A surgical rat model of human Roux-en-Y gastric bypass

Functional and morphologic dysfunctions in the airways of rats submitted to an experimental model of obesity-exacerbated asthma

The obesity-exacerbated asthma phenotype is characterized by more severe asthma symptoms and glucocorticoid resistance. The aim of this study was to standardize an obesity-exacerbated asthma model by a high glycemic level index (HGLI) diet and ovalbumin (OVA) sensitization and challenges in Wistar rats. Animals were divided into groups: control (Ctrl), obese (Ob), asthmatic (Asth), obese asthmatic (Ob + Asth) and obese asthmatic treated with dexamethasone (Ob + Asth + Dexa), and in vivo and in vitro functional and morphological parameters were measured. After HGLI consumption, there was an increase in body weight, fasting blood glucose, abdominal circumferences, body mass index and adiposity index. Respiratory function showed a reduction in pulmonary tidal volume and ventilation. In isolated tracheas, carbachol showed an increase in contractile efficacy in the Ob, Ob + Asth and Ob + Asth + Dexa, but mostly on Ob + Asth. Histological analysis of lungs showed peribronchovascular inflammation and smooth muscle hypertrophy and extracellular remodeling on Ob + Asth and Ob + Asth + Dexa. An obesity-exacerbated asthma model was successfully established. Therefore, this model allows further molecular investigations and the search for new therapies for the treatment and relief of symptoms of patients with obesity-induced resistant asthma.

Bariatric surgery induces morphological changes in the extensor digitorum longus muscle in the offspring of obese rats

INTRODUCTION

The effects of the maternal nutritional environment on the growth and metabolism of the offspring, and its impacts on health in adult life are defined as metabolic programming. Thus, the objective of this study was to evaluate the effects of Roux-en-Y gastric bypass (RYGB) on the morphology of muscle fiber and neuromuscular junction (NMJ) of the offspring of rats submitted to RYGB.

METHODS

Three-week-old Wistar rats were separated into two groups: 1) CAF SHAM which received a cafeteria diet and was submitted to a sham operation and 2) CAF RYGB, which received a cafeteria diet and was submitted to RYGB. The first generation (F1) offspring (male) was named according to the treatment of mothers as CAF SHAM-F1 and CAF RYGB-F1 and received a standard diet after weaning. At 17 weeks, the animals were euthanized, and the extensor digitorum longus muscle (EDL) was collected and processed in light microscopy and transmission electron microscopy for morphological and morphometric analysis.

RESULTS

The CAF RYGB-F1 group showed a reduction in the weight of the EDL muscle and also a reduction in the area of type I, IIa and IIb fibers and a nucleus/fiber ratio. This same group also showed an increase in the capillary density and myofibrillar disorganization and in the Z-line, as well as a reduction in the area of the NMJs.

CONCLUSION

The RYGB surgery in mothers produced morphological changes in the skeletal striated muscles of the offspring.

Effects of Roux-en-Y Gastric Bypass and Sleeve Gastrectomy on Bone Mineral Density in Zucker Diabetic Fatty Rats: A Short-Term Comparative Study

BACKGROUND

While bariatric surgery could result in weight loss as well as glycaemia improvement, the short-term impact on bone health in a high glycemic environment following Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG) remains intriguing.

OBJECTIVE

The aim of this study was to compare the short-term effects of RYGB and SG procedures on bone health in Zucker diabetic fatty (ZDFfa/fa) rats.

METHODS

Thirty age-matched male ZDFfa/fa rats were randomized into RYGB, SG, and sham groups after establishment of the diabetic model. Body weight, blood glucose, bone mineral density (BMD), the level of bone turnover markers (BTM), vitamin D, and serum calcium and phosphorus were measured 4 weeks after the operation.

RESULTS

The RYGB procedure brought about lower blood glucose, BMD, serum calcium and phosphorus levels, as well as a relatively higher bone turnover rate and 1,25(OH)2VD level, compared to the SG and sham groups, while the influences of the SG procedure were not significant. 25(OH)VD demonstrated no significant difference among the 3 groups.

CONCLUSIONS

Despite its excellent ability to provide short-term glycemic control, the RYGB procedure could led to more severe impairment of bone health compared to the SG procedure. Bone health should be procured after bariatric surgery, especially with the RYGB procedure. Early detection of BMD and BTM may help to avoid deterioration of bone.

DUODENAL-JEJUNAL BYPASS REDUCES LIPID ACCUMULATION IN THE BROWN ADIPOSE TISSUE OF HYPOTHALAMIC OBESE RATS

BACKGROUND

Effects of duodenal-jejunal bypass surgery (DJB) on the proliferation of nuclei and the area of adipocytes in the brown adipose tissue of obese rats. Thermogenic activity in the brown adipose tissue (BAT) of obese individuals is reduced, and this condition may be modified by bariatric surgery (BS).

AIM

To characterize fat deposition in BAT from hypothalamic obese (HyO) rats submitted to duodenal-jejunal-bypass (DJB) surgery.

METHODS

For induction of hypothalamic obesity, newborn male Wistar rats were treated with subcutaneous injections of monosodium glutamate (MSG). The control (CTL) group received saline solution. At 90 days, the HyO rats were submitted to DJB or sham operation, generating the HyO-DJB and HyO-SHAM groups. At 270 days, the rats were euthanized, and the BAT was weighed and submitted to histological analysis.

RESULTS

Compared to BAT from CTL animals, the BAT from HyO-SHAM rats displayed increased weight, hypertrophy with greater lipid accumulation and a reduction in nucleus number. DJB effectively increased nucleus number and normalized lipid deposition in the BAT of HyO-SHAM rats, similar to that observed in CTL animals.

CONCLUSION

DJB surgery avoided excessive lipid deposition in the BAT of hypothalamic obese rats, suggesting that this procedure could reactivate thermogenesis in BAT, and contribute to increase energy expenditure.

Gastric Bypass Surgery Improves the Skeletal Muscle Ceramide/S1P Ratio and Upregulates the AMPK/ SIRT1/ PGC-1α Pathway in Zucker Diabetic Fatty Rats

PURPOSE

Roux-en-Y gastric bypass (RYGB) is associated with remission of type 2 diabetes. However, the cellular and molecular mechanisms remain unknown. We hypothesized that RYGB would increase peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), sirtuin-1 (SIRT1), AMPK/pAMPK, and citrate synthase (CS) protein expression and decrease insulin resistance and these changes would be mediated by sphingolipids, including ceramides and the sphingolipid metabolite sphingosine-1 phosphate (S1P).

MATERIALS AND METHODS

Male ZDF rats were randomized to RYGB (n = 7) or sham surgery (n = 7) and harvested after 28 days. Total tissue ceramide, ceramide subspecies (C14:0, C16:0, C18:0, C18:1, C20:0, C24:0, and C24:1), and S1P were quantified in the white gastrocnemius muscle using LC-ESI-MS/MS after separation with HPLC. Total SIRT1, AMPK, PGC-1α, and CS protein expression were measured by Western blot.

RESULTS

Body weight, fasting glucose, insulin, and HOMA-IR decreased significantly after RYGB compared with sham control. These changes were paralleled by lower total ceramide (483.7 ± 32.3 vs. 280.1 ± 38.8 nmol/g wwt), C18:0 ceramide subspecies (P < 0.05), higher S1P (0.83 ± 0.05 vs. 1.54 ± 0.21 nmol/g wwt, P < 0.05), and a lower ceramide/S1P ratio (P < 0.05) in the RYGB versus sham group. AMPK, pAMPK, SIRT1, PGC-1α, and CS protein expression was also higher after RYGB (P < 0.05). The ceramide/S1P ratio correlated with weight loss (r = 0.48, P = 0.08), insulin resistance (r = 0.61, P = 0.02), PGC-1α (r = - 0.51, P < 0.06), CS (r = - 0.63, P = 0.01), and SIRT1 (r = - 0.54, P < 0.04).

