Uncoupling protein 3 (mitochondrial, proton carrier) (UCP3) is a mitochondrial membrane protein expressed in humans selectively in skeletal muscle and brown adipose tissue. It is suggested to protect mitochondria against aging and lipid-induced damage, possibly via modulation of reactive oxygen species (ROS) production. UCP3 is an important potential target for treatment of aging, degenerative diseases, diabetes, and perhaps obesity.