Geographical and ethnic distribution of single nucleotide polymorphisms within genes of the folate/homocysteine pathway metabolism

Association between the MTHFR (rs1801133) gene variation and serum trace elements levels (Copper and Zinc) in individuals diagnosed with neural tube defects

BACKGROUND AND AIMS

Neural tube defects (NTDs) occur when the neural tube fails to close within 28 days of human embryonic development. This results in central nervous system disorders like anencephaly, spina bifida, and encephalocele. Early diagnosis and treatment are crucial to minimize their impact on an individual's health and well-being. The present study aims to define the association between prenatal exposure to trace elements (Cu and Zn) and the single nucleotide polymorphism (SNP) of the MTHFR gene involved in folate metabolism pathways in neural tube defects in children and their mothers.

MATERIAL AND METHODS

A cross-sectional study involving 331 participants (90 NTD cases, 88 healthy mothers, 85 NTD children, and 68 healthy children) from antenatal check-ups in Obstetrics and Gynaecology and Pediatric Surgery for Neural Tube Defects in the Outpatient Department (OPD) and Inpatient Department (IPD). Assessed Cu and Zn concentrations and their associations. Genomic DNA was extracted, and real-time PCR was used to determine genotypes. Atomic absorption spectrophotometry measured trace elements. Statistical analyses included Chi-Square tests, odds ratios, and Mann-Whitney U tests.

RESULTS

Significant associations were found between MTHFR C677T genotypes and NTD risk in mothers (p = 0.0491) and children (p = 0.0297). Allelic frequency analysis indicated a T allele association with NTD risk in children (p = 0.0107). Recessive models showed significant associations in mothers (p = 0.0169) and children (p = 0.1678). Cu levels differed significantly between NTD cases and controls (p < 0.0001), with MTHFR genotypes influencing Cu levels. Zinc levels also varied significantly (p < 0.0001).

CONCLUSION

This study reveals complex associations between MTHFR C677T genotypes, trace element concentrations, and NTD risk in mothers and children. This targeted approach allows healthcare providers to identify at-risk pregnancies early, enabling personalised interventions like folic acid supplementation and counselling to moderate neural tube defect (NTD) risk in a future pregnancy.

We Are What, When, And How We Eat: The Evolutionary Impact of Dietary Shifts on Physical and Cognitive Development, Health, and Disease

"We are what, when, and how we eat": the evolution of human dietary habits mirrors the evolution of humans themselves. Key developments in human history, such as the advent of stone tool technology, the shift to a meat-based diet, control of fire, advancements in cooking and fermentation techniques, and the domestication of plants and animals, have significantly influenced human anatomical, physiological, social, cognitive, and behavioral changes. Advancements in scientific methods, such as the analysis of microfossils like starch granules, plant-derived phytoliths, and coprolites, have yielded unprecedented insights into past diets. Nonetheless, the isolation of ancient food matrices remains analytically challenging. Future technological breakthroughs and a more comprehensive integration of paleogenomics, paleoproteomics, paleoglycomics, and paleometabolomics will enable a more nuanced understanding of early human ancestors' diets, which holds the potential to guide contemporary dietary recommendations and tackle modern health challenges, with far-reaching implications for human well-being, and ecological impact on the planet.

Geographical distribution of MTHFR C677T gene polymorphisms among the reproductive-age women in Chinese Han populations: based on migration

BACKGROUND

Methylenetetrahydrofolate reductase (MTHFR) is essential for the metabolism of folic acid and homocysteine. The MTHFR C677T polymorphism is associated with several disorders. Our study aims to explore the geographical distributions of the MTHFR C677T polymorphism of women in China and how migration affected the polymorphism in Suzhou.

METHODS

A total of 7188 women of reproductive age were recruited in Suzhou of the study. Subjects were classified according to their native places after data extraction. MTHFR C677T gene polymorphisms were detected by quantitative PCR with genomic DNA isolated from blood samples.

RESULTS

The frequencies of the 677T allele and 677TT genotype were higher in northern China than that in southern China and decreased in geographical gradients from north to south. The frequencies were considerably higher in the migrant population than that in the indigenous population of Suzhou. The migrant population have gradually changed the prevalence in Suzhou.

