Duodenal-jejunal bypass (DJB) surgery can improve glucose metabolism and reduce insulin resistance. Here, we present a protocol to establish a stable and reliable mouse model of DJB.
The prevalence of obesity and type 2 diabetes is a serious global health concern. Obesity is a major pathogenic factor in type 2 diabetes, cardiovascular disease, and some cancers. Bariatric surgery offers a long-term and effective treatment option for both obesity and diabetes. Sleeve gastrectomy (SG) and Roux-en-Y gastric bypass (RYGB) are widely recognized as the most popular bariatric surgeries. Additionally, several exploratory bariatric surgeries have demonstrated promising therapeutic effects. Duodenal-jejunal bypass (DJB), specifically tailored for diabetics with low body mass index, has shown beneficial metabolic outcomes. However, its weight-independent metabolic benefits are not fully understood due to limited animal models. In this article, we describe the optimized care protocols and surgical techniques for performing DJB surgery in diet-induced obese (DIO) diabetic mice. Using a mouse model contributes to a better understanding of the nature of changes induced by DJB surgery while facilitating related clinical practice.
Obesity and type 2 diabetes are the most common chronic diseases in the world, and their prevalence is increasing among young individuals1. Bariatric surgery is the most effective treatment for obesity and diabetes, facilitating long-term blood glucose stabilitywhile also improving the complications associated with obesity2,3. There are several types of bariatric surgery, classified by whether they reduce gastric volume or intestinal absorption; these include restrictive, malabsorptive, and combination4,5.
Duodenal-jejunal bypass (DJB) was first developed by Rubino and Marescaux, who demonstrated that type 2 diabetes could be alleviated by connecting the duodenum and jejunum rather than by reducing the gastric volume6,7. DJB preserves the entire stomach and bypasses the entire duodenum and proximal jejunum. The bowel is divided into biliopancreatic, digestive, and common limbs6,8. DJB shares some similarities with bariatric surgeries, including Roux-en-Y gastric bypass (RYGB), mini-gastric bypass, biliopancreatic bypass, duodenal diversion, and DJB plus sleeve gastrectomy9. Compared to RYGB, DJB does not require a gastrointestinal anastomosis, which reduces the operative time and improves the success rate of the procedure. DJB is similar to RYGB in improving glucose metabolism but does not affect body weight10. After DJB surgery, rapid food delivery to the distal small intestine stimulates the secretion of glucagon-like peptide-1 (GLP-1), resulting in improved glucose metabolism11,12.
The use of animal models is essential for understanding the metabolic, cellular, and molecular pathways. Animal models of bariatric surgery have contributed to our understanding of potential mechanisms underlying obesity and diabetes13,14. However, due to the physiological differences between species, it is impossible to perfectly replicate human diseases in animal models15. Among various animal models available for research purposes, the diet-induced obesity (DIO) mouse model most closely resembles human obesity and metabolic syndrome16. Mice were selected for DJB surgery to determine the feasibility of the surgery and to provide techniques for further research. This manuscript provides a comprehensive summary of both technical aspects and experimental details of DJB surgery.
All protocol steps described below follow the guidelines of the Animal Care and Use Committee of the General Hospital of the Southern Theater Command under the approval number 2020112501.
1. General preoperative preparation
NOTE: Thirty 6-week-old male C57BL/6 mice were purchased. Mice were housed in a Specific Pathogen-Free (SPF) laboratory under a 12 h light/dark cycle; temperature, 22 ± 2 °C; and humidity, 55-65%. Mice were given free access to water and fed a 60% kcal fat diet for 6 weeks to induce obesity. An intraperitoneal injection of 40 mg/kg streptozotocin was administered for 5 days to induce diabetes17. Among the thirty mice, twenty-two mice were screened for random blood glucose > 300 mg/dL and randomly assigned to the DJB (n=15) and sham surgery (n=7) groups. Eight mice were excluded from the experiment due to substandard blood glucose.
2. Duodenal jejunal bypass: Surgical Procedure
Figure 1: Duodenal-jejunal bypass procedure. (A) Location of the jejunum 5 cm distal to the ligament of Treitz. (B) Double ligate the jejunum with 6-0 silk, cut through the middle of the ligature. (C) Jejunal-jejunal anastomosis. (D) Make a 0.5-0.6 cm incision, and suture the posterior wall. (E-F) Complete Jejunal-jejunal anastomosis. (G) Pull the distal jejunal to the duodenum 1 cm below the pylorus. (H) Duodenal-jejunal anastomosis. (I) Cut the duodenal-jejunal anastomosis with a 0.5-0.6 cm incision and suture the posterior wall with a simple continuous suture. (J-K) Complete duodenal-jejunal anastomosis. (L) At 2 mm from the distal to the duodenal-jejunal anastomosis, double ligate the duodenum with 6-0 silk and cut through the middle of the ligature. Please click here to view a larger version of this figure.
