The contribution of malabsorption to the reduction in net energy absorption after long-limb Roux-en-Y gastric bypass

Effects of gastric bypass on the digestibility and postprandial metabolic fate of 15N dietary protein in rats

Roux-en-Y Gastric Bypass may be associated with an alteration of protein bioavailability in relation to intestinal remodeling. Our study aimed to test this hypothesis by Roux-en-Y Gastric Bypass. Diet-induced obese rats underwent Roux-en-Y Gastric Bypass surgery (RYGB rats) while a Sham-operated control group was used. All rats received a 15N-labeled protein meal 1 or 3 months after surgery and were euthanized 6h later. Protein digestibility, 15N recovered in organs and urea pool, fractional protein synthesis rate, and intestinal morphometry were assessed. Protein digestibility was similar in all groups (94.2±0.3%). The small intestine was hypertrophied in RYGB rats 1 month after surgery, weighing 9.1±0.2g vs. 7.0±0.3g in Sham rats (P = 0.003). Villus height and crypt depth were increased in the alimentary limb and ileum of RYGB rats. However, Roux-en-Y Gastric Bypass had no impact on the fractional synthesis rate. In the gastrointestinal tract, 15N retention only differed in the ileal mucosa and was higher in RYGB rats at 1 month (0.48±0.2% vs. 0.3±0.09%, P = 0.03). 15N recovery from the liver, muscle, and skin was lower in RYGB rats at 1 month. 15N recovery from urinary and plasma urea was higher in RYGB rats at both times, resulting in increased total deamination (13.2±0.9% vs. 10.1±0.5%, P<0.01). This study showed that Roux-en-Y Gastric Bypass did not affect protein digestibility. Dietary nitrogen sequestration was transitorily and moderately diminished in several organs. This was associated with a sustained elevation of postprandial deamination after Roux-en-Y Gastric Bypass, whose mechanisms merit further studies.

New Lessons from the gut: Studies of the role of gut peptides in weight loss and diabetes resolution after gastric bypass and sleeve gastrectomy

It has been known since 2005 that the secretion of several gut hormones changes radically after gastric bypass operations and, although more moderately, after sleeve gastrectomy but not after gastric banding. It has therefore been speculated that increased secretion of particularly GLP-1 and Peptide YY (PYY), which both inhibit appetite and food intake, may be involved in the weight loss effects of surgery and for improvements in glucose tolerance. Experiments involving inhibition of hormone secretion with somatostatin, blockade of their actions with antagonists, or blockade of hormone formation/activation support this notion. However, differences between results of bypass and sleeve operations indicate that distinct mechanisms may also be involved. Although the reductions in ghrelin secretion after sleeve gastrectomy would seem to provide an obvious explanation, experiments with restoration of ghrelin levels pointed towards effects on insulin secretion and glucose tolerance rather than on food intake. It seems clear that changes in GLP-1 secretion are important for insulin secretion after bypass and appear to be responsible for postbariatric hypoglycemia in glucose-tolerant individuals; however, with time the improvements in insulin sensitivity, which in turn are secondary to the weight loss, may be more important. Changes in bile acid metabolism do not seem to be of particular importance in humans.

Weight loss in adult male Wistar rats by Roux-en-Y gastric bypass is primarily explained by caloric intake reduction and presurgery body weight

Diets varying in macronutrient composition, energy density, and/or palatability may cause differences in outcome of bariatric surgery. In the present study, rats feeding a healthy low-fat (LF) diet or an obesogenic high-fat/sucrose diet (HF/S) were either subjected to Roux-en-Y gastric bypass surgery (RYGB) or sham surgery, and weight loss trajectories and various energy balance parameters were assessed. Before RYGB, rats eating an HF/S (n = 14) diet increased body weight relative to rats eating an LF diet (n = 20; P < 0.01). After RYGB, absolute weight loss was larger in HF/S (n = 6) relative to LF feeding (n = 6) rats, and this was associated with reduced cumulative energy intake (EI; P < 0.05) and increased locomotor activity (LA; P < 0.05-0.001), finally leading to similar levels of reduced body fat content in HF/S and LF rats 3 wk after surgery. Regression analysis revealed that variation in RYGB-induced body weight loss was best explained by models including 1) postoperative cumulative EI and preoperative body weight (R2 = 0.87) and 2) postoperative cumulative EI and diet (R2 = 0.79), each without significant contribution of LA. Particularly rats on the LF diet became transiently more hypothermic and circadianally arrhythmic following RYGB (i.e., indicators of surgery-associated malaise) than HF/S feeding rats. Our data suggest that relative to feeding an LF diet, continued feeding an HF/S diet does not negatively impact recovery from RYGB surgery, yet it promotes RYGB-induced weight loss. The RYGB-induced weight loss is primarily explained by reduced cumulative EI and higher preoperative body weight, leading to comparably low levels of body fat content in HF/S and LF feeding rats.NEW & NOTEWORTHY Relative to feeding an LF diet, continued feeding an HF/S diet does not negatively impact recovery from RYGB surgery in rats. Relative to feeding an LF diet, continued feeding an HF/S diet promotes RYGB-induced weight loss. The RYGB-induced weight loss is primarily explained by reduced cumulative EI and higher preoperative body weight, leading to comparably low levels of body fat content in HF/S and LF feeding rats.

Prospective Monitoring of Small Intestinal Bacterial Overgrowth After Gastric Bypass: Clinical, Biological, and Gas Chromatographic Aspects

BACKGROUND AND AIMS

Obesity is a predisposing factor for small intestinal bacterial overgrowth (SIBO). The aim of this study was to prospectively evaluate the prevalence of SIBO as well as its clinical, biological, and nutritional aspects before and up to 24 months after a Roux-en-Y gastric bypass (RYGB) surgery.

PATIENTS AND METHODS

Fifty-one patients (mean BMI 46.9 kg/m2, 66.7% women) requesting RYGB were included between 2016 and 2020. Each patient underwent a glucose breath test, a standardized interrogation on functional digestive signs, a dietary survey, a blood test, a fecalogram, and anthropometric data gathering. These investigations were carried out before surgery and at 1, 3, 6, 9, 12, 18, and 24 months after RYGB.

RESULTS

Before surgery, we found a prevalence of 17.6% of SIBO (95% CI = [8.9%; 31.4%]). After RYGB, at the end of 24 months of follow-up, 89.5% of patients developed SIBO. Anal incontinence appeared to be very frequent after surgery, affecting 18.8% of our population 18 months after surgery. We observed positive steatorrhea after surgery with an average of 11.1 g of lipids/24 h despite a significant limitation of dietary lipids (p = 0.0282).

CONCLUSION

Our study corroborates data in the literature on the prevalence of SIBO in severe obesity patients. For the first time, we observed the sudden appearance of SIBO after RYGB, with a correlation between exhaled hydrogen on a breath test and lipid malabsorption on the fecalogram. As a result, these patients develop fatty diarrhea, with frequent fecal incontinence.

New insights in the mechanisms of weight-loss maintenance: Summary from a Pennington symposium

Obesity is a chronic disease that affects more than 650 million adults worldwide. Obesity not only is a significant health concern on its own, but predisposes to cardiometabolic comorbidities, including coronary heart disease, dyslipidemia, hypertension, type 2 diabetes, and some cancers. Lifestyle interventions effectively promote weight loss of 5% to 10%, and pharmacological and surgical interventions even more, with some novel approved drugs inducing up to an average of 25% weight loss. Yet, maintaining weight loss over the long-term remains extremely challenging, and subsequent weight gain is typical. The mechanisms underlying weight regain remain to be fully elucidated. The purpose of this Pennington Biomedical Scientific Symposium was to review and highlight the complex interplay between the physiological, behavioral, and environmental systems controlling energy intake and expenditure. Each of these contributions were further discussed in the context of weight-loss maintenance, and systems-level viewpoints were highlighted to interpret gaps in current approaches. The invited speakers built upon the science of obesity and weight loss to collectively propose future research directions that will aid in revealing the complicated mechanisms involved in the weight-reduced state.

