Osmolyte

Osmolytes are organic compounds affecting osmosis. They are soluble in the solution within a cell. They play a role in maintaining cell volume and fluid balance. For example, when a cell swells due to external osmotic pressure, membrane channels open and allow efflux of osmolytes which carry water with them, restoring normal cell volume.

Natural osmolytes include trimethylamine N-oxide (TMAO), dimethylsulfoniopropionate, trimethylglycine, and others.