Frequently Sampled Intravenous Glucose Tolerance Test Research Articles

Abstract 059: (Pro)renin Receptor Ablation In Tyrosine Hydroxylase Neurons In The Paraventricular Nucleus Of The Hypothalamus Improves Insulin Sensitivity In Mice Fed A High-fat Diet

We recently reported that neuron-specific (pro)renin receptor (PRR) deletion reduces blood pressure (BP), fasting blood glucose (BG) and improves glucose tolerance in high-fat diet (HFD)-treated mice. To investigate underlying mechanisms, we focused on tyrosine hydroxylase (TH) neurons in the hypothalamic paraventricular nucleus (TH PVN neurons), a largely GABAergic population that expresses PRR and projects to autonomic centers important for BP and BG regulation. The PRR was ablated specifically in the TH-positive neurons in the PVN using Cre-LoxP approach. Radio telemetric BP recording, fasting blood glucose (FBG) and frequently sampled intravenous glucose tolerance test (FSIVGTT) were performed following 6-week HFD (60% calories from fat). HFD induced elevation of BP within the first week ( p < 0.05) and maintained elevated during 6-week protocol; however, there was no difference in BP between TH PVN PRRKO and WT control mice in both sexes following HFD. In male mice, the controls had higher FBG when compared with the TH PVN PRRKO mice (144.1 ± 5.74 vs. 121.9 ± 4.34 mg/dl, p < 0.05) at the end of the 6-week HFD treatment. Interestingly, PRR ablation in the TH PVN neurons did not reduce FBG in female mice. The TH PVN PRRKO mice showed improved glucose handling during FSIVGTT (AUC: 3481 ± 247.5 vs. 4263 ± 153.9, p < 0.05), while there was no difference in insulin secretion (AUC: 1782 ± 339.2 vs. 2324 ± 495.6, p > 0.05) between the two groups suggesting that TH PVN PRR ablation attenuates HFD-induced glucose intolerance through either an increase in insulin sensitivity or an insulin-independent pathway. Detected by western blot, the glucose transporter 4, an insulin-dependent glucose transporter, was higher on the plasma membrane of skeletal muscle in the TH PVN PRRKO mice (1.9 ± 0.2 vs. 1.0 ± 0.1, p < 0.05) compared with the controls. The hepatic mRNA expression of glucose-6-phosphatase, a gluconeogenic gene transcriptional negative-regulated by insulin, was lower in the TH PVN PRRKO (0.60 ± 0.07 vs. 0.95 ± 0.10, p < 0.05) compared with the control mice, suggesting improvement of insulin sensitivity in the TH PVN PRRKO mice. In conclusion, PRR ablation in TH PVN neurons attenuates FBG and glucose tolerance through improvement of insulin sensitivity without impacting BP.

Validity and reliability of simple surrogate indexes to evaluate beta-cell function and insulin sensitivity.

Simple surrogate indexes (SSI) to assess beta-cell function, insulin sensitivity (IS) and insulin resistance (IR) are an easy and economic tool used in clinical practice to identify glucose metabolism disturbances. To evaluate the validity and reliability of SSI that estimate beta-cell function, IS and IR using as a reference the parameters obtained from the frequently sampled intravenous glucose tolerance test (FSIVGTT). We included 62 subjects aged 20-45 years, with a normal body mass index and without diabetes or prediabetes. SSI were compared with the acute insulin response to glucose (AIRg), insulin sensitivity index (Si) and disposition index (DI) obtained from the FSIVGTT using the minimal model approach. Half of the participants (n = 31) were randomly selected for a second visit two weeks later to evaluate the reliability of all the variables. HOMA1-%B and HOMA2-%B had a significant correlation with AIRg (Spearman Rho (rs) = 0.33 and 0.37 respectively, p < 0.01). The SSI evaluating IS/IR that showed stronger correlation (rs > 0.50) with Si were fasting insulin, HOMA1-IR, HOMA2-IR, HOMA1-%S, HOMA2-%S, QUICKI, and the McAuley index. The parameters that showed good reliability with an intraclass correlation coefficient (ICC) > 0.75 were AIRg, HOMA1-%S, HOMA2-%S, and QUICKI. Our results suggest that most of the SSI are useful and reliable.

1047-P: To Assess the Physiological Changes of Glucose Metabolism Associated with Increased BMI in Pregnancy

