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

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.

Genetic Polymorphisms in Sudden Sensorineural Hearing Loss: An Update

OBJECTIVE

To investigate the association between genetic polymorphisms and sudden sensorineural hearing loss (SSNHL). Most of the SSNHL cases still remain idiopathic, and several etiopathogenetic hypotheses, including a genetic predisposition, have been proposed.

METHODS

A literature review was conducted using different databases: Medline/PubMed, EMBASE, and CINAHL, according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. All databases have been searched from May 2016 to April 2020.

RESULTS

Genetic susceptibility could represent a key element in the pathogenesis of SSNHL. A number of genetic polymorphisms related to (1) inner ear microvascular disease and endothelial dysfunction and (2) to inner ear oxidative stress and inflammation have been addressed in the current literature.

CONCLUSIONS

The potential identification of a genetic profile related to SSNHL could provide a more accurate prognostic evidence of idiopathic SSNHL (ISSNHL), offering to the patients not only early-prevention strategies but eventually information on various inheritance modalities.

Rare Variants of Putative Candidate Genes Associated With Sporadic Meniere's Disease in East Asian Population

Objectives: The cause of Meniere's disease (MD) is unclear but likely involves genetic and environmental factors. The aim of this study was to investigate the genetic basis underlying MD by screening putative candidate genes for MD.

Methods: Sixty-eight patients who met the diagnostic criteria for MD of the Barany Society were included. We performed targeted gene sequencing using next generation sequencing (NGS) panel composed of 45 MD-associated genes. We identified the rare variants causing non-synonymous amino acid changes, stop codons, and insertions/deletions in the coding regions, and excluded the common variants with minor allele frequency >0.01 in public databases. The pathogenicity of the identified variants was analyzed by various predictive tools and protein structural modeling.

Results: The average read depth for the targeted regions was 1446.3-fold, and 99.4% of the targeted regions were covered by 20 or more reads, achieving the high quality of the sequencing. After variant filtering, annotation, and interpretation, we identified a total of 15 rare heterozygous variants in 12 (17.6%) sporadic patients. Among them, four variants were detected in familial MD genes (DTNA, FAM136A, DPT), and the remaining 11 in MD-associated genes (PTPN22, NFKB1, CXCL10, TLR2, MTHFR, SLC44A2, NOS3, NOTCH2). Three patients had the variants in two or more genes. All variants were not detected in our healthy controls (n = 100). No significant differences were observed between patients with and without a genetic variant in terms of sex, mean age of onset, bilaterality, the type of MD, and hearing threshold at diagnosis.

Conclusions: Our study identified rare variants of putative candidate genes in some of MD patients. The genes were related to the formation of inner ear structures, the immune-associated process, or systemic hemostasis derangement, suggesting the multiple genetic predispositions in the development of MD.

Nutritional Mushroom Treatment in Meniere's Disease with Coriolus versicolor: A Rationale for Therapeutic Intervention in Neuroinflammation and Antineurodegeneration

