Purpose: Aldose reductase (AR) has been a drug target because of its involvement in the development of secondary complications of diabetes including cataract. We have previously reported that the aqueous extract of Emblica officinalis and its constituent tannoids inhibit AR in vitro and prevent hyperglycemia-induced lens opacification in organ culture. The purpose of the current study was to investigate the effect of Emblica and its enriched tannoids on streptozotocin (STZ)-induced diabetic cataract in rats.
Methods: Diabetes was induced in Wistar-NIN rats by STZ (35 mg/kg body weight, intraperitoneally) and the animals were divided into three groups (Group II, III, and IV). The control rats (Group I) received only vehicle. While Group I and Group II animals received AIN-93 diet, rats in Groups III and IV received 0.2% of standardized mixture of Emblica tannoids and 2% of Emblica pericarp, respectively, in an AIN-93 diet for a period of eight weeks. Cataract progression due to hyperglycemia was monitored by slit-lamp biomicroscope and classified into four stages. At the end of the eight weeks, the animals were sacrificed and markers of the polyol pathway, oxidative stress, and alterations in protein content and crystallin profile in the lens were measured. Blood glucose and insulin levels were also determined.
Results: Both Emblica and its tannoids did not prevent STZ-induced hyperglycemia as assessed by blood glucose and insulin levels. However, slit lamp microscope observations indicated that these supplements delayed cataract progression. The present studies suggest that Emblica and its tannoids supplementation inhibited AR activity as well as sorbitol formation in the lens. The results also point out that Emblica and its tannoids might counter the polyol pathway-induced oxidative stress as there was a reversal of changes with respect to lipid peroxidation, protein carbonyl content, and activities of antioxidant enzymes. Emblica also prevented aggregation and insolubilization of lens proteins caused by hyperglycemia.
Conclusions: The results provide evidence that Emblica and an enriched fraction of Emblica tannoids are effective in delaying development of diabetic cataract in rats.