Vertical sleeve gastrectomy reduces hepatic steatosis while increasing serum bile acids in a weight-loss-independent manner

Energy expenditure related biomarkers following bariatric surgery: a prospective six-month cohort study

BACKGROUND

Mitochondria dysfunction is one of the major causes of insulin resistance, and other countless complications of obesity. PGC-1α, and UCP-2 play key roles in energy expenditure regulation in the mitochondrial thermogenesis. However, the effects of bariatric surgery on the level of PGC-1α and UCP-2 and their relationships are unclear.

OBJECTIVE

This study aimed to investigate the effect of bariatric surgery on key pathways in energy, and to assess the potential predictive role of body composition and metabolic parameters in this regard.

SETTINGS

Hazrat-e Rasool General Hospital, Center of Excellence of International Federation for Surgery of Obesity.

METHODS

This prospective cohort study was carried out on 45 patients with morbid obesity who underwent Roux-en-Y gastric bypass surgery. The patients have evaluated three-time points at baseline, three, and six months after the surgery. Body composition components, the levels of PGC-1α, UCP-2, and metabolic parameters were measured three times during this study.

RESULTS

Significant changes in TWL%, EBMIL%, and metabolic lab tests were observed at three- and six months post-surgery (P < 0.001). The PGC-1α and UCP-2 had a significant increase three and then six-month post-operation compared with the baseline (P < 0.001). Moreover, multivariate linear regression analysis identified that the changing trend of PGC-1α was associated with insulin, uric Acid, HOMA-IR, fat mass and trunk fat mass. UCP-2 was associated with TSH, AST, fat mass and FFM.

CONCLUSIONS

Bariatric surgery has been shown to have a positive effect on UCP-2 and PGC-1α levels, as well as body composition and metabolic parameters. As a result, it is believed that bariatric surgery could improve thermogenesis and energy expenditure by enhancing mitochondrial biogenesis and function. However, further studies are needed to fully understand the precise mechanisms and possible causal relationship.

Poly-Agonist Pharmacotherapies for Metabolic Diseases: Hopes and New Challenges

The use of glucagon-like peptide-1 (GLP-1) receptor-based multi-agonists in the treatment of type 2 diabetes and obesity holds great promise for improving glycaemic control and weight management. Unimolecular dual and triple agonists targeting multiple gut hormone-related pathways are currently in clinical trials, with recent evidence supporting their efficacy. However, significant knowledge gaps remain regarding the biological mechanisms and potential adverse effects associated with these multi-target agents. The mechanisms underlying the therapeutic efficacy of GLP-1 receptor-based multi-agonists remain somewhat mysterious, and hidden threats may be associated with the use of gut hormone-based polyagonists. In this review, we provide a critical analysis of the benefits and risks associated with the use of these new drugs in the management of obesity and diabetes, while also exploring new potential applications of GLP-1-based pharmacology beyond the field of metabolic disease.

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.

Decreased FXR Agonism in the Bile Acid Pool Is Associated with Impaired FXR Signaling in a Pig Model of Pediatric NAFLD

The objective of this study was to investigate whether the impairment of farnesoid X receptor (FXR)-fibroblast growth factor 19 (FGF19) signaling in juvenile pigs with non-alcoholic fatty liver disease (NAFLD) is associated with changes in the composition of the enterohepatic bile acid pool. Eighteen 15-day-old Iberian pigs, pair-housed in pens, were allocated to receive either a control (CON) or high-fructose, high-fat (HFF) diet. Animals were euthanized in week 10, and liver, blood, and distal ileum (DI) samples were collected. HFF-fed pigs developed NAFLD and had decreased FGF19 expression in the DI and lower FGF19 levels in the blood. Compared with the CON, the HFF diet increased the total cholic acid (CA) and the CA to chenodeoxycholic acid (CDCA) ratio in the liver, DI, and blood. CA and CDCA levels in the DI were negatively and positively correlated with ileal FGF19 expression, respectively, and blood levels of FGF19 decreased with an increasing ileal CA to CDCA ratio. Compared with the CON, the HFF diet increased the gene expression of hepatic 12-alpha-hydrolase, which catalyzes the synthesis of CA in the liver. Since CA species are weaker FXR ligands than CDCA, our results suggest that impairment of FXR-FGF19 signaling in NAFLD pigs is associated with a decrease in FXR agonism in the bile acid pool.

Sleeve gastrectomy causes weight-loss independent improvements in hepatic steatosis

BACKGROUND AND AIMS

Sleeve gastrectomy (VSG) leads to improvement in hepatic steatosis, associated with weight loss. The aims of this study were to investigate whether VSG leads to weight-loss independent improvements in liver steatosis in mice with diet-induced obesity (DIO); and to metabolically and transcriptomically profile hepatic changes in mice undergoing VSG.

METHODS

Mice with DIO were treated with VSG, sham surgery with subsequent food restriction to weight-match to the VSG group (Sham-WM), or sham surgery with return to unrestricted diet (Sham-Ad lib). Hepatic steatosis, glucose tolerance, insulin and glucagon resistance, and hepatic transcriptomics were investigated at the end of the study period and treatment groups were compared with mice undergoing sham surgery only (Sham-Ad lib).

RESULTS

VSG led to much greater improvement in liver steatosis than Sham-WM (liver triglyceride mg/mg 2.5 ± 0.1, 2.1 ± 0.2, 1.6 ± 0.1 for Sham-AL, Sham-WM and VSG respectively; p = 0.003). Homeostatic model assessment of insulin resistance was improved following VSG only (51.2 ± 8.8, 36.3 ± 5.3, 22.3 ± 6.1 for Sham-AL, Sham-WM and VSG respectively; p = 0.03). The glucagon-alanine index, a measure of glucagon resistance, fell with VSG but was significantly increased in Sham-WM (9.8 ± 1.7, 25.8 ± 4.6 and 5.2 ± 1.2 in Sham Ad-lib, Sham-WM and VSG respectively; p = 0.0003). Genes downstream of glucagon receptor signalling which govern fatty acid synthesis (Acaca, Acacb, Me1, Acly, Fasn and Elovl6) were downregulated following VSG but upregulated in Sham-WM.

CONCLUSIONS

Changes in glucagon sensitivity may contribute to weight-loss independent improvements in hepatic steatosis following VSG.

Associations between the gut microbiome and metabolic, inflammatory, and appetitive effects of sleeve gastrectomy

The complex and multifactorial etiology of obesity creates challenges for its effective long-term management. Increasingly, the gut microbiome is reported to play a key role in the maintenance of host health and wellbeing, with its dysregulation associated with chronic diseases such as obesity. The gut microbiome is hypothesized to contribute to obesity development and pathogenesis via several pathways involving food digestion, energy harvest and storage, production of metabolites influencing satiety, maintenance of gut barrier integrity, and bile acid metabolism. Moreover, the gut microbiome likely contributes to the metabolic, inflammatory, and satiety benefits and sustained weight-loss effects following bariatric procedures such as sleeve gastrectomy. While the field of gut microbiome research in relation to obesity and sleeve gastrectomy outcomes is largely in its infancy, the gut microbiome nonetheless holds great potential for understanding some of the mechanisms behind sleeve gastrectomy outcomes as well as for optimizing post-surgery benefits. This review will explore the current literature within the field as well as discuss the current limitations, including the small sample size, variability in methodological approaches, and lack of associative data, which need to be addressed in future studies.

