Bile Routing Modification Reproduces Key Features of Gastric Bypass in Rat

Ileum excision partially reverses improvement of glucose metabolism in diabetic rats after biliopancreatic diversion with duodenal switch

BACKGROUND

Bile acids can stimulate the secretion of glucagon-like peptide-1 (GLP-1) and be mostly reabsorbed in the ileum.

OBJECTIVES

We aimed to investigate whether ileum excision could reverse the glucose improvement after biliopancreatic diversion with duodenal switch (BPD/DS).

SETTING

Peking Union Medical College Hospital.

METHODS

Thirty diabetic rats were randomly divided into the BPD/DS group, BPD/DS plus ileectomy (BDI) group, and control group. The fasting blood glucose, bile acids, and glucagon-like peptide-1(GLP-1) levels in plasma samples were analyzed.

RESULTS

In postoperative week 20, the fasting blood glucose level in the BDI group was significantly higher than that in the BPD/DS group (11.5 ± 1.4 mmol/L versus 7.6 ± 1.0 mmol/L, P < .001), and the AUCOGTT value was also significantly higher than that in the BPD/DS group (2186.1 ± 237.2 mmol/L·min versus 1551.2 ± 136.9 mmol/L·min, P < .001). The plasma level of bile acids in the BDI group was lower than that in the BPD/DS group (P = .012) and was not significantly different from that in the control group (P = .629). The plasma level of GLP-1 in the BDI group was lower than that in the BPD/DS group (P = .009) and was not significantly different from that in the control group (P = .530). Moreover, the intestinal TGR5 expression in the BDI group was significantly lower than that in the BPD/DS group (P < .001).

CONCLUSIONS

The results show that excision of the ileum can partially reverse the improvement in glucose metabolism after BPD/DS.

Farnesoid X receptor is inhibited after ileum transposition in diabetic rats: its hypoglycemic effect

Background: Aim to investigate bile acid profile changes and the Farnesoid X receptor (FXR) status after ileotransposition (IT), and reveal its possible hypoglycemic mechanism. Methods: Twenty male diabetic rats were randomly assigned into the IT group and the sham IT (SH) group. Bile acid profiles were measured using an ultra-performance liquid chromatography-tandem mass spectrometry. Glucose metabolism was monitored after oral administration of FXR inhibitor and agonist. And the expression of key FXR target genes were measured. Results: The levels of β-muricholic acid (P = 0.047), tauro-α-muricholic acid and tauro-β-muricholic acid (P < 0.001) in plasma in the IT group were higher than those in the SH group, and the levels of taurocholic acid (P = 0.049) and turoursodeoxycholic acid (P = 0.030) were lower than those in the SH group. After inhibition of intestinal FXR, the glucose metabolism in the SH group was improved. When FXR agonist was given, the blood glucose level was increased in both groups. After sacrifice, the levels of glycoursodeoxycholic acid, tauro-α-muricholic acid and tauro-β-muricholic acid in liver and ileum tissues were higher than those in the SH group (P < 0.05), the level of α- muricholic acid (P < 0.001) in liver tissues were lower than that in the SH group. Moreover, the expression of CYP7A1 mRNA (P < 0.001) and FGF15 mRNA (P = 0.001) in the IT group was significantly higher, and the expression of PEPCK mRNA (P = 0.004), SREPB1c mRNA (P = 0.005) and SRB1 mRNA (P = 0.001) were significantly lower than that in the SH group. Conclusions: We demonstrate a remarkable heterogeneity of BA profiles after IT, FXR activation might has a detrimental effect on glucose metabolism.

Duodenal-jejunal bypass reduces serum ceramides via inhibiting intestinal bile acid-farnesoid X receptor pathway

BACKGROUND

Bile acids play an important role in the amelioration of type 2 diabetes following duodenal-jejunal bypass (DJB). Serum bile acids are elevated postoperatively. However, the clinical relevance is not known. Bile acids in the peripheral circulation reflect the amount of bile acids in the gut. Therefore, a further investigation of luminal bile acids following DJB is of great significance.

AIM

To investigate changes of luminal bile acids following DJB.

METHODS

Salicylhydroxamic acid (SHAM), DJB, and DJB with oral chenodeoxycholic acid (CDCA) supplementation were performed in a high-fat-diet/streptozotocin-induced diabetic rat model. Body weight, energy intake, oral glucose tolerance test, luminal bile acids, serum ceramides and intestinal ceramide synthesis were analyzed at week 12 postoperatively.

