Sleeve gastrectomy in rats improves postprandial lipid clearance by reducing intestinal triglyceride secretion

Comparative analysis of bile acid composition and metabolism in the liver of Bufo gargarizans aquatic larvae and terrestrial adults

Bile acids are crucial for lipid metabolism and their composition and metabolism differ among species. However, there have been no data on the differences in the composition and metabolism of bile acids between aquatic larvae and terrestrial adults of amphibians. This study explored the differences in composition and metabolism of bile acid between Bufo gargarizans larvae and adults. The results demonstrated that adult liver had a lower total bile acid level and a higher conjugated/total bile acid ratio than larval liver. Meanwhile, histological analysis revealed that the larvae showed a larger cross-sectional area of bile canaliculi lumen compared with the adults. The transcriptomic analysis showed that B. gargarizans larvae synthesized bile acids through both the alternative and the 24-hydroxylase pathway, while adults only synthesized bile acids through the 24-hydroxylase pathway. Moreover, bile acid regulator-related genes FXR and RXRα were highly expressed in adult, whereas genes involved in bile acid synthesis (CYP27A1 and CYP46A1) were highly expressed in larvae. The present study will provide valuable insights into understanding metabolic disorders and exploring novel bile acid-based therapeutics.

Obesity-associated Inflammation and Alloimmunity

Obesity is a worldwide health problem with a rapidly rising incidence. In organ transplantation, increasing numbers of patients with obesity accumulate on waiting lists and undergo surgery. Obesity is in general conceptualized as a chronic inflammatory disease, potentially impacting alloimmune response and graft function. Here, we summarize our current understanding of cellular and molecular mechanisms that control obesity-associated adipose tissue inflammation and provide insights into mechanisms affecting transplant outcomes, emphasizing on the beneficial effects of weight loss on alloimmune responses.

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

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

Bariatric surgery in the prevention of obesity-associated cancers: mechanistic implications

Obesity is associated with an increased risk of at least 13 different cancers, as well as worse cancer outcomes and increased cancer mortality. As rates continue to rise both in the United States and worldwide, obesity is poised to become the leading lifestyle-related risk factor for cancer. Currently, the most effective treatment for patients with severe obesity is bariatric surgery. Multiple cohort studies have demonstrated a consistent >30% decreased risk of cancer incidence in women, but not men, following bariatric surgery. However, the physiologic mechanisms driving obesity-associated cancer and the cancer-protective effect of bariatric surgery are not clearly defined. In this review, we highlight emerging concepts in the mechanistic understanding of obesity-associated cancer. Evidence from both human studies and preclinical animal models suggest that obesity drives carcinogenesis through dysregulation of systemic metabolism, immune dysfunction, and an altered gut microbiome. Additionally, we present related findings to suggest that bariatric surgery may disrupt and even reverse many of these mechanisms. Finally, we discuss the use of preclinical bariatric surgery animal models in the study of cancer biology. The prevention of cancer is emerging as an important indication for bariatric surgery. Elucidating the mechanisms through which bariatric surgery limits carcinogenesis is critical to developing a variety of interventions that intercept obesity-driven cancer.

Gut Factors Mediating the Physiological Impact of Bariatric Surgery

Despite decades of obesity research and various public health initiatives, obesity remains a major public health concern. Our most drastic but most effective treatment of obesity is bariatric surgery with weight loss and improvements in co-morbidities, including resolution of type 2 diabetes (T2D). However, the mechanisms by which surgery elicits metabolic benefits are still not well understood. One proposed mechanism is through signals generated by the intestine (nutrients, neuronal, and/or endocrine) that communicate nutrient status to the brain. In this review, we discuss the contributions of gut-brain communication to the physiological regulation of body weight and its impact on the success of bariatric surgery. Advancing our understanding of the mechanisms that drive bariatric surgery-induced metabolic benefits will ultimately lead to the identification of novel, less invasive strategies to treat obesity.

Nutrients handling after bariatric surgery, the role of gastrointestinal adaptation

Bariatric surgery determines a rearrangement of the gastrointestinal tract that influences nutrient handling and plays a role in the metabolic changes observed after surgery. Most of the changes depend on the accelerated gastric emptying observed in Roux-en-Y gastric bypass (RYGB) and, to a lesser extent, in sleeve gastrectomy (SG). The rapid delivery of meal into the jejunum, particularly after RYGB, contributes to the prompt appearance of glucose in peripheral circulation. Glucose increase is the principal determinant of GLP-1 increase with the consequent stimulation of insulin secretion, the latter balanced by a paradoxical glucagon increase that stimulates EGP to prevent hypoglycaemia. Protein digestion and amino acid absorption appear accelerated after RYGB but not after SG. After RYGB, the adaptation of the gut to the new condition participates to the metabolic change. The intestinal transit is delayed, the gut microbioma is changed, the epithelium becomes hypertrophic and increases the expression of glucose transporter and of the number of cell secreting hormones. These changes are not observed after SG. After RYGB-less after SG-bile acids (BA) increase, influencing glucose metabolism probably modulating FXR and TGR5 with an effect on insulin sensitivity. Muscle, hepatic and adipose tissue insulin sensitivity improve, and the gut reinforces the recovery of IS by enhancing glucose uptake and through the effect of the BA. The intestinal changes observed after RYGB result in a light malabsorption of lipid but not of carbohydrate and protein. In conclusion, functional and morphological adaptations of the gut after RYGB and SG activate inter-organs cross-talk that modulates the metabolic changes observed after surgery.Level of evidence Level V, narrative literature review.

Restored TDCA and valine levels imitate the effects of bariatric surgery

Background

Obesity is widespread and linked to various co-morbidities. Bariatric surgery has been identified as the only effective treatment, promoting sustained weight loss and the remission of co-morbidities.

Methods

Metabolic profiling was performed on diet-induced obese (DIO) mice, lean mice, and DIO mice that underwent sleeve gastrectomies (SGx). In addition, mice were subjected to intraperitoneal (i.p.) injections with taurodeoxycholic acid (TDCA) and valine. Indirect calorimetry was performed to assess food intake and energy expenditure. Expression of appetite-regulating hormones was assessed through quantification of isolated RNA from dissected hypothalamus tissue. Subsequently, i.p. injections with a melanin-concentrating hormone (MCH) antagonist and intrathecal administration of MCH were performed and weight loss was monitored.

Results

Mass spectrometric metabolomic profiling revealed significantly reduced systemic levels of TDCA and L-valine in DIO mice. TDCA and L-valine levels were restored after SGx in both human and mice to levels comparable with lean controls. Systemic treatment with TDCA and valine induced a profound weight loss analogous to effects observed after SGx. Utilizing indirect calorimetry, we confirmed reduced food intake as causal for TDCA/valine-mediated weight loss via a central inhibition of the MCH.

Conclusions

In summary, we identified restored TDCA/valine levels as an underlying mechanism of SGx-derived effects on weight loss. Of translational relevance, TDCA and L-valine are presented as novel agents promoting weight loss while reversing obesity-associated metabolic disorders.

