Impact of methionine synthase gene and methylenetetrahydrofolate reductase gene polymorphisms on the risk of sudden sensorineural hearing loss

A Systematic Review on Heritability of Sudden Sensorineural Hearing Loss

OBJECTIVE

To assess the evidence supporting the heritability and genetic basis of sudden sensorineural hearing loss (SSNHL).

DATA SOURCE

Records were extracted from PubMed, Scopus, and Cochrane databases.

REVIEW METHODS

The protocol was registered on PROSPERO (CRD42022357389) and includes a systematic review on the genetic contribution to SSNHL. The search strategy yielded 1.483 articles from electronic databases. After quality assessment, 34 records were selected, including 369.650 patients with SSNHL from nine prevalence studies, two familial aggregation studies, one twin study, and 22 genetic studies. The prevalence of SSNHL was calculated from data on its incidence from population-based studies (period prevalence). To evaluate the heritability of SSNHL, the sibling recurrence risk ratio (λs) was calculated, by comparing the prevalence of SSNHL among siblings within the same generation to the estimated prevalence in the overall population. Genetic variants were grouped, based on the pathological mechanism related to SSNHL.

RESULTS

The prevalence of SSNHL ranged from 0.1% to 0.0003% in America to 0.12%-0.0093% in Asia. The estimated sibling recurrence risk ratio for SSNHL (λs  = 20.8-83.3) supports a significant familial aggregation. Although several genetic variants were reported to be associated with SSHL in controlled studies, neither was replicated in an independent cohort.

CONCLUSIONS

Evidence supporting heritability of SSNHL is limited to epidemiological studies showing prevalence differences across different populations and familial aggregation. Genetic studies are of low quality and they lack replication cohort to confirm their findings. According to its low prevalence, exome or genome sequencing familial-based studies are needed to identify rare genetic variants in SSNHL.

LEVEL OF EVIDENCE

NA Laryngoscope, 2024.

Deafness gene screening based on a multilevel cascaded BPNN model

Sudden sensorineural hearing loss is a common and frequently occurring condition in otolaryngology. Existing studies have shown that sudden sensorineural hearing loss is closely associated with mutations in genes for inherited deafness. To identify these genes associated with deafness, researchers have mostly used biological experiments, which are accurate but time-consuming and laborious. In this paper, we proposed a computational method based on machine learning to predict deafness-associated genes. The model is based on several basic backpropagation neural networks (BPNNs), which were cascaded as multiple-level BPNN models. The cascaded BPNN model showed a stronger ability for screening deafness-associated genes than the conventional BPNN. A total of 211 of 214 deafness-associated genes from the deafness variant database (DVD v9.0) were used as positive data, and 2110 genes extracted from chromosomes were used as negative data to train our model. The test achieved a mean AUC higher than 0.98. Furthermore, to illustrate the predictive performance of the model for suspected deafness-associated genes, we analyzed the remaining 17,711 genes in the human genome and screened the 20 genes with the highest scores as highly suspected deafness-associated genes. Among these 20 predicted genes, three genes were mentioned as deafness-associated genes in the literature. The analysis showed that our approach has the potential to screen out highly suspected deafness-associated genes from a large number of genes, and our predictions could be valuable for future research and discovery of deafness-associated genes.

The relationship between serum homocysteine levels and sudden sensorineural hearing loss: a meta-analysis

OBJECTIVE

There was disagreement over the association between serum/plasma homocysteine (HCY) levels and sudden sensorineural hearing loss (SSNHL). Through the use of a meta-analysis, this study aims to determine whether there is a significant difference in serum homocysteine levels between the SSNHL group and the control group.

DESIGN

The Cochrane Library, EMBASE, and PubMed databases were all thoroughly searched. The two independent reviewers thoroughly examined the initially searched articles. The data results were calculated by standard mean difference (SMD) or odds ratios (OR). Review Manager (version 5.3) was applied to statistical data.

STUDY SAMPLE

There were 766 participants in the 6 trials with continuous outcomes that were part of the meta-analysis A. In addition, meta-analysis B, which included 961 people, contained a total of 3 studies with dichotomous results.

