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

Sleeve gastrectomy morphology and long-term weight-loss and gastroesophageal reflux disease outcomes

BACKGROUND

The relationship between sleeve gastrectomy (SG) morphology and long-term weight-loss and gastroesophageal reflux disease (GERD) outcomes is unknown.

METHODS

All patients (n = 268) undergoing SG performed by 3 surgeons at a single academic institution from January 1, 2010 to December 31, 2012 were included. Long-term weight-loss and GERD outcomes were available for 90 patients which were incorporated in analyses. SG morphology was determined from postoperative day 1 upper gastrointestinal series (UGIS) available from 50 patients. Images were independently categorized using previously published methodology as Dumbbell (38%), Lower Pouch (22%), Tubular (26%), or Upper Pouch (14%) by Radiologist and Surgeon. Radiologist categorization was used when disagreement occurred (8%). Univariable analyses were conducted to explore potential associations between SG morphology, weight loss, and GERD outcomes.

RESULTS

Follow-up was 8.2 ± 0.9 years. Population characteristics included age of 45.1 ± 10.8 years, female sex in 83.3%, and hiatal hernia repair (HHR) performed at index SG in 17.8%. Surgeons did not preferentially achieve a specific SG morphology. Changes from preoperative obesity and associated diseases comprised body mass index (BMI) (49.5 ± 7.6 vs. 39.2 ± 9.4 kg/m²; p < 0.0001), diabetes mellitus (30.0 vs. 12.2%; p = 0.0006), hypertension (70.0 vs. 54.4%; p = 0.0028), hyperlipidemia (42.2 vs. 24.2%;p = 0.0017), obstructive sleep apnea (41.1 vs. 15.6%; p < 0.0001), osteoarthritis (48.9 vs. 13.3%; p < 0.0001), back pain (46.5 vs. 28.9%; p = 0.0035), and medications (4.8 ± 3.3 vs. 3.7 ± 3.5; p < 0.0001). Dumbbell SG morphology was associated with lesser reduction in BMI at follow-up (--6.8 ± 7.2 vs. -12.4 ± 8.3 kg/m²; p = 0.0196) while greater BMI change was appreciated with Lower Pouch SG shape (-16.9 ± 9.9 vs. -8.4 ± 6.8 kg/m²; p = 0.0017). GERD was more prevalent at follow-up than baseline (67.8 vs. 47.8%; p < 0.0001). GERD-specific outcomes included de novo (51.1%), persistent (27.9%), worsened (58.1%), and resolved (14.0%) disease. Ten patients underwent reoperation for refractory GERD with SG morphology corresponding to Dumbbell (n = 5) and Upper Pouch (n = 1) for those with available UGIS. Univariable analyses showed that patients with GERD experienced a larger reduction in BMI compared with patients without GERD (-11.8 ± 7.7 vs. -7.0 ± 5.1 kg/m²; p = 0.0007). Patient age, surgeon, morphology category, and whether a HHR was done at index SG were not associated with the presence of any, de novo, or worsened GERD. Female sex was associated with worsened GERD (96.0 vs. 4.0%; p = 0.0455). Type of calibration device, distance from staple line to pylorus, and whether staple line reinforcement was used were not associated with SG morphology classification.

CONCLUSION

This is the first study assessing the impact of SG morphology on long-term weight loss and GERD. Our data suggest an association between SG morphology and long-term weight loss but not with GERD outcomes. Current technical standards may be limited in reproducing the same SG morphology. This information may help guide the technical optimization and standardization of SG. Surgeons did not favor a specific SG morphology (1). Our results signal to a relationship between radiographic assessment of SG morphology and long-term weight-loss outcomes with Dumbbell classification correlated with lesser reduction in BMI (2a) and Lower Pouch morphology associated with superior weight loss (2b). SG, sleeve gastrectomy; BMI, body mass index.

Gut Factors Mediating the Physiological Impact of Bariatric Surgery

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

Vertical sleeve gastrectomy induces enteroendocrine cell differentiation of intestinal stem cells through bile acid signaling

