Vertical sleeve gastrectomy activates GPBAR-1/TGR5 to sustain weight loss, improve fatty liver, and remit insulin resistance in mice

Bile Acid Signaling in Metabolic and Inflammatory Diseases and Drug Development

Bile acids are the end products of cholesterol catabolism. Hepatic bile acid synthesis accounts for a major fraction of daily cholesterol turnover in humans. Biliary secretion of bile acids generates bile flow and facilitates biliary secretion of lipids, endogenous metabolites, and xenobiotics. In intestine, bile acids facilitate the digestion and absorption of dietary lipids and fat-soluble vitamins. Through activation of nuclear receptors and G protein-coupled receptors and interaction with gut microbiome, bile acids critically regulate host metabolism and innate and adaptive immunity and are involved in the pathogenesis of cholestasis, metabolic dysfunction-associated steatotic liver disease, alcohol-associated liver disease, type-2 diabetes, and inflammatory bowel diseases. Bile acids and their derivatives have been developed as potential therapeutic agents for treating chronic metabolic and inflammatory liver diseases and gastrointestinal disorders. SIGNIFICANCE STATEMENT: Bile acids facilitate biliary cholesterol solubilization and dietary lipid absorption, regulate host metabolism and immunity, and modulate gut microbiome. Targeting bile acid metabolism and signaling holds promise for treating metabolic and inflammatory diseases.

Shengmai San formula alleviates high-fat diet-induced obesity in mice through gut microbiota-derived bile acid promotion of M2 macrophage polarization and thermogenesis

BACKGROUND

Shengmai San Formula (SMS) is a traditional Chinese medicine (TCM) that has been used to treat wasting-thirst regarded as diabetes mellitus, which occurs disproportionately in obese patients. Therefore, we investigated whether SMS could be used to treat obesity, and explored possible mechanisms by which it might improve glucose and fat metabolism.

METHODS

To investigate the effects of SMS on a high-fat diet (HFD)-induced obesity (DIO) model, we studied glucose metabolism via glucose tolerance testing (GTT) and insulin tolerance testing (ITT). Browning of white adipose tissue (WAT) was evaluated using H&E staining, along with browning-related gene and protein expression. Changes in bile acid (BA) levels in serum, liver, ileum, and inguinal white adipose tissue were detected by Ultra performance liquid chromatography tandem quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS). In addition, antimicrobial mixture (ABX) and fecal microbial transplantation (FMT) experiments were used to verify the role of gut flora in the effects produced by SMS on HFD-induced obesity model.

RESULTS

SMS ameliorated diet-induced dyslipidemia in a dose-dependent manner and reduced glucose intolerance and insulin resistance in DIO mice, helping to restore energy metabolism homeostasis. SMS significantly altered the structure of intestinal microbiome composition, decreasing the abundance of Lactobacillus carrying bile salt hydrolase (BSH) enzymes and thereby increasing the level of conjugated BAs in the blood, ileum, and iWAT. Increased TCA content promoted the secretion of Slit3 from M2 macrophages in iWAT, which activates the protein kinase A/calmodulin-dependent protein kinase II (PKA/CaMKII) signaling pathway in sympathetic neurons via the roundabouts receptor 1(ROBO1). This pathway promotes the synthesis and release of norepinephrine (NE), inducing cyclic adenosine monophosphate (cAMP) release in adipose tissue that activates the cyclic adenosine monophosphate/protein kinase A/phosphorylated hormone-sensitive lipase (cAMP/PKA/pHSL) pathway and enhances WAT browning. ABX treatment eliminated SMS effects on glucose and lipid metabolism in DIO mice, whereas glucose and lipid metabolism in obese mice improved following SMS-FMT and increased the level of serum bile acids.

CONCLUSION

SMS affects intestinal flora and bile acid composition in vivo and increased TCA promotes M2 macrophage polarization and Slit3 release in adipose tissue. This induces NE release and increases WAT browning in obese mice, which may be a mechanism by which SMS could be used to treat obesity.

Cardioprotective benefits of metabolic surgery and GLP-1 receptor agonist-based therapies

Individuals with excessive adipose tissue and type 2 diabetes mellitus (T2DM) face a heightened risk of cardiovascular morbidity and mortality. Metabolic surgery is an effective therapy for people with severe obesity to achieve significant weight loss. Additionally, metabolic surgery improves blood glucose levels and can lead to T2DM remission, reducing major adverse cardiovascular outcomes (MACE). Glucagon-like peptide 1 (GLP-1) receptor agonists (GLP-1RAs) are a class of medication that effectively reduce body weight and MACE in patients with T2DM. This review explores the potential mechanisms underlying the cardioprotective benefits of metabolic surgery and GLP-1RA-based therapies and discusses recent evidence and emerging therapies in this dynamic area of research.

Alterations in bile acid kinetics after bariatric surgery in patients with obesity with or without type 2 diabetes

BACKGROUND

Bariatric surgery is an effective treatment option for obesity and provides long-term weight loss and positive effects on metabolism, but the underlying mechanisms are poorly understood. Alterations in bile acid metabolism have been suggested as a potential contributing factor, but comprehensive studies in humans are lacking.

METHODS

In this study, we analysed the postprandial responses of bile acids, C4 and FGF19 in plasma, and excretion of bile acids in faeces, before and after bariatric surgery in patients (n = 38; 74% females) with obesity with or without type 2 diabetes from the BARIA cohort.

FINDINGS

We observed that total fasting plasma bile acid levels increased, and faecal excretion of bile acids decreased after surgery suggesting increased reabsorption of bile acids. Consistent with increased bile acid levels after surgery we observed increased postprandial levels of FGF19 and suppression of the bile acid synthesis marker C4, suggesting increased FXR activation in the gut. We also noted that a subset of bile acids had altered postprandial responses before and after surgery. Finally, fasting plasma levels of 6α-hydroxylated bile acids, which are TGR5 agonists and associated with improved glucose metabolism, were increased after surgery and one of them, HDCA, covaried with diabetes remission in an independent cohort.

INTERPRETATION

Our findings provide new insights regarding bile acid kinetics and suggest that bariatric surgery in humans alters bile acid profiles leading to activation of FXR and TGR5, which may contribute to weight loss, improvements in glucose metabolism, and diabetes remission.

FUNDING

Novo Nordisk Fonden, Leducq Foundation, Swedish Heart-Lung Foundation, Knut and Alice Wallenberg Foundation, the ALF-agreement, ZonMw.

The Potential Mechanism of Remission in Type 2 Diabetes Mellitus After Vertical Sleeve Gastrectomy

In recent years, there has been a gradual increase in the prevalence of obesity and type 2 diabetes mellitus (T2DM), with bariatric surgery remaining the most effective treatment strategy for these conditions. Vertical sleeve gastrectomy (VSG) has emerged as the most popular surgical procedure for bariatric/metabolic surgeries, effectively promoting weight loss and improving or curing T2DM. The alterations in the gastrointestinal tract following VSG may improve insulin secretion and resistance by increasing incretin secretion (especially GLP-1), modifying the gut microbiota composition, and through mechanisms dependent on weight loss. This review focuses on the potential mechanisms through which the enhanced action of incretin and metabolic changes in the digestive system after VSG may contribute to the remission of T2DM.

