The physiological function of brown adipose tissue is to produceheat using a mitochondrial protein, thermogenin, also calleduncoupling protein-1 (UCP-1). It was previously thought that inhumans, uncoupling proteins (UCPs) were present only in newbornbabies since adult humans lack brown fat; however, two othermembers of the uncoupling protein family, UCP2 and UCP3, wereidentified in adults. This was realized after investigatorsproduced UCP1-knockout mice that were missing the gene for the UCP1protein; even after knockout, they noticed that there was stillfinite proton leakage across the inner membrane that could not beexplained by simple proton diffusion. Subsequent studies intransgenic mice showed that over expression of UCP3 results inreduced body weight gain and adiposity (even after they consumedmore food). Because of studies such as these, UCPs are beingstudied as targets for treating obesity. In adults, UCP2 and UCP3are expressed in white adipose tissue and skeletal muscle. Discusshow and why induction of UCP2 or UCP3 might be helpful in treatingobesity and maintaining a constant amount of adipose tissue.
