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Efeitos do exercício físico sobre a transdução do sinal da adiponectina no músculo esquelético e homeostase glicêmica em ratos idosos : Effects of physical exercise on adiponectin signal in the skeletal muscle and glycemic homeostasis in old rats

Aging is a natural process that is associated with insulin resistance and hyperglycemia. Among the changes related to the senescence process, there are alterations in the insulin signaling pathway in the skeletal muscle, which can be attenuated or prevented by physical exercise. However, the molecular mechanisms associated with improved of insulin signaling and glucose uptake in skeletal muscle in response to exercise in aged organisms are not fully understood. Thus, the objective of this study was to evaluate whether physical training has effects on the signaling pathway of adiponectin in skeletal muscle and to relate this phenomenon to glycemic homeostasis in elderly rats. Fischer 344 rats were distributed in the following groups: Young (Young) animals at 5 months of age; Sedentary Old (Old) rats with 26 months of age that were not exercised; Old Exercise (Old exercised) rats with 26 months of life that were submitted to exercise training protocol. The exercise training protocol consisted of 8 sessions of running on a treadmill, at a speed of 12 meters/min, with a 10 ° slope and a duration of 60 minutes. Blood samples were collected for analysis of fasting glycaemia and glucose tolerance, the skeletal muscle was extracted and the analysis of the proteins of interest was performed through the Western Blot technique. The data were analyzed by Student's t-test, when two groups were compared. And analysis of variance (Anova), followed by Bonferroni's, when appropriate. The statistical significance was set at p <0.05. The results show that old rats present glucose intolerance without increased adiposity. On the other hand, exercise training reversed this disorder, which was associated with a decreases in the levels of the APPL (Adaptive protein containing pleingins domain-binding domain and leucine zipper motif) isoform 2 (APPL2). The isoform 1 content of the APPL (APPL1) and the TRB3 (mammalian homologue of drosophila 3) were not altered in any of the investigated groups. Akt protein phosphorylation was increased only in the group of exercised old rats. There was a reduction in the content of adiponectin receptors 1 and 2 in the old rats. It was concluded that aerobic exercise training was able to decrease the content of APPL2 in the skeletal muscle and this was accompanied by an increase in glucose tolerance in Fischer 344 old rats.