DOCTOR'S VIEW ARCHIVE
Insulin Resistance - Keypoints
Medical Editor: William C. Shiel, Jr., MD, FACP, FACR
"My mother has diabetes. How do I know if I will develop diabetes?" This was the question posed to me by a 48 year old patient last week. This patient is an obese woman who is being treated for high cholesterol and high blood pressure. Her profile fits the high risk group for diabetes, which brings up the subject of insulin resistance.
During the middle of the last century, physicians noticed that patients treated with diabetes could be divided into two major groups: those with type 1 diabetes (requiring insulin to sustain life) and those with type 2 diabetes (non-insulin dependent). Over the next few years, this second group was noted to have high circulating levels of insulin. The term insulin resistance (IR) was coined to describe this subgroup of patients. What exactly does this mean and why is this distinction important?
Insulin is a growth factor that is responsible for many actions within the body. Most of these actions deal with the metabolism and usage of carbohydrates (sugars and starches), lipids (fats), and protein. Insulin is involved with cell growth and regulation. IR is the condition whereby the normal response of the body to a given amount of insulin in transporting glucose (sugar) into cells is diminished.
IR is how type 2 diabetes develops and is present for many years before the actual onset of diabetes. Currently, it is thought that blood glucose and insulin levels are normal for many years. In the presence of factors such as obesity and family history, IR starts to develop. Insulin is necessary for the transport of blood glucose (sugar) into the cells of muscle and fat. The transport of the sugar from the bloodstream into these cells involves insulin receptors located on these tissues and a complicated method of activating these receptors. You can think of it as insulin "knocking" on the door of muscles. The muscles hear the "knock," open up, and let glucose in to be used by the cell. With factors such as obesity, the muscles don't hear the "knocking" of the insulin as well (they are "resistant") and the pancreas is notified to make more insulin, which increases insulin levels in the blood to cause a louder "knock." Eventually, the pancreas produces a lot more insulin than is normal and the muscles continue to be "resistant" to the "knock." As long as the individual can continue to produce enough insulin to overcome this resistance, blood glucose levels remain normal. Once the pancreas is unable to keep up, blood glucose starts to rise; initially after meals, and then eventually in the fasting state too. At this point, overt diabetes occurs.
IR is also a risk factor for heart disease and death.
The ideal treatment of IR has not yet been agreed upon. Diabetes experts can help with options currently available for diabetes. While IR is associated with an increased risk of death, there has been no major study to show that treating IR early reduces the risks of complications. It is my personal opinion that over the next few years, we will see an important shift in the treatment of diabetes. While the actual treatment of diabetes will continue, and be more precise, I think we will start to see doctors focus their attention on the treatment of earlier forms of abnormal sugar metabolism (prediabetes).
In our clinic, we have taken to
measuring fasting insulin and glucose levels in patients at risk for the
development of diabetes, or with associated complaints such as polycystic
ovarian syndrome. If insulin levels are high, we discuss treatment options
including specific lifestyle changes as well as medications. While there are
pros and cons to any argument, one thing is certain. Maintaining a healthy
lifestyle, including exercise and good nutrition, is really the best way to
prevent and reverse the course of IR and its complications down the road.