Soluble Curcumin in the Prevention of Diabetic Retinopathy via Modulation of Anti-Oxidant Activity and Genetic Pathways – In Vivo Model

The aim of the present study was to investigate the protective effects of curcuminoids from regular curcumin Powder (95% curcuminoids), and UltraSOL™ Nutrient System with curcumin (CurcuWIN™ Turmeric Extract, 20% curcuminoids) in dry powder forms on retina and metabolic markers in streptozotocin-induced (STZ) diabetic rats. Male Wistar strain (WNIN) rats (2 months old; 213±14 g BW) were randomly assigned into 4 groups: control group (C), diabetic group (STZ-diabetic rats, D), STZ DM+ Soluble curcumin (SC, CurcuWIN™) and STZ DM +regular curcumin (RC). Daily food intake, weekly body weights, fasting glucose levels and HbA1C were assessed. Electroretinogram, immunohistochemistry and Immunofluorescence were performed in all treatment groups. At the end of 12 weeks, rats were euthanized and retinas harvested for histological and molecular analysis. In streptozotocin (STZ) diabetic rats (D) amplitude of oscillatory potentials (Ops) were reduced (334.2 µV) compared to normal control (C) animals. Curcumin resulted in significant changes in OP amplitudes suggested by sum of OPs, RC (445.7) and SC (455.3). Treatment with curcumin prevented gross morphological changes to a significant extent in diabetic retina. Treatment with RC and SC prevented loss of Rhodopsin (Rho) protein expression and nerve growth factor (NGF) protein expression in diabetic retina indicated by intense fluorescence. Treatment with RC and SC showed decreased protein expression in diabetic retina indicated by lower Hypoxia-inducible factor 1-alpha (HIF- 1-α) positive fluorescence indicating the prevention of hypoxia in the retinas. Treatment with RC did not affect the vascular endothelial growth factor (VEGF) over expression in diabetic retina but the SC reduced the VEGF expression. In STZDM the mRNA levels of Glial fibrillary acidic protein (GFAP), are up regulated drastically, while treatment with SC significantly prevented its increase but there is no significant effect of RC treatment. Therefore, soluble curcumin may have therapeutic potential in the treatment of diabetic retinopathy (DR) and appears to be more effective than regular curcumin.