Postprandial fatty acid-binding protein 4 is associated with muscle insulin resistance.

AIMS/HYPOTHESIS: Fatty acid-binding protein 4 (FABP4) has been reported to act as a hepatic insulin resistance factor. We previously reported that fasting FABP4 was correlated with insulin resistance measurements derived from the glucose clamp, and another study reported that postprandial FABP4 levels were decreased in healthy volunteers but were not reported (or known) in participants with type 2 diabetes. We have limited knowledge about the direct effect of FABP4 on muscle cells. We investigated the postprandial FABP4 levels in participants with type 2 diabetes, and the basic mechanism of muscle insulin resistance and FABP4. METHODS: We performed a meal tolerance test and hyperinsulinaemic-euglycaemic clamp in 22 participants with type 2 diabetes and 26 participants without diabetes. We measured fasting and postprandial serum FABP4. We cultured mouse C2C12 muscle cells, and investigated the effect of FABP4 on glucose uptake. We analysed insulin signalling by western blot and insulin binding assay. RESULTS: The postprandial FABP4 level in participants with type 2 diabetes was higher than that in participants without diabetes. Participants without diabetes had lower postprandial FABP4 than fasting except for one participant, whereas one-third of participants with type 2 diabetes had higher postprandial FABP4 than fasting. Postprandial FABP4 was correlated with the muscle insulin resistance M/I value from a glucose clamp in participants without diabetes (r=-0.42, p<0.05). The increase in FABP4 after a meal correlated with the muscle insulin resistance M/I value (r=-0.44, p<0.05) and the difference between fasting and postprandial glucagon in participants with type 2 diabetes (r=0.36, p<0.05). FABP4 alone appears to increase glucose uptake, and the combination of FABP4 and insulin decreases glucose uptake when compared with insulin alone. FABP4 inhibits insulin signalling of muscle cells through decreases in phosphorylation of insulin receptor substrate 1 and Akt. The physiological concentration of FABP4 did not inhibit insulin binding to muscle cells. CONCLUSIONS/INTERPRETATION: These results suggested that the postprandial FABP4 level is associated with insulin resistance, and FABP4 may suppress insulin signals.

Comparison of an oral mixed meal plus arginine and intravenous glucose, GLP-1 plus arginine to unmask residual islet function in longstanding type 1 diabetes.

Residual beta cells are present in most patients with longstanding type 1 diabetes but it is unknown whether these beta cells react normally to different stimuli. Moreover a defect in proinsulin conversion and abnormal alpha cell response are also part of the islet dysfunction. A three-phase [euglycemia, hyperglycemia, and hyperglycemia + glucagon-like peptide 1 (GLP-1)] clamp was performed in patients with longstanding type 1 diabetes. Intravenous arginine boluses were administered at the end of each phase. On another day, a mixed meal stimulation test with a subsequent intravenous arginine bolus was performed. C-peptide was detectable in a subgroup of subjects at baseline (2/15) or only after stimulation (3/15). When detectable, C-peptide increased 2.9-fold [95% CI: 1.2-7.1] during the hyperglycemia phase and 14.1-fold [95% CI: 3.1-65.2] during the hyperglycemia + GLP-1 phase, and 22.3-fold [95% CI: 5.6-89.1] during hyperglycemia + GLP-1 + arginine phase when compared with baseline. The same subset of patients with a C-peptide response were identified during the mixed meal stimulation test as during the clamp. There was an inhibition of glucagon secretion (0.72-fold, [95% CI: 0.63-0.84]) during the glucose clamp irrespective of the presence of detectable beta cell function. Proinsulin was only present in a subset of subjects with detectable C-peptide (3/15) and proinsulin mimicked the C-peptide response to the different stimuli when detectable. Residual beta cells in longstanding type 1 diabetes respond adequately to different stimuli and could be of clinical benefit.NEW & NOTEWORTHY If beta cell function is detectable, the beta cells react relatively normal to the different stimuli except for the first phase response to intravenous glucose. An oral mixed meal followed by an intravenous arginine bolus can identify residual beta cell function/mass as well as the more commonly used glucose potentiated arginine-induced insulin secretion during a hyperglycemic clamp.

Chronic hyperglycaemia increases the vulnerability of the hippocampus to oxidative damage induced during post-hypoglycaemic hyperglycaemia in a mouse model of chemically induced type 1 diabetes.

