Experimental Metabolic Surgery: Justification and Technical Aspects

Effect of sleeve gastrectomy, Roux-en-Y gastric bypass, and ileal transposition on myocardial ischaemia-reperfusion injury in non-obese non-diabetic rats

Bariatric surgery (BS) improves outcomes in patients with myocardial infarction (MI). Here we tested the hypothesis that BS-mediated reduction in fatal MI could be attributed to its infarct-limiting effect. Wistar rats were randomized into five groups: control (CON), sham (SHAM), Roux-en-Y gastric bypass (RYGB), sleeve gastrectomy (SG), and ileotransposition (IT). Ten weeks later, animals were subjected to 30-min myocardial ischemia plus 120-min reperfusion. Infarct size (IS) and no-reflow area were determined histochemically. Fasting plasma levels of glucagon-like peptide-1 (GLP-1), leptin, ghrelin, and insulin were measured using ELISA. Compared with SHAM, RYGB and SG reduced IS by 22% (p = 0.011) and 10% (p = 0.027), and no-reflow by 38% (p = 0.01) and 32% (p = 0.004), respectively. IT failed to reduce IS and no-reflow. GLP-1 level was increased in the SG and RYGB groups compared with CON. In both the SG and RYGB, leptin level was decreased compared with CON and SHAM. In the SG group, ghrelin level was lower than that in the CON and SHAM. Insulin levels were not different between groups. In conclusion, RYGB and SG increased myocardial tolerance to ischemia-reperfusion injury of non-obese, non-diabetic rats, and their infarct-limiting effect is associated with decreased leptin and ghrelin levels and increased GLP-1 level.

Effects of three types of bariatric interventions on myocardial infarct size and vascular function in rats with type 2 diabetes mellitus

AIMS

The effects of three types of bariatric interventions on myocardial infarct size were tested in the rat model of type 2 diabetes mellitus (T2DM). We also evaluated the effects of bariatric surgery on no-reflow phenomenon and vascular dysfunction caused by T2DM.

MAIN METHODS

Rats with T2DM were assigned into groups: without surgery, sham-operated, ileal transposition, Roux-en-Y gastric bypass, and sleeve gastrectomy. Oral glucose tolerance, glucagon-like peptide-1, and insulin levels were measured. Six weeks after surgery, the animals were subjected to myocardial ischemia-reperfusion followed by histochemical determination of infarct size (IS), no-reflow zone, and blood stasis area size. Vascular dysfunction was characterized using wire myography.

KEY FINDINGS

All bariatric surgery types caused significant reductions in animal body weight and resulted in T2DM compensation. All bariatric interventions partially normalized glucagon-like peptide-1 responses attenuated by T2DM. IS was significantly smaller in animals with T2DM. Bariatric surgery provided no additional IS limitation compared with T2DM alone. Bariatric surgeries reversed T2DM-induced enhanced contractile responses of the mesenteric artery to 5-hydroxytryptamine. Sleeve gastrectomy normalized decreased nitric oxide synthase contribution to the endothelium-dependent vasodilatation in T2DM.

SIGNIFICANCE

T2DM resulted in a reduction of infarct size and no-reflow zone size. Bariatric surgery provided no additional infarct-limiting effect, but it normalized T2DM-induced augmented vascular contractility and reversed decreased contribution of nitric oxide to endothelium-dependent vasodilatation typical of T2DM. All taken together, we suggest that this type of surgery may have a beneficial effect on T2DM-induced cardiovascular diseases.

Roux-en-Y gastric bypass decreases endotoxemia and inflammatory stress in association with improvements in gut permeability in obese diabetic rats

BACKGROUND

Postoperative modulation of the gut microbiome has been suggested to contribute to the metabolic benefits after metabolic surgery, but the mechanisms underlying these metabolic benefits remain unknown. Previously, we reported that Roux-en-Y gastric bypass (RYGB) surgery in Zucker diabetic fatty (ZDF) rats increased the abundance of Proteobacteria and Gammaproteobacteria. However, theoretically, these Gram-negative bacteria may elevate lipopolysaccharide (LPS) levels. Therefore, in this study we further investigated the potential mechanisms by which RYGB improves glucose homeostasis, endotoxemia, and inflammatory stress in ZDF rats.

