Everyone knows that the complications that often go with type 1 diabetes are caused by high blood sugar, right? Well, maybe not, according to researchers at Vanderbilt University Medical Center.
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Head of the research team, Justin Gregory, MD, and his colleagues wondered if the culprit in diabetes complications might not be high blood sugar but too much insulin. They began their investigation with the realization that people with type 1 diabetes not only don’t make insulin in their bodies, but also they’re “resistant” to replacement insulin. And, in order to move glucose from the blood into the muscles, they actually need more insulin than people without diabetes. The researchers speculated that insulin resistance in type 1 diabetes is related to the way in which the body delivers insulin to the muscles. In healthy people, insulin created in the pancreas first travels to the liver, which cuts the amount of insulin in half before passing it to the muscles. In patients who inject insulin, the liver is bypassed. As Gregory explained, “I’m putting insulin in the wrong place…. Too much insulin at muscle and not enough at liver.”
To test the hypothesis that high levels of insulin, and not high levels of blood sugar, cause insulin resistance, the researchers compared people with type 1 diabetes to people with a form of diabetes known as GCK-MODY, which stands for glucokinase-maturity-onset diabetes of the young. GCK-MODY is caused by mutations in the glucokinase (GCK) gene, which plays an important role in the regulation of insulin production. They found that patients with GCK-MODY had the same levels of insulin as healthy patients but patients with type 1 diabetes had insulin levels two and a half times higher.
Gregory concluded, “There’s more to treating type 1 diabetes than just bringing down high blood sugar,” and he and his colleagues said that in treating type 1 diabetes, researchers “need to come up with ways of delivering insulin that replicate the normal balance of insulin” and get the insulin to the liver before the muscles. One way of doing that might be to alter the insulin replacement molecule so that it would go directly to the liver. Another would be to implant an insulin pump that would send insulin to the liver before going to the muscles. And a third method might be to make an oral form of insulin with a protective cover that would prevent the insulin from degrading in the stomach and intestines before it reaches the liver.
A freelance writer and editor based in the Chicago area, Gustaitis has a degree in journalism from Columbia University.