Effects of chronic acarbose treatment on adipocyte insulin responsiveness, serum levels of leptin and adiponectin and hypothalamic NPY expression in obese diabetic

1. Inhibitors of intestinal glucosidases have been shown to improve glycaemic control in diabetic and obese humans and animals. In the present study, we have investigated the effect of 3 months treatment with acarbose on adiposity, food intake and the modulation of hypothalamic neuropeptide Y (NPY) in obese diabetic Wistar (WDF) rats and the possible correlation between changes in overall insulin sensitivity and the level of circulating adipokines, leptin and adiponectin. In addition, we investigated the effect of acarbose on adipocyte insulin signalling. 2. Mature male WDF rats were randomly distributed to one of three treatment groups (no acarbose or 20 or 40 mg of acarbose/100 g diet). After 3 months, blood glucose, cholesterol, triglyceride, insulin, leptin and adiponectin were analysed. Insulin signalling was determined in isolated adipocytes as the stimulation of mitogen-activated protein kinase (MAPK) and Akt phosphorylation; the level of hypothalamic NPY was assessed by immunohistochemistry. 3. Acarbose-treated rats had lower levels of blood glucose, cholesterol, triglyceride, insulin and leptin and an increase in adiponectin compared with untreated animals. There were no changes in bodyweight and adiposity. Stimulation of adipocyte MAPK activity by insulin was higher in rats treated with both doses of acarbose, whereas higher stimulation of Akt phosphorylation was observed with the highest dose of acarbose. Although food intake was not significantly reduced in rats treated with acarbose, the acarbose-treated rats had lower NPY expression in the arcuate nucleus. 4. We conclude that the improvement in overall insulin sensitivity in WDF rats after prolonged acarbose treatment is paralleled by increases in circulating adiponectin and adipocyte insulin responsiveness. Acarbose neither decreases food intake nor reverts obesity, but decreases leptin levels and the expression of the orexigenic NPY in the hypothalamus.