29 July 2008
Aim: We investigated whether rosiglitazone protects β-cells from glucolipotoxicity directly. Methods: INS-1 cells were incubated with 25 m M glucose and 0.5 m M palmitate in the absence or presence of 2.5 µ M rosiglitazone. We evaluated caspase-3 expression and nuclear DAPI staining. An in vivo study was performed, in which 18-week-old Otsuka Long-Evans Tokushima Fatty (OLETF) rats were treated with rosiglitazone (4 mg/kg/day, n = 6) and with placebo (n = 6) for 10 weeks. At 28 weeks of age, an oral glucose tolerance test, insulin sensitivity test, TUNEL assay and histologic examination were performed. Results: Rosiglitazone attenuated glucolipotoxicity-induced nuclear change and caspase-3 expression for 8 h after treatment, but this effect was not observed at 12 h in INS-1 cells. Rosiglitazone treatment decreased β-cell apoptosis, preserved β-cell mass and improved glucose tolerance in OLETF rats. Conclusion: The present in vitro findings suggest that rosiglitazone can inhibit the early stage of glucolipotoxicity-induced β-cell apoptosis. Our results suggest that the antidiabetic action of rosiglitazone is, at least in part, related to a direct effect on β-cells rather than simply an indirect effect of improving insulin sensitivity.