Background: Maternal overweight is a risk factor for Gestational Diabetes Mellitus (GDM) . However, there is emerging evidence that increased maternal BMI has considerable impact on the development of large for gestational age (LGA) offspring even in women who do not develop GDM, possibly related to subtle impairments in glucose metabolism. This study aims to assess physiological changes associated with increased BMI. Methods: 21 women with overweight and 21 normal weight controls were included in this explorative study and received a metabolic assessment at early pregnancy (13.3 weeks) (Visit 1) , including a 60 min frequently sampled intravenous glucose tolerance test (FSIGT) . An OGTT was performed between 24 and 28 weeks of gestation (Visit 2) in women who remained normal glucose tolerant. Results: At V1 mothers with overweight showed significantly elevated fasting glucose and HbA1c values, a well as impaired insulin sensitivity at fasting condition and dynamically assessed during the FSIGT, whereby the Calculated Insulin Sensitivity index (CSI) was lower in the overweight group as compared to normal weight controls (3.5 vs. 6.7 10-4⋅[μU/mL]-1⋅min-1, p=0.025) . The Disposition Index (DI) as a parameter of β-cell function was significantly decreased in mothers with overweight. Likewise, maternal BMI was inversely related to fasting (rho=0.56, p=0.005) and dynamically assessed insulin sensitivity (rho=0.51, p=0.014) as well as the DI (rho=0.51, p=0.014) and the AUC of glucose (rho=0.66, p&amp;lt;0.001) and C-Peptide (rho=0.46, p=0.020) during the OGTT in mothers who remained normal glucose tolerant during pregnancy at V2. Conclusions: Increased maternal BMI is associated to insulin resistance and impaired β-cell function already at early pregnancy. We also observed that maternal BMI was associated with impaired glucose metabolism and especially elevated glucose levels during the OGTT at mid gestation in women who did not develop GDM and remained normal glucose tolerant. Disclosure T.Linder: None. D.Eppel: None. C.Monod: None. G.Kotzaeridi: None. A.Tura: None. C.S.Göbl: Research Support; Dexcom, Inc., Sanofi.

Chronic binge alcohol and ovariectomy-mediated impaired insulin responsiveness in SIV-infected female rhesus macaques.

Aging people living with HIV (PLWH), especially postmenopausal women may be at higher risk of comorbidities associated with HIV, antiretroviral therapy (ART), hypogonadism, and at-risk alcohol use. Our studies in simian immunodeficiency virus (SIV)-infected male macaques demonstrated that chronic binge alcohol (CBA) reduced acute insulin response to glucose (AIRG), and at-risk alcohol use decreased HOMA-β in PLWH. The objective of this study was to examine the impact of ovariectomy (OVX) on glucose-insulin dynamics and integrity of pancreatic endocrine function in CBA/SIV-infected female macaques. Female macaques were administered CBA (12-15 g/kg/wk) or isovolumetric water (VEH) intragastrically. Three months after initiation of CBA/VEH administration, all macaques were infected with SIVmac251, and initiated on antiretroviral therapy (ART) 2.5 mo postinfection. After 1 mo of ART, macaques were randomized to OVX or sham surgeries (n = 7 or 8/group), and euthanized 8 mo post-OVX (study endpoint). Frequently sampled intravenous glucose tolerance tests (FSIVGTT) were performed at selected time points. Pancreatic gene expression and islet morphology were determined at study endpoint. There was a main effect of CBA to decrease AIRG at Pre-SIV and study endpoint. There were no statistically significant OVX effects on AIRG (P = 0.06). CBA and OVX decreased the expression of pancreatic markers of insulin docking and release. OVX increased endoplasmic stress markers. CBA but not OVX impaired glucose-insulin expression dynamics in SIV-infected female macaques. Both CBA and OVX altered integrity of pancreatic endocrine function. These findings suggest increased vulnerability of PLWH to overt metabolic dysfunction that may be exacerbated by alcohol use and ovarian hormone loss.

Effects of Colchicine on Measures of Lipolysis in Adults With Obesity

Background: Obesity-associated inflammation promotes adipose tissue (AT) dysfunction and contributes to the progression of type 2 diabetes and cardiovascular disease. Recent clinical studies have demonstrated that colchicine may improve metabolic and cardiovascular outcomes; however, colchicine’s effects on metabolic and inflammatory measures within AT remain unclear. Methods: The aim of this study was to examine if colchicine’s anti-inflammatory effects would improve measures of lipolysis and immune cell populations in subcutaneous AT (SAT). This is a secondary analysis of a double-blind, randomized, placebo-controlled pilot study in which 40 nondiabetic adults with obesity and metabolic syndrome (MetS) were randomized to colchicine 0.6mg or placebo twice daily for 3 months. Blood samples for insulin, glucose, and free fatty acids were collected in the fasted state and during a frequently-sampled intravenous glucose tolerance test. Noninsulin-suppressible (l0), insulin-suppressible (l2), and maximal (l0+l2) lipolysis rates were calculated by minimal model analysis. Body composition was determined by DXA. SAT immune cell populations were characterized by flow cytometry fluorescence-activated single cell sorting of the stromovascular fractions obtained after collagenase digestion of SAT samples obtained using a mini-liposuction technique pre- and post-intervention. Results: Data from 18 subjects in the colchicine group (Mean ± SD: age 48.4 ± 13.5 y; BMI 39.3 ± 6.3 kg/m2; sex: female 72.2%) and 18 subjects in the placebo group (age 44.7 ± 10.2 y; BMI 41.8 ± 8.2 kg/m2; sex: female 77.8%) were available for this study. Colchicine treatment significantly reduced l2 (p = 0.04) and l0+l2 (p = 0.04) versus placebo. These changes were significantly associated with reductions in systemic inflammation, including the changes in high-sensitivity C-reactive protein concentrations, white blood cell count, circulating monocyte and neutrophil populations, and the neutrophil-lymphocyte ratio (p’s < 0.015). Colchicine did not significantly alter SAT immune cell population distributions (p’s > 0.05). Conclusions: In adults with obesity and MetS, colchicine may improve insulin action at the level of AT. These improvements were positively associated with the suppression of systemic inflammation. However, no local AT inflammatory cell populations were significantly affected by colchicine use in our study, suggesting that colchicine’s systemic, rather than local, anti-inflammatory effects may be more consequential in ameliorating AT metabolic pathways in MetS. Further studies are warranted to elucidate the biological mechanisms underlying colchicine’s effects in AT, as these investigations could potentially shed light on treatments to improve metabolic outcomes in human obesity.