Meniere's disease (MD) represents a clinical syndrome characterized by episodes of spontaneous vertigo, associated with fluctuating, low to medium frequencies sensorineural hearing loss (SNHL), tinnitus, and aural fullness affecting one or both ears. To date, the cause of MD remains substantially unknown, despite increasing evidence suggesting that oxidative stress and neuroinflammation may be central to the development of endolymphatic hydrops and consequent otholitic degeneration and displacement in the reuniting duct, thus originating the otolithic crisis from vestibular otolithic organs utricle or saccule. As a starting point to withstand pathological consequences, cellular pathways conferring protection against oxidative stress, such as vitagenes, are also induced, but at a level not sufficient to prevent full neuroprotection, which can be reinforced by exogenous nutritional approaches. One emerging strategy is supplementation with mushrooms. Mushroom preparations, used in traditional medicine for thousands of years, are endowed with various biological actions, including antioxidant, immunostimulatory, hepatoprotective, anticancer, as well as antiviral effects. For example, therapeutic polysaccharopeptides obtained from Coriolus versicolor are commercially well established. In this study, we examined the hypothesis that neurotoxic insult represents a critical primary mediator operating in MD pathogenesis, reflected by quantitative increases of markers of oxidative stress and cellular stress response in the peripheral blood of MD patients. We evaluated systemic oxidative stress and cellular stress response in MD patients in the absence and in the presence of treatment with a biomass preparation from Coriolus. Systemic oxidative stress was estimated by measuring, in plasma, protein carbonyls, hydroxynonenals (HNE), and ultraweak luminescence, as well as by lipidomics analysis of active biolipids, such as lipoxin A4 and F2-isoprostanes, whereas in lymphocytes we determined heat shock proteins 70 (Hsp72), heme oxygenase-1 (HO-1), thioredoxin (Trx), and γ-GC liase to evaluate the systemic cellular stress response. Increased levels of carbonyls, HNE, luminescence, and F2-isoprostanes were found in MD patients with respect to the MD plus Coriolus-treated group. This was paralleled by a significant (p < 0.01) induction, after Coriolus treatment, of vitagenes such as HO-1, Hsp70, Trx, sirtuin-1, and γ-GC liase in lymphocyte and by a significant (p < 0.05) increase in the plasma ratio-reduced glutathione (GSH) vs. oxidized glutathione (GSSG). In conclusion, patients affected by MD are under conditions of systemic oxidative stress, and the induction of vitagenes after mushroom supplementation indicates a maintained response to counteract intracellular pro-oxidant status. The present study also highlights the importance of investigating MD as a convenient model of cochlear neurodegenerative disease. Thus, searching innovative and more potent inducers of the vitagene system can allow the development of pharmacological strategies capable of enhancing the intrinsic reserve of vulnerable neurons, such as ganglion cells to maximize antidegenerative stress responses and thus providing neuroprotection.

Association between Uncoupling Protein 2 Gene Ala55val Polymorphism and Sudden Sensorineural Hearing Loss

OBJECTIVES

The pathology of sudden sensorineural hearing loss, which is known as sudden deafness (SD), remains unknown. The purpose of this study was to investigate the association between mitochondrial uncoupling protein 2 (UCP2) polymorphism and SD risk.

MATERIALS AND METHODS

We compared 83 patients suffering from SD and 2048 controls who participated in the Longitudinal Study of Aging at the National Institute for Longevity Sciences. Multiple logistic regression was used to calculate the odds ratios (ORs) for SD with a polymorphism of the UCP2 (rs660339) gene.

RESULTS

Under the additive model of inheritance, UCP2 polymorphisms showed significant association with a SD risk. The OR was 1.468 (95% confidence interval, 1.056-2.040) with an adjustment for any past history, such as diabetes, dyslipidemia, or hypertension, and for age and sex.

CONCLUSION

Our results imply that the UCP2 (rs660339) polymorphism has a significant association with the risk of developing SD.

Early Magnetic Resonance Imaging for Patients With Idiopathic Sudden Sensorineural Hearing Loss in an Emergency Setting

OBJECTIVE

The role of magnetic resonance (MR) imaging in idiopathic sudden sensorineural hearing loss (ISSHL) is controversial due to the inhomogeneity of clinical and MR protocols. The aim of this work is to relate early MR findings obtained immediately after the admission, with the clinical presentation, the audiological findings, and the outcomes of treatment.

STUDY DESIGN

Prospective observational study.

SETTING

Tertiary referral university center.

PATIENTS

Forty-seven patients (22 M, 25 F; age: 54.4 ± 17.5 yr) consecutively referred to the Department of Emergency for ISSHL.

INTERVENTIONS

All patients underwent the diagnostic and therapeutic work-up for ISSHL, and MR imaging within 72 hours from the admission, independently of the symptoms onset. All patients received the same treatment (systemic steroid therapy, intratympanic steroid injection, and hyperbaric oxygen therapy).

MAIN OUTCOME MEASURE(S)

MR patterns, clinical, and laboratory findings.

RESULTS

MR imaging was positive in 25 of 47 cases (53%), with a perfect agreement between clinical and MR examinations (Cohen K = 1) upon the affected ear. Three different radiological patterns were observed: labyrinthine haemorrhage (n = 5), acute inflammatory process (n = 14), isolated blood-labyrinth barrier breakdown (n = 6). By binary logistic regression, only vertigo was associated with a positive MR imaging [B = 2.8; p = 0.011; OR = 9.5 (95% CI: 2.2-40.8)] and the latter was the only variable associated with an unfavorable outcome [(B = 2.8; p = 0.02 OR = 12.8 (95% CI: 2.9-56.7)].

