Obesity-independent hyperinsulinemia in nondiabetic first-degree relatives of individuals with type 2 diabetes

Parents' cardiovascular risk factors are related to overweight and obesity in young Brazilians with type 1 diabetes

AIM

To identify family background characteristics and cardiovascular disease (CVD) risk factors linked to overweight and obesity in Brazilian with type 1 diabetes (T1D).

METHODS

We performed cross-sectional anthropometric and laboratory analyses in young individuals with T1D.

RESULTS

Among 181 participants, 87 were women and 94 were men (64%/78% normal weight, 27%/15% overweight and 9%/7% obese). Obese men were older; were more likely to be Black; had higher triglyceride levels and diastolic blood pressure (BP), lower estimated glucose disposal rate (eGDR) and higher prevalence of first-degree relatives (FDR) with hypertension and early CVD. Overweight and obese women were more likely to have lower eGDR, and obese women were more likely to have FDR with obesity.

CONCLUSION

One third of young people with T1D were overweight or obese. Excess weight was associated with family history (FH) of obesity for women and FH of early CVD or hypertension for men. BMI was related to decreased insulin sensitivity in both genders, but only men with T1D had metabolic impairment. Our data highlight the importance of considering family background in individuals with T1D.

Hyperinsulinemia in Obesity, Inflammation, and Cancer

The relative insufficiency of insulin secretion and/or insulin action causes diabetes. However, obesity and type 2 diabetes mellitus can be associated with an absolute increase in circulating insulin, a state known as hyperinsulinemia. Studies are beginning to elucidate the cause-effect relationships between hyperinsulinemia and numerous consequences of metabolic dysfunctions. Here, we review recent evidence demonstrating that hyperinsulinemia may play a role in inflammation, aging and development of cancers. In this review, we will focus on the consequences and mechanisms of excess insulin production and action, placing recent findings that have challenged dogma in the context of the existing body of literature. Where relevant, we elaborate on the role of specific signal transduction components in the actions of insulin and consequences of chronic hyperinsulinemia. By discussing the involvement of hyperinsulinemia in various metabolic and other chronic diseases, we may identify more effective therapeutics or lifestyle interventions for preventing or treating obesity, diabetes and cancer. We also seek to identify pertinent questions that are ripe for future investigation.

Intermittent Fasting for Twelve Weeks Leads to Increases in Fat Mass and Hyperinsulinemia in Young Female Wistar Rats

Fasting is known to cause physiological changes in the endocrine pancreas, including decreased insulin secretion and increased reactive oxygen species (ROS) production. However, there is no consensus about the long-term effects of intermittent fasting (IF), which can involve up to 24 hours of fasting interspersed with normal feeding days. In the present study, we analyzed the effects of alternate-day IF for 12 weeks in a developing and healthy organism. Female 30-day-old Wistar rats were randomly divided into two groups: control, with free access to standard rodent chow; and IF, subjected to 24-hour fasts intercalated with 24-hours of free access to the same chow. Alternate-day IF decreased weight gain and food intake. Surprisingly, IF also elevated plasma insulin concentrations, both at baseline and after glucose administration collected during oGTT. After 12 weeks of dietary intervention, pancreatic islets displayed increased ROS production and apoptosis. Despite their lower body weight, IF animals had increased fat reserves and decreased muscle mass. Taken together, these findings suggest that alternate-day IF promote β -cell dysfunction, especially in developing animals. More long-term research is necessary to define the best IF protocol to reduce side effects.

Insulin Resistance in Type 1 Diabetes Mellitus and Its Association with Patient's Micro- and Macrovascular Complications, Sex Hormones, and Other Clinical Data

INTRODUCTION

The main objective of this research was to evaluate the association of insulin resistance (IR) with micro- and macrovascular complications, sex hormones, and other clinical data.

METHODS

Cross-sectional study of patients older than 18 years old with type 1 diabetes mellitus (T1DM) was performed. Participants filled in questionnaires about T1D, disease duration, smoking, glycemic control, chronic diabetes complications, and hypertension status. Data about chronic diabetic complications (neuropathy, retinopathy, and nephropathy) were collected from medical records. History of major cardiovascular events such as angina, myocardial infarction, and stroke were collected from medical records also. Laboratory tests including creatinine, cholesterol levels, testosterone (T), sex hormone-binding globulin (SHBG), estradiol levels, and albumin in 24-h urine sample were performed. IR was calculated using the following formula: estimated glucose disposal rate (eGDR) = 24.31 - [12.22 × waist-to-hip ratio (WHR)] - [3.29 ×  hypertension status (defined as 0 = no, 1 = yes)] - [0.57 × glycated hemoglobin (HbA1c)]. The data was considered statistically significant at p < 0.05.

RESULTS

A total of 200 people (mean age 39.9 ± 12.1 years) with T1D were included in the study. Patients with T1D were analyzed according to eGDR levels stratified by tertiles. The cutoff value of eGDR which reflects IR was less than 6.4 mg kg-1 min-1. When eGDR was less than 6.4 mg kg-1 min-1, diabetes microvascular complications occurred significantly more often (p < 0.001); the cutoff of eGDR for cardiovascular disease (CVD) events was less than 2.34 mg kg-1 min-1. Lower eGDR, longer diabetes duration, and lower HbA1c significantly increased CVD outcomes risk. eGDR was also significantly lower in smokers (7.3 ± 2.5 vs. non-smokers 8.2 ± 2.6, p = 0.011), the obese (lean 8.25 ± 2.47 vs. obese 5.36 ± 2.74, p < 0.000), older patients (less than 50 years 8.0 ± 2.5 vs. more than 50 years 6.2 ± 2.8, p = 0.001), men (men 6.4 ± 2.4 vs. women 8.7 ± 2.2, p < 0.001), patients with long-standing diabetes (< 10 years 7.3 ± 2.6 vs. > 10 years 8.7 ± 2.3, p < 0.001), and chronic diabetes complications (diabetic retinopathy, diabetic nephropathy, diabetic neuropathy, p < 0.001), and patients with CVD (with CVD 5.5 ± 2.4 vs. no CVD 8.0 ± 2.4, p < 0.001). Patients with T1D and a family history of T2D were not susceptible to weight gain during intensive insulin treatment. Metabolic syndrome (MS) phenotype prevalence, including and dyslipidemia rate, were higher in the obese group than in normal weight, but a clear difference was not seen (p = 0.07). Positive linear correlation between men's T and eGDR level was observed (r = 0.33, p = 0.04), i.e., men with higher testosterone level had better insulin sensitivity. Other parameters (like T in women, estrogens, SHBG) did not show any significant association with eGDR.

CONCLUSIONS

According to stratified eGDR, IR was found for one-third of the current T1D population. Insulin resistant patients more frequently had microvascular complications and CVD events. Lower eGDR, longer diabetes duration, and lower HbA1c significantly increased CVD outcomes risk. IR was related to smoking, obesity, gender, age, and diabetes duration. Moreover, men's testosterone had a positive correlation with IR in T1D. Finally, patients with T1D and a positive family history of T2D were not susceptible to weight gain, while MS metabolic phenotype prevalence tended to be higher in obese than in lean patients with T1D, with a tendency to significant difference.

