Oxidative retinal products and ocular damages in diabetic patients

Several evidences suggest a retinal participation to the genesis of diabetic eye complications by means of an increased free radical production at this level. However, no direct proof exists that this happens in humans in vivo. Therefore, the concentrations of malondialdehyde (MDA), carbonyl and sulfhydryl (P-SH) proteins, and vitamin E have been assessed in the subretinal fluid (SF) of patients affected by retinal detachment. Diabetic (n = 19) and nondiabetic (n = 21 ) subjects with comparable age, degree of myopia, and duration of the retinal detachment were considered. A control group of n = 7 subjects was included. The SF was collected after drainage during surgery. The concentrations of total proteins, P-SH, and carbonyl proteins were determined with spectrophotometric methods; the levels of MDA and vitamin E were measured by HPLC. The protein concentration in SF did not differ among groups. A higher concentration of MDA (p < .01) and carbonyl proteins (p < .02) were found in diabetic compared to nondiabetic subjects. Diabetic patients also showed a lower content of P-SH (p < .002) and vitamin E (p < .001) compared to nondiabetic subjects. All these parameters were more markedly altered in patients affected by proliferative diabetic retinopathy and significantly differed between patients and control subjects. In conclusion, oxidative events are associated with retinal detachment in humans. This evidence strongly suggests that the retina is a source of free radical production under certain conditions, such as diabetes.