The Effect Of High-fat Diet On Alzheimer's Disease And The Intervention Effect Of Huanglian Jiedu Decoction

BackgroundAlzheimer's disease(AD)is a progressive neurodegenerative disease related to aging,characterized by the pathological hallmarks of extracellular accumulation of amyloid-?plaques and intracellular accumulation of neurofibrillary tangles.It's caused by the complex interaction of multiple mechanisms,and the etiology of AD is still unclear.AD is generally considered to be related to genetic and environmental factors.Diet and nutrition display potential for nonpharmacological AD prevention;however,different studies examining the effect of a high-fat diet(HFD)on AD pathology in AD models have reported conflicting conclusions.For instance,systemic inflammation and obesity are likely to interfere with immunological processes of the brain and further promote disease progression,which can be reversed,at least partially,by switching to a low-fat diet,even after 7 months of HFD feeding when neuropathological burden was reasonably advanced.However,other studies found that HFD may promote better cognitive function by improving blood-brain barrier function and attenuating brain atrophy in AD,but it does not seem to affect A? levels.Studies have shown that serum cholesterol level has no correlation with AD,as well as statins have no effect on AD course,cognitive decline or dementia cannot be prevented or treated in elderly people at risk of vascular disease.Therefore,the influence of high-fat diet on the progression of AD disease is controversial.A clear understanding of the role of high-fat diet in the course of AD will help improve the quality of life and relieve the demand pressure of aging population on the overall resources of society.Huanglian Jiedu Decoction,recorded in "Zhouhoubeiji Prescription",is composed of Rhizoma coptidis,Radix scutellariae,Cortex phellodendri and Fructus gardenia at a ratio of 3:2:2:3.And which is classic prescriptions for clearing away heat and toxic materials in past dynasties.The active ingredients in the prescription mainly include alkaloids,flavonoids and iridoid glycosides,including berberine,palmatine,baicalin,baicalein and geniposide.Modern research shows that Huanglian Jiedu Decoction has many pharmacological effects,such as anti-inflammatory,antibacterial,antioxidant,lipid-lowering and hypoglycemic,anti-tumor,neuroprotection and so on.The literature researches and previous experiments of our research team shown that Huanglian Jiedu Decoction could reduce the accumulation of A? and Tau in central of APP/PS1 transgenic mice,improve AD mice cognitive ability,and ameliorated the lipids and inflammatory environment in the center and periphery of mice.Furthermore,Huanglian Jiedu Decoction could regulate the metabolism of central neurotransmitters,amino acids and peripheral bile acids,and relieve AD symptoms in combination with intestinal flora.In this study,we will continue to explore the curative effect and mechanism of Huanglian Jiedu Decoction on high fat diet plus AD model mice.ObjectiveThis study mainly discusses the effect of high-fat diet on the course of Alzheimer's model mice,clarifies the intervention effect of high-fat diet and evaluates the efficacy of Huanglian Jiedu Decoction.The effects of high-fat diet on inflammation,cholesterol metabolism and intestinal flora were expounded from both central and peripheral perspectives.Combined with transcriptome technology,the specific intervention mechanism of high-fat diet on Alzheimer's disease and the therapeutic mechanism of Huanglian Jiedu Decoction were discussed.Methods1 After treated by high-fat diet for six months,Morris water maze test was used to evaluate the behavioral cognitive ability of APP/PS1.Then,the brain tissue of mice was removed to observe pathological changes.The morphology of brain tissue was analyzed by HE staining.Congo red staining and immunohistochemistry experiments showed the deposition status of A? protein in AD,and the excessive activation of microglia in the brain(GFAP and MHC class ?)were assessed by immunohistochemistry.2 The levels of inflammatory factors such as IL-6,TNF-? and IL-1? in brain tissue were measured by RT-PCR and Elisa,and the contents of SOD,CAT,GSH-px,NO and MDA in brain tissue were detected to evaluate the oxidative stress state of brain tissue.Total serum levels of cholesterol,triglycerides,high-density lipoprotein cholesterol,low-density lipoprotein cholesterol,free fatty acids,albumin and C-reactive protein were determined using an automatic biochemical analyzer.Meso scale discovery(MSD)multispot assay system proinflammatory panel 1(mouse)kits(K15048D)were used to measure ten inflammatory cytokines(IFN-?,IL-1?,IL-2,IL-4,IL-5,IL-6,KC/GRO,IL-10,IL-12p70,and TNF-?)in serum.3 The level of cholesterol in brain tissue and the content of short chain fatty acids in fecal were detected by GC-MS.The method was established by UPLC-QQQ-MS/MS to detected the bile acids,and