Dietary Strategies to Promote Muscle Protein Anabolism in the Elderly

Aging is associated with the loss of lean muscle mass, termed sarcopenia. Food intake and in particular the ingestion of protein or amino acids has been shown to be a powerful stimulus to promote net muscle protein anabolism. However this anabolic response following a meal-like protein bolus seems to be blunted in the elderly as compared to young adults. The first aim of this proposal is to investigate the post-prandial muscle protein synthesis rates in young and elderly men in response to a meal-like protein bolus after a period of rest or physical activity (study A). The rest trial (REST) will act as a proof-of-principle study to examine the blunted protein synthetic response in the elderly, and as a control trial in comparison with the exercise trial (EXC) to establish the surplus value of physical activity prior to protein intake on muscle protein synthesis. The second aim of this proposal is to determine the surplus value of an increased quantity of the ingested protein bolus (study B). Large amounts of protein (40 and 60 g) will be compared to a meal-like amount of protein (20 g) as a means to maximize plasma amino acid availability and/or to stimulate muscle protein anabolism. The third aim of this proposal is to study the differences in quality of the ingested protein bolus (study C). Instead of significantly increasing the quantity of the protein bolus, we will also apply a more practical approach to augment skeletal muscle protein synthesis rates; modifying the digestibility or amino acid composition of a meal-like protein bolus.

The physical exercise protocol will consist of low intensity cycling and light resistance-type exercise; after 5 minutes of self-paced cycling, subjects will perform 6 sets of 10 repetitions on the horizontal leg press machine (Technogym BV, Rotterdam, The Netherlands) and 6 sets of 10 repetitions on the leg extension machine (Technogym BV, Rotterdam, The Netherlands). The first 2 sets of both resistance exercises will be performed at 40% of the subjects' 1RM. Sets 3-4, and 5-6 will be performed at 55% and 75% of 1RM, respectively, with 2 minutes rest intervals between sets.

All interventions will affect muscle protein synthesis. With the application of amino acid tracer methodology we are able to determine muscle protein synthesis.

Inclusion Criteria: In study A, non-obese male subjects (BMI <27) between the age of 18-30 yrs and 70-85 yrs will be selected. In studies B and C, non-obese male subjects (BMI <27) between the age of 70-85 yrs will be selected. Exclusion Criteria: Type II diabetes or other known diseases Use of medication Female Other ages or BMI than indicated above Participation in any regular exercise program.

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