Catabolic effects of gastric bypass in a diet-induced obese rat model

Weight Regain after Metabolic Surgery: Beyond the Surgical Failure

Patients undergoing metabolic surgery have factors ranging from anatomo-surgical, endocrine metabolic, eating patterns and physical activity, mental health and psychological factors. Some of the latter can explain the possible pathophysiological neuroendocrine, metabolic, and adaptive mechanisms that cause the high prevalence of weight regain in postbariatric patients. Even metabolic surgery has proven to be effective in reducing excess weight in patients with obesity; some of them regain weight after this intervention. In this vein, several studies have been conducted to search factors and mechanisms involved in weight regain, to stablish strategies to manage this complication by combining metabolic surgery with either lifestyle changes, behavioral therapies, pharmacotherapy, endoscopic interventions, or finally, surgical revision. The aim of this revision is to describe certain aspects and mechanisms behind weight regain after metabolic surgery, along with preventive and therapeutic strategies for this complication.

Bariatric Surgery in Obesity: Metabolic Quality Analysis and Comparison of Surgical Options

Obesity is a constantly growing health problem which reduces quality of life and life expectancy. Bariatric surgery (BS) for obesity is considered when all other conservative treatment modalities have failed. Comparison of the multidisciplinary programs with BS regarding to the weight loss showed that substantial and durable weight reduction have been achieved only with bariatric surgical treatments. Although laparoscopic sleeve gastrectomy is the most popular BS, it has high long-term failure rates, and it is claimed that one of every three patients will undergo another bariatric procedure within a 10-year period. Although BS provides weight loss and improvement of metabolic comorbidities, in long-term follow-up, weight gain is observed in half of the patients, while decrease in bone mass and nutritional deficiencies occur in up to 90%. Moreover, despite significant weight loss, several psychological aspects of patients are worsened in comparison to preoperative levels. Nearly one-fifth of postoperative patients with "Loss-of-eating control" meet food addiction criteria. Therefore, the benefits of weight loss following bariatric procedures alone are still debated in terms of the proinflammatory and metabolic profile of obesity.

The role of bariatric surgery in the management of nonalcoholic steatohepatitis

PURPOSE OF REVIEW

Nonalcoholic fatty liver disease (NAFLD) is the leading cause of chronic liver disease in the United States and increasing globally. The progressive form of NAFLD, nonalcoholic steatohepatitis (NASH), can lead to cirrhosis and complications of end-stage liver disease. No FDA-approved therapy for NAFLD/NASH exists. Treatment of NAFLD/NASH includes effective and sustained life-style modification and weight loss. This review reports on the recent findings of bariatric surgery in the management of NASH.

RECENT FINDINGS

NAFLD, at all stages, is common in those who meet indication for bariatric surgery. Bariatric surgery resolves NAFLD/NASH and reverses early stages of fibrosis. Although randomized controlled trials of bariatric surgery in NASH are infeasible, studies defining the metabolic changes induced by bariatric surgery, and their effect on NASH, provide insight for plausible pharmacologic targets for the nonsurgical treatment of NASH.

SUMMARY

Resolution of NASH and fibrosis regression can occur after bariatric surgery. Although the exact mechanism(s) underlying the improvement of NASH and hepatic fibrosis following bariatric surgery is not fully elucidated, emerging data on this topic is vitally important for lending insight into the pharmacotherapies for NASH for patients who are not otherwise suitable candidates for bariatric surgery.

Effect of postbariatric maternal weight loss and surgery to conception interval on perinatal outcomes of nulliparous women

BACKGROUND

Bariatric surgery is associated with an increased risk of delivering a small neonate. The role of maternal weight loss and surgery to conception interval is unclear.

OBJECTIVES

To investigate the effect of maternal weight loss, as a result of bariatric surgery, and surgery to conception interval on fetal growth and birthweight (BW).

