Relationship of MTHFR gene polymorphisms with renal and cardiac disease

Relationship between methylenetetrahydrofolate reductase C677T gene polymorphism and neutrophil gelatinase-associated lipocalin in early renal injury in H-type hypertension

OBJECTIVE

To analyse the relationship between the polymorphisms of the H-type hypertensive methylenetetrahydrofolate reductase (MTHFR) C677T gene and neutrophil gelatinase-associated lipocalin (NGAL) in early kidney injury.

METHOD

A total of 279 hospitalised patients with hypertension were selected and grouped according to their homocysteine (Hcy) level. If their blood Hcy level was ≥ 10 µmol/L they were assigned to the H-type hypertensive group, and if it was < 10 µmol/L they were assigned to the non-H-type hypertensive group. Blood lipid indexes, renal function indexes and blood glucose indexes were collected, and the differences between the two groups were compared. Furthermore, MTHFR C677T genotype distribution and allele frequency and Hcy level of MTHFR C677T genotype were compared, and logistic multiple regression analysis was conducted for the correlation of different genotypes of MTHFR C677T and the early kidney injury marker NGAL.

RESULTS

In the non-H-type hypertensive group, the levels of Hcy and NGAL, cystatin, blood urea nitrogen, serum creatinine, uric acid, serum β2-microglobulin and urinary microalbumin-to-creatinine ratio increased significantly, and the glomerular filtration rate level decreased significantly, when compared with the H-type hypertensive group, with statistical differences (p < 0.05). The H-type hypertensive group and the non-H-type hypertensive group had significant differences in the CC, CT and TT genotypes and allele frequencies at the MTHFR C677T locus. The MTHFR C677T gene mutation rate of the H-type hypertensive group was significantly higher than that of the non-H-type hypertensive group. The H-type hypertensive group had higher levels of the TT genotype and CT genotype Hcy. There was a statistical difference (p < 0.05).

CONCLUSION

Methylenetetrahydrofolate reductase C677T polymorphism is correlated with the Hcy level, and its gene polymorphism will affect the Hcy level. Methylenetetrahydrofolate reductase C677T polymorphism has an interactive effect with NGAL. Screening NGAL and reducing Hcy levels are valuable methods for the prevention and treatment of early renal injury in patients with H-type hypertension and help improve the prognosis of patients and their quality of life.

Role of MTHFR 677C>T and 1298A>C gene polymorphisms on renal toxicity caused by lead exposure in wastewater treatment plant workers

Environmental and occupational lead (Pb) exposures continue to pose major public health problems. Wastewater treatment plant (WWTP) workers proved are exposing to high Pb concentrations in sludge departments. The aim of the work was to investigate the role of MTHFR C677T and MTHFR A1298C gene polymorphisms on alteration of oxidative stress and homocysteine levels in WWTP workers exposed to high Pb concentrations, and study its relations with renal functions. The study included 90 WWTP workers from Abu-Rawash WWTP. Homocysteine, creatinine, urea, malondialdehyde (MDA), and total antioxidant capacity (TAC) were measured. Polymorphisms of MTHFR C677CT and MTHFR A1298C genes were studied using PCR/RFLP. Urine Pb concentrations were also measured. About 32.2% of the workers were with detectable Pb levels. Pb, homocysteine, and MDA levels were significantly higher among workers carrying TT polymorphism compared to other MTHFR C677T gene polymorphisms, while TAC was significantly lower among them compared to other polymorphisms. The same results were found among workers carrying CC compared to other MTHFR A1298C gene polymorphisms. WWTP workers carrying MTHFR 677TT and MTHFR 1298CC are more susceptible to elevation of homocysteine and the urinary Pb compared to the workers with the other polymorphisms. Furthermore, those workers were found to have increase in urea and creatinine. Therefore, MTHFR C677T and MTHFR A1298C gene polymorphisms could be used for prediction of the susceptibility to the risk of kidney impairments among WWTP workers in the sludge departments caused by their exposure to high Pb in their workplace.

