Association Between Metabolism And Regulation Of Glucocorticoids And Metabolic Syndrome

Part IThe effects of high-fat and high-starch diets on insulin resistance of ratsObjective: Glucocorticoid excesses (Cushing's syndrome) show similar fat distribution and metabolic abnormalities, such as hypertension, dyslipidemia and glucose intolerance with metabolic syndrome. Researches have shown that the dysregulation of peripheral metabolism of glucocorticoids is involved in the pathogenesis of metabolic syndrome. In the beginning of this study, we fed rats with high-fat and high-starch diets to induce insulin resistance in order to investigate the effects of different kinds of diets and peroxisome proliferator-activated receptor- γ (PPAR- γ ) and PPAR- α agonists on insulin resistance.Methods: Male Sprague-Dawley rats were divided into seven groups randomly, including chow-fed normal rats (NC group), high-fat-fed rats (FC group), high-fat-fed rats treated with pioglitazone (FP group), high-fat-fed rats treated with fenofibrate (FF group), high-starch-fed rats (SC group), high-starch-fed rats treated with pioglitazone (SP group), and high-starch-fed rats treated with fenofibrate (SF group). After intervention for 8-10 weeks, hyperinsulinemic-euglycemic clamp was made to evaluate the insulinresistance and intravenous glucose tolerance test (IVGTT) was performed to estimate islet functions of rats.Results: High-fat diet and high-starch diet increased the body weight and visceral adipose tissue of rats significantly. Pioglitazone also increased the body weight and visceral adipose tissue of rats significantly because of inducing intake of food. Fenofibrate significantly decreased the body weight and visceral adipose tissue of rats because of its inhibitng of appetite. The mean glucose infusion rates (GIR) during hyperinsulinemic-euglycemic clamp were decreased in FC and SC groups. Fenofibrate improved insulin sensitivity of rats fed on high-fat and high-starch diets significantly. However, Pioglitazone had no effects on improving insulin sensitivity because of increasing body weight and visceral adipose.Conclusions: High-fat and high-starch diets could induce insulin resistance on rats. Fenofibrate improved insulin sensitivity of rats significantly. Pioglitazone had no effects on improving insulin sensitivity because of increasing body weight and visceral adipose.