The Effect Of Folic Acid And DNMT1,DNMT3A Genes On Alzheimer’s Disease

Background:Alzheimer’s disease (AD), the most common type of dementia, is a chronic progressive degenerative age-related disease of the central nervous system, which is characterized by progressive decline in cognitive function, decrease in daily living and may be associated with various psychiatric symptoms and behavior disorders. Neurite plaques (NPS), neurofibrillary tangles (NFTs),and loss of neurons is its characteristic pathological changes. There is a prevalence of about25million worldwide, which has become a serious public health problem. However, the pathogenesis of Alzheimer’s disease is not yet totally clear, Genetic mutations can explain the onset of familial AD, accounting for only1%of AD patients. Abnormal methylation of specific gene promoter region and the decreased global methylation are closely related with the occurrence of sporadic AD. DNA methylation is the following process:under the action of DNA methyltransferase (DNMTS) and Methl binding proteins(MBPs),the methyl(-CH3) from S-adenosylmethionine (SAM) is transferred to specific DNA molecule bases. Folic acid and vitamin B12can modify DNA methylation level by regulating the generation of SAM. Study focousing on DNMTs and MBPs expression in sporadic AD is rare to date, some research about folic acid and vitamin B12levels in sporadic AD lead to contradictory conclusions. We explore the association between DNMT1、DNMT3A and folic acid with Alzheimer’s disease by case control study and cell experiment, which can contribute to an understanding of the pathogenesis of AD and provide new potential ideas for prevention and treatment of Alzheimer’s disease.Part1The serum folate level and the expression of DNMT1,dnmt3A in peripheral blood from sporadic ADObjective:To explore the association between the serum folate level and the expression of DNMT1、DNMT3A with sporadic AD.Methods:1. Collection of clinical cases AD group:55cases of AD outpatients and inpatients were randomly gathered during May2013to January2014in the Second Hospital of Shandong University. All AD patients were mearsured by MMSE, HIS, HAMD and CDR. According to the score of CDR, AD cases were divided into13cases of mild,12cases of moderate, and30cases of severe. Inclusion criteria:①All the patients met the criteria of "probable Alzheimer’s disease" which is made by NINCDS-ADRDA (2010).②MMSE score:Illiteracy≤17, Primary School≤20, secondary school≤22, College level<24; HIS score<4; HAMD score<8.③No brain injury, cerebral hemorrhage, cerebral infarction, coronary heart disease and other diseases of coronary or cerebral blood-vessels. No other serious body disease, such as hydrocephalus, subdural hematoma, malignant tumor, hypothyroidism, infection, liver function abnormalities, neurosyphilis, HIV infection, metabolic disorders and intoxication, etc⑤No neuropsychiatric disease history and dementia family history. Normal control (NC)group:31cases were healthy examination people whose age and sex matched. All cases were measured by MMSE. Inclusion criteria: score≥27.②No brain injury, cerebral hemorrhage, cerebral infarction, coronary heart disease and other diseases of coronary or cerebral blood-vessels.③No other serious body disease, such as hydrocephalus, subdural hematoma, malignant tumor, hypothyroidism, infection, liver function abnormalities, neurosyphilis, HIV infection, metabolic disorders and intoxication, etc④No neuropsychiatric disease history and dementia family history.2. Measurement Index:Blood samples were used for determining the expression of DNMT1、DNMT3A genes and the serum folate level by real-time RT-PCR and Chemiluminescence assay.. The results were analyzed by SPSS16.0.Results:1. There were no significant differences between AD group and NC group in age, sex composition, the education level, height, weight and BMI(P>0.05).2. The expression of DNMT1and DNMT3A gene in AD group were significantly increased compared with NC group(P<0.05).The serum folate level in AD group were significantly decreased compared with NC group(P<0.000).3. There were no significant differences of the expression of DNMT1, DNMT3A and the serum folate level among the mild, moderate and severe cases in AD group.4. There were no significant differences of the expression of DNMT1, DNMT3A and the serum folate level between the male and female cases in AD group.5. There were no significant correlations between the expression of DNMT1, DNMT3A, the serum folate level and age, the education level in both AD group and NC group.6. There were no significant correlations between the folate levels and the expression of DNMT1, DNMT3A gene in both AD group and NC group. Part2The effect of lack of folic acid on SHSY5Y cell and the relationship between lack of folic acid and the expression of DNMT1,DNMT3A genesObjective:To explore the effect of folic acid and the expression of DNMT1,DNMT3A genes on SHSY5Y cellMethods:To cultivate human neuroblastoma cells (SH-SY5Y) with different concentration of folic acid, and then determine the Cell activity by MTT, the concentration of Aβ40by ELISA, the expression of DNMT1、DNMT3A genes by real-time RT-PCR. The results were analyzed by SPSS16.0.Results:1.Compared with NC group, the Cell activity of0、8、16、32ug/ml groups decreased significantly(P<0.05)2.Compared with NC,8,16,32group, the concentration of Aβ40of Oug/ml group increased significantly (P<0.05)3.Compared with NC,8,16,32group, the expression of DNMT1、DNMT3A genes of Oug/ml group increased significantly (P<0.05)Conclusion:1. There is a certain correlation between the expression of DNMT1, DNMT3A and the incidence of Alzheimer’s disease. The expression of DNMT1and DNMT3A gene in peripheral blood may be a new Biomarker for the diagnosis of AD.2.The folate deficiency may be a risk factor for Alzheimer’s disease. Moderate folic acid supplementation can reduce the concentration of A(34O of nerve cells and promote the growth of nerve cells.3. Folate deficiency may cause the elevated expression of DNMT1, DNMT3A genes.