Reduction In Β-cell Function Research Articles

Reduced glucose-stimulated insulin secretion following a 1-wk IGF-1 infusion in late gestation fetal sheep is due to an intrinsic islet defect.

Insulin and insulin-like growth factor-1 (IGF-1) are fetal hormones critical to establishing normal fetal growth. Experimentally elevated IGF-1 concentrations during late gestation increase fetal weight but lower fetal plasma insulin concentrations. We therefore hypothesized that infusion of an IGF-1 analog for 1 wk into late gestation fetal sheep would attenuate fetal glucose-stimulated insulin secretion (GSIS) and insulin secretion in islets isolated from these fetuses. Late gestation fetal sheep received infusions with IGF-1 LR3 (IGF-1, n = 8), an analog of IGF-1 with low affinity for the IGF binding proteins and high affinity for the IGF-1 receptor, or vehicle control (CON, n = 9). Fetal GSIS was measured with a hyperglycemic clamp (IGF-1, n = 8; CON, n = 7). Fetal islets were isolated, and insulin secretion was assayed in static incubations (IGF-1, n = 8; CON, n = 7). Plasma insulin and glucose concentrations in IGF-1 fetuses were lower compared with CON (P = 0.0135 and P = 0.0012, respectively). During the GSIS study, IGF-1 fetuses had lower insulin secretion compared with CON (P = 0.0453). In vitro, glucose-stimulated insulin secretion remained lower in islets isolated from IGF-1 fetuses (P = 0.0447). In summary, IGF-1 LR3 infusion for 1 wk into fetal sheep lowers insulin concentrations and reduces fetal GSIS. Impaired insulin secretion persists in isolated fetal islets indicating an intrinsic islet defect in insulin release when exposed to IGF-1 LR3 infusion for 1 wk. We speculate this alteration in the insulin/IGF-1 axis contributes to the long-term reduction in β-cell function in neonates born with elevated IGF-1 concentrations following pregnancies complicated by diabetes or other conditions associated with fetal overgrowth.NEW & NOTEWORTHY After a 1-wk infusion of IGF-1 LR3, late gestation fetal sheep had lower plasma insulin and glucose concentrations, reduced fetal glucose-stimulated insulin secretion, and decreased fractional insulin secretion from isolated fetal islets without differences in pancreatic insulin content.

Hypertriglyceridaemic waist phenotype and β-cell function in subjects with normal and impaired glucose tolerance

To determine the association between the hypertriglyceridaemic waist phenotype, a combination of enlarged waist circumference and increased triglyceride levels, and β-cell function in subjects with normal glucose tolerance and those with impaired glucose tolerance. We studied 1344 outpatients clinic without diabetes. Overnight fasting blood samples were obtained to measure plasma glucose, insulin and lipids. An oral glucose tolerance test was performed in all subjects. All patients were divided in four groups, two groups with normal glucose tolerance and two with impaired glucose tolerance, with or without the hypertriglyceridaemic waist phenotype. Insulin resistance and β-cell function were calculated by homeostatsis model assessment 2 indices. Twenty per cent of subjects showed the hypertriglyceridaemic waist phenotype and 23.8% had impaired glucose tolerance. We found a progressive significant increase (P < 0.001) of insulin resistance from subjects with normal glucose tolerance without the hypertriglyceridaemic waist phenotype with respect to patients with impaired glucose tolerance with the hypertriglyceridaemic waist phenotype. In subjects with normal glucose tolerance, the hypertriglyceridaemic waist phenotype was associated with a mild, but not significant, increase of homeostatsis model assessment 2-β levels; but, in patients with impaired glucose tolerance, the hypertriglyceridaemic waist phenotype was associated with significantly lower homeostatsis model assessment 2-β levels [127.0 (103.0-162.7) vs. 123.0 (96.0-147.0); P < 0.05]. The hypertriglyceridaemic waist phenotype displayed a higher (odds ratio 95% CI) β-cell dysfunction of 1.8 (1.3-2.6) and insulin resistance of 5.0 (2.7-8.5) compared with 1.3 (0.9-1.9) and 2.4 (1.8-3.2), respectively, of waist circumference alone. In this study, the hypertriglyceridaemic waist phenotype is associated with increased insulin resistance and an overstimulation of β-cell function in subjects with normal glucose tolerance, while patients with impaired glucose tolerance with the hypertriglyceridaemic waist phenotype showed a reduction in β-cell function. These data suggest the importance of the identification of patients with impaired glucose tolerance combined with the hypertriglyceridaemic waist phenotype for an early intervention in relation to the high risk of developing Type 2 diabetes.