The Janus of a disease: Diabetes and metabolic dysfunction-associated fatty liver disease

Metabolic Dysfunction-Associated Fatty Liver Disease and Diabetes Mellitus are two prevalent metabolic disorders that often coexist and synergistically contribute to the progression of each other. Several pathophysiological pathways are involved in the association, including insulin resistance, inflammation, and lipotoxicity, providing a foundation for understanding the complex interrelationships between these conditions. The presence of MASLD has a significant impact on diabetes risk and the development of microvascular and macrovascular complications, and diabetes significantly contributes to an increased risk of liver fibrosis progression in MASLD and the development of hepatocellular carcinoma. Moreover, both pathologies have a synergistic effect on cardiovascular events and mortality. Therapeutic interventions targeting MASLD and diabetes are discussed, considering lifestyle modifications, pharmacological agents, and emerging treatment modalities. The review also addresses the challenges in managing these comorbidities, such as the need for personalized approaches and the potential impact on cardiovascular health. The insights gleaned from this analysis can inform clinicians, researchers, and policymakers in developing integrated strategies for preventing, diagnosing, and managing these metabolic disorders.

Increase in bile acids after sleeve gastrectomy improves metabolism by activating GPBAR1 to increase cAMP in mice with nonalcoholic fatty liver disease

BACKGROUND

Bile acids (BAs) concentration can affect metabolic improvement caused by bariatric surgery and BA concentrations increase in patients after sleeve gastrectomy (SG). Here, how BAs after SG affect metabolism in nonalcoholic fatty liver disease (NAFLD) was studied.

METHODS

Mice were given high-fat diet (HFD) to induce NAFLD and received SG surgery. Hepatic and fecal BA concentrations in mice were detected by liquid chromatography-tandem mass spectrometry method. BA-related genes were detected by quantitative real-time polymerase chain reaction. G protein BA receptor 1 (GPBAR1) expression was identified using western blot analysis. NAFLD mice after SG received GPBAR1 inhibitor Triamterene. The weight of mice and mice liver was detected. Mouse liver tissue was observed by hematoxylin-eosin and Oil Red O staining. Triglyceride (TG), nonesterified fatty acid (NEFA), and cyclic adenosine monophosphate (cAMP) levels in mouse liver tissue were analyzed by metabolic assay and enzyme-linked immune sorbent assay.

RESULTS

SG boosted increase in hepatic total/conjugated BAs and related genes and GPBAR1 expression, and attenuated increase in fecal total BAs/muricholic acid in HFD-induced mice and increased fecal taurine-BAs in HFD-induced mice. Triamterene (72 mg/kg) reversed the inhibitory role of SG in HFD-induced increase of body weight, lipid accumulation, inflammatory cell infiltration, and increase of hepatic weight and TG/NEFA content, and counteracted the positive role of SG in HFD-induced increase of hepatic cAMP concentration in mice.

CONCLUSIONS

BAs improve metabolism via activating GPBAR1 to increase cAMP in NAFLD mice after SG.

Effects of intestine-specific deletion of FGF15 on the development of fatty liver disease with vertical sleeve gastrectomy

BACKGROUND

Vertical sleeve gastrectomy (SGx) is a type of bariatric surgery to treat morbid obesity and metabolic dysfunction-associated steatotic liver disease (MASLD). The molecular mechanisms of SGx to improve MASLD are unclear, but increased bile acids (BAs) and FGF19 (mouse FGF15) were observed. FGF15/19 is expressed in the ileum in response to BAs and is critical in not only suppressing BA synthesis in the liver but also promoting energy expenditure. We hypothesized the reduction of obesity and resolution of MASLD by SGx may be mediated by FGF15/19.

METHODS

First, we conducted hepatic gene expression analysis in obese patients undergoing SGx, with the results showing increased expression of FGF19 in obese patients' livers. Next, we used wild-type and intestine-specific Fgf15 knockout mice (Fgf15ile-/-) to determine the effects of FGF15 deficiency on improving the metabolic effects.

RESULTS

SGx improved metabolic endpoints in both genotypes, evidenced by decreased obesity, improved glucose tolerance, and reduced MASLD progression. However, Fgf15ile-/- mice showed better improvement compared to wild-type mice after SGx, suggesting that other mediators than FGF15 are also responsible for the beneficial effects of FGF15 deficiency. Further gene expression analysis in brown adipose tissue suggests increased thermogenesis.

CONCLUSIONS

FGF15 deficiency, the larger BA pool and higher levels of secondary BAs may increase energy expenditure in extrahepatic tissues, which may be responsible for improved metabolic functions following SGx.

CYP8B1 downregulation mediates the metabolic effects of vertical sleeve gastrectomy in mice

BACKGROUND AND AIMS

Although the benefits of vertical sleeve gastrectomy (VSG) surgery are well known, the molecular mechanisms by which VSG alleviates obesity and its complications remain unclear. We aim to determine the role of CYP8B1 (cytochrome P450, family 8, subfamily B, polypeptide 1) in mediating the metabolic benefits of VSG.

APPROACH AND RESULTS

We found that expression of CYP8B1, a key enzyme in controlling the 12α-hydroxylated (12α-OH) bile acid (BA) to non-12α-OH BA ratio, was strongly downregulated after VSG. Using genetic mouse models of CYP8B1 overexpression, knockdown, and knockout, we demonstrated that overexpression of CYP8B1 dampened the metabolic improvements associated with VSG. In contrast, short hairpin RNA-mediated CYP8B1 knockdown improved metabolism similar to those observed after VSG. Cyp8b1 deficiency diminished the metabolic effects of VSG. Further, VSG-induced alterations to the 12α-OH/non-12α-OH BA ratio in the BA pool depended on CYP8B1 expression level. Consequently, intestinal lipid absorption was restricted, and the gut microbiota (GM) profile was altered. Fecal microbiota transplantation from wild type-VSG mice (vs. fecal microbiota transplantation from wild-type-sham mice) improved metabolism in recipient mice, while there were no differences between mice that received fecal microbiota transplantation from knockout-sham and knockout-VSG mice.

CONCLUSIONS

CYP8B1 is a critical downstream target of VSG. Modulation of BA composition and gut microbiota profile by targeting CYP8B1 may provide novel insight into the development of therapies that noninvasively mimic bariatric surgery to treat obesity and its complications.

Bile acid and nonalcoholic steatohepatitis: Molecular insights and therapeutic targets

BACKGROUND

Nonalcoholic steatohepatitis (NASH) has been the second most common cause of liver transplantation in the United States. To date, NASH pathogenesis has not been fully elucidated but is multifactorial, involving insulin resistance, obesity, metabolic disorders, diet, dysbiosis, and gene polymorphism. An effective and approved therapy for NASH has also not been established. Bile acid is long known to have physiological detergent function in emulsifying and absorbing lipids and lipid-soluble molecules within the intestinal lumen. With more and more in-depth understandings of bile acid, it has been deemed to be a pivotal signaling molecule, which is capable of regulating lipid and glucose metabolism, liver inflammation, and fibrosis. In recent years, a plethora of studies have delineated that disrupted bile acid homeostasis is intimately correlated with NASH disease severity.

AIMS

The review aims to clarify the role of bile acid in hepatic lipid and glucose metabolism, liver inflammation, as well as liver fibrosis, and discusses the safety and efficacy of some pharmacological agents targeting bile acid and its associated pathways for NASH.

KEY SCIENTIFIC CONCEPTS OF REVIEW

Bile acid has a salutary effect on hepatic metabolic disorders, which can ameliorate liver fat accumulation and insulin resistance mainly through activating Takeda G-protein coupled receptor 5 and farnesoid X receptor. Moreover, bile acid also exerts anti-inflammation and anti-fibrosis properties. Furthermore, bile acid has great potential in nonalcoholic liver disease stratification and treatment of NASH.

