glucose was 82 to 182 and 85 to 156 mg/dL respectively.  The similarity in the average and higher range of glucose during the light period was surprising as experience in the rat suggested a more distinct circadian variation with both higher average and higher range of glucose during the dark period.

  CG offers the ability to detect subtle and comprehensive changes in glycemic level and variability not practical with infrequent manual blood samples.  These changes in glycemia are closely correlated with FI.  As such, the HD-XG provides a new tool for the ingestive behavior researcher wishing to better characterize the relationship between eating and glucose homeostasis.

• Continuous glucose and food intake monitoring in the male ZDSD rat: Comparison of normal and high-fat diets - SSIB 2014

  Charles V. Jackson¹, Richard G. Peterson¹, Douglas Compton¹, Edward Ulman¹, Scott Tiesma², Robert Brockway²
  _{1. PreClinOmics, Inc.  2. Data Sciences International, Inc.}

  Poster C1, Society for the Study of Ingestive Behavior Annual Meeting, Seattle, WA, July 2014

  The goal of this study was to assess the effect of a high-fat diet on glucose and food intake (FI) in pre-diabetic ZDSD male rats using continuous glucose (CG) telemetry (DSI, model HD-XG) and the BioDAQ FI monitoring system (Research Diets). Ten male rats, 14 weeks old, were housed singly for three days prior to aseptic surgery to acclimate them to the FI system on control diet (Purina #5008). All rats were implanted with a glucose sensor in the abdominal aorta and transmitter in the peritoneum. The animals were maintained on 5008 for 2 weeks and switched to a high-fat diet (Research Diets #D12468) for an additional 2 weeks. CG monitoring allowed for visualization of the circadian pattern that was not seen with FI and would not have been detected to the same degree using twice daily blood glucose sampling. Twice daily sampling overestimated the light period minimum glucose values by 10.8% for standard diet and 20.1% for high fat diet and underestimated the dark period maximum glucose values by 14.5% for standard diet and 18.0% for high fat diet relative to CG monitoring. This resulted in an underestimation of daily glycemic excursion of 60.2% and 47.9% during normal and HF diets respectively. The combination of CG and FI monitoring offers the ability to detect subtle and comprehensive diet-related changes in glycemic level and variability not practical with infrequent manual blood samples.

• Assessment of Insulin Response in STZ Rats Using Continuous Glucose Telemetry - ADA2014

  Scott Tiesma¹, Robert Brockway¹, Tamer Coskun², Libbey O’Farrell², M Dodson Michael², Amy L Cox² , Kimberly White¹ , Heather Bogie¹
  _{1. Data Sciences International (DSI), USA; 2. Lilly Research Laboratories, USA}

  Poster 1733-P, American Diabetes Association Annual Meeting, San Francisco, CA, June 2014

  Continuous glucose monitoring options have been very limited for research applications in pre-clinical models. Investigators have used periodic sampling of blood glucose to provide a coarse assessment of the efficacy of novel anti-diabetic therapies. The present study employs a newly developed implantable glucose monitor (HD-XG, Data Sciences International) to evaluate the pharmacodynamic (PD) profi le of several commercially available insulins including the basal insulins Humulin® N and Lantus® and the mealtime insulin analogs Humalog®, Novolog®, and Apidra®. The implantable device is 1.4 cc and provides continuous temperature, activity, and arterial blood glucose readings for 4 wks or longer. Continuous assessment of blood glucose was performed in 12 Sprague Dawley rats in which diabetes was induced with streptozotocin (STZ). Data were recorded continuously for 26 d with averages reported every 10 sec. Daily reference glucose values were measured from tail vein blood samples using the Nova StatStrip Xpress glucometer. Following STZ administration, the rats experienced a transient period of hyperglycemia followed by a hypoglycemic period. Over the next 24 hrs, blood glucose steadily increased, and hyperglycemia stabilized with a distinct diurnal fluctuation. Three days after STZ induction, the rats were divided into 2 groups that received either Humulin® N or Lantus® BID to determine an optimal basal insulin regimen. Rats in the Humulin® N group had more sustained glucose lowering so all rats were switched to Humulin® N for individualized dose adjustments. Following the basal insulin assessment, the rats were dosed twice (10 nmol/kg) with each of the three mealtime insulin analogs to assess the PD response. The implanted glucose sensors provided unprecedented time resolution of the glucose response for each insulin dose. These profiles will provide a reference against which to compare novel drugs under development.