PROMISE: effect of protein supplementation on fat-free mass preservation after bariatric surgery, a randomized double-blind placebo-controlled trial

INTRODUCTION

Protein malnutrition after bariatric surgery is a severe complication and leads to significant morbidity. Previous studies have shown that protein intake and physical activity are the most important factors in the preservation of fat-free mass during weight loss. Low protein intake is very common in patients undergoing bariatric surgery despite dietary counseling. Protein powder supplements might help patients to achieve the protein intake recommendations after bariatric surgery and could therefore contribute to preserve fat-free mass. This double-blind randomized placebo-controlled intervention study aims to assess the effect of a daily consumed clear protein powder shake during the first 6 months after bariatric surgery on fat-free mass loss in the first 12 months after laparoscopic Roux-en-Y gastric bypass (LRYGB).

METHODS AND ANALYSIS

Inclusion will take place at the outpatient clinic of the bariatric expertise center for obesity of the Maasstad Hospital. Patients will be randomly assigned to either the intervention or control group before surgery. The intervention group will receive a clear protein powder shake of 200 ml containing 20 g of whey protein dissolved in water which should be taken daily during the first 6 months after LRYGB on top of their normal postoperative diet. The control group will receive an isocaloric, clear, placebo shake containing maltodextrine. Postoperative rehabilitation and physiotherapeutical guidance will be standardized and similar in both groups. Also, both groups will receive the same dietary advice from specialized dieticians. The main study parameter is the percentage of fat-free mass loss 6 months after surgery, assessed by multi-frequency bioelectrical impedance analysis (MF-BIA).

ETHICS AND DISSEMINATION

The protocol, version 2 (February 20, 2022) has been approved by the Medical Research Ethics Committees United (MEC-U) (NL 80414.100.22). The results of this study will be submitted to peer-reviewed journals.

TRIAL REGISTRATION

ClinicalTrials.gov NCT05570474. Registered on October 5, 2022.

Milestones in the journey towards addressing obesity; Past trials and triumphs, recent breakthroughs, and an exciting future in the era of emerging effective medical therapies and integration of effective medical therapies with metabolic surgery

The 21st century is characterized by an increasing incidence and prevalence of obesity and the burden of its associated comorbidities, especially cardiometabolic diseases, which are reaching pandemic proportions. In the late '90s, the "black box" of adipose tissue and energy homeostasis was opened with the discovery of leptin, transforming the adipose tissue from an "inert fat-storage organ" to the largest human endocrine organ and creating the basis on which more intensified research efforts to elucidate the pathogenesis of obesity and develop novel treatments were based upon. Even though leptin was eventually not proven to be the "standalone magic bullet" for the treatment of common/polygenic obesity, it has been successful in the treatment of monogenic obesity syndromes. Additionally, it shifted the paradigm of treating obesity from a condition due to "lack of willpower" to a disease due to distinct underlying biological mechanisms for which specific pharmacotherapies would be needed in addition to lifestyle modification. Subsequently, the melanocortin pathway proved to be an equally valuable pathway for the pharmacotherapy of obesity. Melanocortin receptor agonists have recently been approved for treating certain types of syndromic obesity. Other molecules- such as incretins, implicated in energy and glucose homeostasis- are secreted by the gastrointestinal tract. Glucagon-like peptide 1 (GLP-1) is the most prominent one, with GLP-1 analogs approved for common/polygenic obesity. Unimolecular combinations with other incretins, e.g., GLP-1 with gastric inhibitory polypeptide and/or glucagon, are expected to be approved soon as more effective pharmacotherapies for obesity and its comorbidities. Unimolecular combinations with other compounds and small molecules activating the receptors of these molecules are currently under investigation as promising future pharmacotherapies. Moreover, metabolic and bariatric surgery has also demonstrated impressive results, especially in the case of morbid obesity. Consequently, this broadening therapeutic armamentarium calls for a well-thought-after and well-coordinated multidisciplinary approach, for instance, through cardiometabolic expertise centers, that would ideally address effectively and cost-effectively obesity and its comorbidities, providing tangible benefits to large segments of the population.

Bariatric surgery improves postprandial VLDL kinetics and restores insulin-mediated regulation of hepatic VLDL production

Dyslipidemia in obesity results from excessive production and impaired clearance of triglyceride-rich (TG-rich) lipoproteins, which are particularly pronounced in the postprandial state. Here, we investigated the impact of Roux-en-Y gastric bypass (RYGB) surgery on postprandial VLDL1 and VLDL2 apoB and TG kinetics and their relationship with insulin-responsiveness indices. Morbidly obese patients without diabetes who were scheduled for RYGB surgery (n = 24) underwent a lipoprotein kinetics study during a mixed-meal test and a hyperinsulinemic-euglycemic clamp study before the surgery and 1 year later. A physiologically based computational model was developed to investigate the impact of RYGB surgery and plasma insulin on postprandial VLDL kinetics. After the surgery, VLDL1 apoB and TG production rates were significantly decreased, whereas VLDL2 apoB and TG production rates remained unchanged. The TG catabolic rate was increased in both VLDL1 and VLDL2 fractions, but only the VLDL2 apoB catabolic rate tended to increase. Furthermore, postsurgery VLDL1 apoB and TG production rates, but not those of VLDL2, were positively correlated with insulin resistance. Insulin-mediated stimulation of peripheral lipoprotein lipolysis was also improved after the surgery. In summary, RYGB resulted in reduced hepatic VLDL1 production that correlated with reduced insulin resistance, elevated VLDL2 clearance, and improved insulin sensitivity in lipoprotein lipolysis pathways.

Incidence of Kidney Stones After Metabolic and Bariatric Surgery-Data from the Scandinavian Obesity Surgery Registry

PURPOSE

Obesity is associated with increased incidence of kidney stones, a risk further increased by metabolic and bariatric surgery, particularly after procedures with a malabsorptive component. However, there is a paucity in reports on baseline risk factor and on larger population-based cohorts. The objective was to evaluate incidence and risk factors for kidney stones after bariatric surgery by comparing them to an age-, sex-, and geographically matched cohort from the normal population.

MATERIAL AND METHODS

Patients operated with primary Roux-en-Y gastric bypass (RYGB), sleeve gastrectomy (SG), or biliopancreatic diversion with duodenal switch (BPD-DS) from 2007 until 2017 within the Scandinavian Obesity Surgery registry were matched 1:10 to controls from the normal population. Hospital admission or outpatient visits due to kidney stones registered in the National Patient Registry were considered as endpoint.

RESULTS

The study included 58,366 surgical patients (mean age 41.0±11.1, BMI 42.0±5.68, 76% women) with median follow-up time 5.0 [IQR 2.9-7.0] years and 583,660 controls. All surgical procedures were associated with a significantly increased risk for kidney stones (RYGB, HR 6.16, [95% CI 5.37-7.06]; SG, HR 6.33, [95% CI 3.57-11.25]; BPD/DS, HR 10.16, [95% CI 2.94-35.09]). Higher age, type 2 diabetes hypertension at baseline, and a preoperative history of kidney stones were risk factors for having a postoperative diagnosis of kidney stones.

CONCLUSION

Primary RYGB, SG, and BPD/DS were all associated with a more than sixfold increased risk for postoperative kidney stones. The risk increased with advancing age, two common obesity-related conditions, and among patients with preoperative history of kidney stones.

[Current evidence on loop length in intestinal bypass procedures]

BACKGROUND

Intestinal bypass procedures are well recognized for their long-term weight reduction and control of metabolic comorbidities. The selection of the length of the small bowel loop has a significant influence on the positive and also negative effects of the chosen procedure but national and international standardization are missing.

OBJECTIVE

The aim of this article is to give an overview of the current evidence on the various intestinal bypass procedures and the influence of the chosen small bowel loop length on the desired and adverse postoperative outcomes. The IFSO 2019 consensus recommendations on the standardization of bariatric surgery and metabolic procedures form the basis of these considerations.

MATERIAL AND METHODS

The current literature was searched for comparative studies addressing the question of different small bowel loop lengths in a Roux-en‑Y gastric bypass, one anastomosis gastric bypass, single anastomosis duodenoileal bypass with sleeve gastrectomy and biliopancreatic diversion (with duodenal switch).

RESULTS

Due to the heterogeneity of currently available studies and interindividual differences in total small bowel lengths in humans, it is difficult to give definitive recommendations for the choice of small bowel loop lengths. The longer the biliopancreatic loop (BPL) or the shorter the common channel (CC), the higher is the risk of (severe) malnutrition. To prevent malnutrition, the BPL should not be longer than 200 cm and the CC should have a length of at least 200 cm.

