Live Long. Live Healthy. by Isagenix
Less than a couple of decades ago, most scientists wouldn’t have thought of body fat as anything more than a place where the body stores energy. Later, research found that it is much more than that—a metabolically active organ—capable of spewing out all sorts of inflammatory molecules that could cause the body harm with age and depending on where it’s located.
Now, growing evidence suggests that skeletal muscle also acts as an organ and, especially when exercised, could counteract some of fat’s deadly nature.
Muscle and Myokines
The link between physical activity and lower risk of chronic health problems has had scientists debating for the past 50 years. In the early 2000s, the relationship between exercise and health, or “the exercise factor”, was finally given a face with the identification of muscle as a secretory organ (1). Within the last decade, more answers have emerged and it has to do with a certain class of signaling molecules that only muscle makes called “myokines.”
The discovery of myokines as protein messengers produced and secreted by contracting muscle fibers is a scientific breakthrough, drastically altering traditional views on metabolism and physiology, and finally providing a framework to explain how physical activity and muscle improve health and protect against chronic disease.
Think of myokines as couriers sent out by exercising muscle to relay messages both locally within the muscle itself, as well as to other organs throughout the body such as the brain, pancreas, liver, bone, and adipose tissue. They mimic hormones, much like their more recognized counterpart, adipokines from adipocytes (body fat cells).
Moving Myokines Make Muscle Growth and a Lot More
When skeletal muscle is a dominant organ over body fat – as in lean adults, where muscle can make up about 40 percent of body weight – myokines have ample opportunity to make an impact on many different systems and metabolic processes in the body. With their discovery still in its infancy, the number of identified myokines and their roles continue to grow. So far, studies have found that myokines influence muscle growth, fat breakdown, insulin sensitivity, pancreas function, calorie burning, and risk of certain chronic diseases.
Exercise Plays Key Role
But of the various myokines discovered to date, interleukin-6 (IL-6) and irisin are two of the most interesting, and the human body makes a lot more of them when it moves more, as in performs more physical activity.
When IL-6 was first identified in 2000, scientists noted that levels of it rose 100 times after exercise (2). For this reason, it was believed the myokine was an inflammatory mediator produced in response to muscle damage (2). However, it was later revealed that IL-6 could fight inflammation, depending partly on where it is made such as in muscle.
Irisin is another myokine getting attention within the last few years due to its exciting ability to increase energy expenditure (burning of calories). It does this through the development of a type of body fat called “brown fat”. Brown fat normally exists in small quantities and is found mainly in locations of increased fat burning. It also tends to use up more energy in comparison to “white fat”, which is chiefly used for storage (3).
Exercise and muscle… beyond aesthetics
Up until recently, physical activity has been primarily viewed as a tool to balance energy intake with expenditure and bring about weight loss. The discussion of muscle has primarily revolved around its role in strength and capacity to improve metabolism. But with the existence of myokines coming into the picture, it is expected that even more attention will be devoted to exercise’s role in protecting health.
As with body fat, skeletal muscle is now finally getting the recognition it deserves as an endocrine organ. Did you think that building muscle was only for looking good in a bathing suit? Turns out it’s so much more than just another pretty tissue.
1.) Mohr T et al. Long-term adaptation to electrically induced cycle training in severe spinal cord injured individuals.Spinal Cord. 1997 Jan;35(1):1-16. Erratum in: Spinal Cord 1997 Apr;35(4):262.
2.) Pedersen BK. Muscles and their myokines. J Exp Biol. 2011 Jan 15;214(Pt 2):337-46. doi: 10.1242/jeb.048074.
3.) Boström P et al. A PGC1-α-dependent myokine that drives brown-fat-like development of white fat and thermogenesis. Nature. 2012 Jan 11;481(7382):463-8. doi: 10.1038/nature10777.