Abstract
Although many studies have found psychological depression associated with higher circulating levels of C-reactive protein (CRP), not all findings are consistent. Since DNA sequence variation in the CRP gene has also been shown to predict plasma CRP levels, we hypothesized that plasma CRP may covary with depressive symptomatology as a function of allelic variation in the CRP gene. We tested this hypothesis in 868 healthy community volunteers of European ancestry. Depressive symptomatology was measured using the Center for Epidemiological Studies-Depression (CESD) scale, and plasma CRP was assayed from whole blood. Three polymorphisms [rs1417938 (A/T), rs1800947 (C/G) and rs1205 (C/T)] were genotyped and three-locus haplotypes were generated. Regression models adjusting for demographic and lifestyle-related covariates showed no direct association of CESD depression scores with CRP. In regression models adjusting for age, gender, education, smoking status and statin use, one CRP haplotype (T-G-C) was associated with CRP level (p=0.014) and a second haplotype (A-G-T) showed marginal association (p=0.064, respectively). Neither haplotype was related to depressive symptoms. However, plasma CRP was predicted by the interaction of A-G-T haplotype with depressive symptomatology (p=0.009). Higher CESD scores were associated positively with CRP levels among individuals with the A-G-T haplotype (p=0.004). In secondary analyses, body mass index was found to partially account for the moderating effects of the A-G-T haplotype on the association of depression with circulating CRP. In conclusion, we found that haplotypic variation in the CRP locus moderates an association of depressive symptoms with circulating CRP, which is partially mediated by BMI.