CONCLUSION

The intestinal bypass procedures recommended in the German S3 guidelines are safe and show good long-term outcomes. As part of the postbariatric follow-up, the nutritional status of patients following an intestinal bypass has to be followed-up on the long term in order to avoid malnutrition preferably prior to a clinical manifestation.

Red Meat Intake, Indole-3-Acetate, and Dorea longicatena Together Affect Insulin Resistance after Gastric Bypass

Roux-en-Y Gastric bypass (RYGB) promotes improvement in type 2 diabetes (T2D) shortly after surgery, with metabolic mechanisms yet to be elucidated. This study aimed to investigate the relationship between food intake, tryptophan metabolism, and gut microbiota on the glycemic control of obese T2D women after RYGB surgery. Twenty T2D women who underwent RYGB were evaluated before and three months after surgery. Food intake data were obtained by a seven-day food record and a food frequency questionnaire. Tryptophan metabolites were determined by untargeted metabolomic analysis, and the gut microbiota was determined by 16S rRNA sequencing. The glycemic outcomes were fasting blood glucose, HbA1C, HOMA-IR, and HOMA-beta. Linear regression models were applied to assess the associations between the changes in food intake, tryptophan metabolism, and gut microbiota on glycemic control after RYGB. All variables changed after RYGB (p < 0.05), except for tryptophan intake. Jointly, the variation in red meat intake, plasma indole-3-acetate, and Dorea longicatena was associated with postoperative HOMA-IR {R² 0.80, R² adj 0.74; p < 0.01}. Red meat intake decreased three months after bariatric surgery while indole-3-acetate and Dorea longicatena increased in the same period. These combined variables were associated with better insulin resistance in T2D women after RYGB.

Regulation of body weight: Lessons learned from bariatric surgery

BACKGROUND

Bariatric or weight loss surgery is currently the most effective treatment for obesity and metabolic disease. Unlike dieting and pharmacology, its beneficial effects are sustained over decades in most patients, and mortality is among the lowest for major surgery. Because there are not nearly enough surgeons to implement bariatric surgery on a global scale, intensive research efforts have begun to identify its mechanisms of action on a molecular level in order to replace surgery with targeted behavioral or pharmacological treatments. To date, however, there is no consensus as to the critical mechanisms involved.

SCOPE OF REVIEW

The purpose of this non-systematic review is to evaluate the existing evidence for specific molecular and inter-organ signaling pathways that play major roles in bariatric surgery-induced weight loss and metabolic benefits, with a focus on Roux-en-Y gastric bypass (RYGB) and vertical sleeve gastrectomy (VSG), in both humans and rodents.

MAJOR CONCLUSIONS

Gut-brain communication and its brain targets of food intake control and energy balance regulation are complex and redundant. Although the relatively young science of bariatric surgery has generated a number of hypotheses, no clear and unique mechanism has yet emerged. It seems increasingly likely that the broad physiological and behavioral effects produced by bariatric surgery do not involve a single mechanism, but rather multiple signaling pathways. Besides a need to improve and better validate surgeries in animals, advanced techniques, including inducible, tissue-specific knockout models, and the use of humanized physiological traits will be necessary. State-of-the-art genetically-guided neural identification techniques should be used to more selectively manipulate function-specific pathways.

The impact of bariatric surgery on macronutrient malabsorption depends on the type of procedure

Introduction

Bariatric surgery, currently the most effective treatment for morbidly obese patients, may induce macronutrient malabsorption depending on the type of procedure. Macronutrient malabsorption affects the supply of substrates to the colon, subsequent microbial fermentation and possibly colonic health.

Methods

Using isotope technology, we quantified the extent of macronutrient and bile acid malabsorption and its impact on colonic protein fermentation in patients after Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG) and in controls. Participants consumed a single test meal (day 0) that contained intrinsically labeled (¹³C, ¹⁵N, and ²H) egg protein for quantification of protein digestion, malabsorption and fermentation, respectively, together with a transit marker and a marker for bile acid malabsorption. They collected breath samples up to 6 h and all urine and stool for 48 and 72 h, respectively. Food intake was registered from day -3 to day 2.

Results

Malabsorption of fat, protein and carbohydrates differed between groups (p = 0.040; p = 0.046; and p = 0.003, respectively) and was slightly higher in RYGB but not in SG patients compared to controls. Protein fermentation was increased in both RYGB and SG patients compared to controls (p = 0.001) and was negatively correlated to ²H-recovery as a marker of transit (ρ = -0.47, p = 0.013).

Conclusion

The limited macronutrient malabsorption likely does not affect the nutritional status of the patient. However, the higher protein fermentation may affect colonic health and warrants further investigation.

Resolution of diabetes, gastrointestinal symptoms, and self-reported dietary intake after gastric bypass vs sleeve gastrectomy – a randomized study

BACKGROUND

There is a lack of randomized studies examining diabetes remission and dietary intake between patients undergoing Roux-en-Y gastric bypass (RYGB) versus sleeve gastrectomy (SG).

OBJECTIVE

To examine longitudinal differences in diabetes resolution, dietary intake, and gastrointestinal (GI) symptoms in patients with obesity and type 2 diabetes (T2D) randomized to either RYGB or SG and according to remission of T2D.

SETTING

Four hospitals in Sweden, 2 of which are university hospitals.

METHODS

Dietary intake and GI symptoms were calculated from questionnaires and morphometric differences between surgical methods and T2D remission were compared using the Student t test, effect size (ES) for parametric parameters, and Mann-Whitney U test for nonparametric parameters.

RESULTS

Five years after RYGB or SG there was no significant difference in the rate of remission of T2D between RYGB and SG (43% versus 20%, P = .176). RYGB (n = 19) patients had greater weight loss than SG patients (n = 14) (26.4 [9.5] versus 13.1 [9.6] kg, P < .001), despite reporting higher daily caloric intake (Δ 669 kcal, P = .059, ES .67) and food weight (Δ 1029 g/d, P = .003, ES 1.11). RYGB patients, compared with SG patients, also ate 1 more fruit per day (P = .023). Pooled data showed no differences between patients with and without T2D remission regarding weight loss, but those in remission drank more nonalcoholic drinks and milk.

CONCLUSIONS

Five years postoperatively, patients randomized to RYGB reported considerably higher food intake compared with SG despite lower body weight. The reason and importance of the higher food intake after RYGB compared with SG needs to be further studied.

Metabolic effects of truncal vagotomy when combined with bariatric-metabolic surgery

Bariatric-metabolic surgery (BMS) in patients with obesity frequently leads to remission of concurrent type 2 diabetes mellitus (T2DM), even before body weight loss takes place. This is probably based on the correction of a dysmetabolic cycle in the gastrointestinal physiology of T2DM that includes increased vagus-dependent exocrine pancreatic secretion (EPS) and, hence, amplified digestion and nutrient absorption. The resultant chronic exposure of tissues to high plasma levels of glucose, fatty acids and amino acids causes tissue resistance to the actions of insulin and, at a later stage, β-cell dysfunction and reduction of insulin release. We hypothesize that the addition of a surgical truncal vagotomy (TV) may improve and solidify the beneficial results of BMS on T2DM by stably decreasing EPS, - hence reducing the digestion and absorption of nutrients -, and increasing incretin secretion as a result of increased delivery of unabsorbed nutrients to the distal intestine. This hypothesis is supported by surgical data from gastrointestinal malignancies and peptic ulcer operations that include TV, as well as by vagal blockade studies. We suggest that TV may result in a stable reduction of EPS, and that its combination with the appropriate type of BΜS, may enhance and sustain the salutary effects of the latter on T2DM.

The impact of bariatric surgery procedures on the modulation of cardiometabolic risk factors in patients with severe obesity: a 12-month follow-up

Objective

To evaluate the effects of one anastomosis gastric bypass (OAGB), Roux-en-Y gastric bypass (RYGB), and sleeve gastrectomy (SG) on cardiometabolic risk factors (CMRFs) in patients with severe obesity.

Methods

This retrospective cohort study included patients with severe obesity who had undergone OAGB, RYGB, or SG between 2015 and 2017 and follow-up assessments over 12-months.

