Natural history and physiological determinants of changes in glucose tolerance in a non-diabetic population: the RISC Study

Pancreatic beta cell function and insulin resistance profiles in first-degree relatives of patients with prediabetes and type 2 diabetes

AIMS

To evaluate insulin secretion and insulin resistance profiles in individuals with family history of prediabetes and type 2 diabetes.

METHODS

This was a cross-sectional study to evaluate clinical and metabolic profiles between individuals with type 2 diabetes, prediabetes and their relatives. There were 911 subjects divided into five groups: (i) normoglycemic (NG), (ii) type 2 diabetes, (iii) prediabetes, (iv) first-degree relatives of patients with type 2 diabetes (famT2D), and (v) first-degree relatives of patients with prediabetes (famPD); anthropometrical, biochemical and nutritional evaluation, as well as insulin resistance and pancreatic beta cell function measurement was performed by oral glucose tolerance to compare between groups.

RESULTS

The most prevalent type 2 diabetes risk factors were dyslipidemia (81%), family history of type 2 diabetes (76%), central obesity (73%), male sex (63%), and sedentary lifestyle (60%), and most of them were progressively associated to prediabetes and type 2 diabetes groups. Insulin sensitivity was lower in famT2D groups in comparison to NG group (p < 0.0001). FamPD and famT2D had a 10% lower pancreatic beta cell function (DI) than the NG group (NG group 2.78 ± 1.0, famPD 2.5 ± 0.85, famT2D 2.4 ± 0.75, p˂0.001).

CONCLUSIONS

FamPD and famT2D patients had lower pancreatic beta cell function than NG patients, highlighting that defects in insulin secretion and insulin sensitivity appear long time before the development of hyperglycemia in patients genetically predisposed.

Impact of saturated compared with unsaturated dietary fat on insulin sensitivity, pancreatic β-cell function and glucose tolerance: a systematic review and meta-analysis of randomized, controlled trials

BACKGROUND

The impact of the dietary fat type on type 2 diabetes (T2D) remains unclear.

OBJECTIVES

We aimed to evaluate the effects of replacing dietary saturated fatty acids (SFA) with mono- or poly-unsaturated fatty acids (MUFA and PUFA, respectively) on insulin sensitivity, pancreatic β-cell function, and glucose tolerance, as surrogate endpoints for T2D.

METHODS

We conducted a systematic review and meta-analysis of randomized controlled trials that replaced ≥5% of total energy intake provided by SFA with MUFA or PUFA and reported indexes of insulin sensitivity, β-cell function, and/or glucose tolerance. We searched MEDLINE, Scopus, and the Cochrane Library (CENTRAL) up to 9 January, 2023. Eligible interventions had to be isocaloric, with no significant difference in other macronutrients. Data were synthesized using random-effects model meta-analysis.

RESULTS

Of 6355 records identified, 10 parallel and 20 crossover trials with 1586 participants were included. The mean age of the participants was 42 years, 47% were male, mean body mass index (BMI; in kg/m2) was 26.8, median baseline fasting glucose was 5.13 mmol/L, and the median duration of interventions was 5 weeks. Replacing SFA with MUFA or PUFA had no significant effects on insulin sensitivity [standardized mean difference (SMD) SFA compared with MUFA: 0.01, 95% confidence interval (CI): -0.06 to 0.09, I2 = 0% and SMD SFA compared with PUFA: 0, 95% CI: -0.15 to 0.14, I2 = 0%]. Replacing SFA with MUFA did not significantly impact the β-cell function, evaluated by the disposition index (mean difference: -12, 95% CI: -158 to 133, I2=0%). Evidence on glucose tolerance (SFA compared with MUFA or PUFA) and on β-cell function when SFA were replaced with PUFA was scant.

CONCLUSIONS

Short-term substitution of saturated with unsaturated fat does not significantly affect insulin sensitivity nor β-cell function (the latter in the SFA compared with MUFA comparison). Future studies are needed to elucidate longer term effects of dietary fat saturation on glucose homeostasis. This trial was registered at PROSPERO as CRD42020178382.

Insulin Clearance in Health and Disease

Insulin action is impaired in type 2 diabetes. The functions of the hormone are an integrated product of insulin secretion from pancreatic β-cells and insulin clearance by receptor-mediated endocytosis and degradation, mostly in liver (hepatocytes) and, to a lower extent, in extrahepatic peripheral tissues. Substantial evidence indicates that genetic or acquired abnormalities of insulin secretion or action predispose to type 2 diabetes. In recent years, along with the discovery of the molecular foundation of receptor-mediated insulin clearance, such as through the membrane glycoprotein CEACAM1, a consensus has begun to emerge that reduction of insulin clearance contributes to the disease process. In this review, we consider the evidence suggesting a pathogenic role for reduced insulin clearance in insulin resistance, obesity, hepatic steatosis, and type 2 diabetes.

Reflections on the state of diabetes research and prospects for treatment

Research on the etiology and treatment of diabetes has made substantial progress. As a result, several new classes of anti-diabetic drugs have been introduced in clinical practice. Nonetheless, the number of patients achieving glycemic control targets has not increased for the past 20 years. Two areas of unmet medical need are the restoration of insulin sensitivity and the reversal of pancreatic beta cell failure. In this review, we integrate research advances in transcriptional regulation of insulin action and pathophysiology of beta cell dedifferentiation with their potential impact on prospects of a durable "cure" for patients suffering from type 2 diabetes.

Hypertension in Patients with Insulin Resistance: Etiopathogenesis and Management in Children

Insulin resistance (IR) is a key component in the etiopathogenesis of hypertension (HS) in patients with diabetes mellitus (DM). Several pathways have been found to be involved in this mechanism in recent literature. For the above-mentioned reasons, treatment of HS should be specifically addressed in patients affected by DM. Two relevant recently published guidelines have stressed this concept, giving specific advice in the treatment of HS in children belonging to this group: the European Society of HS guidelines for the management of high blood pressure in children and adolescents and the American Academy of Pediatrics Clinical Practice Guideline for Screening and Management of High Blood Pressure in Children and Adolescents. Our aim is to summarize the main pathophysiological mechanisms through which IR causes HS and to highlight the specific principles of treatment of HS for children with DM.

A Journey in Diabetes: From Clinical Physiology to Novel Therapeutics: The 2020 Banting Medal for Scientific Achievement Lecture

Insulin resistance and β-cell dysfunction are the core pathophysiological mechanisms of all hyperglycemic syndromes. Advances in in vivo investigative techniques have made it possible to quantify insulin resistance in multiple sites (skeletal and myocardial muscle, subcutaneous and visceral fat depots, liver, kidney, vascular tissues, brain and intestine), to clarify its consequences for tissue substrate selection, and to establish its relation to tissue perfusion. Physiological modeling of β-cell function has provided a uniform tool to measure β-cell glucose sensitivity and potentiation in response to a variety of secretory stimuli, thereby allowing us to establish feedbacks with insulin resistance, to delineate the biphasic time course of conversion to diabetes, to gauge incretin effects, and to identify primary insulin hypersecretion. As insulin resistance also characterizes several of the comorbidities of diabetes (e.g., obesity, hypertension, dyslipidemia), with shared genetic and acquired influences, the concept is put forward that diabetes is a systemic disease from the outset, actually from the prediabetic stage. In fact, early multifactorial therapy, particularly with newer antihyperglycemic agents, has shown that the burden of micro- and macrovascular complications can be favorably modified despite the rising pressure imposed by protracted obesity.

Trajectories of Body Weight and Fat Mass in Relation to Incident Prediabetes in a Biracial Cohort of Free-Living Adults

Objectives

Obesity is a risk factor for type 2 diabetes (T2D), but prospective data relating adiposity measures to incident prediabetes are scant.

Methods

The Pathobiology of Prediabetes in A Biracial Cohort study followed normoglycemic African Americans (AA) and European Americans (EA) with parental history of T2D for the primary outcome of incident prediabetes (impaired fasting glucose and/or impaired glucose tolerance) for 5.5 years. Serial assessments included anthropometry and body fat composition. We analyzed weight, body mass index (BMI), waist, total, and abdominal fat mass in relation to incident prediabetes risk.

Results

Of the 376 subjects enrolled (217 AA, 159 EA; mean age 44.2 years, BMI 31.4 kg/m²), 343 (192 AA, 151 EA) had evaluable follow-up data. A total of 101 (52 AA, 49 EA) developed prediabetes during follow-up. Progressors to prediabetes had a mean baseline weight of 90.0 ± 20.4 kg versus 82.9 ± 21.7 kg among nonprogressors (P = 0.0036). During 5.5 (mean 2.62) years of follow-up, the weight change among nonprogressors was 0.63 ± 6.11 kg compared with 2.54 ± 6.91 kg among progressors (ANOVA P = 0.0072). Progressors also showed greater increases in total fat (P = 0.0015) and trunk fat (P = 0.0005) mass than nonprogressors. Adjusted for age and sex, the significant predictors of incident prediabetes were BMI (P = 0.0013), waist (P < 0.0001), total fat (P = 0.0025), and trunk fat (P < 0.0001) mass.

Conclusions

Among obese free-living offspring of parents with T2D, long-term normoglycemic status was associated with a weight gain of ~0.2 kg/y, whereas progression to prediabetes was associated with a weight gain of ~1 kg/y.

