This subproject is one of many research subprojects utilizing theresources provided by a Center grant funded by NIH/NCRR. The subproject andinvestigator (PI) may have received primary funding from another NIH source,and thus could be represented in other CRISP entries. The institution listed isfor the Center, which is not necessarily the institution for the investigator.Background: Many individuals lose muscle mass and strength as they get older. One of the factors that may contribute to this loss is changes in the diet. Specifically, elderly individuals may not eat sufficient dietary protein or the protein they do eat may not be as efficiently assimilated into muscle tissue. Previous studies have examined the effect of protein supplements and amino acids on protein synthesis and muscle growth, but there is a lack of data examining the effect of common sources of dietary protein (i.e., beef) on muscle protein synthesis.Hypothesis: Specific hypotheses to be investigated are:1. In the young, there is a dose response of muscle protein synthesis to the amount of beef ingested.2. In the elderly, the maximal response of muscle protein synthesis to beef intake is the same as in young, but the submaximal response is diminished.3. The greater energy content of high fat (25 %) beef will stimulate muscle protein synthesis more effectively than low fat (10 %) beef despite a similar protein content.4. Prior exercise amplifies muscle protein synthesis following beef ingestion in both young and elderly.
Specific Aims and Procedures (summary): The goal of this study is to measure changes in plasma concentrations of amino acids and muscle protein synthesis in young and elderly individuals following ingestion of beef differing in portion size and fat content.Experimental Design (summary): We will study a total of 90 healthy male and female volunteers between the ages of 20 and 50 (young) and 60 and 85 (elderly). We will use established techniques including stable isotope tracer methodology, blood sampling and muscle biopsies to measure changes in plasma hormone and amino acid concentrations and skeletal muscle synthesis.Significance (summary): We propose to investigate the metabolic response to a practical nutritional intervention that will address a number of the mechanisms contributing to muscle protein synthesis and muscle loss during aging. This project will have direct implications for recommendations concerning both the quality and quantity of protein ingested as part of a daily diet and will also provide new information on the relationship between exercise and protein ingestion in the young and elderly.
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