Chronic binge alcohol impairs glucose‐insulin dynamics in SIV‐infected female rhesus macaques

Background Antiretroviral therapy (ART) has significantly reduced mortality of people living with HIV (PLWH). Older PLWH, especially post-menopausal women, experience complex interactions of HIV, ART, hormonal status, and lifestyle behaviors such as at-risk alcohol use, increasing the risk of metabolic comorbidities. We have previously shown that chronic binge alcohol (CBA) reduces the acute insulin response to a glucose challenge in SIV-infected male macaques and that at-risk alcohol use decreases HOMA-β (a marker for pancreatic beta cell function) in PLWH. Meanwhile, the role of estrogen in pancreatic health maintenance is not fully understood. The objective of this study was to determine the effect of CBA and ovarian hormone loss, resulting from ovariectomy (OVX), on glucose-insulin dynamics and pancreatic integrity in SIV-infected female rhesus macaques. Hypothesis We hypothesized that chronic binge alcohol and ovariectomy would decrease insulin response to a glucose challenge and impair insulin and glucagon expression in pancreatic islets. Methods 28 adult female macaques were used in the study. CBA or isovolumetric water (VEH) was administered through an intragastric catheter for 30 minutes, 5 days a week, with blood alcohol concentrations reaching 50-60 mM. Three months after initiation of CBA/VEH administration, macaques were infected with SIVMac251 and 2.5 months later initiated on ART. After 1 month of ART, macaques underwent sham surgery or ovariectomy. Using a modified frequently sampled intravenous glucose tolerance test (FSIVGTT), blood glucose and serum insulin values were measured. Glucose and insulin dynamic measures including the acute insulin response to glucose (AIRg), insulin sensitivity (Si), disposition index (DI), and glucose effectiveness (Sg) were determined using minimal model software. Insulin and glucagon expression was determined in formalin-fixed, paraffin-embedded pancreatic tissue collected at study endpoint. Corrected total cell fluorescence for insulin and glucagon were calculated using ImageJ software. To confirm these results, total RNA was isolated from pancreas and mRNA expression of insulin and glucagon determined using quantitative PCR. Results There was a main effect of CBA to decrease AIRg (p=0.02) and increase Si (p=0.01). There were no statistically significant effects of OVX on AIRg (p=0.06) or Si (p=0.4). There were also no statistically significant effects of CBA or OVX on DI or Sg. Neither CBA nor OVX altered the protein or mRNA expression of insulin and glucagon in pancreatic islets. Conclusion CBA decreased the acute endogenous insulin release in response to a glucose challenge without significantly altering basal pancreatic islet expression of insulin and glucagon, while OVX did not significantly alter any of these measures. These results indicate that CBA impairs the immediate release of insulin from beta cell insulin secretory vesicles, and we speculate that CBA dysregulates the metabolic signaling pathway of insulin secretion. Determining mechanisms of pancreatic endocrine dysfunction will inform therapeutic strategies to improve alcohol-mediated impaired glucose insulin dynamics in the context of SIV/HIV.

Metabolic Effects of Growth Hormone Treatment in Short Prepubertal Children: A Double-Blinded Randomized Clinical Trial

Introduction: Growth hormone (GH) is a central hormone for regulating linear growth during childhood and also highly involved in the metabolism of lipids, carbohydrates, and protein. However, few studies report on how treatment with GH during childhood influences metabolic parameters. Our aim was to investigate metabolic effects of different doses of GH in short children with GH peak levels in the low to normal range. Design: Thirty-five prepubertal short children (<−2.5 SDS), aged 7–10 years, with peak levels of GH between 7 and 14 μg/L during an arginine-insulin tolerance test, were randomized to 3 different doses (11/33/100 μg/kg/day) of GH treatment for 2 years. Auxological and metabolic investigations were performed. These included metabolites in blood and interstitial microdialysis fluid, dual-energy X-ray absorptiometry, frequently sampled intravenous glucose tolerance test (FSIVGTT), and stable isotope examinations of rates of glucose production and lipolysis. Results: At 24 months, the high-dose group (HD) had higher fasting insulin compared with the standard-dose (SD) and low-dose (LD) groups (HD: 111.7 vs. SD: 61.2 and LD: 46.0 pmol/L [p < 0.001]) and showed signs of insulin resistance (HOMA-IR, HD: 4.20 vs. SD: 2.17 and LD: 1.71 (LD) [p < 0.001]). The FSIVGTT also demonstrated higher acute insulin response (p < 0.05). Few other metabolic differences were found at 24 months, but a decreased insulin sensitivity index (Si) could already be seen at 12 months for both SD and HD compared with the LD group (p < 0.05). Conclusion: Treatment with GH resulted in a dose-dependent decrease in insulin sensitivity, demonstrated by higher levels of fasting insulin and signs of insulin resistance in both HOMA indices and FSIVGTT examinations.

