Postabsorptive hyperglucagonemia in patients with type 2 diabetes mellitus analyzed with a novel enzyme-linked immunosorbent assay

Aims/introduction: The aims of the present study were to investigate the performance of a novel sandwich enzyme-linked immunosorbent assay (ELISA) for measuring glucagon (1-29) with monoclonal antibodies against both the C-and N-terminal regions of glucagon (1-29), and to analyze the differences in plasma levels and responses of glucagon (1-29) to oral glucose loading in normal glucose tolerance (NGT) subjects and patients with type 2 diabetes mellitus. Materials and Methods: The cross-reactivity against proglucagon fragments using the ELISA kit and two types of conventional radioimmunoassay (RIA) kits was evaluated. A 75-g oral glucose tolerance test was carried out with NGT subjects and patients with type 2 diabetes mellitus, and the glucagon (1-29) concentration was measured using three types of kit. Results: The ELISA kit clearly had the lowest cross-reactivity against miniglucagon (19-29) and glicentin (1-61). The oral glucose tolerance test was carried out with 30 NGT and 17 patients with type 2 diabetes mellitus. The glucagon (1-29) levels measured by the ELISA kit after glucose loading were significantly higher at all time-points in the type 2 diabetes mellitus group than in the NGT group. However, the glucagon (1-29) levels measured by one RIA kit were significantly higher in the NGT group, and those measured with the other RIA kit were approximately the same among the groups. Conclusions: The novel sandwich ELISA accurately determines plasma glucagon (1-29) concentrations with much less cross-reactivity against other proglucagon fragments than conventional RIA kits.