Hepatocyte-specific IKK-β activation enhances VLDL-triglyceride production in APOE*3-Leiden mice

J Lipid Res. 2011 May;52(5):942-50. doi: 10.1194/jlr.M010405. Epub 2011 Feb 28.

Abstract

Low-grade inflammation in different tissues, including activation of the nuclear factor κB pathway in liver, is involved in metabolic disorders such as type 2 diabetes and cardiovascular diseases (CVDs). In this study, we investigated the relation between chronic hepatocyte-specific overexpression of IkB kinase (IKK)-β and hypertriglyceridemia, an important risk factor for CVD, by evaluating whether activation of IKK-β only in the hepatocyte affects VLDL-triglyceride (TG) metabolism directly. Transgenic overexpression of constitutively active human IKK-β specifically in hepatocytes of hyperlipidemic APOE*3-Leiden mice clearly induced hypertriglyceridemia. Mechanistic in vivo studies revealed that the hypertriglyceridemia was caused by increased hepatic VLDL-TG production rather than a change in plasma VLDL-TG clearance. Studies in primary hepatocytes showed that IKK-β overexpression also enhances TG secretion in vitro, indicating a direct relation between IKK-β activation and TG production within the hepatocyte. Hepatic lipid analysis and hepatic gene expression analysis of pathways involved in lipid metabolism suggested that hepatocyte-specific IKK-β overexpression increases VLDL production not by increased steatosis or decreased FA oxidation, but most likely by carbohydrate-responsive element binding protein-mediated upregulation of Fas expression. These findings implicate that specific activation of inflammatory pathways exclusively within hepatocytes induces hypertriglyceridemia. Furthermore, we identify the hepatocytic IKK-β pathway as a possible target to treat hypertriglyceridemia.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apolipoprotein E3 / metabolism*
  • Apolipoproteins E / metabolism
  • Blotting, Western
  • Cells, Cultured
  • Hepatocytes / metabolism*
  • Humans
  • Hypertriglyceridemia / genetics
  • Hypertriglyceridemia / metabolism
  • I-kappa B Kinase / genetics
  • I-kappa B Kinase / metabolism*
  • Lipoproteins, VLDL / biosynthesis*
  • Liver / metabolism*
  • Male
  • Mice
  • Triglycerides / biosynthesis*

Substances

  • Apolipoprotein E3
  • Apolipoproteins E
  • Lipoproteins, VLDL
  • Triglycerides
  • very low density lipoprotein triglyceride
  • I-kappa B Kinase