Surgical models of Roux-en-Y gastric bypass surgery and sleeve gastrectomy in rats and mice

Inhibition of somatostatin enhances the long-term metabolic outcomes of sleeve gastrectomy in mice

OBJECTIVE

Bariatric surgery is an effective treatment to obesity, leading to weight loss and improvement in glycemia, that is characterized by hypersecretion of gastrointestinal hormones. However, weight regain and relapse of hyperglycemia are not uncommon. We set to identify mechanisms that can enhance gastrointestinal hormonal secretion following surgery to sustain weight loss.

METHODS

We investigated the effect of somatostatin (Sst) inhibition on the outcomes of bariatric surgery using a mouse model of sleeve gastrectomy (SG).

RESULTS

Sst knockout (sst-ko) mice fed with a calorie-rich diet gained weight normally and had a mild favorable metabolic phenotype compared to heterozygous sibling controls, including elevated plasma levels of GLP-1. Mathematical modeling of the feedback inhibition between Sst and GLP-1 showed that Sst exerts its maximal effect on GLP-1 under conditions of high hormonal stimulation, such as following SG. Obese sst-ko mice that underwent SG had higher levels of GLP-1 compared with heterozygous SG-operated controls. The SG-sst-ko mice regained less weight than controls and maintained lower glycemia months after surgery. Obese wild-type mice that underwent SG and were treated daily with a Sst receptor inhibitor for two months had higher GLP-1 levels, regained less weight, and improved metabolic profile compared to saline-treated SG-operated controls, and compared to inhibitor or saline-treated sham-operated obese mice.

CONCLUSIONS

Our results suggest that inhibition of Sst signaling enhances the long-term favorable metabolic outcomes of bariatric surgery.

Sleeve gastrectomy links the attenuation of diabetic kidney disease to the inhibition of renal tubular ferroptosis through down-regulating TGF-β1/Smad3 signaling pathway

PURPOSE

To investigate how sleeve gastrectomy (SG), a typical operation of bariatric surgery, attenuated symptom, and progression of diabetic kidney disease (DKD).

METHODS

DKD model was induced by high-fat diet (HFD) combined with streptozocin in Wistar rats. SG was performed, and the group subjected to sham surgery served as control. The animals were euthanized 12 weeks after surgery, followed by sample collection for the subsequent experiment. The HK-2, a renal proximal tubular epithelial cell line derived from human, was utilized to investigate the potential mechanisms.

RESULTS

SG improved metabolic parameters and glucose homeostasis, and could alleviate DKD in terms of renal function indices as well as histological and morphological structures in DM rats, accompanied with a significant reduction in renal tubular injury. Compared with sham group, SG reduced the renal tubular ferroptosis. To further clarify the mechanism involved, in vitro experiments were performed. In the presence of high glucose, renal tubular TGF-β1 secretion was significantly increased in HK-2 cell line, which led to activation of ferroptosis through TGF-β1/Smad3 signaling pathway. Inhibition of TGF-β1 receptor and phosphorylation of Smad3 significantly ameliorated TGF-β1-mediated ferroptosis. In vivo experiments also found that SG improved the hyperglycemic environment, reduced renal TGF-β1 concentrations, and down-regulated the TGF-β1/Smad3 signaling pathway.

CONCLUSIONS

With the capacity to lower the glucose, SG could attenuate the ferroptosis by inhibiting TGF-β1/Smad3 signaling pathway in DKD rats, and eventually attenuated DKD.

Weight and Glucose Control in Rats Submitted to Sleeve Gastrectomy with Cafeteria Diet-Induced Obesity

Introduction: Sleeve gastrectomy (SG) has been widely disseminated as a surgical treatment for obesity and associated comorbidities, and currently it is one of the most performed surgeries in the world. Experimental research is becoming increasingly relevant to characterize the pathophysiological mechanisms induced by it. Objective: The aim of this study was to standardize an experimental model of SG in rats with obesity induced using a cafeteria diet (CAF) and evaluate variations in weight and glycemic control after vertical SG, maintaining the CAF. Materials and Methods: Twenty Rattus norvegicus albinus rats, Wistar strain, with an average weight of 250 g were used. The animals were randomized into two groups and underwent 4 weeks of obesity induction before the procedure. In 10 animals of the SG group, vertical SG was performed, and in 10 animals of the control/sham (C) group, simulated surgery was performed, consisting of laparotomy and bidigital compression of the stomach. The animals were followed for a total of 8 weeks, with the weight assessed weekly and fasting blood glucose assessed before the start of the CAF, at the time of surgery, and after 4 weeks of the postoperative period, when they were sacrificed. Results: Before obesity induction, the average weight was 257.8 g in the SG group 266.1 g in the C group. After obesity induction, the average weight was 384 g in the vertical sleeve gastrectomy group and 374.8 g in the C group. In the fourth postoperative week, the average weight was 391.6 g in the VSG group and 436.6 g in the C group. The average blood glucose levels were 88.7, 101.8, and 91.3 mg/dL in the VSG group and 86.6, 103.1, and 109.4 mg/dL in the C group, respectively, before the start of the diet, in the fourth preoperative week, and in the fourth postoperative week. Conclusions: Vertical SG in rats is feasible and promotes glycemic control in the postoperative period. CAF allows induction of obesity and changes in blood glucose.

Modified SADI-S in non-obese diabetic rats: Description of the surgical technique

Background

Single anastomosis duodenoileal bypass with sleeve gastrectomy (SADI-S) is a predominantly malabsorptive technique that has shown excellent results in morbid obese patients. The aim of this study is to establish a rodent model modifying the SADI-S technique by performing a proximal duodenojejunal anastomosis. This model can be useful for the study of glucose metabolism without malabsorption observed after the SADI-S technique.

Methods

Goto-Kakizaki rats, a genetic model of non-obese and non-hypertensive type 2 diabetes mellitus, that develop hyperglycemia at an early age was used. Surgery consisted in a sleeve gastrectomy, duodenojejunal anastomosis and duodenal exclusion using three different techniques: duodenal transection (DT), duodenal ligation with hem-o-lock (DLH), and duodenal ligation with suture (DLS). Surgery time, weight loss, morbidity and mortality were recorded.

Results

A total of 16 animals were subjected to surgical intervention and overall mortality was 25 %, with the DT group showing the highest mortality rate (42.9 %). No differences were observed among groups in terms of weight loss.

Conclusion

The surgical technique described in this work is feasible and reproducible. Weight loss is comparable regardless of the technique used for duodenal exclusion.

New Mouse Models of Roux-en Y Gastric Bypass and One Anastomosis Gastric Bypass for Type 2 Diabetes

BACKGROUND

Current bariatric surgery models primarily utilize mice with obesity, overlooking those with type 2 diabetes (T2DM). These models have limitations in replicating clinical procedures accurately and achieving broad applicability. This study aimed to develop novel mouse models of Roux-en-Y gastric bypass (RYGB) and one anastomosis gastric bypass (OAGB) surgeries specifically designed for T2DM research, utilizing simplified surgical techniques closely resembling clinical procedures.

METHODS

Eight-week-old C57/Bl6 mice, except for the Blank-Control group, were induced with T2DM by combining a high-fat diet and streptozotocin injection. RYGB involved creating a 10% gastric pouch, a 4-cm biliopancreatic limb (BL), and a 4-cm Roux limb (RL). Similarly, OAGB maintained a 10% gastric pouch and a 4-cm BL. To assess the efficacy of these models, we measured the body weight and fasting blood glucose (FBG) and conducted intraperitoneal glucose tolerance test (IPGTT), insulin tolerance test (ITT), and liver B-ultrasound, as well as a histopathological analysis of multiple organs 12 weeks post-operation.

RESULTS

The survival rates in the Blank-Control, T2DM-Sham, T2DM-RYGB, and T2DM-OAGB groups were 100% (6/6), 100% (6/6), 85.7% (6/7), and 100% (6/6), respectively. Both RYGB and OAGB surgeries similarly led to sustained weight loss, reduced the FBG levels, improved the IPGTT and ITT results, and alleviated the histopathological manifestations in multiple organs.

CONCLUSION

The innovative mouse models of RYGB and OAGB surgeries effectively improve T2DM. Both surgeries demonstrate comparable efficacy in ameliorating T2DM, even when utilizing a gastric pouch of the same size and the same length of BL in OAGB.

Differential effects of bariatric surgery and caloric restriction on hepatic one-carbon and fatty acid metabolism

Weight loss interventions, including dietary changes, pharmacotherapy, or bariatric surgery, prevent many of the adverse consequences of obesity, and may also confer intervention-specific benefits beyond those seen with decreased weight alone. We compared the molecular effects of different interventions on liver metabolism to understand the mechanisms underlying these benefits. Male rats on a high-fat, high-sucrose diet underwent sleeve gastrectomy (SG) or intermittent fasting with caloric restriction (IF-CR), achieving equivalent weight loss. The interventions were compared to ad-libitum (AL)-fed controls. Analysis of liver and blood metabolome and transcriptome revealed distinct and sometimes contrasting metabolic effects between the two interventions. SG primarily influenced one-carbon metabolic pathways, whereas IF-CR increased de novo lipogenesis and glycogen storage. These findings suggest that the unique metabolic pathways affected by SG and IF-CR contribute to their distinct clinical benefits, with bariatric surgery potentially influencing long-lasting changes through its effect on one-carbon metabolism.

