The Secret Life of Insulin
Do you know how insulin works? You may think you do, but you probably don’t.
We all know that it lowers blood sugar, but how exactly is that accomplished? The mechanism for this is amazingly complex and not yet completely understood.
You also need to know that glucose requires its own special “door” to enter cells. This is called a receptor. There are at least 4 different glucose “doors”. Different body tissues have different populations of “door” types. For muscle and fat cells, which are very important for storing extra glucose, as either glycogen or fat respectively, the door type is known as GLUT-4.
The action of insulin involves its binding to a receptor site on the cell membrane, and this initiates a signal to send more glucose “doors” to the cell surface. Insulin has not been shown to move into cells, rather it sits outside on the cell receptor. It is like the coach, directing activity but never entering the game itself.
Contrary to popular belief, insulin does not “unlock” the glucose “door”. For most cells, there are always a few “doors” open for glucose movement even without insulin present, but this does not move much glucose. Insulin “coaches” cells to recruit more glucose “doors”, sending them into the “game” to meet the need imposed by rising blood sugar. Additional “doors” allow more glucose to be removed from the blood. This is similar to having more cashiers at a store in order to move more people through check-out lines at any given time.
Conveniently, cells just happen to have extra “doors” assembled and available if insulin signals that they are needed. This allows the body to rapidly deal with food ingestion or other metabolic states where the blood sugar is raised. So this is how insulin works to prevent hyperglycemia.
When the amount of insulin in the blood falls, the number of “doors” on the cell’s surface also diminishes. This means less glucose is taken from the blood for storage.
The most obvious defect of diabetes is that the cells are not properly “coached” to open their glucose “doors”, and high blood sugar is the result. Taking insulin from an outside source is how we manage diabetes, but it’s not the same as having your own “coach”. When taking insulin by pump or injection, your cells can be inappropriately “coached” to have lots of open “doors”, and hypoglycemia ensues. It’s like having a coach who doesn’t fully understand the game.
The process of diabetes, especially type 1 diabetes, involves more than just this, but it is what we are most effected by on a day to day basis.