Mean platelet volume (MPV) as new marker of diabetic macrovascular complications in patients with different glucose homeostasis : Platelets in cardiovascular risk.

BACKGROUND: Platelets play an important role in the development of cardiovascular disease (CVD). Mean platelet volume (MPV) is considered as biological marker of platelets activity and function. The aim of the present study was to evaluate MPV values and its possible correlation with arterial stiffness and subclinical myocardial damage, in normal glucose tolerance patients (NGT), in newly diagnosed type 2 diabetic (T2DM) patients and in individuals with pre-diabetes. METHODS: We enrolled 400 newly diagnosed hypertensive patients. All patients underwent an Oral Glucose Tolerance test (OGTT). Arterial stiffness (AS) was evaluated with the measurement of carotid-femoral pulse wave velocity (PWV), augmentation pressure (AP) and augmentation index (AI). Echocardiographic recordings were performed using an E-95 Pro ultrasound system. RESULTS: Among groups there was an increase in fasting plasma glucose (FPG) (p < 0.0001), fasting plasma insulin (FPI) (p < 0.0001), high sensitivity c reactive protein (hs-CRP) levels (p < 0.0001) and a decrease in renal function as demonstrated by e-GFR values (p < 0.0001). From the NGT group to the T2DM group there was a rise in MPV value (p < 0.0001). Moreover, in the evaluation of arterial stiffness and subclinical myocardial damage, MPV showed a positive correlation with these parameters. CONCLUSIONS: In the present study we highlighted that MPV is significantly increased, not only in newly diagnosed T2DM patients, but also in early stage of diabetes, indicating that subjects with pre-diabetes present increased platelets reactivity. Moreover, our results suggest that MPV is associated with increased arterial stiffness and subclinical myocardial damage, indicating MPV as new marker of CV risk.

New potential biomarkers for early chronic kidney disease diagnosis in patients with different glucose tolerance status.

Background: The purpose of the present study was to investigate the role of oxidative stress, platelet activation, and endocan levels in renal dysfunction in normal glucose tolerance (NGT) patients with 1-h plasma glucose values ≥155 mg/dl (NGT ≥ 155), compared to NGT < 155, impaired glucose tolerance (IGT), and type 2 diabetes mellitus (T2DM) newly diagnosed subjects. We enlisted 233 patients subjected to an oral glucose tolerance test (OGTT). Materials and methods: The serum levels of platelet activation (glycoprotein VI and sP-selectin), oxidative stress biomarkers (8-isoprostane and Nox-2), and endocan were evaluated using an ELISA test. Results: Among NGT < 155 patients and the T2DM group, there was a statistically significant increase in 8-isoprostane (p < 0.0001), Nox-2 (p < 0.0001), glycoprotein VI (p < 0.0001), and sP-selectin (p < 0.0001) serum levels. Higher serum endocan levels were found with the worsening of metabolic profile (p < 0.0001); specifically, NGT ≥ 155 patients presented higher serum endocan values when compared to NGT < 155 patients (p < 0.0001). From the multivariate linear regression analysis, 1-h glucose resulted in the major predictor of estimated glomerular filtration rate (e-GFR) justifying 23.6% of its variation (p < 0.0001); 8-isoprostane and Nox-2 added respectively another 6.0% (p < 0.0001) and 3.2% (p = 0.001). Conclusion: Our study confirmed the link between 1-h post-load glucose ≥155 mg/dl during OGTT and the possible increased risk for chronic kidney disease (CKD) in newly diagnosed patients. The novelty is that we demonstrated a progressive increase in oxidative stress, platelet activation, and serum endocan levels with the worsening of metabolic profile, which becomes evident early during the progression of CKD.

One-hour post-load glucose and subclinical left atrial myocardial dysfunction in hypertensive patients.

