Association between end-stage diabetic nephropathy and MTHFR (C677T and A1298C) gene polymorphisms

A review of deoxyribonucleic acid-based single-nucleotide polymorphisms in diabetic kidney disease among Asian populations: Challenges and future directions

Diabetic kidney disease (DKD) is a persistent disorder that occurs as a result of long-term diabetes mellitus with genetic and environmental risk factors. The identification of DKD associated single-nucleotide polymorphisms (SNPs) is pivotal for patient screening. This manuscript briefly outlines the pathophysiology and the role of genetic factors in DKD expansion. It further discusses the utility of bioinformatic tools and laboratory techniques requried for the identification of DKD-specific SNPs along with integrated data analysis pipelines valuable to enhance the accuracy of genetic interpretation. A comparative analysis of various SNPs has also been made across diverse Asian populations in conjunction with environmental and lifestyle factors. The clinical relevance of SNPs in predicting DKD progression and stratifying patient risk is highlighted, with focus on gene-specific pathways and associated functional outcomes. The advances in genetic screening, gene-specific therapies, and microbiome-based therapy should help expand the utility of SNPs-based identification of DKD under diverse clinical settings. A structured clinical decision-making framework is proposed to support customized treatment based on SNP profiles. However, this domain has yet to gain widespread recognition with regard to variability in the effects of SNPs across diverse demographies, challenges in clinical translation, and ethical considerations in genetic testing.

The MTHFR C677T/A1298C polymorphism is associated with increased risk of microangiopathy in type 2 diabetes mellitus: A systematic review and meta-analysis

Extensive case-control association studies have been conducted over the past few decades to investigate the relationship between MTHFR polymorphism and type 2 diabetes mellitus (T2DM) microangiopathy. However, the strength of the evidence and clinical significance are unclear. Consequently, a meta-analysis was performed to examine the correlations between two prevalent MTHFR single nucleotide polymorphisms, MTHFR C677T and A1298C, and T2DM microangiopathy. Randomized controlled trials were systematically searched in PubMed, Cochrane, Embase, Web of Science, CNKI, VIP database, China Biology Medicine, and Wanfang until August 2023. A total of 42 studies were included. Random-effect models were utilized to estimate odds ratios (ORs) with 95% confidence intervals (CIs) to assess the association between MTHFR polymorphisms and T2DM microangiopathy susceptibility. T2DM microangiopathy was significantly associated with the MTHFR C677T polymorphism in the overall population (T vs C, OR = 1.43, 95% CI = 1.25-1.64; TT + CT vs CC: OR = 1.56, 95% CI = 1.30-1.88; TT vs CT + CC: OR = 1.66, 95% CI = 1.38-1.99; TT vs CC: OR = 2.03, 95% CI = 1.58-2.60). Additionally, the dominant model revealed that the MTHFR A1298C polymorphism was associated with T2DM microangiopathy (OR = 1.27, 95% CI: 1.09-1.47). This meta-analysis revealed that MTHFR may be involved in the pathogenesis of T2DM microangiopathy, providing a reference for early diagnosis and treatment of T2DM.

Physiological Associations between Vitamin B Deficiency and Diabetic Kidney Disease

The number of people living with chronic kidney disease (CKD) is growing as our global population continues to expand. With aging, diabetes, and cardiovascular disease being major harbingers of kidney disease, the number of people diagnosed with diabetic kidney disease (DKD) has grown concurrently. Poor clinical outcomes in DKD could be influenced by an array of factors-inadequate glycemic control, obesity, metabolic acidosis, anemia, cellular senescence, infection and inflammation, cognitive impairment, reduced physical exercise threshold, and, importantly, malnutrition contributing to protein-energy wasting, sarcopenia, and frailty. Amongst the various causes of malnutrition in DKD, the metabolic mechanisms of vitamin B (B1 (Thiamine), B2 (Riboflavin), B3 (Niacin/Nicotinamide), B5 (Pantothenic Acid), B6 (Pyridoxine), B8 (Biotin), B9 (Folate), and B12 (Cobalamin)) deficiency and its clinical impact has garnered greater scientific interest over the past decade. There remains extensive debate on the biochemical intricacies of vitamin B metabolic pathways and how their deficiencies may affect the development of CKD, diabetes, and subsequently DKD, and vice-versa. Our article provides a review of updated evidence on the biochemical and physiological properties of the vitamin B sub-forms in normal states, and how vitamin B deficiency and defects in their metabolic pathways may influence CKD/DKD pathophysiology, and in reverse how CKD/DKD progression may affect vitamin B metabolism. We hope our article increases awareness of vitamin B deficiency in DKD and the complex physiological associations that exist between vitamin B deficiency, diabetes, and CKD. Further research efforts are needed going forward to address the knowledge gaps on this topic.