CONCLUSIONS

Our study suggested that the prevalence of MTHFR C677T polymorphisms among women varied across different geographical regions in Chinese Han populations. The 677T allele frequencies of the northern populations were significantly higher than those of the southern populations. The migrant population gradually changed the prevalence of the MTHFR C677T polymorphism in Suzhou.

Effects of Methylenetetrahydrofolate Reductase (MTHFR) Polymorphisms on Retinal Tissue Perfusion in Mild Diabetic Retinopathy Patients Receiving the Medical Food, Ocufolin®

Purpose

We evaluate the effects of methylenetetrahydrofolate reductase (MTHFR) polymorphisms on retinal tissue perfusion in patients with mild diabetic retinopathy (DR + PM) taking the medical food, Ocufolin^®, for 6 months.

Methods

Prospective, case-controlled study. Eight early diabetic retinopathy patients with common reduced function MTHFR polymorphisms (DR+PM) and 15 normal controls (NC) were recruited. MTHFR polymorphisms were subtyped as normal, C677T, or A1298C. Best corrected visual acuity (BCVA) was evaluated. Retinal blood flow velocity (BFV) was measured using Retinal Function Imager. Retinal tissue perfusion (RTP, blood flow rate per inner retinal volume) was calculated within a 2.5 mm diameter circle centered on the fovea. The medical food is intended to address ocular ischemia with high doses of vitamin B-complexes and antioxidants, including L-methylfolate, methylcobalamin, zinc, copper, lutein, vitamins C, D, E, and n-acetylcysteine. The subjects were provided with a medical food for a period of 6 months.

Results

BCVA and vascular indices of DR + PM patients at baseline were initially below those of NC and improved after medical food. Compared to baseline, DR + PM patients after the medical food had significantly improved BCVA during the follow-up period (P < 0.05). In comparison, overall RTP and arteriolar BFV were significantly increased at 6 months (P < 0.05). The changes varied with MTHFR subtypes. In patients with the C677T and the C677T/A1298C compound mutations, RTP was increased at 6 months as compared to that at baseline and 4 months (P < 0.05). In patients with only the A1298C mutation, all microcirculation metrics were increased from baseline at 4 and 6 months, but with less improvement at 6 months than at 4 months (P < 0.05).

Conclusion

Medical food was effective in improving both visual acuity and retinal tissue perfusion in DR + PM patients. The degree of improvement of retinal microcirculation varied among MTHFR subtypes.

Juvenile patients with the homozygous MTHFR C677T genotype develop ischemic stroke 5 years earlier than wild type

To compare age at 1st ischaemic stroke (IS) in a cohort of juvenile (< 46 years of age) IS patients evaluated for the rs1801133 polymorphism (C → T677) of the methylene tetrahydrofolate reductase (MTHFR) gene; to identify predictors of age at IS and of type of cerebral vessel involvement, small vessel disease (SVD) vs large vessel disease (LVD) responsible for the IS; to evaluate possible associations between other clinical and laboratory variables. Retrospective cohort study on 82 MTHFR TT, 54 MTHFR TC and 34 MTHFR CC participants; data regarding age, sex, age at IS, history of dyslipidaemia, hypertension, smoking, migraine and homocysteine (HC) as well as neuroimaging were collected. Age at IS was lower in MTHFR TT than MTHFR TC and CC (35 ± 4 vs 38 ± 0 vs 40 ± 3 years, respectively, p = 0.002); plasma HC (median, interquartile range) was higher in MTHFR TT than in the other groups [16.7 (11.8, 28.6) vs 11.4 (8.2, 16.1) vs 9.8 (7.9, 1.3) respectively, p < 0.0001)] and was higher in SVD than LVD [17.4 (12.4, 32.5) vs  11.4 (8.8, 16.4) p < 0.0001]. MTHFR TT independently predicted age at IS (p = 0.0008) alongside smoking both as a categorical (p = 0.003) or continuous variable (p = 0.02), whereas HC independently predicted SVD as categorical (p = 0.01) and continuous variable (p < 0.0001). Smoking positively predicted plasma HC (p = 0.005) and negatively the activated partial thromboplastin ratio (aPTTr) (p = 0.02). Juvenile IS carriers of the MTHFR TT genotype develop their 1st occlusion on average 5 years earlier compared to the CC genotype; smoking contributes to this prematurity adversely affecting plasma HC and coagulation whereas plasma HC predicts IS secondary to SVD. Public health campaigns against smoking should highlight the prematurity of IS in the juvenile population.