Results

Among 485 included patients, anthropometric measurements, body composition, fasting blood glucose (FBG), lipid profile, and comorbidities were significantly improved for all three procedures throughout the follow-up period. Weight, % total weight loss (%TWL), body mass index, fat mass and fat mass to fat-free mass ratio improvements were higher with RYGB and OAGB than SG. There were no significant differences between procedures in all other variables. A significant trend toward remission rate of dyslipidemia and type 2 diabetes mellitus was observed with all three procedures, with no significant difference between the three groups. %TWL statistically correlated with fat mass, FBG, and triglycerides.

Conclusions

OAGB, RYGB, and SG had a beneficial impact on CMRFs and comorbidities during 12 months of follow-up. Of note, RYGB and OAGB may result in better outcomes, particularly anthropometric and body composition indices. Further large-sample, long-term follow-up studies are required to expand on the present findings.

Early effects of Roux-en-Y gastric bypass on dietary fatty acid absorption and metabolism in people with obesity and normal glucose tolerance

INTRODUCTION

Roux-en-Y gastric bypass (RYGB) surgery markedly increases the rate of intestinal nutrient exposure after food intake, accelerates intestinal absorption of dietary glucose and protein, and alters the postprandial gut hormone response. However, our understanding of postprandial fat absorption and metabolism after RYGB is incomplete.

METHODS

Stable palmitate tracers were administered intravenously (K-[2,2-²H₂]palmitate) and orally with a mixed meal ([U-¹³C₁₆]palmitate) to study fatty acid absorption and metabolism before and 3 months after RYGB in 10 participants with obesity and normal glucose tolerance.

RESULTS

There was a tendency toward reduced fasting plasma nonesterified palmitate concentrations after RYGB, but neither fasting palmitate kinetics nor fasting triacylglycerol (TAG) concentrations changed compared with before surgery. Postprandial TAG concentrations were numerically, but nonsignificantly, reduced 3-4 h after meal intake after compared with before RYGB. However, the postprandial appearance of the oral palmitate tracer in the plasma TAG pool and overflow into the nonesterified palmitate pool were initially faster but overall reduced after RYGB by 50% (median, IQR: [47;64], P = 0.004) and 46% (median, IQR: [33;70], P = 0.041), respectively. The maximal postprandial suppression of plasma nonesterified palmitate concentrations was slightly greater but shorter lasting after RYGB ('time × visit' interaction: P < 0.001), without detectable effects of surgery on the rate of appearance and disappearance of plasma palmitate.

CONCLUSION

RYGB resulted in an initially accelerated but overall ~50% reduced 4-h postprandial systemic appearance of dietary palmitate in participants with obesity and normal glucose tolerance. This is likely a result of faster but incomplete intestinal fat absorption combined with enhanced chylomicron-TAG clearance, but it needs further investigation in studies specifically designed to investigate these mechanisms.

Nutrients handling after bariatric surgery, the role of gastrointestinal adaptation

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

Bariatric Surgery in NAFLD

Currently, there are no approved medications to treat patients with nonalcoholic steatohepatitis (NASH) with fibrosis or cirrhosis. Although the management goal in these patients is weight reduction by 7-10% with lifestyle modifications, only less than 10% of patients achieve this target at 1-year, and fewer maintain the weight loss at 5 years. Bariatric surgery is an option that may be considered in those who fail to lose weight by lifestyle changes. Bariatric surgery has been shown to improve liver histology including fibrosis secondary to NASH, in addition to other benefits including an improvement or resolution of type 2 diabetes mellitus, dyslipidemia, and hypertension, and a reduction of cardiovascular morbidity or mortality. There are no guidelines of bariatric surgery indications for the management of NASH. The purpose of this review is to critically appraise the current knowledge of the role of bariatric surgery and the potential mechanisms for its perceived benefits in the management of patients with NASH-related liver disease.

Role of the Autonomic Nervous System in Mechanism of Energy and Glucose Regulation Post Bariatric Surgery

Even though lifestyle changes are the mainstay approach to address obesity, Sleeve gastrectomy (SG) and Roux-en-Y gastric bypass (RYGB) are the most effective and durable treatments facing this pandemic and its associated metabolic conditions. The traditional classifications of bariatric surgeries labeled them as “restrictive,” “malabsorptive,” or “mixed” types of procedures depending on the anatomical rearrangement of each one of them. This conventional categorization of bariatric surgeries assumed that the “restrictive” procedures induce their weight loss and metabolic effects by reducing gastric content and therefore having a smaller reservoir. Similarly, the “malabsorptive” procedures were thought to induce their main energy homeostatic effects from fecal calorie loss due to intestinal malabsorption. Observational data from human subjects and several studies from rodent models of bariatric surgery showed that neither of those concepts is completely true, at least in explaining the multiple metabolic changes and the alteration in energy balance that those two surgeries induce. Rather, neuro-hormonal mechanisms have been postulated to underly the physiologic effects of those two most performed bariatric procedures. In this review, we go over the role the autonomic nervous system plays- through its parasympathetic and sympathetic branches- in regulating weight balance and glucose homeostasis after SG and RYGB.

Meal Patterns and Food Choices of Female Rats Fed a Cafeteria-Style Diet Are Altered by Gastric Bypass Surgery

After Roux-en-Y gastric bypass surgery (RYGB), rats tend to reduce consumption of high-sugar and/or high-fat foods over time. Here, we sought to investigate the behavioral mechanisms underlying these intake outcomes. Adult female rats were provided a cafeteria diet comprised of five palatable foodstuffs varying in sugar and fat content and intake was monitored continuously. Rats were then assigned to either RYGB, or one of two control (CTL) groups: sham surgery or a nonsurgical control group receiving the same prophylactic iron treatments as RYGB rats. Post-sur-gically, all rats consumed a large first meal of the cafeteria diet. After the first meal, RYGB rats reduced intake primarily by decreasing the meal sizes relative to CTL rats, ate meals more slowly, and displayed altered nycthemeral timing of intake yielding more daytime meals and fewer nighttime meals. Collectively, these meal patterns indicate that despite being motivated to consume a cafeteria diet after RYGB, rats rapidly learn to modify eating behaviors to consume foods more slowly across the entire day. RYGB rats also altered food preferences, but more slowly than the changes in meal patterns, and ate proportionally more energy from complex carbohydrates and protein and proportionally less fat. Overall, the pattern of results suggests that after RYGB rats quickly learn to adjust their size, eating rate, and distribution of meals without altering meal number and to shift their macronutrient intake away from fat; these changes appear to be more related to postingestive events than to a fundamental decline in the palatability of food choices.

Secretin as a Satiation Whisperer With the Potential to Turn into an Obesity-curbing Knight

The obesity pandemic requires effective preventative and therapeutic intervention strategies. Successful and sustained obesity treatment is currently limited to bariatric surgery. Modulating the release of gut hormones is considered promising to mimic bariatric surgery with its beneficial effects on food intake, body weight, and blood glucose levels. The gut peptide secretin was the first molecule to be termed a hormone; nevertheless, only recently has it been established as a legitimate anorexigenic peptide. In contrast to gut hormones that crosstalk with the brain either directly or by afferent neuronal projections, secretin mediates meal-associated brown fat thermogenesis to induce meal termination, thereby qualifying this physiological mechanism as an attractive, peripheral target for the treatment of obesity. In this perspective, it is of pivotal interest to deepen our as yet superficial knowledge on the physiological roles of secretin as well as meal-associated thermogenesis in energy balance and body weight regulation. Of note, the emerging differences between meal-associated thermogenesis and cold-induced thermogenesis must be taken into account. In fact, there is no correlation between these 2 entities. In addition, the investigation of potential effects of secretin in hedonic-driven food intake, bariatric surgery and chronic treatment using suitable application strategies to overcome pharmacokinetic limitations will provide further insight into its potential to influence energy balance. The aim of this article is to review the facts on secretin's metabolic effects, address prevailing gaps in our knowledge, and provide an overview on the opportunities and challenges of the therapeutic potential of secretin in body weight control.

