In order to evaluate the potential role of the gastrointestinal (GI) tract in the postprandial hyperglucagonemia, which characterizes type 1 diabetes mellitus (T1DM) (as well as type 2 diabetes mellitus (T2DM)), we wish to investigate the secretion of glucagon in patients with T1DM without residual beta-cell function during 50-g oral glucose tolerance test (OGTT) and during isoglycemic iv glucose infusion. By evaluating C-peptide negative patients with T1DM we aim to describe the glucagon response to glucose (+/-stimulation of the GI tract) independently of the potentially very important regulation of glucagon secretion by endogenous insulin secretion. A more detailed understanding of the inappropriate glucagon secretion in T1DM is highly needed in order to establish new intervention strategies in the future treatment of the growing numbers of T1DM patients.

Inclusion Criteria:

• Caucasian over 18 years with T1DM (diagnosed according to WHO's criteria) treated with long-acting insulin
• No residual beta-cell function (arginine test without increment in plasma C-peptide - see below)
• BMI <30 kg/m2
• Normal haemoglobin
• Informed consent

Exclusion Criteria:

• Residual beta-cell function (increment in plasma C-peptide during arginine test - see below)
• Known liver disease or affected liver enzymes (ALAT/ASAT > 2 x upper normal limit)
• Diabetic nephropathy (se-creatinin > 130 µM and/or albuminuria)
• Proliferative diabetic retinopathy (anamnestic)
• Treatment with medication that cannot be discontinued for 14 hours

Patients with type 1 diabetes mellitus and no residual beta-cell function (C-peptide negative)