Serum folic acid and RFC A80G polymorphism in Alzheimer's disease and vascular dementia

Association of Biochemical Parameters and Screening for Mutations in the MCU Gene in Alzheimer's Disease Patients

The most prevalent form of dementia, Alzheimer's disease (AD) is a chronic illness that is on the rise among the geriatric population. Even though research into its biochemical, genetic, and cytogenetic pathways has advanced, its aetiology is still unclear and complex. In this study, we recruited sixty-eight participants diagnosed with AD where the cytogenetic, biochemical parameters and genetic mutations were analysed. Our results revealed chromosomal aberrations such as aneuploidies in the peripheral blood of Alzheimer's disease patients. Biochemical parameters revealed no statistical significance in the study though a pattern could be observed in the serum levels. Further few novel mutations at the c.21 C > T, c.56G > A were observed in the MCU gene of mitochondrial calcium uniporter. All these findings reveal the need for a larger cohort study to gain a better and more detailed understanding of the aetiology of Alzheimer's disease.

Genetic Susceptibility Variants of Vascular Dementia among Asians: A Systematic Review and Meta-Analysis

INTRODUCTION

Vascular dementia (VaD), a neurocognitive impairment directly related to vascular injury, is the second most common cause of age-related dementia. Although numerous studies have investigated candidate genetic polymorphisms associated with VaD in Asia, the genetics of VaD remains unclear.

METHODS

This review provides an updated meta-analysis of genetic polymorphisms associated with VaD in Asians, using the PRISMA guidelines. Published literature up to May 2021 was extracted from the PubMed, Scopus, Ovid, and EBSCOhost databases. Meta-analysis was conducted using the Open Meta analyst, Review Manager, and MedCalc® Statistical Software. Trial sequential analysis (TSA) was performed using TSA viewer software.

RESULTS

A total of 46 eligible studies, comprising 23 genes and 35 single nucleotide polymorphisms, were retrieved. The meta-analysis was conducted on the following genetic polymorphisms, APOE ε2/3/4, MTHFR rs1801131, ACE rs4340 (I/D) gene polymorphism, and a PSEN1 intron 8 variant. The pooled odds ratio (ORs) revealed a significant increase in the risk of VaD in the apolipoprotein E (APOE) ε4 allelic model (OR, 1.79, p < 0.001), and the methylenetetrahydrofolate reductase (MTHFR) rs1801133 polymorphism T allele in the allelic model (OR, 1.23, p = 0.013).

CONCLUSION

Our findings provide evidence that genetic polymorphisms of the APOE ε4 allele and MTHFR rs1801133 T allele increase the risk of developing VaD in Asians. However, future large-scale investigations examining particularly on South-Eastern and West-Asian populations are highly recommended.

AGE-RAGE axis culminates into multiple pathogenic processes: a central road to neurodegeneration

Advanced glycation end-products (AGEs; e.g., glyoxal, methylglyoxal or carboxymethyl-lysine) are heterogenous group of toxic compounds synthesized in the body through both exogenous and endogenous pathways. AGEs are known to covalently modify proteins bringing about loss of functional alteration in the proteins. AGEs also interact with their receptor, receptor for AGE (RAGE) and such interactions influence different biological processes including oxidative stress and apoptosis. Previously, AGE-RAGE axis has long been considered to be the maligning factor for various human diseases including, diabetes, obesity, cardiovascular, aging, etc. Recent developments have revealed the involvement of AGE-RAGE axis in different pathological consequences associated with the onset of neurodegeneration including, disruption of blood brain barrier, neuroinflammation, remodeling of extracellular matrix, dysregulation of polyol pathway and antioxidant enzymes, etc. In the present article, we attempted to describe a new avenue that AGE-RAGE axis culminates to different pathological consequences in brain and therefore, is a central instigating component to several neurodegenerative diseases (NGDs). We also invoke that specific inhibitors of TIR domains of TLR or RAGE receptors are crucial molecules for the therapeutic intervention of NGDs. Clinical perspectives have also been appropriately discussed.

One-carbon metabolism pathway genes and their non-association with the development of amyotrophic lateral sclerosis

Although of unknown etiology, some mechanisms associated with the metabolic cycle of folate are speculated to be related to the genesis of amyotrophic lateral sclerosis (ALS). Thus, the aim of the study was to analyze the role of genetic polymorphisms rs1051266 in SLC19A1 gene and rs1805087 in MTR gene and their associations with ALS development. A case-control study was conducted with 101 individuals with ALS and 119 individuals without diagnosis of neurodegenerative diseases, from the Brazilian central population. The polymorphisms were determined using the polymerase chain reaction-restriction fragment length polymorphism technique. The results showed no statistically significant differences, even when genotypes were analyzed by the dominant, recessive, codominant, and overdominant inheritance models. It was observed a statistical significance relating alcohol consumption with individuals in the case group (p = 0.01). Therefore, the need for more studies to evaluate the influence of genetic variants is highlighted, seeking to provide information on the etiopathogenesis of ALS.

