期刊
AMERICAN JOURNAL OF PHYSIOLOGY-ENDOCRINOLOGY AND METABOLISM
卷 288, 期 5, 页码 E922-E929出版社
AMER PHYSIOLOGICAL SOC
DOI: 10.1152/ajpendo.00358.2004
关键词
aging; leg extension; protein turnover; plasma proteins
资金
- NCRR NIH HHS [M01-RR-00073] Funding Source: Medline
- NIA NIH HHS [R01-AG21539, P60-AG-17231-01, P30 AG024832] Funding Source: Medline
We sought to determine whether exercise-induced muscle protein turnover alters the subsequent production of hepatically derived acute-phase plasma proteins, and whether age affects how these proteins are regulated. We measured arteriovenous (a-v) balance and the synthesis of mixed muscle protein, albumin ( A) and fibrinogen ( F) before exercise ( REST) and from the beginning of exercise to 10, 60, and 180 min following a single bout of moderate-intensity leg extension exercise (POST-EX) in postabsorptive untrained older (n = 6) and younger (n = 6) men using L-[ring-H-2(5)]phenylalanine (Phe). Subjects performed 6 sets of 8 repetitions of leg extension at 80% of their 1-RM (one-repetition maximum). All data are presented as the difference from REST (Delta from REST at 10, 60, and 180 min POST-EX). Mixed muscle fractional synthesis rate (FSR-M) increased significantly from the beginning of exercise until 10 min POST-EX in the older men (Delta FSR-M: 0.044%/h), whereas FSR-M in the younger men was not elevated until 180 min POST-EX (Delta FSR-M: 0.030%/h). FSR-A and FSR-F increased at all POST-EX periods in the older men (Delta FSR-A = 10 min: 1.90%/day; 60 min: 2.72%/day; 180 min: 2.78%/day; Delta FSR-F = 10 min: 1.00%/day; 60 min: 3.01%/day; 180 min: 3.73%/day). No change occurred in FSR-A in the younger men, but FSR-F was elevated from the beginning of exercise until 10 and 180 min POST-EX (10 min: 3.07%/day and 180 min: 3.96%/day). Net balance of Phe was positive in the older men in the immediate POST-EX period. Our data indicate that mixed muscle and hepatic derived protein synthesis is differentially regulated in younger and older men in response to a single bout of moderate-intensity leg extension exercise. Moreover, our data suggest that with age may come a greater need to salvage or make available amino acids from exercise-induced muscle protein breakdown to mount an acute-phase response.
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