title: Toenail mercury and dyslipidemia: Interaction with selenium.
abstract: BACKGROUND
  Although compelling evidences from in vivo and in vitro studies exist, limited studies have examined the association between chronic mercury exposure and dyslipidemia. Particularly, data are sparse regarding the influence of selenium on this association of mercury with dyslipidemia in humans.
  
  
  OBJECTIVE
  The purpose of the current study was to examine the associations of toenail mercury with dyslipidemia and its components, and to examine whether selenium in toenails modifies these associations.
  
  
  METHODS
  We performed cross-sectional analyses using baseline data from a cohort in the Yeungnam area in South Korea, including 232 men and 269 women. Toenail mercury and selenium concentrations were quantified using neutron activation analysis, and fasting serum lipid measurements were obtained through the medical examination. Odds ratios of the prevalent hypercholesterolemia, hyper-LDL-cholesterolemia, hypo-HDL-cholesterolemia, hypertriglyceridemia, and dyslipidemia in correlation with mercury levels were calculated using multivariable logistic regression.
  
  
  RESULTS
  The mean levels of toenail mercury were 0.47μg/g for men and 0.34μg/g for women. After adjustment for multiple confounding variables, participants in the highest tertile of toenail mercury levels had 4.08 (95% CI 1.09-15.32, p for trend=0.02) times higher risk of hyper-LDL-cholesterolemia, and 2.24 (95% CI 1.15-4.37, p for trend=0.004) times higher risk of dyslipidemia than those in the lowest tertile. Selenium is a significant effect-modifier for these associations; the highest tertile of toenail mercury were significantly associated with a higher risk of hypercholesterolemia (OR 5.25, 95% CI 1.04-26.38) and dyslipidemia (OR 2.98, 95% CI 1.16-7.66) compared to the lowest tertile at toenail selenium levels ≤0.685μg/g, while these associations became weak and non-significant, showing OR 0.98 and 95% CI 0.25-3.80 for hypercholesterolemia and OR 1.99 and 95% CI 0.73-5.45 for dyslipidemia at toenail selenium levels >0.685μg/g.
  
  
  CONCLUSIONS
  We confirmed the beneficial effects of selenium against the harmful effects of mercury in humans with relatively high consumption of fish. Our finding has important implications in making dietary recommendations regarding optimal levels of fish and selenium intakes. Further studies are warranted to determine the appropriate level of fish consumption, considering both methylmercury and selenium exposure, in a larger prospective cohort or RCT.
authors.affiliation: Department of Food and Nutrition, Yeungnam University, Gyeongsan, Gyeongbuk, Republic of Korea. Electronic address: kypark@ynu.ac.kr.
authors.forename: Kyong
authors.initials: K
authors.lastname: Park
authors.affiliation: Department of Food and Nutrition, Yeungnam University, Gyeongsan, Gyeongbuk, Republic of Korea.
authors.forename: Eunmin
authors.initials: E
authors.lastname: Seo
mesh_terms: D000328:Adult; D003430:Cross-Sectional Studies; D050171:Dyslipidemias / Q000097:blood / Q000378:metabolism*; D005260:Female; D006801:Humans; D008297:Male; D008628:Mercury / Q000032:analysis*; D008875:Middle Aged; D009262:Nails / Q000737:chemistry*; D056910:Republic of Korea; D012643:Selenium / Q000032:analysis*
chemical_list: D008628:Mercury; D012643:Selenium
keywords: Dyslipidemia; Interaction; Korean; Mercury; Selenium