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Inhibition of macrophage fatty acid β-oxidation exacerbates palmitate-induced inflammatory and endoplasmic reticulum stress responses

Diabetologia volume 57, pages 1067–1077 (2014)Cite this article

Abstract

Aims/hypothesis

Saturated fatty acids (SFAs) such as palmitate activate inflammatory pathways and elicit an endoplasmic reticulum (ER) stress response in macrophages, thereby contributing to the development of insulin resistance linked to the metabolic syndrome. This study addressed the question of whether or not mitochondrial fatty acid β-oxidation (FAO) affects macrophage responses to SFA.

Methods

We modulated the activity of carnitine palmitoyl transferase 1A (CPT1A) in macrophage-differentiated THP-1 monocytic cells using genetic or pharmacological approaches, treated the cells with palmitate and analysed the proinflammatory and ER stress signatures.

Results

To inhibit FAO, we created THP-1 cells with a stable knockdown (KD) of CPT1A and differentiated them to macrophages. Consequently, in CPT1A-silenced cells FAO was reduced. CPT1A KD in THP-1 macrophages increased proinflammatory signalling, cytokine expression and ER stress responses after palmitate treatment. In addition, in human primary macrophages CPT1A KD elevated palmitate-induced inflammatory gene expression. Pharmacological inhibition of FAO with etomoxir recapitulated the CPT1A KD phenotype. Conversely, overexpression of a malonyl-CoA-insensitive CPT1A M593S mutant reduced inflammatory and ER stress responses to palmitate in THP-1 macrophages. Macrophages with a CPT1A KD accumulated diacylglycerols and triacylglycerols after palmitate treatment, while ceramide accumulation remained unaltered. Moreover, lipidomic analysis of ER phospholipids revealed increased palmitate incorporation into phosphatidylethanolamine and phosphatidylserine classes associated with the CPT1A KD.

Conclusions/interpretation

Our data indicate that FAO attenuates inflammatory and ER stress responses in SFA-exposed macrophages, suggesting an anti-inflammatory impact of drugs that activate FAO.

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Abbreviations

AMPK:

AMP-dependent protein kinase

CPT1:

Carnitine palmitoyl transferase 1

CPT1A:

Liver isoform of carnitine palmitoyl transferase 1

CV:

Control virus

DAG:

Diacylglycerol

DFPU:

Difluorophenylurethane

eIF2α:

Eukaryotic initiation factor 2α

ER:

Endoplasmic reticulum

FAO:

Fatty acid β-oxidation

IRE1α:

Inositol requiring enzyme 1α

IκB:

Inhibitor of κB

KD:

Knockdown

LC–MS/MS:

Liquid chromatography–tandem mass spectrometry

MAPK:

Mitogen-activated protein kinase

NLS:

Neutral loss scan

OCR:

Oxygen consumption rate

PBA:

Phenylbutyric acid

PC:

Phosphatidylcholine

PE:

Phosphatidylethanolamine

PEMT:

Phosphatidylethanolamine-methyltransferase

PERK:

Protein kinase RNA-like endoplasmic reticulum kinase

PIS:

Precursor ion scan

PKC:

Protein kinase C

PMA:

Phorbol 12-myristate 13-acetate

PS:

Phosphatidylserine

SFA:

Saturated fatty acid

shRNA:

Small hairpin RNA

siRNA:

Small interfering RNA

sXBP1:

Spliced X-box binding protein 1

TAG:

Triacylglycerol

TLR:

Toll-like receptor

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Acknowledgements

We thank I. Elschner (Institute of Biochemistry I, Goethe University Frankfurt, Frankfurt, Germany) for technical assistance. We also thank D. Kauhanen and K. Tarasov (Zora Biosciences Oy, Espoo, Finland) for assistance with the shotgun lipidomics analyses.

Funding

This work was supported by grants from Deutsche Forschungsgemeinschaft (grant no. BR999) and by the Else Kröner Fresenius Foundation (Translational Research Innovation—Pharma [TRIP]). Mass spectrometric measurements of DAGs were supported by a grant (RCM) from the US National Institutes of Health (Lipid Maps, GM006938).

Duality of interest

The authors declare that there is no duality of interest associated with this manuscript.

Contribution statement

DN acquired data, drafted and revised the manuscript. SL acquired data and edited the manuscript. TJL and RCM contributed to DAG analysis and revised the manuscript. KE contributed to the shotgun lipidomics analysis and revised the manuscript. NF and GG contributed to ceramide analysis and revised the manuscript. BB analysed data and revised the manuscript. All of the authors approved the final version of the manuscript. BB is responsible for the integrity of the work as a whole.

Author information

Affiliations

  1. Faculty of Medicine, Institute of Biochemistry I/ZAFES, Goethe University Frankfurt, Theodor-Stern-Kai 7, 60590, Frankfurt, Germany

    Dmitry Namgaladze, Sebastian Lips & Bernhard Brüne

  2. Department of Pharmacology, University of Colorado Denver, Aurora, CO, USA

    Thomas J. Leiker & Robert C. Murphy

  3. Zora Biosciences Oy, Espoo, Finland

    Kim Ekroos

  4. pharmazentrum Frankfurt/ZAFES, Institute of Clinical Pharmacology, Goethe University Frankfurt, Frankfurt, Germany

    Nerea Ferreiros & Gerd Geisslinger

Authors
  1. Dmitry Namgaladze
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  2. Sebastian Lips
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  3. Thomas J. Leiker
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  4. Robert C. Murphy
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  8. Bernhard Brüne
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Corresponding author

Correspondence to Bernhard Brüne.

Additional information

Dmitry Namgaladze and Sebastian Lips contributed equally to this study.

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Namgaladze, D., Lips, S., Leiker, T.J. et al. Inhibition of macrophage fatty acid β-oxidation exacerbates palmitate-induced inflammatory and endoplasmic reticulum stress responses. Diabetologia 57, 1067–1077 (2014). https://doi.org/10.1007/s00125-014-3173-4

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  • DOI: https://doi.org/10.1007/s00125-014-3173-4

Keywords

  • β-Oxidation
  • Endoplasmic reticulum stress
  • Fatty acids
  • Inflammation
  • Macrophages