CONCLUSION

Our data demonstrate that sphingolipid balance, and increased AMPK, SIRT1, PGC-1α, and CS protein expression are part of the mechanism that contributes to the remission of diabetes after RYGB surgery.

Optimization of a Technique to Standardize the Rodent Roux-En-Y Gastric Bypass Model and Troubleshooting of Postoperative Failures

BACKGROUND

Rodent models are required in studies on the mechanism of Roux-en-Y gastric bypass (RYGB). However, the construction of the model is hard, and there are various causes of death after surgery in rats.

METHODS

RYGB models with procedures containing a series of anatomic landmark were established in rats. Optimized procedures during surgery, possible complications after surgery, and corresponding solutions were studied.

RESULTS

With the introduction of perioperative nursing and optimized surgery procedures, less time-consuming surgeries were performed and higher survival rates were achieved. Trouble-shooting data based on death time points are listed and discussed for various causes of failure.

CONCLUSIONS

This study provides practical suggestions for investigators to perform RYGB surgery on rats. The troubleshooting suggestions will help operators to efficiently identify problems in their procedures.

Preserving Duodenal-Jejunal (Foregut) Transit Does Not Impair Glucose Tolerance and Diabetes Remission Following Gastric Bypass in Type 2 Diabetes Sprague-Dawley Rat Model

BACKGROUND

Possible mechanisms underlying diabetes remission following Roux-en-Y gastric bypass (RYGB) include eradication of putative factor(s) with duodenal-jejunal bypass.

OBJECTIVE

The objective of this study is to observe the effects of duodenal-jejunal transit on glucose tolerance and diabetes remission in gastric bypass rat model.

METHOD

In order to verify the effect of duodenal-jejunal transit on glucose tolerance and diabetes remission in gastric bypass, 22 type 2 diabetes Sprague-Dawley rat models established through high-fat diet and low-dose streptozotocin (STZ) administered intraperitoneally were assigned to one of three groups: gastric bypass with duodenal-jejunal transit (GB-DJT n = 8), gastric bypass without duodenal-jejunal transit (RYGB n = 8), and sham (n = 6). Body weight, food intake, blood glucose, as well as meal-stimulated insulin, and incretin hormone responses were assessed to ascertain the effect of surgery in all groups. Oral glucose tolerance test (OGTT) and insulin tolerance test (ITT) were conducted three and 7 weeks after surgery.

RESULTS

Comparing our GB-DJT to the RYGB group, we saw no differences in the mean decline in body weight, food intake, and blood glucose 8 weeks after surgery. GB-DJT group exhibited immediate and sustained glucose control throughout the study. Glucagon-like peptide 1 (GLP-1) and gastric inhibitory polypeptide (GIP) levels were also significantly increased from preoperative level in the GB-DJT group (p < 0.05). Insulin and GLP-1 area under curve (AUC) as well as improved glycemic excursion on OGTT did not differ between GB-DJT and RYGB groups. Outcomes with sham operation did not differ from preoperative level.

CONCLUSION

Preserving duodenal-jejunal transit does not impede glucose tolerance and diabetes remission after gastric bypass in type-2 diabetes Sprague-Dawley rat model.

The effect of distal-ileal exclusion after Roux-en-Y gastric bypass on glucose tolerance and GLP-1 response in type-2 diabetes Sprague-Dawley rat model

BACKGROUND

An increase in glucagon-like peptide-1 (GLP-1) mediating early diabetes remission after Roux-en-Y gastric bypass (RYGB) is believed to be associated with distal-ileal stimulation.

OBJECTIVE

To observe the effect of distal-ileal exclusion on glucose tolerance and GLP-1 response after RYGB.

SETTING

Affiliated Hospital of Xuzhou Medical University, Xuzhou, Jiangsu, China.

METHODS

A type 2 diabetes model was created in 40 Sprague-Dawley rats that were randomly assigned to a RYGB group (n = 32) and a sham group (n = 8). Four weeks after surgery, the RYGB group was further divided into the RYGB control group (n = 8) and the distal-ileal exclusion group (RYGB-IEx, n = 24). Rats in the RYGB-IEx group underwent laparotomy, and the last 20 cm of ileum was excluded. An oral glucose tolerance test, insulin tolerance test, and mixed-meal tolerance test conducted preoperatively were repeated in all groups at 4 and 8 weeks postoperatively.

RESULTS

Compared with preoperative level, GLP-1 was significantly increased after RYGB. GLP-1 area under the curve recorded after oral gavage at week 4 postoperatively was significantly higher than the preoperative level (P < .05). GLP-1, insulin area under the curve, and improved glucose-excursion on oral glucose tolerance test 4 weeks after gastric bypass were not reversed at week 8 after distal-ileal exclusion in the RYGB-IEx group. Food intake increased significantly after distal-ileal exclusion in the RYGB-IEx group.

CONCLUSION

These findings suggest that distal-ileal stimulation might not be required for incretin response and diabetes remission after gastric bypass in the type 2 diabetes Sprague-Dawley rat model.

Effect of Roux-en-Y Gastric Bypass on the NLRP3 Inflammasome in Pancreatic Islets from Zucker Diabetic Fatty Rats

PURPOSE

Diabetes and obesity are associated with inflammasome-mediated low-grade, chronic inflammation that may induce pancreatic beta-cell dysfunction and apoptosis. We examined the effects of Roux-en-Y gastric bypass (RYGB) surgery on NOD-like receptor family, pyrin domain containing-3 (NLRP3) inflammasome-related genes from pancreatic islets of Zucker diabetic fatty rats.

MATERIALS AND METHODS

Islets were collected from Zucker diabetic fatty sham control and RYGB, 30 days after surgery. We assessed expression of genes that regulate glucose metabolism and the NLRP3 inflammasome (NLRP3, caspase-1, IL-1β, IL-18, apoptosis-associated speck-like protein), IL-6, and monocyte chemoattractant protein-1.

RESULTS

Gene expression for NLRP3 (p < 0.02), IL-1β (p < 0.04), and IL-6 (p < 0.01) was reduced by RYGB and positively correlated with change in body weight. IL-1β positively correlated with glucose AUC response.

CONCLUSION

Suppression of the NLRP3 inflammasome in pancreatic islets may contribute to improved glycemic control after RYGB.

Hypercaloric Diet Establishes Erectile Dysfunction in Rat: Mechanisms Underlying the Endothelial Damage

Obesity is characterized by an excessive increase in body mass, leading to endothelial damage that may favor the development of erectile dysfunction (ED). ED is defined as the inability to achieve or maintain a penile erection long enough to have a sexual intercourse. In this context, different ED models were developed, however the high price of special animals or the long period to establish the disease has limited studies in this field. Therefore, this study proposed to establish and characterize a novel model of ED in rats associated to a hypercaloric diet consumption. Animals were randomly divided into control group (CG), which received a standard diet, and obese group (OG), fed with a hypercaloric diet during 8 weeks. Rat's erectile function was evaluated in vivo and in vitro. Food and caloric intake of OG were reduced compared to CG, due to an increased diet energy efficiency. However, OG presented an increased body mass, inguinal, retroperitoneal and epididymal adipose tissues, as well as body adiposity index at the end of experimental protocol. In erectile function analysis, there was a decrease in the number and the latency of penile erections in OG. Additionally, the contractile reactivity of corpus cavernosum was increased in OG, favoring penile detumescence and related to a reduced nitric oxide bioavailability and an increased in contractile prostaglandins levels as a consequence of endothelial damage. Moreover, the endothelium-relaxation reactivity of corpus cavernosum was attenuated in OG associated to the oxidative stress. Thus, it was provided a model for advances in sexual dysfunction field and drug discovery for ED treatment.

