The effect of gliclazide on plasma insulin, intact and 32/33 split proinsulin in South Asian subjects with Type 2 diabetes mellitus

Aims Previous studies have shown that in Caucasian subjects with Type 2 dia betes mellitus (DM), the sulphonylurea glibenclamide increased insulin secr etion without causing an increase in 32/33 split proinsulin secretion. Sout h Asian subjects with Type 2 DM are thought to be more insulin resistant an d the effect of sulphonylureas may be different. We therefore investigated the effect of sulphonylurea therapy with gliclazide on beta-cell function i n South Asian subjects with newly diagnosed Type 2 DM. Methods Glucose, insulin, and intact and 32/33 split proinsulin were measur ed at diagnostic oral glucose tolerance test (OGTT). After 8-12 weeks on a conventional diet, subjects with a fasting glucose >6 mmol/l (n = 16) were commenced on gliclazide. Results At diagnosis, those requiring gliclazide were more hyperglycaemic b ut there was no difference in weight or fasting insulin concentration than in the diet group. Following diet, in the gliclazide group, weight fell (P < 0.04) with no change in fasting glucose concentration. Fasting intact pro insulin, insulin and 32/33 split proinsulin remained unchanged. After glicl azide therapy weight remained unchanged, but fasting glucose fell (P < 0.00 3). Fasting insulin and intact proinsulin remained unchanged but 32/33 spli t proinsulin fell (P < 0.05). Pasting insulin to glucose ratio significantl y improved after gliclazide (P < 0.006). Conclusions In South Asian subjects treated with gliclazide the reduction i n fasting glucose concentrations appears to be due to an improvement in ins ulin sensitivity as well as in beta-cell function.