Abstract
Purpose::
Increased levels of vascular endothelial growth factor (VEGF) have been implicated in neovascularization in the diabetic retina. Formation of advanced glycation endproducts (AGE) are linked to the development of diabetic retinopathy and particularly carboxy methyl lysine (CML)-AGE is known to induce VEGF expression. The purpose of the study was to investigate the effect of curcumin and its dietary source, turmeric on CML levels and VEGF expression in streptozotocin (STZ) induced diabetic rat retina.
Methods::
Diabetes was induced in 2-months old Wistar-NIN rats by STZ and divided into four groups (II-V). The control (group-I) rats received only vehicle. Group I and II animals received control AIN-93 diet and those in groups III, IV and V received 0.002 and 0.01% curcumin and 0.5% turmeric respectively, in AIN-93 diet for a period of 8 weeks. At the end of 8 weeks, the animals were sacrificed and retina was dissected. RNA and protein were isolated from retina and VEGF gene expression was analyzed by real time qPCR. VEGF and CML levels were assessed by Western blotting .
Results::
There was an increase in VEGF expression both at mRNA and protein level in diabetic rat retina compared to controls. The increased VEGF expression in STZ-induced diabetic group was lowered upon curcumin and turmeric treatment. Interestingly, the increased CML levels in STZ groups were also decreased upon curcumin and turmeric treatment.
Conclusions::
These results indicate that curcumin and turmeric appears to be effective in controlling the VEGF expression in diabetic rat retina probably by modulating CML levels.
Keywords: diabetic retinopathy • retina • antioxidants