Plant-derived bioactive components regulate gut microbiota to prevent depression and depressive-related neurodegenerative diseases: Focus on neurotransmitters

Depression is a prevalent neuropsychiatric disorder that affects people all around the world. Alzheimer's disease (AD) and Parkinson's disease (PD) are two neurodegenerative diseases that are comorbid with depression behaviors. Mounting evidence reveals that gut microbiota is subject to brain activity and function. Therefore, targeting the gut microbiota may be a potential avenue to further the treatment and alleviate symptoms. Studies in animal models and clinical have determined that the gut microbiota can promote neurotransmitter production and transmission. Disturbance of neurotransmitters has long been thought to play a role in the etiology of neuropsychiatric disorders, but particular dietary intake can alter neurotransmitters by modulating the makeup of the gut microbiota and microbial metabolites, which speed up the treatment process. Therefore, we outline how neurotransmitters play a part in the major pathways related to the gut-brain axis (GBA). Additionally, the potential pathogenesis of the gut microbiota in AD and PD and the beneficial effects of plant-derived bioactive components are discussed. In this article, we mainly focus on neurotransmitters derived from the microbiota of γ-aminobutyric acid (GABA), serotonin (5-HT), and dopamine and their effects on depression and neurodegenerative diseases via GBA. We discuss the dietary intervention of ingesting plant-derived active components such as polyphenols, polysaccharides, and peptides that may provide benefits by regulating the gut microbiota and releasing neurotransmitters/neuroactive metabolites, which provide a better understanding of dietary regulation to play part in anti-depressive and anti-degenerative processes.