Relationship Between Genetic Polymorphism Of GSTP1 CYP19 And Alzheimer Disease

Introduction:Alzheimer's disease(AD),the major cause of presenile dementia and senile dementia,is a common progressive neurodegenerative disease in central nervous system with clinical manifestations as progressive memory decline,cognitive dysfunction,personality changes and language barriers.It was first discovered between 1906 and 1907 by Alois Alzheimer,a German neurologist.At present,20 or 30 million people are diagnosed with AD all over the world.Statisticas from Europe and the U.S.show that the prevalence rate of dementia in elderly population over 65 is from 3.0%to 5.0%and more than half of them with AD.In the United States,AD is considered as the fourth leading cause of death after cardiovascular diseases,cancer and stroke.In china,more than 100 thousand people are diagnosed with AD and the prevalence rate of dementia reported in elderly population over 60 is from 0.75%to 4.69%.With the world's aging population,SD is becoming one of the most toughest challenges ever in gerontology.Duing to its unclear etiology and pathogenesis,AD is generally considered as heterogeneity in complex disease and it may be caused by various factors(genetic and enviromental factors,neurotransmitters and immunocompetence,etc.).The transformation of exogenous chemical substances in the body is the result of joint action and active balance between multiple enzymes,and is dependent on toxicant-metabolizing enzymes. Such as cytochrome P450 enzyme,phaseⅠenzyme,,can alter the functional genes of substances or decompose them via oxidation,reduction and hydrolysis.The phaseⅡenzyme(like glutathione S-transferase and N-acetyltransferase) serves as catalyst activating the binding reaction between exogenous chemical substances and certain strong polar groups(like methyl and acetyl).Then the polarity and water solubility of those substances will be enhenced as a result,which will help them eject with urine and bile.The transformation of exogenous chemical substances in the body is the result of joint action and active balance between multiple enzymes.As a phaseⅡenzyme,Glutathione S-transferase(GST) is an important detoxification enzyme in vivo and serves as catalyst activating the binding reaction between electrophiles and reduced glutathione to disable electrophiles and make them eject with urine and bile.Thus it play an significant role in metabolizing environmental carcinogens and chemotherapy drugs.GSTs is a super-gene family with detoxification including membrane-type,cytosol-type,mitochondrion-type and LTC4 synthase.It is common in almost all cells and tissues but are found in highest concentrations in liver,colon and gonad.Population polymorphisms is revealed in GSTM1 and GSTP1.The relationshaip between the genetic polymorphisms of GSTs and environment afects our susceptibilities to certain diseases.Therefore,it is of great significance to correctly understsand their relationship to find out the role of GSTs in the incidence of deiseases and improve disease prediction.There is polymorphism in GSTP1 gene and it's exon 5(Ile105→Val).GSTP1 enzyme,the encoding product of GSTP1 gene,consists of 210 kinds of amino acid.It is reported that section 105 in amino acid sequence is vital for the biological functions of proteins as it determines the size and hydrophobicity of amino acid then finally impact enzyme thermal stability.GSTP1-Ile105 is reportedly about 2-3 times better than GSTP1-Val105 in thermal stability.Along with the gradual development of study on GSTP1 structure and function,it is realized that enzymes stem from GSTP1 allelic encoding are totally different.Therefore,the polymorphism of GSTP1 gene encoding is probably related with the genetic susceptibility of AD.Studies concluded that the ndogenous estrogen level in postmenopausal patients with AD is obviously lower than that of patients of the same age without AD.In AD patients,the local formation of estrogen has significant neurotrophic and neuroprotective effects and thus play a role in the promotion of neurotrophic factor expression Upregulation of neurotrophic factor receptor.On contrary,neurotrophic factors help cells conbined with estrogen to amplify signals and strenthen neurotrophic effects.The mechanism of estrogen in AD treatment(particularly in AD prevetion) is becoming a study hotspot both at home and abroud.Aromatase belongs to cytochrome P450 superfamily and is the last rate-limiting enzyme in estrogen