Researchers have discovered small amounts of the body’s natural GLP-1 hormone in joint fluid for the first time, a finding that could pave the way for new arthritis treatments using popular diabetes and weight loss drugs. The discovery, published in The Lancet Rheumatology, provides the first biological evidence that GLP-1 medications like Ozempic, Zepbound and Mounjaro might act directly inside joints to reduce inflammation and protect tissue.
The study analyzed blood and joint fluid samples from the INART biobank at Aarhus University Hospital in Denmark. Participants had either rheumatoid arthritis or spondyloarthritis, conditions that cause joint pain, swelling and reduced quality of life. By comparing these samples with those from healthy volunteers, scientists detected natural GLP-1 hormone in the synovial fluid of all groups. Crucially, the amount of GLP-1 in joint fluid closely matched levels in the blood, suggesting the hormone enters joints from the bloodstream.
“This provides a biological basis for considering whether pharmacological GLP-1 therapies could also reach the joint and potentially have local effects,” said lead author Dr. Tue Wenzel Kragstrup, associate professor at Aarhus University. The team became interested in GLP-1-based therapies because experimental studies suggest they may have direct anti-inflammatory and tissue-protective effects in joint disease, separate from their well-known benefits for weight loss and blood sugar control. Recent clinical trials have already reported benefits for osteoarthritis and psoriatic arthritis, but it was unclear whether those effects came from weight loss or direct action in the joints.
Dr. Jeffrey Zarin, an orthopedic surgeon at Cedars-Sinai Medical Center in Los Angeles, urged caution about overinterpreting the early findings. He noted that GLP-1 levels were significantly lower in joint fluid than in blood, and there was no difference between arthritis patients and healthy controls. “It would be incorrect to conclude that because these proteins are present in joint fluid, that using a medication that affects their levels will change the nature of arthritis,” Zarin said. He stressed that the study represents a very early stage of research to establish basic understanding.
The next step, Kragstrup explained, is to determine whether GLP-1 drugs reach joints in high enough concentrations to have biological effects there. His team plans to analyze blood samples from patients who have received GLP-1 treatment or undergone bariatric surgery to separate the drug’s direct effects from those related to weight loss. If a clear correlation emerges between joint GLP-1 levels and arthritis symptoms, researchers could then test whether boosting those levels with existing medications leads to meaningful improvements for millions of people living with joint disease.