Chronic Exercise Reduces The Sirt1 S-nitrosation In The Liver Of Old Mice

Abstract

The SIRT1 deacetylase protein plays a crucial role in cellular metabolism. It is known that during aging decreases in SIRT1 activity can contributes to development of metabolic disorders. PURPOSE: Determine if the reduction in iNOS genetically (knockout) or by exercise is related to increased activity of SIRT1 by S-nitrosation and/or the post-translational mechanisms responsible for this phenomenon. METHOD: “Young” (Y) (2 months), “sedentary-old” (O) (30 mo) “trained old” (TO) (30 mo) and “iNOS KO old” (iNOSKO) (30 mo) groups were submitted to a treadmill training for 4 weeks (5 days/week) at the intensity of 60% of maximum power (n=5). During the last experimental week, we performed a pyruvate tolerance test (PTT) and glucose samples were collected at rest, 30 and 60 minutes after pyruvate administration. 24 hours after the last exercise bout the animals were euthanized and the liver extracted for western blotting analysis. The database ´genenetwork.org` was used to perform bioinformatics analysis from data containing mRNA values from liver samples of bxd mices and humans, using mitochondrial biogenesis markers that were strongly correlated with the iNOS gene. Results were analyzed by One-Way ANOVA and Bonferroni post hoc test when necessary. RESULTS: “Y” and “TO” animal had reduced glucose production compared to “O” at minute 30 (Y=72.8±4.6 vs TO= 124.9±1.5 vs O= 261.9±32.2 mg/dl, p<0.05) during the PTT and area under glucose curve during PTT was increased in “O” animals compared to “Y” (Y= 5352.8±786.6 vs O=9738.7±1390.0 mg/dl.60min, p<0.05). Liver analysis showed reduced levels of gluconeogenesis enzymes G6Pase and PEPCK in “Y”, “TO” and “iNOSKO” compared to “O” animals. We found reduced iNOS expression, SIRT1 S-nitrosation and inproved mitochondrial complexes responsible for ATP synthesis and fatty acid oxidation (MTCO1 and Uqcrc1) in both “TO” and “iNOSKO” groups compared to “Y” and “O” groups. Bioinformatics analysis shows that bxd iNOS mRNA is negatively correlated to mitochondrial biogenesis markers. Such finding corroborates human analysis. CONCLUSION: The chronic physical exercise promotes attenuated expression of iNOS and S-nitrosation of SIRT1 contributing to increased activity of SIRT1 protein, improving liver function in aging mice. Supported by CNPq, Capes and FAPESP (2013/20293-2).