Association of vitreous vitamin C depletion with diabetic macular ischemia in proliferative diabetic retinopathy

Abstract

Purpose Vitreous vitamin C, as an anti-oxidant, is responsible for regulating oxygen tension and oxidative stress in the eye. Oxidative stress and retinal ischemia are implicated in the development of proliferative diabetic retinopathy (PDR). In this study, we aimed to determine whether vitreous level of vitamin C is compromised in patients with PDR and to investigate the association of diabetic macular ischemia and vitamin C. Methods This prospective study enrolled forty patients who underwent pars plana vitrectomy for the treatment of PDR (PDR group, n = 20) and idiopathic epiretinal membrane (control group, n = 20). Serum, aqueous humor, and the vitreous were collected for the analysis of vitamin C level by HPLC. Diabetic macular ischemia (DMI) in PDR group was evaluated with fluorescein angiography (FA). Results PDR patients (60.4 ± 2.1 y) were younger than non-diabetic control patients (67.4 ± 1.2 y). Serum, aqueous, and vitreous levels of vitamin C in PDR were 38.7%, 22.5%, and 11.1% of non-diabetic control group, respectively. All PDR patients had DMI (grade 1: 25%, grade 2: 30%, grade 3: 30%, grade 4: 15%). DMI grade was inversely correlated with the level of vitreous vitamin C (r = -0.546, P = 0.019), not with HbA1C, serum, or aqueous vitamin C level. In addition, the level of vitreous vitamin C (4.5 ± 2.6 μg/ml) in high DMI group (Gr 3 &4) was lower than that (31.0 ± 9.1 μg/ml) in low DMI group (Gr 1&2) ( P = 0.015). Conclusions Vitreous level of vitamin C in PDR patients showed a tenfold decrease, which was associated with the degree of macular ischemia. This suggests that vitreous vitamin C depletion may cause macula ischemia in PDR patients.

Adjuvant Therapies in Diabetic Retinopathy as an Early Approach to Delay Its Progression: The Importance of Oxidative Stress and Inflammation

“…Oxidative Medicine and Cellular Longevity ability to act in redox state and as a cofactor for many human enzymes [81,82]. Ascorbic acid has been found to be in higher concentration in healthy patients, contrary to those with DR who have lower concentrations than patients with DM who have not developed this complication [83] and especially in those who develop diabetic macular ischemia who showed dramatically decreased concentrations compared to nondiabetic controls [84]. This effect is due to its ability to prevent propagation of free radical-induced chain reactions [85], thereby directly scavenging ROS (see Figure 2), preventing breakdown of nitric oxide (NO) and decreasing low-density lipid oxidation [46,86,87].…”

Importance of the Use of Oxidative Stress Biomarkers and Inflammatory Profile in Aqueous and Vitreous Humor in Diabetic Retinopathy

“…The ascorbic acid found inside the vitreous body reaches concentrations of approximately 2 mmol/L; this is 33 times more than the plasma concentration. As an antioxidant, ascorbic acid is oxidized to convert superoxide anions and lipid hydroperoxidases into stable forms, thereby preventing lipid peroxidation [55]. Vitamin B2 (riboflavin) has been detected in the human vitreous (0.8 µg/100 mL) and animal (8.0 µg/L).…”

Vitreous Antioxidants, Degeneration, and Vitreo-Retinopathy: Exploring the Links

“…AA concentration within the vitreous body approximates to 2 mmol/L, about 33 times higher than plasma concentration [99]. Also, AA within intact gel vitreous is higher than in liquefied vitreous and in vitreous of proliferative diabetic retinopathy (PDR) patients [27,100]. As an antioxidant, AA is oxidized in order to convert superoxide anions and lipid hydroperoxidases into stable forms, thereby preventing lipid peroxidation, the oxidative damage of lipids.…”