Steady-state Glucose Infusion Rate Research Articles

Sex Hormone Binding Globulin is an Independent Predictor for Insulin Resistance in Male Patients with Newly Diagnosed Type2 Diabetes Mellitus.

This study explored the correlation between sex hormones, sex hormone binding globulin (SHBG), and insulin resistance in male patients with newly diagnosed type2 diabetes mellitus (T2DM). A total of 48 male patients with newly diagnosed T2DM were enrolled in this study between March 2022 and December 2022. Clinical characteristics, sex hormones, and SHBG levels were collected. All enrolled subjects received intensive hypoglycemic treatment with insulin pump for 1week to achieve glycemic control, then the steady-state glucose infusion rate (GIR), an indicator of insulin sensitivity, was determined by the hyperinsulinemic-euglycemic clamp. Correlation analysis and multivariate logistic regression analysis were performed to explore the association of clinical characteristics, sex hormones, and SHBG with insulin sensitivity. The optimal cutoff value to predict insulin resistance was calculated using receiver operating characteristic (ROC) curve. According to the GIR cut-point value of 5.700mg/(kgmin), there were 40 patients with insulin resistance (IR group) and 8 patients without (non-IR group). The IR group exhibited lower testosterone and SHBG levels than the non-IR group (all p < 0.050). Correlation analysis showed that insulin sensitivity was positively associated with testosterone and SHBG, while negatively associated with body mass index, fasting blood glucose, alanine aminotransferase, aspartate aminotransferase, total cholesterol, triglyceride, and apolipoproteinB (all p < 0.050). Multivariate logistic regression analysis demonstrated that SHBG is an independent predictor for insulin resistance (p = 0.029). Further ROC curve analysis revealed that the optimal cutoff value of SHBG to predict insulin resistance is 17.200nmol/L, with the corresponding area under the curve (AUC) and its 95% confidence interval (CI) being 0.813 and 0.691-0.934. SHBG is an independent predictor for insulin resistance in male patients with newly diagnosed T2DM. KY20220314-01.

Diabetes is accompanied by changes in the levels of proteins involved in endosomal GLUT4 trafficking in obese human skeletal muscle.

IntroductionThe regulated delivery of the glucose transporter GLUT4 from intracellular stores to the plasma membrane underpins insulin‐stimulated glucose transport. Insulin‐stimulated glucose transport is impaired in skeletal muscle of patients with type‐2 diabetes, and this may arise because of impaired intracellular trafficking of GLUT4. However, molecular details of any such impairment have not been described. We hypothesized that GLUT4 and/or levels of proteins involved in intracellular GLUT4 trafficking may be impaired in skeletal muscle in type‐2 diabetes and tested this in obese individuals without and without type‐2 diabetes.MethodsWe recruited 12 participants with type‐2 diabetes and 12 control participants. All were overweight or obese with BMI of 25–45 kg/m2. Insulin sensitivity was measured using an insulin suppression test (IST), and vastus lateralis biopsies were taken in the fasted state. Cell extracts were immunoblotted to quantify levels of a range of proteins known to be involved in intracellular GLUT4 trafficking.ResultsObese participants with type‐2 diabetes exhibited elevated fasting blood glucose and increased steady state glucose infusion rates in the IST compared with controls. Consistent with this, skeletal muscle from those with type‐2 diabetes expressed lower levels of GLUT4 (30%, p = .014). Levels of Syntaxin4, a key protein involved in GLUT4 vesicle fusion with the plasma membrane, were similar between groups. By contrast, we observed reductions in levels of Syntaxin16 (33.7%, p = 0.05), Sortilin (44%, p = .006) and Sorting Nexin‐1 (21.5%, p = .039) and −27 (60%, p = .001), key proteins involved in the intracellular sorting of GLUT4, in participants with type‐2 diabetes.ConclusionsWe report significant reductions of proteins involved in the endosomal trafficking of GLUT4 in skeletal muscle in obese people with type 2 diabetes compared with age‐ and weight‐matched controls. These abnormalities of intracellular GLUT4 trafficking may contribute to reduced whole body insulin sensitivity.

Reduced Insulin Sensitivity in Patients with Myeloid Malignancies and Clonal Hematopoiesis Mutations

