Association Between Asthma and Meniere's Disease: A Nested Case-Control Study

The Tryptophan Index Is Associated with Risk of Ischemic Stroke: A Community-Based Nested Case-Control Study

BACKGROUND

The relative availability of the essential amino acid tryptophan in the brain, as indicated by the tryptophan index, which is the ratio of tryptophan to its competing amino acids (CAAs) in circulation, has been related to major depression. However, it remains unknown whether tryptophan availability is involved in the pathogenesis of ischemic stroke.

AIMS

We aimed to investigate the relationship between the tryptophan index and the risk of ischemic stroke.

METHODS

We performed a nested case-control study within a community-based cohort in eastern China over the period 2013 to 2018. The analysis included 321 cases of ischemic stroke and 321 controls matched by sex and date of birth. The plasma levels of tryptophan and CAAs, including tyrosine, valine, phenylalanine, leucine, and isoleucine, were measured by ultra-high-performance liquid chromatography-tandem mass spectrometry. Conditional logistic regression analyses were employed to determine incidence rate ratios (IRRs) and their 95% confidence intervals (CIs).

RESULTS

After adjustment for body mass index, current smoking status, educational attainment, physical activity, family history of stroke, hypertension, diabetes, hyperlipidemia, and estimated glomerular filtration rate, an elevated tryptophan index was significantly associated with a reduced risk of ischemic stroke in a dose-response manner (IRR, 0.76; 95% CI, 0.63-0.93, per standard deviation increment). The plasma tryptophan or CAAs were not separately associated with the risk of ischemic stroke.

CONCLUSIONS

The tryptophan index was inversely associated with the risk of ischemic stroke. Our novel observations suggest that the availability of the essential amino acid tryptophan in the brain is involved in the pathogenesis of ischemic stroke.

An overload of missense variants in the OTOG gene may drive a higher prevalence of familial Meniere disease in the European population

Meniere disease is a complex inner ear disorder with significant familial aggregation. A differential prevalence of familial MD (FMD) has been reported, being 9-10% in Europeans compared to 6% in East Asians. A broad genetic heterogeneity in FMD has been described, OTOG being the most common mutated gene, with a compound heterozygous recessive inheritance. We hypothesize that an OTOG-related founder effect may explain the higher prevalence of FMD in the European population. Therefore, the present study aimed to compare the allele frequency (AF) and distribution of OTOG rare variants across different populations. For this purpose, the coding regions with high constraint (low density of rare variants) were retrieved in the OTOG coding sequence in Non-Finnish European (NFE).. Missense variants (AF < 0.01) were selected from a 100 FMD patient cohort, and their population AF was annotated using gnomAD v2.1. A linkage analysis was performed, and odds ratios were calculated to compare AF between NFE and other populations. Thirteen rare missense variants were observed in 13 FMD patients, with 2 variants (rs61978648 and rs61736002) shared by 5 individuals and another variant (rs117315845) shared by two individuals. The results confirm the observed enrichment of OTOG rare missense variants in FMD. Furthermore, eight variants were enriched in the NFE population, and six of them were in constrained regions. Structural modeling predicts five missense variants that could alter the otogelin stability. We conclude that several variants reported in FMD are in constraint regions, and they may have a founder effect and explain the burden of FMD in the European population.

Ménière's disease and allergy: Epidemiology, pathogenesis, and therapy

The etiology of Ménière's disease (MD) remains controversial. Allergies are potential extrinsic factors that, in conjunction with underlying intrinsic factors, may cause MD. The link between allergies and MD was first described in 1923. For nearly a century, studies have demonstrated a possible link between allergies and MD, even though a causal relationship has not been definitively determined. Previous reviews have mainly focused on clinical epidemiology studies of patients. In this review, we shed light on the association between allergies and MD not only in terms of its epidemiology, but also from an immunology, pathophysiology, and immunotherapy perspective in both patients and animal models. Patients with MD tend to have a high risk of comorbid allergies or an allergy history, showing positive allergy immunology characteristics. Other MD-related diseases, such as migraine, may also interact with allergies. Allergy mediators such as IgE may worsen the symptoms of MD. Deposits of IgE in the vestibular end organs indicate the ability of the inner ear to participate in immune reactions. Allergic challenges can induce vertigo in animals and humans. Anti-allergy therapy plays a positive role in patients with MD and animal models of endolymphatic hydrops.

Immune-Related Disorders Associated With Ménière's Disease: A Systematic Review and Meta-analysis

OBJECTIVE

To analyze evidence supporting an association between immune-related diseases and Ménière's disease (MD) since it has long been thought to be related to autoimmune disorders and allergies.

DATA SOURCES

We retrieved records from Pubmed, Web of Science, Scopus, and Cochrane Library to identify studies published between January 2002 and October 2022.

REVIEW METHODS

Articles were independently assessed by 2 reviewers and verified by a third reviewer. Published cross-sectional studies, cohort/longitudinal studies, case series, and noncomparative cohort studies were considered eligible for inclusion. We conducted a systematic review and meta-analysis according to a registered protocol on the International Prospective Register of Systematic Reviews and Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines. Selected studies were classified into 2 groups: epidemiological and genetic association studies. Relative frequencies and odds ratios (ORs) for each autoinflammatory/autoimmune disease or genetic marker reported to be associated with MD.

RESULTS

Fifteen studies from 6 countries met our inclusion criteria. Nine are epidemiological studies and 6 are genetic association studies. The epidemiological studies were used to perform 3 different meta-analyses. Airway allergic disease and autoimmune thyroid disease showed a significant association with MD (OR = 2.27 [2.08-2.48] and OR = 1.35 [1.25-1.46]); while rheumatoid arthritis did not (OR = 0.63 [0.28-1.41]). Other comorbidities also showed a significant association with MD like chronic obstructive pulmonary disease, vitiligo, fibromyalgia, arthritis, and psoriasis.

CONCLUSION

Epidemiological evidence supports an association between MD and immune-related disorders in European and Asian populations, with population-specific effects. The evaluation of thyroid diseases, airway allergic diseases, and other inflammatory diseases should be implemented in the clinical management of MD patients.