Short-term intensive insulin as induction and maintenance therapy for the preservation of beta-cell function in early type 2 diabetes (RESET-IT Main): A 2-year randomized controlled trial.

Aim: To test the hypothesis that the addition of periodic courses of short-term intensive insulin therapy (IIT) could enhance the effect of metformin (MET) maintenance therapy on preservation of beta-cell function following induction IIT.

Methods: In this multicentre, randomized controlled trial, 108 adults with type 2 diabetes (median 1.3 years' duration; HbA1c 6.6% ± 0.6%) were randomized to 3 weeks of induction IIT (glargine, lispro) followed by MET maintenance, either with or without periodic 2-week courses of IIT every 3 months for 2 years. Beta-cell function was assessed by the Insulin Secretion Sensitivity Index-2 (ISSI-2) at an oral glucose tolerance test every 3 months.

Results: In both arms, induction IIT increased ISSI-2, improved whole-body insulin sensitivity and reduced hepatic insulin resistance (all P ≤ .0004). The primary outcome of baseline-adjusted ISSI-2 at 2 years was not improved by the addition of intermittent IIT (MET + IIT) and was slightly higher in the MET arm (baseline-adjusted difference -35 [95% CI: -66, -3]), with three additional beta-cell measures showing no significant differences. Baseline-adjusted HbA1c at 2 years did not differ between MET and MET + IIT (6.3% ± 0.1% vs. 6.4% ± 0.1%, P = .46), with 32.6% of participants in each arm maintaining HbA1c of 6.0% or less at 2 years.

Conclusion: Although initial induction IIT induces metabolic improvement, subsequent repeat courses of IIT every 3 months do not further enhance the effect of MET maintenance therapy on beta-cell function.