High-density lipoprotein inhibits ox-LDL-induced adipokine secretion by upregulating SR-BI expression and suppressing ER Stress pathway

Sci Rep. 2016 Jul 29:6:30889. doi: 10.1038/srep30889.

Abstract

Endoplasmic reticulum stress (ERS) in adipocytes can modulate adipokines secretion. The aim of this study was to explore the protective effect of high-density lipoprotein (HDL) on oxidized low-density lipoprotein (ox-LDL)-induced ERS-C/EBP homologous protein (CHOP) pathway-mediated adipokine secretion. Our results showed that serum adipokines, including visfatin, resistin and TNF-α, correlated inversely with serum HDL cholesterol level in patients with abdominal obesity. In vitro, like ERS inhibitor 4-phenylbutyric acid (PBA), HDL inhibited ox-LDL- or tunicamycin (TM, an ERS inducer)-induced increase in visfatin and resistin secretion. Moreover, HDL inhibited ox-LDL-induced free cholesterol (FC) accumulation in whole cell lysate and in the endoplasmic reticulum. Additionally, like PBA, HDL inhibited ox-LDL- or TM-induced activation of ERS response as assessed by the decreased phosphorylation of protein kinase-like ER kinase and eukaryotic translation initiation factor 2α and reduced nuclear translocation of activating transcription factor 6 as well as the downregulation of Bip and CHOP. Furthermore, HDL increased scavenger receptor class B type I (SR-BI) expression and SR-BI siRNA treatment abolished the inhibitory effects of HDL on ox-LDL-induced FC accumulation and CHOP upregulation. These data indicate that HDL may suppress ox-LDL-induced FC accumulation in adipocytes through upregulation of SR-BI, subsequently preventing ox-LDL-induced ER stress-CHOP pathway-mediated adipocyte inflammation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 3T3-L1 Cells
  • Activating Transcription Factor 6 / metabolism
  • Adipokines / blood
  • Adipokines / metabolism*
  • Animals
  • CD36 Antigens / antagonists & inhibitors
  • CD36 Antigens / genetics
  • CD36 Antigens / metabolism*
  • Cholesterol, HDL / blood
  • Cholesterol, LDL / blood
  • Endoplasmic Reticulum Stress / drug effects*
  • Humans
  • Lipoproteins, HDL / blood
  • Lipoproteins, HDL / pharmacology*
  • Lipoproteins, LDL / pharmacology*
  • Mice
  • Nicotinamide Phosphoribosyltransferase / analysis
  • Nicotinamide Phosphoribosyltransferase / metabolism
  • Obesity / metabolism
  • Obesity / pathology
  • Phenylbutyrates / pharmacology
  • RNA Interference
  • Resistin / analysis
  • Resistin / metabolism
  • Transcription Factor CHOP / metabolism
  • Tunicamycin / pharmacology
  • Up-Regulation / drug effects*
  • eIF-2 Kinase / metabolism

Substances

  • Activating Transcription Factor 6
  • Adipokines
  • Atf6 protein, mouse
  • CD36 Antigens
  • Cholesterol, HDL
  • Cholesterol, LDL
  • Ddit3 protein, mouse
  • Lipoproteins, HDL
  • Lipoproteins, LDL
  • Phenylbutyrates
  • Resistin
  • oxidized low density lipoprotein
  • Tunicamycin
  • Transcription Factor CHOP
  • 4-phenylbutyric acid
  • Nicotinamide Phosphoribosyltransferase
  • PERK kinase
  • eIF-2 Kinase