The Association of Methylenetetrahydrofolate Reductase (MTHFR) A1298C Gene Polymorphism with Susceptibility to Diabetic Nephropathy: A Meta-Analysis

This meta-analysis was conducted to investigate the association between MTHFR A1298C polymorphism and susceptibility to diabetic nephropathy. PubMed, Embase, Web of Science, Cochrane Library, China national knowledge infrastructure (CNKI) and China Wanfang database were searched for studies on the association between MTHFR A1298C single nucleotide polymorphism and susceptibility to diabetic nephropathy until May 2022. Data were analyzed by Stata 15.0 software. Odds ratio (OR) was used as the effect size. A total of 7 articles were identified, including 1287 cases in the diabetic nephropathy group and 1431 cases in the control group. The pooled OR of allele C at MTHFR A1298C was 1.28 (95% CI: 1.02-1.59, p=0.03) compared with allele A. The pooled OR values of dominant, and heterozygous genetic models were 1.45 (95% CI: 1.13-1.86), and 1.42 (95% CI: 1.19-1.70), respectively, and the differences were all statistically significant. There was no statistical significance in the recessive (OR=1.06, 95% CI: 0.62-1.82), and homozygous gene inheritance models (OR=1.29, 95% CI: 0.72-2.31). In conclusion, MTHFR A1298C polymorphism is associated with susceptibility to diabetic nephropathy. Allele C, genotype CC+AC, and AC at MTHFR A1298C locus can increase the risk of diabetic nephropathy.

MTHFR C667T polymorphism and diabetic nephropathy susceptibility in patients with type 2 diabetes mellitus: An updated meta-analysis

Background

Numerous studies indicated that there exists a relationship between methylenetetrahydrofolate reductase (MTHFR) C667T polymorphism and diabetic nephropathy (DN) susceptibility; nonetheless, available proof reported from individual studies has not been consistent, so we performed an updated meta-analysis to evaluate the relationship between MTHFR C667T variant and DN.

Materials and methods

Relevant studies published before February 2022 were searched from the electronic databases PubMed, Embase, Scopus, Chinese Biology Medicine and the Chinese National Knowledge Infrastructure. The strength of the association was examined by odds ratio (OR) with 95% confidence interval (CI).

Results

The findings illustrated that there was a significant relationship between the polymorphism of C677T and DN compared with that to DM controls in allele (OR = 1.59, 95% CI = 1.39–1.82), dominant (OR = 1.76, 95% CI = 1.47–2.11) and recessive (OR = 1.85, 95% CI = 1.56–2.20) models in all populations. Moreover, as compared with the healthy controls, a significant relationship between C677T and DN was found in three genetic comparison models (allele: OR = 1.81, 95% CI = 1.43–2.29; dominant: OR = 2.09, 95% CI = 1.54–2.85; recessive: OR = 2.02, 95% CI = 1.51–2.70). Furthermore, stratifying data by race, diabetes duration and whether in Hardy–Weinberg equilibrium revealed substantially augmented vulnerability to DN in all subgroups.

Conclusion

The current meta-analysis highlighted conclusive results for the robust association between C677T polymorphisms and DN susceptibility.

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.

