TAMARINDUS INDICA SEED EXTRACT ATTENUATES RETINAL NEURODEGENERATION AND GLIOSIS IN DIABETIC RATS: COMPARISON WITH METFORMIN AND INSULIN

Diabetes mellitus damages retinal neurons and glia as well as retinal vessels. This study compared ethanolic Tamarindus indica seed extract with metformin and insulin on retinal histology in streptozotocin (STZ)-induced diabetic rats. Sixty male Wistar rats were allocated to six groups (n = 10): normal control (NC), extract only (TO), and STZ-diabetic rats (70 mg/kg, intraperitoneally) given extract (DT; 200 mg/kg), metformin (DM; 100 mg/kg), insulin glargine (DI; 4 IU/day) and untreated diabetic control (DC) for six weeks. Retinal sections were stained with haematoxylin and eosin, phosphotungstic acid haematoxylin (PTAH), cresyl fast violet (CFV), glial fibrillary acidic protein (GFAP) immunohistochemistry and Masson’s trichrome. The extract was non-toxic up to 3000 mg/kg. By week 6, fasting glucose was 41.3 mmol/L in DC but 5.1, 6.7 and 6.5 mmol/L in DT, DM and DI. DC retinas showed pyknotic nuclei, vacuolation, reduced cell density, marked thinning and disorganisation of the inner and outer nuclear layers, exaggerated PTAH-positive glial processes, intense GFAP immunoreactivity and extensive collagen in the inner plexiform and photoreceptor layers. All treated groups showed fewer pyknotic cells and less gliosis; DT retained near-normal thickness of the ganglion cell, inner nuclear and outer nuclear layers, whereas DM and DI showed residual thinning. Collagen deposition was prominent in DM and DI and reduced but present in DT. Ethanolic T. indica seed extract attenuated diabetic retinal neurodegeneration and gliosis at least as well as metformin and insulin, but did not prevent collagen deposition.