Exogenous Glucose Infusion Research Articles

Obesity risk is associated with brain glucose uptake and insulin resistance.

To investigate whether alterations in brain glucose uptake (BGU), insulin action in the brain-liver axis and whole-body insulin sensitivity occur in young adults in pre-obese state. Healthy males with either high risk (HR; n = 19) or low risk (LR; n = 22) for developing obesity were studied with [18F]fluoro-d-glucose ([18F]FDG)-positron emission tomography during hyperinsulinemic-euglycemic clamp. Obesity risk was assessed according to BMI, physical activity and parental overweight/obesity and type 2 diabetes. Brain, skeletal muscle, brown adipose tissue (BAT), visceral adipose tissue (VAT) and abdominal and femoral s.c. adipose tissue (SAT) glucose uptake (GU) rates were measured. Endogenous glucose production (EGP) was calculated by subtracting the exogenous glucose infusion rate from the rate of disappearance of [18F]FDG. BGU was analyzed using statistical parametric mapping, and peripheral tissue activity was determined using Carimas Software imaging processing platform. BGU was higher in the HR vs LR group and correlated inversely with whole-body insulin sensitivity (M value) in the HR group but not in the LR group. Insulin-suppressed EGP did not differ between the groups but correlated positively with BGU in the whole population, and the correlation was driven by the HR group. Skeletal muscle, BAT, VAT, abdominal and femoral SAT GU were lower in the HR group as compared to the LR group. Muscle GU correlated negatively with BGU in the HR group but not in the LR group. Increased BGU, alterations in insulin action in the brain-liver axis and decreased whole-body insulin sensitivity occur early in pre-obese state.

PSUN304 CRN04777 an Oral, Nonpeptide SST5-selective Somatostatin Agonist Dose Dependently Suppresses Basal and Stimulated Insulin Secretion

Abstract Congenital hyperinsulinism (HI) is the most common cause of persistent hypoglycemia in neonates, infants, and children, and is caused by genetic mutations in the insulin secretion pathway in pancreatic beta-cells. Current medical and surgical treatments are often highly burdensome, only partially effective, and associated with significant morbidity. CRN04777 is a potent orally bioavailable SST5 agonist (EC50=0.41 nM) that is >1300 fold selective over other SST receptor subtypes. CRN04777 has been shown to suppress both glucose- and sulfonylurea (SU)-induced insulin secretion in rats. The latter is a model for the most common known monogenic form of human congenital HI. We report initial results from a randomized, double-blinded, placebo-controlled single ascending dose study evaluating the safety, pharmacokinetics and pharmacodynamics of CRN04777 in 74 healthy volunteers. Endogenous insulin secretion was stimulated using intravenous glucose tolerance tests (IVGTT) or SU challenges in separate cohorts of volunteers. In the IVGTT cohorts, single doses of CRN04777 (0.5-120 mg) were administered after an overnight fast and 1 hour prior to an IV bolus of 300 mg/kg glucose, followed by serial measurements of blood glucose and insulin over 180 minutes. The SU-challenge cohorts received single doses of CRN04777 (30 and 60 mg) one hour after SU administration (5 mg of glibenclamide/glyburide), followed by measurement of the IV glucose infusion rate (GIR) over 8 hours under automated euglycemic clamp conditions (ClampArt®). CRN04777 was orally absorbed (Tmax 1-3 hours) and demonstrated a dose dependent increase in systemic exposures with an apparent terminal elimination t1/2 of approximately 40 hours. Basal insulin secretion was reduced dose-dependently, with a 73% reduction following 120 mg of CRN04777. Likewise, glucose stimulated insulin secretion during the IVGTT (plasma insulin AUC) was reduced dose-dependently by approximately 50% with a parallel doubling of plasma glucose AUC following 120 mg of CRN04777. CRN04777 resulted in dose-dependent reversal of SU-induced insulin secretion, with 79% and 90% reductions in insulin AUC5-180min, respectively, at 30 and 60 mg doses. At the 60 mg dose of CRN04777, no exogenous glucose infusion was needed to prevent SU-induced hypoglycemia. CRN04777 was well tolerated across the dose range evaluated. All adverse events (AEs) were considered mild or moderate and there were no serious AEs. The data from this single-dose, proof-of-concept study show that the selective SST5 agonist CRN04777 is well tolerated after oral administration in healthy volunteers, is suitable for once daily dosing and suppresses insulin secretion under basal and stimulated conditions, including in a pharmacologic model of congenital HI. Multiple ascending dose evaluations in healthy volunteers are underway to support future studies in congenital HI patients. Presentation: Sunday, June 12, 2022 12:30 p.m. - 2:30 p.m.

