White adipose tissue

White adipose tissue (WAT) or white fat is one of the two types of adipose tissue found in mammals. The other kind of adipose tissue is brown adipose tissue.

In humans, white adipose tissue composes as much as 20% of the body weight in men and 25% of the body weight in women. Its cells contain a single large fat droplet, which forces the nucleus to be squeezed into a thin rim at the periphery. They have receptors for insulin, growth hormones, norepinephrine and glucocorticoids.

White adipose tissue is used as a store of energy. Upon release of insulin from the pancreas, white adipose cells' insulin receptors cause a dephosphorylation cascade that lead to the inactivation of hormone-sensitive lipase. Upon release of glucagon from the pancreas, glucagon receptors cause a phosphorylation cascade that activates hormone-sensitive lipase, causing the breakdown of the stored fat to fatty acids, which are exported into the blood and bound to albumin, and glycerol, which is exported into the blood freely. Fatty acids are taken up by muscle and cardiac tissue as a fuel source, and glycerol is taken up by the liver for gluconeogenesis.

White adipose tissue also acts as a thermal insulator, helping to maintain body temperature.