GIP, GLP-1 and GLP-2 in Type 2 Diabetic Hyperglucagonemia

Patients with T2DM are not able to suppress their secretion of glucagon after a meal or after oral ingestion of glucose. Patients actually respond with pathological high plasmaglucagon concentrations to these stimuli. Previous studies have shown that postprandial hyperglucagonemia results in increased hepatic glucose production and therefore contributes significantly to the hyperglycemia characterizing these patients. Recently we have shown that patients with T2DM exhibit a normal suppression of glucagon secretion following an adjustable intravenous (iv) glucose challenge mimicking the glucose excursion following a 50-g oral glucose tolerance test (OGTT) with the latter resulting in lack of glucagon suppression. Why this difference? A possible explanation could be that the oral administration stimulates intestinal factors resulting in a differentially glucagon response to the two similar glucose excursions. We wish to establish whether GIP, GLP-1 and/or GLP-2 are responsible for the inappropriate glucagon suppression following OGTT and meals in patients with T2DM.