Funding

This work has been supported in part by a grant from NIH (UO-1 A1 132898 to S.G.T., DP and MA). M.Q. was supported by the IFB Integrated Research and Treatment Centre Adiposity Diseases (Leipzig, Germany) and the German Research Foundation (QU 420/1-1). J.I. was supported by the Biomedical Education Program (BMEP) of the German Academic Exchange Service (DAAD). T.H. (HE 7457/1-1) and F.K. (KR 4362/1-1) were supported by the German Research Foundation (DFG). H.R.C.B. was supported the Swiss Society of Cardiac Surgery. Y.N. was supported by the Chinese Scholarship Council (201606370196) and Central South University. H.U., T.M. and R.M. were supported by the Osaka Medical Foundation. C.S.F. was supported by the German Research Foundation (DFG, SFB738, B3).

Cardiovascular Risk Reduction Following Metabolic and Bariatric Surgery

Cardiovascular disease (CVD) remains a leading cause of morbidity and mortality in developed countries, with worsening pandemics of type 2 diabetes mellitus and obesity as major cardiovascular (CV) risk factors. Clinical trials of nonsurgical obesity treatments have not shown benefits in CVD, although recent diabetes trials have demonstrated major CV benefits. In many retrospective and prospective cohort studies, however, metabolic (bariatric) surgery is associated with substantial and reproducible CVD benefits. Despite a lack of prospective, randomized clinical trials, data suggest metabolic surgery may be the most effective modality for CVD risk reduction, likely through weight loss and weight loss-independent mechanisms.

Curbing Obesity from One Generation to Another: the Effects of Bariatric Surgery on the In Utero Environment and Beyond

Approximately 250,000 individuals seek bariatric surgery each year in the USA for the long-term resolution of obesity-related comorbidities. Greater than 80% of these individuals are women and approximately half are of child-bearing age. Although there are many positive metabolic benefits that are realized through surgical weight loss for both men and women, the various long-term hormonal, molecular, nutrient, and epigenetic changes following bariatric surgery have not been evaluated for the surgical recipient or in the context of pregnancy and the offspring. Pregnancy may be a vulnerable period of time for the bariatric surgery recipient, and thoughtful consideration of pregnancy management should be taken by health care providers and recipients alike. The purpose of this review is to explore potential etiologies of some of the gestation-specific outcomes for the mother and offspring.

Oea Signaling Pathways and the Metabolic Benefits of Vertical Sleeve Gastrectomy

OBJECTIVE

The aim of this study was to determine whether downstream [peroxisome proliferator-activated-receptor alpha (PPARα) and the G-protein coupled receptor, GPR119] and upstream (a fatty acid translocase, CD36) signaling targets of N-oleoylethanolamide (OEA) were necessary for weight loss, metabolic improvements, and diet preference following vertical sleeve gastrectomy (VSG).

SUMMARY BACKGROUND DATA

OEA is an anorectic N-acylethanolamine produced from dietary fats within the intestinal lumen that can modulate lipid metabolism, insulin secretion, and energy expenditure by activating targets such as PPARα and GPR119.

METHODS

Diet-induced obese mice, including wild-type or whole body knockout (KO) of PPARα, GPR119, and CD36, were stratified to either VSG or sham surgery before body weight, body composition, diet preference, and glucose and lipid metabolic endpoints were assessed.

RESULTS

We found increased duodenal production of OEA and expression of both GPR119 and CD36 were upregulated in wild-type mice after VSG. However, weight loss and glucose tolerance were improved in response to VSG in PPARαKO, GPR119KO, and CD36KO mice. In fact, VSG corrected hepatic triglyceride dysregulation in CD36KO mice, and circulating triglyceride and cholesterol levels in PPARαKO mice. Lastly, we found PPARα-mediated signaling contributes to macronutrient preference independent of VSG, while removal of CD36 signaling blunts the VSG-induced shift toward carbohydrate preference.

CONCLUSIONS

In the search for more effective and less invasive therapies to help reverse the global acceleration of obesity and obesity-related disease OEA is a promising candidate; however, our data indicate that it is not an underlying mechanism of the effectiveness of VSG.

Vertical Sleeve Gastrectomy Attenuates the Progression of Non-Alcoholic Steatohepatitis in Mice on a High-Fat High-Cholesterol Diet

OBJECTIVE

To determine whether vertical sleeve gastrectomy (VSG) attenuates fibrosis in mice on a high-fat high-cholesterol (HFHC) diet.

BACKGROUND

Bariatric surgery mitigates non-alcoholic steatohepatitis in 85-90% of obese patients. While animal models demonstrate similar results on a high-fat diet, none have observed the effects of bariatric surgery on a combined HFHC diet.

METHODS

Mice on a HFHC diet were used to confirm the development of hepatic fibrosis at 8 (n = 15) and 24 (n = 15) weeks. A separate cohort of mice on a HFHC diet for 12 weeks was subjected to either VSG (n = 18) or sham (n = 12) operations and remained on a HFHC diet for an additional 20 weeks. Changes in weight, dyslipidemia, and the development of steatosis and fibrosis were documented. Serum was obtained for bile acid analysis by liquid chromatography and mass spectrometry, while hepatic gene expression by RT-PCR was performed to evaluate intrahepatic lipid metabolism.

RESULTS

Hepatic steatosis and fibrosis developed after 8 weeks on the HFHC diet. After VSG, mice demonstrated a sustained decrease in weight with a significant decrease in fibrosis compared to sham mice. Serum total cholesterol, HDL, and LDL were significantly reduced following surgery, while serum bile acids were significantly elevated. Intra-hepatic cholesterol excretion was not upregulated based on hepatic gene expression of CYP7A1 and ABCG5/8.

CONCLUSIONS

VSG attenuates the development of hepatic fibrosis in diet-induced obese mice, presumably through enhancement of cholesterol elimination at the intestinal level.

Is bariatric surgery resolving NAFLD via microbiota-mediated bile acid ratio reversal? A comprehensive review

Despite the fact that there is still insufficient evidence to consider non-alcoholic fatty liver disease (NAFLD) as an stand-alone indication for bariatric surgery, many clinical and histopathological beneficial effects on both NAFLD and non-alcoholic steatohepatitis (NASH) have been shown. Although weight loss seems to be the obvious mechanism, weight-loss independent factors are also believed to be involved. Among them, changes in gut microbiota and bile acids (BA) composition may be playing an unappreciated role in the improvement of NAFLD. In this review we examine the mechanisms and interdependence of the gut microbiota and BA, and their influence on NAFLD pathogenesis and its reversal following bariatric surgery. According to the currently available evidence, gut microbiota has a major influence on BA composition. In fact, both BA and microbiome disturbances (dysbiosis) play a role in the etiopathogenesis of NAFLD and might be potential therapeutic targets. In addition, bariatric surgery can modify the intraluminal ileal environment in a way that causes significant repopulation of the gut microbiota and a reversal of the plasma primary/secondary BA ratio, which, in turn, induces weigh-independent metabolic improvements.