Co-stimulation modulation with abatacept in patients with recent-onset type 1 diabetes: a randomised, double-blind, placebo-controlled trial

The immunopathogenesis of type 1 diabetes mellitus is associated with T-cell autoimmunity. To be fully active, immune T cells need a co-stimulatory signal in addition to the main antigen-driven signal. Abatacept modulates co-stimulation and prevents full T-cell activation. We evaluated the effect of abatacept in recent-onset type 1 diabetes.In this multicentre, double-blind, randomised controlled trial, patients aged 6-45 years recently diagnosed with type 1 diabetes were randomly assigned (2:1) to receive abatacept (10 mg/kg, maximum 1000 mg per dose) or placebo infusions intravenously on days 1, 14, 28, and monthly for a total of 27 infusions over 2 years. Computer-generated permuted block randomisation was used, with a block size of 3 and stratified by participating site. Neither patients nor research personnel were aware of treatment assignments. The primary outcome was baseline-adjusted geometric mean 2-h area-under-the-curve (AUC) serum C-peptide concentration after a mixed-meal tolerance test at 2 years' follow-up. Analysis was by intention to treat for all patients for whom data were available. This trial is registered at ClinicalTrials.gov, NCT00505375.112 patients were assigned to treatment groups (77 abatacept, 35 placebo). Adjusted C-peptide AUC was 59% (95% CI 6·1-112) higher at 2 years with abatacept (n=73, 0·378 nmol/L) than with placebo (n=30, 0·238 nmol/L; p=0·0029). The difference between groups was present throughout the trial, with an estimated 9·6 months' delay (95% CI 3·47-15·6) in C-peptide reduction with abatacept. There were few infusion-related adverse events (36 reactions occurred in 17 [22%] patients on abatacept and 11 reactions in six [17%] on placebo). There was no increase in infections (32 [42%] patients on abatacept vs 15 [43%] on placebo) or neutropenia (seven [9%] vs five [14%]).Co-stimulation modulation with abatacept slowed reduction in β-cell function over 2 years. The beneficial effect suggests that T-cell activation still occurs around the time of clinical diagnosis of type 1 diabetes. Yet, despite continued administration of abatacept over 24 months, the decrease in β-cell function with abatacept was parallel to that with placebo after 6 months of treatment, causing us to speculate that T-cell activation lessens with time. Further observation will establish whether the beneficial effect continues after cessation of abatacept infusions.US National Institutes of Health.

Number of children and change in markers of metabolic health over 9-years in men and women. Data from the DESIR study

Aim Parity is associated with an increased risk of coronary heart disease and type 2 diabetes, possibly mediated by long-term modification of metabolic health. Studying associations between the number of children with health and disease in men in addition to women allows for differentiation between the social and lifestyle influences of child-rearing, and the biological influences of childbearing. We sought to determine whether the number of children is associated with the incidence of raised fasting glucose (fasting plasma glucose ≥ 6.1 mmol/L) and changes in glucose, insulin, insulin resistance and β-cell function over 9-years. Methods Analysis of 1798 women and 1737 men from the DESIR study. Results The number of children was associated with change in fasting glucose for women ( P trend = 0.02) and men ( P trend = 0.03), and increased incidence of raised fasting glucose by 30% (95% CI: 15, 47%) per child for men, but not women (3% [95% CI: −8, 15%]). There was a J-shaped association between number of children and change in insulin ( P = 0.01) and insulin resistance ( P = 0.005) for women, and a reduction in β-cell function in parous women ( P = 0.07). Men with children had increases in insulin ( P = 0.02), insulin resistance ( P = 0.02), and β-cell function ( P = 0.07). Conclusions The number of children a person has is associated with changes in metabolic health indices long after childbirth for both men and women. The distinct gender differences in deterioration of metabolic health indices emphasize that childbearing and child-rearing are likely to have differential influences on metabolic health.

Type 2 Diabetes

This is the first of a series of articles based on presentations at the American Diabetes Association (ADA) 70th Scientific Sessions held on 25–29 June 2010 in Orlando, Florida, pertaining to thiazolidinedione(s) (TZD) and to approaches to insulin treatment for type 2 diabetes. At a symposium on the role of TZD, Thomas Buchanan (Los Angeles, CA) discussed the β-cell benefits of TZD and their action to slow the progression of diabetes. Clinically, the agents increase body fat, acting to increase appetite, but making fat “behave better” and leading to a reduction in insulin resistance and improved glycemia. TZDs alter circulating lipids, lower blood pressure, reduce coronary artery restenosis after percutaneous intervention, and decrease ultrasonographic progression of carotid and coronary artery disease but increase the risk of distal extremity (and perhaps other skeletal) fracture and of congestive heart failure. They may alter the risk of acute occlusive events. To set the stage for understanding the TZD effect on β-cell function, Buchanan reviewed the hyperbolic relationship between insulin sensitivity and insulin secretion. The product of the two parameters, the disposition index, decreases as diabetes develops. Cross-sectional data suggest that, as the fasting glucose increases from under 100 to 100–140 and again from 140 to 180 mg/dL, there is particularly great deterioration in β-cell function, with lesser deterioration as glucose levels increase further (1). Buchanan reviewed his studies, comparing those who had developed diabetes with those who had not after having had gestational diabetes. There was a nonlinear relationship between reduction in β-cell function and elevations in glucose levels, with greater reduction leading to the development of diabetes (2). Although he pointed out that higher blood glucose, lesser β-cell function, and worse degrees of insulin resistance “doesn't actually tell you why they develop diabetes,” Buchanan reviewed further analysis showing weight gain to …

