Biologists at The Scripps Research Institute (TSRI) in La Jolla, California, have identified a signaling pathway that switches on a powerful calorie-burning process in brown fat cells. The study, which was reported online on July 28, 2014 in PNAS, sheds light on a process known as "brown fat thermogenesis," which is of great interest to medical researchers because it naturally stimulates weight loss and may also protect against diabetes. "This finding offers new possibilities for the therapeutic activation of brown fat thermogenesis," said team leader Dr. Anastasia Kralli, associate professor in TSRI's Departments of Chemical Physiology and Cell Biology. Most fat cells in our bodies are "white fat" cells that store fat as a reserve energy supply. But we and other mammals also have depots of "brown fat" cells. These apparently evolved not to store but to burn energy—quickly, as a way of generating heat and keeping the body warm in cold conditions, as well as possibly to get rid of excess caloric intake. Human babies as well as mammals that hibernate have relatively extensive brown fat tissues. Scientists have found in recent years that many adult humans have significant levels of brown fat, which are located mostly in the neck and shoulders, and appear to help regulate body weight and blood sugar. Low temperatures activate the brown-fat thermogenesis process via the sympathetic nervous system: Nerve ends in brown fat tissue release the neurotransmitter norepinephrine, and that triggers a shift in metabolism within the brown fat cells, which are densely packed with tiny biological energy reactors called mitochondria. "The mitochondria start generating heat instead of useful chemical energy; it's like revving the engines of a lot of parked cars," said first author Dr.
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