Variability in Estimated Modelled Insulin Secretion.

The ability to measure insulin secretion from pancreatic beta cells and monitor glucose-insulin physiology is vital to current health needs. C-peptide has been used successfully as a surrogate for plasma insulin concentration. Quantifying the expected variability of modelled insulin secretion will improve confidence in model estimates. Forty-three healthy adult males of Māori or Pacific peoples ancestry living in New Zealand participated in an frequently sampled, intravenous glucose tolerance test (FS-IVGTT) with an average age of 29 years and a BMI of 33 kg/m2. A 2-compartment model framework and standardized kinetic parameters were used to estimate endogenous pancreatic insulin secretion from plasma C-peptide measurements. Monte Carlo analysis (N = 10 000) was then used to independently vary parameters within ±2 standard deviations of the mean of each variable and the 5th and 95th percentiles determined the bounds of the expected range of insulin secretion. Cumulative distribution functions (CDFs) were calculated for each subject for area under the curve (AUC) total, AUC Phase 1, and AUC Phase 2. Normalizing each AUC by the participant's median value over all N = 10 000 iterations quantifies the expected model-based variability in AUC. Larger variation is found in subjects with a BMI > 30 kg/m2, where the interquartile range is 34.3% compared to subjects with a BMI ≤ 30 kg/m2 where the interquartile range is 24.7%. Use of C-peptide measurements using a 2-compartment model and standardized kinetic parameters, one can expect ~±15% variation in modelled insulin secretion estimates. The variation should be considered when applying this insulin secretion estimation method to clinical diagnostic thresholds and interpretation of model-based analyses such as insulin sensitivity.

Mifepristone Improves Adipose Tissue Insulin Sensitivity in Insulin Resistant Individuals.

Increased tissue cortisol availability has been implicated in abnormal glucose and fat metabolism in patients with obesity, metabolic syndrome, and type 2 diabetes (T2DM). Our objective was to evaluate whether blockade of glucocorticoid receptor (GR) with mifepristone ameliorates insulin resistance (IR) in overweight/obese subjects with glucose intolerance. We conducted a randomized, double-blinded, placebo-controlled, crossover study in overweight/obese individuals (n = 16, 44% female) with prediabetes or mild T2DM but not clinical hypercortisolism. Mifepristone (50 mg every 6 h) or placebo was administered for 9 days, followed by crossover to the other treatment arm after a washout period of 6 to 8weeks. At baseline and following each treatment, oral glucose tolerance test (OGTT) and frequently sampled intravenous glucose tolerance test (FSIVGTT) were performed. Insulin sensitivity was measured using FSIVGTT [primary outcome: insulin sensitivity index (SI)] and OGTT [Matsuda index (MI) and oral glucose insulin sensitivity index (OGIS)]. Hepatic and adipose insulin resistance were assessed using hepatic insulin resistance index (HIRI), and adipose tissue insulin sensitivity index (Adipo-SI) and adipo-IR, derived from the FSIVGTT. Mifepristone administration did not alter whole-body glucose disposal indices of insulin sensitivity (SI, MI, and OGIS). GR blockade significantly improved Adipo-SI (61.7 ± 32.9 vs 42.8 ± 23.9; P = 0.002) and reduced adipo-IR (49.9 ± 45.9 vs 65.5 ± 43.8; P = 0.004), and HIRI (50.2 ± 38.7 vs 70.0 ± 44.3; P = 0.08). Mifepristone increased insulin clearance but did not affect insulin secretion or β-cell glucose sensitivity. Short-term mifepristone administration improves adipose and hepatic insulin sensitivity among obese individuals with hyperglycemia without hypercortisolism.

Circulating microRNAs in insulin resistant horses and ponies

Insulin resistance is a prevalent disorder among horses and is associated with abnormal adiposity, laminitis, equine metabolic syndrome, and pituitary pars intermedia dysfunction. The processes leading to equine insulin resistance and associated conditions remain subject for study. MicroRNAs (miRNAs) are involved in regulation of many biological processes and diseases. The current study aimed to investigate the circulating miRNA profile of insulin resistant horses and ponies. It was hypothesized that insulin resistant horses would have a different circulating miRNA profile compared to healthy ones. 12 Thoroughbred/ Thoroughbred-cross and 12 Welsh/Dartmoor non-pregnant mares were evaluated for insulin sensitivity using frequent sampling intravenous glucose tolerance test (FSIGTT). Serum samples were collected for miRNA profiling through RT-qPCR analysis. Horses and ponies were divided into insulin sensitive (IS) or insulin resistant (IR) groups and their miRNA profiles compared. Results demonstrated that 13 miRNAs were differently expressed between IR and IS horses, 15 between IR and IS ponies, 17 between horses and ponies, and 10 between IR and IS animals (horses and ponies combined) (p<0.05). Finally, 8 miRNAs were proposed as potential regulators of equine insulin resistance. miRNA profiling is a potential tool to evaluate insulin resistance and associated conditions.