Review of methods for detecting glycemic disorders

Prediabetes (intermediate hyperglycemia) consists of two abnormalities, impaired fasting glucose (IFG) and impaired glucose tolerance (IGT) detected by a standardized 75-gram oral glucose tolerance test (OGTT). Individuals with isolated IGT or combined IFG and IGT have increased risk for developing type 2 diabetes (T2D) and cardiovascular disease (CVD). Diagnosing prediabetes early and accurately is critical in order to refer high-risk individuals for intensive lifestyle modification. However, there is currently no international consensus for diagnosing prediabetes with HbA1c or glucose measurements based upon American Diabetes Association (ADA) and the World Health Organization (WHO) criteria that identify different populations at risk for progressing to diabetes. Various caveats affecting the accuracy of interpreting the HbA1c including genetics complicate this further. This review describes established methods for detecting glucose disorders based upon glucose and HbA1c parameters as well as novel approaches including the 1-hour plasma glucose (1-h PG), glucose challenge test (GCT), shape of the glucose curve, genetics, continuous glucose monitoring (CGM), measures of insulin secretion and sensitivity, metabolomics, and ancillary tools such as fructosamine, glycated albumin (GA), 1,5- anhydroglucitol (1,5-AG). Of the approaches considered, the 1-h PG has considerable potential as a biomarker for detecting glucose disorders if confirmed by additional data including health economic analysis. Whether the 1-h OGTT is superior to genetics and omics in providing greater precision for individualized treatment requires further investigation. These methods will need to demonstrate substantially superiority to simpler tools for detecting glucose disorders to justify their cost and complexity.

Insulin Resistance and Atherosclerosis: Implications for Insulin-Sensitizing Agents

Patients with type 2 diabetes mellitus (T2DM) are at high risk for macrovascular complications, which represent the major cause of mortality. Despite effective treatment of established cardiovascular (CV) risk factors (dyslipidemia, hypertension, procoagulant state), there remains a significant amount of unexplained CV risk. Insulin resistance is associated with a cluster of cardiometabolic risk factors known collectively as the insulin resistance (metabolic) syndrome (IRS). Considerable evidence, reviewed herein, suggests that insulin resistance and the IRS contribute to this unexplained CV risk in patients with T2DM. Accordingly, CV outcome trials with pioglitazone have demonstrated that this insulin-sensitizing thiazolidinedione reduces CV events in high-risk patients with T2DM. In this review the roles of insulin resistance and the IRS in the development of atherosclerotic CV disease and the impact of the insulin-sensitizing agents and of other antihyperglycemic medications on CV outcomes are discussed.

Post-transplant diabetes mellitus in patients with solid organ transplants

Solid organ transplantation (SOT) is a life-saving procedure and an established treatment for patients with end-stage organ failure. However, transplantation is also accompanied by associated cardiovascular risk factors, of which post-transplant diabetes mellitus (PTDM) is one of the most important. PTDM develops in 10-20% of patients with kidney transplants and in 20-40% of patients who have undergone other SOT. PTDM increases mortality, which is best documented in patients who have received kidney and heart transplants. PTDM results from predisposing factors (similar to type 2 diabetes mellitus) but also as a result of specific post-transplant risk factors. Although PTDM has many characteristics in common with type 2 diabetes mellitus, the prevention and treatment of the two disorders are often different. Over the past 20 years, the lifespan of patients who have undergone SOT has increased, and PTDM becomes more common over the lifespan of these patients. Accordingly, PTDM becomes an important condition not only to be aware of but also to treat. This Review presents the current knowledge on PTDM in patients receiving kidney, heart, liver and lung transplants. This information is not only for transplant health providers but also for endocrinologists and others who will meet these patients in their clinics.

Stem-cell based organ-on-a-chip models for diabetes research

Diabetes mellitus (DM) ranks among the severest global health concerns of the 21st century. It encompasses a group of chronic disorders characterized by a dysregulated glucose metabolism, which arises as a consequence of progressive autoimmune destruction of pancreatic beta-cells (type 1 DM), or as a result of beta-cell dysfunction combined with systemic insulin resistance (type 2 DM). Human cohort studies have provided evidence of genetic and environmental contributions to DM; yet, these studies are mostly restricted to investigating statistical correlations between DM and certain risk factors. Mechanistic studies, on the other hand, aimed at re-creating the clinical picture of human DM in animal models. A translation to human biology is, however, often inadequate owing to significant differences between animal and human physiology, including the species-specific glucose regulation. Thus, there is an urgent need for the development of advanced human in vitro models with the potential to identify novel treatment options for DM. This review provides an overview of the technological advances in research on DM-relevant stem cells and their integration into microphysiological environments as provided by the organ-on-a-chip technology.

Decreased beta-cell function in breastfeeding obese and non-obese women: A prospective observational study

BACKGROUND & AIMS

Obesity is associated with lower breastfeeding rates. The underlying pathophysiological mechanisms are not well-understood, but there is increasing evidence on an association between parameters of maternal glucose metabolism and prolactin concentrations. In this cross-sectional observational study we investigate the relationship between breastfeeding, maternal obesity, and maternal glucose metabolism postpartum with beta cell function as a primary outcome measure.

METHODS

We investigated 106 women (44% obese) prospectively recruited during the pregnancy, who underwent a 75 g - 2 h oral glucose tolerance test (OGTT) between the 3rd and 5th months postpartum. At this time point, we tested the relationship between breastfeeding status, maternal prolactin concentrations, maternal obesity, and fasting and dynamic indices of glucose metabolism using multivariate logistic regression in a post hoc analysis of prospective observational data.

RESULTS

During the study visit at a mean of 122 (SE 9.3) days after delivery, 47% of obese women and 68% of non-obese women were breastfeeding (p < 0.05). Lactation and higher prolactin concentrations were associated with lower prepregnancy weight and lower postpartum insulin concentrations. Prehepatic beta-cell function was decreased in both obese (mean (SD); 0.16 (0.04) vs. 0.19 (0.05), p < 0.05) and non-obese (0.12 (0.05) vs. 0.16 (0.06), p < 0.01), lactating women. Obese lactating women have significantly lower first (1135.1 (306.7) pmol/L vs. 1517.3 (475.8) pmol/L, p < 0.01) and second phase insulin secretion (mean (SD), 300.2 (70.7) pmol/L vs. 393.1 (115.5) pmol/L, p < 0.01) as shown by Stumvoll indices when comparing to obese non-lactating women. Prehepatic beta-cell function and Stumvoll 1st phase insulin secretion index, but not BMI, were independently and negatively associated with breastfeeding and circulating prolactin concentrations.

CONCLUSIONS

Beta-cell function during lactation relates to breastfeeding and circulating prolactin concentrations independently of obesity. The well-known positive effects of lactation on maternal and offspring outcomes might reflect a causative relationship of higher breastfeeding rates in metabolically healthier women.

New insights from continuous glucose monitoring into the route to diabetes

AIM

Type 2 diabetes mellitus (T2DM) is preceded by a period of impaired glucoregulation. We investigated if continuous glucose monitoring system (CGMS) (1) could improve our capacity to predict the development of T2DM in subjects at risk. (2) Find out if impaired fasting glucose/impaired glucose tolerance differentiation through CGMS would also elucidate differences in clinical phenotypes.

MATERIAL AND METHODS

Observational study of 209 hypertensive patients, aged 18 to 85 years who wore at entry a CGMS. Two CGMS metrics, percent of time under the 100 mg/dL glycaemic threshold (TU100) (impaired fasting glucose surrogate phenotype) and area above the 140 mg/dL glycemic threshold (AO140) (impaired glucose tolerance surrogate phenotype) were measured. The median follow-up was 32 months (6-72 mo), and there were 17 new cases of T2DM.

RESULTS

In a multivariate Cox proportional hazard survival analysis including the conventional prediabetes-defining criteria and the 2 CGMS-derived variables, only TU100 and HbA_1c were significant and independent variables in predicting T2DM development. An increase in 0.1 in TU100 resulted in a 0.69 (95% CI, 0.54-0.88; P < .01) odds ratio of developing T2DM. With cut-off points of 0.5 for TU100 and 5.7% for HbA_1c , the test "TU < 0.5 and HbA_1c  > 5.7%" had a sensitivity of 0.81 (SD, 0.10), a specificity of 0.83 (SD, 0.03), and a likelihood ratio of 4.82 (SD, 1.03) for T2DM development.

CONCLUSIONS

Continuous glucose monitoring system allows for a better T2DM risk-development categorization than fasting glucose and HbA_1c in a high-risk population. Continuous glucose monitoring system-derived phenotyping reveals clinical differences, not disclosed by conventional fasting plasma glucose/HbA_1c categorization. These differences may correlate with distinct pathophysiological mechanisms.

