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Glucagon-like Receptor Agonists01:24

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Incretins include glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), which stimulate insulin secretion post-meals. In type 2 diabetes, GIP's efficacy is reduced, making GLP-1 a viable drug target. GIP originates from preproGIP.
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The pancreatic islets comprising only 1%-2% of the volume are highly vascularized and innervated mini-organs. They contain five endocrine cell types, including β cells that secrete insulin, which is synthesized as a single polypeptide chain, preproinsulin, processed to proinsulin, and finally to insulin and C-peptide. This process is complex and regulated, involving the Golgi complex, the endoplasmic reticulum, and the secretory granules of the β cell.
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Isolated Pancreatic Islet Treatment and Apoptosis Measurement
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Published on: May 2, 2025

Apelin is a novel islet peptide.

Camilla Ringström1, Marloes Dekker Nitert, Hedvig Bennet

  • 1Department of Experimental Medical Science, Lund University, Lund, Sweden.

Regulatory Peptides
|March 30, 2010
PubMed
Summary

Apelin, a peptide regulating feeding and glucose, is found in human and animal islets. Its expression is altered in type 2 diabetes and by glucocorticoids, suggesting a role in insulin regulation.

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Area of Science:

  • Endocrinology
  • Molecular Biology
  • Metabolic Research

Background:

  • Apelin is a peptide hormone with diverse physiological roles, including regulation of feeding behavior and glucose metabolism.
  • Its presence and function within pancreatic islets, particularly concerning insulin secretion, remain incompletely understood.

Purpose of the Study:

  • To investigate apelin expression in human and animal islets.
  • To explore the regulation of islet apelin and its effects on insulin secretion.
  • To determine the presence of the apelin receptor (APJ) in islets.

Main Methods:

  • Immunocytochemistry and in situ hybridization for apelin localization.
  • Real-time PCR for quantifying apelin and APJ receptor expression.
  • Insulin secretion assays in INS-1 (832/13) beta cells.

Main Results:

  • Apelin is expressed in beta and alpha cells of human and murine islets, and in beta cells of porcine and feline islets.
  • Apelin receptor (APJ) is present in human and mouse islets and INS-1 cells.
  • Low concentrations of apelin inhibit insulin secretion, while high concentrations moderately increase it.
  • Apelin is upregulated in type 2 diabetic animal models (db/db mice, GK-rats) but not affected by glucose in human islets.
  • Glucocorticoids downregulate apelin expression in human islets.

Conclusions:

  • Apelin is a novel peptide hormone involved in insulin regulation within human and animal islets.
  • Islet apelin expression is modulated by glucocorticoids and is upregulated in animal models of type 2 diabetes.
  • The presence of the apelin receptor suggests autocrine or paracrine signaling roles for apelin within the islets.