Effect of yoga on Irisin hormone- the magic behind weight loss

Debopriya Ghosh, UIET. Panjab University, Chandigarh

Yoga, which means “union” in Sanskrit, is defined as the collection of physical, mental, and spiritual disciplines that originated in ancient India. Yoga-based exercises have been revealed in numerous studies to help in the reduction of extra body fat, in improving immunity and lung capacity. Achieving such results becomes possible due to the multi-dimensional approach that yoga encompasses, i.e., a balanced nutritious diet alongside practicing asana/poses, pranayamas (breathing exercises), bandhas (physiological locks), kriyas (cleansing process), and mudras (help maintain psychophysiological and hormonal balance). These have been shown to improve blood circulation, body metabolism, endocrine functions, and inhibit processes causing obesity. Yoga-based exercises produce the irisin hormone in the blood, which helps to reduce fat, in addition to controlled endocrine processes.

Irisin hormone and its multiple functions

The Irisin hormone was discovered in 2012 by Harvard Medical School researchers, who showed that it could be produced by both mice and humans after a workout. Irisin is released adipose tissues (which stores triglycerides), therefore is known as an adipokine and mediates the beneficial metabolic effects of exercise. The word ‘Irisin’ comes from the ancient Greek goddess Iris, who was the divine carrier of good news from Gods to mankind in Greek mythology. This term was chosen because it pertains to Irisin’s principal function as a chemical messenger, which is to communicate the favorable effects of physical activity to adipose tissue (browning and thermogenesis) and other organs involved in metabolism. Irisin is released while performing resistance exercise or High-intensity workouts by engaging muscles and adipose tissues. Irisin is an adipomyokine (adipokine and myokine).

Myokines are a class of cytokines released by the muscles; these myokines can communicate between muscles and other organs such as adipose tissues, the liver, and even the brain. IL-6 (Interleukin-6), IL-7(Interleukin-7), IL-15(Interleukin-15), insulin-like 6, fibroblast growth factor-21, follistatin-like 1, musclin, and irisin are a few of the myokines that play a role in myogenesis, fat oxidation, osteogenesis, endothelial function, fat browning, and other metabolic activities.

Irisin is a hormone that aids in the transformation of white adipose tissue (WAT) to brown adipose tissue (BAT) following physical activity.  Irisin releases energy in the form of heat and mediates some of the therapeutic benefits of exercise in humans, such as weight loss and thermoregulation. In obese people, exercise and lifestyle improvements induce plasma irisin levels to rise. Irisin levels have been linked to a negative association between waist-to-hip ratio and waist circumference, as well as a positive relationship between circulating irisin and BMI has been established.

Irisin promotes glucose uptake by skeletal muscles, improves hepatic glucose and lipid metabolism, and thus works as an insulin-sensitizing hormone, reducing hyperlipidemia and hyperglycemia associated with obesity and metabolic syndrome. By lowering the number of insulin receptors, irisin can alter organs and tissues associated with type 2 diabetes, such as the liver and the pancreas. As a result, irisin may have a beneficial effect on the liver and pancreatic islets, lowering the chance of developing type 2 diabetes mellitus.

White adipose tissue (WAT) Vs. Brown adipose tissue (BAT):

Fat in humans is mostly made up of white adipose tissue (WAT), which plays an important role in homeostasis and can communicate with other tissues and organs via auto, para-, and endocrine pathways. Adipokines (adipocytokines) are cytokines that influence inflammation, angiogenesis, and metabolic processes. However, it is apparent that WAT primarily stores triglycerides and fatty acids (the greatest energy reserve) and is made up of cells that have a single (unilocular) lipid droplet and few blood arteries, giving it a white-yellow appearance. WAT accumulates in various regions of the body leading to many health issues.

Whereas, BAT has a beneficial effect on metabolic processes and boosts overall energy expenditure, resulting in a reduction in body mass. BAT generates endocrine factors (fibroblast growth factor-21) as well as distant signals with systemic implications. BAT can improve blood glucose and lipid metabolism independent of weight loss by increasing their uptake.

The magic of the Irisin hormone!

Although irisin has been best recognized as a myokine, it is also an adipokine as it is released from adipose tissue and mediates the favorable metabolic effects of exercise. The contribution of adipose tissue to circulating levels of irisin was substantiated by molecular animal-based studies demonstrating that adipose tissue secretions contribute to circulating FNDC5/irisin.

FNDC5 is a glycosylated type I membrane protein formed of N-terminal signal peptides and fibronectin type III repeats and is highly expressed in skeletal muscles. In FNDC5, the C-terminal tail of FNDC5 is in the cytoplasm, whereas the extracellular N-terminal part is liberated for circulation as irisin. Thus, irisin is produced by the proteolytic cleavage of FNDC5 in skeletal muscles. Whenever the extracellular part of the FNDC5 type 1 transmembrane protein is broken down and is released into the bloodstream as irisin during exercise, this can be observed and measured in the blood by tests.

How does irisin work?

Research suggests that physical activity stimulated the transcriptional regulator– PGC-1α in skeletal muscle. This is responsible for the synthesis of fibronectin type III domain-containing protein 5 (FNDC5). PGC1α facilitates the programming of energy metabolism in transcriptional biological systems, controls mitochondrial biogenesis, angiogenesis, fiber-type switching, and oxidative metabolism in many cell types.

As a result, those who engage in exercise-rich activities, tend to have higher circulating irisin levels. While those who are less active and sedentary have lower amounts. Given the overall positive health benefits of exercise on cardiovascular, obesity, diabetes, skeletal, and other such related disorders, it is fair to assume that irisin may play a key role in several activities associated with physical exertion.

Phenomenal results observed!

In Pune, an experiment was conducted on sixty obese females (Indians) aged 40-50 years. They were split into two groups at random: 30 experimental and 30 controls. The obese participants were chosen based on their BMI (Body Mass Index). Their blood samples were collected pre-test, post-test, and follow-up tests to determine the level of irisin hormone using Elisa Reader instruments. The experimental group received 6 months of yogic exercise training, while the control group received no such training. The results of the post-training test revealed that yoga training created a significant difference from those in the control group, in terms of boosting the amount of irisin hormone in their bodies. This showed that yoga as an exercise program had helped for weight loss among the subjects.

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References:

• Sadokpam B, Bera TK. (2018). Effect of yoga exercises on irisin hormone in obese people. International Journal of Health Sciences and Research. 8(6):158-163. https://www.ijhsr.org/IJHSR_Vol.8_Issue.6_June2018/25.pdf
• Arhire, L. I., Mihalache, L., & Covasa, M. (2019). Irisin: A hope in understanding and managing obesity and metabolic syndrome. Frontiers in Endocrinology, 10, 524. https://doi.org/10.3389/fendo.2019.00524

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