SETTING

Inner London Teaching Hospital METHODS: We studied prospectively nulliparous women with previous bariatric surgery. Information on type, time, and presurgery weight was obtained. Surgery-to-conception interval was calculated as the time between surgery and conception, defined as the fourteenth day of the pregnancy dated by first trimester ultrasound scan. In the first trimester, maternal weight was measured. Assessment of maternal weight change between presurgery and first trimester of pregnancy was defined as total weight loss (TWL) (%). Fetal ultrasound scans were performed twice; 30-32 and 35-37 weeks' gestation and estimated fetal weight (EFW) was calculated. Fetal growth rate was calculated as the ratio of EFW increase (in grams) between 30-32 and 35-37 weeks divided by the time interval (in days) between the 2 examinations. BW was recorded.

RESULTS

The study included 54 pregnant women, 26 with a restrictive procedure (gastric band or vertical sleeve gastrectomy) and 28 with a gastric bypass. Surgery to conception interval was not a significant predictor of the offspring's growth. Maternal TWL was a significant predictor of fetal growth rate (P = .04) and predictor of BW (P = .005), even after adjustment for confounders.

CONCLUSIONS

Maternal weight loss, as a result of bariatric surgery, has an inverse correlation with fetal growth rate and BW.

Effect of weight reductions on estimated kidney function: Post-hoc analysis of two randomized trials

AIMS

Weight loss-induced serum creatinine reduction may increase creatinine-based estimated glomerular filtration rate (eGFR) producing incorrect estimates of kidney function. We investigated whether weight changes in the SCALE program with liraglutide 3.0mg were associated with changes in serum creatinine.

METHODS

Post hoc analysis of two 56-week, randomized, double-blind trials: SCALE Obesity and Prediabetes (n=3731, without type 2 diabetes [T2D], randomized [2:1] to liraglutide 3.0mg [n=2487] or placebo [n=1244]); SCALE Diabetes (n=846 with T2D, randomized [2:1:1] to liraglutide 3.0mg [n=423], 1.8mg [n=211, excluded from this analysis] or placebo [n=212]). NCT01272219/NCT01272232.

RESULTS

In SCALE Obesity and Prediabetes, mean (±SD) weight loss (baseline to week 56) with liraglutide was 8.0±6.7% (2.6±6.9% with placebo); baseline creatinine with liraglutide was 76±15μmol/L and 74±15μmol/L after 56weeks (similar across treatment groups). In SCALE Diabetes, weight loss with liraglutide was 5.9±5.5% (2.0±4.3% with placebo); baseline creatinine was 79±19μmol/L (77±16μmol/L, placebo) and 79±20μmol/L after 56weeks (76±15μmol/L, placebo). No association between changes in weight and changes in serum creatinine was observed (P≥0.05, both trials, all tests).

CONCLUSIONS

Moderate gradual body weight reductions observed in the SCALE program were not associated with changes in serum creatinine.

Does Bariatric Surgery Improve Obesity Associated Comorbid Conditions

Obesity is a constantly growing health problem which reduces quality of life and life expectancy. Bariatric surgery for obesity is taken into account when all other conservative treatment modalities have failed. Comparison of the multidisciplinary programs with bariatric surgery regarding to weight loss showed that substantial and durable weight reduction have been achieved only with bariatric surgical treatments. However, the benefits of weight loss following bariatric procedures are still debated regarding the pro-inflammatory and metabolic profile of obesity.

Bariatric surgery relieves type 2 diabetes and modulates inflammatory factors and coronary endothelium eNOS/iNOS expression in db/db mice

