Mechanisms of action of glucagon-like peptide 1 in the pancreas

Máire E. Doyle, Josephine M. Egan

Research output: Contribution to journalReview article

Abstract

Glucagon-like peptide 1 (GLP-1) is a hormone that is encoded in the proglucagon gene. It is mainly produced in enteroendocrine L cells of the gut and is secreted into the blood stream when food containing fat, protein hydrolysate, and/or glucose enters the duodenum. Its particular effects on insulin and glucagon secretion have generated a flurry of research activity over the past 20 years culminating in a naturally occurring GLP-1 receptor (GLP-1R) agonist, exendin 4 (Ex-4), now being used to treat type 2 diabetes mellitus (T2DM). GLP-1 engages a specific guanine nucleotide-binding protein (G-protein) coupled receptor (GPCR) that is present in tissues other than the pancreas (brain, kidney, lung, heart, and major blood vessels). The most widely studied cell activated by GLP-1 is the insulin-secreting β cell where its defining action is augmentation of glucose-induced insulin secretion. Upon GLP-1R activation, adenylyl cyclase (AC) is activated and cAMP is generated, leading, in turn, to cAMP-dependent activation of second messenger pathways, such as the protein kinase A (PKA) and Epac pathways. As well as short-term effects of enhancing glucose-induced insulin secretion, continuous GLP-1R activation also increases insulin synthesis, β cell proliferation, and neogenesis. Although these latter effects cannot be currently monitored in humans, there are substantial improvements in glucose tolerance and increases in both first phase and plateau phase insulin secretory responses in T2DM patients treated with Ex-4. This review will focus on the effects resulting from GLP-1R activation in the pancreas.

Original languageEnglish (US)
Pages (from-to)546-593
Number of pages48
JournalPharmacology and Therapeutics
Volume113
Issue number3
DOIs
StatePublished - Mar 1 2007
Externally publishedYes

Keywords

  • Differentiation
  • Epac
  • Exendin (9-39)
  • Exendin 4
  • FoxO1
  • GLP-1 receptor
  • IRS2
  • Insulin synthesis and secretion
  • Islet of Langerhans
  • PDX-1
  • PI3 kinase
  • PKA
  • Proliferation
  • cAMP
  • β cell

ASJC Scopus subject areas

  • Pharmacology
  • Pharmacology (medical)

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