Abstract
Adiponectin is a protein synthesized from adipose t issue, increases peripheral glucose utilization in liver and skeletal muscle. Adiponectin expression and sec retion are decreased during obesity and insulin resistance. In this study, the effect of insulin, m etformin and dexamethasone on serum lipid profiles was examined in Type 2 Diabetic (T2D) rats. T2D was induced by feeding rats a high fat diet for 4 weeks plus medium dose of Streptozotocin (STZ, 35 mk kg -1 BW). Adiponectin, adiponectin receptors (AdipoR-1 and AdipoR-2), leptin, Peroxisome Prolifrator Activated Receptor gamma (PPAR-γ), Hormone Sensitive Lipase (HSL), Pyruvate Kinase (PK), enolase and Glucose Trasporter-2 (GLUT-2) expression in epididymal adipose and liver tissue w ere examined using RT-PCR. Results showed that metformin improved insulin resistance by normalizin g serum lipid profiles in diabetic rats, while dexamethasone did not alter it. Metformin up-regula ted adiponectin, AdipoR-1 and AdipoR-2 expression, while insulin and dexamethasone down-regulated them. Leptin expression was decreased while PPAR γ, HSL, PK, enolase and GLUT-2 expression was increased by metformin administration. Dexamethasone failed to improve insulin resistance in T2D rats. I n conclusion, metformin ameliorates T2D through controlling adiponectin expression and its conseque nt genes of lipids and glucose metabolism.
Highlights
Improvements in technology lead to a sedentary lifestyle and an increase in body weight and obesity (Goldstein and Scalia, 2004)
We examined the effects of metformin, insulin and dexamethasone on insulin resistance with regarding to adiponectin and gene expression of lipids and glucose
Dexamethasone administration failed to improve such changes in lipid profiles compared to diabetic rats
Summary
Improvements in technology lead to a sedentary lifestyle and an increase in body weight and obesity (Goldstein and Scalia, 2004). Diez and Iglesias (2003) suggested that plasma level of adiponectin has been reduced in clinical conditions associated with insulin resistance, including obesity, type 2 diabetes, dyslipidemia and hypertension. Treatment of type 2 diabetes depends on oral hypoglycemic drugs that contain Peroxisome Prolifrator Activated Receptor Gamma (PPARγ) and thiazolidinediones, among which metformin is the most common. Catecholamines (Fu et al, 2007), growth hormones (Xu et al, 2004), insulin (Fasshauer et al, 2004) and glucocorticoids (Fasshauer et al, 2001) are mostly examined Both in vitro and in vivo studies have shown that glucocorticoids reduce plasma levels of adiponectin and inhibit adiponectin expression (Jang et al, 2008). We examined the effects of metformin, insulin and dexamethasone on insulin resistance with regarding to adiponectin and gene expression of lipids and glucose
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