Benefitial Effects of Docosahexaenoic Acid in Experimental Diabetic Retinopathy

Abstract

Purpose: : To assess the effect of docosahexanoic acid (DHA) (with anti-inflammatory and antioxidant properties) on experimental diabetic retinopathy.

Methods: : Male Wistar rats were studied: non-diabetic controls, untreated diabetic controls, and diabetic rats treated DHA or the combination of DHA + insulin for 12 weeks. Oxidative stress and inflammatory markers, apoptosis and functional tests were studied to confirm biochemical and functional changes in retina of diabetic rats. Malondialdehyde (MDA) and glutathione concentrations (GSH) and glutathione peroxidase activity (GPx) were measured as oxidative stress markers. TUNEL assay and caspase-3 immunohistochemistry and electroretinogram were performed.

Results: : Diabetes increases oxidative stress, nitrotyrosine concentrations and apoptosis in the retina. At 12 weeks after onset of diabetes, total thickness of retinas of diabetic rats was significantly less than that in control rats. Specifically, the thickness of the outer and inner nuclear layers was reduced significantly in diabetic rats and demonstrated a loss of cells in the GCL. These retinal changes were avoided by the administration of insulin, and DHA alone or in combination with insulin. Impairment of the electroretinogram (b-wave amplitude and latency time) was observed in diabetic rats. DHA prevented all these changes even under hyperglycemic conditions.

Conclusions: : DHA is capable of normalizing all the diabetes-induced biochemical, histological and functional modifications. Especially the cell death mechanisms involved deserve further studies, to allow the proposal as potential adjuvant therapies to help prevent vision loss in diabetic patients.

Keywords: apoptosis/cell death • diabetic retinopathy • electroretinography: non-clinical