Severe Anemia in Sprague-Dawley Rats After Roux-en-Y Gastric Bypass Surgery

Roux-en-Y gastric bypass (RYGB) surgery is one of the most commonly performed bariatric procedures for weight loss in humans. However, this procedure is not risk-free, and patients may experience complications that include small bowel obstruction, gastrointestinal bleeding, chronic diarrhea, ulcers, malnutrition, and anemia. In particular, anemia is a recognized long-term complication and can be severe. Rats have been used as a model to study the effects of gastric bypass surgeries. They can experience similar complications as people, but the development of severe anemia has not previously been reported in rats. We observed 2 cases of severe anemia in female Sprague-Dawley rats after RYGB surgery. These cases prompted us to further investigate the frequency and severity of anemia after RYGB in rats. Blood work and necropsies were performed on 9 additional female Sprague-Dawley rats (5 with RYGB, 4 with sham surgery). In these 9 rats, only one had signs of clinical anemia. These 3 anemic rats displayed moderate to severe pallor of the eyes and ears. Necropsy findings in anemic RYGB rats included pale internal organs and eccentric heart enlargement, which led to a significantly higher heart:body weight ratio in RYGB rats as compared with sham controls. Anemic rats had either a macrocytic normochromic anemia, consistent with vitamin B12 or folate deficiency, or microcytic hypochromic anemia, indicative of iron deficiency. Researchers who perform RYGB surgery in rats should be aware of the potential complication of severe anemia. Plans for the diagnosis and management of this complication and the development of criteria for humane endpoints for severe anemia are recommended as a refinement to these studies.

Physical properties of food or bile redirection do not contribute to the intestinal adaptations after Roux-en-Y Gastric Bypass in rats

Objective

Metabolic and morphological adaptations of the intestine have been suggested to play a role in the various therapeutic benefits of Roux-en-Y Gastric Bypass (RYGB) surgery. However, the precise underlying mechanisms remain unclear. In this study, the effects of physical properties of ingested food and redirection of biliopancreatic secretions on intestinal remodeling were investigated in RYGB operated rats.

Methods

RYGB employing two different Roux Limb (RL) lengths was performed on high fat diet induced obese rats. Post-operatively, rats were fed either Solid or isocaloric Liquid diets. Metabolic and morphological remodeling of intestine was compared across both diet forms (Solid and Liquid diets) and surgical models (Short RL and Long RL).

Results

RYGB surgery in rats induced weight loss and improved glucose tolerance which was independent of physical properties of ingested food and biliopancreatic secretions. Intestinal glucose utilization after RYGB was not determined by either food form or biliopancreatic secretions. The GLUT-1 expression in RL was not influenced by physical properties of food. Furthermore, both physical properties of food and biliopancreatic secretions showed no effects on intestinal morphological adaptations after RYGB.

Conclusion

Results of this study demonstrate that physical properties of food and bile redirection are not major determinants of intestinal remodeling after RYGB in rats.

Effects of Whey Protein, Omega-3 Fatty Acid and Roux-En-Y Gastric Bypass on Body Weight, Biochemical Parameters and Organ Functions in an Obese Rat Model: Experimental Research

PURPOSE

Extreme obesity (EO) is one of the biggest public health problems in the world and has grown considerably over the years. The aim of the study is to examine the effect of Roux-en-Y gastric bypass (RYGB), whey protein (WP), and omega-3 polyunsaturated fatty acid (PUFA) supplementation applied to EO rats on weight loss, histopathological changes in internal organs and biochemical alterations.

MATERIALS AND METHODS

Wistar albino female rats (n = 28) were used in the study and randomly divided into four groups. All rats were made obese by adding high fructose corn syrup (HFCS) to their drinking water. After the EO, WP and omega-3 PUFA supplementation was given and RYGB process was applied. At the end of the study, glucose, total cholesterol, HDL, VLDL, AST, ALT and uric acid changes and liver, kidney and pancreatic tissues were evaluated histopathologically.

RESULTS

WP and omega-3 PUFA supplementation decreased body weight (p > 0.05). Omega-3 PUFA and RYGB caused a decrease in total cholesterol (p < 0.05), WP decreased HDL (p < 0.05), WP and omega-3 PUFA caused an increase in ALT (p < 0.05). WP has been shown to have greater curative effects in rat liver and kidney tissues. It has been determined that RYGB causes necrosis in the liver and HFCS causes inflammation in the kidney.

CONCLUSION

In the study; the positive effects of WP, omega-3 PUFA and bariatric surgery on obesity and dyslipidemia have been demonstrated. With this result, it was determined that WP, omega-3 PUFA supplementation and bariatric surgery were not superior to each other.

Sleeve Gastrectomy Improves Hepatic Glucose Metabolism by Downregulating FBXO2 and Activating the PI3K-AKT Pathway

Type 2 diabetes mellitus (T2DM), a chronic metabolic disease, is a public health concern that seriously endangers human health. Sleeve gastrectomy (SG) can relieve T2DM by improving glucose homeostasis and enhancing insulin sensitivity. However, its specific underlying mechanism remains elusive. SG and sham surgery were performed on mice fed a high-fat diet (HFD) for 16 weeks. Lipid metabolism was evaluated via histology and serum lipid analysis. Glucose metabolism was evaluated using the oral glucose tolerance test (OGTT) and insulin tolerance test (ITT). Compared with the sham group, the SG group displayed a reduction in liver lipid accumulation and glucose intolerance, and western blot analysis revealed that the AMPK and PI3K-AKT pathways were activated. Furthermore, transcription and translation levels of FBXO2 were reduced after SG. After liver-specific overexpression of FBXO2, the improvement in glucose metabolism observed following SG was blunted; however, the remission of fatty liver was not influenced by the over expression of FBXO2. Our study explores the mechanism of SG in relieving T2DM, indicating that FBXO2 is a noninvasive therapeutic target that warrants further investigation.

Obesity aggravated hippocampal-dependent cognitive impairment after sleeve gastrectomy in C57/BL6J mice via SIRT1/CREB/BDNF pathway

Postoperative cognitive dysfunction (POCD) is characterized by cognitive impairments following anesthesia/surgery, but the role of obesity and the underlying mechanisms are not known. We investigated the impact of obesity on POCD. Eighty male C57BL/6 J mice were assigned randomly to two groups fed a normal chow diet (ND, n = 40) or a high-fat diet (HD, n = 40) for 20 weeks. Then, they were divided randomly into eight subgroups of 10: ND control (NDC), ND with surgery (NDS), HD control (HDC), HD with surgery (HDS); NDS + DMSO (NDS + DS), NDS + SRT1720 (NDS + SRT), HDS + DMSO (HDS + DS), and HDS + SRT1720 (HDS + SRT). Body weight, blood glucose level, and serum lipid levels were measured. Staining methods on liver tissues were used to determine hepatic steatosis. A POCD model was established by sleeve gastrectomy (SG) under isoflurane anesthesia. Cognitive function was assessed using the Morris water maze test (MWMT). Expression of sirtuin1 (SIRT1), phosphorylated cAMP-responsive element binding protein (p-CREB), CREB and brain-derived neurotrophic factor (BDNF) in the hippocampus were measured. High-fat diet-fed mice for 20 weeks could establish an obesity model with hyperlipidemia and hepatic steatosis. Cognitive impairment was significantly worse in the HDC and HDS groups than that in the NDC and NDS groups, respectively. Hippocampal expression of SIRT1, p-CREB, and BDNF in the HDS group was significantly lower than that of the HDC group. SRT1720 (SIRT1 activator) pretreatment could attenuate cognitive impairment by upregulating SIRT1 expression. These data suggest that obesity exacerbated postoperative hippocampal-dependent cognitive impairment via a SIRT1 pathway, and SRT1720 pretreatment could alleviate it.

The Association of lncRNA and mRNA Changes in Adipose Tissue with Improved Insulin Resistance in Type 2 Obese Diabetes Mellitus Rats after Roux-en-Y Gastric Bypass

Objective

Roux-en-Y gastric bypass (RYGB) has shown good effects in improving obesity and type II diabetes mellitus (T2DM), but the underlying mechanisms remain unclear. This study explored the changes of related lncRNAs, mRNAs, and signaling pathways in white adipose tissue of T2DM rats after RYGB based on RNA-Seq sequencing, with the aim to provide a theoretical basis for RYGB treatment.

Methods

T2DM rat models were established by continuous feeding with a high-fat diet and injection of streptozotocin (STZ), after which they underwent RYGB or sham surgery. After the surgery, their body weight was measured weekly. Their fasting blood glucose (FBG) and fasting serum insulin (FSI) were also measured. A homeostasis model assessment of insulin resistance (HOMA-IR) was calculated at weeks 0, 8, and 12. Besides, white adipose tissue of T2DM rats was collected for RNA-Seq sequencing and validated by qRT-PCR. A series of bioinformatics analyses, such as differential expression genes (DEGs) screening, was performed. GO and KEGG functional enrichment analysis and protein-protein interaction (PPI) network construction were conducted based on the sequencing data.

Results

RYGB surgery could significantly inhibit the weight growth rate and decrease the FBG, FSI, and HOMA-IR of T2DM rats. Bioinformatics analysis of RNA sequencing (RNA-Seq) results revealed that 87 DE- lncRNAs (49 upregulated and 38 downregulated) and 1,824 DEGs (896 upregulated and 928 downregulated) were present in between the RYGB group and Sham group. GO and KEGG analysis showed that the target genes of DEGs and differentially expressed lncRNAs (DE-lncRNAs) were mainly associated with amino acid metabolism, fatty acid metabolism, channel activity, and other processes. In addition, the PPI network diagram also displayed that genes such as Fasn, Grin3a, and Nog could be key genes playing a role after RYGB. qRT-PCR showed that the expression level of Grin3a in the RYGB group was significantly increased compared with the Sham group, while the expression of Fasn and Nog was significantly decreased, which was consistent with the sequencing results.

Conclusion

Using RNA-Seq sequencing, this study revealed the changes of related lncRNAs, mRNAs, and signaling pathways in the white adipose tissue of T2DM rats after RYGB and identified Fasn, Grin3a, and Nog as potential key genes to function after RYGB.

Sleeve Gastrectomy with Pyloroplasty in Wistar Rats: Assessment of Gastric Emptying, Intestinal Transit, and Possible Duodenogastric Alkaline Reflux

BACKGROUND

Studies indicate sleeve gastrectomy (SG) as a factor of aggravation or even emergence of symptoms of gastroesophageal reflux disease. Accelerated gastric emptying is described as a mitigating factor. SG may be potentiated by adding a pyloroplasty, although with the potential risk of resulting in duodenogastric alkaline reflux. The objective was to standardize sleeve gastrectomy with pyloroplasty in rats, analyze the complementation in terms of mortality and weight evolution, and conduct assessments on gastric emptying, intestinal transit, and genesis of possible duodenogastric reflux.

