Insulin is a hormone produced by the pancreas. The pancreas is a small organ located in the upper right side of the abdomen. Insulin is made by the pancreatic islet cells (also called the beta cells), then secreted into the blood where it travels throughout the body to help regulate blood glucose (blood sugar). Insulin plays a key role in the body’s ability to use and store glucose. It also promotes the synthesis of fatty acids in the liver. The amount of insulin in circulation has widespread effects throughout the body.
Insulin binds with receptors on cells like a key would fit into a lock. Once the insulin key has unlocked the cell door, the glucose can pass from the blood into the cell. Inside the cell, glucose is either used for energy or stored as glycogen for future use. Glycogen is the stored form of glucose found in liver and muscle cells. Starch is the plant form of stored glucose.
An effect of insulin is to decrease the concentration of glucose in blood as described by the lock and key mechanism above. As blood glucose concentrations fall, insulin secretion slows down because its job is done.
Insulin also promotes synthesis of fatty acids and inhibits breakdown of fat in adipose tissue. It slows the breakdown of triglycerides which in turn leads to a reduction of free fatty acids in blood stream. The outcome is an accumulation of triglyceride in fat cells. If fat is in the cells, then that means less fat is being used as energy.
Insulin wants your body to use carbohydrates for energy. Only in the absence of insulin will your body use alternative fuels like fatty acids for energy. Some organs and tissues like the brain and neurons can only use glucose for energy and this is provided for short-term use from the glycogen reserves.
Diabetes mellitus, an important metabolic disease, is an insulin deficiency state in human beings. There are two forms of this disease:
Type 1 or insulin-dependant diabetes is a result of the destruction of pancreatic beta cells. It is seen as an autoimmune disorder in regards to the pancreas and typically happens after a trauma. In this case, your body can no longer make insulin, so the blood glucose cannot be lowered by your body. Treatment is with insulin replacement therapy and diet. Diet therapy includes counting carbohydrates because carbohydrates are the macronutrient that raises blood sugar. Carbohydrates are still necessary in the diet because they are a good source of energy.
Type 2 or non-insulin-dependant begins as insulin resistance. Your pancreas is still producing and secreting insulin, but your body and tissues fail to respond appropriately. Your pancreas can become overworked because it thinks that it is not making enough insulin. In time, these people may turn into type 1 because the pancreas wares itself out and becomes useless. This form is highly controlled by diet therapy. Other treatments include hypoglycemic agents which help the body use the circulating insulin.