Liver steatosis in hypothalamic obese rats improves after duodeno-jejunal bypass by reduction in de novo lipogenesis pathway

AIMS

Hypothalamic obesity is a severe condition without any effective therapy. Bariatric operations appear as an alternative treatment, but the effects of this procedure are controversial. We, herein, investigated the effects of duodeno-jejunal bypass (DJB) surgery upon the lipid profile and expression of genes and proteins, involved in the regulation of hepatic lipid metabolism, in hypothalamic obese (HyO) rats.

METHODS

During the first 5days of life, male newborn Wistar rats received subcutaneous injections of monosodium glutamate [4g/kg body weight, HyO group] or saline (control, CTL group). At 90days of life, HyO rats were randomly submitted to DJB (HyO DJB) or Sham-operations (HyO Sham group). Six months after DJB, adiposity, hepatic steatosis and lipid metabolism were verified.

KEY FINDINGS

HyO Sham rats were obese, hyperinsulinemic, insulin resistant and dyslipidemic. These rats had higher liver contents of trygliceride (TG) and presented disorganization of the hepatocyte structures, in association with higher hepatic contents of acetyl-CoA carboxylase (ACC), fatty acid synthase (FASN), and stearoyl-CoA desaturase-1 mRNAs and protein. DJB surgery normalized insulinemia, insulin resistance, and dyslipidemia in HyO rats. TG content in the liver and the hepatic microscopic structures were also normalized in HyO DJB rats, while the expressions of ACC and FASN proteins were decreased in the liver of these rodents.

SIGNIFICANCE

The DJB-induced amelioration in hepatic steatosis manifested as a late effect in HyO rats, and was partly associated with a downregulation in hepatic de novo lipogenesis processes, indicating that DJB protects against liver steatosis in hypothalamic obesity.

Duodenal-jejunal bypass normalizes pancreatic islet proliferation rate and function but not hepatic steatosis in hypothalamic obese rats

Modifications in life-style and/or pharmacotherapies contribute to weight loss and ameliorate the metabolic profile of diet-induced obese humans and rodents. Since these strategies fail to treat hypothalamic obesity, we have assessed the possible mechanisms by which duodenal-jejunal bypass (DJB) surgery regulates hepatic lipid metabolism and the morphophysiology of pancreatic islets, in hypothalamic obese (HyO) rats. During the first 5 days of life, male Wistar rats received subcutaneous injections of monosodium glutamate (4 g/kg body weight, HyO group), or saline (CTL). At 90 days of age, HyO rats were randomly subjected to DJB (HyO DJB group) or sham surgery (HyO Sham group). HyO Sham rats were morbidly obese, insulin resistant, hypertriglyceridemic and displayed higher serum concentrations of non-esterified fatty acids (NEFA) and hepatic triglyceride (TG). These effects were associated with higher expressions of the lipogenic genes and fatty acid synthase (FASN) protein content in the liver. Furthermore, hepatic genes involved in β-oxidation and TG export were down-regulated in HyO rats. In addition, these rats exhibited hyperinsulinemia, β-cell hypersecretion, a higher percentage of islets and β-cell area/pancreas section, and enhanced nuclear content of Ki67 protein in islet-cells. At 2 months after DJB surgery, serum concentrations of TG and NEFA, but not hepatic TG accumulation and gene and protein expressions, were normalized in HyO rats. Insulin release and Ki67 positive cells were also normalized in HyO DJB islets. In conclusion, DJB decreased islet-cell proliferation, normalized insulinemia, and ameliorated insulin sensitivity and plasma lipid profile, independently of changes in hepatic metabolism.

Body Composition, Food Intake, and Energy Expenditure in a Murine Model of Roux-en-Y Gastric Bypass Surgery

BACKGROUND

The mechanisms by which Roux-en-Y gastric bypass surgery (RYGB) so effectively lowers body weight and improves glycemic control are not well understood, and murine models are essential for identifying the crucial signaling pathways involved. The aim of this study is to characterize the time course of RYGB on body weight, body composition, food intake, and energy expenditure in diet-induced obese mice and establish a tissue bank for global "omics" or targeted biochemical and structural analyses.

METHODS

High-fat diet-induced obese mice were subjected to RYGB using an improved surgical technique with a small gastric pouch. The effects on body weight, body composition, food intake, and energy expenditure were compared to sham surgery, high-fat diet-restricted weight-matched controls, and never-obese chow-fed controls.

RESULTS

Without mortality or complications, RYGB surgery in high-fat diet-induced obese mice gradually decreased body weight to a plateau that was more or less sustained for up to 12 weeks (33 g, -18 %, p < 0.01) and significantly lower compared with sham-operated mice (51 g, +25 %, p < 0.01), but higher (+18 %, p < 0.01) than age-matched, chow-fed control mice (27 g). Energy intake after RYGB was significantly suppressed compared to sham only for the first 10 days, but significantly higher compared to weight-matched mice. Energy expenditure after RYGB was higher throughout the study compared with weight-matched, but not sham animals.

CONCLUSIONS

RYGB surgery in diet-induced obese mice results in similar body weight and body composition changes as observed in humans, but in contrast with humans, this is achieved mainly through increased energy expenditure rather than decreased food intake.

Roux-en-Y gastric bypass augments the feeding responses evoked by gastrin-releasing peptides

BACKGROUND

Roux-en-Y gastric bypass (RYGB) is the most effective method for the treatment of obesity, and metabolic disease RYGB may reduce body weight by altering the feeding responses evoked by the short-term satiety peptides.

MATERIALS AND METHODS

Here, we measured meal size (MS, chow), intermeal interval (IMI) length, and satiety ratio (SR, IMI/MS; food consumed per a unit of time) by the small and the large forms of gastrin-releasing peptide (GRP) in rats, GRP-10 and GRP-29 (0, 0.1, 0.5 nmol/kg) infused in the celiac artery (CA, supplies stomach and upper duodenum) and the cranial mesenteric artery (CMA, supplies small and large intestine) in an RYGB rat model.

RESULTS

GRP-10 reduced MS, prolonged the IMI, and increased the SR only in the RYGB group, whereas GRP-29 evoked these responses by both routes and in both groups.

CONCLUSIONS

The RYGB procedure augments the feeding responses evoked by exogenous GRP, possibly by decreasing total food intake, increasing latency to the first meal, decreasing number of meals or altering the sites of action regulating MS and IMI length by the two peptides.

Lipocalin-type prostaglandin D2 synthase (L-PGDS) modulates beneficial metabolic effects of vertical sleeve gastrectomy

BACKGROUND

Vertical sleeve gastrectomy (VSG) ameliorates metabolic complications in obese and diabetic patients through unknown mechanisms.

OBJECTIVE

The objective of this study was to investigate the role of lipocalin-type prostaglandin D₂ synthase (L-PGDS) in glucose regulation in response to VSG using L-PGDS knock-out (KO), knock-in (KI), and C57BL/6 (wild type) mice.

