Mammals have two main types of fat: brown fat and white fat. Brown fat is especially abundant in newborns and in mammals undergoing hibernation. The primary function of brown fat is to produce body heat so that the animal does not shiver. In contrast to white fat cells, which contain a single lipid droplet, brown fat cells contain numerous smaller droplets and a higher number of mitochondria, and it is these mitochondria and their high iron content that makes this fat tissue brown. Brown fat also contains more small blood vessels than white fat, since it has a greater need for oxygen than most tissues.
Recently, researchers at the University of Utah School of Medicine have identified stem cells from brown fat. The principal researcher of this project, Amit Patel, associate professor of medicine, refuted an old dogma – that adult humans do not possess brown fat. Children have large amounts of brown fat that is highly metabolically active. Children can eat a great deal and not gain any weight, relative to adults. Adults, on the other hand, have an abundance of white fat, and accumulation of white fat leads to weight gain and cardiovascular disease (something not seen in brown fat). As people age, the amount of white fat increases and the amount of brown fat decreases, which contributes to the onset of diabetes and high cholesterol.
As Patel put it, “If you have more brown fat, you weigh less, you’re metabolically efficient, and you have fewer instances of diabetes and high cholesterol. The unique identification of human brown fat stem cells in the chest of patients aged 28-34 years is profound. We were able to isolate the human stem cells, culture and grow them, and implant them into a pre-human model which has demonstrated positive effects on glucose levels.”
This new discovery of finding brown fat stem cells may help in identifying potential drugs that may increase the body’s own ability to make brown fat or find novel ways to directly implant brown fat stem cells into patients.