Differences in the effects of laparoscopic sleeve gastrectomy and laparoscopic Roux-en-Y gastric bypass on gut hormones: systematic and meta-analysis

The enteroendocrine axis and its effect on gastrointestinal function, nutrition, and inflammation

PURPOSE OF REVIEW

Gastrointestinal (GI) dysfunction limits enteral nutrition (EN) delivery in critical illness and contributes to systemic inflammation. The enteroendocrine (EE) axis plays an integral role in this interface between nutrition, inflammation, and GI function in critical illness. In this review, we present an overview of the EE system with a focus on its role in GI inflammation and function.

RECENT FINDINGS

Enteroendocrine cells have been primarily described in their role in macronutrient digestion and absorption. Recent research has expanded on the diverse functions of EE cells including their ability to sense microbial peptides and metabolites and regulate immune function and inflammation. Therefore, EE cells may be both affected by and contribute to many pathophysiologic states and interventions of critical illness such as dysbiosis , inflammation, and alternative EN strategies. In this review, we present an overview of EE cells including their growing role in nonnutrient functions and integrate this understanding into relevant aspects of critical illness with a focus on EN.

SUMMARY

The EE system is key in maintaining GI homeostasis in critical illness, and how it is impacted and contributes to outcomes in the setting of dysbiosis , inflammation and different feeding strategies in critical illness should be considered.

Gut motility and hormone changes after bariatric procedures

PURPOSE OF REVIEW

Metabolic and bariatric surgery (MBS) and endoscopic bariatric therapies (EBT) are being increasingly utilized for the management of obesity. They work through multiple mechanisms, including restriction, malabsorption, and changes in the gastrointestinal hormonal and motility.

RECENT FINDINGS

Roux-en-Y gastric bypass (RYGB) and laparoscopic sleeve gastrectomy (LSG) cause decrease in leptin, increase in GLP-1 and PYY, and variable changes in ghrelin (generally thought to decrease). RYGB and LSG lead to rapid gastric emptying, increase in small bowel motility, and possible decrease in colonic motility. Endoscopic sleeve gastroplasty (ESG) causes decrease in leptin and increase in GLP-1, ghrelin, and PYY; and delayed gastric motility.

SUMMARY

Understanding mechanisms of action for MBS and EBT is critical for optimal care of patients and will help in further refinement of these interventions.

Gut peptides before and following Roux-En-Y gastric bypass: A systematic review and meta-analysis

A systematic search was conducted in Medline Ovid, Embase, Scopus, and Cochrane Central Register of Controlled Trials up until March 2021 following PRISMA guidelines. Studies included evaluated ghrelin, GLP-1, PYY or appetite sensation via visual analogue scales (VASs) before and after Roux-en-Y gastric bypass (RYGB) in adults. A multilevel model with random effects for study and follow-up time points nested in study was fit to the data. The model included kcal consumption as a covariate and time points as moderators. Among the 2559 articles identified, k = 47 were included, among which k = 19 evaluated ghrelin, k = 40 GLP-1, k = 22 PYY, and k = 8 appetite sensation. Our results indicate that fasting ghrelin levels are decreased 2 weeks post-RYGB (p = 0.005) but do not differ from baseline from 6 weeks to 1-year post-RYGB. Postprandial ghrelin and fasting GLP-1 levels were not different from pre-surgical values. Postprandial levels of GLP-1 increased significantly from 1 week (p < 0.001) to 2 years post-RYGB (p < 0.01) compared with pre-RYGB. Fasting PYY increased at 6 months (p = 0.034) and 1 year (p = 0.029) post-surgery; also, postprandial levels increased up to 1 year (p < 0.01). Insufficient data on appetite sensation were available to be meta-analyzed.

Metabolic surgery and oral health: A register-based study

OBJECTIVE

The impact of weight loss surgery on oral health is not clear. The aim of the present study was to investigate its impact on the risk for dental interventions.