532-P: Voluntary Exercise during Food Restriction Promotes a Sustained Increase in Hepatic Oxidative Metabolism

Exercise is an important lifestyle intervention for the prevention and treatment of NAFLD. Importantly, exercise can reduce hepatic steatosis independent of changes in body mass, which may stem from increased oxidative demand in liver during exercise. Increased hepatic gluconeogenesis (GNG) and tricarboxylic acid (TCA) cycle flux have been observed during exercise in rodents, but it is unclear whether this adaptation is chronically maintained outside of the exercise window. Liver metabolism is also altered by nutritional status. Fasting promotes hepatic fat oxidation, ketogenesis and GNG, while feeding promotes glycogen storage and fat synthesis. Hence, fasting and exercise may have a positive interaction, whereas exogenous nutrient intake or glucose infusion is known to reduce the induction of GNG during exercise. Here, we tested whether nutritional status impacts exercise induced hepatic metabolic adaptations. Sprague-Dawley rats were kept sedentary or provided voluntary wheel running (VWR) for 4 weeks in the presence or absence of food restriction during the dark phase when rats spontaneously run. Experiments were conducted one day following the last exercise bout. Hepatic metabolic flux was examined by in vivo stable isotope infusions of [U-13C3]propionate, [3,4-13C2]glucose and 2H2O in rats using mass spectrometry and computational analysis. Chronic VWR in the fed state had no effect on basal hepatic fluxes outside of the exercise window. However, exercise during food restriction chronically induced a 2-fold induction of TCA cycle turnover, increase in GNG from glycerol and lowered ketogenesis outside of the exercise window. Thus, VWR during food restriction triggered an increase in hepatic energy demand that was sustained for at least 24 hours, while the effects of exercise in the fed state dissipated by 24 hours. These data suggest that acute nutritional state may be an important factor in the long-term programming of liver metabolism by exercise. Disclosure S.Deja: None. B.Kucejova: None. A.Maurer: None. M.N.Mizerska: None. X.Fu: None. J.P.Thyfault: None. S.C.Burgess: n/a. Funding National Institutes of Health (R01DK121497, R01DK078184, P41EB015908)

1307-P: Leptin Action in the Nucleus of the Solitary Tract

Obesity and diabetes are characterized by a disruption in energy balance and glucose homeostasis in association with leptin resistance. Leptin action in the hypothalamus regulates glucose levels and body weight, but whether other brain regions facilitate leptin action remain unclear. Here, we investigate whether the nucleus of the solitary tract (NTS) of the brainstem is a crucial site for leptin action in regulating glucose homeostasis in 3d high-fat (HF) -fed male rats, as recent studies report leptin activates leptin receptor in the NTS to regulate feeding. In this study, we performed brain stereotaxic bilateral surgery targeting the NTS followed one week later by catheterization of the left carotid artery and right internal jugular vein for infusion/sampling purposes. Rats that attained >90% of presurgical weight received 3d of Lard oil enriched HF diet and were fasted 4-6 hr before undergoing a 2min pancreatic (basal insulin) -euglycemic clamp studies together with tracer glucose infusion to assess glucose metabolism independent of changes in plasma insulin and glucagon levels. Leptin (91.7 ng/uL at 0.33 ul/hr) or saline was infused into the NTS throughout the duration of the clamp studies. Correct placement of the NTS catheter was verified by infusion of bromophenol blue dye through the brain cannula. For the first time, we found that leptin vs. saline infusion into the NTS markedly increased the exogenous glucose infusion [lep: 4.6±0.2 vs. sal: 1.3±0.4 mg/kg/min; p<0.005; n=12, 5] required to maintain euglycemia [lep: 137.5±2.2 vs. sal: 145±3.1 mg/dl; p>0.05; n=12, 5], during the clamps. The drop in plasma glucose levels was due to an inhibition of glucose production [lep: 4.9±0.1 vs. sal: 8.4±0.7 mg/kg/min; p<0.01; n=12, 5], but not an increase in glucose uptake [lep: 10.4±0.5 vs. sal: 9.7±0.3 mg/kg/min; p>0.05; n=12, 5]. These findings demonstrate that the NTS mediates leptin action on glucose homeostasis. Future studies are needed to investigate the NTS leptin signaling cascade in glucose homeostasis in obesity and diabetes. Disclosure K.Bruce: None. R.Li: None. Y.Lim: None. J.T.Yue: None. T.K.Lam: None. Funding Canadian Institutes of Health Research Foundation Grant (FDN-143204)

The effect of the menstrual cycle and hyperglycaemia on hormonal and metabolic responses during exercise