RESULTS

Compared to SHAM, DJB achieved rapid and durable improvement in glucose tolerance and led to increased total luminal bile acid concentrations with preferentially increased proportion of farnesoid X receptor (FXR) - inhibitory bile acids within the common limb. Intestinal ceramide synthesis was repressed with decreased serum ceramides, and this phenomenon could be partially antagonized by luminal supplementation of FXR activating bile acid CDCA.

CONCLUSION

DJB significantly changes luminal bile acid composition with increased proportion FXR-inhibitory bile acids and reduces serum ceramide levels. There observations suggest a novel mechanism of bile acids in metabolic regulation after DJB.

Metabolomic signatures after bariatric surgery - a systematic review

Metabolomics emerged as an important tool to gain insights on how the body responds to therapeutic interventions. Bariatric surgery is the most effective treatment for severe obesity and obesity-related co-morbidities. Our aim was to conduct a systematic review of the available data on metabolomics profiles that characterize patients submitted to different bariatric surgery procedures, which could be useful to predict clinical outcomes including weight loss and type 2 diabetes remission. For that, the Preferred Reporting Items for Systematic Reviews and Meta-Analyses - PRISMA guidelines were followed. Data from forty-seven original study reports addressing metabolomics profiles induced by bariatric surgery that met eligibility criteria were compiled and summarized. Amino acids, lipids, energy-related and gut microbiota-related were the metabolite classes most influenced by bariatric surgery. Among these, higher pre-operative levels of specific lipids including phospholipids, long-chain fatty acids and bile acids were associated with post-operative T2D remission. As conclusion, metabolite profiling could become a useful tool to predict long term response to different bariatric surgery procedures, allowing more personalized interventions and improved healthcare resources allocation.

A systematic review and meta-analyses of food preference modifications after bariatric surgery

This systematic review and meta-analyses aimed to synthesize evidence of the link between bariatric surgery and changes in food preferences, considering the method of assessment. MEDLINE, Cochrane Library, Web of Science, Cinahl, PsychINFO, ProQuest, and Open grey were searched incorporating two blocks of terms ("Intervention" and "Food Preferences"). Interventional or observational studies involving patients (BMI ≥ 35 kg m^-2 ) with sleeve gastrectomy (SG) or Roux-en-Y Gastric Bypass (RYGB) and a control group were included. Meta-analyses were performed comparing the standardized daily mean percentage energy from proteins, carbohydrates, and lipids between preoperative and postoperative patients. Fifty-seven studies concerning 2,271 patients with RYGB and 903 patients with SG met the inclusion criteria, of which 24 were eligible for meta-analysis. Despite a total reduction in macronutrient intakes, the meta-analyses revealed a postoperative increase in percentage energy from proteins at 12 months (0.24, 95% CI: 0.03, 0.46, {I² } = 73%) and a decrease in percentage energy from fat at 1 month (-0.47, 95% CI: 0.86, 0.09, {I² } = 72%), up to 24 months (-0.20, 95% CI: -0.31, 0.08, {I² } = 0%). In conclusion, the present systematic review and meta-analyses showed changes of food preferences in terms of macronutrient, food selection and, overall food appreciation up to 5 years following bariatric surgery.

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.

Liver gene transfection by retrograde intrabiliary infusion facilitated by temporary biliary obstruction

BACKGROUND

The hepatobiliary tract may be a valuable administration site for gene delivery. We demonstrated the role of temporary biliary obstruction for gene transfection by retrograde intrabiliary infusion.

METHODS

Male Sprague-Dawley rats received intrabiliary infusion of luciferase plasmid via an artificial common bile duct, with temporary biliary obstruction for 0 minutes (NO group), 30 minutes (30 min group) and 24 hours (24 h group), respectively (n = 4 for each group). Gene expression levels were evaluated by luciferase bioluminescence on postoperative days (POD) 1, 2 and 7. Serum and livers were collected on POD 1 and 14 for liver biochemistry, hematoxylin and eosin staining, and immunohistochemistry.

RESULTS

On POD 1, luciferase chemoluminescence was significantly higher in the 24 h group than in the NO group (p = 0.002) and the 30 min group (p = 0.002). However, it decreased rapidly after reversal of the obstruction in the 24 h group (POD 1 versus POD 2, p = 0.002; POD 1 versus POD 7, p = 0.002). Liver biochemistry was changed on POD 1, but no significant differences were detected after 14 days of recovery (p > 0.05). Similar histological changes were found in the three groups, with no unwanted proliferation of biliary epithelial cells. The obstruction did not cause serious liver damage.

