Cholinergic Hypofunction in Presbycusis-Related Tinnitus With Cognitive Function Impairment: Emerging Hypotheses

Combination Therapy of Choline Alfoscerate With Ginkgo biloba Monotherapy in Age-Related Hearing Loss: Effects and Outcomes

BACKGROUND AND OBJECTIVES

Ginkgo biloba and choline alfoscerate are used as adjuvant treatment for presbycusis, but studies on how the monotherapy differs from the combination therapy are lacking. Therefore, this study aimed to compare the audiologic outcomes between Ginkgo biloba monotherapy and Ginkgo biloba and choline alfoscerate combination therapy. Subjects and.

METHODS

The study groups are divided into three: negative control, monotherapy, and combination therapy groups. All groups' pure tone audiometry was measured by dividing the study period into Initial, 3-6, 6-9, 9-12, 12-15 months, and checked whether differences between groups were present.

RESULTS

The combination therapy showed less gradient gap than the monotherapy, indicating less hearing loss rate than the monotherapy. Based on the Kaplan-Meier curve, the combination therapy showed better results in terms of survival time of hearing.

CONCLUSIONS

As a pharmacological treatment for presbycusis, combination therapy shows better results than monotherapy.

Understanding How Physical Exercise Improves Alzheimer’s Disease: Cholinergic and Monoaminergic Systems

Alzheimer’s disease (AD) is an age-related neurodegenerative disorder, characterized by the accumulation of proteinaceous aggregates and neurofibrillary lesions composed of β-amyloid (Aβ) peptide and hyperphosphorylated microtubule-associated protein tau, respectively. It has long been known that dysregulation of cholinergic and monoaminergic (i.e., dopaminergic, serotoninergic, and noradrenergic) systems is involved in the pathogenesis of AD. Abnormalities in neuronal activity, neurotransmitter signaling input, and receptor function exaggerate Aβ deposition and tau hyperphosphorylation. Maintenance of normal neurotransmission is essential to halt AD progression. Most neurotransmitters and neurotransmitter-related drugs modulate the pathology of AD and improve cognitive function through G protein-coupled receptors (GPCRs). Exercise therapies provide an important alternative or adjunctive intervention for AD. Cumulative evidence indicates that exercise can prevent multiple pathological features found in AD and improve cognitive function through delaying the degeneration of cholinergic and monoaminergic neurons; increasing levels of acetylcholine, norepinephrine, serotonin, and dopamine; and modulating the activity of certain neurotransmitter-related GPCRs. Emerging insights into the mechanistic links among exercise, the neurotransmitter system, and AD highlight the potential of this intervention as a therapeutic approach for AD.

Too Blind to See the Elephant? Why Neuroscientists Ought to Be Interested in Tinnitus

A curative therapy for tinnitus currently does not exist. One may actually exist but cannot currently be causally linked to tinnitus due to the lack of consistency of concepts about the neural correlate of tinnitus. Depending on predictions, these concepts would require either a suppression or enhancement of brain activity or an increase in inhibition or disinhibition. Although procedures with a potential to silence tinnitus may exist, the lack of rationale for their curative success hampers an optimization of therapeutic protocols. We discuss here six candidate contributors to tinnitus that have been suggested by a variety of scientific experts in the field and that were addressed in a virtual panel discussion at the ARO round table in February 2021. In this discussion, several potential tinnitus contributors were considered: (i) inhibitory circuits, (ii) attention, (iii) stress, (iv) unidentified sub-entities, (v) maladaptive information transmission, and (vi) minor cochlear deafferentation. Finally, (vii) some potential therapeutic approaches were discussed. The results of this discussion is reflected here in view of potential blind spots that may still remain and that have been ignored in most tinnitus literature. We strongly suggest to consider the high impact of connecting the controversial findings to unravel the whole complexity of the tinnitus phenomenon; an essential prerequisite for establishing suitable therapeutic approaches.

