More regular exercise produces more irisin, which could help with fat reduction, stronger bones, and better cardiovascular health.
A professor of cell biology and a team at Harvard Medical School discovered the hormone dubbed "irisin" in 2012. They isolated the natural hormone from muscle cells that trigger some of the health-promoting properties of exercise, which, they say, could be developed into novel treatments for diabetes, obesity, and cancer.
In the previous study, the Harvard-affiliated team also found that as irisin levels rise through exercise, the hormone switches on genes that convert white fat into brown fat - the "good" fat. This conversion is beneficial, as brown fat burns off more excess calories than exercise alone.
Dr. Li-Jun Yang, a professor of hematopathology in the Department of Pathology, Immunology and Laboratory Medicine at the University of Florida College of Medicine, directed the new research.
Dr. Yang and colleagues aimed to understand the role of irisin in humans better and increase the knowledge base of how the hormone helps convert calorie-storing white fat cells into energy-burning brown fat cells.
The researchers note that they believe the research to be the first of its kind to explore irisin's effects on human fat tissue and fat cells.
According to the researchers, irisin hormone - which surges when the heart and other muscles are exerted - may also inhibit the formation of fatty tissue.
The study findings, published in the American Journal of Physiology - Endocrinology and Metabolism, confirms previous conclusions that irisin may be a promising target to support people with obesity and type 2 diabetes.
Irisin works via a mechanism that boosts the activity of genes and a protein that are crucial to turning white fat cells into brown fat cells. The researchers also found irisin to have a role in burning fat by significantly increasing the amount of energy used by brown fat cells.
Dr. Yang and team conducted the research by collecting fat cells donated by 28 participants who had undergone breast reduction surgery. Scientists exposed the fat samples to irisin, and as a result, saw an almost fivefold increase in cells that contain the UCP1 protein - a protein crucial to fat burning.
"We used human fat tissue cultures to prove that irisin has a positive effect by turning white fat into brown fat and that it increases the body's fat-burning ability," says Dr. Yang.
Fat cell formation significantly suppressed by irisin hormone
Among the analyzed fat tissue samples, Dr. Yang and collaborators found that irisin suppresses fat cell formation by reducing the number of mature fat cells by 20-60 percent, when compared with the control group.
This finding indicates that the irisin hormone reduces fat storage in the body by hindering the process that turns undifferentiated stem cells into fat cells, while also promoting the stem cells' differentiation into bone-forming cells, the researchers say.
More than two thirds of U.S adults are considered to be overweight or obese. While there is no single approach to prevent or treat overweight and obesity, exercise in combination with behavioral treatment and diet can aid weight loss. The knowledge that the body produces small quantities of fat-fighting irisin emphasizes the importance of regular exercise.
Dr. Yang says that while the beneficial effects of irisin could potentially be developed into therapies in the future, the viability of an irisin-based treatment is uncertain and would not happen imminently.
"Instead of waiting for a miracle drug, you can help yourself by changing your lifestyle. Exercise produces more irisin, which has many beneficial effects including fat reduction, stronger bones, and better cardiovascular health."
Dr. Li-Jun Yang
Irisin's role in regulating fat cells sheds light on the way physical activity helps people stay slender, says Dr. Yang. "Irisin can do a lot of things. This is another piece of evidence about the mechanisms that prevent fat buildup and promote the development of strong bones when you exercise," she adds.
This study adds to increasing information regarding irisin's health benefits. Previous studies by Dr. Yang's group found that irisin improves heart function by boosting calcium levels that are critical for heart contractions. They also showed that the hormone reduced arterial plaque buildup in mouse models by preventing inflammatory cells from accumulating, thus reducing atherosclerosis.
Future work for the team will focus on irisin's effect on abdominal fat, which is associated with insulin resistance and high lipid levels.