Meal test for glucose-dependent insulinotropic peptide (GIP) in obese and type 2 diabetic patients.

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 introduce 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. 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 AUCGIP during 90 min of the meal stimulation was significantly lower in diabetic patients than in other two groups (p<0.03). Insulin concentration at 30 min was lower in diabetic than in non-diabetic persons and the GIP action was delayed. The deltaIRI/deltaGIP 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.