Effects of Roux-en-Y Gastric Bypass and Sleeve Gastrectomy on Non-Alcoholic Fatty Liver Disease: A 12-Month Follow-Up Study with Paired Liver Biopsies

Roux-en-Y gastric bypass (RYGB) improves, and can sometimes resolve, non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH) but data based on histological assessment for the efficacy of sleeve gastrectomy (SG) in resolving NAFLD are sparse. Consequently, we aimed to compare the efficacy of RYGB vs. SG on NAFLD 12 months after surgery. In a prospective cohort study, 40 patients with obesity underwent bariatric surgery (16 RYGB and 24 SG). During surgery, a liver biopsy was taken and repeated 12 months later. NAFLD severity was evaluated using the NAFLD Activity Score (NAS) and Kleiner Fibrosis score. RYGB and SG patients were comparable at baseline. Mean (standard deviation, SD) NAS was 3.3 (0.9) in RYGB and 3.1 (1.4) in SG (p = 0.560) with similar degrees of steatosis, inflammation, and ballooning. Two RYGB patients, and six SG patients, had NASH (p = 0.439). Twelve months after surgery, NAS was significantly and comparably (p = 0.241) reduced in both RYGB (−3.00 (95% CI −3.79–−2.21), p < 0.001) and SG (−2.25 (95% CI −2.92–−1.59), p < 0.001) patients. RYGB patients had significantly more reduced (p = 0.007) liver steatosis (−0.91 (95% CI −1.47–−1.2) than SG patients (−0.33 (95% CI −0.54–−0.13) and greater improvement in the plasma lipid profile. Fibrosis declined non-significantly. NASH was resolved in seven of eight patients without a worsening of their fibrosis. RYGB and SG have similar beneficial effects on NAS and NASH without the worsening of fibrosis. RYGB is associated with a more pronounced reduction in liver steatosis.

The Relationship Between Bariatric Surgery and Diet Quality: a Systematic Review

BACKGROUND

Bariatric surgery is currently the most effective treatment for morbid obesity. These procedures change the gastrointestinal system with the aim of reducing dietary intake. Improving diet quality is essential in maintaining nutritional health and achieving long-term benefits from the surgery. The aim of this systematic review was to examine the relationship between bariatric surgery and diet quality at least 1 year after surgery.

METHODS

A systematic search of five databases was conducted. Studies were included that reported diet quality, eating pattern, or quality of eating in adult patients who had undergone laparoscopic-adjusted gastric banding (LAGB), Roux-en-Y gastric bypass (RYGB), and sleeve gastrectomy (SG) procedures. Data was extracted to determine the relationship between having had bariatric surgery and subsequent diet quality.

RESULTS

A total of 34 study articles (described in 36 articles) met the inclusion criteria. The majority of studies were observational in nature and showed a reduction in energy intake following surgery, as well as inadequate intakes of micronutrients and protein, and an excessive intake of fats. There was evidence of nutrient imbalances, suboptimal compliance with multivitamin and mineral supplementation, and limited follow-up of patients.

CONCLUSION

The current evidence base suggests that despite being effective in reducing energy intake, bariatric surgery can result in unbalanced diets, inadequate micronutrient and protein intakes, and excessive intakes of fats. In combination with suboptimal adherence to multivitamin and mineral supplementation, this may contribute to nutritional deficiencies and weight regain. There is a need for high-quality nutrition studies, to identify optimal dietary compositions following bariatric surgery.

Physiologic Mechanisms of Weight Loss Following Metabolic/Bariatric Surgery

Bariatric and metabolic surgery has evolved from simple experimental procedures for a chronic problem associated with significant morbidity into a sophisticated multidisciplinary treatment modality rooted in biology and physiology. Although the complete mechanistic narrative of bariatric surgery cannot yet be written, significant advance in knowledge has been made in the past 2 decades. This article provides a brief overview of the most studied hypotheses and their supporting evidence. Ongoing research, especially in frontier areas, such as the microbiome, will continue to refine, and perhaps even revise, current mechanistic understanding.

Cardiovascular Risk Reduction Following Metabolic and Bariatric Surgery

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

Prevention and treatment of nutritional complications after bariatric surgery

Obesity and the corresponding burden of related diseases is a major public health issue worldwide that is reaching pandemic proportions. Bariatric surgery is the only intervention that has been shown to result in substantial and lasting weight loss, and a decrease in overall mortality for patients with severe obesity. Consequently, the population of patients having undergone this procedure is increasing. Multifactorial weight-dependent and independent mechanisms underlying metabolic diseases could also drive preventable, but potentially life-threatening, long-term nutritional complications. However, given post-bariatric patients are prone to functional gastrointestinal symptoms and substantial weight loss, nutritional complications might be challenging. This Review is focused on the prevention and treatment of nutritional complications after bariatric surgery in the clinical setting.

The Phantom Satiation Hypothesis of Bariatric Surgery

The excitation of vagal mechanoreceptors located in the stomach wall directly contributes to satiation. Thus, a loss of gastric innervation would normally be expected to result in abrogated satiation, hyperphagia, and unwanted weight gain. While Roux-en-Y-gastric bypass (RYGB) inevitably results in gastric denervation, paradoxically, bypassed subjects continue to experience satiation. Inspired by the literature in neurology on phantom limbs, I propose a new hypothesis in which damage to the stomach innervation during RYGB, including its vagal supply, leads to large-scale maladaptive changes in viscerosensory nerves and connected brain circuits. As a result, satiation may continue to arise, sometimes at exaggerated levels, even in subjects with a denervated or truncated stomach. The same maladaptive changes may also contribute to dysautonomia, unexplained pain, and new emotional responses to eating. I further revisit the metabolic benefits of bariatric surgery, with an emphasis on RYGB, in the light of this phantom satiation hypothesis.

Are There Ideal Small Bowel Limb Lengths for One-Anastomosis Gastric Bypass (OAGB) to Obtain Optimal Weight Loss and Remission of Comorbidities with Minimal Nutritional Deficiencies?

BACKGROUND

Ideal jejunal and ileal lengths in bariatric/metabolic procedures to be left in alimentary continuity still remain unclear. We aimed to evaluate different lengths of biliopancreatic limb (BPL) and common limb (CL) performed in a series of patients submitted to OAGB, and correlate them with weight loss and nutritional deficits.

PATIENTS AND METHODS

A prospective observational study of 350 consecutive morbidly obese patients undergoing OAGB was performed. BPL and CL lengths were determined intraoperatively; BPL/TBL and CL/TBL ratios were then calculated. Anthropometric variables, remission of comorbidities and specific supplementation needs were recorded at 1, 2 and 5 years after surgery.

RESULTS

Three hundred patients were included for final analysis. BPL length and BPL/TBL ratio directly correlated with Units of BMI lost (UBMIL). Conversely, CL length and CL/TBL ratio showed an inverse correlation with UBMIL. Establishing a BMI ≤ 25 kg/m² as ideal, the most accurate AUC, to predict achieving an ideal BMI at 1, 2 and 5 years after surgery, was obtained for the CL/TBL ratio, followed by the CL length at 1, 2 and 5 years. An ideal range was established between 0.40 and 0.43 for the CL/TBL ratio, and 200 to 220 cm for the CL length. Among these ranges, there were no cases of protein or calorie malnutrition.

CONCLUSION

TBL measurement is essential to obtain optimal outcomes after OAGB, both in terms of excellent weight loss and remission/improvement of comorbidities, as well as with a low risk of nutritional deficiencies. The CL/TBL ratio, followed by CL length, are the most accurate parameters to predict a 5-year postoperative BMI ≤ 25 kg/m².

Intestinal stem cell-derived enteroids from morbidly obese patients preserve obesity-related phenotypes: Elevated glucose absorption and gluconeogenesis

Objective

The mechanisms behind the efficacy of bariatric surgery (BS) for treating obesity and type 2 diabetes, particularly with respect to the influence of the small bowel, remain poorly understood. In vitro and animal models are suboptimal with respect to their ability to replicate the human intestinal epithelium under conditions induced by obesity. Human enteroids have the potential to accelerate the development of less invasive anti-obesity therapeutics if they can recapitulate the pathophysiology of obesity. Our aim was to determine whether adult stem cell-derived enteroids preserve obesity-characteristic patient-specific abnormalities in carbohydrate absorption and metabolism.

Methods

We established 24 enteroid lines representing 19 lean, overweight, or morbidly obese patients, including post-BS cases. Dietary glucose absorption and gluconeogenesis in enteroids were measured. The expression of carbohydrate transporters and gluconeogenic enzymes was assessed and a pharmacological approach was used to dissect the specific contribution of each transporter or enzyme to carbohydrate absorption and metabolism, respectively.

