Gut-brain axis in depression: Crosstalk between neuroinflammation and gut microbiota

Abstract

Depression is the most common mental disorder and the leading cause of disability and suicide worldwide. Recently, during the COVID-19 pandemic, there has been a dramatic increase in the number of patients with depression on a global scale. Therefore, new insights into the underlying pathophysiology of depression are urgently required to develop more effective therapeutic strategies. An interesting fact is the coexistence of increased intestinal permeability and disrupted blood-brain barrier observed in patients with depression and animal models. A growing number of studies have revealed that a bidirectional interaction exists between the brain and the gastrointestinal tract, commonly termed the gut-brain axis. Emerging evidence has suggested that the regulation of neuroinflammation and gut homeostasis through the gut-brain axis is influenced by stress and depression, in which gut microbiota and microbe-derived short-chain fatty acids play a crucial role. Here, we describe the molecular and cellular mechanisms involved in the crosstalk between neuroinflammation and gut microbiota in depression. We further highlight fecal microbiota transplantation and dietary supplementation in depression and discuss their potential as therapeutic targets for depression.