Insulin is a hormone critical for regulating blood glucose levels. If you have problems making or utilizing insulin, your blood glucose levels will be chronically high, which leads to diabetes. Unusually high or low blood glucose levels can be very dangerous and insulin allows the body to keep tight control of blood glucose under normal circumstances.
Understanding Insulin
Insulin is a hormone that is made by cells in the pancreas known as islet cells; these cells also make other hormones that are critical for regulating blood glucose levels including glucagon. Insulin is a small protein and as such, you cannot take synthetic insulin orally. Instead, you must inject it, as the digestive tract would otherwise break down this protein. The pancreas secretes insulin in response to elevated blood glucose levels.
Insulin Effects
The main physiological effect of insulin is to cause certain cells, such as muscle, fat and liver cells, to pull glucose out of the blood. When insulin levels rise, these cells increase the levels of special proteins, known as glucose transporters, which are able to move glucose out of the blood and into the cell. When blood glucose levels go down, insulin levels also fall and these transporting proteins are moved back inside the cell.
Insulin Signaling
Like all hormones, insulin is able to affect cells by binding to special proteins known as receptors. The receptors for insulin are located on the surface of cells and have two distinct parts. The first part, sometimes known as the alpha subunit, is responsible for binding to insulin. The second part, known as the beta subunit, sends out a chemical signal inside of the cell when insulin binds to the alpha subunit. This chemical signal ultimately tells the cell to send more glucose transporting proteins to the cell's surface.
Other Effects
Insulin also has a few other important roles in the body. Insulin facilitates the storing of excess glucose in the form of glycogen in the liver. Elevated levels of insulin also cause the liver to make more fatty acids. Insulin inhibits the breakdown of fat in adipose tissue for energy. Insulin also allows cells in the body to take up more amino acids, so that they can make more proteins.
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