• Assessment of Insulin Response in STZ Rats Using Continuous Blood Glucose Telemetry – Keystone 2014

  Scott Tiesma¹, Robert Brockway¹, Tamer Coskun², Libbey O’Farrell², M Dodson Michael², Amy L Cox^2.
  _{1. Data Sciences International, St. Paul, USA; 2. Lilly Research Laboratories, Indianapolis, USA}

  Poster 3025, Keystone Symposia:  Challenges and Opportunities in Diabetes Research and Treatment, Vancouver, Canada, January 2014

  Continuous glucose monitoring options have been very limited for research applications in pre-clinical models. Investigators have used periodic sampling of blood glucose to provide a coarse assessment of the efficacy of novel anti-diabetic therapies. The present study employs a newly developed implantable glucose monitor (HD-XG, Data Sciences International) to evaluate the pharmacodynamic (PD) profile of several commercially available insulins including the basal insulins Humulin^® N and Lantus^® and the mealtime insulin analogs Humalog^®, Novolog^®, and Apidra^®. The implantable device is 1.4 cc and provides continuous temperature, activity, and arterial blood glucose readings for 4 wks or longer. Continuous assessment of blood glucose was performed in 12 Sprague Dawley rats in which diabetes was induced with streptozotocin (STZ). Data were recorded continuously for 26 d with averages reported every 10 sec. Daily reference glucose values were measured from tail vein blood samples using the Nova StatStrip Xpress glucometer. Following STZ administration, the rats experienced a transient period of hyperglycemia followed by a hypoglycemic period. Over the next 24 hrs, blood glucose steadily increased, and hyperglycemia stabilized with a distinct diurnal fluctuation. Three days after STZ induction, the rats were divided into 2 groups that received either Humulin® N or Lantus® BID to determine an optimal basal insulin regimen.  Rats in the Humulin® N group had more sustained glucose lowering so all rats were switched to Humulin® N for individualized dose adjustments. Following the basal insulin assessment, the rats were dosed twice (10 nmol/kg) with each of the three mealtime insulin analogs to assess the PD response. The implanted glucose sensors provided unprecedented time resolution of the glucose response for each insulin dose. These profiles will provide a reference against which to compare novel drugs under development.

• Continuous Glucose Monitoring via Telemetry in Rats - EASD 2013

  Robert Brockway¹, Tamer Coskun², Libbey O’Farrell², Paul Haefner¹, Kimberly White¹, Charles V. Jackson³, Richard G. Peterson³
  _{1. Data Sciences International, St. Paul, MN 2. Eli Lilly and Company, Indianapolis, IN 3. PreClinOmics, Indianapolis, IN}

  Poster 1099, European Association for the Study of Diabetes Annual Meeting, Barcelona, Spain, September 2013

  Background and aims: The current standard for routine glucose measurements in preclinical research is often glucometers and test strips. These pose significant limitations in terms of accuracy, animal stress, and frequency of sampling. Until now, continuous monitoring options for preclinical research have been very limited. The present study evaluates the use of a novel prototype device (Data Sciences International) for acute and chronic glucose measurements in rats.

  Materials and methods: The device is 1.4cc and provides temperature, activity, and direct continuous blood glucose readings for 4 weeks or longer. The devices were evaluated in 4 diabetic and 4 normal Zucker fa/fa (ZDF) rats and in 10 Zucker diabetic/Sprague Dawley (ZDSD) rats. Each animal was surgically instrumented with glucose sensors in the abdominal aorta and the telemetry device placed in the intraperitoneal (ip) cavity. Continuous glucose readings were recorded for 5-7 weeks with periodic fasting GTTs (glucose, 2-3 g/kg, po or ip). Daily and GTT reference values were recorded with a StatStrip Xpress glucometer (Nova Biomedical).

