Revisiting the connection between intramyocellular lipids and insulin resistance: a long and winding road.

In the mid-1990s, researchers began to re-examine type 2 diabetes from a more 'lipocentric' perspective; giving strong consideration to the idea that systemic lipid imbalances give rise to glucose dysregulation, rather than vice versa. At the forefront of this paradigm shift was a report by Krssak and colleagues (Diabetologia 1999; 42:113-116) showing that intramyocellular lipid content, measured via the (then) novel application of proton nuclear magnetic resonance spectroscopy, served as a robust indicator of muscle insulin sensitivity in healthy individuals. A subsequent wave of investigations produced compelling correlative evidence linking ectopic lipid deposition within skeletal myocytes to the development of obesity-associated insulin resistance. But this relationship has proven much more complex than originally imagined, and scientists today are still left wondering if and how the intramyocellular accumulation of lipid droplets has a direct bearing on insulin action. Originally viewed as a simple storage depot, the lipid droplet is now recognised as an essential and sophisticated organelle that actively participates in numerous cellular processes. This edition of 'Then and now' revisits the connection between intramuscular lipids and insulin resistance and looks to future research aimed at understanding the dynamic interplay between lipid droplet biology and metabolic health.