Endocrine functions of bile acids

Bile Acids Transporters of Enterohepatic Circulation for Targeted Drug Delivery

Bile acids (BAs) are important steroidal molecules with a rapidly growing span of applications across a variety of fields such as supramolecular chemistry, pharmacy, and biomedicine. This work provides a systematic review on their transport processes within the enterohepatic circulation and related processes. The focus is laid on the description of specific or less-specific BA transport proteins and their localization. Initially, the reader is provided with essential information about BAs′ properties, their systemic flow, metabolism, and functions. Later, the transport processes are described in detail and schematically illustrated, moving step by step from the liver via bile ducts to the gallbladder, small intestine, and colon; this description is accompanied by descriptions of major proteins known to be involved in BA transport. Spillage of BAs into systemic circulation and urine excretion are also discussed. Finally, the review also points out some of the less-studied areas of the enterohepatic circulation, which can be crucial for the development of BA-related drugs, prodrugs, and drug carrier systems.

Sea Cucumber Body Vesicular Syndrome Is Driven by the Pond Water Microbiome via an Altered Gut Microbiota

Apostichopus japonicus (sea cucumber) is one of the most valuable aquaculture species in China; however, different diseases can limit its economic development. Recently, a novel disease, body vesicular syndrome (BVS), was observed in A. japonicus aquaculture. Diseased animals displayed no obvious phenotypic characteristics; however, after boiling at the postharvest stage, blisters, lysis, and body ruptures appeared. In this study, a multiomics strategy incorporating analysis of the gut microbiota, the pond microbiome, and A. japonicus genotype was established to investigate BVS. Detailed analyses of differentially expressed proteins (DEPs) and metabolites suggested that changes in cell adhesion structures, caused by disordered fatty acid β-oxidation mediated by vitamin B5 deficiency, could be a putative BVS mechanism. Furthermore, intestinal dysbacteriosis due to microbiome variations in pond water was considered a potential reason for vitamin B5 deficiency. Our BVS index, based on biomarkers identified from the A. japonicus gut microbiota, was a useful tool for BVS diagnosis. Finally, vitamin B5 supplementation was successfully used to treat BVS, suggesting an association with BVS etiology.

IMPORTANCE Body vesicular syndrome (BVS) is a novel disease in sea cucumber aquaculture. As no phenotypic features are visible, BVS is difficult to confirm during aquaculture and postharvest activities, until animals are boiled. Therefore, BVS could lead to severe economic losses compared with other diseases in sea cucumber aquaculture. In this study, for the first time, we systematically investigated BVS pathogenesis and proposed an effective treatment for the condition. Moreover, based on the gut microbiota, we established a noninvasive diagnostic method for BVS in sea cucumber.

Potential Roles of the Gut Microbiota in Pancreatic Carcinogenesis and Therapeutics

The intestinal microenvironment is composed of normal gut microbiota and the environment in which it lives. The largest microecosystem in the human body is the gut microbiota, which is closely related to various diseases of the human body. Pancreatic cancer (PC) is a common malignancy of the digestive system worldwide, and it has a 5-year survival rate of only 5%. Early diagnosis of pancreatic cancer is difficult, so most patients have missed their best opportunity for surgery at the time of diagnosis. However, the etiology is not entirely clear, but there are certain associations between PC and diet, lifestyle, obesity, diabetes and chronic pancreatitis. Many studies have shown that the translocation of the gut microbiota, microbiota dysbiosis, imbalance of the oral microbiota, the interference of normal metabolism function and toxic metabolite products are closely associated with the incidence of PC and influence its prognosis. Therefore, understanding the correlation between the gut microbiota and PC could aid the diagnosis and treatment of PC. Here, we review the correlation between the gut microbiota and PC and the research progresses for the gut microbiota in the diagnosis and treatment of PC.