CONCLUSIONS

Temporary biliary obstruction for 24 hours facilitated the safe, feasible and effective transfection of plasmid DNA into the liver via the hepatobiliary tract. In the future, endoscopic retrograde cholangiopancreatography and its dilation balloon could be used to create biliary obstruction and allow the direct gene delivery into the liver. More research is necessary for achieving stable gene expression, as well as in terms of weighing its benefits against potential complications.

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.

Increased Bile Acid Signals After Duodenal-Jejunal Bypass Improve Non-alcoholic Steatohepatitis (NASH) in a Rodent Model of Diet-Induced NASH

BACKGROUND

The increasing incidence of non-alcoholic steatohepatitis (NASH) has resulted in it becoming a common cause of liver-related mortality; however, no efficient treatment has been established. It has been reported that bariatric surgery improves metabolic comorbidities, such as diabetes mellitus and NASH. Although the mechanism is unclear, it is thought that the changes in bile acid (BA) signaling via its nuclear receptor, farnesoid X receptor (FXR), produce various metabolic effects. We sought to investigate the effects and mechanisms of bariatric surgery on NASH improvement.

METHODS

Male Sprague-Dawley rats were fed by a high-fat and high-fructose diet, which results in obesity, insulin resistance, and NASH. Rats underwent duodenal-jejunal bypass (DJB), which is a main component of bariatric procedures. The liver pathological findings and the expression level of mRNA of FXR were investigated. The plasma BA level was measured in peripheral and portal vein blood.

RESULTS

DJB suppressed weight gain, improved insulin resistance, and ameliorated NASH mainly in a point of inflammation. The plasma BA level along with the expression of FXR and its target transcriptional factor, small heterodimer partner (SHP), in the liver were elevated.

CONCLUSIONS

DJB has a direct effect on NASH improvement, and there is a possibility that an anti-inflammatory effect is functioning as a part of the mechanism. The increase of plasma bile acid level followed by the stimulation of FXR signaling may contribute to this phenomenon.

Bile acid changes after metabolic surgery are linked to improvement in insulin sensitivity

Background

Metabolic surgery is associated with a prompt improvement in insulin resistance, although the mechanism of action remains unknown. The literature on bile acid changes after metabolic surgery is conflicting, and insulin sensitivity is generally assessed by indirect methods. The aim of this study was to investigate the relationship between improvement in insulin sensitivity and concentration of circulating bile acids after biliopancreatic diversion (BPD) and Roux‐en‐Y gastric bypass (RYGB).

Methods

This was a prospective observational study of nine patients who underwent BPD and six who had RYGB. Inclusion criteria for participation were a BMI in excess of 40 kg/m², no previous diagnosis of type 2 diabetes and willingness to participate. Exclusion criteria were major endocrine diseases, malignancies and liver cirrhosis. Follow‐up visits were carried out after a mean(s.d.) of 185·3(72·9) days. Fasting plasma bile acids were assessed by ultra‐high‐performance liquid chromatography coupled with a triple quadrupole mass spectrometer, and insulin sensitivity was measured by means of a hyperinsulinaemic–euglycaemic clamp.

Results

A significant increase in all bile acids, as well as an amelioration of insulin sensitivity, was observed after metabolic surgery. An increase in conjugated secondary bile acids was significantly associated with an increase in insulin sensitivity. Only the increase in glycodeoxycholic acid was significantly associated with an increase in insulin sensitivity in analysis of individual conjugated secondary bile acids.

Conclusion

Glycodeoxycholic acid might drive the improved insulin sensitivity after metabolic surgery.

Bile Diversion Improves Metabolic Phenotype Dependent on Farnesoid X Receptor (FXR)

OBJECTIVE

The current study investigated whether bile diversion (BD) improves metabolic phenotype under farnesoid X receptor (FXR) deficiency.

METHODS

BD was performed in high-fat diet (HFD)-fed FXR knockout (FXRko) and wild-type (WT) animals. Metabolic phenotypes, circulating enteroendocrine hormones, total bile acids (BAs) and BA composition, and cecal gut microbiota were analyzed.