The Effects of Polymorphisms in One-carbon Metabolism Genes on Manifestation of Ichthyosis Vulgaris

BACKGROUND: Ichthyosis vulgaris is the most common type of Mendelian disorders of cornification, caused by loss-of-function mutations in the gene encoding epidermal protein filaggrin (FLG), namely R501X and 2282del4. FLG 2282del4 mutation in heterozygotes is incompletely penetrant. Polymorphisms in one-carbon metabolism genes could be associated with clinical manifestation of ichthyosis vulgaris. AIM: The purpose of the present study was to analyze the effects of MTHFR, MTR and MTRR polymorphisms in patients with ichthyosis vulgaris. METHODS: 31 patients with ichthyosis vulgaris, 7 their FLG heterozygous relatives without symptoms of disorder, and 150 healthy controls were enrolled in study. FLG null mutations —R501X (rs61816761) and 2282del4 (rs558269137) — and one-carbon metabolism gene polymorphisms — MTHFR C677T (rs1801133), MTHFR A1298C (rs1801131), MTR A2756G (rs1805087) and MTRR A66G (rs1801394) — were analyzed by a polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) assay. RESULTS: Among patients with ichthyosis, heterozygous for FLG 2282del4 mutation, the distributions of genotypes for folate metabolism genes were: MTHFR C677T CC:CT:TT —29.4%:70.6%:0.0%; MTHFR A1298C AA:AC:CC — 52.9%:47.1%:0.0%; MTR A2756G AA:AG:GG — 70.3%:23.5%:5.9%; MTRR A66G AA:AG:GG — 23.4%:52.9%:23.5%. The frequencies of MTR 2756AA and MTRR 66GG genotypes were 1.4–1.6 times higher in affected individuals heterozygous for 2282del4 than in patients with other FLG genotypes. In affected 2282del4 heterozygotes, the frequency of MTR 2756AA genotype was 1.6 times greater than in healthy controls (p<0.01). The strongest association was found between MTHFR 677CT/MTHFR 1298AA/MTR 2756AA/MTRR 66AG genotype and ichthyosis — OR=11.23 (95% CI 2.51−50.21, p=0.002). CONCLUSIONS: Various genotypes of one-carbon metabolism genes increase the risk of ichthyosis in heterozygotes for the FLG 2282del4 mutation (OR 2.799‑11.231). The most probable predisposing genotype is 677CT/1298AA/2756AA+AG/66AG.

The distribution in native populations from Mexico and Central America of the C677T variant in the MTHFR gene

OBJECTIVES

To explore evolutionary hypotheses for the high frequencies of a substitution in the methylenetetrahydrofolate reductase (MTHFR) gene, in Mexican and Central American Indigenous populations.

MATERIALS AND METHODS

We obtained allele frequencies for the C677T variant in the MTHFR gene and ecological information for 37 indigenous samples from Mexico and Central America. We calculated Hardy-Weinberg equilibrium and computed Fst statistics. We computed correlations between the samples' allele frequencies and ecological and geochemical variables.

RESULTS

Many of the samples have extremely high frequencies of the T allele ( q ¯  = 0.62, median = 0.66). In this region, the frequency of the T allele decreases from Southeast to Northwest and is significantly correlated with longitude, latitude, altitude, and insolation.

CONCLUSIONS

The native people of Central America and Mexico evolved high frequencies of an allele which has been shown to produce deleterious clinical effects including neural tube effects, cardiovascular events, and cancer. This allele has a clinal distribution in the region, perhaps associated with solar irradiation. As (Contreras-Cubas et al., 2016) noted, the traditional diet of these populations, which is high in folate, has likely mitigated the negative effect of the allele. It is of primary importance that their rights to their homeland and traditional diets be respected. It is a matter of Public Health to investigate whether this allele is a factor in the current wave of cardiovascular diseases affecting the majority population of this region, since it descends from the Native peoples and the Mediterranean population, which also has high frequencies of the allele.

