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

Clinical practice guidelines for the diagnosis and management of acute sensorineural hearing loss

OBJECTIVE

Acute sensorineural hearing loss represents a spectrum of conditions characterized by sudden onset hearing loss. The "Clinical Practice Guidelines for the Diagnosis and Management of Acute Sensorineural Hearing Loss" were issued as the first clinical practice guidelines in Japan outlining the standard diagnosis and treatment. The purpose of this article is to strengthen the guidelines by adding the scientific evidence including a systematic review of the latest publications, and to widely introduce the current treatment options based on the scientific evidence.

METHODS

The clinical practice guidelines were completed by 1) retrospective data analysis (using nationwide survey data), 2) systematic literature review, and 3) selected clinical questions (CQs). Additional systematic review of each disease was performed to strengthen the scientific evidence of the diagnosis and treatment in the guidelines.

RESULTS

Based on the nationwide survey results and the systematic literature review summary, the standard diagnosis flowchart and treatment options, including the CQs and recommendations, were determined.

CONCLUSION

The guidelines present a summary of the standard approaches for the diagnosis and treatment of acute sensorineural hearing loss. We hope that these guidelines will be used in medical practice and that they will initiate further research.

Genome-wide association study for age-related hearing loss in CFW mice

Age-related hearing impairment is the most common cause of hearing loss and is one of the most prevalent conditions affecting the elderly globally. It is influenced by a combination of environmental and genetic factors. The mouse and human inner ears are functionally and genetically homologous. Investigating the genetic basis of age-related hearing loss (ARHL) in an outbred mouse model may lead to a better understanding of the molecular mechanisms of this condition. We used Carworth Farms White (CFW) outbred mice, because they are genetically diverse and exhibit variation in the onset and severity of ARHL. The goal of this study was to identify genetic loci involved in regulating ARHL. Hearing at a range of frequencies was measured using Auditory Brainstem Response (ABR) thresholds in 946 male and female CFW mice at the age of 1, 6, and 10 months. We obtained genotypes at 4.18 million single nucleotide polymorphisms (SNP) using low-coverage (mean coverage 0.27x) whole-genome sequencing followed by imputation using STITCH. To determine the accuracy of the genotypes we sequenced 8 samples at >30x coverage and used calls from those samples to estimate the discordance rate, which was 0.45%. We performed genetic analysis for the ABR thresholds for each frequency at each age, and for the time of onset of deafness for each frequency. The SNP heritability ranged from 0 to 42% for different traits. Genome-wide association analysis identified several regions associated with ARHL that contained potential candidate genes, including Dnah11, Rapgef5, Cpne4, Prkag2, and Nek11. We confirmed, using functional study, that Prkag2 deficiency causes age-related hearing loss at high frequency in mice; this makes Prkag2 a candidate gene for further studies. This work helps to identify genetic risk factors for ARHL and to define novel therapeutic targets for the treatment and prevention of ARHL.

Endothelial Dysfunction and Metabolic Disorders in Patients with Sudden Sensorineural Hearing Loss

Sudden sensorineural hearing loss (SSNHL) is defined as a sensorineural hearing loss of 30 dB or greater on at least three contiguous audiometric frequencies occurring within a 72 h period. Although SSNHL is commonly encountered in clinical audiology and otolaryngology practice, its etiopathogenesis continues to be poorly understood. Scientific investigations have highlighted the vulnerability of cochlear microcirculation to blood flow alterations. Even mild hypoperfusion can lead to immediate dysfunction in the organ of Corti, given the heightened susceptibility of cochlear hair cells to hypoxia and ischemic damage. The purpose of this review paper is to present evidence of endothelial and vascular involvement in SSNHL and the risk factors, such as metabolic syndrome, that may negatively impact the inner ear's vascular supply, influencing the onset pattern, incidence, and prognosis of SSNHL. By addressing these variables, we can deepen our comprehension of the mechanisms underlying SSNHL and potentially uncover strategies for prevention.

