Sleeve gastrectomy rapidly enhances islet function independently of body weight

Vertical sleeve gastrectomy improves glucose-insulin homeostasis by enhancing β-cell function and survival via FGF15/19

Vertical sleeve gastrectomy (VSG) restores glucose homeostasis in obese mice and humans. In addition, the increased fibroblast growth factor (FGF)15/19 circulating level postsurgery has been implicated in this effect. However, the impact of FGF15/19 on pancreatic islets remains unclear. Using a diet-induced obese mice model, we demonstrate that VSG attenuates insulin hypersecretion in isolated pancreatic islets, likely due to morphological alterations in the endocrine pancreas such as reduction in islet, β-cell, and α-cell mass. In addition, VSG relieves gene expression of endoplasmic reticulum (ER) stress and inflammation markers in islets from obese mice. Incubation of INS-1E β-cells with serum from obese mice induced dysfunction and cell death, whereas these conditions were not induced with serum from obese mice submitted to VSG, implicating the involvement of a humoral factor. Indeed, VSG increased FGF15 circulating levels in obese mice, as well as the expression of FGF receptor 1 (Fgfr1) and its coreceptor β-klotho (Klb), both in pancreatic islets from VSG mice and in INS-1E cells treated with the serum from these mice. Moreover, exposing INS-1E cells to an FGFR inhibitor abolished the effects of VSG serum on insulin secretion and cell death. Also, recombinant FGF19 prevents INS-1E cells from dysfunction and death induced by serum from obese mice. These findings indicate that the amelioration of glucose-insulin homeostasis promoted by VSG is mediated, at least in part, by FGF15/19. Therefore, approaches promoting FGF15/19 release or action may restore pancreatic islet function in obesity.NEW & NOTEWORTHY Vertical sleeve gastrectomy (VSG) decreases insulin secretion, endoplasmic reticulum (ER) stress, and inflammation in pancreatic islets from obese mice. In addition, VSG increased fibroblast growth factor (FGF)15 circulating levels in obese mice, as well as the expression of FGF receptor 1 (Fgfr1) and its coreceptor β-klotho (Klb), both in pancreatic islets from VSG mice and in INS-1E β-cells treated with the serum from these mice. Serum from operated mice protects INS-1E cells from dysfunction and apoptosis, which was mediated by FGF15/19.

Effect of Bariatric Surgery on Metabolic Syndrome in Chinese Patients with Low Body Mass Index: a Propensity Score Matching Study

BACKGROUND

Bariatric surgery (BS) is known to improve the components of metabolic syndrome (MS) in patients with obesity. However, few studies have evaluated the effect of BS on patients with MS at low BMI levels. The study aims to assess the effect of BS on MS in patients with low BMI by comparing BS with medical therapy (MT).

METHODS

A total of 271 patients with MS who underwent BS and MT at a single institution were reviewed in this retrospective cohort study. A 1:1 propensity score matching was performed for the BS and MT groups with BMI<35 kg/m2. We analyzed the 5 years effect of BS versus MT on the remission of MS, its components, atherosclerotic cardiovascular disease (ASCVD) risk, and medication used.

RESULTS

Patients in the MT group showed a decrease in the prevalence of MS to 62% at the 1st year and 10% at the 5th year. In the BS group, MS prevalence in patients with BMI<35 kg/m2 decreased to 30% and 9% at the 1st and 5th year, whereas in patients with BMI≥35 kg/m2 was 26% and 7%, respectively. The 10-year ASCVD risk and the lifetime ASCVD were significantly decreased 5 years after BS in patients with BMI<35 kg/m2. The number and daily drug dose of hypoglycemic drugs, antihypertensive medications, and lipid-lowering drugs were reduced from baseline in both BS and MT groups.

CONCLUSION

Bariatric surgery significantly improves MS remission rates and long-term cardiovascular risk in Chinese patients with metabolic syndrome and a BMI <35 kg/m2.

