The neurohormonal regulation of energy intake in relation to bariatric surgery for obesity

The Neuro-Endo-Microbio-Ome Study: A Pilot Study of Neurobiological Alterations Pre- Versus Post-Bariatric Surgery

BACKGROUND

Plausible phenotype mechanisms following bariatric surgery include changes in neural and gastrointestinal physiology. This pilot study aims to investigate individual and combined neurologic, gut microbiome, and plasma hormone changes pre- versus post-vertical sleeve gastrectomy (VSG), Roux-en-Y gastric bypass (RYGB), and medical weight loss (MWL). We hypothesized post-weight loss phenotype would be associated with changes in central reward system brain connectivity, differences in postprandial gut hormone responses, and increased gut microbiome diversity.

METHODS

Subjects included participants undergoing VSG, n = 7; RYGB, n = 9; and MWL, n = 6. Ghrelin, glucagon-like peptide-1, peptide-YY, gut microbiome, and resting state functional magnetic resonance imaging (rsfMRI; using fractional amplitude of low-frequency fluctuations [fALFF]) were measured pre- and post-intervention in fasting and fed states. We explored phenotype characterization using clustering on gut hormone, microbiome, and rsfMRI datasets and a combined analysis.

RESULTS

We observed more widespread fALFF differences post-bariatric surgery versus post-MWL. Decreased post-prandial fALFF was seen in food reward regions post-RYGB. The highest number of microbial taxa that increased post-intervention occurred in the RYGB group, followed by VSG and MWL. The combined hormone, microbiome, and MRI dataset most accurately clustered samples into pre- versus post-VSG phenotypes followed by RYGB subjects.

CONCLUSION

The data suggest surgical weight loss (VSG and RYGB) has a bigger impact on brain and gut function versus MWL and leads to lesser post-prandial activation of food-related neural circuits. VSG subjects had the greatest phenotype differences in interactions of microbiome, rsfMRI, and gut hormone features, followed by RYGB and MWL. These results will inform future prospective research studying gut-brain changes post-bariatric surgery.

The Assessment of Food Addiction and the Yale Food Addiction Scale in Bariatric Surgery Populations

Food addiction (FA) appears among bariatric weight loss surgery candidates who struggle to control the intake of hyperpalatable/refined foods have high rates of psychopathology and related health problems. Despite this, prevalence rates of FA in the bariatric sector are reported as low or variable. We investigated the prevalence of FA and the applicability of conventionally used metrics for 166 pre-surgery candidates from a weight management centre (USA) and a major metropolitan hospital (Australia). Self-report measures assessed FA (Yale Food Addiction Scale (YFAS)), body mass index (BMI), disordered eating, addictive personality, psychopathology, and diet. Consistent with prior research, standard YFAS scoring, requiring the endorsement of a distress/impairment (D/I) criterion (FA + D/I), yielded a FA prevalence rate of 12.7%, compared to 37.3% when D/I was omitted (FA − D/I). We compared profiles for those with FA using each scoring method against those ‘without’, who did not meet a minimum of three YFAS symptoms (non-FA ≤ 2). Both methods differentiated those with and without FA on addictive traits, disordered eating and hyperpalatable food consumption. Only FA + D/I differentiated markers of psychological distress or impairment, including depression, anxiety and quality of life. Results indicate a need for further FA research in bariatric settings.

Sensory cue reactivity: Sensitization in alcohol use disorder and obesity

Neuroimaging techniques to measure the function of the human brain such as electroencephalography (EEG), positron emission tomography (PET), and functional magnetic resonance imaging (fMRI), are powerful tools for understanding the underlying neural circuitry associated with alcohol use disorder (AUD) and obesity. The sensory (visual, taste and smell) paradigms used in neuroimaging studies represent an ideal platform to investigate the connection between the different neural circuits subserving the reward/executive control systems in these disorders, which may offer a translational mechanism for novel intervention predictions. Thus, the current review provides an integrated summary of the recent neuroimaging studies that have applied cue-reactivity paradigms and neuromodulation strategies to explore underlying alterations in neural circuitry as well in treatment strategies in AUD and obesity. Finally, we discuss literature on mechanisms associated with increased alcohol sensitivity post-bariatric surgery (BS) which offers guidance for future research to use sensory percepts in elucidating the relation of reward signaling in AUD development post-BS.

Changes in Alcohol Use after Metabolic and Bariatric Surgery: Predictors and Mechanisms

PURPOSE OF REVIEW

This review synthesized the literature on predictors and mechanisms of post-bariatric alcohol problems, in order to guide future research on prevention and treatment targets.

RECENT FINDINGS

Consistent evidence suggests an elevated risk of developing problems with alcohol following bariatric surgery. While there is a paucity of empirical data on predictors of problematic alcohol use after bariatric surgery, being male, a younger age, smoking, regular alcohol consumption, pre-surgical alcohol use disorder, and a lower sense of belonging have predicted alcohol misuse post-operatively. This review synthesizes potential mechanisms including specific bariatric surgical procedures, peptides and reinforcement/reward pathways, pharmacokinetics, and genetic influences. Finally, potential misperceptions regarding mechanisms are explored. Certain bariatric procedures elevate the risk of alcohol misuse post-operatively. Future research should serve to elucidate the complexities of reward signaling, genetically mediated mechanisms, and pharmacokinetics in relation to alcohol use across gender and developmental period by surgery type.

