Brain glycogen decrease and supercompensation with prolonged exhaustive exercise

Abstract

Energy sources for the brain include not only blood glucose, but also astrocytic glycogen, especially when the blood-borne glucose supply is short (e.g., hypoglycemia). Although untested, it is hypothesized that during prolonged exercise that induces hypoglycemia, the resultant hypoglycemia may cause a decrease in brain glycogen. Here, we tested this hypothesis and provide evidence that brain glycogen decreases during prolonged exercise with hypoglycemia. Furthermore, in the cortex, we show that the decrease in brain glycogen levels during prolonged exercise is associated with activation of monoamine metabolism, which could be a factor inducing central fatigue. We also provide evidence that exhaustive exercise induces glycogen supercompensation not only in skeletal muscles, but also in the brain. Furthermore, we observed exercise training-induced increases in basal glycogen levels in the cortex and hippocampus, which are involved in motor control and cognitive function. These findings suggest that brain glycogen is an important energy source during exercise for the brain, which adapts metabolically like skeletal muscles, probably to meet the increased energy demands, and to enhance the stamina of the exercise performance and cognitive function.