Results

Four phenotypes representing the relationship between patients’ BMI and intestinal dietary sugar absorption were found, suggesting that human enteroids retain obese patient phenotype heterogeneity. Intestinal glucose absorption and gluconeogenesis were significantly elevated in enteroids from a cohort of obese patients. Elevated glucose absorption was associated with increased expression of SGLT1 and GLUT2, whereas elevated gluconeogenesis was related to increased expression of GLUT5, PEPCK1, and G6Pase.

Conclusions

Obesity phenotypes preserved in human enteroids provide a mechanistic link to aberrant dietary carbohydrate absorption and metabolism. Enteroids can be used as a preclinical platform to understand the pathophysiology of obesity, study the heterogeneity of obesity mechanisms, and identify novel therapeutics.

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Human stem cell-derived enteroids preserve the heterogeneity of obesity-related phenotypes.

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Four phenotypes representing the relationship between patients' BMI and intestinal dietary glucose absorption were found.

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Glucose absorption and gluconeogenesis were elevated in enteroids from a cohort of obese patients.

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Elevated glucose absorption was associated with increased expression of SGLT1 and GLUT2 in enteroids.

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Elevated gluconeogenesis was associated with increased expression of GLUT5, PEPCK1, and G6Pase in enteroids.

The effect of a duodenal-jejunal bypass liner on lipid profile and blood concentrations of long chain polyunsaturated fatty acids

BACKGROUND & AIMS

Duodenal-jejunal bypass liners (DJBLs) prevent absorption in the proximal small intestine, the site of fatty acid absorption. We sought to investigate the effects of a DJBL on blood concentrations of essential fatty acids (EFAs) and bioactive polyunsaturated fatty acids (PUFAs).

METHODS

Sub-study of a multicentre, randomised, controlled trial with two treatment groups. Patients aged 18-65 years with type-2 diabetes mellitus and body mass index 30-50 kg/m² were randomised to receive a DJBL for 12 months or best medical therapy, diet and exercise. Whole plasma PUFA concentrations were determined at baseline, 10 days, 6 and 11.5 months; data were available for n = 70 patients per group.

RESULTS

Weight loss was significantly greater in the DJBL group compared to controls after 11.5 months: total body weight loss 11.3 ± 5.3% versus 6.0 ± 5.7% (mean difference [95% CI] = 5.27% [3.75, 6.80], p < 0.001). Absolute concentrations of both EFAs, linoleic acid and α-linolenic acid, and their bioactive derivatives, arachidonic acid, eicosapentaenoic acid, docosapentaenoic acid and docosahexaenoic acid, were significantly lower in the DJBL group than in the control group at 6 and 11.5 months follow-up. Total serum cholesterol, LDL-cholesterol and HDL-cholesterol were also significantly lower in the DJBL group.

CONCLUSION

One year of DJBL therapy is associated with superior weight loss and greater reductions in total serum cholesterol and LDL-cholesterol, but also depletion of EFAs and their longer chain derivatives. DJBL therapy may need to be offset by maintaining an adequate dietary intake of PUFAs or by supplementation.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier NCT02459561.

Bariatric Surgery: Remission of Inflammation, Cardiometabolic Benefits, and Common Adverse Effects

Obesity is associated with increased mortality as a result of several comorbidities which occur in tandem with the obese state. Chronic inflammation is well documented in obesity, and evidence from numerous studies support the notion that the increased inflammation in individuals with obesity accentuates the comorbidities seen in this condition. The remission of comorbidities such as metabolic, cardiovascular, and neurological complications occurs following bariatric procedures. Bariatric surgery significantly reduces mortality and results in remarkable weight loss and reversal in several obesity-related comorbidities. There is indisputable evidence that the resolution of inflammation that occurs after bariatric surgery mitigates some of these comorbidities. With the increasing use of bariatric surgery for the treatment of severe obesity, it is pivotal to elucidate the underlying mechanisms responsible for the notable improvements seen after the procedure. This review summarizes underlying mechanisms responsible for the remission of obesity-related abnormalities and discusses the common adverse effects of bariatric surgery. Well-stratified, large-scale studies are still needed for a proper evaluation of these underlying mechanisms.

Reported nutrient intake over 7 years after Roux-en-Y gastric bypass in the Longitudinal Assessment of Bariatric Surgery-3 (LABS-3) psychosocial study

BACKGROUND

Bariatric surgery is the most effective therapy for severe obesity. It reduces gastric capacity and may modify regulation of appetite, satiety, insulin, and other physiologic processes, resulting in weight loss.

OBJECTIVE

Long-term data on postsurgical nutrient intake are lacking.

SETTING

The Longitudinal Assessment of Bariatric Surgery-3 psychosocial study.

METHODS

Reported dietary intake was assessed in a subset of participants (n = 72) of the Longitudinal Assessment of Bariatric Surgery-3 psychosocial study who underwent Roux-en-Y gastric bypass surgery. Two 24-hour diet recalls at presurgery and annual assessments over 7 years were obtained. Reported diets were evaluated for energy, macro- and micronutrient intake, and assessed for adequacy by comparison to the dietary reference intakes.

RESULTS

After surgery, reported intake of total energy, and all macronutrients were significantly reduced. At least a quarter of participants reported protein intake below the recommended dietary allowance. Over half of participants reported intake of several vitamins (C, D, A, E, thiamin, folate) and minerals (zinc, calcium) below recommended levels over 7 years. Compared with presurgery, reported energy intake was reduced over 7 years. This study was registered at ClinicalTrials.gov as NCT02495142.

CONCLUSIONS

The reduction in energy resulted in intakes below the dietary reference intakes for many micronutrients among the majority of participants and below the recommended dietary allowance for protein in a substantial subgroup. These data support continued long-term nutrition education, monitoring, and supplementation.

Shortening of the Common Channel as a Rescue Surgery After Gastric Bypass Failure

BACKGROUND

After Roux-en-Y gastric bypass (RYGB), up to 30% failures in weight loss have been reported. Among multiple solutions available, we report our experience with shortening of the common channel (SCC) by performing a limb distalization of the alimentary or the biliopancreatic limb.

SETTINGS

University Hospital.

METHODS

We reviewed data from 23 patients that underwent limb distalization between 2001 and 2019 due to inadequate weight loss after an initial RYGB in our center. All patients who failed to achieve an excess weight loss reduction of > 50% or maintained a body mass index (BMI) above 35 kg/m² were included. Multiple variables were analyzed during the follow-up at five time points: initial, after RYGB, before SCC, after SCC, and current.

RESULTS

The mean BMI prior to the RYGB was 51.8 kg/m², after RYGB was 37.6 kg/m², before SCC was 43.6 kg/m², after SCC was 36.1 kg/m², and the final BMI was 36.3 kg/m². No morbidity was seen after SCC. Long-term associated nutritional deficiencies were only identified in 3 patients which had iron deficiency and 1 patient with vitamin D deficiency. Patients with associated comorbidities significantly improved or were withdrawn from medications after the RYGB, with minor variations after SCC.

CONCLUSIONS

Limb distalization with SCC is a safe and effective technique for patients who failed to achieve an adequate weight loss after RYGB. There is a slight increase in excess of weight loss after the SCC compared with RYGB. In addition, no further weight regain was documented.

Induction of Meal-related Symptoms as a Novel Mechanism of Action of the Duodenal-Jejunal Bypass Sleeve

BACKGROUND

Treatment with a duodenal-jejunal bypass sleeve (DJBS) induces clinically significant weight loss, but little is known about the mechanisms of action of this device.

AIM

The aim of this study was to characterize the mechanisms of action of the DJBS and determine the durability of weight loss and metabolic improvements.

MATERIALS AND METHODS

We studied a cohort of 19 subjects with severe obesity and type 2 diabetes (baseline body mass index: 43.7±5.3 kg/m). Anthropometry, body composition, blood pressure, biochemical measures, and dietary intake were monitored for 48 weeks after DJBS implantation, and then for 1 year after device removal. Gastric emptying and triglyceride absorption were measured at baseline, 8 weeks after implant, and within 3 weeks of device explant. Visceral sensory function was assessed at baseline, 4 weeks after implant, and within 3 weeks after explant.