SETTING

Winthrop University Hospital Research Institute.

METHODS

Animals were divided into 6 groups: L-PGDS KO sham/VSG (n = 5), L-PGDS KI sham/VSG (n = 5), and C57BL/6 (wild type) sham/VSG (n = 5). Related parameters were measured in fasting animals after 10 weeks.

RESULTS

Our intraperitoneal glucose tolerance tests and homeostatic model assessment insulin resistance results showed significant glycemic improvement 10 weeks post-VSG in both C57BL/6 and KI groups compared with the sham group. In contrast, the KO group developed glucose intolerance and insulin resistance similar to or greater than the sham group 10 weeks post-VSG. Interestingly, weight gain was insignificant 10 weeks post-VSG in all the groups and even trended higher in the KO group compared with sham. Peptide YY levels in the KO group post-VSG were slightly increased but significantly less than other groups. Similarly, the KO group showed significantly less leptin sensitivity in response to VSG compared with the KI group. Total cholesterol level remained unchanged in all groups irrespective of sham or surgery but interestingly, the KO group had significantly higher cholesterol levels. In parallel, adipocyte size was also found to be significantly increased in the KO group post-VSG compared with the sham group.

CONCLUSION

Our findings propose that L-PGDS plays an important role in the beneficial metabolic effects observed after VSG.

Gastric bypass surgery is protective from high-fat diet-induced non-alcoholic fatty liver disease and hepatic endoplasmic reticulum stress

AIM

High-fat diets are known to contribute to the development of obesity and related co-morbidities including non-alcoholic fatty liver disease (NAFLD). The accumulation of hepatic lipid may increase endoplasmic reticulum (ER) stress and contribute to non-alcoholic steatohepatitis and metabolic disease. We hypothesized that bariatric surgery would counter the effects of a high-fat diet (HFD) on obesity-associated NAFLD.

METHODS

Sixteen of 24 male Sprague Dawley rats were randomized to Sham (N = 8) or Roux-en-Y gastric bypass (RYGB) surgery (N = 8) and compared to Lean controls (N = 8). Obese rats were maintained on a HFD throughout the study. Insulin resistance (HOMA-IR), and hepatic steatosis, triglyceride accumulation, ER stress and apoptosis were assessed at 90 days post-surgery.

RESULTS

Despite eating a HFD for 90 days post-surgery, the RYGB group lost weight (-20.7 ± 6%, P < 0.01) and improved insulin sensitivity (P < 0.05) compared to Sham. These results occurred with no change in food intake between groups. Hepatic steatosis and ER stress, specifically glucose-regulated protein-78 (Grp78, P < 0.001), X-box binding protein-1 (XBP-1) and spliced XBP-1 (P < 0.01), and fibroblast growth factor 21 (FGF21) gene expression, were normalized in the RYGB group compared to both Sham and Lean controls. Significant TUNEL staining in liver sections from the Obese Sham group, indicative of accelerated cell death, was absent in the RYGB and Lean control groups. Additionally, fasting plasma glucagon like peptide-1 was increased in RYGB compared to Sham (P < 0.02).

CONCLUSION

These data suggest that in obese rats, RYGB surgery protects the liver against HFD-induced fatty liver disease by attenuating ER stress and excess apoptosis.

Amelioration of glycemic control by sleeve gastrectomy and gastric bypass in a lean animal model of type 2 diabetes: restoration of gut hormone profile

BACKGROUND

In obese diabetic patients, bariatric surgery has been shown to induce remission of type 2 diabetes. Along with weight loss itself, changes in gut hormone profiles after surgery play an important role in the amelioration of glycemic control. However, the potential of gastrointestinal surgery regarding diabetes remission in non-severely obese diabetic patients has yet to be defined. In the present experimental study, we explored the effect of established bariatric procedures with and without duodenal exclusion on glycemic control and gut hormone profile in a lean animal model of type 2 diabetes.

METHODS

Forty 12- to 14-week-old non-obese diabetic Goto-Kakizaki (GK) rats were randomly assigned to four groups: control group (GKC), sham surgery (GKSS), sleeve gastrectomy (GKSG), and gastric bypass (GKGB). Age-matched Wistar rats served as a non-diabetic control group (WIC). Glycemic control and plasma lipids were assessed at the beginning of the observation period and 4 weeks after surgery. Fasting and mixed meal-induced plasma levels of ghrelin, glucagon-like peptide-17-36 (GLP-1), and peptide tyrosine-tyrosine (PYY) were measured.

RESULTS

In GK rats, glycemic control improved after sleeve gastrectomy (SG) and gastric bypass (GB). Mixed meal-induced gut hormone profiles in Wistar rats (WIC) were significantly different from those of sham-operated or control group GK rats. After SG and GB, GK rats showed a similar postprandial decrease in ghrelin as observed in non-diabetic WIC. Following both surgical procedures, a significant meal-induced increase in PYY and GLP-1 could be demonstrated.

CONCLUSIONS

SG and GB induce a similar improvement in overall glycemic control in lean diabetic rodents. Meal-induced profiles of ghrelin, GLP-1, and PYY in GK rats are significantly modified by SG and GB and become similar to those of non-diabetic Wistar rats. Our data do not support the hypothesis that duodenal exclusion and early contact of food with the ileal mucosa alone explain changes in gut hormone profile in GK rats after gastrointestinal surgery.

Effect of Roux-en-Y Gastric Bypass on the NLRP3 Inflammasome in Adipose Tissue from Obese Rats

Objective

Obesity is associated with low-grade chronic inflammation. We hypothesized that Roux-en-Y gastric bypass (RYGB) surgery would reduce activation of the NLRP3 inflammasome in metabolically active adipose tissue (AT) of obese rats, and this change would be related to decreases in body weight and improved glycemic control.

Methods

Omental, mesenteric and subcutaneous fat depots were collected from Sprague-Dawley rats: Sham control and RYGB; 90-days after surgery. NLRP3, caspase–1, apoptosis-associated speck-like protein (ASC), IL–1β, IL–18, IL–6 and MCP–1 gene and protein expression were quantified. Glucose metabolism was assessed by oral glucose tolerance test (OGTT).

Results

Compared to Sham surgery controls, RYGB surgery decreased IL–6, MCP–1, NLRP3, IL–18, caspase–1 and ASC in omental fat, and decreased IL–6, MCP1, IL–1β, IL–18, caspase–1 and ASC gene expression in mesenteric fat. We observed differential gene expression between visceral and subcutaneous fat for IL–6 and IL–1β, both being downregulated by RYGB in visceral, and upregulated in subcutaneous depots. These changes in gene expression were accompanied by a decrease in NLRP3, ASC, IL–18, caspase–1 and IL–1β protein expression in omental tissue. We found a positive correlation between caspase–1, ASC, MCP–1, IL–18 and IL–6 gene expression following surgery and glucose AUC response in omental fat, while the change in glucose AUC response correlated with caspase–1 gene expression in subcutaneous fat.

Conclusion

This study demonstrates that bariatric surgery reverses inflammation in visceral adipose tissue by suppressing NLRP3 inflammasome activation. These are the first data to implicate the NLRP3 inflammasome in diabetes remission after RYGB surgery.

