Dose and time dependent effects of leucine or carbohydrate supplements to reduce AMPK and eEF2 phosphorylation and extend postprandial muscle protein synthesis in rats

Abstract

These experiments evaluated the potential for supplemental leucine (Leu) or carbohydrates (CHO) to prolong elevated muscle protein synthesis (MPS) after a meal. Male Sprague‐Dawley rats (~256 g) were food deprived for 12 h, and euthanized 0, 90, 155, 180, or 255 min after a standard 4 g test meal. At 135 min post‐meal, rats were gavaged with 270 mg Leu (Leu270), 80:40:40 mg Leu, isoleucine, and valine, respectively (Leu80), 2.63 g CHO (CHO2.6), 1 g CHO (CHO1.0), or water (Sham control). Following test meal consumption, MPS peaked at 90 min then declined at 180 min even though translation initiation signaling remained elevated. In contrast, rats administered Leu270 or CHO2.6 supplements at 135 min post‐meal maintained peak MPS through 180 min; while Leu80 and CHO1.0 supplements elicited intermediate responses. Leu and CHO treatments were able to raise MPS above sham values from 155–180 min post‐meal, while MPS for both treatments returned to sham values at 255 min post‐meal. Lastly, MPS was inversely associated with markers of cellular energy status and translation elongation. We conclude that the incongruity between MPS and translation initiation at 180 min reflects a block in translation elongation due to reduced cellular energy, and Leu or CHO supplements are able to enhance energy status and prolong the period of muscle anabolism.