Genetic variation is associated with C-reactive protein levels in the third national health and nutrition examination survey

Background-Increased serum C-reactive protein (CRP) is an independent risk factor for cardiovascular disease. Previous studies have suggested that genetic variation within the CRP gene is associated with serum CRP. Methods and Results-We genotyped CRP genetic variants in 7159 individuals from the Third National Health and Nutrition Examination Survey (NHANES III). NHANES III is American population-based sample linked to hundreds of phenotypes, including CRP; however, the CRP assay used in this survey is not a high-sensitivity CRP assay, and 65% of participants (n=4679) had CRP measurements at or below the level of detection. Despite these limitations, we identified specific CRP single-nucleotide polymorphisms (SNPs) and haplotypes associated with serum CRP levels in the general population. Two variants were associated with increased levels of serum CRP: SNP rs3093058 (in linkage disequilibrium with a CRP promoter SNP rs3093062) in the non-Hispanic black sample and the triallelic promoter SNP rs3091244 in the non-Hispanic black and Mexican American samples. Two other SNPs were associated with decreased levels of serum CRP in either the non-Hispanic black (rs1205 and rs2808630) or Mexican American (rs1205) samples. Three haplotypes inferred from 7 SNPs (ATTGCGA, TTAGCGA, and AAAGAGA) were associated (P <= 0.01) with increased levels of serum CRP in the non-Hispanic black sample; 2 haplotypes (ATTGCGA and AAAGCGA) were associated (P < 0.05) with increased levels in the Mexican American sample; and 1 haplotype (AAAGCGA) was associated (P < 0.03) with increased levels in the non-Hispanic white sample. Post hoc analysis suggests that the AA genotype of the triallelic SNP rs3091244, after adjustment for covariates, was associated with prevalent coronary heart disease in the non-Hispanic white population sample. Conclusions-Genetic variation within CRP is associated with serum CRP levels in the general population and may be associated with prevalent coronary heart disease.