The catabolic effects of prolonged inactivity and acute hypercortisolemia are offset by dietary supplementation

We compared the anabolic stimulus provided by an essential amino acid and carbohydrate (AA/CHO) supplement to a mixed clinical meal during bed rest ( BR) and episodic hypercortisolemia ( similar to 24 mu g center dot dl(-1)). In the experimental (EXP; n = 7) and control ( CON; n = 6) groups, femoral arteriovenous blood samples and vastus lateralis biopsy samples were obtained during a primed constant infusion of L-[ring-H-2(5)] phenylalanine and a 14-h infusion of hydrocortisone sodium succinate ( 60 mu g center dot kg center dot h(-1)) before (pre-BR) and after (post-BR) 28 d of BR. Muscle protein kinetics were calculated during the postabsorptive state, for 2.5 h after ingestion of a meal and for 2.5 h after ingestion of an AA/CHO supplement ( EXP) or placebo ( CON). Postabsorptive net phenylalanine balance values were as follows: EXP, - 35.14 +/- 2.93, and CON, - 32.60 +/- 6.65 (pre-BR); and EXP, - 32.91 +/- 5.67, and CON, - 30.43 +/- 6.28 nmol phe center dot ml(-1) center dot 100 ml leg volume(-1) (post-BR). After AA/CHO supplementation, net phenylalanine balance improved to 33.51 +/- 8.06 (pre-BR) and 24.15 +/- 11.4 nmol phe center dot ml(-1) center dot 100 ml leg volume(-1) (post-BR), but remained negative after the meal. Cumulative 5.5- h mixed muscle fractional synthetic rate was greater in the EXP group pre-BR ( EXP, 0.108 +/- 0.01, and CON, 0.073 +/- 0.04% center dot h(-1)) and post-BR( EXP, 0.111 +/- 0.015, and CON, 0.05 +/- 0.002% center dot h(-1)). Unlike a typical clinical meal, AA/ CHO supplementation stimulated net muscle protein synthesis despite acute hypercortisolemia and prolonged inactivity.