METHODS

Ninety-three male Wistar rats were divided into a pilot study (standardization of the surgical technique and the scintigraphic study), and the main study. They were then subdivided into the SHAM group, the sleeve gastrectomy (SG) group, and the sleeve gastrectomy with pyloroplasty (SGP) group. After 3 months, the animals were submitted to two scintigraphic experiments and histological analysis of gastric biopsies.

RESULTS

The surgical groups (SG and SGP) lost initially more weight than the SHAM group, and the gastric emptying and intestinal transit in the first were more accelerated. However, no difference was found between the SG and SGP groups. Scintigraphic and histological analyses did not reveal statistical differences among the SG and SGP groups regarding gastroesophageal and duodenogastric refluxes.

CONCLUSIONS

Pyloroplasty did not affect weight reduction or increase duodenogastric reflux, after three postoperative months in this animal model of sleeve gastrectomy.

Generation and characterization of a mouse model for one anastomosis gastric bypass surgery

One anastomosis gastric bypass (OAGB) surgery became a common bariatric procedure in recent years. In this surgery, the distal stomach, duodenum, and proximal jejunum are bypassed, leading to weight loss, improvement in metabolic parameters, and a change in hormonal secretion. We sought to generate and characterize a mouse model for OAGB. Mice fed for 26 wk on a high-fat diet were assigned to OAGB, sham surgery, or caloric restriction and were followed for 50 more days on a high-fat diet. Physiological and histological parameters of the mice were compared during and at the end of the experiment. OAGB-operated mice lost weight and displayed low levels of plasma lipids, high insulin sensitivity, and rapid glucose metabolism compared with sham-operated mice. OAGB-operated mice had higher energy expenditure, higher levels of glucagon-like peptide (GLP-1), and lower albumin than weight-matched calorie-restricted mice. There was no difference in the histology of the endocrine pancreas. The livers of OAGB mice had little hepatic steatosis yet presented with a large number of phagocytic cells. The OAGB mouse model recapitulates many of the phenotypes described in patients that underwent OAGB and enables molecular and physiological studies on the outcome of this surgery.NEW & NOTEWORTHY A mouse model for one anastomosis gastric bypass (OAGB) surgery displays similar outcomes to clinical reports and enables to study the weight loss-dependent and -independent effects of this bariatric surgery.

Early Postoperative Exposure to High-Fat Diet Does Not Increase Long-Term Weight Loss or Fat Avoidance After Roux-en-Y Gastric Bypass in Rats

Background

Bariatric surgery alters food preferences in rats and reportedly decreases desire to consume high-fat high-sugar food in humans. The aim of this study was to investigate whether early post-operative exposure to high-fat food could increase body weight loss after Roux-en-Y gastric bypass (RYGB) by triggering fat avoidance.

Methods

Male Wistar rats underwent either RYGB (n = 15) or sham-operations (n = 16). Preoperatively a standardized 4-choice cafeteria diet [dietary options: low-fat/low-sugar (LFLS), low-fat/high-sugar (LFHS), high-fat/low-sugar (HFLS), high-fat/high-sugar (HFHS)] was offered. First, each option was available for 4 days, thereafter rats were offered the 4 options simultaneously for 3 days preoperatively. Post-surgery, 8 rats in the RYGB- and 8 in the sham-group were exposed to a high-fat content diet (Oatmeal + 30% lard, OM+L) for 10 days, while 7 RYGB rats and 8 sham-rats received OM alone. From the 11th postoperative day, the 4-choice cafeteria diet was reintroduced for 55-days. The intake of all available food items, macronutrients and body weight changes were monitored over 8 weeks. Main outcomes were long-term body-weight and daily change in relative caloric intake during the postoperative cafeteria period compared to the preoperative cafeteria.

Results

During the first 12 days of postoperative cafeteria access, RYGB-rats exposed to OM+L had a higher mean caloric intake per day than RYGB rats exposed to OM alone (Δ10 kCal, P_adj = 0.004), but this difference between the RYGB groups disappeared thereafter. Consequently, in the last 33 days of the postoperative cafeteria diet, the mean body weight of the RYGB+OM+L group was higher compared to RYGB+OM (Δ51 g, P_adj < 0.001). RYGB rats, independently from the nutritional intervention, presented a progressive decrease in daily consumption of calories from fat and increased their daily energy intake mainly from non-sugar carbohydrates. No such differences were detected in sham-operated controls exposed to low- or high fat postoperative interventions.

Conclusion

A progressive decrease in daily fat intake over time was observed after RYGB, independently from the nutritional intervention. This finding confirms that macronutrient preferences undergo progressive changes over time after RYGB and supports the role of ingestive adaptation and learning. Early postoperative exposure to high-fat food failed to accentuate fat avoidance and did not lead to superior weight loss in the long-term.

Rewiring of the Liver Transcriptome across Multiple Time-Scales Is Associated with the Weight Loss-Independent Resolution of NAFLD Following RYGB

Roux-en-Y gastric bypass (RYGB) surgery potently improves obesity and a myriad of obesity-associated co-morbidities including type 2 diabetes and non-alcoholic fatty liver disease (NAFLD). Time-series omics data are increasingly being utilized to provide insight into the mechanistic underpinnings that correspond to metabolic adaptations in RYGB. However, the conventional computational biology methods used to interpret these temporal multi-dimensional datasets have been generally limited to pathway enrichment analysis (PEA) of isolated pair-wise comparisons based on either experimental condition or time point, neither of which adequately capture responses to perturbations that span multiple time scales. To address this, we have developed a novel graph network-based analysis workflow designed to identify modules enriched with biomolecules that share common dynamic profiles, where the network is constructed from all known biological interactions available through the Kyoto Encyclopedia of Genes and Genomes (KEGG) resource. This methodology was applied to time-series RNAseq transcriptomics data collected on rodent liver samples following RYGB, and those of sham-operated and weight-matched control groups, to elucidate the molecular pathways involved in the improvement of as NAFLD. We report several network modules exhibiting a statistically significant enrichment of genes whose expression trends capture acute-phase as well as long term physiological responses to RYGB in a single analysis. Of note, we found the HIF1 and P53 signaling cascades to be associated with the immediate and the long-term response to RYGB, respectively. The discovery of less intuitive network modules that may have gone overlooked with conventional PEA techniques provides a framework for identifying novel drug targets for NAFLD and other metabolic syndrome co-morbidities.

Rise in Postprandial GLP-1 Levels After Roux-en-Y Gastric Bypass: Involvement of the Vagus Nerve-Spleen Anti-inflammatory Axis in Type 2 Diabetic Rats

PURPOSE

The mechanism underlying postprandial glucagon-like peptide-1 (GLP-1) changes after metabolic surgery remains mostly unclarified. This investigation aimed to address whether the vagus nerve-spleen anti-inflammatory axis is involved in the rise in postprandial GLP-1 levels in type 2 diabetes mellitus (T2DM) rats following metabolic surgery.

MATERIALS AND METHODS

T2DM rat model was established with a high-fat diet and a low dose of streptozotocin and subjected to Roux-en-Y gastric bypass (RYGB) and splenic denervation. A mixed-meal tolerance test for postprandial GLP-1 response was performed. TNF-α in the plasma, spleen, and ileum was measured by ELISA, and alpha 7 nicotinic acetylcholine receptor (α7nAChR) expression in the spleen was analyzed by Western blot.

RESULTS

Postprandial GLP-1 improvement by RYGB was accompanied by the reduction of TNF-α levels in spleen and ileum and up-regulation of splenic α7nAChR in T2DM rats. Splenic denervation abrogates a rise in postprandial GLP-1 levels in response to the mixed-meal challenge, along with higher TNF-α levels in spleen and ileum and down-regulation of splenicα7nAChR, compared with denervated sham rats.

CONCLUSION

Our results reveal that the vagus nerve-spleen anti-inflammatory axis mediates the rise of postprandial GLP-1 response after RYGB through lowering TNF-α contents in the intestinal tissue in T2DM rats.

Sleeve gastrectomy attenuated diabetes-related cognitive decline in diabetic rats

OBJECTIVE

To investigate the effects of sleeve gastrectomy (SG) on diabetes-related cognitive decline (DCD) in rats with diabetic mellitus (DM).

METHODS AND METHODS

Forty Wistar rats were randomly divided into control (CON) group (n=10), diabetes mellitus (DM) group (n=10), sham operation (SHAM) group (n=10) and SG group (n=10). DM model was established by high-fat diet (HFD) combined with intraperitoneal injection of streptozocin (STZ). Behavioral evaluation was given using Morris water maze test and Y-maze. In addition, PET-CT, TUNEL assay, histological analysis, transmission electron microscopy (TEM), immunohistochemistry (IHC) and Western blot analysis were used to evaluate the alleviating effects and potential mechanisms of SG on DCD in DM rats.

RESULTS

Compared with the sham group, SG induced significant improvement in the metabolic indices such as blood glucose and body weight. Besides, it could attenuate the insulin resistance compared with SHAM group. In addition, SG could improve the cognitive function of DM rats, which were featured by significant decrease in the escape latency (P<0.05), and significant increase in the time in target quadrant and platform crossings (P<0.05) compared with the SHAM group. SG induced significant elevation in the spontaneous alternation compared with SHAM group (P<0.05). Moreover, SG could improve the arrangement and biosynthesis of hippocampus neuron. Moreover, SG triggered the inhibition of apoptosis of hippocampus neurons, and Western blot analysis showed SG induced significant increase in the ratios of Bcl-2/Bax and Caspase3/cleaved Caspase 3. TEM demonstrated SG could significantly improve the microstructure of hippocampus neurons compared with the SHAM group. Western blot and IHC confirmed the significant decrease in the phosphorylation of tau at Ser404 and Ser396 sites in the SG group. Furthermore, SG activated the PI3K signaling pathway by elevating the phosphorylation of PI3K and Akt and GSK3β compared with the SHAM group.