Gastric mucosal devitalization improves blood pressure, renin and cardiovascular lipid deposition in a rat model of obesity

Background and study aims  In lieu of the drawbacks of metabolic surgery, a method of mimicking resection of the gastric mucosa could be of value to those with obesity-related cardiovascular disease (CVD). Our study aims to investigate the effect of gastric mucosal devitalization (GMD) on blood pressure (BP) and cardiovascular lipid deposition in a rat model of obesity. Methods  GMD of 70 % of the stomach was achieved by argon plasma coagulation. GMD was compared to sleeve gastrectomy (SG) and sham (SH) in a high-fat-diet-induced rat model of obesity (48 rats). At 8 weeks, we measured noninvasive BP, renin, vessel relaxation and ghrelin receptor regulation in the aorta. In addition, we quantified cardiac lipid deposition and lipid droplet deposition in cardiac muscle and aorta. Results  GMD and SG were observed to have similar reductions in body weight, visceral adiposity, and serum lipid profile compared to SH rats. GMD resulted in a significant reduction in arterial BP compared to SH. Furthermore, there were significant reductions in plasma renin activity and percentage of phenylnephrine constriction to acetylcholine at the aortic ring in GMD rats compared to SH, providing insights into the mechanisms behind the reduced BP. Interestingly, the reduced BP occurred despite a reduction in endothelial ghrelin recteptor activation. Cardiac lipid content was significantly reduced in GMD rats. Lipid deposition, as illustrated by Nile Red stain, was reduced in cardiac muscle and the aorta. Conclusion  GMD resulted in a significant improvement in BP, renin and cardiovascular lipid deposition. GMD deserves further attention as a method of treating obesity-related CVD.

Mechanisms of Weight Loss After Sleeve Gastrectomy and Adjustable Gastric Banding: Far More Than Just Restriction

Obesity has reached global epidemic proportions in recent decades. Bariatric surgery is currently accepted as most effective in alleviating morbid obesity and related disorders. Sleeve gastrectomy (SG) and adjustable gastric banding (AGB) have gained popularity since the beginning of this century because of their efficacy, safety, and simplicity. SG, in particular, has emerged as the most popular bariatric procedure because of its simpler concept and shorter operative time compared with gastric bypass. Caloric restriction, however, cannot account for the sustained weight loss and improved glucose metabolism seen following SG and AGB. Other mechanisms, including changes in gastrointestinal hormone secretion, rearrangement of hypothalamic and vagal control, alteration in energy expenditure, and re-regulation of bile acid metabolism and the intestinal flora environment, are thought to contribute to the postoperative benefits. This review focuses on clinical and experimental literature addressing the potential mechanisms for SG and AGB procedures in human and animal models. Understanding such mechanisms can provide important insight into how current gastric restrictive procedures work and how future treatments of obesity, both surgical and nonsurgical, can be developed.

Roux-en-Y Gastric Bypass Is More Effective than Sleeve Gastrectomy in Improving Postprandial Glycaemia and Lipaemia in Non-diabetic Morbidly Obese Patients: a Short-term Follow-up Analysis

PURPOSE

We aimed to compare the effects of Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG) on postprandial glucose and lipid metabolism in addition to weight loss and fasting metabolic profile, in non-diabetic patients undergoing bariatric surgery.

METHODS

Seventy-one patients were consecutively recruited and studied preoperatively, 3 and 6 months after surgery. Of these, 28 underwent RYGB (7 males, age 38 ± 9 years, BMI 46.9 ± 5.0 kg/m²), and 43 SG (9 males, age 38 ± 9 years, BMI 50.2 ± 7.0 kg/m²). A semi-liquid mixed meal was consumed, and blood samples were taken before, and every 30 min after meal ingestion up to 180 min postprandially, for measurement of glucose, insulin, and lipids. The overall postprandial response was assessed as area under the concentration-time curve (AUC).

RESULTS

Baseline metabolic parameters were similar between RYGB and SG. Both groups experienced comparable weight loss, and a similar improvement in fasting glucose, insulin, and insulin resistance. Total and LDL cholesterol levels were lower at 6 months after RYGB compared to SG, while there was no difference in HDL cholesterol or triglycerides. Glucose AUC was lower after RYGB compared to SG at both 3 (p = 0.008) and 6 months (p = 0.016), without any difference in postprandial insulin response. Triglyceride AUC was also lower in RYGB vs. SG at 3 and 6 months (p ≤ 0.001).

CONCLUSIONS

RYGB is superior to SG in improving postprandial glycaemia and lipaemia and cholesterol profile 6 months postoperatively in non-diabetic, severely obese patients. These findings imply procedure-specific effects, such as the malabsorptive nature of RYGB, and less likely a different incretin postoperative response.

Roux-en-Y gastric bypass surgery reprograms enterocyte triglyceride metabolism and postprandial secretion in rats

OBJECTIVE

Roux-en-Y gastric bypass (RYGB) surgery produces rapid and persistent reductions in plasma triglyceride (TG) levels associated with fewer cardiovascular events. The mechanisms of the reduction in systemic TG levels remain unclear. We hypothesized that RYGB reduces intestinal TG secretion via altered enterocyte lipid handling.

METHODS

RYGB or Sham surgery was performed in diet-induced obese, insulin-resistant male Sprague-Dawley rats. First, we tested whether RYGB reduced test meal-induced TG levels in the intestinal lymph, a direct readout of enterocyte lipid secretion. Second, we examined whether RYGB modified TG enterocyte secretion at the single lipid level and in comparison to other lipid subclasses, applying mass spectrometry lipidomics to the intestinal lymph of RYGB and Sham rats (0-21 days after surgery). Third, we explored whether RYGB modulated the metabolic characteristics of primary enterocytes using transcriptional and functional assays relevant to TG absorption, reesterification, storage in lipid droplets, and oxidation.

RESULTS

RYGB reduced overall postprandial TG concentrations compared to Sham surgery in plasma and intestinal lymph similarly. RYGB reduced lymphatic TG concentrations more than other lipid subclasses, and shifted the remaining TG pool towards long-chain, unsaturated species. In enterocytes of fasted RYGB rats, lipid uptake was transcriptionally (Fatp4, Fabp2, Cd36) and functionally reduced compared to Sham, whereas TG reesterification genes were upregulated.

CONCLUSION

Our results show that RYGB substantially reduces intestinal TG secretion and modifies enterocyte lipid absorption and handling in rats. These changes likely contribute to the improvements in the plasma TG profile observed after RYGB in humans.

Mechanisms for the metabolic success of bariatric surgery

To date, bariatric surgery remains the most effective strategy for the treatment of obesity and its comorbidities. However, given the enormity of the obesity epidemic, and sometimes variable results, it is not a feasible strategy for the treatment of all obese patients. A simple PubMed search for 'bariatric surgery' reveals over 28 000 papers that have been published since the 1940s when the first bariatric surgeries were performed. However, there is still an incomplete understanding of the mechanisms for the weight loss and metabolic success of surgery. An understanding of the mechanisms is important because it may lead to greater understanding of the pathophysiology of obesity and thus surgery-alternative strategies for the treatment of all obese patients. In this review, the potential mechanisms that underlie the success of surgery are discussed, with a focus on the potential endocrine, neural and other circulatory factors (eg, bile acids) that have been proposed to play a role.

