Irisin Hormone May Underlie Benefits of Aerobic Exercise for RRMS
Six weeks of aerobic exercise led to benefits in cognition, fatigue, and depression among people with relapsing-remitting multiple sclerosis (RRMS), which may be due to increases in blood levels of a hormone called irisin, according to data from a randomized, controlled trial.
“Considering the high prevalence of neuropsychiatric symptoms such as depression, fatigue, and cognitive impairment in MS, our results indicated that more impressive improvements could be achieved with the moderate level aerobic exercises,” the researchers wrote.
The study, “Aerobic exercise increases irisin serum levels and improves depression and fatigue in patients with relapsing remitting multiple sclerosis: A randomized controlled trial,” was published in the journal Multiple Sclerosis and Related Disorders.
Some studies have suggested that aerobic exercise, which increases the heart rate — known to many as “cardio” — can help lower fatigue and depression in multiple sclerosis (MS), although the underlying mechanisms remain unclear.
The irisin hormone has been shown to play a number of beneficial roles in the brain, including increasing levels of anti-inflammatory proteins, promoting nerve processes involved in memory, and reducing depression.
As irisin is released from skeletal muscles during exercise, and its blood levels also increase after exercise, the protein may be behind cardio’s beneficial effects.
To investigate this, a research team in Turkey set out to evaluate the effects of aerobic exercise on irisin levels and symptoms of depression and fatigue in RRMS patients.
Included in the trial were 32 adults, ages 19–65, with mild-to-moderate RRMS, who were split into two groups of 16 and randomly assigned to do Frenkel coordination exercises plus aerobic exercise, or coordination exercises only (control group) in sessions three times per week for six weeks. At each session, coordination exercises were performed for 20–30 minutes. In the aerobic group, sessions also included aerobic exercise consisting of a five-minute warm-up, 20 minutes of moderate exercise on a stationary bicycle, and a five-minute cool-down. All exercises were adjusted to each patient’s capacity.
In the aerobic exercise group, 15 of the 16 participants were female, and the mean age was 28.3. Among controls, 12 of 16 were female, and mean age was 32.5.
Blood irisin levels were measured at the study’s start and again after the exercise program. The researchers found irisin levels rose significantly in the participants who performed aerobic exercise, which was not observed in the control group.
“This increase may be due to the effect of large muscles working during aerobic exercise because serum [blood] irisin level is known to be released from skeletal muscle,” the researchers wrote.
Aerobic capacity, or the body’s ability to take in and use oxygen during exercise, was also improved in the aerobic group. Cognitive performance, measured with the Paced Auditory Serial Addition Test with 3-second stimulus, was significantly improved in both groups.
Participants also completed questionnaires to monitor fatigue (Fatigue Impact Scale) and depression (Beck Depression Inventory).
Results showed that both fatigue and depression were significantly eased with aerobic exercise. While depression was also decreased among the control group, this effect was more significant in those who performed aerobic exercise.
While the findings suggest a beneficial role of exercise in MS, the necessary exercise program may vary by individual, the team pointed out.
“Although there are MS-specific and evidence-based physical activity guidelines, the quite different symptoms in MS make it nearly impossible to develop a common exercise protocol,” the researchers wrote.
Still, “[people with MS] should be encouraged to participate in regular physical activity.”
While the team hypothesized that increased irisin levels underlie the observed benefits in the aerobic exercise group, a causal relationship could not be determined from this study. However, the overall findings are “promising in terms of elucidating the mechanism underlying the beneficial effects of aerobic exercise,” the researchers wrote, adding that “these results will shed light on future studies.”
Larger studies including participants with other MS types will be necessary to confirm their findings, the researchers noted.