The Effect Of Swimmimg Training On The Expression Of PPAR-γ And Glucose Metabolismin Mice With Insulin Resistance

Objectives:Using a model of Insulin resistance (IR) mice which were fed with high-fat diet, to investigate the role of peroxisome proliferators-activated receptor-γ(PPAR-γ),pyruvate dehydrogenase kinase4(PDK4),pyruvate dehydrogenase(PDH) in the development of IR in liver tissue, and to explore the mechanism that swimming exercise improves IR.Methods:Thirty one healthy male C57BL/6J mice 8 weeks old were randomly divided into three groups:normal group(n=10), high-fat diet group (n=10), and exercise group (n=11). Normal group were fed with basic diet. High-fat diet group and exercise group were fed with high-fat diet. Mice in exercise group were completed 12 weeks swimming exercise. Body weights were observed weekly. Fasting blood glucose was measured With Fast blood glucose meter. After 12 weeks intervention, fasting insulin levels were measured using radioimmunoassay, the morphology of the liver evaluation was performed by Light and Electron microscopy, while the expression of PPAR-γ,PDK4 and PDH mRNA in liver were detected by RT-PCR.Results:①Compared with the normal group:the body weight of mice in the high fat diet group was significantly higher(P<0.05), and there were not statistical differences in exercise group. Compared with the high fat diet group:The body weight of the exercise group was significantly lower(P<0.05).②Compared with the normal group:fasting blood glucoses,fasting insulin of the high fat diet and exercise group were significantly higher(P<0.01); IRI in the exercise group was no significant difference(P>0.05). Compared with the high fat diet group:fasting blood glucose,fasting insulin of the exercise group were lower(P<0.05); IRI in the exercise group was significantly decreased(P<0.01).③HE staining: liver cells in the high-fat mice showed diffuse fatty degeneration, cytoplasm filled with large round lipid droplets of varying sizes. Lipid droplets were around one side of the nucleus or the cytoplasm and the nucleus were pushed to one side, some liver cells showed a signet-ring shape. The lipid droplets were seen in cytoplasm occasionally in the exercise group. Further observation by electron microscopy showed that hepatic cells can be seen a large number of lipid droplets in high-fat group, and liver cells in the exercise group have lipofuscin-like residues and no lipid droplets.④Compared with the normal group:the expression of PPAR-y mRNA in the high fat diet group had a declining trend, but no significant difference(P>0.05); the expression of PDK4 mRNA was significantly increased(P<0.Ol); the expression of PDH mRNA was significantly decreased(P<0.01). Compared with the high fat diet group: the expression of PPAR-y and PDH mRNA were further raised (P<0.01); the expression of PPAR-y mRNA in the exercise group was decreased (P<0.01).Conclusions:These findings suggest that exercise training can improve insulin resistance, and the mechanism may be related to increasing the expression of PPAR-y mRNA, reducing the expression of PDK4 mRNA, which consequently lead to raise the expression of PDH mRNA in liver tissue, and improve glucose metabolism.