First-degree family history of diabetes and its relationship with serum osteocalcin levels independent of liver fat content in a non-diabetic Chinese cohort

BACKGROUND

First-degree relatives of patients with diabetes (FDR) tend to have impaired insulin activity, which lead to the alternation of circulating cytokine levels. Liver is a main target tissue of insulin action; therefore, liver fat content (LFC) has a close relationship with insulin resistance. This study aimed to find the alteration in serum osteocalcin levels in FDR and the relationship of serum osteocalcin levels with FDR and non-alcoholic fatty liver disease (NAFLD).

METHODS

In total, 1206 subjects including 413 men and 793 women from the communities, aged 59.7 (range, 54.8-64.3) years, were enrolled. An electrochemiluminescence immunoassay was performed to measure the levels of serum osteocalcin. LFC was measured using quantitative ultrasonography.

RESULTS

A significant decrease was found in serum osteocalcin levels in subjects with NAFLD (P < 0.001) as well as in FDR (19.8 ± 5.7 ng/mL versus 20.7 ± 6.8 ng/mL, P = 0.028). Furthermore, among the subjects with NAFLD, those with FDR had lower levels of osteocalcin than those without FDR (P = 0.011). The presence of FDR remained a predictor for decreased serum osteocalcin levels after adjusting for body mass index, blood glucose, blood lipids, and LFC (standardized β = - 0.057, P = 0.028).

CONCLUSIONS

FDR had lower serum osteocalcin levels than non-FDR. The inverse association between FDR and serum osteocalcin levels was independent of metabolic factors.

Hyperinsulinemia: An Early Indicator of Metabolic Dysfunction

Hyperinsulinemia is strongly associated with type 2 diabetes. Racial and ethnic minority populations are disproportionately affected by diabetes and obesity-related complications. This mini-review provides an overview of the genetic and environmental factors associated with hyperinsulinemia with a focus on racial and ethnic differences and its metabolic consequences. The data used in this narrative review were collected through research in PubMed and reference review of relevant retrieved articles. Insulin secretion and clearance are regulated processes that influence the development and progression of hyperinsulinemia. Environmental, genetic, and dietary factors are associated with hyperinsulinemia. Certain pharmacotherapies for obesity and bariatric surgery are effective at mitigating hyperinsulinemia and are associated with improved metabolic health. Hyperinsulinemia is associated with many environmental and genetic factors that interact with a wide network of hormones. Recent studies have advanced our understanding of the factors affecting insulin secretion and clearance. Further basic and translational work on hyperinsulinemia may allow for earlier and more personalized treatments for obesity and metabolic diseases.

The influence of insulin resistance in the occurence of non-alcoholic fatty liver disease among first degree relatives of type 2 diabetes

BACKGROUND

First degree relatives (FDR) of type 2 diabetes mellitus (T2DM) predisposes individuals to have earlier metabolic and vascular disorders independent of insulin resistance (IR) such as thicker carotid intima media thickness than that of non-FDR. Non-alcoholic fatty liver disease (NAFLD) is the most commonly found chronic liver disease in T2DM which is IR dependent. Studies about NAFLD in FDR of T2DM populations are very limited and inconclusive. It is unclear whether the occurrence of NAFLD in FDR of T2DM is IR dependent or due to genetic vulnerability.

AIMS

The aim of this study is to determine the association between NAFLD and FDR of T2DM.

METHOD AND MATERIALS

A total of 118 young adults (19-39 years old) with normal glucose tolerance (59 FDR of T2DM and age-sex matched 59 non-FDR subjects) were included in this cross-sectional study. Anthropometric measurement and routine laboratory analysis (fasting blood glucose/FBG, HbA1c, lipid profile, alanine aminotransferase (ALT), aspartate transaminase (AST)) were examined. Fatty liver was diagnosed by ultrasonography (US) using standard criteria.

RESULTS

Twenty-six (22,03%) subjects with NAFLD were detected by ultrasound with similar proportion for each group. Low HDL-C level and metabolic syndrome were found higher in FDR group (p = 0.004, OR 3.81, CI95 = 1.47-9,91; p = 0.023, OR 4.28, CI95 = 1.13-16.23). Based on logistic regression analysis, central obesity and obesity had statistically significant influence towards NAFLD.

CONCLUSION

The occurrence of NAFLD in FDR of T2DM was influenced by IR (central obesity and obesity).

Insulin resistance and metabolic syndrome criteria in lean, normoglycemic college-age subjects

AIMS

The goal of this study was to determine insulin sensitivity in a fasted state and during an oral glucose tolerance test (OGTT), in normoglycemic (NGT), lean (L) (n = 35) and, for comparison, overweight/obese (OW/O) (n = 9) college-aged subjects.

MATERIALS AND METHODS

Insulin sensitivity for 44 NGT, normotensive subjects, age 18-26 yrs., was determined by homeostasis model assessment (HOMA-IR) and from Matsuda index (ISI Matsuda).

RESULTS

Subjects were normoglycemic fasted (4.59 + 0.35 mmol/L) and at two hours post OGTT (4.52  + 1.35 mmol/L). Besides anthropometric measures, there were significant differences between OW/O and L for fasting insulin (P < 0.001) and both measures of insulin sensitivity (P < 0.05). All subjects exhibited a 9-fold range in HOMA-IR (0.88 + 0.51, range 0.3-2.7) and an 8-fold range in ISI Matsuda (11.9 + 4.7, range 3.0-24.2). The latter was inversely correlated with systolic blood pressure (r = 0.35, P = 0.04) even though subjects were normotensive. In lean subjects, 2.3% were IR by HOMA-IR > 2.1, 5.7% by ISI Matsuda < 5.9, and 22.9% had >one criteria for metabolic syndrome (MetS); 28.6% had some negative metabolic biomarker.

CONCLUSIONS

Insulin resistance is present in lean, NGT college-age subjects even without MetS criteria and is discernable with an easily applicable OGTT-derived index.

Does a First-Degree Family History of Diabetes Impact Placental Maternal and Fetal Vascular Circulation and Inflammatory Response?

CONTEXT

Heritability of diabetes is associated with hyperinsulinemia, impaired endothelial function, and inflammatory up-regulation. However, no studies have examined whether a family history of diabetes (FHD) effects placental vascular circulation.

OBJECTIVE

The current study was designed to investigate the impact of a first-degree FHD on placental vascular circulation and inflammatory lesions.

DESIGN

Observational cohort study.

SETTING

Pregnant women who gave birth at Edith Wolfson Medical Center.

PATIENTS

Three hundred thirty-nine pregnant women were divided into two groups according to presence of FHD: group 1 included 225 subjects without FHD, and group 2 included 114 subjects with FHD.

INTERVENTION

Placental histopathological examination.

MAIN OUTCOME MEASURES

Placental vascular supply abnormalities of maternal and fetal origin.