The impact of prior obesity surgery on glucose metabolism after body contouring surgery: A pilot study

Body contouring surgery enhances physical appearance by means of surgical subcutaneous fat removal (SSFR). However, it remains unclear how SSFR may affect glucose metabolism and its broader effects on the endocrine system, especially in individuals who have undergone obesity (bariatric) surgery. This study aimed to evaluate the impact of SSFR on glucose excursion and insulin resistance in such patients, by examining them over three visits (within 1 week before surgery, 1 week after surgery, and 6 weeks after surgery). The independent impact of SSFR and history of obesity surgery on glucose homeostasis was evaluated in 29 participants, of whom ten patients (34%) had a history of obesity surgery. Indices of glucose metabolism were evaluated using cluster robust-error logistic regression. Results indicated that SSFR led to a gross improvement in insulin resistance at 6 weeks after the surgery in all patient's irrespective of BMI, type 2 diabetes mellitus (T2D) status, or history of obesity surgery (OR 0.22; p = 0.042). However, no effect was observed on glucose excursion except for a transient increase at visit 2 (1 week after surgery) in those without prior obesity surgery. Interestingly, participants with a history of obesity surgery had approximately half the odds being in the upper tertile for HOMA-IR (OR 0.44; p = 0.142) and ten-folds lower odds of having severely abnormal glucose excursion (OR 0.09; p = 0.031), irrespective of their BMI, T2D status, or time post SSFR. In conclusion, this study showed that body contouring surgery through SSFR resulted in (at least) short-term improvement in insulin resistance (independent of the participant's BMI, T2D status, or history of obesity surgery) without affecting glucose excursion under the GTT. On the contrary, obesity surgery may have a long-term effect on glucose excursion, possibly due to sustained improvement of pancreatic ß-cell function.

Temporal Relationship Between Insulin Resistance and Lipid Accumulation After Bariatric Surgery: a Multicenter Cohort Study

PURPOSE

Insulin resistance (IR) is closely associated with lipid accumulation. Here, we investigated the temporal relationship between the two conditions after bariatric surgery.

MATERIALS AND METHODS

In total, 409 participants were enrolled from three bariatric centers in China from 2009 to 2018. We evaluated whether baseline IR (proxied by homeostasis model assessment of insulin resistance (HOMA-IR)) and lipid accumulation (proxied by visceral adiposity index (VAI) and lipid accumulation product (LAP)) were associated with follow-up IR and lipid accumulation (3 months postoperatively) using linear regression models. We then conducted a cross-lagged panel analysis model to simultaneously examine the bidirectional relationship between IR and lipid accumulation.

RESULTS

Multivariable linear regression analyses showed that baseline HOMA-IR was associated with follow-up VAI (β = 0.430, 95% CI: 0.082-0.778, p = 0.016) and LAP (β = 0.070, 95% CI: 0.010-0.130, p = 0.022). There was no relationship between baseline lipid accumulation and follow-up IR. Further cross-lagged panel analyses indicated that the path coefficient from baseline HOMA-IR to follow-up VAI (β₂ = 0.145, p = 0.003) was significantly greater than the coefficient from baseline VAI to follow-up HOMA-IR (β₁ =  - 0.013, p = 0.777). Similarly, the path coefficient from baseline HOMA-IR to follow-up LAP (β₂ = 0.141, p = 0.003) was significantly greater than the coefficient from baseline LAP to follow-up HOMA-IR (β₁ = 0.041, p = 0.391).

CONCLUSION

Our study demonstrated a unidirectional relationship from HOMA-IR to VAI and LAP, suggesting that the change in IR may precede lipid accumulation after surgery.

