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Liver has a principal role in glucose regulation and lipids homeostasis. It is under a complex control by substrates such as hormones, nutrients and neuronal impulses. Insulin promotes glycogen synthesis, lipogenesis and lipoprotein synthesis, and inhibits gluconeogenesis, glycogenolysis, and VLDL secretion by modifying the expression and enzymatic activity of specific molecules. To understand the pathophysiologic mechanisms leading to metabolic-liver disease, we analyzed liver protein patterns expressed in a mice model of diabetes by proteomic approaches. We used insulin receptor knockout (IR-/-) and heterozygous (IR+/-) mice as a murine model of liver metabolic dysfunction associated with diabetic ketoacidosis and insulin resistance. We evaluated liver fatty acid levels by microscopic examination and protein expression profiles by orthogonal experimental strategies using protein 2-DE MALDI-TOF/TOF and peptic nLC-MS/MS shotgun profiling. Identified proteins were then loaded into Ingenuity Pathways Analysis to find possible molecular networks. Twenty-eight proteins identified by 2-DE analysis and 24 identified by nLC-MS/MS shotgun, were differentially expressed among the 3 genotypes. Bioinformatic analysis revealed a central role of High Mobility Group Box 1/2 and huntigtin never reported before in the association with metabolic and related liver disease. A different modulation of these proteins both in blood and hepatic tissue further suggests their role in these processes. These results provide new insight into pathophysiology of insulin resistance and hepatic steatosis, and could be useful in identifying novel biomarkers to predict risk for diabetes and its complications. [ABSTRACT FROM AUTHOR]

The most important goal in the treatment of patients with diabetes is to prevent the risk of cardiovascular disease (CVD), the first cause of mortality in these subjects. Thiazolidinediones (TZDs), a class of antidiabetic drugs, act as insulin sensitizers increasing insulin-dependent glucose disposal and reducing hepatic glucose output. TZDs including pioglitazone, rosiglitazone and troglitazone, by activating PPAR-γ have shown pleiotropic effects in reducing vascular risk factors and atherosclerosis. However, troglitazone was removed from the market due to its hepatoxicity, and rosiglitazone and pioglitazone both have particular warnings due to being associated with heart diseases. Specific genetic variations in genes involved in the pathways regulated by TDZs have demonstrated to modify the variability in treatment with these drugs, especially in their side effects. Therefore, pharmacogenomics and pharmacogenetics are an important tool in further understand intersubject variability per se but also to assess the therapeutic potential of such variability in drug individualization and therapeutic optimization. [ABSTRACT FROM AUTHOR]

nhanced oxidative stress contributes to the pathogenesis of diabetes and its complications. Peroxiredoxin 6 (PRDX6) is a key regulator of cellular redox balance, with the peculiar ability to neutralize peroxides, peroxynitrite, and phospholipid hydroperoxides. In the current study, we aimed to define the role of PRDX6 in the pathophysiology of type 2 diabetes (T2D) using PRDX6 knockout (-/-) mice. Glucose and insulin responses were evaluated respectively by intraperitoneal glucose and insulin tolerance tests. Peripheral insulin sensitivity was analyzed by euglycemic-hyperinsulinemic clamp, and molecular tools were used to investigate insulin signaling. Moreover, inflammatory and lipid parameters were evaluated. We demonstrated that PRDX6-/- mice developed a phenotype similar to early-stage T2D caused by both reduced glucose-dependent insulin secretion and increased insulin resistance. Impaired insulin signaling was present in PRDX6-/- mice, leading to reduction of muscle glucose uptake. Morphological and ultrastructural changes were observed in islets of Langerhans and livers of mutant animals, as well as altered plasma lipid profiles and inflammatory parameters. In conclusion, we demonstrated that PRDX6 is a key mediator of overt hyperglycemia in T2D glucose metabolism, opening new perspectives for targeted therapeutic strategies in diabetes care. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The use of bariatric surgery in the clinical management of type 2 diabetes has been recently endorsed in the clinical practice recommendations released by the most influential diabetologic associations. However, authoritative critic voices about the application of metabolic surgery in type 2 diabetes continue to appear in diabetologic literature. In this review, we will try therefore to understand what the reasons for this apparent dichotomy. In this paper, we revised what we believe are now clear evidences about the role of bariatric surgery in the treatment of type 2 diabetes in patients with morbid obesity: the efficacy of bariatric surgery in metabolic control, the existence of plausible weight-independent metabolic mechanisms at least in some bariatric procedure, and the importance of the early referral to surgery in patients with firm indications. However, we stressed also the lack of clear high-quality long-term data about the effects of bariatric surgery in the prevention of both macro- and micro-vascular hard endpoints in patients with type 2 diabetes. The accrual of these results will be critical to completely clarify the risk/benefit ratio of bariatric surgery in diabetes, as compared to current pharmacologic therapies. This may be particularly important in patients in which data on long-term efficacy are still not completed, such as in patients with lower BMI levels. [ABSTRACT FROM AUTHOR]