Exercise Increases Insulin Sensitivity and Skeletal Muscle AMPK Expression in Systemic Lupus Erythematosus: A Randomized Controlled Trial

Systemic lupus erythematosus (SLE) patients may show increased insulin resistance (IR) when compared with their healthy peers. Exercise training has been shown to improve insulin sensitivity in other insulin-resistant populations, but it has never been tested in SLE. Therefore, the aim of the present study was to assess the efficacy of a moderate-intensity exercise training program on insulin sensitivity and potential underlying mechanisms in SLE patients with mild/inactive disease. A 12-week, randomized controlled trial was conducted. Nineteen SLE patients were randomly assigned into two groups: trained (SLE-TR, n = 9) and non-trained (SLE-NT, n = 10). Before and after 12 weeks of the exercise training program, patients underwent a meal test (MT), from which surrogates of insulin sensitivity and beta-cell function were determined. Muscle biopsies were performed after the MT for the assessment of total and membrane GLUT4 and proteins related to insulin signaling [Akt and AMP-activated protein kinase (AMPK)]. SLE-TR showed, when compared with SLE-NT, significant decreases in fasting insulin [−39 vs. +14%, p = 0.009, effect size (ES) = −1.0] and in the insulin response to MT (−23 vs. +21%, p = 0.007, ES = −1.1), homeostasis model assessment IR (−30 vs. +15%, p = 0.005, ES = −1.1), a tendency toward decreased proinsulin response to MT (−19 vs. +6%, p = 0.07, ES = −0.9) and increased glucagon response to MT (+3 vs. −3%, p = 0.09, ES = 0.6), and significant increases in the Matsuda index (+66 vs. −31%, p = 0.004, ES = 0.9) and fasting glucagon (+4 vs. −8%, p = 0.03, ES = 0.7). No significant differences between SLT-TR and SLT-NT were observed in fasting glucose, glucose response to MT, and insulinogenic index (all p > 0.05). SLE-TR showed a significant increase in AMPK Thr 172 phosphorylation when compared to SLE-NT (+73 vs. −12%, p = 0.014, ES = 1.3), whereas no significant differences between groups were observed in Akt Ser 473 phosphorylation, total and membrane GLUT4 expression, and GLUT4 translocation (all p > 0.05). In conclusion, a 12-week moderate-intensity aerobic exercise training program improved insulin sensitivity in SLE patients with mild/inactive disease. This effect appears to be partially mediated by the increased insulin-stimulated skeletal muscle AMPK phosphorylation.

Inside out the Ragbag of Glucose Intolerance in Obese Adolescents

BACKGROUND/AIMS

The prevalence of impaired glucose tolerance (IGT) is rising among obese adolescents in parallel with epidemic obesity. In some cases, IGT reverts to normal glucose tolerance (NGT) by the end of puberty. The aims of the present study were to investigate metabolic factors determining changes over time of glucose at 120 min (Glu120) following an oral glucose tolerance test (OGTT), and to verify whether preserved β-cell glucose sensitivity (βCGS) protects against persistent IGT.

METHODS

We performed a cohort study of 153 severely obese children and adolescents evaluated with a 5-point OGTT at baseline and at follow-up with measurements of glucose, insulin, and C-peptide to estimate several empirical parameters of insulin sensitivity (includ ing oral glucose insulin sensitivity [OGIS] and OGTT-derived glucose effectiveness) and secretion.

RESULTS

At follow-up (range 0.9-4.8 year), 113 (73.9%) patients remained with NGT, 9 (5.9%) had IGT, and 28 (18.3%) had reverted to NGT; 3 NGT patients had developed IGT. In multivariable models, change in loge(βCGS) was inversely associated with time-related change in loge(Glu120), with (model 2) and without (model 1) correction for the change in loge(OGIS). Model 2 was more strongly associated with change in loge(Glu120).

CONCLUSIONS

Changes in βCGS and insulin sensitivity were inversely associated with changes in Glu120 at follow-up, contributing a likely explanation for the reversal of IGT to NGT.

Controversies and Advances in Gestational Diabetes-An Update in the Era of Continuous Glucose Monitoring

Diabetes in pregnancy, both preexisting type 1 or type 2 and gestational diabetes, is a highly prevalent condition, which has a great impact on maternal and fetal health, with short and long-term implications. Gestational Diabetes Mellitus (GDM) is a condition triggered by metabolic adaptation, which occurs during the second half of pregnancy. There is still a lot of controversy about GDM, from classification and diagnosis to treatment. Recently, there have been some advances in the field as well as recommendations from international societies, such as how to distinguish previous diabetes, even if first recognized during pregnancy, and newer diagnostic criteria, based on pregnancy outcomes, instead of maternal risk of future diabetes. These new recommendations will lead to a higher prevalence of GDM, and important issues are yet to be resolved, such as the cost-utility of this increase in diagnoses as well as the determinants for poor outcomes. The aim of this review is to discuss the advances in diagnosis and classification of GDM, as well as their implications in the field, the issue of hyperglycemia in early pregnancy and the role of hemoglobin A1c (HbA1c) during pregnancy. We have looked into the determinants of the poor outcomes predicted by the diagnosis by way of oral glucose tolerance tests, highlighting the relevance of continuous glucose monitoring tools, as well as other possible pathogenetic factors related to poor pregnancy outcomes.

Identification of novel biomarkers to monitor β-cell function and enable early detection of type 2 diabetes risk

A decline in β-cell function is a prerequisite for the development of type 2 diabetes, yet the level of β-cell function in individuals at risk of the condition is rarely measured. This is due, in part, to the fact that current methods for assessing β-cell function are inaccurate, prone to error, labor-intensive, or affected by glucose-lowering therapy. The aim of the current study was to identify novel circulating biomarkers to monitor β-cell function and to identify individuals at high risk of developing β-cell dysfunction. In a nested case-control study from the Relationship between Insulin Sensitivity and Cardiovascular disease (RISC) cohort (n = 1157), proteomics and miRNA profiling were performed on fasting plasma samples from 43 individuals who progressed to impaired glucose tolerance (IGT) and 43 controls who maintained normal glucose tolerance (NGT) over three years. Groups were matched at baseline for age, gender, body mass index (BMI), insulin sensitivity (euglycemic clamp) and β-cell glucose sensitivity (mathematical modeling). Proteomic profiling was performed using the SomaLogic platform (Colorado, USA); miRNA expression was performed using a modified RT-PCR protocol (Regulus Therapeutics, California, USA). Results showed differentially expressed proteins and miRNAs including some with known links to type 2 diabetes, such as adiponectin, but also novel biomarkers and pathways. In cross sectional analysis at year 3, the top differentially expressed biomarkers in people with IGT/ reduced β-cell glucose sensitivity were adiponectin, alpha1-antitrypsin (known to regulate adiponectin levels), endocan, miR-181a, miR-342, and miR-323. At baseline, adiponectin, cathepsin D and NCAM.L1 (proteins expressed by pancreatic β-cells) were significantly lower in those that progressed to IGT. Many of the novel prognostic biomarker candidates were within the epithelial-mesenchymal transition (EMT) pathway: for example, Noggin, DLL4 and miR-181a. Further validation studies are required in additional clinical cohorts and in patients with type 2 diabetes, but these results identify novel pathways and biomarkers that may have utility in monitoring β-cell function and/ or predicting future decline, allowing more targeted efforts to prevent and intercept type 2 diabetes.

Deterioration of insulin release rate response to glucose during oral glucose tolerance test is associated with an increased risk of incident diabetes in normal glucose tolerance subjects

β-Cell dedifferentiation, characterized by loss of glucose sensitivity (β-cell glucose sensitivity [βCGS]), has been reported to play an important role in the development of type 2 diabetes (T2D). Traditionally, βCGS was derived from C-peptide-based method. However, C-peptide was not routinely examined in normal subjects and diabetes never treated with insulin. Thus, the aim of the study was to evaluate the use of insulin in oral glucose tolerance test (OGTT) in estimation of β-cell glucose response ability. A total of 1,599 subjects including normal glucose tolerance (NGT), impaired glucose tolerance (IGT) and T2D were included in the study. A subgroup of NGT subjects (n = 591) were followed up for an average duration of 56.88 ± 20.76 months. Insulin release rate (IRR_INS ) in the function of glucose (IRR_INS response to glucose [IRRG]) during OGTT was compared with βCGS. Both βCGS derived from C-peptide by deconvolution approach and IRRG by insulin release progressively declined from NGT to IGT and T2D. Both βCGS and IRRG were associated with deposit of first-phase insulin secretion (DI_1st ). After 56.88 ± 20.76 months, 32 (5.41%) NGT subjects had developed T2D. NGT subjects who progressed to diabetes after follow-up had lower IRRG and DI_1st levels than those who did not (P < 0.01). Furthermore, multiple logistic regression analyses showed that decreased IRRG was a significant independent risk predictor for future diabetes after adjustment of age, body mass index (BMI), homeostasis model assessment (HOMA)-insulin resistance, DI_1st and family history. NGT subjects with decreased IRRG during OGTT had defective early insulin secretion and were at higher risk of developing diabetes. IRRG could be a useful T2D predictor in NGT subjects. © 2017 IUBMB Life, 69(9):756-766, 2017.

Sodium-Glucose Co-transporters and Their Inhibition: Clinical Physiology

Sodium-glucose cotransporter-2 (SGLT2) is selectively expressed in the human kidney, where it executes reabsorption of filtered glucose with a high capacity; it may be overactive in patients with diabetes, especially in the early, hyperfiltering stage of the disease. As a therapeutic target, SGLT2 has been successfully engaged by orally active, selective agents. Initially developed as antihyperglycemic drugs, SGLT2 inhibitors have deployed a range of in vivo actions. Consequences of their primary effect, i.e., profuse glycosuria and natriuresis, involve hemodynamic (plasma volume and blood pressure reduction) and metabolic pathways (increase in lipid oxidation and ketogenesis at the expense of carbohydrate utilization); the hormonal mediation extends to insulin, glucagon, and gastrointestinal peptides. Their initial trial in high-risk patients with diabetes has provided evidence for marked reduction of cardiovascular risk. This review focuses on the quantitative pharmacology of SGLT2 inhibitors, which can be exploited to discover new physiology, in the heart, kidney, and brain.

Shape of the OGTT glucose curve and risk of impaired glucose metabolism in the EGIR-RISC cohort

OBJECTIVE

To study whether the shape of the oral glucose tolerance test (OGTT)-glucose curve is a stable trait over time; it is associated with differences in insulin sensitivity, ß-cell function and risk of impaired fasting glucose (IFG) and glucose tolerance (IGT) in the Relationship between Insulin Sensitivity and Cardiovascular Disease (RISC) cohort.

