TGR5 reduces macrophage migration through mTOR-induced C/EBPβ differential translation

J Clin Invest. 2014 Dec;124(12):5424-36. doi: 10.1172/JCI76289. Epub 2014 Nov 3.

Abstract

The bile acid-responsive G protein-coupled receptor TGR5 is involved in several metabolic processes, and recent studies suggest that TGR5 activation may promote pathways that are protective against diet-induced diabetes. Here, we investigated the role of macrophage-specific TGR5 signaling in protecting adipose tissue from inflammation and associated insulin resistance. Examination of adipose tissue from obese mice lacking macrophage Tgr5 revealed enhanced inflammation, increased chemokine expression, and higher macrophage numbers compared with control obese animals. Moreover, macrophage-specific deletion of Tgr5 exacerbated insulin resistance in obese animals. Conversely, pharmacological activation of TGR5 markedly decreased LPS-induced chemokine expression in primary macrophages. This reduction was mediated by AKT-dependent activation of mTOR complex 1, which in turn induced the differential translation of the dominant-negative C/EBPβ isoform, liver inhibitory protein (LIP). Overall, these studies reveal a signaling pathway downstream of TGR5 that modulates chemokine expression in response to high-fat diet and suggest that targeting this pathway has the potential to be therapeutically exploited for prevention of chronic inflammatory diseases and type 2 diabetes mellitus.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adipose Tissue / metabolism
  • Adipose Tissue / pathology
  • Animals
  • CCAAT-Enhancer-Binding Protein-beta / genetics
  • CCAAT-Enhancer-Binding Protein-beta / metabolism*
  • Cell Movement*
  • Chemokines / genetics
  • Chemokines / metabolism
  • Diabetes Mellitus, Type 2 / genetics
  • Diabetes Mellitus, Type 2 / metabolism
  • Diabetes Mellitus, Type 2 / pathology
  • Gene Expression Regulation
  • Insulin Resistance / genetics
  • Lipopolysaccharides / toxicity
  • Macrophages / metabolism*
  • Macrophages / pathology
  • Mechanistic Target of Rapamycin Complex 1
  • Mice
  • Mice, Knockout
  • Mice, Obese
  • Multiprotein Complexes / genetics
  • Multiprotein Complexes / metabolism
  • Protein Biosynthesis*
  • Receptors, G-Protein-Coupled / genetics
  • Receptors, G-Protein-Coupled / immunology*
  • Signal Transduction / drug effects
  • Signal Transduction / genetics
  • TOR Serine-Threonine Kinases / genetics
  • TOR Serine-Threonine Kinases / metabolism*

Substances

  • CCAAT-Enhancer-Binding Protein-beta
  • Cebpb protein, mouse
  • Chemokines
  • Gpbar1 protein, mouse
  • Lipopolysaccharides
  • Multiprotein Complexes
  • Receptors, G-Protein-Coupled
  • mTOR protein, mouse
  • Mechanistic Target of Rapamycin Complex 1
  • TOR Serine-Threonine Kinases