Genetic Variants Shaping Inter-individual Differences in Response to Dietary Intakes-A Narrative Review of the Case of Vitamins

Recent advances in the field of nutrigenetics have provided evidence on how genetic variations can impact the individuals' response to dietary intakes. An objective and reliable assessment of dietary exposures should rely on combinations of methodologies including frequency questionnaires, short-term recalls or records, together with biological samples to evaluate markers of intake or status and to identify genetic susceptibilities. In an attempt to present current knowledge on how genetic fingerprints contribute to an individual's nutritional status, we present a review of current literature describing associations between genetic variants and levels of well-established biomarkers of vitamin status in free-living and generally healthy individuals. Based on the outcomes of candidate gene, genome-wide-association studies and meta-analyses thereof, we have identified several single nucleotide polymorphisms (SNPs) involved in the vitamins' metabolic pathways. Polymorphisms in genes encoding proteins involved in vitamin metabolism and transport are reported to have an impact on vitamin D status; while genetic variants of vitamin D receptor were most frequently associated with health outcomes. Genetic variations that can influence vitamin E status include SNPs involved in its uptake and transport, such as in SCAR-B1 gene, and in lipoprotein metabolism. Variants of the genes encoding the sodium-dependent vitamin C transport proteins are greatly associated with the body's status on vitamin C. Regarding the vitamins of the B-complex, special reference is made to the widely studied variant in the MTHFR gene. Methodological attributes of genetic studies that may limit the comparability and interpretability of the findings are also discussed. Our understanding of how genes affect our responses to nutritional triggers will enhance our capacity to evaluate dietary exposure and design personalized nutrition programs to sustain health and prevent disease.

High MTHFR promoter methylation levels in men confer protection against ischemic stroke

The MTHFR gene encodes methylenetetrahydrofolate reductase required for the metabolism of homocysteine (Hcy) - a previously reported independent risk factor for ischemic stroke (IS). In this study, we first aimed to clarify the association between DNA methylation levels in the MTHFR promoter and the risk of IS, followed by the analysis of potential interactions between environmental factors and DNA methylation levels that affect IS risk. We recruited 164 patients with hypertension and IS (case group) and 345 age-matched and sex-matched patients with hypertension only (control group). Demographic and clinical information was obtained using questionnaires, and blood samples were collected for biochemical analyses. Fluorescence quantitative methylation-specific PCR (qMSP) was used to detect MTHFR promoter methylation levels. A logistic regression analysis was performed to determine the relationship between environmental factors, MTHFR promoter methylation levels, and IS risk. We finally generated a receiver operating characteristic curve to determine whether MTHFR promoter methylation levels can predict IS. The mean MTHFR methylation levels in the case group (8.10 ± 6.14) were significantly lower than those in the control group (17.44 ± 3.16; p < 0.05). MTHFR promoter methylation levels were also lower in patients with plasma Hcy levels ≥15 μmol/L (10.65 ± 4.05) than in those with Hcy levels <15 μmol/L (16.74 ± 4.26, p < 0.001). Finally, we found that MTHFR hypermethylation is a protective factor for IS, particular in men (OR in men: 0.07; 95% CI: 0.02-0.16; p < 0.001). Further, sex and MTHFR promoter methylation levels exhibited a preliminary interaction effect on IS risk. These results indicate that MTHFR promoter methylation status might have diagnostic value in IS.

Methylene tetrahydrofolate reductase and methionine synthase gene polymorphisms as genetic determinants of pre-eclampsia

BACKGROUND

Pre-eclampsia (PE) is a leading cause of maternal and neonatal mortality in Africa; and has been associated with the interplay of genetic, metabolic and environmental factors. Polymorphisms of methylene tetrahydrofolate reductase (MTHFR) and methionine synthase (MTR) folate cycle genes, have been controversially associated with pre-eclampsia in studies from different human populations.

OBJECTIVES

To determine the distribution of MTHFR C677T and MTR A2756G polymorphisms in a Nigerian population and evaluate possible associations with the occurrence of pre-eclampsia and homocysteine metabolic derangement.

MATERIALS AND METHODS

This study was a hospital based study carried out in Lagos, South-western Nigeria. Two hundred pregnant women clinically diagnosed with pre-eclampsia (study group) and 200 apparently healthy non-pre-eclamptic pregnant women (control group) were recruited for the study after written informed consent. Pre-eclampsia was diagnosed based on the International Society for the Study of Hypertension in Pregnancy re-classification of 2013. MTHFR C677T and MTR A2756G polymorphisms were determined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method. Statistical analyzes were performed using SPSS version 23. Hardy-Weinberg distribution were tested with χ2 test. Logistic regression model was used to evaluate the relationship of variables with pre-eclampsia. A value of p < 0.05 was considered statistically significant.