METHODS

OGTT-glucose curve shape was classified as monophasic, biphasic, triphasic and anomalous in 915 individuals. Oral glucose insulin sensitivity (OGIS), Matsuda insulin sensitivity index (ISI) and ß-cell function were assessed at baseline and 3years apart.

RESULTS

The OGTT-glucose curve had the same baseline shape after 3years in 540 people (59%; κ=0.115; p<0.0001). Seventy percent of the participants presented with monophasic OGTT-glucose curve shape at baseline and after 3years (percent positive agreement 0.74). Baseline monophasic shape was associated with significant increased risk of IFG (OR 1.514; 95% CI 1.084-2.116; p=0.015); biphasic shape with reduced risk of IGT (OR 0.539; 95% CI 0.310-0.936) and triphasic shape with reduced risk of IFG (OR 0.493; 95% CI 0.228-1.066; P=0.043) after 3years. Increased risks of IFG (OR 1.509; 95% CI 1.008-2.260; p=0.05) and IGT (OR 1.947; 95% CI 1.085-3.494; p=0.02) were found in people who kept stable monophasic morphology over time and in switchers from biphasic to monophasic shape (OR of IGT=3.085; 95% CI 1.377-6.912; p=0.001).

CONCLUSION

After 3years follow-up, the OGTT-glucose shape was stable in 59% of the RISC cohort. Shapes were associated with different OGIS and ß-cell function; persistence over time of the monophasic shape and switch from biphasic to monophasic shape with increased risk of impaired glucose metabolism.

Role of Adipose Tissue Insulin Resistance in the Natural History of Type 2 Diabetes: Results From the San Antonio Metabolism Study

In the transition from normal glucose tolerance (NGT) to type 2 diabetes mellitus (T2DM), the role of β-cell dysfunction and peripheral insulin resistance (IR) is well established. However, the impact of dysfunctional adipose tissue has not been fully elucidated. The aim of this study was to evaluate the role of resistance to the antilipolytic effect of insulin (adipose tissue IR [Adipo-IR]) in a large group of subjects with NGT, impaired glucose tolerance (IGT), and T2DM. Three hundred two subjects with varying glucose tolerance received an oral glucose tolerance test (OGTT) and euglycemic insulin clamp. We evaluated Adipo-IR (fasting and mean OGTT plasma free fatty acid [FFA] × insulin concentrations), peripheral IR (1/[Matsuda index] and (M/I)^-1 value), and β-cell function (calculated as the ratio of the increment in plasma insulin to glucose [OGTT/IR (ΔI/ΔG ÷ IR)]). Fasting Adipo-IR was increased twofold in obese subjects with NGT and IGT versus lean subjects with NGT (8.0 ± 1.1 and 9.2 ± 0.7 vs. 4.1 ± 0.3, respectively) and threefold in subjects with T2DM (11.9 ± 0.6; P < 0.001). Progressive decline in ΔI/ΔG ÷ IR was associated with a progressive impairment in FFA suppression during OGTT, whereas the rise in mean plasma glucose concentration only became manifest when subjects became overtly diabetic. The progressive decline in β-cell function that begins in individuals with NGT is associated with a progressive increase in FFA and fasting Adipo-IR.

Changes in Weight and Glucose Can Protect Against Progression in Early Diabetes Independent of Improvements in β-Cell Function

CONTEXT

Evidence-based strategies to prevent progression of dysglycemia in newly diagnosed type 2 diabetes are needed.

OBJECTIVE

To undertake a secondary analysis of the Early Diabetes Intervention Program (EDIP) in order to understand the features that were protective against worsening glycemia.

DESIGN

EDIP was a randomized, placebo-controlled trial.

SETTING

Two university diabetes centers.

PATIENTS

A total of 219 overweight individuals with fasting glucose < 7.8 mmol/L and 2-hour oral glucose tolerance test (OGTT) glucose > 11.1 mmol/L.

INTERVENTIONS

Acarbose versus placebo, on a background of dietary recommendations, with quarterly visits to assess glycemia and intervention adherence for up to 5 years.

MAIN OUTCOME MEASURES

Progression of fasting glucose ≥ 7.8 mmol/L on two consecutive quarterly visits. Cox proportional hazards modeling and ANOVA were performed to evaluate determinants of progression.

RESULTS

Progression-free status was associated with reductions in weight, fasting glucose, 2-hour OGTT glucose, and increases in the high-density lipoprotein/triglyceride ratio. The reduction in fasting glucose was the only effect that remained significantly associated with progression-free status in multivariable Cox modeling. The reduction in fasting glucose was in turn primarily associated with reductions in weight and in 2-hour OGTT glucose. Acarbose treatment did not explain these changes.

CONCLUSIONS

In early diabetes, reductions in glucose, driven by reductions in weight, can delay progressive metabolic worsening. These observations underscore the importance of lifestyle management including weight loss as a tool to mitigate worsening of glycemia in newly diagnosed diabetes.

Risk Factors for Spontaneously Self-Reported Postprandial Hypoglycemia After Bariatric Surgery

CONTEXT

Postprandial hypoglycemia (PPHG) is a recognized complication of Roux-en-Y gastric bypass (RYGB) surgery. Data on PPHG after laparoscopic sleeve gastrectomy (LSG) are scant.

OBJECTIVE

The objective of the study was to identify preoperative predictors of PPHG in subjects spontaneously self-reporting PPHG after RYGB or LSG. Patients, Setting, and Intervention: Nondiabetic patients spontaneously self-reporting symptoms/signs of PPHG (PPHG group, 21 RYGB and 11 LSG) were compared in a case-control design with subjects who never experienced spontaneous or oral glucose tolerance test (OGTT)-induced hypoglycemia over 24 months after surgery (No-PPHG group, 13 RYGB and 40 LSG). Paired pre- and postoperative 3-hour OGTTs were analyzed in all participants.

MAIN OUTCOME MEASURES

Insulin sensitivity was assessed by the oral glucose insulin sensitivity index and β-cell function by mathematical modeling of the C-peptide response to glucose.

RESULTS

Before surgery, the body mass index was lower in PPHG than No-PPHG patients in the RYGB (P = .002) and trended similarly in the LSG group (P = .08). Fasting glycemia and the glucose-OGTT nadir were lower in the PPHG than the No-PPHG subjects in both surgery groups. Before surgery, insulin sensitivity was higher in PPHG than No-PPHG in the RYGB (393 ± 55 vs 325 ± 44 mL/min^-1 · m^-2, P = .001) and LSG groups (380 ± 48 vs 339 ± 60 mL/min^-1 · m^-2, P = .05) and improved to a similar extent in all groups after surgery. Before surgery, β-cell glucose sensitivity was higher in PPHG than No-PPHG in both RYGB (118 ± 67 vs 65 ± 24 pmol/min^-1 · m² · mM^-1) and LSG patients (114 ± 32 vs 86 ± 33) (both P = .02) and improved in all subjects after surgery.

CONCLUSIONS

In subjects self-reporting PPHG after surgery, lower presurgery plasma glucose concentrations, higher insulin sensitivity, and better β-cell glucose sensitivity are significant predictors of PPHG after both RYGB and LSG.

α-Hydroxybutyric Acid Is a Selective Metabolite Biomarker of Impaired Glucose Tolerance

OBJECTIVE

Plasma metabolites that distinguish isolated impaired glucose tolerance (iIGT) from isolated impaired fasting glucose (iIFG) may be useful biomarkers to predict IGT, a high-risk state for the development of type 2 diabetes.

RESEARCH DESIGN AND METHODS

Targeted metabolomics with 23 metabolites previously associated with dysglycemia was performed with fasting plasma samples from subjects without diabetes at time 0 of an oral glucose tolerance test (OGTT) in two observational cohorts: RISC (Relationship Between Insulin Sensitivity and Cardiovascular Disease) and DMVhi (Diabetes Mellitus and Vascular Health Initiative). Odds ratios (ORs) for a one-SD change in the metabolite level were calculated using multiple logistic regression models controlling for age, sex, and BMI to test for associations with iIGT or iIFG versus normal. Selective biomarkers of iIGT were further validated in the Botnia study.

RESULTS

α-Hydroxybutyric acid (α-HB) was most strongly associated with iIGT in RISC (OR 2.54 [95% CI 1.86-3.48], P value 5E-9) and DMVhi (2.75 [1.81-4.19], 4E-5) while having no significant association with iIFG. In Botnia, α-HB was selectively associated with iIGT (2.03 [1.65-2.49], 3E-11) and had no significant association with iIFG. Linoleoyl-glycerophosphocholine (L-GPC) and oleic acid were also found to be selective biomarkers of iIGT. In multivariate IGT prediction models, addition of α-HB, L-GPC, and oleic acid to age, sex, BMI, and fasting glucose significantly improved area under the curve in all three cohorts.

CONCLUSIONS

α-HB, L-GPC, and oleic acid were shown to be selective biomarkers of iIGT, independent of age, sex, BMI, and fasting glucose, in 4,053 subjects without diabetes from three European cohorts. These biomarkers can be used in predictive models to identify subjects with IGT without performing an OGTT.

Reduced β-cell function in early preclinical type 1 diabetes

OBJECTIVE

We aimed to characterize insulin responses to i.v. glucose during the preclinical period of type 1 diabetes starting from the emergence of islet autoimmunity.

DESIGN AND METHODS

A large population-based cohort of children with HLA-conferred susceptibility to type 1 diabetes was observed from birth. During regular follow-up visits islet autoantibodies were analysed. We compared markers of glucose metabolism in sequential intravenous glucose tolerance tests between 210 children who were positive for multiple (≥2) islet autoantibodies and progressed to type 1 diabetes (progressors) and 192 children testing positive for classical islet-cell antibodies only and remained healthy (non-progressors).

