Insulinotropic action of L-carnitine and branched-chain amino acids following energy intake in healthy, young Japanese women: a non-randomized controlled trial

Purpose: The present study uses healthy human volunteers to examine the insulinotropic action of L-carnitine and branched-chain amino acids (BCAAs) after energy intake.Methods: A total of 39 young, healthy human volunteers were assigned to receive oral doses of either L-carnitine alone (L group, n=10) or L-carnitine combined with a single or long-term continuous dose of BCAAs. Controls (C group, n=16) received none of these. L-carnitine was administered orally at 1,000 mg/d for 14 days, and BCAA was administered orally either once just before exercise (L+SB group, n=6), or every day for 14 days (L+CB group, n=7) until 2 days before the experiment. After overnight fasting, 200 kcal of glucose and oral nutritional supplement were administered to prevent hypoglycemia. Blood glucose, free-fatty acid, and serum insulin levels were measured to examine the insulinotropic action before and after exercise.Results: Blood glucose and serum insulin levels in the L group were significantly lower than those in the C group. While the serum insulin levels were higher after energy administration than those in the fasting state in all groups, these were significantly higher in the L+SB group and in the L+CB group compared with those in the L group. The insulinotropic action after energy intake remained even after the repeated administration of BCAA discontinued 2 days before the experi¬ment and even after serum BCAA levels remained the same.Conclusion: While the insulinotropic action appeared after a single dose of BCAA, it was also potentiated by long-term repeated oral administration of BCAA.