title: Inverse correlation between serum interleukin-6 and iron levels among Japanese adults: a cross-sectional study.
abstract: BACKGROUND
  Interleukin-6 (IL-6) is a multifunctional cytokine that is produced by many different cell types, and plays an important role in the regulation of inflammation, immune responses, the acute-phase response, and hematopoiesis. Previous laboratory and clinical studies have shown that IL-6 causes a significant decrease in serum iron levels. Therefore, we conducted an epidemiological study to examine the association between serum IL-6 and iron levels.
  
  
  METHODS
  In total, 280 Japanese individuals aged 20-78 years were enrolled when they visited a clinic located in an urban area for Helicobacter pylori (H. pylori) infection tests and subsequent eradication; 65.3% were infected with H. pylori. Subjects with gastric cancer, idiopathic thrombocytopenia, or IL-6 > 10 pg/mL were excluded from the study. Serum iron and IL-6 levels were measured using the 2-nitroso-5-(N-propyl-3-sulfopropylamino) phenol method and chemiluminescence enzyme immunoassay, respectively.
  
  
  RESULTS
  Geometric mean iron and IL-6 levels were 111.5 μg/dL and 1.77 pg/mL, respectively, for men, and 89.4 μg/dL and 1.55 pg/mL, respectively, for women. The logarithm of serum iron levels was negatively correlated with the logarithm of IL-6 levels in men (r = -0.19, p = 0.047), but not in women (r = -0.035, p = 0.65). Regression analysis, adjusted for sex, age, and H. pylori infection status, showed that the logarithm of serum iron levels was significantly associated with a decreased logarithm of IL-6 levels (β = -0.053, p = 0.041). The odds ratio for low serum iron levels adjusted for sex, age, and H. pylori infection status was 7.88 (95% CI 1.29-48.06) in those with an IL-6 level > 4 pg/mL.
  
  
  CONCLUSIONS
  Lower serum iron levels are significantly associated with higher serum IL-6 levels among Japanese adults.
authors.affiliation: Department of Preventive Medicine, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya 466-8550, Japan. nakagawa.hiroko@g.mbox.nagoya-u.ac.jp.
authors.forename: Hiroko
authors.initials: H
authors.lastname: Nakagawa
authors.forename: Takashi
authors.initials: T
authors.lastname: Tamura
authors.forename: Yoko
authors.initials: Y
authors.lastname: Mitsuda
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Goto
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Kamiya
authors.forename: Takaaki
authors.initials: T
authors.lastname: Kondo
authors.forename: Kenji
authors.initials: K
authors.lastname: Wakai
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Hamajima