Influence of Bariatric Surgery on Gut Microbiota Composition and Its Implication on Brain and Peripheral Targets

Obesity remains a significant global health challenge, with bariatric surgery remaining as one of the most effective treatments for severe obesity and its related comorbidities. This review highlights the multifaceted impact of bariatric surgery beyond mere physical restriction or nutrient malabsorption, underscoring the importance of the gut microbiome and neurohormonal signals in mediating the profound effects on weight loss and behavior modification. The various bariatric surgery procedures, such as Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG), act through distinct mechanisms to alter the gut microbiome, subsequently impacting metabolic health, energy balance, and food reward behaviors. Emerging evidence has shown that bariatric surgery induces profound changes in the composition of the gut microbiome, notably altering the Firmicutes/Bacteroidetes ratio and enhancing populations of beneficial bacteria such as Akkermansia. These microbiota shifts have far-reaching effects beyond gut health, influencing dopamine-mediated reward pathways in the brain and modulating the secretion and action of key gut hormones including ghrelin, leptin, GLP-1, PYY, and CCK. The resultant changes in dopamine signaling and hormone levels contribute to reduced hedonic eating, enhanced satiety, and improved metabolic outcomes. Further, post-bariatric surgical effects on satiation targets are in part mediated by metabolic byproducts of gut microbiota like short-chain fatty acids (SCFAs) and bile acids, which play a pivotal role in modulating metabolism and energy expenditure and reducing obesity-associated inflammation, as well as influencing food reward pathways, potentially contributing to the regulation of body weight and reduction in hedonic eating behaviors. Overall, a better understanding of these mechanisms opens the door to developing non-surgical interventions that replicate the beneficial effects of bariatric surgery on the gut microbiome, dopamine signaling, and gut hormone regulation, offering new avenues for obesity treatment.

Gut microbiota and therapy for obesity and type 2 diabetes

There has been a major increase in Type 2 diabetes and obesity in many countries, and this will lead to a global public health crisis, which not only impacts on the quality of life of individuals well but also places a substantial burden on healthcare systems and economies. Obesity is linked to not only to type 2 diabetes but also cardiovascular diseases, musculoskeletal disorders, and certain cancers, also resulting in increased medical costs and diminished quality of life. A number of studies have linked changes in gut in obesity development. Dysbiosis, a deleterious change in gut microbiota composition, leads to altered intestinal permeability, associated with obesity and Type 2 diabetes. Many factors affect the homeostasis of gut microbiota, including diet, genetics, circadian rhythms, medication, probiotics, and antibiotics. In addition, bariatric surgery induces changes in gut microbiota that contributes to the metabolic benefits observed post-surgery. Current obesity management strategies encompass dietary interventions, exercise, pharmacotherapy, and bariatric surgery, with emerging treatments including microbiota-altering approaches showing promising efficacy. While pharmacotherapy has demonstrated significant advancements in recent years, bariatric surgery remains one of the most effective treatments for sustainable weight loss. However, access to this is generally limited to those living with severe obesity. This underscores the need for non-surgical interventions, particularly for adolescents and mildly obese patients. In this comprehensive review, we assess longitudinal alterations in gut microbiota composition and functionality resulting from the two currently most effective anti-obesity treatments: pharmacotherapy and bariatric surgery. Additionally, we highlight the functions of gut microbiota, focusing on specific bacteria, their metabolites, and strategies for modulating gut microbiota to prevent and treat obesity. This review aims to provide insights into the evolving landscape of obesity management and the potential of microbiota-based approaches in addressing this pressing global health challenge.

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.

Mechanism of action of the bile acid receptor TGR5 in obesity

G protein-coupled receptors (GPCRs) are a large family of membrane protein receptors, and Takeda G protein-coupled receptor 5 (TGR5) is a member of this family. As a membrane receptor, TGR5 is widely distributed in different parts of the human body and plays a vital role in regulating metabolism, including the processes of energy consumption, weight loss and blood glucose homeostasis. Recent studies have shown that TGR5 plays an important role in glucose and lipid metabolism disorders such as fatty liver, obesity and diabetes. With the global obesity situation becoming more and more serious, a comprehensive explanation of the mechanism of TGR5 and filling the gaps in knowledge concerning clinical ligand drugs are urgently needed. In this review, we mainly explain the anti-obesity mechanism of TGR5 to promote the further study of this target, and show the electron microscope structure of TGR5 and review recent studies on TGR5 ligands to illustrate the specific binding between TGR5 receptor binding sites and ligands, which can effectively provide new ideas for ligand research and promote drug research.

Impact of Bariatric Surgery on Outcomes of Patients with Inflammatory Bowel Disease: a Nationwide Inpatient Sample Analysis, 2005-2018

PURPOSE

The global prevalence of inflammatory bowel disease (IBD) has steadily risen over the past few decades. Bariatric surgery stands out as an effective strategy for inducing weight loss. This study investigated the impacts of bariatric surgery on the clinical outcomes in patients with IBD.

MATERIALS AND METHODS

Data of hospitalized patients aged ≥ 18 years with IBD were extracted from the Nationwide Inpatient Sample (NIS) 2005-2018. The patients were categorized according to whether they underwent bariatric surgery or not. Univariate and multivariable logistic regression analyses were performed to determine the associations between bariatric surgery, prolonged LOS, unfavorable discharge, hospital mortality, and morbidity.

RESULTS

Data from 807,843 hospitalized patients with IBD were extracted. After exclusions and propensity-score matching, 80,545 patients were analyzed, with 16,109 undergoing bariatric surgery and 64,436 not. A total of 23% of patients had a prolonged LOS, 8% had unfavorable discharge, and the mortality rate was 1.2%. Multivariable analyses revealed that, compared to patients without bariatric surgery, patients with bariatric surgery had significantly decreased odds of prolonged LOS (adjusted odds ratio [aOR], 0.89; 95% CI 0.85-0.93), unfavorable discharge (aOR, 0.83; 95% CI: 0.77-0.89), and mortality (aOR, 0.54; 95% CI: 0.44-0.67), but had increased odds of morbidity (aOR, 1.09; 95% CI 1.04-1.13).

CONCLUSION

In adults with IBD, bariatric surgery is associated with favorable outcomes concerning hospital LOS, discharge status, and mortality. However, the risk of overall morbidity is slightly increased in those who received bariatric surgery compared to those who did not.

TGR5 deficiency-induced anxiety and depression-like behaviors: The role of gut microbiota dysbiosis

BACKGROUND AND PURPOSE

Anxiety and depression have been associated with imbalances in the gut microbiota and bile acid metabolism. Takeda G protein-coupled receptor 5 (TGR5), a bile acid receptor involved in metabolism, is influenced by the gut microbiota. This study aimed to investigate the relationship between anxiety, depression, and microbiota using TGR5 knockout mice.

METHODS

We employed the following methods: (1) Assessment of behavioral changes, (2) Measurement of 5-HT levels and protein expression, (3) Analysis of stool samples, (4) Utilization of gene sequencing and statistical analysis to identify microbial signatures, (5) Examination of correlations between microbial signatures and 5-HT levels, and (6) Fecal microbiota transplantation experiments of TGR5-/- mice.

RESULTS

The deletion of TGR5 was found to result in increased anxiety- and depression-like behaviors in mice. TGR5 knockout mice exhibited significant reductions in 5-hydroxytryptamine (5-HT) levels in both serum and hippocampus, accompanied by a decrease in the expression of 5-HT1A receptor in the hippocampus. Moreover, TGR5 deficiency was associated with a decrease in the species richness of the gut microbiota. Specifically, the gut microbiota compositions of TGR5 knockout mice displayed distinct differences compared to their littermates, characterized by higher abundances of Anaeroplasma, Prevotella, Staphylococcus, Jeotgalicoccus, and Helicobacter, and a lower abundance of Bifidobacterium. Notably, a strong association between Jeotgalicoccus as well as Staphylococcus and serum 5-HT levels was observed in co-occurrence network. Furthermore, mice that received fecal microbiota transplants from TGR5-/- mice displayed anxiety and depression -like behaviors, accompanied by alterations in 5-HT levels in the hippocampus and serum.

