Methylenetetrahydrofolate Reductase Gene Polymorphisms and Cardio
Cell & Developmental Biology

Cell & Developmental Biology
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Review Article - (2016) Volume 5, Issue 2

Methylenetetrahydrofolate Reductase Gene Polymorphisms and Cardiovascular Diseases

Mohammad Afaque Alam*
Department of Pediatrics, College of Medicine, Drexel University, Philadelphia, PA, USA
*Corresponding Author: Mohammad Afaque Alam, Department of Pediatrics, College of Medicine, Drexel University, 894 Union Ave, Memphis,, TN 38103, USA, Tel: +1-901-518-6443 Email:


A growing body of evidence suggests that mutations in MTHFR gene are involved in cardiovascular diseases (CVD) - cardiac development, atherosclerosis, myocardial infarction, heart failure, hypertension, aneurysms- and several other disease- cancers, neurological and metabolic disorders. Genetic variations in other genes are added risk for CVD- a leading cause of morbidity and mortality around the globe. Accumulating data over the decade has enhanced our understanding of MTHFR deficiency and diseases associated risk. The frequency of MTHFR 677 C→T and 1298 A→C gene mutations varies substantially in different regions of the world among different racial and ethnic groups. In particular, 677C→T and 1298 A→C variant are associated with clinical manifestation of almost all noncommunicable diseases. This review describes the roles of MTHFR gene mutation in CVD and prospective therapies for heart disease treatment.


Keywords: Polymorphism; MTHFR gene; Mutations

Methylenetetrahydrofolate Reductase (MTHFR) Gene

Methylenetetrahydrofolate reductase (MTHFR) is a cytosolic enzyme, which contains a non-covalently bound Flavin Adenine Dinucleotide (FAD) cofactor and uses NADPH as the reducing agent. This is an essential enzyme for folate and homocysteine (hcy) metabolisms and exhibits a risk factor for a number of heart diseases [1,2]. MTHFR is responsible for converting the circulating form of folate 5,10-methylenetetrahydrofolate to 5-methyltetrahydrofolate in multistep processes that converts homocysteine- an amino acid to another amino acid, methionine and S-adenosyl methionine - the common methyl donor for the maintenance of several biological processes (Figure 1). The body uses methionine to make proteins and other important compounds for growth and metabolism. On the other hand, appropriate methylation facilitates the clearance of harmful substances, metabolites and waste products more efficiently.


Figure 1: Homocysteine metabolism.

Over the decade researchers have enhanced our understanding of pathophysiological relation with common and rare MTHFR mutations, enzyme deficiency, elevated hcy and low folate levels in circulation. Of note, it has been reported that compromised MTHFR enzyme activity leads to elevated levels of hcy. Homocysteine is a sulpher containing amino acid, is an oxidant, and play a vital role in oxidation of lipids and lipoproteins, hence augmenting CVD risk [3,4]. Mudd et al. [5] have discovered a severe form of MTHFR enzyme deficiency, which leads to a very serious health conditions- homocysteinuria - in which hcy excretes out in urine. Since the discovery of the role of MTHFR gene mutation in human diseases, this enzyme has received much interest in establishing the association with increased concentration of hcy and heart diseases. There are several case control, retrospective and meta analyses that have demonstrated that MTHFR polymorphism is associated with increased blood hcy concentration and CVD [3,6-9]. The MTHFR 677C→T and 1298 A→C homozygous genotype is associated with premature CAD and other cardiovascular disorders [1,2,10].

On the other hand in the mid-nineties a great piece of discovery - cDNA synthesis - has been published, which paved the way for functional analysis of the MTHFR gene [11]. This transformed the MTFHR research which followed by identification of several rare and common variants including missense variant of alanine to valine at nucleotide 677, which encodes the thermolabile form of the enzyme [3,12].