RESULTS

Maternal vascular supply (MVS) abnormalities of the placenta were significantly higher in subjects with FHD, compared with subjects without FHD (P < 0.005). Fetal vascular supply abnormalities, as well as maternal and fetal inflammatory response did not differ significantly between groups. In the general linear modeling analysis, FHD was an independent and significant predictor of MVS abnormalities and more than doubled the risk of this outcome. Gestational diabetes mellitus (GDM) incidence was significantly higher in subjects with FHD (P < 0.0001). Significant by-group differences in GDM persisted even after adjustment for age and body mass index. Although incidence of gestational hypertensive disorders was significantly higher in individuals with FHD, after adjustment FHD did not significantly predict this outcome.

CONCLUSIONS

A first-degree FHD is significantly and independently associated with an increased rate of maternal vascular perfusion abnormalities and risk of GDM.

Selective Enhancement of Insulin Sensitivity in the Endothelium In Vivo Reveals a Novel Proatherosclerotic Signaling Loop

Rationale:

In the endothelium, insulin stimulates endothelial NO synthase (eNOS) to generate the antiatherosclerotic signaling radical NO. Insulin-resistant type 2 diabetes mellitus is associated with reduced NO availability and accelerated atherosclerosis. The effect of enhancing endothelial insulin sensitivity on NO availability is unclear.

Objective:

To answer this question, we generated a mouse with endothelial cell (EC)–specific overexpression of the human insulin receptor (hIRECO) using the Tie2 promoter–enhancer.

Methods and Results:

hIRECO demonstrated significant endothelial dysfunction measured by blunted endothelium-dependent vasorelaxation to acetylcholine, which was normalized by a specific Nox2 NADPH oxidase inhibitor. Insulin-stimulated phosphorylation of protein kinase B was increased in hIRECO EC as was Nox2 NADPH oxidase–dependent generation of superoxide, whereas insulin-stimulated and shear stress–stimulated eNOS activations were blunted. Phosphorylation at the inhibitory residue Y657 of eNOS and expression of proline-rich tyrosine kinase 2 that phosphorylates this residue were significantly higher in hIRECO EC. Inhibition of proline-rich tyrosine kinase 2 improved insulin-induced and shear stress–induced eNOS activation in hIRECO EC.

Conclusions:

Enhancing insulin sensitivity specifically in EC leads to a paradoxical decline in endothelial function, mediated by increased tyrosine phosphorylation of eNOS and excess Nox2-derived superoxide. Increased EC insulin sensitivity leads to a proatherosclerotic imbalance between NO and superoxide. Inhibition of proline-rich tyrosine kinase 2 restores insulin-induced and shear stress–induced NO production. This study demonstrates for the first time that increased endothelial insulin sensitivity leads to a proatherosclerotic imbalance between NO and superoxide.

Elevation in fibroblast growth factor 23 and its value for identifying subclinical atherosclerosis in first-degree relatives of patients with diabetes

Accumulating evidence supported an association between diabetes and fibroblast growth factor 23 (FGF23). The goal of the present study was to explore alteration in serum FGF23 levels and to assess its value for identifying subclinical atherosclerosis in normoglycemic individuals with a first-degree family history of diabetes (FHD). The study enrolled 312 subjects with a first-degree FHD and 1407 subjects without an FHD. Serum FGF23 levels were detected by a sandwich enzyme-linked immunosorbent assay. Serum FGF23 levels were much higher in subjects with a first-degree FHD than in those without an FHD (P = 0.006). A first-degree FHD was positively associated with serum FGF23 levels, independent of C-IMT and cardiovascular factors (both P < 0.05). In subjects with a first-degree FHD, only those with serum FGF23 levels in the upper quartile were more likely to have an increased C-IMT (odds ratio = 2.263, P < 0.05). As conclusions, a first-degree FHD contributes to the increased serum FGF23 levels independently. Subjects with a first-degree FHD need higher serum FGF23 levels to indicate subclinical atherosclerosis. The influence of a first-degree FHD on serum FGF23 levels should be considered to avoid overestimating the risk of cardiovascular disease in normoglycemic individuals with a first-degree FHD.

Suppression of hyperinsulinaemia in growing female mice provides long-term protection against obesity

AIMS/HYPOTHESIS

Hyperinsulinaemia is associated with obesity but its causal role in the onset of obesity remains controversial. In this study, we tested the hypothesis that transient attenuation of diet-induced insulin hypersecretion in young mice can provide sustained protection against obesity throughout adult life.

METHODS

Using 'genetically humanised' mice lacking both alleles of rodent-specific Ins1, we compared mice heterozygous for the ancestral insulin gene Ins2 with Ins2(+/+) controls. Female Ins1(-/-):Ins2(+/-) and Ins1(-/-):Ins2(+/+) littermates were fed chow or high-fat diet (HFD). Insulin secretion, metabolic health variables and body mass/composition were tracked for over 1 year. We examined islet function and adipose transcript levels of adipogenic, lipogenic and lipolytic genes at two time points.

RESULTS

In control Ins1(-/-):Ins2(+/+) mice, HFD resulted in elevated fasting and glucose-stimulated insulin secretion between 8 weeks and 27 weeks of age. Hyperinsulinaemia was reduced by nearly 50% in Ins1(-/-):Ins2(+/-) mice during this period, without lasting adverse effects on glucose homeostasis. This corresponded with attenuated weight gain and adiposity. White adipose tissue from Ins1(-/-):Ins2(+/-) mice had fewer large lipid droplets, although transcriptional changes were not detected. Importantly, Ins1(-/-):Ins2(+/-) mice remained lighter than Ins1(-/-):Ins2(+/+) littermates despite reaching an equivalent degree of hyperinsulinaemia on HFD by 52 weeks.

CONCLUSIONS/INTERPRETATION

These data demonstrate that attenuation of hyperinsulinaemia in young, growing female mice provides a long-lasting protection against obesity. This protection persists despite a late-onset emergence of hyperinsulinaemia in HFD-fed Ins1(-/-):Ins2(+/-) mice. Given the evolutionary conserved roles of insulin, it is possible that suppressing hyperinsulinaemia early in life may have far-reaching consequences on obesity in full-grown adult humans.

Association between family history risk categories and prevalence of diabetes in Chinese population

AIM

To investigate the association between different family history risk categories and prevalence of diabetes in the Chinese population.

METHODS

The family history of diabetes was obtained from each subject, and an oral glucose tolerance test was performed for measuring the fasting and postload glucose and insulin levels based on a national representative cross-sectional survey of 46,239 individuals (age ≥ 20 years) in the 2007-2008 China National Diabetes and Metabolism Disorders Study. The family history risk categories of diabetes were high, moderate, and average (FH2 and FH1: at least two generations and one generation of first-degree relatives with diabetes, respectively; FH0: no first-degree relatives with diabetes).