  Results: The glucose sensors provided high resolution data and demonstrated the ability to accurately assess chronic diurnal patterns matching with the feeding pattern of rats from 3 days up to 7 weeks after surgery.

  Conclusion: These devices hold great potential for comparing physiologic processes associated with glucose regulation in normal and disease condition rats; monitoring diabetes progression and developing preventive treatments for type II diabetes.

• Comparison of Continuous Glucose Monitoring Systems in Type 1 Rat Model - ADA 2013

  Paul Haefner¹, Kimberly Holliday-White¹, Dr. Mark Clements².
  _{1. Data Sciences International, (DSI) St. Paul, MN 2. Children’s Mercy Hospital, Kansas City, MO}

  Poster 39-LB, American Diabetes Association Annual Meeting, Chicago, IL, June 2013

  Presently, few continuous monitoring glucose options are available for preclinical research. This study compares the performance of an existing interstitial system (Medtronic MiniMed) with a fully implantable direct blood monitoring prototype (Data Sciences International). Prototype sensors were surgically implanted in the abdominal aorta of 10 weight matched Sprague Dawley rats at 8 weeks of age. One week later, interstitial sensors were placed in the dorsal skin near the scapulae and the rats dosed with streptozotocin (65 mg/kg). Daily glucose measurements and approximately weekly GTT’s (dextrose, 1-2.6 g/kg, ip; insulin, 0.5-1.0 unit/kg, im) were measured with a StatStrip glucometer (Nova Biomedical). Sensors were calibrated via an interpolated one point calibration method utilizing daily readings. A relative absolute difference was calculated for each sensor, on both GTT’s and daily readings. Diabetes was induced in 8 of 10 animals. Two of 10 interstitial sensors and 2 of 10 blood monitoring sensors (improperly implanted) failed to perform correctly. Both sensor types exhibited larger errors at lower glucose. Interstitial sensors functioned an average of 5.6 days with an average delay of 8.8 minutes. Blood monitoring sensors functioned an average of 24.9 days with an average delay of -0.8 minutes. These prototype devices provide a promising alternative for chronic preclinical continuous glucose monitoring in a free roaming type 1 rat model.

• Continuous Glucose Monitoring via Telemetry in Rats – ADA 2013

  Tamer Coskun¹, Libbey O’Farrell¹, Robert Brockway², Paul Haefner², Kimberly White², Richard G. Peterson³, Charles V. Jackson³
  _{1. Eli Lilly and Company, Indianapolis, IN 2. Data Sciences International, St. Paul, MN 3. PreClinOmics, Indianapolis, IN}

  Poster 38-LB, American Diabetes Association Annual Meeting, Chicago, IL, June 2013

  The current standard for routine glucose measurements in preclinical research is often glucometers and test strips. These pose significant limitations in terms of accuracy, animal stress, and frequency of sampling. Until now, continuous monitoring options for preclinical research have been very limited. The present study evaluates the use of a novel prototype device (Data Sciences International) for acute and chronic glucose measurements in rats. The device is 1.4cc and provides temperature, activity, and direct continuous blood glucose readings for 4 weeks or longer. The devices were evaluated in 4 diabetic and 4 normal Zucker fa/fa (ZDF) rats and in 10 Zucker diabetic/Sprague Dawley (ZDSD) rats. Each animal was surgically instrumented with glucose sensors in the abdominal aorta and the telemetry device placed in the intraperitoneal (ip) cavity. Continuous glucose readings were recorded for 5-7 weeks with periodic fasting GTTs (glucose, 2-3 g/kg, po or ip). Daily and GTT reference values were recorded with a StatStrip Xpress glucometer (Nova Biomedical). The glucose sensors provided high resolution data and demonstrated the ability to accurately assess chronic diurnal patterns matching with the feeding pattern of rats from 3 days up to 7 weeks after surgery. These devices hold great potential for comparing physiologic processes associated with glucose regulation in normal and disease condition rats; monitoring diabetes progression and developing preventive treatments for type II diabetes.