BACKGROUND: Recently, studies demonstrated that normal glucose-tolerant subjects (NGT) with 1-h post-load plasma glucose value ≥155 mg/dL during oral glucose tolerance test (OGTT) (NGT ≥ 155) present an impaired cardio-metabolic profile, with subclinical myocardial damage. Atrial morphological and functional alterations, closely related to diastolic dysfunction, are important predictors of atrial fibrillation (AF), cardiovascular (CV) events and mortality in the entire population as well as in diabetic patients. The aim of our study was to evaluate subclinical atrial myocardial damage, assessed with speckle tracking echocardiography, in NGT≥155 mg/dL patients, comparing to NGT < 155 mg/dL subjects, impaired glucose tolerant (IGT) individuals and patients with newly diagnosed type 2 diabetes (T2DM). METHODS: We enrolled 229 Caucasian patients. All subjects underwent anthropometrical and haemodynamic parameters evaluation, OGTT, advanced Colour-Doppler echocardiography with evaluation of main atrial and ventricular parameters. RESULTS: As expected, from first to the fourth group there was a worsening of the metabolic profile as attested by fasting, 1- and 2-h post-load plasma glucose levels, during OGTT. Moreover, from NGT < 155 to T2DM group there was an impairment in reservoir and pump atrial function (PALS and PACS, respectively) (p < .0001). CONCLUSION: Present data demonstrated for the first time that NGT≥155 subjects present subclinical atrial dysfunction. These results may be clinically relevant because they highlight how atrial myopathy occurs early in pre-diabetes stage regardless of fibrotic and morphological alterations of the ventricular myocardium.

Short-term effect of sacubitril/valsartan on endothelial dysfunction and arterial stiffness in patients with chronic heart failure.

Heart failure (HF) is associated to endothelial dysfunction that promotes the increase of arterial stiffness thus augmenting myocardial damage. Sacubitril/Valsartan is used in the treatment of HF reduced ejection fraction (HFrEF) and has been proven effective in reducing cardiovascular disease (CVD) progression and all-cause mortality. The aim of this study was to evaluate the effect of Sacubitril/Valsartan on endothelial dysfunction, arterial stiffness, oxidative stress levels and platelets activation in patients with HFrEF, at baseline and after 6 months of treatment. We enrolled 100 Caucasian patients. Endothelial function was evaluated by the reactive hyperemia index (RHI) and arterial stiffness (AS) by the measurement of carotid-femoral pulse wave velocity (PWV), augmentation pressure (AP) and augmentation index (AI). At baseline, among enrolled outpatients, 43% showed a NYHA class II and 57% a NYHA class III. At 6 months, there was a significant improvement of several hemodynamic, clinical and metabolic parameters with a significant reduction in oxidative stress indices such as 8-isoprostane (p < 0.0001) and Nox-2 (p < 0.0001), platelets activity biomarkers such as sP-selectin (p < 0.0001) and Glycoprotein-VI (p < 0.0001), and inflammatory indices. Moreover, we observed a significant improvement in arterial stiffness parameters and in endothelial function indices. Our study demonstrated that 6 months treatment with Sacubitril/Valsartan, in patients with HFrEF, improves endothelial dysfunction and arterial stiffness, by reducing oxidative stress, platelet activation and inflammation circulating biomarkers, without adverse effects.

Chronic Exercise Improves Mitochondrial Function and Insulin Sensitivity in Brown Adipose Tissue.

The aim of the present work was to study the consequences of chronic exercise training on factors involved in the regulation of mitochondrial remodeling and biogenesis, as well as the ability to produce energy and improve insulin sensitivity and glucose uptake in rat brown adipose tissue (BAT). Male Wistar rats were divided into two groups: (1) control group (C; n = 10) and (2) exercise-trained rats (ET; n = 10) for 8 weeks on a motor treadmill (five times per week for 50 min). Exercise training reduced body weight, plasma insulin, and oxidized LDL concentrations. Protein expression of ATP-independent metalloprotease (OMA1), short optic atrophy 1 (S-OPA1), and dynamin-related protein 1 (DRP1) in BAT increased in trained rats, and long optic atrophy 1 (L-OPA1) and mitofusin 1 (MFN1) expression decreased. BAT expression of nuclear respiratory factor type 1 (NRF1) and mitochondrial transcription factor A (TFAM), the main factors involved in mitochondrial biogenesis, was higher in trained rats compared to controls. Exercise training increased protein expression of sirtuin 1 (SIRT1), peroxisome proliferator-activated receptor γ coactivator 1α (PGC1α) and AMP-activated protein kinase (pAMPK/AMPK ratio) in BAT. In addition, training increased carnitine palmitoyltransferase II (CPT II), mitochondrial F1 ATP synthase α-chain, mitochondrial malate dehydrogenase 2 (mMDH) and uncoupling protein (UCP) 1,2,3 expression in BAT. Moreover, exercise increased insulin receptor (IR) ratio (IRA/IRB ratio), IRA-insulin-like growth factor 1 receptor (IGF-1R) hybrids and p42/44 activation, and decreased IGF-1R expression and IR substrate 1 (p-IRS-1) (S307) indicating higher insulin sensitivity and favoring glucose uptake in BAT in response to chronic exercise training. In summary, the present study indicates that chronic exercise is able to improve the energetic profile of BAT in terms of increased mitochondrial function and insulin sensitivity.