Self-nanoemulsifying drug delivery systems ameliorate the oral delivery of silymarin in rats with Roux-en-Y gastric bypass surgery

Roux-en-Y gastric bypass (RYGB) is a popular surgery to reduce the body weight of obese patients. Although food intake is restricted by RYGB, drug absorption is also decreased. The purpose of this study was to develop novel self-nanoemulsifying drug delivery systems (SNEDDS) for enhancing the oral delivery of silymarin, which has poor water solubility. The SNEDDS were characterized by size, zeta potential, droplet number, and morphology. A technique of RYGB was performed in Sprague-Dawley rats. SNEDDS were administered at a silymarin dose of 600 mg/kg in normal and RYGB rats for comparison with silymarin aqueous suspension and polyethylene glycol (PEG) 400 solution. Plasma silibinin, the main active ingredient in silymarin, was chosen for estimating the pharmacokinetic parameters. SNEDDS diluted in simulated gastric fluid exhibited a droplet size of 190 nm with a spherical shape. The nanocarriers promoted silibinin availability via oral ingestion in RYGB rats by 2.5-fold and 1.5-fold compared to the suspension and PEG 400 solution, respectively. A significant double-peak concentration of silibinin was detected for RYGB rats receiving SNEDDS. Fluorescence imaging showed a deeper and broader penetration of Nile red, the fluorescence dye, into the gastrointestinal mucosa from SNEDDS than from PEG 400 solution. Histological examination showed that SNEDDS caused more minor inflammation at the gastrointestinal membrane as compared with that caused by PEG 400 solution, indicating a shielding of direct silymarin contact with the mucosa by the nanodroplets. SNEDDS generally showed low-level or negligible irritation in the gastrointestinal tract. Silymarin-loaded SNEDDS were successfully developed to improve the dissolution, permeability, and oral bioavailability of silymarin. To the best of our knowledge, this is the first investigation reporting the usefulness of SNEDDS for improving drug malabsorption elicited by gastric bypass surgery.

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

Bariatric surgery is the only definitive solution currently available for the present obesity pandemic. These operations typically involve reconfiguration of gastrointestinal tract anatomy and impose profound metabolic and physiological benefits, such as substantially reducing body weight and ameliorating type II diabetes. Therefore, animal models of these surgeries offer unique and exciting opportunities to delineate the underlying mechanisms that contribute to the resolution of obesity and diabetes. Here we describe a standardized procedure for mouse and rat models of Roux-en-Y gastric bypass (80-90 min operative time) and sleeve gastrectomy (30-45 min operative time), which, to a high degree, resembles operations in humans. We also provide detailed protocols for both pre- and postoperative techniques that ensure a high success rate in the operations. These protocols provide the opportunity to mechanistically investigate the systemic effects of the surgical interventions, such as regulation of body weight, glucose homeostasis and gut microbiome.

Glucagon secretion after metabolic surgery in diabetic rodents

Excessive or inadequate glucagon secretion promoting hepatic gluconeogenesis and glycogenolysis is believed to contribute to hyperglycemia in patients with type 2 diabetes. Currently, metabolic surgery is an accepted treatment for obese patients with type 2 diabetes and has been shown to improve glycemic control in Goto-Kakizaki (GK) rats, a lean animal model for type 2 diabetes. However, the effects of surgery on glucagon secretion are not yet well established. In this study, we randomly assigned forty 12- to 14-week-old GK rats to four groups: control group (GKC), sham surgery (GKSS), sleeve gastrectomy (GKSG), and gastric bypass (GKGB). Ten age-matched Wistar rats served as a non-diabetic control group (WIC). Glycemic control was assessed before and 4 weeks after surgery. Fasting- and mixed-meal-induced plasma levels of insulin and glucagon were measured. Overall glycemic control improved in GKSG and GKGB rats. Fasting insulin levels in WIC rats were similar to those for GKC or GKSS rats. Fasting glucagon levels were highest in GKGB rats. Whereas WIC, GKC, and GKSS rats showed similar glucagon levels, without any significant meal-induced variation, a significant rise occurred in GKSG and GKGB rats, 30 min after a mixed meal, which was maintained at 60 min. Both GKSG and GKGB rats showed an elevated glucagon:insulin ratio at 60 min in comparison with all other groups. Surprisingly, the augmented post-procedural glucagon secretion was accompanied by an improved overall glucose metabolism in GKSG and GKGB rats. Understanding the role of glucagon in the pathophysiology of type 2 diabetes requires further research.

Bone metabolism after bariatric surgery

Bariatric surgery is a popular and effective treatment for severe obesity but may have negative effects on the skeleton. This review summarizes changes in bone density and bone metabolism from animal and clinical studies of bariatric surgery, with specific attention to Roux-en-Y gastric bypass (RYGB), adjustable gastric banding (AGB), and sleeve gastrectomy (SG). Skeletal imaging artifacts from obesity and weight loss are also considered. Despite challenges in bone density imaging, the preponderance of evidence suggests that bariatric surgery procedures have negative skeletal effects that persist beyond the first year of surgery, and that these effects vary by surgical type. The long-term clinical implications and current clinical recommendations are presented. Further study is required to determine mechanisms of bone loss after bariatric surgery. Although early studies focused on calcium/vitamin D metabolism and mechanical unloading of the skeleton, it seems likely that surgically induced changes in the hormonal and metabolic profile may be responsible for the skeletal phenotypes observed after bariatric surgery.

Duodenal-jejunal bypass and jejunectomy improve insulin sensitivity in Goto-Kakizaki diabetic rats without changes in incretins or insulin secretion

Gastric bypass surgery can dramatically improve type 2 diabetes. It has been hypothesized that by excluding duodenum and jejunum from nutrient transit, this procedure may reduce putative signals from the proximal intestine that negatively influence insulin sensitivity (SI). To test this hypothesis, resection or bypass of different intestinal segments were performed in diabetic Goto-Kakizaki and Wistar rats. Rats were randomly assigned to five groups: duodenal-jejunal bypass (DJB), jejunal resection (jejunectomy), ileal resection (ileectomy), pair-fed sham-operated, and nonoperated controls. Oral glucose tolerance test was performed within 2 weeks after surgery. Baseline and poststimulation levels of glucose, insulin, glucagon-like peptide 1 (GLP-1), and glucose-dependent insulinotropic polypeptide (GIP) were measured. Minimal model analysis was used to assess SI. SI improved after DJB (SI = 1.14 ± 0.32 × 10(-4) min(-1) ⋅ pM(-1)) and jejunectomy (SI = 0.80 ± 0.14 × 10(-4) min(-1) ⋅ pM(-1)), but not after ileectomy or sham operation/pair feeding in diabetic rats. Both DJB and jejunal resection normalized SI in diabetic rats as shown by SI levels equivalent to those of Wistar rats (SI = 1.01 ± 0.06 × 10(-4) min(-1) ⋅ pM(-1); P = NS). Glucose effectiveness did not change after operations in any group. While ileectomy increased plasma GIP levels, no changes in GIP or GLP-1 were observed after DJB and jejunectomy. These findings support the hypothesis that anatomic alterations of the proximal small bowel may reduce factors associated with negative influence on SI, therefore contributing to the control of diabetes after gastric bypass surgery.

