Regulation of muscle protein synthesis in humans.
OBJECTIVE
Investigations into the regulation of muscle protein synthesis (MPS) are a cornerstone of understanding the control of muscle mass. Rates of MPS are finely tuned according to levels of activity, nutrient availability and health status. For instance, rates of MPS are positively regulated by exercise and nutrition, and negatively regulated by inactivity (e.g. disuse), ageing (i.e. sarcopenia) and in muscle-wasting related diseases (e.g. cancer).


RESULTS
Skeletal muscles display a high degree of intrinsic regulation. Increases in MPS after exercise occur independently of the systemic milieu for example growth hormone/testosterone concentrations. In the absence of exercise, increases in MPS after feeding are of finite duration despite enduring precursor availability; that is muscles can sense they are 'full'. Intriguingly, exercise delays this 'muscle-full' response to allow for building and repair. In contrast, muscle-wasting conditions exhibit a premature 'muscle-full' response to nutrition and exercise (i.e. anabolic resistance), which may cause atrophy. Observations of 'dissociations' between MPS and anabolic signalling pathways have cast doubt on how much we understand of the molecular regulation of human MPS.


CONCLUSIONS
Anabolic and anticatabolic interventions in health and disease should be aimed at manipulating the 'muscle-full' set point to maximize muscle maintenance/hypertrophy.
Division of Clinical Physiology, School of Graduate Entry Medicine and Health, University of Nottingham, Derby, UK.
Bethan E
BE
Phillips
Derek S
DS
Hill
Philip J
PJ
Atherton
D000818:Animals; D015444:Exercise / Q000502:physiology*; D006801:Humans; D009124:Muscle Proteins / Q000096:biosynthesis*; D018482:Muscle, Skeletal / Q000378:metabolism*; D009133:Muscular Atrophy / Q000503:physiopathology*; D009747:Nutritional Physiological Phenomena; D009929:Organ Size; D014176:Protein Biosynthesis
D009124:Muscle Proteins