Vertical sleeve gastrectomy (VSG) results in an increase in the number of hormone-secreting enteroendocrine cells (EECs) in the intestinal epithelium; however, the mechanism remains unclear. Notably, the beneficial effects of VSG are lost in a mouse model lacking the nuclear bile acid receptor farnesoid X receptor (FXR). FXR is a nuclear transcription factor that has been shown to regulate intestinal stem cell (ISC) function in cancer models. Therefore, we hypothesized that the VSG-induced increase in EECs is due to changes in intestinal differentiation driven by an increase in bile acid signaling through FXR. To test this, we performed VSG in mice that express EGFP in ISC/progenitor cells and performed RNA-Seq on GFP-positive cells sorted from the intestinal epithelia. We also assessed changes in EEC number (marked by glucagon-like peptide-1, GLP-1) in mouse intestinal organoids following treatment with bile acids, an FXR agonist, and an FXR antagonist. RNA-Seq of ISCs revealed that bile acid receptors are expressed in ISCs and that VSG explicitly alters expression of several genes that regulate EEC differentiation. Mouse intestinal organoids treated with bile acids and 2 different FXR agonists increased GLP-1-positive cell numbers, and administration of an FXR antagonist blocked these effects. Taken together, these data indicate that VSG drives ISC fate toward EEC differentiation through bile acid signaling.

Associations Between Video Evaluations of Surgical Technique and Outcomes of Laparoscopic Sleeve Gastrectomy

Importance

In any surgical procedure, various aspects of technique may affect patient outcomes. As new procedures enter practice, it is difficult to evaluate the association of each aspect of technique with patient outcomes.

Objective

To examine the associations between technique and outcomes in laparoscopic sleeve gastrectomy.

Design, Setting, and Participants

In this cohort study of bariatric surgery programs participating in a statewide surgical quality improvement collaborative, 30 surgeons submitted intraoperative videos from representative sleeve gastrectomies performed on 6915 patients with morbid obesity. These videos were reviewed by blinded peer surgeons on key technical elements, and 605 reviews were linked to sleeve gastrectomy outcomes of all of the surgeons' patients from January 1, 2015, to December 31, 2016.

Exposures

Surgeons' technical approaches to 5 controversial aspects of laparoscopic sleeve gastrectomy: dissection of the proximal stomach, sleeve caliber, sleeve anatomy, staple line reinforcement, and leak testing.

Main Outcomes and Measures

The 30-day outcomes were rate of postoperative hemorrhage and staple line leak. The 1-year outcomes were percentage of total weight lost and reflux severity (Gastroesophageal Reflux Disease Health-Related Quality of Life instrument).

Results

A total of 30 surgeons submitted 46 videos of operations performed on 6915 patients (mean [SD] age, 45.4 [11.7] years; 5494 [79.5%] female; 4706 [68.1%] White). Complete dissection of the proximal stomach was associated with reduced hemorrhage rates (higher ratings for complete mobilization of fundus were associated with a decrease in hemorrhage rate from 2.1% [25th percentile] to 1.0% [75th percentile], P = .01; higher ratings for visualization of the left crus were associated with a decrease in hemorrhage rate from 1.5% to 0.94%, P = .006; and higher ratings for complete division of the short gastrics were associated with a decrease in hemorrhage rate from 2.8% to 1.2%, P = .03). The reduction in hemorrhage rates came at the expense of higher leak rates (higher ratings for complete mobilization of fundus were associated with an increase in leak rate from 0.05% [25th percentile] to 0.16% [75th percentile], P < .001; higher ratings for visualization of the left crus were associated with an increase in leak rate from 0.1% to 0.2%, P = .003; and higher ratings for complete division of the short gastrics were associated with an increase in leak rate from 0.02% to 0.1%, P = .01). Surgeons who stapled more tightly to the bougie had smaller decreases in reflux than those who stapled less tightly (-2.0 to -1.3 on a 50-point scale, P = .002). Staple line reinforcement (buttressing and oversewing) was associated with a small (2 of 1000 cases) decrease in hemorrhage rates. Staple line buttressing was also associated with a similarly small increase in leak rates (1 of 1000 cases). Leak testing was associated with a statistically insignificant change in the staple line leak rate (0.16%-0.22%, P = .47).

Conclusions and Relevance

Variations in surgical technique can be measured by video review and are associated with differences in patient outcomes.

The Unconventional Role for Gastric Volume in the Response to Bariatric Surgery for Both Weight Loss and Glucose Lowering

OBJECTIVE

To study the relationship between the amount of surgery-induced gastric volume reduction and long-term weight loss and glucose tolerance.

BACKGROUND DATA

Vertical sleeve gastrectomy (VSG) has recently surpassed gastric bypass to become the most popular surgical intervention to induce sustained weight loss. Besides inducing significant weight loss, VSG also improves glucose tolerance. Although no clear correlation has been observed between the size of the residual stomach and sustained weight loss, this begs the question whether less aggressive gastric volume reduction may provide sufficient efficacy when weight loss is not the major goal of the surgical intervention.