The mutant TT genotype is linked to elevated circulating hcy levels and the individuals carrying this mutation exhibits low folate levels [13]. 677C→T variant is the most common and prevalent form of MTHFR genetic polymorphisms, which depicts mild to high level of hcy and associated disease manifestation [13-15]. Nonetheless, this variant located in the catalytic domain of the gene and thermolabile in nature affects hcy and folate metabolism. In 1998, another common polymorphism in the MTHFR gene was described, the 1298 A→C transition, which caused an amino acid substitution of glutamate by alanine [16,17]. Sibani et al. [18] reported 33 severe mutation and two common mutations, however Martin et al. [19] reported 65 mutations in MTHFR gene. MTHFR- as a central modulator of folatehcy- methionine pathway, inspired investigators from all fields to identify and characterize novel mutations in relation to human health. Therefore hundreds (~ 109) of polymorphism - that includes mutations, deletions, duplications, and splicing variants- have been identified [19] and investigations continue to establish the role in CVD risk [20].

Correspondingly, to explore the cause of diseases pathology as a consequence of MHFR gene mutation, scientists developed Mthfr knockout mice. They have exhibited a remarkably lower (>60%) enzyme activity in 677C→T variant, resulting in high hcy level among mutant group and also observed high lipid deposition in the major arteries [21]. Cascading effect of hyperhomocysteinemia is the causative factor for high cholesterol deposition in the vessel which initiates atherosclerosis generation and progression, that would lead to myocardial infarction and heart failure. MTHFR gene exists in dimeric form, consisting of 656 amino acid translating a protein that migrates at ~ 74-77 kDa. This is an evolutionary conserved gene throughout organisms from yeast to human. However, mouse depicts the highest homology (>90%). MTHFR gene is located at the short arm of chromosome 1 (1p36.3) and spans ~ 21 Kb. The cDNA sequence is 2.2 kb long and it consists of 11 exons ranging from 102 bp to 432 bp. Intron size ranges from 250 bp to 1.5 kb with one exception of 4.2 kb. Additionally, it has a close physical linkage with CLCN6 [22].

677C→T Mutation and CVD Risk

Indeed CVD is multifactorial disease and causes more than 15 million deaths and huge number of morbid patients. In fact hundreds of genes, environmental and epigenetic factors are involved in CVD manifestation. Correspondingly, mutations in atherogenic lipid and lipoprotein genes are responsible for high cholesterol levels in CVD. Thus it is true with MTHFR 677C→T gene mutation and increased hcy level in CVD. Moreover the findings of meta-statistical analyses reported significant link between hcy levels and MHTFR genotypes [23].

MTHFR, a gene involved in the metabolism of Hcy, is of particular medical interest as being a versatile member of the genetic risk factors for many diseases. Of note, numerous results have been published showing augmented risk of CVD and TT genotype. Therefore, the finding of an increased risk of CVD associated with MTHFR is not surprising because TT genotype is a strong genetic determinant for hyperhomocysteinemia. Similar observation was reported that 677TT genotype could be an inherited risk factor for heart disease [15,24,25].

Additionally many previous studies have demonstrated mild to high risk of CVD development and progression or no effect at all [26-30]. This discrepancy could be due to different selection criteria, different methods for hcy and folate measurements. The finding of the studies could be different as some countries have folic acid supplementation in their food habits that may cause lower hcy levels and reduced CVD risk [31].

Large meta-analyses were conducted on individual data from case–control studies relating the 677C→T MTHFR genotype and CVD. In one report, 40 studies comprising 11,162 patients with CAD were selected, whereas in the other report 120 studies were considered comprising 19,993 patients with different forms of vascular disease (CVD, DVT and stroke). Consistently, both studies concluded that subjects with the MTHFR 677TT genotype have modest but statistically significant increased risk of CVD when compared with those bearing the wild-type genotype [4,32]. In view of that, another meta-analysis consisting of more than 20,000 subjects determined an increased CVD risk of subjects carrying 677TT MTHFR genotype. This supports the underlying link of 677TT genotype with increased hcy and CVD [33-35].

