Neuro-hormonal mechanisms underlying changes in reward related behaviors following weight loss surgery: Potential pharmacological targets

Binge drinking at time of bariatric surgery is associated with liver disease, suicides, and increases long-term mortality

BACKGROUND AND AIMS

Alcohol use disorder has been reported in patients undergoing bariatric procedures, but the pattern of alcohol consumption has not been evaluated. We investigated the prevalence, risk factors, and impact of binge drinking (BD) at the time of surgery and during follow-up.

METHODS

A prospective, longitudinal study of subjects undergoing bariatric surgery was included in the LABS-2 registry between 2006 and 2009. Participants with AUDIT questionnaire at the time of surgery and a minimum of 12 months follow-up were included. BD was defined as consuming ≥5 drinks on at least 1 occasion in the previous month. Liver biopsies were obtained during bariatric procedures in not all cases. Survival analysis was performed with the adjusted Cox regression model and competing risk.

RESULTS

A total of 2257 subjects were included, with a median follow-up of 79 months. The prevalence of BD at time of surgery was 12%, and it raised up to 23% during follow-up. Patients with BD predominantly had a binge eating disorder (OR=1.35 [95% CI: 1.04-1.76]), regularly consumed fast food [OR=1.4 (95% CI: 1.07-1.85)] and used other drugs (OR=2.65 [95% CI: 1.74-4.04]). Within liver biopsies evaluation, BD showed higher hepatic iron deposits (OR=3.00 [95% CI: 1.25-7.21]). BD at the time of surgery was associated with a higher risk of BD during follow-up (OR=10.49 [95% CI: 7.86-14.00]) and long-term mortality (HR: 3.21 [95% CI: 1.67-6.18]). Specific causes of death in these patients with BD were liver disease (p=0.020), suicide (p=0.015), neoplasms (p=0.034), and respiratory (p=0.025).

CONCLUSIONS

The prevalence of BD in patients undergoing bariatric surgery is high and increases the risk of postoperative liver disease, suicides, and long-term mortality.

Bariatric surgery and mental health outcomes: an umbrella review

Aims

To evaluate the breadth, depth and effectiveness of the evidence quality of all existing studies on bariatric surgery and mental health outcomes.

Design

Umbrella review of existing Systematic review and meta-analyses.

Data sources

PubMed, Embase, Web of Science, and the Cochrane Liberally databases of Systematic review and meta-analyses, and hand searching the reference lists of eligible publications.

Results

The search identified nine studies and 20 mental health outcomes from 1251 studies. Evidence shows that bariatric surgery is associated with significant improvement in areas such as anxiety, depression and eating disorders (including binge-eating disorder), and there is a significant harmful association with suicide, self-harm and alcohol use disorder (AUD). Among them, the most studied outcome is depression (4 articles). High-quality evidence proves that the score of depressive symptoms can be significantly improved after bariatric surgery within a two-year follow-up period and is not affected by the follow-up time. Low-quality evidence shows that bariatric surgery can significantly reduce depressive symptoms regardless of age and BMI, with an odds ratio (OR) of 0.49. Regardless of the postoperative BMI, the anxiety symptoms of women over 40 still decreased significantly, with an OR of 0.58. Regardless of the type of surgery, surgery can significantly reduce the incidence of eating disorders and symptoms. However, there is no obvious change in the follow-up time of AUD in the first two years after bariatric surgery, and the risk increases obviously in the third year, with an OR of 1.825. The evidence of moderate research shows that the risk of suicide and self-harm increases after bariatric surgery. The odds ratios in the same population and the control group were 1.9 and 3.8 times, respectively.

Conclusion

Bariatric surgery is beneficial for improving most mental health-related outcomes. However, we should be cautious about the increased risk of adverse mental health after surgery, such as suicide, self-harm, and AUD.

Distinct adaptations of endocrine and cognitive functions may contribute to high variability in long-term weight loss outcome after bariatric surgery

BACKGROUND

Bariatric surgery has been widely recognized as the most efficient long-term treatment method in severe obesity, yet therapy success shows considerable interindividual variability. Postoperative metabolic adaptations, including improved gut hormone secretion (GLP-1, PYY and ghrelin), and restored executive function may play an explanatory role in weight loss, yet causes for poor success in individual patients remain unknown. This study investigates gut-hormonal and cognitive characteristics in extreme weight loss responders to bariatric surgery.

