“…TAAR9 can be activated by various amines, such as N, N-dimethylcyclohexylamine, N-methylpiperidine, and triethylamine, and polyamines, especially cadaverine, putrescine, spermidine, and spermine [ 19 , 20 , 21 ]. Dietary polyamines are absorbed in the small intestine, and the gut microbiota, primarily, Bacteroides spp., Fusobacterium spp., and Clostridia [ 66 ], is the major source of polyamines in the lower part of the intestine [ 22 , 24 , 27 , 67 , 68 ]. Polyamine synthesis pathways seem to be generated in the gut microbial community, where enzymes produced by different species of bacteria collectively enable the synthesis of polyamines from precursors [ 30 , 69 ].…”