RESULTS

Significant weight loss (P<0.01) occurred following DJBS placement, with a mean weight reduction of 17.0±6.5% at 48 weeks. The symptom burden following a standardized nutrient challenge was increased after DJBS implantation (P<0.05), returning to baseline after DJBS removal. Neither gastric emptying nor triglyceride absorption changed with the device in situ. A significant reduction in energy intake was observed [baseline: 7703±2978 kJ (1841±712 kcal), 24 weeks: 4824±2259 kJ (1153±540 kcal), and 48 weeks: 4474±1468 kJ (1069±351 kcal)]. After 1 year, anthropometry remained significantly improved, but there was no durable impact on metabolic outcomes.

CONCLUSIONS

DJBS treatment resulted in substantial weight loss. Weight loss is related to reduced caloric intake, which seems linked to an augmented upper gastrointestinal symptom response, but not altered fat absorption.

Differential Effects of Roux-en-Y Gastric Bypass Surgery and Laparoscopic Sleeve Gastrectomy on Fatty Acid Levels

BACKGROUND

Bariatric surgery is associated with improved cardiovascular outcomes and also affects lipid levels, but few studies have compared the effects of Roux-en-Y gastric bypass (RYGB) surgery with those of laparoscopic sleeve gastrectomy (LSG) on serum fatty acid levels. The present study compares the effects of RYGB and LSG surgeries on serum fatty acid levels.

METHODS

The study participants were women who were undergoing either RYGB or LSG and body mass index (BMI)-matched controls. Fasting blood samples to measure glucose, insulin, and fatty acids were drawn at baseline and at 6 and 18 months from baseline.

RESULTS

Serum fatty acid data were available for 57 participants at baseline, of whom 56 had data at 6 months and 41 had data at 18 months from baseline. Compared with baseline, serum non-esterified fatty acids (NEFAs) levels were significantly higher at 6 and 18 months in the LSG group compared with the RYGB group. In the RYGB group, 2 saturated fatty acids (SFAs), 2 monounsaturated fatty acids (MUFAs), and 1 polyunsaturated fatty acid (PUFA) were significantly decreased after surgery, compared with those of the LSG group.

CONCLUSIONS

A significant increase in NEFAs was seen after LSG, compared with RYGB. Compared with the LSG group, several serum fatty acids were significantly reduced after RYGB.

TRIAL REGISTRATION

NCT01228097.

Revision of Roux-en-Y Gastric Bypass with Limb Distalization for Inadequate Weight Loss or Weight Regain

BACKGROUND

Of patients undergoing Roux-en-Y gastric bypass (RYGB), 15-35% of patients fail to achieve "adequate" weight loss or regain significant weight. Multiple solutions have been proposed, but not well studied. We report our experience with limb distalization with lengthening the biliopancreatic (BP) limb and shortening the common channel (CC).

METHODS

We retrospectively reviewed data from patients undergoing laparoscopic limb distalization for excess weight loss (EWL) <50% or BMI >35 kg/m² after RYGB from 2012 to 2017. The BP limb was lengthened and CC was shortened to 100-200 cm. Perioperative outcomes such as morbidity, weight loss, nutritional deficiencies, comorbidity remission, and operative details were analyzed.

RESULTS

Twenty-two patients were included. The mean BMI prior to RYGB was 54.1 ± 8.5 kg/m² and 43.0 ± 5.5 kg/m² prior to limb distalization. The mean follow-up was 18.3 ± 12.9 months with a mean BMI change, %EWL, and %TWL (total weight loss) of 11.8 ± 7.4 kg/m², 62.3 ± 32.4%, and 25.4 ± 14.4%, respectively. The total mean BMI change, %EWL, and %TWL from RYGB was 22.2 ± 9.9 kg/m², 77.8 ± 23.6%, and 40.2 ± 13.3%, respectively. Of patients with persistent comorbidities, remission rates of diabetes, hypertension, and gastroesophageal reflux disease were 100%, 17%, and 38%, respectively. The mean operative time was 132.6 ± 54.4 min and mean hospital stay was 2.2 ± 1.3 days. Overall morbidity was 27.3%. Three patients (13.6%) developed nutritional deficiencies requiring reversal surgery.

CONCLUSION

In patients with inadequate weight loss or weight regain after RYGB, limb distalization with lengthening of the BP limb is an effective procedure for additional weight loss and further improvement of comorbidities. Nutritional complications are a risk, but can be minimized with close follow-up and patient compliance.

Nonalcoholic Steatohepatitis After Liver Transplantation

Currently, nonalcoholic steatohepatitis (NASH) is the second leading indication for liver transplantation (LT), behind alcohol-related liver disease. After transplant, both recurrent and de novo nonalcoholic fatty liver disease are common; however, recurrence rates of NASH and advanced fibrosis are low. Identification of high-risk groups and optimizing treatment of metabolic comorbidities both before and after LT is paramount to maintaining a healthy allograft, especially with the additional consequences of longterm immunosuppression. In addition, NASH LT recipients are at an increased risk of cardiovascular events and malignancy, and their condition warrants a tailored approach to management. The optimal approach to NASH LT recipients including metabolic comorbidities management, tailored immunosuppression, the role of bariatric surgery, and nutritional and pharmacotherapy of NASH are discussed in this review. Overall, aggressive management of metabolic syndrome after LT via medical and surgical modalities and a minimalist approach to immunosuppression is advised.

Gut Peptide Agonism in the Treatment of Obesity and Diabetes

Obesity is a global healthcare challenge that gives rise to devastating diseases such as the metabolic syndrome, type-2 diabetes (T2D), and a variety of cardiovascular diseases. The escalating prevalence of obesity has led to an increased interest in pharmacological options to counteract excess weight gain. Gastrointestinal hormones such as glucagon, amylin, and glucagon-like peptide-1 (GLP-1) are well recognized for influencing food intake and satiety, but the therapeutic potential of these native peptides is overall limited by a short half-life and an often dose-dependent appearance of unwanted effects. Recent clinical success of chemically optimized GLP-1 mimetics with improved pharmacokinetics and sustained action has propelled pharmacological interest in using bioengineered gut hormones to treat obesity and diabetes. In this article, we summarize the basic biology and signaling mechanisms of selected gut peptides and discuss how they regulate systemic energy and glucose metabolism. Subsequently, we focus on the design and evaluation of unimolecular drugs that combine the beneficial effects of selected gut hormones into a single entity to optimize the beneficial impact on systems metabolism. © 2020 American Physiological Society. Compr Physiol 10:99-124, 2020.

Proceedings of the 2017 ASPEN Research Workshop-Gastric Bypass: Role of the Gut

The goal of the National Institutes of Health-funded American Society for Parenteral and Enteral Nutrition 2017 research workshop (RW) "Gastric Bypass: Role of the Gut" was to focus on the exciting research evaluating gut-derived signals in modulating outcomes after bariatric surgery. Although gastric bypass surgery has undoubted positive effects, the mechanistic basis of improved outcomes cannot be solely explained by caloric restriction. Emerging data suggest that bile acid metabolic pathways, luminal contents, energy balance, gut mucosal integrity, as well as the gut microbiota are significantly modulated after bariatric surgery and may be responsible for the variable outcomes, each of which was rigorously evaluated. The RW served as a timely and novel academic meeting that brought together clinicians and researchers across the scientific spectrum, fostering a unique venue for interdisciplinary collaboration among investigators. It promoted engaging discussion and evolution of new research hypotheses and ideas, driving the development of novel ameliorative, therapeutic, and nonsurgical interventions targeting obesity and its comorbidities. Importantly, a critical evaluation of the current knowledge regarding gut-modulated signaling after bariatric surgery, potential pitfalls, and lacunae were thoroughly addressed.

Metabolic benefits of gastric bypass surgery in the mouse: The role of fecal losses

Objective

Roux-en-Y gastric surgery (RYGB) promotes a rapid and sustained weight loss and amelioration of glucose control in obese patients. A high number of molecular hypotheses were previously tested using duodenal-jejunal bypass (DJB) performed in various genetic models of mice with knockouts for various hormones or receptors. The data were globally negative or inconsistent. Therefore, the mechanisms remained elusive. Intestinal gluconeogenesis is a gut function that has been suggested to contribute to the metabolic benefits of RYGB in obese patients.

Methods

We studied the effects of DJB on body weight and glucose control in obese mice fed a high fat-high sucrose diet. Wild type mice and mice with a genetic suppression of intestinal gluconeogenesis were studied in parallel using glucose- and insulin-tolerance tests. Fecal losses, including excretion of lipids, were studied from the feces recovered in metabolic cages.