PurposeVariations in substrate metabolism have been identified in women during continuous steady-state aerobic exercise performed at the same relative intensity throughout discrete phases of the menstrual cycle, although some evidence exists that this is abolished when carbohydrate is ingested. This investigation examined the effects of a supraphysiologic exogenous glucose infusion protocol, administered during two phases of the menstrual cycle (follicular and luteal) in eumenorrheic women to identify differences between metabolic, hormonal and substrate oxidative responses.MethodsDuring the experimental conditions, blood glucose was infused intravenously at rates to “clamp” blood glucose at 10 mM in seven healthy females (age 20 ± 1 y, mass 55.0 ± 4.1 kg, dot V{O_{2peak}} 40.0 ± 1.8 ml/kg/min). Following 30 min of seated rest, participants exercised on a cycle ergometer for 90 min at 60% dot V{O_{2peak}}. During the rest period and throughout exercise, blood metabolites and hormones were collected at regular intervals, in addition to expired air for the measurement of substrate oxidation.ResultsSignificant differences between ovarian hormones and menstrual phase were identified, with estrogen significantly higher during the luteal phase compared to the follicular phase (213.28 ± 30.70 pmol/l vs 103.86 ± 13.85 pmol/l; p = 0.016), and for progesterone (14.23 ± 4.88 vs 2.11 ± 0.36 nmol/l; p = 0.042). However, no further significance was identified in any of the hormonal, metabolite or substrate utilisation patterns between phases.ConclusionThese data demonstrate that the infusion of a supraphysiological glucose dose curtails any likely metabolic influence employed by the fluctuation of ovarian hormones in eumenorrheic women during moderate exercise.

A decrease in plasma glucose levels is required for increased endogenous glucose production with a single administration of a sodium-glucose co-transporter-2 inhibitor tofogliflozin.

To investigate whether changes in endogenous glucose production (EGP) and insulin and glucagon levels are elicited by the decrease in plasma glucose (PG) levels induced by the sodium-glucose co-transporter-2 (SGLT2) inhibitor tofogliflozin. We evaluated EGP in 12 Japanese patients with type 2 diabetes under the conditions of no drugs administered (CON), single administration of the SGLT2 inhibitor tofogliflozin (TOF), and single administration of TOF with adjustment of PG levels with exogenous glucose infusion to mimic changes in PG levels observed with CON (TOF + G). We evaluated changes in EGP and levels of C-peptide and glucagon from baseline to 180 minutes after drug administration. Endogenous glucose production decreased in the CON (-0.22 ± 0.11 mg/kg·min) and TOF + G experiments (-0.31 ± 0.24 mg/kg·min), but not in the TOF experiment (+0.08 ± 0.19 mg/kg·min). The decrease in C-peptide was significantly greater in the TOF experiment (-0.11 ± 0.06 nmol/L) than in the CON (-0.03 ± 0.06 nmol/L) and the TOF + G experiments (-0.01 ± 0.11 nmol/L), while the increase in glucagon was significantly greater in the TOF experiment (+11.1 ± 6.3 pmol/L), but not in the TOF + G experiment (+8.6 ± 7.6 pmol/L) compared to the CON experiment (+5.1 ± 4.3 pmol/L). These results indicate that the decrease in PG levels induced by SGLT2 inhibitor administration is required for the increase in EGP and decrease in insulin secretion.

1135-P: Acute Increase in Endogenous Glucose Production by a Single Administration of Tofogliflozin Is Disappeared by Suppressing Its Glucose Lowering Effect in the Patients with Type 2 Diabetes Mellitus