METHODS

Patients (n=47) with high or low excessive weight loss (EWL) at least 2 years after Roux-en-Y-gastric bypass or sleeve gastrectomy were allocated into good responders (GR, EWL 82.4 ± 11.6%) and poor responders (PR, EWL 24.0 ± SD 12.8%) to study differences in postprandial secretion of GLP-1, PYY, ghrelin and in working memory (WM).

RESULTS

Mean BMI was 47.1 ± 6.2 kg/m² in PR (n=21) and 28.9 ± 3.1 kg/m² in GR (n=26, p < 0.001). Fasted GLP-1 and PYY were comparable for GR and PR (p > 0.2) and increased strongly after a standardized test meal (300 kcal liquid meal) with a peak at 15 to 30 minutes. The increase was stronger in GR compared to PR (GLP-1, PYY: Time x Group p < 0.05). Plasma ghrelin levels already differed between groups at fasted state, showing significantly higher levels for GR (p < 0.05). Postprandially, ghrelin secretion was suppressed in both groups, but suppression was higher in GR (Time x Group p < 0.05). GR showed significantly higher WM scores than PR (p < 0.05). Postprandial ghrelin (iAUC), but not GLP-1 or PYY plasma levels, significantly mediated the relationship between EWL and a WM subscore (IS score, CI = 0.07 - 1.68), but not WM main score (MIS score, CI = -0.07 - 1.54), in mediation analyses.

CONCLUSION

Excess weight loss success after bariatric surgical procedures is associated with distinct profiles of gut-hormones at fasted and postprandial state, and differences in working memory. Better working memory performance in GR might be mediated by higher postprandial reduction in ghrelin plasma levels. Future studies need to integrate longitudinal data, larger samples and more sensitive cognitive tests.

Successful naltrexone-bupropion treatment after several treatment failures in a patient with severe monogenic obesity

We describe the therapeutic journey of a 33-year-old patient with early-onset obesity (BMI 56.7 kg/m²) and hyperphagia due to a likely pathogenic heterozygous melanocortin-4 receptor (MC4R) gene variant. She was unsuccessfully treated with several intensive lifestyle interventions, gastric bypass surgery (-40 kg weight loss, followed by +39.8 kg weight regain), liraglutide 3 mg (-3.8% weight loss with sustained hyperphagia), and metformin treatment. However, naltrexone-bupropion treatment led to -48.9 kg (-26.7%) weight loss, of which -39.9 kg (-38.3%) was fat mass, in 17 months of treatment. Importantly, she reported improved hyperphagia and quality of life. We describe the potential beneficial effects of naltrexone-bupropion on weight, hyperphagia, and quality of life in a patient with genetic obesity. This extensive journey shows that various anti-obesity agents can be initiated, subsequently terminated when ineffective and substituted with other anti-obesity agents to identify the most efficient anti-obesity treatment.

Bariatric Surgery Is Associated with Alcohol-Related Liver Disease and Psychiatric Disorders Associated with AUD

BACKGROUND/AIMS

Bariatric surgery can increase the risk of addictive disorders and nutritional deficiencies. The aim of this study was to evaluate the association between bariatric surgery and alcohol use disorder (AUD), alcohol-related liver disease (ALD), and psychiatric disorders associated with AUD. The impact of vitamin D deficiency in these associations was also investigated.

METHODS

A cross-sectional study was performed using the National Inpatient Sample database and its ICD-9 codes information. Diagnostic and comorbidity data from hospital discharges were obtained from patients with bariatric surgery and other abdominal surgeries between 2005 and 2015. The two groups were then compared for alcohol-related outcomes after propensity-score matching.

RESULTS

The final study cohort included 537,757 patients with bariatric surgery and 537,757 with other abdominal surgeries. The bariatric surgery group had an increased risk of AUD [odds ratio (OR): 1.90; 95% CI: 1.85-1.95], ALD [OR: 1.29; 95% CI: 1.22-1.37], cirrhosis [OR, 1.39; 95% CI: 1.37-1.42], and psychiatric disorders associated with AUD [OR, 3.59; 95% CI: 3.37-3.84]. Vitamin D deficiency did not impact in the association between bariatric surgery and AUD, ALD, or psychiatric disorders associated with AUD.

