Eating Behavior and Glucagon-Like Peptide-1-Producing Cells in Interposed Ileum and Pancreatic Islets in Rats Subjected to Ileal Interposition Associated with Sleeve Gastrectomy

The Impacts of Gastroileostomy Rat Model on Glucagon-like Peptide-1: a Promising Model to Control Type 2 Diabetes Mellitus

BACKGROUND

One of the new current treatment options for Diabetes Mellitus is about increasing glucagon-like peptide-1 (GLP-1) activity. GLP-1 with its incretin effect showed major role in glucose homeostasis. Gastroileostomy can increase GLP-1 secretion by rapid delivery of undigested food to the terminal ileum. We studied the early effects of a gastroileostomy on serum levels of GLP-1, glucose, and insulin in rats.

METHODS

Gastroileostomies with side-to-side anastomosis were performed on 15 male New Zealand rats. Blood samples were obtained before and 1 week after the gastroileostomy.

RESULTS

Our results showed that the rats lost a lot of weight from start (330 ± 15 g) to the end (240 ± 25 g) of the experiment (p = 0.048). The data analysis showed that the gastroileostomy surgery elevates the level of GLP-1in plasma significantly (89.1852 vs. 177.440 respectively; p < 0.001) and caused a significant decrease in plasma glucose as well (92.00 and 66.29 mg/dL respectively; p < 0.001). However, the insulin state elevated after the surgery significantly (8.03 vs. 9.89; p < 0.001).

CONCLUSION

In this study, we showed the effectiveness of gastroileostomy treatment to decrease body weight and plasma glucose with increased GLP-1 in rats. This small rat model suggests the potential of this surgery to treat type 2 diabetes mellitus.

Sleeve gastrectomy activates the GLP-1 pathway in pancreatic β cells and promotes GLP-1-expressing cells differentiation in the intestinal tract

Db/db mouse was used to study the underlying mechanisms by which Sleeve gastrectomy (SG) improves β-cell function. We investigated β-cell function, plasma active GLP-1 levels, the GLP-1R pathway in β cells and L cell differentiation. After SG, β-cell function was significantly increased, and the GLP-1R-PKCζ-PDX-1 pathway was active in β cells. Plasma active GLP-1 levels, as well as the number of L cells in the jejunum, were significantly increased after SG. The expression of early transcription factors (TF), including Ngn3, FoxA1 and Nkx2.2, was not compromised by chronic hyperglycemia. In contrast, the expression of the downstream TF PAX6 was affected, and this down-regulation could be reversed by SG. So, SG can maintain L cell differentiation, increase plasma active GLP-1 level, sustain the activation of the GLP-1R pathway and improve β cell function in Db/db mice. Our results show that SG can overall improve the function of the entero-insular axis.

GLP-1: a mediator of the beneficial metabolic effects of bariatric surgery?

There has been increasing interest in the role that gut hormones may play in contributing to the physiological changes produced by certain bariatric procedures, such as Roux-en-Y gastric bypass and sleeve gastrectomy. Here, we review the evidence implicating one such gut hormone, glucagon-like peptide-1, as a mediator of the metabolic benefits of these two procedures.

Ileal Interposition in Rats with Experimental Type 2 Like Diabetes Improves Glycemic Control Independently of Glucose Absorption

Bariatric operations in obese patients with type 2 diabetes often improve diabetes before weight loss is observed. In patients mainly Roux-en-Y-gastric bypass with partial stomach resection is performed. Duodenojejunal bypass (DJB) and ileal interposition (IIP) are employed in animal experiments. Due to increased glucose exposition of L-cells located in distal ileum, all bariatric surgery procedures lead to higher secretion of antidiabetic glucagon like peptide-1 (GLP-1) after glucose gavage. After DJB also downregulation of Na(+)-d-glucose cotransporter SGLT1 was observed. This suggested a direct contribution of decreased glucose absorption to the antidiabetic effect of bariatric surgery. To investigate whether glucose absorption is also decreased after IIP, we induced diabetes with decreased glucose tolerance and insulin sensitivity in male rats and investigated effects of IIP on diabetes and SGLT1. After IIP, we observed weight-independent improvement of glucose tolerance, increased insulin sensitivity, and increased plasma GLP-1 after glucose gavage. The interposed ileum was increased in diameter and showed increased length of villi, hyperplasia of the epithelial layer, and increased number of L-cells. The amount of SGLT1-mediated glucose uptake in interposed ileum was increased 2-fold reaching the same level as in jejunum. Thus, improvement of glycemic control by bariatric surgery does not require decreased glucose absorption.