It has been shown that a single administration of SGLT2 inhibitor (SGLT2i) to the patients with type 2 diabetes mellitus (T2DM) decreases plasma glucose (PG), but increases endogenous glucose production (EGP); however, its underlying mechanism has been totally unknown. We hypothesized that a single administration of SGLT2i lowers PG, thereby suppresses insulin level and increases glucagon level, which in turn rises EGP. To test this hypothesis, we recruited 12 Japanese patients with type 2 diabetes mellitus without taking any hypoglycemic agents (BMI 24.9±2.5 kg/m2, HbA1c 7.7±0.9%). In each patient, by [6,6-2H2]-glucose infusion, we evaluated basal EGP and EGP under the conditions with: (i) no administration of drugs (CON), (ii) single administration of a SGLT2i, Tofogliflozin (TOF), and (iii) TOF + glucose adjustment (TOF+G) in which we adjusted PG level by exogenous glucose infusion to mimic PG level during CON. In each patient, we measured EGP under three condition at 1-2 week intervals. Also, we evaluated changes in insulin, glucagon and EGP between basal period and after each 3h condition. The decrement of PG during 3h experimental period in TOF was significantly greater than that in CON, and this change was inhibited by glucose infusion (delta PG: CON; -14.6 mg/dl, TOF; -26.4 mg/dl, TOF+G; -15.6 mg/dl). In CON, EGP was decreased by 11.1%, but it was significantly increased by 4.5% in TOF. However, similar to CON, EGP was decreased by 15.7% in TOF+G. In addition, insulin level was decreased by 24% and glucagon level was increased by 36% in TOF; however, these hormonal changes were not observed in CON and TOF+G. In conclusion, acute EGP elevation by a single administration of SGLT2i was disappeared by suppression of glucose lowering effect of SGLT2i. Changes in insulin and glucagon by rapid decline of PG after SGLT2i administration may be a main inducer of EGP elevation. Disclosure N. Yamasaki: None. Y. Tamura: Advisory Panel; Self; Astellas Pharma Inc. Research Support; Self; Kowa Company, Ltd. Speaker’s Bureau; Self; Novo Nordisk Inc., Ono Pharmaceutical Co., Ltd. H. Kaga: None. M. Sato: None. M. Kiya: None. S. Kadowaki: None. R. Suzuki: None. Y. Furukawa: None. D. Sugimoto: None. T. Funayama: None. Y. Someya: None. R. Kawamori: None. H. Watada: Advisory Panel; Self; Abbott, Ajinomoto, Astellas Pharma Inc., Boehringer Ingelheim Pharmaceuticals, Inc., Fuji Film, Janssen Pharmaceuticals, Inc., Kowa Company, Ltd., Kyowa Hakko Kirin Co., Ltd., Mitsubishi Tanabe Pharma Corporation, Novo Nordisk Inc., Ono Pharmaceutical Co., Ltd., Sanofi-Aventis, Takeda Pharmaceutical Company Limited, Terumo Medical Corporation. Research Support; Self; Astellas Pharma Inc., Bayer Yakuhin, Ltd., Boehringer Ingelheim Pharmaceuticals, Inc., Daiichi Sankyo, Eli Lilly Japan K.K., Kissei Pharmaceutical Co., Ltd., Kowa Company, Ltd., Kyowa Hakko Kirin Co., Ltd., Merck Sharp & Dohme Corp., Mitsubishi Tanabe Pharma Corporation, Novartis Pharma K.K., Novo Nordisk Inc., Ono Pharmaceutical Co., Ltd., Otsuka Pharmaceutical Co., Ltd., Pfizer Japan Inc., Sanofi-Aventis, Sanwa Kagaku Kenkyusho, Shionogi & Co., Ltd., Sumitomo Dainippon Pharma Co., Ltd., Sumitomo Dainippon Pharma Co., Ltd., Taisho Pharmaceutical Co., Ltd., Takeda Pharmaceutical Company Limited, Teijin Pharma Limited, Yakult. Speaker’s Bureau; Self; Astellas Pharma Inc., AstraZeneca, Bayer Yakuhin, Ltd., Boehringer Ingelheim Pharmaceuticals, Inc., Daiichi Sankyo, Eli Lilly Japan K.K., Kissei Pharmaceutical Co., Ltd., Kowa Company, Ltd., Kyowa Hakko Kirin Co., Ltd., Merck Sharp & Dohme Corp., Mitsubishi Tanabe Pharma Corporation, Novartis Pharmaceuticals Corporation, Novo Nordisk Inc., Ono Pharmaceutical Co., Ltd., Sanofi-Aventis, Sanwa Kagaku Kenkyusho, Sumitomo Dainippon Pharma Co., Ltd., Takeda Pharmaceutical Company Limited. Funding Kowa Company, Ltd.

104-OR: Glucoregulatory Effects of Hypothalamic Glucocorticoid Action In Vivo

Diabetes is characterized by dysregulated glucose homeostasis that leads to hyperglycemia, due in part to increased hepatic glucose production (GP) and insulin resistance. Excessive levels and/or action of glucocorticoids (GCs) are associated with obesity, insulin resistance, and hyperglycemia. We aim to delineate a mechanism of GC action in the mediobasal hypothalamus (MBH) that modulates GP in normal and pre-obese rodents. Male SD rats underwent stereotaxic MBH bilateral cannulation and intravenous (iv) and intraarterial catheterization to enable simultaneous direct infusions into the MBH, iv infusions, and blood sampling, respectively. Mildly hyperinsulinemic-euglycemic clamps with tracer dilution methodology combined with MBH GC infusion ± GC receptor (GR) inhibition enables measurement of GP and utilization while assessing MBH GC interaction with its MBH receptors independent of changes in plasma insulin, glucagon, and glucose levels. MBH GC infusion potently stimulates GP and lowers the requirement for exogenous glucose infusion without altering glucose utilization. This effect is mediated via GRs since co-infusion of GR antagonist mifepristone, or a HSP90 inhibitor, negates the ability of MBH GCs to increase GP. MBH GCs similarly increased glucose excursions during iv glucose tolerance tests, which was reversed with concomitant MBH mifepristone infusion. Rats fed with high fat diet (HFD) for 3 days had altered glucose kinetics and increased basal plasma corticosterone, insulin, and blood glucose levels without changes in body weight. Chronic MBH GR inhibition with MBH GR shRNA lowered GP compared to MBH mismatch control HFD rats with MBH vehicle infusions, suggesting that blocking excessive MBH GC action resulting from HFD-feeding attenuates GP to improve glucose homeostasis. We provide novel evidence that MBH GC action modulates GP in healthy and pre-obese rats. Importantly, targeted inhibition of MBH GC action may help improve glucose regulation in obesity-related metabolic disease. Disclosure E. Beaulieu-Bayne: None. M. Cardoso: None. H. Kim: None. S. Yang: None. J.T. Yue: None. Funding Diabetes Canada; Natural Sciences and Engineering Research Council of Canada; Alberta Diabetes Institute; Canadian Institutes of Health Research

Spexin alleviates insulin resistance and inhibits hepatic gluconeogenesis via the FoxO1/PGC-1α pathway in high-fat-diet-induced rats and insulin resistant cells.