RESULTS

FXR-deficient mice were resistant to HFD-induced obesity; however, FXR-deficient mice also developed hyperglycemia and exhibited increased liver weight, liver steatosis, and circulating triglycerides. BD increased circulating total BAs and taurine-b-muricholic acid, which were in line with normalized hyperglycemia and improved glucose tolerance in HFD-fed WT mice. FXR deficiency also increased total BAs and taurine-b-muricholic acid, but these animals remained hyperglycemic. While BD improved metabolic phenotype in HFD-fed FXRko mice, these improvements were not as effective as in WT mice. BD increased liver expression of fibroblast growth factor 21 and peroxisome proliferator-activated receptor γ coactivator-1β and elevated circulating glucagon-like peptide-1 levels in WT mice but not in FXRko mice. FXR deficiency altered gut microbiota composition with a specific increase in phylum Proteobacteria that may act as a possible microbial signature of some diseases. These cellular and molecular changes in FXRko mice may contribute to resistance toward improved metabolism.

CONCLUSIONS

FXR signaling plays a pivotal role in improved metabolic phenotype following BD surgery.

Role of Bile Acids in Bariatric Surgery

Bariatric surgery has been proved to be effective and sustainable in the long-term weight-loss and remission of metabolic disorders. However, the underlying mechanisms are still far from fully elucidated. After bariatric surgery, the gastrointestinal tract is manipulated, either anatomically or functionally, leading to changed bile acid metabolism. Accumulating evidence has shown that bile acids play a role in metabolic regulation as signaling molecules other than digestive juice. And most of the metabolism-beneficial effects are mediated through nuclear receptor FXR and membrane receptor TGR5, as well as reciprocal influence on gut microbiota. Bile diversion procedure is also performed on animals to recapitulate the benefits of bariatric surgery. It appears that bile acid alteration is an important component of bariatric surgery, and represents a promising target for the management of metabolic disorders.

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.

Metabolic Effect of Foregut Exclusion Demonstrated by the Impact of Gastrogastric Fistula on Recurrence of Diabetes

BACKGROUND

Type 2 diabetes mellitus (T2DM) resolves in >80% of patients after Roux-en-Y gastric bypass (RYGB). It has been hypothesized that foregut exclusion is mechanistically important to this observation. This study aimed to determine whether gastrogastric (GG) fistula, with a loss of foregut exclusion, is associated with T2DM relapse, and to assess whether closure of GG fistula is associated with T2DM resolution.

STUDY DESIGN

A matched cohort study of patients who experienced T2DM remission after RYGB. Cases (patients with GG fistula) were matched to controls (patients without GG fistula) based on age, BMI, weight regain, and duration from RYGB. Primary end point was T2DM relapse. Time-to-event analysis was performed to identify an association between GG fistula and time to T2DM resolution.

RESULTS

One hundred and twenty-six patients (42 cases and 84 controls) were included. Cases experienced a higher rate of T2DM relapse than controls (48% vs 13%; odds ratio 18; p < 0.0001). On multivariable analysis, GG fistula remained a significant predictor of T2DM relapse after controlling for sex and insulin use (odds ratio 6.3; p = 0.02). Of the 42 cases, 20 experienced T2DM relapse, with 1 spontaneous resolution. Of 19, thirteen underwent fistula revision and experienced a higher rate of T2DM resolution than the nonrevision group (69% vs 0%; odds ratio 27; p = 0.036). Time to T2DM resolution was shorter in the revision group compared with the nonrevision group (p = 0.006).

CONCLUSIONS

The RYGB patients with GG fistula have a higher rate of T2DM relapse, compared with those without GG fistula with similar BMI and weight regain. Successful fistula revision is associated with resolution of T2DM.

Gastric Bypass-Related Effects on Glucose Control, β Cell Function and Morphology in the Obese Zucker Rat

BACKGROUND

Roux-en-Y gastric bypass (RYGB) may improve beta cell function by mechanisms other than caloric restriction and body weight loss. We aimed to assess the impact of anatomical and hormonal alterations specific to RYGB on glucose homeostasis, β cell function and morphology.

METHODS

Male Zucker(fa/fa) rats underwent either RYGB (n = 11) or sham surgeries (n = 10). Five of the shams were then food restricted and body weight matched (BWM) to the RYGB rats. Six male Zucker(fa/+) rats underwent sham surgery and served as additional lean controls. Twenty-seven days after surgery, an oral glucose tolerance test (OGTT) was performed and plasma levels of glucose, insulin and glucagon-like peptide-1 (GLP-1) were measured. Immunohistological analysis of pancreatic islets was performed, and GLP-1 receptor and PDX-1 mRNA content were quantified.

RESULTS

Shams consumed more food and gained more weight compared to both RYGB and BWM (p < 0.001). Hyperglycaemia was evident in ad libitum-fed shams, whilst postprandial glucose levels were lower in RYGB compared to the BWM sham group (p < 0.05). During the OGTT, RYGB rats responded with >2.5-fold increase of GLP-1. Histology revealed signs of islet degeneration in ad libitum-fed shams, but not in RYGB and sham BWM controls (p < 0.001). GLP-1 receptor and PDX-1 mRNA content was similar between the RYGB and BWM shams but higher compared to ad libitum shams (p < 0.05).