Overexpression of endothelial nitric oxide synthetase (eNOS)/inducible nitric oxide synthase (iNOS) and inhibition of inflammatory factors can improve vascular function. We hypothesized that bariatric (gastric bypass) surgery could inhibit inflammatory factors and improve the eNOS/iNOS expression of coronary arterioles in the db/db mice. The animals were randomly allocated to the following groups: sham-operated lean mice, lean mice that underwent surgery, sham-operated db/db mice, and db/db mice that underwent surgery (5, 10, 20, and 30 days post-operation). The plasma levels of adiponectin, ghrelin, and IL-6, as well as the protein expression of eNOS/iNOS in coronary arterioles were measured with Western blot. Bariatric surgery decreased body mass and blood glucose levels in db/db mice. Ghrelin receptor and GHS-R1a expression in the hypothalamus were increased in db/db mice, but surgery attenuated GHS-R1a expression. Bariatric surgery elevated plasma concentration and protein expression of adiponectin and ghrelin, and attenuated plasma concentration and protein expression of IL-6. Coronary protein expression of eNOS and SOD2 was lower in the sham-operated db/db mice, and bariatric surgery increased eNOS and SOD2 expression. Gastric bypass surgery upregulates ghrelin and adiponectin expression, and decreases IL-6 expression, which might induce up-regulation of eNOS and SOD2, and down-regulation of iNOS. These interactions could counteract the endothelium dysfunction in type 2 diabetes mellitus.

Evaluation of gastric fundus invagination for weight loss in a porcine model

Gastric fundus compliance allows stomach volume increase in response to food intake. Absence of this postprandial relaxation alters hormonal signals and induces early satiety and weight loss. This study demonstrates the effect of gastric fundus invagination on the growth rate of juvenile pigs. After institutional animal care and use committee approval, 15 juvenile pigs were divided into two groups. In the first group, six pigs were anesthetized, weighed, and submitted to laparotomy, stomach manipulation, and short gastric vessel ligation. This is the control group and is referred to as "Sham". In the second group, gastric fundus invagination was added by using a circular stapler. This is the procedure group and is designated as "GFI". Postoperatively, body weight and food intake were measured for 5 weeks. Pigs were euthanized and the stomachs examined. Growth patterns were compared. Three animals were excluded from the analysis. At the end of the 5-week study period, six GFI pigs had intact anastomosis with an invaginated fundus. The mean percent growth rate for the GFI group (54.2 ± 2.8 %) was significantly less than the Sham group (77.7 ± 4.9 %). Gastric fundus invagination significantly decreases the growth rate in juvenile pigs.

Laparoscopic reconversion of Roux-en-Y gastric bypass to original anatomy: technique and preliminary outcomes

BACKGROUND

Laparoscopic Roux-en-Y gastric bypass (RYGB) is one of the most common bariatric procedures performed. Dumping syndrome, intolerance to RYGB-induced restriction, and weight loss issues are possible problems bariatric surgeons are confronted with. This study reports the feasibility, safety, and outcomes of laparoscopic reconversion of RYGB to original anatomy (OA) as treatment of these complications.

METHODS

Between January 2005 and April 2008, eight patients benefited from laparoscopic reconversion of RYGB to OA. Reason was dumping syndrome without postprandial hypoglycemia (three), intolerance to RYGB-induced restriction (three), too much (one) and too little weight loss (one). Mean weight and body mass index (BMI) at RYGB were 104.7±19.3 kg and 38.7±6 kg/m(2), respectively. Four patients suffered of obesity co-morbidities. Mean time between RYGB and reconversion was 21±18.8 months. Mean weight, BMI, and % excess weight loss at reconversion was 66.8±21.7 kg, 20.1±7 kg/m(2), and 23.7±55%, respectively. The procedure involved dismantling both gastrojejunostomy and jejunojejunostomy, reanastomosing gastric pouch to gastric remnant, and proximal alimentary limb end to distal biliary limb end.

RESULTS

Mean operative time was 132.2±29.5 min. There were no conversions to open surgery and no early complications. Gastrogastrostomy was performed manually (four) and by linear stapler (four), and jejunojejunostomy by linear stapler (eight). Mean hospital stay was 7.7±3.5 days. After a mean follow-up of 18.3±9.2 months, two patients continued to further lose weight, two patients maintained the same weight, and four patients presented weight regain. Gastroesophageal reflux disease appeared in three patients.

CONCLUSIONS

Laparoscopic reconversion of RYGB to OA is feasible and safe. Dumping syndrome and intolerance to RYGB-induced restriction are resolved. The anatomy remains one of the aspects besides nutritional and psychological factors in cases of reconversion for weight issues.

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.