Verification of Safety and Efficacy of Sleeve Gastrectomy Based on National Registry by Japanese Society for Treatment of Obesity

In Japan, bariatric surgical treatment was started in 1982. The Japanese Society for Treatment of Obesity (JSTO) was established in 2007, and then, JSTO started the national registry of bariatric surgery cases and multidisciplinary educational program. A total of 44 facilities registered 4055 bariatric surgical cases until 2021. In this study, the purpose is to clarify the indication, the safety and the effectiveness of the sleeve gastrectomy using national registry database compiled by JSTO. Preoperative BMI ranged from 27.6 to 90.7 kg/m², and the mean value was 42.7. With regard to gender, men/women was 1/1.3. Age was 42.2 as mean. As preoperative comorbidities, DM ratio was 54.4% of the patients, hypertension 64.5%, dyslipidemia 65.1%, and sleep apnea syndrome 69.8%. As an operation method, laparoscopic method was conducted in 99.7% of the cases. The intraoperative incidence rate was 0.9%. Conversion rate to open method was 1.1%. Postoperative morbidity ratio was 5.6%, and mortality was 0%. Reoperations were performed in 1.5% of the cases. Postoperative hospital stay was 5 days in median value. Body weight loss was 27.6 kg in the mean value after follow-up days of 279 ± 245. As the effect on the preoperative metabolic comorbidities, DM has improved in 82.9% of the cases, hypertension 67.9% and dyslipidemia 66.6%. In conclusion, using JSTO database, we evaluated the indication, postoperative complications and weight loss effect of sleeve gastrectomy in Japan. Regarding the evaluation of the effect on preoperative comorbidities, future follow-up based on more detailed criteria was considered to be necessary.

Regulation of body weight: Lessons learned from bariatric surgery

BACKGROUND

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

SCOPE OF REVIEW

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

MAJOR CONCLUSIONS

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

The role of FXR and TGR5 in reversing and preventing progression of Western diet-induced hepatic steatosis, inflammation, and fibrosis in mice

Nonalcoholic steatohepatitis (NASH) is the most common chronic liver disease in the US, partly due to the increasing incidence of metabolic syndrome, obesity, and type 2 diabetes. The roles of bile acids and their receptors, such as the nuclear receptor farnesoid X receptor (FXR) and the G protein-coupled receptor TGR5, on the development of NASH are not fully clear. C57BL/6J male mice fed a Western diet (WD) develop characteristics of NASH, allowing determination of the effects of FXR and TGR5 agonists on this disease. Here we show that the FXR-TGR5 dual agonist INT-767 prevents progression of WD-induced hepatic steatosis, inflammation, and fibrosis, as determined by histological and biochemical assays and novel label-free microscopy imaging techniques, including third harmonic generation, second harmonic generation, and fluorescence lifetime imaging microscopy. Furthermore, we show INT-767 decreases liver fatty acid synthesis and fatty acid and cholesterol uptake, as well as liver inflammation. INT-767 markedly changed bile acid composition in the liver and intestine, leading to notable decreases in the hydrophobicity index of bile acids, known to limit cholesterol and lipid absorption. In addition, INT-767 upregulated expression of liver p-AMPK, SIRT1, PGC-1α, and SIRT3, which are master regulators of mitochondrial function. Finally, we found INT-767 treatment reduced WD-induced dysbiosis of gut microbiota. Interestingly, the effects of INT-767 in attenuating NASH were absent in FXR-null mice, but still present in TGR5-null mice. Our findings support treatment and prevention protocols with the dual FXR-TGR5 agonist INT-767 arrest progression of WD-induced NASH in mice mediated by FXR-dependent, TGR5-independent mechanisms.

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.

Gut Factors Mediating the Physiological Impact of Bariatric Surgery

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

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

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

Gut HIF2α signaling is increased after VSG, and gut activation of HIF2α decreases weight, improves glucose, and increases GLP-1 secretion

Gastric bypass and vertical sleeve gastrectomy (VSG) remain the most potent and durable treatments for obesity and type 2 diabetes but are also associated with iron deficiency. The transcription factor HIF2α, which regulates iron absorption in the duodenum, increases following these surgeries. Increasing iron levels by means of dietary supplementation or hepatic hepcidin knockdown does not undermine the effects of VSG, indicating that metabolic improvements following VSG are not secondary to lower iron levels. Gut-specific deletion of Vhl results in increased constitutive duodenal HIF2α signaling and produces a profound lean, glucose-tolerant phenotype that mimics key effects of VSG. Interestingly, intestinal Vhl deletion also results in increased intestinal secretion of GLP-1, which is essential for these metabolic benefits. These data demonstrate a role for increased duodenal HIF2α signaling in regulating crosstalk between iron-regulatory systems and other aspects of systemic physiology important for metabolic regulation.

Bariatric surgery remains the most potent treatment for obesity and type 2 diabetes but also reduces iron levels. Evers et al. find that the machinery for absorbing iron is activated after VSG. Activation of this machinery recapitulates multiple effects of VSG. These findings may lead to less invasive therapies.

Sleeve gastrectomy improves lipid dysmetabolism by downregulating the USP20-HSPA2 axis in diet-induced obese mice

INTRODUCTION

Obesity is a metabolic disease accompanied by abnormalities in lipid metabolism that can cause hyperlipidemia, non-alcoholic fatty liver disease, and artery atherosclerosis. Sleeve gastrectomy (SG) is a type of bariatric surgery that can effectively treat obesity and improve lipid metabolism. However, its specific underlying mechanism remains elusive.

METHODS

We performed SG, and sham surgery on two groups of diet-induced obese mice. Histology and lipid analysis were used to evaluate operation effect. Immunohistochemistry, immunoblotting, real-time quantitative PCR, immunoprecipitation, immunofluorescence and mass spectrometry were used to reveal the potential mechanisms of SG.

RESULTS

Compared to the sham group, the SG group displayed a downregulation of deubiquitinase ubiquitin-specific peptidase 20 (USP20). Moreover, USP20 could promote lipid accumulation in vitro. Co-immunoprecipitation and mass spectrometry analyses showed that heat-shock protein family A member 2 (HSPA2) potentially acts as a substrate of USP20. HSPA2 was also downregulated in the SG group and could promote lipid accumulation in vitro. Further research showed that USP20 targeted and stabilized HSPA2 via the ubiquitin-proteasome pathway.

CONCLUSION

The downregulation of the USP20-HSPA2 axis in diet-induced obese mice following SG improved lipid dysmetabolism, indicating that USP20-HSPA2 axis was a noninvasive therapeutic target to be investigated in the future.