CONCLUSION

SG attenuated the DCD in DM rats, which may be related to the activation of PI3K signaling pathway.

Sleeve Gastrectomy Ameliorates Diabetes-Induced Cardiac Hypertrophy Correlates With the MAPK Signaling Pathway

Background: Cardiac hypertrophy as a main pathological manifestation of diabetic cardiomyopathy (DCM), is a significant complication of diabetes. Bariatric surgery has been proven to relieve DCM; however, whether it can alleviate diabetes-induced cardiac hypertrophy is undefined.

Methods: Diabetic and obese rats were performed sleeve gastrectomy (SG) after having diabetes for 16weeks. The rats were euthanized 8weeks after SG. Metabolic parameters, heart function parameters, myocardial glucose uptake, morphometric and histological changes, and the expression level of mitogen-activated protein kinases (MAPKs) were determined and compared among the control group (CON group), diabetes mellitus group (DM group), sham operation group (SHAM group), and SG group.

Results: Compared with the SHAM group, the blood glucose, body weight, insulin resistance, and other metabolic parameters were significantly improved in the SG group. There was also a marked improvement in myocardial morphometric and histological parameters after SG. Furthermore, the myocardial glucose uptake and heart function were reversed after SG. Additionally, the phosphorylation of MAPKs was inhibited after SG, including p38 MAPKs, c-Jun N-terminal kinases (JNKs), and extracellular signal-regulated kinases 1/2 (ERK1/2). The expression of DUSP6, which dephosphorylates ERK1/2, was upregulated after SG. These findings suggest that SG ameliorated diabetes-induced cardiac hypertrophy correlates with the MAPK signaling pathway.

Conclusion: These results showed that diabetes-induced cardiac hypertrophy was ameliorated after SG was closely related to the inhibition of the MAPK signaling pathway and upregulation of DUSP6. Therefore, this study provides a novel strategy for treating diabetes-induced cardiac hypertrophy.

Reducing NADPH Synthesis Counteracts Diabetic Nephropathy through Restoration of AMPK Activity in Type 1 Diabetic Rats

Diabetic nephropathy (DN) is a major complication of diabetes mellitus and a primary cause of end-stage renal failure. Clinical studies indicate that metabolic surgery improves DN; however, the mechanism remains unclear. Here, we report that Roux-en-Y Gastric Bypass (RYGB) surgery significantly blocked and reversed DN without affecting the insulin signaling pathway. This protective role of RYGB surgery is almost blocked by either inhibition or knockout of 5'AMP-activated protein kinase (AMPK) in podocytes. Furthermore, mRNA microarray data reveal that RYGB surgery obviously reduced the gene expression involved in nicotinamide adenine dinucleotide phosphate (NAPDH) synthesis. The expression of a key NADPH synthase, hexose-6-phosphate dehydrogenase (H6PD), was inhibited by the low plasma corticosterone level after surgery. In addition, blocking NAPDH synthesis by knocking down H6PD mimicked the beneficial role of RYGB surgery through activation of AMPK in podocytes. Therefore, this study demonstrates that reducing NADPH production is critical for renal AMPK activation in response to RYGB surgery.

Designing Relevant Preclinical Rodent Models for Studying Links Between Nutrition, Obesity, Metabolism, and Cancer

Diet and nutrition are intricately related to cancer prevention, growth, and treatment response. Preclinical rodent models are a cornerstone to biomedical research and remain instrumental in our understanding of the relationship between cancer and diet and in the development of effective therapeutics. However, the success rate of translating promising findings from the bench to the bedside is suboptimal. Well-designed rodent models will be crucial to improving the impact basic science has on clinical treatment options. This review discusses essential experimental factors to consider when designing a preclinical cancer model with an emphasis on incorporating these models into studies interrogating diet, nutrition, and metabolism. The aims of this review are to (a) provide insight into relevant considerations when designing cancer models for obesity, nutrition, and metabolism research; (b) identify common pitfalls when selecting a rodent model; and (c) discuss strengths and limitations of available preclinical models. Expected final online publication date for the Annual Review of Nutrition, Volume 41 is September 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Effect of oligofructose on resistance to postoperative high-fat diet-induced damage of metabolism in diabetic rats after sleeve gastrectomy

BACKGROUND

Sleeve gastrectomy (SG) can induce prominent remission of type 2 diabetes mellitus. However, the long-term remission rate of diabetes usually decreases over time. Oligofructose has been verified to modulate host metabolism. The aim of this study was to explore the protective effect of oligofructose on high-fat diet (HFD)-induced metabolic dysfunction after SG.

AIM

To study the effect and mechanism of oligofructose on diabetic remission in diabetic rats after SG.

METHODS

SG and SHAM operation were performed on diabetes rats induced with an HFD, nicotinamide, and low-dose streptozotocin. Then the rats in the SHAM and SG groups were continuously provided with the HFD, and the rats in sleeve gastrectomy-oligofructose group were provided with a specific HFD containing 10% oligofructose. Body weight, calorie intake, oral glucose tolerance test, homeostasis model assessment of insulin resistance, lipid profile, serum insulin, glucagon-like peptide 1 (GLP-1), total bile acids, lipopolysaccharide (LPS), and colonic microbiota levels were determined and compared at the designated time points. All statistical analyses were performed using Statistic Package for Social Science version 19.0 (IBM, United States), and the statistically significant difference was considered at P < 0.05.

RESULTS

At 2 wk after surgery, rats that underwent SG exhibited improved indexes of glucose and lipid metabolism. Compared with the SG group, the rats from SG-oligofructose group exhibited better parameters of glucose and lipid metabolism, lower body weight (526.86 ± 21.51 vs 469.25 ± 21.84, P < 0.001), calorie intake (152.14 ± 9.48 vs 129.63 ± 8.99, P < 0.001), homeostasis model assessment of insulin resistance (4.32 ± 0.57 vs 3.46 ± 0.52, P < 0.05), and LPS levels (0.19 ± 0.01 vs 0.16 ± 0.01, P < 0.05), and higher levels of insulin (1.17 ± 0.17 vs 1.58 ± 0.16, P < 0.001) and GLP-1 (12.39 ± 1.67 vs 14.94 ± 1.86, P < 0.001), and relative abundances of Bifidobacterium (0.0034 ± 0.0014 vs 0.0343 ± 0.0064, P < 0.001), Lactobacillus (0.0161 ± 0.0037 vs 0.0357 ± 0.0047, P < 0.001), and Akkermansia muciniphila (0.0050 ± 0.0024 vs 0.0507 ± 0.0100, P < 0.001) at the end of the study. However, no difference in total bile acids levels was observed between the two groups.

CONCLUSION

Oligofructose partially prevents HFD-induced glucose and lipid metabolism damage after SG, which may be due to the changes of calorie intake, insulin, GLP-1, LPS, and the gut microbiota in rats.

Adiponectin/SIRT1 Axis Induces White Adipose Browning After Vertical Sleeve Gastrectomy of Obese Rats with Type 2 Diabetes

PURPOSE

White adipose tissue (WAT) browning plays a crucial role in energy metabolism. However, it remains unclear whether WAT browning is involved in the adipose reduction following sleeve gastrectomy (SG). Adiponectin is upregulated after Roux-en-Y gastric bypass surgery. The role of adiponectin in SG was further investigated in the current study.

MATERIALS AND METHODS

Diabetic Sprague Dawley rats were randomly divided into control, sham + libitum, sham + food restriction, and sleeve groups. Browning markers, including uncoupling protein 1 (UCP1), peroxisome proliferator-activated receptor (PPAR) γ, and PPARγ coactivator-1 alpha (PGC-1α), were examined 4 weeks after the operation.

RESULTS

UCP1, PPARγ, and PGC-1α expression were significantly higher in the sleeve group compared to the other study groups. The adipose tissue of the sleeve group exhibited tissue weight loss and additional morphological browning features. In addition, adiponectin expression in the sleeve group was significantly increased. Adiponectin upregulated the expression of the browning genes and sirtuin 1 (SIRT1) in 3T3-L1 adipocytes. SIRT1 could increase the WAT browning levels, revealing that adiponectin induced the browning process via the upregulation of SIRT1. Furthermore, SIRT1 represented a positive regulatory feedback loop for adiponectin. SIRT1 activated adenosine monophosphate-activated protein kinase (AMPK), which can mediate WAT browning. Inhibition of the AMPK signaling pathway by dorsomorphin decreased UCP1, PPARγ, and PGC-1α expression. However, additional studies are needed to understand the relationship between adiponectin and glucose homeostasis.

CONCLUSIONS

Sleeve gastrectomy increased adiponectin levels, which in turn upregulated SIRT1. Thus, SIRT1 may function as an endocrine signal to mediate WAT browning.

Alterations of Serum Uric Acid Level and Gut Microbiota After Roux-en-Y Gastric Bypass and Sleeve Gastrectomy in a Hyperuricemic Rat Model

Background

The objective of this study was to observe alterations of serum uric acid (SUA) level and gut microbiota after Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG) surgery in a hyperuricemic rat model.

Method

We performed Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG) surgery in a hyperuricemic rat model. Serum uric acid (UA), xanthine oxidase (XO) activity, IL-6, TNF-α and lipopolysaccharide (LPS) level changes, and 16S rDNA of gut microbiota were analyzed.

Results

After the surgery, the RYGB and SG procedures significantly reduced body weight, serum UA, IL-6, TNF-α and LPS levels, and XO activity. In addition, the RYGB and SG procedures altered the diversity and taxonomic composition of the gut microbiota. Compared with Sham group, RYGB and SG procedures were enriched in the abundance of phylum Verrucomicrobia and species Akkermansia muciniphila, while the species Escherichia coli was reduced.