MATERIALS AND METHODS

All adults who underwent metabolic surgery in Sweden between January 1, 2009 and December 31, 2018 were identified in the Scandinavian Obesity Surgery Registry (SOReg; n = 53,643). A control cohort from the general population was created, matched 10:1 on sex, age and place of residence (n = 536,430). All individuals were followed in the Swedish Dental Register regarding event rates for four types of dental intervention: restorative, endodontic and periodontal interventions, and tooth extractions.

RESULTS

The surgical cohort had increased interventional rates postoperatively regarding all studied outcomes except periodontal interventions. Dental interventions were more common in the surgical cohort both pre- and postoperatively. The difference between the groups increased markedly in the postoperative period. The between-group comparison postoperatively showed increased event rates for restorations (IRR 1.8; 95% CI 1.7-1.8), extractions (1.9; 95% CI 1.9-2.0) and endodontics (2.1; 95% CI 2.0-2.1).

CONCLUSION

The surgical intervention might cause a substantial negative impact on oral health. These results imply an important role for counselling metabolic surgery patients regarding preventive oral health measures.

Bariatric surgery, through beneficial effects on underlying mechanisms, improves cardiorenal and liver metabolic risk over an average of ten years of observation: A longitudinal and a case-control study

BACKGROUND

Bariatric surgery has long-term beneficial effects on body weight and metabolic status, but there is an apparent lack of comprehensive cardiometabolic, renal, liver, and metabolomic/lipidomic panels, whereas the underlying mechanisms driving the observed postoperative ameliorations are still poorly investigated. We aimed to study the long-term effects of bariatric surgery on metabolic profile, cardiorenal and liver outcomes in association with underlying postoperative gut hormone adaptations.

METHODS

28 individuals who underwent bariatric surgery [17 sleeve gastrectomy (SG), 11 Roux-en-Y gastric bypass (RYGB)] were followed up 3, 6 and 12 and at 10 years following surgery. Participants at 10 years were cross-sectionally compared with an age-, sex- and adiposity-matched group of non-operated individuals (n = 9) and an age-matched pilot group of normal-weight individuals (n = 4).

RESULTS

There were durable effects of surgery on body weight and composition, with an increase of lean mass percentage persisting despite some weight regain 10 years postoperatively. The improvements in metabolic and lipoprotein profiles, cardiometabolic risk markers, echocardiographic and cardiorenal outcomes persisted over the ten-year observation period. The robust improvements in insulin resistance, adipokines, activin/follistatin components and postprandial gastrointestinal peptide levels persisted 10 years postoperatively. These effects were largely independent of surgery type, except for a lasting reduction of ghrelin in the SG subgroup, and more pronounced increases in proglucagon products, mainly glicentin and oxyntomodulin, and in the cardiovascular risk marker Trimethylamine-N-oxide (TMAO) within the RYGB subgroup. Despite similar demographic and clinical features, participants 10 years after surgery showed a more favorable metabolic profile compared with the control group, in conjunction with a dramatic increase of postprandial proglucagon product secretion.

CONCLUSIONS

We demonstrate that cardiorenal and metabolic benefits of bariatric surgery remain robust and largely unchanged ten years postoperatively and are associated with durable effects on gastrointestinal- muscle- and adipose tissue-secreted hormones.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT04170010.

The role of glucagon after bariatric/metabolic surgery: much more than an "anti-insulin" hormone

The biological activity of glucagon has recently been proposed to both stimulate hepatic glucose production and also include a paradoxical insulinotropic effect, which could suggest a new role of glucagon in the pathophysiology type 2 diabetes mellitus (T2DM). An insulinotropic role of glucagon has been observed after bariatric/metabolic surgery that is mediated through the GLP-1 receptor on pancreatic beta cells. This effect appears to be modulated by other members of the proglucagon family, playing a key role in the beneficial effects and complications of bariatric/metabolic surgery. Glucagon serves a dual role after sleeve gastrectomy (SG) and Roux-en-Y gastric bypass (RYGB). In addition to maintaining blood glucose levels, glucagon exhibits an insulinotropic effect, suggesting that glucagon has a more complex function than simply an "anti-insulin hormone".