RESULTS

The age- and gender-adjusted prevalence rates of diabetes were 32.7% (95% confidence interval (CI): 26.4-39.7%) in FH2, 20.1% (95% CI: 18.2-22.1%) in FH1, and 8.4% (95% CI: 7.9-8.9%) in FH0 (P < 0.0001). The calculated homeostatic model assessment-estimated insulin resistance (HOMA-IR), Matsuda insulin sensitivity index (ISI), and insulinogenic index (ΔI30/ΔG30) values showed significant trending changes among the three risk categories, with the most negative effects in FH2. Multivariate logistic regression analysis showed that the odds ratios of having diabetes were 6.16 (95% CI: 4.46-8.50) and 2.86 (95% CI: 2.41-3.39) times higher in FH2 and FH1, respectively, than in FH0 after adjustment for classical risk factors for diabetes.

CONCLUSIONS

Family history risk categories of diabetes have a significant, independent, and graded association with the prevalence of this disease in the Chinese population.

PWD/PhJ mice have a genetically determined increase in nutrient-stimulated insulin secretion

PWD/PhJ (PWD) is a wild-derived inbred mouse strain unrelated to commonly studied strains, such as C57BL/6J (B6). A chromosome substitution panel with PWD chromosomes transferred into the B6 background is commercially available and will facilitate genetic analysis of this strain. We have previously shown that the PWD strain is a model of primary fasting hyperinsulinemia. To identify more specific phenotypes affected by the genetic variation in PWD compared to B6 mice, we examined physiological mechanisms that may contribute to their elevated insulin levels. PWD mice had increased nutrient-stimulated insulin secretion due to factors inherent to their pancreatic islets. Insulin secretion responses to glucose, palmitate, and the metabolic intermediate α-ketoisocaproate were increased ~2-fold in islets from PWD mice compared to B6 islets. In contrast, there were no strain differences in processes affecting insulin secretion downstream of β cell depolarization. PWD mice tended to have larger but fewer islets than B6 mice, resulting in similar insulin-staining areas and insulin content per unit of pancreatic tissue. However, pancreata of PWD mice were smaller, resulting in reduced total β cell mass and pancreatic insulin content compared to B6 mice. Combined, these data suggest that the elevated fasting insulin levels in PWD mice result from increased generation of metabolic signals leading to β cell depolarization and insulin secretion. Identification of the genetic differences underlying the enhanced nutrient-stimulated insulin secretion in this model may lead to new approaches to appropriately modulate insulin secretion for the treatment of obesity and type 2 diabetes.

Early decrease of insulin sensitivity in offspring of individuals with type 2 diabetes. The Mexican Diabetes Prevention Study

BACKGROUND AND AIMS

Defects in insulin sensitivity (IS) and insulin secretion have been recognized as risk factors for type 2 diabetes (T2D) and its complications. We undertook this study to establish the relationship between healthy type 2 diabetic offspring (OFD) from a Mexican population with IS.

METHODS

A total of 602 Mexican subjects, 359 first-degree offspring of T2D (OFD+) and 243 first-degree non-offspring of T2D (OFD-) were classified as young adults (age range, 18-44 years) and middle-aged adults (age range, 45-65 years). Groups were clinically and biochemically characterized. Quantitative insulin sensitivity check index (QUICKI) was used to estimate IS and the homeostasis model assessment B (HOMA-B) was used to estimate B cell function.

RESULTS

IS decreased significantly (p <0.05) in OFD+ middle-aged (QUICKI 0.330 ± 0.03) compared with OFD- (0. 370 ± 0.03). Middle-aged adults (OFD+) had the highest prevalence of increased fasting insulin levels (FIL) (13.6%) and decreased IS (22.9%) compared with OFD- groups (3.2%). A binary regression analysis showed the association of OFD+ with increased FIL (odds ratio [OR], 3.71; 95% confidence interval [95% CI], 1.68-8.2; p = 0.001), and QUICKI (OR, 10.87; 95% CI, 2.36-44.69; p <0.01) adjusted by gender, age, and obesity.

CONCLUSIONS

Our results suggest that decreased IS itself could be recognized as one of the earliest detectable abnormalities in middle-aged adults. Moreover, prevalence increases with age and is associated with type 2 diabetic offspring, regardless of obesity.

The effect of a glucagon-like peptide-1 receptor agonist on glucose tolerance in women with previous gestational diabetes mellitus: protocol for an investigator-initiated, randomised, placebo-controlled, double-blinded, parallel intervention trial

INTRODUCTION

Pregnancy is associated with decreased insulin sensitivity, which is usually overcome by a compensatory increase in insulin secretion. Some pregnant women are not able to increase their insulin secretion sufficiently, and consequently develop gestational diabetes mellitus (GDM). The disease normally disappears after delivery. Nevertheless, women with previous GDM have a high risk of developing type 2 diabetes (T2D) later in life. We aim to investigate the early development of T2D in women with previous GDM and to evaluate whether treatment with the glucagon-like peptide-1 receptor (GLP-1R) agonist, liraglutide, may modify their risk of developing T2D.

METHODS AND ANALYSES

100 women with previous GDM will be randomised to either liraglutide or placebo treatment for 1 year (blinded) with an open-label extension for another 4 years. Additionally, 15 women without previous GDM will constitute a baseline control group. Women will be tested with an oral glucose tolerance test (primary endpoint: area under the curve for plasma glucose) and an isoglycaemic intravenous glucose infusion at baseline, after 1 year and after 5 years. Additional evaluations include a glucagon test, dual-energy X-ray absorptiometry, imaging of the liver (ultrasound elastography and fibroscanning), an ad libitum meal for food intake evaluation and questionnaires related to appetite, quality of life and alcohol consumption habits.

ETHICS AND DISSEMINATION

The protocol has been approved by the Danish Medicines Agency, the Scientific-Ethical Committee of the Capital Region of Denmark, and the Danish Data Protection Agency and will be carried out under the surveillance and guidance of the GCP unit at Copenhagen University Hospital Bispebjerg in compliance with the ICH-GCP guidelines and in accordance with the Helsinki Declaration. Positive, negative and inconclusive results will be published at scientific conferences and as one or more scientific manuscripts in peer-reviewed journals.

REGISTRATIONS

The trial is registered at https://eudract.ema.europa.eu (2012-001371-37) and http://www.clinicaltrials.gov (NCT01795248).