LIMITATIONS

Study limitations for gut bacteria were analyzed at the genus level only.

CONCLUSION

TGR5 deletion in mice induces anxiety and depression-like behaviors, linked to reduced 5-HT levels in serum and the hippocampus. Gut microbiota changes play a direct role in these behaviors and serotonin alterations. This implicates TGR5 and gut bacteria in mood regulation, with potential therapeutic implications.

Quercetin activates energy expenditure to combat metabolic syndrome through modulating gut microbiota-bile acids crosstalk in mice

Abdominal obesity-related metabolic syndrome (MetS) has emerged as a significant global public health issue that affects human health. Flavonoids, such as quercetin, have been reported to exert obvious anti-obesity and lipid-lowering effects in both humans and animal models. However, the precise underlying mechanism remains elusive. In this study, we investigated the potential roles of gut microbiota-bile acids (BAs) interactions in quercetin-induced anti-obesity effects and metabolic benefits. Oral administration of quercetin significantly enhanced energy metabolism through activating thermogenesis of brown adipose tissues (BAT) and browning of white adipose tissues (WAT), thus mitigating metabolic dysfunctions in an abdominal obesity-related MetS mouse model. Further mechanistic studies demonstrated that quercetin treatment substantially promoted the generation of non-12α-hydroxylated BAs (non-12OH BAs), particularly ursodeoxycholic acid (UDCA) and lithocholic acid (LCA), in serum via regulating the overall structure of gut microbiota and enriching Lactobacillus. High level of non-12OH BAs bind to Takeda G protein-coupled receptor 5 (TGR5) on adipocytes to stimulate thermogenesis. Remarkably, fecal microbiota transplantation (FMT) from quercetin-treated mice replicated the effects of quercetin on non-12OH BAs generation and energy expenditure, which suggested gut microbiota reshape and concomitant BAs regulation were responsible for the benefits on energy metabolism of quercetin in the MetS mouse model. Our findings not only highlighted the critical role of gut microbiota-BAs crosstalk in mediating quercetin-induced energy expenditure, but also enriched the pharmacological mechanisms of quercetin in ameliorating MetS-related diseases.

Microbial sensing in the intestine

The gut microbiota plays a key role in host health and disease, particularly through their interactions with the immune system. Intestinal homeostasis is dependent on the symbiotic relationships between the host and the diverse gut microbiota, which is influenced by the highly co-evolved immune-microbiota interactions. The first step of the interaction between the host and the gut microbiota is the sensing of the gut microbes by the host immune system. In this review, we describe the cells of the host immune system and the proteins that sense the components and metabolites of the gut microbes. We further highlight the essential roles of pattern recognition receptors (PRRs), the G protein-coupled receptors (GPCRs), aryl hydrocarbon receptor (AHR) and the nuclear receptors expressed in the intestinal epithelial cells (IECs) and the intestine-resident immune cells. We also discuss the mechanisms by which the disruption of microbial sensing because of genetic or environmental factors causes human diseases such as the inflammatory bowel disease (IBD).

The emerging role of bile acids in white adipose tissue

The effects of bile acids (BAs) on liver, enteroendocrine function, small intestine, and brown adipose tissue have been described extensively. Outside the liver, BAs in the peripheral circulation system represent a specific but underappreciated physiological compartment. We discuss how systemic BAs can be regarded as specific steroidal hormones that act on white adipocytes, and suggest the name 'bilokines' ('bile hormones') for the specific FXR/TGR5 receptor interaction in adipocytes. Some BAs and their agonists regulate adipocyte differentiation, lipid accumulation, hypoxia, autophagy, adipokine and cytokine secretion, insulin signaling, and glucose uptake. BA signaling could provide a new therapeutic avenue for adipoflammation and metaflammation in visceral obesity, the causal mechanisms underlying insulin resistance and type 2 diabetes mellitus (T2D).

Role of gut microbiota in the postnatal thermoregulation of Brandt's voles

Homeothermy is crucial for mammals. Postnatal growth is the key period for young offspring to acquire gut microbiota. Although gut microbiota may affect mammal thermogenesis, the impact of developmental regulation of gut microbiota on the ability of young pups to produce heat remains unclear. Antibiotics were used to interfere with the establishment of gut microbiota during the development of Brandt's voles, and their thermogenic development and regulatory pathways were determined. Deprivation of microbiota by antibiotics inhibits the development of thermogenesis in pups. Butyric acid and bile acid, as metabolites of gut microbiota, participated in the thermoregulation of pups. We propose that gut microbiota promote the development of thermoregulation through the butyric acid-free fatty acid receptor-2-uncoupling protein-1 or the deoxycholic acid-Takeda-G-protein-receptor-5-uncoupling protein-1 pathway in pups. These results show a relationship between gut microbiota and thermogenesis and expand the mechanism of postnatal development of thermogenesis in small mammals.

Mechanisms of bariatric surgery for weight loss and diabetes remission

Obesity and type 2 diabetes(T2D) lead to defects in intestinal hormones secretion, abnormalities in the composition of bile acids (BAs), increased systemic and adipose tissue inflammation, defects of branched-chain amino acids (BCAAs) catabolism, and dysbiosis of gut microbiota. Bariatric surgery (BS) has been shown to be highly effective in the treatment of obesity and T2D, which allows us to view BS not simply as weight-loss surgery but as a means of alleviating obesity and its comorbidities, especially T2D. In recent years, accumulating studies have focused on the mechanisms of BS to find out which metabolic parameters are affected by BS through which pathways, such as which hormones and inflammatory processes are altered. The literatures are saturated with the role of intestinal hormones and the gut-brain axis formed by their interaction with neural networks in the remission of obesity and T2D following BS. In addition, BAs, gut microbiota and other factors are also involved in these benefits after BS. The interaction of these factors makes the mechanisms of metabolic improvement induced by BS more complicated. To date, we do not fully understand the exact mechanisms of the metabolic alterations induced by BS and its impact on the disease process of T2D itself. This review summarizes the changes of intestinal hormones, BAs, BCAAs, gut microbiota, signaling proteins, growth differentiation factor 15, exosomes, adipose tissue, brain function, and food preferences after BS, so as to fully understand the actual working mechanisms of BS and provide nonsurgical therapeutic strategies for obesity and T2D.

Polysaccharides: The Potential Prebiotics for Metabolic Associated Fatty Liver Disease (MAFLD)

Metabolic (dysfunction) associated fatty liver disease (MAFLD) is recognized as the most prevalent chronic liver disease globally. However, its pathogenesis remains incompletely understood. Recent advancements in the gut-liver axis offer novel insights into the development of MAFLD. Polysaccharides, primarily derived from fungal and algal sources, abundantly exist in the human diet and exert beneficial effects on glycometabolism, lipid metabolism, inflammation, immune modulation, oxidative stress, and the release of MAFLD. Numerous studies have demonstrated that these bioactivities of polysaccharides are associated with their prebiotic properties, including the ability to modulate the gut microbiome profile, maintain gut barrier integrity, regulate metabolites produced by gut microbiota such as lipopolysaccharide (LPS), short-chain fatty acids (SCFAs), and bile acids (BAs), and contribute to intestinal homeostasis. This narrative review aims to present a comprehensive summary of the current understanding of the protective effects of polysaccharides on MAFLD through their interactions with the gut microbiota and its metabolites. Specifically, we highlight the potential molecular mechanisms underlying the prebiotic effects of polysaccharides, which may give new avenues for the prevention and treatment of MAFLD.