Identification of the Metabolomics Signature of Human Follicular Fluid from PCOS Women with Insulin Resistance

Context. Polycystic ovary syndrome (PCOS) is a gynecological endocrine disease, and approximately 60% of patients with PCOS have different degrees of insulin resistance (IR). The regulatory role of metabolic networks in human follicular fluid (FF) related to IR in PCOS remains unclear. Aims. To explore the effect of IR on the metabolism of PCOS by analyzing the changes in FF metabolites in PCOS patients who are undergoing assisted reproductive technology based on the metabonomic platform of ultraperformance gas chromatography coupled to mass spectrometry (GC/MS). Method. Eight PCOS patients with IR (PCOS-IR) and 8 PCOS patients without IR (PCOS-NIR) were enrolled. All patients received controlled ovarian stimulation by using the gonadotropin-releasing hormone (GnRH) antagonist protocol, and the FF of a single dominant follicle was collected on the day of oocyte retrieval. The metabolite profiles of the FF were determined by GC/MS. Key Results. A total of 20 differentially expressed metabolites in FF were identified. Compared with levels in the PCOS-NIR group, stearic acid, palmitic acid, pentadecanoic acid, stigmasterol, citric acid, isocitric acid, thymine, and pyruvic acid in FF were significantly increased in the PCOS-IR group. Lithocholic acid and sinapinic acid in FF decreased significantly. The affected metabolic pathways with potential regulatory roles were identified by KEGG annotation. Conclusion. Compared with the PCOS-NIR group, the PCOS-IR group showed more significant metabolic abnormalities. Implications. These results will help us to understand the pathogenesis of PCOS combined with IR and will provide new clues for studying metabolic disorders associated with PCOS, e.g., IR.

Determination of individual bile acids in acute respiratory distress syndrome reveals a specific pattern of primary and secondary bile acids and a shift to the acidic pathway as an adaptive response to the critical condition

OBJECTIVES

Cholestasis and elevated serum bile¹ acid levels are common in critically ill patients. This study aims to define the specific pattern of bile acids associated with acute respiratory distress syndrome (ARDS) and the changes in pattern over time.

METHODS

Prospective observational study. Serum samples of 70 ARDS patients were analyzed for primary bile acids (cholic acid, chenodeoxycholic acid) and secondary bile acids (deoxycholic acid, litocholic acid, and ursodeoxycholic acid) as well as their glycine and taurine glycation products.

RESULTS

Primary bile acid levels increased from day zero to day five by almost 50% (p<0.05). This change bases on a statistically significant increase in all primary bile acids between day 0 and day 5 (cholic acid [CA] p=0.001, taurocholic acid [TCA] p=0.004, glycocholic acid [GCA] p<0.001, chenodeoxycholic acid [CDCA] p=0.036, taurochenodeoxycholic acid [TCDCA] p<0.001, glycochenodeoxycholic acid [GCDCA] p<0.001). Secondary bile acids showed predominantly decreased levels on day 0 compared to the control group and remained stable throughout the study period; the differences between day zero and day five were not statistically significant. Non-survivors exhibited significantly higher levels of TCDCA on day 5 (p<0.05) than survivors. This value was also independently associated with survival in a logistic regression model with an odds ratio of 2.24 (95% CI 0.53-9.46).

CONCLUSIONS

The individual bile acid profile of this ARDS patient cohort is unique compared to other disease states. The combination of changes in individual bile acids reflects a shift toward the acidic pathway of bile acid synthesis. Our results support the concept of ARDS-specific plasma levels of bile acids in a specific pattern as an adaptive response mechanism.

Pleiotropic roles of FXR in liver and colorectal cancers

Nuclear receptor farnesoid X receptor (FXR) is generally considered a cell protector of enterohepatic tissues and a suppressor of liver cancer and colorectal carcinoma (CRC). Loss or reduction of FXR expression occurs during carcinogenesis, and the FXR level is inversely associated with the aggressive behaviors of the malignancy. Global deletion of FXR and tissue-specific deletion of FXR display distinct effects on tumorigenesis. Epigenetic silencing and inflammatory context are two main contributors to impaired FXR expression and activity. FXR exerts its antitumorigenic function via the following mechanisms: 1) FXR regulates multiple metabolic processes, notably bile acid homeostasis; 2) FXR antagonizes hepatic and enteric inflammation; 3) FXR impedes aberrant activation of some cancer-related pathways; and 4) FXR downregulates a number of oncogenes while upregulating some tumor suppressor genes. Restoring FXR functions via its agonists provides a therapeutic approach for patients with liver cancer and CRC. However, an in-depth understanding of the species-specific pharmacological effects is a prerequisite for assessing the clinical safety and efficacy of FXR agonists in human cancer treatment.