Discussion

We here concluded that bariatric surgery-induced weight loss and resolution of inflammatory remarkers as well as changes of gut microbiota may be responsible for the reduced XO activity and SUA level. To have a better understanding of the underlying mechanism of UA metabolism following bariatric surgery, further research is needed.

Gastric Bypass Increases Circulating Bile Acids and Activates Hepatic Farnesoid X Receptor (FXR) but Requires Intact Peroxisome Proliferator Activator Receptor Alpha (PPARα) Signaling to Significantly Reduce Liver Fat Content

BACKGROUND

We interrogate effects of gastric bypass (RYGB), compared with a low-calorie diet, on bile acid (BA), liver fat, and FXR, PPARα, and targets in rats with obesity and non-alcoholic fatty liver disease (NAFLD).

METHODS

Male Wistar rats received a high-fat diet (obese/NAFLD, n=24) or standard chow (lean, n=8) for 12 weeks. Obese/NAFLD rats had RYGB (n=11), sham operation pair-fed to RYGB (pair-fed sham, n=8), or sham operation (sham, n=5). Lean rats had sham operation (lean sham, n=8). Post-operatively, five RYGB rats received PPARα antagonist GW6417. Sacrifice occurred at 7 weeks. We measured weight changes, fasting total plasma BA, and liver % steatosis, triglycerides, and mRNA expression of the nuclear receptors FXR, PPARα, and their targets SHP and CPT-I.

RESULTS

At sacrifice, obese sham was heavier (p<0.01) than all other groups that had lost similar weight loss. Obese sham had lower BA levels and lower hepatic FXR, SHP, and CPT-I mRNA expression than lean sham (P<0.05, for all comparisons). RYGB had increased BA levels compared with obese and pair-fed sham (P<0.05, for both), while pair-fed sham had BA levels, similar to obese sham. Compared with pair-fed sham, RYGB animals had increased liver FXR and PPARα expression and signaling (P<0.05). Percentage of steatosis was lower in RYGB and lean sham, relative to obese and pair-fed sham (P<0.05, for all comparisons). PPARα inhibition after RYGB resulted in similar weight loss but higher liver triglyceride content (P=0.01) compared with RYGB alone.

CONCLUSIONS

RYGB led to greater liver fat loss than low-calorie diet, an effect associated to increased fasting BA levels and increased expression of modulators of liver fat oxidation, FXR, and PPARα. However, intact PPARα signaling was necessary for resolution of NAFLD after RYGB.

Clostridium butyricum Alleviates Gut Microbiota Alteration-Induced Bone Loss after Bariatric Surgery by Promoting Bone Autophagy

Bariatric surgery is the most common and effective treatment of severe obesity; however, these bariatric procedures always result in detrimental effects on bone metabolism by underlying mechanisms. This study aims to investigate the skeletal response to bariatric surgery and to explore whether Clostridium butyricum alleviates gut microbiota alteration-induced bone loss after bariatric surgery. Consequently, male SD rats received Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG) surgery, respectively, followed by body weight recording. The bone loss after bariatric surgery was further determined by dual-energy X-ray absorptiometry (DXA), micro-CT measurement, histologic analyses, and Western blot. Besides, 16S rDNA gene sequencing was performed to determine the gut microbiota alteration after surgery, and intervention with fecal microbiota from RYGB donor was conducted in obese SD rats, followed by C. butyricum administration. Accordingly, rats in the RYGB and SG groups maintained sustained weight loss, and DXA and micro-CT measurement further demonstrated significant bone loss after bariatric surgery. Besides, histologic and Western blot analyses validated enhanced osteoclastogenesis and inhibited osteoblastogenesis and defective autophagy after surgery. The 16S rDNA gene sequencing suggested a significant alteration of gut microbiota composition in the RYGB group, and intervention with fecal microbiota from RYGB donor further determined that this kind of alteration contributed to the bone loss after RYGB. Meanwhile, C. butyricum might protect against this postoperative bone loss by promoting osteoblast autophagy. In summary, this study suggests novel mechanisms to clarify the skeletal response to bariatric surgery and provides a potential candidate for the treatment of bone disorder among bariatric patients. SIGNIFICANCE STATEMENT: The significance of this study is the discovery of obvious bone loss and defective autophagy after bariatric surgery. Besides, it is revealed that gut microbiota alterations could be the reason for impaired bone mass after bariatric surgery. Furthermore, Clostridium butyricum could alleviate the gut microbiota alteration-induced bone loss after bariatric surgery by promoting osteoblast autophagy.

Sleeve Gastrectomy Ameliorates Diabetes-Related Spleen Damage by Improving Oxidative Stress Status in Diabetic Obese Rats

PURPOSE

Oxidative stress and inflammation are important pathogenic mediators in diabetes-related organ damage. Accumulating evidence suggests that immunodeficiency in diabetes is associated with diabetes-induced spleen damage. Sleeve gastrectomy (SG) has been proved to improve diabetes and its multiple associated complications. However, the ameliorative role of SG against spleen damage in diabetes has not been investigated.

MATERIALS AND METHODS

Animal model of diabetic obese rats induced by high-fat diet (HFD) combined with streptozotocin (STZ) was treated with sham operation, caloric restriction, and SG. Metabolic parameters were measured, and the morphological and histopathological changes, status of oxidative stress, and levels of inflammatory factors were evaluated.

RESULTS

SG reduced body weight and improved glucose tolerance and insulin sensitivity in diabetic obese rats. SG significantly reversed splenic atrophy and alleviated abnormalities of white and red pulp. Additionally, SG also reversed the increased splenocyte apoptosis (P < 0.001). Meanwhile, indicators of oxidative stress including reactive oxygen species (ROS), nitric oxide (NO), malondialdehyde (MDA), and protein carbonylation were reduced, and the activity and expression of antioxidant enzymes including SOD and CAT were improved after SG. The mRNA expression of inflammatory factors in SG groups such as TNF-α (P < 0.001), IL-6 (P < 0.001), MCP-1 (P < 0.01), and ICAM-1 (P < 0.001) was also significantly reduced.

CONCLUSION

SG ameliorates diabetes-related splenic injury by restoring the balance between oxidative stress process and antioxidant defense systems as well as reducing inflammation in the spleen. These findings indicate that SG is an appropriate therapeutic strategy for diabetes-related spleen damage.

Effect of Sleeve Gastrectomy on Glycometabolism via Forkhead Box O1 (FoxO1)/Lipocalin-2 (LCN2) Pathway

BACKGROUND The mechanism by which sleeve gastrectomy (SG) improves glycometabolism has remained unclear so far. Increasing evidence has demonstrated that bone is a regulator of glucose metabolism, and osteoblast-derived forkhead box O1 (FoxO1) and lipocalin-2 (LCN2) are regulators of energy metabolism. The aim of this study was to investigate whether the FOXO1/LCN2 signaling pathway is involved in the anti-diabetic effect of SG. MATERIAL AND METHODS Insulin resistance was induced in Wistar rats, which were then intraperitoneally injected with streptozotocin to induce a type 2 diabetic state. Levels of fasting blood glucose, serum insulin, HbA1c, and LCN2 were analyzed at corresponding time points after SG and sham surgeries. The expressions of FOXO1, LCN2, and the melanocortin 4 receptor (MC4R) in bone and hypothalamus were detected by immunofluorescence. FOXO1 siRNA was applied to downregulate FOXO1 expression in osteoblasts of rats. The influence of FOXO1 gene on expression of LCN2 was investigated in cultured osteoblasts by western blot and PCR. RESULTS Glucose metabolism in the SG group was significantly improved. The LCN2 expression in bone in the SG group was higher than that in the sham group, whereas FOXO1 expression in the SG group was lower than that in the sham group. The binding rate of LCN2 and MC4R in the hypothalamus was also higher in the SG group compared with that in the sham group. The downregulation of FOXO1 expression in osteoblasts was accompanied by upregulation of LCN2 expression. CONCLUSIONS These results suggest that the FOXO1/LCN2 signaling pathway participates in the anti-diabetic effect of SG.

Surgical Mouse Models of Vertical Sleeve Gastrectomy and Roux-en Y Gastric Bypass: a Review

Reviewed here are multiple mouse models of vertical sleeve gastrectomy (VSG) and Roux-en Y gastric bypass (RYGB) that have emerged over the past decade. These models use diverse approaches to both operative and perioperative procedures. Scrutinizing the benefits and pitfalls of each surgical model and what to expect in terms of post-operative outcomes will enhance our assessment of studies using mouse models, as well as advance our understanding of their translational potential. Two mouse models of bariatric surgery, VSG-lembert and RYGB-small pouch, demonstrate low mortality and most closely recapitulate the human forms of surgery. The use of liquid diets can be minimized, and in mice, RYGB demonstrates more reliable and longer lasting effects on weight loss compared to that of VSG.

Effect of Sleeve Gastrectomy on Bone Metabolism and Serum 5-Hydroxytryptamine in Obese Rats

BACKGROUND Studies have shown that bariatric surgery, such as sleeve gastrectomy (SG), has an adverse effect on bone, including decreased bone mineral density (BMD) and bone metabolism. Peripheral 5-hydroxytryptamine (5-HT) has an adverse regulatory effect on bone formation. Here, we assessed changes in bone metabolism and whether 5-HT is involved in the effect of SG on bone metabolism. MATERIAL AND METHODS A rat model of obesity was established using Wistar rats. After successful modeling, rats were randomly assigned to 2 groups - the SG group and the Sham group - with 10 rats in each group. We then performed sleeve gastrectomy or sham operation. Bone metabolic markers and BMD of rats were measured at 2 and 16 weeks after the operation and the level of 5-HT in serum was determined. Rats were killed at 16 weeks after the operation, and bones of the hind limbs were harvested to measure 5-HT by immunofluorescence. RESULTS BMD was decreased and bone metabolism demonstrated a trend of bone destruction in the rats after SG. A significantly increasing trend in the level of serum 5-HT was found, and bone immunofluorescence showed increased expression of 5-HT. CONCLUSIONS BMD was decrease and bone metabolism demonstrated a trend of bone destruction after SG. SG can affect the level of 5-HT in serum or bone tissue and the 5-HT may be involved in the process through which SG affects bone metabolism.

