New research has found that even without weight loss or a change in diet, exercise reduces symptoms of arthritis in obese mice.
A study from OMRF scientist Tim Griffin, Ph.D., and researchers at Duke University shows that overweight mice that exercised had increased protection against osteoarthritis, even when the exercise didn’t cause weight loss. “This suggests that weight loss alone isn’t the only way that exercise can protect against osteoarthritis,” said Griffin.
The researchers fed mice a high-fat diet, and the animals gained weight. After 8 weeks, they gave half of the mice exercise wheels. Researchers then compared the arthritis symptoms in these animals, which ran an average of about 3 ½ miles per day for 4 weeks, with the sedentary mice.
The mice that ran experienced fewer arthritis-related problems, despite the fact that they shed no weight and continued on the same high-fat diet as the sedentary mice.
“We found that in some areas of the joints, exercise provided protection against osteoarthritis,” said Griffin. “The active mice also had improved blood markers associated with inflammation and diabetes, factors that may contribute to arthritis progression.”
Osteoarthritis is the most common joint disorder. Its symptoms, pain and stiffness, typically begin in middle age. Often, its causes are unknown, but obesity is a significant risk factor and one of the major questions in the field is whether exercise will help or harm obese patients.
“Some believe that the increased impact on the joint during exercise causes further harm,” said Griffin. “But these results suggest the opposite.”
Indeed, a 2008 study from Eliza Chakravarty, M.D., now a researcher at OMRF, and colleagues at Stanford University found that runners over the age of 50 suffered fewer disabilities than their non-running counterparts. The researchers also found that running was not associated with greater risk of osteoarthritis.
Griffin is currently conducting more studies with lean and overweight mice to examine the long-term effects of exercise on osteoarthritis.
“It’s a horrible disease to live with and one that significantly decreases the quality of life for those who have it,” said Griffin. “Hopefully, we’ll be able to use this research to find ways to mitigate and reverse that pain.”
The study appears in the new issue of the journal Arthritis and Rheumatism. In addition to Griffin, study authors include Farshid Guilak, Ph.D., Janet Huebner, M.S., Virginia Kraus, M.D., Ph.D., and Zhen Yan, Ph.D..
The research was supported by grants from the National Institute of Arthritis and Musculoskeletal and Skin Diseases, the National Institute of Aging, the National Institute of Biomedical Imaging and Bioengineering, and the Arthritis Foundation.