Objective: Recent studies demonstrate circulating serum spexin levels are reduced in obesity or type 2 diabetes mellitus (T2DM) patients and may play a role in glucose metabolism. The mechanism underlying is not known. In this study, we explore whether spexin has a role in insulin resistance and hepatic glucose metabolism.Methods: The correlation between serum spexin levels and the homeostasis model assessment of insulin resistance (HOMA-IR) was studied in newly diagnosed T2DM patients. After intraperitoneal injection of exogenous spexin for 8 weeks, the effect of spexin on exogenous glucose infusion rates (GIR), and hepatic glucose production (HGP) were assessed by extended hyperinsulinemic-euglycemic clamp in high-fat-diet (HFD)-induced rats. Glucose concentration with CRISPR/Cas9-mediated disruption of spexin expression in HepG2 cells culture was observed. Expression of transcription factors (Forkhead box O1, FoxO1 and peroxisome proliferator-activated receptor gamma coactivator 1-alpha, PGC-1α) and key enzymes (G-6-Pase and PEPCK) of gluconeogenesis pathway were observed in vitro and in vivo.Results: The serum spexin level was significantly low in newly diagnosed T2DM patients as compared with healthy patients and significantly negatively correlated with the HOMA-IR values. Exogenous spexin treatment resulted in weight loss and decrease of HOMA-IR value in high-fat-diet (HFD)-induced rats. The exogenous glucose infusion rates (GIR) were higher in the HFD + spexin group than that in the HFD group (358 ± 32 vs. 285 ± 24 μmol/kg/min, P < 0.05). Steady-state hepatic glucose production (HGP) was also suppressed by ~50% in the HFD + spexin group as compared with that in the HFD group. Furthermore, spexin inhibited gluconeogenesis in dose-dependent and time-dependent manner in the insulin-resistant cell model. CRISPR/Cas9-mediated knockdown of spexin in HepG2 cells activated gluconeogenesis. Moreover, spexin was shown regulating gluconeogenesis by inhibiting FoxO1/PGC-1α pathway, and key gluconeogenic enzymes, (PEPCK and G-6-Pase) in both HFD-induced rats and insulin-resistant cells.Conclusions: Spexin plays an important role in insulin resistance in HFD-induced rats and insulin-resistant cells. Regulation of the effects of spexin on insulin resistance may hold therapeutic value for metabolic diseases.

The effect of exogenous glucose infusion on early embryonic development in lactating dairy cows

The objective of this study was to examine the effect of intravenous infusion of glucose on early embryonic development in lactating dairy cows. Nonpregnant, lactating dairy cows (n = 12) were enrolled in the study (276 ± 17 d in milk). On d 7 after a synchronized estrus, cows were randomly assigned to receive an intravenous infusion of either 750 g/d of exogenous glucose (GLUC; 78 mL/h of 40% glucose wt/vol) or saline (CTRL; 78 mL/h of 0.9% saline solution). The infusion period lasted 7 d and cows were confined to metabolism stalls for the duration of the study. Coincident with the commencement of the infusion on d 7 after estrus, 15 in vitro-produced grade 1 blastocysts were transferred into the uterine horn ipsilateral to the corpus luteum. All animals were slaughtered on d 14 to recover conceptuses, uterine fluid, and endometrial tissue. Glucose infusion increased circulating glucose concentrations (4.70 ± 0.12 vs. 4.15 ± 0.12 mmol/L) but did not affect milk production or dry matter intake. Circulating β-hydroxybutyrate concentrations were decreased (0.51 ± 0.01 vs. 0.70 ± 0.01 mmol/L for GLUC vs. CTRL, respectively) but plasma fatty acids, progesterone, and insulin concentrations were unaffected by treatment. Treatment did not affect either uterine lumen fluid glucose concentration or the mRNA abundance of specific glucose transporters in the endometrium. Mean conceptus length, width, and area on d 14 were reduced in the GLUC treatment compared with the CTRL treatment. A greater proportion of embryos in the CTRL group had elongated to all length cut-off measurements between 11 and 20 mm (measured in 1-mm increments) compared with the GLUC treatment. In conclusion, infusion of glucose into lactating dairy cows from d 7 to d 14 post-estrus during the critical period of conceptus elongation had an adverse impact on early embryonic development.