• Time-dependent effects of ipragliflozin on behaviour and energy homeostasis in normal and type 2 diabetic rats: continuous glucose telemetry analysis

  Iuchi H, Sakamoto M, Matsutani D, Suzuki H, Kayama Y, Takeda N, Minamisawa S, Utsunomiya K

  Scientific Reports 7, Article number: 11906 (2017) doi: 10.1038/s41598-017-12106-y

  Sodium–glucose cotransporter 2 (SGLT2) inhibitors are oral antidiabetic drugs that promote urinary glucose excretion. Conversely, they cause behavioural changes, such as hyperphagia, that result in a positive energy balance. The relationship between energy homeostasis and SGLT2 inhibitors induced behavioural changes remains unclear. Here we show that ipragliflozin, a SGLT2 inhibitor, time-dependently affects behaviour and enhances energy expenditure in normal and type 2 diabetic Goto–Kakizaki (GK) rats, using continuous glucose telemetry. Alongside increased urinary glucose excretion, ipragliflozin increased total food and water intakes in normal and GK rats. In normal rats, ipragliflozin treatment acutely disturbed the circadian rhythms of food and water intakes, activity, and body temperature. Subsequently, these rhythms gradually returned towards a normal state. However, activity and body temperature remained suppressed. In GK rats, ipragliflozin did not affect circadian rhythms. Blood glucose values assessed by glucose telemetry were significantly reduced in both ipragliflozin-treated groups. Despite these behavioural and glycaemic changes, ipragliflozin significantly increased oxygen consumption during dark and light periods in both groups. Ipragliflozin reduced body weight in normal rats only. Thus, ipragliflozin decreases blood glucose beyond compensatory hyperphagia in normal and GK rats, resulting in enhanced basal energy expenditure, despite acutely altering circadian rhythms in normoglycaemic individuals.

• Decreased complexity of glucose dynamics preceding the onset of diabetes in mice and rats

  Zhang XD, Pechter D, Yang L, Ping X, Yao Z, Zhang R, Shen X, Li NX, Connick J, Nawrocki AR, Chakravarthy M, Li C

  PLoS ONE (2017) 12(9): e0182810. doi: 10.1371/journal.pone.0182810

  Continuous glucose monitoring (CGM) is a platform to measure blood glucose (BG) levels continuously in real time with high enough resolution to document their underlying fluctuations. Multiscale entropy (MSE) analysis has been proposed as a measure of time-series complexity, and when applied to clinical CGM data, MSE analysis revealed that diabetic patients have lower MSE complexity in their BG time series than healthy subjects. To determine if the clinical observations on complexity of glucose dynamics can be back-translated to relevant preclinical species used routinely in diabetes drug discovery, we performed CGM in both mouse (ob/ob) and rat (Zucker Diabetic Fatty, ZDF) models of diabetes. We demonstrate that similar to human data, the complexity of glucose dynamics is also decreased in diabetic mice and rats. We show that low complexity of glucose dynamics is not simply a reflection of high glucose values, but rather reflective of the underlying disease state (i.e. diabetes). Finally, we demonstrate for the first time that the complexity of glucose fluctuations in ZDF rats, as probed by MSE analysis, is decreased prior to the onset of overt diabetes, although complexity undergoes further decline during the transition to frank diabetes. Our study suggests that MSE could serve as a novel biomarker for the progression to diabetes and that complexity studies in preclinical models could offer a new paradigm for early differentiation, and thereby, selection of appropriate clinical candidate molecules to be tested in human clinical trials.

