Mar. 23, 2000 (Eugene, Ore.) -- A substantial number of people with type 1 diabetes also have a condition called insulin resistance, which dramatically increases their risk of developing heart disease. Fortunately, physicians can evaluate who is most likely to have insulin resistance by doing some routine tests, according to a new study published in the April issue of the journal Diabetes, a journal of the American Diabetes Association.
There are two major types of diabetes -- type 1 and type 2. Type 2 diabetes generally occurs in older and/or obese patients; it is diagnosed when the body can no longer properly control blood sugar levels because it can't respond appropriately to insulin, a hormone required for the control of sugar in the body. This process is generally referred to as insulin resistance or regulation
On the other hand, type 1 diabetes was thought to be a much simpler concept. It occurs when the body simply doesn't make enough insulin. Insulin resistance was not thought to be a part of type 1 diabetes, but perhaps it is.
"Insulin resistance does play a role in type 1 diabetes," says Katherine Williams, MD, MPH. "In the past, the focus in this disease has been on the pancreas not producing insulin. There hasn't been much emphasis on an additional problem: that some people are also not responding to insulin." Williams is an instructor in medicine at the University of Pittsburgh School of Medicine, and the clinical investigator on the study.
"We have identified a subgroup of patients with type 1 diabetes who [also] have insulin resistance and therefore are at increased risk of cardiovascular disease. They probably need special treatment such as increased exercise, weight loss, and possibly [medication]," says Trevor Orchard, MBBCh, MMS, senior author of the article.
Additional research is needed to confirm the study's results, Orchard says. "Meanwhile, we think the major risk factors identified here -- waist-hip ratio, [high blood pressure], and a family history of type 2 diabetes -- are important predictors of the risk of heart disease in type 1 diabetics." Orchard is professor of medicine, epidemiology, and pediatrics at the University of Pittsburgh School of Public Health.
The research team looked at various factors that might predict the likelihood of insulin resistance in adults with type 1 diabetes, including high blood pressure, waist-hip ratio, triglyceride and HDL (or 'good') cholesterol levels, family history of type 2 diabetes, and level of blood sugar control.
They found a high waist-hip ratio was the strongest predictor of insulin resistance. That means being overweight -- and especially carrying that weight around the belly -- puts type 1 diabetics at increased risk for heart disease.
"If you are in that situation, get your weight down," advises Ronald Goldberg, MD. "Getting weight down to normal levels is much more important than we ever thought." Goldberg is professor of medicine and associate director of the Diabetes Research Institute at the University of Miami School of Medicine.
Orchard estimates that about 20% of people with type 1 diabetes are likely to have insulin resistance, although this varies with age. Meanwhile, the research emphasizes how important it is for people with type 1 diabetes to discuss these risk factors with their doctors. "If you have any family history of heart problems or type 2 diabetes, make sure your doctor knows about it," Orchard says.
In addition, he says, people need to get their controllable risk factors under control. That means getting a reasonable amount of exercise, controlling weight, and lowering high blood pressure. "The essence of this approach is that the risk of heart disease in diabetes goes way beyond controlling blood sugar levels," Orchard says. "If you are at risk of being insulin resistant ... then you should be aware of these issues and talk with your doctor about ways of reducing insulin resistance."
- In people who have type 1 diabetes, the pancreas makes little to no insulin, the principal hormone regulating blood sugar. Some of these patients also face an increased risk of heart disease because they are insulin resistant, in which the body can't use insulin properly. A new study reports that doctors can use some simple measures to predict the presence of insulin resistance.
- The authors and observers add that in order to reduce the risk of insulin resistance and the heart disease it can cause, it is important for patients to control their blood pressure and their weight, especially for people with a lot of abdominal fat.
- A family history of type 2 diabetes (where the body makes insulin but can't use it well) also is a risk for developing insulin resistance.