title: Resistance training, and IGF involvement in the maintenance of muscle mass during the aging process.
abstract: Sarcopenia is the decline of muscle mass and strength with age. Sarcopenia leads to significant impairment in the ability to carry out normal daily function and thus there is a great need for interventions that will lead to muscle regeneration and repair in the aging population. Age-related sarcopenia in humans, characterized by loss of type I and type II muscle fibers and a decrease in fiber cross-sectional area primarily in type II fibers, can be attenuated by mechanical load on the muscle, which increases cross-sectional area of the remaining fibers, but does not restore fiber numbers characteristic of young muscle. Considerable evidence also implicates age-related declines in muscle insulin-like growth factor action in sarcopenia. IGF-I promotes myoblast proliferation, differentiation, and protein accretion in muscle through multiple signaling mechanisms, including the PI3-kinase, MAP kinase and calcineurin pathways. Exercise and injury induce increases in IGF-I, IGF-I receptors and IGF-I-activated signaling pathways. Although there is evidence that aging muscle retains the ability to synthesize IGF-I, there is also evidence that aging may be associated with attenuation of the ability of exercise to induce an isoform of IGF-I that promotes satellite cell proliferation. Moreover, aging muscle may be resistant to IGF-I, an effect that is reversed by exercise. However, it is clear that over-expression of IGF-I in muscle can protect against age-related sarcopenia.
authors.affiliation: Department of Biochemistry and The Barshop Institute for Aging and Longevity Studies, The University of Texas Health Science Center at San Antonio, San Antonio, TX 78229-3900, USA.
authors.forename: Martin L
authors.initials: ML
authors.lastname: Adamo
authors.forename: Roger P
authors.initials: RP
authors.lastname: Farrar
mesh_terms: D000375:Aging / Q000378:metabolism*; D017398:Alternative Splicing; D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D018482:Muscle, Skeletal / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009133:Muscular Atrophy / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control*; D010806:Physical Education and Training; D012333:RNA, Messenger / Q000378:metabolism; D014162:Transfection
chemical_list: D012333:RNA, Messenger; D007334:Insulin-Like Growth Factor I