Serum c-reactive protein (CRP) relationship with macular pigment and response to carotenoid supplementation in open-angle glaucoma

Abstract

Purpose : To evaluate CRP response to carotenoid supplementation and analyse its relationship to macular pigment optical density (MPOD) in glaucoma.

Methods : A randomised, double-blind, placebo-controlled clinical trial was conducted on 62 open-angle glaucoma subjects, with no known underlying systemic or ocular pathology. Subjects were randomly assigned (2:1 ratio) to treatment or placebo control groups and were required to ingest a daily dietary supplement for 18 months. The treatment group received the active capsule comprised of 10mg lutein, 2mg zeaxanthin and 10mg meso-zeaxanthin. Serum CRP levels, MPOD (Spectralis) and microperimetry (MAIA II) were measured at baseline and following 18 months supplementation.

Results : No significant differences in CRP and MPOD were found between treatment groups at baseline. MP volume was statistically significantly higher in the treatment group relative to placebo at 18 months (p<0.01; Table 1), but no significant difference in CRP was observed between groups. A statistically significant, inverse correlation was found between CRP and MP volume in the central 6⁰ macular area (Fig. 1) and MPOD at 0.23, 0.51, 0.74 and 1.02 retinal eccentricities (p<0.01 for all). No significant correlation existed between CRP and glaucoma severity (p=0.4). To assess the direct effect of supplementation on CRP levels, a linear mixed model analysis was conducted with log(CRP) as the dependent variable and added fixed effects of time*treatment interaction. Baseline and 18 month data were used and participant ID was included as a random intercept to account for within-person correlation. No significant effect of supplementation on log(CRP) levels was found (estimate±SE: -2.5±1.64; t-test:-1.52; p=0.13).

Conclusions : The relationship between CRP and MPOD agrees with previous observations. The substantial increase in MP in response to supplementation, however, did not lead to a meaningful change in serum CRP (albeit that the treatment group mean CRP reduced and placebo group mean CRP more than doubled). Although further analysis is required with a larger study population, it appears that macular carotenoid supplementation has limited impact on this inflammatory marker among individuals with open angle glaucoma.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.

 

Table 1: MP and CRP characteristics at baseline and 18 months across treatment groups

 

Fig 1: Inverse relationship between CRP and MPOD