Functional Magnetic Resonance Imaging (fMRI) of Neural Responses to Visual and Auditory Food Stimuli Pre and Post Roux-en-Y Gastric Bypass (RYGB) and Sleeve Gastrectomy (SG)

Of current obesity treatments, bariatric surgery induces the most weight loss. Given the marked increase in the number of bariatric surgeries performed, elucidating the mechanisms of action is a key research goal. We compared whole brain activation in response to high-energy dense (HED) vs. low-energy dense (LED) visual and auditory food cues before and approximately 4 months after Roux-en-Y Gastric Bypass (RYGB) (n = 16) and Sleeve Gastrectomy (SG) (n = 9). We included two control groups: a low-calorie diet weight loss group (WL) (n = 14) and a non-treatment group (NT) (n = 16). Relative to the control groups, the surgery groups showed increased dorsolateral prefrontal cortex (dlPFC) and decreased parahippocampal/fusiform gyrus (PHG/fusiform) activation in response to HED vs. LED, suggesting greater cognitive dietary inhibition and decreased rewarding effects and attention related to HED foods. dlPFC activation was significantly more increased in RYGB vs. SG. We also found that postprandial increases in GLP-1 concentrations (pre to postsurgery) correlated with postsurgical decreases in RYGB brain activity in the inferior temporal gyrus and the right middle occipital gyrus in addition to increases in the right medial prefrontal gyrus/paracingulate for HED > LED stimuli, suggesting involvement of these attention and inhibitory regions in satiety signaling postsurgery.

Deriving functional human enteroendocrine cells from pluripotent stem cells

Enteroendocrine cells (EECs) are a minor cell population in the intestine yet they play a major role in digestion, satiety and nutrient homeostasis. Recently developed human intestinal organoid models include EECs, but their rarity makes it difficult to study their formation and function. Here, we used the EEC-inducing property of the transcription factor NEUROG3 in human pluripotent stem cell-derived human intestinal organoids and colonic organoids to promote EEC development in vitro An 8-h pulse of NEUROG3 expression induced expression of known target transcription factors and after 7 days organoids contained up to 25% EECs in the epithelium. EECs expressed a broad array of human hormones at the mRNA and/or protein level, including motilin, somatostatin, neurotensin, secretin, substance P, serotonin, vasoactive intestinal peptide, oxyntomodulin, GLP-1 and INSL5. EECs secreted several hormones including gastric inhibitory polypeptide (GIP), ghrelin, GLP-1 and oxyntomodulin. Injection of glucose into the lumen of organoids caused an increase in both GIP secretion and K-cell number. Lastly, we observed formation of all known small intestinal EEC subtypes following transplantation and growth of human intestinal organoids in mice.

Adiposity and the Role of Neuroendocrine Hormones in Energy Balance

Obesity is a worldwide health concern and, given the risk for developing associated co-morbidities that increase mortality, obesity has health implications for individuals and populations. Obesity involves multifactorial regulatory mechanisms, and recognition of these mechanisms will enhance the care critical care nurses provide to their patients. This article reviews the general physiological mechanisms of energy storage and the regulation of adiposity related to key neuroendocrine hormones. The authors also highlight the implications for nursing care for critically ill patients suffering from obesity.

Surgery for Diabetes: Clinical and Mechanistic Aspects

According to the most recent publication by the Canadian Public Health Agency, obesity affects 25% of adults. In addition, there is a clear association between the recent rise in obesity and the increased prevalence of type 2 diabetes. Medical therapy for obesity has shown limited long-term effectiveness, and surgical treatment is now recognized by medical authorities as part of the armamentarium for the management of type 2 diabetes in severely obese patients. The current indications for obesity surgery and postoperative management are reviewed. The choice of surgery should balance expected benefits associated with weight loss (including remission rate of type 2 diabetes), side effects and the risks for early and long-term complications. Long-term outcomes of metabolic surgery for diabetes vary according to the type of surgery (ranging between 20% and 90% remission rates) and the underlying metabolic changes. Several controlled trials have been published in recent years confirming the superiority of metabolic surgery over medical treatment for the management of type 2 diabetes associated with severe obesity. Some of the known underlying mechanisms of action include a combination of caloric restriction, hormonal changes, decreased nutrient absorption and changes in bile acids, microbiota and incretins. Further research is needed to clarify the mechanistic changes associated with each surgical procedure and their respective long-term outcomes.

The history of metabolic and bariatric surgery: Development of standards for patient safety and efficacy

Weight loss surgery, also referred to as bariatric surgery, has been in existence since the 1950's. Over the decades, it has been demonstrated to successfully achieve meaningful and sustainable weight loss in a large number of patients who undergo these procedures. Additionally, the benefits observed across a number of metabolic disorders such as type 2 diabetes mellitus and hyperlipidemia, are often to a degree, independent of the weight loss, thus the term "metabolic bariatric surgery (MBS)" has become a better descriptor. Throughout its long history, MBS has evolved from an era of high morbidity and mortality to one of laudable safety despite the high-risk nature of the patients undergoing these major gastrointestinal procedures. This article will describe the historic evolution of MBS and concentrate on those events that were instrumental in reducing the morbidity of these operations.

Hedonic Changes in Food Choices Following Roux-en-Y Gastric Bypass

It has been suggested that a shift in food choices leading to a diet with a lower energy density plays an important role in successful weight loss after Roux-en-Y gastric bypass (RYGB) surgery. A decreased hedonic drive to consume highly palatable foods may explain these changes in eating behavior. Here, we review the literature examining postoperative changes in mechanisms contributing to hedonic drive (food preferences, reinforcing value of food, dopamine signaling, and activity reward-related brain regions). The majority of studies reviewed support that RYGB decrease the hedonic drive to consume highly palatable foods. Still, in order to fully understand the complexity of these changes, we need studies combining sociological and psychological approaches with objective measures of actual food choices examining different measures of hedonic drive.

Endoluminal weight loss and metabolic therapies: current and future techniques

Obesity is a public health epidemic associated with a number of comorbidities, most notably type 2 diabetes and hypertension, as well as elevated all-cause mortality. The treatment for obesity and its associated comorbidities has most recently expanded into the field of bariatric endoscopy. This field bridges a gap between lifestyle counseling with or without pharmaceutical treatment and the most effective treatment of obesity, bariatric surgery. Because of its minimally invasive nature, bariatric endoscopic therapy has the potential to appeal to the large sector of the obese population that resists surgery, as well as those early in the onset of obesity. To date, five endoscopic devices have been approved by the U.S. Food and Drug Administration for the treatment of obesity, and many more are in development, undergoing clinical trials, or being used around the world. Here, we present the current state of the field, highlight recent developments, and describe the clinical outcomes of these minimally invasive procedures in terms of weight loss, improvement in metabolic profile, and reduction in comorbidities.