Pharmacological Dose-Effect Profiles of Various Concentrations of Humanised Primary Bile Acid in Encapsulated Cells

Bile acids (BA)s are known surfactants and well-documented to play a major role in food digestion and absorption. Recently, potential endocrinological and formulation-stabilisation effects of BAs have been explored and their pharmacological effects on supporting cell survival and functions have gained wide interest. Hence, this study aimed to explore the hyper-glycaemic dependent dose-effect of the BA chenodeoxycholic acid (CDCA) when encapsulated with pancreatic β-cells, allowing assessment of CDCA's impacts when encapsulated. Four different concentrations of the BA were prepared, and viable cells were encapsulated and incubated for 2 days. Multiple analyses were carried out including confocal imaging, glucose-induced cellular mitochondrial viability indices, insulin production, inflammatory biomarker analyses and cellular bioenergetics measurements. There was a significant dose-effect with different concentrations of the BA, affecting cellular viability and antioxidant activities, cell functions and insulin release, inflammatory biomarkers, and cellular-bioenergetics at different oxidative stress levels. The results demonstrate that, when encapsulated, the BA CDCA exerts positive pharmacological effects at the cellular level, and such effects are concentration dependent.

Intestinal Microbiota Remodeling Protects Mice from Western Diet-Induced Brain Inflammation and Cognitive Decline

It has been shown that the Western diet (WD) induces systemic inflammation and cognitive decline. Moreover, probiotic supplementation and antibiotic treatment reduce diet-induced hepatic inflammation. The current study examines whether shaping the gut microbes by Bifidobacterium infantis (B. infantis) supplementation and antibiotic treatment reduce diet-induced brain inflammation and improve neuroplasticity. Furthermore, the significance of bile acid (BA) signaling in regulating brain inflammation was studied. Mice were fed a control diet (CD) or WD for seven months. B. infantis was supplemented to WD-fed mice to study brain inflammation, lipid, metabolomes, and neuroplasticity measured by long-term potentiation (LTP). Broad-spectrum coverage antibiotics and cholestyramine treatments were performed to study the impact of WD-associated gut microbes and BA in brain inflammation. Probiotic B. infantis supplementation inhibited diet-induced brain inflammation by reducing IL6, TNFα, and CD11b levels. B. infantis improved LTP and increased brain PSD95 and BDNF levels, which were reduced due to WD intake. Additionally, B. infantis reduced cecal cholesterol, brain ceramide and enhanced saturated fatty acids. Moreover, antibiotic treatment, as well as cholestyramine, diminished WD-induced brain inflammatory signaling. Our findings support the theory that intestinal microbiota remodeling by B. infantis reduces brain inflammation, activates BA receptor signaling, and improves neuroplasticity.

Alternating Dual-Collision Energy Scanning Mass Spectrometry Approach: Discovery of Novel Microbial Bile-Acid Conjugates

Bile acids (BAs) are a type of gut microbiota-host cometabolites with abundant structural diversity, and they play critical roles in maintaining host-microbiota homeostasis. In this study, we developed a new N-(4-aminomethylphenyl) pyridinium (AMPP) derivatization-assisted alternating dual-collision energy scanning mass spectrometry (AMPP-dual-CE MS) method for the profiling of BAs derived from host-gut microbiota cometabolism in mice. Using the proposed method, we discovered two new types of amino acid conjugations (alanine conjugation and proline conjugation) and acetyl conjugation with host BAs, for the first time, from mouse intestine contents and feces. Additionally, we also determined and identified nine new leucine- and phenylalanine-conjugated BAs. These findings broaden our knowledge of the composition of the BA pool and provide insight into the mechanism of host-gut microbiota cometabolism of BAs.

Cholecystectomy Concomitant with Bariatric Surgery: Safety and Metabolic Effects

BACKGROUND

Obesity and fast weight loss in the postoperative period of bariatric surgery increase significantly the risk of cholelithiasis. Moreover, emerging evidence has pointed out the role of bile acids as possible metabolism and weight loss enhancers. This study aims to analyze the influence of cholecystectomy (CL) concomitant with bariatric surgery on weight loss, metabolic repercussions, and postoperative morbidity.

STUDY DESIGN

Retrospective cohort study. A total of 363 medical records were analyzed between 2002 and 2017, with 255 patients divided into four groups: with concomitant CL: sleeve gastrectomy (SG + CL group) and Roux-en-Y gastric bypass (GB + CL group); without concomitant CL: sleeve gastrectomy (SG group) and RYGB (GB group).