AIMS/HYPOTHESIS: Chronic hyperglycaemia and recurrent hypoglycaemia are independently associated with accelerated cognitive decline in type 1 diabetes. Recurrent hypoglycaemia in rodent models of chemically induced (streptozotocin [STZ]) diabetes leads to cognitive impairment in memory-related tasks associated with hippocampal oxidative damage. This study examined the hypothesis that post-hypoglycaemic hyperglycaemia in STZ-diabetes exacerbates hippocampal oxidative stress and explored potential contributory mechanisms. METHODS: The hyperinsulinaemic glucose clamp technique was used to induce equivalent hypoglycaemia and to control post-hypoglycaemic glucose levels in mice with and without STZ-diabetes and Nrf2-/- mice (lacking Nrf2 [also known as Nfe2l2]). Subsequently, quantitative proteomics based on stable isotope labelling by amino acids in cell culture and biochemical approaches were used to assess oxidative damage and explore contributory pathways. RESULTS: Evidence of hippocampal oxidative damage was most marked in mice with STZ-diabetes exposed to post-hypoglycaemic hyperglycaemia; these mice also showed induction of Nrf2 and the Nrf2 transcriptional targets Sod2 and Hmox-1. In this group, hypoglycaemia induced a significant upregulation of proteins involved in alternative fuel provision, reductive biosynthesis and degradation of damaged proteins, and a significant downregulation of proteins mediating the stress response. Key differences emerged between mice with and without STZ-diabetes following recovery from hypoglycaemia in proteins mediating the stress response and reductive biosynthesis. CONCLUSIONS/INTERPRETATION: There is a disruption of the cellular response to a hypoglycaemic challenge in mice with STZ-induced diabetes that is not seen in wild-type non-diabetic animals. The chronic hyperglycaemia of diabetes and post-hypoglycaemic hyperglycaemia act synergistically to induce oxidative stress and damage in the hippocampus, possibly leading to irreversible damage/modification to proteins or synapses between cells. In conclusion, recurrent hypoglycaemia in sub-optimally controlled diabetes may contribute, at least in part, to accelerated cognitive decline through amplifying oxidative damage in key brain regions, such as the hippocampus. DATA AVAILABILITY: The datasets generated during and/or analysed during the current study are available in ProteomeXchange, accession no. 1-20220824-173727 ( www.proteomexchange.org ). Additional datasets generated during and/or analysed during the present study are available from the corresponding author upon reasonable request.

Precision and accuracy of hyperglycemic clamps in a multicenter study.

Application of glucose clamp methodologies in multicenter studies brings challenges for standardization. The Restoring Insulin Secretion (RISE) Consortium implemented a hyperglycemic clamp protocol across seven centers using a combination of technical and management approaches to achieve standardization. Two-stage hyperglycemic clamps with glucose targets of 200 mg/dL and >450 mg/dL were performed utilizing a centralized spreadsheet-based algorithm that guided dextrose infusion rates using bedside plasma glucose measurements. Clamp operators received initial and repeated training with ongoing feedback based on surveillance of clamp performance. The precision and accuracy of the achieved stage-specific glucose targets were evaluated, including differences by study center. We also evaluated robustness of the method to baseline physiologic differences and on-study treatment effects. The RISE approach produced high overall precision (3%-9% variance in achieved plasma glucose from target at various times across the procedure) and accuracy (SD < 10% overall). Statistically significant but numerically small differences in achieved target glucose concentrations were observed across study centers, within the magnitude of the observed technical variability. Variation of the achieved target glucose over time in placebo-treated individuals was low (<3% variation), and the method was robust to differences in baseline physiology (youth vs. adult, IGT vs. diabetes status) and differences in physiology induced by study treatments. The RISE approach to standardization of the hyperglycemic clamp methodology across multiple study centers produced technically excellent standardization of achieved glucose concentrations. This approach provides a reliable method for implementing glucose clamp methodology across multiple study centers.NEW & NOTEWORTHY The Restoring Insulin Secretion (RISE) study centers undertook hyperglycemic clamps using a simplified methodology and a decision guidance algorithm implemented in an easy-to-use spreadsheet. This approach, combined with active management including ongoing central data surveillance and routine feedback to study centers, produced technically excellent standardization of achieved glucose concentrations on repeat studies within and across study centers.

Chronic treatment of JTP-109192, a novel G-protein coupled receptor 119 agonist, improves metabolic abnormalities in Zucker Fatty rats.