CONCLUSION

Patients affected by ISSHL with associated vertigo show a higher likelihood of having a positive MR imaging, which, in turn, seems to predict an unfavorable outcome.

Genetic Polymorphisms and Susceptibility to Sudden Sensorineural Hearing Loss: A Systematic Review

BACKGROUND

Recently, genetic factors have been considered as an important risk factor for sudden sensorineural hearing loss (SSNHL). Many studies analyzed the association between SSNHL and polymorphisms. However, most of them gave inconclusive results. Key Message: We performed a systematic review to find out the association between polymorphisms and susceptibility to SSNHL. Finally, 47 studies involving 5,230 SSNHL patients and 68 genes were included for analysis and discussion of results. Polymorphisms in 26 genes have been suggested to be correlated with the susceptibility to SSNHL.

SUMMARY

Although a great number of studies support that polymorphisms in genes are associated with susceptibility to SSNHL, we need large multicenter studies, which evaluate multiple single nucleotide polymorphisms in SSNHL patients, to find real genetic risk factors for susceptibility to SSNHL. This is very helpful in designing more effective prevention and treatment strategies for patients with SSNHL.

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.

Prognostic impact of gene polymorphisms in patients with idiopathic sudden sensorineural hearing loss

OBJECTIVE

To investigate whether genetic polymorphisms (single-nucleotide polymorphism [SNPs]) have a prognostic influence on hearing recovery after standardized corticosteroid therapy.

METHODS

A total of 192 gene samples from idiopathic sudden sensorineural hearing loss (SSNHL) patients registered in the Intractable Inner Ear Disease Gene Bank were enrolled and, as the candidate genes, 16 SNPs from 13 genes were selected for this study. Fischer's exact test was used to compare allele frequencies in each SNP between the patients with good hearing recovery and patients with poor hearing recovery.

RESULTS

The SNPs of the GSR gene (rs2251780 and rs3779647) and NOS3 gene (rs1799983) were associated with treatment outcome (p < .05). Furthermore, there was a marginal correlation between the SNP of the NR3C1 gene (rs4912910) and treatment outcome (p = .05).

CONCLUSIONS

The results of this study indicate that the analysis of genetic factors might make it possible to predict the treatment outcome, at least in part, in patients with idiopathic SSNHL.

Endothelial Dysfunction in Idiopathic Sudden Sensorineural Hearing Loss: A Review

An endothelial dysfunction has been described in idiopathic sudden sensorineural hearing loss (ISSHL) patients. The purpose of our review was to: i) identify, evaluate and review recent research about cardiovascular risk factors involvement and signs of endothelial dysfunction in ISSHL; ii) implication of these discovering in clinical practice and future research. A Medline literature search was conducted to identify any study on the involvement of endothelial dysfunction in ISSHL, published in the English language in the last decade. The following MEDLINE search terms were used: sudden sensorineural hearing loss (SSHL) and endothelial dysfunction (text words). Additional studies were identified by hand searching the references of original articles and review articles. Studies were not excluded on the basis of the qualitative or quantitative definitions of SSHL, treatment regimens, or outcome measures. Data were extracted from included papers by a reviewer. Information on the patients, investigations, methods, interventions, and outcomes were systematically analyzed. Characteristics and results of all included studies were reviewed systematically. High levels of adhesion molecules, hyperhomocysteinemia and lower folate levels, unbalanced oxidative status, a lower value of flow-mediated dilatation of brachial artery and a reduced percentage of circulating endothelial progenitor cells in patients affected by ISSHL support the hypothesis that this syndrome should be considered as a microcirculation disorder based on endothelial dysfunction and drive clinicians to implement all the traditional strategies used for preventing cardiovascular events, to also reduce the likelihood of ISSHL occurrence.

SOD1 gene polymorphisms in sudden sensorineural hearing loss

CONCLUSION

The results suggest that SOD1 rs4998557 could be associated with susceptibility to SSNHL in the Japanese population.

