Scientists at Tsinghua University in Beijing have discovered a new regulatory mechanism that helps the body control the speed of fat metabolism. New drugs that help in burning stored fat and reduce body weight could be developed through this finding. The study is published in the journal PLOS Biology.
Fat tissue can be white, brown, or beige, differing not only in color but also in metabolism. White fat is principally a storage tissue, with a low rate of metabolism; brown fat tissue, on the other hand, is rich in mitochondria, and burns up stored fat, releasing heat to warm the body, a process called thermogenesis. After prolonged cold exposure, brown-like fat cells develop within white fat, making it beige, and beige fat cells also burn fat to keep the body warm.
A key stimulus for thermogenesis is the hormone norepinephrine, which exerts its effects at the cell surface, and is then taken up into the cell and degraded to prevent overstimulation. A mechanism for the uptake of norepinephrine from fat cells has previously been described, but its rate of uptake is relatively low, suggesting there may be another pathway.
Gratifyingly, when they looked at human genetic association databases, the authors found that possessing versions of the OCT3 gene that make OCT3 protein with a reduced transport function was associated with a higher metabolic rate. Together, these results indicate that OCT3 plays an important role in regulating the rate of beige fat production and thermogenesis in both mice and humans.
"Our finding that a reduction in OCT3 activity can lead to more beige fat and increased thermogenesis indicating the importance of this transporter in catecholamine recycling in adipose tissues." Chen said. "Developing specific OCT3 inhibitors would open up new therapeutic possibilities for metabolic diseases."