Microbiota-brain interaction: The role of gut-derived proteins in addressing various neurological disorders including Parkinson's (PD) and Alzheimer's diseases (AD).

The microbiota-brain interaction is a complex network connecting gut microbiota to the enteric nervous system (ENS) and the central nervous system (CNS) that are crucial for neurotransmission and neurological health. Metabolites such as short-chain fatty acids (SCFA), neurotransmitters, and neuromodulators from the gut microbiota influence behavior and brain function. This review focuses on the study related with gut bacteria, including Bifidobacterium infantis and Lactobacillus species, producing various metabolites in gut including bile acids, SCFA, histamine, and others to communicate with the brain or CNS. Dysbiosis can lead to neurological conditions such as anxiety, depression, PD, and AD. SCFAs from gut bacteria bind to the free fatty acid receptors of intestinal epithelial cells (IECs), affecting neurones and influencing neuroactivity. Gut bacteria also produce neurotransmitters that regulate growth hormone release through interactions with the CNS and endocrine systems. Brain signals interact directly with the pituitary and adrenal glands through the hypothalamic-pituitary-adrenal (HPA) axis, which in turn communicates with enteroendocrine cells (EECs). Investigating probiotics, prebiotics, and dietary changes could open new avenues for treatment for mental and neurological problems.