Carbohydrate content of post-operative diet influences the effect of vertical sleeve gastrectomy on body weight reduction in obese rats

VERTICAL GASTRECTOMY VS. EXTENDED VERTICAL GASTRECTOMY: WHAT IS THE IMPACT ON GASTROESOPHAGEAL REFLUX DISEASE IN OBESE RATS?

BACKGROUND

Extended vertical gastrectomy is a variation of the vertical gastrectomy technique requiring studies to elucidate safety in relation to gastroesophageal reflux.

AIM

To analyze comparatively vertical gastrectomy (VG) and extended vertical gastrectomy (EVG) in rats with obesity induced by cafeteria diet in relation to the presence of reflux esophagitis, weight loss and macroscopic changes related to the procedures.

METHODS

Thirty Wistar rats were randomized into three groups, and after the obesity induction period by means of a 28-day cafeteria diet, underwent a simulated surgery (CG), VG and VGA. The animals were followed up for 28 days in the post-operative period, and after euthanasia, the reflux esophagitis evaluation was histopathologically performed. Weight and macroscopy were the other variables; weight was measured weekly and the macroscopic evaluation was performed during euthanasia.

RESULTS

All animals presented some degree of inflammation and the presence of at least one inflammation criterion; however, there was no statistically significant difference in the analysis among the groups. In relation to weight loss, the animals in CG showed a gradual increase during the whole experiment, evolving to super-obesity at the end of the study, while the ones with VG and EVG had weight regain after the first post-operative period; however, a less marked regain compared to CG, both for VG and EVG.

CONCLUSION

There is no difference in relation to reflux esophagitis VG and EVG, as well as macroscopic alterations, and both techniques have the ability to control the evolution of weight during postoperative period in relation to CG.

A rodent model of partial intestinal diversion: a novel metabolic operation

BACKGROUND

Metabolic surgery is safe and the most effective therapy for obesity and its co-morbidities. New procedures may allow for better tailoring of metabolic surgery to the individual patient.

OBJECTIVE

To evaluate the impact, comparative effectiveness, and mechanisms of the partial intestinal diversion (PID), vertical sleeve gastrectomy (VSG), and the combination of PID and VSG on weight and glucose regulation.

SETTING

University research facility, United States.

METHODS

Three cohorts of high-fat diet-induced obese male rats were randomized to distal PID (DPID), proximal PID (PPID), VSG, VSG and DPID (VSG/DPID), or sham operation (Sham). Animals were followed for 11 (cohort 1) or 10 (cohorts 2 and 3) weeks. Outcomes included weight and composition, food intake, glucose metabolism, lipids, bile acids, and energy balance. Statistical comparisons were performed using Tukey's multiple comparison test applied to analysis of variance.

RESULTS

DPID and not PPID resulted in significant weight and body fat reductions relative to Sham. Improved glucose tolerance was seen in all surgical groups though this reached statistical significance for only DPID and VSG compared with Sham. Improvements in baseline glucose and insulin, corresponding insulin resistance, and plasma lipids were noted in DPID compared with Sham. Though the magnitude of weight and body composition changes and metabolic benefit tended to be larger for VSG relative to DPID, it only reached statistical significance for lipids. VSG and VSG/DPID resulted in similar outcomes. Markedly reduced food intake occurred after VSG and more modestly after DPID. Stool caloric content was higher in DPID relative to all groups.

CONCLUSIONS

DPID is an effective metabolic operation resulting in notable weight and fat loss and metabolic improvement relative to sham-operated rodents. Interestingly, combining VSG with DPID added little additional benefit to the effects of VSG.

A comparison of rodent models of vertical sleeve gastrectomy

BACKGROUND

Although vertical sleeve gastrectomy (VSG) is fashioned in humans by applying multiple staple loads, rodent VSG is generally created through a single-staple load application.

OBJECTIVES

To investigate the impact of a 2-staple load VSG rat model more closely resembling the multistaple load operation done in humans on weight, metabolic outcomes, and the microbiome and how these compare with those obtained with the standard one-staple load model.

SETTING

University research facility, United States.

METHODS

High-fat diet-induced obese male rats were randomized to single-staple load VSG (VSG1), 2-staple load VSG (VSG2), or sham operation (Sham). Outcomes included weight and composition, food intake, glucose metabolism, lipids, bile acids, and intestinal microbiome. Statistical comparisons were performed using analysis of variance.

RESULTS

Both procedures resulted in substantial weight and body fat loss compared with Sham-treated animals. Weight loss was modestly greater for VSG2 compared with VSG1. Food intake was reduced in both procedures and accounted for the observed weight reduction. Glucose tolerance and plasma and hepatic lipid profiles were improved comparably in VSG1 and VSG2 relative to Sham. Bile acids were higher for VSG2 compared with Sham but not significantly different between VSG1 and VSG2. Neither procedure impacted intestinal microbiome richness and diversity compared with Sham across multiple intestinal sections. Colonic Actinobacteria was more abundant in VSG2 than in Sham. Relative abundances of bacterial phyla did not differ among VSG1, VSG2, and Sham across the remaining intestinal sections.