Lack of oncostatin M receptor β leads to adipose tissue inflammation and insulin resistance by switching macrophage phenotype

Oncostatin M (OSM), a member of the IL-6 family of cytokines, plays important roles in a variety of biological functions, including inflammatory responses. However, the roles of OSM in metabolic diseases are unknown. We herein analyzed the metabolic parameters of OSM receptor β subunit-deficient (OSMRβ(-/-)) mice under normal diet conditions. At 32 weeks of age, OSMRβ(-/-) mice exhibited mature-onset obesity, severer hepatic steatosis, and insulin resistance. Surprisingly, insulin resistance without obesity was observed in OSMRβ(-/-) mice at 16 weeks of age, suggesting that insulin resistance precedes obesity in OSMRβ(-/-) mice. Both OSM and OSMRβ were expressed strongly in the adipose tissue and little in some other metabolic organs, including the liver and skeletal muscle. In addition, OSMRβ is mainly expressed in the adipose tissue macrophages (ATMs) but not in adipocytes. In OSMRβ(-/-) mice, the ATMs were polarized to M1 phenotypes with the augmentation of adipose tissue inflammation. Treatment of OSMRβ(-/-) mice with an anti-inflammatory agent, sodium salicylate, improved insulin resistance. In addition, the stimulation of a macrophage cell line, RAW264.7, and peritoneal exudate macrophages with OSM resulted in the increased expression of M2 markers, IL-10, arginase-1, and CD206. Furthermore, treatment of C57BL/6J mice with OSM increased insulin sensitivity and polarized the phenotypes of ATMs to M2. Thus, OSM suppresses the development of insulin resistance at least in part through the polarization of the macrophage phenotypes to M2, and OSMRβ(-/-) mice provide a unique mouse model of metabolic diseases.

Hyperinsulinemia drives diet-induced obesity independently of brain insulin production

Hyperinsulinemia is associated with obesity and pancreatic islet hyperplasia, but whether insulin causes these phenomena or is a compensatory response has remained unsettled for decades. We examined the role of insulin hypersecretion in diet-induced obesity by varying the pancreas-specific Ins1 gene dosage in mice lacking Ins2 gene expression in the pancreas, thymus, and brain. Age-dependent increases in fasting insulin and β cell mass were absent in Ins1(+/-):Ins2(-/-) mice fed a high-fat diet when compared to Ins1(+/+):Ins2(-/-) littermate controls. Remarkably, Ins1(+/-):Ins2(-/-) mice were completely protected from diet-induced obesity. Genetic prevention of chronic hyperinsulinemia in this model reprogrammed white adipose tissue to express uncoupling protein 1 and increase energy expenditure. Normalization of adipocyte size and activation of energy expenditure genes in white adipose tissue was associated with reduced inflammation, reduced fatty acid spillover, and reduced hepatic steatosis. Thus, we provide genetic evidence that pathological circulating hyperinsulinemia drives diet-induced obesity and its complications.

Hyperinsulinemia precedes insulin resistance in mice lacking pancreatic beta-cell leptin signaling

The adipocyte hormone leptin acts centrally and peripherally to regulate body weight and glucose homeostasis. The pancreatic beta-cell has been shown to be a key peripheral target of leptin, with leptin suppressing insulin synthesis and secretion from beta-cells both in vitro and in vivo. Mice with disrupted leptin signaling in beta-cells (lepr(flox/flox) RIPcre tg+ mice) display hyperinsulinemia, insulin resistance, glucose intolerance, obesity, and reduced fasting blood glucose. We hypothesized that hyperinsulinemia precedes the development of insulin resistance and increased adiposity in these mice with a defective adipoinsular axis. To determine the primary defect after impaired beta-cell leptin signaling, we treated lepr(flox/flox) RIPcre tg+ mice with the insulin sensitizer metformin or the insulin-lowering agent diazoxide with the rationale that pharmacological improvement of the primary defect would alleviate the secondary symptoms. We show that improving insulin sensitivity with metformin does not normalize hyperinsulinemia, whereas lowering insulin levels with diazoxide improves insulin sensitivity. Taken together, these results suggest that hyperinsulinemia precedes insulin resistance in beta-cell leptin receptor-deficient mice, with insulin resistance developing as a secondary consequence of excessive insulin secretion. Therefore, pancreatic beta-cell leptin receptor-deficient mice may represent a model of obesity-associated insulin resistance that is initiated by hyperinsulinemia.

Does abnormal insulin action or insulin secretion explain the increase in prevalence of impaired glucose metabolism with age in populations of different ethnicities?

BACKGROUND

Age is associated with both impaired glucose and insulin metabolism. To what extent the age-related changes in insulin resistance (IR) and beta-cell function contribute to the increase in prevalence of impaired fasting glucose (IFG) and impaired glucose tolerance (IGT) is less known, and this is investigated in this study.

METHODS

This study included 6610 men and 7664 women of different ethnic groups aged 30-69 years. IR and beta-cell function were examined by the homeostasis model assessment of insulin resistance (HOMA-IR) and homeostasis model assessment of beta-cell function (HOMA-B). Odds ratios (ORs) and 95% confidence intervals (95% CIs) were estimated using logistic regression analysis adjusting for body mass index and study.

RESULTS

In Chinese men, the ORs (95% CIs) for IFG were 2.69 (1.70, 4.26), 2.51 (1.49, 4.21) and 2.89 (1.68, 4.97), respectively, in age groups of 40-49, 50-59 and 60-69 years compared with 30-39 years (p < 0.001 for trend); the corresponding figures for IGT were 1.73 (1.25, 2.38), 2.54 (1.78, 3.63) and 3.57 (2.46, 5.19) (p < 0.001 for trend). Similar trends for IGT were observed also in Chinese women and other ethnic groups, but not for IFG in Mauritius Indian and Creole men. Adjustment for HOMA-IR and HOMA-B reduced the ORs in all age groups of all ethnicities for both IFG and IGT, but the risk gradient between age groups remained particularly for the IGT.

CONCLUSIONS

The age-related increase in glucose intolerance may not be fully explained by the defect in HOMA-IR and HOMA-B. As HOMA-IR and HOMA-B are only surrogate measures of insulin sensitivity and insulin secretion, the results need to be further investigated.

The addition of rosiglitazone to insulin in adolescents with type 1 diabetes and poor glycaemic control: a randomized-controlled trial

OBJECTIVE

To evaluate the effect of rosiglitazone, an insulin sensitizer, on glycaemic control and insulin resistance in adolescents with type 1 diabetes mellitus (T1DM) RESEARCH DESIGN AND METHODS: Randomized, double-blind, placebo-controlled crossover trial of rosiglitazone (4 mg twice daily) vs. placebo (24 wk each, with a 4 wk washout period). Entry criteria were diabetes duration >1 yr, age 10-18 yr, puberty (>or=Tanner breast stage 2 or testicular volume >4 mL), insulin dose >or=1.1 units/kg/day, and haemoglobin A1c (HbA1c) >8%. Responses to rosiglitazone were compared with placebo using paired t-tests.

RESULTS

Of 36 adolescents recruited (17 males), 28 completed the trial. At baseline, age was 13.6 +/- 1.8 yr, HbA1c 8.9 +/- 0.96%, body mass index standard deviation scores (BMI-SDS) 0.94 +/- 0.74 and insulin dose 1.5 +/- 0.3 units/kg/day. Compared with placebo, rosiglitazone resulted in decreased insulin dose (5.8% decrease vs. 9.4% increase, p = 0.02), increased serum adiponectin (84.8% increase vs. 26.0% decrease, p < 0.01), increased cholesterol (+0.5 mmol/L vs. no change, p = 0.02), but no significant change in HbA1c (-0.3 vs. -0.1, p = 0.57) or BMI-SDS (0.08 vs. 0.04, p = 0.31). Insulin sensitivity was highly variable in the seven subjects who consented to euglycaemic hyperinsulinaemic clamps. There were no major adverse effects attributable to rosiglitazone.