The Hyperinsulinemic Isoglycemic Hyperlactemic Clamp

The Cori Cycle (glucose-lactate interchange) dominates carbohydrate fluxes. Glucose-to-lactate flux follows peripheral disposal; lactate-to-glucose occurs during gluconeogenesis. As glucose flux can be assessed by the change in an exogenous glucose infusion rate (GIR) required to maintain a constant concentration (glucose clamp), so too can lactate flux be assessed from an exogenous lactate infusion rate (LIR) required to maintain isolactemia. Simultaneous assessment of both fluxes will enable estimation of lactate-derived gluconeogenesis (GNG), and its contribution to the rate of glucose appearance (Ra) without using radiolabeled tracers, the mainstay of flux measurement. Anesthetized Sprague-Dawley rats were intubated, catheterized via artery and vein, and partially pancreatectomized to eliminate endogenous glucagon secretion. Establishment of a hyperinsulinemic (100mU/kg/h), hyperglycemic (7mM) clamp was followed by a hyperlactemic (4mM) clamp via independent variable infusions of glucose/Na-lactate in response to 5-min measures of plasma concentrations (YSI 2950D Analyzer with glucose/lactate electrodes). Hyperlactemia (∼10x resting) rendered it the dominant gluconeogenic substrate. After at least 30 min of isolactemia, glucagon was infused for 60 min (0, 1, 3, 10 or 50 µg/kg/h) to enable dose/concentration response analysis. Glucagon administration dose-dependently reduced the GIR and increased the LIR necessary to maintain isoglycemia/isolactemia (respective ED50’s 1.33, 0.98 µg/kg/h). δ-GIR of up to -12.2 mmol/kg/h potentially represented increased glucose Ra. δ-LIR of up to +8.6 mmol/kg/h potentially represented GNG. Since 2 lactate moieties are required per glucosyl, GNG contributed ∼35% of glucagon-stimulated glucose Ra (∼65% being glycogenolysis). In conclusion, the hyperinsulinemic isoglycemic hyperlactemic clamp enables a quantitative assessment of hepatic processes, complementing that of peripheral processes revealed with the glucose clamp. Disclosure D. Zaretsky: Employee; Self; Intarcia Therapeutics, Inc. A.A. Young: Employee; Self; Intarcia Therapeutics, Inc.. Stock/Shareholder; Self; GlaxoSmithKline plc..

Combining Various Methods to Assess Insulin Sensitivity in Nonobese Rat after Sleeve Gastrectomy.

Sleeve gastrectomy (SG) procedure has been proved to improve insulin sensitivity and sustain anti-diabetic effects. Our aim is to co-use several methods to measure insulin sensitivity and investigate the effect of SG on hepatic and peripheral insulin sensitivity at early and long-term stages of postoperation. Thirty 11-week-old male Goto-Kakizaki rats were divided into SG, sham-operated SG (SOSG), and control groups. They were observed before operation and for 36 weeks of postoperation. Insulin tolerance test (ITT) and homeostasis model of assessment for insulin resistance index(HOMA-IR)were used to measure insulin resistance before operations and at 2 and 36 weeks of postoperation; Pyruvate challenge test (PCT) was administrated to assess the gluconeogenesis capability in order to reflect hepatic insulin sensitivity before operation and at 2 and 36 weeks of postoperation; Hyperinsulinemic euglycemic clamps (HIEC) was conducted before operation and at 2 and 36 weeks of postoperation to calculate the endogenous hepatic glucose production (HGP) at the basal and steady-state for evaluation of hepatic insulin sensitivity, and calculate the exogenous glucose infusion rate (GIR) at the steady-state for evaluation of peripheral insulin sensitivity. The data showed that compared with rats in the sham and control groups, rats in SG group had 1) significantly lower AUCITT, HOMA-IR and AUC PCT values at 2 and 36 weeks of postoperation, 2) lower basal state HGP, but not steady-state GIR at 2 weeks of postoperation, and 3) significantly different basal and steady-state HGP and steady-state GIR at 36 weeks of postoperation. In addition, the basal and steady-state HGP and the steady-state GIR were significantly different between rats in SG group at 2 and 36 weeks of postoperation. This study explored insulin sensitivity of rats after SG by jointly using a variety of techniques. The results showed that SG time-dependently improved the hepatic and peripheral insulin sensitivity.

1049 The effect of exogenous glucose infusion on early embryonic development in lactating dairy cows

1049 The effect of exogenous glucose infusion on early embryonic development in lactating dairy cows

Static output feedback ℋ ∞ control for a fractional-order glucose-insulin system

This paper presents the $H_\infty$ static output feedback control of nonlinear fractional-order systems. Based on the extended bounded real lemma, the $H_\infty$ control is formulated and sufficient conditions are derived in terms of linear matrix inequalities (LMIs) formulation by using the fractional Lyapunov direct method where the fractional-order α belongs to 0 < $\alpha$ < 1. The control approach is finally applied to the regulation of the glucose level in diabetes type 1 treatment. Therefore, it is attempted to incorporate fractional-order into the mathematical minimal model of glucose-insulin system dynamics and it is still an interesting challenge to show, how the order of a fractional differential system affects the dynamics of the system in the presence of meal disturbance. Numerical simulations are carried out to illustrate our proposed results and show that the nonlinear fractional-order glucose-insulin systems are, at least, as stable as their integer-order counterpart in the presence of exogenous glucose infusion or meal disturbance.

Glucose counterregulation in advanced type 2 diabetes: effect of β-adrenergic blockade.

