Beta cell response to oral glimepiride administration during and following a hyperglycaemic clamp in NIDDM patients

The aim of the present study was to assess the beta cell response to glimepiride, administered orally, during and following a hyperglycaemic clamp in 14 NIDDM patients (7 males), aged 62.5 (St. Dev. 7.7) years with a body mass index of 27.3 (2.8) kg m(-2) and HbA(Ic) of 7.0 (0.7)% at baseline, in a placebo controlled study. All patients were on stable treatment with a second generation sulphonylurea for at least 8 weeks prior to randomization and received placebo (P) or 5 mg glimepiride (G) daily for 7 days and 10 mg prior to a hyperglycaemic clamp (10.9 mmol l(-1) for 60 min, preceded by i.v. insulin infusion to stabilize fasting blood glucose levels at 4.0 mmol l(-1)). The clamp was followed by an observation period of 2 h in 5 subjects and 3.5 h in the next 9 subjects, during which blood glucose and plasma insulin, C-peptide and proinsulin levels were measured at regular intervals to determine the effect of glimepiride on the interaction between changes in glycaemia and plasma levels of beta cell products. Neither G nor P elicited a first phase insulin response. Areas under plasma insulin curve during the 1 h hyperglycaemic clamp were 94.2 (39.5) vs 69.1 (26.5) pmol.h l(-1) in G and P clamps, respectively (p = 0.002). Total areas (AUC) under the plasma insulin curve were 377 (145) vs 271 (113) pmol.h l(-1) in G and P clamps (< 0.05). Total AUCs of C-peptide were 309 (96) and 259 (102 pmol.h.(-1), in G and P clamps, respectively, p = 0.01. Total AUCs of proinsulin were 176 (77) versus 119 (56) pmol.h l(-1) in G and P clamps, respectively, p = 0.004. Five hours after G and P administration blood glucose levels were 4.7) 92.1) mmol(-1) in the G clamp vs 6.2 (1.9) mmol l(-1) in the P clamp (p = 0.001). The number of hypoglycaemic events (blood glucose < 3.0 mmol l(-1)) in the 3.5 h observation period was 3 in G clamps vs 0 in P clamps (p = ns). In conclusion, glimepiride stimulates the second phase insulin and proinsulin secretion. The lowering of blood glucose levels is not accompanied by a commensurate inhibition of the insulin secretion. Further studies are required to compare this new drug with currently available oral hypoglycaemic agents, with respect to glycaemic control and the risk of hypoglycaemia.