RISING STARS: Endocrine regulation of metabolic homeostasis via the intestine and gut microbiome

The gastrointestinal system is now considered the largest endocrine organ, highlighting the importance of gut-derived peptides and metabolites in metabolic homeostasis. Gut peptides are secreted from intestinal enteroendocrine cells in response to nutrients, microbial metabolites, and neural and hormonal factors, and they regulate systemic metabolism via multiple mechanisms. While extensive research is focused on the neuroendocrine effects of gut peptides, evidence suggests that several of these hormones act as endocrine signaling molecules with direct effects on the target organ, especially in a therapeutic setting. Additionally, the gut microbiota metabolizes ingested nutrients and fiber to produce compounds that impact host metabolism indirectly, through gut peptide secretion, and directly, acting as endocrine factors. This review will provide an overview of the role of endogenous gut peptides in metabolic homeostasis and disease, as well as the potential endocrine impact of microbial metabolites on host metabolic tissue function.

Fibroblast growth factor 15, induced by elevated bile acids, mediates the improvement of hepatic glucose metabolism after sleeve gastrectomy

BACKGROUND

Fibroblast growth factor (FGF) 15/19, which is expressed in and secreted from the distal ileum, can regulate hepatic glucose metabolism in an endocrine manner. The levels of both bile acids (BAs) and FGF15/19 are elevated after bariatric surgery. However, it is unclear whether the increase in FGF15/19 is induced by BAs. Moreover, it remains to be understood whether FGF15/19 elevations contribute to improvements in hepatic glucose metabolism after bariatric surgery.

AIM

To investigate the mechanism of improvement of hepatic glucose metabolism by elevated BAs after sleeve gastrectomy (SG).

METHODS

By calculating and comparing the changes of body weight after SG with SHAM group, we examined the weight-loss effect of SG. The oral glucose tolerance test (OGTT) test and area under the curve of OGTT curves were used to assess the anti-diabetic effects of SG. By detecting the glycogen content, expression and activity of glycogen synthase as well as the glucose-6-phosphatase (G6Pase) and phosphoenolpyruvate carboxykinase (Pepck), we evaluated the hepatic glycogen content and gluconeogenesis activity. We examined the levels of total BA (TBA) together with the farnesoid X receptor (FXR)-agonistic BA subspecies in systemic serum and portal vein at week 12 post-surgery. Then the histological expression of ileal FXR and FGF15 and hepatic FGF receptor 4 (FGFR4) with its corresponding signal pathways involved in glucose metabolism were detected.

RESULTS

After surgery, food intake and body weight gain of SG group was decreased compare with the SHAM group. The hepatic glycogen content and glycogen synthase activity was significantly stimulated after SG, while the expression of the key enzyme for hepatic gluconeogenesis: G6Pase and Pepck, were depressed. TBA levels in serum and portal vein were both elevated after SG, the FXR-agonistic BA subspecies: Chenodeoxycholic acid (CDCA), lithocholic acid (LCA) in serum and CDCA, DCA, LCA in portal vein were all higher in SG group than that in SHAM group. Consequently, the ileal expression of FXR and FGF15 were also advanced in SG group. Moreover, the hepatic expression of FGFR4 was stimulated in SG-operated rats. As a result, the activity of its corresponding pathway for glycogen synthesis: FGFR4-Ras-extracellular signal regulated kinase pathway was stimulated, while the corresponding pathway for hepatic gluconeogenesis: FGFR4- cAMP regulatory element-binding protein- peroxisome proliferator-activated receptor γ coactivator-1α pathway was suppressed.

CONCLUSION

Elevated BAs after SG induced FGF15 expression in distal ileum by activating their receptor FXR. Furthermore, the promoted FGF15 partly mediated the improving effects on hepatic glucose metabolism of SG.

Vertical sleeve gastrectomy-derived gut metabolite licoricidin activates beige fat thermogenesis to combat obesity

Obesity is a chronic metabolic disease, affecting individuals throughout the world. Bariatric surgery such as vertical sleeve gastrectomy (VSG) provides sustained weight loss and improves glucose homeostasis in obese mice and humans. However, the precise underlying mechanisms remain elusive. In this study, we investigated the potential roles and the mechanisms of action of gut metabolites in VSG-induced anti-obesity effect and metabolic improvement. Methods: High-fat diet (HFD)-fed C57BL/6J mice were subjected to VSG. Energy dissipation in mice was monitored using metabolic cage experiments. The effects of VSG on gut microbiota and metabolites were determined by 16S rRNA sequencing and metabolomics, respectively. The metabolic beneficial effects of the identified gut metabolites were examined in mice by both oral administration and fat pad injection of the metabolites. Results: VSG in mice greatly increased thermogenic gene expression in beige fat, which was correlated with increased energy expenditure. VSG reshaped gut microbiota composition, resulting in elevated levels of gut metabolites including licoricidin. Licoricidin treatment promoted thermogenic gene expression in beige fat by activating the Adrb3-cAMP-PKA signaling pathway, leading to reduced body weight gain in HFD-fed mice. Conclusions: We identify licoricidin, which mediates the crosstalk between gut and adipose tissue in mice, as a VSG-provoked anti-obesity metabolite. Identification of anti-obesity small molecules should provide new insights into treatment options for obesity and its associated metabolic diseases.

Glucose metabolism after bariatric surgery: implications for T2DM remission and hypoglycaemia

Although promising therapeutics are in the pipeline, bariatric surgery (also known as metabolic surgery) remains our most effective strategy for the treatment of obesity and type 2 diabetes mellitus (T2DM). Of the many available options, Roux-en-Y gastric bypass (RYGB) and vertical sleeve gastrectomy (VSG) are currently the most widely used procedures. RYGB and VSG have very different anatomical restructuring but both surgeries are effective, to varying degrees, at inducing weight loss and T2DM remission. Both weight loss-dependent and weight loss-independent alterations in multiple tissues (such as the intestine, liver, pancreas, adipose tissue and skeletal muscle) yield net improvements in insulin resistance, insulin secretion and insulin-independent glucose metabolism. In a subset of patients, post-bariatric hypoglycaemia can develop months to years after surgery, potentially reflecting the extreme effects of potent glucose reduction after surgery. This Review addresses the effects of bariatric surgery on glucose regulation and the potential mechanisms responsible for both the resolution of T2DM and the induction of hypoglycaemia.

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.

Sleeve gastrectomy decreases high-fat diet induced colonic pro-inflammatory status through the gut microbiota alterations

Background

High-fat diet (HFD) induced obesity is characterized with chronic low-grade inflammation in various tissues and organs among which colon is the first to display pro-inflammatory features associated with alterations of the gut microbiota. Sleeve gastrectomy (SG) is currently one of the most effective treatments for obesity. Although studies reveal that SG results in decreased levels of inflammation in multiple tissues such as liver and adipose tissues, the effects of surgery on obesity related pro-inflammatory status in the colon and its relation to the microbial changes remain unknown.

Methods

To determine the effects of SG on the colonic pro-inflammatory condition and the gut microbiota, SG was performed on HFD-induced obese mice. To probe the causal relationship between alterations of the gut microbiota and improvements of pro-inflammatory status in the colon following SG, we applied broad-spectrum antibiotics cocktails on mice that received SG to disturb the gut microbial changes. The pro-inflammatory shifts in the colon were assessed based on morphology, macrophage infiltration and expressions of a variety of cytokine genes and tight junction protein genes. The gut microbiota alterations were analyzed using 16s rRNA sequencing. RNA sequencing of colon was conducted to further explore the role of the gut microbiota in amelioration of colonic pro-inflammation following SG at a transcriptional level.

