Diabetes type 2 is caused by insufficient levels of insulin to keep blood glucose under control. Excessive levels of another hormone, glucagon, can also contribute to diabetes type 2 by causing the liver to flood the body with stored glucose. Diabetes type 2 does not arise overnight, but slowly progresses for many years as a condition known as prediabetes. In prediabetes, blood sugar rises to excessive levels after a meal, but is normal or nearly normal after an overnight fast. Researchers are seeking ways to prevent prediabetes from progressing to diabetes. Besides diet and exercise, the diabetic drug metformin can slow the onset of diabetes.
In the March 2011 issue of Experimental Biology and Medicine researchers in the Department of Nutrition at Case Western Reserve University determined whether a newer diabetes drug, sitagliptin, might be effective in prediabetes. Sitagliptin works by boosting the levels of an intestinal factor known as GLP-1. This factor increases insulin output while also decreasing glucagon output. They used an animal model with prediabetes, the SHROB rat, which was developed at Case Western Reserve University beginning in the 1970's. These rats are extremely obese and have normal glucose after fasting but high glucose after a meal, like prediabetic humans. Also like prediabetic humans, they have excessive levels of glucagon.
The prediabetic rats were divided into three groups and treated with either a placebo, sitagliptin, or another older diabetes medication, glyburide, which acts by boosting the production of insulin by the pancreas. Sitagliptin and glyburide were equally effective in lowering glucose levels after a meal. Surprisingly, only sitagliptin raised the total output of insulin by the pancreas and only sitagliptin lowered glucagon to normal levels.
Neither of the diabetes medications had any effect on body weight, total body fat or food intake. This matches studies in humans, which show no loss or
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