G-protein coupled receptor 119 (GPR119) expression in pancreatic ß-cells and intestinal L cells is a potential therapeutic target for treating type 2 diabetes. A natural GPR119 agonist oleoylethanolamide is well known to enhance a glucose-stimulated insulin secretion (GSIS) and glucagon-like peptide-1 (GLP-1) secretion by elevating intracellular cAMP levels. In the present study, a glucose lowering effect of the GPR119 agonist, JTP-109192 leading to improvement of insulin sensitivity was examined in Zucker Fatty (ZF) rats. We investigated the in vitro effects of JTP-109192 on GSIS in the rat pancreatic ß-cell line (INS1E) cells and on GLP-1 secretion in the murine enteroendocrine cell line (GLUTag) cells. We also investigated the effect of JTP-109192 on GSIS in Sprague-Dawley (SD) rats with single administration and its effect on glucose metabolism in ZF rats with repeated administration once daily for about 6 weeks. After repeated administration, the hyperinsulinaemic euglycaemic glucose clamp test was performed to evaluate insulin sensitivity. JTP-109192 increased intracellular cAMP levels (EC50 value: 3.6 nmol/L) and enhanced GSIS in the INS1E cells and GLP-1 secretion in GLUTag cells. In SD rats, a single administration of JTP-109192 enhanced GSIS at high blood glucose levels. The repeated administrations in ZF rats improved glucose metabolism without lack of drug efficacy (tachyphylaxis) and increased glucose infusion rates due to improvement of insulin sensitivity.

Carbohydrate oxidation and glucose utilisation under hyperglycaemia in aged and young males during exercise at the same relative exercise intensity.

PURPOSE: The purpose of the present study was to investigate the age-related carbohydrate oxidation and glucose utilisation rate response during exercise at the same relative intensity under hyperglycaemia in aged and young males. METHODS: 16 endurance-trained aged (n = 8; 69.1 ± 5.2 year) and young (n = 8; 22.4 ± 2.9 year) males were studied during 40 min of cycling exercise (60% [Formula: see text]) under both hyperglycaemic and euglycaemic (control) conditions. Venous blood samples were collected at baseline, post-infusion, mid- and post-exercise. Carbohydrate and fat oxidation rates were determined at both 15 and 35 min during exercise, and glucose utilisation rates were calculated. RESULTS: The aged group displayed significantly lower rates of carbohydrate oxidation during exercise during maintained hyperglycemia (15 min = 2.3 ± 0.4 vs. 1.6 ± 0.5 g min-1; 35 min = 2.3 ± 0.5 vs. 1.5 ± 0.5 g min-1) and control (15 min = 2.2 ± 0.4 vs. 1.6 ± 0.7 g min-1; 35 min = 1.9 ± 0.7 vs. 1.3 ± 0.7 g min-1) conditions (P = 0.01). The rate of glucose utilisation during exercise was also significantly reduced (85.76 ± 23.95 vs. 56.67 ± 15.09 µM kg-1 min-1). There were no differences between age groups for anthropometric measures, fat oxidation, insulin, glucose, NEFA, glycerol and lactate (P > 0.05) although hyperglycemia resulted in elevated glucose and insulin, and attenuated fat metabolite levels. CONCLUSION: Our findings highlight that ageing results in a reduction in carbohydrate oxidation and utilisation rates during exercise at the same relative exercise intensity.

[Quality Assessment of Euglycemic Glucose Clamp Test].