Results

Although SG did not lead to pronounced changes of colonic morphology and macrophage infiltration in the colon, there were significant decreases in the expressions of several pro-inflammatory cytokines including interleukin-1β (IL-1β), IL-6, IL-18, and IL-23 as well as increased expressions of some tight junction proteins in the colon following SG, suggesting an improvement of pro-inflammatory status. This was accompanied by changing populations of the gut microbiota such as increased richness of Lactobacillus subspecies following SG. Importantly, oral administrations of broad-spectrum antibiotics to delete most intestinal bacteria abrogated surgical effects to relieve colonic pro-inflammation. This was further confirmed by transcriptional analysis of colon indicating that SG regulated inflammation related pathways in a manner that was gut microbiota relevant.

Conclusion

These results support that SG decreases obesity related colonic pro-inflammatory status through the gut microbial alterations.

Combinatorial therapy with BAR502 and UDCA resets FXR and GPBAR1 signaling and reverses liver histopathology in a model of NASH

Non-alcoholic steatosis (NAFLD) and steatohepatitis (NASH) are two highly prevalent human disorders for which therapy remains suboptimal. Bile acids are signaling molecules acting on two main receptors the Farnesoid-x-receptor (FXR) and G protein coupled receptor GPB AR1. Clinical trials have shown that FXR agonism might result in side effects along with lack of efficacy in restoring liver histopathology. For these reasons a multi-targets therapy combined FXR agonists with agent targeting additional molecular mechanisms might have improved efficacy over selective FXR agonists. In the present study we have compared the effects of BAR502, a dual FXR/GPBAR1 ligand) alone or in combination with ursodeoxycholic acid (UDCA) in a model of NAFLD/NASH induced by feeding mice with a Western diet for 10 weeks. The results demonstrated that while BAR502 and UDCA partially protected against liver damage caused by Western diet, the combination of the two, reversed the pro-atherogenic lipid profile and completely reversed the histopathology damage, attenuating liver steatosis, ballooning, inflammation and fibrosis. Additionally, while both agents increased insulin sensitivity and bile acid signaling, the combination of the two, modulated up top 85 genes in comparison of mice feed a Western diet, strongly reducing expression of inflammatory markers such as chemokines and cytokines. Additionally, the combination of the two agents redirected the bile acid metabolism toward bile acid species that are GPBAR1 agonist while reduced liver bile acid content and increased fecal excretion. Together, these data, highlight the potential role for a combinatorial therapy based on BAR502 and UDCA in treating of NAFLD.

Downregulation of hepatic lncRNA Gm19619 improves gluconeogenesis and lipogenesis following vertical sleeve gastrectomy in mice

Long non-coding RNAs (lncRNAs) are emerging important epigenetic regulators in metabolic processes. Whether they contribute to the metabolic effects of vertical sleeve gastrectomy (VSG), one of the most effective treatments for sustainable weight loss and metabolic improvement, is unknown. Herein, we identify a hepatic lncRNA Gm19619, which is strongly repressed by VSG but highly up-regulated by diet-induced obesity and overnight-fasting in mice. Forced transcription of Gm19619 in the mouse liver significantly promotes hepatic gluconeogenesis with the elevated expression of G6pc and Pck1. In contrast, AAV-CasRx mediated knockdown of Gm19619 in high-fat diet-fed mice significantly improves hepatic glucose and lipid metabolism. Mechanistically, Gm19619 is enriched along genomic regions encoding leptin receptor (Lepr) and transcription factor Foxo1, as revealed in chromatin isolation by RNA purification (ChIRP) assay and is confirmed to modulate their transcription in the mouse liver. In conclusion, Gm19619 may enhance gluconeogenesis and lipid accumulation in the liver.

Sleeve Gastrectomy-Induced Weight Loss Increases Insulin Clearance in Obese Mice

Sleeve gastrectomy (SG) successfully recovers metabolic homeostasis in obese humans and rodents while also resulting in the normalization of insulin sensitivity and insulinemia. Reduced insulin levels have been attributed to lower insulin secretion and increased insulin clearance in individuals submitted to SG. Insulin degradation mainly occurs in the liver in a process controlled, at least in part, by the insulin-degrading enzyme (IDE). However, research has yet to explore whether liver IDE expression or activity is altered after SG surgery. In this study, C57BL/6 mice were fed a chow (CTL) or high-fat diet (HFD) for 10 weeks. Afterward, the HFD mice were randomly assigned to two groups: sham-surgical (HFD-SHAM) and SG-surgical (HFD-SG). Here, we confirmed that SG improves glucose-insulin homeostasis in obese mice. Additionally, SG reduced insulinemia by reducing insulin secretion, assessed by the analysis of plasmatic C-peptide content, and increasing insulin clearance, which was evaluated through the calculation of the plasmatic C-peptide:insulin ratio. Although no changes in hepatic IDE activity were observed, IDE expression was higher in the liver of HFD-SG compared with HFD-SHAM mice. These results indicate that SG may be helpful to counteract obesity-induced hyperinsulinemia by increasing insulin clearance, likely through enhanced liver IDE expression.

Role of bile acids in overweight and obese children and adolescents

Bile acids (BAs) are amphipathic molecules synthetized in the liver. They are primarily involved in the digestion of nutrients. Apart from their role in dietary lipid absorption, BAs have progressively emerged as key regulators of systemic metabolism and inflammation. In the last decade, it became evident that BAs are particularly important for the regulation of glucose, lipid, and energy metabolism. Indeed, the interest in role of BA in metabolism homeostasis is further increased due to the global public health increase in obesity and related complications and a large number of research postulating that there is a close mutual relationship between BA and metabolic disorders. This strong relationship seems to derive from the role of BAs as signaling molecules involved in the regulation of a wide spectrum of metabolic pathways. These actions are mediated by different receptors, particularly nuclear farnesoid X receptor (FXR) and Takeda G protein coupled receptor 5 (TGR5), which are probably the major effectors of BA actions. These receptors activate transcriptional networks and signaling cascades controlling the expression and activity of genes involved in BA, lipid and carbohydrate metabolism, energy expenditure, and inflammation. The large correlation between BAs and metabolic disorders offers the possibility that modulation of BAs could be used as a therapeutic approach for the treatment of metabolic diseases, including obesity itself. The aim of this review is to describe the main physiological and metabolic actions of BA, focusing on its signaling pathways, which are important in the regulation of metabolism and might provide new BA -based treatments for metabolic diseases.

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.

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

INTRODUCTION

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

METHODS

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

RESULTS

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

DISCUSSION

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

CONCLUSION

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

Modulatory role of gut microbiota in cholesterol and glucose metabolism: Potential implications for atherosclerotic cardiovascular disease Atherosclerosis

Accumulating evidence suggests an important role of gut microbiota in physiological processes of host metabolism as well as cardiometabolic disease. Recent advances in metagenomic and metabolomic research have led to discoveries of novel pathways in which intestinal microbial metabolism of dietary nutrients is linked to metabolic profiles and cardiovascular disease risk. A number of metaorganismal circuits have been identified by microbiota transplantation studies and experimental models using germ-free rodents. Many of these pathways involve gut microbiota-related bioactive metabolites that impact host metabolism, in particular lipid and glucose homeostasis, partly via specific host receptors. In this review, we summarize the current knowledge of how the gut microbiome can impact cardiometabolic phenotypes and provide an overview of recent advances of gut microbiome research. Finally, the potential of modulating intestinal microbiota composition and/or targeting microbiota-related pathways for novel preventive and therapeutic strategies in cardiometabolic and cardiovascular diseases will be discussed.

