title: The relation between bone mineral density, insulin-like growth factor I, lipoprotein (a), body composition, and muscle strength in adolescent males.
abstract: Osteoporosis is the most common metabolic bone disease. A low peak bone mass is regarded a risk factor for osteoporosis. Heredity, physical activity, and nutrition are regarded important measures for the observed variance in peak bone mass. Lp(a) lipoprotein is a well-known risk factor for atherosclerosis. Serum insulin-like growth factor I (IGF-I) has been found to be increased in males with early cardiovascular disease. In this study, we evaluated the association between bone mass, body constitution, muscle strength, Lp(a), and IGF-I in 47 Caucasian male adolescents (mean age, 16.9 yr). Bone mineral density (BMD) and body composition were measured by dual x-ray absorptiometry, muscle strength of thigh using an isokinetic dynamometer, IGF-I by RIA, and Lp(a) by enzyme-linked immunosorbent assay. IGF-I was only associated with Lp(a) (r = 0.38, P < 0.01). Lp(a) was related to total body (r = 0.40, P < 0.01), skull (r = 0.45, P < 0.01), and femoral neck BMD (r = 0.44, P < 0.01). Lp(a) was also related to fat mass (r = 0.34, P < 0.05) and muscle strength (r = 0.30-0.42, P < 0.05). After multiple regression and principal component (PC) analysis, the so-called PC body size (weight, fat mass, lean body mass, and muscle strength) was the most significant predictor of BMD (beta = 0.28-0.51, P < 0.05-0.01), followed by the so-called PC physical activity (beta = 0.28-0.38, P < 0.05-0.01, weight-bearing locations). However, the PC analysis confirmed that Lp(a) was an independent predictor of total body, skull, and femoral neck BMD (beta = 0.33-0.36, P < 0.01). The present investigation confirms that BMD, body size, and muscle strength are closely related and that the level of physical activity is a major determinant of BMD. However, the positive relation of Lp(a), a major risk factor for cardiovascular disease, to BMD has not previously been described. The importance of this observation has to be further investigated.
authors.affiliation: Department of Orthopaedics, Umeå University, Sweden. kim.thorsen@idrott.umu.se
authors.forename: K
authors.initials: K
authors.lastname: Thorsen
authors.forename: P
authors.initials: P
authors.lastname: Nordström
authors.forename: R
authors.initials: R
authors.lastname: Lorentzon
authors.forename: G H
authors.initials: GH
authors.lastname: Dahlén
mesh_terms: D000293:Adolescent; D001696:Biomechanical Phenomena; D001823:Body Composition; D015519:Bone Density; D015444:Exercise; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D017270:Lipoprotein(a) / Q000097:blood; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology*; D011627:Puberty; D012016:Reference Values; D012044:Regression Analysis
chemical_list: D017270:Lipoprotein(a); D007334:Insulin-Like Growth Factor I