Opioid Analgesics after Bariatric Surgery: A Scoping Review to Evaluate Physiological Risk Factors for Opioid-Related Harm

The persisting use of opioids following bariatric surgery has emerged as a prevalent complication, heightening the probability of opioid-related harm (ORM), such as opioid-related fatalities and prescription opioid use disorder (OUD). A comprehensive review of PubMed literature from 1990 to 2023 was conducted to pinpoint physiological influences on postoperative ORM. As a result, we found that patients undertaking bariatric operations often exhibit an inherently higher risk for substance use disorders, likely attributable to genetic predisposition and related neurobiological changes that engender obesity and addiction-like tendencies. Furthermore, chronic pain is a common post-bariatric surgery complaint, and the surgical type impacts opioid needs, with increased long-term opioid use after surgeries. Additionally, the subjective nature of pain perception in patients with obesity can distort pain reporting and the corresponding opioid prescription both before and after surgery. Furthermore, the postoperative alterations to the gastrointestinal structure can affect the microbiome and opioid absorption rates, resulting in fluctuating systemic exposure to orally ingested opioids. The prospect of ORM development post-bariatric surgery appears amplified due to a preexisting susceptibility to addictive habits, surgically induced pain, modified gut-brain interaction and pain management and the changed pharmacokinetics post-surgery. Further research is warranted to clarify these potential risk variables for ORM, specifically OUD, in the bariatric population.

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.

Changes in Bone Turnover Markers after Roux-en-Y Gastric Bypass Versus Sleeve Gastrectomy: a Systematic Review and Meta-Analysis

This systematic review and meta-analysis was performed to compare the alterations in bone turnover markers between SG and RYGB. A literature search was conducted in PubMed, Medline, Scopus, Web of Science, and the Cochrane Central Register of Controlled Trials (CENTRAL) databases to find the studies. There was significant less increment in osteocalcin [WMD =  - 5.98, 95% CI (- 9.30, - 2.47) P < 0.01] and parathyroid hormone (PTH) [WMD =  - 9.59, 95% CI (- 15.02, - 4.16) P < 0.01] in the SG group compared to the RYGB group. No significant differences were seen in change of C-terminal telopeptide of type I collagen (CTX), N-terminal propeptide of type I collagen (PINP), Ca, and 25(OH)-D between SG and RYGB groups. According to our meta-analysis, bone formation markers appear to have more increment following RYGB than SG. This observation is accompanied by a larger increase in PTH after RYGB patients compared to SG patients. PROSPERO: CRD42022308985.

Updates in Endoscopic Bariatric and Metabolic Therapies

The rising prevalence of obesity, and related morbidity and mortality, has necessitated the development of therapeutic weight loss strategies. Lifestyle modifications alone have only yielded modest benefit, and while bariatric surgery has shown significant short- and long-term results, only a minority of eligible patients end up receiving this treatment. Endoscopic bariatric and metabolic therapies (EBMTs) are a rapidly evolving field, which provides a less invasive middle ground treatment option for weight loss. Here we discuss the efficacy, as well as short- and long-term outcomes with restrictive, malabsorptive/metabolic and aspiration endoscopic techniques, and their effects on metabolic parameters.

Hypothalamic integrity is necessary for sustained weight loss after bariatric surgery: A prospective, cross-sectional study

OBJECTIVE

The hypothalamus is the main integrator of peripheral and central signals in the control of energy homeostasis. Its functional relevance for the effectivity of bariatric surgery is not entirely elucidated. Studying the effects of bariatric surgery in patients with hypothalamic damage might provide insight.

SUMMARY BACKGROUND DATA

Prospective study to analyze the effects of bariatric surgery in patients with hypothalamic obesity (HO) vs. matched patients with common obesity (CO) with and without bariatric surgery.