Homocysteine and Folic Acid: Risk Factors for Alzheimer's Disease-An Updated Meta-Analysis

Background: Recent studies have reported that homocysteine (Hcy) may play a vital role in the pathogenesis of vascular dementia (VaD) and Alzheimer's disease (AD). Our study explored the relationship between the plasma Hcy and folate levels and the risk of dementia.

Methods: We searched Embase, PubMed, and Web of Science for published literature, including case-control studies and prospective cohort studies, and performed a systematic analysis.

Results: The results of our meta-analysis, consisting of case-control studies, showed higher levels of Hcy and lower levels of folate in dementia, AD, and VaD patients than those in non-demented controls (for dementia: SMD = 0.812, 95% CI [0.689, 0.936], p = 0.000 for Hcy; SMD = −0.677, 95% CI [−0.828, −0.525], p = 0.000 for folate). AD patients showed significantly lower plasma Hcy levels compared to VaD patients (SMD = −0.278, 95% CI [−0.466, −0.09], p = 0.000). Subgroup analysis revealed that ethnicity, average age, and dementia type had no significant effect on this association. Furthermore, from the analysis of prospective cohort studies, we identified that elevated plasma Hcy levels were associated with an increased risk of dementia, AD, and VaD (RR_dementia = 1.22, 95% CI [1.08, 1.36]; RR_AD = 1.07, 95% CI [1.04, 1.11]; RR_VaD = 1.13, 95% CI [1.04, 1.23]). In addition, every 5 μmol/L increase in the plasma Hcy level was associated with a 9% increased risk of dementia and a 12% increased risk of AD.

Conclusion: Hcy and folic acid are potential predictors of the occurrence and development of AD. A better understanding of their function in dementia could provide evidence for clinicians to rationalize clinical intervention strategies.

Pharmacogenetic evaluation of 6-mercaptopurine-mediated toxicity in pediatric acute lymphoblastic leukemia patients from a South Indian population

Aim: To evaluate the variants in the genes coding for the proteins involved in thiopurine and folate metabolism with treatment related adverse effects (TRAEs). Materials & methods: Eleven variants in seven candidate genes were genotyped in 127 pediatric acute lymphoblastic leukemia patients under 6-mercaptopurine (6-MP) treatment to infer the association of selected genotypes with TRAEs. Results: Among the genotypes inspected, NUDT15 (c.415C>T) and SLC19A1 (c.80G>A) showed a significant association with the TRAEs (odds ratio = 4.01, p = 0.002 and odds ratio = 7.78, p = 0.002). Conclusion: SLC19A1 and NUDT15 play an important role in the metabolism of 6-MP and it is necessary to spot other variants in associated pathways and investigate the factors that can impact 6-MP metabolism.

The Association Between Folate and Alzheimer's Disease: A Systematic Review and Meta-Analysis

Alzheimer's disease (AD) is the most common type of neurodegenerative disease leading to dementia in the elderly. Increasing evidence indicates that folate plays an important role in the pathogenesis of AD. To investigate the role of folate deficiency/possible deficiency in the risk of AD and the benefical effect of sufficient folate intake on the prevention of AD, a systematic review and meta-analysis were performed. The Web of Science, PubMed, CENTRAL, EBSCO, CNKI, CQVIP, and Wanfang databases were searched. The analysis of cross-sectional studies showed that the standardized mean difference (SMD) was −0.60 (95% confidence interval (CI): −0.65, −0.55), indicating that plasma/serum folate level is lower in AD patients than that in controls. Moreover, the combined odds ratio (OR) of case-control studies was 0.96 (95% CI: 0.93, 0.99), while the combined ORs were 0.86 (95% CI: 0.46, 1.26) and 1.94 (95% CI: 1.02, 2.86) in populations with normal levels of folate (≥13.5 nmol/L) and folate deficiency/possible deficiency (<13.5 nmol/L), respectively. In addition, the risk ratio (RR) of the cohort studies was 1.88 (95% CI: 1.20, 2.57) in populations with folate deficiency/possible deficiency. Furthermore, when the intake of folate was equal to or higher than the recommended daily allowance, the combined RR and hazard ratio (HR) were 0.44 (95% CI: 0.18, 0.71) and 0.76 (95% CI: 0.52, 0.99), respectively. These results indicate that folate deficiency/possible deficiency increases the risk for AD, while sufficient intake of folate is a protective factor against AD.

