title: Determinants of bone microarchitecture and mechanical properties in obese men.
abstract: BACKGROUND
  Recent studies have suggested that obesity in men is associated with increased fracture risk. Obesity in men is also associated with dysregulation of the GH/IGF-I and gonadal steroid axes, important regulators of bone homeostasis.
  
  
  OBJECTIVE
  The aim of the study was to investigate body composition and endocrine determinants of bone microarchitecture and mechanical properties in obese men.
  
  
  METHODS
  We conducted a cross-sectional study at a clinical research center.
  
  
  METHODS
  Thirty-five obese men (mean age, 33.8 ± 6.4 yr; mean body mass index, 36.5 ± 5.8 kg/m(2)) participated in the study.
  
  
  METHODS
  Distal radius microarchitecture and mechanical properties were measured by three-dimensional high-resolution peripheral quantitative computed tomography and microfinite element analysis; body composition by computed tomography; bone marrow fat by proton magnetic resonance spectroscopy; total and free estradiol and testosterone; IGF-I; peak glucagon-stimulated GH; 25-hydroxyvitamin D.
  
  
  RESULTS
  Men with high visceral adipose tissue (VAT) had impaired mechanical properties compared to men with low VAT (P < 0.05), despite comparable body mass index. VAT was inversely associated and thigh muscle was positively associated with mechanical properties (P < 0.05). Bone marrow fat was inversely associated with cortical parameters (P ≤ 0.02). Free estradiol was positively associated with total density (P = 0.05). Free testosterone was positively associated with trabecular thickness and inversely with trabecular number (P ≤ 0.05). Peak stimulated GH was positively associated with trabecular thickness, as was IGF-I with cortical area (P ≤ 0.04).
  
  
  CONCLUSIONS
  VAT and bone marrow fat are negative predictors and muscle mass is a positive predictor of microarchitecture and mechanical properties in obese men. Testosterone, estradiol, and GH are positive determinants of trabecular microarchitecture, and IGF-I is a positive determinant of cortical microarchitecture. This supports the notion that VAT is detrimental to bone and that decreased GH and testosterone, characteristic of male obesity, may exert deleterious effects on microarchitecture, whereas higher estradiol may be protective.
authors.affiliation: Massachusetts General Hospital, Yawkey 6E, 55 Fruit Street, Boston, Massachusetts 02114, USA. mbredella@partners.org
authors.forename: Miriam A
authors.initials: MA
authors.lastname: Bredella
authors.forename: Eleanor
authors.initials: E
authors.lastname: Lin
authors.forename: Anu V
authors.initials: AV
authors.lastname: Gerweck
authors.forename: Melissa G
authors.initials: MG
authors.lastname: Landa
authors.forename: Bijoy J
authors.initials: BJ
authors.lastname: Thomas
authors.forename: Martin
authors.initials: M
authors.lastname: Torriani
authors.forename: Mary L
authors.initials: ML
authors.lastname: Bouxsein
authors.forename: Karen K
authors.initials: KK
authors.lastname: Miller
mesh_terms: D000273:Adipose Tissue / Q000000981:diagnostic imaging*; D000293:Adolescent; D000328:Adult; D001823:Body Composition / Q000502:physiology*; D015992:Body Mass Index; D015519:Bone Density / Q000502:physiology*; D001842:Bone and Bones / Q000000981:diagnostic imaging / Q000503:physiopathology*; D003430:Cross-Sectional Studies; D004958:Estradiol / Q000097:blood; D013006:Growth Hormone / Q000097:blood; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000097:blood / Q000000981:diagnostic imaging / Q000503:physiopathology*; D011859:Radiography; D013739:Testosterone / Q000097:blood; D014807:Vitamin D / Q000031:analogs & derivatives / Q000097:blood
chemical_list: D014807:Vitamin D; D013739:Testosterone; D004958:Estradiol; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone; C104450:25-hydroxyvitamin D