Inflammatory responses to dietary and surgical weight loss in male and female mice

BACKGROUND

Weight loss by surgery or lifestyle changes is strongly recommended for obese individuals to improve metabolic health, but the underlying impairments that persist from a history of obesity remain unclear. Recent investigations demonstrate a persistent inflammatory state with weight loss and bariatric surgery, but the mechanism and impact are not fully understood. Additionally, these studies have not been performed in females although women are the majority of individuals undergoing weight loss interventions.

METHODS

The goal of this study was to determine the sex differences in metabolically induced inflammation after dietary weight loss (WL) or bariatric surgery. Following a 60% high-fat diet (HFD) for 12 weeks, C57Bl/6j mice underwent either a dietary switch to normal chow for WL or vertical sleeve gastrectomy (VSG) and were evaluated 8 weeks after intervention. WL effects on myelopoiesis were further evaluated with bone marrow chimeras.

RESULTS

Both sexes had a decrease in adiposity and total weight following WL or VSG intervention. With HFD, females had very little inflammation and no further increase with WL, but males had persistent inflammation even after WL despite metabolic improvement. Interestingly, after VSG, myeloid inflammation was increased in the livers of males and to a lesser extent in females.

CONCLUSIONS

These studies demonstrate that regardless of sex, it is critical to assess an individuals' history of obesity rather than just rely on current weight status in medical decision-making. There are long-lasting effects on tissue inflammation in both sexes especially with surgical weight loss. Dietary change is overall most effective to improve meta-inflammation in obese males on its own or in combination with surgical weight loss.

Targeting Bile Acid-Activated Receptors in Bariatric Surgery

Bariatric surgical procedures, including Roux-en-Y gastric bypass and vertical sleeve gastrectomy, are currently the most effective clinical approaches to achieve a significant and sustainable weight loss. Bariatric surgery also concomitantly improves type 2 diabetes and other metabolic diseases such as nonalcoholic steatohepatitis, cardiovascular diseases, and hyperlipidemia. However, despite the recent exciting progress in the understanding how bariatric surgery works, the underlying molecular mechanisms of bariatric surgery remain largely unknown. Interestingly, bile acids are emerging as potential signaling molecules to mediate the beneficial effects of bariatric surgery. In this review, we summarize the recent findings on bile acids and their activated receptors in mediating the beneficial metabolic effects of bariatric surgery. We also discuss the potential to target bile acid-activated receptors in order to treat obesity and other metabolic diseases.

Food Intake and Eating Behavior After Bariatric Surgery

Obesity is an escalating global chronic disease. Bariatric surgery is a very efficacious treatment for obesity and its comorbidities. Alterations to gastrointestinal anatomy during bariatric surgery result in neurological and physiological changes affecting hypothalamic signaling, gut hormones, bile acids, and gut microbiota, which coalesce to exert a profound influence on eating behavior. A thorough understanding of the mechanisms underlying eating behavior is essential in the management of patients after bariatric surgery. Studies investigating candidate mechanisms have expanded dramatically in the last decade. Herein we review the proposed mechanisms governing changes in eating behavior, food intake, and body weight after bariatric surgery. Additive or synergistic effects of both conditioned and unconditioned factors likely account for the complete picture of changes in eating behavior. Considered application of strategies designed to support the underlying principles governing changes in eating behavior holds promise as a means of optimizing responses to surgery and long-term outcomes.

Gut adaptation after metabolic surgery and its influences on the brain, liver and cancer

Metabolic surgery is the best treatment for long-term weight loss maintenance and comorbidity control. Metabolic operations were originally intended to change anatomy to alter behaviour, but we now understand that the anatomical changes can modulate physiology to change behaviour. They are no longer considered only mechanically restrictive and/or malabsorptive procedures; rather, they are considered metabolic procedures involving complex physiological changes, whereby gut adaptation influences signalling pathways in several other organs, including the liver and the brain, regulating hunger, satiation, satiety, body weight, glucose metabolism and immune functions. The integrative physiology of gut adaptation after these operations consists of a complex mechanistic web of communication between gut hormones, bile acids, gut microbiota, the brain and both enteric and central nervous systems. The understanding of nutrient sensing via enteroendocrine cells, the enteric nervous system, hypothalamic peptides and adipose tissue and of the role of inflammation has advanced our knowledge of this integrative physiology. In this Review, we focus on the adaptation of gut physiology to the anatomical alterations from Roux-en-Y gastric bypass and vertical sleeve gastrectomy and the influence of these procedures on food intake, weight loss, nonalcoholic fatty liver disease (NAFLD) and cancer. We also aim to demonstrate the underlying mechanisms that could explain how metabolic surgery could be used as a therapeutic option in NAFLD and certain obesity-related cancers.

Therapeutic reduction of lysophospholipids in the digestive tract recapitulates the metabolic benefits of bariatric surgery and promotes diabetes remission

OBJECTIVE

Obesity and obesity-related metabolic disorders are major health problems worldwide. The most effective obesity intervention is bariatric surgery. This study tested the hypothesis that bariatric surgery alters phospholipid metabolism in the gastrointestinal tract to favor a metabolically healthy gut microbiota profile and therapeutic intervention of phospholipid metabolism in the gastrointestinal may have similar metabolic benefits.

METHODS

The first study compared plasma levels of the bioactive lipid metabolites lysophospholipid and trimethylamine N-oxide (TMAO) as well as gut microbiota profile in high fat/carbohydrate (HFHC) diet-fed C57BL/6 mice with or without vertical sleeve gastrectomy (VSG) and in Pla2g1b^-/- mice with group 1B phospholipase A₂ gene inactivation. The second study examined the effectiveness of the non-absorbable secretory phospholipase A₂ inhibitor methyl indoxam to reverse hyperglycemia and hyperlipidemia in HFHC diet-fed C57BL/6 mice after diabetes onset.

RESULTS

Both bariatric surgery and PLA2G1B inactivation were shown to reduce lysophospholipid content in the gastrointestinal tract, resulting in resistance to HFHC diet-induced alterations of the gut microbiota, reduction of the cardiovascular risk factors hyperlipidemia and TMAO, decreased adiposity, and prevention of HFHC diet-induced diabetes. Importantly, treatment of wild type mice with methyl indoxam after HFHC diet-induced onset of hyperlipidemia and hyperglycemia effectively restored normal plasma lipid and glucose levels and replicated the metabolic benefits of VSG surgery with diabetes remission and TMAO reduction.

CONCLUSION

These results provided pre-clinical evidence that PLA2G1B inhibition in the digestive tract may be a viable alternative option to bariatric surgery for obesity and obesity-related cardiometabolic disorder intervention.

