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Biochim Biophys Acta Mol Cell Biol Lipids. 2017 Sep;1862(9):1001-1012. doi: 10.1016/j.bbalip.2017.06.012. Epub 2017 Jun 23.

Adipose tissue conditioned media support macrophage lipid-droplet biogenesis by interfering with autophagic flux.

Author information

1
The Department of Clinical Biochemistry and Pharmacology, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva 84103, Israel; The National Institute of Biotechnology in the Negev (NIBN), Ben-Gurion University of the Negev, Beer-Sheva 84103, Israel.
2
The National Institute of Biotechnology in the Negev (NIBN), Ben-Gurion University of the Negev, Beer-Sheva 84103, Israel; Department of Life Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel.
3
Bert W. Strassburger Lipid Center, Sheba Medical Center, Tel-Hashomer, Israel; Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv 69978, Israel.
4
Institute of Anatomy, University of Leipzig, 04103 Leipzig, Germany.
5
The Department of Clinical Biochemistry and Pharmacology, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva 84103, Israel.
6
The Department of Clinical Biochemistry and Pharmacology, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva 84103, Israel; The National Institute of Biotechnology in the Negev (NIBN), Ben-Gurion University of the Negev, Beer-Sheva 84103, Israel. Electronic address: rudich@bgu.ac.il.

Abstract

Obesity promotes the biogenesis of adipose tissue (AT) foam cells (FC), which contribute to AT insulin resistance. Autophagy, an evolutionarily-conserved house-keeping process, was implicated in cellular lipid handling by either feeding and/or degrading lipid-droplets (LDs). We hypothesized that beyond phagocytosis of dead adipocytes, AT-FC biogenesis is supported by the AT microenvironment by regulating autophagy. Non-polarized ("M0") RAW264.7 macrophages exposed to AT conditioned media (AT-CM) exhibited a markedly enhanced LDs biogenesis rate compared to control cells (8.3 Vs 0.3 LDs/cells/h, p<0.005). Autophagic flux was decreased by AT-CM, and fluorescently following autophagosomes over time revealed ~20% decline in new autophagic vesicles' formation rate, and 60-70% decrease in autophagosomal growth rate, without marked alternations in the acidic lysosomal compartment. Suppressing autophagy by either targeting autophagosome formation (pharmacologically, with 3-methyladenine or genetically, with Atg12±Atg7-siRNA), decreased the rate of LD formation induced by oleic acid. Conversely, interfering with late autophago-lysosomal function, either pharmacologically with bafilomycin-A1, chloroquine or leupeptin, enhanced LD formation in macrophages without affecting LD degradation rate. Similarly enhanced LD biogenesis rate was induced by siRNA targeting Lamp-1 or the V-ATPase. Collectively, we propose that secreted products from AT interrupt late autophagosome maturation in macrophages, supporting enhanced LDs biogenesis and AT-FC formation, thereby contributing to AT dysfunction in obesity.

KEYWORDS:

Adipose tissue macrophages; Autophagy; Foam cells; Lipid handling; Obesity

PMID:
28652194
DOI:
10.1016/j.bbalip.2017.06.012
[Indexed for MEDLINE]
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