Dilatation of Sleeve Gastrectomy: Myth or Reality?

OBJECTIVES

The success of longitudinal sleeve gastrectomy (LSG) is perceived as being potentially limited by dilatation of the remaining gastric tube during the follow-up. The aim of this prospective study was to determine the incidence and the characteristics of sleeve dilatation during the first post-operative year.

MATERIALS AND METHODS

Gastric volumetry using 3D gastric computed tomography with gas expansion was performed in 54 successive subjects who underwent an LSG for morbid obesity at 3 and 12 months following surgery. Total gastric volume, volume of the gastric tube and the antrum, and diameter of the gastric tube were assessed after multiplanar reconstructions. An increase of at least 25 % of the total gastric volume was considered as sleeve dilatation. Percentage of excess BMI loss (%EBMIL) and daily caloric intakes were recorded during the first 18 months.

RESULTS

Sixty-one percent of the subjects experienced sleeve dilatation 1 year after surgery. The gastric tube was mainly involved in the sleeve dilatation process (+91 %). Sleeve dilatation occurred especially in subjects with smaller total gastric volume at baseline (189 vs 236 ml, p = 0.02). Daily caloric intake was similar between the groups at each point of the follow-up. No difference concerning %EBMIL was observed between the groups during the 18 months of follow-up.

CONCLUSIONS

Sleeve dilatation occurred in more than 50 % of the patients. Dilatation was not necessarily linked to an increase of daily caloric intake and insufficient weight loss during the first 18 months following surgery. Small LSG at baseline is at higher risk of dilatation.

Bariatric Surgery and Liver Transplantation

Obesity is an important public health and medical concern in the United States. The rate of obesity has steadily risen for the past several decades. Obesity is associated with the development of nonalcoholic steatohepatitis, which is one of the leading indications for liver transplantation. After liver transplantation, recipients tend to gain weight and develop recurrent fatty liver. Over time, recurrent fatty liver may impact patient and graft survival. A bariatric surgical approach may be beneficial in select patients.

Current status of intragastric balloon for obesity treatment

Endoscopic bariatric therapy may be a useful alternative to pharmacological treatment for obesity, and it provides greater efficacy with lower risks than do conventional surgical procedures. Among the various endoscopic treatments for obesity, the intragastric balloon is associated with significant efficacy in body weight reduction and relief of comorbid disease symptoms. Anatomically, this treatment is based on gastric space-occupying effects that increase the feeling of satiety and may also affect gut neuroendocrine signaling. The simplicity of the intragastric balloon procedure may account for its widespread role in obesity treatment and its applicability to various degrees of obesity. However, advances in device properties and procedural techniques are still needed in order to improve its safety and cost-effectiveness. Furthermore, verification of the physiological outcomes of intragastric balloon treatment and the clinical predictive factors for treatment responses should be considered. In this article, we discuss the types, efficacy, safety, and future directions of intragastric balloon treatment.

Evaluation of laparoscopic sleeve gastrectomy compared with laparoscopic Roux-en-Y gastric bypass for people with morbid obesity: A systematic review and meta-analysis

BACKGROUND

Prevalence of obesity in the world, in both developed and developing countries, is growing rapidly. Bariatric surgery is now accepted as the treatment for morbid obesity.

OBJECTIVE

This study compares laparoscopic sleeve gastrectomy's effectiveness (LSG) with the most common bariatric surgery, laparoscopic Roux-en-Y (LRYGB) gastric bypass.

METHODS

A systematic review was performed using relevant search data bases, including Cochrane library, PubMed, Magi ran, Iranmedex, SID and Trip database, with no time limit. Data bases were searched until July 2014 for randomized control trials. The studied population included people aged between 18-60 years, with BMI≥35 and at least one obesity-related disease, or people with BMI≥40. BMI change, as the research outcome, was investigated at least in one-year follow-up period. Cochrane criteria were used to assess quality of studies. The results were extracted from the articles.

RESULTS

In total, 384 articles were obtained in the search; six RCTs were included in this study. There was no significant difference between the two laparoscopic sleeve gastrectomy and laparoscopic Roux-en-Y gastric bypass procedures in BMI, and both groups were similar in weight loss CI [-.1.31, 0.43], p=0.32.

CONCLUSION

The two procedures of bariatric surgery are effective and reliable treatments. Performing more trial studies with greater sample size and longer follow-up period for making final decision in selecting a certain surgical procedure is essential.

Regulation of appetite, satiation, and body weight by enteroendocrine cells. Part 2: therapeutic potential of enteroendocrine cells in the treatment of obesity

Obesity is an epidemic and medical issue. Investigating the pathways regulating appetite, food intake, and body weight is crucial to find strategies for the prevention and treatment of obesity. In the context of therapeutic strategies, we focus here on the potential of enteroendocrine cells (EECs) and their secreted hormones in the regulation of body weight. We review the role of the enteroendocrine system during weight loss after lifestyle intervention or after bariatric surgery. We discuss the therapeutic potential of EECs and their hormones as targets for new treatment strategies. In fact, targeting nutrient receptors of EECs with a nutritional approach, pharmaceutical agents or prebiotics delivered to the lumen may provide a promising new approach.

Physiological and Psychological Changes Following Liposuction of Large Volumes of Fat in Overweight and Obese Women

BACKGROUND

Liposuction can remove a substantial amount of body fat. We investigated the effects of liposuction of large volumes of fat on anthropometrics, body composition (BIA), metabolic hormones, and psychological measures in overweight/obese women. To our knowledge, this is the first study to examine both physiological and psychological changes following liposuction of large volumes of fat in humans.

