Elevated serum dipeptidyl peptidase-4 activity in type 1 diabetes mellitus: a direct comparison

Abstract

Dipeptidyl peptidase-4 (DPP-4) has an important role in the carbohydrate metabolism with the degradation of incretin hormones. We assessed the serum DPP-4 activity both in fasting and postprandial condition in patients with type 1-, type 2 diabetes and healthy controls. Serum DPP-4 activities were determined at fasting sate and at 60 and 180 minutes after test meal. DPP-4 activity was measured by microplate-based kinetic assay in 41 type 1-, and in 87 type 2 diabetic patients and in 25 healthy volunteers. Serum DPP-4 activities were found significantly higher both in fasting and postprandial state in patients with type 1 diabetes than in type 2 and control subjects. No change in the enzyme activities was found after test meal. Correlation was neither detected between the fasting plasma glucose nor between the HbA(1C) and the DPP-4 values in any of the groups studied. RESULTS suggest that it is not the hyperglycemia, rather the type of diabetes which determinates the serum DPP-4 enzymatic activity. The exact background of this phenomenon is not yet clear, however, increased serum DPP-4 enzyme activity in type 1 diabetes mellitus may refer to pancreatic autoimmune process, concomitant autoimmune diseases, hormonal feed back mechanism, or even target organ damage.