CONCLUSIONS

Although VSG1 or VSG2 offer effective and overall comparable platforms for the study of obesity, VSG2 resulted in superior weight loss.

Does bariatric surgery improve adipose tissue function?

Bariatric surgery is currently the most effective treatment for obesity. Not only do these types of surgeries produce significant weight loss but also they improve insulin sensitivity and whole body metabolic function. The aim of this review is to explore how altered physiology of adipose tissue may contribute to the potent metabolic effects of some of these procedures. This includes specific effects on various fat depots, the function of individual adipocytes and the interaction between adipose tissue and other key metabolic tissues. Besides a dramatic loss of fat mass, bariatric surgery shifts the distribution of fat from visceral to the subcutaneous compartment favoring metabolic improvement. The sensitivity towards lipolysis controlled by insulin and catecholamines is improved, adipokine secretion is altered and local adipose inflammation as well as systemic inflammatory markers decreases. Some of these changes have been shown to be weight loss independent, and novel hypothesis for these effects includes include changes in bile acid metabolism, gut microbiota and central regulation of metabolism. In conclusion bariatric surgery is capable of improving aspects of adipose tissue function and do so in some cases in ways that are not entirely explained by the potent effect of surgery. © 2016 World Obesity.

Roux-en-Y gastric bypass surgery but not vertical sleeve gastrectomy decreases bone mass in male rats

The most effective treatment for obesity is bariatric surgery. However, there is increasing concern that bariatric surgery can cause nutrient deficiencies that translate into metabolic bone disease. Whether this is true for all surgery types is not yet clear. We therefore investigated the effects of 2 commonly applied bariatric surgeries (Roux-en-Y gastric bypass [RYGB] and vertical sleeve gastrectomy) on energy and bone metabolism in rats 60 days after surgery. Both surgeries resulted in similar reductions of body weight, body fat, and food intake. Glucose tolerance was improved to a similar extent after both surgeries and was accompanied by increased postprandial secretion of glucose-dependent insulinotropic peptide. Using microcomputed tomography, we found that, relative to sham-operated rats, bone volume was significantly reduced after RYGB but not vertical sleeve gastrectomy. RYGB rats also had markedly reduced lipid absorption from the intestine and significantly lower serum 25-hydroxyvitamin D and calcium levels. Importantly, dietary supplementation with calcium and vitamin D could not fully rescue the reduced bone volume after RYGB surgery. Both surgeries resulted in a significant increase in stomach pH, which may have worsened the malabsorption in RYGB rats. Our findings suggest that bone loss in RYGB rats is not exclusively driven by calcium and vitamin D malabsorption but also by additional factors that may not be rescuable by dietary supplementation. These data point toward important similarities and differences between bariatric procedures that should be considered in clinical settings as guidance for which procedure will be best for specific patient populations.

Sleeve gastrectomy and Roux-en-Y gastric bypass exhibit differential effects on food preferences, nutrient absorption and energy expenditure in obese rats

OBJECTIVE

All available treatments directed towards obesity and obesity-related complications are associated with suboptimal effectiveness/invasiveness ratios. Pharmacological, behavioral and lifestyle modification treatments are the least invasive, but also the least effective options, leading to modest weight loss that is difficult to maintain long-term. Gastrointestinal weight loss surgery (GIWLS) is the most effective, leading to >60-70% of excess body weight loss, but also the most invasive treatment available. Sleeve gastrectomy (SGx) and Roux-en-Y gastric bypass (RYGB) are the two most commonly performed GIWLS procedures. The fundamental anatomic difference between SGx and RYGB is that in the former procedure, only the anatomy of the stomach is altered, without surgical reconfiguration of the intestine. Therefore, comparing these two operations provides a unique opportunity to study the ways that different parts of the gastrointestinal (GI) tract contribute to the regulation of physiological processes, such as the regulation of body weight, food intake and metabolism.

DESIGN

To explore the physiologic mechanisms of the two procedures, we used rodent models of SGx and RYGB to study the effects of these procedures on body weight, food intake and metabolic function.

RESULTS

Both SGx and RYGB induced a significant weight loss that was sustained over the entire study period. SGx-induced weight loss was slightly lower compared with that observed after RYGB. SGx-induced weight loss primarily resulted from a substantial decrease in food intake and a small increase in locomotor activity. In contrast, rats that underwent RYGB exhibited a substantial increase in non-activity-related (resting) energy expenditure and a modest decrease in nutrient absorption. Additionally, while SGx-treated animals retained their preoperative food preferences, RYGB-treated rats experienced a significant alteration in their food preferences.

CONCLUSIONS

These results indicate a fundamental difference in the mechanisms of weight loss between SGx and RYGB, suggesting that the manipulation of different parts of the GI tract may lead to different physiologic effects. Understanding the differences in the physiologic mechanisms of action of these effective treatment options could help us develop less invasive new treatments against obesity and obesity-related complications.