RESULTS

In the progressors, the first phase insulin response (FPIR) was decreased as early as 4-6 years before the diagnosis when compared to the non-progressors (P=0.001). The difference in FPIR between the progressors and non-progressors was significant (P<0.001) in all age groups, increasing with age (at 2 years: difference 50% (95% CI 28-75%) and at 10 years: difference 172% (95% CI 128-224%)). The area under the 10-min insulin curve showed a similar difference between the groups (P<0.001; at 2 years: difference 36% (95% CI 17-58%) and at 10 years: difference 186% (95% CI 143-237%)). Insulin sensitivity did not differ between the groups.

CONCLUSIONS

FPIR is decreased several years before the diagnosis of type 1 diabetes, implying an intrinsic defect in β-cell mass and/or function.

ß-cell pancreatic dysfunction plays a role in hyperglycemic peaks observed after gastric bypass surgery of obese patients

BACKGROUND

Early and intense hyperglycemic peaks are observed after Roux-en-Y gastric bypass (RYGB).

OBJECTIVES

The aim of this observational study was to compare the ß-cell pancreatic function of patients with (PEAK) and without hyperglycemic peaks (NOPEAK).

SETTING

Referral bariatric surgery center.

METHODS

Insulin secretion rate, clearance, and sensitivity and ß-cell and rate sensitivities were computed after a 75-g oral glucose tolerance test in 42 patients who underwent RYGB.

RESULTS

PEAK patients (n = 18; 30-min glycemia>10.4 mmol/L) did not differ from NOPEAK patients (n = 24) in their presurgery or weight loss characteristics. PEAK patients had significantly higher plasma concentrations of glucose and C-peptide than did NOPEAK patients, whereas insulin and glucagon-like peptide-1 concentrations did not differ. The insulin secretion rate and whole-body insulin clearance (208%) were significantly greater, but insulin sensitivity was significantly less (48%) in PEAK patients. Insulin secretion normalized to plasma glucose was significantly lower in PEAK patients, and the disposition index was reduced (35% to 41% of the values in NOPEAK patients).

CONCLUSION

We conclude that RYGB reveals a series of dysfunctions leading to hyperglycemia in a subset of patients. In PEAK patients, an insufficient adaptation of ß-cell function to glycemia, an increased insulin clearance, and a decreased insulin sensitivity cumulated to contribute to hyperglycemic peaks.

Elevated heart rate predicts β cell function in non-diabetic individuals: the RISC cohort

CONTEXT

Elevated heart rate has been associated with insulin resistance and incident type 2 diabetes but its relationship with β-cell function is not known. Our aim was to investigate whether baseline heart rate is associated with β-cell function and hyperglycaemia.

METHODS

We used the prospective RISC cohort with 1005 non-diabetic individuals who had an oral glucose tolerance test (OGTT) at baseline and after 3 years. Impaired glucose regulation was defined as a fasting plasma glucose ≥ 6.1 mmol/l or a 2-h plasma glucose ≥ 7.8 mmol/l. Insulin sensitivity was assessed by the OGIS index and insulin secretion and β-cell glucose sensitivity at both baseline and 3 years.

RESULTS

Baseline heart rate was positively related to both fasting (P < 0.0001) and 2 h glucose levels (P = 0.02) at year 3 and predicted the presence of impaired glucose regulation at year 3 in a logistic regression model adjusting for insulin sensitivity at inclusion (OR/10 beats per min: 1.31; 95% CI (1.07-1.61); P = 0.01). Baseline heart rate was associated with lower insulin sensitivity (β = -0.11; P < .0001), a decrease in both β-cell glucose sensitivity (β = -0.11; P = 0.003) and basal insulin secretion rate (β = -0.11; P = 0.002) at 3 years in an adjusted multivariable regression model. Baseline heart rate predicted the 3-year decrease in β-cell glucose sensitivity (β = -0.10; P = 0.007) and basal insulin secretion (β = -0.12; P = 0.007).

CONCLUSIONS

Heart rate predicts β-cell function and impaired glucose regulation at 3 years in non-diabetic individuals, independently of the level of insulin sensitivity. These findings suggest a possible effect of the sympathetic nervous system on β-cell dysfunction, which deserves further investigation.

Type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) is an expanding global health problem, closely linked to the epidemic of obesity. Individuals with T2DM are at high risk for both microvascular complications (including retinopathy, nephropathy and neuropathy) and macrovascular complications (such as cardiovascular comorbidities), owing to hyperglycaemia and individual components of the insulin resistance (metabolic) syndrome. Environmental factors (for example, obesity, an unhealthy diet and physical inactivity) and genetic factors contribute to the multiple pathophysiological disturbances that are responsible for impaired glucose homeostasis in T2DM. Insulin resistance and impaired insulin secretion remain the core defects in T2DM, but at least six other pathophysiological abnormalities contribute to the dysregulation of glucose metabolism. The multiple pathogenetic disturbances present in T2DM dictate that multiple antidiabetic agents, used in combination, will be required to maintain normoglycaemia. The treatment must not only be effective and safe but also improve the quality of life. Several novel medications are in development, but the greatest need is for agents that enhance insulin sensitivity, halt the progressive pancreatic β-cell failure that is characteristic of T2DM and prevent or reverse the microvascular complications. For an illustrated summary of this Primer, visit: http://go.nature.com/V2eGfN.

Effects of Vitamin D Supplementation on C-peptide and 25-hydroxyvitamin D Concentrations at 3 and 6 Months

The link between African-Americans' disproportionate rates of diabetes, obesity and vitamin D deficiency may be marked by C-peptide as an indicator of insulin secretion. We hypothesize that vitamin D supplementation will increase C-peptide, a marker of insulin secretion. During 3 winters from 2007-2010, 328 healthy African-Americans (median age, 51 years) living in Boston, MA were randomized into a 4-arm, double-blind trial for 3 months of placebo, 1000, 2000, or 4000 IU of vitamin D3. The differences in non-fasting C-peptide between baseline and 3 months were -0.44 ng/mL for those receiving placebo, -0.10 ng/mL for those receiving 1000 IU/d, 0 ng/mL for those receiving 2000 IU/d, 1.24 ng/mL for those receiving 4000 IU/d (C-peptide increased 0.42 ng/mL for each additional 1000 IU/d of vitamin D3, p < 0.001). Vitamin D supplementation increased C-peptide in overweight African-Americans and may be compatible with other recommendations for diabetes prevention and management including weight loss and increased physical activity.

Delayed timing of post-challenge peak blood glucose predicts declining beta cell function and worsening glucose tolerance over time: insight from the first year postpartum

AIMS/HYPOTHESIS

On cross-sectional assessment, a delayed timing of the peak blood glucose level at ≥60 min post-challenge on an OGTT is associated with beta cell dysfunction. In this context, we hypothesised that longitudinal changes in the timing of this peak might predict changes in glucose metabolism. We thus sought to evaluate the longitudinal associations of changes in the timing of the peak glucose level with changes over time in insulin sensitivity, beta cell function and glucose tolerance.

METHODS

A total of 532 women underwent an OGTT at both 3 months and 12 months postpartum. The participants were stratified into four groups according to the change in timing of their glucose peak between the two visits: women with no change in timing of the glucose peak at 30 min (n = 217), those whose glucose peak shifted to an earlier time point (n = 120), those whose peak shifted to a later time point (n = 87) and women with an unchanged glucose peak at ≥60 min (n = 108). Beta cell function was measured using the Insulin Secretion-Sensitivity Index-2 (ISSI-2).

RESULTS

Compared with an unchanged glucose peak at 30 min, both the shift of the glucose peak to a later time point and a peak that was unchanged at ≥60 min were independently associated with declining ISSI-2 scores (β = -127.5, p < 0.001 and β = -98.8, p = 0.006, respectively) and increased 2 h post-challenge glucose levels (β = 1.28, p < 0.001 and β = 0.91, p < 0.001, respectively) between the two visits. Furthermore, both these patterns of change in peak were independently associated with worsening glucose tolerance (from normal to prediabetes [defined as impaired fasting glucose or impaired glucose tolerance]/diabetes or from prediabetes to diabetes) (OR 8.1, 95% CI 3.0, 22.1 and OR 3.7, 95% CI 1.2, 11.7, respectively).

CONCLUSIONS/INTERPRETATION

A delayed timing of the post-challenge peak glucose level is associated with declining beta cell function and worsening glucose tolerance over time.

Identifying glucose thresholds for incident diabetes by physiological analysis: a mathematical solution

Plasma glucose thresholds for diagnosis of type 2 diabetes are currently based on outcome data (risk of retinopathy), an inherently ill-conditioned approach. A radically different approach is to consider the mechanisms that control plasma glucose, rather than its relation to an outcome. We developed a constraint optimization algorithm to find the minimal glucose levels associated with the maximized combination of insulin sensitivity and β-cell function, the two main mechanisms of glucose homeostasis. We used a training cohort of 1,474 subjects (22% prediabetic, 7.7% diabetic) in whom insulin sensitivity was measured by the clamp technique and β-cell function was determined by mathematical modeling of an oral glucose tolerance test. Optimized fasting glucose levels were ≤87 and ≤89 mg/dl in ≤45-yr-old women and men, respectively, and ≤92 and ≤95 mg/dl in >45-yr-old women and men, respectively; the corresponding optimized 2-h glucose levels were ≤96, ≤98, ≤103, and ≤105 mg/dl. These thresholds were validated in three prospective cohorts of nondiabetic subjects (Relationship Between Insulin Sensitivity and Cardiovascular Disease Study, Botnia Study, and Mexico City Diabetes Study) with baseline and follow-up oral glucose tolerance tests. Of 5,593 participants, 452 progressed to diabetes. Similarly, in the three cohorts, subjects with glucose levels above the estimated thresholds had an odds ratio of 3.74 (95% confidence interval = 2.64–5.48) of progressing, substantially higher than the risk carried by baseline conventionally defined prediabetes [odds ratio = 2.32 (95% confidence interval = 1.91–2.81)]. The concept that optimization of glucose concentrations by direct measures of insulin sensitivity and β-cell function identifies gender- and age-specific thresholds that bear on disease progression is proven in a physiologically sound, quantifiable manner.

