Intestinal Adaptations after Bariatric Surgery: Consequences on Glucose Homeostasis

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.

Ten-Year Results of Laparoscopic Sleeve Gastrectomy: a Retrospectively Designed Study of a Single Tertiary Center

PURPOSE

Laparoscopic sleeve gastrectomy (SG) is the most popular bariatric surgery. Nonetheless, only a few studies have reported its long-term outcomes. This study aimed to evaluate changes in weight and body mass index (BMI) parameters, resolution of comorbidities, and frequency of re-operations in a follow-up period of at least 10 years.

MATERIALS AND METHODS

Data was available from 180 patients' records who underwent SG between 2008 and 2011 in the Tel Aviv Sourasky Medical Center. Eighty patients agreed to partake in a follow-up assessment that was completed via a phone call questionnaire and hospital computed registry.

RESULTS

Patients' mean preoperative BMI was 43.86 ± 6.36 kg/m² which was significantly higher when compared to mean nadir BMI and last follow-up BMI (29.44 ± 7.12 and 36.34 ± 9.7; p < 0.001). Mean percentage of excess weight loss (%EWL) at 10 years was 42.65 ± 36.02% and mean percentage of total weight loss was 19.33 ± 16.73%. Twenty-eight patients (35%) maintained at least 50% EWL. Twenty-seven (33.75%) patients underwent at least one surgical procedure following SG. Eleven patients (13.75%) underwent a conversion to Roux-en-Y gastric bypass and six patients (7.5%) underwent conversion to one anastomosis gastric bypass. Resolution of type 2 diabetes (T2D), hypertension, and hypercholesterolemia occurred in 47%, 43.7%, and 48.4%, respectively. De-novo cases of gastroesophageal reflux (GERD) were present in 40%.

CONCLUSION

SG shows high long-term failure rates. One of every three patients will undergo another surgical procedure within a 10-year period.

Duodenal Mucosa: A New Target for the Treatment of Type 2 Diabetes

OBJECTIVE

After a high-fat and high-sugar diet, the duodenal mucosa of rodents proliferate and trigger the signal of insulin resistance, which may be the cause of type 2 diabetes (T2D). In response to this phenomenon, researchers have designed the duodenal mucosal resurfacing (DMR) procedure, mainly through the hydrothermal ablation procedure, to restore the normal mucosal surface, thereby correcting this abnormal metabolic signal. This article aims to understand the changes in duodenum before and after the onset or treatment of T2D, and the potential mechanisms of DMR procedure.

METHODS

A literature search of PubMed and Web of Science was conducted using appropriate keywords.

RESULTS

Both animal and clinical studies have shown that the villus thickness, intestinal cells, glucose transporters, enteric nerves, and gut microbiota and their metabolites in the duodenum undergo corresponding changes before and after the onset or treatment of T2D. These changes may be related to the pathogenesis of T2D. DMR procedure may produce beneficial glycemic and hepatic metabolic effects by regulating these changes.

CONCLUSION

The duodenum is an important metabolic signaling center, and limiting nutrient exposure to this critical region will have powerful metabolic benefits. The DMR procedure may regulate glycemic and hepatic parameters through various mechanisms, which needs to be further confirmed by a large number of animal and clinical studies.

Serum glucose excretion after Roux-en-Y gastric bypass: a potential target for diabetes treatment

OBJECTIVE

The mechanisms underlying type 2 diabetes resolution after Roux-en-Y gastric bypass (RYGB) are unclear. We suspected that glucose excretion may occur in the small bowel based on observations in humans. The aim of this study was to evaluate the mechanisms underlying serum glucose excretion in the small intestine and its contribution to glucose homeostasis after bariatric surgery.

DESIGN

2-Deoxy-2-[¹⁸F]-fluoro-D-glucose (FDG) was measured in RYGB-operated or sham-operated obese diabetic rats. Altered glucose metabolism was targeted and RNA sequencing was performed in areas of high or low FDG uptake in the ileum or common limb. Intestinal glucose metabolism and excretion were confirmed using ¹⁴C-glucose and FDG. Increased glucose metabolism was evaluated in IEC-18 cells and mouse intestinal organoids. Obese or ob/ob mice were treated with amphiregulin (AREG) to correlate intestinal glycolysis changes with changes in serum glucose homeostasis.