Vertical sleeve gastrectomy associates with airway hyperresponsiveness in a murine model of allergic airway disease and obesity

Introduction

Asthma is a chronic airway inflammatory disease marked by airway inflammation, remodeling and hyperresponsiveness to allergens. Allergic asthma is normally well controlled through the use of beta-2-adrenergic agonists and inhaled corticosteroids; however, a subset of patients with comorbid obesity experience resistance to currently available therapeutics. Patients with asthma and comorbid obesity are also at a greater risk for severe disease, contributing to increased risk of hospitalization. Bariatric surgery improves asthma control and airway hyperresponsiveness in patients with asthma and comorbid obesity, however, the underlying mechanisms for these improvements remain to be elucidated. We hypothesized that vertical sleeve gastrectomy (VSG), a model of metabolic surgery in mice, would improve glucose tolerance and airway inflammation, resistance, and fibrosis induced by chronic allergen challenge and obesity.

Methods

Male C57BL/6J mice were fed a high fat diet (HFD) for 13 weeks with intermittent house dust mite (HDM) allergen administration to induce allergic asthma, or saline as control. At week 11, a subset of mice underwent VSG or Sham surgery with one week recovery. A separate group of mice did not undergo surgery. Mice were then challenged with HDM or saline along with concurrent HFD feeding for 1-1.5 weeks before measurement of lung mechanics and harvesting of tissues, both of which occurred 24 hours after the final HDM challenge. Systemic and pulmonary cytokine profiles, lung histology and gene expression were analyzed.

Results

High fat diet contributed to increased body weight, serum leptin levels and development of glucose intolerance for both HDM and saline treatment groups. When compared to saline-treated mice, HDM-challenged mice exhibited greater weight gain. VSG improved glucose tolerance in both saline and HDM-challenged mice. HDM-challenged VSG mice exhibited an increase in airway hyperresponsiveness to methacholine when compared to the non-surgery group.

Discussion

The data presented here indicate increased airway hyperresponsiveness in allergic mice undergoing bariatric surgery.

Bariatric Surgery: Targeting pancreatic β cells to treat type II diabetes

Pancreatic β-cell function impairment and insulin resistance are central to the development of obesity-related type 2 diabetes mellitus (T2DM). Bariatric surgery (BS) is a practical treatment approach to treat morbid obesity and achieve lasting T2DM remission. Traditionally, sustained postoperative glycemic control was considered a direct result of decreased nutrient intake and weight loss. However, mounting evidence in recent years implicated a weight-independent mechanism that involves pancreatic islet reconstruction and improved β-cell function. In this article, we summarize the role of β-cell in the pathogenesis of T2DM, review recent research progress focusing on the impact of Roux-en-Y gastric bypass (RYGB) and vertical sleeve gastrectomy (VSG) on pancreatic β-cell pathophysiology, and finally discuss therapeutics that have the potential to assist in the treatment effect of surgery and prevent T2D relapse.

Discovery of a potent GIPR peptide antagonist that is effective in rodent and human systems

OBJECTIVE

Glucose-dependent insulinotropic polypeptide (GIP) is one of the two major incretin factors that regulate metabolic homeostasis. Genetic ablation of its receptor (GIPR) in mice confers protection against diet-induced obesity (DIO), while GIPR neutralizing antibodies produce additive weight reduction when combined with GLP-1R agonists in preclinical models and clinical trials. Conversely, GIPR agonists have been shown to promote weight loss in rodents, while dual GLP-1R/GIPR agonists have proven superior to GLP-1R monoagonists for weight reduction in clinical trials. We sought to develop a long-acting, specific GIPR peptide antagonist as a tool compound suitable for investigating GIPR pharmacology in both rodent and human systems.

METHODS

We report a structure-activity relationship of GIPR peptide antagonists based on the human and mouse GIP sequences with fatty acid-based protraction. We assessed these compounds in vitro, in vivo in DIO mice, and ex vivo in islets from human donors.

