PPARβ/δ prevents endoplasmic reticulum stress-associated inflammation and insulin resistance in skeletal muscle cells through an AMPK-dependent mechanism
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Endoplasmic reticulum (ER) stress, which is involved in the link between inflammation and insulin resistance, contributes to the development of type 2 diabetes mellitus. In this study, we assessed whether peroxisome proliferator-activated receptor (PPAR)β/δ prevented ER stress-associated inflammation and insulin resistance in skeletal muscle cells.
Studies were conducted in mouse C2C12 myotubes, in the human myogenic cell line LHCN-M2 and in skeletal muscle from wild-type and PPARβ/δ-deficient mice and mice exposed to a high-fat diet.
The PPARβ/δ agonist GW501516 prevented lipid-induced ER stress in mouse and human myotubes and in skeletal muscle of mice fed a high-fat diet. PPARβ/δ activation also prevented thapsigargin- and tunicamycin-induced ER stress in human and murine skeletal muscle cells. In agreement with this, PPARβ/δ activation prevented ER stress-associated inflammation and insulin resistance, and glucose-intolerant PPARβ/δ-deficient mice showed increased phosphorylated levels of inositol-requiring 1 transmembrane kinase/endonuclease-1α in skeletal muscle. Our findings demonstrate that PPARβ/δ activation prevents ER stress through the activation of AMP-activated protein kinase (AMPK), and the subsequent inhibition of extracellular-signal-regulated kinase (ERK)1/2 due to the inhibitory crosstalk between AMPK and ERK1/2, since overexpression of a dominant negative AMPK construct (K45R) reversed the effects attained by PPARβ/δ activation.
Overall, these findings indicate that PPARβ/δ prevents ER stress, inflammation and insulin resistance in skeletal muscle cells by activating AMPK.
KeywordsAMPK ER stress ERK1/2 NF-κB PPAR β/δ
Acetyl-CoA carboxylase 2
AMP-activated protein kinase
Activating transcription factor-6
Εukaryotic initiation factor 2α
Electrophoretic mobility shift assay
Extracellular signal-regulated kinase
Inhibitor of κB
Inositol-requiring 1 transmembrane kinase/endonuclease-1α
Eukaryotic translation initiation factor-2α kinase 3
Peroxisome proliferator-activated receptor
Unfolded protein response
X-box binding protein-1
We thank A. Orozco (Department of Biochemistry and Molecular Biology of the University of Barcelona, Spain) for experimental assistance with human myotube cultures. We thank M. J. Birnbaum (Howard Hughes Medical Institute, University of Pennsylvania, Philadelphia, PA, USA) for the pcDNA3/pAMPKalpha2-K45R plasmid.
This study was partly supported by funds from the Spanish Ministerio de Economía y Competitividad (SAF2009-06939 and SAF2012-30708) and the European Union ERDF. CIBER de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM) is an Instituto de Salud Carlos III project. LS was supported by an FPI grant from the Spanish Ministerio de Economía y Competitividad. We thank the University of Barcelona’s Language Advisory Service for revising the manuscript.
LS, EB, AMG-F, XP, LM, WW and MV-C processed the samples, analysed and prepared the data and were involved in drafting the article. LS, EB, AG-F, XP, LM and WW contributed to the interpretation of the data and revised the article. MV-C and LS designed the experiments and analysed and interpreted the data. MV-C wrote the manuscript and is responsible for the integrity of the work as a whole. All authors approved the final version of the manuscript.
Duality of interest
The authors declare that there is no duality of interest associated with this manuscript.
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