Serum Glucagon, Bile Acids, and FGF-19: Metabolic Behavior Patterns After Roux-en-Y Gastric Bypass and Vertical Sleeve Gastrectomy

BACKGROUND

Metabolic/bariatric surgery is a highly effective treatment for obesity and metabolic diseases. Serum glucagon, bile acids, and FGF-19 are key effectors of various metabolic processes and may play central roles in bariatric surgical outcomes. It is unclear whether these factors behave similarly after Roux-en-Y gastric bypass (RYGB) vs vertical sleeve gastrectomy (VSG).

METHODS

Serum glucagon, bile acids (cholic acid [CA], chenodeoxycholic acid [CDCA], deoxycholic acid [DCA]), and FGF-19 were analyzed in samples of fasting blood collected before bariatric surgery, on postoperative days 2 and 10, and at 3- and 6-month follow-up.

RESULTS

From September 2016 to July 2017, patients with obesity underwent RYGB or VSG; 42 patients (RYGB n = 21; VSG n = 21) were included in the analysis. In the RYGB group, glucagon, CA, and CDCA increased continuously after surgery (p = 0.0003, p = 0.0009, p = 0.0001, respectively); after an initial decrease (p = 0.04), DCA increased significantly (p = 0.0386). Serum FGF-19 was unchanged. In the VSG group, glucagon increased on day 2 (p = 0.0080), but decreased over the 6-month study course (p = 0.0025). Primary BAs (CA and CDCA) decreased immediately after surgery (p = 0.0016, p = 0.0091) and then rose (p = 0.0350, p = 0.0350); DCA followed the curve of the primary BAs until it fell off at 6 months (p = 0.0005). VSG group serum FGF-19 trended upward.

CONCLUSION

RYGB and VSG involve different surgical techniques and final anatomical configurations. Between postoperative day 2 and 6-month follow-up, RYGB and VSG resulted in divergent patterns of change in serum glucagon, bile acids, and FGF-19.

Intestinal-derived FGF15 protects against deleterious effects of vertical sleeve gastrectomy in mice

Bariatric surgeries such as the Vertical Sleeve Gastrectomy (VSG) are invasive but provide the most effective improvements in obesity and Type 2 diabetes. We hypothesized a potential role for the gut hormone Fibroblast-Growth Factor 15/19 which is increased after VSG and pharmacologically can improve energy homeostasis and glucose handling. We generated intestinal-specific FGF15 knockout (FGF15^INT-KO) mice which were maintained on high-fat diet. FGF15^INT-KO mice lost more weight after VSG as a result of increased lean tissue loss. FGF15^INT-KO mice also lost more bone density and bone marrow adipose tissue after VSG. The effect of VSG to improve glucose tolerance was also absent in FGF15^INT-KO. VSG resulted in increased plasma bile acid levels but were considerably higher in VSG-FGF15^INT-KO mice. These data point to an important role after VSG for intestinal FGF15 to protect the organism from deleterious effects of VSG potentially by limiting the increase in circulating bile acids.

The mechanisms that mediate the effects of weight loss surgeries such as vertical sleeve gastrectomy (VSG) are incompletely understood. Here the authors show that intestinal FGF15 is necessary to improve glucose tolerance and to prevent the loss of muscle and bone mass after VSG, potentially via protection against bile acid toxicity.

Gut Microbiota and Cardiovascular Diseases: A Critical Review

The human intestine contains the largest and most diverse ecosystem of microbes. The main function of the intestinal bacterial flora is to limit the growth of potentially pathogenic microorganisms. However, the intestinal microbiota is increasingly emerging as a risk factor for the development of cardiovascular disease (CVD). The gut microbiota-derived metabolites, such as short-chain fatty acids, trimethylamine-N-oxide, bile acids, and polyphenols play a pivotal role in maintaining healthy cardiovascular function, and when dysregulated, can potentially lead to CVD. In particular, changes in the composition and diversity of gut microbiota, known as dysbiosis, have been associated with atherosclerosis, hypertension, and heart failure. Nonetheless, the underlying mechanisms remain yet to be fully understood. Therefore, the microbiota and its metabolites have become a new therapeutic target for the prevention and treatment of CVD. In addition to a varied and balanced diet, the use of prebiotic and probiotic treatments or selective trimethylamine-N-oxide inhibitors could play a pivotal role in the prevention of CVD, especially in patients with a high metabolic risk.

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.

Restored TDCA and valine levels imitate the effects of bariatric surgery

Background

Obesity is widespread and linked to various co-morbidities. Bariatric surgery has been identified as the only effective treatment, promoting sustained weight loss and the remission of co-morbidities.

Methods

Metabolic profiling was performed on diet-induced obese (DIO) mice, lean mice, and DIO mice that underwent sleeve gastrectomies (SGx). In addition, mice were subjected to intraperitoneal (i.p.) injections with taurodeoxycholic acid (TDCA) and valine. Indirect calorimetry was performed to assess food intake and energy expenditure. Expression of appetite-regulating hormones was assessed through quantification of isolated RNA from dissected hypothalamus tissue. Subsequently, i.p. injections with a melanin-concentrating hormone (MCH) antagonist and intrathecal administration of MCH were performed and weight loss was monitored.

Results

Mass spectrometric metabolomic profiling revealed significantly reduced systemic levels of TDCA and L-valine in DIO mice. TDCA and L-valine levels were restored after SGx in both human and mice to levels comparable with lean controls. Systemic treatment with TDCA and valine induced a profound weight loss analogous to effects observed after SGx. Utilizing indirect calorimetry, we confirmed reduced food intake as causal for TDCA/valine-mediated weight loss via a central inhibition of the MCH.

Conclusions

In summary, we identified restored TDCA/valine levels as an underlying mechanism of SGx-derived effects on weight loss. Of translational relevance, TDCA and L-valine are presented as novel agents promoting weight loss while reversing obesity-associated metabolic disorders.

Funding

This work has been supported in part by a grant from NIH (UO-1 A1 132898 to S.G.T., DP and MA). M.Q. was supported by the IFB Integrated Research and Treatment Centre Adiposity Diseases (Leipzig, Germany) and the German Research Foundation (QU 420/1-1). J.I. was supported by the Biomedical Education Program (BMEP) of the German Academic Exchange Service (DAAD). T.H. (HE 7457/1-1) and F.K. (KR 4362/1-1) were supported by the German Research Foundation (DFG). H.R.C.B. was supported the Swiss Society of Cardiac Surgery. Y.N. was supported by the Chinese Scholarship Council (201606370196) and Central South University. H.U., T.M. and R.M. were supported by the Osaka Medical Foundation. C.S.F. was supported by the German Research Foundation (DFG, SFB738, B3).