A novel test for IGT utilizing metabolite markers of glucose tolerance

The oral glucose tolerance test (OGTT) is the only method to diagnose patients having impaired glucose tolerance (IGT), but its use has diminished considerably in recent years. Metabolomic profiling studies have identified a number of metabolites whose fasting levels are associated with dysglycemia and type 2 diabetes. These metabolites may serve as the basis of an alternative test for IGT. Using the stable isotope dilution technique, quantitative assays were developed for 23 candidate biomarker metabolites. These metabolites were measured in fasting plasma samples taken just prior to an OGTT from 1623 nondiabetic subjects: 955 from the Relationship between Insulin Sensitivity and Cardiovascular Disease Study (RISC Study; 11.7% IGT) and 668 subjects from the Diabetes Mellitus and Vascular Health Initiative (DMVhi) cohort from the DEXLIFE project (11.8% IGT). The associations between metabolites, anthropometric, and metabolic parameters and 2hPG values were assessed by Pearson correlation coefficients and Random Forest classification analysis to rank variables for their ability to distinguish IGT from normal glucose tolerance (NGT). Multivariate logistic regression models for estimating risk of IGT were developed and evaluated using AUCs calculated from the corresponding ROC curves. A model based on the fasting plasma levels of glucose, α-hydroxybutyric acid, β-hydroxybutyric acid, 4-methyl-2-oxopentanoic acid, linoleoylglycerophosphocholine, oleic acid, serine and vitamin B5 was optimized in the RISC cohort (AUC = 0.82) and validated in the DMVhi cohort (AUC = 0.83). A novel, all-metabolite-based test is shown to be a discriminate marker of IGT. It requires only a single fasted blood draw and may serve as a more convenient surrogate for the OGTT or as a means of identifying subjects likely to be IGT.

Modifications of the homeostasis model assessment of insulin resistance index with age

The aim of the study was to analyze the association between aging and insulin resistance estimated by the homeostasis model assessment of insulin resistance (HOMA-IR). This work involved two studies: (1) the Di@bet.es study is a cross-sectional study including 4,948 subjects, comprising a representative sample of the adult Spanish population; (2) the Pizarra study is a population-based cohort study undertaken in Pizarra (Spain), in which 1,051 subjects were evaluated at baseline and 714 completed the 6-year follow-up study. Study variables included a clinical and demographic structured survey, a lifestyle survey, a physical examination, and an oral glucose tolerance test in subjects without diabetes. In the Di@bet.es study overall, an increase occurred in blood glucose until the age of 50, after which it remained stable (data adjusted for gender, body mass index, abnormal glucose regulation [AGR]). The HOMA-IR increased significantly with age (p = 0.01), due to a higher prevalence of obesity (p < 0.0001) and AGR (p < 0.001). In non-obese subjects without AGR, HOMA-IR values were not modified with age (p = 0.30), but they were with body mass index (p < 0.001). In the Pizarra study, the HOMA-IR was significantly lower after 6-year follow-up in the whole study population. Subjects with a HOMA-IR level higher than the 75th percentile at baseline were more likely to develop diabetes (OR 2.2, 95 % CI 1.2-3.9; p = 0.007) than subjects with a lower HOMA-IR. We concluded that age per se did not increase HOMA-IR levels, changes that might be related to higher rates of obesity and AGR in older subjects. The HOMA-IR was associated with an increased risk of developing type 2 diabetes 6 years later.

The threshold shift paradigm of obesity: evidence from surgically induced weight loss

BACKGROUND

The high prevalence of obesity has called attention to the near-intractable problem of sustained weight reduction and its underlying mechanisms. With diet-induced weight loss, achieved body weight is closely related to initial body weight.

OBJECTIVE

The objective was to compare the relation between initial and achieved body mass index (BMI) in patients treated with diet-induced weight loss or bariatric surgery.

DESIGN

We analyzed data from a cohort of 223 healthy individuals who lost a mean (±SD) of 5 ± 3 kg body weight over 3 y by diet (diet group) and data from 182 obese individuals [BMI (in kg/m(2)) ≥35] who had lost an average of 47 ± 17 kg 1 y after Roux-en-Y gastric bypass (a restrictive procedure; n = 71) or biliopancreatic diversion (a malabsorptive procedure; n = 111) (surgery group).

RESULTS

In the diet group, final BMI was strongly related to initial BMI (r = 0.96, P < 0.0001). By multivariate analysis, the decrease in BMI at 3 y was age independent and was predicted only by initial BMI and sex (both P < 0.0001). Strikingly, final BMI was also strongly related to initial BMI (r = 0.67, P < 0.0001) in the surgery group, irrespective of the type of operation. The surgically induced decrease in BMI was predicted by age (P = 0.0002) and initial BMI (P < 0.0001). In 110 surgery patients, serum leptin concentrations decreased from 39 ± 16 to 10 ± 5 ng/mL after surgery (P < 0.0001) and were correlated with BMI both before and after surgery, but the slope of the relation was significantly (P < 0.01) flatter after surgery.

CONCLUSION

The strong predictivity of initial BMI for achieved BMI observed even when voluntary control of energy intake is interfered with through diverse anatomical rearrangements of the gastrointestinal tract supports the concept of a weight "threshold" paradigm: in the obese, anabolic responses are triggered by adiposity-related signals at a higher threshold, which leads to defense of a higher body weight.

We can change the natural history of type 2 diabetes

As diabetes develops, we currently waste the first ∼10 years of the natural history. If we found prediabetes and early diabetes when they first presented and treated them more effectively, we could prevent or delay the progression of hyperglycemia and the development of complications. Evidence for this comes from trials where lifestyle change and/or glucose-lowering medications decreased progression from prediabetes to diabetes. After withdrawal of these interventions, there was no "catch-up"-cumulative development of diabetes in the previously treated groups remained less than in control subjects. Moreover, achieving normal glucose levels even transiently during the trials was associated with a substantial reduction in subsequent development of diabetes. These findings indicate that we can change the natural history through routine screening to find prediabetes and early diabetes, combined with management aimed to keep glucose levels as close to normal as possible, without hypoglycemia. We should also test the hypothesis with a randomized controlled trial.

β-Cell function in type 2 diabetes

Different in vivo tests explore different aspects of β-cell function. Because intercorrelation of insulin secretion indices is modest, no single in vivo test allows β-cell function to be assessed with accuracy and specificity comparable to insulin sensitivity. Physiologically-based mathematical modeling is necessary to interpret insulin secretory responses in terms of relevant parameters of β-cell function. Models can be used to analyze intravenous glucose tests, but secretory responses to intravenous glucose may be paradoxical in subjects with diabetes. Use of oral glucose (or mixed meal) data may be preferable not only for simplicity but also for physiological interpretation. While the disposition index focuses on the relationship between insulin secretion and insulin resistance, secretion parameters reflecting the dynamic response to changing glucose levels over a time frame of minutes or hours--such as β-cell glucose sensitivity--are key to explain changes in glucose tolerance and are largely independent of insulin sensitivity. Pathognomonic of the β-cell defect of type 2 diabetes is a reduced glucose sensitivity, which is accompanied by normal or raised absolute insulin secretion rates--compensatory to the attendant insulin resistance--and impaired incretin-induced potentiation. As β-cell mass is frequently within the range of nondiabetic individuals, these defects are predominantly functional and potentially reversible. Any intervention, on lifestyle or with drugs, that improves glucose tolerance does so primarily through increased β-cell glucose sensitivity. So far, however, no intervention has proven unequivocally capable of modifying the natural course of β-cell dysfunction.

Possible role of interleukin-1β in type 2 diabetes onset and implications for anti-inflammatory therapy strategies

Increasing evidence of a role of chronic inflammation in type 2 diabetes progression has led to the development of therapies targeting the immune system. We develop a model of interleukin-1β dynamics in order to explain principles of disease onset. The parameters in the model are derived from in vitro experiments and patient data. In the framework of this model, an IL-1β switch is sufficient and necessary to account for type 2 diabetes onset. The model suggests that treatments targeting glucose bear the potential of stopping progression from pre-diabetes to overt type 2 diabetes. However, once in overt type 2 diabetes, these treatments have to be complemented by adjuvant anti-inflammatory therapies in order to stop or decelerate disease progression. Moreover, the model suggests that while glucose-lowering therapy needs to be continued all the way, dose and duration of the anti-inflammatory therapy needs to be specifically controlled. The model proposes a framework for the discussion of clinical trial outcomes.