RESULTS

MTHFR genotype frequencies of CC, CT and TT were 59.8%; 31.2% and 9.0% in study group and 76.6%; 22.3% and 1.0% in the control group respectively. MTR A2756G genotype frequencies of AA, AG and GG genotypes were 71.9%; 20.1% and 8.0% for the study group and 81.5%; 16.4% and 2.1% for the control group. Occurrence of pre-eclampsia was significantly associated with presence of T allele of MTHFR (OR = 1.855; p < 0.05) and G allele of MTR genes (OR = 1.269; p < 0.05), Homozygosity of TG haplotype significantly increased the occurrence of pre-eclampsia among Nigerian women (OR = 2.252; p < 0.05). Population attributable risk fraction percent for the T and G alleles were 16.4% and 11.5% respectively. Mean plasma Hcy level was not, however, significantly affected by MTHFR/MTR haplotypes (F = 1.54; p = 0.157).

CONCLUSION

MTHFR C677T and MTR A2756G polymorphisms were associated with pre-eclampsia in a population of pregnant women in Lagos, Nigeria.

Genetic polymorphisms of key enzymes in folate metabolism affect the efficacy of folate therapy in patients with hyperhomocysteinaemia

The aim of this study is to analyse the efficacy rate of folate for the treatment of hyperhomocysteinaemia (HHcy) and to explore how folate metabolism-related gene polymorphisms change its efficacy. This study also explored the effects of gene-gene and gene-environment interactions on the efficacy of folate. A prospective cohort study enrolling HHcy patients was performed. The subjects were treated with oral folate (5 mg/d) for 90 d. We analysed the efficacy rate of folate for the treatment of HHcy by measuring homocysteine (Hcy) levels after treatment. Unconditioned logistic regression was conducted to analyse the association between SNP and the efficacy of folic acid therapy for HHcy. The efficacy rate of folate therapy for HHcy was 56·41 %. The MTHFR rs1801133 CT genotype, TT genotype and T allele; the MTHFR rs1801131 AC genotype, CC genotype and C allele; the MTRR rs1801394 GA genotype, GG genotype and G allele; and the MTRR rs162036 AG genotype and AG+GG genotypes were associated with the efficacy of folic acid therapy for HHcy (P<0·05). No association was seen between other SNP and the efficacy of folic acid. The optimal model of gene-gene interactions was a two-factor interaction model including rs1801133 and rs1801394. The optimal model of gene-environment interaction was a three-factor interaction model including history of hypertension, history of CHD and rs1801133. Folate supplementation can effectively decrease Hcy level. However, almost half of HHcy patients failed to reach the normal range. The efficacy of folate therapy may be genetically regulated.

Clinical and Vitamin Response to a Short-Term Multi-Micronutrient Intervention in Brazilian Children and Teens: From Population Data to Interindividual Responses

SCOPE

Micronutrients are in small amounts in foods, act in concert, and require variable amounts of time to see changes in health and risk for disease. These first principles are incorporated into an intervention study designed to develop new experimental strategies for setting target recommendations for food bioactives for populations and individuals.

METHODS AND RESULTS

A 6-week multivitamin/mineral intervention is conducted in 9-13 year olds. Participants (136) are (i) their own control (n-of-1); (ii) monitored for compliance; (iii) measured for 36 circulating vitamin forms, 30 clinical, anthropometric, and food intake parameters at baseline, post intervention, and following a 6-week washout; and (iv) had their ancestry accounted for as modifier of vitamin baseline or response. The same intervention is repeated the following year (135 participants). Most vitamins respond positively and many clinical parameters change in directions consistent with improved metabolic health to the intervention. Baseline levels of any metabolite predict its own response to the intervention. Elastic net penalized regression models are identified, and significantly predict response to intervention on the basis of multiple vitamin/clinical baseline measures.

CONCLUSIONS

The study design, computational methods, and results are a step toward developing recommendations for optimizing vitamin levels and health parameters for individuals.