OBJECTIVE: To explorethe quality of euglycemic glucose clamptest performed in the West China Hospital from 2014 to 2017 and to evaluate whether the quality control indexes are suitable for the quality assessment of the clamp test. METHODS: The data collected from 80 euglycemic glucose clamp tests performed between 2014 and2017 were divided into 4 groups according to the coefficient of variation of the blood glucose concentrations (CVBG): group A (CVBG≤4.5%), group B (4.5% < CVBG≤5.0%), group C (5.0% < CVBG≤5.5%) and group D(CVBG > 5.5%).The differences in percentage of glucose excursion from target range (GEFTR), the duration of GEFTR, the area under curve (AUC) of GEFTR, the mean value of excursion from target glucose (GEFT) and the AUC of GEFT were calculated and compared. RESULTS: In group A, the mean value of CVBG was 3.75%. In group B, the mean value of CVBG was 4.76%. In group C, the mean value of CVBG was 5.28%. The median value of CVBG in group D was 6.07%. The percentage of GEFTR, the duration of GEFTR, the AUC of GEFTR, the mean value of GEFT and the AUC of GEFT in group A were all less than those of other groups (P < 0.05).For the same indexes, there were no significant differences between group B and C, while they were higher in group D compared with the other three groups. CVBG was positively correlated with other quality control indexes (correlation coefficient r was 0.770-0.805). Based on the cut-off point 5% of CVBG, the cut-off points of the percentage of GEFTR, the duration of GEFTR, the AUC of GEFTR, the mean value of GEFT and the AUC of GEFT were 5.8%, 14.6 min, 22.82 mg/dL×min, 3.23 mg/dL, 216.25 mg/dL×min/h respectively, with the sensitivity range from 79.3% to 100% and the specificity range from 74.5% to 89.7%.Combined with these indexes, 8.11% of euglycemic clamps were found to havepoor quality in group A, while 66.67% of euglycemic clamps showed acceptable quality in group C. CONCLUSIONS: The investigators should provide an estimation of the quality of the clamps when reporting the results of the insulin analogues' PK/PD characteristics using euglycemic clamps. CVBG less than 4.5% indicates a good quality, and the above-mentioned quality control indexes especially the AUC of GEFT(cut-off point: 216.25 mg·/dL×min/h) should be evaluated when CVBG is more than 4.5%.False high quality and false low quality euglycemic clamps will be detected and a more precise estimation of quality assessment should be made by the combination of these indexes.

Prediction of clamp-derived insulin sensitivity from the oral glucose insulin sensitivity index.

AIMS/HYPOTHESIS: The euglycaemic-hyperinsulinaemic clamp is the gold-standard method for measuring insulin sensitivity, but is less suitable for large clinical trials. Thus, several indices have been developed for evaluating insulin sensitivity from the oral glucose tolerance test (OGTT). However, most of them yield values different from those obtained by the clamp method. The aim of this study was to develop a new index to predict clamp-derived insulin sensitivity (M value) from the OGTT-derived oral glucose insulin sensitivity index (OGIS). METHODS: We analysed datasets of people that underwent both a clamp and an OGTT or meal test, thereby allowing calculation of both the M value and OGIS. The population was divided into a training and a validation cohort (n = 359 and n = 154, respectively). After a stepwise selection approach, the best model for M value prediction was applied to the validation cohort. This cohort was also divided into subgroups according to glucose tolerance, obesity category and age. RESULTS: The new index, called PREDIcted M (PREDIM), was based on OGIS, BMI, 2 h glucose during OGTT and fasting insulin. Bland-Altman analysis revealed a good relationship between the M value and PREDIM in the validation dataset (only 9 of 154 observations outside limits of agreement). Also, no significant differences were found between the M value and PREDIM (equivalence test: p < 0.0063). Subgroup stratification showed that measured M value and PREDIM have a similar ability to detect intergroup differences (p < 0.02, both M value and PREDIM). CONCLUSIONS/INTERPRETATION: The new index PREDIM provides excellent prediction of M values from OGTT or meal data, thereby allowing comparison of insulin sensitivity between studies using different tests.

Short-term effects of dapagliflozin on insulin sensitivity, postprandial glucose excursion and ketogenesis in type 1 diabetes mellitus: A randomized, placebo-controlled, double blind, cross-over pilot study.

We investigated the short-term effects of dapagliflozin as adjunct to insulin on insulin sensitivity, postprandial glucose excursions and ketone body production in type 1 diabetes mellitus (T1DM). A total of seven male patients completed the randomized, double-blind, placebo-controlled cross-over trial, receiving 10 mg of dapagliflozin daily for 3 days, followed by placebo, or the reverse. At Day 3, hyperinsulinaemic, euglycaemic clamps and oral glucose tolerance test clamps with repeated blood sampling were performed. Required glucose infusion and blood glucose excursions did not differ significantly between dapagliflozin treatment and placebo (P = 0.491; P = 0.342). Prior to oral glucose, total ketone bodies showed a higher trend following dapagliflozin treatment (P = 0.051). Following oral glucose, total ketone bodies decreased while concentrations of total GLP-1 were higher following dapagliflozin (P = 0.009). Non-esterified free fatty acids did not differ between dapagliflozin treatment and placebo and ketonuria was absent under both conditions. In T1DM, short-term addition of dapagliflozin to insulin influenced neither postprandial glucose excursions nor insulin sensitivity. Following oral glucose, total ketone bodies decreased in parallel with an increase in GLP-1 concentrations, which were higher under dapagliflozin treatment as compared with placebo.

Sagittal abdominal diameter resembles waist circumference as a surrogate marker of insulin resistance in adolescents-Brazilian Metabolic Syndrome Study.

