The incessant increase curve during oral glucose tolerance tests in Chinese adults with type 2 diabetes and its association with gut hormone levels.

Glucose curve shapes during oral glucose tolerance tests (OGTTs) are mainly classified as incessant increase, monophasic and biphasic. Youth with an incessant increase curve have worse β-cell function. The aim of this paper was to investigate the incessant increase curve in Chinese adults with type 2 diabetes (T2DM), and its association with β-cell function and gut hormone levels. Eighty-nine Chinese patients (59 males and 30 females) were included in this study with a mean age of 50.56 ± 16.00 years. They were all recently diagnosed with T2DM and underwent 180-min OGTTs. Data on demographics, β-cell function, and insulin sensitivity were also collected. Gut hormones, including glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic polypeptide (GIP), and ghrelin, were also detected during the OGTT. A total of 39.3 % of subjects had an incessant increase in the glucose response curve, while 59.6 % had a monophasic curve. Because only one curve was classified as biphasic, patients with a biphasic curve were omitted from further research. Lower plasma C-peptide, HOMA2-β, area under the curve (AUC) of C-peptide, and ratio of AUC of insulin to AUC of glucose were found in patients with incessant increase curves compared to those with monophasic curves (P < 0.05). Higher glycated hemoglobin (HbA1c) was found in subjects with an incessant increase curve (P < 0.05). Importantly, fasting plasma ghrelin was lower and incremental ghrelin at 120 min was higher in the incessant increase group (P < 0.05), irrespective of age, sex, body mass index (BMI), fasting glucose, and fasting insulin. Time to peak is also a parameter of the OGTT curve shape. In the late-peak group, GLP-1 at 120 min and the AUC of GLP-1 were elevated compared with those in the early-peak group (P < 0.05). In Chinese adults with T2DM, the incessant increase in OGTT shape indicated impaired insulin secretion. Lower fasting ghrelin and absence of ghrelin drops after glucose load may be associated with the incessant increase OGTT shape. In addition, compensatory elevated GLP-1 dose not prevent peak delay in the OGTT curve. Gut hormones may have an effect on OGTT shapes in T2DM adults.