Table 1B.

Endocrine communication pathway.

Microbiota-gut-brain communication routes		GI and Brain effects	References
A. Enteroendocrine cells (EEC)	A1. Ghrelin Cholecystokinin (CCK) Glucagon-like peptide 1 (GLP-1) Peptide YY (PYY) Serotonin (5-HT) → ENS	A1.1 Regulation of appetite, digestive processes, inflammation and neurological functions	Guilloteau et al., 2006; Berthoud, 2008; Bauer et al., 2016; Westfall et al., 2017; Breit et al., 2018; Farzi et al., 2018
B. Directly from the gut to the bloodstream	B1. Lipopolysaccharide (LPS), Neurotoxins, SCFA	B1.1 ± Systemic immune system, affect the blood brain barrier (BBB), and brain functions	Carabotti et al., 2015; Ho et al., 2018