Metabolic and histopathological effects of sleeve gastrectomy and gastric plication: an experimental rodent model

Gastrin: a new branch of the gastropancreatic axis that can explain the effect of sleeve gastrectomy on glucose metabolism

BACKGROUND

Among bariatric techniques, sleeve gastrectomy (SG) stands out owing to its efficiency. The role of the stomach as a secretory organ of many substances, such as gastrin, related to insulin secretion is well known. Gastrin induces insulin release in isolated pancreatic islets, limiting somatostatin-14 intraislet release, and has been associated with blood glucose level improvement in diabetic models after SG. SG involves gastric resection along the greater curvature. This study aimed to determine the role of gastrin in glucose metabolism improvement after SG with the aid of the gastrin antagonist netazepide.

METHODS

In 12 sham-operated, 12 SG-operated, and 12 SG-operated/netazepide-treated Wistar rats, we compared medium- and long-term plasma insulin, oral glucose tolerance test (OGTT) results, and plasma gastrin levels. In addition, gastrin expression was assessed in the gastric remnant, and the beta-cell mass was measured.

RESULTS

SG induced a medium-term elevation of the insulin response and plasma gastrin levels without modification of the OGTT results. However, long-term depletion of the insulin response with elevated OGTT areas under the curve and plasma gastrin levels appeared after SG. Netazepide prevented the SG effect on these parameters. Gastrin tissue expression was greater in SG animals than in SG/netazepide-treated or control animals. The beta-cell mass was lower in the SG group than in the control or SG/netazepide group.

CONCLUSION

Gastrin plays a central role in glucose improvement after SG. It stimulates a medium-term strong insulin response but also causes long-term beta-cell mass depletion and a loss of insulin response. These effects are prevented by gastrin antagonists such as netazepide.

No Long-Term Mucosal Lesions in the Esophagus but More Gastric Mucosal Lesions after Sleeve Gastrectomy in Obese Rats

Sleeve gastrectomy (SG) often induces gastroesophageal reflux, with few and discordant long-term data on the risk of Barrett's esophagus (BE) in operated patients. The aim of this study was to analyze the impact of SG on esogastric mucosa in a rat model at 24 weeks postoperatively, which corresponds to approximately 18 years in humans. After 3 months of a high-fat diet, obese male Wistar rats were subjected to SG (n = 7) or sham surgery (n = 9). Esophageal and gastric bile acid (BA) concentrations were measured at sacrifice, at 24 weeks postoperatively. Esophageal and gastric tissues were analyzed by routine histology. The esophageal mucosa of the SG rats (n = 6) was not significantly different in comparison to that of the sham rats (n = 8), with no esophagitis or BE. However, there was more antral and fundic foveolar hyperplasia in the mucosa of the residual stomach 24 weeks after SG than in the sham group (p < 0.001). Luminal esogastric BA concentrations did not differ between the two groups. In our study, SG induced gastric foveolar hyperplasia but no esophageal lesions at 24 weeks postoperatively in obese rats. Therefore, long-term endoscopic esophageal follow-up that is recommended in humans after SG to detect BE may also be useful for detecting gastric lesions.

Is the colon mucosa affected by ten days of gastric restriction in an animal model?

PURPOSE

To identify whether the colon mucosa is affected by ten days of gastric restriction in an animal model.

METHODS

An experimental model of gastric restriction was devised using rats. The animals were submitted to surgical gastrostomy, and a cylindrical loofah was inserted into the stomach. We studied 30 adult male Wistar rats divided into three groups: the stomach restriction group (R10); the sham group (S10), which underwent the same procedure except for the loofah insertion; and the control group (C10). The expression of neutral and acid mucins was evaluated using histochemical techniques. Goblet cells and protein content were compared between groups using generalized estimation equations (GEEs). Bonferroni's multiple comparison was applied to identify differences between the groups. All tests considered a 5% significance level.

RESULTS

There was an increased expression of neutral mucins, acid mucins and goblet cells in the R10 group. Collagen was also enhanced in the R10 group.

CONCLUSION

The colon mucosa is affected by ten days of gastric restriction in an animal model, increasing neutral mucins, acid mucins and collagen content with trophic maintenance.

The effect of hypergastrinemia following sleeve gastrectomy and pantoprazole on type 2 diabetes mellitus and beta-cell mass in Goto-Kakizaki rats

PURPOSE

Metabolic surgery alters the secretion of gastrointestinal hormones that influence glycemic control. Elevated gastrin has been suggested to benefit patients with type 2 diabetes and has been reported following sleeve gastrectomy in rats. The present study compares the effect of hypergastrinemia following sleeve gastrectomy with proton-pump inhibitor therapy on glycemic control and beta-cell mass in lean, diabetic animals.

