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Pigment epithelium-derived factor (PEDF) ameliorates advanced glycation end product (AGE)-induced hepatic insulin

T Yoshida1, S Yamagishi, K Nakamura

  • 1Department of Medicine, Kurume University School of Medicine, Kurume, Japan.

Hormone and Metabolic Research = Hormon- Und Stoffwechselforschung = Hormones Et Metabolisme
|September 17, 2008
PubMed

Insights

Pigment epithelium-derived factor (PEDF) combats insulin resistance caused by advanced glycation end products (AGEs). PEDF improves AGE-induced insulin resistance in liver cells by blocking key signaling pathways, suggesting a protective role in diabetes.

Area of Science:

  • Cell Biology
  • Endocrinology
  • Biochemistry

Background:

  • Advanced glycation end products (AGEs) are linked to insulin resistance, but underlying mechanisms remain unclear.
  • Pigment epithelium-derived factor (PEDF) is known to inhibit AGE-signaling pathways.
  • Understanding PEDF's role in AGE-induced insulin resistance is crucial for potential therapeutic strategies.

Purpose of the Study:

  • To investigate whether PEDF improves insulin resistance in AGE-exposed hepatoma cells (Hep3B).
  • To elucidate the molecular mechanisms by which PEDF exerts its protective effects against AGEs.
  • To determine PEDF's potential role in combating hepatic insulin resistance.

Main Methods:

  • Proteins from AGE-exposed Hep3B cells were analyzed using Western blot and immunoprecipitation.
  • Insulin receptor substrate-1 (IRS-1) phosphorylation and interactions were assessed.
  • Glycogen synthesis was measured using radiolabeled glucose ([ (14)C]-d-glucose).
  • The role of Rac-1 activation and downstream signaling pathways (JNK, IKK) was examined.

Main Results:

  • AGEs activated Rac-1, increased serine phosphorylation of IRS-1, and activated JNK and IkappaB kinase (IKK) pathways.
  • PEDF inhibited AGE-induced Rac-1 activation and downstream signaling.
  • AGEs reduced tyrosine phosphorylation of IRS-1, impairing PI3K association and glycogen synthesis.
  • PEDF reversed these AGE-induced impairments in insulin signaling and glucose metabolism.

Conclusions:

  • PEDF improves AGE-elicited insulin resistance in Hep3B cells by suppressing Rac-1 activation.
  • PEDF inhibits JNK- and IKK-dependent serine phosphorylation of IRS-1.
  • PEDF may offer a protective effect against hepatic insulin resistance in diabetes.

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