Pancreatic fat accumulation is associated with decreased β-cell function and deterioration in glucose tolerance in Korean adults.

This study was designed to investigate the association between pancreatic fat content (PFC) and insulin secretory capacity as well as glucose tolerance in Korean adults. A total of 39 participants (mean age 49.9 years, 53% males) without a previous history of diabetes, or those previously diagnosed as having diabetes but with less than 10years of disease duration and no medication history were included. They were stratified according to the results of the oral glucose tolerance test (OGTT): normal glucose tolerance, prediabetes, and diabetes. All participants underwent the proton magnetic resonance spectroscopy (1 H-MRS) to assess PFC. Insulin sensitivity and β-cell function were measured by the frequently sampled intravenous glucose tolerance tests (FSIVGTT) and OGTT-derived indices. As glucose tolerance deteriorated, parameters such as Stumvoll index, oral glucose insulin sensitivity index, homeostatic model assessment (HOMA)-β, insulinogenic index and oral disposition index from the OGTT, and acute insulin response to glucose (AIR) and disposition index (DI) from the FSIVGTT were decreased. PFC increased with deterioration in glucose tolerance (NGT: 12.0%, prediabetes: 23.7%, and diabetes: 31.9%). Correlation analysis indicated that glucose levels at 60 and 120min during the OGTT were positively correlated with PFC. Also, there was a significant negative correlation between PFC and DI as well as AIR derived from the FSIVGTT. PFC evaluated by 1 H-MRS in Korean adults was higher in those diagnosed with diabetes than those with normal glucose tolerance status. PFC also showed a significant negative correlation with indices reflecting beta cell function.

Effect of oral aleurone supplementation on glucose and insulin dynamics of horses in training

Aleurone is known to have positive effects on energy metabolism in pigs and mice. Our aim was to study the effect of oral aleurone supplementation on glucose and insulin dynamics in healthy trained horses in a cross-over training trial. Sixteen Standardbred mares (3-4y) were trained for 2 periods of 8 weeks, fed iso-energetic diets with and without 200 gr/day aleurone. A frequently sampled intravenous glucose tolerance test (FSIGTT) and an oral glucose tolerance test (OGTT) were executed before and after each training period. For the OGTT outcome variables included: Maximumglucose, AUCglucose, Maximuminsulin, AUCinsulin, and Time to peakinsulin; for the FSIGTT: acute insulin response to glucose (AIRg), insulin sensitivity (SI), glucose effectiveness (Sg) and disposition index (DI). Either a paired T-test was applied or a paired Wilcoxon test. Training without aleurone induced significant OGTT variable changes, which were not seen in the FSIGTT. OGTT Maximuminsulin was significantly lower (P=0.005); Time to peakinsulin was higher (P=0.03) and AUCinsulin was lower after training (P=0.001). Training with aleurone decreased AIRg (P=0.03) and increased Sg (P=0.02). When comparing the FSIGTT variables after training with aleurone to those after training without aleurone AIRg was significantly lower in the aleurone fed group (P=0.004). Aleurone has a beneficial effect on glucose and insulin dynamics on top of training in healthy horses. This is attributable to increased tissue glucose uptake capacity. However, more research is needed to elucidate the mode of action of aleurone at the level of the skeletal muscle and the gut.

Assessment of insulin sensitivity during hyperbaric oxygen treatment.

Previous studies using a hyperinsulinaemic, euglycaemic glucose clamp have demonstrated an increase in peripheral insulin sensitivity in men with and without Type-2 diabetes mellitus on the third and thirtieth hyperbaric oxygen treatment (HBOT) session. In two studies using different techniques for assessment of insulin sensitivity, we investigated the onset and duration of this insulin-sensitising effect of HBOT. Men who were obese or overweight but without diabetes were recruited. One study performed a hyperinsulinaemic euglycaemic glucose clamp (80 mU.m-2.min-1) at baseline and during the first HBOT exposure (n = 9) at a pressure of 203 kPa. Data were analysed by paired t-test. The other study assessed insulin sensitivity by a frequently sampled intravenous glucose tolerance test (FSIGT) at three time points: baseline, during the third HBOT and 24-hours post-HBOT (n = 9). Results were analysed by repeated-measures ANOVA. There was a significant 23% increase in insulin sensitivity by clamp measured during the first HBOT exposure. The FSIGT showed no significant changes in insulin sensitivity. The hyperinsulinaemic, euglycaemic glucose clamp demonstrated a significant increase in peripheral insulin sensitivity during a single, 2-hour HBOT session in a group of men who were obese or overweight but without diabetes. As an alternate technique for assessing insulin sensitivity during HBOT, the FSIGT failed to show any changes during the third HBOT and 24-hours later, however modification of the study protocol should be considered.

