Elsevier

Surgery

Volume 138, Issue 2, August 2005, Pages 283-290
Surgery

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

https://doi.org/10.1016/j.surg.2005.05.013Get rights and content

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.

Section snippets

Methods

Approval for the experiments was obtained from the Committee for the Humane Use of Animals at SUNY Upstate Medical University. Animal care was in accordance with guidelines established by the National Institutes of Health.

Body weight

Figure 2 shows the changes in BW at day 0 (before the operation) and at postoperative days 14, 28, and 90. The 3 groups had no difference in BW before the operation. During the first 7 postoperative days, all groups lost weight because of postoperative stress and an inadequate oral liquid intake. The rate of weight loss in the SO Obese was −8.2 ± 1.4 g per day, while the rate of BW loss in RYGB and PF was −14.3 ± 2.3 g per day and −11.6 ± 1.5 g per day, respectively. On day 7, chow was given

Discussion

The endocrine L cells secrete PYY in response to intraluminal nutrients. These cells are found in progressively higher gradient concentrations from the duodenum and jejunum, where PYY is released at relatively lower concentrations, to the terminal ileum and the colon, where PYY is secreted in high concentrations.25 PYY's biological function includes inhibiting food intake, decreasing GE, and slowing GI motility.18, 26 Ninety days after the operation, the SO Obese rats weighed more than before

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    Presented at the 66th Annual Meeting of the Society of University Surgeons, Nashville, Tennessee, February 9-12, 2005.

    Supported in part by grants from the Hendrick's Fund, American Society for Bariatric Surgery and American Diabetes Association. C.G.G. is supported, in part, by a postdoctoral grant from SUNY Upstate Medical University Hendrick's Fund #130230-52. Material support was provided via generous grants from Ethicon (Cincinnati, Ohio) and Boost-Plus from Mead Johnson (Evansville, Ind).

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