RESULTS

CL concomitant with bariatric surgery is not related to worse long-term metabolic outcomes when compared to isolated bariatric surgery. In the postoperative follow-up of the isolated bariatric surgeries, 18 (16.5%) patients underwent cholecystectomy. There was no statistical difference between the groups regarding post-surgical complications.

CONCLUSION

CL did not lead to worse metabolic outcomes and was also not related to a higher incidence of postoperative complications. Cholelithiasis and cholecystitis are important concerns in the postoperative period of bariatric surgery and a careful evaluation of the concomitant procedure should be performed.

Structural and Dynamic Determinants of Molecular Recognition in Bile Acid-Binding Proteins

Disorders in bile acid transport and metabolism have been related to a number of metabolic disease states, atherosclerosis, type-II diabetes, and cancer. Bile acid-binding proteins (BABPs), a subfamily of intracellular lipid-binding proteins (iLBPs), have a key role in the cellular trafficking and metabolic targeting of bile salts. Within the family of iLBPs, BABPs exhibit unique binding properties including positive binding cooperativity and site-selectivity, which in different tissues and organisms appears to be tailored to the local bile salt pool. Structural and biophysical studies of the past two decades have shed light on the mechanism of bile salt binding at the atomic level, providing us with a mechanistic picture of ligand entry and release, and the communication between the binding sites. In this review, we discuss the emerging view of bile salt recognition in intestinal- and liver-BABPs, with examples from both mammalian and non-mammalian species. The structural and dynamic determinants of the BABP-bile-salt interaction reviewed herein set the basis for the design and development of drug candidates targeting the transcellular traffic of bile salts in enterocytes and hepatocytes.

Pharmacological Effects of Secondary Bile Acid Microparticles in Diabetic Murine Model

AIM

Examine bile acids effects in Type 2 diabetes.

BACKGROUND

In recent studies, the bile acid ursodeoxycholic acid (UDCA) has shown potent antiinflammatory effects in obese patients while in type 2 diabetics (T2D) levels of the pro-inflammatory bile acid lithocholic acid were increased, and levels of the anti-inflammatory bile acid chenodeoxycholic acid were decreased, in plasma.

OBJECTIVE

Hence, this study aimed to examine applications of novel UDCA microparticles in diabetes.

METHODS

Diabetic balb/c adult mice were divided into three equal groups and gavaged daily with either empty microcapsules, free UDCA, or microencapsulated UDCA over two weeks. Their blood, tissues, urine, and faeces were collected for blood glucose, inflammation, and bile acid analyses. UDCA resulted in modulatory effects on bile acids profile without antidiabetic effects suggesting that bile acid modulation was not directly linked to diabetes treatment.

RESULTS

UDCA resulted in modulatory effects on bile acids profile without antidiabetic effects suggesting that bile acid modulation was not directly linked to diabetes treatment.

CONCLUSION

Bile acids modulated the bile profile without affecting blood glucose levels.

Bile acids as regulatory molecules and potential targets in metabolic diseases

Bile acids are important hydroxylated steroids that are synthesized in the liver from cholesterol for intestinal absorption of lipids and other fatty-nutrient. They also display remarkable and immense functions such as regulating immune responses, managing the apoptosis of cells, participating in glucose metabolism, and so on. Some bile acids were used for the treatment or prevention of diseases such as gallstones, primary biliary cirrhosis, and colorectal cancer. Meanwhile, the accumulation of toxic bile acids leads to apoptosis, necrosis, and inflammation. Alteration of bile acids metabolism, as well as the gut microbiota that interacted with bile acids, contributes to the pathogenesis of metabolic diseases. Therefore, the purpose of this review is to summarize the current functions and pre-clinical or clinical applications of bile acids, and to further discuss the alteration of bile acids in metabolic disorders as well as the manipulation of bile acids metabolism as potential therapeutic targets.

