title: The association between leptin, interleukin-6, and hip radiographic osteoarthritis in older people: a cross-sectional study.
abstract: BACKGROUND
  The associations between leptin, interleukin (IL)-6, and hip radiographic osteoarthritis (OA) have not been reported, and their roles in obesity-related hip OA are unclear. The aim of this study was to describe the associations between leptin, IL-6, and hip radiographic osteoarthritis (ROA) in older adults.
  
  
  METHODS
  A cross-sectional sample of 193 randomly selected subjects (mean age, 63 years; range, 52 to 78 years; 48% female subjects) were studied. Hip ROA, including joint-space narrowing (JSN) and osteophytes, was determined by anteroposterior radiograph. Serum levels of leptin and interleukin (IL)-6 were measured with radioimmunoassay. Fat mass was measured with dual-energy x-ray absorptiometry (DXA). Body mass index (BMI) and waist-to-hip ratio (WHR) were calculated.
  
  
  RESULTS
  In multivariable analysis, hip JSN was associated with serum levels of leptin in the whole sample (beta=0.046 per microg/L, P=0.024 for superior; beta=0.068 per microg/L, P=0.004 for axial compartment) and IL-6 only in females (beta=0.241 per pg/ml, P=0.002 for superior; beta=0.239 per pg/ml, P=0.001 for axial compartment). The positive associations between body-composition measures (BMI, WHR, percentage total fat mass, and percentage trunk fat mass) and hip JSN in women became nonsignificant after adjustment for leptin but not for IL-6. No significant associations were found between leptin, IL-6, and the presence or severity of osteophytes.
  
  
  CONCLUSIONS
  This study suggests that metabolic and inflammatory mechanisms may play a role in the etiology of hip OA and that the associations between body composition and hip JSN are mediated by leptin, particularly in women.
authors.affiliation: Menzies Research Institute, University of Tasmania, Private Bag 23, Hobart, Tasmania 7000, Australia.
authors.forename: Oliver P
authors.initials: OP
authors.lastname: Stannus
authors.forename: Graeme
authors.initials: G
authors.lastname: Jones
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Quinn
authors.forename: Flavia M
authors.initials: FM
authors.lastname: Cicuttini
authors.forename: Dawn
authors.initials: D
authors.lastname: Dore
authors.forename: Changhai
authors.initials: C
authors.lastname: Ding
mesh_terms: D000368:Aged; D015415:Biomarkers / Q000097:blood; D001823:Body Composition / Q000502:physiology; D015992:Body Mass Index; D003430:Cross-Sectional Studies; D005260:Female; D006621:Hip Joint / Q000000981:diagnostic imaging; D006801:Humans; D015850:Interleukin-6 / Q000097:blood*; D020738:Leptin / Q000097:blood*; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D015207:Osteoarthritis, Hip / Q000097:blood* / Q000000981:diagnostic imaging* / Q000503:physiopathology; D011859:Radiography; D012720:Severity of Illness Index; D012727:Sex Characteristics
chemical_list: D015415:Biomarkers; D015850:Interleukin-6; D020738:Leptin