RESULTS

The AREG/EGFR/mTOR/AKT/GLUT1 signal transduction pathway was activated in areas of increased glycolysis and intestinal glucose excretion in RYGB-operated rats. Intraluminal GLUT1 inhibitor administration offset improved glucose homeostasis in RYGB-operated rats. AREG-induced signal transduction pathway was confirmed using IEC-18 cells and mouse organoids, resulting in a greater capacity for glucose uptake via GLUT1 overexpression and sequestration in apical and basolateral membranes. Systemic and local AREG administration increased GLUT1 expression and small intestinal membrane translocation and prevented hyperglycaemic exacerbation.

CONCLUSION

Bariatric surgery or AREG administration induces apical and basolateral membrane GLUT1 expression in the small intestinal enterocytes, resulting in increased serum glucose excretion in the gut lumen. Our findings suggest a novel, potentially targetable glucose homeostatic mechanism in the small intestine.

Effect of Roux-en-Y gastric bypass on the pharmacokinetic-pharmacodynamic relationships of liquid and controlled-release formulations of oxycodone

The physiological changes following Roux-en-Y gastric bypass (RYGB) surgery may impact drug release from mechanistically different controlled-release tablets, making generic substitution inappropriate. This study aimed to characterise the pharmacokinetic-pharmacodynamic relationships of oxycodone from a lipid-based and water-swellable controlled-release tablet in RYGB patients. Twenty RYGB patients received 10-mg oral solution oxycodone or 20-mg controlled-release (water-swellable or lipid-based) oxycodone in a three-way, randomised, semiblinded and cross-over study. Blood sampling and pupillary recordings were conducted over a 24-h period. A previously established pharmacokinetic-pharmacodynamic model of these three formulations in healthy volunteers was used in the analysis as a reference model. No differences in absorption kinetics were seen between controlled-release formulations in patients. However, the absorption lag time was 11.5 min in patients vs 14 min in healthy volunteers for controlled-release tablets (P < 0.001). Furthermore, oral bioavailability was 14.4% higher in patients compared to healthy volunteers regardless of formulation type (P < 0.001). Oxycodone pharmacodynamics were not significantly affected by formulation or patient status. However, baseline pupil diameter was inversely correlated with age (P < 0.001) and plasma concentrations of oxycodone at half-maximum effect were 31% lower in males compared to females (P < 0.05). Generic substitution of monophasic lipid-based and water-swellable controlled-release oxycodone tablets may be considered safe in RYGB patients.

One-anastomosis gastric bypass (OAGB) in patients with BMI < 30 kg/m2 and diabetes mellitus type 2 (DM2)

INTRODUCTION

type-2 diabetes mellitus (DM2) is a major health problem, as it leads to increased morbidity and mortality. Metabolic surgery has shown good results in glycemic control; however, its use has not become popular.

OBJECTIVES

to evaluate DM2 remission, as well as changes in body mass index (BMI), in overweight diabetic patients after undergoing metabolic surgery.

METHODS

a retrospective review was carried out of all patients with DM2 and BMI between 25 and 29.9 kg/m2 who underwent laparoscopic one-anastomosis gastric bypass (OAGB) as metabolic procedure between 2016 and 2019.

RESULTS

a total of 15 patients were included with a mean age of 46.6 ± 11.25 years. Mean BMI was 28.41 ± 0.94 kg/m2. Average duration was 5.4 ± 2.79 years, and presurgical fasting glucose was 288.53 ± 65.22 mg/dL. Preoperative glycated hemoglobin (HbA1c) was 9.58 ± 1.66 %. Two years after surgery HbA1c was 5.21 ± 0.26 %. The remission rate of DM2 was 100 %. All patients maintained a normal BMI range.

