Active GLP-1 receptor in bone-forming cells that works separately from the usual cAMP-linked receptor

Specific binding of [(125)I]-GLP-1 to MC3T3-E1 cells was observed to be time- and temperature-dependent, peaking at 30 minutes.

• GLP-1 binding to MC3T3-E1 cells is dissociable and can be partially displaced by GLP-2, but not by exendin-4, exendin-9, glucagon, or insulin.
• Scatchard analysis reveals the presence of high and low affinity binding sites for GLP-1.
• GLP-1 induces immediate hydrolysis of glycosylphosphatidylinositols (GPIs), producing short-lived inositolphosphoglycans (IPGs).
• GLP-1 increases activities of phosphatidylinositol-3 kinase (PI3K) and mitogen activated protein kinase (MAPK).
• GLP-1 decreases Runx2 gene expression while increasing osteocalcin gene expression in MC3T3-E1 cells.
• These cells do not express the pancreatic GLP-1 receptor, suggesting GLP-1 may interact via a different pathway.

Simplified