Fig. 9

Summary of sex differences in the skeletal muscle of young and aged mice and the response to acute exhaustive exercise. Muscle from young males (top left panel) contains fewer mitochondria of higher functionality, less lysosomes, and their transcriptional regulator TFEB in comparison to young females (top right panel). With aging, there are decrements in mitochondrial content and function in males (bottom left). Alternatively, in females, mitochondrial content was relatively unchanged, although function was reduced. These changes were associated with a greater upregulation in the autophagy-lysosome system in females with age. With exercise, there was an induction of autophagy and nuclear TFEB in young males that was not present in young females or aged animals of either sex. Overall, exercise was capable of enhancing TFEB promoter activity. Font size represents the relative amount of TFEB; thickness of black arrows represents the relative contribution of the autophagy-lysosome system at baseline; red front dictates change with exercise (↑ represents increase, = represents no change). Orange mitochondria are healthy, and green are unhealthy