METHODS

A series of strategies to reduce gastric volume were developed and tested in Long Evans male rats, namely: VSG, Fundal (F)-Resection, Gastric Sleeve Plication (GSP), Fundal-Plication, and Fundal-Constrained.

RESULTS

All surgical interventions resulted in a reduction of gastric volume relative to sham, but none of the interventions were as effective as the VSG. Gastric volume was linearly correlated to increased gastric emptying rate as well as increased GLP-1 response. Overall, cumulative food intake was the strongest correlate to weight loss and was logarithmically related to gastric volume. Regression modeling revealed a nonlinear inverse relation between body weight reduction and gastric volume, confirming that VSG is the only effective long-term weight loss strategy among the experimental operations tested.

CONCLUSIONS

The data suggest a minimum threshold volume of the residual stomach that is necessary to induce sustained weight loss. Although all gastric volume interventions increased the GLP-1 response, none of the interventions, except VSG, significantly improved glucose tolerance. In conclusion, if weight loss is the primary goal of surgical intervention, significant volume reduction is required, and this most likely requires excising gastric tissue.

Sleeve gastrectomy enhances glucose utilization and remodels adipose tissue independent of weight loss

Sleeve gastrectomy (SG) induces weight loss-independent improvements in glucose homeostasis by unknown mechanisms. We sought to identify the metabolic adaptations responsible for these improvements. Nonobese C57BL/6J mice on standard chow underwent SG or sham surgery. Functional testing and indirect calorimetry were used to capture metabolic phenotypes. Tissue-specific glucose uptake was assessed by 18-fluorodeoxyglucose (18-FDG) PET/computed tomography, and RNA sequencing was used for gene-expression analysis. In this model, SG induced durable improvements in glucose tolerance in the absence of changes in weight, body composition, or food intake. Indirect calorimetry revealed that SG increased the average respiratory exchange ratio toward 1.0, indicating a weight-independent, systemic shift to carbohydrate utilization. Following SG, orally administered 18-FDG preferentially localized to white adipose depots, showing tissue-specific increases in glucose utilization induced by surgery. Transcriptional analysis with RNA sequencing demonstrated that increased glucose uptake in the visceral adipose tissue was associated with upregulation in transcriptional pathways involved in energy metabolism, adipocyte maturation, and adaptive and innate immune cell chemotaxis and differentiation. SG induces a rapid, weight loss-independent shift toward glucose utilization and transcriptional remodeling of metabolic and immune pathways in visceral adipose tissue. Continued study of this early post-SG physiology may lead to a better understanding of the anti-diabetic mechanisms of bariatric surgery.

Continuous glucose monitoring reveals glycemic variability and hypoglycemia after vertical sleeve gastrectomy in rats

Objective

Post–bariatric surgery hypoglycemia (PBH) is defined as the presence of neuroglycopenic symptoms accompanied by postprandial hypoglycemia in bariatric surgery patients. Recent clinical studies using continuous glucose monitoring (CGM) technology revealed that PBH is more frequently observed in vertical sleeve gastrectomy (VSG) patients than previously recognized. PBH cannot be alleviated by current medication. Therefore, a model system to investigate the mechanism and treatment is required.

Methods

We used CGM in a rat model of VSG and monitored the occurrence of glycemic variability and hypoglycemia in various meal conditions for 4 weeks after surgery. Another cohort of VSG rats with CGM was used to investigate whether the blockade of glucagon-like peptide-1 receptor (GLP-1R) signaling alleviates these symptoms. A mouse VSG model was used to investigate whether the impaired glucose counterregulatory system causes postprandial hypoglycemia.

Results

Like in humans, rats have increased glycemic variability and hypoglycemia after VSG. Postprandial hypoglycemia was specifically detected after liquid versus solid meals. Further, the blockade of GLP-1R signaling raises the glucose nadir but does not affect glycemic variability.

Conclusions

Rat bariatric surgery duplicates many features of human post–bariatric surgery hypoglycemia including postprandial hypoglycemia and glycemic variability, while blockade of GLP-1R signaling prevents hypoglycemia but not the variability.

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VSG causes glycemic variability during ad lib feeding condition.

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Single liquid meal ingestion causes post-VSG hypoglycemia.

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Blockade of GLP-1 receptor prevents post-VSG hypoglycemia.

A comparison of rodent models of vertical sleeve gastrectomy

BACKGROUND

Although vertical sleeve gastrectomy (VSG) is fashioned in humans by applying multiple staple loads, rodent VSG is generally created through a single-staple load application.