METHODS

65 participants were included (HO-surgery: n = 8, HO-control: n = 10, CO-surgery: n = 12, CO-control: n = 12, Lean-control: n = 23). Body weight, levels of anorexic hormones, gut microbiota, as well as subjective well-being/health status, eating behavior, and brain activity (via functional MRI) were evaluated.

RESULTS

Patients with HO lost significantly less weight after bariatric surgery than CO-participants (total body weight loss %: 5.5 % vs. 26.2 %, p = 0.0004). After a mixed meal, satiety and abdominal fullness tended to be lowest in HO-surgery and did not correlate with levels of GLP-1 or PYY. Levels of PYY (11,151 ± 1667 pmol/l/h vs. 8099 ± 1235 pmol/l/h, p = 0.028) and GLP-1 (20,975 ± 2893 pmol/l/h vs. 13,060 ± 2357 pmol/l/h, p = 0.009) were significantly higher in the HO-surgery vs. CO-surgery group. Abundance of Enterobacteriaceae and Streptococcus was increased in feces of HO and CO after bariatric surgery. Comparing HO patients with lean-controls revealed an increased activation in insula and cerebellum to viewing high-caloric foods in left insula and cerebellum in fMRI.

CONCLUSIONS

Hypothalamic integrity is necessary for the effectiveness of bariatric surgery in humans. Peripheral changes after bariatric surgery are not sufficient to induce satiety and long-term weight loss in patients with hypothalamic damage.

Roux-en-Y gastric bypass and laparoscopic sleeve gastrectomy effects on obesity comorbidities: A systematic review and meta-analysis

Roux-en-Y gastric bypass (LRYGB) and laparoscopic sleeve gastrectomy (LSG) are the most commonly used bariatric procedures. There is an increasing awareness about a comorbidity-based indication for bariatric surgery regardless of weight (metabolic surgery). The best operation to mitigate obesity-associated comorbidities is a matter of controversy. This review is aimed at comparing LRYGB and LSG for the treatment of diabetes, hypertension, dyslipidemias, obstructive sleep apnea (OSA), and gastroesophageal reflux (GERD). We searched PubMed, MEDLINE, SCOPUS, Web of Science, and Cochrane library for articles comparing these two commonly used bariatric approaches. We identified 2,457 studies, 1,468 of which stood after the removal of duplications; from them, 81 full texts were screened and only 16 studies were included in the final meta-analysis. LRYGB was equal weight to LSG for diabetes (P-value = 0.10, odd ratio, 1.24, 95% CI, 0.96-1.61, I ² for heterogeneity = 30%, P-value for heterogeneity, 0.14), and OSA (P-value = 0.38, odd ratio, 0.79, 95% CI, 0.47-1.33, I ² for heterogeneity = 0.0%, P-value for heterogeneity, 0.98). However, LRYGB was superior to LSG regarding hypertension (P-value = 0.009, odd ratio, 1.55, 95% CI, 1.20-2.0, I ² for heterogeneity = 0.0%, P-value for heterogeneity, 0.59), dyslipidemia (odd ratio, 2.18, 95% CI, 1.15-4.16, P-value for overall effect, 0.02), and GERD (P-value = 0.003, odd ratio, 3.16, 95% CI, 1.48-6.76). LRYGB was superior to LSG for gastroesophageal reflux, hypertension, and dyslipidemia remission. While the two procedures were equal regarding diabetes and obstructive sleep, further reviews comparing LSG, and one anastomosis gastric bypass are recommended.

A single FTO gene variant rs9939609 is associated with weight change and insulin resistance improvement in response to a robotic sleeve gastrectomy in individuals with severe obesity

BACKGROUND

Genetic mechanisms have been involved in the weight response secondary to bariatric surgery.

OBJECTIVE

The aim of our study was to evaluate the effects of the rs9939609 genetic variant on weight loss and metabolic parameters after sleeve gastrectomy.

SETTING

Tertiary hospital.