Gastric mucosal devitalization is safe and effective in reducing body weight and visceral adiposity in a porcine model

BACKGROUND AND AIMS

The early improvement in metabolic profile after sleeve gastrectomy (SG) indicates that the significant benefits of metabolic surgery are gastric in origin. We have previously demonstrated that devitalization of the gastric mucosa (without a reduction in gastric volume) in metabolically disturbed obese rats results in an improvement of obesity and its associated comorbidities. The aims of this study were to assess the technical feasibility, efficacy, and safety of gastric mucosal devitalization (GMD) in a large animal (porcine) model.

METHODS

A 3-arm (GMD versus SG versus sham [SH]) prospective randomized controlled trial with an 8-week follow-up period was performed. The primary endpoint was relative weight loss. Secondary endpoints were absolute body weight, abdominal visceral adiposity, abdominal subcutaneous adiposity, organ lipid content, and serum ghrelin level.

RESULTS

GMD resulted in a significant relative weight loss of 36% over SH at 8 weeks (P < .05). There was no significant difference in relative weight loss between GMD and SG at 4 weeks; however, SG resulted in a 29% superior relative weight loss at 8 weeks (P < .05). With regard to visceral adiposity, there was a significant benefit of GMD over SH at 8 weeks. Despite differences in relative weight loss, there was no significant difference in visceral adiposity between SG and GMD at 8 weeks. Significant improvements in GMD over SH were noted with regard to skeletal and heart muscle lipid content. GMD pigs at 8 weeks demonstrated regeneration of the gastric mucosa without ulceration or significant scarring. Despite mucosal regeneration, the abundance of serum ghrelin was significantly lower in the GMD cohort compared with the SG and SH cohorts.

CONCLUSIONS

GMD was technically feasible and resulted in relative weight loss and an improvement in visceral adiposity. The benefits noted were out of proportion to what would be expected with weight loss alone.

Vertical sleeve gastrectomy corrects metabolic perturbations in a low-exercise capacity rat model

OBJECTIVE

Bariatric surgery is currently our most effective strategy at weight loss, yet the mechanisms for its success remain unknown. Low exercise capacity, in humans and rodents, predicts poor metabolic outcome. The objective of this manuscript was to determine if bariatric surgery could restore metabolic perturbations in rats with low intrinsic exercise capacity.

METHODS

We performed vertical sleeve gastrectomy (VSG) or sham surgery in high fat-fed rats selectively bred for low running capacity.

RESULTS

We found that VSG reduced body mass through a reduction in fat mass, caused early reductions in food intake, and shifted macronutrient preference away from fat and toward carbohydrates. VSG had no impact on basal glucose but did improve the return to baseline after an oral glucose load. As has been shown previously, VSG increased postprandial insulin, GLP-1, and bile acids. There was no significant impact of VSG on plasma triglycerides, hepatic triglycerides, or cholesterol. Interestingly, the brown adipose tissue to white adipose tissue ratio tended to be greater in VSG compared to sham surgery animals. While VSG positively impacted several aspects of metabolism, it did not enhance maximal oxygen capacity and seemed to lower metabolic efficiency as indicated by lower resting oxygen consumption and fat and carbohydrate oxidation.

CONCLUSION

VSG can improve the metabolic status of animals with a low exercise capacity independently of exercise capacity.

Vertical sleeve gastrectomy improves indices of metabolic disease in rodent model of surgical menopause

OBJECTIVE

Although women are the most common recipients of weight loss surgeries for the amelioration of the comorbidities of obesity, few studies have addressed the efficacy of these procedures with specific attention to reproductive stage. Here we ask in a rodent model of vertical sleeve gastrectomy (VSG) whether improvements to metabolic health are realized in women having received surgical menopause. Specifically we were interested in knowing whether rats made menopausal through surgical means would exhibit persistent hepatic steatosis as reported in previously pregnant, freely cycling female VSG rats or if it is resolved as reported in male VSG rats.

METHODS

All the rats first received ovariectomy (OVX) and then were placed on high-fat diet before either sham or VSG surgery (N = 12, 9) and then were monitored for resolution of obesity-related comorbidities.

RESULTS

VSG was sufficient to reduce weight and adiposity in OVX females in comparison to obese rats (P < 0.001). Glucose tolerance (P < 0.05) was improved in OVX-VSG females with no change in insulin sensitivity. Both circulating (P < 0.01) and hepatic triglyceride (P < 0.01) levels were also reduced after VSG. Liver integrity was improved in OVX-VSG in comparison to OVX-obese as reflected by reduced aspartate aminotransferase levels (P < 0.05). The ability of mitochondria to generate adenosine triphosphate was maintained, and an increase in complex IV may decrease the production of mitochondrial reactive oxygen species.

CONCLUSIONS

Taken together, VSG in OVX rats experience many positive benefits including the resolution of hepatic steatosis that persists in reproductively intact female rats after VSG.

Gastric mucosal devitalization reduces adiposity and improves lipid and glucose metabolism in obese rats

BACKGROUND AND AIMS

The gastric mucosa is an endocrine organ that regulates satiation pathways by expression of orexigenic and anorexigenic hormones. Vertical sleeve gastrectomy (VSG) excludes gastric mucosa and reduces gastric volume. Our study aimed to investigate the independent effects of altering gastric mucosa on obesity and its related comorbidities.

METHODS

Gastric mucosa devitalization (GMD) of 70% of the stomach was achieved by argon plasma coagulation in a high-fat diet rat model and was compared with VSG and sham surgery. In an 8-week follow-up study, we quantified body weight, visceral adiposity, insulin resistance index, cholesterol profiles, and free fatty acid profiles by enzyme-linked immunosorbent assay (ELISA). Following a 2-hour oral glucose tolerance test, the kinetics of ghrelin, glucagon-like peptide-1, peptide YY, and serum and liver bile acid levels were measured. Liver lipid content was quantified by ELISA.

RESULTS

GMD resulted in significant reductions in body weight, visceral and subcutaneous adipose tissue, and hepatic steatosis as well as an improvement in lipid metabolism. GMD resulted in significant reductions in food intake and intestinal malabsorption of free fatty acids, both contributing to improved body composition and metabolic profile. Mechanistically, GMD resulted in a significant reduction in serum palmitate levels as well as an increase in serum and liver bile acid levels, known to alter glucose and lipid metabolism. Similar changes were noted when VSG rats were compared with sham surgery rats.

CONCLUSIONS

Devitalization of gastric mucosa, independent of altering gastric volume, was able to reduce obesity-related comorbidities. The gastric mucosa may be a potential target for treating obesity and its associated comorbidities.

Metabolic Effects of Bariatric Surgery

BACKGROUND

Obesity can be defined as a chronic subcortical brain disease, as there is an important neurophysiological component to its etiology based on changes in the functioning of those areas of the brain controlling food intake and reward. Extensive metabolic changes accompany bariatric surgery-based treatment of obesity. Consequently, the term “metabolic” surgery is being increasingly adopted in relation to the beneficial effects these procedures have on chronic diseases like type 2 diabetes.

CONTENT

In the present review, we focus on the key biochemical and physiological changes induced by metabolic surgery and highlight the beneficial effects accrued systemically with the use of an organ-based approach. Understanding the impact on and interactions between the gut, brain, adipose tissue, liver, muscle, pancreas, and kidney is key to understanding the sum of the metabolic effects of these operations.

