Effect of sesamol on diabetes-associated cognitive decline in rats

Emerging epidemiologic data indicates that diabetes is a potential predisposing factor for neuropsychiatric deficits as stroke, cerebrovascular diseases, diabetes-associated cognitive decline, depression and anxiety. Diabetes-associated cognitive decline, characterized by impaired cognitive functions and neurochemical and structural abnormalities, involves direct neuronal damage caused by intracellular glucose. The present study was designed to investigate the effect of sesamol (3,4-methylenedioxyphenol), a phenolic antioxidant and anti-inflammatory molecule, on cognitive functions, oxidative stress and inflammation in diabetic rats. Learning and memory behaviors were investigated using a spatial version of the Morris water maze test. Acetylcholinesterase activity, a marker of cholinergic dysfunction, was increased by 80% in the cerebral cortex of diabetic rats. There was 107 and 121% rise in thiobarbituric acid reactive substance levels in cerebral cortex and hippocampus of diabetic rats, respectively. Reduced glutathione levels and enzymatic activities of superoxide dismutase and catalase were decreased in both cerebral cortex and hippocampal regions of diabetic rat brain. Nitrite levels in cerebral cortex and hippocampus was increased by 138 and 109%, respectively. Serum tumor necrosis factor-alpha, a marker for inflammation, was found to increase by 1,100% in diabetic rats. Chronic treatment with sesamol (2, 4 and 8 mg/kg; p.o.) significantly and dose-dependently attenuated cognitive deficit, reduced acetylcholinesterase, oxidative stress and inflammation in diabetic rats. The results emphasize the involvement of oxidative stress and inflammation in the development of cognitive impairment in diabetic animals and point towards the therapeutic potential of sesamol in diabetes-associated cognitive decline.