3. General postoperative care
Figure 2: The diagram of DJB surgery. (A) Duodenal-jejunal anastomosis. (B) Jejunal-jejunal anastomosis. (C) Biliopancreatic limb. (D) Digestive limb. (E) Common limb. Please click here to view a larger version of this figure.
Figure 3: Anatomy of DJB surgery. (A) Duodenal-jejunal anastomosis. (B) Jejunal-jejunal anastomosis. (C) Biliopancreatic limb. (D) Digestive limb. (E) Common limb. Please click here to view a larger version of this figure.
4. Postoperative evaluation of metabolic parameters
General conditions
The mean operative time for the DJB procedure was 84.5 ± 2.6 min. Fifteen mice underwent DJB surgery, nine mice survived. As shown in Table 1, the majority of deaths occurred during surgery or in the following 7 days. The causes of postoperative death were bleeding (n=2) on postoperative day 1, anastomotic leakage (n=1) on postoperative day 4, anastomotic obstruction (n=2) on postoperative day 7, and unknown cause (n=1) three weeks after surgery.
For 8 weeks prior to this experiment, we performed DJB surgery on 10 mice weekly as a pre-experiment to simplify the operation. As shown in Figure 4, we obtained a trend of the weekly survival rate of the mice during the pre-experiment. We observed a progressive improvement in the survival rate, indicating that intensive surgical training is required to master the DJB technique.
Figure 4: The survival rate of mice seven days after the DJB Surgery. The data show the benefit of the pre-experiment on the survival rate of DJB mice. The data are shown as the survival rate 7 days post-surgery (%). Please click here to view a larger version of this figure.
Body weight, food intake, and glucose homeostasis
The mice had similar body weights and food intakes before surgery and 8 weeks after surgery. DJB mice showed no significant weight loss compared to the sham control mice at 8 weeks after surgery (P > 0.05; Figure 5A). Daily food intake was reduced after the 7 days following DJB and sham control surgery and returned to preoperative levels 3 weeks later (P > 0.05; Figure 5B). We have observed improvements in fasting blood glucose levels and glucose tolerance after DJB surgery (P < 0.01; Figure 5C, 5D).
Figure 5: Effect of DJB on body weight, daily food intake, random blood glucose, and oral glucose tolerance test. The data are shown as the mean ± SD, n=6. ns: not significant; ** p <0.01 (Mann-Whitney and ANOVA tests). Please click here to view a larger version of this figure.
In 1953, Varco et al.18 performed the first jejuno-ileal bypass as the beginning of bariatric surgery. Since then, numerous bariatric surgeries have been performed by surgeons. These surgeries have resulted in weight loss and improved metabolic complications4,19,20. Furthermore, in 1967, Mason and Ito21 performed the first Roux-en-Y gastric bypass (RYGB), which can effectively reduce weight and improve metabolic syndrome. Similar to RYGB, DJB is a stomach-preserving deformation of RYGB that divides the small intestine into the biliopancreatic, digestive, and common limbs. DJB surgery provides significantly durable glycemic control without relying on reduced food intake or weight loss22,23. Therefore, DJB has been recommended as a suitable bariatric surgery for type 2 diabetics with low body mass index24.
The development of bariatric surgery is inseparable from the study of animal models, and most researchers have performed DJB in rats25,26. To date, few studies have used a mouse model to study DJB despite its suitability for studying changes in metabolic indicators after intestinal reconstruction27. The paucity of such studies is due to the fact that surgical models of DJB cannot fully replicate human procedures, making it difficult to compare results between different research groups28. Liang et al.29 initially demonstrated the significant therapeutic effect of DJB surgery on obesity and T2DM in db/db mice. The duodenum was double ligated with 5-0 suture, transected 2 mm distal to the pylorus, cut 4-5 cm below the ligament of Treitz, and the distal jejunum was sutured to the pylorus with a single interrupted end-to-end suture of 9-0 silk thread. The opening of the biliopancreatic limb was sutured with 9-0 silk ~4 cm distal to the jejunal anastomosis. Barataud et al. have also successfully established a mouse model of DJB using db/db mice30. Therefore, in our study, the small bowel was transected 5 cm below the ligament of Treitz. A jejunojejunostomy was performed on the distal 5 cm of the small bowel. The distal jejunum and duodenum were then sutured.