CONCLUSIONS

Bariatric surgery is associated with an increased prevalence of AUD, ALD, and psychiatric disorders associated with AUD. These associations appear to be independent from vitamin D deficiency.

Prevalence of food addiction among patients undergoing metabolic/bariatric surgery: A systematic review and meta-analysis

Candidates for metabolic/bariatric surgery show a high prevalence of food addiction (FA). However, few studies have investigated FA prevalence after bariatric surgery, especially using longitudinal studies. This systematic review with a meta-analysis aimed to determine pre- and postoperative prevalence of FA among patients undergoing metabolic/bariatric surgery. It included both cross-sectional and longitudinal studies that used the Yale Food Addiction Scale (YFAS). The following databases were searched: MEDLINE, ScienceDirect, LILACS, PsycArticles, CENTRAL, greylit.org, and opengrey.eu. Studies that used the YFAS to evaluate FA in pre- or postoperative patients were included. A random-effects meta-analysis was performed with cross-sectional studies to calculate the weighted prevalence of FA at the pre- and postoperative moments. For longitudinal studies, which measured FA at both time points for the same individuals, absolute prevalence reduction (APR) was calculated. Of the 6626 records, 40 studies were included in the meta-analysis. The preoperative weighted prevalence of FA was 32% (95% CI: 27-37%; 33 groups), whereas the postoperative prevalence was 15% (95% CI: 12-18%; 14 groups). Seven longitudinal studies showed a weighted APR of 26 p.p. (95% CI: 10-41 p.p.). Observational data suggest a reduction in the prevalence of FA among patients that undergo bariatric surgery. Interventional studies are needed to confirm these findings.

Changes in Plasma Ghrelin Levels Following Surgical and Non-Surgical Weight-Loss in Female Rats Predict Alcohol Use

The weight-loss surgery Roux-en Y gastric bypass (RYGB) is a relatively effective, long-term treatment option for patients with morbid obesity. However, accumulating clinical evidence suggests that patients receiving RYGB may be at increased risk of developing alcohol use disorder. This observation has been repeatedly supported by preclinical studies showing rodents increase intake of ethanol (EtOH) after RYGB, and has been further confirmed by human studies. A promising alternative to RYGB is sleeve gastrectomy (SG), which has resulted in decreased EtOH consumption in some rodent studies. The exact mechanism underlying the differential alcohol outcomes after RYGB versus SG has yet to be elucidated. However, the gut hormone ghrelin has emerged as a potential candidate from previous preclinical studies specific to RYGB surgeries and due to its action to stimulate food and alcohol intake and cravings. To directly assess changes in plasma ghrelin levels following weigh loss surgeries in the context of alcohol intake, 24 female rats were separated into three surgical groups receiving RYGB, SG, or Sham surgery followed by caloric restriction to produce adiposity matched controls (Sham-AM). Blood was drawn for fasted and fed plasma ghrelin (acyl and des-acyl) assays at multiple time points: while on a normal diet (ND), after 5-week exposure to a high fat diet (HFD), following surgery, and after a series of two-bottle alcohol choice test with increasing concentrations (2%, 4%, 6%, 8%) of EtOH. Consistent with previous observations, RYGB rats drank more EtOH than SG rats across all concentrations. As expected, fasted ghrelin levels were blunted after HFD feeding, compared to normal diet baseline. After RYGB, fasted ghrelin levels returned to higher levels while remained blunted after SG and Sham-AM. Fed acyl ghrelin levels were significantly increased to above "normal" levels after RYGB, but remain low after SG and Sham-AM. Given that post-RYGB acyl ghrelin levels are raised to a fasted state regardless of actual prandial status, we conclude that RYGB may results in a hormonal state reminiscence of a fasted state with the inability of feeding to inhibit ghrelin production, an effect which could potentially contribute to increased EtOH intake following the surgery. In contrast, following SG, ghrelin levels in rats remain consistent with the fed state regardless of prandial status, potentially explaining lower alcohol intake and lower risk of developing AUD.

Self-care model and body image in adults after a bariatric surgery

OBJECTIVE

the aim of the present article was to test a self-care model explained by the relationship between self-efficacy, body image, obsessive-compulsive disorder, and depression in people with bariatric surgery in the city of Tijuana, Baja California, Mexico.

