Amino Acid Sensing in Muscle: Role of the lysosome and the effect of protein supplementation on improving amino acid sensitivity in aging muscle

Protein ingestion is a well-studied stimulus for increasing skeletal muscle protein synthesis. Only recently has the mechanism for this phenomenon been elucidated at the cellular level. To this point, most of the mechanistic research into this process has been conducted in human embryonic kidney cells. Therefore, it is necessary to determine if this cellular mechanism is conserved in muscle. If so, it may be possible to manipulate this mechanism in order to enhance skeletal muscle protein turnover, that is the balance between protein synthesis and protein breakdown. Potentially a protein supplement that could exploit this mechanism to promote protein anabolism through either increasing protein synthesis or decreasing protein breakdown would result in improved skeletal muscle health. Reduced strength and muscle mass are predictors of early mortality. This highlights the importance of developing more effective methods to increase muscle mass and strength. Reduced muscle mass and weakness increases the risk for falls in older adults. A fall can lead to a loss of independence and placement in a care facility. Excessive muscle wasting and weakness is also considered a key risk factor for survival with cancer and other diseases. A better understanding of the biology of muscle wasting is needed to develop evidence-based rehabilitation protocols for improving muscle function for a variety of clinical conditions associated with muscle loss.