Changes of GLP-1 and GIP in Patients with Non-alcoholic Fatty Liver Disease after Oral Glucose

OBJECTIVE To determine the secretion of incretins after oral glucose administration in non-alcoholic liver disease(NAFLD) patients. METHODS Standardized oral glucose tolerance test was performed on patients with NAFLD(n=34) and healthy controls(n=42). Glucose, insulin, glucagon, glucagon-likepeptide-1(GLP-1) and glucose-dependent insulinotropic ploypeptide (GIP) plasma levels were measured sequentially for 120 minutes after glucose administration. RESULTS Glucose induced GLP-1 secretion was significantly decreased in patients compared with control group(P<0.01). In contrast, GIP secretion was unchanged. All patients were insulin resistant. Fasting and glucose- induced insulin secretion was higher in NAFLD compared with control group, while the glucose lowering effect was diminished. Concomitantly, fasting glucagon secretion was significantly elevated in NAFLD. CONCLUSION Glucose-induced GLP-1 secretion is deficient in patients with NAFLD. GIP secretion is contrarily preserved. Insulin resistance, with hyperinsulinemia and hyperglucagonemia, is present in all patients.