Lack of association between MTHFR A1298C variant and Alzheimer's disease: evidence from a systematic review and cumulative meta-analysis

The methylenetetrahydrofolate reductase C677T and A1298C genetic polymorphisms and plasma homocysteine in Alzheimer's disease in an Algerian population

BACKGROUND

The etiology of Alzheimer's disease (AD) is multifactorial. The most important challenge of research is the identification of potential biomarkers associated with AD pathogenesis that may significantly contribute to early diagnosis of the disease. We aim to explore an eventual association of the C677T and A1298C genetic polymorphisms in the MTHFR gene with AD risk in an Algerian population.

METHODS

This case-control study involved comparing a group of 106 patients that had developed AD to another group of 104 non-demented individuals. The MTHFR genotypes were determined using PCR-RFLP method. Additionally, the homocysteine level was evaluated.

RESULTS

Genotypes analysis did not show an association for both MTHFR677CT and 677TT variants with AD risk (OR = 1.12; p = 0.66; OR = 1.76; p = 0.09) respectively. As expected, the 677CC wild type genotype showed a protective role against AD (OR = 0.52; p = 0.03). For 1298AC MTHFR variant, the distribution of different genotypes did not show a statistical significant difference between the two cohorts. However the silmutaneous carrier, CT/AC presented association with AD (OR = 5.96; p = 0.05). On the other hand, carrier-state of MTHFR T allele showed a relationship with AD (OR = 1.98; p = 0.02). Additionally, hyperhomocysteinemia seems to be a risk factor for AD (OR = 1.08; p = 0.02).

CONCLUSION

Our exploration reveals that the silmutaneous carrier, CT/AC, carrier-state of MTHFR T allele, and hyperhomocysteinemia seem to be risk factors for AD.

Systematic evaluation of urinary formic acid as a new potential biomarker for Alzheimer's disease

INTRODUCTION

The accumulation of endogenous formaldehyde is considered a pathogenic factor in Alzheimer's disease (AD). The purpose of this study was to investigate the relationship between urinary formic acid and plasma biomarkers in AD.

MATERIALS AND METHODS

Five hundred and seventy-four participants were divided into five groups according to their diagnosis: 71 with normal cognitive (NC), 101 with subjective cognitive decline (SCD), 131 with cognitive impairment without mild cognitive impairment (CINM), 158 with mild cognitive impairment (MCI), and 113 with AD.

RESULTS

With the progression of the disease, urinary formic acid levels showed an overall upward trend. Urinary formic acid was significantly correlated with Mini-Mental State Examination (MMSE) scores, the Chinese version of Addenbrooke's Cognitive Examination III (ACE-III) scores, and Montreal Cognitive Assessment-Basic (MoCA-B) time. The areas under the receiver operating characteristic curves (AUC) of urinary formic acid in distinguishing NC from AD was 0.797, which was similar to that of plasma neurofilament light chain (NfL; AUC = 0.768) and better than other plasma biomarkers (Aβ40, Aβ42, Aβ42/Aβ40, T-tau, P-tau181, and P-tau181/T-tau). We also found that using urinary formic acid and formaldehyde levels could improve the accuracy of using plasma biomarkers to determine AD disease stage.

DISCUSSION

Our study revealed the possibility of urinary formic acid as a potential novel biomarker for the early diagnosis of AD.

Folate Related Pathway Gene Analysis Reveals a Novel Metabolic Variant Associated with Alzheimer’s Disease with a Change in Metabolic Profile

Metabolic disorders may be important potential causative pathways to Alzheimer’s disease (AD). Cerebrospinal fluid (CSF) decreasing output, raised intracranial pressure, and ventricular enlargement have all been linked to AD. Cerebral folate metabolism may be a key player since this is significantly affected by such changes in CSF, and genetic susceptibilities may exist in this pathway. In the current study, we aimed to identify whether any single nucleotide polymorphism (SNPs) affecting folate and the associated metabolic pathways were significantly associated with AD. We took a functional nutrigenomics approach to look for SNPs in genes for the linked folate, methylation, and biogenic amine neurotransmitter pathways. Changes in metabolism were found with the SNPs identified. An abnormal SNP in methylene tetrahydrofolate dehydrogenase 1 (MTHFD1) was significantly predictive of AD and associated with an increase in tissue glutathione. Individuals without these SNPs had normal levels of glutathione but significantly raised MTHFD1. Both changes would serve to decrease potentially neurotoxic levels of homocysteine. Seven additional genes were associated with Alzheimer’s and five with normal ageing. MTHFD1 presents a strong prediction of susceptibility and disease among the SNPs associated with AD. Associated physiological changes present potential biomarkers for identifying at-risk individuals.

Allelic Distribution of Genes for Apolipoprotein E and MTHFR in Patients with Alzheimer's Disease and Their Epistatic Interaction

Background:

Genetic risk factors play an important role in the pathogenesis of Alzheimer’s disease (AD). However, the gene-gene interaction (epistasis) between specific allelic variants is only partially understood.

Objective:

In our study, we examined the presence of the ɛ4 allele of apolipoprotein E (APOE) and the presence of C677T and A1298C (rs1801133 and rs1801131) polymorphisms in the methylenetetrahydrofolate reductase (MTHFR) gene in patients with AD and controls. We also evaluated the epistatic interaction between MTHFR and the APOE variants.

Methods:

A total of 564 patients with AD and 534 cognitively unimpaired age-matched controls were involved in the study.

