Lipid peroxidation and total antioxidant capacity in vitreous, aqueous humor, and blood samples from patients with diabetic retinopathy

Abstract

Purpose: To evaluate levels of malondialdehyde and the total antioxidant capacity (TAC) in the blood, aqueous humor, and vitreous bodies of diabetic and nondiabetic patients. We also measured the blood energy charge potential (ECP).

Methods: We examined 19 patients with type 2 diabetes mellitus and diabetic retinopathy. Ten were scheduled for cataract surgery and pars plana vitrectomy because of proliferative diabetic retinopathy (PDR). The other nine, with mild nonproliferative PDR (NPDR), and fourteen nondiabetic, age-matched subjects enrolled as a control group were scheduled for cataract surgery and vitrectomy because of epiretinal membranes. Blood, aqueous humor and vitreous body samples were collected at the time of surgery. Malondialdehyde concentrations and blood ECP were measured with high-performance liquid chromatography. The TAC of the samples was estimated with the oxygen radical absorbance capacity method.

Results: The level of blood and vitreous malondialdehyde in the PDR group was significantly higher compared to controls and to NPDR patients. PDR patients also had lower levels of TAC at the vitreous body and aqueous humor level, but not at the blood level, compared to controls and with NPDR patients. In all diabetic patients, the blood ECP values were significantly lower, compared to control subjects.

Conclusions: Our data support the hypothesis that oxidative stress and the decrease of antioxidant defenses are associated with the progression of diabetic retinopathy to its proliferative form. Antioxidant supply may have the effect of correcting oxidative stress and inhibiting disease progression.

Figure 1

Malondialdehyde (MDA) levels in the blood, aqueous humor and vitreous of diabetic patients and controls. The levels of MDA were measured by High Performance Liquid chromatography in the blood, aqueous humor and vitreous of the control (white columns), non-proliferative diabetic retinopathy (NPDR; gray columns) and proliferative diabetic retinopathy (PDR; black columns) groups. Blood MDA levels in PDR patients were significantly increased over those of control and NPDR group (both, p<0.001). In the aqueous humor no significant differences between the groups were found. In the vitreous body, PDR patients, but not NPDR subjects, had increased MDA levels as compared with controls (p=0.050). Data are expressed in µmol/ml and represent mean±standard deviation (bars). ANOVA test was used.

Figure 2

Total antioxidant capacity in the blood, aqueous humor, and vitreous of control and diabetic patients. The total antioxidant capacity (TAC) was measured by the oxygen radical absorbance capacity assay in the blood, aqueous humor and vitreous of controls (white columns) and of patients with non-proliferative diabetic retinopathy (NPDR; gray columns) and with proliferative diabetic retinopathy (PDR; black columns). The control group displayed significantly higher TAC levels than diabetic sub-groups in both the vitreous (p<0.001) and aqueous humor (p=0.003). No significant differences were observed in blood. Similar findings emerged from subgroup analyses. PDR patients had decreased TACs in the vitreous and aqueous humors as compared with control subjects (p=0.002 and p=0.003 respectively) and with the NPDR patient subgroup (p<0.001 and p=0.032 respectively). Data are expressed in µmol Trolox Equi/g and represent mean±standard deviation (bars). ANOVA test analysis was used.