Link between GIP and osteopontin in adipose tissue and insulin resistance

Diabetes. 2013 Jun;62(6):2088-94. doi: 10.2337/db12-0976. Epub 2013 Jan 24.

Abstract

Low-grade inflammation in obesity is associated with accumulation of the macrophage-derived cytokine osteopontin (OPN) in adipose tissue and induction of local as well as systemic insulin resistance. Since glucose-dependent insulinotropic polypeptide (GIP) is a strong stimulator of adipogenesis and may play a role in the development of obesity, we explored whether GIP directly would stimulate OPN expression in adipose tissue and thereby induce insulin resistance. GIP stimulated OPN protein expression in a dose-dependent fashion in rat primary adipocytes. The level of OPN mRNA was higher in adipose tissue of obese individuals (0.13 ± 0.04 vs. 0.04 ± 0.01, P < 0.05) and correlated inversely with measures of insulin sensitivity (r = -0.24, P = 0.001). A common variant of the GIP receptor (GIPR) (rs10423928) gene was associated with a lower amount of the exon 9-containing isoform required for transmembrane activity. Carriers of the A allele with a reduced receptor function showed lower adipose tissue OPN mRNA levels and better insulin sensitivity. Together, these data suggest a role for GIP not only as an incretin hormone but also as a trigger of inflammation and insulin resistance in adipose tissue. Carriers of the GIPR rs10423928 A allele showed protective properties via reduced GIP effects. Identification of this unprecedented link between GIP and OPN in adipose tissue might open new avenues for therapeutic interventions.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adipose Tissue / drug effects
  • Adipose Tissue / metabolism*
  • Adolescent
  • Adult
  • Aged
  • Alleles
  • Animals
  • Cells, Cultured
  • Female
  • Gastric Inhibitory Polypeptide / pharmacology*
  • Humans
  • In Vitro Techniques
  • Insulin Resistance / genetics
  • Insulin Resistance / physiology*
  • Male
  • Mice
  • Middle Aged
  • Osteopontin / genetics
  • Rats
  • Receptors, Gastrointestinal Hormone / genetics
  • Receptors, Gastrointestinal Hormone / metabolism
  • Young Adult

Substances

  • Receptors, Gastrointestinal Hormone
  • Osteopontin
  • Gastric Inhibitory Polypeptide
  • gastric inhibitory polypeptide receptor