Appetite hormone key marker for arthritis?

The absence of the appetite hormone leptin can determine whether someone experiences arthritis, no matter how heavy they are, says a study.

The researchers studied mice that were leptin-deficient or deficient in leptin receptors - mice that did not have any effective leptin in their bodies. Both types of mice ate excessively and gained weight.

"We knew from other studies that obese people got arthritis in their hands, too, which do not bear weight. This indicated that something besides just body-weight level affected their joints," said Tim Griffin from Oklahoma Medical Research Foundation in the US.

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

"We were completely surprised to find that mice that became extremely obese had no arthritis if their bodies did not have leptin," Farshid Guilak, director of orthopaedic research in the Duke University noted.

"Although there was some earlier evidence that leptin might be involved in the arthritis disease process, we did not think that there would be no arthritis at all," Guilak added.

"In fact, the joints from the obese mice in the study looked better than those of the normal control mice," Guilak said.

The results suggested that leptin may have a dual role in the development of osteoarthritis by regulating both the skeletal and immune systems.

The study appeared in the journal Arthritis & Rheumatism.