OBJECTIVE: To evaluate the association of the sagittal abdominal diameter (SAD) with insulin resistance (IR) and metabolic syndrome (MetS) components, and to compare SAD with waist circumference (WC). SUBJECTS/METHODS: This was a multicenter, cross-sectional study of 520 adolescents (10- to 18-years old). IR was assessed using the homeostasis model assessment of IR (HOMA-IR) and the hyperglycaemic clamp (n = 76). RESULTS: SAD and WC were positively correlated with HOMA-IR (r = 0.637 and r = 0.653) and inversely correlated with the clamp-derived insulin sensitivity index (ISI) (r = -0.734 and r = -0.731); P < .001. In the multivariable linear regression analysis, SAD was positively associated with HOMA-IR (B = 0.046 ± 0.003) and inversely associated with the clamp-derived ISI (B = -0.084 ± 0.009) after adjusting for sex, age, and Tanner's stages (P < .001). When WC replaced the SAD, it was positively associated with HOMA-IR (B = 0.011 ± 0.001) and inversely associated with the clamp-derived ISI (B = -0.018 ± 0.002); P < .001. The values of the areas under the curves (AUC) were 0.823 and 0.813 for SAD and WC, respectively. In Bland-Altman analysis, there were agreement between both, SAD and WC, with the clamp-derived ISI (mean = 0.00; P > .05). The SAD and WC were positively associated with blood pressure, triglycerides, and uric acid, and inversely associated with high-density lipoprotein (HDL)-cholesterol after adjusting for sex, age, and Tanner's stages. CONCLUSION: The SAD was associated with IR and MetS components, with a good discriminatory power for detecting IR. When compared to WC, SAD showed equivalent results.

Insulin-Sensitizer Effects of Fenugreek Seeds in Parallel with Changes in Plasma MCH Levels in Healthy Volunteers.

In developed, developing and low-income countries alike, type 2 diabetes mellitus (T2DM) is one of the most common chronic diseases, the severity of which is substantially a consequence of multiple organ complications that occur due to long-term progression of the disease before diagnosis and treatment. Despite enormous investment into the characterization of the disease, its long-term management remains problematic, with those afflicted enduring significant degradation in quality-of-life. Current research efforts into the etiology and pathogenesis of T2DM, are focused on defining aberrations in cellular physiology that result in development of insulin resistance and strategies for increasing insulin sensitivity, along with downstream effects on T2DM pathogenesis. Ongoing use of plant-derived naturally occurring materials to delay the onset of the disease or alleviate symptoms is viewed by clinicians as particularly desirable due to well-established efficacy and minimal toxicity of such preparations, along with generally lower per-patient costs, in comparison to many modern pharmaceuticals. A particularly attractive candidate in this respect, is fenugreek, a plant that has been used as a flavouring in human diet through recorded history. The present study assessed the insulin-sensitizing effect of fenugreek seeds in a cohort of human volunteers, and tested a hypothesis that melanin-concentrating hormone (MCH) acts as a critical determinant of this effect. A test of the hypothesis was undertaken using a hyperinsulinemic euglycemic glucose clamp approach to assess insulin sensitivity in response to oral administration of a fenugreek seed preparation to healthy subjects. Outcomes of these evaluations demonstrated significant improvement in glucose tolerance, especially in patients with impaired glucose responses. Outcome data further suggested that fenugreek seed intake-mediated improvement in insulin sensitivity correlated with reduction in MCH levels.

A new model to estimate insulin resistance via clinical parameters in adults with type 1 diabetes.

AIMS/HYPOTHESIS: Insulin resistance (IR) is a risk factor to assess the development of micro- and macro-vascular complications in type 1 diabetes (T1D). However, diabetes management in adults with T1D is limited by the difficulty of lacking simple and reliable methods to estimate insulin resistance. The aim of this study was to develop a new model to estimate IR via clinical parameters in adults with T1D. METHODS: A total of 36 adults with adulthood onset T1D (n = 20) or childhood onset T1D (n = 16) were recruited by quota sampling. After an overnight insulin infusion to stabilize the blood glucose at 5.6 to 7.8 mmol/L, they underwent a 180-minute euglycemic-hyperinsulinemic clamp. Glucose disposal rate (GDR, mg kg-1  min-1 ) was calculated by data collected from the last 30 minutes during the test. Demographic factors (age, sex, and diabetes duration) and metabolic parameters (blood pressure, glycated hemoglobin A1c [HbA1c ], waist to hip ratio [WHR], and lipids) were collected to evaluate insulin resistance. Then, age at diabetes onset and clinical parameters were used to develop a model to estimate lnGDR by stepwise linear regression. RESULTS: From the stepwise process, a best model to estimate insulin resistance was generated, including HbA1c , diastolic blood pressure, and WHR. Age at diabetes onset did not enter any of the models. We proposed the following new model to estimate IR as in GDR for adults with T1D: lnGDR = 4.964 - 0.121 × HbA1c (%) - 0.012 × diastolic blood pressure (mmHg) - 1.409 × WHR, (adjusted R2  = 0.616, P < .01). CONCLUSIONS/INTERPRETATION: Insulin resistance in adults living with T1D can be estimated using routinely collected clinical parameters. This simple model provides a potential tool for estimating IR in large-scale epidemiological studies of adults with T1D regardless of age at onset.

