Effects of post‐exercise lactate administration on glycogen recovery in mouse skeletal muscle

Abstract

During high‐intensity exercise, glycogen content in skeletal muscle and liver decreases, while lactate accumulates in the circulation. Although sports nutrition guidelines recommend carbohydrate intake for glycogen recovery, the metabolic interaction between ingested carbohydrate and circulating lactate after exercise is unclear. In this study, we examined whether elevated circulating lactate additively enhances post‐exercise glycogen restoration. Eight‐week‐old male ICR mice were allocated to one of four groups as follows: PBS + water (PW) group, lactate + water (LW) group, PBS + glucose (PG) group, and lactate + glucose (LG) group. Animals performed treadmill running (20 m/min, 60 min) following overnight fasting (16 hours). Immediately after the exercise, animals received intraperitoneal injection of PBS or lactate (1 g/kg BW), followed by oral ingestion of water or glucose (2 g/kg BW). At 30, 45, 60 minutes of recovery, blood glucose concentration was higher in the LW group than in the PW group (p<0.05). In contrast, blood glucose level at 15 and 30 minutes of recovery and its iAUC were lower in the LG group than in the PG group (p<0.05). At 60 minutes of recovery, glucose ingestion resulted in higher glycogen content in the soleus, plantaris, and gastrocnemius muscles and the liver of the PG and LG groups compared with the PW group, although plasma insulin level at 15 minutes recovery (p<0.01) and its iAUC (p<0.05) were lower in the LG group than in the PG group. Moreover, lactate injection enhanced glycogen content in the plantaris and gastrocnemius muscles of the LW and LG groups (p<0.05), but not in the soleus muscle and the liver. Our current findings suggest that elevated circulating lactate additively enhances post‐exercise glycogen recovery in glycolytic phenotype muscle.