Influence of additional resection of the gastric fundus on excessive weight loss in laparoscopic very very long limb Roux-en-Y gastric bypass

Roux-en-Y gastric bypass (RYGB) is the gold standard in bariatric surgery. The effect of the procedure is based on restriction, malabsorption and changes in hormonal axis. Ghrelin is an important appetite hormone which is produced mainly in the gastric fundus. By adding a resection of the gastric fundus, we hypothesized that excessive weight loss will be more prominent and the satiety feelings less pronounced compared to standard RYGB. A total of 73 patients with standard very very long limb (VVLL) RYGB (group A) were compared with 44 patients with VVLL RYGB with resection of the fundus (group B). Outcome measures were excessive weight loss (EWL), body mass index (BMI), early postoperative morbidity, change of co-morbidities, and appetite reduction as assessed by an appetite questionnaire over a postoperative period of 24 months. Groups were comparable in basic preoperative descriptions. Additional fundus resection did not influence EWL (group A 66.1 % vs. group B 70.6 %, p = 0.383) or BMI (group A 29 kg/m(2) vs. group B 27 kg/m(2), p = 0.199). No significant difference in morbidity or change of co-morbidities occurred. The appetite and satiety questionnaire showed no difference between group A and group B, respectively. Adding a resection of the gastric fundus in RYGB did not alter the clinical results, i.e., increased excessive weight loss, decrease of appetite, or increase of satiety. The value of removing a part of the ghrelin-producing cells might be overestimated.

Duodenal-jejunal bypass surgery enhances glucose tolerance and beta-cell function in Western diet obese rats

BACKGROUND

The aim of this study was to investigate the effect of the duodenal-jejunal bypass (DJB) on glucose homeostasis and islet insulin secretion in Western diet (WD) obese rats.

METHODS

Male Wistar rats received a standard rodent chow diet (CTL group) or WD ad libitum. After 32 weeks of diet, WD rats were submitted to duodenal-jejunal bypass (WD DJB) or sham (WD S-DJB) operation. Intraperitoneal (ip) glucose tolerance test was performed 1 week after surgery. Body weight, fat pad depots, glycemia, insulinemia, HOMA-IR, and glucose-induced insulin secretion were evaluated 1 month after surgery.

RESULTS

Body weight and fat pads of the WD group were higher than those of the CTL group. Sham and DJB surgeries did not alter these parameters. WD and WD S-DJB rats were glucose intolerant, insulin resistant, and hyperinsulinemic. WD DJB rats showed similar glucose tolerance, insulin sensitivity, and plasma insulin levels to those of CTL rats. WD rats presented higher fat and glycogen contents in the liver. DJB surgery normalized fat and glycogen stores in the liver of the WD DJB group. Insulin release at 11.1-mM glucose, in isolated islets from WD and WD S-DJB rats, was higher than from islets of CTL rats. In contrast, DJB surgery improves the beta-cell secretory capacity with increased glucose-induced secretion at 5.6-, 11.1-, and 22.2-mM glucose in WD DJB islets, compared with CTL islets.

CONCLUSIONS

DJB surgery improves glucose homeostasis and enhances beta-cell glucose responsiveness in rats submitted to the WD diet without any modification in adiposity.

Resting energy expenditure and energetic cost of feeding are augmented after Roux-en-Y gastric bypass in obese mice

Although the prevalence of obesity has increased dramatically throughout the world during the last 25 yr, its long-term control remains poor. Currently, only gastrointestinal weight loss surgery, especially Roux-en-Y gastric bypass (RYGB), is associated with substantial and sustained weight loss and resolution or significant improvement of diabetes mellitus and other metabolic obesity-induced complications. Clinical observations and recent studies have suggested that RYGB induces its effects by changing the physiology of weight regulation. Understanding the underlying mechanisms of these profound and sustainable effects could facilitate the development of novel and less invasive treatments against obesity and its complications. To study the physiological mechanisms of RYGB, we have developed a mouse RYGB model that replicates the human operation. The aims of this study were to develop a roadmap for assessing energy expenditure (EE) in animal models of weight loss surgery and to examine the effects of RYGB on EE. We first measured EE by indirect calorimetry in groups of animals that underwent RYGB or a sham operation. Calorimetry data were analyzed using three different methods: normalization by total body mass, allometric scaling, and analysis of covariance modeling. RYGB in mice induced a significant increase in EE that was independent of the method used. An energy balance analysis was then performed, which also confirmed that RYGB-treated animals have higher energy maintenance needs. Finally, we determined the EE components that account for the observed increase in EE, and we found that resting EE and postprandial thermogenesis are the major contributors to this increase.

Challenges and pitfalls of experimental bariatric procedures in rats

INTRODUCTION

The impact of Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG) on obesity and obesity-related diseases is unquestionable. Up to now, the technical descriptions of these techniques in animals/rats have not been very comprehensive.

METHODS

For SG and RYGB, operating time, learning curve, and intraoperative mortality in relation to weight of the rat and type of anesthesia were recorded. Furthermore, a review of the literature on experimental approaches towards SG and RYGB in rats was carried out, merging in a detailed technical description for both procedures.

RESULTS

The data presented here revealed that the mean operating time for SG (69.4 ± 22.2 min (SD)) was shorter than for RYGB (123.0 ± 20.7 min). There is a learning curve for both procedures, resulting in a reduced operating time of up to 60% in SG and 35% in RYGB (p < 0.05; t-test). However, with increased weight, operating time increases to about 80 min for SG and about 120 min for RYGB. Obese rats have an increased intraoperative mortality rate of up to 50%. After gaseous anesthesia the mortality can be even higher. The literature search revealed 40 papers dealing with SG and RYGB in rats. 18 articles (45%) contained neither photographs nor illustrations; 14 articles (35%) did not mention the applied type of anesthesia. The mortality rate was described in 15 papers (37.5%).

CONCLUSION

Experimental obesity surgery in rats is challenging. Because of the high mortality in obese rats operated under gaseous anesthesia, exercises to establish the techniques should be performed in small rats using intraperitoneal anesthesia.

Gastrostomy tube placement in gastric remnant at gastric bypass: a rat model for selective gut stimulation

BACKGROUND

Roux-en-Y gastric bypass (RYGB) surgery achieves high remission rates of type 2 diabetes mellitus in obese diabetic patients. It has been hypothesized that the changes in bowel nutrient exposure after RYGB results in altered release of gut hormones and improved glucose homeostasis. Our objective was to assess the feasibility of, and report on, our technique and initial experience with selective gut stimulation in a gastric bypass rat model at an academic medical center in the United States.

METHODS

We performed RYGB with simultaneous placement of a gastrostomy tube in the excluded gastric remnant in 8 obese Sprague-Dawley rats. A second group of 8 obese Sprague-Dawley rats underwent gastrostomy tube placement without gastric bypass and served as the controls. Each rat was tested for oral glucose tolerance preoperatively. On postoperative days 14 and 28, glucose tolerance was re-evaluated using the oral and gastrostomy tube routes.

RESULTS

The gastrostomy tubes were successfully inserted in all the rats with no tube-related complications. The area under the curve after oral glucose gavage decreased significantly after gastric bypass (P = .01 at 14 d and P = .003 at 28 d). The gastric remnant glucose gavage after RYGB essentially reversed the effects of surgery on glucose metabolism. The areas under the curve showed no significant differences in the control group between the preoperative and postoperative oral or tube results.

CONCLUSION

Placing a gastrostomy tube into the gastric remnant at RYGB in a rat model is technically feasible. Our initial findings support the role of duodenal exclusion in improving glucose metabolism after RYGB.