Euglycaemic glucose clamp: what it can and cannot do, and how to do it.

The hyperinsulinaemic-euglycaemic glucose clamp has always been regarded as the "gold standard" for the assessment of pharmacodynamic (PD) properties of insulin preparations; however, there has been controversy over a variety of methodogical details, such as study population, dosing time and the initial stabilization of blood glucose (BG) concentrations at the clamp target level, among clamp groups. As the impact of these details on PD results is unclear, the present review provides an overview of different methodological approaches for both the manual and the automated hyperinsulinaemic-euglycaemic glucose clamp. The advantages and limitations of several methodological details are discussed as well as the relevance of clamp results for the prediction of clinical outcomes. Overall, the best method strongly depends on the exact objective of the trial. If, for instance, duration of action is the primary objective, studies should be carried out in patients with type 1 diabetes to avoid any interference of endogenous insulin. This is less important for variables such as onset of action or early metabolic activity. The hyperinsulinaemic-euglycaemic glucose clamp has a high sensitivity to detect even minor differences between different insulin preparations. The practical relevance of potential differences, however, needs to be investigated in clinical studies. A major prerequisite for obtaining reliable glucose clamp results is the attainment of high clamp quality (i.e. keeping BG concentrations close to the clamp target throughout the experiments). Unfortunately, measures of clamp quality are often under-reported, as is the variability in PD profiles, although these might explain some unconfirmed extreme results obtained in a few clamp studies.

Does GLP-1 suppress its own basal secretion?

PURPOSE/AIM: Negative feedback controls in endocrine regulatory systems are well recognized. The incretins and their role in glucose regulation have been of major interest recently. Whether the same negative control system applies to the regulation of incretin secretion is not clear. We sought to examine the hypothesis that exogenous administration of glucagon like peptide-1, GLP-1(7-36) amide or its metabolite GLP-1(9-36) amide, reduces the endogenous basal release of this incretin. MATERIALS AND METHODS: We evaluated the endogenous basal release of GLP-1 using two separate study designs. In protocol A we examined the GLP-1(7-36) amide levels during the infusion of GLP-1(9-36) amide. In protocol B, we used PYY and GLP-2 as biomarkers for the endogenous basal release of GLP-1(7-36) amide and assessed the endogenous basal release of these two hormones during the GLP-1(7-36) infusion. Twelve lean and 12 obese subjects were enrolled in protocol A and 10 obese volunteers in protocol B. RESULTS: The plasma levels of GLP-1(7-36) amide in protocol A and PYY and GLP-2 in protocol B remained unchanged during the exogenous infusion of GLP-1(9-36) and GLP-1(7-36) amide, respectively. CONCLUSIONS: The negative feedback control system as described by inhibition of the release of endogenous hormone while infusing it exogenously was not observed for the basal secretion of GLP-1(7-36) amide.

Early Clinical Detection of Pharmacologic Response in Insulin Action in a Nondiabetic Insulin-Resistant Population.