METHODS

Thirty-three diabetic Goto-Kakizaki rats were randomized into pantoprazole + sham operation (GK-PPI), sleeve gastrectomy (GK-SG) and vehicle + sham operation (GK-V). Body weight, glucose parameters, HbA1c, glucagon-like peptide 1, gastrin, insulin and lipids were evaluated for eighteen postoperative weeks. Total beta-cell mass was quantified by optical projection tomography.

RESULTS

After surgery, body weight development was equal among groups (P _g = 0.75). Fasting and stimulated gastrin increased for GK-PPI and GK-SG vs. GK-V (p < 0.05 for all). Fasting blood glucose was decreased for GK-PPI and GK-SG vs. GK-V (p < 0.05 and p = 0.052). HbA1c was lower for GK-SG vs. GK-V at 6 weeks and for GK-PPI vs. GK-V at twelve- and eighteen weeks postoperative (p < 0.05 for all); a borderline difference was observed for GK-SG vs. GK-V at 18 weeks (p = 0.054). Total- and LDL cholesterol was elevated for GK-PPI compared to the other two groups (p < 0.05 for all). Beta-cell mass did not differ among groups (p = 0.35).

CONCLUSIONS

Hypergastrinemia following sleeve gastrectomy and pantoprazole has a similar, modest effect on glycemic control in Goto-Kakizaki rats but does not enhance beta-cell mass after 18 weeks. Hypergastrinemia in the setting of T2DM might be of clinical relevance.

Role of serotonin hormone in weight regain after sleeve gastrectomy

Laparoscopic sleeve gastrectomy (LSG) is gaining popularity as bariatric surgery, a small percentage of subjects regain weight after surgery. This study was designed to evaluate body weight changes over a period of two years after LSG and investigate the role of serotonin in regulating energy balance. This is a prospective cohort study. A total of 92 patients with morbid obesity (64 women and 28 men) underwent LSG. All the participants were subjected to physical examination and detailed medical history. Anthropometric measurements were accomplished pre-operative and post-operatively at a frequency of four times per year for two years follow-up. Laboratory investigations were performed pre-operatively, and one and two years post-operatively. Blood samples were collected in the fasting state; for glucose, lipid profile and hormonal assays. Hormones measured were plasma insulin, leptin, serotonin and ghrelin. Results revealed that 35.7% weight loss occurred after one year. However, there was variability in the individual weight loss curve during the period between the first and second post-operative years. Thus, patients were divided into two groups: group I included 78 patients (84%) who maintained the lost weight, and group II included 14 patients (16.0%) who regained weight within 24 months post-operatively. Correlation with BMI revealed positive correlation with leptin and serotonin, whilst negative correlation with ghrelin in group II patients. Mechanisms of weight loss after LSG are not only attributable to gastric restriction but also to the neurohormonal changes. In addition, serotonin may possibly contribute to the interplay of regulatory systems of energy homeostasis.

Serum Leptin, Obestatin, and Ghrelin Levels and Gastric Emptying Rates of Liquid and Solid Meals in Non-obese Rats with Roux-en-Y Bypass Surgery or Prosthesis Placement: Implications for the Role of Vagal Afferents

BACKGROUND

The present study aimed to investigate the effects of Roux-en-Y gastric bypass (RYGB) and prosthesis placement on gastric emptying rate in conjunction with serum ghrelin-obestatin-leptin responses in non-obese rats with intact or denervated afferent innervation.

METHODS

Under anesthesia, male Sprague-Dawley rats underwent either sham operation, RYGB, prosthesis, and/or Gregory cannula placement. Three weeks later, liquid or solid gastric emptying tests were performed and serum ghrelin, leptin and obestatin levels were measured.

RESULTS

Both prosthesis placement and RYGB surgery delayed non-nutrient liquid emptying; while solid nutrient emptying was delayed only by RYGB. Nutrient-dependent (acid, hyperosmolal and peptone) delay in liquid emptying was abolished in rats with prosthesis. By vagal afferent denervation, delayed liquid emptying was abolished, while solid emptying was further delayed in rats with prosthesis. Ghrelin and obestatin levels were depressed in prosthesis-placed rats, but RYGB surgery had no impact on both levels. Leptin level was elevated in solid-food-given rats with prosthesis, but not changed in RYGB group, while it was reduced following liquid meal. All the changes observed in ghrelin, obestatin, or leptin levels in response to meal ingestion were reversed with vagal afferent denervation.

CONCLUSIONS

Both RYGB and prosthesis placement had delaying effects on gastric emptying rate of non-obese rats. Our results indicate that the short-term changes in gastric motility and hormone responses induced by volume reduction are reversed by afferent denervation, suggesting that sparing the vagal innervation could be essential for reaching optimum motility and hormone changes expected after bariatric surgery.