677T Allele and Genotypes

Involvement of MTHFR in hcy-methionine cycle makes it an important player to investigate the causal ‘T’ allele/genotype frequency in CVD. The prevalence of MTHFR 677C→T gene polymorphism varies substantially with ethnic and racial groups worldwide. A diverse nature of ‘T’ allele incidence ranging from 59.0% in Mexicans, 44.9% in Brazilians, 33.3 to 43.8% in South European countries, 37.0 to 42.0% in Japanese, 33.0 to 38.0% in Chinese 38.0% in Canadian, 32.2% in Americans, 20% to 33.3% in Middle East Asia, 20.8% in Asians, 18.6% in European, 6.6% in Africans, and 4.7% in Australian [2,3,13,27,35,36].

A few studies reported from India and Indian subcontinent [24,37], have shown that mutant ‘T’ allele prevalence varies greatly across India, which is similar to the pattern reported in Chinese populations [36]. In our previous study, we found that the ‘T’ allele frequency was 17.0% [24], which is very similar to previous results (18.4%) from our centre [38]. However, there is a wide variation between north Indian (14.5-18.4%) and south Indians (9.0%) and a very low prevalence in Sri Lankans (4.9%) [39].

In the same way, MTHFR 677TT genotype in CVD subjects is ~ 7.9 %, which is higher than the general populations. It means that TT genotype may be the risk factor of heart disease [24]. The TT genotype frequency in Caucasians, Chinese and Japanese populations is 10-16% [35,40]. The precise reasons underlying the relatively low prevalence among Indians are not known.

Overall the frequency of T allele and mutant TT genotype are highly diverse in the population, so their risk in disease development also varies significantly dependent on the ethnic, race and food habits.

1298A→C Mutation and CVD Risk

Indeed, another most common MTHFR genetic polymorphism 1298A→C, which change glutamate to alanine at the 1298 nucleotide. This variant resides at exon 7 in the regulatory domain, while 677 C→T variant resides at exon 4 in the catalytic domain. It plays a critical role in various diseases including CVD. The effect of enzymatic activity of 1298A→C changes is lesser than 677 C→T change, which is an ~35 % decrease, meaning that it retains 65% of the total enzymatic activity.

On the other hand, 1298A→C variant has been less studied than 677 C→T variant. Moreover, the effect of 1298 A→C of hcy and folate level is milder, therefore the disease risk severity is less than 677 C→T variant [27,39-42]. Subsequently, a few studies did not find increase in hcy levels among homozygous (1298CC) even though they had decreased enzymatic activity, which may be due to non-thermolabile nature [16,17].

Furthermore, investigators dissect the effect of these two common variants at molecular levels using recombinant technology. They demonstrated how FAD binds and dissociates from the enzyme complex during the multistep metabolic pathways. It also help in determining metabolites, cofactors which is very important in MTHFR enzyme activity [43,44].

1298 C Allele and Genotypes

The ‘C’ allele frequency also varies greatly across the globe. Canadians and Europeans (36%), Israelites (34%), Americans (32%) and Portuguese (28.3%), and higher compared to Chinese (17%) [36] and Africans (21%) [41]. The ‘C’ allele frequency in Indians varies geographically and ethnically. South Indians represents higher prevalence (36%) [39], compared to North Indians 10-23% [24].

Similarly, the mutant (1298 CC) genotype frequency is ethnic and race dependent. The prevalence in Caucasians is ~ 10% [41,45], Arabians (9.1%) [29], while in Indians it ranges from 3.0% to 17.8% with varying amount of disease severity [24,39,42].


Having variant MTHFR allele and elevated hcy levels is an indicator of CVD risk and severity. MTHFR 677C→T and MTHFR 1298 A→C are two common polymorphisms that are associated with increased risk for many diseases due to the impaired enzymatic activity of the protein encoded by the minor alleles. Determination of MTHFR status for either 677 C→T or 1298 A→C has predictive value. Indeed MTHFR variations appear to be medically irrelevant, if an individual’s homocysteine level is normal. Of note, recent studies indicate that lowering an elevated homocysteine level may decrease the risk of atherosclerosis and CVD. Further study to explore the association at the molecular level and folic acid supplementation in lowering blood hcy levels is warranted, since increased folate levels are beneficial for a number health conditions.


