Effects of Increasing Insulin Secretion on Acute Postexercise Blood Glucose Disposal

Background: Coingestion of protein and/or free amino acids with carbohydrate has been reported to accelerate postexercise muscle glycogen synthesis due to an increase in the insulin response. Purpose: To determine the extent to which the combined ingestion of carbohydrate and a casein protein hydrolysate with or without additional free leucine can increase insulin levels during postexercise recovery in endurance-trained athletes. To determine how this affects whole-body plasma glucose disposal during postexercise recovery. Methods: Fourteen male athletes (age: 24.3 +/- 0.8 yr; 62.9 +/- 1.4 mL(.)kg(-1.)min(-1)) were subjected to three randomized crossover trials in which they performed 2 h of exercise (55% Wmax). Thereafter, subjects were studied for 3.5 It during which they ingested carbohydrate (CHO: 0.8 g(.)kg(-1.)h(-1)), carbohydrate and a protein hydrolysate (CHO-PRO: 0.8 and 0.4 g(.)kg(-1.)h(-1). respectively), or carbohydrate, a protein hydrolysate, and free leucine (CHO-PRO-LEU: 0.8, 0.4. and 0.1 respectively) in a double-blind fashion. Continuous infusions with [6,6-H-2(2)] glucose were applied to quantify plasma glucose appearance (Ra) and disappearance rates (Rd). Results: Plasma insulin responses were 108 +/- 17 and 190 +/- 33% greater in the CHO-PRO and CHO-PRO-LEU trial, respectively, compared with the CHO-trial (P <0.01). Plasma glucose responses were lower in the CHO-PRO and CHO-PRO-LEU trial compared with the CHO-trial (35 +/- 5 and 42 +/- 11% lower, respectively; P <0.01). Plasma glucose Ra and Rd were greater in the CHO versus the CHO-PRO and CHO-PRO-LEU trials (P <0.05). Glucose Rd represented 100 +/- 0.03% of Ra in all trials. Conclusions: The combined ingestion of a protein hydrolysate and/or free leucine with carbohydrate (0.8 g(.)kg(-1.)h(-1)) substantially augments insulin secretion, but does not affect plasma glucose disposal during the first 3.5 h of postexercise recovery in trained athletes.