BACKGROUND: Insulin resistance heightens the risk for type 2 diabetes mellitus and cardiovascular disease. Amelioration of insulin resistance may reduce this risk. The thiazolidinedone class of insulin sensitizers improves insulin action in individuals with insulin-resistant diabetes and nondiabetic individuals. However, there are few reports on the time of onset of such effects independent of reversal of glucotoxicity. OBJECTIVE: The goal of our study was to test whether the thiazolidinedione pioglitazone has prominent early metabolic effects that can be detected in an obese, nondiabetic, insulin-resistant population. METHODS: We conducted a randomized, double-blind, placebo-controlled, parallel-group trial in men with nondiabetic insulin resistance using a hyperinsulinemic euglycemic clamp technique (at low and high doses of insulin at 10 and 40 mU/m(2)/min, respectively). The patients were given 30 mg daily oral pioglitazone or placebo for 28 days. Patients underwent a baseline clamp before initiation of treatment, and again at 14 and 28 days of treatment. RESULTS: Compared with placebo, under high-dose hyperinsulinemia, pioglitazone led to significant increases in glucose disposal rates (GDR) of 1.29 mg/kg/min (90% CI, 0.43-2.15; 39%; P=0.008) that were detectable at 2 weeks of treatment and persisted at 4 weeks of treatment. Under low-dose hyperinsulinemia, significant increases in GDR of 0.40 mg/kg/min (90% CI, 0.17-0.62; 95%; P=0.003) were observed at 4 weeks of treatment. These responses were accompanied by robust suppression of free fatty acids under hyperinsulinemic conditions, and by significant increases in circulating basal total adiponectin at 2 and 4 weeks of treatment. CONCLUSIONS: Significant changes in insulin action across multiple insulin-sensitive tissues can be detected within 2 weeks of initiation of insulin-sensitizing therapy with pioglitazone in obese patients with nondiabetic insulin resistance. ClinicalTrials.gov identifier: NCT01115712.

Estimation of insulin sensitivity in children: methods, measures and controversies.

Insulin resistance is defined as a state where insulin produces a diminished biological response, primarily in its capacity as a glucose-regulating hormone. Insulin resistance is commonly diagnosed by pediatric clinicians, but is rarely measured directly in children or adolescents. This review provides an overview of the techniques that can be used to assess insulin sensitivity in children, summarizing the methods involved, the assumptions, pitfalls, and appropriate uses of each technique, as well as their validation and reproducibility in pediatric samples.

Dual amylin and calcitonin receptor agonist treatment improves insulin sensitivity and increases muscle-specific glucose uptake independent of weight loss.

Dual amylin and calcitonin receptor agonists (DACRAs) are known to induce significant weight loss as well as improve glucose tolerance, glucose control, and insulin action in rats. However, to what extent DACRAs affect insulin sensitivity beyond that induced by weight loss and if DACRAs affect glucose turnover including tissue-specific glucose uptake is still unknown. Hyperinsulinemic glucose clamp studies were carried out in pre-diabetic ZDSD and diabetic ZDF rats treated with either the DACRA KBP or the long-acting DACRA KBP-A for 12 days. The glucose rate of disappearance was assessed using 3-3H glucose and tissue-specific glucose uptake was evaluated using 14C-2-deoxy-D-glucose (14C-2DG). In diabetic ZDF rats, KBP treatment significantly reduced fasting blood glucose and improved insulin sensitivity independent of weight loss. Furthermore, KBP increased the rate of glucose clearance, likely by increasing glucose storage, but without altering the endogenous glucose production. This was confirmed in pre-diabetic ZDSD rats. Direct assessment of tissue-specific glucose uptake showed, that both KBP and KBP-A significantly increased glucose uptake in muscles. In summary, KBP treatment significantly improved insulin sensitivity in diabetic rats and markedly increased glucose uptake in muscles. Importantly, in addition to their well-established weight loss potential, the KBPs have an insulin-sensitizing effect independent of weight loss, highlighting DACRAs as promising agents for the treatment of type 2 diabetes and obesity.

The threshold value for identifying insulin resistance (HOMA-IR) in an admixed adolescent population: A hyperglycemic clamp validated study.

Objective: To validate the homeostasis model assessment (HOMA) of insulin resistance (IR) as a surrogate to the hyperglycemic clamp to measure IR in both pubertal and postpubertal adolescents, and determine the HOMA-IR cutoff values for detecting IR in both pubertal stages. Subjects and methods: The study sample comprised 80 adolescents of both sexes (aged 10-18 years; 37 pubertal), in which IR was assessed with the HOMA-IR and the hyperglycemic clamp. Results: In the multivariable linear regression analysis, adjusted for sex, age, and waist circumference, the HOMA-IR was independently and negatively associated with the clamp-derived insulin sensitivity index in both pubertal (unstandardized coefficient - B = -0.087, 95% confidence interval [CI] = -0.135 to -0.040) and postpubertal (B = -0.101, 95% CI, -0.145 to -0.058) adolescents. Bland-Altman plots showed agreement between the predicted insulin sensitivity index and measured clamp-derived insulin sensitivity index in both pubertal stages (mean =-0.00 for pubertal and postpubertal); all P > 0.05. The HOMA-IR showed a good discriminatory power for detecting IR with an area under the receiver operator characteristic curve of 0.870 (95% CI, 0.718-0.957) in pubertal and 0.861 (95% CI, 0.721-0.947) in postpubertal adolescents; all P < 0.001. The optimal cutoff values of the HOMA-IR for detecting IR were > 3.22 (sensitivity, 85.7; 95% CI, 57.2-98.2; specificity, 82.6; 95% CI, 61.2-95.0) for pubertal and > 2.91 (sensitivity, 63.6; 95% CI, 30.8-89.1, specificity, 93.7; 95%CI, 79.2-99.2) for postpubertal adolescents. Conclusion: The threshold value of the HOMA-IR for identifying insulin resistance was > 3.22 for pubertal and > 2.91 for postpubertal adolescents.

