Dynamics of skeletal muscle lipid pools

• Intramyocellular triglycerides (IMTG) dynamics determine skeletal muscle fat oxidation.
• Disruption of IMTG dynamics may promote insulin resistance.
• Adipose triglyceride lipase (ATGL) is a dominant lipase in skeletal muscle.
• The molecular mechanism of contraction-mediated lipolysis still remain unclear.

Intramyocellular triacylglycerol (IMTG) is emerging as an important energy fuel source during muscle contraction and are adaptively increased in response to exercise, without adverse physiological effects. Paradoxically, elevated IMTG content in obese and type 2 diabetics has been linked to insulin resistance, highlighting the importance of IMTG pools in physiology and pathology. Two separate views suggest that IMTG dynamics are determinant for skeletal muscle fat oxidation, and that disruption of IMTG dynamics facilitates the accumulation of lipotoxic intermediates such as diacylglycerols and ceramides that interfere with insulin signaling. Thus, understanding the factors that control IMTG dynamics is crucial. Here we discuss recent literature describing the regulation of IMTG pools with a particular emphasis on lipases and lipid droplet (LD)-associated proteins.