  1. Rothenbacher D, Fischer HG, Hoffmeister A, Hoffmann MM, März W, et al. (2002) Homocysteine and methylenetetrahydrofolatereductase genotype: association with risk of coronary heart disease and relation to inflammatory, hemostatic, and lipid parameters.  Atherosclerosis 162: 193-200.
  2. Liew SC, Gupta ED (2015)Methylenetetrahydrofolatereductase (MTHFR) C677T polymorphism: epidemiology, metabolism and the associated diseases. Eur J Med Genet 58:1-10.
  3. Frosst P, Blom HJ, Milos R, Goyette P, Sheppard CA, et al. (1995) A candidate genetic risk factor for vascular disease: a common mutation in methylenetetrahydrofolatereductase. Nature Genet 10: 111-113.
  4. Klerk M, Verhoef P, Clarke R, Blom HJ, Kok FJ, et al. (2002) MTHFR 677C-->T polymorphism and risk of coronary heart disease: a meta-analysis.  JAMA 288: 2023-2031.
  5. Mudd SH, Uhlendorf BW, Freeman JM, Finkelstein JD, Shih VE (1972)Homocystinuria associated with decreased methylenetetrahydrofolatereductase activity. BiochemBiophys Res Commun 46: 905-912.
  6. Kang SS, Wong PW, Susmano A, Sora J, Norusis M, et al. (1991) Thermolabilemethylenetetrahydrofolatereductase: an inherited risk factor for coronary artery disease.  Am J Hum Genet 48: 536-545.
  7. Herrmann W, Herrmann M, Obeid R (2007) Hyperhomocysteinaemia: a critical review of old and new aspects. Curr Drug Metab 8: 17-31.
  8. Amouzou EK, Chabi NW, Adjalla CE, Rodriguez-Guéant RM, Feillet F, et al. (2004) High prevalence of hyperhomocysteinemia related to folate deficiency and the 677C-->T mutation of the gene encoding methylenetetrahydrofolatereductase in coastal West Africa. Am J ClinNutr 79: 619-624.
  9. Mager A, Koren-Morag N, ShohatM, Harell D, Battler A (2005) Family history, plasma homocysteine, and age at onset of symptoms of myocardial ischemia in patients with different methylenetetrahydrofolatereductase genotypes. Am J Cardiol 95: 1420-1424.
  10. Inbal A, Freimark D, Modan B, Chetrit A, Matetzky S, et al. (1999) Synergistic effects of prothrombotic polymorphisms and atherogenic factors on the risk of myocardial infarction in young males.  Blood 93: 2186-2190.
  11. Goyette P, Sumner JS, Milos R, Duncan AM, Rosenblatt DS, et al. (1994) Human methylenetetrahydrofolatereductase: Isolation of cDNA, mapping and mutation identification. Nature Genet 7: 195-200.
  12. Froese DS, Huemer M, et al. (2016) Mutation Update and Review of Severe MethylenetetrahydrofolateReductase Deficiency.  Hum Mutat 37: 427-438.
  13. Xuan C,Bai XY, Gao G, Yang Q, He GW (2011) Association between polymorphism of methylenetetrahydrofolatereductase (MTHFR) C677T and risk of myocardial infarction: a meta-analysis for 8,140 cases and 10,522 controls. Arch Med Res 42: 677-685.
  14. Moll S, Varga EA (2015) Homocysteine and MTHFR Mutations.  Circulation 132: e6-9.
  15. Li WX, Dai SX, Zheng JJ, Liu JQ, Huang JF (2015)Homocysteine Metabolism Gene Polymorphisms (MTHFRC677T, MTHFR A1298C, MTR A2756G and MTRR A66G) Jointly Elevate the Risk of Folate Deficiency. Nutrients 7: 6670-6687.
  16. van der Put NM, Gabreëls F, Stevens EM, Smeitink JA, Trijbels FJ, et al. (1998) A second common mutation in the methylenetetrahydrofolatereductase gene: an additional risk factor for neural-tube defects? Am J Hum Genet 62: 1044-1051.
