Making Mice Fat or Thin with an Injection
Stressed mice get fat, according to a study out of Georgetown University Medical Center. And now they know the mechanism that does it; in fact, they can manipulate that mechanism to make the mice fat, or they can block the mechanism and keep the mice from getting fat no matter how stressed they may be.
Dr. Zofia Zukowska, who led the study, stressed out her mice for two weeks by making them stand in cold water or forcing them to face an aggressive alpha mouse. She found that the stressed mice, when fed a high fat "junk food" diet, gained twice as much fat as expected from their intake, all of it around their belly.
Not only did the stressed mice get twice as fat as non-stressed mice on the same diet, but they also showed signs of metabolic syndrome, including glucose intolerance, high blood pressure, inflamed blood vessels, and fat in their livers and muscles.
The researchers not only used stress to make the mice fat; they also discovered, and then played with, the mechanism by which stress leads to weight gain in mice. Stress activates a neurotransmitter called Neuropeptide Y (NPY) to bind to its receptor, called Neuropeptide Y Receptor (Y2R), in fat tissue, causing the fat cells to swell in both size and number and leading to apple-shaped obesity and metabolic syndrome.
By injecting mice with NPY, the researchers were able to generate fat in mice wherever they wanted it. And by injecting Y2R blocker into the mice's abdominal fat, they were able to shrink the fat accumulation by fifty percent in only two weeks and eliminate the metabolic syndrome.
Plastic surgeons, of course, are excited about eventually using an NPY injection to build fat in wrinkled lips and using a Y2R injection to melt away fat without surgery. That peculiar prospect aside, the findings should comfort those of us who are stressed out and seem to grow fat out of all proportion to the amount we eat. In addition to eating right, activities that lower stress may help get rid of that spare tire.
Georgetown Medical Center news release