SUMMARY

Further mechanistic studies are essential to assess the true potential of metabolic surgery to treat metabolic comorbidities of obesity beyond type 2 diabetes. Approaches that may mitigate the metabolic side effects of surgery also require attention. Understanding the positive impact of metabolic surgery on metabolic health may result in a wider acceptance of this intervention as treatment for metabolic, comorbid conditions.

The Role of GLP-1 in the Metabolic Success of Bariatric Surgery

Two of the most popular bariatric procedures, vertical sleeve gastrectomy (VSG) and Roux-en-Y gastric bypass (RYGB), are commonly considered metabolic surgeries because they are thought to affect metabolism in a weight loss-independent manner. In support of this classification, improvements in glucose homeostasis, insulin sensitivity, and even discontinuation of type 2 diabetes mellitus (T2DM) medication can occur before substantial postoperative weight loss. The mechanisms that underlie this effect are unknown. However, one of the common findings after VSG and RYGB in both animal models and humans is the sharp postprandial rise in several gut peptides, including the incretin and satiety peptide glucagonlike peptide-1 (GLP-1). The increase in endogenous GLP-1 signaling has been considered a primary pathway leading to postsurgical weight loss and improvements in glucose metabolism. However, the degree to which GLP-1 and other gut peptides are responsible for the metabolic successes after bariatric surgery is continually debated. In this review we discuss the mechanisms underlying the increase in GLP-1 and its potential role in the metabolic improvements after bariatric surgery, including remission of T2DM. Understanding the role of changes in gut peptides, or lack thereof, will be crucial in understanding the critical factors necessary for the metabolic success of bariatric surgery.

Roux-en-Y gastric bypass reduces plasma cholesterol in diet-induced obese mice by affecting trans-intestinal cholesterol excretion and intestinal cholesterol absorption

OBJECTIVE

Bariatric surgery appears as the most efficient therapeutic alternative in morbidly obese patients. In addition to its efficiency to decrease body weight, it also improves metabolic complications associated to morbid obesity, including dyslipidemia. Although the cholesterol-lowering effect varies with the bariatric procedures, the underlying molecular mechanisms remain poorly defined. This study aims to assess the consequence of both restrictive (sleeve gastrectomy; SG) and malabsorptive (Roux-en-Y gastric bypass; RYGB) procedures on cholesterol metabolism in mice.

SUBJECTS

Ten-week-old C57BL6/J males were fed with a high-fat diet for 8-14 weeks before sleeve or RYGB surgery.

RESULTS

SG has a modest and transient effect on plasma cholesterol levels, linked to a reduction in food intake. In contrast, modified RYGB led to a sustained ≈35% reduction in plasma cholesterol concentrations with a drastic increase in fecal cholesterol output. Mechanistically, RYGB exerts a synergystic effect on cholesterol metabolism by inducing the trans-intestinal cholesterol efflux and reducing the intestinal cholesterol absorption.

CONCLUSIONS

In mice, RYGB, but not sleeve, strongly favors plasma cholesterol elimination by concomitantly increasing trans-intestinal cholesterol excretion and by decreasing intestinal cholesterol absorption. Our models open new perspective for deciphering the hypocholesterolemic effects of bariatric procedures.

Different effects of bariatric surgical procedures on dyslipidemia: a registry-based analysis

BACKGROUND

The scale and variables linked to bariatric surgery's effect on dyslipidemia have not been conclusive.

OBJECTIVE

To compare the effect of Roux-en-Y gastric bypass (RYGB), sleeve gastrectomy (SG), and adjustable gastric banding (LAGB) on dyslipidemia SETTING: National bariatric surgery registry.

METHODS

Plasma lipids and associated variables were compared at baseline and 1 year (12±4 mo) after surgery for registry patients with dyslipidemia enrolled from June 2013 to August 2014.

RESULTS

The greatest mean total-cholesterol (TC) reduction was observed post-RYGB, 226.7±26.4 to 181.3±30.9 mg/dL (19.9%, n = 208), followed by post-SG, 227.9±24.4 to 206.7±34.2 mg/dL (8.9%, n = 1515; P<.001). Normal TC levels of below 200 mg/dL were achieved by 76% post-RYGB patients compared with 43.5% post-SG patients (odds ratio [OR] = 6.24, 95% confidence interval [CI]: 3.69-10.53) and 25.6% post-LABG patients (OR = 9.66, 95% CI: 4.11-22.67; P<.01). Although equivalent patterns were observed for low-density-lipoprotein cholesterol (LDL), the levels of high-density-lipoprotein cholesterol (HDL) were most improved post-SG, reaching normal levels in 58.1% of SG male patients versus 39.5% of RYGB male patients (OR = 1.56, 95% CI: 1.04-2.35), (P = .02). The lowering of triglyceride levels by approximately 75% was comparable after SG and RYGB procedures. The type of surgery was the strongest independent predictor for all lipid level improvements or remissions. Male sex was an independent predictor for LDL normalization only (OR = 1.88, 95% CI: 1.24-2.85). Excess weight loss offered no meaningful prediction for lipid improvement (OR = 1.01-1.03).

CONCLUSION

Particular types of bariatric surgeries had different effects on dyslipidemia, independent of weight loss. Overall, the RYGB achieved the biggest reduction in plasma lipids (TC and LDL), although SG did affect HDL. Our results could aid in the decision-making process regarding the most appropriate procedure for patients with dyslipidemia.

Bariatric surgery emphasizes biological sex differences in rodent hepatic lipid handling

Background

Eighty percent of patients who receive bariatric surgery are women, yet the majority of preclinical studies are in male rodents. Because sex differences drive hepatic gene expression and overall lipid metabolism, we sought to determine whether sex differences were also apparent in these endpoints in response to bariatric surgery.

Methods

Two cohorts of age-matched virgin male and female Long-Evans rats were placed on a high fat diet for 3 weeks and then received either Sham or vertical sleeve gastrectomy (VSG), a surgery which resects 80% of the stomach with no intestinal rearrangement.

Results

Each sex exhibited significantly decreased body weight due to a reduction in fat mass relative to Sham controls (p < 0.05). Microarray and follow-up qPCR on liver revealed striking sex differences in gene expression after VSG that reflected a down-regulation of hepatic lipid metabolism and an up-regulation of hepatic inflammatory pathways in females vs. males after VSG. While the males had a significant reduction in hepatic lipids after VSG, there was no reduction in females. Ad lib-fed and fasting circulating triglycerides, and postprandial chylomicron production were significantly lower in VSG relative to Sham animals of both sexes (p < 0.01). However, hepatic VLDL production, highest in sham-operated females, was significantly reduced by VSG in females but not males.

Conclusions

Taken together, although both males and females lose weight and improve plasma lipids, there are large-scale sex differences in hepatic gene expression and consequently hepatic lipid metabolism after VSG.

