Postprandial glucose, insulin and incretin responses to different carbohydrate tolerance tests

Background Few studies have focused on postprandial incretin responses to different carbohydrate meals. Therefore, we designed a study to compare the different effects of two carbohydrates (75 g oral glucose, a monosaccharide and 100 g standard noodle, a polysaccharide, with 75 g carbohydrates equivalently) on postprandial glucose, insulin and incretin responses in different glucose tolerance groups. Methods This study was an open-label, randomized, two-way crossover clinical trial. 240 participants were assigned to take two carbohydrates in a randomized order separated by a washout period of 5–7 days. The plasma glucose, insulin, c-peptide, glucagon and active glucagon-like peptide-1 (AGLP-1) were measured. The incremental area under curve above baseline from 0 to 120 min of insulin (iAUC0–120 min-INS) and AGLP-1(iAUC0–120 min-AGLP-1) was calculated. Results Compared with standard noodles, the plasma glucose and insulin after consumption of oral glucose were higher at 30 min (both P < 0.001) and 60 min (both P < 0.001), while lower at 180 min (both P < 0.001), but no differences were found at 120 min. The glucagon at 180 min was higher after consumption of oral glucose (P = 0.010). The AGLP-1 response to oral glucose was higher at 30 min (P < 0.001), 60 min (P < 0.001) and 120 min (P = 0.022), but lower at 180 min (P = 0.027). In normal glucose tolerance (NGT), oral glucose elicited a higher insulin response to the corresponding AGLP-1 (P < 0.001), which was represented by iAUC0–120 min-INS /iAUC0–120 min-AGLP-1, while in type 2 diabetes mellitus (T2DM), standard noodles did (P = 0.001). Conclusions Monosaccharide potentiated more rapid and higher glycemic and insulin responses. Oral glucose of liquid state would elicit a more potent release of AGLP-1. The incretin effect was amplified after consumption of standard noodles in T2DM.