METHOD

Nine premenopausal healthy overweight/obese women (age = 35.9 ± 7.1 SD, weight = 84.4 kg ± 13.6, BMI = 29.9 kg/m² ± 2.9) underwent liposuction, removing 3.92 kg ± 1.04 SD of fat. Following an overnight fast, height, weight, waist, and hip circumferences were measured at baseline (one week pre-surgery) and post-surgery (wk 1,4,12). Blood samples were drawn for fasting concentrations of glucose, insulin, leptin, and ghrelin. The Body Shape Questionnaire (BSQ), Body Dysmorphic Disorder (BDD) Examination Self-Report (BDDE-SR), and Zung Self-Rating Depression Scale (ZDS) were administered.

RESULTS

Body weight, BMI, waist circumference, and body fat consistently decreased over time (p < .05). Glucose did not change significantly, but insulin decreased from wk 1 to wk 12 (p < .05). Leptin decreased from baseline to wk 1 (p = .01); ghrelin increased but not significantly. Changes in body fat and waist circumference (baseline to wk 1) correlated positively with changes in insulin during that period, and correlated inversely with changes in ghrelin (p < .05). BSQ scores decreased significantly over time (p = .004), but scores for BDDE-SR (p = .10) and ZDS (p = .24) did not change significantly.

CONCLUSION

Liposuction led to significant decreases in body weight and fat, waist circumference, and leptin levels. Changes in body fat and waist circumference correlated with concurrent changes in the adipose-related hormones, insulin and ghrelin (baseline to wk 1), and body shape perception improved. Thus, besides the obvious cosmetic effects, liposuction led to several positive body composition, hormonal, and psychological changes.

Impact of Weight Loss Surgery on Esophageal Physiology

Bariatric surgery has come to the forefront of weight loss treatment due to its complex interactions via anatomic, physiologic, and neurohormonal changes leading to sustained weight loss. Unlike lifestyle and pharmacologic options, which fail to show long-term sustained weight loss, bariatric surgery has been shown to decrease overall mortality and morbidity. Bariatric surgery can be purely restrictive, such as laparoscopic adjustable gastric band (LAGB) or laparoscopic sleeve gastrectomy (LSG), or restrictive-malabsorptive, such as Roux-en-Y gastric bypass (RYGB). These surgeries cause specific anatomic changes that promote weight loss; however, they also have unintended effects on the esophagus, particularly in terms of gastroesophageal reflux disease (GERD) and esophageal motility. Via restrictive surgery, LAGB has been widely reported to cause significant weight loss, although studies have also shown an increase and worsening of GERD as well as elevated rates of esophageal dilation, aperistalsis, and alterations in lower esophageal sphincter pressure. Along with LAGB, LSG has shown not only a worsening of GERD, but also the formation of de novo GERD in patients who were asymptomatic before the operation. In a restrictive-malabsorptive approach, RYGB has been reported to improve GERD and preserve esophageal motility. Bariatric surgery is a burgeoning field with immense implications on overall mortality. Future randomized, controlled trials are needed to better understand which patients should undergo particular surgeries, with greater emphasis on esophageal health and prevention of GERD and esophageal dysmotility.

Caloric intake capacity as measured by a standard nutrient drink test helps to predict weight loss after bariatric surgery

BACKGROUND

Instruments that enable to select individuals that will benefit most from bariatric surgery (BS) are necessary to increase its cost-efficiency. Our goal was to assess if intake capacity, measured with a standardized test, predicts response to BS.

METHODS

Patients with criteria for BS were randomly allocated to laparoscopic gastric bypass (LRYGB) or sleeve gastrectomy (LSG). We measured caloric intake capacity before and 1 year after surgery using a standardized nutrient drink test. We evaluated if pre-surgery satiation could predict satiation and weight loss (%) 1 year after surgery using multiple regression modeling. Descriptive statistics are given as mean ± SD.

RESULTS

Fourteen women (48 ± 9 years old, BMI 41 ± 3 kg/m(2)) were evaluated before and 11 ± 2.6 months after surgery (seven LRYGB, seven LSG). Caloric intake capacity diminished after surgery (-950 ± 85 kcal on average [70 ± 8 % decrease over basal intake capacity]; p=0.002) and similarly in both LRYGB (72 ± 7 % decrease) and LSG groups (68 ± 8 % decrease); p=0.5. There was a significant weight reduction after surgery (-32 ± 10 kg [30 ± 8 % of total basal weight]) with a mean post-surgery BMI of 29 ± 2 kg/m(2). The best predictive model of weight loss (%) after surgery (R (2)=89 %, p=0.0009) included: BMI (p=0.0004), surgery type (p=0.01) and pre-surgery intake capacity (p=0.006). Weight loss was higher in heavier patients and those undergoing LRYGB. Patients with higher intake capacity had a poorer outcome independently of basal BMI and surgery type.

CONCLUSIONS

Caloric intake capacity, as measured by a standard nutrient drink test, helps to predict weight loss after bariatric surgery. This test might be useful in algorithms of obesity treatment decision.

Roux-en-Y gastric bypass attenuates the progression of cardiometabolic complications in obese diabetic rats via alteration in gastrointestinal hormones

BACKGROUND

Roux-en-Y gastric bypass (RYGB) ameliorates type 2 diabetes (T2DM) and obesity through alteration in gastrointestinal (GI) hormones.

OBJECTIVE

The objective of this study was to investigate the effect of RYGB on GI hormones and cardiometabolic parameters in Zucker diabetic fatty (ZDF) rodents.

SETTING

Winthrop University Hospital, Research and Academic Center

METHODS

Animals were divided into 3 groups, pair-fed (n = 4), ad lib (n = 4), and RYGB (n = 5). This study was carried out for 4 weeks and all related parameters were measured pre- and postsurgery in fasted obese diabetic Zucker rodents.

