Effects of troglitazone and voluntary running on insulin resistance induced high fat diet in the rat

It is well known that troglitazone and voluntary running have the rapacity to improve insulin resistance. The purpose of this study was to evaluate th e combination effect of troglitazone and voluntary running on insulin actio n. Female rats aged 7 weeks were divided into high-fat diet (HF), high-fat diet + troglitazone (0.3% in diet; Tg), high-fat diet + voluntary running ( for 3 wks: Tr), high-fat diet + troglitazone + voluntary running (Tg-Tr), a nd control (C) groups. A sequential euglycemic clamp experiment with two di fferent insulin infusion rates of 3.0 IL-clamp) and 30.0 mU/kg BW/min (H-cl amp) was performed on these rats after an overnight fast. Blood glucose con centrations were kept at fasting levels by periodic adjustment of the intra venous glucose infusion rate during the clamp experiment. Glucose infusion rates (GIRs) calculated from 60 to 90, 150 to 180 min were regarded as an i ndex of whole body insulin action. After the clamp experiment, we determine d the amount of glycogen content in the gastrocnemius muscle. Fat feeding m arkedly reduced GIRs in both L- and H- clamp experiments compared with C. T roglitazone treatment did not improve high-fat induced insulin resistance. In both L- and H-clamp experiments, GIRs were increased by voluntary runnin g compared with HF, and reached the same levels as in C. GIRs of Tg-Tr were not greater than those of Tr. Glycogen content in gastrocnemius muscle sho wed the same trend as the results for GIRs. Therefore, the combination effe ct of troglitazone and voluntary running on insulin action was not found, b ut the effect of voluntary running was shown in fat-induced insulin resista nce.