Glucocorticoid receptor (NR3C1) genetic polymorphisms and the outcomes of sudden sensorineural hearing loss

BACKGROUND

The glucocorticoid receptor gene (NR3C1) encodes the receptor to which cortisol and other glucocorticoids bind. Steroids in either oral, intratympanic, or intravascular forms are the treatment of choice for sudden sensorineural hearing loss (SSNHL), but the outcome varies. The outcomes of SSNHL have been investigated for related factors, including age, initial hearing loss severity and pattern, vertigo, genetic variations, and the time between onset and treatment. The objective of the present study was to analyze the association of genetic polymorphisms of NR3C1 with the outcomes of SSNHL.

MATERIALS AND METHODS

We conducted a comparison study of 93 cases with a poor outcome (control) and 100 cases with a good outcome (case) in SSNHL patients. Six single nucleotide polymorphisms (SNPs) were selected. The genotypes were determined using TaqMan technology.

RESULTS

The heterozygous AT genotype of rs17100289 was associated with a poor outcome in comparison with the major homozygous AA genotype after adjustments for age and sex (OR = 0.50; 95% CI 0.26-0.95; P = 0.035) in SSNHL patients. The CT genotype of rs4912912 was also associated with a poor outcome compared with the major homozygous TT genotype after the adjustments (OR = 0.47; 95% CI 0.24-0.92; P = 0.026).

CONCLUSION

These results suggest that NR3C1 genetic polymorphisms may influence the outcomes of SSNHL.

Polymorphisms of genes related to phase II metabolism and resistance to clopidogrel

Clopidogrel is an antiplatelet drug commonly used to prevent coagulation. This review aimed to investigate the effect of polymorphisms of G6PD, GCLC, GCLM, GSS, GST, GSR, HK and GLRX genes on clopidogrel during phase II metabolism through exploring previous studies. The results revealed that low glutathione plasma levels caused by several alleles related to these genes could affect the bioactivation process of the clopidogrel prodrug, making it unable to inhibit platelet aggregation perfectly and thus leading to severe consequences in patients with a high risk of blood coagulation. However, the study recommends platelet reactivity tests to predict clopidogrel efficacy rather than studying gene mutations, as most of these mutations are rare and other nongenetic factors could affect the drug's efficacy.

Utilizing Single Cell RNA-Sequencing to Implicate Cell Types and Therapeutic Targets for SSNHL in the Adult Cochlea

OBJECTIVE

To identify genes implicated in sudden sensorineural hearing loss (SSNHL) and localize their expression in the cochlea to further explore potential pathogenic mechanisms and therapeutic targets.

STUDY DESIGN

Systematic literature review and bioinformatics analysis.

DATA SOURCES

The following sources were searched from inception through July 2, 2020: PubMed-NCBI, MEDLINE, Embase, CINAHL, Cochrane Library, ClinicalTrials.gov, OpenGrey, GreyNet, GreyLiterature Report, and European Union Clinical Trials Registry. PubMed-NCBI and MEDLINE were additionally searched for human temporal bone histopathologic studies related to SSNHL.

METHODS

Literature review of candidate SSNHL genes was conducted according to PRISMA guidelines. Existing temporal bone studies from SSNHL patients were analyzed to identify the most commonly affected inner ear structures. Previously published single-cell and single-nucleus RNA-Seq datasets of the adult mouse stria vascularis, as well as postnatal day 7 and 15 mouse cochlear hair cells and supporting cells, were utilized for localization of the SSNHL-related genes curated through literature review.

CONCLUSIONS

We report 92 unique single nucleotide polymorphisms (SNPs) in 76 different genes that have been investigated in relation to SSNHL in the literature. We demonstrate that a subset of these genes are expressed by cell types in the adult mouse stria vascularis and organ of Corti, consistent with findings from temporal bone studies in human subjects with SSNHL. We highlight several potential genetic targets relevant to current and possible future SSNHL treatments.

Genetic Susceptibility Study of Chinese Sudden Sensorineural Hearing Loss Patients with Vertigo

OBJECTIVE

To investigate the genetic causes of sudden sensorineural hearing loss (SSNHL) patients in China. This study focused on analyzing variations of coding sequence of common genes related to deafness, revealing the molecular pathogenesis of sudden deafness from a genomics perspective, discovering molecular markers associated with the onset of deafness, and then supplying prevention to high-risk populations, classifying disease according to accurate etiology, and choosing a much more precision therapy.