RESULTS

We report the discovery of a GIP_(5-31) palmitoylated analogue, [N^α-Ac, L14, R18, E21] hGIP_(5-31)-K11 (γE-C16), which potently inhibits in vitro GIP-mediated cAMP generation at both the hGIPR and mGIPR. In vivo, this peptide effectively blocks GIP-mediated reductions in glycemia in response to exogenous and endogenous GIP and displays a circulating pharmacokinetic profile amenable for once-daily dosing in rodents. Co-administration with the GLP-1R agonist semaglutide and this GIPR peptide antagonist potentiates weight loss compared to semaglutide alone. Finally, this antagonist inhibits GIP- but not GLP-1-stimulated insulin secretion in intact human islets.

CONCLUSIONS

Our work demonstrates the discovery of a potent, specific, and long-acting GIPR peptide antagonist that effectively blocks GIP action in vitro, ex vivo in human islets, and in vivo in mice while producing additive weight-loss when combined with a GLP-1R agonist in DIO mice.

Do bariatric patient's in rural areas achieve comparative weight loss as national average? single center experience in appalachia west virginia

INTRODUCTION

Obesity is one of the leading public health concerns with over half a million Americans being classified as obese and almost two billion classified as overweight. This has an impact on overall health of the individual, with increased comorbidities and premature death, as well as increased economic cost. This study evaluates the weight loss of patients with limited societal support and resources cared for at a single bariatric center of excellence, The Center for Surgical Weight Control, in Cabell County, West Virginia.

METHODS

Retrospective review of patients that have undergone either a Vertical Sleeve Gastrectomy (VSG) or a Roux-en-Y gastric bypass (RNYGB) between the years of 2017 and 2018 At the Center for Surgical Weight Control. Weight loss was evaluated at 6 months, 1 year, and 2 years.

RESULTS

There were 290 patients between 2017 and 2018. On average, the VSG group lost 46% of excess body weight (EBW) at 6 months, 57% of EBW at 1 year, and 61% of EBW at 2 years. In the RNYGB group patients lost on average 54% of EBW at 6 months, 65% of EBW at 1 year, and 88% of EBW at 2 years.

DISCUSSION

A loss of 5-15% of EBW can improve obesity-related comorbidities. These comorbidities include diabetes, hypertension, hyperlipidemia, gastroesophageal reflux disease, and obstructive sleep apnea. Improvement in these comorbidities not only benefits each patient individually, but will also help improve the effects on society as a whole.

CONCLUSION

Obesity is a debilitating and deadly disease, thus makes it very important to address in order to reduce burden on both patients and society as a whole. There is an expected amount of weight loss a patient should have depending on the type of surgery they undergo. Our patients were successful at meeting and exceeding the expected percentage of EBW loss after both VSG and RNYGB.

Vertical sleeve gastrectomy normalizes circulating glucocorticoid levels and lowers glucocorticoid action tissue-selectively in mice

Objectives

Glucocorticoids produced by the adrenal cortex are essential for the maintenance of metabolic homeostasis. Glucocorticoid activation is catalysed by 11β-hydroxysteroid dehydrogenase 1 (11β-HSD1). Excess glucocorticoids are associated with insulin resistance and hyperglycaemia. A small number of studies have demonstrated effects on glucocorticoid metabolism of bariatric surgery, a group of gastrointestinal procedures known to improve insulin sensitivity and secretion, which were assumed to result from weight loss. In this study, we hypothesize that a reduction in glucocorticoid action following bariatric surgery contributes to the widely observed euglycemic effects of the treatment.

Methods

Glucose and insulin tolerance tests were performed at ten weeks post operatively and circulating corticosterone was measured. Liver and adipose tissues were harvested from fed mice and 11β-HSD1 levels were measured by quantitative RT-PCR or Western (immuno-) blotting, respectively. 11β-HSD1 null mice (Hsd11b1 -/-) were generated using CRISPR/Cas9 genome editing. Wild type and littermate Hsd11b1 -/- mice underwent Vertical Sleeve Gastrectomy (VSG) or sham surgery.

