GLP-1 (7-37) vs Oxyntomodulin

Binds GLP-1 receptors in the pancreas, gut, and brain. Stimulates glucose-dependent insulin secretion and suppresses glucagon. Central GLP-1 receptor activation reduces food intake via hypothalamic pathways.

GLP-1(7-37) is the native 30-amino-acid active form of glucagon-like peptide 1, an endogenous incretin hormone secreted by intestinal L-cells in response to nutrient ingestion, that acts at GLP-1 receptors throughout the body to stimulate glucose-dependent insulin secretion, suppress glucagon release, slow gastric emptying, reduce appetite, and protect beta-cell mass; it is the endogenous ligand underlying the pharmacology of the GLP-1 receptor agonist drug class. The GLP-1 receptor is expressed on pancreatic beta cells, hypothalamic appetite-regulating neurons, gastric enteric neurons, and cardiovascular tissue; GLP-1(7-37) activates cAMP/PKA signaling in beta cells to potentiate insulin release strictly during hyperglycemia, providing intrinsic hypoglycemia protection, and centrally reduces caloric intake through satiety signaling. A randomized controlled trial of continuous subcutaneous native GLP-1 infusion in patients with type 2 diabetes demonstrated significant reductions in plasma glucose and appetite, confirming receptor-mediated effects of the native peptide in humans; the peptide's very short plasma half-life of approximately 2 minutes due to rapid DPP-IV degradation makes continuous infusion the only practical administration route for the native form. Native GLP-1(7-37) has no FDA approval as a drug; FDA-approved GLP-1 receptor agonists — including semaglutide, liraglutide, dulaglutide, and tirzepatide — are chemically modified DPP-IV-resistant analogs developed to overcome the native peptide's pharmacokinetic limitations, and research-grade native GLP-1 is used exclusively as a tool compound in metabolic pharmacology studies.

Dual GLP-1/glucagon receptor agonist. GLP-1 component suppresses appetite; glucagon component increases energy expenditure and fatty acid oxidation. Net effect is reduced caloric intake and elevated metabolic rate.

Oxyntomodulin is an endogenous 37-amino-acid proglucagon-derived peptide co-secreted with GLP-1 and PYY by intestinal L-cells in response to nutrient ingestion, distinguished from GLP-1 by a C-terminal octapeptide extension that enables dual agonism at both the GLP-1 receptor and the glucagon receptor, producing combined effects on appetite suppression, energy expenditure, and glucose homeostasis. GLP-1 receptor activation by oxyntomodulin reduces food intake through central satiety signaling, while concurrent glucagon receptor activation stimulates hepatic glucose production, thermogenesis in brown adipose tissue, and elevated energy expenditure — a combination that theoretically produces greater weight loss than GLP-1 receptor activation alone while the glucogenic and GLP-1 effects approximately offset each other's glycemic impact. A double-blind randomized controlled trial of subcutaneous oxyntomodulin in overweight and obese human subjects demonstrated significant body weight reduction versus placebo over a 4-week treatment period, establishing proof-of-concept for dual GLP-1/glucagon receptor co-agonism as a human anti-obesity mechanism and validating the pharmacological rationale for long-acting dual agonist drug development programs. Native oxyntomodulin has no FDA approval; its short plasma half-life from DPP-IV degradation precludes clinical development in its native form, and commercial research interest has shifted to stabilized long-acting dual agonist analogs such as cotadutide and retatrutide, which use this dual mechanism in engineered molecules with drug-like pharmacokinetics.