METHODS

Rats were divided into three groups: (a) an RYGB group (RY); (b) a sham-operated group pair-fed with the RY group; and (c) a sham-operated group fed ad libitum. Changes in LPS, cytokine levels, intestinal permeability (evaluated using the fluorescein isothiocyanate-dextran method), and intestinal epithelial tight junction proteins zona occludins (ZO)-1, occludin, and claudin-1 were assessed 10 weeks postoperatively.

RESULTS

Rats that underwent RYGB exhibited sustained weight loss and reduced glucose, as well as lower cytokine and LPS concentrations, than rats in the control groups. In the colonic epithelium, ZO1 and claudin-1 (Cldn1) mRNA levels were higher in the RY than control groups. Intestinal permeability declined in the RY group and was positively correlated with LPS levels and negatively correlated with ZO-1, occludin, and claudin-1 expression.

CONCLUSIONS

The results demonstrate that RYGB can reduce the extent of endotoxemia and inflammation, which is associated with improved tight junction integrity and intestinal barrier strength. These effects may explain why a low level of inflammation is maintained after RYGB and the postoperative increase in Gram-negative bacteria.

Gastric Plication and Sleeve Gastrectomy in an Experimental Model of Obesity: New Insights into Weight Loss, Intake and Metabolic Results

AIM

Laparoscopic gastric plication (LGP) is a bariatric surgical technique based on the anatomical principles of laparoscopic sleeve gastrectomy (LSG), but its effects on the metabolic profile are still uncertain. The aim of our study is to compare the changes in weight, metabolic parameters and gastric histology following intervention by gastric plication (GP) and sleeve gastrectomy (SG) in an experimental model of obesity.

METHODS

To conduct the study, 32 8-week-old male Sprague-Dawley rats (Charles River®) were fattened by means of a cafeteria diet and randomly assigned to the following experimental groups: group 1: GP (n = 12); group 2: SG (n = 12) and group 3: sham (n = 8).

RESULTS

Unlike the SG group, the GP group attained the weight of the sham group at the end of the experiment (week 16). The GP group continued to eat more cafeteria diet than the SG group. In addition, the SG group achieved better glycaemic control than the GP group. Significantly higher plasma ghrelin levels were observed at week 16 in the GP group than in the SG group (2.29 ± 0.5 vs 1.07 ± 0.4, p < 0.05), which also occurred for the glucagon plasmatic levels (62.71 ± 36.2 vs 24.63 ± 9.3, p < 0.05).

CONCLUSIONS

GP is not as effective as SG and cannot be considered a metabolic surgery due to observed hormonal variations. The animals subjected to a GP continued to have a high appetite for the cafeteria diet unlike the animals submitted to an SG. Hormonal mechanisms possibly related to glucagon and ghrelin may be involved in this metabolic response.

Gut microbiota after Roux-en-Y gastric bypass and sleeve gastrectomy in a diabetic rat model: Increased diversity and associations of discriminant genera with metabolic changes

Recent work with gut microbiota after bariatric surgery is limited, and the results have not been in agreement. Given the role of the gut microbiota in regulating host metabolism, we explored the effect of Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG) on the modifications of gut microbiota with regard to the potential influence of food intake and/or weight loss and examined their links with host metabolism. Zucker diabetic fatty rats were divided into the following groups: RYGB; sham-operated with pair-fed as RYGB; sham-operated fed ad libitum; and SG. The metabolic effects and gut microbiota profile were analyzed 10 weeks postoperatively. Associations between discriminating genera and metabolic markers after RYGB were explored. The 2 procedures induced similar glucose improvement and increased flora diversity after 10 weeks compared with sham-operated groups. RYGB induced a marked higher relative abundance of Proteobacteria/Gammaproteobacteria and Betaproteobacteria and increased emergence of Fusobacteria and Clostridium, whereas SG resulted in more abundant Actinobacteria compared with other groups. Most of the 12 discriminant genera correlated with changes in metabolic phenotype, but only 28.6% of these correlations were independent of weight, and 4 discriminant genera still negatively correlated with serum insulin level independent of food intake and weight loss after RYGB. These data demonstrate that RYGB and SG surgery produced similar diversity but different microbiota compositions changes in Zucker diabetic fatty rats. These findings stimulate deeper explorations of functions of the discriminate microbiota and the mechanisms linking postsurgical modulation of gut microbiota and improvements in insulin resistance.

