Combined supplementation of carbohydrate, alanine, and proline is effective in maintaining blood glucose and increasing endurance performance during long-term exercise in mice.

Carbohydrate supplementation is extremely important during prolonged exercise because it maintains blood glucose levels during later stages of exercise. In this study, we examined whether maintaining blood glucose levels by carbohydrate supplementation could be enhanced during long-term exercise by combining this supplementation with alanine and proline, which are gluconeogenic amino acids, and whether such a combination would affect exercise endurance performance. Male C57BL/6J mice were orally administered either maltodextrin (1.25 g/kg) or maltodextrin (1.0 g/kg) with alanine (0.225 g/kg) and proline (0.025 g/kg) 15 min before running for 170 min. Combined supplementation of maltodextrin, alanine, and proline induced higher blood glucose levels than isocaloric maltodextrin alone during the late exercise phase (100-170 min). The hepatic glycogen content of mice administered maltodextrin, alanine, and proline was higher than that of mice ingesting maltodextrin alone 60 min after beginning exercise, but the glycogen content of the gastrocnemius muscle showed no difference. We conducted a treadmill running test to determine the effect of alanine and proline on endurance performance. The test showed that running time to exhaustion of mice that were supplemented with maltodextrin (2.0 g/kg) was longer than that of mice that were supplemented with water alone. Maltodextrin supplementation (1.0 g/kg) with alanine (0.9 g/kg) and proline (0.1 g/kg) further increased running time to exhaustion compared to maltodextrin alone (2.0 g/kg). These results indicate that combined supplementation of carbohydrate, alanine, and proline is effective for maintaining blood glucose and hepatic glycogen levels and increasing endurance performance during long-term exercise in mice.