METHOD

this was a correlational cross-sectional study carried out between August and December 2020. Validated instruments were administered to 102 participants to measure their self-care capacity, general self-efficacy, psychopathological symptoms, and body image perception and satisfaction. The variables of interest were analyzed using descriptive statistics and the Pearson and Spearman correlation coefficients were used to develop a model using path analysis.

RESULT

a significant model was obtained with adequate goodness-of-fit indicators (chi-square χ2 (8) = 11.451, p = .177; root mean square error of approximation (RMSEA)= 0.000; goodness-of-fit index (GFI)= 0.965; comparative fit index (CFI)= 0.985; parsimonious normed fit index (PNFI)= 0.509, and Akaike information criterion (AIC)= 37.451). Self-efficacy (Zβ=0.294) and body image dissatisfaction (So= -0.376) were shown to influence self-care abilities while psychopathological symptoms influenced body dissatisfaction: obsessive-compulsive disorder (Zβ=0.370) and depression (Zβ=0.320).

CONCLUSION

adequate levels of self-efficacy and body satisfaction predict a high capacity for self-care.

Involvement of the Dorsal Vagal Complex in Alcohol-Related Behaviors

The neurobiological mechanisms that regulate the development and maintenance of alcohol use disorder (AUD) are complex and involve a wide variety of within and between systems neuroadaptations. While classic reward, preoccupation, and withdrawal neurocircuits have been heavily studied in terms of AUD, viable treatment targets from this established literature have not proven clinically effective as of yet. Therefore, examination of additional neurocircuitries not classically studied in the context of AUD may provide novel therapeutic targets. Recent studies demonstrate that various neuropeptides systems are important modulators of alcohol reward, seeking, and intake behaviors. This includes neurocircuitry within the dorsal vagal complex (DVC), which is involved in the control of the autonomic nervous system, control of intake of natural rewards like food, and acts as a relay of interoceptive sensory information via interactions of numerous gut-brain peptides and neurotransmitter systems with DVC projections to central and peripheral targets. DVC neuron subtypes produce a variety of neuropeptides and transmitters and project to target brain regions critical for reward such as the mesolimbic dopamine system as well as other limbic areas important for the negative reinforcing and aversive properties of alcohol withdrawal such as the extended amygdala. This suggests the DVC may play a role in the modulation of various aspects of AUD. This review summarizes the current literature on neurotransmitters and neuropeptides systems in the DVC (e.g., norepinephrine, glucagon-like peptide 1, neurotensin, cholecystokinin, thyrotropin-releasing hormone), and their potential relevance to alcohol-related behaviors in humans and rodent models for AUD research. A better understanding of the role of the DVC in modulating alcohol related behaviors may lead to the elucidation of novel therapeutic targets for drug development in AUD.

Gut peptide regulation of food intake - evidence for the modulation of hedonic feeding

The number of people living with obesity has tripled worldwide since 1975 with serious implications for public health, as obesity is linked to a significantly higher chance of early death from associated comorbidities (metabolic syndrome, type 2 diabetes, cardiovascular disease and cancer). As obesity is a consequence of food intake exceeding the demands of energy expenditure, efforts are being made to better understand the homeostatic and hedonic mechanisms governing food intake. Gastrointestinal peptides are secreted from enteroendocrine cells in response to nutrient and energy intake, and modulate food intake either via afferent nerves, including the vagus nerve, or directly within the central nervous system, predominantly gaining access at circumventricular organs. Enteroendocrine hormones modulate homeostatic control centres at hypothalamic nuclei and the dorso-vagal complex. Additional roles of these peptides in modulating hedonic food intake and/or preference via the neural systems of reward are starting to be elucidated, with both peripheral and central peptide sources potentially contributing to central receptor activation. Pharmacological interventions and gastric bypass surgery for the treatment of type 2 diabetes and obesity elevate enteroendocrine hormone levels and also alter food preference. Hence, understanding of the hedonic mechanisms mediated by gut peptide action could advance development of potential therapeutic strategies for the treatment of obesity and its comorbidities.

The rewarding effects of alcohol after bariatric surgery: do they change and are they associated with pharmacokinetic changes?

BACKGROUND

Research shows that surgery patients who have undergone Roux-en-Y gastric bypass (RYGB) are at increased risk for an alcohol use disorder (AUD). However, the mechanisms through which this increased risk is incurred are poorly understood. A host of variables have been proposed as potentially causal in developing AUDs, but empirical examination of many of these variables in human samples is lacking.