OBJECTIVES

To investigate the impact of a 2-staple load VSG rat model more closely resembling the multistaple load operation done in humans on weight, metabolic outcomes, and the microbiome and how these compare with those obtained with the standard one-staple load model.

SETTING

University research facility, United States.

METHODS

High-fat diet-induced obese male rats were randomized to single-staple load VSG (VSG1), 2-staple load VSG (VSG2), or sham operation (Sham). Outcomes included weight and composition, food intake, glucose metabolism, lipids, bile acids, and intestinal microbiome. Statistical comparisons were performed using analysis of variance.

RESULTS

Both procedures resulted in substantial weight and body fat loss compared with Sham-treated animals. Weight loss was modestly greater for VSG2 compared with VSG1. Food intake was reduced in both procedures and accounted for the observed weight reduction. Glucose tolerance and plasma and hepatic lipid profiles were improved comparably in VSG1 and VSG2 relative to Sham. Bile acids were higher for VSG2 compared with Sham but not significantly different between VSG1 and VSG2. Neither procedure impacted intestinal microbiome richness and diversity compared with Sham across multiple intestinal sections. Colonic Actinobacteria was more abundant in VSG2 than in Sham. Relative abundances of bacterial phyla did not differ among VSG1, VSG2, and Sham across the remaining intestinal sections.

CONCLUSIONS

Although VSG1 or VSG2 offer effective and overall comparable platforms for the study of obesity, VSG2 resulted in superior weight loss.

A new proposed mechanism of action for gastric bypass surgery: Air hypothesis

Roux-en-Y gastric bypass (RYGB) surgery is one of the most effective treatments for obesity and type II diabetes. RYGB was originally believed to work by mechanically restricting caloric intake or causing macronutrient malabsorption. However, such mechanical effects play no role in the remarkable efficacy of gastric bypass. Instead, mounting evidence shows that altered neuroendocrine signaling is responsible for the weight reducing effects of RYGB. The exact mechanism of this surgical response is still a mystery. Here, we propose that RYGB leads to weight loss primarily by inducing a functional shift in the gut microbiome, manifested by a relative expansion of aerobic bacteria numbers in the colon. We point to compelling evidence that gastric bypass changes the function of the microbiome by disrupting intestinal gas homeostasis, causing excessive transit of swallowed air (oxygen) into the colon.

The endogenous preproglucagon system is not essential for gut growth homeostasis in mice

OBJECTIVE

The prevalence of obesity and related co-morbidities is reaching pandemic proportions. Today, the most effective obesity treatments are glucagon-like peptide 1 (GLP-1) analogs and bariatric surgery. Interestingly, both intervention paradigms have been associated with adaptive growth responses in the gut; however, intestinotrophic mechanisms associated with or secondary to medical or surgical obesity therapies are poorly understood. Therefore, the objective of this study was to assess the local basal endogenous and pharmacological intestinotrophic effects of glucagon-like peptides and bariatric surgery in mice.

METHODS

We used in situ hybridization to provide a detailed and comparative anatomical map of the local distribution of GLP-1 receptor (Glp1r), GLP-2 receptor (Glp2r), and preproglucagon (Gcg) mRNA expression throughout the mouse gastrointestinal tract. Gut development in GLP-1R-, GLP-2R-, or GCG-deficient mice was compared to their corresponding wild-type controls, and intestinotrophic effects of GLP-1 and GLP-2 analogs were assessed in wild-type mice. Lastly, gut volume was determined in a mouse model of vertical sleeve gastrectomy (VSG).

RESULTS

Comparison of Glp1r, Glp2r, and Gcg mRNA expression indicated a widespread, but distinct, distribution of these three transcripts throughout all compartments of the mouse gastrointestinal tract. While mice null for Glp1r or Gcg showed normal intestinal morphology, Glp2r-/- mice exhibited a slight reduction in small intestinal mucosa volume. Pharmacological treatment with GLP-1 and GLP-2 analogs significantly increased gut volume. In contrast, VSG surgery had no effect on intestinal morphology.

CONCLUSION

The present study indicates that the endogenous preproglucagon system, exemplified by the entire GCG gene and the receptors for GLP-1 and GLP-2, does not play a major role in normal gut development in the mouse. Furthermore, elevation in local intestinal and circulating levels of GLP-1 and GLP-2 achieved after VSG has limited impact on intestinal morphometry. Hence, although exogenous treatment with GLP-1 and GLP-2 analogs enhances gut growth, the contributions of endogenously-secreted GLP-1 and GLP-2 to gut growth may be more modest and highly context-dependent.