title: An inverted J-shaped association of serum uric acid with muscle strength among Japanese adult men: a cross-sectional study.
abstract: BACKGROUND
  Uric acid (UA) may protect muscle function from oxidative damage due to reactive oxygen species through its powerful antioxidant capacity. However, several studies have demonstrated that hyperuricemia is closely related to systemic inflammation and has oxidant properties effects, both of which may increase the risk of muscle strength loss. The purpose of this study was to examine the association of serum UA concentration with grip strength and leg extension power in adult men.
  
  
  METHODS
  This study is a cross-sectional survey in which 630 Japanese male employees aged 30 years and older participated. Five hundred and eighty-six subjects participated in the measurement of grip strength, and 355 subjects participated in the measurement of leg extension power. Blood samples were obtained for serum UA analysis.
  
  
  RESULTS
  After adjustment for potential confounders, grip strength differed significantly between participants with and those without hyperuricemia (geometric mean and 95% confidence interval [CI]: 40.3 [39.2-41.3] kg vs. 41.9 [41.3-42.5] kg; P = 0.01). In addition, serum UA levels (quartiles) showed an inverted J-shaped curve with grip strength (mean and 95% CI: Q1, 41.6 [40.6-42.6] kg; Q2, 42.2 [41.2-43.2] kg; Q3, 41.8 [40.8-42.8] kg; Q4, 40.4 [39.3-41.4] kg; P for quadratic trend = 0.05). The results in the leg extension power group were similar to those observed in the grip strength group.
  
  
  CONCLUSIONS
  This population-based cross-sectional study shows for the first time that hyperuricemia is associated with poor muscle strength. Moreover, the results indicate an inverted J-shaped association between serum UA quartiles and muscle strength.
authors.affiliation: Department of Medicine and Science in Sports and Exercise, Tohoku University Graduate School of Medicine, Sendai 980-8575, Japan. nagatomi@med.tohoku.ac.jp.
authors.forename: Cong
authors.initials: C
authors.lastname: Huang
authors.forename: Kaijun
authors.initials: K
authors.lastname: Niu
authors.forename: Yoritoshi
authors.initials: Y
authors.lastname: Kobayashi
authors.forename: Lei
authors.initials: L
authors.lastname: Guan
authors.forename: Haruki
authors.initials: H
authors.lastname: Momma
authors.forename: Yufei
authors.initials: Y
authors.lastname: Cui
authors.forename: Masahiro
authors.initials: M
authors.lastname: Chujo
authors.forename: Atsushi
authors.initials: A
authors.lastname: Otomo
authors.forename: Hui
authors.initials: H
authors.lastname: Guo
authors.forename: Hiroko
authors.initials: H
authors.lastname: Tadaura
authors.forename: Ryoichi
authors.initials: R
authors.lastname: Nagatomi
mesh_terms: D000328:Adult; D000367:Age Factors; D044466:Asian People; D015415:Biomarkers / Q000097:blood; D003430:Cross-Sectional Studies; D018737:Hand Strength; D006801:Humans; D033461:Hyperuricemia / Q000097:blood* / Q000175:diagnosis / Q000208:ethnology / Q000503:physiopathology; D007564:Japan / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D053580:Muscle Strength; D018482:Muscle, Skeletal / Q000503:physiopathology*; D012307:Risk Factors; D012737:Sex Factors; D014527:Uric Acid / Q000097:blood*
chemical_list: D015415:Biomarkers; D014527:Uric Acid