Endocrine Abstracts

Glucose-dependent insulinotropic peptide (GIP) contributes to incretin effect of insulin secretion which is impaired in type 2 diabetes mellitus. The aim of this study was to develop a simple meal test for evaluation of GIP secretion and action and to examine GIP changes in type 2 diabetic patients. Seventeen type 2 diabetic patients, 10 obese non-diabetic and 17 non-obese control persons have been examined before and after 30, 60 and 90 min stimulation by meal test. In a mixed meal challenge, breakfast composed from 200 ml Resource drink containing 28 g saccharides, 7 g fats and 18.8 g protein with one roll (50 g) and 10 g butter. The total caloric content of this standard testing breakfast was 445 kcal (1850 kJ). Serum concentrations of insulin, C-peptide and GIP were estimated during the test. Impaired GIP secretion was found in type 2 diabetic patients as compared with obese non-diabetic and non-obese control persons. The AUC_GIP during 90 min of the meal stimulation was significantly lower in diabetic patients than in other two groups (13.6±3.8 vs 17.5±6.5 and 18.8±3.8, P<0.03). Insulin concentration in 30 min was lower in diabetic than in non-diabetic persons (P<0.05) and the GIP action was delayed. The ΔIRI/ΔGIP ratio increased during the test in diabetic patients whereas it progressively decreased in obese and non-obese control persons. Simple meal test could demonstrate impaired GIP secretion and delayed insulin secretion in type 2 diabetic patients as compared to obese non-diabetic and non-obese healthy control individuals. No significant difference was found in GIP secretion between obese and non-obese non-diabetic persons.