Bariatric Surgery Affects Plasma Levels of Alanine Aminotransferase Independent of Weight Loss: A Registry-Based Study

Patients that undergo bariatric surgery experience weight loss and a reduction in the plasma levels of the hepatic enzymes alanine aminotransferase (ALT) and aspartate aminotransferase (AST). We used the Israeli national bariatric registry, which includes demographic, clinical, and biochemical data on 19,403 patients, of which 1335 patients had two-year follow-up data on ALT, AST, A1C, and BMI, to test the dependence of the reduction in the levels of ALT and AST on weight loss. The data were analyzed using regression models, retrospective matching, and time course analyses. Changes in liver enzymes did not correlate with change in BMI, and linear regression models did not demonstrate that the change in ALT and AST values were dependent on pre-operative levels of BMI or the extent of weight loss. ALT and AST levels were reduced two years after surgery compared with a cohort of retrospectively matched patients for ethnicity, sex, age, BMI, and A1C. Finally, patients who regained weight displayed a reduction in levels of liver enzymes. Our results suggest that bariatric surgery affects AST and ALT levels via weight loss dependent and independent mechanisms. Mechanistic studies that will identify the nature of this effect and the clinical relevance of ALT and AST levels to the post-bariatric liver function are warranted.

The role of bariatric surgery in the management of nonalcoholic steatohepatitis

PURPOSE OF REVIEW

Nonalcoholic fatty liver disease (NAFLD) is the leading cause of chronic liver disease in the United States and increasing globally. The progressive form of NAFLD, nonalcoholic steatohepatitis (NASH), can lead to cirrhosis and complications of end-stage liver disease. No FDA-approved therapy for NAFLD/NASH exists. Treatment of NAFLD/NASH includes effective and sustained life-style modification and weight loss. This review reports on the recent findings of bariatric surgery in the management of NASH.

RECENT FINDINGS

NAFLD, at all stages, is common in those who meet indication for bariatric surgery. Bariatric surgery resolves NAFLD/NASH and reverses early stages of fibrosis. Although randomized controlled trials of bariatric surgery in NASH are infeasible, studies defining the metabolic changes induced by bariatric surgery, and their effect on NASH, provide insight for plausible pharmacologic targets for the nonsurgical treatment of NASH.

SUMMARY

Resolution of NASH and fibrosis regression can occur after bariatric surgery. Although the exact mechanism(s) underlying the improvement of NASH and hepatic fibrosis following bariatric surgery is not fully elucidated, emerging data on this topic is vitally important for lending insight into the pharmacotherapies for NASH for patients who are not otherwise suitable candidates for bariatric surgery.

Hepatic Ago2 Regulates PPARα for Oxidative Metabolism Linked to Glycemic Control in Obesity and Post Bariatric Surgery

Argonaute 2 (Ago2) is the main component of the RNA-induced silencing complex. We recently showed that liver-specific Ago2-deficiency in mice (L-Ago2 knockout [KO] mice) enhances mitochondrial oxidation and alleviates obesity-associated pathophysiology. However, the precise mechanisms behind the role of hepatic Ago2 in regulating the mitochondrial oxidation associated with glucose metabolism are still unclear. Here, we show that hepatic Ago2 regulates the function of peroxisome proliferator-activated receptor α (PPARα) for oxidative metabolism. In both genetically and diet-induced severe obese conditions, L-Ago2 KO mice developed obesity and hepatic steatosis but exhibited improved glucose metabolism accompanied by lowered expression levels of pathologic microRNAs (miRNAs), including miR-802, miR-103/107, and miR-152, and enhanced expression of PPARα and its target genes regulating oxidative metabolism in the liver. We then investigated the role of hepatic Ago2 in the outcomes of vertical sleeve gastrectomy (VSG) in which PPARα plays a crucial role in a drastic transcription reprogram associated with improved glycemia post VSG. Whereas VSG reduced body weight and improved fatty liver in wild-type mice, these effects were not observed in hepatic Ago2-deficient mice. Conversely, glucose metabolism was improved in a hepatic Ago2-dependent manner post VSG. Treating Ago2-deficient primary hepatocytes with WY-14643, a PPARα agonist, showed that Ago2-deficiency enhances sensitivity to WY-14643 and increases expression of PPARα target genes and mitochondrial oxidation. Our findings suggest that hepatic Ago2 function is intrinsically associated with PPARα that links Ago2-mediated RNA silencing with mitochondrial functions for oxidation and obesity-associated pathophysiology.

Significance of intestinal microbiota in implementing metabolic effects of bariatric surgery

Bariatric surgery is among successful methods of obesity treatment, with effects going beyond weight reduction alone, but rather involving improved glucose tolerance, along with control or remission of the type 2 diabetes mellitus. The precise mechanisms causing metabolic effects of bariatric surgery are not fully elucidated, even though substantial evidence suggest that they include changes in the gut microbiota, bile acid homeostasis, and the close interactions of these factors. Intestinal microflora is directly involved in the energy metabolism of a host human. Obesity and type 2 diabetes mellitus are associated with certain changes in the species composition and diversity of intestinal microflora, which are considered important factors in the development and progression of these ailments. Bariatric surgery leads to significant and persistent changes in the composition of the intestinal microbiota, often bringing it closer to the characteristics of the microbiota of an average person with a normal weight. An important role in implementing the metabolic effects of bariatric surgery, primarily in the improvement of glucose metabolism, belongs to postoperative changes in homeostasis of bile acids. These changes imply close metabolism. Moreover, changes in the bile acid metabolism after bariatric surgery affect the microbiota of the host. Further study of these relationships would clarify the mechanisms underlying metabolic surgery, make it more predictable, targeted and controlled, as well as open new therapeutic targets in the treatment of obesity and associated conditions.

Visual Analysis of Biomarkers Reveals Differences in Lipid Profiles and Liver Enzymes before and after Gastric Sleeve and Bypass

INTRODUCTION

Bariatric surgery results in both intentional and unintentional metabolic changes. In a high-volume bariatric center, extensive laboratory panels are used to monitor these changes pre- and postoperatively. Consecutive measurements of relevant biochemical markers allow exploration of the health state of bariatric patients and comparison of different patient groups.

OBJECTIVE

The objective of this study is to compare biomarker distributions over time between 2 common bariatric procedures, i.e., sleeve gastrectomy (SG) and gastric bypass (RYGB), using visual analytics.

METHODS

Both pre- and postsurgical (6, 12, and 24 months) data of all patients who underwent primary bariatric surgery were collected retrospectively. The distribution and evolution of different biochemical markers were compared before and after surgery using asymmetric beanplots in order to evaluate the effect of primary SG and RYGB. A beanplot is an alternative to the boxplot that allows an easy and thorough visual comparison of univariate data.

RESULTS

In total, 1,237 patients (659 SG and 578 RYGB) were included. The sleeve and bypass groups were comparable in terms of age and the prevalence of comorbidities. The mean presurgical BMI and the percentage of males were higher in the sleeve group. The effect of surgery on lowering of glycated hemoglobin was similar for both surgery types. After RYGB surgery, the decrease in the cholesterol concentration was larger than after SG. The enzymatic activity of aspartate aminotransferase, alanine aminotransferase, and alkaline phosphate in sleeve patients was higher presurgically but lower postsurgically compared to bypass values.

