How we can stop stress from making us obese

Contact: Dr. Branwen Morgan
b.morgan@garvan.org.au
61-043-407-1326
Research Australia

Professor Herbert Herzog, Director of the Neuroscience Research Program at the Garvan Institute of Medical Research, together with scientists from the US and Slovakia, have shown that neuropeptide Y (NPY), a molecule the body releases when stressed, can ‘unlock’ Y2 receptors in the body’s fat cells, stimulating the cells to grow in size and number. By blocking those receptors, it may be possible to prevent fat growth, or make fat cells die.

“We have known for over a decade that there is a connection between chronic stress and obesity,” said Professor Herzog. “We also know that NPY plays a major role in other chronic stress-induced conditions, such as susceptibility to infection. Now we have identified the exact pathway, or chain of molecular events, that links chronic stress with obesity.”

“There is not much we can do about the increased levels of NPY caused by stress, but we can do something about the damage it causes. If we can interfere before it causes fat to amass, it could have a major impact on cardiovascular disease, diabetes, and cancer (which all have links with obesity).”

“Basically, when we have a stress reaction, NPY levels rise in our bodies, causing our heart rate and blood pressure to go up, among other things. Stress reactions are normal, unavoidable, and generally serve a useful purpose in life. It’s when stress is chronic that its effects become damaging.”

Scientists at Georgetown University (Washington D.C), part of this collaborative study, have found a direct connection between stress, a high calorie diet and unexpectedly high weight gain. Stressed and unstressed mice were fed normal diets and high calorie (high fat and high sugar, or so called ‘comfort food’) diets. The mice on normal diets did not become obese. However, stressed mice on high calorie diets gained twice as much fat as unstressed mice on the same diet. The novel and unexpected finding was that when stressed and non-stressed animals ate the same high calorie foods, the stressed animals utilised and stored fat differently.

“Our findings suggest that we may be able to reverse or prevent obesity caused by stress and diet, including the worst kind of obesity; the apple-shaped type, which makes people more susceptible to heart disease and diabetes,” says senior author of the Nature Medicine paper, Professor Zofia Zukowska of Georgetown University. “Using animal models, in which we have either blocked the Y2 receptor, or selectively removed the gene from the abdominal fat cells, we have shown that stressed mice on high calorie diets do not become obese. “Even more surprisingly, in addition to having flatter bellies, adverse metabolic changes linked to stress and diet, which include glucose intolerance and fatty liver, became markedly reduced. We do not know yet exactly how that happens, but the effect was remarkable,” she said.

Professor Herzog believes that these research findings will have a profound effect on the way society will deal with the obesity epidemic. “There are millions of people around the world who have lived with high levels of stress for so long their bodies think it’s ‘normal’. If these people also eat a high fat and high sugar diet, which is what many do as a way to reduce their stress, they will become obese.”

“Until now, the pharmaceutical industry has focused on appetite suppressants with only moderate success. Our hope is that in the near future pharmaceutical companies, using the results of our research, will develop antagonists against the Y2 receptor that will bring about a reduction in fat cells.”

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Notes to editors:

Stress-activated adipogenic pathway in fat tissue exaggerates diet-induced obesity and metabolic syndrome.
Kuo, L.E., Kitlinska, J.B., Tilan, J.U., Li, L., Baker, S.B., Johnson, M.D., Lee, E.W., Burnett, M.S., Fricke, S.T., Kvetnansky, R.K., Herzog, H. & Zukowska, Z.
Nature Medicine advance online publication, 1 July 2007

The study was co-funded by the National Institutes of Health, the American Heart Association, and the Slovak Research and Development Agency.

ABOUT GARVAN

The Garvan Institute of Medical Research was founded in 1963. Initially a research department of St Vincent’s Hospital in Sydney, it is now one of Australia’s largest medical research institutions with approximately 400 scientists, students and support staff. Garvan’s main research programs are: Cancer, Diabetes & Obesity, Arthritis & Immunology, Osteoporosis, and Neuroscience. The Garvan’s mission is to make significant contributions to medical science that will change the directions of science and medicine and have major impacts on human health. The outcome of Garvan’s discoveries is the development of better methods of diagnosis, treatment, and ultimately, prevention of disease.

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Common hip condition may not always cause osteoarthritis in some racial groups

Contact: Amy Molnar
amolnar@wiley.com
John Wiley & Sons, Inc.

Osteoarthritis is the most common joint disorder worldwide, yet the cause of osteoarthritis of the hip is still unknown. One condition that may play a role is femoro-acetabular impingement (FAI), in which the femoral head of the thighbone causes damage by rubbing abnormally on the hip socket (acetabulum). FAI caused by an abnormality in the hip socket can lead to osteoarthritis, but it is not known if FAI that is not caused by a defect can also lead to the condition. Recognizing that the Asian lifestyle requires a larger range of hip motion than the Western lifestyle, a new study examined FAI in Japanese patients with normal hips. The study will publish online in the Journal of Orthopaedic Research (http://www.interscience.wiley.com/journal/jor), the official journal of the Orthopaedic Research Society.

