title: Determinants of bone mineral density in obese premenopausal women.
abstract: Despite being a risk factor for cardiovascular disease and diabetes mellitus, obesity has been thought to protect against osteoporosis. However, recent studies have demonstrated a differential impact of specific fat compartments on bone mineral density (BMD) with visceral adipose tissue (VAT) having potential detrimental effects on BMD. Visceral obesity is also associated with dysregulation of the GH/IGF-1 axis, an important regulator of bone homeostasis. The purpose of our study was to evaluate the differential effects of abdominal fat depots and muscle, vitamin D, and hormonal determinants, including insulin-like growth factor-1 (IGF-1), testosterone, and estradiol, on trabecular BMD of the lumbar spine. We studied 68 healthy obese premenopausal women (mean BMI, 36.7±4.2 kg/m(2)). Quantitative computed tomography (QCT) was used to assess body composition and lumbar trabecular BMD. There was an inverse association between BMD and VAT, independent of age and BMI (p=0.003). IGF-1 correlated positively with BMD and negatively with VAT and, in stepwise multivariate regression modeling, was the strongest predictor of BMD and procollagen type 1 amino-terminal propeptide (P1NP). Thigh muscle cross sectional area (CSA) and thigh muscle density were also associated with BMD (p<0.05), but 25-hydroxyvitamin D [25(OH)D], testosterone, free testosterone, and estradiol levels were not. 25(OH)D was associated inversely with BMI, total, and subcutaneous abdominal adipose tissue (p<0.05). These findings support the hypothesis that VAT exerts detrimental effects, whereas muscle mass exerts positive effects on BMD in premenopausal obese women. Moreover, our findings suggest that IGF-1 may be a mediator of the deleterious effects of VAT on bone health through effects on bone formation.
authors.affiliation: Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Yawkey 6E, 55 Fruit Street, Boston, MA 02114, USA. mbredella@partners.org
authors.forename: Miriam A
authors.initials: MA
authors.lastname: Bredella
authors.forename: Martin
authors.initials: M
authors.lastname: Torriani
authors.forename: Reza Hosseini
authors.initials: RH
authors.lastname: Ghomi
authors.forename: Bijoy J
authors.initials: BJ
authors.lastname: Thomas
authors.forename: Danielle J
authors.initials: DJ
authors.lastname: Brick
authors.forename: Anu V
authors.initials: AV
authors.lastname: Gerweck
authors.forename: Lindsey M
authors.initials: LM
authors.lastname: Harrington
authors.forename: Anne
authors.initials: A
authors.lastname: Breggia
authors.forename: Clifford J
authors.initials: CJ
authors.lastname: Rosen
authors.forename: Karen K
authors.initials: KK
authors.lastname: Miller
mesh_terms: D000293:Adolescent; D000328:Adult; D015992:Body Mass Index; D015519:Bone Density; D005260:Female; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D008875:Middle Aged; D056128:Obesity, Abdominal / Q000000981:diagnostic imaging / Q000503:physiopathology*; D017697:Premenopause; D012738:Sex Hormone-Binding Globulin / Q000378:metabolism; D013739:Testosterone / Q000097:blood; D014057:Tomography, X-Ray Computed; D055815:Young Adult
chemical_list: D012738:Sex Hormone-Binding Globulin; D013739:Testosterone; D007334:Insulin-Like Growth Factor I