The Switch from Sulfonylurea to Preprandial Short- Acting Insulin Analog Substitution Has an Immediate and Comprehensive β-Cell Protective Effect in Patients with Type 2 Diabetes Mellitus

Background: Supplementary insulin therapy provides assistance to meal-time insulin secretion in patients with type 2 diabetes and may have protective effects on β-cell function. Methods: This study explored the immediate effect of supplementary insulin therapy on β- cell function in patients with glimepiride monotherapy (five women, 15 men; 61.8 ± 6.4 years old; body mass index, 31.1 ± 4.4 kg/m2; hemoglobin A1c, 7.0 ± 1.3%). After 1 week of continued glimiperide therapy, the patients were randomized either to continue with their oral treatment or to switch to a fixed-dose supplementary insulin therapy (8 U of insulin aspart subcutaneously before each meal) for another week. Oral glucose tolerance tests (OGTTs) after drug uptake were performed at days 7 and 14, with measurement of glucose, insulin, C-peptide, intact and total proinsulin, glucagon, lactate, free fatty acids, and adiponectin. Results: Significant reductions from baseline were seen in the supplementary insulin therapy group for the fasting va...