RESULTS

Postoperatively, RYGB significantly decreased fasting blood glucose by 32% compared with ad lib. Plasma insulin and leptin levels were also found to be significantly decreased, by 66% and 38%, respectively, after surgery. Moreover, both glucose-dependent insulinotropic polypeptide (GIP) and peptide tyrosine-tyrosine (PYY) were significantly increased after RYGB-by 300% and 51%, respectively. Glucagon-like peptide-1 (GLP-1) levels were also increased, but the increase was not statistically significant. Total cholesterol levels of the RYGB group remained unchanged for 4 weeks. However, total cholesterol in the ad lib and pair-fed groups increased by 25% and 34%, respectively, compared with initial levels. The cholesterol/high-density lipoprotein (HDL) ratio was decreased in the RYGB group by 14% and 30% compared with the ad lib and pair-fed group, respectively. The RYGB group had a significant decrease in aortic wall thickness of 25% compared with the ad lib and pair-fed groups. Similarly, the RYGB group had a 20-unit (mm Hg) decrease in systolic blood pressure compared with the presurgical value.

CONCLUSION

RYGB has beneficial cardiometabolic effects through alterations in GI hormones in a severely obese and diabetic rodent model.

Obesity: pathophysiology and intervention

Obesity presents a major health hazard of the 21st century. It promotes co-morbid diseases such as heart disease, type 2 diabetes, obstructive sleep apnea, certain types of cancer, and osteoarthritis. Excessive energy intake, physical inactivity, and genetic susceptibility are main causal factors for obesity, while gene mutations, endocrine disorders, medication, or psychiatric illnesses may be underlying causes in some cases. The development and maintenance of obesity may involve central pathophysiological mechanisms such as impaired brain circuit regulation and neuroendocrine hormone dysfunction. Dieting and physical exercise offer the mainstays of obesity treatment, and anti-obesity drugs may be taken in conjunction to reduce appetite or fat absorption. Bariatric surgeries may be performed in overtly obese patients to lessen stomach volume and nutrient absorption, and induce faster satiety. This review provides a summary of literature on the pathophysiological studies of obesity and discusses relevant therapeutic strategies for managing obesity.

The effectiveness and risks of bariatric surgery: an updated systematic review and meta-analysis, 2003-2012

IMPORTANCE

The prevalence of obesity and outcomes of bariatric surgery are well established. However, analyses of the surgery impact have not been updated and comprehensively investigated since 2003.

OBJECTIVE

To examine the effectiveness and risks of bariatric surgery using up-to-date, comprehensive data and appropriate meta-analytic techniques.

DATA SOURCES

Literature searches of Medline, Embase, Scopus, Current Contents, Cochrane Library, and Clinicaltrials.gov between 2003 and 2012 were performed.

STUDY SELECTION

Exclusion criteria included publication of abstracts only, case reports, letters, comments, or reviews; animal studies; languages other than English; duplicate studies; no surgical intervention; and no population of interest. Inclusion criteria were a report of surgical procedure performed and at least 1 outcome of interest resulting from the studied surgery was reported: comorbidities, mortality, complications, reoperations, or weight loss. Of the 25,060 initially identified articles, 24,023 studies met the exclusion criteria, and 259 met the inclusion criteria.

DATA EXTRACTION AND SYNTHESIS

A review protocol was followed throughout. Three reviewers independently reviewed studies, abstracted data, and resolved disagreements by consensus. Studies were evaluated for quality.

MAIN OUTCOMES AND MEASURES

Mortality, complications, reoperations, weight loss, and remission of obesity-related diseases.

RESULTS

A total of 164 studies were included (37 randomized clinical trials and 127 observational studies). Analyses included 161,756 patients with a mean age of 44.56 years and body mass index of 45.62. We conducted random-effects and fixed-effect meta-analyses and meta-regression. In randomized clinical trials, the mortality rate within 30 days was 0.08% (95% CI, 0.01%-0.24%); the mortality rate after 30 days was 0.31% (95% CI, 0.01%-0.75%). Body mass index loss at 5 years postsurgery was 12 to 17. The complication rate was 17% (95% CI, 11%-23%), and the reoperation rate was 7% (95% CI, 3%-12%). Gastric bypass was more effective in weight loss but associated with more complications. Adjustable gastric banding had lower mortality and complication rates; yet, the reoperation rate was higher and weight loss was less substantial than gastric bypass. Sleeve gastrectomy appeared to be more effective in weight loss than adjustable gastric banding and comparable with gastric bypass.

CONCLUSIONS AND RELEVANCE

Bariatric surgery provides substantial and sustained effects on weight loss and ameliorates obesity-attributable comorbidities in the majority of bariatric patients, although risks of complication, reoperation, and death exist. Death rates were lower than those reported in previous meta-analyses.

The effectiveness and risks of bariatric surgery: an updated systematic review and meta-analysis, 2003-2012

IMPORTANCE

The prevalence of obesity and outcomes of bariatric surgery are well established. However, analyses of the surgery impact have not been updated and comprehensively investigated since 2003.

OBJECTIVE

To examine the effectiveness and risks of bariatric surgery using up-to-date, comprehensive data and appropriate meta-analytic techniques.

DATA SOURCES

Literature searches of Medline, Embase, Scopus, Current Contents, Cochrane Library, and Clinicaltrials.gov between 2003 and 2012 were performed.

STUDY SELECTION

Exclusion criteria included publication of abstracts only, case reports, letters, comments, or reviews; animal studies; languages other than English; duplicate studies; no surgical intervention; and no population of interest. Inclusion criteria were a report of surgical procedure performed and at least 1 outcome of interest resulting from the studied surgery was reported: comorbidities, mortality, complications, reoperations, or weight loss. Of the 25,060 initially identified articles, 24,023 studies met the exclusion criteria, and 259 met the inclusion criteria.

DATA EXTRACTION AND SYNTHESIS

A review protocol was followed throughout. Three reviewers independently reviewed studies, abstracted data, and resolved disagreements by consensus. Studies were evaluated for quality.

MAIN OUTCOMES AND MEASURES

Mortality, complications, reoperations, weight loss, and remission of obesity-related diseases.