Obesity surgery and gut-brain communication

The prevalence of obesity, and the cluster of serious metabolic diseases it is associated with, continues to rise globally, and hopes for effective treatment with drugs have been considerably set back. Thus, success with bariatric surgeries to induce sustained body weight loss and effectively cure most of the associated co-morbidities appears almost "miraculous" and systematic investigation of the mechanisms at work has gained momentum. Here, we will discuss the basic organization of gut-brain communication and review clinical and pre-clinical investigations on the potential mechanisms by which gastric bypass surgery leads to its beneficial effects on energy balance and glucose homeostasis. Although a lot has been learned regarding changes in energy intake and expenditure, secretion of gut hormones, and improvement in glucose homeostasis, there has not yet been the "breakthrough observation" of identifying a key signaling component common to the beneficial effects of the surgery. However, given the complexity and redundancy of gut-brain signaling and gut signaling to other relevant organs, it is perhaps more realistic to expect a number of key signaling changes that act in concert to bring about the "miracle".

Renal glomerular and tubular injury after gastric bypass in obese rats

OBJECTIVE

Roux-en-Y gastric bypass (RYGB) surgery is the most common surgical intervention for long-term weight loss in morbidly obese patients. By decreasing obesity-associated hyperfiltration, diabetes, and hypertension, RYGB is touted to stabilize, if not prevent, progression of chronic renal disease. To test this, the renal histology of diet-induced obese rats that underwent RYGB surgery was compared with that of pair-fed and sham obese controls.

METHODS

Sprague-Dawley rats, fed a high-fat, low-oxalate diet to induce gross obesity, were randomized to RYGB (n = 6), gastrointestinal-intact sham-operated obese controls (sham, n = 4), or gastrointestinal-intact sham-operated obese pair-fed controls (fed, n = 8). Daily body weight and food intake were recorded. On postoperative day 42, renal histology and immunohistochemistry were examined. Renal pathology was assessed by a categorical glomerular lesion score and a quantitative glomerular/tubular scoring system by experienced veterinary pathologists. Osteopontin and ED-1 (monocyte/macrophage cell) stainings were estimated by the percentage of stained area and the number of counted cells/high-power field, respectively.

RESULTS

Compared with sham and fed controls, RYGB rats had significant decreases in body weight (P < 0.001), more glomerular lesions (P = 0.02), and received higher glomerular and tubular lesion scores (P < 0.01). RYGB rodents had significantly stronger staining for osteopontin within the inner medullary region (P < 0.005) and ED-1 within the outer medullary region (P < 0.02) compared with sham and fed controls.

CONCLUSION

In this diet-induced obese rat model, RYGB is associated with chronic glomerulosclerosis and tubulointerstitial nephritis, confirmed by histology and immunohistochemistry. Prospective studies to better define the injurious mechanisms in this model are underway.

Lessons learned from gastric bypass operations in rats

Numerous studies using gastric bypass rat models have been recently conducted to uncover underlying physiological mechanisms of Roux-en-Y gastric bypass. Reflecting on lessons learned from gastric bypass rat models may thus aid the development of gastric bypass models in mice and other species. This review aims to discuss technical and experimental details of published gastric bypass rat models to understand advantages and limitations of this experimental tool. The review is based on PubMed literature using the search terms 'animal model', 'rodent model', 'bariatric surgery', 'gastric bypass', and 'Roux-en-Y gastric bypass'. All studies published up until February 2011 were included. 32 studies describing 15 different rat gastric bypass models were included. Description of surgical technique differs in terms of pouch size, limb lengths, preservation of the vagal nerve, and mortality rate. Surgery was carried out exclusively in male rats of different strains and ages. Pre- and postoperative diets also varied significantly. Technical and experimental variations in published gastric bypass rat models complicate comparison and identification of potential physiological mechanisms involved in gastric bypass. In summary, there is no clear evidence that any of these models is superior, but there is an emerging need for standardization of the procedure to achieve consistent and comparable data.

Effect of the oral administration of monosodium glutamate during pregnancy and breast-feeding in the offspring of pregnant Wistar rats

PURPOSE

Determine the effects of the MSG (monosodium glutamate) in the offspring of pregnant rats through the comparison of the weight, NAL (nasal-anal length) and IL (Index of Lee) at birth and with 21 days of life.

METHODS

Pregnant Wistar rats and their offspring were divided into 3 groups: GC, G10 and G20. Each of the groups received 0%, 10% and 20% of MSG, respectively from coupling until the end of the weaning period.

RESULTS

Neither weight nor NAL were different among the groups at birth. The group G20 at birth had an IL lower than the group GC (p<0,05) and with 21 days of life presented weight and NAL lower than the groups G10 and this lower than the GC (p<0,01). Otherwise the G20 at 21 days of life had the IL similar to the other two groups. The weight profit percentage from birth to the 21st day of life was lower in the G20 regarding the other two groups (p<0,01). The G20 had a NAL increase percentage from birth to the 21st day of life lower than the G10 and this lower than the GC (p<0,01).

CONCLUSIONS

MSG presented a dose-dependent relation in the variables weight and NAL. It caused a decrease in the growth pattern as well as in the weight gain pattern until the 21st day of life. The IL of the group 20% had an increased in relation to the control group after 3 weeks of follow up.

Gastric bypass surgery alters behavioral and neural taste functions for sweet taste in obese rats

Roux-en-Y gastric bypass surgery (GBS) is the most effective treatment for morbid obesity. GBS is a restrictive malabsorptive procedure, but many patients also report altered taste preferences. This study investigated the effects of GBS or a sham operation (SH) on body weight, glucose tolerance, and behavioral and neuronal taste functions in the obese Otsuka Long-Evans Tokushima Fatty (OLETF) rats lacking CCK-1 receptors and lean controls (LETO). OLETF-GBS rats lost body weight (-26%) and demonstrated improved glucose tolerance. They also expressed a reduction in 24-h two-bottle preference for sucrose (0.3 and 1.0 M) and decreased 10-s lick responses for sucrose (0.3 through 1.5 M) compared with OLETF-SH or LETO-GBS. A similar effect was noted for other sweet compounds but not for salty, sour, or bitter tastants. In lean rats, GBS did not alter responses to any stimulus tested. Extracellular recordings from 170 taste-responsive neurons of the pontine parabrachial nucleus revealed a rightward shift in concentration responses to oral sucrose in obese compared with lean rats (OLETF-SH vs. LETO-SH): overall increased response magnitudes (above 0.9 M), and maximum responses occurring at higher concentrations (+0.46 M). These effects were reversed by GBS, and neural responses in OLETF-GBS were statistically not different from those in any LETO groups. These findings confirm obesity-related alterations in taste functions and demonstrate the ability of GBS to alleviate these impairments. Furthermore, the beneficial effects of GBS appear to be independent of CCK-1 receptor signaling. An understanding of the underlying mechanisms for reduced preferences for sweet taste could help in developing less invasive treatments for obesity.

Decrease in sweet taste in rats after gastric bypass surgery

BACKGROUND

The literature contains evidence that Roux-en-Y gastric bypass (RYGB) surgery has an effect in humans on taste and preference for carbohydrate-rich foods. This study tested the hypothesis that RYGB affects sweet taste behavior using a rat model.

METHODS

Male Sprague-Dawley rats underwent either RYGB or sham surgery. Then 4 weeks after surgery, the rats were given taste-salient, brief-access lick tests with a series of sucrose concentrations.

RESULTS

The RYGB rats, but not the sham rats, lost weight over the 5-week postoperative period. The RYGB rats showed a significant decrease in mean licks for the highest concentration of sucrose (0.25-1.0 mol/l) but not for the low concentrations of sucrose or water.

CONCLUSIONS

The findings showed that RYGB surgery affected sweet taste behavior in rats, with postsurgical rats having lower sensitivity or avidity for sucrose than sham-treated control rats. This finding is similar to human reports that sweet taste and preferences for high-caloric foods are altered after bypass surgery.