CONCLUSIONS

Beanplots allow intuitive visualization of population distributions. Analysis of this large population-based data set using beanplots suggests comparable efficacies of both types of surgery in reducing diabetes. RYGB surgery reduced dyslipidemia more effectively than SG. The trend toward a larger decrease in liver enzyme activities following SG is a subject for further investigation.

Intestinal extracellular vesicles are altered by vertical sleeve gastrectomy

Bariatric surgery is the most effective treatment for obesity and its comorbidities. However, our understanding of the molecular mechanisms behind its beneficial effects is limited. Extracellular vesicles (EVs) comprise an important mode of intercellular communication. They carry nucleic acids, hormones, and signaling molecules and regulate multiple processes. Our aim was to test the role of EVs in the effects of vertical sleeve gastrectomy (VSG) using a mouse model. Small intestinal EVs were obtained from the mice that underwent VSG or control surgery and were on chow or high-fat diet or diet-restricted, and then they were subjected to the proteomic analysis. Enteroid and bacterial cultures were treated with EVs to evaluate their survival effect. A mouse cohort received intraduodenal administration of EVs from VSG or Sham mice for 10 days. Body weight, glucose metabolism, and intestinal morphology were evaluated. EVs were enriched in the intestinal lumen and mucus of VSG compared with Sham mice. Protein composition of VSG and Sham-derived EVs was highly distinct. When introduced into culture, VSG EVs decreased survival of intestinal enteroids and, conversely, promoted proliferation of bacteria. Mice administered with EVs obtained from VSG and Sham groups did not show differences in body weight, food intake, or glucose metabolism. Intestinal morphology was altered, as VSG EVs caused reduction of ileal villi length and decreased epithelial proliferation in the jejunum and ileum. VSG causes remodeling of intestinal EVs, which results in unique protein composition. VSG-derived EVs exhibit cytotoxic effects on epithelial cells and reduce proliferation of intestinal progenitor cells in mice.NEW & NOTEWORTHY This is the first study that investigates the impact of bariatric surgery on protein composition of intestinal extracellular vesicles. Extracellular vesicle composition is greatly altered after vertical sleeve gastrectomy and may potentially modulate various signaling pathways. In our study, extracellular vesicles from vertical sleeve gastrectomy-treated mice promote bacterial proliferation but exhibit cytotoxic effect on epithelial cells and reduce proliferation of intestinal progenitor cells in mice.

Vertical sleeve gastrectomy induces distinctive transcriptomic responses in liver, fat and muscle

Vertical sleeve gastrectomy (VSG) is the most commonly performed bariatric/metabolic surgery, exhibiting a high rate of diabetes remission in humans. To elucidate the molecular mechanisms of VSG, we performed transcriptomic analysis of the liver, fat, and muscle in VSG mice. C57BL/6 mice fed a high-fat diet were randomly assigned to sham or VSG surgery. The sham-operated mice were fed ad libitum (sham group) or pair-fed (sham-PF group) matching their food intake to the VSG-operated mice. Comparative transcriptomic analysis of the liver, fat, and muscle using RNA sequencing was performed. VSG reduced body weight and improved glucose tolerance compared to the sham group, but not more than the sham-PF group. Improvement in fatty liver and adipose tissue inflammation was comparable between VSG and sham-PF. However, global gene expression profiles showed distinctive changes in the liver, fat, and muscle of the VSG group compared to both the sham or sham-PF groups. The liver showed the most prominent gene expression changes. Immune response-related pathways were commonly upregulated in the three organs of the VSG group compared to the sham or sham-PF. VSG induces organ-specific gene expression changes in the liver, fat, and muscle, which may play critical roles in metabolic improvements after VSG.

Alterations in Small Intestine and Liver Morphology, Immunolocalization of Leptin, Ghrelin and Nesfatin-1 as Well as Immunoexpression of Tight Junction Proteins in Intestinal Mucosa after Gastrectomy in Rat Model

The stomach is responsible for the processing of nutrients as well as for the secretion of various hormones which are involved in many activities throughout the gastrointestinal tract. Experimental adult male Wistar rats (n = 6) underwent a modified gastrectomy, while control rats (n = 6) were sham-operated. After six weeks, changes in small intestine (including histomorphometrical parameters of the enteric nervous plexuses) and liver morphology, immunolocalization of leptin, ghrelin and nesfatin-1 as well as proteins forming adherens and tight junctions (E-cadherin, zonula occludens-1, occludin, marvelD3) in intestinal mucosa were evaluated. A number of effects on small intestine morphology, enteric nervous system ganglia, hormones and proteins expression were found, showing intestinal enteroplasticity and neuroplasticity associated with changes in gastrointestinal tract condition. The functional changes in intestinal mucosa and the enteric nervous system could be responsible for the altered intestinal barrier and hormonal responses following gastrectomy. The results suggest that more complicated regulatory mechanisms than that of compensatory mucosal hypertrophy alone are involved.

Improving glucose and lipids metabolism: drug development based on bile acid related targets

Bariatric surgery is one of the most effective treatment options for severe obesity and its comorbidities. However, it is a major surgery that poses several side effects and risks which impede its clinical use. Therefore, it is urgent to develop alternative safer pharmacological approaches to mimic bariatric surgery. Recent studies suggest that bile acids are key players in mediating the metabolic benefits of bariatric surgery. Bile acids can function as signaling molecules by targeting bile acid nuclear receptors and membrane receptors, like FXR and TGR5 respectively. In addition, the composition of bile acids is regulated by either the hepatic sterol enzymes such as CYP8B1 or the gut microbiome. These bile acid related targets all play important roles in regulating metabolism. Drug development based on these targets could provide new hope for patients without the risks of surgery and at a lower cost. In this review, we summarize the most updated progress on bile acid related targets and development of small molecules as drug candidates based on these targets.

Curbing Obesity from One Generation to Another: the Effects of Bariatric Surgery on the In Utero Environment and Beyond

Approximately 250,000 individuals seek bariatric surgery each year in the USA for the long-term resolution of obesity-related comorbidities. Greater than 80% of these individuals are women and approximately half are of child-bearing age. Although there are many positive metabolic benefits that are realized through surgical weight loss for both men and women, the various long-term hormonal, molecular, nutrient, and epigenetic changes following bariatric surgery have not been evaluated for the surgical recipient or in the context of pregnancy and the offspring. Pregnancy may be a vulnerable period of time for the bariatric surgery recipient, and thoughtful consideration of pregnancy management should be taken by health care providers and recipients alike. The purpose of this review is to explore potential etiologies of some of the gestation-specific outcomes for the mother and offspring.

