Metabolic Adaptations to Aerobic Exercise Training in Aging Mice

Exercise training is a lifestyle intervention proposed to treat age-related chronic diseases, such as obesity or Type 2 Diabetes. However, the type and intensity of exercise is difficult to predict in humans of advanced age, rendering exercise treatment as a less than ideal option. The purpose of this study was to gain an understanding of the metabolic effects resulting from initiating exercise training late in life in the mouse. We used 12 weeks of voluntary wheel running as an exercise intervention to test our hypothesis that initiating exercise training later in the life of a mouse improves metabolic function. We found that, although aged mice exercise on the voluntary running wheel significantly less than young mice, there are still notable exercise-induced metabolic improvements in aged mice. Exercise training decreases glucose stimulated insulin secretion and hypoglycemia stimulated glucagon secretion in aged mice. In aged, exercise trained mice, resting respiratory quotient is decreased compared to both young and aged sedentary mice indicating a greater shift towards fat oxidation. Paradoxically, only young exercise trained mice have a decrease in hepatic lipid content compared to age matched sedentary mice. Despite these metabolic adaptations, aged exercise trained mice are resistant to the exercise induced increase in energy expenditure (EE) observed in young mice. Initiating exercise training late in life produces some but not all metabolic improvements seen in young mice