CONCLUSIONS

OAGB is a valid alternative for complete DM2 remission no matter if it is not accompanied by some degree of obesity, since in this case the length of the biliopancreatic limb and common channel is modified to make a less malabsorptive procedure.

Pharmacokinetics of oral levonorgestrel and ethinylestradiol in women after Roux-en-Y gastric bypass surgery

BACKGROUND

Most patients undergoing Roux-en-Y gastric bypass (RYGB) are women in reproductive age. It is not known if bariatric surgery affects the pharmacokinetics of oral contraceptives.

OBJECTIVES

The primary objective was to evaluate ethinylestradiol (EE) and levonorgestrel (LNG) absorption in women undergoing RYGB, compared with nonoperated controls matched by age and body mass index (BMI). A secondary objective was to assess whether the time since surgery and BMI in the postoperative period influenced the absorption parameters.

SETTING

University hospital, Brazil.

METHODS

This study was designed to compare the maximum plasma concentration (Cmax), the time to the peak plasma level (Tmax), the area under the curve (AUC0-8 and AUC0-∞) after a single dose of a combined oral contraceptive with 0.03 mg EE and 0.15 mg LNG among 20 women after RYGB and 20 controls. Blood samples were obtained for 8 hours.

RESULTS

The mean LNG AUC0-8 and LNG AUC0-∞ were higher in RYGB group (P = .048 and P = .004, respectively). We found a positive correlation for LNG AUC0-8 (P = .045) and AUC0-∞ (P = .004) and the time since surgery, and we found a negative correlation for LNG Cmax (P = .018), AUC0-8 (P = .003), and AUC0-∞ (P = .001) and BMI.

CONCLUSION

No significant differences were found in oral EE pharmacokinetics. The operated group showed higher mean LNG AUC0-8 and AUC0-∞ but it was not considered clinically significant. The present study suggests that RYGB may not affect EE and LNG absorption.

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.

Intestinal sodium/glucose cotransporter 3 expression is epithelial and downregulated in obesity

AIM

We aimed to determine whether the sodium/glucose cotransporter family member SGLT3, a proposed glucose sensor, is expressed in the intestine and/or kidney, and if its expression is altered in mouse models of obesity and in humans before and after weight-loss surgery.

MAIN METHODS

We used in-situ hybridization and quantitative PCR to determine whether the Sglt3 isoforms 3a and 3b were expressed in the intestine and kidney of C57, leptin-deficient ob/ob, and diabetic BTBR ob/ob mice. Western blotting and immunohistochemistry were also used to assess SGLT3 protein levels in jejunal biopsies from obese patients before and after weight-loss Roux-en-Y gastric bypass surgery (RYGB), and in lean healthy controls.

KEY FINDINGS

Sglt3a/3b mRNA was detected in the small intestine (duodenum, jejunum and ileum), but not in the large intestine or kidneys of mice. Both isoforms were detected in epithelial cells (confirmed using intestinal organoids). Expression of Sglt3a/3b mRNA in duodenum and jejunum was significantly lower in ob/ob and BTBR ob/ob mice than in normal-weight littermates. Jejunal SGLT3 protein levels in aged obese patients before RYGB were lower than in lean individuals, but substantially upregulated 6 months post-RYGB.

SIGNIFICANCE

Our study shows that Sglt3a/3b is expressed primarily in epithelial cells of the small intestine in mice. Furthermore, we observed an association between intestinal mRNA Sglt3a/3b expression and obesity in mice, and between jejunal SGLT3 protein levels and obesity in humans. Further studies are required to determine the possible role of SGLT3 in obesity.