RESULTS

Both meta-analyses revealed the same conclusion that serum/plasma HCY levels in the SSNHL patients are higher than those in the controls (SMD 0.41, 95 % confidence interval (CI) 0.11 to 0.72, P < 0.01; OR 3.27, 95 % CI 2.16 to 4.94, P < 0.01).

CONCLUSION

This study demonstrated that the SSNHL patients' serum/plasma HCY levels were greater than those of the control group.

MTHFR AND ApoE genetic variants association with sudden sensorineural hearing loss

HYPOTHESIS

Although the pathogenesis of sudden sensorineural hearing loss (SSNHL) is not clear, however several causes including genetic factors seems to be implicated. We hypothesized that common genetic variants might be involved in SSNHL.

BACKGROUND

SSNHL is known to be an idiopathic disease because the causative factors have not been identified. Several causes including genetic and viral infection besides immune system reaction, neurological disorders, medications, etc. have been previously reported. We examined the association between ApoE and MTHFR gene variants in SSNHL.

METHODS

This study includes case-control scheme encompassing a total of 177 individuals, include patients inflicted with SSNHL and healthy subjects as control group. Genotyping of MTHFR and ApoE variants was conducted by PCR - RFLP method.

RESULT

Our study showed that MTHFR rs1801133 allele frequency is significantly different between cases and controls. Also genotype distribution of ApoE was significantly different between patients and healthy controls.

CONCLUSIONS

MTHFR C677T and ApoE gene variant may be associated with sudden sensorineural hearing loss in an Iranian population.

Cause of idiopathic sudden sensorineural hearing loss: The stress response theory

The stress response theory is a relatively new concept about the cause of idiopathic sudden sensorineural hearing loss (ISHL). A number of possible etiologies have been proposed in the literature, as discussed in this paper, but each proposed etiology has been both supported and refuted in the literature. However, the stress response theory can integrate hypotheses that have been advocated so far. The word “stress” refers to a constellation of physical and psychological stimuli including systemic viral and bacterial illness, systemic inflammatory disorders, and physical, mental or metabolic stress. Numerous studies have demonstrated adverse effects of systemic stress on health. Stress causes changes in the immune system and cytokine network through activation of the hypothalamus-pituitary-adrenal axis and the sympathetic nervous system. Several types of catecholamine and cytokine receptors are in the cochlea cells other than capillary cells, and then they can respond to systemic stressors. However, there are few studies examining how systemic stress is associated with cochlear dysfunction. The stress response theory addresses this question. In the theory, a variety of stressors and risk factors contribute to the onset of ISHL in varying degrees. The lateral wall of the cochlea has very unique responses to systemic stressors. It plays a critical role in causing ISHL. Systemic stressors converge at the lateral wall and trigger pathological activation of nuclear factor κ-light-chain-enhancer of activated B cells, a transcriptional factor known as a stress sensor. This activation enhances local expression of genes associated with immune and inflammatory system, resulting in cochlear dysfunction. We review the original stress response theory advocated by Adams et al and the integrative stress response theory that integrates our knowledge about the etiologies of ISHL so far.

Association between polymorphisms in genes encoding methylenetetrahydrofolate reductase and the risk of Ménière's disease

Folate metabolism is essential for cellular functioning. Despite extensive research on the roles of folate-metabolism-related gene polymorphisms in the pathophysiology of many diseases, such as cardiovascular disease, cancers, and sudden sensorineural hearing loss, little is known about their association with Ménière's disease (MD). The aim of this study was to investigate the effect of methylenetetrahydrofolate reductase (MTHFR) gene polymorphisms (C677T and A1298C) on the risk of MD in a Japanese population. We examined the C677T and A1298C (rs1801133 and rs1801131) polymorphisms in the MTHFR gene and compared them between 1946 adults (986 men and 960 women) participating in the National Institute for Longevity Sciences Longitudinal Study of Aging and 86 cases of MD. A multiple logistic regression was performed to obtain odds ratios (ORs) for the risk of MD regarding the MTHFR polymorphisms before (model 1) and after (model 2) adjustment for age and sex factors. The OR of MTHFR C677T for the risk of MD was 0.669 (95% confidence interval [CI], 0.479-0.934) in model 1 and 0.680 (95% CI, 0.484-0.954) in model 2. In contrast, the OR of MTHFR A1298C for the risk of MD was 1.503 (95% CI, 1.064-2.123) in model 1 and 1.505 (95% CI, 1.045-2.167) in model 2. Our results imply that the MTHFR C677T and A1298C polymorphisms are associated with the risk of MD.

