Science News: The Link Between Your Gut Bacteria and Your Painful Joints

Russell Skinner, MD

According to a new study published in JCI Insight, bacteria in the gut, known as the gut microbiome, could be the culprit behind osteoarthritis, a condition that plagues people who are obese.
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What is Osteoarthritis?
Osteoarthritis is also known as the “wear and tear” arthritis. It is characterized by loss of joint cartilage that leads to pain and loss of function primarily in the knees and hips.

​According to the World Health Organization (WHO), osteoarthritis is the single most common cause of disability in older adults. It affects 9.6% of men and 18% of women aged >60 years. Around 31 million people suffer from this disease in the United States alone. It is expected to become the fourth leading cause of disability by the year 2020.

One of the major causes of osteoarthritis is obesity. People who are obese tend to put extra strain on their joints, and that causes them to suffer from osteoarthritis.

But, Can the bacteria in your gut be responsible for your joint pain?
In the past, joint pain was mainly associated with old age, injuries to the joints, bone deformities, and genetics. It was never linked to gut health.

However, a group of researchers from the University of Rochester Medical Centre, New York, demonstrated the connection between osteoarthritis, gut bacteria, obesity, and diet. Their study  has shed light on the possibility that gut bacteria may cause inflammation throughout the body, leading to very rapid joint deterioration.

Can You Eat Your Cake and Avoid Joint Pain, Too?

Just 12 weeks of “standard American diet” of cheeseburgers made mice obese and diabetic, nearly doubling their body fat percentage compared to mice fed a 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 mice had signs of systemic inflammation, including in their knees where the researchers tore the menisci – the cartilages’ cushion between the thigh and shin bone – to induce 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.

Surprisingly, the effects of obesity on gut bacteria, inflammation, and osteoarthritis were completely prevented when the high fat diet of the obese mice was next supplemented with a common prebiotic, called oligofructose. Upon consuming the oligofructose supplement, the knee cartilage of the obese mice was indistinguishable from that of the lean mice. Oligofructose even made the obese mice less diabetic, but it didn’t change their body weight.

Just reducing inflammation was enough to protect joint cartilage from degeneration, supporting the idea that inflammation – not bio-mechanical forces – drive osteoarthritis and joint degeneration.

“That reinforces the idea that osteoarthritis is another secondary complication of obesity - just like diabetes, heart disease, and stroke, which all have inflammation as part of their cause,” said Mooney. “Perhaps, they all share a similar root, and the microbiome might be that common root.”Research is being conducted now on veterans who have obesity-related osteoarthritis to to further determine the connections between gut microbes and joint health.

“There are no treatments that can slow progression of osteoarthritis – and definitely nothing reverses it,” said first author Eric Schott, Ph.D., postdoctoral fellow at URMC and soon-to-be clinical research scientist at Solarea Bio, Inc. “But this study sets the stage to develop therapies that target the microbiome and actually treat the disease.”