Results

DJB induced a dramatic decrease in body weight and improvement in glucose control (glucose- and insulin-tolerance) in obese wild type mice fed a high calorie diet, for 25 days after the surgery. The DJB-induced decrease in food intake was transient and resumed to normal in 7–8 days, suggesting that decreased food intake could not account for the benefits. Total fecal losses were about 5 times and lipid losses 7 times higher in DJB-mice than in control (sham-operated and pair-fed) mice, and could account for the weight loss of mice. The results were comparable in mice with suppression of intestinal gluconeogenesis. There was no effect of DJB on food intake, body weight or fecal loss in lean mice fed a normal chow diet.

Conclusions

DJB in obese mice fed a high calorie diet promotes dramatic fecal loss, which could account for the dramatic weight loss and metabolic benefits observed. This could dominate the effects of the mouse genotype/phenotype. Thus, fecal energy loss should be considered as an essential process contributing to the metabolic benefits of DJB in obese mice.

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Duodenal-jejunal bypass (DJB) promotes weight loss in mice fed a high calorie diet.

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DJB induces dramatic fecal energy losses in mice fed a high calorie diet.

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DJB has no effect in mice fed a control (starch-based) diet.

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There is no fecal losses in DJB-mice fed a control diet.

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Fecal energy loss is a cause of body weight loss in DJB-mice fed high calorie diet.

Effect of different bariatric surgeries on dietary protein bioavailability in rats

Bariatric surgery may induce protein malabsorption, although data are scarce. This study aims at evaluating dietary protein bioavailability after different bariatric surgeries in rats. Diet-induced obese Wistar rats were operated for vertical sleeve gastrectomy (VSG) or Roux-en-Y gastric bypass (RYGB). The control group was composed of pair-fed, sham-operated rats (Sham). Two weeks after surgery, rats were fed a ¹⁵N protein meal. Protein bioavailability was assessed by determination of ¹⁵N recovery in the gastrointestinal tract and organs 6 h after the meal. Fractional protein synthesis rate (FSR) was assessed using a flooding dose of ¹³C valine. Weight loss was the highest in RYGB rats and the lowest in Sham rats. Surprisingly, RYGB (95.6 ± 0.7%) improved protein digestibility (P = 0.045) compared with Sham (93.5 ± 0.5%) and VSG (93.8 ± 0.6%). In contrast, ¹⁵N retained in the liver (P = 0.001) and plasma protein (P = 0.037) was lower than in Sham, with a similar trend in muscle (P = 0.052). FSR was little altered by bariatric surgery, except for a decrease in the kidney of RYGB (P = 0.02). The ¹⁵N distribution along the small intestinal tissue suggests that dietary nitrogen was considerably retained in the remodeled mucosa of RYGB compared with Sham. This study revealed that in contrast to VSG, RYGB slightly improved protein digestibility but altered peripheral protein bioavailability. This effect may be ascribed to a higher uptake of dietary amino acids by the remodeled intestine.NEW & NOTEWORTHY Using a sensitive ¹⁵N meal test, we found that gastric bypass slightly improved protein digestibility compared with sleeve gastrectomy or control but, in contrast, lowered protein retention in the liver and muscles. This paradox can be due to a higher uptake of dietary nitrogen by the intestinal mucosa that was hypertrophied. This study provides new insight on the digestive and metabolic fate of dietary protein in different models of bariatric surgery in rats.

The Effects of Bariatric Surgery on Islet Function, Insulin Secretion, and Glucose Control

Although bariatric surgery was developed primarily to treat morbid obesity, evidence from the earliest clinical observations to the most recent clinical trials consistently demonstrates that these procedures have substantial effects on glucose metabolism. A large base of research indicates that bariatric surgeries such as Roux-en-Y gastric bypass (RYGB), vertical sleeve gastrectomy (VSG), and biliopancreatic diversion (BPD) improve diabetes in most patients, with effects frequently evident prior to substantial weight reduction. There is now unequivocal evidence from randomized controlled trials that the efficacy of surgery is superior to intensive life-style/medical management. Despite advances in the clinical understanding and application of bariatric surgery, there remains only limited knowledge of the mechanisms by which these procedures confer such large changes to metabolic physiology. The improvement of insulin sensitivity that occurs with weight loss (e.g., the result of diet, illness, physical training) also accompanies bariatric surgery. However, there is evidence to support specific effects of surgery on insulin clearance, hepatic glucose production, and islet function. Understanding the mechanisms by which surgery affects these parameters of glucose regulation has the potential to identify new targets for therapeutic discovery. Studies to distinguish among bariatric surgeries on key parameters of glucose metabolism are limited but would be of considerable value to assist clinicians in selecting specific procedures and investigators in delineating the resulting physiology. This review is based on literature related to factors governing glucose metabolism and insulin secretion after the commonly used RYGB and VSG, and the less frequently used BPD and adjustable gastric banding.

Influence of Energy Balance on the Rate of Weight Loss Throughout One Year of Roux-en-Y Gastric Bypass: a Doubly Labeled Water Study

OBJECTIVE

To investigate the influence of changes in energy balance and body composition on the rate of weight loss throughout 1 year of Roux-en-Y gastric bypass.

METHODS

Variables were collected pre-, 6, and 12 months (M) post-surgery from 18 women (BMI ≥ 40 and ≤ 50 kg m^-2, 20 to 45 years). Total energy expenditure (TEE_m), fat-free mass (FFM), and fat mass (FM) were measured by doubly labeled water. Self-reported energy intake (EI_sr) was obtained from three non-consecutive food diaries. Metabolic adaptation was assessed via deviations from TEE predictive equation, and the calculated energy intake (EI_c) via the sum of TEE and change in body stores.

RESULTS

BMI significantly decreased (mean ± SD) from 45 ± 2 kg m^-2 to 32 ± 3 kg m^-2 at 6 M, and to 30 ± 3 kg m^-2 at 12 M after surgery. The TEE_m reduced significantly at both time points when compared with pre-surgery (6 M: - 612 ± 317 kcal day^-1; 12 M: - 447 ± 516 kcal day^-1). At 6 M, a metabolic adaptation was observed and the energy balance was - 1151 ± 195 kcal day^-1, while at 12 M it was - 332 ± 158 kcal day^-1. Changes in the values of TEE_m were associated with changes in body weight at 12 M post-surgery. A significant underreporting was observed for EI_sr (1057 ± 385 kcal day^-1) vs. EI_c (2083 ± 309 kcal day^-1) at 12 M post-operative.

CONCLUSION

The higher rate of weight loss at 6 M post-surgery was a response to energy imbalance, which was caused by high restriction in energy intake even with the presence of metabolic adaptation at this time. The EI_sr was not sufficiently accurate to assess the energy consumption of this population.

REGISTRATION OF CLINICAL TRIALS (OBSERVATIONAL STUDY)

Brazilian Clinical Trials Registry: RBR-8k5jsj. Universal Trial Number: U1111-1206-0858.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Intestine-Specific Overexpression of LDLR Enhances Cholesterol Excretion and Induces Metabolic Changes in Male Mice

Roux-en-Y gastric bypass (RYGB) surgery is one of the most effective treatment options for severe obesity and related comorbidities, including hyperlipidemia, a well-established risk factor of cardiovascular diseases. Elucidating the molecular mechanisms underlying the beneficial effects of RYGB may facilitate development of equally effective, but less invasive, treatments. Recent studies have revealed that RYGB increases low-density lipoprotein receptor (LDLR) expression in the intestine of rodents. Therefore, in this study we first examined the effects of RYGB on intestinal cholesterol metabolism in human patients, and we show that they also exhibit profound changes and increased LDLR expression. We then hypothesized that the upregulation of intestinal LDLR may be sufficient to decrease circulating cholesterol levels. To this end, we generated and studied mice that overexpress human LDLR specifically in the intestine. This perturbation significantly affected intestinal metabolism, augmented fecal cholesterol excretion, and induced a reciprocal suppression of the machinery related to luminal cholesterol absorption and bile acid synthesis. Circulating cholesterol levels were significantly decreased and, remarkably, several other metabolic effects were similar to those observed in RYGB-treated rodents and patients, including improved glucose metabolism. These data highlight the importance of intestinal cholesterol metabolism for the beneficial metabolic effects of RYGB and for the treatment of hyperlipidemia.