METHODS

A total of 95 participants were enrolled. Co-morbidities, biochemical evaluation, and anthropometric parameters were registered before and after 3-, 6-, and 12-month follow-up. Genotype of the rs9939609 fat mass and obesity-associated (FTO) gene was evaluated.

RESULTS

We grouped the participants into 2 groups: carriers of A allele (TA+AA, 69.5%) and noncarriers of A allele (TT, 30.5%). We detected a statistically significant reduction of blood pressure, biochemical, and anthropometric parameters at 3 times during follow-up. After 6 months, changes of some parameters were greater in non-A allele carriers: weight (-39.6 + 4.0 kg versus -24.6 + 2.8 kg; P = .02), waist circumference (-21.1 + 2.1 cm versus -16.2 + 1.8 cm; P = .04), insulin (-12.3 + .9 mUI/L versus -8.9.1 + .2 mUI/L; P = .02), and homeostasis model assessment of insulin resistance (-3.1 + .1 units versus -2.3 + .1 units; P = .02 ). After 12 months, changes of the aforementioned parameters remained greater in non-A allele carriers. The percentage of participants with diabetes diminished earlier in the non-A allele carriers than A allele carriers at 6-month follow-up. The percentage of participants with diabetes at the end of the study was lower in non-A allele carriers (3.4% versus 12.1%; P = .02).

CONCLUSIONS

Our data suggest that non-A allele carriers of the genetic variant (rs9939609) of the FTO gene showed a better improvement of anthropometric and insulin levels in non-A allele carriers after a robotic sleeve gastrectomy. Both improvements are associated with a lower percentage of participants with diabetes at 12 months.

Worth the wait? Preconception weight reduction in women and men with obesity and infertility: a narrative review

Short and long-term weight reduction interventions are considered in the preconception period for women and men with obesity and infertility as obesity is associated with poorer reproductive outcomes. Short-term weight loss achieved with diet, exercise, and medications does not improve per cycle conception or live birth rates in women undergoing ovulation induction, intrauterine insemination, or in vitro fertilization (IVF), but may increase the rate of natural conception. Long-term weight loss achieved through surgical interventions may increase spontaneous conceptions, particularly among women with polycystic ovary syndrome, and may increase the live birth rate from IVF, though these findings are limited by recent evidence. There is a clear need for additional treatment options and well-designed weight loss intervention trials that address the heterogeneous causes of obesity among women and men with infertility and include fertility outcomes and perinatal morbidity as outcome measures.

Effect of ursodeoxycholic acid on gallstone formation after bariatric surgery: An updated meta-analysis

OBJECTIVE

Bariatric surgery increases the risk of postoperative gallstone formation. Many studies have proposed ursodeoxycholic acid (UDCA) as a preventive agent for postoperative gallstone formation. This study aimed to investigate the effect of UDCA on gallstone formation after bariatric surgery in patients without preoperative gallstones.

METHODS

PubMed, the Web of Science, the Cochrane Library, and EBSCO were searched for articles assessing the effect of UDCA on gallstone formation after bariatric surgery. The outcome was the incidence of postoperative gallstones. Odds ratios were used to assess dichotomous variables, and random-effects models were used for statistical analyses.

RESULTS

A total of 18 studies including 4,827 participants met the inclusion criteria. The statistical results showed that the incidence of gallstones in the UDCA group was significantly lower than in the control group. Furthermore, the occurrence of symptomatic gallstones and cholecystectomy was significantly reduced.

CONCLUSIONS

In patients without preoperative gallstones, UDCA can effectively prevent the formation of gallstones after bariatric surgery. In addition, UDCA can significantly reduce the occurrence of symptomatic gallstones and the risk of postoperative cholecystectomy. Doses of 500 to 600 mg/d can be used as a measure to prevent postoperative gallstone formation.