Glucose Homeostasis, Fetal Growth and Gestational Diabetes Mellitus in Pregnancy after Bariatric Surgery: A Scoping Review

Background: Pregnancies in women with a history of bariatric surgery are becoming increasingly prevalent. Surgically induced metabolic changes benefit mother and child, but can also lead to some adverse pregnancy outcomes. Knowledge about glucose homeostasis in these pregnancies could elucidate some of the mechanisms behind these outcomes. This review focusses on glucose homeostasis and birth weight. Methods: We considered papers dealing with glucose homeostasis, gestational diabetes mellitus (GDM) and/or small-for-gestational age infants (SGA) in pregnancies with a history of sleeve gastrectomy (SG) or Roux-en-y gastric bypass (RYGB). Results: Since an OGTT is unreliable to diagnose GDM in a pregnancy after bariatric surgery, the true incidence of GDM is unknown. Alternative screening strategies are needed. Furthermore, these pregnancies are marked by frequent hypoglycemic events as well as wide and rapid glycemic excursions, an issue that is very likely underreported. There is a lack of uniformity in reporting key outcomes and a large variation in study design and control population. Conclusion: Alteration of glucose homeostasis in a pregnancy after bariatric surgery should be further studied using unequivocal definition of key concepts. Glycemic control may prove to be a modifiable risk factor for adverse pregnancy outcomes such as the delivery of an SGA baby.

Short Bowel Syndrome: A Paradigm for Intestinal Adaptation to Nutrition?

Short bowel syndrome (SBS) is a rare disease that results from extensive resection of the intestine. When the remaining absorption surface of the intestine cannot absorb enough macronutrients, micronutrients, and water, SBS results in intestinal failure (IF). Patients with SBS who suffer from IF require parenteral nutrition for survival, but long-term parenteral nutrition may lead to complications such as catheter sepsis and metabolic diseases. Spontaneous intestinal adaptation occurs weeks to months after resection, resulting in hyperplasia of the remnant gut, modification of gut hormone levels, dysbiosis, and hyperphagia. Oral nutrition and presence of the colon are two major positive drivers for this adaptation. This review aims to summarize the current knowledge of the mechanisms underlying spontaneous intestinal adaptation, particularly in response to modifications of luminal content, including nutrients. In the future, dietary manipulations could be used to treat SBS.

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.

Intestinal plasticity in response to nutrition and gastrointestinal surgery

The plasticity of a material corresponds to its capacity to change its feature under the effect of an external action. Intestinal plasticity could be defined as the ability of the intestine to modify its size or thickness and intestinal cells to modulate their absorption and secretion functions in response to external or internal cues/signals. This review will focus on intestinal adaptation mechanisms in response to diet and nutritional status. These physiological mechanisms allow a fine and rapid adaptation of the gut to promote absorption of ingested food, but they can also lead to obesity in response to overnutrition. This plasticity could thus become a therapeutic target to treat not only undernutrition but also obesity. How the intestine adapts in response to 2 types of surgical remodeling of the digestive tract-extensive bowel resection leading to intestinal failure and surgical treatment of pathological obesity (ie, bariatric surgeries)-will also be reviewed.

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.

Intestinal Glucose Absorption Was Reduced by Vertical Sleeve Gastrectomy via Decreased Gastric Leptin Secretion

BACKGROUND

The unique effects of gastric resection after vertical sleeve gastrectomy (VSG) on type 2 diabetes mellitus remain unclear. This work aimed to investigate the effects of VSG on gastric leptin expression and intestinal glucose absorption in high-fat diet-induced obesity.

METHODS

Male C57BL/6J mice were fed a high-fat diet (HFD) to induce obesity. HFD mice were randomized into VSG and sham-operation groups, and the relevant parameters were measured at 8 weeks postoperation.

RESULTS

Higher gastric leptin expression and increased intestinal glucose transport were observed in the HFD mice. Furthermore, VSG reduced gastric leptin expression and the intestinal absorption of alimentary glucose. Both exogenous leptin replenishment during the oral glucose tolerance test (OGTT) and the addition of leptin into the everted isolated jejunum loops in vitro restored the glucose transport capacity in VSG-operated mice, and this effect was abolished when the glucose transporter GLUT2 was blocked with phloretin. Moreover, phloretin almost completely suppressed glucose transport in the HFD mice. Intestinal immunohistochemistry in the obese mice showed increased GLUT2 and diminished sodium glucose co-transporter 1 (SGLT-1) in the apical membrane of enterocytes. Decreased GLUT2 and enhanced SGLT1 were observed following VSG. VSG also reduced the phosphorylation status of protein kinase C isoenzyme β II (PKCβ II) in the jejunum, which was stimulated by the combination of leptin and glucose.

