Determining the Muscle Anabolic Properties of Phosphatidic Acid.

Ageing is characterized by a loss of muscle mass that is detrimental for physical function and metabolic health and increases the risk of mortality. The loss of muscle protein mass with ageing is characterized by a blunted muscle anabolic response to nutrition and exercise. Thus, interventions to counteract muscle anabolic blunting in old age might assist in the long-term maintenance of muscle mass. Phosphatidic acid (hereafter defined as 'PA') is a novel nutrient compound that has been suggested to play an important role in muscle growth. Oral consumption of PA may amplify the signalling response to nutrition and exercise and restore muscle anabolic sensitivity in older adults. In order for PA to be 'clinically' applied as a means to mitigate muscle loss in aged populations, we must first understand the efficacy and mechanisms underlying the anabolic properties of this compound, which have yet to be defined in man. The proposed pilot study is needed to investigate the acute muscle metabolic properties of oral PA supplementation in older individuals. Sixteen healthy (non-obese, non-diabetic, non-smokers) older males aged 65-75 yrs will initially complete a lower-limb strength assessment and undergo a body composition scan. Between 4-14 days after these initial assessments, participants will be assigned to co-ingest 1.5g of either phosphatidic acid (N= 8; PA) or a non-caloric placebo (N=8; PL) after following a bout of moderate intensity, single leg resistance exercise. A stable isotope infusion will be combined with serial muscle biopsies from the thigh of each leg to determine the measure rates of muscle protein synthesis in the fasted state and in the 'early' and 'late' phase of feeding-only and exercise-plus-feeding.