Vulnerability to chronic stress and the phenotypic heterogeneity of presbycusis with subjective tinnitus

Lipid parameters and depression in patients with chronic tinnitus: A cross-sectional observation

BACKGROUND

Pathophysiological theories assume importance of metabolic abnormalities in patients with major depression - and possibly chronic tinnitus. Although chronic tinnitus frequently correlates with depression, links between high-density lipoprotein (HDL) and depression are uninvestigated.

METHODS

Two-hundred patients with chronic tinnitus (Mage = 55; 51% female) were examined. Serum levels of total cholesterol (TC), triglycerides (TGs), HDL, low-density lipoprotein cholesterol (LDL), non-HDL, as well as LDL/HDL and TC/HDL ratios were analysed. Questionnaires included depression subscales of the ICD-10 Symptom Rating, the Hospital Anxiety and Depression Scale (HADS_D), and the Berlin Mood Questionnaire (BSF). Multivariate analyses of covariance and linear regression models - which controlled age, tinnitus-related distress and perceived stress - investigated between-subgroup differences (p < 0.05) and linear associations between HDL indices and depression (p < 0.01).

RESULTS

HDL levels did not differ for tinnitus-symptom durations, smoking and alcohol use levels, statin or antihypertensive drug use, and body-mass indices. Relative to non-to-mildly depressed patients with chronic tinnitus, patients with moderate-to-severe depression (n = 45; 23%) had significantly lower HDL levels (d = -0.35) and higher LDL/HDL (d = 0.39) and TC/HDL ratios (d = 0.40). Across participants, HDL-levels were negatively associated with depression as measured by the HADS_D and BSF_indifference scales.

CONCLUSIONS

In keeping with general depression research, low serum HDL levels correlate with depressive symptomatology in patients with chronic tinnitus. This association may be influenced by proximal (e.g. modulations of HPA-axis activity) or distal factors (e.g. maladaptive coping behaviours) - both of which should be conceptualized within psychological stimulus-processing frameworks.

The potassium channels: Neurobiology and pharmacology of tinnitus

Tinnitus is a widespread public health issue that imposes a significant social burden. The occurrence and maintenance of tinnitus have been shown to be associated with abnormal neuronal activity in the auditory pathway. Based on this view, neurobiological and pharmacological developments in tinnitus focus on ion channels and synaptic neurotransmitter receptors in neurons in the auditory pathway. With major breakthroughs in the pathophysiology and research methodology of tinnitus in recent years, the role of the largest family of ion channels, potassium ion channels, in modulating the excitability of neurons involved in tinnitus has been increasingly demonstrated. More and more potassium channels involved in the neural mechanism of tinnitus have been discovered, and corresponding drugs have been developed. In this article, we review animal (mouse, rat, hamster, and guinea-pig), human, and genetic studies on the different potassium channels involved in tinnitus, analyze the limitations of current clinical research on potassium channels, and propose future prospects. The aim of this review is to promote the understanding of the role of potassium ion channels in tinnitus and to advance the development of drugs targeting potassium ion channels for tinnitus.