ESSENTIAL AMINO ACIDS AND RESISTANCE EXERCISE IN AGING

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Background: Muscle wasting is a common phenomenon in many conditions, such as cancer, AIDS, trauma, sepsis, kidney failure, and is also particularly prevalent in the elderly. The loss of muscle mass leads to overall weakness, immobility and physical dependence, and can be responsible for an impaired response to stress, which is associated with higher mortality rates during infection, surgery, and trauma. Amino acids from protein and weight lifting can both increase muscle size. It has been shown that muscle growth post-exercise is less in the elderly as compared to young volunteers. However, there have been no studies that have examined the combined effect of amino acids and resistance exercise. Hypothesis: Providing amino acids following a bout of weight lifting exercise will improve short-term muscle growth in older men. However, we also think that this response will still be less than that seen in young healthy men. Specific Aims and Procedures (summary): To determine if 20 grams of essential amino acids ingested one hour following a bout of weight lifting exercise will stimulate short-term muscle growth in older men to the same extent as seen in the young. Experimental Design (summary): Six healthy young and older male volunteers will be recruited and screened at the General Clinical Research Center. We will begin each study by placing two peripheral catheters (one in each arm) and by infusing two stable isotopes to measure muscle protein synthesis. We will collect two muscle biopsies prior to exercise, one following a bout of weight lifting exercise on the legs (8 sets x 8 repetitions at 70% of the subjects maximal weight they can lift), and then again at 3 hours and 6 hours post exercise. One hour following the exercise session each subject will receive 20 grams of essential amino acids. We will then assess changes in blood amino acid content, hormone changes such as insulin and testosterone from the blood samples. Each muscle sample will be used to measure muscle protein synthesis and to assess changes in cell signaling pathways the control protein synthesis. Each study will begin around 7 am and will be completed by 4 pm. Significance (summary): These studies will provide insight into why muscle loss is occurring with age and will then help us to develop scientifically-based interventions for improving muscle size in conditions such as aging, trauma, cancer, and AIDS.