Objective: To determine the levels of plasma glucagon and associated factors in individuals with different glucose metabolism.
Methods: One hundred and ten outpatient patients received an oral glucose tolerance test (OGTT) voluntarily. The patients were divided into three groups according to their OGTT results: normal glucose golerance (NGT) group (n=33), impaired glucose regulation (IGR) group (n=35), newly diagnosed type 2 diabetes (DM2) group (n=42). Plasma glucagon (GLC) and insulin (INS) at 0 min (0 h), 30 min (0.5 h), 60 min (1 h) and 120 min (2 h) were measured by radio immunity and electrochemiluminescence assay, respectively. We calculated the area of glucagon under the curve (AUCglc), the value of early phase glucagon secretion (deltaGLC = GLC(0.5 h) - GLC(0 h)) and the ratio of insulin to glucagon (INS/GLC).
Results: (1) There was no significant difference in the level of GLC(0 h) among the three groups (P > 0.05). (2) Patients in the IGR group had higher levels of GLC(0.5 h) and GLC(1 h), greater values of AUC(glc), and deltaGLC, and lower values of INS(0.5 h)/GLC(0.5 h) than those in the NGT group (P < 0.05). (3) Patients in the DM2 group had higher levels of GLC(0.5 h) and GLC(1 h), greater values of AUC(glc) and deltaGLC, and lower values of INS(0.5 h)/GLC(0.5 h) and INS(1 h)/GLC(1 h) than those in the NGT group (P < 0.05). (4) Patients in the DM2 group had higher levels of GLC(1 h), greater values of AUC(glc), and lower values of INS(0.5 h)/GLC(0.5 h), INS(1 h)/GLC(1 h), and INS(2 h)/GLC(2 h), than those in the IGR group (P < 0.05). (5) The multiple linear regression analysis showed that the value of AUC(glc). was positively correlated with HOMA-IR (adjust R2 = 0.219, P = 0.001).
Conclusion: There are no significant differences in fasting plasma glucagon levels among the individuals with different glucose metabolism. Hypersecretion of glucagon and reduced glucagon suppressing effect of insulin occur in IGR patients, which is exacerbated when DM2 are developed. HOMA-IR is an important factor associated with glucagon hypersecretion.