Obese and lean Zucker rats respond similarly to intraperitoneal administration of gastrin-releasing peptides

The Zucker rat is an animal model used to study obesity and the control of food intake by various satiety peptides. The amphibian peptide bombesin (Bn) reduces cumulative food intake similarly in both obese and lean weanling Zucker rats. Here, we hypothesized that intraperitoneal (i.p) administration of gastrin-releasing peptides-10, -27 and -29 (GRP-10, GRP-27, GRP-29), which are the mammalian forms of Bn, would reduce first meal size (MS, 10% sucrose) and prolong the intermeal interval (IMI, time between first and second meals) similarly in obese and lean adult Zucker rats. To test this hypothesis, we administered GRP-10, GRP-27 and GRP-29 (0, 2.1, 4.1 and 10.3 nmol/kg) i.p. to obese and lean male Zucker rats (who were deprived of overnight food but not water) and then measured the first and second MS, IMI and satiety ratio (SR, IMI/MS). We found that in both obese and lean rats, all forms of GRP reduced the first MS, and in lean rats, they also decreased the second MS. Additionally, GRP-10 and GRP-29 prolonged the IMI in both obese and lean rats, but GRP-27 only prolonged it in lean rats. Finally, we found that all forms of GRP increased the SR in both obese and lean rats. In agreement with our hypothesis, we conclude that all forms of GRP reduce food intake in obese and lean adult Zucker rats similar to Bn in weanling rats.

Duodeno-jejunal tube placement in an experimental model of obesity: effects on food behaviour and basal energy expenditure

BACKGROUND

Metabolic surgery can modulate weight as well as food intake and basal energy expenditure. In this study, we evaluate the effectiveness of duodenal exclusion by analysing anthropometric results, intake variations, food behaviour and calorimetric parameters.

METHODS

This is an experimental study with 8-week-old Sprague-Dawley male rats. The sequences used are as follows: Cafeteria diet for 3 weeks, followed by surgery and sacrifice at 4 weeks. Four experimental groups are as follows: two non-obese groups (n = 15; surgery = 10, sham = 5) and two obese groups by cafeteria diet (n = 15; surgery = 10, sham = 5). Surgery performed was duodenal exclusion with physical barrier. Weight, intake, glycaemia and basal energy expenditure by indirect calorimetry were monitored before and after surgery.

RESULTS

Weight changes in groups that underwent intervention were significant. The reduction in calorie consumption after surgery was significant in the obese intervention group despite an increased standard feed consumption (161 ± 11 vs 139 ± 13 Kcal/day, p < 0.05; due to a lower consumption of cafeteria diet). In non-obese animals, changes were transient. Basal energy expenditure decreased in both intervention groups: 6.2 ± 0.5 vs 5.5 ± 0.4 Kcal/kg/h in non-obese animals and 5.6 ± 0.3 vs 4.7 ± 0.3 Kcal/kg/h in obese animals (p < 0.05).

CONCLUSIONS

Duodeno-jejunal tube placement stops weight gain in obese and non-obese animals. In obese animals, there is an important qualitative change in appetite towards standard feed with a significant decrease in caloric intake. In non-obese animals, changes in quantitative intake are transient. This surgery decreases basal energy expenditure in obese animals. This may be attributed to an enhanced thermogenic effect of food and a slowing in the animal's weight gain.

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.