A new Harvard Health Letter reports that a recent study by scientists at Harvard Medical School has discovered a previously unknown natural hormone in muscle cells that is produced by exercise. The new hormone, which the scientists called “Irisin,” appears to trigger some of the key health benefits of exercise — including weight loss and prevention of diabetes.
The study, conducted on mice, found that this newly discovered hormone produced by exercise converts white fat cells — which store fat — into (good) “brown fat cells” — which burn fat and continue burning calories even after exercise. In addition, the study found that Irisin helps prevent or overcome the insulin resistance that is associated with diabetes.
The June, 2012 Harvard Health Letter reports on the study by Dr. Bruce Spiegelman, a Harvard Medical School professor, and colleagues, which was published in the journal Nature in January 2012.
“Our muscle cells need a source of energy when they exercise,” Dr. Anthony Komaroff, a professor at Harvard Medical School, explained to the editors of the Harvard Health Letter. “Muscles get that energy by burning fat and sugar brought to them by the blood. That’s been known for nearly a century. However, it’s not the whole story.”
“Irisin travels throughout the body in the blood, and alters fat cells,” Dr. Komaroff explained. “Body fat is stored inside fat cells. Most of these fat cells are called white fat cells, and their function is to store fat.”
“Brown fat cells don’t store fat: they burn fat. If your goal is to lose weight, you want to increase the number of your brown fat cells and to decrease your white fat cells,” said Dr. Komaroff.
The new study showed that “Irisin does that, at least in mice,” the Harvard Health Letter reports. “And those newly-created brown fat cells keep burning calories after exercise is over. But it gets better,” says the Harvard Health Letter. “In addition to its effect in creating brown fat cells, [Irisin] also helps prevent or overcome insulin resistance, which leads to type 2 diabetes,” the Harvard Health Letter states.
“Although Dr. Spiegelman did his studies in mice, he found that humans have irisin, too. While not yet proven, it is very likely that irisin has similar effects in humans,” according to the Harvard Health Letter.
“[T]he discovery of irisin also could have some very practical and beneficial applications,” Dr. Komaroff told the Harvard Health editors. “Theoretically, irisin could become a treatment to help us maintain a healthy body weight and reduce the risk of diabetes,” Dr. Komaroff said.
The Study: Background, Methodology and Findings
“There has been a feeling in the field that exercise ‘talks to’ various tissues in the body,” Senior author of the Harvard study, Dr Bruce Spiegelman, from the Dana-Farber Cancer Institute and also professor of cell biology at Harvard Medical School in Boston, told the Harvard Gazette. “But the question has been, how?”
In examining the effect of exercise on a key “master metabolic regulator gene called PGC1-alpha,” which Dr. Spiegelman’s team had identified in previous work, they discovered that in fact exercise appears to produce a new hormone in the outer membranes of muscle cells.
Dr. Spiegelman’s team “named [this newly discovered hormone produced by exercise] “irisin,” after the Greek messenger goddess, and believe it is a promising candidate for developing drugs to treat diabetes, obesity and maybe even cancer,” Medical News Today reported.
For this study, the researchers used lab cultures to analyze the effects of irisin on white fat tissue in mice. Deposits of white fat tissue beneath the skin store excess calories, and produce obesity.
With exercise, levels of irisin in the muscles go up, the researchers found, and this activates a gene that triggers conversion of white fat cells into “good” brown fat cells.
The researchers injected small amounts of irisin into sedentary mice that were obese and pre-diabetic, and found that this mimicked the effect of exercise. The number of white fat cells decreased while the number of brown fat cells increased, and the energy expenditure of the mice increased, even “with no changes in movement or food intake,” the researchers found.
The study authors explained that brown fat, whether produced by exercise or by an injection of irisen, burns off excess calories stored in white fat. And, when produced by exercise, continues to burn white fat, even after exercise.
The researchers also found that, in addition to triggering the conversion of white fat into brown fat, irisin also improved glucose tolerance in mice that were fed a high-fat diet.
“Improved glucose tolerance is a key indicator of metabolic health, and the better a person’s metabolic health, the lower their risk of developing cardiovascular diseases and diabetes,” Medical News Today reported.
The mice developed this improved glucose tolerance within only 10 days after treatment, and they also lost a small amount of weight.
Dr. Spiegelman told Medical News Today that he believes the effect could have been greater if the treatment had lasted longer.
Conclusions; Implications
The discovery of Irisin “is an important first step in understanding the biological mechanisms that translate physical exercise into beneficial changes throughout the body, both in healthy people and in preventing or treating disease,” Dr. Spiegelman said in the Harvard Gazette.
“The discovery won’t allow people to skip the gym and build muscles by taking irisin supplements, Spiegelman cautioned, because the hormone doesn’t appear to make muscles stronger. Experiments showed that irisin levels increase as a result of repeated bouts of prolonged exercise, but not during short-term muscle activity.”
However, according to the Harvard Gazette, the researchers say that Irisin, which serves as a chemical messenger, is a highly promising candidate for development as a new drug, which could provide a novel treatment for diabetes, obesity, and perhaps other disorders, including cancer.
“[O]ther medicines with a similar promise have come and gone. However, irisin is not an unnatural pharmaceutical. Rather, it’s part of our natural body chemistry,” the June Harvard Health Letter points out. “That may make it more potent and less likely to have adverse effects. So there is justifiable excitement about the discovery of irisin, and about the speed with which science is discovering the chemistry of exercise, appetite, metabolic rate and body weight.”
“The last thing in the world we’re trying to do is substitute for diet and exercise,” Dr. Spiegelman said in a report by CommonHealth, a publication of wbur, Boston’s NPR news station. “But first of all, there are many people who can’t exercise, whether because of paralysis or age or illness, he said. Work on irisin could potentially help them.”
“Second, yes, everybody should exercise and eat right but they don’t,” Dr. Spiegelman pointed out. “Obesity and diabetes are worldwide epidemics costing untold billions. If irisin proves able to help fight them, it could benefit all of us,” he said.
According to the Harvard Gazette, the irisin discovery has been licensed by Dana-Farber exclusively to Ember Therapeutics for drug development. Ember is a Boston-based startup co-founded by Dr. Spiegelman and scientists at the Harvard-affiliated Joslin Diabetes Center and the Scripps Research Institute in Florida.
But, “We don’t have to wait for a magic potion,” says Dr. Komaroff in the Harvard Health Letter. “We already have a proven treatment that profoundly protects our health: exercise.”
More Information
See related HelpingYouCare™ reports on:
Exercise Changes DNA for the Better, New Study Finds
Physically Active Seniors May Live Longer, Study Suggests
Experts Advocate Dancing for Health
Fitness Lowers Odds of Death from Dementia, Study Finds
Physical Activity of All Kinds Lowers Risk of Alzheimer’s, Study Finds
Benefits of Weight Training for People Over 50
Harvard Guide to Exercise – A Program You Can Live With
You’re Never Too Old to Exercise
For more information on exercise and other lifestyle factors that promote wellness and prevent diseases, see the HelpingYouCare™ resource pages on Wellness/ Healthy Living for Seniors & Caregivers, including:
- Diet & Nutrition: Physical Wellness;
- Exercise: Physical Wellness;
- Sleep, Hygiene, Quit Smoking & Other Healthy Practices: Physical Wellness;
- Activities to Preserve Mental Acuity: Intellectual Wellness;
- Social Interaction & A Sense of Connection With Others: Social Wellness;
- Other Areas of Wellness: Emotional, Ethical/ Spiritual & Vocational Wellness; and
- Examples of Healthy Aging: Stories of Inspiring Seniors.
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