The gastrointestinal tract (GIT) of humans and animals is host to a complex community of
different microorganisms whose activities significantly influence host nutrition and health through
enhanced metabolic capabilities, protection against pathogens, and regulation of the gastrointestinal
development and immune system. New molecular technologies and concepts have revealed distinct
interactions between the gut microbiota and dietary amino acids (AAs) especially in relation to AA
metabolism and utilization in resident bacteria in the digestive tract, and these interactions may play
significant roles in host nutrition and health as well as the efficiency of dietary AA supplementation.
After the protein is digested and AAs and peptides are absorbed in the small intestine, significant levels
of endogenous and exogenous nitrogenous compounds enter the large intestine through the ileocaecal
junction. Once they move in the colonic lumen, these compounds are not markedly absorbed by the
large intestinal mucosa, but undergo intense proteolysis by colonic microbiota leading to the release of
peptides and AAs and result in the production of numerous bacterial metabolites such as ammonia,
amines, short-chain fatty acids (SCFAs), branched-chain fatty acids (BCFAs), hydrogen sulfide, organic
acids, and phenols. These metabolites influence various signaling pathways in epithelial cells,
regulate the mucosal immune system in the host, and modulate gene expression of bacteria which results
in the synthesis of enzymes associated with AA metabolism. This review aims to summarize the
current literature relating to how the interactions between dietary amino acids and gut microbiota may
promote host nutrition and health.
Regulation of rat magnocellular neurosecretory system by D-aspartate: evidence for biological role(s) of a naturally occurring free D-amino acid in mammals
