| Homocysteine(Hcy)is a sulfhydryl-containing amino acid,and intermediate metabolite formed in metabolising methionine(Met)to cysteine(Cys);defective Met metabolism can increase Hcy.The effect of hyperhomocysteinemia(HHcy)on human health was first described in the mid-20th century by Kilmer S.Mc Cully.Since then,many epidemiologic reports indicated that HHcy is associated with multiple clinical conditions,while controlled Hcy level in high risk group associated with improved physical and mental health.It is considered as an independent risk factor for cardiovascular disease,as well as for stroke and myocardial infarction by the American Heart Association.Studies have identified a strong association between HHcy and induction of inflammatory determinants including the expression of adhesion molecules,leukocyte adhesion,endothelial dysfunction,oxidative stress,and reduced nitric oxide bioavailability in both human and experimental models.In HHcy state,NF?B,a transcription factor that regulates the transcription of various genes involved in inflammatory and immune responses is activated.HHcy induces inflammatory responses via increasing the pro-inflammatory cytokines and downregulation of anti-inflammatory cytokines which lead to Hcy-induced cell apoptosis.Although it is not directly involved in protein synthesis,the exposure to a toxic effect of Hcy,induced cytotoxicity that lead to a reduction of cultured endothelial cells viability through a direct and indirect effect on the pathway of apoptosis.In HHcy patients,supporting evidence indicate that the development of homocysteine-associated vascular disease may be prevented by the maintenance of normal Hcy levels.However,despite lowered Hcy levels,the clinical picture of pathophysiological conditions caused by an elevated Hcy level may not be reversible for certain conditions.Therefore,prevention of HHcy may be more important than treatment.Enzyme defects associated with Hcy metabolism are considered the most prevalent cause of HHcy.These genetic enzyme polymorphisms especially the polymorphisms of the main enzymes involved in Hcy metabolism such as Cystathionineb-synthase(CBS)deficiency,Methylenetetrahydrofolate reductase(MTHFR)deficiency,Methionine synthase(MS)deficiency,and betaine-homocysteine methyltransferase(BHMT)deficiency can decrease enzyme activity and cause abnormal homocysteine metabolism.In addition to genetic causes,many other factors related to age,lifestyle such as cigarette smoking,alcohol consumption and nutritional deficiencies in folic acid,vitamin B6,vitamin B12,and betaine are as responsible for HHcy.The human gene MTHFR is one of the most investigated genetic variations.MTHFR is one of the key enzymes of Hcy remethylation metabolism,and an important biological enzyme that degrades Hcy in the body.Methylation of Hcy generates Methionine(Met).The polymorphism of MTHFR can lead to the decrease of MTHFR activity,destroying the normal metabolism of Hcy and folic acid.The remethylation of Hcy is blocked and accumulates in the cell,eventually leading to HHcy.One of the most studied polymorphisms in MTHFR is C677T.This polymorphism is responsible for an increase of Hcy concentration and folate deficiency compared to a normal genotype individual?Genotype frequencies at the C677T locus of MTHFR vary widely by ethnicity,raising the possibility that any association between this SNP and the risk of disease may likewise depend on ethnicity.It is estimated that 10%of the global population is homozygous(TT genotype),which may vary in different populations reaching 25%.As a risk factor for diseases,Hcy may be related to the risk factors of diseases that have been discovered,such as hypertension,diabetes,hyperlipidemia,smoking,drinking,obesity,etc.,and participate in the occurrence and development of the disease.The relationship between MTHFR polymorphism and disease has been a hot and frontier issue studied by domestic and foreign experts in recent years.The study is based on