Neuro-fuzzy model of homocysteine metabolism

In view of well-documented association of hyperhomocysteinaemia with a wide spectrum of diseases and higher incidence of vitamin deficiencies in Indians, we proposed a mathematical model to forecast the role of demographic and genetic variables in influencing homocysteinemetabolism and investigated the influence of life style modulations in controlling homocysteine levels. Total plasma homocysteine levels were measured in fasting samples using reverse phase HPLC. Multiple linear regression (MLR) and neuro-fuzzy models were developed. The MLR model explained 64% variability in homocysteine, while the neurofuzzy model showed higher accuracy in predicting homocysteine with a mean absolute error of 0.00002 μmol/L. Methylene tetrahydrofolate reductase (MTHFR) C677T, 5-methyltetrahydrofolate homocysteine methyltransferase (MTR) A2756G and 5- methyltetrahydrofolate homocysteine methyltransferase reductase (MTRR) A66G were shown to be positively associatiated with homocysteine, while nonvegetarian diet, serine hydroxymethyltransferase 1 (SHMT1) C1420T and TYMS 5'-UTR 28 bp tandem repeat exhibited negative association with homocysteine. The protective role of SHMT1 C1420T was attributed to more H-bonding interactions in the mutant modelled compared to the wild type, as shown through in silico analysis. To conclude, polymorphisms in genes regulating remethylation of homocysteine strongly influence homocysteine levels. The restoration of one-carbon homeostasis by SHMT1 C1420T or increased flux of folate towards remethylation due to TYMS 5'-UTR 28 bp tandem repeat or nonvegetarian diet can lower homocysteine levels.

Tailoring Nutritional Advice for Mexicans Based on Prevalence Profiles of Diet-Related Adaptive Gene Polymorphisms

Diet-related adaptive gene (DRAG) polymorphisms identified in specific populations are associated with chronic disorders in carriers of the adaptive alleles due to changes in dietary and lifestyle patterns in recent times. Mexico’s population is comprised of Amerindians (AM) and Mestizos who have variable AM, European (EUR) and African genetic ancestry and an increased risk of nutrition-related chronic diseases. Nutritional advice based on the Mexican genome and the traditional food culture is needed to develop preventive and therapeutic strategies. Therefore, we aimed to provide a prevalence profile of several DRAG polymorphisms in the Mexican population, including Central West (CW) Mexico subpopulations. Geographic heat maps were built using ArcGIS10 (Esri, Redlands, CA, USA) software, based on the published data of the MTHFR C677T (rs1801133), ABCA1 Arg230Cys (rs9282541), APOE T388C (rs429358)/C526T (rs7412), LCT C-13910T (rs4988235) polymorphisms and AMY1 copy number variation (CNV). Also, new data obtained by allelic discrimination-real-time polymerase chain reaction (RT-PCR) assays for the MTHFR, ABCA1, and APOE polymorphisms as well as the AMY1 CNV in the CW Mexico subpopulations with different proportions of AM and EUR ancestry were included. In the CW region, the highest frequency of the MTHFR 677T, ABCA1 230C and APOE ε4 adaptive alleles was observed in the AM groups, followed by Mestizos with intermediate AM ancestry. The LCT-13910T allele frequency was highest in Mestizos-EUR but extremely low in AM, while the AMY1 diploid copy number was 6.82 ± 3.3 copies. Overall, the heat maps showed a heterogeneous distribution of the DRAG polymorphisms, in which the AM groups revealed the highest frequencies of the adaptive alleles followed by Mestizos. Given these genetic differences, genome-based nutritional advice should be tailored in a regionalized and individualized manner according to the available foods and Mexican traditional food culture that may lead to a healthier dietary pattern.

Interethnic variability of pharmacogenetic biomarkers in Mexican healthy volunteers: a report from the RIBEF (Ibero-American Network of Pharmacogenetics and Pharmacogenomics)

Mexico presents a complex population diversity integrated by Mexican indigenous (MI) (7% of Mexico's population) and Mexican mestizos (MMs). This composition highlights the importance of pharmacogenetic studies in Mexican populations. The aims of this study were to analyze the reported frequencies of the most relevant pharmacogenetic biomarkers and metabolic phenotypes in healthy volunteers from Mexican populations and to assess its interethnic variability across MI and MM populations. After a literature search in PubMed, and according to previously defined inclusion criteria, 63 pharmacogenetic studies performed in Mexican healthy volunteers up to date were selected. These reports comprised 56,292 healthy volunteers (71.58% MM). Allele frequencies in 31 pharmacogenetic biomarkers, from 121 searched, are described. Nine of these biomarkers presented variation within MM and MI groups. The frequencies of CYP2D6*3, *4, *5, *10, *17, *35 and *41 alleles in the MM group were different from those reported in the MI group. CYP2C9*2 and *3 alleles were more frequent in MM than in MI populations (χ2 test, p<0.05). CYP2C19*3 allele was not found in the MM or MI populations reported. For UGT1A1*28, only one study was found. HLA-A*31:01 and HLA-B*15:02 were present in some MM and MI populations. Poor metabolizers for CYP2D6 and CYP2C9 were more frequent in MM than in MI groups (χ2 test, p<0.05). Only 26% of the relevant pharmacogenetic biomarkers searched have been studied in Mexican healthy volunteers; therefore, further studies are warranted. The frequency variation of biomarkers in MM and MI populations could be important for the clinical implementation of pharmacogenetics in Mexico.