  17. Weisberg I, Tran P, Christensen B, Sibani S, Rozen RA (1998) Second genetic polymorphism in methylenetetrahydrofolatereductase (MTHFR) associated with decreased enzyme activity. Mol Genet Metab 64: 169-172.
  18. Sibani S, Leclerc D, Weisberg IS, O'Ferrall E, Watkins D, et al. (2003) Characterization of mutations in severe methylenetetrahydrofolatereductase deficiency reveals an FAD-responsive mutation. Hum Mutat 21: 509-520.
  19. Martin YN, Salavaggione OE, Eckloff BW, Wieben ED, Schaid DJ,et al. (2006) Human methylenetetrahydrofolatereductase pharmacogenomics: gene resequencing and functional genomics. Pharmacogenet Genomics 4: 265-277.
  20. Machnik G, Zapala M, Pelc E, Gasecka-Czapla M, Kaczmarczyk G, et al. (2013) A new and improved method based on polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) for the determination of A1298C mutation in themethylenetetrahydrofolatereductase (MTHFR) gene. Ann Clin Lab Sci 43:436-440.
  21. Chen Z, Karaplis AC, Ackerman SL, Pogribny IP, Melnyk S, et al. (2001) Mice deficient in methylenetetrahydrofolatereductase exhibit hyperhomocysteinemia and decreased methylation capacity, with neuropathology and aortic lipid deposition. Human Mol Genet 10: 433-443.
  22. Gaughan DJ, Barbaux S, Kluijtmans LAJ, Whitehead AS (2000)The human and mouse methylenetetrahydrofolatereductase (MTHFR) genes: Genomic organization, mRNA structure and linkage to the CLCN6 gene. Gene 257: 279-289.
  23. Xuan C, Li H, Zhao JX, Wang HW, Wang Y, et al. (2014) Association between MTHFR polymorphisms and congenital heart disease: a meta-analysis based on 9,329 cases and 15,076 controls. Sci Rep 4: 7311.
  24. Alam MA, Husain SA, Narang R, Chauhan SS, Kabra M, et al. (2008) Association of polymorphism in the thermolabile 5, 10-methylene tetrahydrofolatereductase gene and hyperhomocysteinemia with coronary artery disease. Mol Cell Biochem 310: 111-117.
  25. Heidari MM, Khatami M, Hadadzadeh M, Kazemi M, Mahamed S, et al. (2015) Polymorphisms in NOS3, MTHFR, APOB and TNF-α Genes and Risk of Coronary Atherosclerotic Lesions in Iranian Patients.  Res Cardiovasc Med 5: e29134.
  26. Bennouar N, Allami A, Azeddoug H, Bendris A, Laraqui A, et al. (2007)ThermolabileMethylenetetrahydrofolateReductase C677T Polymorphism and Homocysteine Are Risk Factors for Coronary Artery Disease in Moroccan Population. J Biomed Biotechnol2007:80687-80695.
  27. Morita H, Taguchi J, Kurihara H, Kitaoka M, Kaneda H, et al. (1997) Genetic polymorphism of 5,10-methylenetetrahydrofolate reductase (MTHFR) as a risk factor for coronary artery disease. Circulation 95: 2032-2036.
  28. Pisciotta L, Cortese C, Gnasso A, Liberatoscioli L, Pastore A, et al. (2005) Serum homocysteine, methylenetetrahydrofolatereductase gene polymorphism and cardiovascular disease in heterozygous familial hypercholesterolemia. Atherosclerosis 179: 333-338.
  29. Abu-Amero KK, Wyngaard CA, Dzimiri N (2003) Prevalence and role of methylenetetrahydrofolatereductase 677 C-->T and 1298 A-->C polymorphisms in coronary artery disease in Arabs.  Arch Pathol Lab Med 127: 1349-1352.
  30. Mager A, Koren-Morag N, Shohat M, Harell D, Battler A (2005) Family history, plasma homocysteine, and age at onset of symptoms of myocardial ischemia in patients with different methylenetetrahydrofolatereductase genotypes. Am J Cardiol 95: 1420-1424.
