Abstract
PurposeProgressive loss of skeletal muscle mass with aging (sarcopenia) forms a global health concern. It has been suggested that an impaired capacity to increase muscle protein synthesis rates in response to protein intake is a key contributor to sarcopenia. We assessed whether differences in post-absorptive and/or post-prandial muscle protein synthesis rates exist between large cohorts of healthy young and older men.ProceduresWe performed a cross-sectional, retrospective study comparing in vivo post-absorptive muscle protein synthesis rates determined with stable isotope methodologies between 34 healthy young (22±1 y) and 72 older (75±1 y) men, and post-prandial muscle protein synthesis rates between 35 healthy young (22±1 y) and 40 older (74±1 y) men.FindingsPost-absorptive muscle protein synthesis rates did not differ significantly between the young and older group. Post-prandial muscle protein synthesis rates were 16% lower in the older subjects when compared with the young. Muscle protein synthesis rates were >3 fold more responsive to dietary protein ingestion in the young. Irrespective of age, there was a strong negative correlation between post-absorptive muscle protein synthesis rates and the increase in muscle protein synthesis rate following protein ingestion.ConclusionsAging is associated with the development of muscle anabolic inflexibility which represents a key physiological mechanism underpinning sarcopenia.
Highlights
Aging is associated with the development of muscle anabolic inflexibility which represents a key physiological mechanism underpinning sarcopenia
Sarcopenia refers to the progressive loss of skeletal muscle mass that occurs with normal, healthy aging [1]
Post-prandial muscle protein synthesis rates were 16% lower in older men when compared with the young
Summary
Sarcopenia refers to the progressive loss of skeletal muscle mass that occurs with normal, healthy aging [1]. Relevant gains or losses of skeletal muscle mass are attributed to a persistent change in muscle protein synthesis rates, breakdown rates, or a combination of both. Dietary protein and/or amino acid intake strongly increase muscle protein synthesis rates and inhibit muscle protein breakdown, thereby allowing net muscle protein accretion. These post-prandial periods offset the loss of muscle protein during post-absorptive conditions. Both basal muscle protein turnover rates as well as the post-prandial stimulation of muscle protein synthesis are viewed as the key sites upon which skeletal muscle mass maintenance is regulated
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