Plasma homocysteine levels and C677T MTHFR gene polymorphism in stable renal graft recipients

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.

Genetic Predisposition and Renal Allograft Failure

Renal allograft rejection or dysfunction often results in graft failure, and remains the major obstacle in the success of renal transplantation. Various immunological and nonimmunological factors are involved in allograft rejection. In addition to human leukocyte antigen loci, several genetically controlled molecules have been identified in recent years as playing important roles in the process of rejection. Genetic variants in genes encoding different T-helper (Th) type 1 and Th2 cytokines, chemokines and their receptors, growth factors, molecules of the renin-angiotensin system, enzymes of the homocysteine pathway, and proteins acting as substrates of immunosuppressive drugs impact on the success of engraftment and highlight the concept of genetic predisposition to allograft rejection. This review evaluates specific genetic variants and their functional roles in graft failure, with an emphasis on the latest methodologies available for genotyping, and appropriate strategies to enable them to become a tool of predictive and individualized medicine to ensure better transplant outcome.

Role of thrombotic risk factors in end-stage renal disease

INTRODUCTION

Genetic polymorphisms that are found among factors of the coagulation cascade are factor V leiden mutation (FVL), prothrombin (PT), and methylenetetrahydrofolate reductase (MTHFR), reported for thrombotic complications. We have investigated the associations of these gene polymorphisms in patients with end-stage renal disease (ESRD).

METHODS

We genotyped 258 patients for FV G1691A, PT G20210A, and MTHFR (C677T, A1298C) gene by using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis and were compared with 569 healthy controls. Serum folate, total homocysteine (tHcys), and vitamin B(12) were measured in both patients with ESRD and controls.

RESULTS

No homozygous individuals for the mutant AA genotype of FVL G1691A were observed in this study. The frequency of the heterozygous genotypes was (11.2%), which was nearly 3 times higher than that observed in controls (3.2%), with a odds ratio of 3.87 (P = .0001, 95% CI = 2.11-7.11). PT G20210A mutation was missing in both patients and the controls. At MTHFR locus, TT genotype of C677T was present in 9.6% among ESRD, while CC genotype of A1298C was present in 11.7% of the ESRD. In control group, it was significantly low that is, 4.2% and 3.2%, respectively (P = .0034; OR = 2.44, 95% CI = 1.36-4.36 and P < .0001; OR = 4.03; 95% CI = 2.2-7.37). The combined analysis of the 2 genotypes showed further increased risk in ESRD ~15 folds. Further, the carrier of TT and CC genotypes of C677T and A1298C had significantly higher total homocysteine (tHcys) level than those with CC and AA genotypes (P < .001).

CONCLUSION

The carrier of FVL, TT genotype of C677T, and CC genotype of A1298C polymorphisms may act as risk factors for ESRD.

Is there additional effect of MTHFR C677T mutation on lipid abnormalities in renal allograft recipients?

BACKGROUND

The MTHFR C677T mutation and elevated atherogenic lipoprotein levels are known as cardiovascular risk factors in patients with renal transplantation treated with cyclosporine (CsA). The aim of the present study was to eveluate the contribution of MTHFR C677T mutation to the risk of dyslipidemia in renal transplant recipients. We also studied the effect of the MTHFR-C677 T genotype on transplant survival.

METHODS

The study included 29 nondiabetic renal transplant recipients and 27 healthy controls. MTHFR C677T genotypes were determined by PCR and RFLP techniques. Biochemical parameters were measured in a computerized autoanalyzer.

RESULTS

In the patient group, the distribution of the CC, CT, and TT genotypes was 44.8% (n = 13), 37.9% (n = 11), and 17.2% (n = 5), respectively. The frequencies of the C and T alleles were 0.64 and 0.36, respectively. Subjects with the T allele had the highest levels of TC (P <.05) and LDL-C (P <.05); subjects with the CC genotype had the lowest.

CONCLUSIONS

We observed that the MTHFR T allele has an unfavorable effect on serum lipid profile, leading to a rise in the total and LDL cholesterol concentrations. Thus, we believe that MTHFR C allele has a protective effect and MTHFR T allele has a detrimental effect on the serum lipid profile.

Hyperhomocysteinemia in renal transplant recipients

Renal transplantation is a commonly performed curative procedure for end-stage renal disease. With the increase in renal allograft half-lives, attention is now being focused on cardiovascular morbidity and death in the renal transplant recipient (RTR) population. Among the more novel cardiovascular disease (CVD) risk factors for which this group is at risk is hyperhomocysteinemia. Hyperhomocysteinemia has been associated with an increased risk of CVD, although prospective randomized trials designed to prove causality are still ongoing. Since plasma total homocysteine levels are inversely related to renal function, RTRs have a greatly increased prevalence of hyperhomocysteinemia. Other determinants of homocysteine include B-vitamins, albumin, age, and genetic polymorphisms. Although RTRs are resistant to the typical B-vitamin doses used to correct hyperhomocysteinemia in the general population, they do respond to supraphysiologic dose therapy. In terms of prevalence, etiology, and treatment of hyperhomocysteinemia, RTRs are very similar to the much larger chronic renal insufficiency population. For this reason, RTRs have been chosen as an ideal study population in investigating the effect of reducing hyperhomocysteinemia on CVD outcomes.