genetic background,with the MTHFR gene which codes the key enzyme that degrades Hcy as the research target.Through regional population research,the Hcy metabolizing enzyme MTHFR 677genotype is determined to understand the prevalence of MTHFR C677T polymorphism in Jincheng,Shanxi.Through measuring the corresponding Hcy levels of different MTHFR 677 genotypes,to explore the correlation between the MTHFR C677T gene polymorphism and serum homocysteine,and to further understand the influence of the MTHFR C677T gene polymorphism on the serum Hcy level of the population in the region.By measuring the corresponding blood lipid levels of different MTHFR 677 genotypes,the correlation between the MTHFR C677T gene polymorphism and blood lipids was explored.It provides a theoretical basis for studying the significance of the genetic risk factor of MTHFR 677C>T gene polymorphism in HHcy and hyperlipidemia and its metabolic abnormalities in the region(such as cardiovascular disease,stroke,diabetes,etc.).It provides a theoretical basis for using MTHFR 677 genotype testing as a disease risk assessment indicator and playing a certain role in disease prevention and theropy.Chapter ?:The characteristics of MTHFR 677C>T polymorphism in Jincheng area of Shanxi ProvinceObjective1.To study the MTHFR 677C>T polymorphism of Han population in Jincheng,Shanxi Province,and to understand the epidemic distribution of MTHFR 677C>T genotype in this area.2.To provide a theoretical basis for race-based MTHFR related research.Methods1.All the subjects were selected from outpatient department,inpatient department and the physical examination center from December 2012 to March 2018.The fasting venous blood 3?4ml was collected in the morning and stored in red vacuum blood vessel,then the blood serum was separated by centrifugation within 2hours,and the serum Hcy and blood lipid were measured within 1 hour.2?3ml was placed in EDTA anticoagulant tube and stored at 2??8?.DNA was extracted within 1 day for detection of MTHFR gene.2.The frequency of MTHFR 677genotypes and alleles was statistically analyzed.Chi-square test was used to verify whether the sample conformed to Hardy-Weinberg genetic equilibrium,whether it was representative of the population and suitable for genetic analysis,and the distribution characteristics of MTHFR 677C>T polymorphism were described.Results1.5163 samples of MTHFR C677T gene polymorphisms are collected,of which of which the CC/CT/TT genotype frequency is 16.9%(72 cases),48.8%(2520 cases)and 34.3%(1717 cases).By?~2 test,there was no significant difference,and the distribution of alleles is in accordance with the Hardy-Weinberg balance.The frequency Allele C is 41.3%,allele T is 58.7%.2.In 3357 males,the frequency of CC/CT/TT genotype is 16.2%(543 cases),49.4%(1660 cases)and 34.4%(617cases).There is no statistical difference between them.The allele distribution is in accordance with Hardy-Weinberg balance.The frequency of allele C is 40.9%,and the frequency of allele T is 59.1%.3.Among the 1806 female samples,the frequency of CC/CT/TT genotype is18.2%(329 cases),47.7%(860 cases)and 34.2%(617 cases).There is no statistical difference between them by?~2 test(P>0.05),and the allele distribution is in accordance with Hardy-Weinberg equilibrium.4.Heterozygous and homozygous mutations in males were slightly higher than those in females,and there was no significant difference in allele frequency(P>0.05).ConclusionMTHFR 677 TT/CT are the main genotype of Han population in Jincheng,Shanxi Province,its distribution characteristics are different from other areas domestic or foreign,TT genotype is about 34.3%,and the distribution of male is slightly higher than female,this gender distribution difference is not statistically significant.Chapter ?:The relationship between MTHFR 677C>T polymorphism and serum Hcy levelObjectiveAnalyze the relationship between MTHFR 677C>T gene polymorphism and serum homocysteine(Hcy)level in local population.Explore the significance of MTHFR 677C>T gene polymorphism in HHcy and its metabolic disorders(such as Hypertension,stroke,diabetes,etc.).Methods1.The levels of serum Hcy were detected by circular enzyme method.Adopting the method of case-control research,1158 healthy people are randomly selected for Hcy determination by cyclic enzyme method,and the distribution of MTHFR C677T gene is statistically analyzed,and?