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The Warsaw Voice » Other » December 3, 2008
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How Stress Can Make You Fat
December 3, 2008   
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Polish scientist Zofia 真kowska led a team of researchers in the United States that discovered the mechanism by which mice gain weight when under stress. Experts say this kind of mechanism may also apply to humans. If so, it could revolutionize medicine as well as cosmetology and plastic surgery.

The researchers, working at the Georgetown University Medical Center (GUMC) in Washington, D.C., have developed a "vaccine" that adds or removes fat in specific places in the bodies of laboratory animals. The results of their research work have been published by the premier biomedical research journal Nature Medicine.

Prof. 真kowska and her U.S. associates, including plastic surgeon Stephen Baker and oncologist Michael Johnson, have proved that while you can lose weight due to short-term stress, a long-lasting state of nervous tension induces weight gain. This would explain why people living in constant stress get fatter than they should considering their calorie intake. The most important thing about this research is that 真kowska has learned to control and influence this mechanism.

Stress + food = weight gain
To gain an insight into the mysterious relationship between stress and weight gain, the GUMC scientists conducted a series of experiments on mice. They fed some of them the equivalent of junk food, adding up to a high-fat and high-carbohydrate diet; the other mice received standard food. All the animals were subjected to prolonged stress. They were kept in cold water for an hour each day or locked in the same cage with aggressive alpha males.

It turned out that the stressed-out animals who ate normally did not gain weight, while those on a high-fat diet did. Interestingly, this weight gain was much greater than the scientists expected considering the animals' daily calorie intake.

"The mice gained twice the amount of weight they should have," says Lydia Kuo, a medical student who worked with 真kowska's team as part of her Ph.D. "Eating the same amounts of the same food as the unstressed animals, they became fatter. That means their metabolism must have changed."

The research also showed that the stressed mice started showing symptoms of metabolic disorders and cardiovascular diseases. The animals in this group quickly started displaying glucose intolerance, hypertension, blood vessel inflammation, and fat deposition in their liver and muscles.

Food for thought
The researchers decided to investigate the causes. They found that the main role was played by two biological molecules, the neuropeptide Y (NPY) and the neuropeptide receptor Y2 (Y2R). The neuropeptide is a protein hormone that serves as a neurotransmitter and is found in the medulla oblongata, the hypothalamus and the autonomous nervous system. Its role is to regulate the body's daily rhythm, response to stress, sexual function and hunger (it increases the appetite). NPY also augments the action of noradrenaline (narrowing the blood vessels) and regulates the immune system's response to infections by activating immune cells to seek out pathogens and suppressing them when they are no longer needed. The neuropeptide's release increases after physical exertion, under the influence of stress and as a result of irritation with high-frequency electrical impulses.

真kowska's team discovered that there is a special neurochemical route in the body that is responsible for seeing NPY released into the blood under the influence of stress, which causes fat to start depositing in the animal's body. This mechanism is activated in two types of fat tissue cells: endothelial cells lining the blood vessels and fat cells themselves.

To prove they were right, the scientists injected NPY into different parts of the mice's bodies. They discovered that both NPY and Y2R are activated during stress and are directly responsible for the development of obesity and metabolic syndrome, a set of interrelated factors that contribute to the development of atherosclerosis, type-2 diabetes, and cardiovascular diseases, including heart attack and stroke. Further experiments showed that blocking the NPY receptors prevents fat from depositing and leads to rapid weight loss. Just two weeks after receiving a blocker for this molecule, the mice started getting thinner.

"We couldn't believe such manipulation of fatty tissue was possible at all," 真kowska says. "Various experiments lasting over four years confirmed our suspicions, at least with regard to mice." She hopes the mechanism could be similar in humans. This is suggested by the fact that stress-inducing situations, such as frequent clashes with our boss, our child's chronic disease or everyday traffic jams, cause us imperceptibly to change our diet to a high-calorie one, which can lead to obesity with time.

One important aspect of 真kowska's discovery is that it proved that NPY directly affects fatty tissue, and not only the brain, experts say. "These are the first studies to show that stress has a direct impact on the accumulation of fatty tissue in the body, weight gain and metabolism as such, and that it has nothing to do with the brain," Kuo says. "It's simply a physiological response from fatty tissue."

Great expectations
"We hope our discovery will lead to the development of tools to help treat metabolic syndrome and obesity in humans as well," says 真kowska. "We have observed that the weight loss in mice that we have achieved reduces the fat deposition in their livers and skeletal muscles as well as limiting their glucose intolerance (pre-diabetes state), insulin resistance, hypertension, and various inflammatory diseases. We hope that blocking Y2R might work in people the same way it does in rodents. Further research is needed, however."

Today metabolic syndrome and related diseases have reached epidemic proportions. In 2000 in America alone, 60 million people suffered from metabolic syndrome. "Though we don't expect that people will be able to eat anything they want in the future and still look like film stars just by blocking their Y2R, we do hope our discovery will help improve human health," 真kowska says.

Perhaps in the near term the research could also be applied in cosmetology and plastic surgery. Physiologically implanting fat, using NPY injections, could be used in face rejuvenating treatments, breast, buttock and lip enhancements as well as face reconstruction. The researchers say this method would not only be simple, cheap and safe but also effective and permanent-the effects would last throughout the patient's life.

Another benefit from the discovery, one that takes advantage of the possibility of "shedding" fat from places where it is undesirable by blocking Y2R, could be a revolutionary treatment for obesity eliminating the need for complicated liposuction operations or stomach-shrinking surgery and replacing them with simple injections.

Dr. Roxanne Guy, who chairs the American Society of Plastic Surgeons, says a lot more research is needed before the method can be used on humans, but even today it is possible to imagine that supplying a long-lasting and natural wrinkle filler or a non-surgical method for removing excess fat would revolutionize modern plastic surgery.

Julia Czechowicz

Prof. Zofia 真kowska graduated from the Medical University of Warsaw and obtained her Ph.D. degree in 1979. She specializes in cardiovascular physiology and hypertension. In 1978-1980 she was a lecturer and researcher at the Medical University of Warsaw's Internal Medicine, Hypertension and Angiology Clinic, and worked with the U.S. National Institutes of Health in 1980-1986. She has been a professor at Georgetown University since 1986 and currently heads the Department of Physiology and Biophysics and the Stress Physiology and Research Center of the Georgetown University Medical Center.

真kowska is a member of many scientific societies, including the American Physiological Society, the Council for High Blood Pressure Research, the Council on Atherosclerosis, the Society for Hypertension, the Polish Academy of Sciences, and the Society for Neuroscience. Her publications have appeared in leading medical journals all over the world, including Science, American Journal of Physiology, Proceedings of the National Academy of Sciences, and the Journal of Pharmacology and Experimental Therapeutics.

She received an award from the Polish Cardiac Society in 1980 and the Nicolaus Copernicus Award for Excellence in Neuropeptide Research in 2002. In 1989 she won the Adele Melbourne Holmes Award from the American Heart Association.
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