What makes a fat fat cells? Overeating, of course, is a reason for these cells pack the fat molecules further. Now scientists have discovered that a protein called leptin, which is known to suppress appetite, also lights a fire under the individual cells - cells not only fat, but those in the muscles and pancreas also - to burn fat reserves . The discovery, published in today's issue of Proceedings of the National Academy of Sciences suggests that leptin could be the alter ego of the hormone insulin: Although the socks of insulin fat away in individual cells, leptin may be the key to unlocking it.
Previous studies have shown that leptin triggers a brain region called the hypothalamus to send unidentified signals that suppress appetite. To probe how leptin influences individual cells, Roger Unger and colleagues at the University of Texas Southwestern Medical Center at Dallas have injected mice with a retrovirus carrying extra copies of the gene for leptin, which the virus inserted into the genome mouse. The mice with high levels of leptin in blood stored 80% less fat in muscle, liver and pancreatic cells than untreated counterparts on an identical scheme.
next team pancreatic cells in culture Unger with leptin and palmitate (fat long molecule chain), tritium labeled, a radioactive form of hydrogen. They found that the pancreatic cells bathed leptin took 52% less of the labeled palmitate and burned 42% more fat reserves than did cells in a free leptin culture.
The results suggest that, in addition to the suppression of appetite in the brain, leptin acts as a cell micromanager, regulation of energy storage in individual cells with insulin. Thus, Unger said, leptin are not simply "to turn people into models of fashion." Work "raises strong indications" that leptin acts on individual cells, says Jeffrey Flier, an endocrinologist at Beth Israel Medical Center Deaconess in Boston. But he warned that "it is not known at this stage" if the hypothalamus or individual cells are the primary target of leptin.
0 Komentar