The Influence of Depression, Anxiety and Cognition on the Treatment Effects of Ginkgo biloba Extract EGb 761® in Patients with Tinnitus and Dementia: A Mediation Analysis

Background: Comorbid occurrence of tinnitus and emotional symptoms of anxiety and depression is highly prevalent. The Ginkgo biloba extract EGb 761^® has been shown to be effective in reducing neuropsychiatric symptoms in patients with dementia and tinnitus. Methods: We performed a mediation analysis to evaluate direct effects of EGb 761^® on tinnitus severity, as well as indirect effects mediated by symptoms of depression and anxiety and by changed cognition. We pooled data from subsets of patients suffering from tinnitus that were enrolled in three double-blind, randomized, placebo-controlled clinical trials, which investigated the efficacy of EGb 761^® (240 mg/day for 22–24 weeks) in dementia with concomitant neuropsychiatric symptoms. Results: In total, 594 patients suffered from tinnitus (EGb 761^®, 289; placebo, 305). Direct effects of EGb 761^® on tinnitus severity (p < 0.001) in patients with mild to moderate dementia were found to represent about 60% of the total effect, whereas the indirect effects (p < 0.001) mediated by improvement of anxiety, depression and cognition represented about 40% of the total effect. Conclusions: EGb 761^® could be considered as a supporting treatment for tinnitus in elderly patients suffering from dementia, with added benefit in those with symptoms of depression or anxiety.

Supplementary Effect of Choline Alfoscerate on Speech Recognition in Patients With Age-Related Hearing Loss: A Prospective Study in 34 Patients (57 Ears)

To investigate the effect of choline alfoscerate (CA) on hearing amplification in patients with age related hearing loss, we performed a prospective case-control observational study from March 2016 to September 2020. We assessed patients with bilateral word recognition score (WRS) <50% using monosyllabic words. The patients were 65-85 years old, without any history of dementia, Alzheimer's disease, parkinsonism, or depression. After enrollment, all patients started using hearing aids (HA). The CA group received a daily dose of 800 mg CA for 11 months. We performed between-group comparisons of audiological data, including pure tone audiometry, WRS, HA fitting data obtained using real-ear measurement (REM), and the Abbreviated Profile of Hearing Aid benefit scores after treatment. After CA administration, the WRS improved significantly in the CA group (4.2 ± 8.3%), but deteriorated in the control group (-0.6 ± 8.1%, p = 0.035). However, there was no significant between-group difference in the change in pure tone thresholds and aided speech intelligibility index calculated from REM. These findings suggest that the difference in WRS was relevant to central speech understanding rather than peripheral audibility. Therefore, administering oral CA could effectively enrich listening comprehension in older HA users.

Heterogeneous Influence of Frailty Phenotypes in Age-Related Hearing Loss and Tinnitus in Chinese Older Adults: An Explorative Study

Background

Fried physical frailty, with mobility frailty and non-motor frailty phenotypes, is a heterogeneous syndrome. The coexistence of the two phenotypes and cognitive impairment is referred to as cognitive frailty (CF). It remains unknown whether frailty phenotype has a different association with hearing loss (HL) and tinnitus.

Methods

Of the 5,328 community-dwelling older adults, 429 participants aged ≥58 years were enrolled in the study. The participants were divided into robust, mobility, and non-mobility frailty, mobility and non-mobility CF (subdivided into reversible and potentially reversible CF, RCF, and PRCF), and cognitive decline [subdivided into mild cognitive impairment (MCI) and pre-MCI] groups. The severity and presentations of HL and/or tinnitus were used as dependent variables in the multivariate logistic or nominal regression analyses with forward elimination adjusted for frailty phenotype stratifications and other covariates.

Results

Patients with physical frailty (mobility frailty) or who are robust were found to have lower probability of developing severe HL and tinnitus, and presented HL and/or tinnitus than those with only cognitive decline, or CF. Patients with RCF and non-mobility RCF had higher probability with less HL and tinnitus, and the presentation of HL and/or tinnitus than those with PRCF and mobility RCF. Other confounders, age, cognitive and social function, cardiovascular disease, depression, and body mass index, independently mediated the severity of HL and tinnitus, and presented HL and/or tinnitus.

Conclusion

Frailty phenotypes have divergent association with HL and tinnitus. Further research is required to understand the differential mechanisms and the personalized intervention of HL and tinnitus.

Clinical Trial Registration

ClinicalTrials.gov identifier, NCT2017K020.