Hypercortisolism in patients with cholestasis is associated with disease severity

BACKGROUND

Cholestasis might lead to an impairment of adrenal function as suggested by in vitro and in vivo data as well as by clinical findings. Bile acid and adrenal steroid metabolism not only share the receptors farnesoid X receptor (FXR) and the G protein-coupled bile acid receptor 1 (TGR5), but supraphysiological bile acid levels were found to stimulate steroidogenesis independent of FXR and TGR5. Our previous experimental findings revealed that mice fed bile acids or subjected to common bile duct ligation develop hypercortisolemia. We thus aimed to assess adrenal gland function in patients with cholestasis.

METHODS

Adrenal gland function was assessed in 36 patients with cholestasis and in 32 patients without cholestasis by measuring total serum cortisol, adrenocorticotropic hormone (ACTH), as well as the increase of cortisol 20 and 30 min after administration of 1 µg of ACTH. Bile acid levels and bile acid pool composition were determined by high-resolution mass spectrometry.

RESULTS

Patients with cholestasis per definition had markedly elevated levels of alkaline phosphatase (AP), bilirubin and serum bile acids. Baseline cortisol and maximum cortisol after ACTH stimulation were significantly higher in patients with cholestasis compared to controls. Increase of cortisol after ACTH stimulation and ACTH did not differ. In the cholestasis group, baseline cortisol correlated with bilirubin but not with AP, total serum bile acids and levels of conjugated and unconjugated bile acid species. Patients with duration of cholestasis < 6 months (n = 30) had significantly higher baseline cortisol levels than those with long standing cholestasis (> 6 months), together with higher bilirubin levels.

CONCLUSIONS

We find no evidence of adrenal insufficiency in non-cirrhotic patients with cholestasis. In contrast, patients with cholestasis show hypercortisolism associated with disease severity as mirrored by levels of bilirubin. Lack of ACTH increase in cholestasis suggests a direct effect of cholestasis on adrenals and not on the pituitary gland. Further studies are needed to elucidate the mechanism of cortisol elevation in patients with cholestasis and its clinical significance.

Profile of Bile Acid Metabolomics in the Follicular Fluid of PCOS Patients

Polycystic ovary syndrome (PCOS) is a complex heterogeneous endocrine disease affected by genetic and environmental factors. In this manuscript, we aimed to describe the composition of bile acid metabolomics in the follicular fluid (FF) of PCOS. The FF was collected from 31 control patients and 35 PCOS patients diagnosed according to the Rotterdam diagnostic criteria. The Bile Acid Assay Kit and ultra-performance liquid chromatography/tandem mass spectrometry (UPLC-MS/MS) were used in this study to detect the total bile acid and 24 bile acid metabolites. Glycocholic acid (GC3A), taurocholic acid (TCA), glycochenodeoxycholic acid (GCDCA), and chenodeoxycholic acid-3-β-d-glucuronide (CDCA-3Gln) were elevated in the PCOS group. GCDCA was positively correlated with the serum follicle-stimulating hormone (FSH) (r = 0.3787, p = 0.0017) and luteinizing hormone (LH) (r = 0.2670, p = 0.0302). The level of CDCA-3Gln also rose with the increase in antral follicle counts (AFC) (r = 0.3247, p = 0.0078). Compared with the control group, the primary bile acids (p = 0.0207) and conjugated bile acids (p = 0.0283) were elevated in PCOS. For the first time, our study described the changes in bile acid metabolomics in the FF of PCOS patients, suggesting that bile acids may play an important role in the pathogenesis of PCOS.

Sub-chronic exposure to realgar induces liver injury via upregulating the TXNIP/NLRP3 pathway and disturbing bile acid homeostasis in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Realgar is a traditional Chinese medicine used in China for a long history. Long-time or excessive use of realgar causes liver injury. However, its underlying mechanism is not fully clarified.

AIM OF THE STUDY

In this study, we investigated the toxic effect of sub-chronic exposure to realgar on mice liver, and further revealed its underlying mechanism focused on the TXNIP/NLRP3 pathway and bile acid homeostasis.

MATERIAL AND METHODS

Mice were divided into control and different doses of sub-chronic realgar exposed groups. Total arsenic levels in the blood and liver were determined by atomic fluorescence spectrometry. The effect of realgar on liver function was evaluated by biochemical analysis and histopathological examination. Assay kits were applied for the measurement of oxidative stress indexes, MPO and plasma inflammatory cytokines. The mRNA and proteins involved in the TXNIP/NLRP3 and NF-κB pathways were determined by RT-qPCR, western blot, Immunofluorescence and Immunohistochemistry. UHPLC/MS/MS was used for the quantitative analysis of bile acids (BAs) in mice plasma, liver and urine. The genes related to BAs metabolism were measured by RT-qPCR.

