Elevated C-reactive protein levels and ARMS2/HTRA1 gene variants in subjects without age-related macular degeneration

PURPOSE: To investigate the association between the serum high sensitivity C-reactive protein (hs-CRP) levels and variants in age-related maculopathy susceptibility 2 (ARMS2)/HtrA serine peptidase 1 (HTRA1) genes in normal subjects with no evidence of age-related macular degeneration (AMD). METHODS: After clinical evaluation, information related to medical and social history was collected from 476 Japanese individuals (age range 17–89 years) along with blood samples. These subjects were medical checkup participants recruited at Nagoya University Hospital with no macular disease, as confirmed by fundus photographs. Serum hs-CRP levels were measured using a highly sensitive latex aggregation immunoassay. The genotypes of three polymorphisms in the ARMS2/HTRA1 locus, i.e., *372_815del443ins54 (del/ins), rs10490924, and rs11200638 were determined using direct sequencing and/or PCR-based assays. After the haplotype was constructed and analyzed, the associations between hs-CRP levels and representative del/ins genotypes were studied with and without adjustment for potential confounding factors. RESULTS: All three polymorphisms in the ARMS2/HTRA1 region were in almost complete linkage disequilibrium. Haplotype analyses showed the existence of only two common haplotypes, together comprising 98.9%. Regression analyses showed that the level of hs-CRP was positively correlated with increasing age. This age-dependent increase of hs-CRP levels was greatest in those with homozygous del/ins alleles and lowest in those with homozygous wild-type alleles, which was significant assuming an additive model for gene-dosage association (univariate analyses: p=0.016, multivariate analyses including smoking status, past medical history, and BMI: p=0.043). Consequently, the level of hs-CRP was greatest in those with homozygous del/ins alleles and lowest in those with homozygous wild-type alleles when subjects older than 60 were analyzed. This was significant assuming an additive model for gene-dosage association (univariate analyses: p=0.032). CONCLUSIONS: An age-dependent elevation of serum hs-CRP levels may be accelerated in normal subjects with one or two risk alleles in the ARMS2/HTRA1 locus compared to those with homozygous wild-type alleles. The results of the current study show that the as-yet undetermined function of variants in the ARMS2/HTRA1 locus might be linked to inflammation, possibly contributing to the development of neovascular AMD.