Figure 4. Autophagy in the metabolism of cellular lipid stores.
A. Autophagy constitutively mobilizes cellular lipid droplets by macrolipophagy. Lipid droplets are sequestered inside autophagosomes and delivered to the lysosomes for degradation, resulting in free fatty acid release for cellular respiration. B. During acute lipid challenge most cells maximally activate macrolipophagy to prevent excessive cellular lipid accumulation. C. Chronically maintained lipid challenges reduce macroautophagic degradation of lipids by decreasing the efficiency of autophagosome-lysosomal fusion, leading to further cellular lipid accumulation.