CONCLUSION

Our data demonstrated that the decreased secretion of gastric leptin in VSG results in a decrease in intestinal glucose absorption via modulation of GLUT2 translocation.

Importance of the gastrointestinal tract in type 2 diabetes. Metabolic surgery is more than just incretin effect

Bariatric and metabolic surgery is creating new concepts about how the intestine assimilates food. Recent studies highlight the role of the gastrointestinal tract in the genesis and evolution of type 2 diabetes. This article has been written to answer frequent questions about metabolic surgery results and the mechanisms of action. For this purpose, a non-systematic search of different databases was carried out, identifying articles published in the last decade referring to the mechanisms of action of metabolic techniques. Understanding these mechanisms will help grasp why some surgeries are more effective than others and why the results can be so disparate among patients undergoing the same surgical approach.

Enhancing enterocyte fatty acid oxidation in mice affects glycemic control depending on dietary fat

Studies indicate that modulating enterocyte metabolism might affect whole body glucose homeostasis and the development of diet-induced obesity (DIO). We tested whether enhancing enterocyte fatty acid oxidation (FAO) could protect mice from DIO and impaired glycemic control. To this end, we used mice expressing a mutant form of carnitine palmitoyltransferase-1a (CPT1mt), insensitive to inhibition by malonyl-CoA, in their enterocytes (iCPT1mt) and fed them low-fat control diet (CD) or high-fat diet (HFD) chronically. CPT1mt expression led to an upregulation of FAO in the enterocytes. On CD, iCPT1mt mice had impaired glycemic control and showed concomitant activation of lipogenesis, glycolysis and gluconeogenesis in their enterocytes. On HFD, both iCPT1mt and control mice developed DIO, but iCPT1mt mice showed improved glycemic control and reduced visceral fat mass. Together these data indicate that modulating enterocyte metabolism in iCPT1mt mice affects glycemic control in a body weight-independent, but dietary fat-dependent manner.

Bariatric surgery and gene expression in the gut

PURPOSE OF REVIEW

The current review provides an overview of recent literature on new findings related to bariatric surgery and gut gene expression.

RECENT FINDINGS

Bariatric surgery modulates the expression of intestinal genes. Experimental and clinical investigations have demonstrated the association of gut rearrangement with changes in intestinal expression of genes related to glucose metabolism. Recent data suggest that bariatric surgery also affects expression of genes belonging to other pathways, including nutrient transporters and metabolism of vitamin B12, decreasing pathway-encoding genes that may contribute to vitamin B12 deficiency in the postoperative period.

SUMMARY

Bariatric surgery is an effective intervention strategy against severe obesity, resulting in sustained weight loss and reduction of comorbidities. Nutritional genomic changes appear in response to bariatric surgery, possibly due to adaptive gut response. Improved understanding of the molecular pathways modulated by this intervention may facilitate weight and comorbidities management.

Surgical treatment of obesity

Obesity prevalence continues to increase worldwide, as do the numerous chronic diseases associated with obesity, including diabetes, non-alcoholic fatty liver disease, dyslipidemia, and hypertension. The prevalence of bariatric surgery also continues to increase and remains the most effective and sustainable treatment for obesity. Over the last several years, numerous prospective and longitudinal studies have demonstrated the benefits of bariatric surgery on weight loss, mortality, and other chronic diseases. Even though the mechanisms underlying many of these beneficial effects remain poorly understood, surgical management of obesity continues to increase given its unmatched efficacy. In this commentary, we discuss recent clinical advancements as well as several areas needed for future research, including indications for bariatric and metabolic surgery, determination of responders and non-responders, metabolic surgery in non-obese individuals, and the evolving role of bariatric surgery in adolescents.