Vitamin B12 and chronic kidney disease

Chronic Kidney Disease (CKD) is an emerging public health issue with a fast-growing global prevalence. Impairment in vitamin B12 metabolism is considered a nontraditional risk factor of poor outcomes associated with CKD, and there is greater interest from the scientific community than ever before to explore the role and influence of vitamin B12 in CKD. Homocysteine metabolism forms an important component of the vitamin B12 metabolic pathway. Hyperhomocysteinemia is frequently observed in CKD and End-Stage Kidney Disease (ESKD), but its representation as a prognostic marker for CKD outcomes is still not fully clear. This chapter reviews the vitamin B12 and homocysteine metabolic pathways and their dysfunction in CKD states. Biochemical factors and the MTHFR genetic polymorphisms which disrupt vitamin B12 and homocysteine metabolism are explored. The mechanisms of homocysteine-mediated and vitamin B12-mediated tissue damage in CKD are discussed. This chapter reviews current perspective on definition and measurement of plasma vitamin B12 levels in the CKD population. Updated evidence investigating the prognostic role of vitamin B12 for CKD outcomes is presented. Findings from major clinical trials conducted relating to outcomes from multivitamin (including folic acid and vitamin B12) supplementation in nondialysis and dialysis-dependent CKD are highlighted. The prognostic value of vitamin B12 and effects of vitamin B12 supplementation in the context of kidney transplantation and acute kidney injury is also reviewed. Future research considerations are summarized based on evidence gaps in our knowledge base of this topic. Greater abundance of high-level evidence to guide an approach toward vitamin B12 measurement, monitoring and supplementation in CKD may contribute to improved clinical outcomes.

Deciphering key genes in cardio-renal syndrome using network analysis

Cardio-renal syndrome (CRS) is a rapidly recognized clinical entity which refers to the inextricably connection between heart and renal impairment, whereby abnormality to one organ directly promotes deterioration of the other one. Biological markers help to gain insight into the pathological processes for early diagnosis with higher accuracy of CRS using known clinical findings. Therefore, it is of interest to identify target genes in associated pathways implicated linked to CRS. Hence, 119 CRS genes were extracted from the literature to construct the PPIN network. We used the MCODE tool to generate modules from network so as to select the top 10 modules from 23 available modules. The modules were further analyzed to identify 12 essential genes in the network. These biomarkers are potential emerging tools for understanding the pathophysiologic mechanisms for the early diagnosis of CRS. Ontological analysis shows that they are rich in MF protease binding and endo-peptidase inhibitor activity. Thus, this data help increase our knowledge on CRS to improve clinical management of the disease.

Decisive evidence corroborates a null relationship between MTHFR C677T and chronic kidney disease: A case-control study and a meta-analysis

BACKGROUND

Previous meta-analyses have explored the association between the C677T polymorphism of methyltetrahydrofolate reductase (MTHFR) and chronic kidney disease (CKD) but there were no studies with a decisive conclusion. Furthermore, the high heterogeneity among different populations is not yet interpreted.

OBJECTIVES

This study used trial sequential analysis (TSA) to evaluate whether the nowadays conclusion supported by current cumulative samples. We also applied case-weighted meta-regression to explore the potential gene-environment interactions.

METHODS

For the first stage of this study we conducted a case-control study involving 847 dialysis patients from 7 hemodialysis centers in Taipei during 2015 to 2018 and 755 normal controls from a health center in the Tri-Service General Hospital. The second stage combined the results from the first stage with previous studies. The previous studies were collected from PubMed, EMBASE, and Web of Science databases before January 2018.

RESULTS

From the case-control study, the T allele of MTHFR C677T appeared to have a protective effect on end-stage renal disease compared with the C allele [odds ratio (OR): 0.80, 95% CI (confidence interval) = 0.69-0.93]. However, the meta-analysis contradicted the results in Asian (OR = 1.12, 95% CI = 0.96-1.30). The same analysis was also applied in Caucasian and presented similar results from Asian (OR = 1.18, 95% CI = 0.98-1.42). The TSA showed our case-control study to be the decisive sample leading to a null association among Asian population. The high heterogeneity (I = 75%) could explain the contradictory results between the case-control study and the meta-analysis. However, further case-weighted meta-regression did not find any significant interaction between measured factors and MTHFR C677T on CKD.

CONCLUSIONS

High heterogeneities were found in both Caucasian and Asian, which caused the null relationship in meta-analysis while there were significant effects in individual studies. Future studies should further explore the high heterogeneity that might be hidden in unmeasured gene-environment interactions, to explain the diverse findings among different populations.

Folic Acid and Vitamin B12 Administration in CKD, Why Not?

