Biophysical cues regulating structural organization of fat in adipocytes upon caloric excess

Obesity is an alarmingly common and serious disease. Adipose tissue stores excess calories as triacylglycerol (TAG) and cholesterol ester in lipid droplets (LDs) and mobilizes them as needed. How adipose tissue regulates fat packing in the different depots—white versus brown—during obesity remains poorly understood. We show that adipose LDs are not simple emulsions as originally thought. TAG distributes among LD rims as solid-like and LD cores as liquid-like. During obesity, the number of TAG lamellae increases in a manner that is adipose depot—specific. Additionally, collagen packs randomly in white fat forming a permissive environment for LD expansion but is highly–oriented in brown fat.