The focus of this project is to examine physiological and cellular mechanisms that regulate human skeletal muscle growth. Maintenance of an adequate muscle mass is critical not only for mobility and energy/protein metabolism, but also for survival. Muscle mass is maintained or increased only when adequate anabolic stimuli counteract the protein catabolism that characterizes the basal state and many of the conditions that lead to muscle wasting. Our preliminary studies have shown that nutrition and resistance exercise are two major anabolic stimuli for skeletal muscle. During the previous grant cycle we have shown that the mTOR signaling pathway appears to be an involved in both the resistance exercise and nutrient stimulation of muscle protein synthesis in humans. We have also shown that the mTOR pathway is activated following a novel treatment (blood flow restriction during low-intensity resistance exercise). This finding has potential use in patient populations (e.g., in patients undergoing physical therapy following surgery, frail elderly, orthopedic patients, etc.) that cannot perform resistance exercise at the intensity level needed to induce muscle growth. Therefore, based on our preliminary data, our general hypothesis is that anabolic nutrients, metabolic stress/reactive hyperemia, and age are independent factors that can regulate anabolic signaling, anabolic and catabolic gene expression, and muscle protein synthesis following a bout of resistance exercise. Specifically, we hypothesize that in healthy human subjects: (1) Activation of the mTOR signaling pathway is the primary cellular mechanism responsible for the stimulation of muscle protein synthesis following resistance exercise and/or anabolic nutrient ingestion. (2) Blood flow restriction during low-intensity resistance exercise induces muscle metabolic stress and reactive hyperemia which activates anabolic pathways. (3) Aging is associated with a reduced anabolic response to resistance exercise, and this defect can be overcome by post-exercise ingestion of anabolic nutrients and/or the novel treatment of blood flow restriction. These acute studies will provide insight into physiological and cellular mechanisms that regulate human muscle protein balance, and will be utilized as a basis from which to develop scientifically-based interventions for improving muscle protein balance in conditions such as aging, rehabilitation, trauma, cancer, and AIDS.

Public Health Relevance

The focus of this project is to examine how nutrients and resistance exercise regulate human muscle growth. In this application we propose several human studies to: 1) determine whether a key cellular pathway (mTOR) is responsible for controlling muscle growth;2) examine the mechanisms of how a novel exercise treatment with potential clinical significance can promote muscle growth;3) determine whether the muscle growth response can be improved in the elderly with the use of nutrient supplementation following exercise. These studies will provide insight into the mechanisms that regulate human muscle growth, and will be used as a basis from which to develop scientifically-based interventions for improving muscle growth and function in conditions such as aging, rehabilitation, trauma, cancer, and AIDS.

Agency
National Institute of Health (NIH)
Institute
National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS)
Type
Research Project (R01)
Project #
5R01AR049877-09
Application #
8314117
Study Section
Skeletal Muscle and Exercise Physiology Study Section (SMEP)
Program Officer
Boyce, Amanda T
Project Start
2003-04-01
Project End
2014-08-31
Budget Start
2012-09-01
Budget End
2014-08-31
Support Year
9
Fiscal Year
2012
Total Cost
$410,641
Indirect Cost
$126,045
Name
University of Texas Medical Br Galveston
Department
Other Health Professions
Type
Schools of Allied Health Profes
DUNS #
800771149
City
Galveston
State
TX
Country
United States
Zip Code
77555
Porter, Craig; Reidy, Paul T; Bhattarai, Nisha et al. (2015) Resistance Exercise Training Alters Mitochondrial Function in Human Skeletal Muscle. Med Sci Sports Exerc 47:1922-31
Porter, Craig; Herndon, David N; Børsheim, Elisabet et al. (2014) Uncoupled skeletal muscle mitochondria contribute to hypermetabolism in severely burned adults. Am J Physiol Endocrinol Metab 307:E462-7
Dickinson, Jared M; Gundermann, David M; Walker, Dillon K et al. (2014) Leucine-enriched amino acid ingestion after resistance exercise prolongs myofibrillar protein synthesis and amino acid transporter expression in older men. J Nutr 144:1694-702
Reidy, P T; Walker, D K; Dickinson, J M et al. (2014) Soy-dairy protein blend and whey protein ingestion after resistance exercise increases amino acid transport and transporter expression in human skeletal muscle. J Appl Physiol (1985) 116:1353-64
Glynn, Erin L; Fry, Christopher S; Timmerman, Kyle L et al. (2013) Addition of carbohydrate or alanine to an essential amino acid mixture does not enhance human skeletal muscle protein anabolism. J Nutr 143:307-14
Fry, Christopher S; Drummond, Micah J; Glynn, Erin L et al. (2013) Skeletal muscle autophagy and protein breakdown following resistance exercise are similar in younger and older adults. J Gerontol A Biol Sci Med Sci 68:599-607
Dickinson, Jared M; Volpi, Elena; Rasmussen, Blake B (2013) Exercise and nutrition to target protein synthesis impairments in aging skeletal muscle. Exerc Sport Sci Rev 41:216-23
Dickinson, Jared M; Drummond, Micah J; Fry, Christopher S et al. (2013) Rapamycin does not affect post-absorptive protein metabolism in human skeletal muscle. Metabolism 62:144-51
Dickinson, Jared M; Drummond, Micah J; Coben, Jennifer R et al. (2013) Aging differentially affects human skeletal muscle amino acid transporter expression when essential amino acids are ingested after exercise. Clin Nutr 32:273-80
Szczesny, Bartosz; Olah, Gabor; Walker, Dillon K et al. (2013) Deficiency in repair of the mitochondrial genome sensitizes proliferating myoblasts to oxidative damage. PLoS One 8:e75201

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