360-OR: BETA-2 Score Is Highly Correlated with Acute Insulin Response to Intravenous Glucose: An Analysis of the Clinical Islet Transplantation Consortium Trials

Accurate measurement of islet function after clinical islet transplantation (CIT) is challenging. Maximum insulin secretion can be estimated from the acute insulin response to glucose (AIRg) during frequently sampled intravenous glucose tolerance tests (FSIGT). BETA-2, a composite measure derived from a single blood test is practical for routine use. To test the validity of BETA-2, we examined its relationship with AIRg in subjects participating in CIT Consortium trials. 128 C-peptide negative subjects (48.2 ± 10.9 yrs, 38.7% male) underwent 355 FSIGTs prior to and every 6 months after CIT. They received 1-3 islet infusions of &amp;gt;4000 IE/kg. AIRg was derived using the minimal model. BETA-2 was calculated within 90 days of FSIGT (&amp;gt;75% were within 1 day). BETA-2 is plotted against log (AIRg+1) with a loess smoothing curve. BETA-2 is linearly related to log(AIRg) particularly when AIRg &amp;gt; ∼ 6.5 (ie log(AIRg +1) &amp;gt; 2). A linear regression, after raising AIRgs below 6.5 to 6.5, shows an intercept close to 0, a slope of 8.71, and an R2 of 0.69. Limiting the linear regression to test pairs done on successive days had no significant or meaningful effect on this relation. BETA-2 is highly correlated with AIRg, which is related to maximum insulin release and can be used as a validated measure to estimate beta cell mass in CIT. Disclosure P.A. Senior: None. M.R. Rickels: Consultant; Self; Semma Therapeutics, Inc. Research Support; Self; Xeris Pharmaceuticals, Inc. T. Eggerman: None. L. Bayman: None. J. Qidwai: None. R. Alejandro: None. J.F. Markmann: None. L.G. Hunsicker: Advisory Panel; Self; Allergan plc., Bristol-Myers Squibb.

SAT-624 Predictive Ability of Lipoprotein Insulin Resistance (LPIR) Score in South Asians: A Comparison of Surrogate Indices of Insulin Sensitivity/Resistance

South Asians (SA) are at higher risk for developing insulin resistance (IR) and type 2 diabetes. Consequently, identifying IR in this population is important. Lack of standardization and harmonization of insulin assays limit the clinical use of insulin-based surrogate indexes of insulin resistance. The lipoprotein insulin resistance (LPIR) score, a metabolomic marker, reflects the lipoprotein abnormalities observed in insulin-resistant states. The reliability of the LPIR score to predict IR in South Asians is currently unknown. In this study, we aimed to evaluate the predictive accuracy of LPIR compared to other fasting-based surrogate indices in SA.In a cross-sectional study of 59 non-diabetic SA subjects (age 36 ± 8 years, BMI 26.5 ± 5.2 kg/m2), we used calibration model analysis to assess the ability of the LPIR score and other simple surrogate indices [homeostasis model assessment (HOMA-IR), quantitative insulin sensitivity check index (QUICKI) and Adipose tissue insulin sensitivity (Adipo-SI)] to predict insulin sensitivity derived from the reference frequently sampled intravenous glucose tolerance test (FSIVGTT) and Minimal Model analysis (SiMM). LPIR scores were calculated using six lipoprotein particle concentrations and sizes measured by nuclear magnetic resonance (NMR) spectroscopy. Further, quantitative predictive accuracy and index comparisons were determined by root mean squared error (RMSE) of prediction and leave-one-out cross-validation-type RMSE of prediction (CVPE). Receiver operating characteristic (ROC) curve analysis was performed to determine how well LPIR distinguished insulin resistant individuals, categorized as an SiMM < 3.As determined by calibration model analysis, Adipo-SI, HOMA-IR, and QUICKI showed moderate correlations with for SiMM (Adipo-SI: r = 0.66; HOMA-IR: r = 0.60; QUICKI: r = 0.57, p = <0.0001). No significant differences were noted among CVPE or RMSE from any of the routinely used surrogate indices when compared with LPIR. The ROC area under the curve was 0.76 (95% CI 0.64–0.87) suggesting that LPIR performed well in identifying insulin resistant subjects. The optimal cut-off in IR individuals was LPIR >46 (sensitivity: 75.9 %, specificity: 70.0%). We conclude that NMR-derived LPIR may be an appropriate index to assess insulin resistance in South Asians.

Bacitracin attenuates haemolysis-induced insulin degradation during insulin sensitivity testing: Repurposing an old drug for use in metabolic research.

Haemolysis of serially collected insulin serum samples frequently causes falsely-low measured concentrations because of the release of intracellular insulin degrading enzyme (IDE). We investigated if bacitracin, an in vitro IDE inhibitor, could prevent haemolysis-induced insulin degradation during insulin sensitivity testing. Blood samples were collected from adults undergoing serial sampling for insulin sensitivity. A dose-finding study measured insulin from experimentally haemolysed samples containing five bacitracin concentrations (0-2.5 g/L) and from non-experimentally haemolysed samples. To confirm the utility of bacitracin in the clinical setting, we compared insulin in samples collected with and without 1 g/L bacitracin from a frequently sampled intravenous glucose tolerance test (FSIVGTT), where haemolysis often occurs accidentally. In the dose-finding study, bacitracin 0.25, 1 and 2.5 g/L all maximally prevented insulin degradation in experimentally haemolysed samples. Among FSIVGTT unintentionally haemolysed samples, insulin concentrations from bacitracin-containing samples were significantly higher than from those without bacitracin (P < .01), and not different from non-haemolysed samples obtained simultaneously from a second intravenous catheter (P = .07). Bacitracin did not significantly alter insulin concentrations in non-haemolysed samples. Bacitracin attenuates haemolysis-associated insulin degradation in clinical samples, enabling a more accurate assessment of insulin sensitivity and glucose homeostasis.