Cancer survivors are at increased risk for insulin resistance, which can lead to diabetes mellitus, dyslipidemia, and cardiovascular disease. Whether susceptibility to insulin resistance is due to shared onco-metabolic risk factors, like obesity and older age, or if it originates from malignancy and its treatment is unknown. We investigated metabolic and malignancy-associated risk factors and their effect on insulin sensitivity in patients with treated hematological malignancies. Due to previous glucocorticoid exposure, we hypothesized that patients with lymphoid malignancies would be less insulin sensitive. Nineteen adult patients with treated hematological malignancies but without diabetes mellitus were evaluated with a 2-hour, 75-gram, oral glucose tolerance test (OGTT) and a hyperinsulinemic-euglycemic clamp. Hyperinsulinemic-euglycemic clamps were performed to measure steady-state glucose infusion rate (M-value) as an indicator of whole-body glucose utilization during high-dose insulin stimulation. Decreasing M-values reflect increasing insulin resistance. Patient characteristics were analyzed and compared with OGTT and clamp results. The majority of individuals had myeloid malignancies [MDS/AML (n=7) and CML/MPN (n = 4)]. The remainder were diagnosed with NHL (n=7) and CML lymphoid blast crisis (n=1). All patients were treated before metabolic testing. Sixteen individuals (84%) received cytotoxic chemotherapy and 3 (16%) were administered only tyrosine kinase inhibitors. Median lines of systemic treatment were 2 (range, 1-6), and median time from cancer diagnosis to metabolic testing was 10 months (range, 3-132). Immediately before OGTTs and clamps, 10 (53%) patients were in a complete response, and 9 (47%) had persistent/stable disease. During OGTTs, impaired fasting glucose (plasma glucose 100-125 mg/dL) and impaired glucose tolerance (2-hour plasma glucose 140-199 mg/dL) were respectively observed in 5 (26%) and 6 (32%) patients. M-values were decreased in patients with impaired glucose tolerance. Overweight and obese cancer patients also had lower M-values than individuals with normal body mass indices (BMI) (Table 1). There were otherwise no differences in insulin resistance per age, sex, performance status, ethnicity, or diabetes family history. Differences in insulin resistance were not observed based on exposure to cytotoxic chemotherapy, non-cranial irradiation, numbers of lines of treatment, response, or malignancy duration. Previous glucocorticoid exposure did not impact insulin sensitivity. Surprisingly, patients with myeloid malignancies demonstrated lower M-values (6.92 + 0.54 vs. 12.11 + 1.89; p=0.026) than did those with lymphoid cancers. Acquired mutations involved with myeloid malignancies and clonal hematopoiesis (CH) can increase the risk for atherosclerosis and cardiovascular disease, which are sequelae of insulin resistance. Accordingly, insulin resistance was increased in patients with both a myeloid malignancy and mutations involving either DNMT3A, TET2, ASXL1, or JAK2 compared to myeloid malignancies with unknown/absent CH mutations or lymphoid cancers (6.71 + 0.77 vs. 7.28 + 0.72 vs. 12.11 + 1.89; p=0.031). After adjustment for interaction effect in linear regression modeling, both myeloid malignancy and elevated BMI continued to predict lower insulin sensitivity (Table 2). Pre-diabetes was diagnosed by fasting glucose or OGTT in 26-32% of patients with treated hematological cancers, more than double the prevalence of impaired fasting glucose or impaired glucose tolerance reported by the National Health and Nutrition Examination Survey III. Contrary to our hypothesis, lymphoid cancers and short-term steroids did not contribute to insulin resistance. Instead, myeloid malignancies and CH mutations were associated with reduced insulin sensitivity. Interventions targeting energy balance and obesity will be needed to prevent the harmful sequelae of insulin resistance in long-term cancer survivors. Alternatively, elimination of CH mutations could prove to be a novel treatment of insulin resistance. Disclosures Dholaria: bms: Research Funding; Poseida: Research Funding; Angiocrine: Research Funding; Takeda: Research Funding; J&amp;J: Research Funding.

1951-P: Glucose Effectiveness Fails to Compensate for Insulin Resistance after Fat Feeding in Dogs

Glucose homeostasis involves actions of both insulin and glucose per se (“glucose effectiveness, SG”). While consumption of a high fat diet typically induces insulin resistance, it is unclear whether SG is altered by fat feeding. We quantified SG from the intravenous glucose tolerance test (IVGTT; n=36) or hyperglycemic clamp at basal insulin (HGC; n=5) in dogs, tested before and after 6 weeks fat feeding (+ 6 g/kg per day). SG from IVGTTs were quantified by minimal model (SG-MINMOD). In HGCs, glucose was sequentially raised to 125, 180, and 250 mg/dl during somatostatin (SRIF) and basal insulin replacement; SG-HGC was calculated as the slope of steady state glucose infusion rate and plasma glucose. Insulin sensitivity (SI) was calculated from IVGTTs and from euglycemic clamps. Fat feeding induced weight gain (28.8±0.4 to 31.2±2.5 kg; p&amp;lt;0.0001) and insulin resistance at both liver (p&amp;lt;0.0001) and periphery (p&amp;lt;0.0001). SG-MINMOD was reduced after fat feeding (0.036±0.002 vs. 0.041±0.002 min-1; p&amp;lt;0.001). The direct measure of SG from HGCs at basal insulin (SG-HGC) suggest similar diet-induced reduction (21%), although sample size was diminished due to SRIF breakthrough and resulting hyperinsulinemia in 2 animals. After fat feeding, there was no increase in glucose effectiveness that may be expected as compensation for diet-induced insulin resistance. Rather, glucose effectiveness decreased. These data indicate that obesity results in diminished actions of both insulin and glucose per se on glucose homeostasis. Disclosure M. Ader: None. C.M. Kolka: Research Support; Self; AstraZeneca. R.N. Bergman: None. Funding National Institutes of Health (DK29867, DK27619)

