Hepatic regulation of VLDL receptor by PPARβ/δ and FGF21 modulates non-alcoholic fatty liver disease

Abstract

[Objective] The very low-density lipoprotein receptor (VLDLR) plays an important role in the development of hepatic steatosis. In this study, we investigated the role of Peroxisome Proliferator-Activated Receptor (PPAR)b/d and fibroblast growth factor 21 (FGF21) in hepatic VLDLR regulation. [Methods] Studies were conducted in wild-type and Pparb/d-null mice, primary mouse hepatocytes, human Huh-7 hepatocytes, and liver biopsies from control subjects and patients with moderate and severe hepatic steatosis. [Results] Increased VLDLR levels were observed in liver of Pparb/d-null mice and in Pparb/d-knocked down mouse primary hepatocytes through mechanisms involving the heme-regulated eukaryotic translation initiation factor 2a (eIF2a) kinase (HRI), activating transcription factor (ATF) 4 and the oxidative stress-induced nuclear factor (erythroid-derived 2)-like 2 (Nrf2) pathways. Moreover, by using a neutralizing antibody against FGF21, Fgf21-null mice and by treating mice with recombinant FGF21, we show that FGF21 may protect against hepatic steatosis by attenuating endoplasmic reticulum (ER) stress-induced VLDLR upregulation. Finally, in liver biopsies from patients with moderate and severe hepatic steatosis, we observed an increase in VLDLR levels that was accompanied by a reduction in PPARb/d mRNA abundance and DNA-binding activity compared with control subjects. [Conclusions]: Overall, these findings provide new mechanisms by which PPARb/d and FGF21 regulate VLDLR levels and influence hepatic steatosis development. ; This study was partly supported by funds from the Spanish Ministry of the Economy and Competitiveness (SAF2015-64146-R to MVC, SAF2014-55725 to FV, and SAF2015-65267-R to AMV) and European Union ERDF funds. CIBER de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM) and CIBER Fisiopatologia de la Obesidad y Nutrición (CIBERobn) are Carlos III Health Institute projects. WW is supported by Start-Up Grants from the Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, and by the Région Midi-Pyrénées, France, and TQL is supported by a CONACyT (National Council for Science and Technology in Mexico) Ph.D. scholarship. ; Peer reviewed