Decreased clearance of serum retinol-binding protein and elevated levels of transthyretin in insulin-resistant ob/ob mice

Nimesh Mody, Timothy E Graham, Yuki Tsuji, Qin Yang, Barbara B Kahn

Research output: Contribution to journalArticle

66 Citations (Scopus)

Abstract

Serum retinol-binding protein (RBP4) is secreted by liver and adipocytes and is implicated in systemic insulin resistance in rodents and humans. RBP4 normally binds to the larger transthyretin (TTR) homotetramer, forming a protein complex that reduces renal clearance of RBP4. To determine whether alterations in RBP4-TTR binding contribute to elevated plasma RBP4 levels in insulin-resistant states, we investigated RBP4-TTR interactions in leptin-deficient ob/ob mice and high-fat-fed obese mice (HFD). Gel filtration chromatography of plasma showed that 88-94% of RBP4 is contained within the RBP4-TTR complex in ob/ob and lean mice. Coimmunoprecipitation with an RBP4 antibody brought down stoichiometrically equal amounts of TTR and RBP4, indicating that TTR was not more saturated with RBP4 in ob/ob mice than in controls. However, plasma TTR levels were elevated approximately fourfold in ob/ob mice vs. controls. RBP4 injected intravenously in lean mice cleared rapidly, whereas the t(1/2) for disappearance was approximately twofold longer in ob/ob plasma. Urinary fractional excretion of RBP4 was reduced in ob/ob mice, consistent with increased retention. In HFD mice, plasma TTR levels and clearance of injected RBP4 were similar to chow-fed controls. Hepatic TTR mRNA levels were elevated approximately twofold in ob/ob but not in HFD mice. Since elevated circulating RBP4 causes insulin resistance and glucose intolerance in mice, these findings suggest that increased TTR or alterations in RBP4-TTR binding may contribute to insulin resistance by stabilizing RBP4 at higher steady-state concentrations in circulation. Lowering TTR levels or interfering with RBP4-TTR binding may enhance insulin sensitivity in obesity and type 2 diabetes.
Original languageEnglish
Pages (from-to)E785-E793
Number of pages9
JournalAmerican Journal of Physiology: Endocrinology and Metabolism
Volume294
Issue number4
Early online date19 Feb 2008
DOIs
Publication statusPublished - Apr 2008

Keywords

  • animals
  • blotting, western
  • body weight
  • diabetes mellitus, type 2
  • dietary fats
  • female
  • injections, intravenous
  • insulin resistance
  • leptin
  • metabolic syndrome X
  • mice
  • mice, obese
  • obesity
  • prealbumin
  • retinol-binding proteins, plasma
  • adipose
  • high-fat diet

Fingerprint Dive into the research topics of 'Decreased clearance of serum retinol-binding protein and elevated levels of transthyretin in insulin-resistant ob/ob mice'. Together they form a unique fingerprint.

  • Cite this