Sylvie Caspar-Bauguil1,2,3, Catherine-Ines Kolditz1,2, Corinne Lefort1,2, Isabelle Vila1,2, Etienne Mouisel1,2, Diane Beuzelin1,2, Geneviève Tavernier1,2, Marie-Adeline Marques1,2, Alexia Zakaroff-Girard2,4,5, Christiane Pecher2,4, Marianne Houssier1,2, Lucile Mir1,2, Sarah Nicolas1,2, Cédric Moro1,2, Dominique Langin6,7,8. 1. Inserm, UMR1048, Institute of Metabolic and Cardiovascular Diseases, I2MC, Obesity Research Laboratory, Team 4, CHU Rangueil, 1 avenue Jean Poulhès, BP 84225, 31432, Toulouse Cedex 4, France. 2. University of Toulouse, UMR1048, Paul Sabatier University, Toulouse, France. 3. Toulouse University Hospitals, Department of Clinical Biochemistry, Toulouse, France. 4. Inserm, UMR1048, Cytometry Facility, Institute of Metabolic and Cardiovascular Diseases, Toulouse, France. 5. Inserm, UMR1048, Team 1, Institute of Metabolic and Cardiovascular Diseases, Toulouse, France. 6. Inserm, UMR1048, Institute of Metabolic and Cardiovascular Diseases, I2MC, Obesity Research Laboratory, Team 4, CHU Rangueil, 1 avenue Jean Poulhès, BP 84225, 31432, Toulouse Cedex 4, France. dominique.langin@inserm.fr. 7. University of Toulouse, UMR1048, Paul Sabatier University, Toulouse, France. dominique.langin@inserm.fr. 8. Toulouse University Hospitals, Department of Clinical Biochemistry, Toulouse, France. dominique.langin@inserm.fr.
Abstract
AIMS/HYPOTHESIS: Activation of macrophages by fatty acids (FAs) is a potential mechanism linking obesity to adipose tissue (AT) inflammation and insulin resistance. Here, we investigated the effects of FAs released during adipocyte lipolysis on AT macrophages (ATMs). METHODS: Human THP-1 macrophages were treated with media from human multipotent adipose-derived stem (hMADS) adipocytes stimulated with lipolytic drugs. Macrophages were also treated with mixtures of FAs and an inhibitor of Toll-like receptor 4, since this receptor is activated by saturated FAs. Levels of mRNA and the secretion of inflammation-related molecules were measured in macrophages. FA composition was determined in adipocytes, conditioned media and macrophages. The effect of chronic inhibition or acute activation of fat cell lipolysis on ATM response was investigated in vivo in mice. RESULTS: Whereas palmitic acid alone activates THP-1, conditioned media from hMADS adipocyte lipolysis had no effect on IL, chemokine and cytokine gene expression, and secretion by macrophages. Mixtures of FAs representing de novo lipogenesis or habitual dietary conditions also had no effect. FAs derived from adipocyte lipolysis were taken up by macrophages and stored as triacylglycerol droplets. In vivo, chronic treatment with an antilipolytic drug did not modify gene expression and number of ATMs in mice with intact or defective Tlr4. Stimulation of adipocyte lipolysis increased storage of neutral lipids by macrophages without change in number and phenotype. CONCLUSIONS/ INTERPRETATION: Our data suggest that adipocyte lipolysis does not activate inflammatory pathways in ATMs, which instead may act as scavengers of FAs.
AIMS/HYPOTHESIS: Activation of macrophages by fatty acids (FAs) is a potential mechanism linking obesity to adipose tissue (AT) inflammation and insulin resistance. Here, we investigated the effects of FAs released during adipocyte lipolysis on AT macrophages (ATMs). METHODS:HumanTHP-1 macrophages were treated with media from human multipotent adipose-derived stem (hMADS) adipocytes stimulated with lipolytic drugs. Macrophages were also treated with mixtures of FAs and an inhibitor of Toll-like receptor 4, since this receptor is activated by saturated FAs. Levels of mRNA and the secretion of inflammation-related molecules were measured in macrophages. FA composition was determined in adipocytes, conditioned media and macrophages. The effect of chronic inhibition or acute activation of fat cell lipolysis on ATM response was investigated in vivo in mice. RESULTS: Whereas palmitic acid alone activates THP-1, conditioned media from hMADS adipocyte lipolysis had no effect on IL, chemokine and cytokine gene expression, and secretion by macrophages. Mixtures of FAs representing de novo lipogenesis or habitual dietary conditions also had no effect. FAs derived from adipocyte lipolysis were taken up by macrophages and stored as triacylglycerol droplets. In vivo, chronic treatment with an antilipolytic drug did not modify gene expression and number of ATMs in mice with intact or defective Tlr4. Stimulation of adipocyte lipolysis increased storage of neutral lipids by macrophages without change in number and phenotype. CONCLUSIONS/ INTERPRETATION: Our data suggest that adipocyte lipolysis does not activate inflammatory pathways in ATMs, which instead may act as scavengers of FAs.
Entities:
Keywords:
Adipocyte; Adipose tissue; De novo lipogenesis; Fatty acids; Inflammatory response; Insulin resistance; Lipolysis; Macrophage; TLR4; Triacylglycerol
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