Gymnema montanum H. Protects Against Alloxan-induced Oxidative Stress and Apoptosis in Pancreatic β-cells

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Abstract
The present study evaluated the molecular mechanism of antidiabetic property of G. montanum leaf extract (GLEt) against alloxan-induced apoptotic cell death in rat insulinoma cells (RINm5F). The pre-treatment of GLEt (5 μg and 10 μg/ml) resulted in significant decrease in intracellular Ca2+ concentration, nitric oxide (NO) production along with increase in mitochondrial membrane potential in alloxan (7mM/ml) treated cells. Further GLEt reduced apoptosis by inhibiting the release of cytochrome c and subsequent cleavage of PARP and caspase-3. The immunochemical staining of 8-hydroxydeoxyguanosine (8-OHdG) also evidenced the suppression of oxidative stress by GLEt. The cell cycle analysis, annexin-V labelling assay and TUNEL assay showed the suppression of apoptosis by the treatment of GLEt. Moreover, GLEt significantly increased the cellular antioxidant levels and decreased the lipid peroxides in alloxan-treated RINm5F cells. Taken together, these findings suggest that G. montanum protects pancreatic β-cells against reactive oxygen species (ROS) by counteracting with mitochondrial membrane permeability and inhibition of the apoptotic pathway.