1889-P: Light Exercise and Liraglutide Synergistically Improve Muscle Insulin Action in Diet-Induced Obesity

Insulin recruits muscle microvasculature which contributes to insulin’s metabolic action but is blunted in humans with obesity. Both exercise and glucagon-like peptide 1 (GLP-1) are potent enhancers of muscle microvascular perfusion and their actions are preserved in the insulin resistant states. To examine whether light exercise and GLP-1 receptor agonism modulate insulin’s microvascular and metabolic actions during the development of obesity, adult male rats were fed a high-fat diet (HFD) for 2 weeks with either free access to running wheel (light exercise), liraglutide (200 mcg/kg subcutaneously twice daily), or light exercise + liraglutide. Rats were then fasted overnight and received a euglycemic insulin clamp (3 mU/kg/min) for 120 min. Insulin-mediated muscle microvascular recruitment was measured using contrast-enhanced ultrasound. Rats on HFD alone (control) displayed marked microvascular insulin resistance. Light exercise increased basal plasma nitric oxide levels and fully rescued insulin’s microvascular action. Liraglutide similarly increased basal plasma NO contents but did not reverse microvascular insulin resistance. Both light exercise and liraglutide improved insulin-stimulated whole body glucose disposal in the first 30 min but did not significantly increase the steady-state glucose infusion rates. Combined light exercise and liraglutide treatment not only fully restored microvascular insulin responses but also significantly enhanced insulin-stimulated whole body glucose disposal (&amp;gt;50%, p&amp;lt;0.01). We conclude that light exercise and liraglutide differentially modulate microvascular insulin responses but synergistically enhance metabolic insulin actions during the development of obesity. Our findings provide a novel insight into the exercise and liraglutide interplay and support the early use of exercise and GLP-1 receptor agonism to correct microvascular and metabolic insulin resistance during the development of obesity. Disclosure J. Liu: None. K.W. Aylor: None. Z. Liu: None. Funding American Diabetes Association (1-17-ICTS-059 to Z.L.); National Institutes of Health (R01HL094722, R01DK102359)

4164 Body mass index, not chemotherapy is the major predictor of insulin resistance in patients with hematological malignancies

OBJECTIVES/GOALS: Cancer survivors are at increased risk for type 2 diabetes mellitus.It is not clear if diabetes susceptibility is due to shared risk factors for cancer and diabetes, such as obesity, or if it is directly related to cancer and its treatment. We investigated the association between malignancy and insulin resistance, a major risk factor for diabetes. METHODS/STUDY POPULATION: 20 adult patients with treated hematological malignancies and 21 controls without cancer were included in the study. Individuals with pre-existing diabetes were excluded. All patients underwent a 2-hour 75-gram oral glucose tolerance test (OGTT). Hyperinsulinemic-euglycemic clamps were performed to measure the steady-state glucose infusion rate (M-value) as an indicator of whole-body glucose utilization during insulin stimulation. Insulin sensitivity index was calculated by dividing M-value over the steady-state plasma insulin (M/I). RESULTS/ANTICIPATED RESULTS: Fasting or postprandial plasma glucose levels during the OGTT did not differ significantly between malignancy patients and controls (Table 2). Difference in the insulin-stimulated glucose utilization (M-value) was not statistically significant among cancer patients and controls (median, 7.2 [IQR, 6.2-10.4] vs. 7.3 [IQR, 5.5-8.9] mg/kg/min; P = 0.261). M/I index was significantly higher in malignancy patients compared to controls (median, 42.4 mg/kg/min/(µU/ml) [IQR, 33.9-67.2] vs. 23.4 mg/kg/min/(µU/ml) [IQR, 12.9-29.2], P &lt;0.001), however insulin clearance was also lower in the controls. In multivariate analysis, only BMI was significantly associated with M-value (β = −0.2 (95% CI −0.4, −0.1), P = 0.004), and M/I (β = −2 (95% CI −3.4, −0.5), P = 0.009). DISCUSSION/SIGNIFICANCE OF IMPACT: Our data suggest that the major contributor to diabetes development after diagnosis of cancer in adults is obesity-induced insulin resistance, not malignancy related factors. These findings emphasize the importance of obesity management in long-term survival of cancer patients, as diabetes is a risk factor for mortality in this patient population.

Abstract P432: Racial Differences In Endothelial Function And Insulin Sensitivity

