Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Scientists Find Obesity Alone Does Not Cause Arthritis in Animals

11.07.2014

The link between obesity and osteoarthritis may be more than just the wear and tear on the skeleton caused by added weight.

A Duke University study has found that the absence of the appetite hormone leptin can determine whether obese mice experience arthritis, no matter how heavy they are.

"We were completely surprised to find that mice that became extremely obese had no arthritis if their bodies didn't have leptin," said Farshid Guilak, PhD, director of orthopaedic research in the Duke Department of Surgery.

"Although there was some earlier evidence that leptin might be involved in the arthritis disease process, we didn't think that there would be no arthritis at all."

In fact, the joints from the obese mice in the study appearing in the journal Arthritis & Rheumatism looked better than those of the normal control mice, Guilak said. "However, in another study, we found that mice that gained half as much weight on a high-fat diet but processed leptin normally showed significant knee osteoarthritis."

Leptin influences many of the factors involved in osteoarthritis -- body weight, inflammation, sex hormone levels, and bone metabolism, said lead author Tim Griffin, PhD, who was at Duke Orthopaedic Department and now is an assistant member of the Free Radical Biology and Aging Program at the Oklahoma Medical Research Foundation.

"That also makes leptin challenging to study, however, because it's difficult to isolate which pathway is being altered to prevent the development of osteoarthritis."

Leptin is a well-known regulator of appetite, but this is the first time scientists have reported a role for leptin as a metabolic link between obesity and altered cartilage metabolism in joints.

The role of obesity as a risk factor for arthritis is well characterized, but it was thought to be merely a case of overloading joints with extra weight.

"It hadn't been studied beyond that," Guilak said. "We knew from other studies that obese people got arthritis in their hands, too, which don't bear weight. This indicated that something besides just body-weight level affected their joints."

The Duke team set out to learn whether the increased body fat of obesity causes an inflammatory response in joints -- an imbalance of the immune system signaling proteins called cytokines and other chemicals in osteoarthritis.

They studied mice that were leptin-deficient or deficient in leptin receptors -- mice that didn't have any effective leptin in their bodies. Both types of mice overate and gained weight.

Then they compared the study mice with normal mice to document knee osteoarthritis. The measurements included pro- and anti-inflammatory cytokines present in arthritis, and several tests to assess bone changes in the knees of the mice.

The knee bones of the leptin-free, obese mice did change, but without forming osteoarthritis. The levels of inflammatory cytokines, which correlate with arthritis, were largely unchanged in these mice. The results suggested that leptin may have a dual role in the development of osteoarthritis by regulating both the skeletal and immune systems.

What does this mean for people? "Obesity is still the number one preventable risk factor of osteoarthritis, but now it seems body fat by itself is not what is causing it," Guilak said.

"If you are obese, there are benefits to losing weight in terms of arthritis. For example, if you are obese and lose just 10 pounds, pain decreases significantly. Pain modulation is another clue it might be a chemical or systemic metabolic effect, rather than just a mechanical effect of less weight on the joints."

As with many studies that yield unanticipated findings, "we have a lot of additional questions and experiments that need to be done to further understand how leptin mediates the development of osteoarthritis," Griffin said.

"With obesity and osteoarthritis, there are good similarities between humans and mice," Guilak said. "If we can find a pathway that links a high-fat diet with arthritis, then we can try to identify and block the inflammatory mediators that are linked with the dietary fat."

The study was sponsored by the National Institute for Arthritis, Musculoskeletal and Skin Diseases and the Arthritis Foundation. Lead author Timothy M. Griffin, formerly of the Duke Department of Surgery, is now with the Oklahoma Medical Research Foundation. Co-authors Janet L. Huebner and Virginia B. Kraus are with the Duke Department of Medicine.

Sarah Avery | Eurek Alert!
Further information:
http://corporate.dukemedicine.org/news_and_publications/news_office/news/scientists_find_obesity_alone_does_not_cause_arthritis_in_animals/view

Further reports about: Arthritis Arthritis in Animals cytokines hormone inflammatory knee obesity osteoarthritis weight

More articles from Life Sciences:

nachricht Fish Oil-Diet Benefits May be Mediated by Gut Microbes
28.08.2015 | University of Gothenburg

nachricht Bio-fabrication of Artificial Blood Vessels with Laser Light
28.08.2015 | Fraunhofer-Institut für Lasertechnik ILT

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: OU astrophysicist and collaborators find supermassive black holes in quasar nearest Earth

A University of Oklahoma astrophysicist and his Chinese collaborator have found two supermassive black holes in Markarian 231, the nearest quasar to Earth, using observations from NASA's Hubble Space Telescope.

The discovery of two supermassive black holes--one larger one and a second, smaller one--are evidence of a binary black hole and suggests that supermassive...

Im Focus: What would a tsunami in the Mediterranean look like?

A team of European researchers have developed a model to simulate the impact of tsunamis generated by earthquakes and applied it to the Eastern Mediterranean. The results show how tsunami waves could hit and inundate coastal areas in southern Italy and Greece. The study is published today (27 August) in Ocean Science, an open access journal of the European Geosciences Union (EGU).

Though not as frequent as in the Pacific and Indian oceans, tsunamis also occur in the Mediterranean, mainly due to earthquakes generated when the African...

Im Focus: Self-healing landscape: landslides after earthquake

In mountainous regions earthquakes often cause strong landslides, which can be exacerbated by heavy rain. However, after an initial increase, the frequency of these mass wasting events, often enormous and dangerous, declines, in fact independently of meteorological events and aftershocks.

These new findings are presented by a German-Franco-Japanese team of geoscientists in the current issue of the journal Geology, under the lead of the GFZ...

Im Focus: FIC Proteins Send Bacteria Into Hibernation

Bacteria do not cease to amaze us with their survival strategies. A research team from the University of Basel's Biozentrum has now discovered how bacteria enter a sleep mode using a so-called FIC toxin. In the current issue of “Cell Reports”, the scientists describe the mechanism of action and also explain why their discovery provides new insights into the evolution of pathogens.

For many poisons there are antidotes which neutralize their toxic effect. Toxin-antitoxin systems in bacteria work in a similar manner: As long as a cell...

Im Focus: Fraunhofer IPA develops prototype of intelligent care cart

It comes when called, bringing care utensils with it and recording how they are used: Fraunhofer IPA is developing an intelligent care cart that provides care staff with physical and informational support in their day-to-day work. The scientists at Fraunhofer IPA have now completed a first prototype. In doing so, they are continuing in their efforts to improve working conditions in the care sector and are developing solutions designed to address the challenges of demographic change.

Technical assistance systems can improve the difficult working conditions in residential nursing homes and hospitals by helping the staff in their work and...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Networking conference in Heidelberg for outstanding mathematicians and computer scientists

20.08.2015 | Event News

Scientists meet in Münster for the world’s largest Chitin und Chitosan Conference

20.08.2015 | Event News

Large agribusiness management strategies

19.08.2015 | Event News

 
Latest News

Interstellar seeds could create oases of life

28.08.2015 | Physics and Astronomy

An ounce of prevention: Research advances on 'scourge' of transplant wards

28.08.2015 | Health and Medicine

Fish Oil-Diet Benefits May be Mediated by Gut Microbes

28.08.2015 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>