Genetic polymorphisms and folate status

Moderate hyperhomocysteinemia-induced low folate status is an independent risk factor for cardiovascular disease, dementia, and depression. Folate is an essential cofactor in the one-carbon metabolism pathway and is necessary in amino acid metabolism, purine and thymidylate synthesis, and DNA methylation. In the folate cycle and homocysteine metabolism, folate, vitamin B12, vitamin B6, and vitamin B2 are important cofactors. Many enzymes are involved in folate transport and uptake, the folate pathway, and homocysteine (Hcy) metabolism, and various polymorphisms have been documented in these enzymes. Serum folate and total Hcy (tHcy) levels are influenced by folate intake and genetic polymorphisms in 5,10-methylenetertahydrofolate reductase (MTHFR) such as C677T. The prevalence of the MTHFR 677TT genotype varies across ethnic groups and regions, with a frequency of approximately 15% in Japanese populations. Individuals with the TT genotype have significantly higher tHcy levels and lower folate levels in serum than those with the CT and TT genotypes. However, administration of folic acid has been shown to eliminate these differences. Moreover, data have suggested that interventions based on genotype may be effective for motivating individuals to change their lifestyle and improve their nutrition status. Accordingly, in this review, we discuss the effects of MTHFR C677T polymorphisms on serum tHcy and folate levels with folic acid intervention and evaluate approaches for overcoming folic acid deficiency and related symptoms.

Geographical and ethnic distribution of MTHFR gene polymorphisms and their associations with diseases among Chinese population

Numerous studies have investigated the distribution of methylenetetrahydrofolate reductase (MTHFR) C677T and A1298C polymorphisms and their associations with diseases in China. In this study we conducted a systematic review and meta-analysis of these studies (715 eligible studies in total).Results revealed that the frequencies of the MTHFR C677T and A1298C polymorphisms varied markedly in different areas and ethnicities, and even showed geographical gradients. The MTHFR C677T polymorphism was significantly associated with 42 clinical disorders (p < 0.05), mostly relating to the diseases of circulatory system, birth defects and cancers. The association of the A1298C polymorphism with three diseases (coronary heart disease, breast cancer and neural tube defects fathers) was statistically significant (p < 0.05). However, according to the Venice criteria, only the associations of the C677T polymorphism with breast and ovarian cancers were assessed as having strong epidemiological credibility. This is the first study to provide a comprehensive assessment of the current status and gaps in genetic epidemiological study of the two polymorphisms in China, and its findings may be useful for medical and public health practices. Future studies are warranted to focus on the interactions of MTHFR genes with environmental exposure and with other genes, and to improve their methodological quality and reporting of findings.

The association of the MTHFR C677T polymorphism with inflammatory bowel diseases in the Israeli Jewish population: An example of genetic heterogeneity

MTHFR C677T is a common gene polymorphism that has been shown to be associated with hyperhomocysteinemia. Studies on the role of MTHFR in inflammatory bowel diseases (IBD) have yielded conflicting results, perhaps due in part to genetic heterogeneity. The prevalence of the MTHFR C677T variant allele varies according to Jewish subpopulations: Ashkenazi vs non-Ashkenazi. The aim of this study was to examine the association between MTHFR C677T genotype and IBD in the different Jewish populations.DNA samples were assessed for the presence of the MTHFR C677T variant allele in 445 Jewish Israeli IBD patients: 338 with Crohn's disease [CD] (214 Ashkenazi and 124 non-Ashkenazi Jews) and 107 with ulcerative colitis [UC] (73 Ashkenazi and 34 non-Ashkenazi Jews), and in 347 healthy controls: 173 Ashkenazi and 174 Non-Ashkenazi Jews. Possible genotype-phenotype associations were investigated.We showed a significantly higher frequency of MTHFR 677T variant genotypes in non-Ashkenazi CD patients: Odds ratio of 1.86 for heterozygotes (CT) and 2.89 for homozygotes (TT) compared to non-Ashkenazi healthy controls. No significant association was found for UC in non-Ashkenazi patients or for CD or UC in Ashkenazi patients.Our findings suggest that the MTHFR 677T variant may contribute to the risk of CD in non-Ashkenazi but not Ashkenazi Jews. This may result from genetic heterogeneity and highlights the complexity of the genetic etiology of IBD.