OBJECTIVES

Our objective was to examine the extent to which alcohol pharmacokinetics (PK), the rewarding effects of alcohol, and the relationship between these variables change from before to after weight loss surgery.

SETTING

Large healthcare facility in the Midwest United States METHODS: Thirty-four participants completed assessments before and 1 year after RYGB. They completed laboratory sessions and provided data on the PK of alcohol and the extent to which alcohol was reinforcing to them at each timepoint.

RESULTS

Findings show that the PK effects of alcohol (P < .01) and how rewarding alcohol was reported to be (P < .01) changed from before to 1 year after weight loss surgery. Further, statistically significant increases in the association between these variables were witnessed from before to 1 year after surgery (P < .01).

CONCLUSION

These results implicate changes (from before surgery to one year after) in the reinforcing and PK effects of alcohol as possible mechanisms for increased risk of alcohol use disorder following Roux-en-Y gastric bypass surgery.

Self-care model and body image in adults after a bariatric surgery

Objective:

the aim of the present article was to test a self-care model explained by the relationship between self-efficacy, body image, obsessive-compulsive disorder, and depression in people with bariatric surgery in the city of Tijuana, Baja California, Mexico.

Method:

this was a correlational cross-sectional study carried out between August and December 2020. Validated instruments were administered to 102 participants to measure their self-care capacity, general self-efficacy, psychopathological symptoms, and body image perception and satisfaction. The variables of interest were analyzed using descriptive statistics and the Pearson and Spearman correlation coefficients were used to develop a model using path analysis.

Result:

a significant model was obtained with adequate goodness-of-fit indicators (chi-square χ² (8) = 11.451, p = .177; root mean square error of approximation (RMSEA)= 0.000; goodness-of-fit index (GFI)= 0.965; comparative fit index (CFI)= 0.985; parsimonious normed fit index (PNFI)= 0.509, and Akaike information criterion (AIC)= 37.451). Self-efficacy (Zβ=0.294) and body image dissatisfaction (So= -0.376) were shown to influence self-care abilities while psychopathological symptoms influenced body dissatisfaction: obsessive-compulsive disorder (Zβ=0.370) and depression (Zβ=0.320).

Conclusion:

adequate levels of self-efficacy and body satisfaction predict a high capacity for self-care.

Modelo de autocuidado e imagen corporal en adultos post-cirugía bariátrica

Resumen Objetivo: probar un modelo de autocuidado explicado por la relación entre autoeficacia, imagen corporal, obsesión-compulsión y depresión en personas con cirugía bariátrica de la ciudad de Tijuana, B.C. Método: estudio transversal correlacional realizado entre agosto y diciembre de 2020. Se aplicaron instrumentos validados a 102 participantes para medir su capacidad de autocuidado, autoeficacia general, síntomas psicopatológicos, percepción y satisfacción de la imagen corporal. Las variables de interés fueron analizadas mediante estadística descriptiva y correlaciones de Pearson y Spearman para finalmente elaborar un modelo mediante análisis de ruta (Path Analysis). Resultados: se obtuvo un modelo significativo con buenos indicadores de bondad de ajuste (chi-cuadrado χ 2 (8)= 11.451, p = .177; error de aproximación raíz-media-cuadrada (RMSEA)= 0.000; índice de bondad de ajuste (GFI)= 0.965; índice de ajuste comparativo (CFI)= 0.985; índice de ajuste normado parsimonioso (PNFI)= 0.509 y criterio de información de Akaike (AIC)= 37.451). Se demostró que la autoeficacia (Zβ= 0.294) y la insatisfacción de la imagen corporal (Zβ= -0.376) tienen un efecto sobre las capacidades de autocuidado mientras que los síntomas psicopatológicos influyen sobre la insatisfacción corporal: obsesión-compulsión (Zβ= 0.370) y depresión (Zβ= 0.320). Conclusión: los niveles adecuados de autoeficacia y satisfacción corporal predicen una alta capacidad de autocuidado.