MTHFR 677T is a strong determinant of the degree of hearing loss among Polish males with postlingual sensorineural hearing impairment

Hearing impairment (HI) is the most common sensory handicap. Congenital HI often has a genetic basis, whereas the etiology of nonsyndromic postlingual HI (npHI) usually remains unidentified. Our purpose was to test whether the MTHFR C677T (rs1801133) polymorphism affecting folate metabolism is associated with the occurrence or severity of npHI. We studied rs1801133 genotypes in 647 npHI patients (age <40, sudden sensorineural loss excluded, HI characterized as mean of better ear hearing thresholds for 0.5-8 kHz) and 3273 adult controls from the background population. Genotype distribution among patients and controls was similar, but among male cases (n = 302) we found a dose-dependent correlation of MTHFR 677T with the degree of HI (mean thresholds in dB: 38.8, 44.9, and 53.3, for CC, CT, and TT genotypes, respectively; p = 0.0013, p(cor.) = 0.017). Among male patients rs1801133 TT significantly increased the risk of severe/profound HI (odds ratio = 4.88, p = 0.001). Among controls the known effect of MTHFR 677T on plasma total homocysteine was more pronounced in men than in women (p<0.00004 for genotype-sex interaction) suggesting that in Poland folate deficiency is more prevalent in males. In conclusion, we report a novel strong effect of MTHFR 677T among males with npHI. The functional significance of rs1801133 suggests that these patients may benefit from folate supplementation-an intervention which is simple, cheap, and devoid of side effects.

Contribution of complement factor H Y402H polymorphism to sudden sensorineural hearing loss risk and possible interaction with diabetes

Sudden sensorineural hearing loss (SSNHL) is one of the most common diseases encountered by otolaryngologists; however, the etiology is unclear. The aim of this study was to assess the association between SSNHL and polymorphism of complement factor H (CFH) Y402H, which is implicated in age-related macular degeneration. We conducted a case-control study, in which the cases were 72 SSNHL patients and the controls were 2161 residents selected randomly from the resident register. The odds ratio (OR) for SSNHL risk was determined using the additive-genetic model of CFH Y402H polymorphism. The OR for SSNHL risk was 1.788 (95% confidence interval [CI]: 1.008-3.172) with no adjustments and 1.820 (CI: 1.025-3.232) after adjusting for age and sex. Of the three lifestyle-related diseases hypertension, dyslipidemia, and diabetes, only diabetes was significantly associated with SSNHL risk. We classified both the controls and SSNHL patients into those with or without diabetes, and the OR for SSNHL risk was 6.326 (CI: 1.885-21.225) in diabetic subjects and 1.214 (CI: 0.581-2.538) in nondiabetic subjects. We conclude that CFH Y402H polymorphism and SSNHL risk are significantly related, and that diabetic CFH Y402H minor allele carriers may be susceptible to SSNHL.

Systematic review and meta-analysis of the risk factors for sudden sensorineural hearing loss in adults

OBJECTIVES/HYPOTHESIS

To review the medical literature evidence of potential risk factors for sudden sensorineural hearing loss (SSNHL) in the adult general population.

STUDY DESIGN

Systematic review of prospective and retrospective studies; meta-analysis of case-controlled studies.

METHODS

Three researchers independently reviewed MEDLINE (January 1, 1950-November 30, 2010), Embase (January 1, 1980-November 30, 2010), and Evidence-Based Medicine Reviews databases in addition to conducting a manual reference search. Randomized controlled trials, prospective cohort studies, consecutive/nonconsecutive case series, and retrospective reviews in which a clear definition of SSNHL was stated were included in the study. Researchers individually extracted data regarding patient information and the presumed risk factors. Discrepancies were resolved by mutual consensus.

RESULTS

Twenty-two articles met the inclusion criteria. Cardiovascular risk factors (smoking, increased alcohol consumption) appeared to be associated with a higher risk of developing SSNHL. A low level of serum folate may also be implicated as a risk factor. Factor V Leiden and MTHFR gene polymorphisms were found to occur more frequently in patients with SSNHL in several studies, suggesting these inherited prothrombophilic mutations could be independent risk factors of SSNHL.