Assessment of the role of FGF15 in mediating the metabolic outcomes of murine Vertical Sleeve Gastrectomy (VSG)

Vertical sleeve gastrectomy (VSG) is the best current therapy for remission of obesity and its co-morbidities. It is understood to alter the enterohepatic circulation of bile acids in vivo. Fibroblast growth factor 19 (FGF19) in human and its murine orthologue Fgf15 plays a pivotal role in this bile acid driven enterohepatic signaling. The present study evaluated the metabolic outcomes of VSG in Fgf15 deficient mice. 6-8 weeks old male wildtype mice (WT) and Fgf15 deficient mice (KO) were fed a high fat diet (HFD) for 8 weeks. At 8th week of diet, both WT and KO mice were randomly distributed to VSG or sham surgery. Post-surgery, mice were observed for 8 weeks while fed a HFD and then euthanized to collect tissues for experimental analysis. Fgf15 deficient (KO) mice lost weight post VSG, but glucose tolerance in KO mice did not improve post VSG compared to WT mice. Enteroids derived from WT and KO mice proliferated with bile acid exposure in vitro. Post VSG both WT and KO mice had similarly altered bile acid enterohepatic flux, however Fgf15 deficient mice post VSG had increased hepatic accumulation of free and esterified cholesterol leading to lipotoxicity related ER stress, inflammasome activation, and increased Fgf21 expression. Intact Fgf15 mediated enterohepatic bile acid signaling, but not changes in bile acid flux, appear to be important for the metabolic improvements post-murine bariatric surgery. These novel data introduce a potential point of distinction between bile acids acting as ligands compared to their canonical downstream signaling pathways.

Surgical Mouse Models of Vertical Sleeve Gastrectomy and Roux-en Y Gastric Bypass: a Review

Reviewed here are multiple mouse models of vertical sleeve gastrectomy (VSG) and Roux-en Y gastric bypass (RYGB) that have emerged over the past decade. These models use diverse approaches to both operative and perioperative procedures. Scrutinizing the benefits and pitfalls of each surgical model and what to expect in terms of post-operative outcomes will enhance our assessment of studies using mouse models, as well as advance our understanding of their translational potential. Two mouse models of bariatric surgery, VSG-lembert and RYGB-small pouch, demonstrate low mortality and most closely recapitulate the human forms of surgery. The use of liquid diets can be minimized, and in mice, RYGB demonstrates more reliable and longer lasting effects on weight loss compared to that of VSG.

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.

Do Bariatric Surgeries Enhance Brown/Beige Adipose Tissue Thermogenesis?

Bariatric surgeries induce marked and durable weight loss in individuals with morbid obesity through powerful effects on both food intake and energy expenditure. While alterations in gut-brain communication are increasingly implicated in the improved eating behavior following bariatric surgeries, less is known about the mechanistic basis for energy expenditure changes. Brown adipose tissue (BAT) and beige adipose tissue (BeAT) have emerged as major regulators of whole-body energy metabolism in humans as well as in rodents due to their ability to convert the chemical energy in circulating glucose and fatty acids into heat. In this Review, we critically discuss the steadily growing evidence from preclinical and clinical studies suggesting that Roux-en-Y gastric bypass (RYGB) and vertical sleeve gastrectomy (VSG), the two most commonly performed bariatric surgeries, enhance BAT/BeAT thermogenesis. We address the documented mechanisms, highlight study limitations and finish by outlining unanswered questions in the subject. Further understanding how and to what extent bariatric surgeries enhance BAT/BeAT thermogenesis may not only aid in the development of improved obesity pharmacotherapies that safely and optimally target both sides of the energy balance equation, but also in the development of novel hyperglycemia and/or hyperlipidemia pharmacotherapies.

Vertical Sleeve Gastrectomy Attenuates the Progression of Non-Alcoholic Steatohepatitis in Mice on a High-Fat High-Cholesterol Diet

OBJECTIVE

To determine whether vertical sleeve gastrectomy (VSG) attenuates fibrosis in mice on a high-fat high-cholesterol (HFHC) diet.

BACKGROUND

Bariatric surgery mitigates non-alcoholic steatohepatitis in 85-90% of obese patients. While animal models demonstrate similar results on a high-fat diet, none have observed the effects of bariatric surgery on a combined HFHC diet.

METHODS

Mice on a HFHC diet were used to confirm the development of hepatic fibrosis at 8 (n = 15) and 24 (n = 15) weeks. A separate cohort of mice on a HFHC diet for 12 weeks was subjected to either VSG (n = 18) or sham (n = 12) operations and remained on a HFHC diet for an additional 20 weeks. Changes in weight, dyslipidemia, and the development of steatosis and fibrosis were documented. Serum was obtained for bile acid analysis by liquid chromatography and mass spectrometry, while hepatic gene expression by RT-PCR was performed to evaluate intrahepatic lipid metabolism.

RESULTS

Hepatic steatosis and fibrosis developed after 8 weeks on the HFHC diet. After VSG, mice demonstrated a sustained decrease in weight with a significant decrease in fibrosis compared to sham mice. Serum total cholesterol, HDL, and LDL were significantly reduced following surgery, while serum bile acids were significantly elevated. Intra-hepatic cholesterol excretion was not upregulated based on hepatic gene expression of CYP7A1 and ABCG5/8.

CONCLUSIONS

VSG attenuates the development of hepatic fibrosis in diet-induced obese mice, presumably through enhancement of cholesterol elimination at the intestinal level.

Improvement in Non-alcoholic Fatty Liver Disease Score Correlates with Weight Loss in Obese Patients Undergoing Laparoscopic Sleeve Gastrectomy: a Two-Centre Study from an Asian Cohort

PURPOSE

Incidence of non-alcoholic fatty liver disease (NAFLD) is on the rise and is one of the most common causes of chronic liver disease worldwide. Obesity and metabolic syndrome are considered the most significant risk factors. Bariatric surgery is the only treatment modality in morbid obesity which allows long-term weight loss with improvement in associated co-morbid conditions. However, the effects of bariatric surgery on NAFLD are not well established. NAFLD fibrosis score (NFS) is a validated non-invasive scoring system used to assess advanced fibrosis. We used the NFS to analyse the impact of weight loss on NAFLD following sleeve gastrectomy.

MATERIALS AND METHODS

174 patients who underwent bariatric surgery between 2010 and 2016 were retrospectively reviewed. Multivariate analysis was performed using pre-operative patient characteristics, biochemical markers and TANITA body analysis measurements to determine significant risk factors for NFS > 0.675. Additionally, the NFS was calculated at 6 months, 1 year and 2 years post-operatively to determine correlation with weight loss.

RESULTS

Pre-operatively, 13.8% of our patients had significant fibrosis by NFS. Mean change in NFS was - 0.46 ± 1.02, - 0.55 ± 0.98 and - 0.55 ± 1.12 at 6 months, 1 year and 2 years respectively. This was significantly correlated with percent of total weight loss with R coefficients of 0.253, 0.292 and 0.274 respectively (P < 0.05). 79.2% of patients with NFS > 0.675 achieved resolution by 2 years post-operatively.

CONCLUSION

Based on our study, we conclude that sleeve gastrectomy may be a viable treatment option for management of NAFLD in the obese.