Serum leptin levels are inversely correlated with omental gene expression of adiponectin and markedly decreased after gastric bypass surgery

BACKGROUND

Adipose tissue is the most abundant endocrine tissue in the body, producing leptin, a hormone important in regulating hunger, and adiponectin, a hormone involved in insulin sensitivity and inflammation. This study aimed to assess the impact of gastric bypass surgery (GBS) on leptin levels and its relation to the adipose tissue expression of adiponectin.

METHODS

Omental and subcutaneous adipose tissue and serum were obtained from 40 obese patients undergoing GBS, from 13 patients 1 year or more after GBS, and from 16 non-obese individuals with a body mass index of 20 to 29 kg/m(2). Adiponectin gene expression was measured by quantitative real-time polymerase chain reaction, and the gene expression was normalized for the GAPDH gene. Serum leptin and adiponectin were measured by a high-sensitivity enzymatic assay.

RESULTS

Leptin levels were significantly lower in the post-GBS patients (19.8 ± 6.7) than in the pre-GBS patients (59.0 ± 5.1; P = 0.0001), and similar to those in the non-obese control subjects (18.2 ± 4; P = 0.8). Univariate analysis showed an inverse correlation between serum leptin levels and omental adiponectin gene expression (r = -0.32; P = 0.01).

CONCLUSIONS

Gastric bypass surgery results in resolution of the leptin resistance status that characterizes obese subjects. The study also demonstrated a significant correlation between leptin and adiponectin. This correlation provides preliminary evidence for studying a potential adiponectin-leptin cross-talking that may represent one of the physiologic pathways responsible for the regulation of food intake in humans.

Sleeve gastrectomy prevents lipoprotein receptor-1 expression in aortas of obese rats

AIM: To investigate the effects of sleeve gastrectomy on adipose tissue infiltration and lectin-like oxidized low density lipoprotein receptor-1 (LOX-1) expression in rat aortas.

METHODS: Twenty-four rats were randomized into three groups: normal chow (control), high fat diet (HD) and high fat diet with sleeve gastrectomy (SG). After surgery, the HD and SG groups were fed a high fat diet. Animals were sacrificed and plasma high density lipoprotein (HDL) and low density lipoprotein (LDL) levels were determined. LOX-1 protein and LOX-1 mRNA expression was also measured. Aortas were stained with Nile red to visualize adipose tissue.

RESULT: Body weights were higher in the HD group compared to the other groups. HDL levels in control, HD, and SG groups were 32.9 ± 6.2 mg/dL, 43.4 ± 4.0 mg/dL and 37.5 ± 4.3 mg/dL, respectively. LDL levels in control, HD, and SG groups were 31.8 ± 4.5 mg/dL, 53.3 ± 5.1 mg/dL and 40.5 ± 3.7 mg/dL, respectively. LOX-1 protein and LOX-1 mRNA expression was greater in the HD group versus the other groups. Staining for adipose tissue in aortas was greater in the HD group in comparison to the other groups. Thus, a high fat diet elevates LOX-1 protein and mRNA expression in aorta.

CONCLUSION: Sleeve gastrectomy decreases plasma LDL levels, and downregulates LOX-1 protein and mRNA expression.

Biliopancreatic diversion induces villi elongation and cholecystokinin and ghrelin increase

INTRODUCTION

Factors leading to weight loss and weight stabilization after bariatric surgery are not fully understood. Our aim was to evaluate, in Sprague-Dawley rats, the histological and gut hormonal changes after Larrad-biliopancreatic diversion (Larrad-BPD).

MATERIALS AND METHODS

Rats randomly underwent the following protocols: Larrad-BPD (n=4) versus pair fed (PF) (n=4). Weight and food intake were measured every day. By immunohistochemistry ghrelin was examined in the stomach, while cholecystokinin (CCK), glucagon-like-peptide-1 (GLP-1), peptide YY (PYY) and serotonin (5-HT) expression were analyzed in alimentary limb and ileum following or not the Larrad-BPD.