Neurohormonal Changes in the Gut–Brain Axis and Underlying Neuroendocrine Mechanisms following Bariatric Surgery

Obesity is a complex, multifactorial disease that is a major public health issue worldwide. Currently approved anti-obesity medications and lifestyle interventions lack the efficacy and durability needed to combat obesity, especially in individuals with more severe forms or coexisting metabolic disorders, such as poorly controlled type 2 diabetes. Bariatric surgery is considered an effective therapeutic modality with sustained weight loss and metabolic benefits. Numerous genetic and environmental factors have been associated with the pathogenesis of obesity, while cumulative evidence has highlighted the gut–brain axis as a complex bidirectional communication axis that plays a crucial role in energy homeostasis. This has led to increased research on the roles of neuroendocrine signaling pathways and various gastrointestinal peptides as key mediators of the beneficial effects following weight-loss surgery. The accumulate evidence suggests that the development of gut-peptide-based agents can mimic the effects of bariatric surgery and thus is a highly promising treatment strategy that could be explored in future research. This article aims to elucidate the potential underlying neuroendocrine mechanisms of the gut–brain axis and comprehensively review the observed changes of gut hormones associated with bariatric surgery. Moreover, the emerging role of post-bariatric gut microbiota modulation is briefly discussed.

Bariatric surgery and health outcomes: An umbrella analysis

BACKGROUND

There is a relative lack of data that systematically investigates the breadth and validity of the association between bariatric surgery and health-related outcomes. We aimed to evaluate the quantity, validity, and credibility of evidence regarding the association between bariatric surgery and health-related outcomes using an umbrella review of meta-analyses.

METHODS

We systematically searched PubMed, Embase, and the Web of Science databases from inception until December 2, 2021, to identify meta-analyses of observational or interventional studies that investigated the association between bariatric surgery and multiple health outcomes. We extracted the summary effect size and 95% confidence interval (CI) data. The Assessment of Multiple Systematic Reviews (AMSTAR-2) and Grading of Recommendations, Assessment, Development, and Evaluations (GRADE) guidelines were used for methodological and evidence quality assessments, respectively.

RESULTS

Twenty-eight studies with 82 different health-related outcomes were included in this umbrella review. Beneficial effects of bariatric surgery have been observed in cancer incidence, mortality, cardiovascular risk, polycystic ovary syndrome (PCOS), anxiety symptoms, depressive symptoms, gestational diabetes mellitus, gestational hypertension, large for gestational age (LGA), macrosomia, post-term birth, risk of kidney stones, albuminuria, urinary incontinence, fecal incontinence, Barrett's esophagus, and diabetic retinopathy. However, adverse effects of bariatric surgery were observed for maternal anemia, perinatal mortality, congenital anomalies, preterm birth, neonatal intensive care unit (NICU) admission, intrauterine growth restriction, small for gestational age (SGA), fracture risk, upper limb fracture, suicide, self-harm, and alcohol use disorder (AUD).

CONCLUSIONS

Current evidence suggests that bariatric surgery improves the majority of health-related outcomes; however, caution is advised given it may increase the risk of adverse mental effects, perinatal problems, and fractures.

Bariatric surgery alleviates depression in obese patients: A systematic review and meta-analysis

BACKGROUND

With the rapid increase in the incidence of depression, there have been studies investigating whether bariatric surgery can alleviate this condition. In this study, we aimed to explore the effect of bariatric surgery on depression in obese patients.

METHODS

We searched the PubMed, Embase, Web of Science and the Cochrane Library databases for studies on bariatric surgery and depression. Then, the clinical significance of bariatric surgery on depression was evaluated based on Beck Depression Inventory (BDI), Hospital Anxiety and Depression Scale (HADS) or Patient Health Questionnaire (PHQ-9). Subgroup analysis was carried out in terms of surgery types, assessment tool, follow-up time and nationalism. Dichotomous data were analyzed using odds ratio (OR), and continuous data were evaluated using the weighted mean difference (WMD) or standardized mean difference (SMD).