Led by Mitsuyoshi Yamamura of Kyowakai Hospital in Osaka, Japan, researchers conducted a study on five healthy female volunteers between the ages of 18 and 26. They defined impingement using an open-configuration MRI, which allows imaging of the hip joint throughout the entire range of motion, by imaging subjects in the W-sitting position (in which the legs are bent behind the person) in two variations with the legs flexed to different degrees. Images were then obtained for 5 sitting positions, including sitting straight, bowing while sitting straight, sitting cross-legged, W-sitting, and squatting. Most of these positions are used in eating, socializing and in religious or traditional ceremonies and squatting is the position usually used for defecation in Asia and the Middle East.

The results showed that impingement occurred in all subjects in the W-sitting position and was also seen in 2 subjects in the squatting position. The largest hip internal rotation angle was seen in the W-sitting position. “No subjects complained of hip pain while maintaining any of the positions, even though the MR imaging process took from 10 to 14 minutes,” the authors note.

Populations in the Middle East and Asia have a low incidence of osteoarthritis in those with normal hips even though they regularly adopt positions that induce FAI, which suggests that FAI might not cause degenerative change in the hips. The researchers speculate that this may be related to soft tissue laxity around the hip, citing reports that joint laxity or range of motion differ by race. In addition, they note that impingement did not appear to be associated with pathology both in the present study and another study involving the shoulder area. Another reason FAI may not cause hip damage is that the positions in the study were static, as opposed to repetitive trauma, which the study did not evaluate.

The authors acknowledge that since the study was so small, the findings cannot necessarily be generalized to all Asian populations. Also, it is not known whether the subject in the study will develop osteoarthritis in the future. However, they note it is remarkable that FAI was seen in all 5 subjects. “This suggests that, depending on race, femoro-acetabular impingement might not always be a cause of osteoarthritis of the hip,” they conclude. “Further work in this area, including healthy males and patients with abnormalities, will confirm this conclusion.”

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Article: “An Open-Configuration MRI Study of Femoro-Acetabular Impingement,” Mitsuyoshi Yamamura, Hidenobu Miki, Nobuo Nakamura, Masakazu Murai, Hideki Yoshikawa, Nobuhiko Sugano, Journal of Orthopaedic Research, July 2007; (DOI: 10.1002/jor.20448).

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US soldiers in Iraq fighting drug-resistant bacteria after injuries

Contact: Amy Jenkins
amy@jenkinspr.com
312-836-0613
University of Chicago Press Journals

ALEXANDRIA, Va. — US soldiers in Iraq do not carry the bacteria responsible for difficult-to-treat wound infections found in military hospitals treating soldiers wounded in Iraq, according to an article to be published electronically on Wednesday, May 16, 2007, in Infection Control and Hospital Epidemiology. The article will appear in the June issue of the journal.

Investigator Matthew E. Griffith, MD, (Brooke Army Medical Center at Fort Sam Houston, San Antonio, Texas) and colleagues found that drug-resistant strains of Acinetobacter calcoaceticus-baumannii complex are not present on the skin of uninjured soldiers in Iraq, as had been expected.

A. calcoaceticus-baumannii complex is an important cause of trauma-associated and hospital-acquired infection throughout the world, and multidrug-resistant strains of the bacteria have been infecting injured soldiers treated in US military hospitals in Iraq.

“We need to know where these infections are coming from,” explains Dr. Griffith. “One of the possibilities was that A. calcoaceticus-baumannii was on the soldiers’ skin before injury and simply traveled to the wound site to cause the infection. However, our research shows that this is not the case.”

Although the consequences of the outbreak A. calcoaceticus-baumannii infection in US military hospitals serving soldiers wounded in Iraq are well described, the source of the outbreak is unknown.

To determine whether A. calcoaceticus-baumannii complex is carried on the skin of healthy US Army soldiers, investigators cultured skin swab specimens from 102 active military soldiers stationed at a base in Iraq. The base is in an environment representative of all Iraqi environments with desert, irrigated farmland and an urban area nearby.

Several previous reports have described skin carriage of Acinetobacter species in healthy people. The carriage rates have been found to vary with climate and geography. These reports may not be generalizable to US Army soldiers in Iraq, which has an extremely dry climate.

“If skin carriage is not the source of A. calcoaceticus-baumannii complex infection, then the other possibility is that the bacteria contaminates the wounds after injury,” explains Dr. Griffith. “This could happen while an injured soldier is awaiting treatment or in the hospital during or after receiving medical care.”

“This observation refutes the concept that the bacterium is acquired prior to injury among soldiers deployed to Iraq,” Dr. Griffith says. “In addition, this observation adds to the ever growing body of evidence implicating nosocomial transmission as the cause of the ongoing military outbreak.”

Because of this and similar research, an increased emphasis on infection control has been put in place in the US military’s combat hospitals.

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Infection Control and Hospital Epidemiology provides original, peer-reviewed scientific articles for anyone involved with an infection control or epidemiology program in a hospital or healthcare facility. Written by infection control practitioners and epidemiologists and guided by an editorial board composed of the nation’s leaders in the field, ICHE provides a critical forum for this vital information.

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