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Method Article

Roux-en-Y Gastric Bypass Operation in Rats

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DOI:

10.3791/3940

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June 11th, 2012

 ,  ,  ,  , 
1Department of Surgery, University Hospital Zürich, 2Zürich Centre for Integrative Human Physiology, University of Zürich, 3Institute of Veterinary Physiology, Vetsuisse Faculty, University of Zürich, 4Imperial Weight Centre, Department of Investigative Medicine, Imperial College London

In This Article

Summary

Numerous studies using gastric bypass rat models have been recently conducted to uncover the underlying physiological mechanisms of Roux-en-Y gastric bypass operations. This article aims to demonstrate and discuss the technical and experimental details of our published gastric bypass rat model to understand advantages and limitations of this experimental tool.

Abstract

Currently, the most effective therapy for the treatment of morbid obesity to induce significant and maintained body weight loss with a proven mortality benefit is bariatric surgery1,2. Consequently, there has been a steady rise in the number of bariatric operations done worldwide in recent years with the Roux-en-Y gastric bypass (gastric bypass) being the most commonly performed operation3. Against this background, it is important to understand the physiological mechanisms by which gastric bypass induces and maintains body weight loss. These mechanisms are yet not fully understood, but may include reduced hunger and increased satiation4,5, increased energy expenditure6,7, altered preference for food high in fat and sugar8,9, altered salt and water handling of the kidney10 as well as alterations in gut microbiota11. Such changes seen after gastric bypass may at least partly stem from how the surgery alters the hormonal milieu because gastric bypass increases the postprandial release of peptide-YY (PYY) and glucagon-like-peptide-1 (GLP-1), hormones that are released by the gut in the presence of nutrients and that reduce eating12.

During the last two decades numerous studies using rats have been carried out to further investigate physiological changes after gastric bypass. The gastric bypass rat model has proven to be a valuable experimental tool not least as it closely mimics the time profile and magnitude of human weight loss, but also allows researchers to control and manipulate critical anatomic and physiologic factors including the use of appropriate controls. Consequently, there is a wide array of rat gastric bypass models available in the literature reviewed elsewhere in more detail 13-15. The description of the exact surgical technique of these models varies widely and differs e.g. in terms of pouch size, limb lengths, and the preservation of the vagal nerve. If reported, mortality rates seem to range from 0 to 35%15. Furthermore, surgery has been carried out almost exclusively in male rats of different strains and ages. Pre- and postoperative diets also varied significantly.

Technical and experimental variations in published gastric bypass rat models complicate the comparison and identification of potential physiological mechanisms involved in gastric bypass. There is no clear evidence that any of these models is superior, but there is an emerging need for standardization of the procedure to achieve consistent and comparable data. This article therefore aims to summarize and discuss technical and experimental details of our previously validated and published gastric bypass rat model.

Protocol

1. Preoperative Care

  1. Remove food from rat overnight prior to surgery.
  2. Induce anaesthesia in chamber with 4-5% isoflurane and O2 flow of 2 l/min.
  3. Shave abdomen from sternum to pelvis using electric razor.
  4. Place anaesthetised rat in supine position on isothermal heating pad.
  5. Apply eye ointment (Vitagel) before placing the rats' snout in nosecone.
  6. Maintain anaesthesia with isoflurane concentration of 2-3% and O2 flow of 2 l/min.
  7. Disinfect skin with Betadine-Solution.
  8. Confirm depth of anaesthesia with forceps pinch between toes of hind leg.
  9. Administer 5.7 mg/kg Enrofloxacin intraperitoneally as perioperative antibiotic prophylaxis, and 1 mg/kg Flunixin for analgesia.

2. Median Laparotomy

  1. Perform midline incision using scalpel starting just below xyphoid process (Blade No. 10).
  2. Mobilise skin circumferentially from underlying abdominal muscles using Metzenbaum scissors.
  3. Open abdominal cavity.
  4. Install retractors to facilitate best possible exposure of the operation field.

3. Biliopancreatic and Alimentary Limb

  1. Identify where the duodenum or proximal jejunum passes under the colon.
  2. Transect small bowel about 10 cm aborally from here and ligate both ends of the gut (PDS 5-0).
  3. Place proximal stump of the two ends in left upper quadrant of abdomen as it will be later used to form the biliopancreatic limb of Roux-en-Y reconstruction.
  4. Place distal stump of the two ends in right upper quadrant of abdomen as it will be later used to form the alimentary limb of Roux-en-Y reconstruction.

