Effects of insulin versus sulphonylurea on beta-cell secretion in recently diagnosed type 2 diabetes patients: a 6-year follow-up study

Abstract

Background: Early insulin treatment is considered more beneficial than anti-diabetic medication with sulphonylureas, because the latter may exert negative effects on beta-cell function, while the former may help preserve it. In a previous study, we found that C-peptide response was increased in the insulin-treated group, whereas it was decreased in the glibenclamide group. However, it was not certain whether the advantage remained in the longer term.

Aim: In this study, we tested whether early insulin treatment is more beneficial than glibenclamide against a 6-year follow-up perspective.

Methods: We designed a randomized clinical trial in subjects with newly diagnosed type 2 diabetes. Glucagon stimulatory tests, measuring C-peptide and islet amyloid polypeptide (IAPP), were performed after 2, and 3, days of temporary insulin and glibenclamide withdrawal.

Results: 18 subjects initially randomized to glibenclamide, and 16 randomized to two daily injections of insulin, participated in end-of-study investigations. C-peptide response to glucagon deteriorated (p < 0.01 vs. baseline) in initially glibenclamide-treated patients (n = 18), but not in insulin-treated patients (p < 0.05 for difference between groups, after 2 days of treatment withdrawal). The IAPP response to glucagon declined in the glibenclamide group (p < 0.001), but not in insulin-treated subjects (p = 0.05 for difference between groups).

Conclusions: Early insulin treatment preserves beta-cell secretory function better than glibenclamide even in a 6-year perspective.

Figure 1. Study design

The figure shows the number of patients included into the study after assessment, the number allocated to one of the groups (glibenclamide or insulin), and the number of patients lost for follow-up during the 6-yr study period.

Figure 2

Delta C-peptide responses to glucagon (A) baseline vs. end-of-study, between the insulin-treated group (Insulin, n = 16), and the glibenclamide-treated group (SU, n = 18). Data are mean ± SEM. ^* p < 0.05 vs. SU. C-peptide (B) and IAPP (C) responses to glucagon in the glibenclamide-treated group (SU, n = 18), and the insulin-treated group (Insulin, n = 16), at baseline and at the end of the study. Data are mean ± SEM. ^§ p = 0.009, ^# p = 0.006, ⁺ p < 0.001 for effects within groups vs. baseline.