title: A polymorphism in metallothionein 1A (MT1A) is associated with cadmium-related excretion of urinary beta 2-microglobulin.
abstract: OBJECTIVE
  Cadmium (Cd) toxicity of the kidney varies between individuals despite similar exposure levels. In humans Cd is mainly bound to metallothioneins (MT), which scavenge its toxic effects. Here we analyzed whether polymorphisms in MT genes MT1A and MT2A influence Cd-related kidney damage.
  
  
  METHODS
  In a cross-sectional study N=512 volunteers were selected from three areas in South-Eastern China, which to varying degree were Cd-polluted from a smelter (control area [median Cd in urine U-Cd=2.67 μg/L], moderately [U-Cd=4.23 μg/L] and highly [U-Cd=9.13 μg/L] polluted areas). U-Cd and blood Cd (B-Cd) concentrations were measured by graphite-furnace atomic absorption spectrometry. MT1A rs11076161 (G/A), MT2A rs10636 (G/C) and MT2A rs28366003 (A/G) were determined by Taqman assays; urinary N-Acetyl-beta-(D)-Glucosaminidase (UNAG) by spectrometry, and urinary β2-microglobulin (UB2M) by ELISA.
  
  
  RESULTS
  Higher B-Cd (natural log-transformed) with increasing number of MT1A rs11076161 A-alleles was found in the highly polluted group (p-value trend=0.033; all p-values adjusted for age, sex, and smoking). In a linear model a significant interaction between rs11076161 genotype and B-Cd was found for UNAG (p=0.001) and UB2M concentrations (p=0.001). Carriers of the rs11076161 AA genotype showed steeper slopes for the associations between Cd in blood and natural log-transformed UB2M (β=1.2, 95% CI 0.72-1.6) compared to GG carriers (β=0.30, 95% CI 0.15-0.45). Also for UNAG (natural log-transformed) carriers of the AA genotype had steeper slopes (β=0.55, 95% CI 0.27-0.84) compared to GG carriers (β=0.018, 95% CI -0.79-0.11).
  
  
  CONCLUSIONS
  MT1A rs11076161 was associated with B-Cd concentrations and Cd-induced kidney toxicity at high exposure levels.
authors.affiliation: Department of Occupational Health, School of Public Health, Fudan University, Shanghai, China.
authors.forename: Lijian
authors.initials: L
authors.lastname: Lei
authors.forename: Xiuli
authors.initials: X
authors.lastname: Chang
authors.forename: Gerda
authors.initials: G
authors.lastname: Rentschler
authors.forename: Liting
authors.initials: L
authors.lastname: Tian
authors.forename: Guoying
authors.initials: G
authors.lastname: Zhu
authors.forename: Xiao
authors.initials: X
authors.lastname: Chen
authors.forename: Taiyi
authors.initials: T
authors.lastname: Jin
authors.forename: Karin
authors.initials: K
authors.lastname: Broberg
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002105:Cadmium Poisoning / Q000235:genetics* / Q000378:metabolism / Q000652:urine*; D002681:China; D003430:Cross-Sectional Studies; D004247:DNA / Q000737:chemistry / Q000235:genetics; D004785:Environmental Pollutants / Q000506:poisoning*; D005260:Female; D005838:Genotype; D006801:Humans; D007674:Kidney Diseases / Q000139:chemically induced* / Q000235:genetics / Q000378:metabolism / Q000652:urine; D016015:Logistic Models; D008297:Male; D008668:Metallothionein / Q000235:genetics* / Q000378:metabolism; D008875:Middle Aged; D016133:Polymerase Chain Reaction; D020641:Polymorphism, Single Nucleotide; D001613:beta 2-Microglobulin / Q000097:blood / Q000378:metabolism / Q000652:urine*
chemical_list: D004785:Environmental Pollutants; C530099:MT1A protein, human; C491053:MT2A protein, human; D001613:beta 2-Microglobulin; D004247:DNA; D008668:Metallothionein