4. Jejuno-Jejunostomy

  1. Identify caecum with ileocoecal valve and ileum.
  2. Follow ileum orally for approximately 25 cm. The Jejuno-Jejunostomy will be placed here as starting point of the common channel of Roux-en-Y reconstruction.
  3. Retrieve biliopancreatic limb from left upper quadrant of abdomen and position it next to common channel where you plan to perform Jejuno-Jejunostomy.
  4. Secure biliopancreatic limb and common channel with retention stitch (PDS 6-0).
  5. Incise both loops over approximate 10 mm by using micro scissors.
  6. Create Jejuno-Jejunostomy by performing side-to-side anastomosis using interrupted sutures (PDS 6-0).
  7. First complete dorsal side and then ventral side of anastomosis.

5. Gastric Pouch

  1. Identify gastro-oesophageal junction.
  2. Mobilise this area by dissecting gastro-hepatic and gastro-splenic ligaments using Metzenbaum scissors.
  3. Move left gastric artery and vagal fibres of left para-oesophageal bundle laterally to prevent major bleedings and vagal nerve damage when small gastric pouch is created.
  4. Expose gastro-oesophageal junction by placing cotton swab retro-oesophageally.
  5. Coagulate small vessels of frontal stomach by using commercially available cautery device - also to prevent bleedings.
  6. Transect stomach approximately 5 mm below gastro-oesophageal junction creating gastric pouch of a size of no more than 2-3% of original stomach size using delicate, curved scissors.
  7. Close gastric remnant (PDS 5-0).

6. Gastro-Jejunostomy

  1. Retrieve alimentary limb from right upper quadrant of abdomen and position it next to gastric pouch.
  2. Create Gastro-Jejunostomy by performing end-to-side anastomosis (PDS 7-0).
  3. First complete back side and then front side of anastomosis.

7. Abdominal Closure

  1. Reduce anaesthesia by reducing isoflurane concentration to 1.5%.
  2. Close muscle layer of abdominal wall using continuous sutures (PDS 4-0).
  3. Administer 100 μl of 0.3 mg/ml buprenorphine solution subcutaneously for analgesia.
  4. Further reduce isoflurane concentration down to 1%.
  5. Close the skin using interrupted sutures (Vicryl 4-0).

8. Postoperative Care

  1. Stop isoflurane and continue with O2.
  2. Administer 5 ml of warm saline for fluid replacement in three subcutaneous depots.
  3. Position rat under red light until full recovery.
  4. Return the rat to home cage.

9. Representative Results

Animals and housing

Male Wistar rats (Harlan Laboratories Inc., Blackthorn, UK; Elevage Janvier, Le-Genest-St. Isle, France) weighing between 350 and 500 g were individually housed under a 12 h /12 h light-dark cycle at a room temperature of 21±2 °C. Water and standard chow were available ad libitum, unless otherwise stated. All experiments were performed under a license issued by the Home Office, UK (PL70-6669) or approved by the Veterinary Office of the Canton Zurich, Switzerland. All rats were given one week of acclimatization before being randomized to gastric bypass or sham-operation. After surgery, rats received liquid diet for 3 days before access to normal chow was reinstalled.

Body weight

Data of our rat gastric bypass model are consistent with previous findings that gastric bypass surgery is effective to reduce body weight and especially to maintain body weight loss (Figure 2). Average pre-surgical body weight of rats used for gastric bypass and sham-operations was similar (sham: 433.4 ± 8.3 g vs. bypass: 420.7 ± 8.4 g, p= 0.28). Five days after surgery sham-operated controls weighed significantly more compared to gastric bypass rats (sham: 422.2 ± 8.3 g vs. bypass: 374.7 ± 7.6 g, p<0.001). On postoperative day 60, difference in body weight was almost 170 g (sham: 533.2 ± 8.1 g vs. bypass: 366.2 ± 10.8 g, p<0.001).

Food intake

Food intake followed similar patterns as body weight and was reduced in gastric bypass rats when compared to sham-operated ad libitum fed rats. Figure 3 shows the average daily food intake for both groups (postoperative day 1-60). Daily food intake was consistently lower after gastric bypass (sham: 29.9 ± 0.2 g vs. bypass: 25.7 ± 0.3 g, p<0.001).

Gut hormones

Blood from all rats was collected on the day of study termination 8,16. Animals had ad libitum food access the night before and were decapitated at the beginning of the light cycle on postoperative day 60. Blood was obtained, immediately centrifuged at 3000 rpm for 10 minutes at 4°C, and stored at -20°C until the samples were assayed in duplicate in a single run. PYY-like immunoreactivity was measured with a specific and sensitive radioimmunoassay, which measures, both the full length (PYY1-36) and the fragment (PYY3-36). GLP-1 was measured by established in-house radioimmunoassays17,18. Differences in food intake may be partly explained by increased postprandial plasma levels of peptide YY (PYY) and glucagon-like peptide 1 (GLP-1) as gastric bypass rats showed significantly higher levels for PYY (sham: 26 ± 2 pmol/L vs. bypass: 141 ± 14 pmol/L, p<0.001) and GLP-1 (sham: 40 ± 5 pmol/L vs. bypass: 215 ± 23 pmol/L, p<0.001; Figure 4).

