Abstract: ［Abstract］Objective〖HTSS〗To observe the effect of swimming training on liver fat content and peroxisome proliferator activated receptor-γ(PPAR-γ) signaling pathway in mice and discuss the mechanism of exercise improving insulin resistance.
〖HTH〗〖WTHZ〗Methods〖HTSS〗Thirty-one healthy 8-week-old male C57BL/6J mice were randomly divided into normal group(n=10), high-fat group(n=10) and exercise group(n=11). Insulin resistance animal model was established by high fat diet. The exercise group was given 12 weeks swimming training. The weight of mice was recorded before and after intervention. Fasting blood glucose(FBG) and fasting insulin(FINS) were measured. Insulin resistance index(IRI) was calculated by HOMA. PPAR-γ and pyruvate dehydrogenase kinase 4(PDK4) in liver tissue were detected by reverse transcription polymerase chain reaction(RT-PCR). The expression levels of kinase 4, PDK4 and pyruvate dehydrogenase(PDH) were observed by light and electron microscopy.
〖HTH〗〖WTHZ〗Results〖HTSS〗After 12 weeks of intervention, the weight of the three groups was significantly higher than that before intervention, and the weight of the high-fat group was significantly higher than that of the normal group and the exercise group(P＜0.05). FINS, FBG and IRI in the high-fat group and the sports group were significantly higher than those in the normal group, while FINS, FBG and IRI in the sports group were significantly lower than those in the high-fat group(P＜0.05). HE staining showed that hepatocytes in the high-fat group presented diffuse steatosis, and the cytoplasm was filled with a large number of round lipid droplets of different sizes. Lipid droplets wrap around the nucleus or cytoplasmic side, squeezing the nucleus to one side, some in signed-ring shape. Lipid droplet formation was observed occasionally in the cytoplasm of hepatocytes of mice in the exercise group. Electron microscopy showed that a large number of lipid droplets were deposited in the hepatocytes of the high-lipid group. There were residual lipofuscin-like substances in liver cells of exercise group. The expression of PPAR-γ mRNA in the high-fat group was lower than that in the normal group, the expression of PPAR-γ mRNA in the exercise group was higher than that in the normal group, the expression of PDK4 mRNA in the high-fat group and exercise group was higher than that in the normal group, and the expression of PDH mRNA was lower than that in the normal group. The expression of PPAR-γ mRNA and PDH mRNA in the exercise group was significantly higher than that in the high-fat group, and the expression increase of PDK4 mRNA was lower than that in the high-fat group(P＜0.05).
〖HTH〗〖WTHZ〗Conclusion〖HTSS〗Exercise can improve insulin resistance, which may be related to reducing liver steatosis in mice, up-regulating the expression of PPAR-γ mRNA in mouse liver tissue, reducing the expression of PDK4 mRNA, and increasing the expression of PDH mRNA.

Key words: insulin resistance； peroxisome proliferator activated receptor-&gamma, ； swimming