As shown in Table 1, the mice were divided into DJB (n=15) and sham surgery (n=7), nine mice survived in the DJB group, with a survival rate of 60.0%. We have also shown the dead cases and percentage of postoperative deaths in each group. As shown in Table 2, to increase the success rate of this technique, we have continuously improved each step. Intestinal anastomotic bleeding is the most common type of postoperative bleeding, and this complication is the leading cause of death. Therefore, the operation must be performed carefully. An intestinal incision was made at the anti-intestinal mesenteric border to keep away from the blood vessels. In our study, the anastomotic leakage was duodenojejunal anastomosis, which may be due to excessive tension in the anastomosis. Anastomotic leakage has been observed in the duodenal intestinal stump. Therefore, the corners of the anastomosis should be carefully checked during surgery, and if the suture is inadequate, the suture can be used for reinforcement. The suture distance should not be excessively long to reduce anastomotic leakage. Anastomotic obstruction was observed in the jejunal-jejunal anastomosis. Due to the unique physiological structure of the intestine in mice, the small bowel was easily twisted. The anastomotic stoma was shorter than expected when the sutures were pulled tight. During the operation, the mesentery should be adequately dissected, and the bowel should be smoothed out as much as possible to provide enough space for the placement. We should also take care of the suture tightness and the size of the anastomosis.
The main limitation of this DJB technique is that it is performed in mice. The use of microscopic equipment is becoming increasingly important in the establishment of DJB mouse models, as it provides a clear surgical field of view31,32,33. After extensive preliminary experiments, we were familiar with the anatomical structures involved in the surgical procedure and were able to skillfully perform microsurgical manipulations with improved suture precision, reduced surgical injury, and significantly shortened surgical time, thereby enabling DJB surgery in mice. However, the skilled operation of microscopic instruments is a gradual process. We analyzed the causes of death in mice in order to improve the surgical procedure, including shortening the surgical and postoperative recovery times, strengthening the postoperative feeding management, and improving the overall survival rate of the mice.
In conclusion, the application of this surgery in mice allows for a better understanding of the mechanisms underlying the powerful metabolic effects of this procedure. We believe that our study provides a solid foundation for further improving the application of DJB in the treatment of diabetes.
The authors have nothing to disclose.
This study was supported by a grant from the Science and Technology Planning Project of Guangdong Province of China (No. 202002020069).
Abdominal retractor | F.S.T | 17000-03 | Colibri Retractor -3cm,retractor range 1.5cm/3cm long |
1% sodium pentobarbital solution | Guangzhou Chemical Reagent Factory | / | Dissolved 500mg of pentobarbital sodium powder in 50ml of normal saline to obtain 1% pentobarbital sodium solution. |
Benzylpenicillin sodium for Injection | North China Pharmaceutical Company Ltd. | F2062121 | Penicillin |
Buprenorphine | Guangzhou Chemical Reagent Factory | / | Analgesia |
Buprenorphine | Guangzhou Otsuka Pharmaceutical Co., Ltd | / | Analgesic |
Citric acid-sodium citrate buffer | LEAGENE | R00522 | Buffer solution |
Cotton buds | HaoZheng Medical | 60220610 | Cotton swabs |
Depilatory paste | Veet | AAPR-S222 | Hair removal cream |
Ear tag | ZEYA | SUS304 | Ear-mark |
Electric blanket | ZOSEN | ZS-CWDRT | Heat pad |
Electronic scale | WETTLER TOLEDO | 20060902-6 | Measure the weight |
Enteral nutritional powder | Abbott Laboratories | / | Nutrition powder |
Eye ointment | Guangzhou Otsuka Pharmaceutical Co., Ltd | / | Protect the eyes |
Glucometer | Roche | 6993788001 | Assess blood glucose |
Graphpad Prism version 9.4.1 | GraphPad Software | version 9.4.1 | Software for statistical analysis |
High-fat diet (High Fat [60FDC] Purified Rodent Diet) | Dyets | 112252 | 60kcal% High Fat Diet |
Micro Forceps | Jinzhong Medical | 18-1140 | Micro forceps |
Micro needle holder | Jinzhong Medical | EMT-160-Z | Needle holder |
Micro Scissors | Jinzhong Medical | YBC010 | Micro scissors |
Microscope camera | LAPSUN | E 2000 | Video |
Ophthalmic scissors | Jinzhong Medical | Y00030 | Surgical scissors |
Pentobarbital | Guangzhou Chemical Reagent Factory | / | Narcosis |
Sodium chloride Injection | Guangzhou Otsuka Pharmaceutical Co., Ltd | B21L0301 | NaCl 0.9% |
Stereo microscope | ZEISS | Stemi 305 | Binocular stereomicroscope |
Streptozotocin | Sigma | S110910-1g | STZ |
Suture line | LINGQIAO SUTURE | ZS-LQPMRZ5/0 | Prolene 6/0,Prolene 10/0 |
Tissue forceps | Jinzhong Medical | H1701 | Surgical forceps |