The prevalence of obesity continues to rise in the United States. Total and abdominal obesity increase the risk for coronary heart disease and mortality among women. Moreover, there is an accumulation of fat in the abdominal region during the aging process with an increase in the infiltration of fat around and within skeletal muscle which adversely affects glucose and lipoprotein metabolism. A main focus of my research is the study of obesity, body fat distribution, intramuscular fat and their role in insulin resistance with emphasis on the effects of weight loss and exercise training on muscle and glucose metabolism in sedentary, overweight individuals. The basic research includes the study of mechanisms by which diet and exercise interventions (aerobic and resistive training) affect skeletal muscle and adipose tissue metabolism, insulin signaling and gene expression in muscle, and in vivo insulin action in sedentary older individuals.
In addition, my research involves the study of residual hemiparesis following stroke which leads to physical deconditioning and possibly muscle atrophy and abnormal metabolism due to disuse or aberrant neural innervation. We have described skeletal muscle atrophy and greater fat deposition within the muscle of the hemiparetic limb in chronic hemiparetic stroke patients which may contribute to functional disability and increased cardiovascular disease risk in chronic hemiparetic stroke patients. We are currently examining the muscle molecular phenotype and its relationship to gait deficit severity and interventions designed to prevent muscle atrophy and reduce insulin resistance which are needed to minimize the loss of functional independence and cardiovascular disease risk in older chronically disabled stroke patients.
Ryan AS, Nicklas BJ, Berman DM. Aerobic exercise is necessary to induce improvements in glucose utilization with moderate weight loss in obese postmenopausal women. Obes Res, 2006; in press.
Ferrara CM, Goldberg AP, Ortmeyer HK, Ryan AS. Effects of aerobic and resistive exercise training on glucose disposal and skeletal muscle metabolism in older men. J Gerontol, 2006; in press.
Ivey FM, Ryan AS, Hafer-Macko CE, Garrity BM, Sorkin JD, Goldberg AP, Macko RF, 2006. High prevalence of abnormal glucose metabolism and poor sensitivity of fasting plasma glucose in the chronic phase of stroke. Cerebrovasc Dis 2006; in press.
Yang R-Z, Lee M-J, Hu H, Pollin TI, Ryan AS, Nicklas BJ, Snitker S, Horenstein RB, Hull K, Goldberg NH, Goldberg AP, Shuldiner AR, Fried SK, Gong D-W. Acute-phase serum amyloid A is a pro-inflammatory adipokine in humans and a potential link between obesity and its metabolic complications. PLoS Medicine 2006; in press.
Ortmeyer HK, Adall Y, Marciani KR, Katsiaras A, Ryan AS, Bodkin NL, Hansen BC. Skeletal muscle glycogen synthase subcellular localization: effects of insulin and PPAR-α agonist (K-111) administration in rhesus monkeys. Am J Physiol, 2005;288:R1509-R1517.
Rabon-Stith KM, Hagberg JM, Phares DB, Kostek MC, Delmonico MJ, Roth SM, Ferrell RE, Conway JM, Ryan AS, Hurley BF. Vitamin D receptor FOK1 genotype influences bone mineral density response to strength training. Experimental Physiol, 90: 653-661, 2005.
Hafer-Macko CE, Yu S, Ryan AS, Ivey FM, Macko RF. Elevated tumor necrosis factor-alpha in skeletal muscle after stroke. Stroke, 36:2021-2023, 2005.
Ferrara CM, McCrone SH, Brendle D, Ryan AS, Goldberg AP. Additive effects of resistive exercise on oral glucose tolerance in aerobically-conditioned older men. Int J Sport Nutr Exerc Metab, 2004;14:73-80.
Ryan AS, Ivey FM, Hurlbut DE, Martel GF, Lemmer JT, Sorkin JD, Metter J, Fleg J, Hurley BF. Regional bone mineral density after resistive training in young and older men and women. Scand J Med Sci Sports, 2004;14:16-23.
Berman DM, Nicklas BJ, Ryan AS, Rogus EM, Dennis KE, Goldberg AP. Regulation of lipolysis and lipoprotein lipase after weight loss in obese, postmenopausal women. Obes Res, 2004;12(1):32-39.
De Deyne PG, Hafer-Macko CE, Ivey FM, Ryan AS, Macko RF. Muscle molecular phenotype after stroke is associated with gait deficit severity. Muscle & Nerve, 2004;30(2):209-215.
You T, Berman DM, Ryan AS, Nicklas BJ. Efects of hypocaloric diet and exercise training on inflammation and adipocyte lipolysis in obese postmenopausal women. J Clin Endocrinol Metab, 2004; 89:1739-1746.
Ryan AS, Nicklas BJ. Reductions in plasma cytokine levels with weight loss improve insulin sensitivity in overweight and obese postmenopausal women. Diabetes Care, 2004; 27:1699-1705.
Phares DA, Halverstadt AA, Shuldiner AR, Ferrell RE, Douglass LW, Ryan AS, Goldberg AP, Hagberg JM. Association between body fat response to exercise training and multilocus adrenergic receptor genotypes. Obes Res, 2004;12(5):807-815.
Tittlebach T, Berman DM, Nicklas BJ, Ryan AS, Goldberg AP. Racial differences in regional adipocyte hypertrophy and its relationship to the abnormalities of the metabolic syndrome in obese postmenopausal women. Obes Res, 2004; 12(6):990-998.
You T, Ryan AS, Nicklas BJ. The metabolic syndrome in obese postmenopausal women: Relationship to body composition, visceral fat and inflammation. J Clin Endocrinol Metab, 2004; 89:5517-5522.