Evaluation of Beta Cell Dysfunction by Mixed Meal Tolerance Test and Oral L-arginine in Patients with Newly Diagnosed Type 2 Diabetes Mellitus

Abstract

Defective insulin secretion is required for the development of frank diabetes mellitus. We evaluated the secretory response of pancreatic beta cells after the ingestion of mixed meal plus oral L-arginine in newly diagnosed type 2 diabetic patients. Twenty-four newly diagnosed type 2 diabetic patients were enrolled in this study. All patients were ingested a mixed meal of 553 kcal. Serum insulin levels were measured at time 0 just before the mixed meal and at 1, 2, 3, 4 and 5 h after the ingestion of the mixed meal. Twenty-four hours later, all patients ingested mixed meal followed by oral 8 g L-Arginine, and insulin levels were again measured at 0, 1, 2, 3, 4 and 5 h after the ingestion of the meal. Insulin levels reached to peak values at the 2 (nd) hour, and decreased to baseline levels at the 5 (th) hour measurements both after the ingestion of mixed meal only and after the ingestion of mixed meal plus oral L-Arginine. First and 2 (nd) hour insulin levels were significantly higher after the ingestion of mixed meal plus oral L-Arginine. In this study we used for the first time the combination of oral L-arginine with mixed meal test to evaluate the beta cell dysfunction in type 2 diabetic patients. Increments regarding serum insulin levels after the ingestion of mixed meal plus oral L-Arginine suggest that oral L-Arginine could be benefical for the evaluation of beta cell function and secretory defects.