Study Of The Variation In One Carbon Metabolism Components On Genome Stability In Alzheimer’s Patients

Alzheimer’s disease(AD)is a progressive degenerative disease of the central nervous system with an insidious onset and associated with aging,and there are currently no effective strategies to ameliorate the disease or halt its progression,so far,more than 7 million patients have suffered from ad in China.The increasing degree of aging has caused great pressure on public health maintenance and economic development in our country.One carbon metabolism(OCM)is an important metabolic network concerning DNA synthesis,methylation and genome stability,which is composed of folate metabolism as the core organic with methionine metabolism and homocysteine(Hcy)transsulfuration pathway,which is the obligatory way for body one carbon group generation and transfer.This metabolic network involves various forms of folate,coenzymes,cofactors and various enzymes including methylenetetrahydrofolate reductase(MTHFR),methionine synthase(MS),betaine hydroxymethyltransferase(BHMT),cystathionine beta synthase(CBS).Molecular epidemiological studies have found decreased genomic stability in patients with AD,but whether this trend correlates with the uptake and metabolism of relevant micronutrients in the patient’s OCM,and various key enzyme variants is still lacking precise analysis and accumulation of data.In this study,with informed consent,we analyzed and compared the levels of key metabolic components of OCM and genomic stability between AD and control subjects through a case-control study;the effects of polymorphisms in genes encoding key metabolic enzymes involved of OCM in AD patients on their plasma folate,vitamin B6,B12,and Hcy levels,as well as the association of these changes with their genomic stability,were dissected;Studies have also statistically analyzed the possible association of brain atrophy status and the various component variants of OCM in AD patients.The study recruited 62 volunteers who attented Kunming Second People’s Hospital from April 2019 to December 2020,25 AD patients diagnosed by the mini mental state examination scale(MMSE),and 37 non-AD controls.Anticoagulation a total of 8 ml of peripheral blood samples from volunteers were collected,of which 2 ml of isolated plasma was used to detect folate,B6,and B12 as well as Hcy levels by chemiluminescence;400 μl of extracted DNA to analyze key metabolic enzyme gene polymorphisms.The remaining blood samples were used for isolation and culture of lymphocytes.Cytosolic blocking micronucleus cytome analysis(CBMN-Cyt)was used to evaluate lymphocyte genomic stability.We found that:1.The AD case-control study found that the AD group had significantly(P < 0.05)higher plasma Hcy levels,genomic instability(GIN)represented by binucleated cell micronuclei(MN),and increased rates of apoptosis and necrosis(P < 0.01),with no significant differences in the other measures;2.Considered on the genotoxicity level,plasma levels of folate,B6,B12,and Hcy were not significantly associated with genetic stability in patients with AD.Considered from the cytotoxicity level,individuals with higher levels of Hcy(> 15 μM)and lower levels of Hcy(< 15 μM)had a significantly increased rate of lymphocyte apoptosis(P< 0.05);3.Considering that Hcy variant levels are associated with OCM multiple metabolic enzyme polymorphisms,studies simultaneously considered the effect of combined OCM metabolic enzyme polymorphisms on Hcy levels,and the combined effect of metabolic enzyme polymorphisms and Hcy levels on genome stability in AD patients.Founding that individuals with the combined MTHFR 677 TT and BHMT742 GG genotypes had significantly higher plasma Hcy levels than the other individuals with the combined genotype(P < 0.05).Individuals with the combined MTHFR 677 TT and MTHFR 1298 AA genotypes had significantly higher plasma Hcy levels than the other individuals with the combined two genotypes(P < 0.05).Individuals with the MTHFR 1298 AC genotype who had high levels of Hcy had a significantly higher rate of GIN nuclear buds(NBud)than other individuals with the MTHFR 1298 AA or CC genotypes that synergized with Hcy(P < 0.05).Individuals with the 1298 CC genotype who had high levels of Hcy had significantly(P < 0.05)higher rates of GIN nucleoplasmic bridges(NPB)than other individuals with the MTHFR 1298 AA or AC genotypes that synergized with Hcy;4.Analysis of clinical data found that the severity of brain atrophy in AD patients was positively correlated with their plasma Hcy levels(P < 0.05).In summary,High levels of Hcy are one of the main causes of genomic instability and cytotoxicity in AD patients.Mutations in genes encoding metabolic enzymes of the OCM pathway can disturb the balance of Hcy production,and in particular,polymorphisms in the methylenetetrahydrofolate reductase gene have the most dramatic effect.Meanwhile,the synergistic effect of high Hcy levels and mutant forms of methylenetetrahydrofolate reductase gene increased the genomic instability of AD patients to some extent.Compared with controls,the AD case group presented a greater clinical,biochemical phenotypic diversity and heterogeneity,which was associated with various factors such as age,life habits,disease course,suffering from other diseases,self-administered micronutrient intervention,and toxicity of various therapeutic agents,which also varied among the groups.Follow up studies need to expand the number of cases,excavate various physiological,pathological,and biochemical variables,and carry out classification studies,so as to gradually construct a "Alzheimer’s disease one carbon metabolism key component variation and genomic damage " database based on expanding and refining the existing data,so as to provide early warning information for the prevention and occurrence and development of AD.