Hypoglycemia after Bariatric Surgery in Mice and Optimal Dosage and Efficacy of Glucose Supplementation

The Roux-en-Y Gastric Bypass (RYGB) mouse model is a vital tool for studying the pathophysiology of bariatric surgery and contributes greatly to research on obesity and diabetes. However, complications including postsurgical hypoglycemia can have profoundly negative effects. Unlike in humans, blood glucose (BG) is not typically managed in postoperative rodents, despite their critical role as translational models; without this management, rodents can experience hypoglycemia, potentially impairing wound healing, decreasing survivability, complicating interpretation of research data, and limiting translational utility. In this project, we sought to identify an optimal method for minimally invasive administration of dextrose in C57BL/6N (n = 16; 8 male, 8 female) mice. To do so, we characterized BG pharmacokinetic profiles after subcutaneous and oral-transmucosal (OTM) administration of dextrose. Compared with OTM dosage, the subcutaneous route provided more consistent and reliable delivery of glucose and did not cause significant adverse reactions. We then evaluated the frequency of hypoglycemic events after RYGB in C57BL/6N mice (n = 16; 8 male, 8 female) and the effects of subcutaneous dextrose supplementation on morbidity and mortality. BG measurement and behavioral pain assessment (grimace test) were performed for 3 d after surgery. Hypoglycemic (BG ≤ 60 mg/dL) animals were assigned to dose (5% dextrose SC) or no-dose treatment groups. Nearly all (87%) mice became hypoglycemic; 2 of these mice died. No significant intergroup difference in grimace score or mortality was detected. Overall, our results demonstrate that hypoglycemia is a frequent adverse event after RYGB in mice and that subcutaneous injection of dextrose is a safe and effective way to manage hypoglycemia. Further studies are necessary to optimize the intervention threshold and optimal dosage; regardless, we recommend glycemic management after RYGB surgery in mice.

Impact of sleeve gastrectomy and dietary change on metabolic and hepatic function in an obesity rat model - Experimental research

PURPOSE

Sleeve gastrectomy (SG) is an effective procedure to treat morbid obesity. SG induces remission of type 2 diabetes and metabolic syndrome and improves non-alcoholic fatty liver disease (NAFLD). However, it is imperative to clarify the extent to which these beneficial effects may be attributed to SG among other concomitant changes including postoperative diet. The current study addresses this question in a rodent model of obesity by subjecting it to SG, normal diet, or a combination of the two.

METHODS

Male Wistar-rats were fed with either high fat diet (HF, n = 32) or received chow diet (CD, n = 8). After 15 weeks, the HF-fed rats underwent either SG or sham operation, following which they were randomised to either continue HF or switched to CD for another 6 weeks. Body weight, fasting blood glucose level, blood pressure, and adipokine expression (leptin, adiponectin, MCP-1) in the adipose tissue along with triglycerides level in the blood serum were assessed to evaluate metabolic function. Hepatic function was assessed by histological evaluation of liver fibrosis (Hydroxyproline, Sirius Red) and reverse transcription polymerase chain reaction (RT-PCR) of the inflammation marker monocyte chemoattractant protein-1 (MCP-1).

RESULTS

Postoperative dietary change improved adipose tissue inflammation and arterial blood pressure regardless of the surgical intervention, while SG improved hyperglycaemia, blood triglyceride levels and, regardless of the postoperative diet, hepatic inflammation and fibrosis. However, combined administration of SG with post-operative normal diet was the most effective with regard to reducing the body weight.

CONCLUSION

HF for 15 weeks induced obesity with metabolic syndrome and NAFLD in rats. SG and dietary intervention improved metabolic state and NAFLD; however, their combination was significantly more effective.

Increased Energy Expenditure and Energy Loss Through Feces Contribute to the Long-Term Outcome of Roux-en-Y Gastric Bypass in a Diet-Induced Obese Mouse Model

BACKGROUND

Roux-en-Y gastric bypass (RYGB) has been proved to be more effective than other bariatric procedures in the long term on body-weight loss and remission of diabetes. However, the mechanism remains poorly understood. Long-term changes in energy metabolism after RYGB have rarely been reported.

OBJECTIVE

To investigate the long-term effects of RYGB on energy metabolism on a diet-induced obesity (DIO) mouse model.

METHODS

DIO mice fed a high-fat diet were assigned to two groups: RYGB (n=8) and sham (n=7), followed by high-fat diet feeding until 12 weeks after surgery. Body weight and food intake were recorded weekly. Measurement of body composition and energy metabolism by metabolic chamber were conducted at weeks 4, 8, and 12 after surgery. Fecal energy measurement, intraperitoneal glucose-tolerance tests, and insulin-tolerance tests were conducted at postoperative week 12.

RESULTS

Food intake was reduced in the RYGB group within the first 3 weeks after surgery and increased to the same as the sham group from postoperative week 4. At 12 weeks after surgery, body weight had reduced by 36%±3.2% in the RYGB group compared to a 16%±2% body-weight gain in the sham group, while fat mass had reduced significantly in the RYGB group compared to the sham group (9.2%±1.5% versus 30.1%±0.7%). Energy expenditure was significantly higher at postoperative week 8 in the RYGB group than the sham group. In comparison with the sham group, the respiratory exchange ratio was unchanged, decreased, and increased in the RYGB group at postoperative weeks 4, 8, and 12, respectively. Fecal energy measurement showed that feces from mice in the RYGB group contained higher energy levels than the sham group. Glucose metabolism had significantly improved in the RYGB group, in contrast to the sham group, demonstrated by intraperitoneal glucose tolerance tests (AUC 1,502±104 versus 2,277±198, respectively) and insulin tolerance tests (AUC 524±50 versus 838±63, respectively).

CONCLUSION

Increased energy expenditure and energy loss through feces contribute to long-term body-weight control after RYGB. Enhanced glucose utilization might play a role in long-term improvement in glucose metabolism.

Roux-en-Y Gastric Bypass in Obese Diabetic Rats Promotes Autophagy to Improve Lipid Metabolism through mTOR/p70S6K Signaling Pathway

PURPOSE

To investigate the effects of Roux-en-Y gastric bypass (RYGB) surgery on markers of liver mitochondrial dynamics and find new therapeutic basis on obese type 2 diabetes mellitus (T2DM) patients. Materials and Methods. Thirty-two rats were divided into nondiabetic group, diabetic group, sham group, and RYGB group. The Dual-energy X-ray absorptiometry (DEXA) was used to detect short-term curriculum vitae for rat body component and fat and lean mass. Hepatic lipid content and triglyceride levels were detected by Oil Red O staining. Western blotting was used to examine autophagy and mammalian target of rapamycin/P70S6 kinase (mTOR/p70S6K) pathway-related proteins. The carbon dioxide production from the oxidation of [¹⁴C] oleate was measured. Plasma glucose was measured by glucose oxidase assay. The insulin and C-peptide were detected. Triacylglyceride (TG) and free fat acid (FFA) in plasma were determined by enzymatic colorimetric assays.

RESULTS

RYGB improved metabolic parameters and enhanced plasma GLP-1 level, ameliorated the lipopexia, and increased insulin sensitivity in the liver; RYGB promoted the hepatic autophagy and inhibited the mTOR/p70S6K signaling pathway. GLP-1 reduced fat load and increased fatty acid β-oxidation by activated autophagy to regulate the hepatic lipid pathway through mTOR/p70S6K signaling pathway.

CONCLUSIONS

RYGB may reduce liver lipid toxicity and improve insulin sensitivity through activating the hepatic fat hydrolysis pathway and inhibiting the liver fat synthesis pathway. However, the transport pathway of liver fat does not play a key role.

Technical Feasibility of a Murine Model of Sleeve Gastrectomy with Ileal Transposition

BACKGROUND

Sleeve gastrectomy with ileal transposition has been shown to be superior to sleeve gastrectomy alone for promoting weight loss in rat and porcine models. The absence of a mouse model for this procedure has impeded efforts to understand the molecular physiology underlying its efficacy. This study demonstrates the long-term survivability of sleeve gastrectomy with ileal transposition in mice.

MATERIALS AND METHODS

In this study of technical feasibility, a sleeve gastrectomy with ileal transposition (SGIT), sleeve gastrectomy (SG), or sham surgery (SH) was performed on 7- to 8-week-old C57Bl/6J mice (n = 8 for each). To evaluate long-term survivability, mice were placed on an obesogenic diet and weighed weekly for 10 weeks. The intestinal identity of the transposed segment was assessed with gene expression analysis of duodenal-, jejunal-, and ileal-specific hormones using quantitative polymerase chain reaction.

RESULTS

Overall, SGIT better prevented weight gain than the SG or sham procedures (10-week post-operative weight: SH 45.3 ± 1.0 g, SG 41.25 ± 1.6 g, SGIT 35.4 ± 0.8 g). Gene expression pattern analysis of three markers of intestinal identity (gastrin, cholecystokinin, and peptide YY) suggests that the ileal identity of the transposed segment is maintained 10 weeks after transposition.

CONCLUSIONS

We demonstrate for the first time a reproducible mouse model of sleeve gastrectomy with ileal transposition. Future studies utilizing this model will expand our understanding of the molecular pathways through which the hindgut regulates satiety.

Role of ghrelin isoforms in the mitigation of hepatic inflammation, mitochondrial dysfunction, and endoplasmic reticulum stress after bariatric surgery in rats

BACKGROUND/OBJECTIVES

Bariatric surgery improves nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH), but the underlying mechanisms remain elusive. We evaluated the potential role of ghrelin isoforms in the amelioration of hepatic inflammation after sleeve gastrectomy and Roux-en-Y gastric bypass (RYGB).

