Diabetologia, 2014, Vol.57(5), pp.1067-1077
Byline: Dmitry Namgaladze (1), Sebastian Lips (1), Thomas J. Leiker (2), Robert C. Murphy (2), Kim Ekroos (3), Nerea Ferreiros (4), Gerd Geisslinger (4), Bernhard Brune (1) Keywords: [beta]-Oxidation; Endoplasmic reticulum stress; Fatty acids; Inflammation; Macrophages 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 [beta]-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. Author Affiliation: (1) Faculty of Medicine, Institute of Biochemistry I/ZAFES, Goethe University Frankfurt, Theodor-Stern-Kai 7, 60590, Frankfurt, Germany (2) Department of Pharmacology, University of Colorado Denver, Aurora, CO, USA (3) Zora Biosciences Oy, Espoo, Finland (4) pharmazentrum Frankfurt/ZAFES, Institute of Clinical Pharmacology, Goethe University Frankfurt, Frankfurt, Germany Article History: Registration Date: 13/01/2014 Received Date: 25/11/2013 Accepted Date: 02/01/2014 Online Date: 01/02/2014 Article note: Dmitry Namgaladze and Sebastian Lips contributed equally to this study. Electronic supplementary material The online version of this article (doi: 10.1007/s00125-014-3173-4) contains peer-reviewed but unedited supplementary material, which is available to authorised users.
β-Oxidation ; Endoplasmic reticulum stress ; Fatty acids ; Inflammation ; Macrophages
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