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
Our project, Nutrition, Physical Activity, and Sarcopenia in the Elderly, has made significant progress on all objective outlined in our project plan. In the current project year, we have fully or substantially met all of our approved milestones. We have initiated the planned studies under subobjective 1a (Determine the mechanisms and efficacy of nutrient modulation on overload-induced skeletal muscle hypertrophy.) To date we have completed the experiments designed to examine how aging influences the growth capacity of skeletal muscle in response to repeated high intensity exercise. We found that in older animals this response is blunted and leads to a smaller increase in muscle size following exercise than compared to younger animals. Work in the next project year will begin to refine the influence of dietary factors on skeletal muscle growth capacity in older animals. We are also in the process of completing complementary studies of muscle growth capacity in older humans as a subobjective (Perform parallel clinical studies to determine the influence of physical activity/exercise and nutrition on the control of muscle growth in older adults with defined low muscle mass and functional limitations). We are presently completing studies examining differences in skeletal muscle growth capacity in young and older healthy adults in the current project year. Once these studies have been completed, we will examine whether skeletal muscle growth capacity is further reduced in states of sarcopenia and/or physical frailty. Work on all of the proposed studies under Subobjective 2a. (Determine the efficacy of selected nutritional and lifestyle behaviors on age-related changes in skeletal muscle physiology and physical functioning) has been initiated. A key feature of these studies will be our approach to evaluate these responses in populations of adults who, due to a multitude of co-morbidities and behaviors, are at the greatest risk for the development of late life disability. We are nearing completion of a randomized study examining the influence of 40 g per day supplement of whey protein and changes in muscle mass, strength, physical performance in older men and women with mobility limitations. Recruitment is presently ongoing for this study and will be completed in Year 2 of the current project period. In addition, we have initiated recruitment for the Lifestyle Interventions for Independence in the Elderly (LIFE) study. A total of 1600 older men and women (200 at HNRCA Field Center) will be recruited at 8 field centers to examine whether a structured program of physical activity will prevent the development of late life disability in at risk older adults. When completed, the LIFE study will be the largest study of a physical activity intervention ever conducted in older adults. For publications related to project, see parent project #1950-51000-068-00D.
1. Muscle performance and physical function are associated with voluntary rate of neuromuscular activation in older adults Aging leads to weakness and poor mobility (for example, slower walking speed or difficulty rising from a chair), but the cause of weakness and the link between weakness and mobility is not fully understood. Because there are large differences in health status and physical activity levels between older adults, it is difficult to determine if weakness is normal with healthy aging or if it happens because of other diseases. The way muscles generate force may be dependent in part on how well the nervous systems can turn on or activate the muscles. It is important to determine whether poor nervous system activation of muscles occurs in all older adults or just some, and whether this issue might contribute to poor mobility. ARS-funded researchers from Tufts University in Boston, MA found that muscle activation (a measure of the nervous systems ability to make muscles move) was slower in older adults with limitations in their mobility but not healthy older adults. We also found that women have slower rates of muscle activation than men. The slowness of muscle activation was related to the subject’s muscle strength or how much weight a person can lift. Our results suggest that the rate of muscle activation is a good indicator of problems in the nervous system that might contribute to poor mobility in older adults.
5. Significant Activities that Support Special Target Populations
Few opportunities exist in the Greater Boston, MA area for the elderly to learn about nutrition, physical activity and sarcopenia. ARS funded researchers at Tufts University in Boston, MA continue to maintain a strong collaboration with Kit Clark Senior Services and continues to support The Fit-4-Life Program. The Fit-4-Life Program is a physical activity and nutrition counseling intervention at Kit Clark Senior Services’ Madden Senior Center, Dorchester, MA. This senior center serves a large and diverse population of underserved seniors living mainly in the Dorchester, Roxbury, South Boston, and Mattapan sections of Greater Boston, many of whom have limited incomes, little education and few resources. To date, over 188 seniors have enrolled in the program, and our outcome data suggests that Fit-4-Life is having a beneficial impact in the lives of many seniors in terms of weight management, improved physical functioning, and an overall reduced burden of chronic disease. Furthermore, the success of the program to-date has helped to recently secure additional funding that will be used for program expansion and development. The Fit-4-Life Program is now being offered in several languages, including Spanish, Vietnamese, and Cape Verdean and Haitian Creole.