Increased Lipid Metabolism in Response to Repetitive Aerobic Exercise During Proestrus in Type 1 Diabetes Mellitus Rats
Abstract
In response to repetitive bouts of aerobic exercise, type I diabetes mellitus (T1DM) female rats demonstrate greater post-exercise blood glucose (BG) recovery during proestrus than T1DM males. Fuel selection differences may explain sex-related differences in the blunted counterregulatory responses to subsequent exercise and estrogen (E2) has shown to mediate fuel metabolism. Evidence of E2’s activation of AMP-kinase (AMPK) may mediate the metabolic actions of E2. This study aimed to examine sex-related differences in lipid and glucose metabolism in response to a 4-day aerobic exercise protocol in skeletal muscle and liver tissue of male and female T1DM-induced (n = 5) and non-T1DM (n = 5) rats. Western blot analysis and phenol sulphuric acid and β-oxidation activity assays were used to assess AMPK and gluconeogenic enzyme protein expression, muscle glycogen content, and lipid oxidation. T1DM and non-T1DM females demonstrated significantly greater β-oxidation activity in muscle compared to males but this fuel shift towards lipids was not associated with higher AMPK activity. No muscle glycogen content differences between the sexes were found. T1DM and non-T1DM females demonstrated higher hepatic G6Pase expression than males. Therefore, T1DM females may be less susceptible to repeated exercise-induced hypoglycemia through E2-mediated shift towards lipid oxidation during the proestrus phase.