Suchergebnisse

12 páginas, 8 figuras.-- et al. ; Metabolic syndrome-associated dyslipidemia is mainly initiated by hepatic overproduction of the plasma lipoproteins carrying triglycerides. Here we examined the effects of the peroxisome proliferator-activated receptors (PPAR)-β/δ activator GW501516 on high-fat diet (HFD)-induced hypertriglyceridemia and hepatic fatty acid oxidation. Exposure to the HFD caused hypertriglyceridemia that was accompanied by reduced hepatic mRNA levels of PPAR-γ coactivator 1 (PGC-1)-α and lipin 1, and these effects were prevented by GW501516 treatment. GW501516 treatment also increased nuclear lipin 1 protein levels, leading to amplification in the PGC-1α-PPARα signaling system, as demonstrated by the increase in PPARα levels and PPARα-DNA binding activity and the increased expression of PPARα-target genes involved in fatty acid oxidation. These effects of GW501516 were accompanied by an increase in plasma β-hydroxybutyrate levels, demonstrating enhanced hepatic fatty acid oxidation. Moreover, GW501516 increased the levels of the hepatic endogenous ligand for PPARα, 16:0/18:1-phosphatidilcholine and markedly enhanced the expression of the hepatic Vldl receptor. Interestingly, GW501516 prevented the reduction in AMP-activated protein kinase (AMPK) phosphorylation and the increase in phosphorylated levels of ERK1/2 caused by HFD. In addition, our data indicate that the activation of AMPK after GW501516 treatment in mice fed HFD might be the result of an increase in the AMP to ATP ratio in hepatocytes. These findings indicate that the hypotriglyceridemic effect of GW501516 in HFD-fed mice is accompanied by an increase in phospho-AMPK levels and the amplification of the PGC-1α-lipin 1-PPARα pathway. ; This work was partly supported by funds from the Spanish Ministerio de Ciencia e Innovación (SAF2009-06939 and BFU2010-18826) and the European Union European Regional Development Fund funds. R.R.-C. was supported by a grant from the Fundación Ramón Areces. L.S.-M. was supported by a Formación de Personal Investigador grant from the Spanish Ministerio de Ciencia e Innovación. A.M.A. was supported by a predoctoral fellowship from the Regional Government of Castilla y León (Spain). ; Peer reviewed

Peroxisome proliferator-activated receptor β/δ (PPARβ/δ) activates AMP-activated protein kinase (AMPK) and plays a crucial role in glucose and lipid metabolism. Here, we examine whether PPARβ/δ activation effects depend on growth differentiation factor 15 (GDF15), a stress response cytokine that regulates energy metabolism. Pharmacological PPARβ/δ activation increases GDF15 levels and ameliorates glucose intolerance, fatty acid oxidation, endoplasmic reticulum stress, and inflammation, and activates AMPK in HFD-fed mice, whereas these effects are abrogated by the injection of a GDF15 neutralizing antibody and in Gdf15-/- mice. The AMPK-p53 pathway is involved in the PPARβ/δ-mediated increase in GDF15, which in turn activates again AMPK. Consistently, Gdf15-/- mice show reduced AMPK activation in skeletal muscle, whereas GDF15 administration results in AMPK activation in this organ. Collectively, these data reveal a mechanism by which PPARβ/δ activation increases GDF15 levels via AMPK and p53, which in turn mediates the metabolic effects of PPARβ/δ by sustaining AMPK activation. ; Published version ; This study was partly supported by grants from the Spanish Ministry of Economy and Competitiveness (SAF2015-64146- R and RTI2018-093999-B-100) and European Union ERDF funds.

[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