To examine counterregulatory glucose kinetics and test the hypothesis that β-adrenergic blockade impairs these in patients with type 2 diabetes mellitus (T2DM) and advanced β-failure. Nine insulin-requiring T2DM subjects and six matched nondiabetic control subjects were studied. β-Cell function was assessed by the C-peptide response to arginine stimulation. Counterregulatory hormonal responses and glucose kinetics were assessed by hyperinsulinemic euglycemic-hypoglycemic clamps with [3-(3)H]glucose infusion. T2DM subjects underwent two clamp experiments in a randomized crossover fashion: once with infusion of the β-adrenergic antagonist propranolol and once with infusion of normal saline. Compared with the control subjects, T2DM subjects had threefold reduced C-peptide responses to arginine stimulation. During the hypoglycemic clamp, glucagon responses were markedly diminished (16.0 ± 4.2 vs. 48.6 ± 6.0 ng/L, P < 0.05), but other hormonal responses and the decrement in the required exogenous glucose infusion rate (GIR) from the euglycemic clamp were normal (-10.4 ± 1.1 vs. -7.8 ± 1.9 µmol · kg(-1) · min(-1) in control subjects); however, endogenous glucose production (EGP) did not increase (-0.8 ± 1.0 vs. 2.2 ± 0.7 µmol · kg(-1) · min(-1) in control subjects, P < 0.05), whereas systemic glucose disposal decreased normally. β-Adrenergic blockade in the T2DM subjects increased GIR ∼20% during the euglycemic clamp (P < 0.01), but neither increased GIR during the hypoglycemic clamp or decreased its decrement from the euglycemic clamp to the hypoglycemic clamp. Overall glucose counterregulation is preserved in advanced T2DM, but the contribution of EGP is diminished. β-Adrenergic blockade may increase insulin sensitivity at normoglycemia but does not impair glucose counterregulation in T2DM patients, even those with advanced β-cell failure.

Effect of eplerenone on insulin action in essential hypertension: a randomised, controlled, crossover study.

An association exists between hyperaldosteronism, hypertension and impaired insulin action. Eplerenone is a selective mineralocorticoid receptor antagonist; however, little is known about its effects on insulin action. The aim of this study was to determine the effect of eplerenone on insulin action in hypertensive adults, using the hyperinsulinaemic euglycaemic clamp. A randomised, controlled, double-blind, crossover design was employed. After a 6-week washout period, hypertensive, non-diabetic patients were treated with either eplerenone 25 mg twice daily or doxazosin 2 mg twice daily for 12 weeks. After each treatment period, insulin action was assessed by a hyperinsulinaemic euglycaemic clamp, with isotope dilution methodology. After washout, treatment groups were crossed over. Fifteen patients completed the study. There were no differences in fasting glucose, or fasting insulin between treatment with eplerenone or doxazosin. The measure of overall insulin sensitivity, exogenous glucose infusion rates during the last 30 min of the clamp, was similar with both treatments; 23.4 (3.9) μmol kg(-1) min(-1) after eplerenone and 23.3 (3.6) μmol kg(-1) min(-1) after doxazosin (P=0.83). Isotopically determined fasting endogenous glucose production rates were similar after both treatments (eplerenone 9.4 (0.6) μmol kg(-1) min(-1) vs doxazosin 10.6 (0.7) μmol kg(-1) min(-1)). There was a trend for lower endogenous glucose production rates during hyperinsulinaemia following eplerenone compared with doxazosin (2.0 (0.8) μmol kg(-1) min(-1) vs 4.1 (0.9) μmol kg(-1) min(-1)). There was no difference in insulin stimulated peripheral glucose utilisation rates after treatment with eplerenone or doxazosin (25.4 (3.6) μmol kg(-1) min(-1) vs 27.0 (3.9) μmol kg(-1) min(-1)). This study gives reassuring evidence of the neutral effect of eplerenone on insulin action in hypertensive, non-diabetic patients.

Closed-loop control scheme for the Euglycemic Hyperinsulinemic Clamp: validation on virtual patients

A closed-loop control scheme is here investigated, for the Euglycemic Hyperinsulinemic Clamp (EHC), the gold standard experiment to estimate the individual insulin sensitivity. During the EHC large amounts of insulin are administered intra-venously to the subject, and plasma glycemia is maintained at a normal, baseline level by means of an exogenous glucose infusion, according to established protocols. Based on a Delay Differential Equation (DDE) model of the glucose-insulin system, a closed-loop control has been recently proposed by the same authors showing that, in way of principle, it is possible to design an observer-based control law for the exogenous glucose profile, by solely exploiting real-time plasma glucose measurements. This note further investigates the closed-loop control scheme in order to validate it in spite of the many sources of uncertainties and malfunctioning that inevitably arise. The main feature is to close the feedback onto a different, large-scale multi-compartmental model (standing for a Virtual Patient, VP), instead of the small-scale, DDE model adopted to design the control law. The chosen large-scale model for the VP has been recently accepted by the Food and Drug Administration as a substitute to animal trials for the preclinical testing of control strategies in artificial pancreas. A benchmark based on a population of heterogeneous virtual patients has been implemented and the very good results show the robustness of the proposed methodology.