Definition of intervention points in prediabetes

With respect to clinical phenotype and pathophysiology, prediabetes is akin to diabetes. Prediabetes is prevalent in the global population, and those affected are at high risk of progression to overt diabetes, and also at risk of cardiovascular disease (CVD). Progression to diabetes can occur because of worsening insulin resistance, β-cell dysfunction, or both, but the timecourse can be non-linear and, therefore, unpredictable. Intervention-by lifestyle modification, glucose-lowering drugs, or a combination-can postpone deterioration of glucose control, but effects of intervention are variable and can be transient. Furthermore, to what extent interventions can reduce cardiovascular risk is uncertain. Lifestyle intervention mainly hinges on weight loss; as such, risk of failure in the long-term is high, and implementation at the community level is difficult. The ideal candidate for intervention is an individual with prediabetes-identified by targeted screening-with many well documented cardiovascular risk factors, and who is highly motivated to initiate and maintain multifactorial risk-control using a personalised mix of lifestyle-adaptation and pharmacological treatment.

β-cell failure in type 2 diabetes: postulated mechanisms and prospects for prevention and treatment

OBJECTIVE

This article examines the foundation of β-cell failure in type 2 diabetes (T2D) and suggests areas for future research on the underlying mechanisms that may lead to improved prevention and treatment.

RESEARCH DESIGN AND METHODS

A group of experts participated in a conference on 14-16 October 2013 cosponsored by the Endocrine Society and the American Diabetes Association. A writing group prepared this summary and recommendations.

RESULTS

The writing group based this article on conference presentations, discussion, and debate. Topics covered include genetic predisposition, foundations of β-cell failure, natural history of β-cell failure, and impact of therapeutic interventions.

CONCLUSIONS

β-Cell failure is central to the development and progression of T2D. It antedates and predicts diabetes onset and progression, is in part genetically determined, and often can be identified with accuracy even though current tests are cumbersome and not well standardized. Multiple pathways underlie decreased β-cell function and mass, some of which may be shared and may also be a consequence of processes that initially caused dysfunction. Goals for future research include to 1) impact the natural history of β-cell failure; 2) identify and characterize genetic loci for T2D; 3) target β-cell signaling, metabolic, and genetic pathways to improve function/mass; 4) develop alternative sources of β-cells for cell-based therapy; 5) focus on metabolic environment to provide indirect benefit to β-cells; 6) improve understanding of the physiology of responses to bypass surgery; and 7) identify circulating factors and neuronal circuits underlying the axis of communication between the brain and β-cells.

β-cell failure in type 2 diabetes: postulated mechanisms and prospects for prevention and treatment

OBJECTIVE

This article examines the foundation of β-cell failure in type 2 diabetes (T2D) and suggests areas for future research on the underlying mechanisms that may lead to improved prevention and treatment.

RESEARCH DESIGN AND METHODS

A group of experts participated in a conference on 14-16 October 2013 cosponsored by the Endocrine Society and the American Diabetes Association. A writing group prepared this summary and recommendations.

RESULTS

The writing group based this article on conference presentations, discussion, and debate. Topics covered include genetic predisposition, foundations of β-cell failure, natural history of β-cell failure, and impact of therapeutic interventions.

CONCLUSIONS

β-Cell failure is central to the development and progression of T2D. It antedates and predicts diabetes onset and progression, is in part genetically determined, and often can be identified with accuracy even though current tests are cumbersome and not well standardized. Multiple pathways underlie decreased β-cell function and mass, some of which may be shared and may also be a consequence of processes that initially caused dysfunction. Goals for future research include to (1) impact the natural history of β-cell failure; (2) identify and characterize genetic loci for T2D; (3) target β-cell signaling, metabolic, and genetic pathways to improve function/mass; (4) develop alternative sources of β-cells for cell-based therapy; (5) focus on metabolic environment to provide indirect benefit to β-cells; (6) improve understanding of the physiology of responses to bypass surgery; and (7) identify circulating factors and neuronal circuits underlying the axis of communication between the brain and β-cells.

Longitudinal changes in insulin sensitivity, insulin secretion, beta cell function and glucose effectiveness during development of non-diabetic hyperglycemia in a Japanese population

Since there had been no previous studies of alterations in insulin sensitivity, glucose-stimulated insulin secretion, beta cell function and glucose effectiveness during the development of non-diabetic hyperglycemia in Asian populations, we conducted a longitudinal study of such changes in 244 Japanese adults with normal glucose tolerance (median BMI 23.3 kg/m² and age 51 yrs). The median follow-up period was 3.3 yrs. One hundred and eighty-two subjects maintained normal glucose tolerance (nonprogressors). After excluding the 3 subjects who progressed to diabetes, we analyzed the 59 who developed non-diabetic hyperglycemia (progressors), of which 31 progressed to impaired fasting glucose and 28 to impaired glucose tolerance. Whole body insulin sensitivity was estimated by ISI_Matsuda, glucose-stimulated insulin secretion by [δIRI_0-30/δPG_0-30] and Stumvoll indices, hepatic insulin sensitivity by quantitative insulin sensitivity check index (QUICKI) and 1/fasting IRI, beta cell function by oral disposition index (DI_O) ([δIRI_0-30/δPG_0-30]∙[ISI_Matsuda]), and glucose effectiveness by an OGTT-derived index (SgI_O). ISI_Matsuda (p <0.05), [δIRI_0-30/δPG_0-30], DI_O and SgI_O (both p <0.01), but not QUICKI, 1/fasting IRI, or Stumvoll-1st and -2nd phases, were lower in the progressors at baseline. This group was also characterized by the following: 1) ISI_Matsuda, DI_O and SgI_O were reduced by 34%, 32% and 11%, respectively (all p <0.01); 2) QUICKI and 1/fasting IRI diminished by 21% and 5%, respectively (both p <0.01); and 3) no significant changes were found in [δIRI_0-30/δPG_0-30], Stumvoll-1st and -2nd phases or BMI during the follow-up. In the nonprogressors, no indices changed significantly during the follow-up. Our study concluded that during the transition from normal glucose tolerance to non-diabetic hyperglycemia in this non-obese population, whole body insulin sensitivity, hepatic insulin sensitivity, beta cell function, and glucose effectiveness were all attenuated, but no significant changes in glucose-stimulated insulin secretion occurred. Also of note is the fact that the transition took place without any accompanying increase in BMI.

Impact of glucose dosing regimens on modeling of glucose tolerance and β-cell function by intravenous glucose tolerance test in diet-induced obese mice

Insulin sensitivity declines in overweight and obese individuals and, under normal conditions, insulin secretion adaptively increases which in healthy non‐diabetic subjects maintains normal glycemia. This adaptation is best described by the disposition index derived from modeling of insulin and glucose data from an intravenous glucose tolerance testing (IVGTT). One caveat of the IVGTT is that basing the glucose dose on the individual total body weight can result in large differences in the amount of glucose given to lean and obese individuals. The effect this has on determination of insulin sensitivity and β‐cell function is unknown. In this study, we therefore evaluated alternative glucose dosing regimens for determination of the impact of glucose dosing on measures of β‐cell function in normal and diet‐induced obese (DIO) mice. The glucose dosing regimens used for the IVGTT were 0.35 mg per kg total body weight (BW) or per kg lean BW or a fixed glucose dose based on the average BW for all experimental mice. Each regimen detected a similar decrease in insulin sensitivity in DIO mice. The different glucose dosing regimens gave, however, diverging results in regard to glucose elimination and the acute insulin response. Thus, the fixed‐dose regimen was the only that revealed impairment of glucose elimination, whereas dosing according to total BW was the only regimen which showed significant increases in acute insulin response in DIO mice. The fixed‐dose glucose dosing regimen was the only that revealed a significant decline in the disposition index value in DIO mice, which is characteristic of type 2 diabetes in humans. Our results therefore show that using different glucose dosing regimens during IVGTT in DIO mice one can model different aspects of physiology which are similar to prediabetes and type 2 diabetes in humans, with the fixed‐dose regimen producing a phenotype that most closely resembles human type 2 diabetes.

It is unclear what effect the amount of glucose given during an intravenous glucose tolerance test has on measures of glucose tolerance in diet‐induced obese mice. We tested glucose dosing based on total body weight, lean body mass, or a body weight‐independent fixed dose. The fixed‐dose glucose dosing regimen was the only that revealed impaired insulin sensitivity, insufficient insulin secretion, and a diminished disposition index, all hallmarks of type 2 diabetes, and is thus the optimal glucose dosing regimen for intravenous glucose tolerance testing in diet‐induced obese mice.

Limited recovery of β-cell function after gastric bypass despite clinical diabetes remission

The mechanisms responsible for the remarkable remission of type 2 diabetes after Roux-en-Y gastric bypass (RYGBP) are still puzzling. To elucidate the role of the gut, we compared β-cell function assessed during an oral glucose tolerance test (OGTT) and an isoglycemic intravenous glucose clamp (iso-IVGC) in: 1) 16 severely obese patients with type 2 diabetes, up to 3 years post-RYGBP; 2) 11 severely obese normal glucose-tolerant control subjects; and 3) 7 lean control subjects. Diabetes remission was observed after RYGBP. β-Cell function during the OGTT, significantly blunted prior to RYGBP, normalized to levels of both control groups after RYGBP. In contrast, during the iso-IVGC, β-cell function improved minimally and remained significantly impaired compared with lean control subjects up to 3 years post-RYGBP. Presurgery, β-cell function, weight loss, and glucagon-like peptide 1 response were all predictors of postsurgery β-cell function, although weight loss appeared to be the strongest predictor. These data show that β-cell dysfunction persists after RYGBP, even in patients in clinical diabetes remission. This impairment can be rescued by oral glucose stimulation, suggesting that RYGBP leads to an important gastrointestinal effect, critical for improved β-cell function after surgery.

