Effects of black currant anthocyanins on glaucomatous optic neuropathy

Abstract

In order to study the influence of the black currants anthocyanins (BCACs) on glaucomatous optic neuropathy (GON), a randomized, placebo-controlled, doublemasked trial was assessed in 38 patients with GON. Upon administration of BCACs (50 mg/day, n=19), when compared to the placebo group, we observed statistically significant preservation in visual field mean deviation at 24-month post therapy (P=0.039, unpaired t-test). In addition, the ocular blood flows of the BCACs intake group also increased in comparison with placebo-treated patients during the 24-month observational period. Furthermore, a total of 21 GON patients (BCACs; n=12, placebo; n=9) treated with a single anti-glaucoma medication who had participated in this randomized, doublemasked, placebo-controlled trial were selected and analyzed. Inter-group and betweengroup analyses revealed statistically significant decreases in mean IOP in the GON patients taking BCACs (P=0.027, paired t-test; P=0.024, unpaired t-test) at 24 months after the baseline. To elucidate the underlying mechanisms of these BCACs-induced effects, changes of serum endothelin-1 (ET-1), nitric oxide (NO), and anti-oxidative activities were examined as possible factors affecting GON. From among GON patients who participated in the trial, serum specimens were obtained from BCACs-treated (n=19) or placebo-treated (n=19) patients at baseline and every 6 months. Healthy volunteers (n=20) with age and sex matching the patients were used as a control. Serum ET-1 concentration, [NO2-] and [NO2-+ NO3-] levels, advanced oxidation protein products (AOPP), and antioxidant activities were measured by using commercially available kits. At the trail baseline, serum ET-1 concentrations were significantly lower in OAG patients (BCACs, 3.18±1.06 pg/ml; placebo, 3.44±0.84 pg/ml) than those in healthy volunteers (4.38±1.03 pg/ml) (unpaired t-test, P < 0.05). Upon administration of BCACs, serum ET-1 concentrations increased to the levels of those in healthy volunteers during the 24-month period. In contrast, those of placebo-treated patients remained at lower levels (3.82±1.14 pg/ml). While [NO2-] and [NO2-+ NO3-] levels, AOPP, and anti-oxidative activities of patients from both the BCACs and placebo groups showed comparable levels to those of healthy subjects at baseline, no significant changes were observed during the observational period in either the BCACs or placebo groups. Our results suggest that oral administration of BCACs may be a safe and promising supplement for patients with OAG in addition to anti-glaucoma medication. Among the possible beneficial effects of BCACs on OAG, our present results also suggest that BCACs caused normalization of serum ET-1 levels and this may modulate ET-1- dependent regulation of the ocular blood hemodynamics.