Methylenetetrahydrofolate (MTHFR), the One-Carbon Cycle, and Cardiovascular Risks

The 5-10-methylenetetrahydrofolate reductase (MTHFR) enzyme is vital for cellular homeostasis due to its key functions in the one-carbon cycle, which include methionine and folate metabolism and protein, DNA, and RNA synthesis. The enzyme is responsible for maintaining methionine and homocysteine (Hcy) balance to prevent cellular dysfunction. Polymorphisms in the MTHFR gene, especially C677T, have been associated with various diseases, including cardiovascular diseases (CVDs), cancer, inflammatory conditions, diabetes, and vascular disorders. The C677T MTHFR polymorphism is thought to be the most common cause of elevated Hcy levels, which is considered an independent risk factor for CVD. This polymorphism results in an amino acid change from alanine to valine, which prevents optimal functioning of the enzyme at temperatures above 37 °C. Many studies have been conducted to determine whether there is an association between the C677T polymorphism and increased risk for CVD. There is much evidence in favour of this association, while several studies have concluded that the polymorphism cannot be used to predict CVD development or progression. This review discusses current research regarding the C677T polymorphism and its relationship with CVD, inflammation, diabetes, and epigenetic regulation and compares the evidence provided for and against the association with CVD.

Oxidative Stress Genes in Diabetes Mellitus Type 2: Association with Diabetic Kidney Disease

Diabetic type 2 patients compared to nondiabetic patients exhibit an increased risk of developing diabetic kidney disease (DKD), the leading cause of end-stage renal disease. Hyperglycemia, hypertension, oxidative stress (OS), and genetic background are some of the mechanisms and pathways implicated in DKD pathogenesis. However, data on OS pathway susceptibility genes show limited success and conflicting or inconclusive results. Our study is aimed at exploring OS pathway genes and variants which could be associated with DKD. We recruited 121 diabetes mellitus type 2 (DM2) patients with DKD (cases) and 220 DM2, non-DKD patients (control) of Greek origin and performed a case-control association study using genome-wide association data. PLINK and EIGENSOFT were used to analyze the data. Our results indicate 43 single nucleotide polymorphisms with their 21 corresponding genes on the OS pathway possibly contributing or protecting from DKD: SPP1, TPO, TTN, SGO2, NOS3, PDLIM1, CLU, CCS, GPX4, TXNRD2, EPHX2, MTL5, EPX, GPX3, ALOX12, IPCEF1, GSTA, OXR1, GPX6, AOX1, and PRNP. Therefore, a genetic OS background might underlie the complex pathogenesis of DKD in DM2 patients.

Physical Activity Level Influences MTHFR Gene Methylation Profile in Diabetic Patients

Introduction

MTHFR methylation status is associated with microvascular complications in diabetes, but the factors influencing this profile remain unknown.

Objective

The aim of this study was to evaluate the influence of physical activity level and nutritional status on the methylation profile of the MTHFR gene in patients with type 2 diabetes mellitus (T2DM).

Methods

A total of 111 patients, 43 men and 68 women diagnosed with DM (7.0 ± 2.3 years), answered the International Physical Activity Questionnaire (IPAQ) and underwent blood collection for biochemical analysis, DNA extraction, and MTHFR gene methylation profile determination.

Result

The comparison of the methylation pattern showed that the partially methylated profile predominates in the insufficiently active group (85%), which does not occur in the sufficiently active group (54%) (p = 0.012). No differences were found in the nutritional status comparison. Logistic regression including overweight, waist circumference, gender, age, time of DM, hypertension, dyslipidemia, smoking, alcoholism, and family DM revealed that the association of the level of physical activity with methylation profile proved to be independent of these confounding variables. Considering the partially methylated profile as a result, being physically inactive favors the partially methylated MTHFR pattern in patients with DM.

Conclusion

We concluded that insufficient physical activity is associated with partially methylated pattern of MTHFR promoter.

Methylenetetrahydrofolate reductase genetic polymorphism and the risk of diabetic nephropathy in type 2 diabetic patients

BACKGROUND

As indicated by numerous studies, there exists a relationship between the polymorphism of methylenetetrahydrofolate reductase (MTHFR) and susceptibility to diabetic nephropathy (DN) in various populations; nonetheless, the findings remain inconsistent. Therefore, we carried out a meta-analysis to determine the relationship between the MTHFR gene polymorphism and DN susceptibility.

