Complement C3 gene polymorphisms are associated with lipid levels, but not the risk of coronary artery disease: a case-control study

BACKGROUND: Coronary artery disease (CAD) is the leading cause of mortality and morbidity worldwide. Previous studies have shown that complement component 3 (C3) is associated with atherosclerosis and cardiovascular risk factors. METHODS: We conducted this study to evaluate the associations between tagSNPs in the C3 gene locus and the CAD susceptibility and lipid levels in the Chinese population. A hospital-based case-control study, including 1017 subjects (580 CAD patients and 437 non-CAD controls), was conducted. TagSNPs in the C3 gene were searched and genotyped by using the polymerase chain reaction-ligase detection reaction method. RESULTS: The C3 levels were positively associated with the low-density lipoprotein cholesterol (LDL-C) levels (r = 0.269, P = 0.001). Compared with those in controls, the serum C3 levels in CAD patients were significantly higher (Control: 0.94 + 0.14 g/l; CAD: 1.10 + 0.19 g/l, P < 0.001). No significant differences in genotype or allele frequencies were observed between CAD patients and controls. The minor T allele of rs2287848 was associated with low apolipoprotein A1 (ApoA1) levels in controls (Bonferroni corrected P, Pc = 0.032). Linkage disequilibrium and haplotype analysis established two haplotype blocks (Block1: rs344555-rs2277984, Block 2: rs2287848-rs11672613) and six haplotypes. No significant associations between haplotypes and the risk of CAD were observed (all Pc > 0.05). CONCLUSIONS: The results revealed that C3 gene polymorphisms were associated with the lipid levels, but not CAD susceptibility in the Chinese population.