Insulin is produced in the pancreas by beta cells, which measure glucose (the main source of energy from food) in the blood and secrete insulin to control glucose concentrations. Insulin acts as a key, binding to receptors (locks) expressed by all cells and telling them to let glucose inside.In type 1 diabetes, beta cells are destroyed by the body’s own immune system. White blood cells that ordinarily protect us from bacteria and viruses mistakenly recognize beta cells as foreign and destroy them, reducing or eliminating insulin production.
In type 2 diabetes, the problem is with the insulin receptor—the lock that allows glucose to enter. For reasons that are not clear, the receptor mechanism does not work properly, even when insulin is present. The body responds by producing more insulin. While that works for a time, it overworks the beta cells, which ultimately fail and die.
High circulating glucose levels damage cells. Because glucose moves primarily through blood, the cells lining blood vessels are the most severely hurt. These consequences extend to virtually every organ in the body. Diabetes is a leading cause of blindness, kidney disease, amputation, heart disease and many other conditions.