Roux-en-Y Gastric Bypass Operation in Rats

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 surgery^1,2. 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 satiation^4,5, increased energy expenditure^6,7, altered preference for food high in fat and sugar^8,9, 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 intrape....

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.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Enrofloxacin	Baytril 2.5%	Provet AG	1036
Flunixin	Finadyne	Graeub	908040
Buprenorphin	Temgesic	Reckitt Benckiser	138976
Isoflurane	IsoFlo	Graeub	902035
Vitamin A	Vitagel	Bausch & Lomb	690
Iodine solution	Betadine Puredue Pharma	Mundipharma	111141
NaCl 0.9%	NaCl 0.9%	B. Braun	534534
Table 1. Drugs.
PDS II	4-0	Ethicon	Z924H
PDS II	5-0	Ethicon	Z925H
PDS II	6-0	Ethicon	PUU2971E
PDS II	7-0	Ethicon	Z1370E
Vicryl	4-0	Ethicon	V451H
Table 2. Sutures.
Scalpel handle No. 3	Aesculap	BB073R
Scalpel blades No. 10	Swann-Morton	0301
Needle holder	Aesculap	BM124R
Tissue forceps	Aesculap	BD555R
Metzenbaum scissors, straight	Aesculap	BC022R
Metzenbaum scissors, curved	Aesculap	BC023R
Delicate scissors, curved	Aesculap	BC061R
Artery forceps, curved	Aesculap	BH109R
Artery forceps, curved, 1x2 teeth	Aesculap	BH121R
Probe, double-ended	Aesculap	BN113R
Micro needle holder	Aesculap	FM 541R
Micro forceps	Aesculap	FM571R
Micro scissors	Aesculap	FM470R
Disposable eye cautery	John Weiss International	0111122
Cotton buds	Hartmann AG	9679369
Table 3. Surgical equipment.