Trafficking of nonesterified fatty acids in insulin resistance and relationship to dysglycemia.

In adipose, insulin functions to suppress intracellular lipolysis and secretion of nonesterified fatty acid (NEFA) into plasma. We applied glucose and NEFA minimal models (MM) following a frequently sampled intravenous glucose tolerance test (FSIVGTT) to assess glucose-specific and NEFA-specific insulin resistance. We used total NEFA and individual fatty acids in the NEFA MM, comparing the model parameters in metabolic syndrome (MetSyn) subjects (n = 52) with optimally healthy controls (OptHC; n = 14). Results are reported as mean difference (95% confidence interval). Using the glucose MM, MetSyn subjects had lower [-73% (-82, -57)] sensitivity to insulin (Si) and higher [138% (44, 293)] acute insulin response to glucose (AIRg). Using the NEFA MM, MetSyn subjects had lower [-24% (-35, -13)] percent suppression, higher [32% (15, 52)] threshold glucose (gs), and a higher [81% (12, 192)] affinity constant altering NEFA secretion (ϕ). Comparing fatty acids, percent suppression was lower in myristic acid (MA) than in all other fatty acids, and the stearic acid (SA) response was so unique that it did not fit the NEFA MM. MA and SA percent of total were increased at 50 min after glucose injection, whereas oleic acid (OA) and palmitic acid (PA) were decreased (P < 0.05). We conclude that the NEFA MM, as well as the response of individual NEFA fatty acids after a FSIVGTT, differ between OptHC and MetSyn subjects and that the NEFA MM parameters differ between individual fatty acids.

The effect of pregnancy on nitrogen retention, maternal insulin sensitivity, and mRNA abundance of genes involved in energy and amino acid metabolism in gilts.

Twenty-one of each pregnant (P) and nonserviced, nonpregnant (NP) sister-pairs of gilts were selected to investigate the effect of pregnancy on protein deposition (Pd; whole body and maternal), insulin sensitivity, and mRNA abundance of genes involved in energy and AA metabolism. Between breeding (study day 0) and day 111, P and NP gilts received 2.16 kg of the experimental diet (3.34 Mcal ME/kg, 17.6% crude protein, 0.78% standardized ileal digestible lysine) that was formulated to meet the estimated ME requirements of pregnant gilts (and meet or exceed AA requirements). Nitrogen balances were conducted on day 63 and 102 ± 0.2 of the study during 4-d periods. Blood samples were collected on day 43, 56, 71, 85, 98, and 108 ± 0.3 of the study to determine plasma concentrations of fasted IGF-1, estradiol (E2), and estrone sulfate (E1S). Frequently sampled intravenous glucose tolerance tests (FSIGTT) were conducted on day 75 ± 0.7 in 6 P and 5 NP gilts and on day 107 ± 0.4 in 17 P and 17 NP gilts and the MINMOD approach was applied to evaluate whole body insulin sensitivity and pancreatic responsiveness. Longissimus muscle (LM) and s.c. adipose tissue (AD) samples were excised from 12 P and 12 NP gilts at day 111 ± 0.4 of the study after euthanasia to determine mRNA abundance of key genes. Whole body Pd was greater (P < 0.001) at day 102 and maternal Pd was lower (P < 0.002) at day 63 and 102 for P compared to NP gilts. Plasma concentrations of E1S and E2 increased (P < 0.05) with study day for P gilts and remained constant for NP gilts, which coincided with reduced plasma concentrations of IGF-1 and increased estrogen receptor alpha (ESR1) mRNA abundance in LM of P gilts. Glucose effectiveness was not different between P and NP gilts, but whole body insulin sensitivity was lower (P = 0.004) in P compared to NP gilts on day 75 and 107, which corresponded with reduced mRNA abundances of SLC2A4, HK2, SREBF1, and FASN, and increased abundances of PDK4 and PPARGC1A in LM and AD. When fed identically, P gilts had greater whole body Pd at day 102, which reflects Pd in the pregnancy-associated tissues (at the expense of maternal Pd), likely driven by estrogen-stimulated insulin resistance in peripheral tissue and subsequent modulation of gene expression relating to glucose metabolism.

