Gastric bypass surgery does not increase susceptibility to Helicobacter pylori infection in the stomach of rat or mouse

Probing the mechanisms of the metabolic effects of weight loss surgery in humans using a novel mouse model system

BACKGROUND

Gastrointestinal weight loss surgery, especially Roux-en-Y gastric bypass (RYGB), is the most effective treatment for severe obesity. RYGB is associated with a remarkable decrease in the rate of death from obesity-related complications, such as diabetes mellitus, coronary artery disease, and cancer. Dissecting the mechanisms of RYGB effects could augment our understanding about the pathogenesis of obesity and its complications.

OBJECTIVES AND METHODS

In this study, we describe in detail a mouse model of RYGB that closely reproduces the surgical steps of the human procedure.

RESULTS

We show that RYGB in mice has the same effects as in human patients, proving the high translational validity of this model system. We present an intraoperative video to facilitate the widespread use of this complex and difficult method.

CONCLUSIONS

The study of the mechanisms of RYGB using this model system can greatly facilitate our understanding about the effects of RYGB in human patients. The reverse engineering of the physiological mechanisms of RYGB could lead to discovery of new, effective, and less invasive treatments.

Metabolic surgery: an evolution through bariatric animal models

Metabolic surgery was developed through the application and experience gained from bariatric or weight loss procedures. Much of our knowledge from the procedures comes from the study of animal models, where they have revealed anatomic feasibility, systemic physiological elements and cellular metabolic effects. The first generation of operation included the jejunoileal bypass and partial ileal bypass that led to the development of the current procedures including Roux-en-Y gastric bypass, biliopancreatic diversion, adjustable gastric banding and sleeve gastrectomy. These operations carry significant metabolic benefits and can reduce the risk of diabetes, heart disease and cancer. Further insights from these animal models can reveal genetic, molecular and systemic effects that can enhance and develop the next generation of metabolic operations.

A mouse model for sleeve gastrectomy: applications for diabetes research

INTRODUCTION

Discovery of enhanced glucose tolerance following bariatric surgery has sparked renewed interest in the investigation of unchartered underlying pathways of glucose homeostasis. Delineation of this pathway may ultimately be the first step in the creation of a novel therapy for type II diabetes. Nevertheless, the technical complexity and formidable nature of these surgeries coupled with the fragile nature of small rodents has made the creation of a mouse model to study these effects incredibly challenging. We have created a simplified sleeve gastrectomy mouse model to study the effects of bariatric surgery on glucose tolerance and beta cell proliferation.

METHODS

Nineteen mice were randomized to undergo either sleeve gastrectomy (SG) (9) or sham operation (SH) (10). Weight and serum glucose were measured three times weekly and serum insulin measurements and pancreatic harvest were performed at the time of sacrifice. Five mice from each group were sacrificed after one week and the remainder sacrificed after one month.

RESULTS

Survival of mice was 100% for both groups. The SG group demonstrated an initial drop in weight and serum glucose as compared to SH, which normalized by one month following surgery. Serum insulin levels and rate of beta cell proliferation were similar in both groups after one week and one month.

CONCLUSION

The simplified sleeve gastrectomy is a technically straightforward, low-mortality technique for creating a bariatric mouse model which most faithfully replicates bariatric surgery performed in humans. This model can be a valuable tool to investigate the glucose tolerance and beta cell effects of bariatric surgery.

Can a short course of prophylactic low-dose proton pump inhibitor therapy prevent stomal ulceration after laparoscopic Roux-en-Y gastric bypass?

BACKGROUND

The purpose of this retrospective analysis was to determine if a short course of prophylactic proton pump inhibitor (PPI) therapy can prevent stomal ulceration after laparoscopic Roux-en-Y gastric bypass (LRYGBP).

METHODS

Four hundred forty-nine consecutive patients who underwent LRYGBP and had a minimum of 6 months follow-up were included. Patients were categorized in two groups: patients with Helicobacter pylori at preoperative endoscopy (HP group) and patients without H. pylori (non-HP group). All patients in the HP group were medically treated prior to surgery. In both groups, almost half of the patients received low-dose proton pump inhibitors (omeprazole 20 mg daily) for 1 month following LRYGBP.

RESULTS

The incidence of stomal ulceration in the HP group was not statistically different from the incidence in the non-HP group (7/86, 8.14% vs. 41/363, 11.29%; p = 0.559). When comparing the patients who did receive PPI therapy with the patients who did not receive PPI therapy within the non-HP group, there was no significant reduction in development of stomal ulceration (18/169, 10.65% vs. 23/194, 11.86%; p = 0.743). When comparing the patients who did receive PPI therapy with the patients who did not receive PPI therapy within the HP group, there is a significant reduction in development of stomal ulceration (0/41, 0% vs. 7/45, 15.56%; p = 0.0123).

