Insulin - Your Friend and Enemy

Insulin, made in the pancreas, was first discovered in 1921, and has many different bodily functions, all of which are directly related to cellular metabolism. Its major function is to regulate total body glucose in all body tissues except the brain, and it achieves this effect by stimulating glucose uptake primarily in muscle and fat cells. It is secreted by the pancreas into the bloodstream in response to rising blood glucose levels after a meal. Rising amino acid levels (found in proteins) also stimulate insulin release, though to a lesser extent. Insulin is an anabolic hormone, which means that it is responsible for building and storing various substances within. An example is glycogen, which is the animal storage form of glucose, primarily found in liver and muscle cells. Without insulin, the cells in our muscles and liver could not absorb glucose and therefore could not make glycogen. This is contrasted to catabolic hormones, such as adrenalin, glucagon and cortisol (also known as counter regulatory hormones), which are responsible for helping our bodies break down and utilize various substances, including glycogen and fats. Under the influence of these catabolic hormones, glycogen is broken down to glucose, and fats are broken down to free fatty acids. Both glucose and free fatty acids are important for sustaining exercise.

Some people cannot make insulin, or their bodies’ cells have reduced sensitivity to insulin. Both of these problems are features of diabetes. We also now realize that too much insulin, known as hyperinsulinemia, can also be a problem, and can be associated with many illnesses including high blood pressure, high cholesterol and heart attacks, to name but a few. Normal insulin levels are therefore important for healthy living.