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Abstract: Berberine can improve insulin resistance, lower blood glucose, and regulate lipid metabolism disorders which cause endothelial dysfunction, leading to vascular complications of type 2 diabetes mellitus. The aim of the present study was to investigate the effects of berberine on endothelial dysfunction of aortas in type 2 diabetes mellitus rats and its mechanism. Wistar rats were randomly divided into four groups: diabetic rats, control rats, diabetic rats treated with berberine (100 mg/kg), and control rats treated with berberine. The serum fasting blood glucose, insulin, total cholesterol, triglyceride and nitric oxide (NO) levels were tested. Acetylcholine-induced endothelium-dependent relaxation and sodium nitroprusside induced endothelium-independent relaxation were measured in aortas for estimating endothelial function. The expression of endothelial nitric oxide synthase (eNOS) mRNA was measured by RT-PCR, and the protein expressions of eNOS and NADPH oxidase (NOX4) were analyzed by western blot. The results showed that berberine significantly decreased fasting blood glucose, and triglyceride levels in diabetic rats. Berberine also improved endothelium-dependent vasorelaxation impaired in aorta. The expressions of eNOS mRNA and protein were significantly increased, while NOX4 protein expression was decreased in aortas from diabetic rats with berberine treatment. Moreover, serum NO levels were elevated after berberine treatment. In conclusion, berberine restores diabetic endothelial dysfunction through enhanced NO bioavailability by up-regulating eNOS expression and down-regulating expression of NADPH oxidase. [Copyright &y& Elsevier]

Abstract: Renal cyclooxygenase (COX)-2 expression and arachidonic acid-stimulated prostaglandin release are increased in streptozotocin-diabetic rats and are reduced by tempol treatment, indicating a role for superoxide. Generation of nitric oxide (NO) and its product with superoxide, peroxynitrite, is also increased in diabetes and can induce COX-2. To investigate a role of NO, rats were treated with l-nitroarginine methyl ester (l-NAME; 100 mg/kg/day) to inhibit NO synthase (NOS) for 14–18 days. In isolated perfused kidneys from diabetic rats, prostaglandin release and vasoconstrictor responses to arachidonic acid were increased and renal cortical expression of COX-2 was 2-fold that of control rats. Treatment of diabetic rats with l-NAME reduced arachidonic acid-stimulated release of prostaglandins and the expression of COX-2. l-NAME increased vasoconstrictor responses to AA in diabetic and non-diabetic rats but abolished the differences between the two. These results, coupled with those using tempol, suggest that NO or its product with superoxide may contribute to the induction of renal COX-2 in the diabetic rat. [Copyright &y& Elsevier]

Rutin, a natural bioflavonoid, has demonstrated anti-diabetic and anti-oxidative bioactivity. Oxidative stress is a potential therapeutic target for diabetic cardiomyopathy. We investigated whether rutinadministration (60 mg/kg body weight) reduces diabetic cardiomyopathy in a diabetic ApoE knock out mouse model. Diabetes was induced in ApoEknockout mice (male, C57BL/6 background) with a high fat diet combined with injection of streptozotocin. Cardiac function was evaluated by echocardiography and cardiac catheter hemodynamic analysis. Cardiac myocardial hypertrophy, myocardial fibrosis, lipid content, myocardial capillary density, and oxidative stress were detected by a series of histopathological analyses, western blotting, and reactive oxygen species analysis. Diabetic mice showed myocardial hypertrophy, lipid accumulation, myocardial fibrosis, elevated collagen content, deteriorating oxidative stress, and left ventricular systolic and diastolic dysfunction. Rutin reversed the myocardial hypertrophy, alleviated extracellular collagen deposition, and lipid accumulation, but increased capillary density in diabetic myocardial tissues. Moreover, rutin substantially improved cardiac function while decreasing blood glucose and lipid content. Therapeutic rutin administration reduced cardiac remodeling and improved myocardial function in diabetic mice, at least in part by reducing oxidative damage and ectopic lipid deposition, inhibiting fibrosis, and promoting angiogenesis. Thus, rutin may represent a potential therapeutic agent for diabetic cardiomyopathy. [ABSTRACT FROM AUTHOR]

Abstract: Plasma cell membrane glycoprotein-1, or ectonucleotide pyrophosphatase/phosphodieterase (PC-1/ENPP1) has been shown to inhibit insulin signaling in cultured cells in vitro and in transgenic mice in vivo when overexpressed. Furthermore, both genetic polymorphism and increased expression of PC-1 have been reported to be associated with type 2 diabetes in humans. Thus it was proposed that PC-1 inhibition represents a potential strategy for the treatment of type 2 diabetes. However, it has not been proven that suppression of PC-1 expression or inhibition of its function will actually improve insulin sensitivity. We show in the current study that transient overexpression of PC-1 inhibits insulin-stimulated insulin receptor tyrosine phosphorylation in HEK293 cells, while knockdown of PC-1 with siRNA significantly increases insulin-stimulated Akt phosphorylation in HuH7 human hepatoma cells. Adenoviral vector expressing a short hairpin RNA against mouse PC-1 (PC-1shRNA) was utilized to efficiently knockdown PC-1 expression in the livers of db/db mice. In comparison with db/db mice treated with a control virus, db/db mice treated with the PC-1shRNA adenovirus had ~80% lower hepatic PC-1 mRNA levels, ~30% lower ambient fed plasma glucose, ~25% lower fasting plasma glucose, and significantly improved oral glucose tolerance. Taken together, these results demonstrate that suppression of PC-1 expression improves insulin sensitivity in vitro and in an animal model of diabetes, supporting the proposition that PC-1 inhibition is a potential therapeutic approach for the treatment of type 2 diabetes. [Copyright &y& Elsevier]