SUBJECTS/METHODS

Plasma ghrelin isoforms were measured in male Wistar rats (n = 129) subjected to surgical (sham operation, sleeve gastrectomy, or RYGB) or dietary interventions [fed ad libitum a normal (ND) or a high-fat diet (HFD) or pair-fed diet]. The effect of acylated and desacyl ghrelin on markers of inflammation, mitochondrial dysfunction, and endoplasmic reticulum (ER) stress in primary rat hepatocytes under palmitate-induced lipotoxic conditions was assessed.

RESULTS

Plasma desacyl ghrelin was decreased after sleeve gastrectomy and RYGB, whereas the acylated/desacyl ghrelin ratio was augmented. Both surgeries diminished obesity-associated hepatic steatosis, CD68⁺- and apoptotic cells, proinflammatory JNK activation, and Crp, Tnf, and Il6 transcripts. Moreover, a postsurgical amelioration in the mitochondrial DNA content, oxidative phosphorylation (OXPHOS) complexes I and II, and ER stress markers was observed. Specifically, following bariatric surgery GRP78, spliced XBP-1, ATF4, and CHOP levels were reduced, as were phosphorylated eIF2α. Interestingly, acylated and desacyl ghrelin inhibited steatosis and inflammation of palmitate-treated hepatocytes in parallel to an upregulation of OXPHOS complexes II, III, and V, and a downregulation of ER stress transducers IRE1α, PERK, ATF6, their downstream effectors, ATF4 and CHOP, as well as chaperone GRP78.

CONCLUSIONS

Our data suggest that the increased relative acylated ghrelin levels after bariatric surgery might contribute to mitigate obesity-associated hepatic inflammation, mitochondrial dysfunction, and ER stress.

Body weight-dependent and independent improvement in lipid metabolism after Roux-en-Y gastric bypass in ApoE*3Leiden.CETP mice

BACKGROUND/OBJECTIVES

The incidence of obesity and metabolic syndrome (MetS) has rapidly increased worldwide. Roux-en-Y gastric bypass (RYGB) achieves long-term weight loss and improves MetS-associated comorbidities. Using a mouse model with a humanized lipoprotein metabolism, we elucidated whether improvements in lipid and glucose metabolism after RYGB surgery are body weight loss-dependent or not.

SUBJECTS/METHODS

Male ApoE*3Leiden.CETP (ApoE3L.CETP) mice fed Western type diet for 6 weeks underwent RYGB or Sham surgery. Sham groups were either fed ad libitum or were body weight-matched (BWm) to the RYGB mice to discriminate surgical effects from body weight loss-associated effects. Before and after surgery, plasma was collected to assess the metabolic profile, and glucose tolerance and insulin sensitivity were tested. Twenty days after surgery, mice were sacrificed, and liver was collected to assess metabolic, histological and global gene expression changes after surgery.

RESULTS

RYGB induced a marked reduction in body weight, which was also achieved by severe food restriction in BWm mice, and total fat mass compared to Sham ad libitum mice (Sham AL). Total cholesterol, non-high-density lipoprotein cholesterol (non-HDL-C) and ceramide were strongly reduced 20 days after surgery in RYGB compared to BWm mice. Glucose tolerance and insulin sensitivity improved 13 days after surgery similarly in RYGB and BWm mice. Liver histology confirmed lipid reduction in RYGB and BWm mice while the transcriptomics data indicated altered genes expression in lipid metabolism.

CONCLUSIONS

RYGB surgery improves glucose metabolism and greatly ameliorates lipid metabolism in part in a body weight-dependent manner. Given that ApoE3L.CETP mice were extensively studied to describe the MetS, and given that RYGB improved ceramide after surgery, our data confirmed the usefulness of ApoE3L.CETP mice after RYGB in deciphering the metabolic improvements to treat the MetS.

Fecal Microbial Transplantation and Its Potential Application in Cardiometabolic Syndrome

Newly revealed links between inflammation, obesity, and cardiometabolic syndrome have created opportunities to try previously unexplored therapeutic modalities in these common and life-risking disorders. One potential modulator of these complex disorders is the gut microbiome, which was described in recent years to be altered in patients suffering from features of cardiometabolic syndrome and to transmit cardiometabolic phenotypes upon transfer into germ-free mice. As a result, there is great interest in developing new modalities targeting the altered commensal bacteria as a means of treatment for cardiometabolic syndrome. Fecal microbiota transplantation (FMT) is one such modality in which a disease-associated microbiome is replaced by a healthy microbiome configuration. So far clinical use of FMT has been overwhelmingly successful in recurrent Clostridium difficile infection and is being extensively studied in other microbiome-associated pathologies such as cardiometabolic syndrome. This review will focus on the rationale, promises and challenges in FMT utilization in human disease. In particular, it will overview the role of the gut microbiota in cardiometabolic syndrome and the rationale, experience, and prospects of utilizing FMT treatment as a potential preventive and curative treatment of metabolic human disease.

A New Physiologic Mouse Model of One Anastomosis Gastric Bypass

BACKGROUND

One anastomosis gastric bypass (OAGB) is a modern metabolic operation that has been demonstrated to be a rapid, safe, and effective procedure. As for other bariatric operations, the mechanisms and long-term effects of this procedure remain largely unknown and are difficult to address in human studies. Here, we present a new physiologic mouse model for mechanistic and long-term investigations.

METHODS

Six-week-old C57Bl/6 mice were fed a high-fat diet for 12 weeks and scheduled for OAGB or sham operation. Mice were observed for 2 weeks after the operation, and weight and metabolic condition were monitored.

RESULTS

Six mice were used to adapt the surgical technique. Afterwards, another 7 mice were scheduled for OAGB without further complications. The newly established OAGB procedure resulted in significant weight loss and improvement of glucose metabolism 2 weeks after the operation.

CONCLUSIONS

The operation presented here is an easy-to-learn and physiologic mouse model of OAGB that can be used for further studies in mice.

Non-insulin determinant pathways maintain glucose homeostasis upon metabolic surgery

Insulin is critical for glucose homeostasis, and insulin deficiency or resistance leads to the development of diabetes. Recent evidence suggests that diabetes can be remitted independent of insulin. However, the underlying mechanism remains largely elusive. In this study, we utilized metabolic surgery as a tool to identify the non-insulin determinant mechanism. Here, we report that the most common metabolic surgery, Roux-en-Y gastric bypass (RYGB), reduced insulin production but persistently maintained euglycemia in healthy Sprague-Dawley (SD) rats and C57 mice. This reduction in insulin production was associated with RYGB-mediated inhibition of pancreatic preproinsulin and polypyrimidine tract-binding protein 1. In addition, RYGB also weakened insulin sensitivity that was evaluated by hyperinsulinemic-euglycemic clamp test and downregulated signaling pathways in insulin-sensitive tissues. The mechanistic evidence suggests that RYGB predominately shifted the metabolic profile from glucose utilization to fatty acid oxidation, enhanced the energy expenditure and activated multiple metabolic pathways through reducing gut energy uptake. Importantly, the unique effect of RYGB was extended to rats with islet disruption and patients with type 2 diabetes. These results demonstrate that compulsory rearrangement of the gastrointestinal tract can initiate non-insulin determinant pathways to maintain glucose homeostasis. Based on the principle of RYGB action, the development of a noninvasive intervention of the gastrointestinal tract is a promising therapeutic route to combat disorders characterized by energy metabolism dysregulation.

Establishing a successful rat model of duodenal- jejunal bypass: A detailed guide

Gastric bypass surgery, an operation that restricts the stomach and bypasses the duodenum and part of the jejunum, results in major improvement or remission of type 2 diabetes. Duodenual-jejunal bypass was developed by one of the authors (FR) as an experimental, stomach-sparing variant of gastric bypass surgery to investigate weight-independent mechanisms of surgical control of diabetes. Duodenual-jejunal bypass has been shown to improve various aspects of glucose homeostasis in rodents and in humans, thus providing an experimental model for investigating mechanisms of action of surgery and elusive aspects of gastrointestinal physiology. Performing duodenual-jejunal bypass in rodents, however, is associated with a steep learning curve. Here we report our experience with duodenual-jejunal bypass and provide practical tips for successful surgery in rats. Duodenual-jejunal bypass was performed on 50 lean rats as part of a study aimed at investigating the effect of the procedure on the physiologic mechanisms of glucose homeostasis. During the study, we have progressively refined details of anatomic exposure, technical aspects of duodeno-jejunostomy and peri-operative care. We analysed the role of such refinements in improving operative time and post-operative mortality. We found that refinement of exposure methods of the gastro-duodenal junction aimed at minimizing tension on small visceral vasculature, technical aspects of duodeno-jejunal anastomosis and peri-operative management played a major role in improving the survival rate and operative time. Overall, an experimental model of duodenual-jejunal bypass was successfully reproduced. Based on this experience, we describe here what we believe are the most important technical tips to reduce the learning curve for the procedure.

Takeda G Protein-Coupled Receptor 5-Mechanistic Target of Rapamycin Complex 1 Signaling Contributes to the Increment of Glucagon-Like Peptide-1 Production after Roux-en-Y Gastric Bypass

BACKGROUND

The mechanism by which Roux-en-Y Gastric Bypass (RYGB) increases the secretion of glucagon-like peptide-1 (GLP-1) remains incompletely defined. Here we investigated whether TGR5-mTORC1 signaling mediates the RYGB-induced alteration in GLP-1 production in mice and human beings.

METHODS

Circulating bile acids, TGR5-mTORC1 signaling, GLP-1 synthesis and secretion were determined in lean or obese male C57BL/6 mice with or without RYGB operation, as well as in normal glycemic subjects, obese patients with type 2 diabetes before and after RYGB.