Uric Acid Impairs Insulin Signaling by Promoting Enpp1 Binding to Insulin Receptor in Human Umbilical Vein Endothelial Cells.

High levels of uric acid (UA) are associated with type-2 diabetes and cardiovascular disease. Recent pieces of evidence attributed to UA a causative role in the appearance of diabetes and vascular damage. However, the molecular mechanisms by which UA induces these alterations have not been completely elucidated so far. Among the mechanisms underlying insulin resistance, it was reported the role of a transmembrane glycoprotein, named either ectonucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1) or plasma cell antigen 1, which is able to inhibit the function of insulin receptor (IR) and it is overexpressed in insulin-resistant subjects. In keeping with this, we stimulated human umbilical vein endothelial cells (HUVECs) with insulin and UA to investigate the effects of UA on insulin signaling pathway, testing the hypothesis that UA can interfere with insulin signaling by the activation of ENPP1. Cultures of HUVECs were stimulated with insulin, UA and the urate transporter SLC22A12 (URAT1) inhibitor probenecid. Akt and endothelial nitric oxide synthase (eNOS) phosphorylation levels were investigated by immunoblotting. ENPP1 binding to IR and its tyrosine phosphorylation levels were tested by immunoprecipitation and immunoblotting. UA inhibited insulin-induced Akt/eNOS axis. Moreover, UA induced ENPP1 binding to IR that resulted in an impairment of insulin signaling cascade. Probenecid reverted UA effects, suggesting that UA intracellular uptake is required for its action. In endothelial cells, UA directly interferes with insulin signaling pathway at receptor level, through ENPP1 recruitment. This evidence suggests a new molecular model of UA-induced insulin resistance and vascular damage.

Enhanced expression of indoleamine 2,3-dioxygenase in Helicobacter pylori-infected human gastric mucosa modulates Th1/Th2 pathway and interleukin 17 production.

BACKGROUND: Indoleamine 2,3 dioxygenase (IDO) interferes with immune responses. Host immune response against Helicobacter pylori is involved in the persistence of the infection and its related diseases. AIM: To investigate the role of IDO in the regulation of Th1/Th2 and Th17 pathways in H. pylori infection. METHODS: Gastric biopsy samples were taken from 42 patients who underwent endoscopy and evaluated for the expression of IDO by Western blotting. Gastritis was assessed by the Sydney system score. In a subgroup of patients, biopsies were treated with the IDO inhibitor 1-methyl-L-tryptophan and the expression of interferon-γ (IFN-γ) mRNA and that of T-bet, interleukin-17 (IL-17), and IL-4 determined by real-time PCR and Western blotting, respectively. RESULTS: IDO expression was found to be enhanced (p = .001) in gastric biopsies from H. pylori-infected (n = 18) compared with uninfected (n = 24) patients. Levels of IDO expression were inversely related to the gastritis score (r = -.684, p = .002) in H. pylori-infected gastric mucosa, but not in uninfected mucosa. In gastric biopsy cultures, IDO inhibition increased the expression of IFN-γ mRNA (p = .014), T-bet (p = .045), and IL-17 (p = .02) while decreasing that of IL-4 (p = .048). CONCLUSIONS: In H. pylori-infected human gastric mucosa, an enhanced expression of IDO is capable of modulating Th1/Th2 and Th17 pathways. This mechanism lowers gastric inflammation, possibly contributing to the persistence of H. pylori. Targeting the IDO pathway may be a new strategy for modulating H. pylori-induced mucosal immune response.

