Backgrounds: Generally, a prevalence of obesity increasing constantly represents one of major health care and social problems. Many researchers indicate that obesity has a risk factor for type 2 diabetes mellitus (T2DM), but some persons believe that obesity may occur T2DM. GLP-1 and GIP as incretin hormone are secreted in response to ingestion of nutrients. In the circulation, they are rapidly inactivated by dipeptidyl peptidase-4. We report interesting findings on secretion of incretin after test meal (TM) in Japanese patients with type 1 diabetes mellitus (T1 DM) and T2DM associated with or without obesity.
Materials and Methods: In Japan, ≥25 kg/m2 in BMI are defined as obesity. After overnight fast, subjects were ingested of TM (550 kcal) comprised of 60% carbohydrate, 23% fat and 17% protein. Based on GLP-1, patients with T1DM (n=10) were treated with multiple daily injections of insulin (MDI) or CSII. Non-obese (n=23) and obese (n=24) patients with T2DM with micro- and macroangiopathy were treated with oral drugs for various disease. Based on GIP, patients with T1DM (n=15) and T2DM (n=29) were treated with MDI or CSII for T1DM and oral drugs for T2DM, respectively.
Results: Basal and postprandial levels of plasma active GLP-1 (p-GLP-1) after TM in Japanese patient with T1DM and T2DM are similar to those with control, but basal and postprandial ratio of p-GLP-1/glucose are low compared with controls. AUCs of plasma GIP at early-phase were significant negatively and positively related to BMI in patients with T1DM and T2DM, respectively.
Conclusions: Japanese patients with T2DM regards of obesity may have a low secretion of GLP-1, which may be due to genetic factors. However, there is no T2DM in obese persons without low secretion of GLP-1. Therefore, risk factors for DM are important to diagnose T2DM.