OBJECTIVES

To assess the gene association with sudden sensorineural hearing loss (SSNHL).

METHODS

A two-stage case control study was conducted to explore the relationship of the candidate genes to SSNHL. The 192 gene samples from SSNHL patients registered in the intractable inner ear disease gene bank were enrolled. As the candidate genes, 39 SNPs from 31 genes were selected for the first stage study. The second stage study examined whether the SOD1 gene polymorphisms, defined by significant differences between cases and controls in the first stage study, are associated with SSNHL.

RESULTS

Significant differences were observed in four SNPs from three genes, Glutathione-S-transferase pai 1 (GSTP1), proteine kinase C heta (PRKCH), and superoxide dismutase 1 (SOD1), in terms of allele frequency between SSNHL patients and HapMap controls. In the SOD1 gene, a significant difference was observed in the dominant model study of the SNP rs4998557 in the second stage study. Furthermore, as a result of dividing SSNHL patients based on the clinical data, the difference was more apparent in the case of the over 60 dB group and the tinnitus-positive group.

Dicer Is Down-regulated and Correlated with Drosha in Idiopathic Sudden Sensorineural Hearing Loss

Previously, we reported the expression levels of specific microRNA machinery components, DGCR8 and AGO2, and their clinical association in patients with idiopathic sudden hearing loss (SSNHL). In the present study, we investigated the other important components of microRNA machinery and their association with clinical parameters in SSNHL patients. Fifty-seven patients diagnosed with SSNHL and fifty healthy volunteers were included in this study. We evaluated mRNA expression levels of Dicer and Drosha in whole blood of patients with SSNHL and the control group, using RT & real-time PCR analysis. The Dicer mRNA expression level was down-regulated in patients with SSNHL. However, the Drosha mRNA expression level was not significantly altered in patients with SSNHL. Neither the Dicer nor Drosha mRNA expression level was not associated with any clinical parameters, including age, sex, duration of initial treatment from onset (days), initial Pure tone average, Siegel's criteria, WBC, and Erythrocyte sedimentation rate. However, mRNA expression levels of Dicer and Drosha were positively correlated to each other in patients with SSNHL. In this study, we demonstrated for the first time that the Dicer mRNA expression level was down-regulated in patients with SSNHL, suggesting its important role in pathobiology of SSNHL development.

GJB2 and mitochondrial 12S rRNA susceptibility mutations in sudden deafness

Genetic susceptibility may play an important role in the pathogenesis of sudden deafness. However, the specific genes involved are largely unknown. We sought to explore the frequency of GJB2 and mitochondrial 12S rRNA susceptibility mutations in patients with sudden deafness. Between September 2011 and May 2012, 62 consecutive patients with sudden deafness were seen. In 50 of these, no etiological factors for sudden deafness were found. We detected GJB2 and mitochondrial 12S rRNA variants by direct sequencing in these 50 patients and in 53-aged matched controls with normal hearing. In addition, we undertook functional analyses of the mitochondrial mutations which we detected, applying structural and phylogenetic analysis. GJB2 sequencing identified six mutations, including three pathogenic mutations (c.235delC, c.299-300delAT, c.109G>A) and three polymorphisms, in the study participants, giving an allele frequency of 15.0 %. A homozygous c.109G>A mutation was detected in two participants. A total of 16 variants in mitochondrial 12S rRNA gene were identified in the participants. No significant differences were found in GJB2 heterozygosity or in mitochondrial 12S rRNA variants between patients with sudden deafness and in controls. Our results suggest that the homozygous GJB2 c.109G>A mutation may be a cause of sudden deafness involving both ears. This finding should increase awareness of the likely role of genetic factors in the etiology of sudden deafness in general.