Insulin clearance is associated with carotid artery intima-media thickness.

OBJECTIVE: The aim of this study was to investigate whether insulin clearance is independently associated with carotid artery intima-media thickness (IMT), a well-recognized index of vascular damage. METHODS: 361 Non-diabetic Caucasian subjects were subjected to euglycemic hyperinsulinemic clamp to assess insulin sensitivity, and insulin clearance. IMT of the common carotid was measured by ultrasonography. RESULTS: Among the study group, 270 subjects had normal glucose tolerance, 33 had impaired fasting glucose, and 58 had impaired glucose tolerance. Univariate correlations showed that age, BMI, waist, blood pressure, triglycerides, fasting and 2-h post-load glucose and insulin levels were positively correlated with carotid IMT whereas HDL, insulin clearance, and insulin-stimulated glucose disposal were negatively correlated with IMT. A multivariate regression analysis in a model including, in addition to insulin clearance, age, gender, BMI, waist, blood pressure, triglycerides, HDL, fasting and 2-h post-load glucose, insulin-stimulated glucose disposal, fasting and 2-h post-load insulin showed that the traits independently associated with carotid IMT were BMI (ß = 0.42, P < 0.0001), insulin clearance (ß = -0.29, P < 0.0001), age (ß = 0.19, P < 0.0001), waist (ß = 0.18, P = 0.01), diastolic blood pressure (ß = 0.17, P = 0.01), and 2-h post-load glucose (ß = 0.12, P = 0.03). These factors explained 26% of the variance in carotid IMT. Subjects in the lowest tertile of insulin clearance had a 4.06-fold higher odds of having vascular damage (IMT > 0.9 mm) as compared with those in the highest tertile (OR 4.06, 95%CI 1.15-13.24). CONCLUSIONS: Insulin clearance is independently associated with carotid IMT in adult non-diabetic subjects. Individuals with lower levels of insulin clearance have a higher odds of vascular damage.

Cardiometabolic risk profiles and carotid atherosclerosis in individuals with prediabetes identified by fasting glucose, postchallenge glucose, and hemoglobin A1c criteria.

OBJECTIVE: We evaluated whether cardiometabolic risk profiles differ for subjects identified as having prediabetes by A1C, fasting glucose (FPG), or 2-h postchallenge glucose (2-PG) criteria. RESEARCH DESIGN AND METHODS: Atherosclerosis risk factors, oral glucose tolerance test, and ultrasound measurement of carotid intima-media thickness (IMT) were analyzed in 780 nondiabetic individuals. RESULTS: Poor agreement existed for A1C and FPG criteria for identification of subjects with prediabetes (κ coefficient = 0.332). No differences in cardiometabolic risk profiles were observed among the three groups of individuals with prediabetes by A1C only, FPG only, and both A1C and FPG. Poor agreement also existed for A1C and 2-PG criteria for identification of individuals with prediabetes (κ coefficient = 0.299). No significant differences in cardiometabolic risk factors were observed between IGT-only and individuals with prediabetes by A1C and 2-PG. Compared with subjects with prediabetes identified by A1C only, IGT-only individuals exhibited a worse cardiometabolic risk profile, with significantly higher systolic blood pressure, pulse pressure, 2-h postchallenge insulin, triglycerides, high-sensitivity C-reactive protein, and carotid IMT, and lower HDL cholesterol levels and insulin sensitivity. CONCLUSIONS: These results suggest that considerable discordance between A1C, FPG, and 2-PG exists for the identification of individuals with prediabetes and that the cardiometabolic risk profile of these individuals varies by metabolic parameter, with 2-PG showing the stronger association with cardiometabolic risk factors and subclinical atherosclerosis than FPG or A1C.

Insulin sensitivity, ß-cell function, and incretin effect in individuals with elevated 1-hour postload plasma glucose levels.