CONCLUSIONS

Acquired and inherited cardiovascular risk factors appeared to be associated with an increased risk of developing SSNHL.

Endothelial progenitor cells in sudden sensorineural hearing loss

CONCLUSIONS

Endothelial progenitor cells (EPCs) are a unique subtype of circulating cells with properties similar to those of embryonal angioblasts. They have the potential to proliferate and to differentiate into mature endothelial cells. EPCs are reduced in patients with vascular risk factors due to a decreased mobilization, an increased consumption at the site of damage or a reduced half-life. The results of this study confirm the existence of an endothelial dysfunction in patients with sudden sensorineural hearing loss (SSHL) and support the vascular involvement in the pathogenesis of the disease.

OBJECTIVE

The aim of this study was to evaluate the concentration of EPCs in patients affected by SSHL.

METHODS

Twenty-one patients affected by SSHL were evaluated. The number of EPCs was analyzed by flow cytometry analysis of peripheral blood CD34+KDR+CD133+ cells.

RESULTS

Circulating levels of EPCs were significantly lower in SSHL patients compared with controls. In particular, CD34+KDR+ cells and CD34+CD133+KDR+ cells were significantly reduced (p < 0.05).

Hearing impairment risk and interaction of folate metabolism related gene polymorphisms in an aging study

Background

Recent investigations demonstrated many genetic contributions to the development of human age-related hearing impairment (ARHI), however, reports of factors associated with a reduction in the ARHI risk are rare. Folate metabolism is essential for cellular functioning. Despite the extensive investigations regarding the roles of folate metabolism related gene polymorphisms in the pathophysiology of complex diseases, such as cancer, cardio-cerebrovascular disease, and atherosclerosis, little is known about the association with ARHI. The aim of this study is to investigate the effects of the methionine synthase (MTR) A2756G and methylenetetrahydrofolate reductase (MTHFR) C677T gene polymorphisms on the risk of hearing impairment in middle-aged and elderly Japanese.

Methods

Data were collected from community-dwelling Japanese adults aged 40-84 years who participated in the Longitudinal Study of Aging biennially between 1997 and 2008. We analyzed cumulative data (5,167 samples in accumulated total) using generalized estimating equations.

Results

The MTHFR 677T allele was significantly associated with a reduced risk of hearing impairment only when the subjects were wild-type homozygotes for MTR A2756G. The per-T allele odds ratio of MTHFR for the risk of developing hearing impairment was 0.7609 (95% CI: 0.6178-0.9372) in the MTR AA genotype. In addition, a subgroup analysis demonstrated that the favorable effect of the MTHFR 677T allele on the risk of developing hearing impairment was independent of folate and homocysteine level, whereas plasma total homocysteine level was independently associated with an increased risk of developing hearing impairment. The interactive effect of gene polymorphisms associated with folate metabolism may modify the risk of developing hearing impairment after middle age. These results contribute to the elucidation of the causes of ARHI.

Conclusions

The present study has found that the MTHFR 677T allele has a favorable effect on a risk of hearing impairment in the middle-aged and elderly population, only when the individuals were wild-type homozygotes for MTR A2756G.

Variation in folate pathway genes and distal colorectal adenoma risk: a sigmoidoscopy-based case-control study

Background

Folate-associated one-carbon metabolism (FOCM) is an important pathway in colorectal neoplasia risk but data on genetic variation in this pathway are largely limited to studies of single SNPs in selected genes.

Methods

We used a comprehensive tagSNP approach to study the association between genetic variation in 11 genes in the FOCM pathway and risk of incident distal colorectal adenomas in a sigmoidoscopy-based case–control study. We included 655 cases (one or more adenomas) and 695 controls (no adenomas) recruited from one of two Kaiser Permanente clinics between 1991 and 1995. We assessed a total of 159 tagSNPs selected using Haploview Tagger as well as selected non-synonymous SNPs. We used unconditional logistic regression to model the association between SNPs and risk of distal adenomas, assuming a log-additive model.

