Changes of Plasma Glucagon Level in Individuals with Different Glucose Metabolism

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 (AUC_glc), the value of early phase glucagon secretion （ΔGLC=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 ΔGLC, 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 ΔGLC, 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). ⑤The multiple linear regression analysis showed that the value of AUC_glc was positively correlated with HOMA-IR (adjust R ^2/sup>=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.