RESULTS

Larrad-BPD rats exhibited significant (P<0.05) weight loss compared to PF rats. Villi enlongation was observed in Larrad-BPD rats. In residual stomach, ghrelin was diminished. In the alimentary limb, ghrelin and CCK positive cells were detected more than in the ileum of PF rats. GLP-1 expression was decreased and PYY expression was absent after Larrad-BPD compared with PF rats.

DISCUSSION

Larrad-BPD is followed by histological changes and a pleiotropic gut endocrine response aimed to compensate the reduction of intestinal area exposed to food. Until now, the hormones responsible for the intestinal hypertrophy have not been defined.

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.

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.

An endoluminal sleeve induces substantial weight loss and normalizes glucose homeostasis in rats with diet-induced obesity

To investigate the contributions of two surgical gut manipulations-exclusion of the proximal intestine from alimentary flow and exposure of the jejunum to partially digested nutrients-to body weight regulation and metabolism, we have developed a rat model of an investigational device, the endoluminal sleeve (ELS). The ELS is a 10 cm, nutrient-impermeable, flexible tube designed for endoluminal implantation. ELS devices were surgically implanted in the duodenal bulb of rats with diet-induced obesity. Body weight, food intake, stool caloric content, and glucose homeostasis were subsequently evaluated. ELS-implanted rats demonstrated a 20% reduction of body weight compared to sham-operated (SO) controls. ELS-treated animals consumed an average of 27% fewer kcal/day than SO, and there was no evidence of malabsorption. ELS treatment improved fasting glycemia and glucose tolerance after oral and intraperitoneal (IP) administration. ELS treatment enhanced insulin sensitivity, as demonstrated by decreased fasting and glucose-stimulated insulin levels and confirmed by calculation of homeostasis model assessment of insulin resistance (IR). These data suggest that selective bypass of the proximal intestine by ELS, with enhanced delivery of partially digested nutrients to the jejunum, mimics many of the effects of Roux-en-Y gastric bypass (RYGB) on body weight and glucose metabolism. Thus, ELS implantation may be an effective treatment for obesity and diabetes. Since the ELS device is amenable to endoscopic placement, it may offer a valuable alternative to more invasive surgical approaches in selected patients with obesity and its metabolic complications.

Plasma ghrelin modulation in gastric band operation and sleeve gastrectomy

BACKGROUND

Gastric band operation and sleeve gastrectomy are increasingly popular bariatric surgeries for weight loss. The purpose of this study is to investigate the changes in plasma ghrelin levels and hypothalamic ghrelin receptor expression with weight loss achieved through these surgeries.

METHODS

Twenty-four high fat diet-induced obese rats were used to investigate the effects of gastric band and sleeve operation on Body Mass Index, fat mass, plasma ghrelin levels, and hypothalamic growth hormone secretagogue receptor 1a (GHS-R 1a) protein expression in hypothalamus. In comparison, data of patients who received laparoscopic adjustable gastric banding (LAGB) and laparoscopic sleeve gastrectomy (LSG) in our hospital in 2005 were also summarized.

RESULTS

Body weights and fat mass decreased significantly in rats that received operation. Plasma ghrelin concentrations in the sleeve group were 0.4-fold of control rats and about 2-fold of control in the gastric band group. GHS-R1a protein expression in hypothalamus was 1.5-fold in the sleeve group compared with control group, while it was only 0.9-fold in the gastric band group. Clinical data showed that patients in the LSG group lost 60% excess body weights in 2 years follow-up. After operation, fasting plasma ghrelin concentrations in LAGB was significantly higher than the LSG group.

CONCLUSION

Both LAGB and LSG can decrease patients' excess body weights and fat mass. Plasma ghrelin levels are down-regulated with LSG operation but up-regulated with LAGB operation. Hypothalamic GHS-R1a expression is elevated in sleeve gastrectomy.

Sleeve gastrectomy relieves steatohepatitis in high-fat-diet-induced obese rats

BACKGROUND

Sleeve gastrectomy is thought to decrease the appetite and body weight of morbid obesity patients in the clinic. The purpose is to investigate the effect of sleeve gastrectomy on preventing steatohepatitis in morbid obesity rats.