Farnesoid X receptor contributes to body weight-independent improvements in glycemic control after Roux-en-Y gastric bypass surgery in diet-induced obese mice

Objective

Roux-en-Y gastric bypass surgery (RYGB) can achieve long-term remission of type 2 diabetes. However, the specific molecular mechanism through which this occurs has remained largely elusive. Bile acid signaling through the nuclear hormone receptor farnesoid X receptor (FXR) exerts beneficial effects after sleeve gastrectomy (VSG), which has similar effects to RYGB. Therefore, we investigated whether FXR signaling is necessary to mediate glycemic control after RYGB.

Methods

RYGB or sham surgery was performed in high-fat diet-induced obese FXR−/− (knockout) and FXR+/+ (wild type) littermates. Sham-operated mice were fed ad libitum (S-AL) or by weight matching (S-WM) to RYGB mice via caloric restriction. Body weight, body composition, food intake, energy expenditure, glucose tolerance tests, insulin tolerance tests, and homeostatic model assessment of insulin resistance were performed.

Results

RYGB surgery decreases body weight and fat mass in WT and FXR-KO mice. RYGB surgery has similar effects on food intake and energy expenditure independent of genotype. In addition, body weight-independent improvements in glucose control were attenuated in FXR −/− relative to FXR +/+ mice after RYGB. Furthermore, pharmacologic blockade of the glucagon-like peptide-1 receptor (GLP-1R) blunts the glucoregulatory effects of RYGB in FXR +/+ but not in FXR −/− mice at 4 weeks after surgery.

Conclusions

These results suggest that FXR signaling is not required for the weight loss up to 16 weeks after RYGB. Although most of the improvements in glucose homeostasis are secondary to RYGB-induced weight loss in wild type mice, FXR signaling contributes to glycemic control after RYGB in a body weight-independent manner, which might be mediated by an FXR-GLP-1 axis during the early postoperative period.

•

The reduction in body weight after RYGB is independent of FXR, which is mainly due to a decrease in net energy intake.

•

RYGB prevents the weight loss-induced decrease observed in nonsurgical weight-matched mice in both genotypes.

•

FXR signaling contributes to glycemic control after RYGB in a body weight-independent manner.

•

The early body weight-independent improvements in glucose homeostasis after RYGB might be mediated by an FXR-GLP-1 axis.

Is Roux-en-Y gastric bypass advantageous?-surgical outcomes in obese patients with type-2 diabetes after gastric bypass versus sleeve gastrectomy, a matched retrospective study

Background

There are few comparative studies of the clinical outcomes after Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG). The aim of the study was to compare diabetes- and metabolic disorder-related outcomes following RYGB and SG, based on data for matched participants.

Methods

This was a retrospective matched study using data from 2011–2018. Patients with type-2 diabetes undergoing RYGB (n=35) were matched with up to 2 RYGB participants (n=56) regarding age, sex, body mass index, hemoglobin A1c level, medication use, diabetes duration, and blood pressure.

Results

All surgeries were performed laparoscopically without complications or malnutrition during 24 months of follow-up. Both surgical procedures achieved excellent diabetes remission and weight loss. RYGB was associated with a significantly higher diabetes medication discontinuation rate 24 months postoperatively (RYGB: 87.5% vs. SG: 68.6%; P<0.05), better reduction in serum cholesterol and low-density lipoprotein-c levels, as well as better diabetes control compared with SG. The incidence of microvascular and macrovascular complications showed no significant difference between two groups.

Conclusions

In this matched retrospective study, although RYGB and SG were both excellent surgeries for treating obesity in patients with type-2 diabetes, RYGB was associated with better results compared with SG regarding dyslipidemia remission and metabolic disorder-related medication reduction.

Hepatic HAX-1 inactivation prevents metabolic diseases by enhancing mitochondrial activity and bile salt export

Increasing hepatic mitochondrial activity through pyruvate dehydrogenase and elevating enterohepatic bile acid recirculation are promising new approaches for metabolic disease therapy, but neither approach alone can completely ameliorate disease phenotype in high-fat diet-fed mice. This study showed that diet-induced hepatosteatosis, hyperlipidemia, and insulin resistance can be completely prevented in mice with liver-specific HCLS1-associated protein X-1 (HAX-1) inactivation. Mechanistically, we showed that HAX-1 interacts with inositol 1,4,5-trisphosphate receptor-1 (InsP3R1) in the liver, and its absence reduces InsP3R1 levels, thereby improving endoplasmic reticulum-mitochondria calcium homeostasis to prevent excess calcium overload and mitochondrial dysfunction. As a result, HAX-1 ablation activates pyruvate dehydrogenase and increases mitochondria utilization of glucose and fatty acids to prevent hepatosteatosis, hyperlipidemia, and insulin resistance. In contrast to the reduction of InsP3R1 levels, hepatic HAX-1 deficiency increases bile salt exporter protein levels, thereby promoting enterohepatic bile acid recirculation, leading to activation of bile acid-responsive genes in the intestinal ileum to augment insulin sensitivity and of cholesterol transport genes in the liver to suppress hyperlipidemia. The dual mechanisms of increased mitochondrial respiration and enterohepatic bile acid recirculation due to improvement of endoplasmic reticulum-mitochondria calcium homeostasis with hepatic HAX-1 inactivation suggest that this may be a potential therapeutic target for metabolic disease intervention.

Changes in Serum Nesfatin-1 After Laparoscopic Sleeve Gastrectomy are Associated with Improvements in Nonalcoholic Fatty Liver Disease

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is a serious and widespread disease worldwide. Bariatric surgery is one of the treatments for NAFLD. Nesfatin-1 is located in the brain, periphery and plasma. We studied the relationship between nesfatin-1 changes after laparoscopic sleeve gastrectomy (LSG) and NAFLD remission.

METHODS

A total of 29 patients participated in the study, which collected clinical information on the patients and indicators of liver function, hepatic steatosis score and nesfatin-1 level before and after LSG.

RESULTS

The average BMI of the patients before surgery was 42.63±8.91 kg/m², and the average BMI was 28.54±5.63 kg/m² one year after surgery (p < 0.05). One year after LSG, the total weight loss percentage (TWL%) was 32.11±7.10%. The mean value of nesfatin-1 before surgery was 3.04±0.81 ng/mL, and the mean value of nesfatin-1 was 5.52±1.55 ng/mL at one year after surgery (p < 0.05). The average preoperative hepatic steatosis index (HSI) score of the patients was 52.55±9.17, and the average postoperative HSI score was 38.84±5.82 (p < 0.05). Before LSG (p < 0.05, r= -0.81) and 1 year after surgery (p < 0.05, r = -0.58), HSI and nesfatin-1 were significantly negatively correlated. Percentage of increased nesfatin-1 and percentage of decreased HSI showed positive correlation after LSG.

CONCLUSION

There was a negative correlation between HSI and nesfatin-1 before and after LSG, which may suggest that nesfatin-1 plays a role in NAFLD.