CONCLUSION

The addition of rosiglitazone to insulin did not improve HbA1c in this group of normal weight adolescents with T1DM.

Impact of metabolic syndrome risk factors in first-degree relatives of type 2 diabetic patients

OBJECTIVE

Family members of patients with an established diagnosis of type 2 diabetes mellitus (T2DM) are theoretically at risk of having the metabolic syndrome (MetS). A sample of these family members was studied from a population in a small township in Argentina, which has a high prevalence of T2DM.

METHODS

We examined the clinical and metabolic characteristics of 132 first-degree relatives of T2DM patients (FDR) and 112 age-matched controls. The subjects were categorized according to the International Diabetes Federation (IDF) and National Cholesterol Education Program Adult Treatment Panel III (NCEP-ATPIII) criteria for MetS.

RESULTS

The prevalence of MetS in the FDR group was 34.8 (IDF) and 26.5% (NCEP-ATPIII) respectively, which was significantly different to the prevalence in controls (p < 0.025). According to IDF criteria, the most prevalent factors among FDR subjects with MetS were low HDL-cholesterol (87%) followed by hypertriglyceridemia (69.5%). In the MetS group, which ranged between 20-29 years old (36%), the major risk factor in women was a low HDL-cholesterol serum level. In the MetS group, which ranged between 30-39 years old (44.4%), the most important risk factor in men was hypertriglyceridemia.

CONCLUSION

This study revealed that the prevalence of MetS is high in young FDR adults, who need urgent preventive treatment, including lifestyle changes. The risk of developing T2DM is five times higher in non-diabetic people with MetS than in those without the syndrome.

Insulin resistance, beta-cell function, and glucose tolerance in Brazilian adolescents with obesity or risk factors for type 2 diabetes mellitus

OBJECTIVE

To evaluate insulin resistance (IR), beta-cell function, and glucose tolerance in 119 Brazilian adolescents with obesity or risk factors (RF) for type 2 diabetes mellitus (T2DM).

STUDY DESIGN

We analyzed weight (kg), height (m), body mass index (BMI; kg/m(2)), waist (W; cm), acanthosis nigricans (AN), systolic and diastolic blood pressure (SBP and DBP; mm Hg), fasting plasma glucose (FPG), and 2-h plasma glucose (2hPG) on oral glucose tolerance test (OGTT; 1.75 g of glucose/weight), lipid profile [total cholesterol (TC), fractions, and triglycerides (TGs)], fasting insulin (FI) and 2-h insulin on OGTT (2hI-RIA), HOMA-B (%; beta-cell function--HOMA program), HOMA-S (%; insulin sensitivity--HOMA program) and HOMA-IR [fasting plasma insulin (mU/ml)xfasting plasma glucose (mmol/L)/22.5]. Division according to number of RF-family history of T2DM (FHT2DM), obesity, hypertension, dyslipidemia, polycystic ovary syndrome (PCOS), and AN. G1: subjects with no or one RF; G2: subjects with two or more RFs. Statistical data were nonparametrical.

RESULTS

Fasting plasma glucose (G2: 81.6+/-10.2 vs. G1: 79.8+/-9.9 mg/dl) and 2hPG (88.1+/-18.0 vs. 87.0+/-19.9 mg/dl) were not different between G2 (n=67) and G1 (n=52), and all adolescents had normal glucose tolerance (NGT). Fasting insulin (13.0+/-7.9 vs. 7.6+/-3.9 microIU/ml; P<.001) and 2hI (60.2+/-39.1 vs. 38.3+/-40.0 microIU/ml; P<.001), HOMA-B (169.1+/-131.6% vs. 106.1+/-39.9%; P<.001), and HOMA-IR (2.62+/-1.7 vs. 1.52+/-0.8; P<.001) were higher in G2. HOMA-S (92.5+/-59.5% vs. 152.2+/-100.5%; P<.001) was also lower in this latter group.

CONCLUSION

Brazilian adolescents with two or more RFs for the development of T2DM have higher IR and beta-cell function and lower insulin sensitivity. However, adolescents with impaired glucose tolerance (IGT) or DM have not been found, differently from similar studies. Differences in ethnic background, environment, and lifestyle factors may account for this disparity.

The pancreatic beta cell is a key site for mediating the effects of leptin on glucose homeostasis

The hormone leptin plays a crucial role in maintenance of body weight and glucose homeostasis. This occurs through central and peripheral pathways, including regulation of insulin secretion by pancreatic beta cells. To study this further in mice, we disrupted the signaling domain of the leptin receptor gene in beta cells and hypothalamus. These mice develop obesity, fasting hyperinsulinemia, impaired glucose-stimulated insulin release, and glucose intolerance, similar to leptin receptor null mice. However, whereas complete loss of leptin function causes increased food intake, this tissue-specific attenuation of leptin signaling does not alter food intake or satiety responses to leptin. Moreover, unlike other obese models, these mice have reduced fasting blood glucose. These results indicate that leptin regulation of glucose homeostasis extends beyond insulin sensitivity to influence beta cell function, independent of pathways controlling food intake. These data suggest that defects in this adipoinsular axis could contribute to diabetes associated with obesity.

Insulin resistance in children and adolescents

IR is hypothesized to be the important pathophysiologic link between adiposity and future development of type 2 diabetes and cardiovascular disease. A variety of methods for measuring IR have been validated in children, from the gold-standard hyperinsulinemic euglycemic clamp, to simple fasting measures based on fasting insulin and glucose levels. Studies have shown that there are a number of important risk factors for IR in children, including adiposity and visceral adiposity, race/ethnicity, puberty, a family history of type 2 diabetes, sex, and being small for gestational age or prematurity. However, obesity represents the critical risk factor for IR in children. Greater than 50% of obese adolescents in the US have IR. Formal assessment of IR in obese children may represent an important strategy for improving the efficacy of pharmacologic therapy for weight loss and chronic disease prevention.

Family history of type 2 diabetes is associated with decreased insulin sensitivity and an impaired balance between insulin sensitivity and insulin secretion in white youth

OBJECTIVE

Family history of type 2 diabetes is a major risk factor for type 2 diabetes in youth, which is increasing. This investigation aimed to evaluate the impact of family history of type 2 diabetes on insulin secretion relative to insulin sensitivity in healthy children. beta-Cell compensation for insulin sensitivity was calculated as the product of insulin sensitivity x first-phase insulin secretion, termed glucose disposition index (GDI).

RESEARCH DESIGN AND METHODS

A total of 28 healthy white children (12 boys and 16 girls; 12.1 +/- 0.5 years of age) with a positive family history of type 2 diabetes and 26 healthy white children (13 boys and 13 girls; 11.5 +/- 0.4 years of age) with a negative family history of type 2 diabetes underwent a 3-h 40 mU.m(-2).min(-1) hyperinsulinemic-euglycemic clamp to assess insulin sensitivity and clearance and a 2-h hyperglycemic clamp to assess insulin secretion. Body composition and visceral adiposity were evaluated with dual-energy X-ray absorptiometry and computed tomography at the L4-L5 intervertebral space.