Hypertriglyceridemia is associated with development of metabolic glucose disorders, irrespective of glucose and insulin levels: a 15-year follow-up study

BACKGROUND

Because the role of 2-h postload glucose and insulin levels as confounders in the relationship between hypertriglyceridemia and development of metabolic glucose disorders (MGD) has not been elucidated, the aim of this study was to determine whether triglyceride levels ≥ 1.7 mmol/L are a risk factor of developing MGD in otherwise healthy men and women.

METHODS

A total of 341 healthy men and non-pregnant women, 30 to 50 years of age, were enrolled in a 15-year follow-up study and allocated into the exposed (triglycerides ≥ 1.7 mmol/L) and non-exposed (triglycerides <1.7 mmol/L) groups. Follow-up visits were scheduled every 3 years to complete 5 visits (mean 3.8 visits). At final follow-up, about 15 years later (mean 13.6 years), contact was re-established in 236 individuals to complete 3540 person-years of follow-up. At baseline, all subjects in both groups were required to be free of impaired fasting glucose (IFG), impaired glucose tolerance (IGT), IFG+IGT, and type 2 diabetes.

RESULTS

The Poisson regression models, adjusted by age, sex, family history of diabetes, waist circumference, body mass index, total body fat, blood pressure, fasting and postload glucose, fasting and postload insulin, and HOMA-IR index, showed a significant association between triglycerides ≥ 1.7 mmol/L and IFG (relative risk - RR - 1.40; 95% CI 1.2-2.2), IGT (RR 1.60; 95% CI 1.3-2.2), IFG+IGT (RR 1.80; 95% CI 1.5-2.7), and type 2 diabetes (RR 3.0; 95% CI 2.5-3.8).

CONCLUSIONS

Serum triglyceride levels ≥ 1.7 mmol/L are an independent risk factor of developing IFG, IGT, IFG+IGT, and type 2 diabetes in young and middle-aged, men and women.

Metabolic response to sodium-glucose cotransporter 2 inhibition in type 2 diabetic patients

BACKGROUND

Sodium-glucose cotransporter 2 (SGLT2) inhibitors lower glycemia by enhancing urinary glucose excretion. The physiologic response to pharmacologically induced acute or chronic glycosuria has not been investigated in human diabetes.

METHODS

We evaluated 66 patients with type 2 diabetes (62 ± 7 years, BMI = 31.6 ± 4.6 kg/m(2), HbA1c = 55 ± 8 mmol/mol, mean ± SD) at baseline, after a single dose, and following 4-week treatment with empagliflozin (25 mg). At each time point, patients received a mixed meal coupled with dual-tracer glucose administration and indirect calorimetry.

RESULTS

Both single-dose and chronic empagliflozin treatment caused glycosuria during fasting (median, 7.8 [interquartile range {IQR}, 4.4] g/3 hours and 9.2 [IQR, 5.2] g/3 hours) and after meal ingestion (median, 29.0 [IQR, 12.5] g/5 hours and 28.2 [IQR, 15.4] g/5 hours). After 3 hours of fasting, endogenous glucose production (EGP) was increased 25%, while glycemia was 0.9 ± 0.7 mmol/l lower (P < 0.0001 vs. baseline). After meal ingestion, glucose and insulin AUC decreased, whereas the glucagon response increased (all P < 0.001). While oral glucose appearance was unchanged, EGP was increased (median, 40 [IQR, 14] g and 37 [IQR, 11] g vs. 34 [IQR, 11] g, both P < 0.01). Tissue glucose disposal was reduced (median, 75 [IQR, 16] g and 70 [IQR, 21] g vs. 93 [IQR, 18] g, P < 0.0001), due to a decrease in both glucose oxidation and nonoxidative glucose disposal, with a concomitant rise in lipid oxidation after chronic administration (all P < 0.01). β Cell glucose sensitivity increased (median, 55 [IQR, 35] pmol • min(-1) • m(-2) • mM(-1) and 55 [IQR, 39] pmol • min(-1) • m(-2) • mM(-1) vs. 44 [IQR, 32] pmol • min(-1) • m(-2) • mM(-1), P < 0.0001), and insulin sensitivity was improved. Resting energy expenditure rates and those after meal ingestion were unchanged.

CONCLUSIONS

In patients with type 2 diabetes, empagliflozin-induced glycosuria improved β cell function and insulin sensitivity, despite the fall in insulin secretion and tissue glucose disposal and the rise in EGP after one dose, thereby lowering fasting and postprandial glycemia. Chronic dosing shifted substrate utilization from carbohydrate to lipid. Trial registration. ClinicalTrials.Gov NCT01248364 (EudraCT no. 2010-018708-99). Funding. This study was funded by Boehringer Ingelheim.

The evolution of non-diabetic hyperglycemia: a longitudinal study

The risk factors for impaired fasting glucose (IFG) and impaired glucose tolerance (IGT) have yet to be established. Our aim was to elucidate the predisposing factors for IFG and IGT in Japanese subjects with normal glucose tolerance (NGT). Using a 75 g oral glucose tolerance test (OGTT), we analyzed 604 adults with the ADA-defined NGT. Follow-up glucose tolerance status was determined by 75 g OGTT performed 3.7 yrs later. Glucose-stimulated insulin secretion (GSIS), whole body insulin sensitivity (SI) and beta cell function (BCF) were estimated by Stumvoll indices, ISI(Matsuda), and a product of Stumvoll 1(st) and ISI(Matsuda), respectively, and hepatic SI by quantitative insulin sensitivity check index. Logistic regression analysis revealed that attenuated BCF due to low GSIS was an independent risk factor for IFG. Low whole body SI was an additional risk for IGT. Male gender and high BMI were independently related to the progression to both IFG and IGT, whereas a positive diabetes family history was independently related to IGT. The worsening of glucose tolerance at large was predicted with 66% sensitivity by risk engine with GSIS, whole body SI, gender, BMI and glucose. This finding may help when implementing early intervention strategies for diabetes.

Population impact of increased body mass index and attenuated beta-cell function on worsening of glucose metabolism in subjects with normal glucose tolerance: a pilot study

The population attributable fraction (PAF) of risk factors for the worsening of glucose metabolism in subjects with normal glucose tolerance (NGT) has not been calculated. Our aim was to obtain the PAF of increased body mass index (BMI) and attenuated beta-cell function (BCF) on worsening of glucose metabolism in subjects with NGT. We longitudinally analyzed 604 Japanese adults. The follow-up glucose tolerance status was determined 3.7 years later: 430 participants remained in the NGT category and 102 had progressed to impaired fasting glucose, 67 to impaired glucose tolerance, and 5 to diabetes mellitus. A product of ISIMatsuda and Stumvoll-1, i.e., oral disposition index (DIO), was used as a measure of BCF. The optimal cutoff baseline BMI and DIO values for the prediction of the worsening of glucose metabolism were > 23.1 and < 7.299 kg/m(2), respectively. Isolated increased BMI (iBMIHIGH), isolated low DI (iDIOLOW), and "BMIHIGH and DIOLOW (BMIHIGH/DIOLOW)" were all independently related to the worsening, and the PAF values (95 % CI) for worsening due to iBMIHIGH, iDIOLOW, and BMIHIGH/DIOLOW were 12.9 (3.2-18.4) %, 10.9 (5.0-13.9) %, and 31.4 (22.7-36.3) %, respectively. As much as 55 % of the worsening of glucose metabolism in the NGT subjects was attributable to increased BMI and/or attenuated BCF. The optimal cutoff for BMI was as low as 23.1 kg/m(2) in this population. We believe that these data should form the basis of future public health strategies for the prevention of diabetes in Japan.

Asymmetric dimethylarginine predicts decline of glucose tolerance in men with stable coronary artery disease: a 4.5-year follow-up study

Background

Endothelial dysfunction, largely dependent on impaired nitric oxide bioavailability, has been reportedly associated with incident type 2 diabetes. Our aim was to test the hypothesis that asymmetric dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide formation, might be linked to future deterioration in glucose tolerance in stable coronary artery disease (CAD).

Methods

We studied 80 non-diabetic men (mean age 55 ± 11 years) with stable angina who underwent successful elective complex coronary angioplasty and were receiving a standard medication according to practice guidelines. Plasma ADMA and its structural isomer symmetric dimethylarginine (SDMA) were measured prior to coronary angiography. An estimate of insulin resistance by homeostasis model assessment (HOMA-IR index) was calculated from fasting insulin and glucose. Deterioration in glucose tolerance was defined as development of type 2 diabetes or progression from a normal glucose tolerance to impaired fasting glucose.

Results

Over a median follow-up of 55 months 11 subjects developed type 2 diabetes and 13 progressed to impaired fasting glucose. Incident deterioration of glucose tolerance was associated with ADMA (hazard ratio [HR] per 1-SD increment 1.64 [95% CI: 1.14–2.35]; P = 0.007), log (HOMA-IR index) (HR = 1.60 [1.16–2.20]; P = 0.004) and body-mass index (HR = 1.44 [0.95–2.17]; P = 0.08) by univariate Cox regression. ADMA (HR = 1.65 [1.14–2.38]; p = 0.008) and log (HOMA-IR index) (HR = 1.55 [1.10–2.17]; P = 0.01) were multivariate predictors of a decline in glucose tolerance. ADMA and SDMA were unrelated to body-mass index, HOMA-IR index, insulin or glucose.

Conclusions

ADMA predicts future deterioration of glucose tolerance independently of baseline insulin resistance in men with stable CAD. Whether this association reflects a contribution of endothelial dysfunction to accelerated decline of insulin sensitivity, or represents only an epiphenomenon accompanying pre-diabetes, remains to be elucidated. The observed relationship might contribute to the well-recognized ability of ADMA to predict cardiovascular outcome.