Activation of the gut-brain axis by dietary glutamate and physiologic significance in energy homeostasis
https://pubmed.ncbi.nlm.nih.gov/19587084/#:~:text=l-Glutamate receptors and their,indirectly by these vagal inputs.
l-Glutamate receptors and their cellular transduction molecules have recently been identified in gut epithelial cells. Stimulation of such l-glutamate receptors by luminal l-glutamate activates
vagal afferent nerve fibers and then parts of the brain that are targeted directly or indirectly by these vagal inputs.
l-Glutamate is a multifunctional amino acid involved in
taste perception, intermediary metabolism, and excitatory
neurotransmission. In addition, recent studies have uncovered new roles for l-glutamate in gut-brain axis activation and energy
homeostasis.
l-Glutamate receptors and their cellular transduction molecules have recently been identified in gut epithelial cells. Stimulation of such l-glutamate receptors by luminal l-glutamate activates vagal afferent nerve fibers and then parts of the brain that are targeted directly or indirectly by these vagal inputs.
Notably, 3 areas of the brain—the
medial preoptic area, the
hypothalamic dorsomedial nucleus, and the habenular nucleus—are activated by intragastric l-glutamate but not by glucose or sodium chloride. Furthermore, the chronic, ad libitum
ingestion of a palatable solution of monosodium l-glutamate (1% wt:vol) by rats has also been found to reduce weight gain,
fat deposition, and plasma leptin concentrations compared with rats that ingest water alone. No difference in food intake was observed. Such effects may also be vagally mediated.
Together, such findings contribute to the growing knowledge base that indicates that l-glutamate signaling via taste and gut l-glutamate receptors may influence multiple physiologic functions, such as
thermoregulation and energy homeostasis.
The study focuses on l-glutamate in the diet, not on correct usage in the brain.
