Is Insulin Resistance and/or Glucose Intolerance Pathogenetic in the Development of a Reduced Incretin Effect

• Incremental GLP-1 response during the mixed meal test. Assessed as AUC during the 4 hour test. [ Time Frame: In the mixed meal test ] [ Designated as safety issue: No ]
  

In this study we are going to examine the incretin effect before and after the development of insulin resistance and/or glucose intolerance. The incretin effect is the increased insulin response seen after an oral as apposed to an intravenous glucose challenge with identical plasma glucose profiles. This insulin enhancing effect is greatly reduced in type 2 diabetes.

Since the development of type 2 diabetes is preceded by insulin resistance and glucose intolerance we wanted to examine the incretin effect in the early stages of type 2 diabetes.

To do this, we want to induce insulin resistance and/or glucose intolerance. This is achieved by 5 days of treatment with dexamethasone.

The incretin effect in this study will be examined by 3 investigations prior to the treatment and 3 days following the treatment.

Day 1: Oral glucose challenge with 75 g of glucose.

The subject is asked to drink 75g of glucose suspended in 300mL of water. During the 4 hours of the test, we draw blood at various times during the study to determine the concentration of: Glucose, GLP-1, GIP, Glucagon, Insulin and c-peptide.

Day 2: Intravenous glucose

We duplicate the glucose curve obtained from day 1. We also draw blood during this test to the same end as in day 1.

Day 3: Mixed meal.

The subjects are served a mixed meal. During this 4 hour test, we draw blood to examine the response to a standardized meal. The test involves sampling blood as described for the other days.