RESULTS

Overall, 33 studies with a combined total of 12,556 participants met the inclusion criteria. Statistical results were significantly different whether continuous or dichotomous, and depression was improved in obese patients after surgery (SMD = -0.87, p < 0.001; and OR = 0.29, p < 0.001, respectively). In addition, subgroup analysis showed that bariatric surgery improved depression in obese patients regardless of surgery types, assessment tool, follow-up and country.

CONCLUSION

Bariatric surgery alleviates depression in obese patients. However, further studies are needed to elucidate on the complex effect of between bariatric surgery on depression.

Are the Changes in Gastrointestinal Hormone Secretion Necessary for the Success of Bariatric Surgery? A Critical Review of the Literature

Ghrelin, glucagon-like peptide-1 (GLP-1), and peptide YY (PYY) are involved in energy balance regulation and glucose homeostasis. Obesity is characterized by lower fasting levels and blunted postprandial responses of ghrelin, GLP-1, and possibly PYY. Both Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG) have been shown to increase postprandial GLP-1 and PYY levels. Human studies have shown that enhanced postprandial GLP-1 and PYY release are associated with favorable weight loss outcomes after RYGB. However, studies in knockout mice have shown that GI hormones are not required for the primary metabolic effects of bariatric surgery. Here, we summarize the complex interaction between obesity, bariatric surgery, and GI hormones in order to determine the exact role of GI hormones in the success of bariatric surgery.

Ockham's razor and the metabolic syndrome

The broad effects of bariatric/metabolic surgery on virtually every tissue and organ system remain unexplained. Weight loss, although a major factor, does not fully account for the rapid, full, and durable remission of type 2 diabetes, return of islet function, reduction of the prevalence of cancers, increase in gray matter of the brain, and decrease in all-cause mortality. This review supports the thesis that the metabolic syndrome is not a group of separate diseases but rather multiple expressions of a shared defect in the utilization of carbohydrates and lipids. That error is probably caused by a dysmetabolic signal from the foregut, stimulated by food, that limits entry of 2-carbon fragments into the tricarboxylic acid cycle, the accumulation of lactate and, in turn, increases in glucose and insulin. Surgery limits that signal by reducing contact between food and foregut mucosa. Speciation of that signal(s) may offer a new pathway for drug development.

Gastric Sensory and Motor Functions and Energy Intake in Health and Obesity-Therapeutic Implications

Sensory and motor functions of the stomach, including gastric emptying and accommodation, have significant effects on energy consumption and appetite. Obesity is characterized by energy imbalance; altered gastric functions, such as rapid gastric emptying and large fasting gastric volume in obesity, may result in increased food intake prior to reaching usual fullness and increased appetite. Thus, many different interventions for obesity, including different diets, anti-obesity medications, bariatric endoscopy, and surgery, alter gastric functions and gastrointestinal motility. In this review, we focus on the role of the gastric and intestinal functions in food intake, pathophysiology of obesity, and obesity management.

Do Gut Hormones Contribute to Weight Loss and Glycaemic Outcomes after Bariatric Surgery?

Bariatric surgery is an effective intervention for management of obesity through treating dysregulated appetite and achieving long-term weight loss maintenance. Moreover, significant changes in glucose homeostasis are observed after bariatric surgery including, in some cases, type 2 diabetes remission from the early postoperative period and postprandial hypoglycaemia. Levels of a number of gut hormones are dramatically increased from the early period after Roux-en-Y gastric bypass and sleeve gastrectomy—the two most commonly performed bariatric procedures—and they have been suggested as important mediators of the observed changes in eating behaviour and glucose homeostasis postoperatively. In this review, we summarise the current evidence from human studies on the alterations of gut hormones after bariatric surgery and their impact on clinical outcomes postoperatively. Studies which assess the role of gut hormones after bariatric surgery on food intake, hunger, satiety and glucose homeostasis through octreotide use (a non-specific inhibitor of gut hormone secretion) as well as with exendin 9–39 (a specific glucagon-like peptide-1 receptor antagonist) are reviewed. The potential use of gut hormones as biomarkers of successful outcomes of bariatric surgery is also evaluated.