Sudden sensorineural hearing loss and polymorphisms in iron homeostasis genes: new insights from a case-control study

Background. Even if various pathophysiological events have been proposed as explanations, the putative cause of sudden hearing loss remains unclear. Objectives. To investigate and to reveal associations (if any) between the main iron-related gene variants and idiopathic sudden sensorineural hearing loss. Study Design. Case-control study. Materials and Methods. A total of 200 sudden sensorineural hearing loss patients (median age 63.65 years; range 10-92) were compared with 400 healthy control subjects. The following genetic variants were investigated: the polymorphism c.-8CG in the promoter of the ferroportin gene (FPN1; SLC40A1), the two isoforms C1 and C2 (p.P570S) of the transferrin protein (TF), the amino acidic substitutions p.H63D and p.C282Y in the hereditary hemochromatosis protein (HFE), and the polymorphism c.-582AG in the promoter of the HEPC gene, which encodes the protein hepcidin (HAMP). Results. The homozygous genotype c.-8GG of the SLC40A1 gene revealed an OR for ISSNHL risk of 4.27 (CI 95%, 2.65-6.89; P = 0.001), being overrepresented among cases. Conclusions. Our study indicates that the homozygous genotype FPN1 -8GG was significantly associated with increased risk of developing sudden hearing loss. These findings suggest new research should be conducted in the field of iron homeostasis in the inner ear.

Progress and prospects in human genetic research into age-related hearing impairment

Age-related hearing impairment (ARHI) is a complex, multifactorial disorder that is attributable to confounding intrinsic and extrinsic factors. The degree of impairment shows substantial variation between individuals, as is also observed in the senescence of other functions. This individual variation would seem to refute the stereotypical view that hearing deterioration with age is inevitable and may indicate that there is ample scope for preventive intervention. Genetic predisposition could account for a sizable proportion of interindividual variation. Over the past decade or so, tremendous progress has been made through research into the genetics of various forms of hearing impairment, including ARHI and our knowledge of the complex mechanisms of auditory function has increased substantially. Here, we give an overview of recent investigations aimed at identifying the genetic risk factors involved in ARHI and of what we currently know about its pathophysiology. This review is divided into the following sections: (i) genes causing monogenic hearing impairment with phenotypic similarities to ARHI; (ii) genes involved in oxidative stress, biologic stress responses, and mitochondrial dysfunction; and (iii) candidate genes for senescence, other geriatric diseases, and neurodegeneration. Progress and prospects in genetic research are discussed.

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.

Polymorphisms in genes encoding aquaporins 4 and 5 and estrogen receptor α in patients with Ménière's disease and sudden sensorineural hearing loss

AIMS

The etiologies of Ménière's disease and idiopathic sudden sensorineural hearing loss (SSNHL) remain unclear. The homeostasis of the water and blood circulation in the inner ear is essential for maintaining its hearing and equilibrium functions, and aquaporins and estrogen are involved in the fluid or ion balance in the inner ear. We investigated the associations between genetic polymorphisms in aquaporin 4 (AQP4, rs2075575), aquaporin 5 (AQP5, rs3736309), and estrogen receptor α (ERα1, rs2234693; ERα2, rs9340799) and susceptibility to Ménière's disease or SSNHL.

MAIN METHODS

We compared 86 patients affected by Ménière's disease, 85 patients affected by SSNHL, and 2136 adults who were participants in a comprehensive longitudinal study of aging.

KEY FINDINGS

With the AQP5 polymorphism, the odds ratio for Ménière's disease was 0.676 (95% confidence interval: 0.477-0.957) after adjustment for age and sex, when an additive genetic model was used. The AQP5 polymorphism entailed no significant risk of SSNHL and the polymorphisms of AQP4, ERα1, and ERα2 entailed no significant risk of Ménière's disease or SSNHL in the additive genetic model, regardless of adjustments for age and sex.

SIGNIFICANCE

Our study suggests that the variant G allele of AQP5 polymorphism rs3736309 reduces the risk of Ménière's disease.

Polymorphisms in genes involved in oxidative stress response in patients with sudden sensorineural hearing loss and Ménière's disease in a Japanese population

