1a. Objectives (from AD-416):
1. Investigate the nutritional and activity-related mediators of skeletal muscle atrophy associated with advancing age in animal and human studies. 2. Evaluate the chronic effects of dietary proteins/amino acids and physical activity/inactivity on changes in skeletal muscle structure and function and physical functioning in at-risk older individuals.
1b. Approach (from AD-416):
Sarcopenia, the age-associated loss in skeletal muscle mass, is a contributing factor to the observed declines in physiological capacity and functional performance with advancing age. The economic impact of sarcopenia has been estimated at $18.5 billion, annually. The overall theme of this project will be to use a platform-based approach in the identification, evaluation, and understanding of nutritional and physical activity interventions that possess anabolic properties in skeletal muscle and have the potential to prevent or reverse impaired motor performance and/or physical dysfunction in older individuals. Using our well characterized rodent model of human sarcopenia, we propose to examine the mechanisms and efficacy of nutrient modulation on overload-induced skeletal muscle hypertrophy. We then propose to perform parallel clinical studies to examine the influence of physical activity/exercise and nutrition on the control of muscle protein turnover in older adults with defined low muscle mass and functional limitations. We will also evaluate the chronic effects of dietary protein/amino acids and physical activity/inactivity on changes in skeletal muscle structure and function and physical functioning in at risk older adults. Finally, we will examine the effects of a multi-modal physical activity program on changes in muscle mass, strength, physical functioning, and disability in older individuals with clinically demonstrated functional limitations. The unique pairing of clinical studies examining the influence of protein nutrition and physical activity on sarcopenia with basic approaches that identify the molecular landscape and potential targets in skeletal muscle for preventive interventions (nutritional, physical activity) may accelerate our ability to translate these findings to aging people.
3. Progress Report:
This progress report includes the work of one subordinate project at the HNRCA funded through a Specific Cooperative Agreement with TUFTS UNIVERSITY. For further information and progress reports, see 1950-51000-068-01S (Nutrition, physical activity, and sarcopenia in the elderly).
1. LAB: Nutrition, exercise physiology and sarcopenia: Muscle power failure in mobility-limited older adults. The age associated loss of lower extremity skeletal muscle power has emerged as a critical determinant of functional independence and mobility among older adults. However, limited knowledge exists on the major underlying physiological factors that determine muscle power generation with advancing age in healthy or mobility-limited older populations. ARS-funded researchers at JMUSDA-HNRCA at Tufts University, Boston, MA, found that muscle power, strength, muscle mass, quality and neuromuscular function were significantly lower among mobility-limited elders compared to healthy adults without mobilitylimitations. Conversely, muscle biopsy samples revealed that the contractile properties of single muscle cells were preserved in mobility-limited elders relative to healthy subjects. The dissociation between age-related changes at the whole muscle and cellular level suggest that, even among older adults with overt mobility problems, contractile properties of surviving muscle cells are preserved in an attempt to maintain overall muscle power and function.
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