Oxidative stress-induced cognitive impairment in obesity can be reversed by vitamin D administration in rats

Background: There is evidence that obesity leads to cognitive impairments via several markers of oxidative stress including glutathione peroxidase (GPx), superoxide dismutase (SOD), catalase and malondialdehyde (MDA) in the hippocampus. Increased inflammatory markers in the brain have obesity triggering effects. In the current study we aimed to investigate the effects of vitamin D on cognitive function, nuclear factor (NF)-kappa B, tumor necrosis factor (TNF)-alpha concentration and markers of oxidative stress in the hippocampus of high-fat diet-induced obese rats. Methods and materials: Forty male Wistar rats were divided into two groups: control diet (CD) and high-fat diet (HFD) for 16 weeks; then each group subdivided into two groups including: CD, CD + vitamin D, HFD and HFD + vitamin D. Vitamin D was administered at 500 IU/kg dosage for 5 weeks. Four weeks after supplementation, Morris water maze test was performed. NF-kappa B and TNF-alpha concentration in the hippocampus were determined using ELISA kits. Moreover, oxidative stress markers in the hippocampus including GPx, SOD, MDA and CAT concentrations were measured by spectrophotometry methods. Results: HFD significantly increased TNF-alpha (P = 0.04) and NF-kappa B (P = 0.01) concentrations in the hippocampus compared with CD. Vitamin D treatment led to a significant reduction in hippocampus NF-kappa B concentrations in HFD + vitamin D group (P = 0.001); however, vitamin D had no effect on TNF-alpha concentrations. Moreover, HFD significantly induced oxidative stress by reducing GPx, SOD and increasing MDA concentrations in the hippocampus. Vitamin D supplementation in HFD group also significantly increased GPx, SOD and reduced MDA concentrations. Conclusion: Vitamin D improved hippocampus oxidative stress and inflammatory markers in HFD-induced obese rats and improved cognitive performance. Further studies are needed to better clarify the underlying mechanisms.