15 July 2014 - MNT

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"Our results suggest that dietary factors play a more significant role than mechanical factors in the link between obesity and osteoarthritis," said Farshid Guilak, Ph.D., Laszlo Ormandy Professor of Orthopaedic Surgery at Duke and the study's senior author.

Obesity is one of the primary risk factors for osteoarthritis, although the mechanisms linking these conditions are not fully understood. It has been assumed that increased weight wears the joints out, but this doesn't explain why arthritis is also found in hands and other joints that don't bear weight.

Guilak and his colleagues began studying systemic factors other than body weight to determine their effect on arthritis, and in an earlier study in obese mice, found that the lack of appetite hormone leptin predicted whether the mice had arthritis.

"This made us think that maybe it's not how much weight you gain, but what you eat," Guilak said.

The mice were fed one of three high-fat diets: one rich in saturated fat, one rich in omega 6 fatty acids, and one rich in omega 6 fatty acids but supplemented with a small amount of omega 3 fatty acids.

The researchers found that arthritis was significantly associated with the mice's diets, but not with body weight.

The mice that ate diets high in saturated fat or omega 6 fatty acids experienced significant worsening of their arthritis, while mice consuming a small supplement of omega 3 fatty acids had healthier joints.

"While omega 3 fatty acids aren't reversing the injury, they appear to slow the progression of arthritis in this group of mice," Guilak said.

"In fact, omega 3 fatty acids eliminated the detrimental effects of obesity in obese mice."