Racial disparities in health outcomes continue to be a significant public health concern and African Americans (AA) are disproportionately burdened by several risk factors for cardiovascular disease. Endothelial dysfunction has been shown to be a predictor of CVD and metabolic factors, including insulin resistance, are associated with endothelial dysfunction. Compared to EA, AA have impaired endothelial function and are more insulin resistant (less insulin sensitive). However, it remains unclear how insulin resistance may contribute to endothelial dysfunction in AA and EA. The purpose of the present study was to evaluate the relationship between insulin sensitivity and endothelial function in AA and EA. It was hypothesized that insulin sensitivity would be associated with endothelial function in both AA and EA. Skeletal muscle insulin sensitivity was measured by hyperinsulinemic-euglycemic glucose clamp technique in 112 lean, overweight, and obese AA and EA adults without diabetes. Insulin was infused at 120 mU/m 2 /min for 3 hours and an infusion of 20% dextrose was adjusted to maintain blood glucose at the fasting level. Insulin sensitivity (10 -4 .dL.kg -1 .min -1 /(μU/mL)) was defined as M/(G x ΔI), where M is steady state glucose infusion rate, G is steady state serum glucose concentration, and ΔI is the difference between basal and steady state serum insulin concentrations. M was adjusted for total lean body mass which was measured by dual-energy X-ray absorptiometry (DXA). Endothelial function was assessed by percent change in flow-mediated brachial artery dilatation (FMD). Changes in brachial artery diameter during reactive hyperemia were measured using ultrasound. Increased blood flow was induced via blood pressure cuff around the forearm, with a 5-minute inflation at 50 mmHg above the subject’s systolic blood pressure. Brachial arterial flow was determined using a pulsed-Doppler signal at baseline and 10-15 seconds after cuff release. Arterial diameter was measured at end-diastolic phase from super-VHS recordings. For reactive hyperemia response, measurements with the 5 largest diameters were averaged and the percent increase from baseline was determined as FMD. A total of 55 AA and 57 EA were included in the analysis. Mean insulin sensitivity was 4.89 in AA and 7.97 in EA (p &lt; .0001) and mean FMD was 10.69 in AA and 10.14 in EA (p = .595). Linear regression analysis indicated a significant relationship between insulin sensitivity and endothelial function in AA but not in EA (p= .005 and p= .5, respectively). These results suggest that insulin sensitivity may play a role in determining endothelial function in AA.

Vasodilatory Actions of Glucagon-Like Peptide 1 Are Preserved in Skeletal and Cardiac Muscle Microvasculature but Not in Conduit Artery in Obese Humans With Vascular Insulin Resistance.

Obesity is associated with microvascular insulin resistance, which is characterized by impaired insulin-mediated microvascular recruitment. Glucagon-like peptide 1 (GLP-1) recruits skeletal and cardiac muscle microvasculature, and this action is preserved in insulin-resistant rodents. We aimed to examine whether GLP-1 recruits microvasculature and improves the action of insulin in obese humans. Fifteen obese adults received intravenous infusion of either saline or GLP-1 (1.2 pmol/kg/min) for 150 min with or without a euglycemic insulin clamp (1 mU/kg/min) superimposed over the last 120 min. Skeletal and cardiac muscle microvascular blood volume (MBV), flow velocity and blood flow, brachial artery diameter and blood flow, and pulse wave velocity (PWV) were determined. Insulin failed to change MBV or flow in either skeletal or cardiac muscle, confirming the presence of microvascular insulin resistance. GLP-1 infusion alone increased MBV by ∼30% and ∼40% in skeletal and cardiac muscle, respectively, with no change in flow velocity, leading to a significant increase in microvascular blood flow in both skeletal and cardiac muscle. Superimposition of insulin to GLP-1 infusion did not further increase MBV or flow in either skeletal or cardiac muscle but raised the steady-state glucose infusion rate by ∼20%. Insulin, GLP-1, and GLP-1 + insulin infusion did not alter brachial artery diameter and blood flow or PWV. The vasodilatory actions of GLP-1 are preserved in both skeletal and cardiac muscle microvasculature, which may contribute to improving metabolic insulin responses and cardiovascular outcomes. In obese humans with microvascular insulin resistance, GLP-1's vasodilatory actions are preserved in both skeletal and cardiac muscle microvasculature, which may contribute to improving metabolic insulin responses and cardiovascular outcomes.

Body muscle-to-fat ratio gender-specific cut-off values for impaired insulin sensitivity in patients with treatment-naïve type 2 diabetes mellitus.

We previously reported that the body muscle-to-fat ratio (BMFR), measured using bioelectrical impedance, significantly correlated with whole-body insulin sensitivity. We examined BMFR gender-specific cut-off values for impaired insulin sensitivity in treatment-naïve type 2 diabetes mellitus (T2DM) patients. Subjects included 101 untreated T2DM patients (male, 66; female, 35). We performed a hyperinsulinemic-euglycemic clamp examination to measure the steady-state glucose infusion rate (M value) as an indicator of whole-body insulin resistance. We defined the M value divided by the steady-state serum insulin value as the M/I value. We defined the existence of insulin resistance using an M/I ratio <9.0. The optimal cut-off value for BMFR was calculated by receiver operating characteristics (ROC) analysis. The cut-off value of the BMFR for insulin resistance was 2.75 (area under the curve [AUC] = 0.83, sensitivity 75%, and specificity 76%, P < 0.001) for males and 1.65 (AUC = 0.87, sensitivity 84%, and specificity 81%, P < 0.001) for females. Simple linear regression analysis showed that BMFR was significantly correlated with the M/I value in both genders (males, B = 0.77, P< 0.01; females, B = 0.83, P< 0.01). BMFR cut-off values for impaired insulin sensitivity in treatment-naïve T2DM patients were 2.75 for males and 1.65 for females.