Duodenal-jejunal bypass increases intraduodenal bile acids and upregulates duodenal SIRT1 expression in high-fat diet and streptozotocin-induced diabetic rats

BACKGROUND

The mechanisms underlying diabetes remission after duodenal-jejunal bypass (DJB) remain elusive. In DJB surgery, the duodenum is excluded. However, the duodenum has emerged as an important regulator of glucose homeostasis, and elevated duodenal SIRT1 leads to improved hepatic insulin sensitivity. After DJB, bile acids (BAs) in the duodenum are not mixed and diluted by the ingested food. And activation of BA receptors promotes SIRT1 expression in many tissues. We hypothesized that BA-mediated upregulation of SIRT1 may contribute to diabetic control after DJB.

AIM

To investigate the surgical effects of DJB on duodenal SIRT1 expression and uncover the potential crosslinks between BAs and SIRT1.

METHODS

Twenty diabetic rats were randomly allocated to the sham (n = 10) and DJB (n = 10) groups. Body weight, food intake, fasting blood glucose (FBG), serum and intraduodenal total BA (TBA) levels were measured accordingly. Oral glucose tolerance test (OGTT) and intraperitoneal pyruvate tolerance test (ipPTT) were performed to evaluate the effects of surgeries on systemic glucose disposal and hepatic gluconeogenesis. The key genes of BA signaling pathway in the duodenal mucosa, including farnesoid X receptor (FXR), small heterodimer partner (SHP), and Takeda G-protein-coupled receptor 5 (TGR5) were evaluated by real-time quantitative polymerase chain reaction 8 wk postoperatively. The duodenal SIRT1, AMPK, and phosphorylated AMPK (p-AMPK) levels were evaluated by western blotting. Rat small intestine epithelial IEC-6 cells were treated with GW4064 and INT-777 to verify the effects of BAs on SIRT1 expression in enterocytes.

RESULTS

The DJB group exhibited body weight and food intake comparable to those of the sham group at all postoperative time points. The FBG level and area under the curve for the OGTT and ipPTT were significantly lower in the DJB group. The DJB group exhibited higher fasting and postprandial serum TBA levels than the sham group at both 2 and 8 wk postoperatively. At 8 wk after surgery, the DJB group showed higher intraluminal TBA concentration, upregulated mRNA expression of FXR and SHP, and elevated protein expression of SIRT1 and p-AMPK in the descending and horizontal segments of the duodenum. Activation of FXR and TGR5 receptors by GW4064 and INT-777 increased the mRNA and protein expression of SIRT1 and promoted the phosphorylation of AMPK in IEC-6 cells.

CONCLUSION

DJB elevates intraduodenal BA levels and activates the duodenal BA signaling pathway, which may upregulate duodenal SIRT1 and further contribute to improved glucose homeostasis 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.

Changes of bile acids and resting energy expenditure after laparoscopic cholecystectomy in type 2 diabetes patients: a prospective study

BACKGROUND

We aimed to investigate changes of bile acids and resting energy expenditure (REE) in patients with type 2 diabetes mellitus (T2DM) after laparoscopic cholecystectomy (LC) and the role in metabolic homeostasis.

METHODS

From December 2019 to December 2021, a total of 77 T2DM patients with gallbladder polyps were included in our study. Among them, 40 patients who underwent LC were enrolled into the cholecystectomy group, and 37 patients who did not undergo LC were enrolled into the control group. Preoperative and 6-months postoperative demographic data, body weight, food intake, effects on diabetes control, and biomedical variables were recorded and compared.

RESULTS

The mean level of total bile acids (TBA) was higher than that in the control group (P = 0.033) and increased significantly after LC compared to baseline (P = 0.029). The REE level in the cholecystectomy group was higher than that in the control group (P = 0.032) and increased compared to the baseline (P = 0.011). The utilization of carbohydrates increased significantly after LC (P < 0.001) while the utilization of fat decreased (P < 0.001). The mean level of fasting plasma glucose (P = 0.004), hemoglobin A1C (P < 0.001), and homeostasis model assessment-insulin resistance (P = 0.045) decreased after LC. The mean level of total cholesterol (P = 0.003) and low-density lipoprotein cholesterol significantly decreased (P = 0.021), whereas the level of high-density lipoprotein cholesterol increased (P < 0.001).

CONCLUSIONS

The level of REE and TBA increased after LC in patients with T2DM, and the glucose and lipid metabolism improved. Trial registration This study was registered in the Chinese Clinical Trial Registry on November 30, 2018, registered number: ChiCTR1900027823.

Discovery of farnesoid X receptor and its role in bile acid metabolism

In 1995, the nuclear hormone orphan receptor farnesoid X receptor (FXR, NR1H4) was identified as a farnesol receptor expressed mainly in liver, kidney, and adrenal gland of rats. In 1999, bile acids were identified as endogenous FXR ligands. Subsequently, FXR target genes involved in the regulation of hepatic bile acid synthesis, secretion, and intestinal re-absorption were identified. FXR signaling was proposed as a mechanism of feedback regulation of the rate-limiting enzyme for bile acid synthesis, cholesterol 7⍺-hydroxylase (CYP7A1). The primary bile acids synthesized in the liver are transformed to secondary bile acids by the gut microbiota. The gut-to-liver axis plays a critical role in the regulation of bile acid synthesis, composition and circulating bile acid pool size, which in turn regulates glucose, lipid, and energy metabolism. Dysregulation of bile acid metabolism and FXR signaling in the gut-to-liver axis contributes to metabolic diseases including obesity, diabetes, and non-alcoholic fatty liver disease. This review will cover the discovery of FXR as a bile acid sensor in the regulation of bile acid metabolism and as a metabolic regulator of lipid, glucose, and energy homeostasis. It will also provide an update of FXR functions in the gut-to-liver axis and the drug therapies targeting bile acids and FXR for the treatment of liver metabolic diseases.

Bile acid and receptors: biology and drug discovery for nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD), a series of liver metabolic disorders manifested by lipid accumulation within hepatocytes, has become the primary cause of chronic liver diseases worldwide. About 20%-30% of NAFLD patients advance to nonalcoholic steatohepatitis (NASH), along with cell death, inflammation response and fibrogenesis. The pathogenesis of NASH is complex and its development is strongly related to multiple metabolic disorders (e.g. obesity, type 2 diabetes and cardiovascular diseases). The clinical outcomes include liver failure and hepatocellular cancer. There is no FDA-approved NASH drug so far, and thus effective therapeutics are urgently needed. Bile acids are synthesized in hepatocytes, transported into the intestine, metabolized by gut bacteria and recirculated back to the liver by the enterohepatic system. They exert pleiotropic roles in the absorption of fats and regulation of metabolism. Studies on the relevance of bile acid disturbance with NASH render it as an etiological factor in NASH pathogenesis. Recent findings on the functional identification of bile acid receptors have led to a further understanding of the pathophysiology of NASH such as metabolic dysregulation and inflammation, and bile acid receptors are recognized as attractive targets for NASH treatment. In this review, we summarize the current knowledge on the role of bile acids and the receptors in the development of NAFLD and NASH, especially the functions of farnesoid X receptor (FXR) in different tissues including liver and intestine. The progress in the development of bile acid and its receptors-based drugs for the treatment of NASH including bile acid analogs and non-bile acid modulators on bile acid metabolism is also discussed.

