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·kg -1 ·d -1 and metformin 300 mg·kg -1 ·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.