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Zinc supplementation inhibits complement activation in age-related macular degeneration (AMD)

Session Details

Session Title: AMD III

Session Date/Time: Sunday 20/09/2015 | 11:00-13:00

Paper Time: 11:16

Venue: Athena

First Author: : D.Smailhodzic NETHERLANDS

Co Author(s): :    F. Van Asten   A. Den Hollander   T. Berendschot   M. Daha   C. Hoyng   B. Klevering

Abstract Details

PURPOSE:Oral zinc supplementation can reduce the progression of AMD but the precise mechanism of this protective effect is as yet unclear. It has become increasingly clear that complement-mediated inflammation plays a fundamental role in the etiology of AMD. We designed the present study to investigate whether zinc affects the activity of the alternative complement pathway - defined as the C3d/C3 ratio and C5a - in patients with AMD, which might explain how zinc slows AMD progression. Secondly, we correlate the response to zinc supplements to the complement factor H gene (CFH) and Age-Related Maculopathy susceptibility 2 (ARMS2) genotype.

Setting:

Patients with AMD were at random selected from the EUGENDA database. All data were collected at the department of Ophthalmology of the Radboud university medical center, The Netherlands. A sample size of 70 was calculated to detect a decrease in serum C3d/C3 of 10% with α=0.05 and power of 80.

Methods:

In this open-label clinical study, 72 patients in various stages of AMD received a daily supplement of 50 mg zinc sulphate and 1 mg cupric sulphate for three months. During the course of the study, six venous blood samples were collected. One sample was collected prior to zinc supplementation and served as the baseline sample. Three samples were collected at the end of months 1, 2 and 3 of the three-month period of zinc supplementation. To check for any reversible effects of zinc on complement activation we collected a two blood sample after ending the zinc administration. From one month prior to zinc supplementation through the end of month 5, the patients were prohibited to take any type of other nutritional supplement. All patients were genotype for the CFH variant Y402H (rs1061170) and ARMS2 (A69S; rs10490924). We performed color fundus photography and spectral domain optical coherence tomography to assist AMD grading based on the 5-grade Clinical Age-Related Maculopathy Staging classification scale. To identify clinical manifestations associated with intermittent infections, at every visit, we performed a general physical examination, measured the serum C-reactive protein (CRP) levels and administered a questionnaire that was aimed at identifying clinical manifestations associated with intermittent infections.

Results:

During the three months daily zinc supplementation, serum zinc concentration increased significantly (p<0.001). After zinc supplementation was discontinued, the serum zinc levels returned to baseline levels within 2 months. The C3d/C3 ratio showed non-significant decline during zinc supplementation (p=0.149). The patients with high serum complement catabolism had a steep decline in C3d/C3 ratio during the administration of zinc sulphate (p<0.001). C5a showed a significant decrease during zinc supplementation, indicating that zinc inhibition of the complement pathway can also be detected further downstream. Measurements performed when zinc administration was ended, showed that complement activation had returned to prior baseline levels. Higher baseline C3d/C3 ratio was significantly associated with younger age (r=-0.33, p=0.005) and better visual acuity (OD: r=0.25, p=0.031 and OS: r=0.36, p=0.002). AMD patients with several intermediate-size and large drusen and/or drusenoid RPE detachment in one eye and geographic atrophy or neovascular had significantly the highest C3d/C3 ratio. Change in C3d/C3 ratio or C5a levels were not related to CFH or ARMS2 genotypes. Serum CRP levels were measured at every visit and were not significantly associated with the C3d/C3 ratio (p=0.168) nor the C5a levels (p=0.942).

Conclusions:

Our findings demonstrate that increased levels of complement catabolism in AMD patients can be normalized by the daily oral administration of 50 mg zinc sulphate. However, the effect of complement inhibition seemed to be limited to patients with a high level of complement catabolism. In our study increased levels of serum complement catabolism correlates with the stage of AMD. This may indicate that the level of serum complement catabolism may be a sign of disease activity. The C3d/C3 ratio returned to its baseline value after ending the zinc administration, indicating a reversible effect of zinc supplementation on complement activation. Continuous zinc supplementation may therefore be necessary to inhibit disease activity over longer periods of time. This mechanism could explain how zinc slows AMD progression in subgroups of patients with AMD.

Financial Disclosure:

NO

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