Intestinal Aquaporins

Abstract

Aquaporins (AQPs) are integral, hydrophobic, and transmembrane proteins that facilitate passive transport of water depending on the osmotic pressure on both sides of the cell membrane. Of these channel proteins, those that are permeable only to water are called 'classical aquaporins', those that allow the passage of small molecules such as glycerol in addition to water are called 'aquaglyceroporins', and those with different structures and cellular distributions are called 'super aquaporins'. Aquaporins have a great role in the gastrointestinal tract as well as in the whole organism. Transepithelial transport of fluid in the intestine occurs spontaneously, either by paracellular or cellular routes, or both. The paracellular pathway is mediated by tight junctions in the intestinal epithelium and their passage is regulated based on the size and load of substances, while the cellular pathway is passive diffusion mediated by aquaporins and co-transporters. Among them, aquaporins are the major cellular pathway for bidirectional fluid transport in the gut. Aquaporins have important roles in the gut. Based on these roles, information, and research on whether aquaporins can be regulated by drugs and dietary supplements to increase intestinal health and improve their functions is increasing day by day. In this review, the functions of aquaporins in the intestinal tract, their situations in intestinal diseases, and the drugs and dietary supplements used for the treatment of these diseases are discussed together with current studies.