Gut microbiota and related metabolites in the pathogenesis of nonalcoholic steatohepatitis and its resolution after bariatric surgery

Nonalcoholic fatty liver disease (NAFLD) is increasing in parallel with the rising prevalence of obesity, leading to major health and socioeconomic consequences. To date, the most effective therapeutic approach for NAFLD is weight loss. Accordingly, bariatric surgery (BS), which produces marked reductions in body weight, is associated with significant histopathological improvements in advanced stages of NAFLD, such as nonalcoholic steatohepatitis (NASH) and liver fibrosis. BS is also associated with substantial taxonomical and functional alterations in gut microbiota, which are believed to play a significant role in metabolic improvement after BS. Interestingly, gut microbiota and related metabolites may be implicated in the pathogenesis of NAFLD through diverse mechanisms, including specific microbiome signatures, short chain fatty acid production or the modulation of one-carbon metabolism. Moreover, emerging evidence highlights the potential association between gut microbiota changes after BS and NASH resolution. In this review, we summarize the current knowledge on the relationship between NAFLD severity and gut microbiota, as well as the role of the gut microbiome and related metabolites in NAFLD improvement after BS.

Mechanisms of Weight Loss After Obesity Surgery

Obesity surgery remains the most effective treatment for obesity and its complications. Weight loss was initially attributed to decreased energy absorption from the gut but has since been linked to reduced appetitive behavior and potentially increased energy expenditure. Implicated mechanisms associating rearrangement of the gastrointestinal tract with these metabolic outcomes include central appetite control, release of gut peptides, change in microbiota, and bile acids. However, the exact combination and timing of signals remain largely unknown. In this review, we survey recent research investigating these mechanisms, and seek to provide insights on unanswered questions over how weight loss is achieved following bariatric surgery which may eventually lead to safer, nonsurgical weight-loss interventions or combinations of medications with surgery.

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.

Bile acids, gut microbiota and metabolic surgery

Metabolic surgery, or bariatric surgery, is currently the most effective approach for treating obesity and its complications. Vertical sleeve gastrectomy (VSG) and Roux-en-Y gastric bypass (RYGB) are the top two types of commonly performed metabolic surgery now. The precise mechanisms of how the surgeries work are still unclear, therefore much research has been conducted in this area. Gut hormones such as GLP-1 and PYY have been studied extensively in the context of metabolic surgery because they both participate in satiety and glucose homeostasis. Bile acids, whose functions cover intestinal lipid absorption and various aspects of metabolic regulation via the action of FXR, TGR5, and other bile acid receptors, have also been actively investigated as potential mediators of metabolic surgery. Additionally, gut microbiota and their metabolites have also been studied because they can affect metabolic health. The current review summarizes and compares the recent scientific progress made on identifying the mechanisms of RYGB and VSG. One of the long-term goals of metabolic/bariatric surgery research is to develop new pharmacotherapeutic options for the treatment of obesity and diabetes. Because obesity is a growing health concern worldwide, there is a dire need in developing novel non-invasive treatment options.

Bile Acid-Mediated Activation of Brown Fat Protects From Alcohol-Induced Steatosis and Liver Injury in Mice

BACKGROUND & AIMS

Alcohol-associated liver disease (AALD) is one of the most common causes of liver injury and failure. Limited knowledge of the mechanisms underlying AALD impedes the development of efficacious therapies. Bile acid (BA) signaling was shown to participate in the progression of AALD. However, the mechanisms remain poorly understood.

METHODS

C57BL/6J wild-type (WT), Takeda G-protein-coupled bile acid receptor 5 (TGR5) knockout (KO) and brown adipose tissue (BAT)-specific TGR5 knockdown mice were subjected to ethanol feeding-induced AALD. Liver samples from alcoholic hepatitis patients were used to examine the BA circulation signaling. Human Embryonic Kidney Cells 293 were used for the TGR5 reporter assay. 23(S)-methyl-lithocholic acid was used as a molecular tool to confirm the regulatory functions of BAT in the AALD mouse model.

RESULTS

Ethanol feeding increased the expression of the thermogenesis genes downstream of TGR5 in BAT of WT, but not TGR5 KO, mice. TGR5 deficiency significantly blocked BAT activity and energy expenditure in mice after ethanol feeding. Alcohol increased serum BA levels in mice and human beings through altering BA transportation, and the altered BAs activated TGR5 signaling to regulate metabolism. Compared with ethanol-fed WT mice, ethanol-fed TGR5 KO mice showed less free fatty acid (FFA) β-oxidation in BAT, leading to higher levels of FFA in the circulation, increased liver uptake of FFAs, and exacerbated AALD. BAT-specific TGR5 knockdown mice showed similar results with TGR5 KO mice in AALD. Agonist treatment significantly activated TGR5 signaling in BAT, increased thermogenesis, reduced serum FFA level, and ameliorated hepatic steatosis and injury in AALD mice, while these effects were lost in TGR5 KO mice.

CONCLUSIONS

BA signaling plays a protective role in AALD by enhancing BAT thermogenesis. Targeting TGR5 in BAT may be a promising approach for the treatment of AALD.

The gut microbiota and its products: Establishing causal relationships with obesity related outcomes

Gut microorganisms not only participate in the metabolism of carbohydrate, lipids, protein, and polypeptides in the intestine but also directly affect the metabolic phenotypes of the host. Although many studies have described the apparent effects of gut microbiota on human health, the development of metagenomics and culturomics in the past decade has generated a large amount of evidence suggesting a causal relationship between gut microbiota and obesity. The interaction between the gut microbiota and host is realized by microbial metabolites with multiple biological functions. We concentrated here on several representative beneficial species connected with obesity as well as the mechanisms, with particular emphasis on microbiota-dependent metabolites. Finally, we consider the potential clinical significance of these relationships to fuel the conception and realization of novel therapeutic and preventive strategies.

Inhibition of chylomicron assembly leads to dissociation of hepatic steatosis from inflammation and fibrosis

Regulating dietary fat absorption may impact progression of nonalcoholic fatty liver disease (NAFLD). Here, we asked if inducible inhibition of chylomicron assembly, as observed in intestine-specific microsomal triglyceride (TG) transfer protein knockout mice (Mttp-IKO), could retard NAFLD progression and/or reverse established fibrosis in two dietary models. Mttp-IKO mice fed a methionine/choline-deficient (MCD) diet exhibited reduced hepatic TGs, inflammation, and fibrosis, associated with reduced oxidative stress and downstream activation of c-Jun N-terminal kinase and nuclear factor kappa B signaling pathways. However, when Mttp^flox mice were fed an MCD for 5 weeks and then administered tamoxifen to induce Mttp-IKO, hepatic TG was reduced, but inflammation and fibrosis were increased after 10 days of reversal along with adaptive changes in hepatic lipogenic mRNAs. Extending the reversal time, following 5 weeks of MCD feeding to 30 days led to sustained reductions in hepatic TG, but neither inflammation nor fibrosis was decreased, and both intestinal permeability and hepatic lipogenesis were increased. In a second model, similar reductions in hepatic TG were observed when mice were fed a high-fat/high-fructose/high-cholesterol (HFFC) diet for 10 weeks, then switched to chow ± tamoxifen (HFFC → chow) or (HFFC → Mttp-IKO chow), but again neither inflammation nor fibrosis was affected. In conclusion, we found that blocking chylomicron assembly attenuates MCD-induced NAFLD progression by reducing steatosis, oxidative stress, and inflammation. In contrast, blocking chylomicron assembly in the setting of established hepatic steatosis and fibrosis caused increased intestinal permeability and compensatory shifts in hepatic lipogenesis that mitigate resolution of inflammation and fibrogenic signaling despite 50–90-fold reductions in hepatic TG.

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.