• Comparison of Continuous Glucose Monitoring between Dexcom G4 Platinum and HD-XG Systems in Nonhuman Primates (Macaca Fascicularis)

  Wang B, Qiao W, Ye W, Wang X, Liu Y, Wang Y, Xiao Y

  Scientific Reports 7, Article number: 9596 (2017) doi:10.1038/s41598-017-09806-w

  Timely knowing glucose level helps diabetic patients to manage the disease, including decisions about food, physical activity and medication. This study compared two continuous glucose monitoring systems in conscious and moving-free nonhuman primates (NHPs, Macaca fascicularis). Each normoglycemic or diabetic monkey was implanted with one Dexcom G4 Platinum subcutaneously or one HD-XG glucose sensor arterially for glucose monitoring. The glucose levels measured by both telemetry devices significantly correlated with the glucometer readings. The data of oral glucose tolerance test (oGTT) showed that the glucose levels measured by either Dexcom G4 Platinum or HD-XG transmitter were very similar to glucometer readings. However, compared to HD-XG transmitter or glucometer, Dexcom G4 Platinum detected a decreased glucose peak of ivGTT with approximately 10 min delay due to interstitial glucose far behind blood glucose change. Our data showed the advantages of the telemetry systems are: (1) consecutive data collection (day and night); (2) no bleeding; (3) no anesthesia (moving freely); (4) recording natural response without physical restriction and stress; (5) less labor intensity during ivGTT and other tests; (6) quick outcomes without lab tests. This article summarized and compared the differences of the general characteristics of two continuous glucose monitoring systems in diabetic research.

• Continuous Glucose Monitoring in Female NOD Mice Reveals Daily Rhythms and a Negative Correlation With Body Temperature - En 2017

  Korstanje  R, Ryan JL, Savage HS, Lyons BL, Kane KG, Sukoff Rizzo SJ

  Endocrinology 2017 en.2017-00266. doi: 10.1210/en.2017-00266

  Previous studies with continuous glucose monitoring in mice have been limited to several days or weeks, with the mouse's physical attachment to the equipment impacting behavior and measurements. In the current study we measured blood glucose and body temperature at 10-second intervals for 12 weeks in a cohort of NOD/ShiLtJ female mice using wireless telemetry. This allowed us, for the first time, to obtain a high-resolution profile of the circadian rhythm of these two parameters and the onset of hyperglycemic development in real time. The most striking observations were the nocturnal concentrations of glucose were elevated into the diabetic range days prior to elevations in diurnal glucose (when glucose concentrations are historically measured), and the strong, negative correlation between elevated blood glucose concentrations and body temperature with a steady decline of the body temperature with diabetes development. Taken together this new technological advancement provides improved resolution in the study of diabetes disease trajectory in mouse models including relevant translatability to the current technologies of continuous glucose monitoring now regularly employed in patients.

• Rhythmic Differences of Blood Glucose Circadian Between Normoglycemic and Diabetic Non-Human Primates - ADA 2017

  Wang B, Sun G, Liu Y, Qiao J, Ye W, Wang X, Sun G, Lindquist R, Wang Y, Xiao YF

  Poster 1881-P, American Diabetes Association Annual Meeting, San Diego, CA, June 2017

  Disruptions of humans’ biological rhythms, such as shift work, can increase the risk of developing obesity and diabetes. As the nonhuman primate (NHP) is a great model for metabolic research, this study compared the rhythms of blood glucose circadian among normoglycemic and diabetic cynomolgus macaques. Interestingly, the circadian rhythm of blood glucose in the normoglycemic NHPs differed from that in the diabetic NHPs (Figure 1, upper row panels). The glucose level in the normoglycemic NHPs decreased gradually from 3 am to a low level in 3 hrs and remained low until 3 pm (afternoon feeding time). However, the blood glucose level in the diabetic NHPs increased gradually around 7 am to a noticeably higher level and then was maintained until 9 pm. Postprandial hyperglycemia was observed following 3-pm feeding, but not after morning 10-am feeding. The circadian rhythms of physical activity and body temperature were similar among the normoglycemic and diabetic monkeys (Figure 1, middle row and low row panels). Our data demonstrate that with the telemetry implantation method, the different rhythms of blood glucose circadian were observed among the normoglycemic and diabetic NHPs, which may result from their different responses to both insulin and its counterregulatory hormones. Therefore, continuous glucose monitoring with telemetry device can be highly valuable for future diabetic research and drug discovery.