METHODS

We retrospectively analyzed the clinical characteristics of 51 patients diagnosed as SSNHL with vertigo treated in the Chinese PLA General Hospital. In this study, mutation screening of 307 nuclear genes and mitochondrial genome responsible for human or mouse deafness was performed on the 51 cases of unilateral sudden deafness patients with vertigo.

RESULTS

We identified 51 cases of unilateral sudden deafness, including 2 cases of low-mid frequency hearing impairment, 18 cases of mid-high frequency hearing loss, 11 cases of flat-type hearing loss, and 20 cases of all frequency hearing loss. Among the 51 cases, 8 (15.69%) cases of GJB2 heterozygous variations, 1 (1.96%) case of GJB3 heterozygous variations, 5 (9.8%) cases of SLC26A4 heterozygous variations, 2 (3.92%) cases of COCH heterozygous variations, 14 (27.45%) cases of CDH23 heterozygous variations, 14 (27.45%) cases of OTOF heterozygous variations, 1 (1.96%) case of SLC17A8 heterozygous variations and 2 (3.92%) cases of KCNE1 heterozygous variations. No mtDNA gene variations were identified.

CONCLUSION

SSNHL has some relationship with hereditary in Chinese population, but its complex genetic pathogenic mechanisms need further study.

Association between NR3C1 gene polymorphisms and age-related hearing impairment in Qingdao Chinese elderly

BACKGROUND

Age-related hearing impairment (ARHI) has attracted increasing attention recently. It is caused by genetic and environmental factors. A number of ARHI-related genes have been found. This study aimed to detect the potential association between NR3C1 gene polymorphisms and ARHI by means of weighted allele score.

METHODS

A total of 861 participants from Qingdao city were selected by means of cluster random sampling. We statistically evaluated the characteristics of individuals and used the Mann-Whitney U test or chi-square test for comparison. The publicly available expression quantitative trait locus (eQTL) was queried on the website of the Genotype-Tissue Expression (GTEx). We used the weighted allele score and logistic regression analysis to explore the association between NR3C1 gene polymorphisms and ARHI. Finally, the prediction model was constructed by logistic regression and receiver operating characteristic (ROC) curve.

RESULTS

All individuals over 60 years of age were enrolled in this study. The allele of rs61757411, rs41423247 and rs6877893 were significantly different between the ARHI group and the normal hearing group (P < 0.01). Though eQTL analysis, rs6877893 and rs33388 might affect the occurrence of ARHI by affecting the expression of NR3C1 gene in artery aorta. Then we performed two models: one without adding any covariates into model and the other adjusting for demographic characteristic, smoking and drinking, diet and exercise, and physical conditions. In the multivariate-adjusted model 2, the odds ratio with 95% confidence interval for weighted allele score (NR3C1) was 0.841 (0.710-0.995, P = 0.043). The area under the ROC curve was 0.755, indicating that the model had good predictability.

CONCLUSIONS

Our study suggests that NR3C1 gene polymorphisms was significantly associated with ARHI.

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.

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.

Genetics of guanylyl cyclase pathways in the cochlea and their influence on hearing

Although hearing loss is the most common sensory deficit in Western societies, there are no successful pharmacological treatments for this disorder. Recent experiments have demonstrated that manipulation of intracellular cyclic guanosine monophosphate (cGMP) concentrations can have both beneficial and harmful effects on hearing. In this review, we will examine the role of cGMP as a key second messenger involved in many aspects of cochlear function and discuss the known functions of downstream effectors of cGMP in sound processing. The nitric oxide-stimulated soluble guanylyl cyclase system (sGC) and the two natriuretic peptide-stimulated particulate GCs (pGCs) will be more extensively covered because they have been studied most thoroughly. The cochlear GC systems are attractive targets for medical interventions that improve hearing while simultaneously representing an under investigated source of sensorineural hearing loss.