Role of the foregut in the early improvement in glucose tolerance and insulin sensitivity following Roux-en-Y gastric bypass surgery.

Hansen EN, Tamboli RA, Isbell JM, Saliba J, Dunn JP, Marks-Shulman PA, Abumrad NN
Am J Physiol Gastrointest Liver Physiol. 2011 300 (5): G795-802

PMID: 21372167 · PMCID: PMC3094142 · DOI:10.1152/ajpgi.00019.2011

Bypass of the foregut following Roux-en-Y gastric bypass (RYGB) surgery results in altered nutrient absorption, which is proposed to underlie the improvement in glucose tolerance and insulin sensitivity. We conducted a prospective crossover study in which a mixed meal was delivered orally before RYGB (gastric) and both orally (jejunal) and by gastrostomy tube (gastric) postoperatively (1 and 6 wk) in nine subjects. Glucose, insulin, and incretin responses were measured, and whole-body insulin sensitivity was estimated with the insulin sensitivity index composite. RYGB resulted in an improved glucose, insulin, and glucagon-like peptide-1 (GLP-1) area under the curve (AUC) in the first 6 wk postoperatively (all P ≤ 0.018); there was no effect of delivery route (all P ≥ 0.632) or route × time interaction (all P ≥ 0.084). The glucose-dependent insulinotropic polypeptide (GIP) AUC was unchanged after RYGB (P = 0.819); however, GIP levels peaked earlier after RYGB with jejunal delivery. The ratio of insulin AUC to GLP-1 and GIP AUC decreased after surgery (P =.001 and 0.061, respectively) without an effect of delivery route over time (both P ≥ 0.646). Insulin sensitivity improved post-RYGB (P = 0.001) with no difference between the gastric and jejunal delivery of the mixed meal over time (P = 0.819). These data suggest that exclusion of nutrients from the foregut with RYGB does not improve glucose tolerance or insulin sensitivity. However, changes in the foregut response post-RYGB due to lack of nutrient exposure cannot be excluded. Our findings suggest that foregut bypass may alter the incretin response by enhanced nutrient delivery to the hindgut.

MeSH Terms (22)

Adult Anastomosis, Roux-en-Y Area Under Curve Blood Glucose Body Weight Diabetes Mellitus, Type 2 Duodenum Female Food Gastric Bypass Ghrelin Glucagon-Like Peptide 1 Glucose Tolerance Test Humans Incretins Insulin Insulin Resistance Jejunum Laparoscopy Male Metabolism Middle Aged

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