MATERIALS AND METHOD

Related studies were identified from PubMed, Cochrane Library, EMBASE, and the China National Knowledge Infrastructure database (time period: from building the library to October 2019). The strength of the association was examined using odds ratios (ORs) with 95% confidence intervals (95% CIs).

RESULTS

The findings illustrated that the C677T gene polymorphism was significantly associated with an enhanced susceptibility to DN compared to that with diabetes mellitus in allelic (OR = 1.64, 95% CI = 1.34-2.00, P < .001), dominant (OR = 1.85, 95% CI = 1.40-2.46, P < .001), codominant (heterozygote: OR = 1.67, 95% CI = 1.27-2.21, P < .001; homozygote: OR = 2.55, 95% CI = 1.82-3.57, P < .001), and recessive (OR = 1.89, 95% CI = 1.50-2.38, P < .001) models of the overall population. Moreover, as compared with the healthy controls, a significantly augmented susceptibility to DN was found in all 5 genetic comparison models (allelic: OR = 2.06, 95% CI = 1.58-2.67, P < .001; dominant: OR = 2.52, 95% CI = 1.73-3.69, P < .001; codominant: OR = 3.78, 95% CI = 2.50-5.70, P < .001; recessive: OR = 2.41, 95% CI = 1.96-2.97, P < .001). Furthermore, stratifying data by ethnicity revealed substantially augmented vulnerability to DN in not only Caucasian but also Asian populations.

CONCLUSION

The present study suggests that the C677T polymorphism was associated with an augmented susceptibility to DN.

C677T MTHFR Gene Polymorphism is Contributing Factor in Development of Renal Impairment in Young Hypertensive Patients

Homocysteine concentration affected by the activities of the enzymes methylene tetra-hyrdofolate reductase (MTHFR). Polymorphisms in MTHFR gene associated with an impairment of MTHFR activity. Hyperhomocysteinemia is a result of single nucleotide polymorphisms (SNPs) in MTHFR 677 C>T that can cause homocysteine levels in the blood to increase. The purpose of this study is to investigate the relationships between MTHFR C677T (rs1801133) gene polymorphism, changes in homocysteine concentrations and progress of renal impairment in young adult hypertensive patients. Two hundred young hypertensive patients (age 21-24 years) were involved in this study; they were classified into patients with and without renal impairment in addition to 200 age and sex matched healthy controls. All participants were submitted to laboratory investigations as assay of MTHFR gene polymorphism C677T (rs1801133) by PCR/RFLP, determination of lipid profile, homocysteine and folic acid concentrations in addition to urinary albumin creatinine ratio (UACR). The levels of both homocysteine and UACR in the TT genotype patients were higher than those in the CC genotype group. Individuals who carry the T allele were more risky to hypertension and progress to early renal impairment in young age compared with those carrying the C allele [OR 2.02 (1.33-3.08), P < 0.001]. Genetic variants of C677T MTHFR gene and hyperhomocysteinemia may be responsible for rapid progress of renal impairment in Egyptian young age hypertensive patients. TT genotype or T allele may be considered as a predisposing factor for both elevated Hcy levels and the development of renal impairment. This study believed that lowering of homocysteine level can reduce renal impairment of hypertensive patients.