Metabolic syndrome is a low-grade systemic inflammatory condition

An increase in proinflammatory cytokines, a decrease in endothelial nitric oxide and adiponectin levels and an alteration in hypothalamic peptides and gastrointestinal hormones that regulate satiety, hunger and food intake all occur in metabolic syndrome. Consumption of a diet that is energy dense and rich in saturated and trans-fats by pregnant women and lactating mothers, in childhood and adult life may trigger changes in the hypothalamic and gut peptides and hormones. Such changes modulate immune response and inflammation and lead to alterations in the hypothalamic 'bodyweight/appetite/satiety set point' and result in the initiation and development of the metabolic syndrome. Roux-en-gastric bypass induces weight loss, decreases the levels of cytokines and restores hypothalamic neuropeptides and gut hormones and the hypothalamic bodyweight/appetite/satiety set point to normal. Thus, metabolic syndrome is a low-grade systemic inflammatory condition with its origins in the perinatal period and childhood.

Pancreatic islet isolation after gastric bypass in a rat model: technique and initial results for a promising research tool

BACKGROUND

Roux-en-Y gastric bypass (RYGB) affords a high remission rate of type 2 diabetes mellitus among morbidly obese diabetic patients. We report the use of the isolated islet technique to assess pancreatic function and glucoregulatory mechanisms after RYGB surgery.

METHODS

A total of 15 adult, male, Sprague Dawley diet-induced obese rats were randomly divided into 3 experimental groups: sham, RYGB, and pair-fed, with 5 rats in each group. The body weight was measured at baseline and every week for 4 weeks. Pancreatic islet function was assessed in vitro according to the amount of insulin secreted from isolated islets incubated in 2 mM and 20 mM glucose for 1 hour at 37 °C. Fasting plasma glucose, insulin, glucagon-like peptide-1, PYY3-36, and glucose-dependent insulinotropic peptide were measured at baseline and 28 days after surgery.

RESULTS

The baseline body weight was 917 ± 61, 831 ± 42, and 927 ± 43 g for the sham, RYGB, and pair-fed groups, respectively. The RYGB group lost 32% body weight compared with 16% for the sham and 24% for the pair-fed groups. Glucose-stimulated insulin secretion from the isolated islets in the RYGB group was greater than in the comparison groups (P = .04) at 4 weeks after surgery. Fasting plasma glucagon-like peptide-1 and PYY3-36 were significantly increased at 4 weeks in the RYGB group.

CONCLUSION

Islet isolation and stimulation in the present animal model was feasible, affords a direct measurement of pancreatic islet function, and might provide a useful tool to study the effects of RYGB on pancreatic function and the relationship between islet cell function and incretin production after bariatric surgery.

Obesity: genes, brain, gut, and environment

Obesity, which is assuming alarming proportions, has been attributed to genetic factors, hypothalamic dysfunction, and intestinal gut bacteria and an increase in the consumption of energy-dense food. Obesity predisposes to the development of type 2 diabetes mellitus, hypertension, coronary heart disease, and certain forms of cancer. Recent studies have shown that the intestinal bacteria in obese humans and mice differ from those in lean that could trigger a low-grade systemic inflammation. Consumption of a calorie-dense diet that initiates and perpetuates obesity could be due to failure of homeostatic mechanisms that regulate appetite, food consumption, and energy balance. Hypothalamic factors that regulate energy needs of the body, control appetite and satiety, and gut bacteria that participate in food digestion play a critical role in the onset of obesity. Incretins, cholecystokinin, brain-derived neurotrophic factor, leptin, long-chain fatty acid coenzyme A, endocannabinoids and vagal neurotransmitter acetylcholine play a role in the regulation of energy intake, glucose homeostasis, insulin secretion, and pathobiology of obesity and type 2 diabetes mellitus. Thus, there is a cross-talk among the gut, liver, pancreas, adipose tissue, and hypothalamus. Based on these evidences, it is clear that management of obesity needs a multifactorial approach.

Meal patterns, satiety, and food choice in a rat model of Roux-en-Y gastric bypass surgery

Gastric bypass surgery efficiently and lastingly reduces excess body weight and reverses type 2 diabetes in obese patients. Although increased energy expenditure may also play a role, decreased energy intake is thought to be the main reason for weight loss, but the mechanisms involved are poorly understood. Therefore, the aim of this study was to characterize the changes in ingestive behavior in a rat model of Roux-en-Y gastric bypass surgery (RYGB). Obese (24% body fat compared with 18% in chow-fed controls), male Sprague-Dawley rats maintained for 15 wk before and 4 mo after RYGB or sham-surgery on a two-choice low-fat/high-fat diet, were subjected to a series of tests assessing energy intake, meal patterning, and food choice. Although sham-operated rats gained an additional 100 g body wt during the postoperative period, RYGB rats lost approximately 100 g. Intake of a nutritionally complete and palatable liquid diet (Ensure) was significantly reduced by approximately 50% during the first 2 wk after RYGB compared with sham surgery. Decreased intake was the result of greatly reduced meal size with only partial compensation by meal frequency, and a corresponding increase in the satiety ratio. Similar results were obtained with solid food (regular or high-fat chow) 6 wk after surgery. In 12- to 24-h two-choice liquid or solid diet paradigms with nutritionally complete low- and high-fat diets, RYGB rats preferred the low-fat choice (solid) or showed decreased acceptance for the high-fat choice (liquid), whereas sham-operated rats preferred the high-fat choices. A separate group of rats offered chow only before surgery completely avoided the solid high-fat diet in a choice paradigm. The results confirm anecdotal reports of "nibbling" behavior and fat avoidance in RYGB patients and provide a basis for more mechanistic studies in this rat model.

Weight regain after Roux-en-Y: a significant 20% complication related to PYY

OBJECTIVE

Roux-en-Y gastric bypass (RYGB) produces rapid and dramatic weight loss in very heavy obese patients. Up to 20% cannot sustain their weight loss beyond 2 to 3 y after surgery.

METHODS

To identify putative etiologic factors producing post-RYGB weight regain, a literature survey of metabolic changes in very obese and a review of our diet-induced obese RYGB rat model data was done.

RESULTS

Weight regain suggests an imbalance in physiologic mechanisms regulating appetite and metabolic rate. Weight regain occurred in 25% of our rats, produced by return to presurgical energy intake levels. The 75% of rats that sustained weight loss secreted a significantly larger amount of peptide YY (PYY) while suppressing leptin secretion; those that failed were unable to develop or sustain a sufficiently large plasma PYY:leptin ratio. Metabolic consequences of this failure included reversal of initial postsurgical increases in peripheral fatty acid oxidation, anorexigenic activity in the hypothalamic arcuate nucleus and paraventricular nucleus, and the expression of uncoupling protein-2 in adipose tissues, and decreases in hepatic lipogenesis, free tri-iodothyronine secretion, expression of orexigenic activity in the arcuate nucleus and paraventricular nucleus, expression of adenosine monophosphate kinase in adipose tissues, skeletal muscle mitochondrial mass, and endocannabinoid content and appetite.

CONCLUSION

Weight regain after RYGB occurs in approximately 20% of patients and constitutes a serious complication. Weight regain-promoting consequences are attributed to a failure to sustain elevated plasma PYY concentrations, indicating that combining RYGB with pharmacologic stimulation of PYY secretion in patients after RYGB who exhibit inadequate PYY concentration may increase long-term success of surgical weight reduction in morbidly obese adults.