CONCLUSIONS

Combined molecular, cellular and histological analyses of pancreatic function suggest that weight loss alone, and not the enhancement of GLP-1 responses, is predominant for the short-term β cell protective effects of RYGB.

Bile acids in glucose metabolism in health and disease

Bile acids (BAs) are cholesterol-derived metabolites that facilitate the intestinal absorption and transport of dietary lipids. Recently, BAs also emerged as pivotal signaling molecules controlling glucose, lipid, and energy metabolism by binding to the nuclear hormone farnesoid X receptor (FXR) and Takeda G protein receptor 5 (TGR5) in multiple organs, leading to regulation of intestinal incretin secretion, hepatic gluconeogenesis, glycogen synthesis, energy expenditure, inflammation, and gut microbiome configuration. Alterations in BA metabolism and signaling are associated with obesity and type 2 diabetes mellitus (T2DM), whereas treatment of T2DM patients with BA sequestrants, or bariatric surgery in morbidly obese patients, results in a significant improvement in glycemic response that is associated with changes in the BA profile and signaling. Herein, we review the roles of BAs in glucose metabolism in health and disease; highlight the limitations, unknowns, and challenges in understanding the impact of BAs on the glycemic response; and discuss how this knowledge may be harnessed to develop innovative therapeutic approaches for the treatment of hyperglycemia and diabetes.

Bile acids and bariatric surgery

Bariatric surgery, specifically Roux-en-Y gastric bypass (RYGB) and vertical sleeve gastrectomy (VSG), are the most effective and durable treatments for morbid obesity and potentially a viable treatment for type 2 diabetes (T2D). The resolution rate of T2D following these procedures is between 40 and 80% and far surpasses that achieved by medical management alone. The molecular basis for this improvement is not entirely understood, but has been attributed in part to the altered enterohepatic circulation of bile acids. In this review we highlight how bile acids potentially contribute to improved lipid and glucose homeostasis, insulin sensitivity and energy expenditure after these procedures. The impact of altered bile acid levels in enterohepatic circulation is also associated with changes in gut microflora, which may further contribute to some of these beneficial effects. We highlight the beneficial effects of experimental surgical procedures in rodents that alter bile secretory flow without gastric restriction or altering nutrient flow. This information suggests a role for bile acids beyond dietary fat emulsification in altering whole body glucose and lipid metabolism strongly, and also suggests emerging roles for the activation of the bile acid receptors farnesoid x receptor (FXR) and G-protein coupled bile acid receptor (TGR5) in these improvements. The limitations of rodent studies and the current state of our understanding is reviewed and the potential effects of bile acids mediating the short- and long-term metabolic improvements after bariatric surgery is critically examined.

Bile Acid Control of Metabolism and Inflammation in Obesity, Type 2 Diabetes, Dyslipidemia, and Nonalcoholic Fatty Liver Disease

Bile acids are signaling molecules that coordinately regulate metabolism and inflammation via the nuclear farnesoid X receptor (FXR) and the Takeda G protein-coupled receptor 5 (TGR5). These receptors activate transcriptional networks and signaling cascades controlling the expression and activity of genes involved in bile acid, lipid and carbohydrate metabolism, energy expenditure, and inflammation by acting predominantly in enterohepatic tissues, but also in peripheral organs. In this review, we discuss the most recent findings on the inter-organ signaling and interplay with the gut microbiota of bile acids and their receptors in meta-inflammation, with a focus on their pathophysiologic roles in obesity, type 2 diabetes, dyslipidemia, and nonalcoholic steatohepatitis, and their potential therapeutic applications.

Gut microbial degradation of organophosphate insecticides-induces glucose intolerance via gluconeogenesis

BACKGROUND

Organophosphates are the most frequently and largely applied insecticide in the world due to their biodegradable nature. Gut microbes were shown to degrade organophosphates and cause intestinal dysfunction. The diabetogenic nature of organophosphates was recently reported but the underlying molecular mechanism is unclear. We aimed to understand the role of gut microbiota in organophosphate-induced hyperglycemia and to unravel the molecular mechanism behind this process.