RESULTS

Positive relationships were observed among circulating bile acids, ileal mechanistic target of rapamycin complex 1 (mTORC1) signaling and GLP-1 during changes in energy status in the present study. RYGB increased circulating bile acids, ileal Takeda G protein-coupled receptor 5 (TGR5) and mTORC1 signaling activity, as well as GLP-1 production in both mice and human subjects. Inhibition of ileal mTORC1 signaling by rapamycin significantly attenuated the stimulation of bile acid secretion, TGR5 expression and GLP-1 synthesis induced by RYGB in lean and diet-induced obese mice. GLP-1 production and ileal TGR5-mTORC1 signaling were positively correlated with plasma deoxycholic acid (DCA) in mice. Treatment of STC-1 cells with DCA stimulated the production of GLP-1. This effect was associated with a significant enhancement of TGR5-mTORC1 signaling. siRNA knockdown of mTORC1 or TGR5 abolished the enhancement of GLP-1 synthesis induced by DCA. DCA increased interaction between mTOR-regulatory-associated protein of mechanistic target of rapamycin (Raptor) and TGR5 in STC-1 cells.

INTERPRETATION

Deoxycholic acid-TGR5-mTORC1 signaling contributes to the up-regulation of GLP-1 production after RYGB.

Development of murine bariatric surgery models: lessons learned

Roux-en-Y gastric bypass (RYGB) improves comorbidities such as diabetes and hypertension and lowers the risk of obesity-related cancers. To better understand the physiologic and genetic influences of bariatric surgery, a reliable murine model is needed that can be extended to genetically engineered mice. Given the complexity of these procedures, few researchers have successfully implemented these techniques beyond larger rodent models. The purpose of our study was to develop a technically feasible and reproducible murine model for RYGB and sleeve gastrectomy (SG). Mice were converted to liquid diet perioperatively without fasting and housed in groups on raised wire platforms. SG involved significant reduction of stomach volume followed by multilayer repair of the gastrotomy. RYGB procedure consisted of side-to-side, functional end-to-side bowel anastomoses and exclusion of the stomach medial to the gastroesophageal junction. Sham surgeries consisted of enterotomies and gastrotomy followed by primary repair without resection or rerouting. Survival after incorporation of the aforementioned techniques was 100% in the SG group and 41% in the RYGB group at 1 mo after surgery. Only 26% of RYGB mortality was attributed to leak, obstruction, or stricture; the majority of postoperative mortality was due to stress, dumping, or malnutrition. Much of the survival challenge for this surgical model was related to perioperative husbandry, which is to be expected given their small stature and poor response to stress. Utilization of the perioperative and surgical techniques described will increase survival and feasibility of these technically challenging procedures, allowing for a better understanding of mechanisms to explain the beneficial effects of bariatric surgery.

Refinement of Perioperative Feeding in a Mouse Model of Vertical Sleeve Gastrectomy

Provision of liquid enteral nutrition (LEN) during the perioperative period is standard practice for rodents undergoing bariatric surgery, yet these diets are associated with several challenges, including coagulation of the liquid diet within the delivery system and decreased postoperative consumption. We investigated the use of a commercially available high-calorie dietary gel supplement (DG) as an alternative food source for mice during the perioperative period. C57BL/6J male mice were fed high-fat diet for 8 to 10 wk prior to surgery. The study groups were: vertical sleeve gastrectomy (VSG) +DG, VSG+LEN, sham surgery+DG, and sham+LEN. Food and water intakes, body weight, and body fat composition was monitored throughout the study. Mice that received DG lost significantly more weight preoperatively than those fed LEN. However, during the postoperative period, body weight, body fat composition, and water and caloric intake were similar among all experimental diet groups. Three mice in the VSG+LEN group were euthanized due to clinical illness during the course of the study. In summary, feeding a high-calorie DG to mice undergoing VSG surgery is a viable alternative to LEN, given that DG does not significantly affect the surgical model of weight loss or result in adverse clinical outcomes. We recommend additional metabolic characterization of DG supplementation to ensure that this novel diet does not confound specific research goals in the murine VSG model.

Bile acid profiles within the enterohepatic circulation in a diabetic rat model after bariatric surgeries

Bile acids (BAs), which are synthesized in the liver and cycled in the enterohepatic circulation, have been recognized as signaling molecules by activating their receptors in the intestine and liver. Serum taurine-conjugated BAs have been shown to be elevated after bariatric surgeries although the postoperative BA profiles within the enterohepatic circulation have not been investigated. Clarification of these profiles could help explain the mechanisms by which bariatric surgery leads to BA profile alterations and subsequent metabolic effects. We performed duodenal-jejunal bypass (DJB), sleeve gastrectomy (SG), and sham procedures in an obese diabetic rat model induced by high-fat diet and streptozotocin. The weight loss and antidiabetic effects were evaluated postsurgery. BA profiles in the systemic serum and within the enterohepatic circulation were analyzed, together with the expression of related BA transporters and enzymes at week 12 after surgery. Compared with sham, SG induced sustained weight loss, and both DJB and SG significantly improved glucose tolerance and insulin sensitivity with enhanced glucagon-like peptide 1 secretion. Similar to changes in the serum, BAs, especially taurine-conjugated species, were also elevated in the enterohepatic circulation (bile and portal vein) after DJB and SG. In addition, the expression of key BA transporters and conjugational enzymes was elevated postoperatively, whereas the enzymes responsible for BA synthesis were decreased. In conclusion, DJB and SG elevated BA levels in the systemic serum and enterohepatic circulation, especially taurine-conjugated species, which likely indicates increased ileal reabsorption and hepatic conjugation rather than synthesis. NEW & NOTEWORTHY Bile acids (BAs) have been implicated as potential mediators of the weight-independent effects of bariatric surgery. For the first time, we discovered that duodenal-jejunal bypass and sleeve gastrectomy elevated BAs, particularly the taurine-conjugated species in the enterohepatic circulation, likely through the promotion of ileal reabsorption and hepatic conjugation rather than BA synthesis. These findings will improve our understanding of BA metabolism after bariatric surgery and their subsequent metabolic effects.

Establishing a Reproducible Murine Animal Model of Single Anastomosis Duodenoileal Bypass with Sleeve Gastrectomy (SADl-S)

Single-anastomosis duodenoileal bypass with sleeve gastrectomy (SADI-S) is a simplified biliopancreatic diversion. The objective of this study was to develop a reproducible animal model for SADI-S. We used three techniques for duodenal exclusion and duodenoileal anastomosis: (a) surgical clip and side-to-side anastomosis, (b) ligation and side-to-side anastomosis and (c) sectioning the duodenum, closing the duodenal stump and end-to-side anastomosis. We recorded the surgical technique and complications for each method. Twenty-five of 31 rats survived to the end of the study period. One death occurred from accidental anaesthesia overdose and the others from anastomosis leak. Four duodenal exclusions had repermeabilised at necropsy. Our murine model of SADI-S can be consistently reproduced. Sectioning the duodenum is preferable to avoid repermeabilisation of the duodenum.

Effects of Sleeve Gastrectomy on Serum 12α-Hydroxylated Bile Acids in a Diabetic Rat Model

BACKGROUND

Diabetes mellitus is a prevalent disease that endangers human health. Bariatric surgery can effectively relieve insulin resistance with elevated serum bile acids (BAs). 12α-Hydroxylated BAs were previously reported to be associated with insulin resistance. The aim of this study was to analyze changes in 12α-hydroxylated BA composition and possible associated mechanisms in diabetic rats following sleeve gastrectomy (SG).

METHODS

SG and sham operations were performed in diabetic rats induced by high-fat diet feeding and streptozotocin. Body weight, food intake, oral glucose tolerance test (OGTT), insulin tolerance test (ITT), and serum BAs were analyzed at corresponding time points. Cholesterol 12α-hydroxylase (CYP8B1) and transcription factor V-Maf Avian Musculoaponeurotic Fibrosarcoma Oncogene Homolog G (MAFG) expression levels were assessed by RT-PCR and western blotting.

RESULTS

Compared with the SHAM group, the SG group displayed significant weight loss from 6 weeks postoperatively, accompanied by decreased food intake from 4 weeks after the operation. At 2 and 12 weeks postoperatively, the areas under the curve of OGTT and ITT were significantly decreased in the SG group. At 12 weeks post-operation, the SG group displayed elevated serum BAs, but the percentage of 12α-hydroxylated BAs was reduced. Furthermore, SG rats exhibited higher MAFG and lower CYP8B1 protein and mRNA levels in the liver (P < 0.05).

CONCLUSION

The percentage of 12α-hydroxylated bile acids was reduced after SG, which was relevant with the inhibition of CYP8B1 and overexpression of MAFG. These outcomes may play an important role in the improvement of insulin sensitivity following SG.

Early Weight Loss Independent Effects of Sleeve Gastrectomy on Diet-Induced Cardiac Dysfunction in Obese, Wistar Rats

INTRODUCTION

Several reports suggest that bariatric surgery significantly improves cardiac function in patients with obesity cardiomyopathy. The mechanism is unknown but may be due to weight-loss independent factors. We predict that the changes in gastrointestinal anatomy after a rodent model of sleeve gastrectomy (SG) will have weight-loss independent effects on cardiac dysfunction.

METHODOLOGY

Cardiac dysfunction was induced by feeding a 60% kcal from fat diet to male Wistar rats for 10 weeks. Rats underwent either a SG (n = 12) or pair-fed, PF (n = 8) sham surgery. Echocardiograms were performed pre- and post-operatively at 6 and 13 weeks. Blood samples were obtained at 10 weeks post-operatively for assessment of insulin sensitivity and heart failure.

RESULTS

Forty-four percent of SG rats had a normal ejection fraction (EF) at 13 weeks ("responders") compared to five SG rats who did not recover EF ("non-responders"). Zero percent of the PF rats normalized EF (p = 0.03). SG responders had a smaller left ventricular internal diameter in systole and end systolic volume with improved systolic function compared to SG non-responders (EF 90.7 ± 1.7 vs. 75.4 ± 3.6%, p = <0.001). At 10 weeks post-operatively, plasma glucose and B-type natriuretic peptide levels were significantly lower in SG rats compared to PF rats.

CONCLUSIONS

A SG significantly improved systolic function in 44% of rats with diet-induced obesity and cardiac dysfunction. This improvement is related to weight-loss independent effects of the surgery on the entero-cardiac axis. These results offer a novel weight-loss independent, metabolic role for bariatric surgery as a potential treatment modality for obesity-associated cardiac dysfunction.