Results

Under the conditions used, no differences in weight loss were observed between VSG treated and sham operated mice. However, both lean and obese WT VSG mice displayed significantly improved glucose clearance and insulin sensitivity. Remarkably, VSG restored physiological corticosterone production in HFD mice and reduced 11β-HSD1 expression in liver and adipose tissue post-surgery. Elimination of the 11β-HSD1/Hsd11b1 gene by CRISPR/Cas9 mimicked the effects of VSG on body weight and tolerance to 1g/kg glucose challenge. However, at higher glucose loads, the euglycemic effect of VSG was superior to Hsd11b1 elimination.

Conclusions

Bariatric surgery improves insulin sensitivity and reduces glucocorticoid activation at the tissular level, under physiological and pathophysiological (obesity) conditions, irrespective of weight loss. These findings point towards a physiologically relevant gut-glucocorticoid axis, and suggest that lowered glucocorticoid exposure may represent an additional contribution to the health benefits of bariatric surgery.

Sleeve Gastrectomy Reduces Glycemia but Does Not Affect Cognitive Impairment in Lean 5xFAD Mice

Obesity and hyperglycemia are risk factors for cognitive decline and for the development of Alzheimer’s Disease (AD). Bariatric surgery is an effective treatment for obesity that was shown to improve cognitive decline in obese patients. Bariatric surgery was shown to exert weight loss independent effects on metabolic diseases such as type 2 diabetes. We tested whether sleeve gastrectomy (SG), a common bariatric surgery, can affect the cognitive impairment in lean, normoglycemic female 5xFAD mice, a genetic model for AD. 5xFAD mice and wild-type (WT) littermates underwent SG or sham surgery at the age of 5 months and were tested for metabolic, behavioral, and molecular phenotypes 90 days later. SG led to a reduction in blood glucose levels and total plasma cholesterol levels in 5xFAD mice without inducing weight loss. However, the surgery did not affect the outcomes of long-term spatial memory tests in these mice. Analysis of β-Amyloid plaques corroborated the behavioral studies in showing no effect of surgery on the molecular phenotype of 5xFAD mice. In conclusion, SG leads to an improved metabolic profile in lean female 5xFAD mice without inducing weight loss but does not affect the brain pathology or behavioral phenotype. Our results suggest that the positive effects of bariatric surgery on cognitive decline in obese patients are likely attributed to weight loss and improvement in obesity sequelae, and not to weight loss independent effects of surgery.

Intravital imaging of islet Ca2+ dynamics reveals enhanced β cell connectivity after bariatric surgery in mice

Bariatric surgery improves both insulin sensitivity and secretion and can induce diabetes remission. However, the mechanisms and time courses of these changes, particularly the impact on β cell function, are difficult to monitor directly. In this study, we investigated the effect of Vertical Sleeve Gastrectomy (VSG) on β cell function in vivo by imaging Ca²⁺ dynamics in islets engrafted into the anterior eye chamber. Mirroring its clinical utility, VSG in mice results in significantly improved glucose tolerance, and enhanced insulin secretion. We reveal that these benefits are underpinned by augmented β cell function and coordinated activity across the islet. These effects involve changes in circulating GLP-1 levels which may act both directly and indirectly on the β cell, in the latter case through changes in body weight. Thus, bariatric surgery leads to time-dependent increases in β cell function and intra-islet connectivity which are likely to contribute to diabetes remission.

Vertical sleeve gastrectomy confers metabolic improvements by reducing intestinal bile acids and lipid absorption in mice