Patients affected by chronic kidney disease (CKD) or end-stage renal disease (ESRD) experience a huge cardiovascular risk and cardiovascular events represent the leading causes of death. Since traditional risk factors cannot fully explain such increased cardiovascular risk, interest in non-traditional risk factors, such as hyperhomocysteinemia and folic acid and vitamin B12 metabolism impairment, is growing. Although elevated homocysteine blood levels are often seen in patients with CKD and ESRD, whether hyperhomocysteinemia represents a reliable cardiovascular and mortality risk marker or a therapeutic target in this population is still unclear. In addition, folic acid and vitamin B12 could not only be mere cofactors in the homocysteine metabolism; they may have a direct action in determining tissue damage and cardiovascular risk. The purpose of this review was to highlight homocysteine, folic acid and vitamin B12 metabolism impairment in CKD and ESRD and to summarize available evidences on hyperhomocysteinemia, folic acid and vitamin B12 as cardiovascular risk markers, therapeutic target and risk factors for CKD progression.

MTHFR - Ala222Val Effects on Metabolic Syndrome Progression

Objective: Methylene-tetrahydrofolate reductase (MTHFR) is involved in adapting metabolism to environmental challenges by various mechanisms, including the control of gene expression by epigenetic and post-translational changes of transcription factors. Though a metabolic syndrome candidate gene, association studies of its common polymorphism rs1801133 (MTHFR-Ala222Val) remain inconclusive with important ethnic differences, and the effect on disease progression was not addressed.

Methods: 307 middle-aged metabolic syndrome patients in a central Romanian hospital setting were investigated metabolically, and genotyped by PCR-RFLP. Disease progression was assessed by the age of onset of metabolic components, as well as development of non-alcoholic fatty liver disease and atherosclerotic complications.

Results: The minor allele frequency of rs1801133 was 30.13%. Metabolic parameters showed no statistically significant differences according to genotype, but variant carriers developed dysglycemia and dyslipidemia earlier (53.28±10.8 vs 59.44±9.31 years, p<0.05 and 58.57±11.31 vs 64.72±10.6 years, p<0.1).While the polymorphism did not influence hepatic complications, an inverse association was found for manifest atherosclerosis (OR=0.49, p=0.006, 95%CI:0.29-0.81), which may be folate-status dependent, and needs further investigations. Simultaneous analysis with transcription factor polymorphisms (rs1801282, rs8192678) showed that the more protective genotypes were present the later metabolic disturbances developed, and in the presence of the other two variants the apparent protective cardiovascular effect disappeared.

Conclusions: The common functional polymorphism rs1801133 may influence metabolic syndrome progression, the age of onset of components and development of atherosclerotic complications. Besides simple additive effects, complex mitigating and aggravating variant interactions may exist, and the protective or predisposing outcome may depend on modifiable environmental factors.

Folic Acid and Homocysteine in Chronic Kidney Disease and Cardiovascular Disease Progression: Which Comes First?

Background

Hyperhomocysteinemia (Hhcy) occurs in about 85% of chronic kidney disease (CKD) patients because of impaired renal metabolism and reduced renal excretion. Folic acid (FA), the synthetic form of vitamin B₉, is critical in the conversion of homocysteine (Hcy) to methionine. If there is not enough intake of FA, there is not enough conversion, and Hcy levels are raised.

Summary

Hhcy is regarded as an independent predictor of cardiovascular morbidity and mortality in end-stage renal disease. Hhcy exerts its pathogenic action on the main processes involved in the progression of vascular damage. Research has shown Hhcy suggests enhanced risks for inflammation and endothelial injury which lead to cardiovascular disease (CVD), stroke, and CKD. FA has also been shown to improve endothelial function without lowering Hcy, suggesting an alternative explanation for the effect of FA on endothelial function. Recently, the role of FA and Hhcy in CVD and in CKD progression was renewed in some randomized trials.

Key Messages

In the general population and in CKD patients, it remains a topic of discussion whether any beneficial effects of FA therapy are to be referred to its direct effect or to a reduction of Hhcy. While waiting for the results of confirmatory trials, it is reasonable to consider FA with or without methylcobalamin supplementation as appropriate adjunctive therapy in patients with CKD.

