What is insulin?

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Obligatory disclaimer: I am not a medical doctor, and the content of this website was created for informational purposes only. Such content is not intended as a substitute for medical advice, treatment or diagnosis.

In previous posts we’ve talked about a couple hormones related to our metabolism like ghrelin and leptin. We went over what they are, what they do and the very basics of how they do it. In this post we’ll talk about another hormone which is critical to our life: insulin.

What is insulin?

Insulin is a hormone, produced by the beta-cells of the pancreas, that plays a key role in regulating the blood level of glucose when feeding or fasting, as it is involved in protein, glucose and lipid synthesis and storage. You can think of insulin as the hormone in charge of letting the body know when it’s in times of plenty or scarcity. In times of plenty, excess glucose in our blood is turned into glycogen or fatty-acids. In times of scarcity, the process is the other way around.

What does insulin do?

In broad terms, insulin serves to increase the activity of those enzymes that catalyze (accelerate) the synthesis of lipids, glycogen and protein while also inhibiting the expression of those enzymes that catabolyse (break down) those same substances.

When blood glucose levels are elevated, beta-cells in the pancreas produce insulin. In turn, this stimulates the absorption of glucose by muscle cells and fat cells, while also inhibiting the synthesis of glucose (gluconeogenesis) in the liver. In muscle cells, the uptake of glucose results in the production of glycogen, while the uptake of glucose in fat cells results in further fatty acid production.

Just as we learned that ghrelin and leptin fulfill antagonistic roles, insulin has a hormonal counterpart known as glucagon. Glucagon is produced by the alpha-cells in the pancreas and serves to increase the concentration of glucose and fatty acids in the bloodstream. Glucagon is produced when insulin concentration falls too low in our blood.

In this way, insulin and glucagon are supposed to keep blood levels of glucose within upper and lower bounds, neither too low nor too high. We’ve previously talked about how blood glucose concentration changes after eating a meal on our post on the glycemic index, so check it out if you are interested.

In closing

In this post we’ve covered what insulin is, what it does and how it does it. As you may be aware of, there is a relationship between insulin and diabetes, but we’ll cover it when we deal with diabetes in a post of its own.

Hope you enjoyed this week’s post. If you did and would like to see more content like it, check our page on Rebuttals to Fatlogic. See you next week!

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