Angiotensin-(1-7) contributes to insulin-sensitizing effects of angiotensin-converting enzyme inhibition in obese mice.

Angiotensin-converting enzyme (ACE) inhibitors reduce body weight, lower blood pressure (BP), and improve insulin sensitivity in animal models of cardiometabolic syndrome. These effects are generally attributed to reduced angiotensin (ANG) II formation; however, these therapies also increase levels of ANG-(1-7), a beneficial hormone opposing ANG II actions. We hypothesized that this ANG-(1-7) generation contributes to the insulin-sensitizing effects of ACE inhibition in obese mice. Adult male C57BL/6J mice were placed on a 60% high-fat diet for 11 wk. During the last 3 wk of diet, mice received normal water or water containing the ACE inhibitor captopril (50 mg/l) as well as the ANG-(1-7) mas receptor antagonist A779 (400 or 800 ng·kg-1·min-1) or saline vehicle via subcutaneous osmotic minipumps. At the end of treatment, arterial BP was measured, and hyperinsulinemic-euglycemic clamps were performed in conscious obese mice receiving vehicle, captopril, captopril plus A779, or A779 ( n = 6-13/group). Captopril reduced body weight (28 ± 2 vs. 41 ± 2 g saline; P = 0.001), lowered systolic BP (109 ± 6 vs. 144 ± 7 mmHg saline; P = 0.041), and improved whole-body insulin sensitivity (steady-state glucose infusion rate: 31 ± 4 vs. 16 ± 2 mg·kg-1·min-1 saline; P = 0.001) in obese mice. A779 attenuated captopril-mediated improvements in insulin sensitivity (23 ± 2 mg·kg-1·min-1; P = 0.042), with no effect on body weight (32 ± 2 g; P = 0.441) or BP (111 ± 7 mmHg; P = 0.788). There was no effect of A779 alone on cardiometabolic outcomes. These data suggest that insulin-sensitizing effects of ACE inhibition are in part due to activation of ANG-(1-7)/ mas receptor pathways and provide new insight into mechanisms underlying the positive metabolic effects of these therapies.

Glucagon-Like Peptide-1 (GLP-1) Increases Skeletal and Cardiac Muscle, Microvascular Perfusion, and Improves Metabolic Insulin Action in Obese Humans

Obesity is associated with metabolic and microvascular insulin resistance. The latter is characterized by impaired insulin-mediated microvascular recruitment. GLP-1 engenders vasodilation in addition to its glycemic actions. At physiological concentrations, GLP-1 acutely recruits skeletal and cardiac muscle microvasculature in healthy humans and this action is preserved in the insulin resistant rodents. To examine whether GLP-1 recruits microvasculature and improves insulin’s action in obese humans, 15 obese adults (age 27 ± 2.2, BMI 33.7 ± 1.2) were studied thrice at random order after an overnight fast. Subjects received an intravenous infusion of GLP-1 (1.2 pmol/kg/min) for 150 mins or an intravenous infusion of either normal saline or GLP-1 (1.2 pmol/kg/min) for 150 mins with a euglycemic insulin clamp (1 mU/kg/min) superimposed over the last 120 mins. Skeletal and cardiac muscle microvascular blood volume (MBV), flow velocity (MFV) and blood flow (MBF) were determined at 0, 30 and 150 min. Steady-state glucose infusion rate (GIR) was calculated. Insulin infusion alone did not change MBV or MBF in either skeletal or cardiac muscle, confirming the presence of microvascular insulin resistance. GLP-1 infusion alone increased MBV by ∼30% and ∼40% in skeletal and cardiac muscle respectively (p&amp;lt;0.05) without affecting MFV, leading to a significant increase in MBF in both skeletal and cardiac muscle. Superimposition of insulin infusion to GLP-1 infusion did not further increase MBV or MBF in either skeletal or cardiac muscle, but raised the steady-state GIR from 4.1± 0.4 to 5.0 ± 0.5 mg/kg/min (p&amp;lt;0.05). We conclude that in obese humans with microvascular insulin resistance GLP-1's vasodilatory actions are preserved in both skeletal and cardiac muscle microvasculature. This may contribute to improving metabolic responses to insulin and decreasing cardiovascular morbidity and mortality associated with obesity and diabetes. Disclosure N. Wang: None. A. Tan: None. L. Jahn: None. L. Hartline: None. K.W. Aylor: None. E. Barrett: None. Z. Liu: None.

