Abstract

The main aim of this study is to investigate the impact of bitter gourd on long term pre-diabetic induced retinal abnormalities caused by neonatal streptozotocin (nSTZ). Male Sprague Dawley (SD) rat pups (n=35) of two-day old were taken and injected with STZ (90 mg/kg body weight) dissolved in 0.1M citrate buffer, pH 4.5. Control pups (n=10) received only vehicle. Oral glucose tolerance test (OGTT) was conducted at 2nd and 10th month. All rats were maintained on AIN-93G/M diet in individual cages and a sub set of pre-diabetic animals received 5% bitter gourd in the diet. Functional abnormalities of retina were studied by electroretinogram (ERG) and other biochemical alterations by histology, immunoblotting and gene expression. Majority of nSTZ rats exhibited impaired glucose tolerance (2h glucose>140mg/dl) or pre-diabetes by 2 months and maintained up to 11th month. ERG data showed a decrease in amplitude of scotopic b-wave and also scotopic oscillatory potentials in pre-diabetic rats indicating development of retinal functional abnormalities. Increased expression of vascular endothelial growth factor (VEGF), Glial fibrillary acidic protein (GFAP) and decreased expression of rhodopsin (Rho) in pre-diabetic animals indicate development of angiogenesis and retinal degeneration respectively. Further there was an increase in 4-hydroxynonenal (4-HNE) in retina indicating association of oxidative stress with pre-diabetes. Feeding of bitter gourd to these pre-diabetic rats partially prevented these changes. Pre-diabetes induced retinal abnormalities were prevented by bitter gourd through its hypoglycemic and antioxidant potential. This study will give an additional insight into molecular action of bitter gourd in preventing the pre-diabetic abnormalities thereby leading to the development of therapeutic strategies in controlling diabetes.

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