RESULTS

A total of 164 studies were included (37 randomized clinical trials and 127 observational studies). Analyses included 161,756 patients with a mean age of 44.56 years and body mass index of 45.62. We conducted random-effects and fixed-effect meta-analyses and meta-regression. In randomized clinical trials, the mortality rate within 30 days was 0.08% (95% CI, 0.01%-0.24%); the mortality rate after 30 days was 0.31% (95% CI, 0.01%-0.75%). Body mass index loss at 5 years postsurgery was 12 to 17. The complication rate was 17% (95% CI, 11%-23%), and the reoperation rate was 7% (95% CI, 3%-12%). Gastric bypass was more effective in weight loss but associated with more complications. Adjustable gastric banding had lower mortality and complication rates; yet, the reoperation rate was higher and weight loss was less substantial than gastric bypass. Sleeve gastrectomy appeared to be more effective in weight loss than adjustable gastric banding and comparable with gastric bypass.

CONCLUSIONS AND RELEVANCE

Bariatric surgery provides substantial and sustained effects on weight loss and ameliorates obesity-attributable comorbidities in the majority of bariatric patients, although risks of complication, reoperation, and death exist. Death rates were lower than those reported in previous meta-analyses.

Neuroimaging of gastric distension and gastric bypass surgery

Several neuroimaging studies are presented, which derive from prior work on gastric distension. Using a nonsurgical approach, we inserted gastric balloons into rats, which led to a marked decrease in food intake that normalized at 8 weeks. Body weight, however, remained below controls, which encouraged pursuit of studies in humans. A gastric balloon was inserted in obese and lean subjects, and filled through a tube that led behind the subject with water to 0, 200, 400, 600, 800 mL, on different days prior to ingestion of a liquid meal. As gastric volume increased, intake decreased by about 40%. Stomach capacity was then investigated using a gastric balloon, by assessing subjective (maximal tolerance) and objective measures (gastric compliance). Obese individuals had a much larger stomach capacity than lean by both measures. Next, in a 2-month study, an indwelling gastric balloon was inflated to 400 mL for 1 month and deflated for 1 month in counterbalanced order. Body weight was reduced during the month when the balloon was inflated within the 2nd and 3rd week. The subsequent study involved fMRI in response to gastric distension of 0, 250, and 500 mL while the subject was in a scanner. Ratings of fullness, but not discomfort, increased at 500 mL. Amygdala and insula activation were associated with gastric distension. The amygdala, as part of the limbic system, is involved in emotion and reward, and the insula in interoception. The right amygdala activation was inversely related to BMI, consistent with greater gastric capacity at a higher BMI. The next fMRI study in obese and lean subjects used visual and auditory stimuli of high energy dense (ED) and low ED foods. Increased activation was observed in the midbrain, putamen, posterior cingulate gyrus, hippocampus, and superior temporal gyrus in the obese vs. lean group in response to high vs. low ED food cues. Several of these areas lie within the mesolimbic reward pathway, and greater activation to high ED foods in the obese, suggests they have increased reward-driven eating behavior. Lastly, an fMRI study using the same stimuli was conducted pre and post-gastric bypass surgery. There were postsurgical reductions in neural activity in mesolimbic areas including the prefrontal cortex, and to a greater degree for high ED than low ED cues, reflecting more normalized responses. Through the use of various methodologies, the stomach's influence on food intake, sensations of fullness, and brain activation is presented with suggestions for future research.

Endoscopic sleeve gastroplasty: a potential endoscopic alternative to surgical sleeve gastrectomy for treatment of obesity

BACKGROUND

Obesity and its associated conditions, including type 2 diabetes and cardiovascular disease, have reached epidemic proportions. High-efficacy, high-risk surgical approaches are unlikely to meet the increasing burden of disease. Emerging endoscopic technologies have opened the door for endoscopic approaches to reproduce many of the benefits of GI weight loss surgery and thereby contribute to the effective treatment of obesity and its associated disorders.

OBJECTIVE

To demonstrate the technical feasibility of transoral endoscopic gastric volume reduction with an endoscopic suturing device in a fashion similar to sleeve gastrectomy for the treatment of obesity.

DESIGN

Single-center, pilot feasibility study.

PATIENTS

Four human subjects with obesity.

INTERVENTIONS

Transoral sleeve gastroplasty.

MAIN OUTCOME MEASUREMENTS

Technical feasibility.

RESULTS

We successfully used an endoscopic free-hand suturing system in 4 subjects, thus demonstrating the technical feasibility of a novel technique to mimic the anatomic manipulations created by surgical sleeve gastrectomy endoscopically.

LIMITATIONS

Pilot feasibility study with small number of subjects.

CONCLUSIONS

Endoscopic sleeve gastroplasty for treatment of obesity is feasible.

Improvement in hepatic insulin sensitivity after Roux-en-Y gastric bypass in a rat model of obesity is partially mediated via hypothalamic insulin action

AIMS/HYPOTHESIS

Roux-en-Y gastric bypass (RYGB) surgery, an effective treatment for morbid obesity, commonly leads to near complete resolution of type 2 diabetes. The underlying mechanisms, however, remain unclear and factors other than weight loss alone may be involved.

METHODS

To determine whether increased hypothalamic insulin sensitivity after RYGB drives the rapid improvement in glucose metabolism, high-fat-fed rats received either an insulin receptor (IR) antisense vector or a control lentiviral vector that was microinjected into the ventromedial hypothalamus (VMH). Six weeks later, rats underwent RYGB or control gastrointestinal surgery.

RESULTS

Four weeks after surgery, weight loss was comparable in RYGB and surgical controls. Nevertheless, only RYGB rats that received the control vector demonstrated both improved hepatic and peripheral insulin sensitivity. Insulin suppressed hepatic glucose production (HGP) by 50% (p < 0.05) with RYGB, whereas the effect of insulin on HGP was completely absent in VMH IR knockdown (IRkd) rats. By contrast, both RYGB groups displayed an identical twofold increase in insulin-stimulated peripheral glucose uptake. The animals that underwent control gastrointestinal surgery failed to show any improvement in either hepatic or peripheral insulin sensitivity; VMH IRkd did not influence the magnitude of insulin resistance.

