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

BACKGROUND: After 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.

OBJECTIVE: The objective of this study was to determine the effects of low oral glucose loads on incretin release and gastric emptying.

SETTING: All 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).

METHODS: Eight 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.

RESULTS: No 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.

CONCLUSION: After 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.