Results

Five SNPs in the SLC19A1 (RFC1) gene: rs1051266 (G80A), rs283895, rs2236484, rs12482346, and rs2838958 were associated with adenoma risk after correction for multiple testing (all corrected p values ≤0.043). The non-synonymous SLC19A1 SNP G80A interacted significantly with the MTHFRC677T genotype (interaction p value = 0.018).

Conclusion

Our data suggest that genetic variation in SLC19A1 may modify the risk of distal colorectal adenoma.

Electronic supplementary material

The online version of this article (doi:10.1007/s10552-011-9726-7) contains supplementary material, which is available to authorized users.

Association of the C677T polymorphism in the methylenetetrahydrofolate reductase gene with sudden sensorineural hearing loss

OBJECTIVES/HYPOTHESIS

To investigate the recently reported association of the C677T polymorphism in the methylenetetrahydrofolate reductase (MTHFR) gene with sudden sensorineural hearing loss (SSNHL), we analyzed data from a community-based Japanese population.

STUDY DESIGN

Nested case-control study.

METHODS

Among 2,174 adults (1,096 males and 1,078 females) aged 40 to 79 years old who participated in the National Institute for Longevity Sciences-Longitudinal Study of Aging, we compared 33 cases of prevalent SSNHL, defined as a self-reported otolaryngologist diagnosis, with the other cases. Multiple logistic regression was used to obtain odds ratios (ORs) for SSNHL in subjects with the MTHFR C677T polymorphism, with adjustment for other possibly influential factors under additive, dominant, and recessive genetic models.

RESULTS

The per-allele ORs for SSNHL risk were 1.687 (95% confidence interval [CI], 1.023-2.780) in model 1, with adjustment for age and sex, and 1.654 (CI, 1.003-2.728) in model 2, with adjustment for smoking status, body mass index, histories of heart disease, hypertension, and diabetes, in addition to the factors in model 1. In model 3, a significant association between SSNHL and the C677T polymorphism was observed under all genetic models independent of factors including folic acid and homocysteine, although there were only 25 cases and 1,677 controls due to the addition of moderating factors.

CONCLUSIONS

Our results suggest that the T allele of MTHFR C677T could be associated with susceptibility to SSNHL, and even imply that this mutation could be a risk factor that is independent of blood folic acid and homocysteine.

Methylenetetrahydrofolate reductase C677T gene mutation as risk factor for sudden sensorineural hearing loss: association with plasma homocysteine, folate and cholesterol concentrations

Objective:

Impaired cochlear perfusion appears to be the most important event in the development of sudden sensorineural hearing loss. Methylenetetrahydrofolate reductase gene mutations at nucleotide 677 cause reduced methylenetetrahydrofolate reductase enzyme activity, resulting in vascular impairment.

Methods:

Thirty-three patients and 68 control subjects underwent audiological and haematological investigation.

Results:

No statistically significant association was found between sudden sensorineural hearing loss and the methylenetetrahydrofolate reductase C677T gene mutation. Mean homocysteine and cholesterol concentrations were significantly higher in patients than in controls. Mean folate levels were significantly lower in patients than in controls. Amongst patients with sudden sensorineural hearing loss, no significant differences in mean cholesterol, homocysteine or folate concentration were found, comparing patients with methylenetetrahydrofolate reductase C677T mutation genotypes with those without.

Conclusion:

No statistically significant association was found between the methylenetetrahydrofolate reductase C677T gene mutation and sudden sensorineural hearing loss. There was a statistically significant difference between the homocysteine, folate and cholesterol concentrations of sudden sensorineural hearing loss patients, compared with controls. However, there was no statistically significant difference in these levels, comparing patients with and without the methylenetetrahydrofolate reductase C677T mutation.

Candidate genes of cerebrovascular disease and sudden sensorineural hearing loss

Auditory dysfunction is related to large/small vessel occlusions and hemorrhage. Sudden sensorineural hearing loss (SSNHL) frequently occurs with anterior inferior cerebellar artery occlusion proximal to the internal auditory artery. Moreover, SSNHL has various pathogenetic mechanisms, the main proposed mechanisms being vascular disease, membrane ruptures, infection, and autoimmunity. Tumor necrosis factor (TNF) is an important cytokine in the inflammation process of cerebrovascular diseases. In the current study, the possible effects of polymorphisms in TNF-alpha and TNF-beta genes on SSNHL are evaluated. Two genetic polymorphisms in the TNF locus (TNF-alpha -308 G - ->A and TNF-beta +252 A - ->G) were investigated as risk factors for SSNHL by determining their prevalence in 97 SSNHL patients and in 587 controls. A significant increase was found for the TNF-beta allele 1 in SSNHL patients compared with the controls (chi( 2) = 7.251, P = .007, odds ratio [OR] = 1.534, confidence interval [CI] = 1.12-2.10). These findings suggest that the TNF-beta +252 locus plays an important role in the etiopathogenesis of SSNHL.