OBJECTIVE: Individuals with normal glucose tolerance (NGT), whose 1-h postload plasma glucose is ≥155 mg/dL (NGT 1h-high), have an increased risk of type 2 diabetes. The purpose of this study was to characterize their metabolic phenotype. RESEARCH DESIGN AND METHODS: A total of 305 nondiabetic offspring of type 2 diabetic patients was consecutively recruited. Insulin secretion was assessed using both indexes derived from oral glucose tolerance test (OGTT) and intravenous glucose tolerance test (IVGTT). Insulin sensitivity was measured by hyperinsulinemic-euglycemic clamp. RESULTS: Compared with individuals with a 1-h postload plasma glucose <155 mg/dL (NGT 1h-low), NGT 1h-high individuals exhibited lower insulin sensitivity after adjustment for age, sex, and BMI. Insulin secretion estimated from the OGTT did not differ between the two groups of individuals. By contrast, compared with NGT 1h-low individuals, the acute insulin response during an IVGTT and the disposition index were significantly reduced in NGT 1h-high individuals after adjustment for age, sex, and BMI. Incretin effect, estimated as the ratio between total insulin responses during OGTT and IVGTT, was higher in NGT 1h-high individuals compared with NGT 1h-low individuals. CONCLUSIONS: NGT 1h-high individuals may represent an intermediate state of glucose intolerance between NGT and type 2 diabetes characterized by insulin resistance and reduced ß-cell function, the two main pathophysiological defects responsible for the development of type 2 diabetes. Postload hyperglycemia is the result of an intrinsic ß-cell defect rather than impaired incretin effect.

TIMP3 overexpression in macrophages protects from insulin resistance, adipose inflammation, and nonalcoholic fatty liver disease in mice.

The tissue inhibitor of metalloproteinase (TIMP)3, a stromal protein that restrains the activity of proteases and receptors, is reduced in inflammatory metabolic disorders such as type 2 diabetes mellitus (T2DM) and atherosclerosis. We overexpressed Timp3 in mouse macrophages (MacT3) to analyze its potential antidiabetic and antiatherosclerotic effects. Transgenic mice with myeloid cells targeting overexpression of TIMP3 were generated and fed a high-fat diet for 20 weeks. Physical and metabolic phenotypes were determined. Inflammatory markers, lipid accumulation, and insulin sensitivity were measured in white adipose tissue (WAT), liver, and skeletal muscle. In a model of insulin resistance, MacT3 mice were more glucose tolerant and insulin sensitive than wild-type mice in both in vitro and in vivo tests. Molecular and biochemical analyses revealed that increased expression of TIMP3 restrained metabolic inflammation and stress-related pathways, including Jun NH2-terminal kinase and p38 kinase activation, in WAT and liver. TIMP3 overexpression in macrophages resulted in reduced activation of oxidative stress signals related to lipid peroxidation, protein carbonylation, and nitration in WAT and liver. Our data show that macrophage-specific overexpression of TIMP3 protects from metabolic inflammation and related metabolic disorders such as insulin resistance, glucose intolerance, and nonalcoholic steatohepatitis.

Overexpression of tissue inhibitor of metalloproteinase 3 in macrophages reduces atherosclerosis in low-density lipoprotein receptor knockout mice.

OBJECTIVE: Tissue inhibitor of metalloproteinase 3 (TIMP3) is a stromal protein that inhibits the activity of proteases and receptors. TIMP3 is downregulated in metabolic and inflammatory disorders, such as type 2 diabetes mellitus and atherosclerosis, particularly in regions enriched with monocyte/macrophage cells. To investigate the role of TIMP3 in atherosclerosis, we generated a new mouse model in which Timp3 was overexpressed in the atherosclerotic plaque via a macrophage-specific promoter (MacT3). We elucidated any potential antiatherosclerotic effects of TIMP3, including regulation of monocyte/macrophage recruitment within atherosclerotic plaques, in MacT3 mice crossbred with low-density lipoprotein receptor knockout (LDLR(-/-)) mice. METHODS AND RESULTS: MacT3/LDLR(-/-) mice had an improvement of atherosclerosis and metabolic parameters compared with LDLR(-/-). En face aorta and aortic root examination of MacT3/LDLR(-/-) mice revealed smaller atherosclerotic plaques with features of stability, such as increased collagen content and decreased necrotic core formation. Atherosclerotic plaques in MacT3/LDLR(-/-) mice contained fewer T cells and macrophages. Furthermore, TIMP3 overexpression in macrophages resulted in reduced oxidative stress signals, as evidenced by lower lipid peroxidation, protein carbonylation, and nitration in atheromas. CONCLUSIONS: Our study confirmed that macrophage-specific overexpression of TIMP3 decreases the inflammatory content and the amplitude of atherosclerotic plaques in mice.