RESULTS

Here we demonstrate a high prevalence of diabetes among people directly exposed to organophosphates in rural India (n = 3080). Correlation and linear regression analysis reveal a strong association between plasma organophosphate residues and HbA1c but no association with acetylcholine esterase was noticed. Chronic treatment of mice with organophosphate for 180 days confirms the induction of glucose intolerance with no significant change in acetylcholine esterase. Further fecal transplantation and culture transplantation experiments confirm the involvement of gut microbiota in organophosphate-induced glucose intolerance. Intestinal metatranscriptomic and host metabolomic analyses reveal that gut microbial organophosphate degradation produces short chain fatty acids like acetic acid, which induces gluconeogenesis and thereby accounts for glucose intolerance. Plasma organophosphate residues are positively correlated with fecal esterase activity and acetate level of human diabetes.

CONCLUSION

Collectively, our results implicate gluconeogenesis as the key mechanism behind organophosphate-induced hyperglycemia, mediated by the organophosphate-degrading potential of gut microbiota. This study reveals the gut microbiome-mediated diabetogenic nature of organophosphates and hence that the usage of these insecticides should be reconsidered.

Intestinal bile acid receptors are key regulators of glucose homeostasis

In addition to their well-known function as dietary lipid detergents, bile acids have emerged as important signalling molecules that regulate energy homeostasis. Recent studies have highlighted that disrupted bile acid metabolism is associated with metabolism disorders such as dyslipidaemia, intestinal chronic inflammatory diseases and obesity. In particular, type 2 diabetes (T2D) is associated with quantitative and qualitative modifications in bile acid metabolism. Bile acids bind and modulate the activity of transmembrane and nuclear receptors (NR). Among these receptors, the G-protein-coupled bile acid receptor 1 (TGR5) and the NR farnesoid X receptor (FXR) are implicated in the regulation of bile acid, lipid, glucose and energy homeostasis. The role of these receptors in the intestine in energy metabolism regulation has been recently highlighted. More precisely, recent studies have shown that FXR is important for glucose homeostasis in particular in metabolic disorders such as T2D and obesity. This review highlights the growing importance of the bile acid receptors TGR5 and FXR in the intestine as key regulators of glucose metabolism and their potential as therapeutic targets.

Activation of bile acid signaling improves metabolic phenotypes in high-fat diet-induced obese mice

The metabolic benefits induced by gastric bypass, currently the most effective treatment for morbid obesity, are associated with bile acid (BA) delivery to the distal intestine. However, mechanistic insights into BA signaling in the mediation of metabolic benefits remain an area of study. The bile diversion () mouse model, in which the gallbladder is anastomosed to the distal jejunum, was used to test the specific role of BA in the regulation of glucose and lipid homeostasis. Metabolic phenotype, including body weight and composition, glucose tolerance, energy expenditure, thermogenesis genes, total BA and BA composition in the circulation and portal vein, and gut microbiota were examined. BD improves the metabolic phenotype, which is in accord with increased circulating primary BAs and regulation of enterohormones. BD-induced hypertrophy of the proximal intestine in the absence of BA was reversed by BA oral gavage, but without influencing BD metabolic benefits. BD-enhanced energy expenditure was associated with elevated TGR5, D2, and thermogenic genes, including UCP1, PRDM16, PGC-1α, PGC-1β, and PDGFRα in epididymal white adipose tissue (WAT) and inguinal WAT, but not in brown adipose tissue. BD resulted in an altered gut microbiota profile (i.e., Firmicutes bacteria were decreased, Bacteroidetes were increased, and Akkermansia was positively correlated with higher levels of circulating primary BAs). Our study demonstrates that enhancement of BA signaling regulates glucose and lipid homeostasis, promotes thermogenesis, and modulates the gut microbiota, which collectively resulted in an improved metabolic phenotype.

Recent advances in metabolic and bariatric surgery

Obesity and its associated medical conditions continue to increase and add significant burden to patients, as well as health-care systems, worldwide. Bariatric surgery is the most effective treatment for severe obesity and its comorbidities, and resolution of diabetes is weight loss-independent in the case of some operations. Although these weight-independent effects are frequently described clinically, the mechanisms behind them are not well understood and remain an intense area of focus in the growing field of metabolic and bariatric surgery. Perceptions of the mechanisms responsible for the beneficial metabolic effects of metabolic/bariatric operations have shifted from being mostly restrictive and malabsorption over the last 10 to 15 years to being more neuro-hormonal in origin. In this review, we describe recent basic and clinical findings of the major clinical procedures (adjustable gastric banding, vertical sleeve gastrectomy, Roux-en-Y gastric bypass, and biliopancreatic diversion) as well as other experimental procedures (ileal interposition and bile diversion) that recapitulate many of the metabolic effects of these complex operations in a simpler fashion. As the role of bile acids and the gut microbiome on metabolism is becoming increasingly well described, their potential roles in these improvements following metabolic surgery are becoming better appreciated. Bile acid and gut microbiome changes, in light of recent developments, are discussed in the context of these surgical procedures, as well as their implications for future study.

