Studies on the Involvement of Amino Acids in the Mechanisms Regulating Degradation of Muscle Protein

(JSNFS Award for Excellence in Research (2017))

Abstract

Although the mechanisms underlying muscle atrophy have been clarified, those governing the rates of muscle protein synthesis and degradation are not fully understood. The present study focused on 3-methylhistidine as a measure of the rate of protein degradation rate in skeletal muscle using the samples from urine, plasma, isolated muscles tissue and cultured cells. Ingestion of leucine or lysine suppressed protein degradation in skeletal muscle of rats, and these amino acids were found to down-regulate autophagy through Akt. The effects of lysine were also demonstrated in Senescence Accelerated Mouse Prone (SAMP) 8, a mouse model of sarcopenia in aging. Thus, ingestion of the amino acids can modulate the degradation as well as synthesis of muscle protein, and could be applied for suppression of muscle atrophy related to under-nutrition, diseases and aging.