Intervention Study Of Folic Acid On Patients With Alzheimer’s Disease By DNA Methylation

Objective Alzheimer’s disease(AD) is characterized by the presence of neurofibrillary tangles and senile plaques. Aberrant DNA methylation may increase amyloid-β(Aβ) accumulation and tau phosphorylation. Folate acts through one-carbon metabolism to support DNA methylation. AD is related to aberrant folate metabolism. The study is to evaluate the effect of folic acid on patients with AD and the pathological mechanism of DNA methylation of folic acid on patients with AD.Methods This case-control study consisted of 115 patients with AD and 115 matched controls. Serum folate and vitamin B12 were measured using an automated immunoassay analyzer. Plasma Hcy was measured using high-performance liquid chromatography. Data were presented as means±standard deviation(SD), median(P25, P75) or proportion. Statistical significance was set at P< 0.05. Comparisons between categorical variables were reported by Chi-square test. Comparisons between quantitative variables were performed by two-tailed Student t test(for normally distributed data), by Mann-Whitney U test or Wilcoxon signed-rank test(for non-normally distributed data). Correlation between variables and AD was performed using logistic regression. In this intervention study, all participant received acetylcholinesterase inhibitor(ACh EI). Participants were randomized to intervention group, which received 1.25mg/d of folic acid, and control group for the entire six-month periods. Measures of clinical outcome were assessed at baseline and after 6-month intervals. Key indicators included mini-mental state examination(MMSE), activity of daily living(ADL), folate, vitamin B12, Homocysteine(Hcy), S-adenosylmethionine(SAM), S-adenosylhomocysteine(SAH), Aβ40, Aβ42, interleukin 6(IL6), tumor necrosis factor α(TNFα), amyloid precursor protein-m RNA(APP-m RNA), presenilin1-m RNA(PS1-m RNA), PS2-m RNA, DNA methyltransferase1-m RNA(DNMT1-m RNA), DNMT3a-m RNA, DNMT3b-m RNA, IL6-m RNA and TNFα-m RNA. Data are presented as mean ± standard deviation(SD), median(P25, P75), or proportions.Statistical significance was set at P < 0.05. Biochemical indicators, which were normally distributed originally, or after transformation, were analyzed using the repeated-measures.Results In the case-control study, serum folate concentration was lower among cases(M=5.65ng/ml) than controls(M=8.00 ng/ml, P=0.000). A significant decrease of vitamin B12 in AD group(M=405.00pg/ml) vs controls(M=603.00pg/ml, P=0.000). Significant difference was found in Hcy between AD(M=16.27μmol/L) and control elderly(M=9.69μmol/L, P=0.000). Low folate was associated with patients with AD(adjusted odds ratio [OR]:0.20; 95% confidence interval [CI]: 0.10–0.40). Low vitamin B12 was associated with patients with AD(OR: 0.21; 95% CI: 0.11–0.41). High Hcy was associated with patients with AD(OR: 16.18; 95% CI: 6.77–38.66). In this intervention study, analyses showed that, over 6 months, participants in intervention group had a greater increase in serum folate level(P=0.001, ηp2=0.937), in plasma SAM(P=0.012, ηp2=0.712) and in plasma SAM/SAH(P=0.000, ηp2=0.999), compared with the controls. Participants in intervention group had a greater decrease in blood Aβ40 level(P=0.003, ηp2=0.843), a less decrease inblood Aβ42/Aβ40(P=0.029, ηp2=0.594), a greater decrease in blood TNFα(P=0.021, ηp2=0.638), in blood PS1-m RNA(P=0.306, ηp2=0.175) and TNFα-m RNA(P=0.044, ηp2=0.527), compared with the controls. Participants in intervention group had a greater increase in MMSE(P=0.041, ηp2=0.538), compared with the controls.Conclusions Serum folate and vitamin B12 were possibly protected factor for AD. Hcy was possibly risk factor. It seems that folic acid improved syndromes of patients with AD by the pathway of DNA methylation. There exists a possible combined effect of folic acid for donepezil for patients with AD.