~2 test is used to determine whether it accorded with Hardy-Weinberg genetic balance.2.According to the medical reference level of Hcy,the patients are divided into experimental group and control group.Using SPSS software,?~2 test and analysis of variance are used to compare the difference of MTHFR 677gene distribution under the same serum Hcy level and the difference of serum Hcy level among subjects with different genotypes.The effect of MTHFR gene polymorphism on Hcy is analyzed from two angles.Results1.The Hcy levels in CC/CT/TT group are(18.63±9.58)?mol/L,(21.21±18.21)?mol/L,(35.27±25.71)?mol/L.TT type and CT genotype are significantly higher than CC type(P<0.01),the difference is statistically significant.The distribution ratio of MTHFR C677T genotypes in HHcy group and control group is significantly higher than that in control group(P<0.01).The difference is statistically significant(P<0.01).2.There are 738 cases in HHcy group.Among them,18.3%(135 cases)are CC genotypes,39.0%(288 cases)are CT genotypes,42.7%(315 cases)are TT genotypes.There are 48.55%(408 cases)of allele C in the control group,558 cases(37.8%)of the allele C of HHcy,and 432 cases(51.45%)of the allele T of the control group.3.There are 918 cases(62.2%)of the allele T of HHcy.The distribution of allele C and T in control group and HHcy group is significantly different(P<0.05).The frequency of T allele in Hcy group is significantly higher than that in control group.Conclusion1.The serum Hcy level of homozygous mutation TT type of MTHFR 677genotype is significantly higher than that of heterozygous mutant CT and wild type CC,is the main genetic risk factor leading to the increase of serum Hcy in this area.2.The detection of serum Hcy combined with MTHFR polymorphism has important clinical significance in accurate diagnosis and treatment.Chapter ?:The relationship between MTHFR 677C>T polymorphism and blood lipidsObjectiveTo analyse the relationship between MTHFR 677C>T Gene Polymorphism and blood Lipid in Han population in Jincheng,Shanxi Province.MethodsThe research method is the same as Chapter II.Results1.The distribution of MTHFR C677T gene in 735 hyperlipidemia patients,111CC genotype(15.1%),387 CT genotype(52.6%),237 TT genotype(32.2%),allele C frequency is 41.5%and the T frequency is 58.5%.In 468 normal controls,93 cases(19.9%)of MTHFR CC genotype,204 cases(43.6%)of CT genotype,171 cases(36.5%)of TT genotype,the frequency of allele C is 41.7%,and allele T frequency is58.3%.There is no significant difference in the frequency distribution of alleles between the two groups.The frequency of heterozygous mutation CT(52.6%)in hyperlipidemia patients is higher than that in the control group(43.6%),while homozygous wild type CC(15.1%)and homozygous mutant TT(32.2%)are lower than those in the control group 19.9%and 36.5%,respectively,but the difference is not statistically significant.2.The frequencies of CC,CT and TT in hypercholesterolemic are CC genotype9 cases(10.1%),CT genotype are 48 cases(57.1%),TT genotype are 32 cases(32.1%).C and T allele frequencies are 66(38.65%)and 102(60.65%),respectively.The frequencies of CC,CT and TT genotypes are 93(19.9%),204(43.6%)and 171(36.5%),respectively.The frequency of allele T(58.3%)and allele C(41.7%)in hyperlipidemia group was higher than that in hyperlipidemia group.The analysis of three genotypes(CC,CT and TT)and the level of serum TC in hyperlipidemia group showed that the frequency of allele T is significantly higher in the three genotypes and alleles.The TC levels of the three genotypes in normal controls are 