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How Does Insulin Work in Our Bodies?

What is insulin and how do our bodies use it?

By
Sabrina Stierwalt, PhD,
February 5, 2018
Episode #272

image of insulinThe prevalence of diabetes, a condition related to the body’s inability to appropriately produce a hormone called insulin, has been steadily increasing worldwide over the last 30 years. According to the World Health Organization, over 422 million people worldwide are currently living with diabetes. An estimated 30.3 million of those people, or 9.4% of the population, are in the US. Also in the US, as many as one in four adults with diabetes don’t even know that they have it, and another 84 million people are pre-diabetic which often means they will be diabetic within five years without treatment. These numbers are higher in the American Indian, black, and Hispanic communities.

What is insulin and how do our bodies use it? What progress are scientists making toward regulating the hormone without insulin pumps or injections?

What is Insulin?

Hormones serve as chemical messengers, molecules that travel through our bloodstream to signal to our cells and organs how they should respond or act. They regulate a variety of activities in our bodies from basic needs like hunger to more complex responses like emotions. Our hormones are responsible for our metabolism, our growth, our reproduction, and even the release of other hormones.

Insulin is a hormone produced by the pancreas that specifically regulates the metabolism of carbohydrates and thus the level of glucose or sugar in the blood. When we eat carbohydrates and other sugars, insulin enters the bloodstream and, much like a door-to-door salesperson, convinces muscle and fat cells to open up and take in some of that sugar to be stored as a future energy source.

High resolution imaging has shown that insulin does this job by binding to receptors on a cell’s surface which causes molecules known as GLUT4 to also congregate near the surface of the cell. These GLUT4 molecules then serve as transporters to guide the glucose into the cell.

However, cells can also convert that glucose into fat rather than using it for energy since the process of fat storage often requires less energy to accomplish. Taking in more glucose than your body requires, based on your activity level, will mean the extra glucose is sent to long-term fat storage.

Insulin may also control more than just our regular metabolism. A recent study has shown a link between smelling insulin and overall appetite suppression. Study participants who inhaled an insulin-based nasal spray were less interested in food than those who had not inhaled the hormone. The neuroscientist authors of the study suggest that the extra insulin in the brains of those who inhaled it was able to block signals from the neurotransmitter dopamine that usually tell our brain and the rest of our bodies to go ahead and gorge ourselves.  

What is Insulin Resistance?

In diabetics, sugar remains in the blood stream instead of being absorbed by cells either because their bodies are resistant to insulin and effectively ignore its message, or because the pancreas does not produce the insulin in the first place. Those living with diabetes are able to make up for this lack of insulin either with daily injections or through the use of an insulin pump that can continuously inject the hormone into the fatty tissue under the skin through a small tube.

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