The Effect Of Intermittent Fasting On Cognitive Impairment Of Chronic Cerebral Hypoperfused Rats And Its Underlying Mechanisms

Part ⅠObjective Chronic cerebral hypoperfusion is a common pathological change in both Alzheimer’s disease and Vascular dementia.Whether intermittent fasting(IF)treatment after stroke can prevent its long-term detrimental effects remains unknown.Here,we investigate the effects of postoperative IF on cognitive deficits and its underlying mechanisms in a permanent two-vessel occlusion(2VO)vascular dementia rat model.Methods SD rats were randomly divided into 3 groups:Sham-operated ad libitum feeding(Sham-AL),2VO ad libitum feeding(2VO-AL)and 2VO intermittent fasting(2VO-IF).One week after 2VO surgery,2VO-IF rats were subjected to alternative day fasting protocol.The cognition of rats was assessed using Morris water maze(MWM)8 weeks after surgery.After behavioral testing,hippocampal malondialdehyde(MDA)and glutathione(GSH)concentrations,superoxide dismutase(SOD)activity,gene expression of antioxidative enzymes,inflammatory protein levels,and microglia density were determined.Results Postoperative IF substantially ameliorated the cognitive performance of 2VO rats in the MWM test.The escape latency of 2VO-IF rats during day 2-4 were significantly shorter than that of 2VO-AL rats(P<0.05).Probe trial showed that 2VO-IF rats spent longer time in target quadrant than 2VO-AL rats(P<0.05).Hippocampal Glutathione(GSH)level,Superoxide dismutase(SOD)activity and mRNA level of their upstream regulating enzymes of 2VO-IF rats were significantly higher than those of 2VO-AL rats(P<0.05).On the contrary,Malondialdehyde(MDA)and Nicotinamide adenine dinucleotide phosphate oxidasel(NOX1)mRNA and protein levels were lower in the hippocampus of 2VO-IF rats than in that of 2VO-AL rats(P<0.05),indicating IF increased the antioxidative capability and mitigated the oxidative stress in hippocampus of 2VO rats.Besides,microglial density,Sphingosine-1-phosphate receptor 1(SIP1),TNFα and IL-1β levels were lower in the hippocampus of 2VO-IF rats than in that of 2VO-AL rats(P<0.05),indicating anti-inflammatory role of IF.The amelioration of neuroinflammation and oxidative stress in 2VO-IF rat hippocampus paralleled with increased Postsynaptic density 95(PSD95)and Brain derived neurotrophic factor(BDNF)protein expression,reflecting a better micro environment of hippocampus after IF.Conclusions Our results suggest that postoperative IF suppresses neuroinflammation and oxidative stress induced by chronic cerebral ischemia,thereby preserving cognitive function in a vascular dementia rat model.Part ⅡObjective Since IF can prevent CCH induced cognitive impairment and S1P1 upregulation in the hippocampus of 2VO rats,we investigate whether applying a S1P1 functional inhibitor fingolimod(FTY720)can attenuate the cognitive impairment,neuroinflammation as well as oxidative stress of hippocampus of 2VO rats.Methods SD rats were randomly divided into 3 groups:Sham-operated saline injection(Sham-NS),2VO saline injection(2VO-NS)and 2VO FTY720 treatment(2VO-FTY).One week after 2VO surgery,2VO-FTY rats were subjected to FTY720 peritoneal injection treatment(lmg/kg/d).The cognition of rats was assessed using MWM 8 weeks after surgery.After behavioral testing,hippocampal MDA was tested using biochemical assay kit;the hippocampal protein expression of PSD95,S1P1,NOX1,TNFα and IL-1β were determined by Western Blotting.Results FTY720 substantially ameliorated the cognitive performance of 2VO rats in the MWM test.The escape latency of 2VO-FTY rats during day 4-5 were significantly shorter than that of 2VO-NS rats(P<0.05).Probe trial showed that 2VO-FTY rats spent longer time in target quadrant than 2VO-NS rats(P<0.05).Sphingosine-1-phosphate receptor 1(S1P1),TNFα and IL-1β levels were lower in the hippocampus of 2VO-FTY rats than in that of 2VO-NS rats(P<0.05),indicating anti-inflammatory role of FTY720.Besides,hippocampal MDA and NOX1 protein levels were lower in 2VO-FTY rats than in 2VO-NS rats(P<0.05),indicating FTY720 mitigated the oxidative stress in hippocampus of 2VO rats.FTY720 also increased PSD95 expression in 2VO-FTY rat hippocampus,reflecting a better micro environment of hippocampus after treatment.Conclusions Our results suggest that Fingolimod can mimic postoperative IF in ameliorating the cognitive function of 2VO rats by suppressing neuroinflammation and oxidative stress induced by chronic cerebral ischemia,the underlying mechanism may due to its S1P1 antagonist effect.S1P1 may mediate the neuroprotective effect of IF.