The Role And Mechanism Of Brain LPL Expression Alteration On The Occurrence And Development Of Alzheimer's Disease With High Fat Diet

Objective: Alzheimer disease(AD)is an age-related progressive neurodegenerative disease which the main pathological manifestation is the deposition of ?-amyloid protein(A?)to form senile plaques.Dietary habits can affect the occurrence and development of AD.The role of high-fat diet in AD is controversial,previous studies have suggested that high-fat diet may increase the risk of AD,but recent studies have found that high-fat diet may have protective effects on cognition.Whether high-fat diet can affect A? deposition in the brain has not yet been determined.A recent study has found that high-fat diet can increase the deposition of A? on brain microvascular endothelial cells without affecting the content of A? in the brain.Lipoprotein lipase(Lipoprotein lipase,LPL)is a key enzyme in lipid metabolism,mainly synthesized by adipose and muscle tissue,is also highly expressed in the brain,but the LPL which locate at brain microvascular endothelial cells is considered to be derived from peripheral tissues.LPL is associated with the occurrence and development of AD.A large amount of LPL expression can be detected around the senile plaques in AD patients.LPL can also bind to A? and participate in molecular chaperone-mediated clearance of A? autophagy.At present,the effect of high-fat diet on the expression of LPL is mainly focused on peripheral tissues.There is no report on the effect of high-fat diet on the expression of LPL in the brain.Whether LPL is involved in the deposition of brain microvascular endothelial A? by high-fat diet remains unclear.The influence of high fat diet on the level of autophagy in AD brain remains to be studied.In addition,LPL expression is regulated by histone acetylation and mir-29 a regulation,whereas high-fat diet can affect histone acetylation levels and mir-29 a expression.Therefore,a high-fat diet may affect the development of AD by altering the level of histone acetylation and mir-29 a expression to regulate LPL levels in the brain.In this study,APPswe/PS1 d E9 double transgenic mice were first used as AD model animals to observe the effect of high-fat diet on neurobehavioral and A? deposition in brain of AD mice;secondly,to observe the expression of LPL in the brain and peripheral fat and muscle tissue of AD mice,and the acetylation levels in the brain(Ace-H3K9,Ace-H4K12 and HDAC1/2/3)and autophagy-related proteins(LC3)And P62)changes.Finally,in vitro experiments were performed to analyze the regulation of histone acetylation and mir-29 a on LPL expression.Methods: 1.Animal experiments and grouping: five-month-old APPswe/PS1 d E9 double transgenic mice and littermates born wild-type C57/BL6 mice were divided into AD model group,AD high-fat group,wild control group and wild high-fat group.AD high-fat mice and wild high-fat mice were fed high-fat diet,and AD models and wild-type mice were fed normal diet.During the experiment,the mice freely ingested and drank water,observed the general condition of the mice,weighed regularly,and measured the body composition of the mice and continuously treated for 5 months.At the end of the experiment,neurobehavioral tests were performed.Serum TG triglyceride(TG)and total cholesterol(TC)levels were measured by glycerol-3-phosphate-oxidase-p-amino-phenyl-hydrazine method and cholesterol oxidase method.Serum A? levels were measured by ELISA.Immunohistochemistry was used to detect the level of A? deposition in brain tissue.Immunofluorescence method was used to detect the co-localization of A? or LPL with brain microvascular endothelial marker CD31.RT-q PCR was used to detect the cerebral cortex LPL,HDAC1/2/3,mir-29 a Levels of isogenic expression;Western Blotting was used to detect the expression levels of LPL,LC3,P62,Ace-H3K9,Ace-K4K12,HDAC1/2/3 in cerebral cortex;The LPL gene and protein expression levels in adipose tissue and muscle were measured by RT-q PCR and Western Blotting,respectively.SH-SY5 Y cells were cultured in vitro.The expressions of HDAC1,2,3 were respectively silenced by si-RNA.The expression levels of LPL and mir-29 a genes were measured by RT-q PCR.The expression level of LPL protein was measured by Western Blotting.The mir-29 a inhibitors and mimics were used to intervene cells.RT-q PCR and Western Blotting were used to determine the expression levels of LPL gene and protein.3.Statistical analysis: A database was established using SPSS12.0 for statistical analysis.The results are expressed as mean ± standard deviation.One-way ANOVA followed by post hoc Fisher's least significant difference(LSD)was used for data analysis.Probability values of less than 0.05 were considered to be statistically significant.Results:1.There was no abnormal performance and death in each group during the experiment,and there was no significant difference in food intake.The weight of mice in each group increased,and the body weights of wild high-fat group and AD high-fat group were significantly higher than those in the wild-type control group and the AD model group at the sixth week of intervention(6-14 weeks,P<0.05,15-24.Week,P < 0.01).The brain weights of mice in the wild high-fat group and AD high-fat group were significantly higher than those in the wild and AD model mice(P<0.01).There was no significant difference in the ratio of brain to body ratio between the groups(P>0.05).The body fat ratio in the wild high-fat group and AD high-fat group was higher than that in the wild-type control group and the AD model group one month after feeding the high-fat diet,and the difference was statistically significant(P<0.05,P<0.01),while the muscle content percentage was lower than that in the wild and AD model groups,and the difference was statistically significant(P<0.05,P<0.01).In addition,serum TG and TC levels in the wild high-fat group and AD high-fat group were significantly higher than those in the wild-type control group and AD model