IMG-1 Lowers Insulin Resistance by Decreasing Hepatic Glucose Production in a DIO Mouse Clamp Test

IMG-1 is a novel therapeutic compound for the treatment of diabetes. IMG-1 has been shown to successfully treat both type 1 mice and rats (STZ models) and type 2 ZDF rats. To test how IMG-1 is able to treat type II diabetes, diet-Induced Obese (DIO) C57BL/6J mice were used in a hyperinsulinemic-euglycemic clamp assay. The hyperinsulinemic-euglycemic clamp is the gold-standard method to assess insulin sensitivity. The euglycemic clamp is widely used in clinics and laboratories to measure insulin action on glucose utilization in humans and animals for clinical and basic science research. Sixteen DIO C57BL/6J mice underwent a 2-hour hyperinsulinemic-euglycemic clamping to assess insulin action and glucose metabolism in IMG-1 treated (2µg IMG-1 administered IV via tail vein 48 and 24hours prior to the clamp test, n=8) or PBS treated animals (n=8). IMG-1 treated animals had significantly higher steady-state glucose infusion rates during clamping than PBS treated animals, indicating that IMG-1 is able to decrease insulin resistance in DIO mice. IMG-1 did not affect whole-body glucose turnover, glycolysis or glycogen synthesis in any of the treated animals. Glucose metabolism in skeletal muscle and adipose tissue was not significantly different in either IMG-1 or PBS treated animals during the clamp assay. However, Hepatic Glucose Production (HGP) was dramatically suppressed in all animals treated with IMG-1 (a decrease from 3.mg/kg/m to -6.16 mg/kg/m). Furthermore, hepatic insulin action (the percent suppression of HGP) was increased in all IMG-1 treated animals&amp;#x2028;during the hyperinsulinemic-euglycemic clamp (from 70.9 control to 99.7 IMG-1). IMG-1 is a novel compound for the treatment of diabetes. These results show that IMG-1 decreases insulin resistance in a type 2 diabetic mouse model by suppressing HGP and increasing hepatic insulin action. Disclosure J.B. Pollett: Employee; Self; Imagine Pharma. H. Noh: None. J.K. Kim: None. N. Thai: Board Member; Self; Imagine Pharma.

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.

Morning administration of 0.4 U/kg/day insulin glargine 300 U/mL provides less fluctuating 24-hour pharmacodynamics and more even pharmacokinetic profiles compared with insulin degludec 100 U/mL in type 1 diabetes

AimTo compare steady state pharmacodynamic and pharmacokinetic profiles of insulin glargine 300U/mL (Gla-300) with insulin degludec 100U/mL (Deg-100) in people with type 1 diabetes. MethodsThis single-centre, randomized, double-blind crossover euglycaemic clamp study included two parallel cohorts with fixed once-daily morning dose regimens. For both insulins participants received 0.4 (n=24) or 0.6U/kg/day (n=24), before breakfast, for 8 days prior to the clamp. The main endpoint was within-day variability (fluctuation) of the smoothed glucose infusion rate (GIR) over 24 hours (GIR-smFL0–24). ResultsGla-300 provided 20% less fluctuation of steady state glucose infusion rate profiles than Deg-100 over 24 hours at 0.4U/kg/day (GIR-smFL0–24 treatment ratio 0.80 [90% confidence interval: 0.66 to 0.96], P=0.047), while at the dose of 0.6U/kg/day the difference between insulins was not statistically significant (treatment ratio 0.96 [0.83 to 1.11], P=0.603). Serum insulin concentrations appeared more evenly distributed with both dose levels of Gla-300 versus the same doses of Deg-100, as assessed by relative 6-hour fractions of the area under the curve within 24 hours. Both insulins provided exposure and activity until 30 hours (end of clamp). ConclusionGla-300 provides less fluctuating steady state pharmacodynamic profiles (i.e. lower within-day variability) and more evenly distributed pharmacokinetic profiles, compared with Deg-100 in a once-daily morning dosing regimen of 0.4U/kg/day.

Assisted Reproductive Technologies Predispose to Insulin Resistance and Obesity in Male Mice Challenged With a High-Fat Diet.

Assisted reproductive technology (ART) alters glucose homeostasis in mice and humans, but the underlying mechanisms are incompletely understood. ART induces endothelial dysfunction and arterial hypertension by epigenetic alteration of the endothelial nitric oxide synthase (eNOS) gene. In eNOS-deficient mice, insulin resistance is related to impaired insulin stimulation of muscle blood flow and substrate delivery and defective intrinsic skeletal muscle glucose uptake. We therefore assessed glucose tolerance, insulin sensitivity (euglycemic clamp), insulin stimulation of muscle blood flow in vivo, and muscle glucose uptake in vitro in male ART and control mice fed a normal chow (NC) or challenged with a high-fat diet (HFD) during 8 weeks. Glucose tolerance and insulin sensitivity were similar in NC-fed animals. When challenged with a HFD, however, ART mice developed exaggerated obesity, fasting hyperinsulinemia and hyperglycemia, and a 20% lower insulin-stimulated glucose utilization than did control mice (steady-state glucose infusion rate (GIR), 51.3 ± 7.3 vs 64.0 ± 10.8 mg/kg/min, P = 0.012). ART-induced insulin resistance was associated with defective insulin stimulation of muscle blood flow, whereas intrinsic skeletal muscle glucose uptake was normal. In conclusion, ART-induced endothelial dysfunction, when challenged with a metabolic stress, facilitates glucose intolerance and insulin resistance. Similar mechanisms may contribute to ART-induced alterations of the metabolic phenotype in humans.