RESULTS

Insulin sensitivity was lower in children with a family history of type 2 diabetes versus children without a family history (8.8 +/- 0.9 vs. 12.2 +/- 1.1 micromol.kg(-1).min(-1) per pmol/l, P = 0.02). Similarly, insulin clearance was lower. First- and second-phase insulin levels were not different between groups with and without a positive family history. The GDI was lower in youth with versus youth without a positive family history (4.1 +/- 0.3 vs. 5.2 +/- 0.5 mmol.kg(-1).min(-1), P = 0.039). IGF binding protein-1 (IGFBP-1) was 60% lower in youth with versus youth without the positive family history.

CONCLUSIONS

These results demonstrate that family history of type 2 diabetes in white children is associated with decreased insulin sensitivity and clearance, decreased IGFBP-1, and an impaired relationship between insulin action and beta-cell compensation. Detection of these alterations in hormonal and metabolic parameters in children with a positive family history suggests that at least some of the determinants of GDI are genetic/heritable.

Insulin resistance is independently related to age in Mexican women

Whether the decrease of insulin action is a biological consequence of age or a result of lifestyle changes in elderly people is uncertain. Therefore, we rigorously controlled potential confounders to evaluate the relationship between age and insulin resistance in Mexican women. A total of 100 glucose-tolerant, non-hypertensive women, 30-65 yr of age, inhabitants of the same neighborhood of Durango, a city in the North of Mexico, were randomly enrolled to participate in a case-control study. The study was designed to include 50 cases and 50 controls. Insulin-resistant women were considered as cases and compared vs a control group of non-insulin resistant women, matched by BMI and Waist-to-Hip ratio (WHR). HOMA-IR index equal or greater than 3.0 defined the presence of insulin resistance. Endocrine diseases, pregnancy, smoking, alcohol consumption, and physical activity were exclusion criteria. The results showed insulin resistant women were significantly older than control women (53.7 +/- 12.2 vs 46.3 +/- 10.4, p = 0.0004). Women in the case group showed a direct correlation between age and HOMA-IR index (0.427, p = 0.02), whereas control women did not (0.09, p = 0.626). Step-wise forward selection logistic regression analysis showed an independent relationship between HOMA-IR index and age (OR 1.5, CI95% 1.4-1.8, p = 0.002). The results of this study show an independent relationship between age and high HOMA-IR index in Mexican women, supporting the hypothesis that age per se could be associated with the impairment of insulin action.

Beta-cell function is a major contributor to oral glucose tolerance in high-risk relatives of four ethnic groups in the U.S

First-degree relatives of individuals with type 2 diabetes are at increased risk of developing hyperglycemia. To examine the prevalence and pathogenesis of abnormal glucose homeostasis in these subjects, 531 first-degree relatives with no known history of diabetes (aged 44.1 +/- 0.7 years; BMI 29.0 +/- 0.3 kg/m(2)) underwent an oral glucose tolerance test (OGTT). Newly identified diabetes was found in 19% (n = 100), and impaired fasting glucose (IFG) and/or impaired glucose tolerance (IGT) was found in 36% (n = 191). Thus, only 45% (n = 240) had normal glucose tolerance (NGT). The homeostasis model assessment of insulin resistance (HOMA-IR) was used to estimate insulin sensitivity; beta-cell function was quantified as the ratio of the incremental insulin to glucose responses over the first 30 min during the OGTT (DeltaI(30)/DeltaG(30)). This latter measure was also adjusted for insulin sensitivity as it modulates beta-cell function ([DeltaI(30)/DeltaG(30)]/HOMA-IR). Decreasing glucose tolerance was associated with increasing insulin resistance (HOMA: NGT 12.01 +/- 0.54 pmol/mmol; IFG/IGT 16.14 +/- 0.84; diabetes 26.99 +/- 2.62; P < 0.001) and decreasing beta-cell function (DeltaI(30)/DeltaG(30): NGT 157.7 +/- 9.7 pmol/mmol; IFG/IGT 100.4 +/- 5.4; diabetes 57.5 +/- 7.3; P < 0.001). Decreasing beta-cell function was also identified when adjusting this measure for insulin sensitivity ([DeltaI(30)/DeltaG(30)]/HOMA-IR). In all four ethnic groups (African-American, n = 55; Asian-American, n = 66; Caucasian, n = 217; Hispanic-American, n = 193), IFG/IGT and diabetic subjects exhibited progressively increasing insulin resistance and decreasing beta-cell function. The relationships of insulin sensitivity and beta-cell function to glucose disposal, as measured by the incremental glucose area under the curve (AUCg), were examined in the whole cohort. Insulin sensitivity and AUCg were linearly related so that insulin resistance was associated with poorer glucose disposal (r(2) = 0.084, P < 0.001). In contrast, there was a strong inverse curvilinear relationship between beta-cell function and AUCg such that poorer insulin release was associated with poorer glucose disposal (log[DeltaI(30)/DeltaG(30)]: r(2) = 0.29, P < 0.001; log[(DeltaI(30)/DeltaG(30))/HOMA-IR]: r(2) = 0.45, P < 0.001). Thus, abnormal glucose metabolism is common in first-degree relatives of subjects with type 2 diabetes. Both insulin resistance and impaired beta-cell function are associated with impaired glucose metabolism in all ethnic groups, with beta-cell function seeming to be more important in determining glucose disposal.

Hexosamines as mediators of nutrient sensing and regulation in diabetes

High concentrations of glucose induce insulin resistance, impair insulin secretion, and affect hepatic glucose production in a manner that mirrors Type 2 diabetes, and hexosamines mimic many of these effects. This has led to the hypothesis that cells use hexosamine flux as a glucose- and satiety-sensing pathway. The hexosamine hypothesis for glucose sensing has been validated by overexpressing the rate-limiting enzyme for hexosamine synthesis, glutamine: fructose-6-phosphate amidotransferase (GFA) in several tissues including muscle, liver, fat, and beta cells. With overexpression of GFA in transgenic animals, skeletal muscle becomes insulin resistant, the liver synthesizes excess fatty acid, and the beta cell secretes excess insulin leading to hyperinsulinemia. Thus, excess hexosamine flux leads to a coordinated response whereby fuel is shunted toward long-term storage, mirroring the "thrifty phenotype." Chronically, however, these same adaptive changes result ultimately in obesity, hyperlipidemia, beta cell failure, and Type 2 diabetes. These results suggest a mechanism by which chronic overnutrition leads to the phenotype of Type 2 diabetes.

