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

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.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenine / analogs & derivatives
  • Adenine / pharmacology
  • Adipocytes / metabolism
  • Adipocytes / physiology
  • Adipose Tissue / drug effects
  • Adipose Tissue / metabolism
  • Adipose Tissue / physiology*
  • Animals
  • Autophagosomes / drug effects
  • Autophagosomes / metabolism
  • Autophagosomes / physiology
  • Autophagy / drug effects
  • Autophagy / physiology*
  • Cell Line
  • Culture Media, Conditioned / metabolism*
  • Lipid Droplets / drug effects
  • Lipid Droplets / metabolism*
  • Lipid Droplets / physiology*
  • Lysosomes / drug effects
  • Lysosomes / metabolism
  • Lysosomes / physiology
  • Macrophages / drug effects
  • Macrophages / metabolism*
  • Macrophages / physiology*
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Obesity / metabolism
  • Oleic Acid / pharmacology
  • Phagocytosis / drug effects
  • Phagocytosis / physiology
  • RAW 264.7 Cells


  • Culture Media, Conditioned
  • Oleic Acid
  • 3-methyladenine
  • Adenine