A Prebiotic May Alter the Obese Microbiome and Protect Against Osteoarthritis
Bacteria in the gut, known as the gut microbiome, could be the culprit behind arthritis and joint pain that plagues people who are obese, according to a new study published today in JCI Insight.
Osteoarthritis, a common side effect of obesity, is the greatest cause of disability in the US, affecting 31 million people. Sometimes called "wear and tear" arthritis, osteoarthritis in people who are obese was long assumed to simply be a consequence of undue stress on joints. But researchers at the University of Rochester Medical Center provide the first evidence that bacteria in the gut -- governed by diet -- could be the key driving force behind osteoarthritis.
The scientists found that obese mice had more harmful bacteria in their guts compared to lean mice, which caused inflammation throughout their bodies, leading to very rapid joint deterioration. While a common prebiotic supplement did not help the mice shed weight, it completely reversed the other symptoms, making the guts and joints of obese mice indistinguishable from lean mice.
What a Western, High Fat Diet Can Do
The URMC team, led by Michael Zuscik, Ph.D., associate professor of Orthopaedics in the Center for Musculoskeletal Research (CMSR), Robert Mooney, Ph.D., professor of Pathology and Laboratory Medicine, and Steven Gill, Ph.D., associate professor of Microbiology and Immunology, fed mice a high fat diet akin to a Western 'cheeseburger and milkshake' diet.
Just 12 weeks of the high fat diet made mice obese and diabetic, nearly doubling their body fat percentage compared to mice fed a low fat, healthy diet. Their colons were dominated by pro-inflammatory bacteria, and almost completely lacked certain beneficial, probiotic bacteria, like the common yogurt additive Bifidobacteria.
The changes in the gut microbiomes of the mice coincided with signs of body-wide inflammation, including in their knees where the researchers induced osteoarthritis with a meniscal tear, a common athletic injury known to cause osteoarthritis. Compared to lean mice, osteoarthritis progressed much more quickly in the obese mice, with nearly all of their cartilage disappearing within 12 weeks of the tear.
"Cartilage is both a cushion and lubricant, supporting friction-free joint movements," said Zuscik. "When you lose that, it's bone on bone, rock on rock. It's the end of the line and you have to replace the whole joint. Preventing that from happening is what we, as osteoarthritis researchers, strive to do -- to keep that cartilage."