Association of MTHFR, SLC19A1 Genetic Polymorphism, Serum Folate, Vitamin B12 and Hcy Status with Cognitive Functions in Chinese Adults

Background/Aim: Studies have indicated a relationship between either gene polymorphism or in vivo B vitamins’ nutritional status with cognition in the elderly. However, the combined effects of MTHFR and SLC19A1gene polymorphism with serum folate and vitamin B₁₂ levels on cognition in Chinese adult population remain unclear. Methods: Demographic information of 426 Chinese adults aged from 55 to 90 were collected by a well designed self-administered questionnaire. The Montreal Cognitive Assessment test was utilized to evaluate the cognition status of the participants. MTHFR and SLC19A1 genotyping was analyzed using polymerase chain reaction-ligase detection reaction (PCR- LDR) method. Serum folate, vitamin B₁₂ and homocysteine (Hcy) levels were detected by commercial assay kits. Pearson’s correlation was used for data analyses and statistical significance was set at p < 0.05. Results: Serum Hcylevels demonstrated a negative correlation with serum folate (r = −0.301) and vitamin B₁₂ (r = −0.292) levels. The negative correlation found between serum Hcy levels and attention ability was observed in all 426 studied subjects (r = −0.122). Subjects with MTHFR 677 T/T and 1298 A/A genotypes demonstrated a higher serum Hcy levels (p < 0.05). Carriers of MTHFR (1298 A/C + C/C and 1793 G/A) and SLC19A1 80 G/G genotypes showed lower abstraction and delayed memory ability, respectively (p < 0.05). Subjects with MTHFR 1793 G/A genotype along with low serum folate concentration demonstrated the lowest name and orientation abilities. The effects of MTHFR 1793 G/A genotype on cognitive performance were dependent on the status of serum vitamin B₁₂. Conclusion: Cognition of adults was associated with MTHFR, SLC19A1 gene polymorphism and serum Hcy levels. This study clearly establishes a combined effect of MTHFR gene polymorphism and serum B vitamins levels on cognition in Chinese adults.

Environmental control of microRNAs in the nervous system: Implications in plasticity and behavior

The discovery of microRNAs (miRNAs) a little over 20 years ago was revolutionary given that miRNAs are essential to numerous physiological and physiopathological processes. Currently, several aspects of the biogenic process of miRNAs and of the translational repression mechanism exerted on their targets mRNAs are known in detail. In fact, the development of bioinformatics tools for predicting miRNA targets has established that miRNAs have the potential to regulate almost all known biological processes. Therefore, the identification of the signals and molecular mechanisms that regulate miRNA function is relevant to understanding the role of miRNAs in both pathological and adaptive processes. Recently, a series of studies has focused on miRNA expression in the brain, establishing that their levels are altered in response to various environmental factors (EFs), such as light, sound, odorants, nutrients, drugs and stress. In this review, we discuss how exposure to various EFs modulates the expression and function of several miRNAs in the nervous system and how this control determines adaptation to their environment, behavior and disease state.

A pilot study evaluating the contribution of SLC19A1 (RFC-1) 80G>a polymorphism to Alzheimer's disease in Italian Caucasians

Alzheimer's disease (AD) is the most common neurodegenerative disorder and the primary form of dementia in the elderly. Polymorphisms of genes involved in folate metabolism have been frequently suggested as risk factors for sporadic AD. A common c.80G>A polymorphism (rs1051266) in the gene coding for the reduced folate carrier (SLC19A1 gene, commonly known as RFC-1 gene) was investigated as AD risk factor in Asian populations, yielding conflicting results. We screened a Caucasian population of Italian origin composed of 192 sporadic AD patients and 186 healthy matched controls, for the presence of the RFC-1 c.80G>A polymorphism, and searched for correlation with circulating levels of folate, homocysteine, and vitamin B12. No difference in the distribution of allele and genotype frequencies was observed between AD patients and controls. No correlation was observed among the genotypes generated by the RFC-1 c.80G>A polymorphism and circulating levels of folate, homocysteine, and vitamin B12 either in the whole cohort of subjects or after stratification into clinical subtypes. Present results do not support a role for the RFC-1 c.80G>A polymorphism as independent risk factor for sporadic AD in Italian Caucasians.