The lipid droplet (LD) is a universal organelle governing the storage and turnover of neutral lipids. Mounting evidence indicates that elevated intramuscular triglyceride (IMTG) in skeletal muscle LDs is closely associated with insulin resistance and Type 2 Diabetes Mellitus (T2DM). Therefore, the identification of the skeletal muscle LD proteome will provide some clues to dissect the mechanism connecting IMTG with T2DM.

In a recent study, Professor Pingsheng Liu's group at the Institution of biophysics, Chinese Academy of Sciences identified 324 LD-associated proteins in mouse skeletal muscle LDs through mass spectrometry analysis. Besides lipid metabolism and membrane traffic proteins, a remarkable number of mitochondrial proteins were observed in the skeletal muscle LD proteome. Moreover, their results revealed for the first time that apolipoprotein A-I (apo A-I), the principal apolipoprotein of high density lipoprotein (HDL) particles, was also localized on skeletal muscle LDs. They further verified that apo A-I was expressed endogenously by skeletal muscle cells.

Their work reports the protein composition and characterization of skeletal muscle LDs and describes a novel LD-associated protein, apo A-I. These results offer new insights into the intricate metabolic functions in skeletal muscle and may promote new directions in future research concerning the etiology and treatment of type 2 diabetes. This study was published on Journal of Proteome Research2011,10(10):4757-4768