Glucose vs. insulin

It is a common belief that insulin is of major importance in controlling blood glucose, since it is the only hormone that is able to lower the concentration of glucose in blood. This is why we have major industry to produce insulin and why we mostly use insulin for. It is true, that if we inject enough insulin into a healthy person, this person will lose consciousness because of too little glucose or hypoglycemia. Hypoglycemia is one of the worst-case scenarios that can happen to you. None of the free time sports activities will ever give you such a tsunami of (nor)adrenaline ((nor)epinephrine) as hypoglycemia. It will be so bad that it will make you feel you are going to die. Raised blood glucose, on the other hand, will rather make you feel comfortable. So, why would we need a hormone to lower our blood glucose and drive us to anxiety? Is lowering blood glucose really the major function of insulin in our bodies?

If we observe the relation between blood glucose and insulin a bit more carefully, we shall first find out that the story has a twist. Glucose is a major reason why insulin is released from the cells in a gland we call pancreas. Let us focus our attention to a person we put back into the wilderness. This person is likely feeling very hungry, his glucose is around 4 mM (around 80 mg/dl) and insulin is very low. But feeling hungry does not mean that the cells in his body have no food. It rather means the alarm rings because the food storages are emptying. This person is using proteins and fats to feed his cells in a process we call catabolism. Catabolism can run for tens of days, but after about a half of proteins is used, the structure and function of cells collapses, causing death. To prevent or at least delay such a scenario the body produces several hormones to keep glucose high enough so that any kind of food can further elevate blood glucose to drive the release of insulin and return the proteins and fats back to storages for the times to come. Insulin is an anabolic hormone. Therefore it will also drive glucose into cells for storage. So the only time that insulin lowers blood glucose is after a meal. This happens very rarely out there, in the wilderness, outside the comfort of our civilization.

Loosing ability to produce insulin is actually, very similar to having no food for a longer time. The body fights this situation by trying to boost insulin release by increasing glucose. Trying to prevent or delay wasting of proteins and fats is what it wants to achieve. So blood glucose is raising and raising…And raising even more, since the body has no ability to produce insulin. So, the raise in blood glucose leading to hyperglycemia is an innate defense mechanism of our bodies to stop loosing proteins and fats. When the ability to produce insulin is lost completely, adding insulin from outside sources is one of the solutions. But complete loss of ability to produce insulin is true only in a minority of hyperglycemias and diabetes cases. For all these different shades of gray, there are likely more convenient and safe solutions. Let us talk about the possibilities some other time…