[Speaker] Tapan Behl:1
[Co-author] Thirumurthy Velpandian:3, Anita Kotwani:2
1:Department of Pharmacology, Chitkara College of Pharmacy, Chitkara University, Punjab, India, 2:Department of Pharmacology, Vallabhbhai Patel Chest Institute, University of Delhi, India, 3:Department of Ocular Pharmacology, All India Institute of Medical Sciences, Delhi, India

Background: Retinal vessels are early targets of diabetic damage. Major contributing factor for retinopathy is sustained hyperglycemia but exclusive management of hyperglycemia is not sufficient for the control of long-term complications. Medicines of natural origin/functional foods with anti-hyperglycemic and additional effect to prevent or delay diabetic-induced complications are need of the hour. Hence, the present study investigates the protective effect of Terminalia catappa fruit extract in streptozotocin-induced diabetic retinopathy in rats.

Methods: Streptozotocin-induced chronic diabetic rat model was used. Nine groups (n=8) including hydro-alcoholic fruit extract of Terminalia catappa in 20mg/kg, 30mg/kg and 40mg/kg and standard anti-diabetic drug, glibenclamide (10mg/kg) were studied for 12 weeks. Retinopathy was evaluated by monitoring the lenticular and fundus images and measuring retinal vessels (arteriole and venule) tortuosity index at 2nd, 4th, 6th, 8th, 10th and 12th week in all experimental animals. Oxidative, angiogenic and inflammatory biomarkers were assessed at 12th week in retinal homogenate in all the groups. Histopathological changes in retina were also examined. Data was analyzed using one-way Repeated Measure ANOVA followed by Mann-Whitney test.

Results: Hydro-alcoholic fruit extract of Terminalia catappa (T. catappa) significantly decreased blood glucose (p<0.001) in dose-dependent manner in diabetic rats. Cataract lens grading observed in diabetic rats at 12th week: diabetic control, grade 5; glibenclamide and T. catappa 20mg/kg, grade 2; 30mg/kg, grade 1 and with 40mg/kg lens and T. catappa and glibenclamide lens became clear, like control (grade 0) by eight and sixth week respectively. Hydro-alcoholic fruit extract in all three doses significantly reduced (p<0.01) retinal vessels (arteriole and venule) tortuosity in diabetic rats.
Terminalia catappa in all doses in diabetic rats showed modulatory effect in oxidative, angiogenic and inflammatory biomarkers: reduction in LPO level and increase in GSH, SOD, catalase and T-AOC; decrease in IL-1beta and TNF-alpha level; significant reduction in VEGF, PKC-beta and increase in endostatin levels. No additive effect of glibenclamide was observed when given along with T. catappa 40mg/kg dose.

Conclusion: Terminalia catappa fruit extract reverses the diabetes-induced retinopathy. Hydro-alcoholic fruit extract has shown multiple actions - anti-hyperglycemic, anti-oxidant, anti-angiogenic and anti-inflammatory, therefore, has a potential to be used in diabetes-induced retinopathy.

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