The etiologies of idiopathic sudden sensorineural hearing loss (SSNHL) and Ménière's disease remain unclear. Recently, accumulating evidence has demonstrated that oxidative stress is related to the pathology of inner ear disease. Because genetic factors may contribute partly to the etiologies of SSNHL and Ménière's disease, we investigated the associations between genetic polymorphisms located in oxidative stress response genes and susceptibility to SSNHL and Ménière's disease. We compared 84 patients affected by SSNHL, 82 patients affected by Ménière's disease, and 2107 adults (1056 men and 1051 women; mean age, 59.2 years; range, 40-79 years) who participated in the National Institute for Longevity Sciences, Longitudinal Study of Aging. Multiple logistic regression was used to calculate odds ratios for SSNHL and Ménière's disease in individuals with polymorphisms in the genes glutathione peroxidase 1 (GPX1) (Pro198Leu, rs1050450), paraoxonase 1 (PON1) (Gln192Arg, rs662; and Met55Leu, rs854560), PON2 (Ser311Cys, rs7493), and superoxide dismutase 2 (SOD2) (Val16Ala, rs4880), with adjustment for age and gender. No significant differences in the distribution of the genotypes at these polymorphisms were observed among individuals with SSNHL and Ménière's disease and controls. No significant risk for SSNHL and Ménière's disease was observed in the additive genetic model, regardless of moderating variables. The C allele of SOD2 (rs4880) was more frequent in Ménière's disease cases with a hearing level over 50 dB compared with cases with a hearing level below 50 dB, suggesting that this polymorphism is associated with progression of a hearing loss in Ménière's disease. In conclusion, no significant associations between the polymorphisms of GPX1, PON1, PON2, and SOD2 and risk of SSNHL and Ménière's disease were observed in this Japanese case-control study.

Idiopathic sudden sensorineural hearing loss: classic cardiovascular and new genetic risk factors

BACKGROUND

The main causative process in idiopathic sudden sensorineural hearing loss (iSSNHL) has yet to be explained or demonstrated. The clinical picture supports vascular involvement, but obvious limitations of inner ear study make this difficult to corroborate.

OBJECTIVES

To determine the role of thrombophilic genetic variants that may affect platelet function and to assess the cardiovascular risk profile in a cohort of patients with iSSNHL.

PATIENTS AND METHODS

118 Caucasian patients with iSSNHL were recruited from the same geographical area and enrolled prospectively in this study. Clinical data were obtained for each patient. Polymorphisms of the platelet glycoprotein subunit IIIa gene, ITGB3 (PLA1/A2, rs5918), and of the platelet glycoprotein subunit Ia gene, ITGA2 (C807T, rs1126643) were analyzed. A control group of 161 age- and gender-matched healthy individuals from the same geographical area was recruited for genetic comparisons. In order to determine the cardiovascular risk profile of each patient and of our cohort, a cross-sectional assessment was performed by means of a calibrated Framingham coronary heart disease risk scale. Risk factor proportions were compared to those recommended in European guidelines for coronary prevention, which are also based on the Framingham function.

RESULTS

A significantly high prevalence of the 807T allele of platelet glycoprotein subunit Ia was found in patients compared to controls. There was a significant correlation between the 807TT homozygous genotype and a low probability of recovery. The PLA1/A2 polymorphism of platelet glycoprotein subunit IIIa was not associated with recovery, with a similar genotype prevalence being found in patients and controls. In terms of cardiovascular risk profile, patients did not present an excess of baseline coronary risk factors compared to the general population in the same geographical area.

CONCLUSIONS

Patients with iSSNHL had a higher prevalence of the 807T thrombophilic polymorphism of platelet glycoprotein Ia/IIa. Patients homozygous for this polymorphism are less likely to recover from iSSNHL. Classical cardiovascular risk factors were not related to iSSNHL.

Sudden sensorineural hearing loss: a vascular cause? Analysis of prothrombotic risk factors in head and neck

OBJECTIVE

This aim of this study was to determine the prevalence of thrombophilic risk factors in sudden sensorineural hearing loss, central retinal vein occlusion, and stroke associated with small vessel disease, with the purpose of investigating and reinforcing the vascular hypothesis in the pathogenesis of sudden sensorineural hearing loss.

DESIGN

Case-control study. Genetic and acquired risk factors of these three groups were compared with healthy controls.

STUDY SAMPLE

Forty-nine, 60, and 101 patients affected respectively by sudden sensorineural hearing loss, central retinal vein occlusion, or stroke associated with small vessel disease, enrolled during a three-year period were compared with 210 healthy controls.

RESULTS

The frequency of hyperhomocysteinemia (homocysteine ≥ 15 μmol/L) was higher in each disease group than in controls. A statically significant, albeit weak, correlation between the MTHFR C677T mutation and hyperhomocysteinemia was found in all three diseases.