Metabolic effects of bile acid sequestration: impact on cardiovascular risk factors

PURPOSE OF REVIEW

This article discusses the impact of bile acid sequestrants (BAS) on cardiovascular risk factors (CVRFs), on the basis of recent (pre)clinical studies assessing the metabolic impact of modulation of enterohepatic bile acid signaling via the bile acid receptors farnesoid X receptor (FXR) and Takeda G-protein-coupled receptor 5 (TGR5).

RECENT FINDINGS

BAS decrease low-density lipoprotein-cholesterol by stimulating de novo hepatic bile acid synthesis and lowering intestinal lipid absorption, and improve glucose homeostasis in type 2 diabetes mellitus, at least in part by increasing GLP-1 production, via intestinal TGR5- and FXR-dependent mechanisms. Intestinal and peripheral FXR and TGR5 modulation also affects peripheral tissues, which can contribute to the reduction of CVRFs.

SUMMARY

Bile acids are regulators of metabolism acting in an integrated interorgan manner via FXR and TGR5. Modulation of the bile acid pool size and composition, and selective interference with their receptors could, therefore, be a therapeutic approach to decrease CVRFs. Even though clinical cardiovascular outcome studies using BAS are still lacking, the existing data point to BAS as an efficacious pharmacological approach to reduce CVRFs.

Influence of Roux-en-Y gastric bypass on plasma bile acid profiles: a comparative study between rats, pigs and humans

BACKGROUND

Roux-en-Y gastric bypass (RYGBP) is the most widely used bariatric surgery procedure, which induces profound metabolic and physiological effects, such as substantial improvements in obesity, type 2 diabetes and their comorbidities. Increasing evidence identifies bile acids (BAs) as signaling molecules that contribute to the metabolic improvement after RYGBP. However, how and to what extent BAs mediate the metabolic effects of RYGBP still remains unclear and requires mechanism of action studies using preclinical models. In this study, we compared plasma BA profiles before and after RYGBP in two animal models, rats and pigs, with humans to evaluate their translational potential.

METHODS

Plasma BAs were profiled in rats, pigs and humans by liquid chromatography coupled with tandem mass spectrometry before and after RYGBP.

RESULTS

RYGBP increased baseline plasma total BA concentrations in humans and in the two animal models to a similar extent (∼3-fold increase), despite differences in presurgery BA levels and profiles between the models. However, qualitatively, RYGBP differently affected individual plasma BA species, with similar increases in some free species (cholic acid (CA), chenodeoxycholic acid (CDCA) and deoxycholic acid (DCA)), different increases in glyco-conjugated species depending on the model and globally no increase in tauro-conjugated species whatever the model.

CONCLUSIONS

The tested animal models share similar quantitative RYGBP-induced increases in peripheral blood BAs as humans, which render them useful for mechanistic studies. However, they also present qualitative differences in BA profiles, which may result in different signaling responses. Such differences need to be taken into account when translating results to humans.

Bile Diversion in Roux-en-Y Gastric Bypass Modulates Sodium-Dependent Glucose Intestinal Uptake

Gastro-intestinal exclusion by Roux-en-Y gastric bypass (RYGB) improves glucose metabolism, independent of weight loss. Although changes in intestinal bile trafficking have been shown to play a role, the underlying mechanisms are unclear. We performed RYGB in minipigs and showed that the intestinal uptake of ingested glucose is blunted in the bile-deprived alimentary limb (AL). Glucose uptake in the AL was restored by the addition of bile, and this effect was abolished when active glucose intestinal transport was blocked with phlorizin. Sodium-glucose cotransporter 1 remained expressed in the AL, while intraluminal sodium content was markedly decreased. Adding sodium to the AL had the same effect as bile on glucose uptake. It also increased postprandial blood glucose response in conscious minipigs following RYGB. The decrease in intestinal uptake of glucose after RYGB was confirmed in humans. Our results demonstrate that bile diversion affects postprandial glucose metabolism by modulating sodium-glucose intestinal cotransport.