Vertical sleeve gastrectomy (VSG) is one of the most effective and durable therapies for morbid obesity and its related complications. Although bile acids (BAs) have been implicated as downstream mediators of VSG, the specific mechanisms through which BA changes contribute to the metabolic effects of VSG remain poorly understood. Here, we confirm that high fat diet-fed global farnesoid X receptor (Fxr) knockout mice are resistant to the beneficial metabolic effects of VSG. However, the beneficial effects of VSG were retained in high fat diet-fed intestine- or liver-specific Fxr knockouts, and VSG did not result in Fxr activation in the liver or intestine of control mice. Instead, VSG decreased expression of positive hepatic Fxr target genes, including the bile salt export pump (Bsep) that delivers BAs to the biliary pathway. This reduced small intestine BA levels in mice, leading to lower intestinal fat absorption. These findings were verified in sterol 27-hydroxylase (Cyp27a1) knockout mice, which exhibited low intestinal BAs and fat absorption and did not show metabolic improvements following VSG. In addition, restoring small intestinal BA levels by dietary supplementation with taurocholic acid (TCA) partially blocked the beneficial effects of VSG. Altogether, these findings suggest that reductions in intestinal BAs and lipid absorption contribute to the metabolic benefits of VSG.

EXPERIMENTAL INDUCTION OF TYPE 2 DIABETES MELLITUS AND THE EFFICIENCY OF BARIATRIC SURGERY IN ITS REVERSAL IN RATS

BACKGROUND

Following recent years, there is an increased body of literature on the connections that might exist between type 2 diabetes mellitus and the efficiency of bariatric surgery in its reversal compared to other medical approaches such as dieting.

AIM

To induce experimentally type 2 diabetes mellitus in rats in order to observe the effects of bariatric surgery in the recovery as well as the reestablishment of normal insulin levels in order to extend the findings in house animals.

MATERIALS AND METHODS

This study was conducted in three stages: the first consisted in inducing type 2 diabetes mellitus (T2DM) in 40 young Wistar male rats, by initially feeding them human food high in vegetal fats, oleaginous seeds, simple and complex carbohydrates, sugars, lipids, fats, proteins and fructose for a period of 8 weeks followed by a single low dose of streptozotocin (STZ), administered through intraperitoneal injection. The second stage of the study started when the rats became obese and therefore qualified for the bariatric procedure and the third stage consisted of post-operation supervision and care. The surgical procedure, performed on 10 obese rats, consisted in reducing the size of the stomach by partial gastrectomy of a 1.5 - 2.0 cm wide and 6.5 - 7.5 cm long area on the large curvature.

RESULTS

Showed rapid improvements in body weight and blood sugar control after 9 days.

CONCLUSION

After putting the rats on a diet high in carbohydrates, sugars, lipids and fats and administering them STZ, the induction of type 2 diabetes was successful and the partial gastrectomy led to a better blood sugar control. The bariatric procedure provides a faster therapeutic response than conventional diets.

Does Weight Loss Improve Clinical Outcomes in Overweight and Obese Patients with Heart Failure?

PURPOSE OF REVIEW

Obesity increases the risk of new onset heart failure (HF), and particularly HF with preserved ejection fraction (HFpEF). Despite the observations of favorable clinical outcomes in HF patients with obesity in general, sometimes referred to as the "obesity paradox," it is important to recognize that severe obesity is associated with worse clinical outcomes. This review summarizes the effects of obesity treatment on cardiovascular health and HF clinical outcomes.

RECENT FINDINGS

Treatment for obesity utilizes a variety of modalities to achieve purposeful weight loss including lifestyle intervention, medications, and bariatric surgery. There are a cluster of benefits of obesity treatment in terms of clinical outcomes in HF. The mechanisms of these benefits include both weight loss-dependent and weight loss-independent mechanisms. Obesity treatment is safe and associated with favorable clinical outcomes across the spectrum of the HF population. The potential benefits are facilitated through multiple mechanisms.

