Incretin effects, gastric emptying and insulin responses to low oral glucose loads in patients after gastric bypass and lean and obese controls

BackgroundAfter laparoscopic Roux-en-Y gastric bypass (LRYGB), many patients suffer from dumping syndrome. Oral glucose tolerance tests are usually carried out with 50-75 g of glucose. The aim of this study was to examine whether minimal glucose loads of 10 g and 25 g induce a reliable secretion of satiation peptides without dumping symptoms after LRYGB. In addition, lean and obese controls were examined.ObjectiveThe objective of this study was to determine the effects of low oral glucose loads on incretin release and gastric emptying.SettingAll surgical procedures were performed by the same surgeon (RP) at the St. Claraspital Basel in Switzerland. Oral glucose challenges were carried out at the University Hospital of Basel (Phase 1 Research Unit).MethodsEight patients 10±.4 weeks after LRYGB (PostOP; body mass index [BMI]: 38.6 kg/m2±1.7) as well as 12 lean controls (LC; BMI: 21.8 kg/m2±.6) and 12 obese controls (OC; BMI 38.7 kg/m2±1.3) received 10 g and 25 g of oral glucose. We examined clinical signs of dumping syndrome; plasma glucose, insulin, glucagon-like peptide 1, glucose-dependent insulinotropic peptide, and peptide tyrosine tyrosine concentrations; and gastric emptying with a 13 C-sodium acetate breath test.ResultsNo signs of dumping were seen in PostOP. Compared with OC, LC showed lower fasting glucose, insulin, and C-peptide, and lower homeostasis model assessment (HOMA) and AUC-180 for insulin and C-peptide. In PostOP, fasting insulin, HOMA and AUC-180 for insulin was lower and no difference was found in fasting C-peptide or AUC-180 for C-peptide compared to OC. There was no significant difference in fasting glucose, insulin, C-peptide, HOMA and AUC-180 for insulin in PostOP compared to LC, but AUC-180 for C-peptide was higher in PostOP. AUC-60 for gut hormones was similar in OC and LC and higher in PostOP compared to OC or LC. gastric emptying was slower in LC and OC compared with PostOP.ConclusionAfter LRYGB, 25 g oral glucose is well tolerated and leads to reliable secretion of gut hormones. Fasting glucose, insulin and C-peptide are normalized, while glucagon-like peptide 1, glucose-dependent insulinotropic peptide and peptide tyrosine tyrosine are overcorrected. Pouch emptying is accelerated after LRYGB.