Search

Background: Haptoglobin acts as an antioxidant by limiting peroxidative tissue damage by free hemoglobin. The haptoglobin gene allele Hp2 comprises a 1.7 kb partial duplication. Relative to allele Hp1, Hp2 carriers form protein multimers, suboptimal for hemoglobin scavenging., Objective: To examine the association of haptoglobin genotype with a range of phenotypes, with emphasis on vitamin C and hemoglobin levels., Methods: We applied a quantitative PCR assay for the duplication junction to two population cohorts including 2747 British women and 1198 British men. We examined the association of haptoglobin duplicon copy number with hemoglobin and vitamin C and used the copy number to complete a phenome scan., Results: Hemoglobin concentrations were greater in those with Hp2,2 genotype, in women only (Hp1,1 13.45 g/dL, Hp1,2 13.49 g/dL, Hp2,2 13.61 g/dL; P = 0.002), though statistically there was no evidence of a difference between the sexes (z value = 1.2, P = 0.24). Haptoglobin genotype was not associated with vitamin C or any other phenotype in either cohort., Conclusions: Our results do not support association of haptoglobin genotype with vitamin C or with other phenotypes measured in two population cohorts. The apparent association between haptoglobin genotype and hemoglobin in the women's cohort merits further investigation.

Current literature suggests that ACE SNP rs4343, ACE 2350A>G in exon 17, T202T, may be the best proxy for the ACE Alu I/D whereas rs4363 and rs4362 may be slightly stronger predictors of ACE levels. Considering reported difficulties in genotyping ACE I/D and stronger associations of rs4343 than ACE I/D with plasma ACE levels in Africans, and suitability of rs4343 for allelic mRNA (cDNA) studies, we developed and validated a liquid phase assay for rs4343, which has advantage on both functional and technical grounds. We confirmed that rs4343, is in near perfect linkage disequilibrium (D'=1, r2=0.88, n=64) with ACE I/D in Europeans (A and G alleles of rs4343 marking insertion and deletion alleles of ACE I/D respectively). We then studied its association with metabolic and cardiovascular traits in 3253 British women (60-79 years old). Apart from a nominal trend of association with diastolic blood pressure (p anova=0.08; p trend=0.05), no other associations were observed. A post-hoc vascular and general phenome scan revealed no further associations. We conclude that ACE I/D is not a major determinant of metabolic and cardiovascular traits in this population. Liquid phase genotyping of SNP rs4343 may be preferable to gel based ACE I/D genotyping both for technical and functional reasons.