Low insulin-like growth factor-1 levels are associated with anaemia in adult non-diabetic subjects.

Anaemia is a risk factor for cardiovascular morbidity and mortality. Among factors responsible for anaemia, insulin-like growth factor-1 (IGF-1) is a plausible candidate. We evaluated the association of IGF-1 with haemoglobin (Hb) concentration and anaemia in a cohort of 1,039 Caucasians subjects. Subjects with anaemia exhibited lower IGF-1 (p=0.006), and higher hsCRP levels (p=0.003). To estimate the independent contribution of variables to Hb concentration, a multivariable regression analysis was modeled including age, gender, body mass index (BMI), waist circumference, blood pressure, fasting glucose, fasting insulin, IGF-1, fibrinogen, hsCRP, mean corpuscular haemoglobin (MCH), mean corpuscular volume (MCV), serum iron, estimated glomerular filtration rate (eGFR), and treatment with angiotensin-converting enzyme (ACE) inhibitors or angiotensin II receptor blockers (ARBs). The variables significantly associated with Hb concentration were gender (p<0.0001), IGF-1 (p<0.0001), waist circumference (p=0.02), hsCRP (p<0.04), MCH (p<0.0001), MCV (p<0.0001), serum iron (p=0.001), IGF-1 (p=0.003), hsCRP (p=0.008), and waist circumference (p=0.01), accounting for 54.0% of its variation. Hb concentration was significant lower in subjects in the lowest IGF-1 quartile as compared with those in the third (p=0.02) and fourth (p=0.001). In a logistic regression model adjusted for age, gender, BMI, waist circumference, blood pressure, fasting glucose, fasting insulin, fibrinogen, hsCRP, MCH, MCV, serum iron, eGFR, and treatment with ACE inhibitors or ARBs, subjects in the first quartile of IGF-1 had a 2.49-fold higher risk of having anaemia as compared with those in the fourth (odds ratio 2.70, 95% confidence interval 1.02-7.16). Our data suggest that low IGF-1 may be an important contributor to mild anaemia.

Tissue inhibitor of metalloproteinase 3 deficiency causes hepatic steatosis and adipose tissue inflammation in mice.

BACKGROUND & AIMS: Obesity-driven, low-grade inflammation affects systemic metabolic function and can lead to insulin resistance, hepatic steatosis, and atherosclerosis. Decreased expression of tissue inhibitor of metalloproteinase 3 (Timp3) is a catalyst for insulin resistance and inflammation. Timp3 is a natural inhibitor of matrix metalloproteinases, tumor necrosis factor-alpha-converting enzyme (TACE), and vascular endothelial growth factor receptor 2, and therefore could affect signaling processes involved in inflammation and angiogenesis. METHODS: We assessed the effects of Timp3 on inflammation, tissue remodeling, and intermediary metabolism in mice, under conditions of environmental stress (high-fat diet), genetic predisposition to insulin resistance (insulin receptor [Insr] haploinsufficiency), and varying levels of inflammation (Timp3 or Tace deficiencies). Metabolic tests, immunohistochemistry, real-time polymerase chain reaction, and immunoblotting were used to compare data from wild-type, Insr(+/-), Timp3(-/-), Insr(+/-)Timp3(-/-), and Insr(+/-)Tace(+/-) mice placed on high-fat diets for 10 weeks. RESULTS: Insr(+/-)Timp3(-/-) mice showed a higher degree of adipose and hepatic inflammation compared with wild-type, Insr(+/-), Timp3(-/-), and Insr(+/-)Tace(+/-) mice. In particular, the Insr(+/-)Timp3(-/-) mice developed macrovesicular steatosis and features of severe nonalcoholic fatty liver disease, including lobular and periportal inflammation, hepatocellular ballooning, and perisinusoidal fibrosis. These were associated with increased expression of inflammatory and steatosis markers, including suppressor of cytokine signaling 3 and stearoyl CoA desaturase 1, in both liver and adipose tissue. Interestingly, Insr(+/-)Tace(+/-) mice had a nearly opposite phenotype. CONCLUSIONS: Timp3, possibly through its regulation of TACE, appears to have a role in the pathogenesis of fatty liver disease associated with obesity.