An Overview of Appetite-Regulatory Peptides in Addiction Processes; From Bench to Bed Side

There is a substantial need for new pharmacological treatments of addiction, and appetite-regulatory peptides are implied as possible candidates. Appetite regulation is complex and involves anorexigenic hormones such as glucagon-like peptide-1 (GLP-1) and amylin, and orexigenic peptides like ghrelin and all are well-known for their effects on feeding behaviors. This overview will summarize more recent physiological aspects of these peptides, demonstrating that they modulate various aspects of addiction processes. Findings from preclinical, genetic, and experimental clinical studies exploring the association between appetite-regulatory peptides and the acute or chronic effects of addictive drugs will be introduced. Short or long-acting GLP-1 receptor agonists independently attenuate the acute rewarding properties of addictive drugs or reduce the chronic aspects of drugs. Genetic variation of the GLP-1 system is associated with alcohol use disorder. Also, the amylin pathway modulates the acute and chronic behavioral responses to addictive drugs. Ghrelin has been shown to activate reward-related behaviors. Moreover, ghrelin enhances, whereas pharmacological or genetic suppression of the ghrelin receptor attenuates the responses to various addictive drugs. Genetic studies and experimental clinical studies further support the associations between ghrelin and addiction processes. Further studies should explore the mechanisms modulating the ability of appetite-regulatory peptides to reduce addiction, and the effects of combination therapies or different diets on substance use are warranted. In summary, these studies provide evidence that appetite-regulatory peptides modulate reward and addiction processes, and deserve to be investigated as potential treatment target for addiction.

Risks and Rewards of Bariatric Surgery in Advanced Chronic Liver Diseases

The burden of obesity and metabolic syndrome has determined a sharp increase in bariatric surgery (BS) procedures, which lead to marked weight loss, improved metabolic syndrome, reduced cardiovascular risk, and even improvement in nonalcoholic steatohepatitis (NASH). Despite these promising results, BS in patients with chronic liver disease can rarely lead to worsening of liver function, progression to cirrhosis and its complications, and even liver transplantation. On the other hand, since obesity in patients with cirrhosis is a major cofactor for progression to a decompensated stage of the disease and a risk factor for hepatocellular carcinoma, BS has been used to achieve weight loss in this population. In this review, we critically analyze the existing data on outcomes of BS in patients with cirrhosis and the possible mechanisms leading to fibrosis progression and worsening liver function in patients undergoing BS. Finally, we propose a set of measures that could be taken to improve the multidisciplinary management of liver disease in patients undergoing BS, including early recognition of malnutrition and alcohol misuse.

Bariatric surgery and the liver-Mechanisms, benefits, and risks

The prevalence of obesity and metabolic diseases such as type 2 diabetes and nonalcoholic fatty liver disease (NAFLD) has risen dramatically over the past decades. At present, bariatric surgery is the most effective treatment for this global health problem, through effects on food intake, gut hormone secretion, metabolic signaling pathways, and adipose tissue dysfunction. The liver occupies a central role in carbohydrate, protein, and lipid metabolism. Notably, a reduction in hepatic fat content and an improvement in hepatic insulin resistance are among the earliest beneficial effects of bariatric surgery, which has therefore emerged as an attractive treatment option for NAFLD. However, as the scope and popularity of weight loss surgery have expanded, new questions have arisen regarding its safety in patients with liver cirrhosis, the outcome of liver transplantation in patients with a history of bariatric surgery, and over incidental reports of liver failure following surgery. Studies in humans and rodents have also linked bariatric surgery to an increased risk of developing alcohol use disorder, a major risk factor for liver disease. This review integrates data from clinical and translational research to delineate both the beneficial impact of bariatric surgery on the liver and the potential risks involved.

Differential Response in Ethanol Behaviors of Female Rats Given Various Weight Loss Surgeries

AIMS

Currently, the only effective treatment for morbid obesity and its comorbidities is weight loss surgery (WLS). Growing evidence suggests that different types of WLS, such as Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG), have differential effects on alcohol consumption in humans and rats. Thus, we aimed to directly compare the effects of these two surgical procedures, for the first time in female rats, and to determine whether presence or absence of the ghrelin-producing stomach tissue has critical influence on postoperative alcohol intake.

METHODS

We performed two experiments using an identical behavioral protocol, a continuous-access two-bottle choice protocol for various concentrations of ethanol (EtOH). In Experiment 1, 23 high fat diet (HFD) obese, female rats were randomized to three groups: RYGB, SG or sham-operated food-restricted (Sham) controls. In Experiment 2, HFD obese female rats received either sham (n = 11) or a modified RYGB surgery where the remnant stomach was removed (RYGB-X; n = 12).