Abstract P316: Angiotensin-(1-7) Contributes to the Insulin-sensitizing Effects of Renin-angiotensin System Blockade in High Fat Fed Mice

Angiotensin-converting enzyme (ACE) inhibitors reduce body weight, lower blood pressure, and improve glucose homeostasis in animal models of the cardiometabolic syndrome. These effects are generally attributed to a reduction in angiotensin (Ang) II formation; however, these therapies also increase circulating levels of Ang-(1-7), a peptide with direct anti-hypertensive and insulin-sensitizing effects. In this study, it was hypothesized that endogenous Ang-(1-7) generation contributes to the beneficial cardiometabolic effects of ACE inhibition. To test this hypothesis, diet-induced obesity was produced in adult male C57BL/6J mice by placing them on a 60% high fat diet for 11 weeks. The Ang-(1-7) mas receptor antagonist A779 (400 ng/kg/min) or saline was given after 8 weeks of the high fat diet by subcutaneous osmotic mini-pumps. Immediately following mini-pump implantation, mice received water containing the ACE inhibitor captopril (50 mg/L) or plain tap water. Hyperinsulinemic (4 mU/kg/min) euglycemic clamps were performed in conscious, unrestrained vehicle (n=6), captopril (n=6), or captopril plus A779 (n=13) mice at the end of the 3-week treatment period. Blood pressure was measured via an indwelling carotid artery catheter connected to a transducer on the morning of the clamp. Captopril reduced body weight (28±2 vs. 41±2 g vehicle; p=0.001), lowered blood pressure (systolic: 109±6 vs.144±7 mmHg vehicle; p=0.003), and improved whole-body insulin sensitivity (steady-state glucose infusion rate: 31±4 vs. 16±2 mg/kg/min; p=0.008) in high-fat fed mice. Mas receptor antagonism with A779 attenuated the improvement in insulin sensitivity produced by captopril in high fat fed mice (23±2 mg/kg/min; p=0.042). There was no effect of A779 on the weight loss (32±2 g) or blood pressure lowering effects (111±7 mmHg) of captopril. These findings suggest that the improvement in insulin sensitivity produced by ACE inhibition is at least partly mediated by Ang-(1-7) pathways, and provide new insight into potential mechanisms involved in renin-angiotensin system blockade.

Sedentary Behavior Inversely Relates to Insulin Sensitivity and Mitochondrial Oxidative Capacity in Inactive Obese Adults

Sedentary time (ST) is associated with increased risk for insulin resistance, metabolic syndrome, and type 2 diabetes. The impact of ST on insulin sensitivity and muscle mitochondrial oxidative capacity, key mediators of the aforementioned metabolic diseases, is not fully understood. PURPOSE: We sought to determine the impact of ST on insulin sensitivity and muscle oxidative capacity in obese, physically inactive adults. METHODS: We studied 19 inactive, obese (35+1 kg/m2), middle aged (54+1 y) adults. We measured insulin sensitivity using a standardized two-stage hyperinsulinemic-eugIycemic clamp. In isolated vastus lateralis muscle mitochondria, we measured state-3 oxygen flux rates (JO2) by high-resolution respirometry using substrates for complex I, I+II, and II. Finally, we measured ST (<100 counts per min) and time spent in moderate to vigorous physical activity (MVPA, >2020 counts per min) using accelerometry. We used multivariate regression analysis to test for associations between ST and insulin sensitivity and muscle oxidative capacity adjusted for age and MVPA. RESULTS: Data are presented as mean + SEM. The average steady-state glucose infusion rate to maintain euglycemia during the high-dose insulin infusion was 8.4+1 mg/kgFFM/min. The average JO2 were 232 + 16 pmols/s/ml (complex I) and 307+16 pmols/s/ml (complex II). The average wear-time adjusted times spent in ST and MVPA were 570+30 min/d (9.5+0.5 h/d) and 20.4+0.5 min/d. The partial correlations between ST and the average glucose infusion rate and JO2 rates adjusted for age and MVPA were -0.62 (p=0.007), -0.51 (p=0.027, for complex I), and -0.32 (p=0.21, for complex II). CONCLUSION: ST inversely correlates with insulin sensitivity and complex I mediated muscle oxidative capacity in inactive, middle-aged, obese adults when adjusted for age and MVPA. We propose that reducing ST will improve insulin sensitivity and muscle oxidative capacity.

Chronic Angiotensin-(1-7) Improves Insulin Sensitivity in High-Fat Fed Mice Independent of Blood Pressure.

