Figure 7. Proposed mechanistic model of PLIN5 in skeletal muscle upon various metabolic states.

In the resting state, PLIN5 protects LD from lipolytic attack by lipases. An increase in PLIN5 content (red arrows) slows down lipolysis and FA oxidation, favoring a switch towards glucose utilization. During lipolytic stimulation (i.e. PKA activation or contraction), PLIN5 enhances FA oxidation, thereby increasing CO₂ production. It has been suggested that PLIN5 could provide a physical linkage between LD and mitochondria. We can hypothesize that this relocation has metabolic consequences by facilitating FA channeling from LD to mitochondria, thus allowing a more efficient coupling between IMTG lipolysis and FA oxidation upon increased metabolic demand. Finally, the up-regulation of PLIN5 with high-fat feeding is insufficient to protect from LD-mediated CER accumulation. FA: Fatty Acids; IMTG: Intramyocellular Triacylglycerols; CER: Ceramides.