METHODS

Thirty rats were randomized into normal chow group (NC), high-fat-diet group (HD), and sleeve group (SG). Rats in the SG group received sleeve gastrectomy operation. After operation, rats in SG and HD group received a high-fat diet, while rats in the NC group received normal chow. Body weight was measured every 10 days. Thirty days later, animals were sacrificed and blood samples were collected to check total cholesterol, HDL, and triglyceride. Fresh liver sections were made and stained with Nile red and observed under a fluorescence microscope.

RESULTS

Rats in the SG group received a moderate body weight decrease (191 +/- 16.2 g) in the first 10 days, while this did not happen in the other two groups (213 +/- 13.7 g and 243 +/- 11.9 g). At the sacrifice date, weight of rats in the SG group was still much lower than those in the HD group. Plasma triglycerol (102.3 +/- 18.6 mg/dL) and cholesterol (84.3 +/- 6.1 mg/dL) of rats in the SG group were much lower than those in the HD group (198.5 +/- 18.5 mg/dL, 133.9 +/- 22.0 mg/dL). Under the fluorescence microscope, adipose infiltration was very obvious in the liver of the HD animals, while adipose infiltration was not serious in the SG group.

CONCLUSION

High-fat diet can result in obvious body weight increase and hepatic adipose infiltration compared with normal chow. Sleeve gastrectomy can decrease body weight even in high-fat-diet models. Body weight control caused by sleeve gastrectomy can relieve high-fat-diet-induced steatohepatitis in rats.

Sustained weight loss after Roux-en-Y gastric bypass is characterized by down regulation of endocannabinoids and mitochondrial function

OBJECTIVE

To determine the physiologic importance of endocannabinoids and mitochondrial function in the long-term outcome using a rat model of Roux-en-Y gastric bypass (RYGB) surgery.

BACKGROUND

Sixteen million people are morbidly obese and RYGB surgery is the most effective treatment. Endocannabinoids are implicated in appetite stimulation and regulation of peripheral energy metabolism. We hypothesize that down-regulation of endocannabinoids and alterations in mitochondrial function and hormones favoring catabolism contribute to sustained RYGB-induced weight loss.

METHODS

Diet-induced obese Sprague-Dawley rats were randomized to sham-operated obese controls, RYGB, and sham-operated obese pair-fed rats. Body weight and food intake were recorded, and food efficiency was calculated. Endocannabinoid levels in skeletal muscle and liver, muscle mitochondrial respiratory complex I-V content, and hormones concentrations were determined 14 and 28 days postsurgery, reflecting rapid and sustained weight loss periods after RYGB, respectively.

RESULTS

Compared with pair-fed controls, RYGB rats had significant reduction in body weight and food efficiency (P < 0.001). Increased cholecystokinin, reduced insulin, leptin, adiponectin, T3, and down-regulation of mitochondrial complex I were evident on day 14 postsurgery. On day 28, leptin, insulin, and T3 remained low, whereas adiponectin and cholecystokinin were normal. Along with complex I, the endocannabinoids anandamide in muscle (P = 0.003) and 2-arachidonoylglycerol in liver were significantly down-regulated (P < 0.001).

CONCLUSIONS

The attenuated caloric intake, reduced food efficiency, and normalization of hormonal levels on day 28 post-RYGB were associated with significant down-regulation of endocannabinoids anandamide and 2-arachidonoylglycerol in muscle and liver, respectively. These results suggest a role for endocannabinoids in the mechanism of sustained weight loss and RYGB success, and may have implications for treatment of morbid obesity.

