Researchers have noticed that a drug that doctors commonly use to treat insulin resistance can also address the pain of fibromyalgia, which has provided them with a new clue about this chronic condition.
According to the Centers for Disease Control and Prevention (CDC), fibromyalgia affects 4 million people in the United States alone, which equates to about 2% of the population. However, researchers still have no idea what causes this widespread condition.
Recently though, researchers from The University of Texas Medical Branch in Galveston made an intriguing find.
In collaboration with colleagues from other institutions, the researchers identified a connection between fibromyalgia and insulin resistance. They were also able to treat fibromyalgia-related pain by using a drug that doctors commonly prescribe to help the body regulate blood sugar levels.
"Earlier studies discovered that insulin resistance causes dysfunction within the brain's small blood vessels. Since this issue is also present in fibromyalgia, we investigated whether insulin resistance is the missing link in this disorder."
First author Dr. Miguel Pappolla
"We showed that most — if not all — patients with fibromyalgia can be identified by their A1c levels, which reflects average blood sugar levels over the past 2 to 3 months," Dr. Pappolla adds.
The A1c test is a blood test that allows doctors to measure a person's blood sugar levels by looking at "hemoglobin A1c," a blood cell protein that binds to the simple sugar glucose. Doctors use this test to diagnose prediabetes and type 2 diabetes.
Findings may 'radically change' care
For their study, the researchers recruited 23 people with fibromyalgia whose doctors had referred them to a specialist clinic for the treatment of muscular or connective tissue pain. They published their findings in the journal PLOS ONE.
When the investigators compared the A1c test results of the people with fibromyalgia with those of age-matched controls, they found that the former group had significantly higher levels of hemoglobin A1c than the latter, indicating a measure of insulin resistance.
"[People with prediabetes] with slightly elevated A1c values carry a higher risk of developing central (brain) pain, a hallmark of fibromyalgia and other chronic pain disorders," notes Dr. Pappolla, pointing out that this link between insulin resistance and fibromyalgia has been around for a long time.
Surprisingly, it went unnoticed. "Considering the extensive research on fibromyalgia, we were puzzled that prior studies had overlooked this simple connection," the first author says.
"The main reason for this oversight is that about half of fibromyalgia patients have A1c values currently considered within the normal range. However, this is the first study to analyze these levels normalized for the person's age, as optimal A1c levels do vary throughout life," the researcher continues.
"Adjustment for the patients' age was critical in highlighting the differences between patients and control subjects," he explains.
As part of the study, the researchers administered metformin — a drug that people typically take to treat insulin resistance — to the participants with fibromyalgia and muscular or connective tissue pain.
Metformin successfully reduced pain in this cohort, prompting the researchers to suggest that this common drug could be a viable and less expensive treatment option for some people with this chronic pain condition.
"In the [U.S.] alone, the healthcare cost is around $100 billion [per] year; comparable to reports in European countries," the researchers write in the study paper.
However, they conclude that if other studies confirm them, their findings "may translate not only into a radical paradigm shift for the management of [fibromyalgia] but may also save billions of dollars to healthcare systems around the world."