Reconfiguration of the small intestine and diabetes remitting effects of Roux-en-Y gastric bypass surgery

PURPOSE OF REVIEW

Alterations in small intestinal physiology are proposed to play a causative role in the beneficial impact of Roux-en-Y gastric bypass on type 2 diabetes mellitus. The present article describes the key proposed mechanisms implicated with an emphasis on some of the newer findings in the field.

RECENT FINDINGS

Augmented incretin and diminished anti-incretin effects postsurgery are explored and a model proposed that reconciles the hindgut and foregut hypotheses of improved glycaemic control as being complementary rather than mutually exclusive. Synthesis of recent findings on postbypass changes in intestinal glucose handling then follows. Finally an updated view of the role of distal bile diversion and changes in the microbiota on enteroendocrine signalling is presented.

SUMMARY

A series of nonmutually exclusive changes in small intestinal physiology likely make a significant contribution to improved glycaemic control postgastric bypass. Longitudinal data indicate that these effects do not translate into a long-term cure. A number of surgery-induced changes, however, are amenable to device-based and pharmacology-based mimicry, and this is an area for prioritization of future research focus.

The Influence of Bariatric Surgery on Serum Bile Acids in Humans and Potential Metabolic and Hormonal Implications: a Systematic Review

Recent research suggests a mechanistic role for bile acids (BA) in the metabolic improvement following bariatric surgery. It is believed that the hormonal and metabolic effects associated with changes in systemic BAs may be related to the farnesoid X receptor (FXR) and a G-protein coupled receptor (TGR5). This systematic review examines changes in systemic BAs following bariatric procedures. Studies were included if they reported the measurement of systemic BAs in humans at at least one time point after bariatric surgery. Eleven papers were identified that met the inclusion criteria. Seven studies reported the effect of Roux-en-Y gastric bypass (RYGB) on fasting BAs. The majority (6/7) reported that fasting BAs increased after RYGB. Data regarding fasting BAs after vertical sleeve gastrectomy (VSG) and laparoscopic gastric banding (LAGB) are inconsistent. Data regarding post-prandial BA changes after RYGB, VSG, and LAGB are also inconsistent. More research is needed to investigate the connection between BAs and the metabolic improvement seen after bariatric surgery.

Transforming a Biliopancreatic Derivation in an Ileal Interposition with a Single Anastomosis

The biliopancreatic derivation (BPD) is the most powerful bariatric procedure. However, it never became a very popular procedure, except for Italy, because of the high rate of nutritional problems, intense flatulence, and diarrhea. Here, we describe an extremely simple way (just one anastomosis) to revise the BPD, transforming it into an ileal interposition with duodenal exclusion, solving these described problems.

Weight Loss and the Prevention and Treatment of Type 2 Diabetes Using Lifestyle Therapy, Pharmacotherapy, and Bariatric Surgery: Mechanisms of Action

Weight loss, whether achieved by lifestyle intervention, pharmacotherapy, or bariatric surgery, is highly effective as a primary interventional strategy in both the prevention and treatment of type 2 diabetes. In high-risk patients with prediabetes and/or metabolic syndrome, weight loss effectively prevents progression to type 2 diabetes mellitus (T2DM) and improves cardiovascular risk factors. These benefits are the result of improvements in insulin resistance, which is central to the pathophysiology of cardiometabolic disease. In patients with T2DM, weight loss improves glycemia, while reducing the need for conventional glucose-lowering medicines, by affecting all three processes that produce and sustain the hyperglycemic state, namely via increments in peripheral insulin sensitivity with improvements in insulin signal transduction at the cellular level, more robust insulin secretory responses, and reduced rates of hepatic glucose production. In both nondiabetic and diabetic subjects, hypocaloric feeding (e.g., treatment with very low-calorie diet or bariatric surgery) produces a rapid improvement in insulin sensitivity due to mobilization of fat from the intramyocellular, intrahepatocellular, and intra-abdominal compartments, and via a more long-term mechanism that correlates with the loss of total body fat. In diabetes, by improving glycemia, weight loss also enhances glucose homeostasis by reversing the defects in insulin action and secretion attributable to glucose toxicity. Regardless of the therapeutic approach, weight loss of ∼ 10 % maximally prevents future diabetes in patients with prediabetes or metabolic syndrome. In T2DM, greater degrees of weight loss lead to progressive improvements in glucose homeostasis. Therefore, when accompanied by greater weight loss, the metabolic benefits following bariatric surgery are generally more pronounced than those achieved following lifestyle and medical treatment. In addition, the mechanisms by which bariatric operations improve diabetes may include both weight-dependent and weight-independent mechanisms, and the latter may involve changes in gut hormones, bile acids, or gut microflora.