CONCLUSIONS

Hyperhomocysteinemia proved to be a risk factor for sudden sensorineural hearing loss. Based on these results, we propose to analyse homocysteine in sudden sensorineural hearing loss patients and, if its values are high, to evaluate the presence of MTHFR C677T mutation.

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.

Polymorphisms in genes involved in inflammatory pathways in patients with sudden sensorineural hearing loss

Although the etiology of idiopathic sudden sensorineural hearing loss (SSNHL) remains unclear, the pathologically increased permeability of blood vessels, elucidated by gadolinium-enhanced magnetic resonance imaging (MRI), suggests the involvement of inflammation. Because SSNHL is considered a multifactorial disease, possibly caused by interactions between genetic factors and environmental factors, the authors investigated the associations of polymorphisms of inflammatory mediator genes with susceptibility to SSNHL. The authors compared 72 patients affected by SSNHL and 2010 adults (1010 men and 1000 women; mean age 59.2 years; range 40-79) who participated in the National Institute for Longevity Sciences Longitudinal Study of Aging. Multiple logistic regression was used to obtain odds ratios (ORs) for SSNHL in subjects with polymorphisms in the genes IL-6 C - 572G, IL-4R G1902A, IL-10 A - 592C, TNFα C - 863A, TNFRSF1B G593A, VEGF C936T, VEGF C - 2578A, and VEGF G - 1154A, with adjustment for age, gender, and any history of hypertension, diabetes, or dyslipidemia. The per-allele OR for the risk of SSNHL in subjects bearing IL-6 C - 572G was 1.480 (95% confidence interval [CI], 1.037-2.111) in model 1 (no adjustment), 1.463 (CI, 1.022-2.094) in model 2 (adjusted for age and gender), and 1.460 (CI, 1.016-2.097) in model 3 (adjusted for age, gender, and a history of hypertension, diabetes, or dyslipidemia). Under the dominant model of inheritance, the ORs were 1.734 (CI, 1.080-2.783) in model 1, 1.690 (CI, 1.050-2.721) in model 2, and 1.669 (CI, 1.035-2.692) in model 3. The remaining seven polymorphisms failed to show any associations with the risk of SSNHL. These data need to be confirmed on larger series of patients. In conclusion, the IL-6 C - 572G polymorphism is associated with a risk of SSNHL. Because permeability of blood vessels in the inner ear is frequently increased in patients with SSNHL, inflammation of the inner ear might be involved.

Steroid combination therapy and detoxification enzyme gene polymorphisms in sudden sensorineural hearing loss patients

OBJECTIVE

The purpose of this study was to evaluate the relations among the combined therapy with steroid and the detoxification enzyme gene polymorphisms in patients with sudden sensorineural hearing loss (SSNHL). The pathogenetic mechanism of inner ear dysfunction could involve an increase in lipid peroxidation and a decrease in cellular antioxidant defense. Glutathione S-transferases (GSTs) and cytochrome P450 (CYP) belong to a system of detoxification and antioxidant enzymes that have been demonstrated in the inner ear.

STUDY DESIGN

A prospective study in patients with SSNHL.

PATIENTS AND METHODS

All 441 subjects were genotyped for GSTM1, GSTT1, and CYP1A1 polymorphisms. The polymorphisms were analyzed by polymerase chain reaction amplification, restriction enzyme digestion, and deoxyribonucleic acid fragment separation by electrophoresis.

RESULTS

No significant difference was observed between SSNHL patients and controls in 3 polymorphisms. However, the prevalence of the partial recovery group in patients with the CC genotype of CYP1A1 (22%) was higher than that in the complete recovery (7.4%) or no recovery group (12.5%) for the subjects classified according to modified Siegel's criteria but were not statistically significant.

CONCLUSION

This is the first approach to analyze gene polymorphism and efficacy of clinical treatment of patients with SSNHL, although the observations do not confirm the effect of the GSTM1/T1 and CYP1A1 genotypes as a risk factor for SSNHL.