Insulin secretion in metabolically obese, but normal weight, and in metabolically healthy but obese individuals.

Metabolically obese but normal-weight (MONW) individuals present metabolic disturbances typical of obese individuals. Additionally, metabolically healthy but obese (MHO) individuals have been identified who are relatively insulin sensitive and have a favorable cardiovascular risk profile. We compared insulin secretion patterns of MONW and MHO with those of two age-matched groups comprising nonobese individuals or obese insulin-resistant subjects, respectively. To this end, 110 nonobese subjects and 87 obese subjects were stratified into quartile based on their insulin-stimulated glucose disposal (M(FFM)). Insulin secretion was estimated by acute insulin response (AIR) during an intravenous glucose-tolerance test (IVGTT), and the disposition index was calculated as AIR x M(FFM). We found that, as defined, M(FFM) was lower in MONW, who exhibited higher triglycerides, free-fatty acid (FFA), and 2-h postchallenge glucose levels compared to normal nonobese group. Insulin secretion was higher in MONW than in normal nonobese subjects, but disposition index was lower in MONW. Disposition index did not differ between MONW and insulin-resistant obese. M(FFM) was higher in MHO who exhibited lower waist circumference, blood pressure (BP), triglycerides, FFA, insulin levels, and higher high-density lipoprotein (HDL) cholesterol compared to insulin-resistant obese. Insulin secretion did not differ between insulin-resistant obese and MHO, but disposition index was lower in the former group. In conclusion, MONW and insulin-resistant obese showed decreased compensatory insulin secretion compared to normal nonobese and MHO subjects, respectively. Because these subjects also exhibited a worse metabolic risk profile, these findings may account for their increased risk for type 2 diabetes.

Transgenic mice overexpressing human G972R IRS-1 show impaired insulin action and insulin secretion.

Molecular scanning of human insulin receptor substrate (Irs) genes revealed a single lrs1 prevalent variant, a glycine to arginine change at codon 972 (G972R); previous in vitro studies had demonstrated that the presence of this variant results in an impaired activation of the insulin signalling pathway, while human studies gave controversial results regarding its role in the pathogenesis of insulin resistance and related diseases. To address in vivo impact of this IRS-1 variant on whole body glucose homeostasis and insulin signalling, we have generated transgenic mice overexpressing it (Tg972) and evaluated insulin action in the liver, skeletal muscle and adipose tissue and assessed glucose homeostasis both under a normal diet and a high-fat diet. We found that Tg972 mice developed age-related glucose and insulin intolerance and hyperglycaemia, with insulin levels comparatively low. Glucose utilization and insulin signalling were impaired in all key insulin target tissues in Tg972 mice. There were no differences in pancreatic morphology between Tg972 and wild-type mice, however when insulin secretion was evaluated in isolated islets, it was significantly reduced in Tg972 mice islets at any glucose concentration tested. Under a high-fat diet, Tg972 mice had increased body and adipose tissue weight, and were more prone to develop diet-induced glucose and insulin intolerance. So, we believe that Tg972 mice may represent a useful model to elucidate the interaction between genetic and environmental factors in insulin resistance pathogenesis. Furthermore, they may become an important tool to test novel tailored therapies.

Mice heterozygous for tumor necrosis factor-alpha converting enzyme are protected from obesity-induced insulin resistance and diabetes.