Characterization of weight loss and weight regain mechanisms after Roux-en-Y gastric bypass in rats

Roux-en-Y gastric bypass (RYGB) is the most effective therapy for morbid obesity, but it has a ∼20% failure rate. To test our hypothesis that outcome depends on differential modifications of several energy-related systems, we used our established RYGB model in Sprague-Dawley diet-induced obese (DIO) rats to determine mechanisms contributing to successful (RGYB-S) or failed (RYGB-F) RYGB. DIO rats were randomized to RYGB, sham-operated Obese, and sham-operated obese pair-fed linked to RYGB (PF) groups. Body weight (BW), caloric intake (CI), and fecal output (FO) were recorded daily for 90 days, food efficiency (FE) was calculated, and morphological changes were determined. d-Xylose and fat absorption were studied. Glucose-stimulated vagal efferent nerve firing rates of stomach were recorded. Gut, adipose, and thyroid hormones were measured in plasma. Mitochondrial respiratory complexes in skeletal muscle and expression of energy-related hypothalamic and fat peptides, receptors, and enzymes were quantified. A 25% failure rate occurred. RYGB-S, RYGB-F, and PF rats showed rapid BW decrease vs. Obese rats, followed by sustained BW loss in RYGB-S rats. RYGB-F and PF rats gradually increased BW. BW loss in RYGB-S rats is achieved not only by RYGB-induced decreased CI and increased FO, but also via sympathetic nervous system activation, driven by increased peptide YY, CRF, and orexin signaling, decreasing FE and energy storage, demonstrated by reduced fat mass associated with the upregulation of mitochondrial uncoupling protein-2 in fat. These events override the compensatory response to the drop in leptin levels aimed at conserving energy.

Is a model useful in exploring the catabolic mechanisms of weight loss after gastric bypass in humans?

PURPOSE OF REVIEW

In the USA, approximately 3% of adults are morbidly obese, in whom behavior modification and drug therapy is ineffective in inducing major weight loss. Surgery is their only reliable option. The Roux-en-Y gastric bypass accounts for 90% of all bariatric surgeries because it achieves the best weight loss results. Many studies describe weight loss and changes in metabolic blood parameters after Roux-en-Y gastric bypass. We compare recent human data with the findings in our rats to validate the versatility of using a Roux-en-Y gastric bypass rat model to explore the multifactorial molecular and physiological dimensions of weight loss and weight regain.

RECENT FINDINGS

Not only mechanical factors but also changes in gastrointestinal and adipose hormones and hypothalamic neuropeptides contribute to Roux-en-Y gastric bypass induced weight loss by promoting catabolic processes. Nevertheless, the exact mechanisms of weight loss remain unknown.

SUMMARY

To investigate these catabolic mechanisms we used our Roux-en-Y gastric bypass rat model in diet induced obese rats. We found clear morphometric, physiological and biochemical parallelisms between humans and our rats. It is likely that Roux-en-Y gastric bypass induces similar changes in hypothalamic neuropeptides which can only be studied using the rat model. It therefore provides a useful research tool for exploring and studying the development of adjuvant antiobesity therapies.

Ghrelin treatment causes increased food intake and retention of lean body mass in a rat model of cancer cachexia

Cancer cachexia is a debilitating syndrome of anorexia and loss of lean body mass that accompanies many malignancies. Ghrelin is an orexigenic hormone with a short half-life that has been shown to improve food intake and weight gain in human and animal subjects with cancer cachexia. We used a rat model of cancer cachexia and administered human ghrelin and a synthetic ghrelin analog BIM-28131 via continuous infusion using sc osmotic minipumps. Tumor-implanted rats receiving human ghrelin or BIM-28131 exhibited a significant increase in food consumption and weight gain vs. saline-treated animals. We used dual-energy x-ray absorptiometry scans to show that the increased weight was due to maintenance of lean mass vs. a loss of lean mass in saline-treated animals. Also, BIM-28131 significantly limited the loss of fat mass normally observed in tumor-implanted rats. We further performed real-time PCR analysis of the hypothalami and brainstems and found that ghrelin-treated animals exhibited a significant increase in expression of orexigenic peptides agouti-related peptide and neuropeptide Y in the hypothalamus and a significant decrease in the expression of IL-1 receptor-I transcript in the hypothalamus and brainstem. We conclude that ghrelin and a synthetic ghrelin receptor agonist improve weight gain and lean body mass retention via effects involving orexigenic neuropeptides and antiinflammatory changes.