Factors influencing bioequivalence evaluation of insulin biosimilars based on a structural equation model.

Objective: This study aimed to explore the factors affecting the bioequivalence of test and reference insulin preparations so as to provide a scientific basis for the consistency evaluation of the quality and efficacy of insulin biosimilars. Methods: A randomized, open, two-sequence, single-dose, crossover design was used in this study. Subjects were randomly divided into TR or RT groups in equal proportion. The glucose infusion rate and blood glucose were measured by a 24-h glucose clamp test to evaluate the pharmacodynamic parameters of the preparation. The plasma insulin concentration was determined by liquid chromatography-mass spectrometry (LC-MS/MS) to evaluate pharmacokinetic parameters. WinNonlin 8.1 and SPSS 23.0 were applied for PK/PD parameter calculation and statistical analysis. The structural equation model (SEM) was constructed to analyze the influencing factors of bioequivalence by using Amos 24.0. Results: A total of 177 healthy male subjects aged 18-45 years were analyzed. Subjects were assigned to the equivalent group (N = 55) and the non-equivalent group (N = 122) by bioequivalence results, according to the EMA guideline. Univariate analysis showed statistical differences in albumin, creatinine, Tmax, bioactive substance content, and adverse events between the two groups. In the structural equation model, adverse events (ß = 0.342; p < 0.001) and bioactive substance content (ß = -0.189; p = 0.007) had significant impacts on the bioequivalence of two preparations, and the bioactive substance content significantly affected adverse events (ß = 0.200; p = 0.007). Conclusion: A multivariate statistical model was used to explore the influencing factors for the bioequivalence of two preparations. According to the result of the structural equation model, we proposed that adverse events and bioactive substance content should be optimized for consistency evaluation of the quality and efficacy of insulin biosimilars. Furthermore, bioequivalence trials of insulin biosimilars should strictly obey inclusion and exclusion criteria to ensure the consistency of subjects and avoid confounding factors affecting the equivalence evaluation.

Aldehyde dehydrogenase 2 polymorphism is an important gene for insulin resistance in Japanese patients with type 2 diabetes.

Background: Aldehyde dehydrogenase 2 (ALDH2) is an important enzyme involved in alcohol metabolism. ALDH2 polymorphism has been reported as a risk factor for type 2 diabetes mellitus (T2DM) and is associated with liver insulin resistance due to alcohol consumption in non-diabetic individuals. Herein, we investigated the association between ALDH2 polymorphisms and insulin resistance in patients with T2DM. Methods: We performed a meal tolerance test and the hyperinsulinemic-euglycemic clamp on 71 Japanese participants: 34 patients with T2DM, and 37 non-diabetic participants. We analyzed the ALDH2 polymorphism (ALDH2 rs67); GG type was defined as the T2DM high-risk group, compared with the low-risk AG and AA groups. Results: Glucose levels were similar in the high- and low-risk T2DM groups. The high-risk group for T2DM showed a significantly higher BMI (p < 0.005), insulin resistance in HOMA-IR (p < 0.05), and Insulin sensitivity index (p < 0.05); however, there were no significant differences in insulin resistance in the clamp test (p = 0.10). Alcohol consumption did not differ significantly between groups (p = 0.66). Non-diabetic participants also showed higher HOMA-IR insulin resistance in the high-risk group (p < 0.05), but insulin resistance levels in the glucose clamp tests (p = 0.56) and insulin secretion were not significant. Conclusion: The results suggest that ALDH2 is an important gene associated with insulin resistance and obesity in Japanese patients with type 2 diabetes.