Investigation of MTHFR gene C677T polymorphism in cardiac syndrome X patients

BACKGROUND

Definition of Cardiac Syndrome X (CSX) refers to groups of patients with positive exercise stress test and normal epicardial coronary arteries on coronary angiography accompanied by chest pain. Although the etiology of CSX is not completely understood, there is a common consensus that its pathophysiology may be associated with endothelial dysfunction resulting in impaired coronary flow. Some polymorphisms observed on the MTHFR gene cause inactivation of the MTHFR enzyme, leading to hyperhomocysteinemia and homocysteinuria, which are prominent risk factors of cardiovascular and cerebrovascular diseases. It was aimed to explain the association of the endothelial dysfunction, which is thought to play a role in the pathophysiology of CSX, with C677T polymorphism on MTHFR gene based on genetic basis.

METHODS

A total of 176 CSX patients and 196 healthy subjects with similar age and clinical features were compared in terms of C677T polymorphism of the MTHFR gene.

RESULTS AND CONCLUSION

There was no significant difference in terms of MTHFR gene C677T polymorphism between CSX patients and controls. When genotypic distribution was compared based on gender in both patients and controls, no significant difference was found between male and female subjects (P>.05). As fasting blood sugar and urea values were significantly higher, alanine aminotransferase and gamma-glutamyl transferase levels were significantly lower in the patients than the controls (P<.05). Described family story of the patients was significantly higher than the controls (P<.05). These suggest that homocysteine metabolism in CSX is not directly related to the endothelial dysfunction and thus the effect on the microvascular circulation.

Is hyperhomocysteinemia a causal factor for heart failure? The impact of the functional variants of MTHFR and PON1 on ischemic and non-ischemic etiology

BACKGROUND

Hyperhomocysteinemia was found to be uniformly associated with the development of heart failure (HF) and HF mortality; however, it is uncertain whether this relation is causative or not. We used Mendelian randomization to examine the associations of the methylene tetrahydrofolate gene (MTHFR) and paraoxonase 1 gene (PON1) variants as a proxy for lifelong exposure to high Hcy and Hcy-thiolactone concentrations with the development of HF in men aged ≤60years and the occurrence of adverse effects at one-year follow-up.

METHODS

The study enrolled 172 men with HF: 117 with ischemic etiology (iHF) related to coronary artery disease (CAD) and 55 with non-ischemic etiology (niHF) related to dilated cardiomyopathy (DCM). The reference group of 329 CAD patients without HF and the control group of 384 men were also analyzed.

RESULTS

Hyperhomocysteinemia (OR=2.0, P<0.05) and the MTHFR 677TT/1298AA, 677CC/1298CC genotypes (OR=1.6, P=0.03) were associated with HF regardless of its etiology, especially among normotensives (OR=4.6, P=0.001 and OR=2.3, P=0.003, respectively). In niHF, the PON1 162AA (OR=2.3, P=0.03) and 575AG+GG (OR=0.46, P=0.01) genotypes also influenced the risk. The interaction between HDLC<1mmol/L and the PON1 575GG genotype was found to influence the risk of iHF (OR=7.2, P=0.009). Hyperhomocysteinemia improved the classification of niHF patients as 'high-risk' by 10.1%. Ejection fraction <30% and DCM increased the probability of HF death or re-hospitalization within one year.

CONCLUSION

Our results provide evidence that hyperhomocysteinemia is a causal factor for niHF in DCM, while dysfunctional HDL could contribute to the pathogenesis of iHF.

Associations between Methylenetetrahydrofolate Reductase (MTHFR) Polymorphisms and Non-Alcoholic Fatty Liver Disease (NAFLD) Risk: A Meta-Analysis

Background

C677T and A1298C are the most common allelic variants of Methylenetetrahydrofolate Reductase (MTHFR) gene. The association between MTHFR polymorphisms and the occurrence of non-alcoholic fatty liver disease (NAFLD) remains controversial. This study was thus performed to examine whether MTHFR mutations are associated with the susceptibility to NAFLD.

Methods

A first meta-analysis on the association between the MTHFR polymorphisms and NAFLD risks was carried out via Review Manager 5.0 and Stata/SE 12.0 software. The on-line databases, such as PubMed, EMBASE, CENTRAL, WOS, Scopus and EBSCOhost (updated to April 1^st, 2016), were searched for eligible case-control studies. The odd radio (OR), 95% confidence interval (CI) and P value were calculated through Mantel-Haenszel statistics under random- or fixed-effect model.