• Novel Telemetry Technology for Continuous Glucose Monitoring in Mice - MTS 2016

  Zuliang Yao, Andrea Nawrocki, Xiaoli Ping, Xiaolan Shen, Cai Li

  Poster 205, Merck Technology Symposium, Somerset, NJ, June 29-30, 2016

  Continuous glucose monitoring (CGM) systems are becoming more prevalent providing real-time measures of blood glucose in humans but may also prove invaluable in diabetes research. Data Sciences International (DSI) rolled out a telemetry device incorporating an implantable glucose sensor for acute and chronic glucose measurements in the arterial blood of rats in 2014. Based on the successful implementation of the rat methodology, we collaborated with DSI to validate the practical application and evaluate the commercial value of a similar telemetry device for mouse blood glucose monitoring, a more challenging but valuable tool in preclinical research. The present Alpha study evaluates the use and the performance of the devices in hyperglycemic, obese ob/ob mice and age matched lean C57B mice. The system allows for continuous, real-time, blood glucose measurements and the animals’ response to current standard of care diabetes treatments, such as GLP-1 analogs, SGLT2 inhibitor or Pioglitazone, in parallel with measurements of body temperature, and locomotor activity. Moreover, this system facilitates testing of treatment effects on both prandial and fasting blood glucose levels compared to placebo treatment over a natural feeding cycle and in relation to the circadian rhythm. A future Beta study will benchmark the system against commercial diabetes therapies in diabetic mice to further validate the CGM methodology, determining the use of this novel technology for our diabetes drug discovery research.

• Evaluation of a prototype HD-XG telemetry implant for real-time continuous glucose monitoring in mice - FELASA 2016

  Petra Seebeck, Anne Marowsky, Svende Pfundstein, Scott Tiesma

  Poster PA28, Federation for Laboratory Animal Science Associations Congress, Brussels, Belgium, June 2016

  Blood glucose (BG) measurement is routine during preclinical diabetes and metabolic research. For glucometer and test strip measures blood samples have to be drawn [1]. Data quality strongly depends on the animals’ stress level and significant events might get lost due to gaps between samples. The HD-XG is an implantable telemetry device providing continuous real-time measurements of blood glucose, temperature, and activity in rats [2]. The present study evaluates the use of a novel HD-XG prototype for mice.

• Advantages of Glucose Monitoring with Implantable Telemetry in Freely Moving Conscious Nonhuman Primates - ADA 2016

  Bingdi Wang, Wei Qiao, Guofeng Sun, Yongqiang Liu, Jiqiu Qiao, Weiwei Ye, Hui Wang, Xiaoli Wang, Ryan Lindquist, Yixin (Jim) Wang, Yong-Fu Xiao

  Poster 911-P, American Diabetes Association Annual Meeting, New Orleans, LA, June 2016

  Long-term glucose monitor is challenging. This study was to investigate telemetry monitor of blood glucose in normoglycemia and diabetes cynomolgus monkeys (n=5). Each monkey was subcutaneously implanted with a HD-XG transmitter (DSI, USA) with its glucose sensor being placed in a femoral artery. Blood glucose, body temperature and physical activity were remotely monitored for ≥8 weeks. Diabetes assays, ivGTT, oGTT, ITT, GGI and clamp, were tested. The telemetry glucose results correlated well with the glucometer readings (Figure 1A). The ivGTT data showed that the glucometer and telemetry readings were very similar in both normal and diabetic monkeys, even with dual ivGTTs consecutively (Figure 1B). Glucose clamp results also showed high matches between the 2 methods (Figure 1C). However, the advantages of monitoring blood glucose by the telemetry method are: 1) consecutive data collection (day and night); 2) no bleeding requirement; 3) no restriction (moving freely); 4) no anesthesia needed; 5) no stress and disturbance; 6) less labor intensity during ivGTT and clamp; 7) recording natural response, such as circadian and postprandial effects; 8) instant outcomes without lab test. Our data demonstrate that the telemetry method can monitor blood glucose remotely and continuously in conscious, stress-free, freely moving monkeys, which may bring advantages in diabetes research and drug discovery.