Inhibition of Hepatic Bile Acid Uptake by Myrcludex B Promotes Glucagon-Like Peptide-1 Release and Reduces Obesity

BACKGROUND & AIMS

Bile acids are important metabolic signaling molecules. Bile acid receptor activation promotes body weight loss and improves glycemic control. The incretin hormone GLP-1 and thyroid hormone activation of T4 to T3 have been suggested as important contributors. Here, we identify the hepatic bile acid uptake transporter Na⁺ taurocholate co-transporting polypeptide (NTCP) as target to prolong postprandial bile acid signaling.

METHODS

Organic anion transporting polypeptide (OATP)1a/1b KO mice with or without reconstitution with human OATP1B1 in the liver were treated with the NTCP inhibitor Myrcludex B for 3.5 weeks after the onset of obesity induced by high fat diet-feeding. Furthermore, radiolabeled T4 was injected to determine the role of NTCP and OATPs in thyroid hormone clearance from plasma.

RESULTS

Inhibition of NTCP by Myrcludex B in obese Oatp1a/1b KO mice inhibited hepatic clearance of bile acids from portal and systemic blood, stimulated GLP-1 secretion, reduced body weight, and decreased (hepatic) adiposity. NTCP inhibition did not affect hepatic T4 uptake nor lead to increased thyroid hormone activation. Myrcludex B treatment increased fecal energy output, explaining body weight reductions amongst unaltered food intake and energy expenditure.

CONCLUSIONS

Pharmacologically targeting hepatic bile acid uptake to increase bile acid signaling is a novel approach to treat obesity and induce GLP1- secretion.

Physiological and Epigenetic Features of Yoyo Dieting and Weight Control

Obesity and being overweight have become a worldwide epidemic affecting more than 1.9 billion adults and 340 million children. Efforts to curb this global health burden by developing effective long-term non-surgical weight loss interventions continue to fail due to weight regain after weight loss. Weight cycling, often referred to as Yoyo dieting, is driven by physiological counter-regulatory mechanisms that aim at preserving energy, i.e. decreased energy expenditure, increased energy intake, and impaired brain-periphery communication. Models based on genetically determined set points explained some of the weight control mechanisms, but exact molecular underpinnings remained elusive. Today, gene–environment interactions begin to emerge as likely drivers for the obesogenic memory effect associated with weight cycling. Here, epigenetic mechanisms, including histone modifications and DNA methylation, appear as likely factors that underpin long-lasting deleterious adaptations or an imprinted obesogenic memory to prevent weight loss maintenance. The first part summarizes our current knowledge on the physiology of weight cycling by discussing human and murine studies on the Yoyo-dieting phenomenon and physiological adaptations associated with weight loss and weight re-gain. The second part provides an overview on known associations between obesity and epigenetic modifications. We further interrogate the roles of epigenetic mechanisms in the CNS control of cognitive functions as well as reward and addictive behaviors, and subsequently discuss whether such mechanisms play a role in weight control. The final two parts describe major opportunities and challenges associated with studying epigenetic mechanisms in the CNS with its highly heterogenous cell populations, and provide a summary of recent technological advances that will help to delineate whether an obese memory is based upon epigenetic mechanisms.

A rodent model of partial intestinal diversion: a novel metabolic operation

BACKGROUND

Metabolic surgery is safe and the most effective therapy for obesity and its co-morbidities. New procedures may allow for better tailoring of metabolic surgery to the individual patient.

OBJECTIVE

To evaluate the impact, comparative effectiveness, and mechanisms of the partial intestinal diversion (PID), vertical sleeve gastrectomy (VSG), and the combination of PID and VSG on weight and glucose regulation.

SETTING

University research facility, United States.

METHODS

Three cohorts of high-fat diet-induced obese male rats were randomized to distal PID (DPID), proximal PID (PPID), VSG, VSG and DPID (VSG/DPID), or sham operation (Sham). Animals were followed for 11 (cohort 1) or 10 (cohorts 2 and 3) weeks. Outcomes included weight and composition, food intake, glucose metabolism, lipids, bile acids, and energy balance. Statistical comparisons were performed using Tukey's multiple comparison test applied to analysis of variance.

RESULTS

DPID and not PPID resulted in significant weight and body fat reductions relative to Sham. Improved glucose tolerance was seen in all surgical groups though this reached statistical significance for only DPID and VSG compared with Sham. Improvements in baseline glucose and insulin, corresponding insulin resistance, and plasma lipids were noted in DPID compared with Sham. Though the magnitude of weight and body composition changes and metabolic benefit tended to be larger for VSG relative to DPID, it only reached statistical significance for lipids. VSG and VSG/DPID resulted in similar outcomes. Markedly reduced food intake occurred after VSG and more modestly after DPID. Stool caloric content was higher in DPID relative to all groups.

CONCLUSIONS

DPID is an effective metabolic operation resulting in notable weight and fat loss and metabolic improvement relative to sham-operated rodents. Interestingly, combining VSG with DPID added little additional benefit to the effects of VSG.

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.

Role of ghrelin isoforms in the mitigation of hepatic inflammation, mitochondrial dysfunction, and endoplasmic reticulum stress after bariatric surgery in rats

BACKGROUND/OBJECTIVES

Bariatric surgery improves nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH), but the underlying mechanisms remain elusive. We evaluated the potential role of ghrelin isoforms in the amelioration of hepatic inflammation after sleeve gastrectomy and Roux-en-Y gastric bypass (RYGB).

SUBJECTS/METHODS

Plasma ghrelin isoforms were measured in male Wistar rats (n = 129) subjected to surgical (sham operation, sleeve gastrectomy, or RYGB) or dietary interventions [fed ad libitum a normal (ND) or a high-fat diet (HFD) or pair-fed diet]. The effect of acylated and desacyl ghrelin on markers of inflammation, mitochondrial dysfunction, and endoplasmic reticulum (ER) stress in primary rat hepatocytes under palmitate-induced lipotoxic conditions was assessed.

RESULTS

Plasma desacyl ghrelin was decreased after sleeve gastrectomy and RYGB, whereas the acylated/desacyl ghrelin ratio was augmented. Both surgeries diminished obesity-associated hepatic steatosis, CD68⁺- and apoptotic cells, proinflammatory JNK activation, and Crp, Tnf, and Il6 transcripts. Moreover, a postsurgical amelioration in the mitochondrial DNA content, oxidative phosphorylation (OXPHOS) complexes I and II, and ER stress markers was observed. Specifically, following bariatric surgery GRP78, spliced XBP-1, ATF4, and CHOP levels were reduced, as were phosphorylated eIF2α. Interestingly, acylated and desacyl ghrelin inhibited steatosis and inflammation of palmitate-treated hepatocytes in parallel to an upregulation of OXPHOS complexes II, III, and V, and a downregulation of ER stress transducers IRE1α, PERK, ATF6, their downstream effectors, ATF4 and CHOP, as well as chaperone GRP78.

CONCLUSIONS

Our data suggest that the increased relative acylated ghrelin levels after bariatric surgery might contribute to mitigate obesity-associated hepatic inflammation, mitochondrial dysfunction, and ER stress.

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.