Background: The efficacy of Phosphodiesterase 5 (PDE5) inhibitors to re-establish endothelial function is reduced in diabetic patients. Recent evidences suggest that therapy with PDE5 inhibitors, i.e. sildenafil, may increase the expression of nitric oxide synthase (NOS) proteins in the heart and cardiomyocytes. In this study we analyzed the effect of sildenafil on endothelial cells in insulin resistance conditions in vitro. Methodology/Principal Findings: Human umbilical vein endothelial cells (HUVECs) were treated with insulin in presence of glucose 30 mM (HG) and glucosamine 10 mM (Gluc-N) with or without sildenafil. Insulin increased the expression of PDE5 and eNOS mRNA assayed by Real time-PCR. Cytofluorimetric analysis showed that sildenafil significantly increased NO production in basal condition. This effect was partially inhibited by the PI3K inhibitor LY 294002 and completely inhibited by the NOS inhibitor L-NAME. Akt-1 and eNOS activation was reduced in conditions mimicking insulin resistance and completely restored by sildenafil treatment. Conversely sildenafil treatment can counteract this noxious effect by increasing NO production through eNOS activation and reducing oxidative stress induced by hyperglycaemia and glucosamine. Conclusions/Significance: These data indicate that sildenafil might improve NOS activity of endothelial cells in insulin resistance conditions and suggest the potential therapeutic use of sildenafil for improving vascular function in diabetic patients. [ABSTRACT FROM AUTHOR]

OBJECTIVE--Tumor necrosis factor (TNF)-α is known to affect insulin sensitivity, glucose, and lipid metabolism through alternative and redundant mechanisms at both translational and post-translational levels. TNF-α exerts its paracrine effects once the membrane-anchored form is shed and released from the cell membrane. TNF-α cleavage is regulated by TNF-α 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. Diabetes 56:2541-2546, 2007 [ABSTRACT FROM AUTHOR]

Uncoupling protein (UCP)-2 is a member of the mitochondrial inner membrane carriers that uncouple pro-ton entry in the mitochondrial matrix from ATP synthesis. The -866G/A polymorphism in the UCP2 gene, which enhances its transcriptional activity, was associated with enhanced risk for type 2 diabetes in obese subjects. We addressed the question of whether the -866G/A polymorphism contributes to variation in insulin sensitivity by genotyping 181 nondiabetic offspring of type 2 diabetic patients. Insulin sensitivity, assessed by the hyperinsulinemic-euglycemic clamp, was reduced in -866A/A carriers compared with -866A/G or -866G/G carriers (P = 0.01). To directly investigate the correlation between UCP2 expression and insulin resistance, UCP2 mRNA levels were measured by real-time RT-PCR in subcutaneous fat obtained from 100 obese subjects who underwent laparoscopic adjustable gastric banding. UCP2 mRNA expression was significantly correlated with insulin resistance as assessed by the homeostasis model assessment index (r = 0.27, P = 0.007). We examined the association of the -866A/A genotype in a case-control study including 483 type 2 diabetic subjects and 565 control subjects. The -866A/A genotype was associated with diabetes in women (odds ratio 1.84, 95% CI 1.03-3.28; P = 0.037), but not in men. These results indicate that the -866A/A genotype of the UCP2 gene may contribute to diabetes susceptibility by affecting insulin sensitivity. [ABSTRACT FROM AUTHOR]

Abstract: Objective: To investigate the effect of pioglitazone on endothelial and adipose tissue dysfunction in newly detected IGT patients with CAD. Methods and design: Participants (n =25) were randomized to treatment with either placebo or pioglitazone (30mg/day) for 12 weeks. Before and after treatment we evaluated endothelial function (flow-mediated dilation – FMD – of the brachial artery), circulating adipose and inflammatory markers (adiponectin isoforms, TNF-alpha, and high sensitivity-CRP), and insulin sensitivity (euglycemic hyperinsulinemic clamp). Results: No significant changes were observed in subjects (n =12) treated with placebo. By contrast, subjects (n =13) treated with pioglitazone had significant improvement in FMD (10.8±5.3 vs 13.3±3.6%, p <0.01), accompanied by increased high molecular weight adiponectin (HMW-Ad) (1.7±1.2 vs 4.8±3.6μg/ml, p <0.05) and decreased TNF-alpha (4.3±1.9 vs 3.2±1.2pg/ml, p <0.05) associated to an increased glucose disposal (4.8±1.9 vs 5.4±2.0mgkg−1 min−1, p <0.05). A multiple regression analysis indicated that increasing of HMW-Ad after pioglitazone predicted increased FMD. Conclusion: Pioglitazone significantly improves endothelial and adipose tissue dysfunction in pre-diabetic patients with CAD. [Copyright &y& Elsevier]

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. [ABSTRACT FROM AUTHOR]