Until now, you may have never heard of the hormone called Irisin. I only learned about it a few months ago and it has some truly interesting benefits on metabolism and body composition.
Irisin is a hormone derived from a cell membrane protein called FNDC5. During muscle contraction FNDC5 gets cleaved. The cleaved portion of the FNDC5 molecule is the hormone irisin.
Irisin is produced when the skeletal muscles contract during exercise and recently has also been shown to be produced when they contract to shiver.
Since irisin is derived from skeletal muscle it is in a class of molecules called “myokines”.
Myokines are cytokines or peptides which are secreted by skeletal muscle cells and subsequently released into the circulation to exert endocrine or paracrine effects in other cells, tissues or organs.
Interestingly, irisin has also been categorized as an adipokine. This means that it is secreted by the adipocytes or fat cells in the body. The secretion from fat cells is 100-200 times less compared to the secretion that occurs from skeletal muscle cells so its effects aren’t as large compared to muscle cell secretion.
The release of irisin gets triggered during muscle contraction. During muscle contraction, an increase in the expression in the muscle tissue of peroxisome proliferator-activated receptor gamma coactivator 1 (PGC1α) occurs. This increases the production of FNDC5 which then gets converted into irisin. PGC1A regulates many genes responsible for the body’s metabolism. When triggered it helps to increase mitochondria biogenesis in the muscle and fat cells which increases their metabolic rates.
The Benefits of Irisin
#1. Speeds up your metabolism and improves lipid oxidation
Peroxisome proliferator-activated receptor gamma coactivator 1 (PGC1α) is a master regulator of metabolic genes. Upregulation of this coactivator increases the production of FNDC5 which then gets converted into irisin. When triggered, it helps to increase mitochondria biogenesis in the muscle and fat cells which increases their metabolic rates. This increases fatty acid oxidation and helps to burn more body fat.
#2. Increases insulin sensitivity and protects against diabetes
Irisin improves insulin sensitivity by increasing glucose uptake into the muscle cells. This leads to less fat storage. It also has been shown to protect against diabetes by regulating glucose homeostasis and by also having a protective effect on pancreatic beta cells.
#3. Increased bone density and bone strength
Increases of irisin have demonstrated increases in bone density. In addition, studies on mice show increased bone strength as well.
#4. Promotes longevity
One of the most studied phenomena in longevity research is how telomere length correlates to age. As we age telomeres, which are repetitive, non coding DNA base pairs that form the end of our chromosomes, get shorter. Each time our cells divide, they lose a little piece of the telomere. Therefore, telomere length is a way to measure how much we have aged at the cellular level. According to this study, higher levels of circulating Irisin correspond to longer telomere lengths.
#5. Irisin helps to promote muscle gain
Irisin helps to increase insulin growth factor-1 which has anabolic properties. It also inhibits myostatin. Myostatin is a signalling protein that binds to muscle cells to inhibit growth and cell division. So by inhibiting a muscle growth inhibitor, muscle synthesis is now easier.
#6. Helps to kill cancer cells
In one study, it was observed that irisin was able to reduce the total number of malignant breast cancer cells. It proved to enhance the cytotoxic effect of chemotherapy on the bad bad cells, while preserving more of the non-malignant cancer cells.
#7. Irisin “browns” fat
Irisin has been shown to brown fat. What is fat “browning”? Fat browning is when white fat cells change into “beige” or “brite” fat cells. What happens is white fat cells increase the amount of their mitochondria and also demonstrate a higher expression of uncoupling proteins during the “browning” process. Uncoupling proteins “uncouple” the electron transport chain in the inner mitochondrial membrane. What this does is prevents mitochondria from producing energy molecules and instead produces heat. The production of heat also known as thermogenesis, helps to increase energy expenditure and improves glucose homeostasis. Lipid oxidation or fat burning also is accelerated when this happens.
How to Increase Irisin Levels
So there are two ways to do this and we’ve have touched upon this already a bit.
#1. Exercise increases irisin production.
During exercise muscles contract and irisin is cleaved from the FNDC5 transmembrane protein in skeletal muscle tissue.
#2. Cold Exposure
Cold exposure has demonstrated to increase irisin levels as much are greater than bouts of exercise. For example in this study, 15-20 minutes of cold induced shivering produced as much irisin as an hour of moderate exercise.
There you have it. This is why trying to get in daily periods of cold exposure can be so beneficial for your health.