Digestive system anatomy and Roux-en-Y gastric bypass surgery diagram with labeled sections.
Figure 1. Gastric bypass anatomy. Schematic illustration of the small bowel anatomy before (A) and after (B) gastric bypass operation. The different shades of red approximately represent corresponding segments of the small bowel with the medium red representing the foregut (oesophagus, stomach duodenum and proximal jejunum), the light red representing the midgut (proximal and mid jejunum, proximal ileum) and the dark red representing the hindgut (ileum, caecum).

Body weight change graph; gastric bypass vs sham-operated rats over 60 days post-surgery.
Figure 2. Body weight loss after gastric bypass surgery in rats. Body weight change for a representative group of rats after gastric bypass (- -) (n=52) and sham-operated rats (- -) (n=52) throughout an observation period of 60 days. Data were pooled from previous publications6,8-10 and are shown as mean values ± SEM (*** = p<0.001).

Bar chart comparing average daily food intake in rats post-surgery; significant dietary reduction.
Figure 3. Average food intake after gastric bypass surgery in rats. Average daily food intake of a representative group of rats after gastric bypass (black, n=52) and sham-operated rats (white, n=52) throughout a postoperative period of 60 days. Data were pooled from previous publications6,8-10 and are shown as mean values ± SEM.

Bar chart comparing average daily food intake in rats post-surgery; significant dietary reduction.
Figure 4. Postprandial PYY and GLP-1 serum levels after gastric bypass surgery in rats. Postprandial PYY and GLP-1 serum level for gastric bypass rats (black, n=18) and sham-operated rats (white, n=22). Data were pooled from previous publications8,16 and are shown as mean values ± SEM.

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Discussion

The Roux-en-Y gastric bypass procedure in humans was first described by Mason in 1967 and modified to its current form by Torres in 198319. Currently, the procedure consists of a small gastric pouch and the bypass of the proximal small bowel. A schematic illustration of the pre- and postoperative anatomy is given in Figure 1.

Gastric bypass in humans induces and maintains body weight loss of approximately 15-30%2. The majority of body weight is lost durin...

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Disclosures

No conflicts of interest declared.

Acknowledgements

Marco Bueter and Florian Seyfried were supported by the Deutsche Forschungsgemeinschaft (DFG). Thomas A Lutz was supported by the Swiss National Research Foundation (SNF). Marco Bueter and Thomas A Lutz further receive funding from the National Institute of Health (NIH) and from the Zurich Center for Integrative Human Physiology (ZIHP). Carel W le Roux was supported by a Department of Health Clinician scientist award. Imperial College London receives support from the NIHR Biomedical Research Centre funding scheme.

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Materials

List of materials used in this article
NameCompanyCatalog NumberComments
EnrofloxacinBaytril 2.5%Provet AG1036
FlunixinFinadyneGraeub908040
BuprenorphinTemgesicReckitt Benckiser138976
IsofluraneIsoFloGraeub902035
Vitamin AVitagelBausch & Lomb690
Iodine solutionBetadine Puredue PharmaMundipharma111141
NaCl 0.9%NaCl 0.9%B. Braun534534
Table 1. Drugs.
PDS II4-0EthiconZ924H
PDS II5-0EthiconZ925H
PDS II6-0EthiconPUU2971E
PDS II7-0EthiconZ1370E
Vicryl4-0EthiconV451H
Table 2. Sutures.
Scalpel handle No. 3AesculapBB073R
Scalpel blades No. 10Swann-Morton0301
Needle holderAesculapBM124R
Tissue forcepsAesculapBD555R
Metzenbaum scissors, straightAesculapBC022R
Metzenbaum scissors, curvedAesculapBC023R
Delicate scissors, curvedAesculapBC061R
Artery forceps, curvedAesculapBH109R
Artery forceps, curved, 1x2 teethAesculapBH121R
Probe, double-endedAesculapBN113R
Micro needle holderAesculapFM 541R
Micro forcepsAesculapFM571R
Micro scissorsAesculapFM470R
Disposable eye cauteryJohn Weiss International0111122
Cotton budsHartmann AG9679369
Table 3. Surgical equipment.

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Gastric Bypass Rat ModelGastric Pouch CreationBilio pancreatic LimbElementary LimbSide to side AnastomosisPeptide YY ReleaseGLP 1 SecretionFood Intake ReductionBody Weight Loss
Roux-en-Y Gastric Bypass Operation in Rats
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