Editorial. The article discusses research being done on apolipoprotein A-I (ApoA-I). It references the study "High-Density Lipoprotein Maintains Skeletal Muscle Function by Modulating Cellular Respiration in Mice," by M. Lehti et al. published in the 2013 issue of "Circulation." It is hypothesized that understanding the importance of the mechanistic links between high-density lipoprotein (HDL) and energy metabolism would contribute to the prevention and treatment of type 2 diabetes mellitus.