Contribution of 1425G/A polymorphism in protein kinase C-Eta (PRKCH) gene and brain white matter lesions to the risk of sudden sensorineural hearing loss in a Japanese nested case-control study

Protein kinase C-eta (PRKCH) gene has been recently identified as a susceptible risk locus for cerebral infarction and hemorrhage in the Asian populations. The inner ear artery, a usual branch of anterior inferior cerebellar artery, is an end artery with minimal collaterals, therefore, the inner ear is particularly vulnerable to ischemia. The potential association between the development of stroke and sudden sensorineural hearing loss (SSNHL) has been implied. The authors hypothesized that the PRKCH polymorphism predisposing to stroke is associated with SSNHL risk, in view of brain magnetic resonance imaging (MRI) findings. The authors compared 33 cases of prevalent SSNHL with other cases among 2188 adults aged 40 to 79 years who participated in the Study of Aging, to assess the impact of PRKCH 1425G/A polymorphism in consideration of brain MRI findings. Multiple logistic regression was used to obtain odds ratios (ORs) for SSNHL, with adjustment for other possibly influential factors under additive model of minor allele. The per-allele OR for SSNHL risk was 1.770 (95% confidence interval: 1.024-3.060) after adjustments. The effect of the 1425A-allele varied by white matter lesion (WML) status. A significant impact of the A-allele on SSNHL risk increment was observed in higher-WML group, but not in no- or mild-WML group. The 1425A-allele of PRKCH has probably contributed to the susceptibility to SSNHL, despite the etiological heterogeneity of SSNHL, and the impact of the PRKCH 1425A variation observed in this study may imply underlying vascular pathogenesis of SSNHL.

Association of interleukin-1 gene polymorphisms with sudden sensorineural hearing loss and Ménière's disease

Sudden sensorineural hearing loss (SSNHL) and Ménière's disease are the most common inner ear diseases in which the causes are unknown. As recent magnetic resonance imaging has demonstrated disruption of the blood-labyrinth barrier in these inner ear diseases, inflammatory reaction associated with increased permeability of the blood vessels may be involved. The genotypes of interleukin 1A (IL1A) (-889C/T; rs1800587) and interleukin 1B (IL1B) (-511C/T; rs16944) were determined using an allele-specific primer-polymerase chain reaction method in 72 patients with SSNHL, 68 patients with Ménière's disease, and 2202 control subjects living almost in the same area as the patients. A significantly higher prevalence of the IL1A-889T allele was observed in SSNHL and Ménière's disease compared with controls, although no significant difference in distribution of IL1B-511C/T genotypes was observed between the patients and controls. Adjusted odd ratios for SSNHL and Ménière's disease risks in the -889TT genotypes were 25.89 (95% confidence interval (CI) 12.19-54.98) and 18.20 (95% CI 7.80-42.46), respectively, after age and gender were taken as moderator variables. Our results suggested that IL1A is closely associated with susceptibility of SSNHL and Ménière's disease.

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.

A preliminary study on the role of inherited prothrombotic risk factors in Taiwanese patients with sudden sensorineural hearing loss

Sudden sensorineural hearing loss (SSHL) is a disease with unknown etiology. Recently, several studies revealed that some inherited prothrombotic risk factors are associated with SSHL in western populations. The objective of this study was to investigate the roles of the two most common genetic prothrombotic factors, the factor V Leiden G1691A and prothrombin G20210A in Taiwanese patients with SSHL. Twenty-four patients diagnosed with SSHL of more than 30 dB on average pure tone audiometry (PTA) and thirty-six healthy subjects without a history of hearing loss were enrolled in this study. Genomic DNA was isolated from peripheral blood leukocytes and the single nucleotide polymorphisms (SNPs) genotyping of factor V Leiden G1691A and prothrombin G20210A were analyzed using the TaqMan genotyping assays. Neither factor V Leiden G1691A nor prothrombin G20210A was detected in SSHL patients or in the control subjects. Both the patient group and the control group exhibited wild-type V Leiden 1691GG and wild-type prothrombin 20210GG. In conclusion, the factors V Leiden G1691A and prothrombin G20210A do not seem to play any role in Taiwanese patients with SSHL. Further studies with a large series of patients are needed to identify other possible candidate genes in order to elucidate the pathogenesis of SSHL.