Reduced insulinotropic effect of gastric inhibitory polypeptide in first-degree relatives of patients with type 2 diabetes

In patients with type 2 diabetes, gastric inhibitory polypeptide (GIP) has lost much of its insulinotropic activity. Whether this is similar in first-degree relatives of patients with type 2 diabetes is unknown. A total of 21 first-degree relatives, 10 patients with type 2 diabetes, and 10 control subjects (normal oral glucose tolerance) were examined. During a hyperglycemic "clamp" (140 mg/dl for 120 min), synthetic human GIP (2 pmol. kg(-1). min(-1)) was infused intravenously (30-90 min). With exogenous GIP, patients with type 2 diabetes responded with a lower increment (Delta) in insulin (P = 0.0003) and C-peptide concentrations (P < 0.0001) than control subjects. The GIP effects in first-degree relatives were diminished compared with control subjects (Delta insulin: P = 0.04; Delta C-peptide: P = 0.016) but significantly higher than in patients with type 2 diabetes (P < or = 0.05). The responses over the time course were below the 95% CI derived from control subjects in 7 (insulin) and 11 (C-peptide) of 21 first-degree relatives of patients with type 2 diabetes. In conclusion, a reduced insulinotropic activity of GIP is typical for a substantial subgroup of normoglycemic first-degree relatives of patients with type 2 diabetes, pointing to an early, possibly genetic defect.

Insulin action and secretion in healthy Hispanic-Mexican first-degree relatives of subjects with type 2 diabetes

The aim of this study was to assess the early insulin secretion and insulin action of healthy non-diabetic Hispanic-Mexican subjects with and without family history of Type 2 diabetes (FHD). One hundred and twenty non-relative subjects were compared against 115 first-degree relatives of individuals with Type 2 diabetes. To assign the subjects to the correspondent group, the FHD was carefully ascertained by clinical examination of the participants' parents. Age and gender were matched criteria. Incomplete or unclear data about FHD, previous diagnosis of diabetes or chronic diseases were exclusion criteria. Subjects in both groups were required to have fasting glucose <6.1 mmol/l, and 2-h PG<7.7 mmol/l. Insulin action and secretion were estimated by HOMA (homeostasis model insulin analysis resistance index) and insulinogenic index, respectively. Logistic regression analysis showed an independent relationship between BMI and insulin resistance (HOMA score >5.0) (odds ratio, OR, 1.42, p=0.03), and between FHD and insulin resistance (OR 1.27, p=0.04). On the other hand, there was a strong and independent relationship between FHD and high early insulin secretion (insulinogenic index >0.72) (OR 1.64, p=0.01) but not between BMI and high early insulin secretion (OR 0.93, p=0.3). Healthy Mexican first-degree relatives of subjects with Type 2 diabetes show an independent relationship between FHD and both high early insulin response and decreased insulin action, whereas BMI was only related to insulin resistance.

Insulin secretion, obesity, and potential behavioral influences: results from the Insulin Resistance Atherosclerosis Study (IRAS)

BACKGROUND

This work was conducted to evaluate associations of insulin secretion with overall and central obesity, dietary fats, physical activity, and alcohol.

METHODS

A frequently sampled intravenous glucose tolerance test (FSIGT) was used to assess acute insulin response to glucose (AIR) and insulin sensitivity (S(I)) among adult participants (n=675 with normal, NGT; n=332 with impaired glucose tolerance, IGT) in the Insulin Resistance Atherosclerosis Study (IRAS). Disposition index (DI) was calculated as the sum of the log-transformed AIR and S(I) to reflect pancreatic compensation for insulin resistance. Obesity was measured as body mass index (kg/m(2), BMI) and central fat distribution by waist circumference (cm). Dietary fat intake (total, saturated, polyunsaturated, oleic acid), physical activity, and alcohol intake were assessed by standardized interview.

RESULTS

In unadjusted analyses, BMI and waist were each positively correlated with AIR among NGTs (r=0.26 and 0.23, respectively; p<0.0001) but correlations were weaker among the IGTs (r=0.10, NS; r=0.13, p<0.05 for BMI and waist, respectively). BMI and waist were inversely correlated with DI among NGTs (r=-0.13 and -0.20, respectively; p<0.0001) and among IGTs (r=-0.20 and -0.19, respectively, p<0.0001). Dietary fat variables were positively related, and alcohol was inversely related, to AIR among NGTs (p<0.01) but not among IGTs. With all factors considered simultaneously in a pooled analysis of IGTs and NGTs, waist, but not BMI, was positively associated with AIR (p<0.001) and inversely associated with DI (p<0.01). None of the behavioral variables were independently related to either outcome.

CONCLUSION

Among non-diabetic patients, central obesity appears to be related to higher insulin secretion, but to lower capacity of the pancreas to respond to the ambient insulin resistance.

Obesity and cardiovascular disease. Pathogenetic role of the metabolic syndrome and therapeutic implications

Since obesity is a major risk factor for cardiovascular disease (CVD), the increasing prevalence and degree of obesity in all developed countries has the potential to significantly offset the current efforts to decrease CVD burden in our population. Obesity is pathogenetically related to several clinical and sub-clinical abnormalities that contribute to the development of atherosclerotic placks and their complication, leading to the onset of cardiovascular events. Obesity seems to interact with inheritable factors in determining the onset of insulin resistance, a metabolic abnormality that is responsible for altered glucose metabolism and predisposition to type 2 diabetes, but that also has a major role in the development of dyslipidemia, hypertension and many other sub-clinical abnormalities that contribute to the atherosclerotic process and onset of cardiovascular events. Inheritable factors seem to modulate the onset of type 2 diabetes, dyslipidemia, hypertension and various insulin resistance-related sub-clinical abnormalities, often in a clustering pattern that is commonly referred to as the "metabolic syndrome." Inheritable factors also are involved in the onset of CVD in a given population or individuals with various components of the metabolic syndrome. Intense research is currently undergoing to better understand the molecular mechanisms that could explain the relationship between environmental and inheritable factors that lead from obesity to atherosclerosis and cardiovascular event. The elucidation of these mechanisms will provide improved therapeutic strategies to reduce cardiovascular risk in the obese patients. However, effective therapeutic tools that control each of the known pathophysiological steps mediating CVD in obese patients are already available and should be used more aggressively. Patient education and coordinated approach of physicians, nurses and other health care providers in a multidisciplinary treatment of the obese patient is of fundamental importance to reduce CVD burden in our population.

The adipoinsular axis: effects of leptin on pancreatic beta-cells

The prevalence of obesity and related diabetes mellitus is increasing worldwide. Here we review evidence for the existence of an adipoinsular axis, a dual hormonal feedback loop involving the hormones insulin and leptin produced by pancreatic beta-cells and adipose tissue, respectively. Insulin is adipogenic, increases body fat mass, and stimulates the production and secretion of leptin, the satiety hormone that acts centrally to reduce food intake and increase energy expenditure. Leptin in turn suppresses insulin secretion by both central actions and direct actions on beta-cells. Because plasma levels of leptin are directly proportional to body fat mass, an increase of adiposity increases plasma leptin, thereby curtailing insulin production and further increasing fat mass. We propose that the adipoinsular axis is designed to maintain nutrient balance and that dysregulation of this axis may contribute to obesity and the development of hyperinsulinemia associated with diabetes.