Insulin, Obesity, and Exercise Relationships to Type-2 Diabetes

Introduction
People with type-2 diabetes are characterized by insulin resistance. Their bodies produce enough insulin but they have an impaired ability to move glucose into their cells. Exercise is commonly prescribed as a treatment for those suffering from type-2 diabetes. In addition to the cardiovascular benefits associated with exercise, blood glucose levels are lowered in type-2 diabetics with chronic exercise as their cells are better able to take up glucose. But did you ever wonder why this occurs? After all, if type-2 diabetics are considered "insulin resistant", then why does exercise help lower blood glucose levels? This article will go over the pathology of type-2 diabetes as well as provide a short summary on how and why exercise is beneficial for type-2 diabetics.

Pathology and Physiology
Your skeletal muscle and liver are the two primary organs responsible for maintaining normal blood glucose (1). In a normal person, high blood glucose (primarily from a high carbohydrate or sugary meal) stimulate insulin to be secreted from the pancreas. Insulin then stimulates the movement of glucose transporters, known as GLUT4 transporters, to the surface of their cells to move glucose from the blood into their cells, thus reducing blood glucose levels.

Type-2 diabetics exhibit insulin resistance. Insulin is not able to stimulate as many GLUT4 transporters to the surface of their cells, especially muscle cells (2). This prevents their cells from taking in more glucose and leads them to a chronic state of hyperglycemia, or a constant elevated blood glucose level. Type-2 diabetics are also hyperinsulinemic, meaning their bodies keep producing insulin in response to hyperglycemia in an effort to remove glucose from their blood. But because of insulin's limited effect on GLUT4 transporters, this is only marginally effective and blood glucose levels remain high.