Purple sweet potato color improves hippocampal insulin resistance via down-regulating SOCS3 and galectin-3 in high-fat diet mice.

Hippocampal insulin resistance is the key factor in cognitive deficits. The obesity induces chronic inflammation and the inflammation molecules suppressors of cytokine signaling3 (SOCS3) and galectin-3 directly impair the insulin signaling. The anti-inflammation properties of purple sweet potato color (PSPC) prompted us to investigate the effect of PSPC on cognitive impairment associated with obesity. 60 C57BL/6 mice were randomly divided into four groups: normal, high fat diets (HFD), HFD+PSPC and PSPC. The mice were fed with the HFD or normal diet for 32 weeks. The PSPC (500 mg/kg/day) was administered via oral gavage from 21 to 32 weeks. The results showed the PSPC rectified the abnormal metabolism indexes induced by HFD, including ameliorated obesity, decreased the concentration of fasting blood glucose and improved the glucose tolerance. The Morris water maze test showed the PSPC alleviated the cognitive impairment in HFD mice. The PSPC decreased the expression of Iba1, tumor necrosis factor-α, interleukin-1β, SOCS3 and galectin-3 in hippocampus of HFD mice. The insulin signaling molecules including the p-IRS1 (Tyr608), PI3K p110α and p-AKT (Ser473) were detected and the PSPC treatment improved the insulin resistance in hippocampus of HFD mice. Furthermore, the PSPC increased Bcl-2, diminished the Bak and the cleaved-caspase3 in HFD mice hippocampus. These findings indicated that PSPC could be a potential treatment to improve the cognitive impairment associated with obesity.