OBJECTIVE: Tumor necrosis factor (TNF)-alpha is known to affect insulin sensitivity, glucose, and lipid metabolism through alternative and redundant mechanisms at both translational and post-translational levels. TNF-alpha exerts its paracrine effects once the membrane-anchored form is shed and released from the cell membrane. TNF-alpha cleavage is regulated by TNF-alpha converting enzyme (TACE), which regulates the function of several transmembrane proteins, such as interleukin-6 receptor and epidermal growth factor receptor ligands. The role of TACE in high-fat diet (HFD)-induced obesity and its metabolic complications is unknown. RESEARCH DESIGN AND METHODS: To gain insights into the role of TACE in metabolic disorders, we used Tace(+/-) mice fed a standard or high-fat diet for 16 weeks. RESULTS: We observed that Tace(+/-) mice are relatively protected from obesity and insulin resistance compared with wild-type littermates. When fed an HFD, wild-type mice exhibited visceral obesity, increased free fatty acid and monocyte chemoattractant protein (MCP)1 levels, hypoadiponectinemia, glucose intolerance, and insulin resistance compared with Tace(+/-) mice. Interestingly, Tace(+/-) mice exhibited increased uncoupling protein-1 and GLUT4 expression in white adipose tissue. CONCLUSIONS: Our results suggest that modulation of TACE activity is a new pathway to be investigated for development of agents acting against obesity and its metabolic complications.

Plasma interleukin-6 levels are independently associated with insulin secretion in a cohort of Italian-Caucasian nondiabetic subjects.

We have investigated the relationships between plasma interleukin-6 (IL-6) levels and insulin sensitivity and insulin secretion in a cohort of Italian-Caucasian glucose-tolerant subjects. Insulin sensitivity was assessed by euglycemic-hyperinsulinemic clamp, and first-phase insulin secretion was measured by intravenous glucose tolerance test. Fasting plasma IL-6 concentration was negatively correlated with the rate of insulin-stimulated glucose disposal (M) (P = 0.001). The correlation remained statistically significant, while attenuated, after adjusting for sex, age, and BMI (P < 0.03); after an additional adjustment for free fatty acids (FFAs), a further attenuation was observed, but statistical significance was maintained (P < 0.044). Fasting plasma IL-6 concentration was positively correlated with first-phase insulin secretion assessed as acute insulin response (AIR) (P = 0.001). The correlation remained significant after adjusting for sex, age, and BMI (P = 0.003). To estimate the independent contribution of plasma IL-6 levels to AIR, we carried out forward stepwise linear regression analysis in a model that included sex, age, BMI, waist-to-hip ratio, FFAs, and insulin-stimulated glucose disposal. Only insulin sensitivity and plasma IL-6 concentration were independently associated with AIR, accounting, respectively, for 19.0 and 5.2% of its variation. These data indicate that IL-6 is associated in a reciprocal manner with the two pathophysiological components of type 2 diabetes, i.e., insulin resistance and insulin secretion.

Timp3 deficiency in insulin receptor-haploinsufficient mice promotes diabetes and vascular inflammation via increased TNF-alpha.

Activation of inflammatory pathways may contribute to the beginning and the progression of both atherosclerosis and type 2 diabetes. Here we report a novel interaction between insulin action and control of inflammation, resulting in glucose intolerance and vascular inflammation and amenable to therapeutic modulation. In insulin receptor heterozygous (Insr+/-) mice, we identified the deficiency of tissue inhibitor of metalloproteinase 3 (Timp3, an inhibitor of both TNF-alpha-converting enzyme [TACE] and MMPs) as a common bond between glucose intolerance and vascular inflammation. Among Insr+/- mice, those that develop diabetes have reduced Timp3 and increased TACE activity. Unchecked TACE activity causes an increase in levels of soluble TNF-alpha, which subsequently promotes diabetes and vascular inflammation. Double heterozygous Insr+/-Timp3+/- mice develop mild hyperglycemia and hyperinsulinemia at 3 months and overt glucose intolerance and hyperinsulinemia at 6 months. A therapeutic role for Timp3/TACE modulation is supported by the observation that pharmacological inhibition of TACE led to marked reduction of hyperglycemia and vascular inflammation in Insr+/- diabetic mice, as well as by the observation of increased insulin sensitivity in Tace+/- mice compared with WT mice. Our results suggest that an interplay between reduced insulin action and unchecked TACE activity promotes diabetes and vascular inflammation.