  31. Wald DS, Law M, Morris JK (2002) Homocysteine and cardiovascular disease: evidence on causality from a meta-analysis.  BMJ 325: 1202.
  32. Cronin S, Furie KL, Kelly PJ (2005) Dose-related association of MTHFR 677T allele with risk of ischemic stroke: evidence from a cumulative meta-analysis.  Stroke 36: 1581-1587.
  33. Wang X, Fu J, Li Q, Zeng D (2016) Geographical and Ethnic Distributions of the MTHFR C677T, A1298C and MTRR A66G Gene Polymorphisms in Chinese Populations: A Meta-Analysis. PLoS One 11: e0152414.
  34. Li P, Qin C (2014) Methylenetetrahydrofolatereductase (MTHFR) gene polymorphisms and susceptibility to ischemic stroke: a meta-analysis.  Gene 535: 359-364.
  35. Botto LD, Yang Q (2000) 5,10-Methylenetetrahydrofolate reductase gene variants and congenital anomalies: a HuGE review.  Am J Epidemiol 151: 862-877.
  36. Sun J, Xu Y, Xue J, Zhu Y, Lu H (2005)Methylenetetrahydrofolatereductase polymorphism associated with susceptibility to coronary heart disease in Chinese type 2 diabetic patients. Mol and Cell Endoc 229: 95-101.
  37. Mukherjee M, Joshi S, Bagadi S, Dalvi M, Rao A, et al. (2002) A low prevalence of the C677T mutation in the methylenetetrahydrofolatereductase gene in Asian Indians. Clin Genet 61: 155-159.
  38. Vasisht S, Gulati R, Narang R, Srivastava N, Srivastava LM, et al. (2002) Polymorphism (C677T) in the 5,10-methylenetetrahydrofolate reductase (MTHFR) gene: A preliminary study on north Indian men.  Indian J ClinBiochem 17: 99-107.
  39. Angeline T, Jeyaraj N, Tsongalis GJ (2007) MTHFR Gene polymorphisms, B-vitamins and hyperhomocystinemia in young and middle-aged acute myocardial infarction patients. ExpMolPathol 82: 227-233.
  40. Spronk KJ, Olivero AD, Haw MP, Vettukattil JJ (2015) MethylenetetrahydrofolateReductase C677T: Hypoplastic Left Heart and Thrombosis.  World J PediatrCongenit Heart Surg 6: 643-645.
  41. Hanson NQ, Aras O, YangF, Tsai MY (2001) C677T and A1298C polymorphisms of the methylenetetrahydrofolatereductase gene: incidence and effect of combined genotypes on plasma fasting and post-methionine load homocysteine in vascular disease. ClinChem 47: 661-666.
  42. Kumar J, Das SK, Sharma P, Karthikeyan G, Ramakrishnan L, et al. (2005) Homocysteine levels are associated with MTHFR A1298C polymorphism in Indian population.  J Hum Genet 50: 655-663.
  43. Yamada K, Chen Z, Rozen R, Matthews RG (2001) Effects of common polymorphisms on the properties of recombinant human methylenetetrahydrofolatereductase. ProcNatlAcadSci U S A 98: 14853-14858.
  44. Ueland PM, Hustad S, Schneede J, Refsum H, Vollset SE (2001) Biological and clinical implications of the MTHFR C677T polymorphism.  Trends PharmacolSci 22: 195-201.
  45. Kölling K, Ndrepepa G, Koch W, Braun S, Mehilli J, et al. (2004) Methylenetetrahydrofolatereductase gene C677T and A1298C polymorphisms, plasma homocysteine, folate, and vitamin B12 levels and the extent of coronary artery disease.  Am J Cardiol 93: 1201-1206.
Citation: Alam MA (2016) Methylenetetrahydrofolate Reductase Gene Polymorphisms and Cardiovascular Diseases. Cell Dev Biol 5:172.

Copyright: © 2016 Alam MA. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.