Effects of physical exercise on Rock protein signaling pathway, and lipogenic regulation and gluconeogenesis in the liver of aged rats

Abstract

During the process of senescence, some factors such as the physiological function declining, the increased high fat food intake, and the inactivity are related with impairments in the hepatic metabolism leading to hepatic fat accumulation, also known as nonalcoholic fatty liver disease (NAFLD). Once the NAFLD is presented, there is a risk for non-alcoholic steatohepatitis (NASH) development leading to even more severe impairments in quality of life and life expectancy. In this context, we have sought to identify molecules with regulatory role in the insulin-signaling pathway, so in the lipogenesis and gluconeogenesis processes in the hepatic tissue, and the physical exercise participation in aged organisms. In this context, studies have showed the role of Rho-kinase (Rock) protein to mediate the insulin pathway through the insulin recepetor substrate 1 (IRS-1) phosphorylation at serine 632/635 residue, and thereby increasing the glucose uptake in the skeletal muscle. However, recent studies have also shown that Rock may have a negative effect in the liver, being involved with lipogenesis and hepatic glucose production. Thus, the aim of this study will be to evaluate the effects of physical exercise on Rock signaling pathway, and the effects on lipogenesis and gluconeogenesis in the lliver of old rats. Wistar and Fischer 344 rats will be used and separated in Young (3-5 months old) and Old (17 months old), also in sedentary and trained. The physical exercise training protocol will be the swimming exercise, with 120 minutes of duration, 5 times/week, during 7 days. At the end of the experiment, the adaptions resulting from physical exercise will be evaluated, such as: glucose tolerance, insulin sensitivity, pyruvate tolerance, glycaemia, insulinemia and hepatic glycogen. At the molecular level, will be measured the Rock1 and Rock2 protein, the Rock activator (RhoA) and inhibitory (RhoE), the IRS-1 serine 632/635 and tyrosine 612 phosphorylation, pAkt and total Akt, pGSK3 and total GSK3, and other proteins related to lipogenesis and hepatic glucose production in the liver. For the molecular analysis will be performed immunoblotting and Real time PCR. Moreover, to elucidate the specific mechanism through Rock can be modulated, we will inhibit (Y-27632) and overexpress this protein in HepG2 cells. In summary, it is expected to elucidate the aerobic physical exercise effects on Rock metabolism and the repercussions on lipogenesis and gluconeogenesis in the liver of old rats. (AU)