Electroacupuncture stimulation ameliorates cognitive impairment induced by long-term high-fat diet by regulating microglial BDNF

Abstract

Long-term high-fat diet (HFD) in adolescents leads to impaired hippocampal function and increases the risk of cognitive impairment. Studies have shown that HFD activates hippocampal microglia and induces hippocampal inflammation, which is an important factor for cognitive impairment. Electroacupuncture stimulation (ES), a nerve stimulation therapy, is anti-inflammatory. This study explored its therapeutic potential and mechanism of action in obesity-related cognitive impairment. 4-week-old C57 mice were given either normal or HFD for 22 weeks. At 19 weeks, some of the HFD mice were treated with ES and nigericin sodium salt. The cognitive behavior was assessed through Morris water maze test at 23 weeks. Western blotting was used to detect the expression levels of pro-inflammatory molecules IL-1β and IL-1R, synaptic plasticity related proteins synaptophysin and Postsynaptic Density-95 (PSD-95), and apoptotic molecules (Caspase-3 and Bcl-2), in the hippocampus. The number, morphology, and status of microglia, along with the brain-derived neurotrophic factor（BDNF） content, were analyzed using immunofluorescence. ES treatment improved cognitive deficits in HFD model mice, and decreased the expressions of microglial activation marker, CD68, and microglial BDNF. Inhibition of proinflammatory cytokine, IL-1β, and IL-1R promoted PSD-95 and synaptophysin expressions. Peripheral NLRP3 inflammasome agonist injections exacerbated the cognitive deficits in HFD mice and promoted the expressions of IL-1β and IL-1R in the hippocampus. The microglia showed obvious morphological damage and apoptosis. Collectively, our findings suggest that ES inhibits inflammation, regulates microglial BDNF, and causes remodeling of hippocampal function in mice to counteract obesity-like induced cognitive impairment. Overexcitation of peripheral inflammasome complexes induces hippocampal microglia apoptosis, which hinders the effects of ES.

Keywords: BDNF; ES; High-fat diet; Hippocampal remodeling; Microglia.