Repositioning the Alpha Cell in Postprandial Metabolism

Glucose homeostasis is maintained in large part due to the actions of the pancreatic islet hormones insulin and glucagon, secreted from β- and α-cells, respectively. The historical narrative positions these hormones in opposition, with insulin primarily responsible for glucose-lowering and glucagon-driving elevations in glucose. Recent progress in this area has revealed a more complex relationship between insulin and glucagon, highlighted by data demonstrating that α-cell input is essential for β-cell function and glucose homeostasis. Moreover, the common perception that glucagon levels decrease following a nutrient challenge is largely shaped by the inhibitory effects of glucose administration alone on the α-cell. Largely overlooked is that a mixed nutrient challenge, which is more representative of typical human feeding, actually stimulates glucagon secretion. Thus, postprandial metabolism is associated with elevations, not decreases, in α-cell activity. This review discusses the recent advances in our understanding of how α-cells regulate metabolism, with a particular focus on the postprandial state. We highlight α- to β-cell communication, a term that describes how α-cell input into β-cells is a critical axis that regulates insulin secretion and glucose homeostasis. Finally, we discuss the open questions that have the potential to advance this field and continue to evolve our understanding of the role that α-cells play in postprandial metabolism.

A surrogate of Roux-en-Y gastric bypass (the enterogastro anastomosis surgery) regulates multiple beta-cell pathways during resolution of diabetes in ob/ob mice

BACKGROUND

Bariatric surgery is an effective treatment for type 2 diabetes. Early post-surgical enhancement of insulin secretion is key for diabetes remission. The full complement of mechanisms responsible for improved pancreatic beta cell functionality after bariatric surgery is still unclear. Our aim was to identify pathways, evident in the islet transcriptome, that characterize the adaptive response to bariatric surgery independently of body weight changes.

METHODS

We performed entero-gastro-anastomosis (EGA) with pyloric ligature in leptin-deficient ob/ob mice as a surrogate of Roux-en-Y gastric bypass (RYGB) in humans. Multiple approaches such as determination of glucose tolerance, GLP-1 and insulin secretion, whole body insulin sensitivity, ex vivo glucose-stimulated insulin secretion (GSIS) and functional multicellular Ca2+-imaging, profiling of mRNA and of miRNA expression were utilized to identify significant biological processes involved in pancreatic islet recovery.

FINDINGS

EGA resolved diabetes, increased pancreatic insulin content and GSIS despite a persistent increase in fat mass, systemic and intra-islet inflammation, and lipotoxicity. Surgery differentially regulated 193 genes in the islet, most of which were involved in the regulation of glucose metabolism, insulin secretion, calcium signaling or beta cell viability, and these were normalized alongside changes in glucose metabolism, intracellular Ca2+ dynamics and the threshold for GSIS. Furthermore, 27 islet miRNAs were differentially regulated, four of them hubs in a miRNA-gene interaction network and four others part of a blood signature of diabetes resolution in ob/ob mice and in humans.

INTERPRETATION

Taken together, our data highlight novel miRNA-gene interactions in the pancreatic islet during the resolution of diabetes after bariatric surgery that form part of a blood signature of diabetes reversal.

FUNDING

European Union's Horizon 2020 research and innovation programme via the Innovative Medicines Initiative 2 Joint Undertaking (RHAPSODY), INSERM, Société Francophone du Diabète, Institut Benjamin Delessert, Wellcome Trust Investigator Award (212625/Z/18/Z), MRC Programme grants (MR/R022259/1, MR/J0003042/1, MR/L020149/1), Diabetes UK (BDA/11/0004210, BDA/15/0005275, BDA 16/0005485) project grants, National Science Foundation (310030-188447), Fondation de l'Avenir.

PYY, a Therapeutic Option for Type 2 Diabetes?

Metabolic surgery leads to rapid and effective diabetes reversal in humans, by weight-independent mechanisms. The crucial improvement in pancreatic islet function observed after surgery is induced by alteration in several factors, including gut hormones. In addition to glucagon-like peptide 1 (GLP-1), increasing lines of evidence show that peptide tyrosine tyrosine (PYY) plays a key role in the metabolic benefits associated with the surgery, ranging from appetite regulation to amelioration of islet secretory properties and survival. Here, we summarize the current knowledge and the latest advancements in the field, which pitch a strong case for the development of novel PYY-based therapy for the treatment of diabetes.