RESULTS

Sub-chronic exposure to realgar led to arsenic accumulation and caused oxidative damage and inflammatory infiltration in mouse liver, finally resulting in liver injury. Realgar treatment activated the NF-κB pathway and significantly upregulated the TXNIP/NLRP3 pathway in mouse liver. Realgar altered the metabolic balance of BAs, which is related to the abnormal expression of BAs transporters and enzymes.

CONCLUSION

Sub-chronic exposure to realgar caused liver injury in mouse, and the mechanism may involve the upregulation of the TXNIP/NLRP3 pathway and disordered BAs homeostasis.

Potential of Persimmon Dietary Fiber Obtained from Byproducts as Antioxidant, Prebiotic and Modulating Agent of the Intestinal Epithelial Barrier Function

Appropriate nutrition targets decrease the risk of incidence of preventable diseases in addition to providing physiological benefits. Dietary fiber, despite being available and necessary in balanced nutrition, are consumed at below daily requirements. Food byproducts high in dietary fiber and free and bonded bioactive compounds are often discarded. Herein, persimmon byproducts are presented as an interesting source of fiber and bioactive compounds. The solvent extraction effects of dietary fiber from persimmon byproducts on its techno- and physio-functional properties, and on the Caco-2 cell model after being subjected to in vitro gastrointestinal digestion and probiotic bacterial fermentation, were evaluated. The total, soluble, and insoluble dietary fiber, total phenolic, carotenoid, flavonoid contents, and antioxidant activity were determined. After in vitro digestion, low quantities of bonded phenolic compounds were detected in all fiber fractions. Moreover, total phenolic and carotenoid contents, as well as antioxidant activity, decreased depending on the extraction solvent, whereas short chain fatty acids production increased. Covalently bonded compounds in persimmon fiber mainly consisted of hydroxycinnamic acids and flavanols. After probiotic bacterial fermentation, few phenolic compounds were determined in all fiber fractions. Results suggest that persimmon's dietary fiber functional properties are dependent on the extraction process used, which may promote a strong probiotic response and modulate the epithelial barrier function.

Metabolic Influences of Gut Microbiota Dysbiosis on Inflammatory Bowel Disease

Inflammatory bowel diseases (IBD) are chronic medical disorders characterized by recurrent gastrointestinal inflammation. While the etiology of IBD is still unknown, the pathogenesis of the disease results from perturbations in both gut microbiota and the host immune system. Gut microbiota dysbiosis in IBD is characterized by depleted diversity, reduced abundance of short chain fatty acids (SCFAs) producers and enriched proinflammatory microbes such as adherent/invasive E. coli and H₂S producers. This dysbiosis may contribute to the inflammation through affecting either the immune system or a metabolic pathway. The immune responses to gut microbiota in IBD are extensively discussed. In this review, we highlight the main metabolic pathways that regulate the host-microbiota interaction. We also discuss the reported findings indicating that the microbial dysbiosis during IBD has a potential metabolic impact on colonocytes and this may underlie the disease progression. Moreover, we present the host metabolic defectiveness that adds to the impact of symbiont dysbiosis on the disease progression. This will raise the possibility that gut microbiota dysbiosis associated with IBD results in functional perturbations of host-microbiota interactions, and consequently modulates the disease development. Finally, we shed light on the possible therapeutic approaches of IBD through targeting gut microbiome.

Chenodeoxycholic Acid Pharmacology in Biotechnology and Transplantable Pharmaceutical Applications for Tissue Delivery: An Acute Preclinical Study

INTRODUCTION

Primary bile acids (PBAs) are produced and released into human gut as a result of cholesterol catabolism in the liver. A predominant PBA is chenodeoxycholic acid (CDCA), which in a recent study in our laboratory, showed significant excipient-stabilizing effects on microcapsules carrying insulinoma β-cells, in vitro, resulting in improved cell functions and insulin release, in the hyperglycemic state. Hence, this study aimed to investigate the applications of CDCA in bio-encapsulation and transplantation of primary healthy viable islets, preclinically, in type 1 diabetes.