Prothrombotic Gene Mutations in Patients with Sudden Sensorineural Hearing Loss and Cardiovascular Thrombotic Disease

Objectives:

Impaired cochlear perfusion seems to be an important event in sudden sensorineural hearing loss. Prothrombotic gene mutations have been related to vascular disorders and sudden hearing loss. We assessed the prothrombotic risk in 10 patients with sudden sensorineural hearing loss who had previously experienced cardiovascular events to support its vascular pathogenesis.

Methods:

Ten patients underwent hematologic tests (MTHFR C677T/A1298C, prothrombin G20210A, platelet GlyIIIaA1/A2, and V Leiden G1691A genotyping; fibrinogenemia; cholesterolemia; homocysteinemia; folatemia). The results were compared with those of 100 previously investigated patients with sudden hearing loss alone and those of 200 healthy controls. DNA was isolated from peripheral blood leukocytes, and the gene mutations were investigated by polymerase chain reaction and a LightCycler DNA analyzer.

Results:

Two patients had 2 mutant alleles, 6 had 3, and 2 had 4. The mean homocysteine, cholesterol, and fibrinogen levels were above the upper limit of normal; the mean folate levels were slightly above the lower limit of normal. Multiple mutations were more frequent in the patient group than in the previously analyzed patients and healthy controls.

Conclusions:

The association between inherited and acquired prothrombotic factors in patients with sudden sensorineural hearing loss and thrombotic diseases in other sites suggests that a multifactorial mechanism may underlie microvascular cochlear impairment. Hematologic investigation, including MTHFR, prothrombin, platelet, and V Leiden genotyping, may help to detect patients at potential risk of recurrent hearing loss and multiple microvascular diseases, and could be usefully performed in otherwise idiopathic sudden sensorineural hearing loss.

Genetic and acquired prothrombotic risk factors and sudden hearing loss

OBJECTIVES

Idiopathic sudden sensorineural hearing loss (ISSNHL) is a frequently encountered condition, and various pathogenetic mechanisms have been hypothesized, such as viral infections, autoimmune processes, and ischemic events; however, whatever the cause, impaired cochlear perfusion appears to be the most important event. A number of inherited prothrombotic risk factors and their related genetic alterations have recently been correlated with vascular disorders.

METHODS

To investigate the mechanisms of vascular thrombosis of the inner ear leading to sudden HL, we examined 100 patients with SSNHL for the presence of acquired or inherited prothrombotic risk factors and 200 healthy volunteers as controls. All of the subjects underwent hematologic examinations, including MTHFR C677T and A1298C, prothrombin G20210A, platelet GlyIIIaA1/A2, V Leiden G1691A genotyping, fibrinogenemia, cholesterolemia, homocystinemia, and folatemia. Genomic DNA was isolated from peripheral blood leukocytes using standard methods, and gene mutations were investigated using a LightCycler DNA analyser and polymerase chain reaction.

RESULTS

A statistically significant association was found between SSNHL and the MTHFR C677T/A1298C polymorphisms, the prothrombin G20210A transition, and the platelet GlyIIIa and V Leiden G1691A mutations. Furthermore, the SSNHL patients had significantly higher levels of fibrinogenemia, cholesterolemia, and homocystinemia and lower levels of folatemia than the controls (P < .0001).

CONCLUSIONS

The association between inherited and acquired prothrombotic factors and sudden HL suggests that the microvascular impairment causing SSNHL may be caused by a multifactorial mechanism. All patients with ISSNHL should undergo a comprehensive hematologic investigation of inherited and acquired prothrombotic factors, including MTHFR polymorphisms, the prothrombin transition, and the platelet and V Leiden mutations, to identify a subset of patients at high risk of recurrent HL.