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.

Temporal plasticity of insulin and incretin secretion and insulin sensitivity following sleeve gastrectomy contribute to sustained improvements in glucose control

Objective

Bariatric surgery acutely improves glucose control, an effect that is generally sustained for years in most patients. The acute postoperative glycemic reduction is at least partially mediated by enhanced incretin secretion and islet function, and occurs independent of caloric restriction, whereas the sustained improvement in glucose control is associated with increased insulin sensitivity. However, studies in humans with bariatric surgery suggest that these elevations are not static but undergo coordinated regulation throughout the postoperative time course. The studies described here test the hypothesis that incretin secretion, islet function, and peripheral insulin sensitivity undergo temporal regulation following bariatric surgery as a means to regulate glucose homeostasis.

Methods

Incretin secretion, islet function, and insulin sensitivity in mice with vertical sleeve gastrectomy (VSG) were compared to sham-operated controls that were pair-fed for 90d, matching food consumption and body-weight between groups.

Results

Glucose clearance and insulin secretion were enhanced in VSG mice compared to controls during mixed-meal tolerance tests (MMTT) at 12 and 80 days postoperatively, as were prandial GLP-1, GIP, and glucagon levels. Insulin sensitivity was comparable between groups 14d after surgery, but significantly greater in the VSG group at day 75, despite similar body-weight gain between groups. Glucose stimulated insulin secretion was greater in VSG mice compared to controls in vivo (I.P. glucose injection) and ex vivo (islet perifusion) indicating a rapid and sustained enhancement of β-cell function after surgery. Notably, glycemia following a MMTT was progressively higher over time in the control animals but improved in the VSG mice at 80d despite weight regain. However, meal-stimulated incretin secretion decreased in VSG mice from 10 to 80 days postoperative, as did meal-stimulated and I.P. glucose-stimulated insulin secretion. This occurred over the same time period that insulin sensitivity was enhanced in VSG mice, suggesting postoperative islet output is tightly regulated by insulin demand.

Conclusions

These data demonstrate a dynamic, multifactorial physiology for improved glucose control after VSG, whereby rapidly elevated insulin secretion is complimented by later enhancements in insulin sensitivity. Critically, the glucose lowering effect of VSG is demonstrably larger than that of caloric-restriction, suggesting these adaptations are mediated by surgical modification of gastrointestinal anatomy and not weight-loss per se.

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β-cell glucose sensitivity is enhanced 90d after VSG compared to controls, coincident with improved glucose tolerance.

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Prandial GLP-1 and GIP are elevated 12d following VSG but return to preoperative levels 80d after VSG.

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Insulin sensitivity is enhanced 75d after surgery, but not 14d after surgery, in mice with VSG compared to controls.

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Mixed-meal glucose control is improved from 12d to 80d in VSG mice, but worsens in controls despite similar body-weight.

Meal patterns after bariatric surgery in mice and rats

With behavioral and pharmacological interventions continuously failing to tackle the obesity epidemic, bariatric surgery has been hailed as the most effective treatment strategy. Current literature suggests that bariatric surgery successfully decreases body weight and excess fat mass through targeting both variables of the energy homeostasis - energy intake and energy expenditure. Here we review current knowledge on changes in caloric consumption, an important arm in the energy balance equation, in rodent models of bariatric surgery. In particular, circadian feeding dynamics, post-surgical caloric intake at both "rapid weight loss" phase and "weight maintenance" phase, as well as meal pattern analysis will be the subject of this review. Considering that different types of bariatric surgery may trigger differential energy intake dynamics resulting in variable weight loss outcomes, the effects of most popular surgeries - vertical sleeve gastrectomy (VSG), Roux-en-Y gastric bypass (RYGB), and gastric banding (GB) - are elaborated. Potential candidate mechanisms underlying alterations in food intake and meal patterns following different bariatric procedures are briefly discussed at the end.