Gut as an emerging organ for the treatment of diabetes: focus on mechanism of action of bariatric and endoscopic interventions

Increasing worldwide prevalence of type 2 diabetes mellitus and its accompanying pathologies such as obesity, arterial hypertension and dyslipidemia represents one of the most important challenges of current medicine. Despite intensive efforts, high percentage of patients with type 2 diabetes does not achieve treatment goals and struggle with increasing body weight and poor glucose control. While novel classes of antidiabetic medications such as incretin-based therapies and gliflozins have some favorable characteristics compared to older antidiabetics, the only therapeutic option shown to substantially modify the progression of diabetes or to achieve its remission is bariatric surgery. Its efficacy in the treatment of diabetes is well established, but the exact underlying modes of action are still only partially described. They include restriction of food amount, enhanced passage of chymus into distal part of small intestine with subsequent modification of gastrointestinal hormones and bile acids secretion, neural mechanisms, changes in gut microbiota and many other possible mechanisms underscoring the importance of the gut in the regulation of glucose metabolism. In addition to bariatric surgery, less-invasive endoscopic methods based on the principles of bariatric surgery were introduced and showed promising results. This review highlights the role of the intestine in the regulation of glucose homeostasis focusing on the mechanisms of action of bariatric and especially endoscopic methods of the treatment of diabetes. A better understanding of these mechanisms may lead to less invasive endoscopic treatments of diabetes and obesity that may complement and widen current therapeutic options.

Nutrient re-routing and altered gut-islet cell crosstalk may explain early relief of severe postprandial hypoglycaemia after reversal of Roux-en-Y gastric bypass

BACKGROUND

Roux-en-Y gastric bypass is associated with an increased risk of postprandial hyperinsulinaemic hypoglycaemia, but the underlying pathophysiology remains poorly understood. We therefore examined the effect of re-routing of nutrient delivery on gut-islet cell crosstalk in a person with severe postprandial hypoglycaemia after Roux-en-Y gastric bypass.

CASE REPORT

A person with severe postprandial hypoglycaemia, who underwent surgical reversal of Roux-en-Y gastric bypass, was studied before reversal and at 2 weeks and 3 months after reversal surgery using liquid mixed meal tests and hyperinsulinaemic-euglycaemic clamps. The nadir of postprandial plasma glucose rose from 2.8 mmol/l to 4.1 mmol/l at 2 weeks and to 4.4 mmol/l at 3 months after reversal. Concomitant insulin- and glucagon-like peptide-1 secretion (peak concentrations and area under the curve) clearly decreased after reversal, while concentrations of glucose-dependent insulinotropic polypeptide and ghrelin increased. Insulin clearance declined after reversal, whereas clamp-estimated peripheral insulin sensitivity was unchanged. The person remained without symptoms of hypoglycaemia, but had experienced significant weight gain at 15-month follow-up.

DISCUSSION

Accelerated nutrient absorption may be a driving force behind postprandial hyperinsulinaemic hypoglycaemia after Roux-en-Y gastric bypass. Re-routing of nutrients by reversal of the Roux-en-Y gastric bypass diminished postprandial plasma glucose excursions, alleviated postprandial insulin and glucagon-like peptide-1 hypersecretion and eliminated postprandial hypoglycaemia, which emphasizes the importance of altered gut-islet cell crosstalk for glucose metabolism after Roux-en-Y gastric bypass.

Potential Hormone Mechanisms of Bariatric Surgery

PURPOSE OF REVIEW

In recent years, the role of the gastrointestinal (GI) tract in energy homeostasis through modulation of the digestion and absorption of carbohydrates and the production of incretin hormones is well recognized.

RECENT FINDINGS

Bariatric surgery for obesity has been a very effective method in substantially improving weight, and numerous studies have focused on intestinal adaptation after bariatric procedures. A number of structural and functional changes in the GI tract have been reported postsurgery, which could be responsible for the altered hormonal responses. Furthermore, the change in food absorption rate and the intestinal regions exposed to carbohydrates may affect blood glucose response. This review hopes to give new insights into the direct role of gut hormones, by summarising the metabolic effects of bariatric surgery.