Genetic Variants Associated with Chronic Kidney Disease in a Spanish Population

Chronic kidney disease (CKD) patients have many affected physiological pathways. Variations in the genes regulating these pathways might affect the incidence and predisposition to this disease. A total of 722 Spanish adults, including 548 patients and 174 controls, were genotyped to better understand the effects of genetic risk loci on the susceptibility to CKD. We analyzed 38 single nucleotide polymorphisms (SNPs) in candidate genes associated with the inflammatory response (interleukins IL-1A, IL-4, IL-6, IL-10, TNF-α, ICAM-1), fibrogenesis (TGFB1), homocysteine synthesis (MTHFR), DNA repair (OGG1, MUTYH, XRCC1, ERCC2, ERCC4), renin-angiotensin-aldosterone system (CYP11B2, AGT), phase-II metabolism (GSTP1, GSTO1, GSTO2), antioxidant capacity (SOD1, SOD2, CAT, GPX1, GPX3, GPX4), and some other genes previously reported to be associated with CKD (GLO1, SLC7A9, SHROOM3, UMOD, VEGFA, MGP, KL). The results showed associations of GPX1, GSTO1, GSTO2, UMOD, and MGP with CKD. Additionally, associations with CKD related pathologies, such as hypertension (GPX4, CYP11B2, ERCC4), cardiovascular disease, diabetes and cancer predisposition (ERCC2) were also observed. Different genes showed association with biochemical parameters characteristic for CKD, such as creatinine (GPX1, GSTO1, GSTO2, KL, MGP), glomerular filtration rate (GPX1, GSTO1, KL, ICAM-1, MGP), hemoglobin (ERCC2, SHROOM3), resistance index erythropoietin (SOD2, VEGFA, MTHFR, KL), albumin (SOD1, GSTO2, ERCC2, SOD2), phosphorus (IL-4, ERCC4 SOD1, GPX4, GPX1), parathyroid hormone (IL-1A, IL-6, SHROOM3, UMOD, ICAM-1), C-reactive protein (SOD2, TGFB1,GSTP1, XRCC1), and ferritin (SOD2, GSTP1, SLC7A9, GPX4). To our knowledge, this is the second comprehensive study carried out in Spanish patients linking genetic polymorphisms and CKD.

Association of MTHFR C677T polymorphism and type 2 diabetes mellitus (T2DM) susceptibility

Introduction

Methylenetetrahydrofolate reductase (MTHFR) is essential in mediating folate metabolism, and thus plays an important role in diabetes and diabetic complications. MTHFR C677T (rs1801133 C>T) polymorphism has been proposed to be linked with type 2 diabetes mellitus (T2DM) susceptibility. However, the conclusions are inconsistent. Therefore, we rechecked their linkage aiming to obtain a more reliable estimation by performing an updated meta‐analysis.

Methods

We searched electronic databases PubMed, EMBASE, CNKI, and Wanfang to obtain studies updated to October 2019.

Results

After carefully screening, we finally incorporated 68 studies with 10,812 cases and 8,745 controls. The genotype frequency of C677T polymorphism was analyzed pooled to generate odds ratios (ORs) and 95% confidence intervals (CIs). Pooled results presented that MTHFR C677T polymorphism was significantly associated with T2DM under homozygous (OR = 1.64, 95% CI = 1.39–1.94), heterozygous (OR = 1.38, 95% CI = 1.20–1.59), recessive (OR = 1.41, 95% CI = 1.23–1.61), dominant (OR = 1.47, 95% CI = 1.27–1.70), and allele (OR = 1.37, 95% CI = 1.23–1.52) genetic models. Stratified analysis demonstrated that C677T genotype was associated with T2DM in Asian populations, but not Caucasian and African populations.

Conclusion

Our results indicated that MTHFR C677T polymorphism confers to T2DM, especially in Asian populations. Much more large‐scale case–control studies are needed to strengthen such conclusion in the future.

Assessment of coding region variants in Kuwaiti population: implications for medical genetics and population genomics

Consanguineous populations of the Arabian Peninsula have been underrepresented in global efforts that catalogue human exome variability. We sequenced 291 whole exomes of unrelated, healthy native Arab individuals from Kuwait to a median coverage of 45X and characterised 170,508 single-nucleotide variants (SNVs), of which 21.7% were ‘personal’. Up to 12% of the SNVs were novel and 36% were population-specific. Half of the SNVs were rare and 54% were missense variants. The study complemented the Greater Middle East Variome by way of reporting many additional Arabian exome variants. The study corroborated Kuwaiti population genetic substructures previously derived using genome-wide genotype data and illustrated the genetic relatedness among Kuwaiti population subgroups, Middle Eastern, European and Ashkenazi Jewish populations. The study mapped 112 rare and frequent functional variants relating to pharmacogenomics and disorders (recessive and common) to the phenotypic characteristics of Arab population. Comparative allele frequency data and carrier distributions of known Arab mutations for 23 disorders seen among Arabs, of putative OMIM-listed causal mutations for 12 disorders observed among Arabs but not yet characterized for genetic basis in Arabs, and of 17 additional putative mutations for disorders characterized for genetic basis in Arab populations are presented for testing in future Arab studies.