CONCLUSION

Development of stomal ulceration in patients tested positive for H. pylori prior to LRYGBP can be prevented by prophylactic low-dose PPI therapy following surgery.

Prevalence of Helicobacter pylori infection and value of preoperative testing and treatment in patients undergoing laparoscopic Roux-en-Y gastric bypass

BACKGROUND

Previous studies have reported a high prevalence of Helicobacter pylori infection in patients undergoing Roux-en-Y gastric bypass (RYGB) and a greater incidence of anastomotic ulcer in patients positive for H. pylori, leading to recommendations for routine preoperative screening. Our hypotheses were that the prevalence of H. pylori in patients undergoing RYGB is similar to that of the general population and that preoperative H. pylori testing and treatment does not decrease the incidence of anastomotic ulcer or pouch gastritis.

METHODS

A retrospective analysis of H. pylori serology, preoperative and postoperative endoscopy findings, and the development of anastomotic ulcer or erosive pouch gastritis was performed. All patients positive for H. pylori received treatment. Univariate parametric and nonparametric statistical tests, as well as multiple logistic regression analyses, were performed.

RESULTS

A total of 422 LRYGB patients were included in the study. Of these patients, 259 (61.4%) were tested for H. pylori and 163 (38.6%) were not. Of the 259 patients, 58 (22.4%) tested positive for H. pylori, 197 (76.1%) tested negative, and 4 (1.5%) had an equivocal result. Postoperatively, 53 patients (12.6%) underwent upper endoscopy. Of these 53 patients, 19 (4.5%) had positive endoscopy findings for anastomotic ulcer (n = 16) or erosive pouch gastritis (n = 3). Five patients underwent biopsy at endoscopy; all biopsies were negative for H. pylori. No difference was found in the rate of positive endoscopy between patients tested preoperatively for H. pylori (5%) and patients not tested (3.7%).

CONCLUSION

The results of our study have shown that the prevalence of H. pylori infection in patients undergoing RYGB is similar to that of the general population. Our study has shown that H. pylori testing does not lower the risk of anastomotic ulcer or pouch gastritis.

Is a model useful in exploring the catabolic mechanisms of weight loss after gastric bypass in humans?

PURPOSE OF REVIEW

In the USA, approximately 3% of adults are morbidly obese, in whom behavior modification and drug therapy is ineffective in inducing major weight loss. Surgery is their only reliable option. The Roux-en-Y gastric bypass accounts for 90% of all bariatric surgeries because it achieves the best weight loss results. Many studies describe weight loss and changes in metabolic blood parameters after Roux-en-Y gastric bypass. We compare recent human data with the findings in our rats to validate the versatility of using a Roux-en-Y gastric bypass rat model to explore the multifactorial molecular and physiological dimensions of weight loss and weight regain.

RECENT FINDINGS

Not only mechanical factors but also changes in gastrointestinal and adipose hormones and hypothalamic neuropeptides contribute to Roux-en-Y gastric bypass induced weight loss by promoting catabolic processes. Nevertheless, the exact mechanisms of weight loss remain unknown.

SUMMARY

To investigate these catabolic mechanisms we used our Roux-en-Y gastric bypass rat model in diet induced obese rats. We found clear morphometric, physiological and biochemical parallelisms between humans and our rats. It is likely that Roux-en-Y gastric bypass induces similar changes in hypothalamic neuropeptides which can only be studied using the rat model. It therefore provides a useful research tool for exploring and studying the development of adjuvant antiobesity therapies.

Ulcer disease after gastric bypass surgery

BACKGROUND

The mechanism of marginal ulceration after laparoscopic gastric bypass surgery is poorly understood. We reviewed the incidence, presentation, and outcome of ulcer disease in consecutive patients undergoing laparoscopic gastric bypass surgery.

METHODS

The outcomes of 201 consecutive laparoscopic gastric bypass surgery procedures were prospectively analyzed for complications. All procedures were performed using a linear stapled anastomosis and absorbable suture.

RESULTS

The incidence of marginal ulcer disease was 3.5% (7 patients). One patient, the only smoker, presented with an acute perforation 4 months postoperatively. Three other patients presented with bleeding-all required transfusion. The remaining 3 patients presented with severe pain. At endoscopy, all patients had ulcerations associated with the Roux limb mucosa and were all successfully treated using proton pump inhibitors and sucralfate therapy. Symptoms of marginal ulceration occurred an average of 7.4 months (range 3-14) after surgery. The average follow-up was 19.8 months. No preoperative factors were predictors of ulcer disease, including body mass index, age, gender, or co-morbidities.

CONCLUSION

Marginal ulcers using the linear-stapled technique occurred in 3.5% of patients. Three distinct clinical presentations occurred: bleeding, pain, or perforation. No preoperative risk factors were identified that predicted for this complication. Medical management is an effective treatment.