Monocarboxylate transporter-dependent mechanism is involved in the adaptability of the body to exercise-induced fatigue under high-altitude hypoxia environment

Abstract

Under high-altitude hypoxia environment, the body is more prone to fatigue, which occurs in both peripheral muscles and the central nervous system (CNS). The key factor determining the latter is the imbalance of brain energy metabolism, which makes it difficult to maintain the central nervous system to send peripheral nerve impulse continuously. During strenuous exercise, lactate released from astrocytes is taken up by neurons stored for energy to maintain synaptic transmission, a process mediated by monocarboxylate transporters (MCTs) in CNS. The present study investigated the correlation among the adaptability to exercise-induced fatigue, brain lactate metabolism and neuronal hypoxia injury under high-altitude hypoxia environment. Rats were subjected to exhaustive incremental load treadmill exercise under either normal pressure and normoxic conditions or simulated high-altitude low pressure and hypoxic conditions, with subsequent evaluation of the average exhaustive time as well as the expression of monocarboxylate transporters 2 (MCT2), MCT4, the average neuronal density in the cerebral motor cortex, and the lactate content in rat brain. At the early stage of simulated high-altitude environment, the average exhaustive time and neuronal density of rats decreased rapidly, then gradually recovered to some extent with the extension of altitude acclimatization time. The expression of MCT2, MCT4 and the lactate content in rat brain also increased gradually with the extension of altitude acclimatization time. After the application of lactate transport inhibitor, the recovery of exercise capacity of rats after altitude acclimatization was quickly blocked, and the neuronal injury in the cerebral motor cortex of rats was also significantly aggravated. These findings demonstrate that MCT-dependent mechanism is involved in the adaptability of the body to central fatigue, and provide a potential basis for medical intervention for exercise-induced fatigue under high-altitude hypoxia environment.