group(P<0.01).2.With the increase of experimental days,the escape latency of each group of mice showed a decreasing trend.Compared with the wild control group,the escape latency of the remaining three groups of mice was prolonged,the difference was statistically significant(P<0.01),and the escape latency of AD model group and AD high-fat group was higher than that of wild high-fat group,and the difference was statistically significant(P<0.05).Compared with the wild-type control mice,the remaining three groups of mice on the exploring the number of times and the target quadrant stay time in morris water maze was lower than the wild-type control group,the difference was statistically significant(P<0.05,P<0.01).The dwell time of the mice in the AD model group and the AD high-fat group was lower than that in the wild high-fat group,and the difference was statistically significant(P<0.05).In the open-field test,compared with the wild-type control group and the wild high-fat group,the AD model group and the AD high-fat group had a prolonged latency,reduced number of grid passages and head rising counts,and the difference was statistically significant(P<0.01).There was no significant difference in the latency,number of grids,and head rising counts between AD model group and AD high-fat group(P>0.05).Compared with wild control mice,the number of A? plaques in AD model group and AD high-fat mice group increased significantly(P<0.01);there was no significant difference in the A? plaques in the mouse brain between AD model group and AD high fat diet group.The level of serum A? in AD high fat group was lower than that in AD model group,and the difference was statistically significant(P<0.01).4.The co-localization fluorescence intensity of A? and CD31 in AD high-fat group was significantly higher than that in the other three groups(P<0.05,P<0.01).The co-localization fluorescence intensity of A? and CD31 in the wild high-fat group was higher than that in the wild and AD model groups,and the difference was statistically significant(P<0.05).5.Compared with the wild-type control group,the ratio of LC3II/L3 I in the brain tissue of each group was significantly lower than that in the wild group(P<0.05).The ratio of LC3II/L3 I in AD high-fat group was higher than that in wild high-fat group and AD model group(P<0.05).Compared with the wild control group,the expression of P62 protein in the wild high-fat group and the AD model group was significantly higher(P<0.05).The P62 protein level in AD high-fat group was significantly lower than that in wild high-fat group and AD model group(P<0.05).Compared with the wild control group,the expression of P62 protein in the wild high-fat group and the AD model group was significantly higher(P<0.05).The P62 protein level in AD high-fat group was significantly lower than that in wild high-fat group and AD model group(P<0.05).6,compared with the wild control group,wild high-fat group,AD model group and AD high-fat group LPL m RNA expression were significantly increased(P<0.01).Compared with AD model group,the expression of LPL m RNA in AD high-fat group decreased(P<0.01).There was no statistically significant difference in the LPL protein levels in brain tissue of each group.7.Compared with the wild control mice,the localization fluorescence intensity of LPL and CD31 in the brain of the AD model group was significantly lower(P<0.05);the co-localization fluorescence intensity was significantly higher in the wild-type and AD-model mice than in the control group(P<0.05,P<0.01).8.There was no significant difference in the expression of LPL in muscles.Compared with the wild control group,the LPL m RNA and protein levels in the fat of the wild high-fat group and the AD high-fat group were significantly higher(P<0.01,P<0.05),and the expression of LPL m RNA and protein in the AD model group was significantly decreased(P<0.05,P<0.01).Compared with AD model group,LPL m RNA and protein expression in wild high-fat group and AD high-fat group were significantly higher(P<0.01,P<0.001).9.Compared with the wild control group,the expression of HDAC1,2,3 m RNA and protein in the brain of wild high-fat group,AD model group and AD high-fat group were significantly increased(P<0.05,P<0.01).The m RNA and protein levels of HDAC1,2,3 in AD high-fat group were lower than those in AD model group(P<0.01).Compared with the wild control group,the levels of Ace-H3K9 and Ace-H4K12 in the brain of wild high-fat group,AD model group and AD high-fat group were significantly lowered(P<0.01).The levels of Ace-H3K9 and Ace-H4K12 in brain of AD high-fat group were higher than those in AD model group(P<0.01).10.Compared with the wild control group,the expression of mir-29 a in the wild high-fat group and AD model group were decreased(P<0.01).Compared with AD model group,the expression of mir-29 a in AD high-fat group was increased(P<0.01).11.Silencing HDAC1 can down-regulate LPL expression(P<0.05)but mir-29 a expression does not change(P>0.05).Silencing HDAC2 up-regulates mir-29 a expression and down-regulates LPL expression(P<0.01).Silencing HDAC3 can down-regulate mir-29 a expression and up-regulate LPL expression(P<0.05).12.mir-29 a inhibitors increased the expression of LPL(P<0.01)while mir-29 a mimics inhibited the expression of LPL(P<0.01).Conclusions: 1.High fat diet has no effects on the neurobehavioral changes and the deposition of A? plaque in brain of AD mice,but increases the A? deposition in cerebral microvascular endotheliocyte of AD mice.2.High fat diet alleviates the increase of LPL m RNA expression in cerebral cortex of AD mice,the decrease of LPL expression in cerebral microvascular endotheliocyte and adipose tissue,and the decrease of autophagy level in cerebral cortex of AD mice.3.High fat diet ameliorates the decrease of histone acetylation level in cerebral cortex of AD mice.The mi R-29 a mediates the regulation of LPL expression by HDAC2/3,while HDAC2/3 regulates mi R-29 a in opposite directions.HDAC1 has no effect on mir-29 a expression.