What is GLP-1?Complete Incretin Research Guide — QSC Peptides

Glucagon-like peptide-1 (GLP-1) is a 30–31 amino acid incretin hormone derived from proglucagon by post-translational processing in intestinal L-cells of the ileum and colon, and in NTS neurons of the brainstem. Released in response to nutrient ingestion (particularly fat and carbohydrates), GLP-1 is the primary driver of the incretin effect — the observation that oral glucose stimulates 2–3× more insulin secretion than equivalent intravenous glucose due to gastrointestinal hormone signaling.

The GLP-1 Receptor (GLP-1R)

GLP-1R is a class B GPCR expressed on:

• Pancreatic β-cells: Primary site — GLP-1R drives glucose-dependent insulin secretion and β-cell proliferation
• Hypothalamic neurons (ARC, PVN): POMC/CART activation and NPY/AgRP suppression → appetite reduction and energy homeostasis
• Brainstem (NTS, area postrema): Satiety signaling, vagal afferent modulation
• Stomach: Delayed gastric emptying → prolonged satiety
• Cardiovascular: Cardiomyocytes, endothelium, vascular smooth muscle
• CNS: Hippocampus, cortex — neuroprotective roles

Why Native GLP-1 Cannot Be Used as a Research Tool

Native GLP-1 has a plasma half-life of only ~2 minutes, rapidly cleaved by DPP-IV (dipeptidylpeptidase IV) at the Ala2 position and cleared by renal filtration. This makes it unsuitable for sustained research protocols requiring prolonged GLP-1R activation — necessitating the synthetic, DPP-IV-resistant, long-acting analogs from QSC Peptides.

The GLP-1 Class Hierarchy

All QSC Peptides GLP-1 compounds activate GLP-1R as the foundation, then extend to additional receptor targets for greater metabolic impact:

• Semaglutide (1st gen): GLP-1R only — ~7 day t½ via albumin binding — ~15–17% weight reduction
• Tirzepatide (2nd gen): GLP-1R + GIPR — ~5 day t½ — ~20–22% weight reduction
• Retatrutide (3rd gen): GLP-1R + GIPR + GCGR — ~6 day t½ — ~24–26% weight reduction
• CagriSema (dual-class): GLP-1R + AMYR1/3 — ~7 day t½ — ~22–25% weight reduction