Background: A secretion of plasma active GLP-1 (p-active GLP-1) after ingestion of breakfast test meal (TM) is decreased in obese European patients with type 2 diabetes mellitus (T2DM). However, there was no significant difference in pactive GLP-1 secretion following TM between obese Japanese patients with T2DM and controls. The findings indicate the difference may be due to different races or dietary’s customs of subjects. Aims: We examined whether pactive GLP-1 is truly affected by TM in obese Japanese patients (n = 24, group 1) and obese controls (n = 12, group 2). Methods: Glucose (PG), insulin (s-IRI), C-peptide (s-CPR) and active GLP-1 like substances (p-active GLP-1-S) levels in blood were measured 0, 30 and 60 min after TM. Obese Japanese patients with mean 9 years of diabetes had micro- and macro-vascular disturbances and were treated with diet, exercise and/or oral drugs for hyperglycemia. Results: There was no significant difference in sex, age or BMI between groups. Means HbA1c and PG were significantly higher in group 1 than in group 2. There were no significant differences in means of basal s-IRI, HOMA-R and s-CPR between groups. However, means of HOMA-β, insulinogenic index, postprandial s-IRI, s-CPR and p-active GLP-1-S or p-active GLP-1-S/PG values after TM were significantly lower in group 1 than in group 2. Conclusions: These results indicate that a response of p-active GLP-1-S after TM in obese Japanese patients with T2DM was decreased and secretion of GLP-1 relative to PG was impaired. The method of enhancing function of active GLP-1 may be useful for treatment in some of patients with diabetes mellitus.
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