CONCLUSIONS/INTERPRETATION

Our findings demonstrate that RYGB surgery in high-fat-fed obese rats enhances hepatic and peripheral insulin sensitivity independently of weight loss. The improved hepatic, but not the peripheral, response to insulin is mediated centrally at the level of the VMH. These data provide direct evidence that the metabolic benefits of RYGB surgery are not simply a consequence of weight loss but likely in part involve the central nervous system.

Biological mechanisms that promote weight regain following weight loss in obese humans

Weight loss dieting remains the treatment of choice for the vast majority of obese individuals, despite the limited long-term success of behavioral weight loss interventions. The reasons for the near universal unsustainability of behavioral weight loss in [formerly] obese individuals have not been fully elucidated, relegating researchers to making educated guesses about how to improve obesity treatment, as opposed to developing interventions targeting the causes of weight regain. This article discusses research on several factors that may contribute to weight regain following weight loss achieved through behavioral interventions, including adipose cellularity, endocrine function, energy metabolism, neural responsivity, and addiction-like neural mechanisms. All of these mechanisms are engaged prior to weight loss, suggesting that these so called "anti-starvation" mechanisms are activated via reductions in energy intake, rather than depletion of energy stores. Evidence suggests that these mechanisms are not necessarily part of a homeostatic feedback system designed to regulate body weight, or even anti-starvation mechanisms per se. Although they may have evolved to prevent starvation, they appear to be more accurately described as anti-weight loss mechanisms, engaged with caloric restriction irrespective of the adequacy of energy stores. It is hypothesized that these factors may combine to create a biological disposition that fosters the maintenance of an elevated body weight and works to restore the highest sustained body weight, thus precluding the long-term success of behavioral weight loss. It may be necessary to develop interventions that attenuate these biological mechanisms in order to achieve long-term weight reduction in obese individuals.

Roux-en-Y gastric bypass reverses the effects of diet-induced obesity to inhibit the responsiveness of central vagal motoneurones

Diet-induced obesity (DIO) has been shown to alter the biophysical properties and pharmacological responsiveness of vagal afferent neurones and fibres, although the effects of DIO on central vagal neurones or vagal efferent functions have never been investigated. The aims of this study were to investigate whether high-fat diet-induced DIO also affects the properties of vagal efferent motoneurones, and to investigate whether these effects were reversed following weight loss induced by Roux-en-Y gastric bypass (RYGB) surgery. Whole-cell patch-clamp recordings were made from rat dorsal motor nucleus of the vagus (DMV) neurones in thin brainstem slices. The DMV neurones from rats exposed to high-fat diet for 12-14 weeks were less excitable, with a decreased membrane input resistance and decreased ability to fire action potentials in response to direct current pulse injection. The DMV neurones were also less responsive to superfusion with the satiety neuropeptides cholecystokinin and glucagon-like peptide 1. Roux-en-Y gastric bypass reversed all of these DIO-induced effects. Diet-induced obesity also affected the morphological properties of DMV neurones, increasing their size and dendritic arborization; RYGB did not reverse these morphological alterations. Remarkably, independent of diet, RYGB also reversed age-related changes of membrane properties and occurrence of charybdotoxin-sensitive (BK) calcium-dependent potassium current. These results demonstrate that DIO also affects the properties of central autonomic neurones by decreasing the membrane excitability and pharmacological responsiveness of central vagal motoneurones and that these changes were reversed following RYGB. In contrast, DIO-induced changes in morphological properties of DMV neurones were not reversed following gastric bypass surgery, suggesting that they may be due to diet, rather than obesity. These findings represent the first direct evidence for the plausible effect of RYGB to improve vagal neuronal health in the brain by reversing some effects of chronic high-fat diet as well as ageing. Vagovagal neurocircuits appear to remain open to modulation and adaptation throughout life, and understanding of these mechanisms may help in development of novel interventions to alleviate environmental (e.g. dietary) ailments and also alter neuronal ageing.

Gastric bypass increases ethanol and water consumption in diet-induced obese rats

BACKGROUND

Roux-en-Y gastric bypass surgery (RYGB) is an effective treatment for morbid obesity. Increased alcohol abuse after RYGB resulted in recommendations to exclude patients with alcohol abuse histories from RYGB. The purpose of our study was to examine the effects of a RYGB on ethanol intake in diet-induced obese rats (high-fat diet).

METHODS

The animals underwent RYGB and were habituated along with their sham-operated obese controls and with lean rats to increasing concentrations of ethanol in a two-bottle choice paradigm.

RESULTS

RYGB rats' daily consumption of ethanol averaged 2 g/kg at 2% habituation and 3.8 g/kg at 4% habituation, twice as much as sham-operated obese controls and 50% more than normal-diet lean controls. Obese controls drank on average 1 g/kg of ethanol (2 and 4%), significantly less (50%) than lean controls did. RYGB rats when given higher ethanol concentrations (6 and 8%) or no ethanol drank significantly more water than lean and obese controls did (66 and 100%, respectively), and their enhanced total fluid intake was associated with increased food intake, which was significantly higher than in lean (66% more calories; food + alcohol) and obese controls (44% more calories). The lower alcohol intake in the obese controls than in the lean rats suggests that obesity may interfere with alcohol's rewarding effects and RYGB may remove this protective effect.

CONCLUSIONS

The overall enhancement of consummatory behaviors (both ethanol and water) suggests that RYGB may facilitate alcohol consumption, which in vulnerable individuals could lead to abuse and addiction.