Angiotensin-(1-7) improves glycemic control in animal models of cardiometabolic syndrome. The tissue-specific sites of action and blood pressure dependence of these metabolic effects, however, remain unclear. We hypothesized that Ang-(1-7) improves insulin sensitivity by enhancing peripheral glucose delivery. Adult male C57BL/6J mice were placed on standard chow or 60% high-fat diet for 11 weeks. Ang-(1-7) (400 ng/kg per minute) or saline was infused subcutaneously during the last 3 weeks of diet, and hyperinsulinemic-euglycemic clamps were performed at the end of treatment. High-fat fed mice exhibited modest hypertension (systolic blood pressure: 137 ± 3 high fat versus 123 ± 5 mm Hg chow;P=0.001), which was not altered by Ang-(1-7) (141 ± 4 mm Hg;P=0.574). Ang-(1-7) did not alter body weight or fasting glucose and insulin in chow or high-fat fed mice. Ang-(1-7) increased the steady-state glucose infusion rate needed to maintain euglycemia in high-fat fed mice (31 ± 5 Ang-(1-7) versus 16 ± 1 mg/kg per minute vehicle;P=0.017) reflecting increased whole-body insulin sensitivity, with no effect in chow-fed mice. The improved insulin sensitivity in high-fat fed mice was because of an enhanced rate of glucose disappearance (34 ± 5 Ang-(1-7) versus 20 ± 2 mg/kg per minute vehicle;P=0.049). Ang-(1-7) enhanced glucose uptake specifically into skeletal muscle by increasing translocation of glucose transporter 4 to the sarcolemma. Our data suggest that Ang-(1-7) has direct insulin-sensitizing effects on skeletal muscle, independent of changes in blood pressure. These findings provide new insight into mechanisms by which Ang-(1-7) improves insulin action, and provide further support for targeting this peptide in cardiometabolic disease.

Surrogate measures of insulin sensitivity when compared to euglycemic hyperinsulinemic clamp studies in Asian Indian men without diabetes

AimFasting surrogate measures of insulin sensitivity are increasingly used in research and clinical practice. To assess the reliability of these measures, we aimed to evaluate multiple fasting surrogate measures simultaneously in non-diabetic subjects in comparison with the euglycemic hyperinsulinemic clamp study. MethodsSixteen normoglycemic male South Indian subjects were studied. After an overnight fast, blood samples were collected for glucose, insulin and lipid profile measurements, and stepped euglycemic hyperinsulinemic clamp studies were performed on all subjects. Steady state glucose infusion rates (M value) during low and high insulin phases of the clamp were calculated. Correlation of M value with surrogate markers of insulin sensitivity was performed. Predictive accuracy of surrogate indices was measured in terms of Root Mean Squared Error (RMSE) and leave-one-out cross-validation-type RMSE of prediction using a calibration model. ResultsM values showed a strong and significant correlation (p<0.01) with the following surrogate markers: Fasting insulin (r=−0.714), Fasting glucose to insulin ratio (FGIR, r=0.747) and Raynaud index (r=0.714). FGIR had a significantly lower RMSE when compared with HOMA-IR and QUICKI. ConclusionsAmong the surrogate measures, FGIR had the strongest correlation with M values. FGIR was also the most accurate surrogate measure, as assessed by the calibration model.

Abstract P645: Chronic Angiotensin-(1-7) Improves Whole-Body Insulin Sensitivity in High-Fat Fed Mice by Enhancing Skeletal Muscle Glucose Uptake

Angiotensin (Ang)-(1-7) is a vasodilatory peptide implicated in the pathophysiology of hypertension, in part by opposing deleterious Ang II cardiovascular actions. Recent studies show that Ang-(1-7) restoration lowers blood pressure and improves glycemic control in animal models of cardiometabolic syndrome. The tissue-specific sites of action and blood pressure dependence for these metabolic effects, however, remain unclear. We hypothesized that Ang-(1-7) improves insulin sensitivity by enhancing peripheral glucose delivery. To test this hypothesis, adult male C57BL/6 mice were placed on standard chow or 60% high-fat diet for 11 weeks, with Ang-(1-7) [400 ng/kg/min] or saline given during the last 3 weeks of diet by subcutaneous osmotic mini-pump. Hyperinsulinemic (4 mU/kg/min) euglycemic clamps were performed in conscious, unrestrained mice at the end of the treatment period. High-fat fed mice exhibited modest hypertension (systolic blood pressure: 137±3 high-fat vs. 123±5 mmHg chow; p=0.043), which was not altered by Ang-(1-7) infusion (141±4 mmHg; p=0.516). Body weight, body composition, and fasting plasma glucose and insulin levels were not significantly different following Ang-(1-7) treatment in chow or high-fat fed mice. Ang-(1-7) increased the glucose infusion rate (GIR) needed to maintain euglycemia in high-fat fed mice (steady-state GIR: 31±5 Ang-(1-7) vs. 16±1 mg/kg/min vehicle; p=0.017) indicating enhanced whole-body insulin sensitivity, with no significant effect in chow fed mice. The improvement in insulin sensitivity in high-fat fed mice was due to an enhanced rate of whole-body glucose disappearance (R d : 34±5 Ang-(1-7) vs. 20±2 mg/kg/min vehicle; p=0.049), with increased rates of glucose uptake in gastrocnemius, vastus, and soleus muscle. There was no effect of Ang-(1-7) on insulin-mediated suppression of hepatic glucose production. Our data shows that Ang-(1-7) has direct insulin-sensitizing effects on skeletal muscle, which are independent of changes in body weight or systemic blood pressure. These overall findings provide new insight into mechanisms by which Ang-(1-7) improves insulin action, and provide further support to targeting this peptide for treatment of cardiometabolic disease.