Key Findings:
A strong correlation exists between reactive oxygen species (ROS) production and vascular endothelial growth factor (VEGF) expression in diabetic retinopathy. As the retina is rich in n-3 PUFAs, excess ROS could suppress antioxidant defenses that may contribute to the development of diabetic retinopathy. Diabetes is a low-grade systemic inflammatory condition characterized by increases in hs- CRP, IL-6 and TNF-a. These cytokines augment VEGF production, enhanced VEGF levels in diabetic retinopathy could be due to increased levels of pro-inflammatory cytokines. In STZ-induced diabetic animals an increase in serum IL-6, decrease in serum and retina BDNF, increase in serum and retina VEGF, and decrease in serum glutathione peroxidase levels were noted. All these indices reverted to normal in animals treated with ALA. ALA prevented pro-angiogenic events that occur in STZ induced diabetic animals and reduced the pro-inflammatory and pro-angiogenic events that could lead to diabetic retinopathy.
ABSTRACT:
Background and Aims. Both oxidative stress and inflammation play a significant role in the pathobiology of diabetic retinopathy. Increased consumption of polyunsaturated fatty acids (PUFAs) may prevent or postpone the occurrence of diabetic retinopathy. Hence, the effect of a-linolenic acid (ALA), an essential fatty acid, on oxidative stress, inflammatory indices and production of vascular endothelial growth factor (VEGF) in streptozotocin-induced diabetic retinopathy indices in vivo was studied. Methods. Serum and retina concentrations of vascular endothelial growth factor (VEGF), brain-derived neurotrophic factor (BDNF), interleukin-6 (IL-6), plasma and retina concentrations of lipid peroxides and antioxidant enzymes were estimated in streptozotocin (STZ)-induced diabetic animals. Results. STZ-induced diabetic rats had significantly higher levels of VEGF in the serum and retina and IL-6 in the serum, whereas BDNF was lower in the serum, all of which reverted to near normal in ALA-treated diabetic animals. STZ treatment decreased serum glutathione peroxidase levels, which was restored to normal by both pre- and post-ALA treatment groups. Conclusions. STZ-induced changes in serum glutathione peroxidase, BDNF, VEGF and IL-6 that reverted to near control by ALA treatment, especially in ALA + STZ group, lending support to the concept that both oxidative stress and inflammation participate in DR and ALA treatment is of benefit in its prevention.(Authors abstract)
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