HILPDA Uncouples Lipid Droplet Accumulation in Adipose Tissue Macrophages from Inflammation and Metabolic Dysregulation

Abstract

Summary: Obesity leads to a state of chronic, low-grade inflammation that features the accumulation of lipid-laden macrophages in adipose tissue. Here, we determined the role of macrophage lipid-droplet accumulation in the development of obesity-induced adipose-tissue inflammation, using mice with myeloid-specific deficiency of the lipid-inducible HILPDA protein. HILPDA deficiency markedly reduced intracellular lipid levels and accumulation of fluorescently labeled fatty acids. Decreased lipid storage in HILPDA-deficient macrophages can be rescued by inhibition of adipose triglyceride lipase (ATGL) and is associated with increased oxidative metabolism. In diet-induced obese mice, HILPDA deficiency does not alter inflammatory and metabolic parameters, despite markedly reducing lipid accumulation in macrophages. Overall, we find that HILPDA is a lipid-inducible, physiological inhibitor of ATGL-mediated lipolysis in macrophages and uncouples lipid storage in adipose tissue macrophages from inflammation and metabolic dysregulation. Our data question the contribution of lipid droplet accumulation in adipose tissue macrophages in obesity-induced inflammation and metabolic dysregulation. : Lipid-laden macrophages are believed to play a key role in obesity-induced adipose tissue inflammation. Van Dierendonck et al. show that the lipid-droplet-associated protein HILPDA regulates intracellular triglyceride breakdown by directly inhibiting ATGL and that reduced lipid accumulation in adipose tissue macrophages surprisingly does not affect adipose tissue inflammation. Keywords: Hilpda, ATGL, fatty acid metabolism, lipid droplets, macrophages, inflammation, obesity