Changes in GI hormones and their effect on gastric emptying and transit times after Roux-en-Y gastric bypass in rat model

Background. We determined whether Roux-en-Y gastric bypass (RYGB)-induced protracted weight loss is associated with an increase in anorectic peptide YY (PYY) and decreased gastrointestinal (GI),motility. Methods. RYGB and control sham-operated GI intact obese (SO Obese) and sham-operated GI intact pair-fed (PF) rats were studied. Postoperatively, body weight (BW) and food intake were measured for 90 days. Rats were killed to measure PYY, ghrelin, cholecystokinin (CCK), and glucagonlike peptide-1 (GLP-1). Ninety-day food intake trends were examined by quadratic trend analysis. On the basis of a 28-day weight loss rate, PYY also was measured at 14 and 28 days. Peak 28-day PYY results corresponded with peak BW loss rate; thus, gastric emptying (GE) and intestinal transit time were measured. Data were analyzed by analysis of variance and Tukey's pairwise multiple comparison. Results. At 90 days, BW in SO Obese versus PF versus RYGB rats was 801 +/- 15 g versus 661 +/- 24 g versus 538 +/- 32 g respectively (P < .05). Concentrations of plasma PYY were increased, while plasma ghrelin was decreased in RYGB versus SO Obese and PF (P < .05). CCK and GLP-1 were unchanged. In RYGB versus controls, PYY was increased at 14 and 28 days but was most elevated at 28 days. In RYGB versus controls, GE was delayed (P < .05) and intestinal transit time was longer (P < .05). Conclusions. After RYGB, an increase in PYY and a decrease in ghrelin occurred, probably explaining the decrease in food intake, the slower GE and transit time, which contributed to weight loss. Longitudinal studies can be performed with the use of our RYGB model, providing insight into weight loss mechanisms by generating long-term follow-up data currently not available in human studies.