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The mineralocorticoid receptor (MR) is able to regulate the transcription of a number of genes in the myotube, although its roles in skeletal muscle (SM) metabolism still await demonstration. SM represents a major site for glucose uptake, and its metabolic derangements play a pivotal role in the development of insulin resistance (IR). The aim of this study was to investigate the contribution of SM MR in mediating derangements of glucose metabolism in a mouse model of diet-induced obesity. We observed that mice fed a high-fat diet (HFD mice) showed impaired glucose tolerance compared to mice fed a normal diet (ND mice). Mice fed a 60% HFD treated with the MR antagonist Spironolactone (HFD + Spiro) for 12 weeks revealed an improvement in glucose tolerance, as measured with an intraperitoneal glucose tolerance test, compared with HFD mice. To investigate if blockade of SM MR could contribute to the favorable metabolic effects observed with pharmacological MR antagonism, we analyzed MR expression in the gastrocnemius, showing that SM MR protein abundance is downregulated by HFD compared to ND mice and that pharmacological treatment with Spiro was able to partially revert this effect in HFD + Spiro mice. Differently from what we have observed in adipose tissue, where HDF increased adipocyte MR expression, SM MR protein was down-regulated in our experimental model, suggesting a completely different role of SM MR in the regulation of glucose metabolism. To confirm this hypothesis, we investigated the effects of MR blockade on insulin signaling in a cellular model of IRin C2C12 myocytes, which were treated with or without Spiro. We confirmed MR protein downregulation in insulin-resistant myotubes. We also analyzed Akt phosphorylation upon insulin stimulation, and we did not observe any difference between palmitate- and palmitate + Spiro-treated cells. These results were confirmed by in vitro glucose uptake analysis. Taken together, our data indicate that reduced activity of SM MR does not improve insulin signaling in mouse skeletal myocytes and does not contribute to the favorable metabolic effects on glucose tolerance and IR induced by systemic pharmacological MR blockade.

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.

Objectives: This study investigated the effect of a 12-week long-acting testosterone administration on maximal exercise capacity, ventilatory efficiency, muscle strength, insulin resistance, and baroreflex sensitivity (BRS) in elderly patients with chronic heart failure (CHF)., Background: CHF is characterized by a metabolic shift favoring catabolism and impairment in skeletal muscle bulk and function that could be involved in the pathophysiology of heart failure., Methods: Seventy elderly patients with stable CHF-median age 70 years, ejection fraction 31.8 +/- 7%-were randomly assigned to receive testosterone (n = 35, intramuscular injection every 6 weeks) or placebo (n = 35), both on top of optimal medical therapy. At baseline and at the end of the study, all patients underwent echocardiogram, cardiopulmonary exercise test, 6-min walk test (6MWT), quadriceps maximal voluntary contraction (MVC), and isokinetic strength (peak torque) and BRS assessment (sequences technique)., Results: Baseline peak oxygen consumption (VO(2)) and quadriceps isometric strength showed a direct relation with serum testosterone concentration. Peak VO(2) significantly improved in testosterone but was unchanged in placebo. Insulin sensitivity was significantly improved in testosterone. The MVC and peak torque significantly increased in testosterone but not in placebo. The BRS significantly improved in testosterone but not in placebo. Increase in testosterone levels was significantly related to improvement in peak VO(2) and MVC. There were no significant changes in left ventricular function either in testosterone or placebo., Conclusions: These results suggest that long-acting testosterone therapy improves exercise capacity, muscle strength, glucose metabolism, and BRS in men with moderately severe CHF. Testosterone benefits seem to be mediated by metabolic and peripheral effects.

An abstract of the article "Effect of Nebivolol and Carvedilol on insulin resistance in Chronic Heart Failure patients," by G. Marazzi and colleagues is presented.