Effect of aerobic exercise on age‐related decrease in muscle mitochondrial and sarcoplasmic protein synthesis

Abstract

Whole body and mixed muscle protein synthesis rate declines with age in healthy people. In response to a 4-month aerobic exercise program we showed that mixed muscle protein synthesis rate increased 22%. Several gene transcripts that encode mitochondrial (mito) proteins increased in response to exercise but it remains to be determined whether these are translated to protein synthesis. In this study we tested the hypothesis that mito protein synthesis also increased in response to aerobic exercise training. Healthy men and women (N = 42) from 30–74 y were studied before and after a 4-month program of stationary bicycle training (3d/wk, up to 40min/d at 80% HRmax) or control activity. Muscle protein synthesis rate was measured using [15N] phenylalanine as a tracer. Mito and sarcoplasmic (sarco) proteins were separated from muscle biopsies for analysis. At baseline there was a decline with age (p<0.05) in both mito (6%/decade, r= −0.32) and sarco (5.5%/decade, r= −0.42) protein synthesis rate. Muscle protein synthesis rates did not change in control subjects, but in the exercise group mito synthesis increased 27% (0.046 ± 0.003 %/h pre vs. 0.058 ± 0.005 post, p=0.017, N=25) and there was a trend for 10% higher sarco protein synthesis (0.036 ± 0.002 %/h pre vs. 0.040 ± 0.003 post, p=0.066, N=33). These effects of exercise did not vary with age. We conclude that despite a decline in mito protein synthesis and function with advancing age, the potential for mito biogenesis in response to aerobic exercise remains robust in older muscle, as demonstrated by enhanced mito protein synthesis, gene expression, and enzyme action. Support: NIH RO1DK41973, MO1RR00585.