What are Exerkines?

Why do I need to read this?

To have a better understanding of why exercise is the benchmark therapy for chronic diseases like metabolic syndrome, Type 2 diabetes, hypertension, and cardiovascular disease.

Exerkines

Exerkines are substances released from the skeletal muscles and other organs like the fat (adipokines), liver (hepatokines), brain (neurokines), and kidneys, (nephrokines) after exercise.  The exerkines may be a chain of amino acids (peptides), nucleic acids (RNA), metabolites, mRNA, microRNA, and other RNA species. Thousands of these exerkines are released in the system after exercise, but only some have been well-studied.

The exerkines, which include the myokines, are used by the cells of the body to send signals or communicate with itself (autocrine), the adjacent cells (paracrine) and distant cells (endocrine).  This article presents some of the peptide exerkines and their benefits.

IL-6 (Interleukin-6)

Exercise increases IL-6 and improves glucose entry and fatty acid oxidation (burning) into the skeletal muscle, thus consuming calories! IL-6 also stimulates fat cell degradation (lipolysis) and glucose production in the liver (gluconeogenesis) to provide more fuel for the exercising muscles. IL-6 stimulates the gut to make glucagon-like peptide (GLP-1) from the intestinal cells and pancreatic alpha cells.

GLP-1

GLP-1 increases insulin secretion from pancreatic ß (beta) cells to produce insulin. The combined effect is the normal utilization of glucose to prevents its unwanted increase. The other functions of GLP-1 are in the image below.

IL-15

IL-15 improves the mitochondria of the skin, thus improving its health. It promotes skeletal muscle growth and reduces adipose tissue.  IL-15 muscle glucose uptake and GLUT4 expression.

BDNF (Brain-derived neurotrophic factor)

Brain-derived neurotrophic factors (BDNF) and Leukemia inhibitory factor (LIF) promotes fat oxidation in muscles. Fatty infiltration in skeletal muscles leads to insulin resistance and the inability of the skeletal muscles to use glucose, which leads to high blood sugar.  BDNF regulates glucose and energy metabolism and prevents exhaustion of β cells. Decreased levels of BDNF are associated with neurodegenerative diseases with neuronal loss, such as Parkinson’s disease, Alzheimer’s disease, multiple sclerosis, and Huntington’s disease.

Fibroblast growth factor-2

FGF-2 is involved in the regulation of synaptic plasticity and processes attributed to learning and memory, at least in the hippocampus.

Fibronectin type III domain-containing protein 5

FNDC5 is the precursor of irisin, which is needed for exercise adaptation. Irisin turns the white fat of the body into a calorie burning, weight reducing brown fat.

Fibroblast growth factor 21

FGF21 is a hepatokine that is the antidote to sugar addiction. FGF21 markedly suppresses consumption of simple sugars, but not complex carbohydrates, proteins, or lipids.

Insulin-like growth factor-1

IGF-1 increases pancreatic β cell proliferation and increases insulin production, which explains its beneficial effect on hyperglycemia.

METRNL is both a myokine and adipokine. METRNL also turns white fat into brown fat and improves blood sugar control.

Myonectin fine-tunes the systemic handling of fatty acids

VEGF-A (Vascular endothelial factor-A) maintains the health of the blood vessels.

This article is a summary of peptides as exerkines. There are hundreds of myokines secreted by the body during exercise. Many studies are ongoing to define their functions.  Looking at the image of GLP-1 by itself has abundant beneficial effects to the body.

If you want to read more about the benefits of exercise, take a look at the following:

1. Physical Activity Correlates with Life Span
2. How Does Exercise Prolong Life?
3. Health Benefits of Weight Training
4. Myokines: An Introduction
5. Make that Game Winning Shot that at the Buzzer!
6. How Does Exercise Prolong Life?
7. The Benefits of Resistance Training
8. The Surprising Benefits of Sweating
9. The Good and Faithful Servant
10. Effect of Short Term Exercise on Mortality
11. What are Exerkines?
12. Exercise Guidelines
13. Why do You Need an Excellent Performance Status?
14. What are Exerkines?
15. Exercise and Neurogenesis
16. How to Perform High-Intensity Interval Training
17. How to Get Physically Active

If you want to know how to exercise in a short time, read, No Time to Exercise?. Let’s Fix That.

Thanks for reading.

References:

1. Safdar et al. The potential of endurance exercise-derived exosomes to treat metabolic diseases. Nat Rev Endocrinol. 2016 Sep;12(9):504-17. doi: 10.1038/nrendo.2016.76. Epub 2016 May 27.
2. Ellingsgaard et al.Interleukin-6 enhances insulin secretion by increasing glucagon-like peptide-1 secretion from L cells and alpha cells. Nat Med. 2011 Oct 30;17(11):1481-9. doi: 10.1038/nm.2513.
3. Reuss B, von Bohlen und Halbach O (Aug 2003). “Fibroblast growth factors and their receptors in the central nervous system.” Cell and Tissue Research. 313 (2): 139–157.
4. Von Holstein-Rathlou et al. FGF21 Mediates Endocrine Control of Simple Sugar Intake and Sweet Taste Preference by the Liver. Cell Metab. 2016 February 9; 23(2): 335–343. 

Photo Credits:

• GLP-1 By Lthoms11 – Own work, CC BY-SA 4.0, https://en.wikipedia.org/w/index.php?curid=55236027