Electronic supplementary material

The online version of this article (doi:10.1186/s13293-017-0126-x) contains supplementary material, which is available to authorized users.

Does bariatric surgery improve adipose tissue function?

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

The role of proximal versus distal stomach resection in the weight loss seen after vertical sleeve gastrectomy

The mechanisms involved in the weight loss seen after vertical sleeve gastrectomy (VSG) are not clear. The rat stomach has two morphologically and functionally distinct proximal and distal parts. The rat model for VSG involves complete removal of the proximal part and 80% removal of the distal part along the greater curvature. The purpose of this study was to understand the potential independent contributions of removal of these distinct gastric sections to VSG outcomes. We prepared four surgical groups of male Long-Evans rats: VSG, sham surgery (control), selective proximal section removal (PR), and selective distal section removal (DR). Gastric emptying rate (GER) was highest after VSG compared with all other groups. However, PR, in turn, had significantly greater GER compared with both DR and sham groups. The surgery-induced weight loss followed the same pattern with VSG causing the greatest weight loss and PR having greater weight loss compared with DR and sham groups. The results were robust for rats fed regular chow or a high-fat diet. Body mass analysis revealed that the weight loss was due to the loss of fat mass, and there was no change in lean mass after the surgeries. In conclusion, removal of the proximal stomach contributes to most, but not all, of the physiological impact of VSG.

The Use of Rat and Mouse Models in Bariatric Surgery Experiments

Animal models have been proven to be a crucial tool for investigating the physiological mechanisms underlying bariatric surgery in general and individual techniques in particular. By using a translational approach, most of these studies have been performed in rodents and have helped to understand how bariatric surgery may or may not work. However, data from studies using animal models should always be critically evaluated for their transferability to the human physiology. It is, therefore, the aim of this review to summarize both advantages and limitations of data generated by animal based experiments designed to investigate and understand the physiological mechanisms at the root of bariatric surgery.

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.

Longer-Term Physiological and Metabolic Effects of Gastric Bypass Surgery

Obesity is closely associated with the development of type 2 diabetes. Many strategies have been used in the past to combat these two conditions, but very few provide for stable and durable glycemic control. Bariatric surgery has emerged as a powerful tool for treating obesity and in over 70 % of cases provides a short-term cure for diabetes. While the acute metabolic effects of surgery are striking, it remains important for us to also consider the long-term effects. This review aims to summarize the chronic or long-term metabolic and physiological effects of Roux-en-Y gastric bypass (RYGB) surgery on pancreatic function, skeletal muscle and hepatic insulin sensitivity, and gastrointestinal remodeling. An increased understanding of the current state of research in these areas can provide the basis for stimulating further research that would contribute to new treatment and management strategies for obesity and diabetes.

Recent advances in metabolic and bariatric surgery

Obesity and its associated medical conditions continue to increase and add significant burden to patients, as well as health-care systems, worldwide. Bariatric surgery is the most effective treatment for severe obesity and its comorbidities, and resolution of diabetes is weight loss-independent in the case of some operations. Although these weight-independent effects are frequently described clinically, the mechanisms behind them are not well understood and remain an intense area of focus in the growing field of metabolic and bariatric surgery. Perceptions of the mechanisms responsible for the beneficial metabolic effects of metabolic/bariatric operations have shifted from being mostly restrictive and malabsorption over the last 10 to 15 years to being more neuro-hormonal in origin. In this review, we describe recent basic and clinical findings of the major clinical procedures (adjustable gastric banding, vertical sleeve gastrectomy, Roux-en-Y gastric bypass, and biliopancreatic diversion) as well as other experimental procedures (ileal interposition and bile diversion) that recapitulate many of the metabolic effects of these complex operations in a simpler fashion. As the role of bile acids and the gut microbiome on metabolism is becoming increasingly well described, their potential roles in these improvements following metabolic surgery are becoming better appreciated. Bile acid and gut microbiome changes, in light of recent developments, are discussed in the context of these surgical procedures, as well as their implications for future study.

Reprogramming of defended body weight after Roux-En-Y gastric bypass surgery in diet-induced obese mice

OBJECTIVE

Roux-en-Y gastric bypass surgery (RYGB) results in sustained lowering of body weight in most patients, but the mechanisms involved are poorly understood. The aim of this study was to obtain support for the notion that reprogramming of defended body weight, rather than passive restriction of energy intake, is a fundamental mechanism of RYGB.

METHODS

Male C57BL6J mice reaching different degrees of obesity on a high-fat diet either with ad libitum access or with caloric restriction (weight-reduced) were subjected to RYGB.

RESULTS

RYGB-induced weight loss and fat mass loss were proportional to pre-surgical levels, with moderately obese mice losing less body weight and fat compared with very obese mice. Remarkably, mice that were weight-reduced to the level of chow controls before surgery immediately gained weight after surgery, exclusively accounted for by lean mass gain.

CONCLUSIONS

The results provide additional evidence for reprogramming of a new defended body weight as an important principle by which RYGB lastingly suppresses body weight. RYGB appears to selectively abolish defense of a higher fat mass level, while remaining sensitive to the defense of lean mass. The molecular and physiological mechanisms underlying this reprogramming remain to be elucidated.

Hematological, Biochemical, and Immunological Laboratory and Histomorphological Effects of Sleeve Gastrectomy on Female Rats

Restriction of food intake leads to immunologic and histomorphological changes in rats demonstrated by Moriyama. This study is planned to show how sleeve gastrectomy restricts food intake and its effects on biochemical liver function, immunologic and hematologic laboratory parameters, and histomorphological changes in rats. We used sleeve gastrectomy model on seven young adult female rats and compared study group with sham and control groups. Food consumption of rats was measured. All rats were sacrificed on the 50th day, and blood and tissue samples were collected. There was a significant low food intake in sleeve gastrectomy group (p = 0.013). No differences were observed on hematologic, biochemical, and immunologic laboratory parameters between groups. Toxicity parameters in liver samples such as cytoplasmic atrophy, single-cell hepatocellular necrosis, and necrotic eosinophilic cells were significantly high in sleeve gastrectomy group (p = 0.005). Histomorphological examination of the spleen and kidneys revealed significant changes in sleeve gastrectomy and sham groups compared with controls (p = 0.004 and p = 0.018, respectively). Although sleeve gastrectomy does not lead to alteration in hematologic, biochemical, and immunologic laboratory parameters, it causes decreased food consumption, which results in toxicological histomorphological changes in rat liver as well as some changes in kidney and spleen samples.

Bariatric surgery and diabetes remission: how far have we progressed?

Obesity and type 2 diabetes mellitus have been associated with higher morbidity and mortality. Bariatric surgery results in substantial and sustained weight loss in morbidly obese patients and improves obstructive sleep apnea. Furthermore, bariatric surgery improves diabetes control, hypertension, quality of life, stroke, myocardial infarction and reduces mortality. Interestingly, bariatric surgery induces high rates of short and long-term diabetes remission. While the exact mechanisms behind this are not completely understood, improved insulin action, β-cell function and a complex interplay of hormones in the entero-insular axis appear to play major roles. Insulin action improves proportionally to weight loss and it gets completely normalized especially after bilio-pancreatic diversion. β-Cell function also seems to improve after a variety of bariatric surgeries. Seemingly, baseline β-cell function is able to predict future diabetes remission. This article will review the effectiveness of bariatric procedures on the remission and improvement of diabetes and its implicated mechanisms.