RESULTS

SG rats drank significantly less than RYGB for 4, 6 and 8% and significantly less than Sham for 6, 8 and 8% reinstatement. RYGB-X consumed significantly less EtOH than Sham across all concentrations, reaching significance for 6 and 8% reinstatement.

CONCLUSION

These findings confirm reduced EtOH consumption by female SG rats as opposed to increased intake following RYGB, and provide the first experimental evidence that the remnant stomach in the RYGB procedure is contributory. Future studies in rats and humans are warranted to confirm that ghrelin plays a critical role in susceptibility to AUD development following WLS.

Sweet Taste Is Complex: Signaling Cascades and Circuits Involved in Sweet Sensation

Sweetness is the preferred taste of humans and many animals, likely because sugars are a primary source of energy. In many mammals, sweet compounds are sensed in the tongue by the gustatory organ, the taste buds. Here, a group of taste bud cells expresses a canonical sweet taste receptor, whose activation induces Ca²⁺ rise, cell depolarization and ATP release to communicate with afferent gustatory nerves. The discovery of the sweet taste receptor, 20 years ago, was a milestone in the understanding of sweet signal transduction and is described here from a historical perspective. Our review briefly summarizes the major findings of the canonical sweet taste pathway, and then focuses on molecular details, about the related downstream signaling, that are still elusive or have been neglected. In this context, we discuss evidence supporting the existence of an alternative pathway, independent of the sweet taste receptor, to sense sugars and its proposed role in glucose homeostasis. Further, given that sweet taste receptor expression has been reported in many other organs, the physiological role of these extraoral receptors is addressed. Finally, and along these lines, we expand on the multiple direct and indirect effects of sugars on the brain. In summary, the review tries to stimulate a comprehensive understanding of how sweet compounds signal to the brain upon taste bud cells activation, and how this gustatory process is integrated with gastro-intestinal sugar sensing to create a hedonic and metabolic representation of sugars, which finally drives our behavior. Understanding of this is indeed a crucial step in developing new strategies to prevent obesity and associated diseases.

Changes in the Gut Microbiota Following Bariatric Surgery Are Associated with Increased Alcohol Intake in a Female Rat Model

AIMS

We aimed to investigate if differences in gut microbiota diversity and composition are associated with post-operative alcohol intake following bariatric surgery in a rat model.

METHODS

Twenty-four female rats were randomized to three treatment groups: sham surgery, vertical sleeve gastrectomy (VSG) or Roux-en-Y gastric bypass (RYGB). Stool was collected pre- and post-operatively and 16S rRNA gene amplification and sequencing was performed. Analysis focused on correlating microbial diversity, type of surgery and alcohol (EtOH) intake.

RESULTS

Pre-operative stools samples on regular diet showed similar taxonomic composition and Shannon diversity among the three treatment groups. There was a significant decrease in Shannon diversity and a change in taxonomic composition of the gut microbiota after rats was fed high fat diet. Post-operatively, the RYGB group showed significantly lower taxonomic diversity than the VSG and sham groups, while the VSG and sham groups diversity were not significantly different. Taxonomic composition and function prediction based on PICRUSt analysis showed the RYGB group to be distinct from the VSG and sham groups. Shannon diversity was found to be negatively associated with EtOH intake.

CONCLUSIONS

Changes in the taxonomic profile of the gut microbiota following bariatric surgery, particularly RYGB, are associated with increased EtOH intake and may contribute to increased alcohol use disorder risk through the gut-brain-microbiome axis.

The Function of Gastrointestinal Hormones in Obesity-Implications for the Regulation of Energy Intake

The global burden of obesity and the challenges of prevention prompted researchers to investigate the mechanisms that control food intake. Food ingestion triggers several physiological responses in the digestive system, including the release of gastrointestinal hormones from enteroendocrine cells that are involved in appetite signalling. Disturbed regulation of gut hormone release may affect energy homeostasis and contribute to obesity. In this review, we summarize the changes that occur in the gut hormone balance during the pre- and postprandial state in obesity and the alterations in the diurnal dynamics of their plasma levels. We further discuss how obesity may affect nutrient sensors on enteroendocrine cells that sense the luminal content and provoke alterations in their secretory profile. Gastric bypass surgery elicits one of the most favorable metabolic outcomes in obese patients. We summarize the effect of different strategies to induce weight loss on gut enteroendocrine function. Although the mechanisms underlying obesity are not fully understood, restoring the gut hormone balance in obesity by targeting nutrient sensors or by combination therapy with gut peptide mimetics represents a novel strategy to ameliorate obesity.