Results

Eight articles (785 cases and 1188 controls) contributed data to the current meta-analysis. For C677T, increased NAFLD risks were observed in case group under homozygote model (T/T vs C/C, OR = 1.49, 95% CI = 1.03~2.15, P = 0.04) and recessive model (T/T vs C/C+C/T, OR = 1.42, 95% CI = 1.07~1.88, P = 0.02), but not the other genetics models, compared with control group. For A1298C, significantly increased NAFLD risks were detected in allele model (C vs A, OR = 1.53, 95% CI = 1.13~2.07, P = 0.006), homozygote model (C/C vs A/A, OR = 2.81, 95% CI = 1.63~4.85, P = 0.0002), dominant model (A/C+C/C vs A/A, OR = 1.60, 95% CI = 1.06~2.41, P = 0.03) and recessive model (C/C vs A/A+A/C, OR = 2.08, 95% CI = 1.45~3.00, P<0.0001), but not heterozygote model.

Conclusion

T/T genotype of MTHFR C677T polymorphism and C/C genotype of MTHFR A1298C are more likely to be associated with the susceptibility to NAFLD.

Choline metabolites: gene by diet interactions

PURPOSE OF REVIEW

The review highlights recent advances in our understanding of the interactions between genetic polymorphisms in genes that metabolize choline and the dietary requirements of choline and how these interactions relate to human health and disease.

RECENT FINDINGS

The importance of choline as an essential nutrient has been well established, but our appreciation of the interaction between our underlying genetic architecture and dietary choline requirements is only beginning. It has been shown in both human and animal studies that choline deficiencies contribute to diseases such as nonalcoholic fatty liver disease and various neurodegenerative diseases. An adequate supply of dietary choline is important for optimum development, highlighted by the increased maternal requirements during fetal development and in breast-fed infants. We discuss recent studies investigating variants in PEMT and MTHFR1 that are associated with a variety of birth defects. In addition to genetic interactions, we discuss several recent studies that uncover changes in fetal global methylation patterns in response to maternal dietary choline intake that result in changes in gene expression in the offspring. In contrast to the developmental role of adequate choline, there is now an appreciation of the role choline has in cardiovascular disease through the gut microbiota-mediated metabolite trimethylamine N-oxide. This pathway highlights some of our understanding of how the microbiome affects nutrient processing and bioavailability. Finally, to better characterize the genetic architecture regulating choline requirements, we discuss recent results focused on identifying polymorphisms that regulate choline and its derivative products.

SUMMARY

Here we discuss recent studies that have advanced our understanding of how specific alleles in key choline metabolism genes are related to dietary choline requirements and human disease.

Challenges of liver cancer: Future emerging tools in imaging and urinary biomarkers

Chronic liver disease has become a global health problem as a result of the increasing incidence of viral hepatitis, obesity and alcohol misuse. Over the past three decades, in the United Kingdom alone, deaths from chronic liver disease have increased both in men and in women. Currently, 2.5% of deaths worldwide are attributed to liver disease and projected figures suggest a doubling in hospitalisation and associated mortality by 2020. Chronic liver diseases vary for clinical manifestations and natural history, with some individuals having relatively indolent disease and others with a rapidly progressive course. About 30% of patients affected by hepatitis C has a progressive disease and develop cirrhosis over a 20 years period from the infection, usually 5-10 years after initial medical presentation. The aim of the current therapeutic strategies is preventing the progression from hepatitis to fibrosis and subsequently, cirrhosis. Hepatic steatosis is a risk factor for chronic liver disease and is affecting about the half of patients who abuse alcohol. Moreover non-alcoholic fatty liver disease is part of the metabolic syndrome, associated with obesity, hypertension, type II diabetes mellitus and dyslipidaemia, and a subgroup of patients develops non-alcoholic steatohepatitis and fibrosis with subsequent cirrhosis. The strengths and pitfalls of liver biopsy are discussed and a variety of new techniques to assess liver damage from transient elastography to experimental techniques, such as in vitro urinary nuclear magnetic resonance spectroscopy. Some of the techniques and tests described are already suitable for more widespread clinical application, as is the case with ultrasound-based liver diagnostics, but others, such as urinary metabonomics, requires a period of critical evaluation or development to take them from the research arena to clinical practice.