Evaluation of beta cell dysfunction by mixed meal tolerance test and oral L-arginine in patients with newly diagnosed type 2 diabetes mellitus

Background and aims: 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.

Materials and methods: 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.

Results: 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.

Conclusion: 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.