Factors Related to Weight Loss Maintenance in the Medium-Long Term after Bariatric Surgery: A Review

Despite bariatric surgery being the most effective treatment for obesity, some individuals do not respond adequately, especially in the long term. Identifying the predictors of correct weight maintenance in the medium (from 1 to 3 years after surgery) and long term (from 3 years and above) is of vital importance to reduce failure after bariatric surgery; therefore, we summarize the evidence about certain factors, among which we highlight surgical technique, psychological factors, physical activity, adherence to diet, gastrointestinal hormones or neurological factors related to appetite control. We conducted a search in PubMed focused on the last five years (2015–2021). Main findings are as follows: despite Roux-en-Y gastric bypass being more effective in the long term, sleeve gastrectomy shows a more beneficial effectiveness–complications balance; pre-surgical psychological and behavioral evaluation along with post-surgical treatment improve long-term surgical outcomes; physical activity programs after bariatric surgery, in addition to continuous and comprehensive care interventions regarding diet habits, improve weight loss maintenance, but it is necessary to improve adherence; the impact of bariatric surgery on the gut–brain axis seems to influence weight maintenance. In conclusion, although interesting findings exist, the evidence is contradictory in some places, and long-term clinical trials are necessary to draw more robust conclusions.

Intragastric satiety-inducing device reduces food intake and suppresses body weight gain in a rodent model

BACKGROUND

An intragastric satiety-inducing device (ISD) (Full Sense Device; Baker, Foote, Kemmeter, Walburn, LLC, Grand Rapids, MI) is a novel weight-loss device, which may induce satiety by applying continuous pressure on the gastric cardia. This study investigated the effect of the ISD on food intake and body weight gain in a rodent model.

METHODS

Thirty-two male Sprague-Dawley rats (weight, 250-300 g) were randomly divided into four groups of eight individuals. Single-disk (SD) and double-disk (DD) group animals underwent peroral placement of a single- or double-disk ISD, respectively, under fluoroscopic guidance. The ISD comprised a 4 mm × 1.5 cm nitinol stent placed in the lower esophagus and one (single-disk) or two (double-disk) 2.5-cm-diameter star-shaped nitinol disks placed in the gastric fundus. Esophageal stent (ES) and sham-operated (SO) group animals underwent peroral placement of the ES part of the ISD and a sham operation, respectively.

RESULTS

Food intake was significantly different among the four groups over the 4-week study period (P < 0.001); food intake was significantly lower in the SD and DD groups than in the SO group (P = 0.016 and P = 0.002, respectively) but was not significantly different between the SD and DD groups (P > 0.999) and between the ES and SO groups (P = 0.677). Body weight was significantly different among the four groups by the end of the study period (P < 0.001); body weight was significantly lower in the DD group than in the SD, ES, and SO groups (P = 0.010, P < 0.001, and P < 0.001, respectively) and in the SD group than in the SO group (P = 0.001), but it was not significantly different between the ES and SO groups (P = 0.344).

CONCLUSION

ISD reduced food intake and suppressed body weight gain in a rodent model.

Malnutrition and Alcohol in Patients Presenting with Severe Complications of Cirrhosis After Laparoscopic Bariatric Surgery

Factors and outcomes associated with decompensation of liver disease and liver failure in obese patients who underwent modern bariatric surgery are unclear. We present here a cohort of seventeen consecutive patients referred because of decompensation of liver disease following laparoscopic bariatric surgery. All patients showed signs of malnutrition (sarcopenia in 76.5%). In ten (58.8%), decompensation was associated with alcohol ingestion, which started after bariatric surgery in six patients. One patient died and three patients required liver transplantation, in one case preceded by transjugular intrahepatic portosystemic shunt (TIPS). However, thirteen patients achieved stabilization or full re-compensation with medical therapy and nutritional support. Our cases underline the risk of alcohol intake and malnutrition after laparoscopic bariatric surgery as causes of severe liver decompensation and underline the need for careful interdisciplinary care of these patients after surgery to early identify and treat alcohol misuse, malnutrition, and liver disease.