Heterogenous Distribution of MTHFR Gene Variants among Mestizos and Diverse Amerindian Groups from Mexico

Methylenetetrahydrofolate reductase (MTHFR) is a key enzyme in folate metabolism. Folate deficiency has been related to several conditions, including neural tube defects (NTDs) and cardiovascular diseases. Hence, MTHFR genetic variants have been studied worldwide, particularly the C677T and A1298C. We genotyped the C677T and A1298C MTHFR polymorphisms in Mexican Amerindians (MAs), from the largest sample included in a genetic study (n = 2026, from 62 ethnic groups), and in a geographically-matched Mexican Mestizo population (MEZ, n = 638). The 677T allele was most frequent in Mexican individuals, particularly in MAs. The frequency of this allele in both MAs and MEZs was clearly enriched in the South region of the country, followed by the Central East and South East regions. In contrast, the frequency of the 1298C risk allele in Mexicans was one of the lowest in the world. Both in MAs and MEZs the variants 677T and 1298C displayed opposite allele frequency gradients from southern to northern Mexico. Our findings suggest that in Mestizos the 677T allele was derived from Amerindians while the 1298C allele was a European contribution. Some subgroups showed an allele frequency distribution that highlighted their genetic diversity. Notably, the distribution of the frequency of the 677T allele was consistent with that of the high incidence of NTDs reported in MEZ.

New insights into the metabolic and nutritional determinants of severe combined immunodeficiency

Human mutations in MTHFD1 have recently been identified in patients with severe combined immunodeficiency (SCID). SCID results from inborn errors of metabolism that cause impaired T- and B-cell proliferation and function. One of the most common causes of SCID is adenosine deaminase (ADA) deficiency, which ultimately inhibits DNA synthesis and cell division. MTHFD1 has been shown to translocate to the nucleus during S-phase of the cell cycle; this localization is critical for synthesis of thymidyate (dTMP or the “T” base in DNA) and subsequent progression through the cell cycle and cell proliferation. Identification of MTHFD1 mutations that are associated with SCID highlights the potential importance of adequate dTMP synthesis in the etiology of SCID.

Linking genes to neurological clinical practice: the genomic basis for neurorehabilitation

Large-scale genomics projects such as the Human Genome Project and the International HapMap Project promise significant advances in the ability to diagnose and treat many conditions, including those with a neurological basis. A major focus of research has emerged in the neurological sciences to elucidate the molecular and genetic basis of various neurological diseases. Indeed, genetic factors are implicated in susceptibility for many neurological disorders, with family history studies providing strong evidence of familial risk for conditions such as stroke, Parkinson's, Alzheimer's, and Huntington's diseases. Heritability studies also suggest a strong genetic contribution to the risk for neurological diseases. Genome-wide association studies are also uncovering novel genetic variants associated with neurological disorders. Whole-genome and exome sequencing are likely to provide novel insights into the genetic basis of neurological disorders. Genetic factors are similarly associated with clinical phenotypes such as symptom severity and progression as well as response to treatment. Specifically, disease progression and functional restoration depend, in part, on the capacity for neural plasticity within residual neural tissues. Furthermore, such plasticity may be influenced in part by the presence of polymorphisms in several genes known to orchestrate neural plasticity including brain-derived neurotrophic factor (BDNF) and Apolipoprotein E. (APOE). It is important for neurorehabilitation therapist practicing in the "genomic era" to be aware of the potential influence of genetic factors during clinical encounters, as advances in molecular sciences are revealing information of critical relevance to the clinical rehabilitation management of individuals with neurological conditions. Video Abstract available (See Video, Supplemental Digital Content 1, http://links.lww.com/JNPT/A88) for more insights from the authors.