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 ( approximately 24 microg.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-(2)H(5)]phenylalanine and a 14-h infusion of hydrocortisone sodium succinate (60 microg.kg.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.ml(-1).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.ml(-1).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%.h(-1)) and post-BR (EXP, 0.111 +/- 0.015, and CON, 0.05 +/- 0.002%.h(-1)). Unlike a typical clinical meal, AA/CHO supplementation stimulated net muscle protein synthesis despite acute hypercortisolemia and prolonged inactivity.
Paddon-Jones
Douglas
D
Metabolism Unit, 815 Market Street, Galveston, Texas. djpaddon@utmb.edu.
Sheffield-Moore
Melinda
M
Urban
Randall J
RJ
Aarsland
Asle
A
Wolfe
Robert R
RR
Ferrando
Arny A
AA
D000328:Adult; D000601:Amino Acids, Essential / Q000008:administration & dosage*; D001786:Blood Glucose; D015992:Body Mass Index; D004040:Dietary Carbohydrates / Q000008:administration & dosage*; D006801:Humans; D006854:Hydrocortisone / Q000097:blood*; D007103:Immobilization / Q000009:adverse effects*; D007328:Insulin / Q000097:blood; D008297:Male; D008875:Middle Aged; D009124:Muscle Proteins / Q000096:biosynthesis / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000378:metabolism; D010649:Phenylalanine / Q000097:blood / Q000493:pharmacokinetics
D000601:Amino Acids, Essential; D001786:Blood Glucose; D004040:Dietary Carbohydrates; D007328:Insulin; D009124:Muscle Proteins; D010649:Phenylalanine; D006854:Hydrocortisone