1330-P: Ethnic Differences in Insulin Clearance: Relationship with Admixture Scores, Diet, and Physical Activity

Recent studies showed that hepatic insulin clearance is lower in African Americans (AA) than European Americans (EA). The aim of this work is to elucidate the possible genetic/epigenetic versus lifestyle causes. The frequently-sampled intravenous glucose tolerance test (FSIGT) was performed in 142 children [38 AA, 69 EA, 28 HA (Hispanic Americans), both sexes, age 7-13 years, mean BMI = 19 kg/m2, basal plasma glucose = 99 mg/dL, insulin = 78 pmol/L, C-peptide = 511 pmol/L]. Mathematical modeling provided hepatic (FEL) and extra-hepatic (CLP) insulin clearance values. Two-way analysis of covariance was done (groups: sex and ethnicity, covariates: age, Tanner stage and body fat from DXA). Data are mean (standard error). FEL was lower in AA than EA (18% (2%) vs. 31% (3%), p=0.001), but no difference was observed in HA. CLP was not different among ethnicities. Partial correlation was calculated between FEL, CLP and 1) diet composition (energy intake, % of calories from carbohydrate, fat, protein), 2) physical activity (PA: light, moderate, hard, very hard), 3) admixture scores (African, European, Amerindian). FEL was positively correlated with the European admixture score (r=0.3, p&amp;lt;0.01), and negatively with the African one (r=-0.3, p=0.001); FEL was negatively associated with moderate PA in all the subjects (r=-0.2, p=0.01), and with hard PA in EA (r=-0.4, p&amp;lt;0.01). CLP was positively correlated with moderate PA in AA (r=0.4, p=0.02). Concerning diet, FEL was only correlated with % of calories from fat in EA (r=0.3, p=0.01). Because of its negative association with the African admixture, but positive with the European one, the lower hepatic insulin clearance might be genetic in origin, possibly resulting in hyperinsulinemia and diabetes risk. Our data also suggest that detrimental effects of lower insulin clearance might be mitigated by lifestyle changes such as exercise: moderate PA in AA could lead to a normalization of insulinemia by increasing extra-hepatic insulin clearance. Disclosure F. Piccinini: None. B. Gower: None. J.R. Fernandez: None. R.N. Bergman: Consultant; Self; Zafgen, Inc. Funding National Institute of Diabetes and Digestive and Kidney Diseases (DK067426); Nutrition Obesity Research Center (DK56336); National Institutes of Health (M01RR00032)

OR28-6 Short-Term Mifepristone Treatment Improves Hepatic and Adipose Tissue Insulin Sensitivity in Overweight and Obese Subjects with Glucose Intolerance

Background: Increased tissue cortisol availability and enhanced glucocorticoid action have been implicated in abnormal glucose and fat metabolism in patients with obesity, metabolic syndrome, and type 2 diabetes. Objective: To test the hypothesis that blockade of glucocorticoid receptor (GR) with mifepristone ameliorates insulin resistance in overweight/obese subjects with glucose intolerance. Design: We conducted a randomized, placebo-controlled, double-blind, crossover trial of mifepristone (50 mg orally, every six hr) in overweight/obese subjects (BMI 25-37 kg/m2), with abnormal glucose tolerance (n=16, women=7). Participants (age:56 ± 8 yr) had prediabetes (n=12) or mild type 2 DM (n=4, A1c < 7%) on diet control or stable dose of metformin for 3 months (n=2). Mifepristone or placebo treatment for one week was followed by a 6-8-week washout and crossover to the other arm. At baseline, and after each treatment period, insulin sensitivity was assessed by a frequently sampled intravenous glucose tolerance test (FSIVGTT) and an oral glucose tolerance test (OGTT). Whole body glucose disposal index of insulin sensitivity (SI) was derived using a Minimal model analysis. Adipose tissue-SI, which reflects insulin-induced free fatty acid (FFA) suppression, was estimated by the log-linear slope of FFA levels during the FSIVGTT. Matsuda index, oral glucose insulin sensitivity index (OGIS, ml/min/m2), and hepatic insulin resistance index (HIRI, mg/dL×µU/mL×105) were derived from OGTT. Adipo-IR, a surrogate measure of adipocyte insulin resistance, was calculated by multiplying fasting concentrations of FFA and insulin (mmol×pmol/L). Comparison of various post-treatment parameters was performed using crossover ANOVA. This analysis takes into account specific treatment arm, treatment order, and treatment effects. Thus, we explicitly tested for carryover effects in our crossover study. Results: GR blockade did not affect body weight (p=0.56) or fasting glucose (p=0.67), but significantly decreased fasting insulin levels when compared with placebo [mean (95%CI): -40.7 (-68.53 to -12.91), p=0.007]. Mifepristone administration for one week did not alter whole body glucose disposal indices of insulin sensitivity (FSIVGTT-Si: p=0.52, Matsuda Index: p=0.74; and OGIS: p=0.75). However, GR blockade reduced HIRI [-19.80 (-40.76 to 1.15), p=0.05], Adipo-IR [-15.54 (-31.47 to 0.37), p=0.04], and improved Adipose-SI [-19.75 (-31.41 to -8.08), p=0.003]. Conclusions: In patients with abnormal glucose tolerance, short-term GR blockade improved hepatic and adipose tissue insulin sensitivity without significantly altering whole-body insulin sensitivity. These findings suggest that GR may be a therapeutic target in insulin-resistant states. Unless otherwise noted, all abstracts presented at ENDO are embargoed until the date and time of presentation. For oral presentations, the abstracts are embargoed until the session begins. s presented at a news conference are embargoed until the date and time of the news conference. The Endocrine Society reserves the right to lift the embargo on specific abstracts that are selected for promotion prior to or during ENDO.