Neural responsivity to food cues in fasted and fed states pre and post gastric bypass surgery

Reductions in mesolimbic responsivity have been noted following Roux-en-Y gastric bypass (RYGB; Ochner et al., 2011a). Given potential for postoperative increases in postprandial gut (satiety) peptides to affect mesolimbic neural responsivity, we hypothesized that: (1) post RYGB changes in mesolimbic responsivity would be greater in the fed relative to the fasted state and; (2) fasted vs. fed state differences in mesolimbic responsivity would be greater post-relative to pre-surgery. fMRI was used to asses neural responsivity to high- and low-calorie food cues in five women 1 mo pre- and 1 mo post-RYGB. Scans were repeated in fasted and fed states. Significant post RYGB decreases in the insula, ventromedial prefrontal cortex (vmPFC) and dorsolateral prefrontal cortex (dlPFC) responsivity were found in the fasted state. These changes were larger than neural changes in the fed state, which were non-significant. Preoperatively, fasted vs. fed differences in neural responsivity were greater in the precuneus, with large but nonsignificant clusters in the vmPFC and dlPFC. Postoperatively, however, no fasted vs. fed differences in neural responsivity were noted. Results were opposite to that predicted and appear inconsistent with the initial hypothesis that postoperative increases in postprandial gut peptides are the primary driver of postoperative changes in neural responsivity.

Roux-en-Y gastric bypass in rats increases sucrose taste-related motivated behavior independent of pharmacological GLP-1-receptor modulation

Roux-en-Y gastric bypass (RYGB) surgery has been shown to decrease consummatory responsiveness of rats to high sucrose concentrations, and genetic deletion of glucagon-like peptide-1 receptors (GLP-1R) has been shown to decrease consummatory responsiveness of mice to low-sucrose concentrations. Here we assessed the effects of RYGB and pharmacological GLP-1R modulation on sucrose licking by chow-fed rats in a brief-access test that assessed consummatory and appetitive behaviors. Rats were tested while fasted presurgically and postsurgically and while nondeprived postsurgically and 5 h after intraperitoneal injections with the GLP-1R antagonist exendin-3(9-39) (30 μg/kg), agonist exendin-4 (1 μg/kg), and vehicle in 30-min sessions during which a sucrose concentration series (0.01-1.0 M) was presented in 10-s trials. Other rats were tested postsurgically or 15 min after peptide or vehicle injection while fasted and while nondeprived. Independent of food-deprivation state, sucrose experience, or GLP-1R modulation, RYGB rats took 1.5-3× as many trials as sham-operated rats, indicating increased appetitive behavior. Under nondeprived conditions, RYGB rats with presurgical sucrose experience licked more to sucrose relative to water compared with sham-operated rats. Exendin-4 and exendin-3(9-39) impacted 0.3 M sucrose intake in a one-bottle test, but never interacted with surgical group to affect brief-access responding. Unlike prior reports in both clearly obese and relatively leaner rats given RYGB and in GLP-1R knockout mice, we found that neither RYGB nor GLP-1R blockade decreased consummatory responsiveness to sucrose in our less obese chow-fed rats. Collectively, these results highlight the fact that changes in taste-driven motivated behavior to sucrose after RYGB and/or GLP-1R modulation are very model and measure dependent.

Could the mechanisms of bariatric surgery hold the key for novel therapies? report from a Pennington Scientific Symposium

Bariatric surgery is the most effective method for promoting dramatic and durable weight loss in morbidly obese subjects. Furthermore, type 2 diabetes is resolved in over 80% of patients. The mechanisms behind the amelioration in metabolic abnormalities are largely unknown but may be due to changes in energy metabolism, gut peptides and food preference. The goal of this meeting was to review the latest research to better understand the mechanisms behind the 'magic' of bariatric surgery. Replication of these effects in a non-surgical manner remains one of the ultimate challenges for the treatment of obesity and diabetes. Promising data on energy metabolism, gastrointestinal physiology, hedonic response and food intake were reviewed and discussed.

Cost-effectiveness of bariatric surgery: should it be universally available?

This paper is the first to conduct cost-effectiveness analyses of bariatric surgery comparing obese patients with obesity-related diseases to obese people without comorbidities across different BMI categories, using the meta-analysis results of surgery outcomes for our effectiveness inputs. We find that surgery treatment is in general cost-effective for people whose BMI is greater than 35 kg/m(2) with or without obesity-related comorbidities, and it is even cost-saving for super obese (BMI ≥ 50 kg/m(2)) with obesity-related comorbidities. Our results also suggest that surgery can be cost-effective for the mildly obese (BMI ≥ 30 kg/m(2)). The bottom line is that bariatric surgery should be universally available to all classes of obese people.

Selective reduction in neural responses to high calorie foods following gastric bypass surgery

OBJECTIVE

To investigate changes in neural activation and desire to eat in response to appetitive cues from pre- to postbariatric surgery for obesity.

BACKGROUND

Roux-en-Y gastric bypass (RYGB) is the most common bariatric procedure. However, the mechanisms of action in RYGB are not well understood. A significant proportion of the resulting reduction in caloric intake is unaccounted for by the restrictive and malabsorptive mechanisms and is thought to be mediated by neuroendocrine function. Numerous investigations of postsurgical changes in gut peptides have resulted; however, changes in neural activation after RYGB surgery have not been previously investigated.

METHODS

Functional magnetic resonance imaging and verbal rating scales were used to assess brain activation and desire to eat in response to high- and low-calorie food cues in 10 female patients 1-month pre- and post-RYGB surgery.

RESULTS

Postsurgical reductions in brain activation were found in key areas within the mesolimbic reward pathway, which were significantly more pronounced in response to food cues that were high (vs. low) in caloric density. These changes mirrored concurrent postsurgical reductions in desire to eat, which were also greater in response to food cues that were high versus low in caloric density (P = 0.007).

CONCLUSIONS

Findings support the contention that RYGB surgery leads to substantial changes in neural responses to food cues encountered in the environment, provide a potential mechanism for the selective reduction in preferences for high-calorie foods, and suggest partial neural mediation of changes in caloric intake seen after RYGB surgery.