3.75±0.74mmol/L,(3.56±0.64)mmol/L and(3.59±0.64)mmol/L,respectively.In patients with hypercholesterolemia,the serum TC level of CC genotype is(6.09±4.98)mmol/L,TC level of CT genotype is(5.63±0.54)mmol/L,and the TC level of TT genotype is(5.59±0.40)mmol/L,and there is no significant difference among the three genotypes in serum TC level.There is no significant difference(P>0.05).There is no significant correlation between MTHFR C677T gene polymorphism and serum TC.3.The alleles frequencies of CC genotype 69(17.8%)and TT genotype 120(31.0%).C and T are 336(43.4%)and 48.6%(56.6%)in hypertriglyceridemia TG and control group respectively.The frequencies of CC,CT,TT genotype in 93 cases(19.9%),204 cases(43.6%)and 171 cases(36.5%)in the control group were compared with those in the control group.The frequency of gene C is 41.7%and the frequency of allele T is 58.3%.There are significant differences between the two genotypes and allelic frequencies.The levels of TG in the three genotypes of MTHFR C677T,CC,CT and TT,and the serum TG levels are(1.08±0.36)mmol/L,(1.06±0.30)mmol/L and(0.94±0.30)mmol/L,in the normal control group respectively,the results show that the TG levels of the three genotypes are(1.08±0.36)mmol/L,(1.06±0.30)mmol/L and(0.94±0.30)mmol/L,respectively.The serum TG level of CC genotype is(2.67±0.95)mmol/L,the TG level of CT genotype is(2.74±1.00)mmolr/L,the TG level of TT genotype is(3.33±2.88)mmol/L,and the serum TG level of the three genotypes has no significant difference in the same group.There was no significant difference between the allele T and TG(P>0.05).4.The alleles frequencies of CC genotype is 21(10.9%),CT genotype is 105(54.7%)and TT genotype is 66(34.4%)of low level DHL-C.The alleles frequencies of C and T are 336(43.4%)and 43.8(56.6%)respectively.The frequencies of CC,CT,TT genotype are 93(19.9%),204(43.6%)and 171(36.5%),respectively.The frequency of allele T is 58.3%.There are significant differences in frequency distribution of two genotypes and alleles.The levels of HDL-C in the three genotypes of MTHFR C677T,CC/CT/TT and serum HDL-C are(1.17±0.2)mmol/L,(1.18±0.23)mmol/L,and(1.22±0.23)mmol/L,respectively,in the normal control group.The levels of HDL-C are(1.17±0.20)mmol/L and(1.22±0.23)mmol/L respectively.In patients who with low HDL-C,the serum HDL-C level of CC genotype is(0.72±0.07)mmol/L,CT genotype HDL-C level is(0.73±0.15)mmol/L,TT genotype HDL-C level is(0.75±0.29)mmol/L,there is no significant difference among the three genotypes in serum HDL-C level(P>0.05).There is no significant difference between the polymorphism of MTHFR RC677T gene and the decrease of serum HDL-C(P>0.05)had no obvious correlation.5.The frequencies of alleles C and T are 60(41.7%)and 336(43.4%),respectively,for high LDL-C,CC genotype is 12(16.7%),CT genotype is 36(50.0%),TT genotype is 24(33.3%).The frequency of CC,CT,TT genotype is 93(19.9%),204(43.6%),171(36.5%),the frequency of allele C is 41.7%,and the frequency of allele T is 58.3%.MTHFR C677T genotype and serum LDL-C level in LDL-C patients are significantly different between the two genotypes.The LDL-C levels of the three genotypes are(2.3±0.62)mmol/L,(13±0.62)mmol/L and(2.13±0.56)mmol/L,respectively.In patients with high LDL-C,the serum LDL-C level of CC genotype is(3.65±0.31)mmol/L,LDL-C level of CT genotype is(3.75±0.36)mmol/L,LDL-C level of TT genotypes is(3.83±0.31)mmol/L,there is no significant difference among the three genotypes.There was no significant difference(P>0.05).There is no significant correlation between MTHFR C677T gene polymorphism and serum LDL-C.Conclusion1.There is no obvious correlation between changes in blood lipid profile and MTHFR 677C>T polymorphism There was no significant correlation between MTHFR C677T and lipoprotein metabolism.MTHFR C677T gene polymorphism was a risk assessment index independent of blood lipid.2.MTHFR 677C>T polymorphism is a risk index of a disease independent of dyslipidemia. |
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