Table 2.

Summary on the role of nutrient sensing receptors.

Receptor	Ligand	Expression	Function	Health Outcome
Sweet taste receptors i.e., T1R3	sugars saccharin sucralose aspartame acesulfame K amino acids Na-glutamate	HGE neurons (brain) solitary chemosensory cells (upper airway system) chemosensory brush cell (urinary system) neutrophil granulocytes T and B lymphocytes Enteroendocrine cells Tuft cells Paneth cells Pancreas ß-cells	glucose metabolism, blood-brain axis regulation host-pathogen interaction cell migration cell activation incretin secretion glucose absorption Th2 immunity regulation antimicrobial peptides secretion insulin secretion	feeding behavior circadian rhythm regulation allergic, infectious diseases, chronic rhinosinusitis innate immunity glucose metabolism, metabolic syndrome IBD, helminth and viral infections, inflammation IBD infections, inflammation diabetes mellitus
Bitter taste receptors i.e., T2R38	drugs i.e., chloroquine saccharin acesulfame K sucralose bacterial peptides: i.e., acyl-homoserine lactones	placenta myeloid cells macrophages chemosensory cells (upper airway system) chemosensory brush cell (urinary system) Enteroendocrine cells Goblet cells Paneth cells	unknown migration phagocytosis production of antimicrobial peptides glucose metabolism regulation mucin secretion antimicrobial peptide secretion	unknown innate immunity infection, inflammation chronic rhinosinusitis diabetes mellitus, metabolic syndrome, inflammation inflammation, infections inflammation, infections
CaSR	aromatic L-amino acids	enteroendocrine cells	calcium homeostasis cytokine secretion	calcium homeostasis gut–kidney axis inflammation, IBD? cancer development
GPRC6A	amino acids L-arginine, L-lysine and L-ornithine osteocalcin testosterone	enteroendocrine cells ILC-3 cells	bone metabolism IL-22 secretion tissue repair microbiota balance	bone resorption inflammation, IBD
GPR92 (LPAR5)	partially digested proteins	G cells	gastrin secretion	digestion regulation
FFAR 1, 4	n-6 and n-3 PUFAs, DHA	enteroendocrine cells lymphocytes dendritic cells macrophage	antiinflammatory cytokine secretion Treg/Th17 axis regulation insulin sensitivity	inflammation innate immunity antiviral response diabetes mellitus
FFAR 2,3	short-chain fatty acid	enteroendocrine cells innate immune cells: neutrophil granulocytes pancreatic ß cells	epithelial integrity antiinflammatory cytokine secretion NLRP3 inflammasome modulation alpha defensin secretion glucose metabolism	gut permeability microbiome regulation inflammation IBD diabetes mellitus infection diabetes mellitus

HGE neurons: high glucose-excited neurons, IBD: inflammatory bowel diseases, IL-22: interleukin-22, ILC-3: innate lymphoid cells-3, CaSR: Ca²⁺-sensing receptor, FFAR 1-4: Free fatty acid receptor 1–4, GPRC6A: G protein-coupled receptor class C group 6 member A, GPR92 (LPAR5): lysophosphatidic acid receptor 5, PUFA: polyunsaturated fatty acid, DHA: Docosahexaenoic acid, NLRP3: NLR family pyrin domain containing 3, Th2: T helper 2.