Optimized Human Regular U-500 Insulin Treatment Improves β-Cell Function in Severely Insulin-Resistant Patients with Long-Standing Type 2 Diabetes and High Insulin Requirements

Abstract

To assess β-cell function and insulin sensitivity following improvement in glycemic control in severely insulin-resistant patients with poorly controlled type 2 diabetes (T2D). A subset of patients in a 24-week, open-label, randomized trial comparing thrice-daily (n = 14/162) versus twice-daily (n = 11/163) human regular U-500 insulin (U-500R) underwent mixed meal tolerance testing at baseline and endpoint. Baseline characteristics were similar between treatment groups (combined means: age, 54.0 years; diabetes duration, 13.6 years; body mass index, 38.8 kg/m(2); glycated hemoglobin [HbA1c], 8.3%; U-100 insulin dose, 287.6 units/day, 2.6 units/kg/day). Primary outcome measure was ratio of area under the curve (AUC) for C-peptide to glucose (AUCC-peptide/AUCglucose) at 24-week endpoint. Change from baseline HbA1c, daily U-500R dose, and weight were -1.17% (P = .0002), +80.8 units (P = .0003), and +5.9 kg (P = .33), respectively. β-Cell function significantly improved after 24 weeks of U-500R therapy in combined treatment groups. The AUCC-peptide/AUCglucose increased 34.0% (ratio of least-squares geometric mean, 1.34; 95% confidence interval, 1.18 to 1.52; P = .0001). Integral of total insulin secretion rate increased from 27.0 to 33.7 nmol/m(2), and glucose sensitivity improved from 18.3 to 24.0 pmol/min/m(2)/mM (both, P = .02). Matsuda index improved from 0.8 to 1.3 (P = .008). Despite long-standing diabetes and poor glycemic control at baseline, functional recovery of β-cells was observed with improved glycemic control in these severely insulin-resistant patients with T2D, possibly due to alleviation of glucotoxicity.