Novel canine models of obese prediabetes and mild type 2 diabetes

Human type 2 diabetes mellitus (T2DM) is often characterized by obesity-associated insulin resistance (IR) and beta-cell function deficiency. Development of relevant large animal models to study T2DM is important and timely, because most existing models have dramatic reductions in pancreatic function and no associated obesity and IR, features that resemble more T1DM than T2DM. Our goal was to create a canine model of T2DM in which obesity-associated IR occurs first, followed by moderate reduction in beta-cell function, leading to mild diabetes or impaired glucose tolerance. Lean dogs (n = 12) received a high-fat diet that increased visceral (52%, P < 0.001) and subcutaneous (130%, P < 0.001) fat and resulted in a 31% reduction in insulin sensitivity (S(I)) (5.8 +/- 0.7 x 10(-4) to 4.1 +/- 0.5 x 10(-4) microU x ml(-1) x min(-1), P < 0.05). Animals then received a single low dose of streptozotocin (STZ; range 30-15 mg/kg). The decrease in beta-cell function was dose dependent and resulted in three diabetes models: 1) frank hyperglycemia (high STZ dose); 2) mild T2DM with normal or impaired fasting glucose (FG), 2-h glucose >200 mg/dl during OGTT and 77-93% AIR(g) reduction (intermediate dose); and 3) prediabetes with normal FG, normal 2-h glucose during OGTT and 17-74% AIR(g) reduction (low dose). Twelve weeks after STZ, animals without frank diabetes had 58% more body fat, decreased beta-cell function (17-93%), and 40% lower S(I). We conclude that high-fat feeding and variable-dose STZ in dog result in stable models of obesity, insulin resistance, and 1) overt diabetes, 2) mild T2DM, or 3) impaired glucose tolerance. These models open new avenues for studying the mechanism of compensatory changes that occur in T2DM and for evaluating new therapeutic strategies to prevent progression or to treat overt diabetes.

Pathogenetic Mechanisms of Impaired Glucose Tolerance and Type II Diabetes in African-Americans: The significance of insulin secretion, insulin sensitivity, and glucose effectiveness

To examine the significance of alterations in insulin sensitivity index (S(t)), glucose effectiveness (Sg), and beta-cell function in the pathogenesis of type II diabetes in African-Americans with varying degrees of glucose intolerance. A total of 154 African-Americans residing in Franklin County, Ohio, were studied. There were 101 subjects with normal glucose tolerance (NGT), 36 with impaired glucose tolerance (IGT), and 17 with type II diabetes. An oral glucose tolerance test (OGTT) was performed on each subject. S(t) and Sg were measured by insulin-modified, frequently sampled intravenous glucose tolerance test (FSIGT). The mean fasting and postprandial serum glucose levels were significantly greater in the diabetic groups when compared with the IGT and NGT groups. In contrast, while fasting serum insulin and C-peptide levels tended to be greater in the type II diabetic and IGT groups, the postprandial responses were blunted at 30 min in the IGT and type II diabetic groups when compared with the NGT group. The mean acute first-phase insulin release after intravenous glucose was blunted also in the IGT and type II diabetic groups when compared with the NGT group. The S(t) was significantly lower in the IGT (1.51 +/- 0.19) and type II diabetic (0.61 +/- 0.15) groups when compared with the NGT group (2.94 +/- 0.20 x 10(-4).min-1.microU-1.ml-1). The Sg was not significantly different in the NGT (2.90 +/- 0.20), IGT (2.47 +/- 0.19), and the type II diabetic (2.35 +/- 0.15 x 10(-2)/min) groups. The glucose effectiveness at theoretical zero insulin concentration (GEZI) followed similar patterns as the Sg. Furthermore, the basal insulin effect (BIE) was significantly lower in the IGT and type II diabetic groups compared with the NGT group. In addition, the glucose decay constant (Kg) was significantly lower (P < 0.001) in the IGT (1.21 +/- 0.13) and the type II diabetic (1.07 +/- 0.12) groups when compared with the NGT group (2.03 +/- 0.10% per minute). Our present study demonstrates that African-American patients with IGT and mild type II diabetes have significant reduction in beta-cell function, insulin sensitivity, and BEI but have normal and intact Sg and GEZI when compared with NGT subjects. We conclude the following: 1) a reduction in Sg does not appear to play a significant role in the pathogenetic mechanism of IGT and type II diabetes in African-American patients, and 2) the intact Sg in the IGT and type II diabetic groups could serve as a compensatory mechanism for hyperglycemia in African-Americans.