Reduced neurons in the ileum of proctocolectomized rat models

Ileal pouch-anal anastomosis (IPAA) is the operation of choice following proctocolectomy for patients who suffer from ulcerative colitis and familial adenomatous polyposis. The aim of this study was to morphologically examine the neurons, endocrine cells and mast cells in the ileum of rats subjected to proctocolectomy followed by three different types of ileoanal anastomosis. Rats were subjected to either sham operation or proctocolectomy followed by ileoanal anastomosis end-to-end, side-to-end or IPAA (J-pouch). In comparison to sham-operated rats, the body weight was reduced in rats that underwent proctocolectomy with end-to-end or side-to-end, but not IPAA procedure. In all three models of ileoanal anastomosis, the ileum displayed crypt hyperplasia with a chronic inflammatory infiltrate located in the interstitium, hyperplasia of goblet cells, but reduced protein gene product 9.5 (PGP 9.5)-immunoreactive neurons in the mucosa as well as submucosa. Numbers of endocrine cells in the mucosa (chromogranin A immunostaining) and mast cells in the mucosa and submucosa (Astra blue staining) were unchanged after proctocolectomy. In conclusion, neurons, but neither endocrine cells nor mast cells, were reduced in the ileum of proctocolectomized rats followed by either of three different types of ileoanal anastomosis.

New medications for treatment of obesity: metabolic and cardiovascular effects

The management of obesity remains a major challenge. Dietary therapy often fails, whereas bariatric surgery, although successful, is demanding and applicable to a limited number of patients. Drug therapy has had many setbacks over the past 20 years because of serious adverse effects; however, several new drugs for the treatment of obesity are either licensed in some parts of the world, submitted for registration, or completing phase III trials. These include combinations (at low dose) of existing drugs, e.g., bupropion + naltrexone (Contrave), phentermine + topiramate (Qsymia), higher doses of existing drugs licensed for other indications (liraglutide, 3 mg), and new entities (lorcaserin). We discuss the challenges and opportunities for obesity pharmacotherapy and review in detail the efficacy of the new drugs regarding weight loss and both desirable and potential undesirable cardiovascular (CV) and metabolic risk factors. Substantial barriers remain, even if the drugs are approved, in successfully integrating these agents into weight management practice, largely related to cost, patient acceptability, and clinician willingness to be engaged in obesity treatment. Although hard clinical outcome benefit (at least for CV outcomes) has yet to be established, obesity pharmacotherapy may soon address many of the challenges in the clinical management of obesity, although newer and better drug combinations and more evidence of benefit from appropriately designed outcome trials is needed.

Mechanistic comparison between gastric bypass vs. duodenal switch with sleeve gastrectomy in rat models

Background

Both gastric bypass (GB) and duodenal switch with sleeve gastrectomy (DS) have been widely used as bariatric surgeries, and DS appears to be superior to GB. The aim of this study was to better understand the mechanisms leading to body weight loss by comparing these two procedures in experimental models of rats.

Methods

Animals were subjected to GB, DS or laparotomy (controls), and monitored by an open-circuit indirect calorimeter composed of comprehensive laboratory animal monitoring system and adiabatic bomb calorimeter.

Results

Body weight loss was greater after DS than GB. Food intake was reduced after DS but not GB. Energy expenditure was increased after either GB or DS. Fecal energy content was increased after DS but not GB.

Conclusion

GB induced body weight loss by increasing energy expenditure, whereas DS induced greater body weight loss by reducing food intake, increasing energy expenditure and causing malabsorption in rat models.

Effects of sleeve gastrectomy and ileal transposition, alone and in combination, on food intake, body weight, gut hormones, and glucose metabolism in rats

Bariatric surgeries are hypothesized to produce weight loss and improve diabetes control by multiple mechanisms including gastric restriction and lower gut stimulation; the relative importance of these mechanisms remains poorly understood. We compared the effects of a typical foregut procedure, sleeve gastrectomy, (SG) with a primarily hindgut surgery, ileal transposition (IT), alone and together (SGIT), or sham manipulations, on food intake, body weight, gut hormones, glucose tolerance, and key markers of glucose homeostasis in peripheral tissues of adult male Sprague-Dawley rats (450-550 g, n = 7-9/group). SG, IT, and SGIT surgeries produced transient reduction in food intake and weight gain; the effects of SG and IT on intake and body weight were nonadditive. SG, IT, and SGIT surgeries resulted in increased tissue expression and plasma concentrations of the lower gut hormones glucagon-like peptide-1 and peptide YY and decreased plasma glucose-dependent insulinotropic peptide, insulin, and leptin concentrations. Despite transient effects on intake and weight gain, the SG, IT, and SGIT surgeries produced a significant improvement in glucose tolerance. In support of glycemic improvements, the protein abundance of key markers of glucose metabolism (e.g., GLUT4, PKA, IRS-1) in muscle and adipose tissue were increased, whereas the expression of key gluconeogenic enzyme in liver (G-6-Pase) were decreased following the surgeries. Therefore, our data suggest that enhanced lower gut stimulation following SG, IT, and SGIT surgeries leads to transient reduction in food intake and weight gain together with enhanced secretion of lower gut hormones and improved glucose clearance by peripheral tissues.