Recognizing the role of the vagus nerve in depression from microbiota-gut brain axis

Abstract

Depression is a worldwide disease causing severe disability, morbidity, and mortality. Despite abundant studies, the precise mechanisms underlying the pathophysiology of depression remain elusive. Recently, cumulate research suggests that a disturbance of microbiota-gut-brain axis may play a vital role in the etiology of depression while correcting this disturbance could alleviate depression symptoms. The vagus nerve, linking brain and gut through its afferent and efferent branches, is a critical route in the bidirectional communication of this axis. Directly or indirectly, the vagus afferent fibers can sense and relay gut microbiota signals to the brain and induce brain disorders including depression. Also, brain changes in response to stress may result in gut hyperpermeability and inflammation mediating by the vagal efferents, which may be detrimental to depression. Notably, vagus nerve stimulation owns an anti-inflammatory effect and was proved for depression treatment. Nevertheless, depression was accompanied by a low vagal tone, which may derive from response to stress and contribute to pathogenesis of depression. In this review, we aim to explore the role of the vagus nerve in depression from the perspective of the microbiota-gut-brain axis, highlighting the relationship among the vagal tone, the gut hyperpermeability, inflammation, and depression.

Gut microbiota dysbiosis in polycystic ovary syndrome: Mechanisms of progression and clinical applications

“…At the same time, the gut microbiota forms feedback to the brain by synthesizing hormones and neurotransmitters. For example, the intestinal peptide in the systemic circulation can bind to the homologous receptors of immune cells and the end of the vagus nerve, thus completing the intestinal brain communication (Tan et al, 2022). Gut microbiota disorder may participate in the progress of PCOS through the gut-brain axis (Zhao et al, 2020).…”

Acupuncture treatment for post-stroke depression: Intestinal microbiota and its role

“…There are also considerable literatures suggesting a link between the vagus nerve and depression and gastrointestinal disorders ( Liu et al, 2020a ; Tan et al, 2022 ). The vagus nerve is one of the most important components of the parasympathetic system, which plays a major role in the regulation of gut-brain axis by acupuncture.…”

Putative role of non‐invasive vagus nerve stimulation in cancer pathology and immunotherapy: Can this be a hidden treasure, especially for the elderly?

“…Furthermore, the positive association between depression and anxiety and incidence of cancer and all‐cause mortality 114 ; and the increased risk of depression among patients with cancer are also factors that can be considered as mechanisms through which VNS plays a role in the treatment of cancer 115–117 . This is because VNS is used in the management of depression, which by implication helps improve a symptom associated with cancer and reduce the risk of developing it 118,119 . Similarly, cardiovascular diseases and cancer share many common risk factors such as smoking, metabolic syndrome, age, environmental toxins, and air pollution 120 .…”

“…[115][116][117] This is because VNS is used in the management of depression, which by implication helps improve a symptom associated with cancer and reduce the risk of developing it. 118,119 Similarly, cardiovascular diseases and cancer share many common risk factors such as smoking, metabolic syndrome, age, environmental toxins, and air pollution. 120 Moreover, heart rate variability (HRV), which is the fluctuation in the time intervals between adjacent heartbeats serves as a measure of vagal tone that is used to indicate the overall level of vagal activity.…”