Metabolic, behavioral, and reproductive effects of vertical sleeve gastrectomy in an obese rat model of polycystic ovary syndrome

BACKGROUND

Polycystic ovary syndrome (PCOS) is the most common endocrinopathy affecting women of reproductive age. Its clinical expression is diverse, including metabolic, behavioral, and reproductive effects, with many affected by obesity and decreased quality of life. Women with PCOS who have undergone surgically induced weight loss have reported tremendous benefit, not only with weight loss, but also improvement of hyperandrogenism and menstrual cyclicity.

METHODS

In a rat model of PCOS achieved via chronic administration of dihydrotestosterone (DHT) exposure, we investigated the ability of bariatric surgery, specifically vertical sleeve gastrectomy (VSG), to ameliorate the metabolic, behavioral, and reproductive abnormalities invoked by this PCOS model.

RESULTS

We found that DHT treatment combined with exposure to a high-fat diet resulted in increased body weight and body fat, impaired fasting glucose, hirsutism, anxiety, and irregular cycles. VSG resulted in reduced food intake, body weight, and adiposity with improved fasting glucose and triglycerides. VSG induced lower basal corticosterone levels and attenuated stress responsivity. Once the DHT levels decreased to normal, regular estrous cyclicity was also restored.

CONCLUSIONS

VSG, therefore, improved PCOS manifestations in a comprehensive manner and may represent a potential therapeutic approach for specific aspects of PCOS.

The role of bile acids in reducing the metabolic complications of obesity after bariatric surgery: a systematic review

BACKGROUND

Bariatric surgery is currently the most efficacious treatment for obesity and its associated metabolic co-morbidities, such as diabetes. The metabolic improvements occur through both weight-dependent and weight-independent mechanisms. Bile acids (BAs) have emerged as key signalling molecules that have a central role in modulating many of the physiological effects seen after bariatric surgery. This systematic review assesses the evidence from both human and animal studies for the role of BAs in reducing the metabolic complications of obesity following bariatric surgery.

METHODS

We conducted a systematic search of Medline and Embase databases to identify all articles investigating the role of BAs in mediating the metabolic changes observed following bariatric surgery in both animal and human studies. Boolean logic was used with relevant search terms, including the following MeSH terms: 'bile acids and salts', 'bariatric surgery', 'metabolic surgery', 'gastrointestinal tract/surgery' and 'obesity/surgery'.

RESULTS

Following database searches (n=1197), inclusion from bibliography searches (n=2) and de-duplication (n=197), 1002 search results were returned. Of these, 132 articles were selected for full-text review, of which 38 articles were deemed relevant and included in the review. The findings support the effects of BAs on satiety, lipid and cholesterol metabolism, incretins and glucose homoeostasis, energy metabolism, gut microbiota and endoplasmic reticulum stress following bariatric surgery. Many of these metabolic effects are modulated through the BA receptors FXR and TGR5. We also explore a possible link between BAs and carcinogenesis following bariatric surgery.

CONCLUSIONS

Overall there is good evidence to support the role of BAs in the metabolic effects of bariatric surgery through the above mechanisms. BAs could serve as a novel therapeutic pharmacological target for the treatment of obesity and its associated co-morbidities.

Metabolic changes induced by the biliopancreatic diversion in diet-induced obesity in male rats: the contributions of sleeve gastrectomy and duodenal switch

The mechanisms underlying the body weight and fat loss after the biliopancreatic diversion with duodenal switch (BPD/DS) remain to be fully delineated. The aim of this study was to examine the contributions of the two main components of BPD/DS, namely sleeve gastrectomy (SG) and duodenal switch (DS), on energy balance changes in rats rendered obese with a high-fat (HF) diet. Three different bariatric procedures (BPD/DS, SG, and DS) and three sham surgeries were performed in male Wistar rats. Sham-operated animals fed HF were either fed ad libitum (Sham HF) or pair weighed (Sham HF PW) by food restriction to the BPD/DS rats. A group of sham-operated rats was kept on standard chow and served as normal diet control (Sham Chow). All three bariatric surgeries resulted in a transient reduction in food intake. SG per se induced a delay in body weight gain. BPD/DS and DS led to a noticeable gut malabsorption and a reduction in body weight and fat gains along with significant elevations in plasma levels of glucagon-like peptide-1(7-36) and peptide YY. BPD/DS and DS elevated energy expenditure above that of Sham HF PW during the dark phase. However, they reduced the volume, oxidative metabolism, and expression of thermogenic genes in interscapular brown adipose tissue. Altogether the results of this study suggest that the DS component of the BPD/DS, which led to a reduction in digestible energy intake while sustaining energy expenditure, plays a key role in the improvement in the metabolic profile led by BPD/DS in rats fed a HF diet.

Bile acid nuclear receptor FXR and digestive system diseases

Bile acids (BAs) are not only digestive surfactants but also important cell signaling molecules, which stimulate several signaling pathways to regulate some important biological processes. The bile-acid-activated nuclear receptor, farnesoid X receptor (FXR), plays a pivotal role in regulating bile acid, lipid and glucose homeostasis as well as in regulating the inflammatory responses, barrier function and prevention of bacterial translocation in the intestinal tract. As expected, FXR is involved in the pathophysiology of a wide range of diseases of gastrointestinal tract, including inflammatory bowel disease, colorectal cancer and type 2 diabetes. In this review, we discuss current knowledge of the roles of FXR in physiology of the digestive system and the related diseases. Better understanding of the roles of FXR in digestive system will accelerate the development of FXR ligands/modulators for the treatment of digestive system diseases.

Appetite and body weight regulation after bariatric surgery

Bariatric surgery continues to be remarkably efficient in treating obesity and type 2 diabetes mellitus and a debate has started whether it should remain the last resort only or also be used for the prevention of metabolic diseases. Intense research efforts in humans and rodent models are underway to identify the critical mechanisms underlying the beneficial effects with a view towards non-surgical treatment options. This non-systematic review summarizes and interprets some of this literature, with an emphasis on changes in the controls of appetite. Contrary to earlier views, surgery-induced reduction of energy intake and subsequent weight loss appear to be the main drivers for rapid improvements of glycaemic control. The mechanisms responsible for suppression of appetite, particularly in the face of the large weight loss, are not well understood. Although a number of changes in food choice, taste functions, hedonic evaluation, motivation and self-control have been documented in both humans and rodents after surgery, their importance and relative contribution to diminished appetite has not yet been demonstrated. Furthermore, none of the major candidate mechanisms postulated in mediating surgery-induced changes from the gut and other organs to the brain, such as gut hormones and sensory neuronal pathways, have been confirmed yet. Future research efforts should focus on interventional rather than descriptive approaches in both humans and rodent models.