Changes in the Gene Expression Profiles of the Inferior Colliculus Following Unilateral Cochlear Ablation in Adult Rats

This study aimed to explore gene expression changes in the inferior colliculus (IC) after single-sided deafness (SSD). Forty 8-week-old female Sprague-Dawley rats were used. Twenty rats underwent right-side cochlear ablation, and IC tissues were harvested after 2 weeks (SSD 2-week group). Twenty rats underwent a sham operation and were sacrificed after 2 weeks (control group). Both sides of the IC were analyzed using a gene expression array. Pathway analyses were performed on genes that were differentially expressed compared with their levels in the control group. The expression levels of genes involved in the candidate pathways were confirmed using reverse transcription polymerase chain reaction (RT-PCR). Among the genes with ≥ 1.5-fold changes in expression levels and P < 0.05, there were 7 and 9 genes with increased and decreased expression, respectively, in the ipsilateral IC and 10 and 12 genes with increased and decreased expression, respectively, in the contralateral IC. The pathway analysis did not identify significantly related pathway. In the bilateral analysis, a total of 14 genes were ≥ 1.3-fold downregulated in both the ipsilateral and contralateral IC in the SSD 2-week group compared with their expression in the control group. Pathway analyses of these 14 genes included 7 genes, namely, amine compound solute carrier (Slc)5a7; Slc18a3; Slc6a5; synaptic vesicle glycoprotein 2C (Sv2c); S100 calcium binding protein A10 (S100a10); a gene with sequence similarity to family 111, member A (Fam111a); and peripherin (Prph), that were related to the acetylcholine neurotransmitter release cycle, SLC transporters, and the neurotransmitter release cycle pathways. RT-PCR showed reduced expression of Slc5a7, Sv2c, and Prph in the contralateral IC and Slc18a3 and Slc6a5 in the ipsilateral IC of the SSD 2-week group compared with that in the control group.

Age-related hearing loss and tinnitus, dementia risk, and auditory amplification outcomes

Age-related hearing loss (ARHL) or presbycusis, as the third leading cause of chronic disability in older adults, has been shown to be associated with predisposing cognitive impairment and dementia. Tinnitus is also a chronic auditory disorder demonstrating a growth rate with increasing age. Recent evidence stands for the link between bothersome tinnitus and impairments in various aspects of cognitive function. Both ARHL and age-related tinnitus affect mental health and contribute to developing anxiety, stress, and depression. The present review is a comprehensive multidisciplinary study on diverse interactions among ARHL, tinnitus, and cognitive decline in older adults. This review incorporates the latest evidence in prevalence and risk factors of ARHL and tinnitus, the neural substrates of tinnitus-related cognitive impairments, hypothesized mechanisms concerning the association between ARHL and increased risk of dementia, hearing amplification outcomes in cases with ARHL and cognitive decline, and preliminary findings on the link between ARHL and cognitive impairment in animal studies. Given extensive evidence that demonstrates advantages of using auditory amplification in the alleviation of hearing handicap, depression, and tinnitus, and the improvement of cognition, social communication, and quality of life, regular hearing screening programs for identification and management of midlife hearing loss and tinnitus is strongly recommended.

Chronic Sound-induced Tinnitus and Auditory Attention in Animals

Attention may be an important factor in tinnitus. Individuals most disturbed by their tinnitus differ from those who are not in terms of attention allocation. This study used an operant-conditioning animal model to examine the interaction between tinnitus and auditory vigilant attention as well as auditory selective attention. Tinnitus was induced in 90-day-old rats by a unilateral exposure to band-limited noise (120 dB, SPL). Tinnitus testing began 90 days following exposure; afterward animals were divided into three groups: Unexposed controls without tinnitus, Exposed without tinnitus, and Exposed with tinnitus. Tinnitus was evident in the vicinity of 20 kHz. Vigilant attention was quantified by the behavioral (operant) response to unpredictable sound transitions signaling changes in food availability. Tinnitus animals were more vigilant, i.e., responded more rapidly, to 20-kHz tone onsets than Unexposed or Exposed animals without tinnitus. There were no significant vigilant attention differences between groups to non-tinnitus like sounds. The same animals were further trained and tested on a selective attention task. A brief free-field sound cue, consisting of either a short train of identical noise pulses (standard stimulus), or a noise train with one substituted tone pulse (oddball stimulus), cued a left or right nose poke for food. On this selective attention task, Tinnitus animals performed consistently worse than Non-tinnitus or Unexposed control animals regardless of stimulus features. As predicted, animals with behavioral evidence of tinnitus showed tinnitus-related attentional changes, including impaired selective attention but increased vigilance to sounds approximating their tinnitus.