the content of bile acids in mouse serum was analysed.4 The expression levels of PPARy,LXR and ApoE genes in brain tissue,which was related to cholesterol metabolism,were determined by RT-PCR.And verified by Western Blot.5 16s rRNA sequencing technology was used to sequence the intestinal contents of mice and identify microorganisms,and the changes of intestinal flora of AD mice and AD mice after intervention by high-fat diet were analyzed.6 The whole transcriptomics of mouse brain tissue samples was studied,and the differential expression of mRNA,long-chain non-coding RNA,cyclic RNA and small RNA was measured and analyzed.Combined with competitive endogenous RNA analysis,the transcriptional regulation mechanism of high-fat diet on AD mice was systematically revealed from RNA level.Results1 Compared with normal mice,both AD mice and AD+HFD mice had cognitive impairment and brain A? plaque deposition,but there was no significant difference between AD mice and AD+HFD mice.That is,high-fat diet had no significant effect on AD cognitive ability and A? plaque deposition.2 In the central system,there were obvious inflammatory and oxidative stress reactions in the brain tissues of AD mice and AD+HFD mice,but high-fat diet could alleviate the central inflammatory level and oxidative state.High fat diet could significantly increase the body weight,peripheral blood lipid level and inflammatory cytokine levels of AD mice.3 High fat diet could increase cholesterol content and decrease 24-hydroxy cholesterol level in brain tissue of AD mice.High-fat diet could also regulate peripheral bile acid,which significantly increase the secondary bile acid,lithocholic acid.And the CDCA/CA ratio was increased,the levels of CDCA metabolism-related products also increased,such as UDCA,HDCA,TUDCA,THDCA,GHDCA and TCDCA.It was suggested that the bile acid synthesis pathway was changed in high fat treated mice.4 The expression of LXR? and PPAR? gene in brain tissue of AD mice decreased,while the expression of ApoE gene increased.High-fat diet significantly decreased the expression of ApoE in AD mice,while LXR? and PPAR? increased significantly.The protein level had the same change trend showed in western blot assay.It was revealed that the high fat diet could regulate cholesterol metabolism and neuroinflammation in brain tissue by affecting PPARy-LXR-ApoE pathway.5 High-fat diet could reduce the flora abundance of AD mice and increase the abundance of obesity-related bacteria.Besides,it could partially reshape the intestinal microbial structure,high-fat diet could reverse the changes of Bacteroides and Alistipes,and the reduction of Alistipes in AD mice was significant.6 Huanglian Jiedu Decoction could improve AD+HFD mice cognitive ability,reduce A?deposition in brain tissue.In the central system,the expression of inflammatory cytokine and cholesterol content was inhibited by Huanglian Jiedu Decoction.The blood lipid level were reduce in peripheral serum,and the bile acid level were adjusted by Huanglian Jiedu Decoction,which could reduce the serum CDCA,UDCA,TUDCA,GHDCA and TCDCA levels.Moreover,the level of fecal short-chain fatty acids were improved,and the increase of AA and BA was significantly.High dose of HLJDD could significantly increase the community richness,and reverse various strains,among which Alistipes abundance can be significantly reduced.7 The differentially expressed genes in brain tissues of APP/PS1 mice were critically involved in neurotransmitter metabolism and inflammation.And the high-fat diet had a regulatory effect on the neurotransmitter metabolism and inflammation in brain tissues.Mmu-miR-450b-3p and mmu-miR-6540-3p might associated with the up-regulation of Th and Ddc expression in the high-fat diet group,and miR-551b-5p regulateed the expression of a variety of genes including Slc18a2 and Igfbp3.PCSK9 can accelerate the degradation of LDL,and the up-regulation of PCSK9 expression in AD+HFD group may be closely related to the increase of cholesterol in brain tissue,while Huanglian Jiedu Decoction can significantly down-regulate the expression of PCSK9.conclusionHigh-fat diet could significantly increase the body weight of transgenic APP/PS1 mice and increase the peripheral blood lipid level,but it has no obvious intervention effect on AD typical pathological A? deposition and cognitive ability.On the contrary,high-fat diet could alleviate brain inflammation and oxidative stress.High-fat diet can affect lipid metabolism in brain tissue,regulate cholesterol metabolism and neuroinflammation in brain tissue through PPARy-LXR-ApoE pathway,and partially reshape intestinal flora to influence the metabolism of bile acids and short-chain fatty acids,thus regulating central metabolism.Huanglian Jiedu Decoction could alleviate cognitive impairment in mice with high fat and AD,which was related to improving central and peripheral lipid metabolism and inflammatory reaction,and increasing short chain fatty acid level.