Results:

The presence of the ɛ4 allele of APOE increases the risk of developing AD in a dose-dependent manner (OR 32.7: homozygotes, 15.6: homozygotes + heterozygotes, 14.3: heterozygotes). The combination of genotypes also increases the risk of developing AD in a dose-dependent manner: OR 18.3 (APOE 4/X and 4/4 + CT rs1801133), OR 19.4 (APOE 4/X and 4/4 + CT rs1801133 + AC rs1801131), OR 22.4 (APOE 4/X and 4/4 + TT rs1801133), and OR 21.2 (APOE 4/X and 4/4 + CC rs1801131). Homozygotes for variant alleles of MTHFR as well as patients with AD had significantly higher levels of homocysteine than homozygotes for standard alleles or controls.

Conclusion:

Homozygotes for APOE4 and carriers of APOE4 with TT genotype of rs1801133 were found to be at the highest risk of developing AD. These findings suggest that the epistatic interaction of specific gene variants can have a significant effect on the development of AD.

Meta-analysis of the relationship between methylenetetrahydrofolate reductase C677T and A1298C polymorphism and venous thromboembolism in the Caucasian and Asian

Recent years, it is a highly debated topic that whether methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism and A1298C polymorphism could increase susceptibility to venous thromboembolism (VTE) in the Asian and Caucasian. Therefore, we expect to settle that controversy evidentially. Basic methods: Electronic databases (Pubmed, embase, Cochrane library, scopus, OvidSP, Wiley Online library, Springer link, EBSCO, Elsevier Science Direct, Google scholar) without date limitation were searched. Crude odds ratio (OR) along with 95% confidence interval (95% CI) was calculated to assess the association quantitatively. Finally, a total of 37 eligible studies were included, containing 31 for MTHFR C677T polymorphism and 6 for MTHFR A1298C polymorphism. The pooled results suggested that MTHFR C677T mutation may increase susceptibility to VTE in reverse recessive model (CC+CT vs TT): OR = 0.68 (0.56, 0.83), reverse dominant model (CC vs CT +TT): OR = 0.82 (0.72, 0.94), heterozygote model (CT vs TT): OR = 0.65 (0.52, 0.81), homozygote model (CC vs TT): OR = 0.73 (0.60, 0.89) and allele model (C vs T): OR = 0.80 (0.71, 0.90). Subgroup analysis about Asian also support that results, but Caucasian group not. In addition, MTHFR A1298C polymorphism may be not related to VTE in all genetic model. The results of meta-analysis indicated that MTHFR C677T polymorphism might increase the risk of VTE, especially in Asian population.

Genetic factors associated with the predisposition to late onset Alzheimer's disease

BACKGROUND

Alzheimer's disease is a progressive, irreversible neurodegenerative disorder characterized by loss of memory and cognitive skills. More than 90% of cases are sporadic and have later age of onset. Many studies have shown a genetic predisposition for late onset Alzheimer's disease (LOAD). The most studied genetic predisposition factor is apolipoprotein E gene besides other susceptibility genes involved in vascular pathologies, homocysteine metabolism, and neuronal growth and differentiation such as methylenetetrahydrofolate reductase (MTHFR), angiotensin-converting enzyme (ACE), APOB and brain derived neurotrophic factor (BDNF).

METHODS

In this study Factor V Leiden (G1691A) and H1299R, prothrombin G20210A, Factor XIII V34L, B-fibrinogen -455G>A, PAI-1 5G/4G, HPA1 b/a, MTHFR C677T, MTHFR A1298C, APOE, ACE I/D, BDNF C270T and G196A polymorphisms were evaluated in 100 LOAD patients and 100 age matched healthy controls.

RESULTS

APOE4 allele, MTHFR CC^A1298C and BDNF TT^C270T genotypes were significantly higher in LOAD patients compared to the control group (p < 0.001, p = 0.04, p = 0.03, respectively). There were no significant associations between other genotypes and allele frequencies. Mini-Mental State Examination (MMSE) scores and age at onset of the patients were also evaluated for each and combined genotypes. Age at onset was significantly lowered by about approximately 4 and 5 years in patients carrying BDNF TT^C270T and MTHFR TT^C677T genotypes, respectively.

CONCLUSION

APOE, MTHFR A1298C and BDNF C270T polymorphisms may be associated with LOAD and BDNF and MTHFR alleles may play a role in the age at onset of the LOAD.

Methylenetetrahydrofolate reductase C677T variant and hyperhomocysteinemia in subarachnoid hemorrhage patients from India

Methylenetetrahydrofolate reductase (MTHFR) polymorphism (C677T, A1298C) has been implicated in increased plasma homocysteine (Hcy) levels. The present study was designed to investigate the association between MTHFR polymorphism and increased Hcy levels in subarachnoid haemorrhage (SAH) patients. A total of 150 subjects from North India were included in the study, comprising of 100 SAH patients and 50 healthy controls. Plasma Hcy levels was determined and MTHFR polymorphism (C677T, A1298C) was screened by High resolution melting (HRM) analysis. Plasma Hcy levels were found to be significantly higher (p < 0.001) in SAH patients than in healthy controls. No significant difference in the genotype and allele frequency of MTHFR A1298C was observed. However, frequency of MTHFR C677T genotype, CT (53% vs. 20%; p < 0.001) and TT (15% vs. 2%; p < 0.05) was significantly higher in SAH group as compared to healthy controls. The frequency of T allele (41.5% vs. 12%; p < 0.001) was also found to be higher in SAH patients in comparison to healthy controls. Furthermore, Hcy levels were higher in SAH patients with TT genotype than in patients having CT genotype, whereas CC genotype had lower Hcy levels. The study suggests that higher frequency of MTHFR C677T allele may contribute to etiopathology of SAH through increase in Hcy levels.