Castration-induced testosterone deficiency increases fasting glucose associated with hepatic and extra-hepatic insulin resistance in adult male rats

BackgroundTestosterone deficiency is associated with insulin resistance. However, how testosterone deficiency affects insulin actions remains unclear. The aim of this study was to investigate the influence of castration-induced testosterone deficiency on the metabolic kinetics of glucose and to evaluate the hepatic and extra-hepatic insulin sensitivity, in advanced-age male Sprague–Dawley (SD) rats.MethodsTen-week-old male SD rats were randomly divided into three groups: (1) a control group (n = 10) in which the rats underwent sham castration (2) a castrated group (TD group for testosterone deficiency, n = 10) in which the rats underwent bilateral orchidectomy surgery and (3) a castrated group given testosterone propionate via intraperitoneal injection (25 mg/kg/day) to supplement androgen (TD + TP group, n = 10). At ten weeks after castration in the noted groups, all rats were subjected to an oral glucose tolerance test (OGTT), a pyruvate tolerance test (PTT) and an insulin tolerance test (ITT). Twenty weeks following that treatment, all rats underwent a hyperinsulinemic-euglycemic clamp procedure in conjunction with isotope--labeled glucose and glycerol tracer infusions. The rate of appearance (Ra) of glucose, glycerol and gluconeogenesis (GNG), hepatic glucose production and the rate of glucose disappearance (Rd) were assessed. Glucose uptake was determined by measuring the 2-deoxy-D-14C-glucose in the gastrocnemius muscles.ResultsTen weeks after castration in the TD group, the fasting blood glucose and insulin levels were significantly increased (p < 0.01), the glucose-- induced insulin secretion was impaired and ITT revealed a temporarily increased whole body insulin sensitivity compared with the control group; 30 weeks after castration, the Ra of glucose, Ra of glycerol, as well as the HGP and GNG were also increased (p < 0.01), while the exogenous glucose infusion rate and uptake glucose in the muscle markedly decreased (p < 0.01).ConclusionsCastration-induced testosterone deficiency primarily increases fasting blood glucose levels. The clamp experiments revealed a clear insulin resistance both at the hepatic and extra-hepatic levels.

β2-Adrenergic receptor agonist administration promotes counter-regulatory responses and recovery from hypoglycaemia in rats

We have previously reported that local activation of β2-adrenergic receptors (B2ARs) in the ventromedial hypothalamus (VMH) enhances hypoglycaemic counter-regulation. This study examines whether peripheral delivery of a selective B2AR agonist could also promote counter-regulatory responses and thereby has potential therapeutic value to limit hypoglycaemia risk. Conscious male Sprague-Dawley rats received an intra-arterial injection of the B2AR specific agonist, formoterol, or a control solution either before a hyperinsulinaemic-hypoglycaemic clamp study or immediately before recovery from insulin-induced hypoglycaemia. In addition, the capacity of a VMH-targeted microinjection of a B2AR antagonist to limit the anti-insulin effect of the B2AR agonist was assessed. Systemic delivery of B2AR agonist markedly reduced the exogenous glucose infusion rate (GIR) required during the hypoglycaemic clamp study. This effect was mediated by blockade of insulin's inhibitory effect on endogenous glucose production. Local blockade of B2ARs within the VMH using a specific antagonist partially diminished the effect of systemic activation of B2ARs during hypoglycaemia at least in part by diminishing the adrenaline (epinephrine) response to hypoglycaemia. Peripheral B2AR agonist injection also enhanced glucose recovery from insulin-induced hypoglycaemia. Systemic B2AR agonist administration acts to limit insulin-induced hypoglycaemia by offsetting insulin's inhibitory effect on hepatic glucose production. This effect appears to be predominately mediated via a direct effect on liver B2ARs, but a small stimulatory effect on B2ARs within the VMH cannot be excluded. Our data suggest that formoterol may have therapeutic value to limit the risk of hypoglycaemia in patients with diabetes.

H∞ Static Output Feedback Control for a Fractional-Order Glucose-Insulin System

This paper presents the H∞ static output feedback control of nonlinear fractional-order glucose-insulin systems. In this paper, it is an attempt to incorporate fractional-order into the mathematical minimal model of glucose-insulin system dynamics and it is still an interesting challenge to show, how the order of a fractional differential system affects the dynamics of system in the presence of meal disturbance. A static output feedback control is considered for the problem. Sufficient conditions are derived in terms of linear matrix inequalities (LMIs) formulation by using the fractional Lyapunov direct method where the fractional-order a belongs to 0 < α < 1. Finally, numerical simulations are carried out to illustrate our proposed results and show that the nonlinear fractional-order glucose-insulin systems are as stable as their integer order counterpart in the presence of exogenous glucose infusion or meal disturbance.