Lipid droplet

Lipid droplets, also known as lipid bodies, oil bodies, or adiposomes, are endoplasmic reticulum-derived neutral lipid storage organelles consisting of a core of hydrophobic neutral lipids enveloped by a protein-studded phospholipid monolayer. Lipid droplets (LDs) are conserved across almost all species, from bacteria to archaea through fungi, plants (as oil bodies), algae, insects, and all mammals, including humans.

As organelles, lipid droplets function as a storage compartment for a cell's metabolic energy reserves. Lipid droplets are the only cellular compartment dedicated to the storage of triacylglycerols (TAGs) and other neutral lipids, making these organelles crucial for both energy storage functions and for the aversion of cellular lipotoxicity. Lipid droplets also serve as a reservoir for cholesterol esters (CEs) and fat-soluble vitamins, as well as many other polymeric lipids.

Both the appearance and the distribution of lipid droplets changes by cell type, and may reflect the specialized functions of a given type of cell. Generally, the diameter of lipid droplets ranges from 0.1–5 µm in non-adipocyte cells, but increases to over 100 µm in white adipocytes. Research on lipid droplet function has proved crucial in both health and disease, as these organelles are known to support many large-scale biological processes such as development and aging.

The role of lipid droplets outside of neutral lipid storage remains a topic of ongoing research.