GPR142 is a G protein-coupled receptor that functions as a selective sensor for aromatic amino acids, particularly L-tryptophan and L-phenylalanine, with L-tryptophan being the most potent agonist 12. Upon activation, GPR142 triggers both Gq and Gi protein-coupled signaling pathways 1. The receptor is expressed in pancreatic islets and gastrointestinal enteroendocrine cells, where it regulates glucose homeostasis by coordinating insulin and incretin hormone secretion in response to aromatic amino acid sensing 2. L-tryptophan activation of GPR142 stimulates glucose-dependent insulin secretion and GIP secretion from duodenal K cells, with both CASR and GPR142 contributing to amino acid-induced hormone secretion 3. Notably, GPR142 mediates tryptophan-induced β-cell regeneration through a gut microbiota-tryptophan metabolism-GLP-1 axis in type 2 diabetes models 4. Beyond metabolic regulation, GPR142 expression is directly upregulated by proinflammatory cytokines (TNF-α, IL-6, IL-1β) in ghrelin-producing cells, suggesting roles in inflammatory responses 5. These findings position GPR142 as a therapeutic target for metabolic diseases including type 2 diabetes 6.