[Effects of rosiglitazone and metformin on insulin resistance in high-fat diet rats].

Objective: To observe the effects of rosiglitazone and metformin in rats on insulin resistance induced by high-fat diet.

Methods: Normal 8-week old male SD rats were divided into four groups. They were normal chow group (NC, n = 11), high-fat diet (HF, n = 11), metformin-treated (HF + Met, n = 11) and rosiglitazone-treated group (HF + Ros, n = 11). Rosiglitazone 3 mg x kg(-1) x d(-1) and metformin 300 mg x kg(-1) x d(-1) were given orally to HF + Ros and HF + Met group, respectively. After feeding for 8 weeks, serum insulin, adiponectin, glucose (BG), triglyceride (TG) and free fatty acid (FFA) were measured in all the rats. Insulin sensitivity was measured with glucose infusion rate (GIR) and determined by using euglycemic-hyperinsulinemic clamp method.

Results: High-fat diet induced obesity in SD rats after feeding for 8 weeks. High-fat diet decreased adiponectin level by 43.7% (P < 0.01) and GIR by 51.3% (P < 0.01) as compared with the NC group. Metformin decreased body weight by 8.4% (P < 0.01) and TG level by 40.5% (P < 0.01). Metformin significantly increased GIR by 58.9% (P < 0.01) when compared with the HF group. Rosiglitazone caused an apparent reduction of FFA (-25.3%, P < 0.05) and TG level (-54.0%, P < 0.01). At the same time, rosiglitazone increased adiponectin by 60% (P < 0.01), and improved insulin sensitivity by 149.6% (P < 0.01) as compared with the HF group.

Conclusions: (1) High-fat diet induces insulin resistance in SD rats; this was associated with an increase in visceral fat and a decrease in the level of adiponectin; (2) Metformin treatment improved insulin sensitivity accompanied by a decrease in body weight and TG level; (3) Rosiglitazone treatment ameliorates IR in a greater extent and is accompanied by a reduction of FFA, TG and an increase of adiponectin levels.