synthesis.It's encoding gene CYP19 is located on chromosome 15----band 1 in long arm 21 region,with 123Kb of length.Studies showed that estrogen steming from aromatase is closely related with brain development and regeneration.Normally speaking,aromatase can be found in various tissues of human and other mammals, for example,in central nervous system,placental syncytiotrophoblast cells,ovarian granulosa cells,adipose tissue and its stromal cells and adrenal.In specific brain regions,aromatase helps androgen transforming into estrogen and it's activity is related with the estrogen levels.Studies in recent years revealed that CYP19 comprises many tissue-specific promoters mediating CYP19 expression and determining the tissue-specific pattern of CYP19 expression.There are few studies concerning the relationship between AD and aromatase.Population polymorphisms is revealed in CYP19 and thus the polymorphism of GSTP1 gene encoding is probably related with the genetic susceptibility of AD.Objective:The purpose of this experiment was to investigate the relationship between the genetic susceptibility of AD and CYP19 and it's polymorphism for the purpose of providing molecular biological indicators for AD diagnose.Methods:The blood samples were from 102 AD patients in Beijing Hospital and Military Nursing House and the blood samples in the control group were from 121 old healthy people over 65 with MMSE score higher or equal to 28 in community.As in accordance with ICD-10 diagnostic criteria,uspicious AD patients were taken as study object and MMSE and scale of cognitive function in the elderly were applied in this experiment.Imaging data were used for diagonose and over one year follow-up was conducted in all cases. Two millilitre whole blood was drawn from each testee and anticoagulated with sodium citrate.Peripheral blood leukocyte DNA was extracted with Phenol-chloroform.Polymerase chain reaction -restriction fragment length polymorphism technique was applied and 5'-TGC TAT CGT GGT TAA AAT CCA AGG-3'in upstream and 5'-TTA CCT GAG AGG CCA AGA AAA ACA-3'downstream were used for the amplificationof alleles located on Mfe I on cytochrome CYP19.Mfe I restriction endonuclease was applied to detect A→T polymorphism.5'-ACC CCA GGG CTC TAT GGG AA-3'in upstream and 5'-TGA GGG CAC AAG AAG CCC CT-3' in downsteam were used for the amplification of GSTP1 gene.BsmAⅠrestriction endonuclease was applied to detect the A→G polymorphism of GSTP1 gene.SPSS13.0 statistical package was employed in the comparison of genotype frequency gene frequency.Chi-square test was used to calculate the allele frequency and mutation frequency in AD patients and healthy population.Results:Mfe I restriction endonuclease was applied to detect A→T polymorphism.The result showed that 135 out of 204 AD patients were with allele m1(66.2%)and 69 were with allele m2(33.8%).In the control group,however,196 out of 242 healthy people were with allele ml(81.0%) and 46 were with allele m2(19.0%).There was significant difference between the two groups(χ~2=12.696, P＜0.05,95%CI:1.413～3.357).In the case group,the genotype frequency distributions of m1/m1,m1/m2 and m2/m2 in Mfe I locus of CYP19 were 44.1%, 44.1%and 11.8%respectively,while in the control group were 65.3%.31.4%and 3.3%.There was significant difference between the two groups(χ~2=12.384 P＜0.05). In the case group,the genotype frequency distributions of M1 and M2 were 73.4% and 26.6%respectively,while in the control group were 83.1%and 16.9%.There was statistically significant difference between the two groups(χ~2=6.134 P＜0.05,95%CI: 1.124～2.809).In the case group,the genotype frequency distributions of m1/m1, m1/m2 and m2/m2 in BsmAⅠlocus of CYP19 were 54.9%,36.3%and 8.8% respectively,while in the control group were 70.2%,25.6%and 4.1%.There was significant difference between the two groups(χ~2=6.062 P＜0.05).Conclusion:the genotype frequencies of Mfe I locus and BsmAⅠin CYP19 in the control group was almost consistent with the average frequency of healthy population.Significant differences of genotype frequency and gene frequency in Mfe I locus of GSTP1 gene were found in the case group and the control group,which indicates that carrying mutant gene T can increase that incidence of sporadic AD.Significant differences of genotype frequency and gene frequency in BsmAⅠlocus of GSTP1 gene were found in the case group and the control group,which indicates that carrying mutant gene G can increase that incidence of sporadic AD.