Connective tissue consisting mainly of fat cells, specialized to synthesize and contain large globules of fat, within a structural network of fibres. It is found mainly under the skin but also in deposits between the muscles, in the intestines and in their membrane folds, around the heart, and elsewhere. The fat stored in this tissue comes from dietary fats or is produced in the body. It acts as a fuel reserve for times of starvation or great exertion, helps conserve body heat, and forms pads between organs.
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In endothermic animals, body heat is maintained by signaling the mitochondria to allow protons to run back along the gradient without producing ATP. This can occur since an alternative return route for the protons exists through an uncoupling protein in the inner membrane. This protein, known as uncoupling protein 1 (thermogenin), facilitates the return of the protons after they have been actively pumped out of the mitochondria by the electron transport chain. This alternative route for protons uncouples oxidative phosphorylation and the energy in the PMF is released as heat.
To some degree, all cells of endotherms give off heat, especially when body temperature is below a regulatory threshold. However, brown adipose tissue is highly specialized for this non-shivering thermogenesis. Firstly, each cell has a higher number of mitochondria compared to more typical cells. Secondly, these mitochondria have a higher than normal concentration of thermogenin in the inner membrane.
The burning of brown fat provides a baby with an alternative means of heat regulation.
Osteopontin mediates obesity-induced adipose tissue macrophage infiltration and insulin resistance in mice.(Research Article)
Oct 01, 2007; Obesity is associated with a state of chronic, low-grade inflammation characterized by abnormal cytokine production and...