METHODS

Healthy islets were harvested from balb/c mice, encapsulated in CDCA microcapsules, and transplanted into the epididymal tissues of 6 syngeneic diabetic mice, post diabetes confirmation. Pre-transplantation, the microcapsules' morphology, size, CDCA-deep layer distribution, and physical features such as swelling ratio and mechanical strength were analyzed. Post-transplantation, animals' weight, bile acids', and proinflammatory biomarkers' concentrations were analyzed. The control group was diabetic mice that were transplanted encapsulated islets (without PBA).

RESULTS AND CONCLUSION

Islet encapsulation by PBA microcapsules did not compromise the microcapsules' morphology or features. Furthermore, the PBA-graft performed better in terms of glycemic control and resulted in modulation of the bile acid profile in the brain. This is suggestive that the improved glycemic control was mediated via brain-related effects. However, the improvement in graft insulin delivery and glycemic control was short-term.

Interactions Between the Aging Gut Microbiome and Common Geriatric Giants: Polypharmacy, Frailty, and Dementia

The gut microbiome has pervasive bidirectional relationships with pharmacotherapy, chronic disease, and physical and cognitive function. We conducted a narrative review of the current literature to examine the relationships between the gut microbiome, medication use, sarcopenia and frailty, and cognitive impairment. Data from in vitro experiments, in vivo experiments in invertebrates and complex organisms, and humans indicate associations between the gut microbiome and geriatric syndromes. Better understanding of the direct and indirect roles of the microbiome may inform future prevention and management of geriatric syndromes.

Decreased Abundance of Akkermansia muciniphila Leads to the Impairment of Insulin Secretion and Glucose Homeostasis in Lean Type 2 Diabetes

Although obesity occurs in most of the patients with type 2 diabetes (T2D), a fraction of patients with T2D are underweight or have normal weight. Several studies have linked the gut microbiome to obesity and T2D, but the role of gut microbiota in lean individuals with T2D having unique clinical characteristics remains unclear. A metagenomic and targeted metabolomic analysis is conducted in 182 lean and abdominally obese individuals with and without newly diagnosed T2D. The abundance of Akkermansia muciniphila (A. muciniphila) significantly decreases in lean individuals with T2D than without T2D, but not in the comparison of obese individuals with and without T2D. Its abundance correlates inversely with serum 3β-chenodeoxycholic acid (βCDCA) levels and positively with insulin secretion and fibroblast growth factor 15/19 (FGF15/19) concentrations. The supplementation with A. muciniphila is sufficient to protect mice against high sucrose-induced impairment of glucose intolerance by decreasing βCDCA and increasing insulin secretion and FGF15/19. Furthermore, βCDCA inhibits insulin secretion and FGF15/19 expression. These findings suggest that decreased abundance of A. muciniphila is linked to the impairment of insulin secretion and glucose homeostasis in lean T2D, paving the way for new therapeutic options for the prevention or treatment of diabetes.

Dynamics of the enterohepatic circulation of bile acids in healthy humans

Regulation of bile acid metabolism is normally discussed as the regulation of bile acid synthesis, which serves to compensate for intestinal loss in order to maintain a constant pool size. After a meal, bile acids start cycling in the enterohepatic circulation. Farnesoid X receptor-dependent ileal and hepatic processes lead to negative feedback inhibition of bile acid synthesis. When the intestinal bile acid flux decreases, the inhibition of synthesis is released. The degree of inhibition of synthesis and the mechanism and degree of activation are still unknown. Moreover, in humans, a biphasic diurnal expression pattern of bile acid synthesis has been documented, indicating maximal synthesis around 3 PM and 9 PM. Quantitative data on the hourly synthesis schedule as compensation for intestinal loss are lacking. In this review, we describe the classical view on bile acid metabolism and present alternative concepts that are based on the overlooked feature that bile acids transit through the enterohepatic circulation very rapidly. A daily profile of the cycling and total bile acid pool sizes and potential controlled and uncontrolled mechanisms for synthesis are predicted. It remains to be elucidated by which mechanism clock genes interact with the Farnesoid X receptor-controlled regulation of bile acid synthesis. This mechanism could become an attractive target to enhance bile acid synthesis at night, when cholesterol synthesis is high, thus lowering serum LDL-cholesterol.

The Microbiota and the Gut-Brain Axis in Controlling Food Intake and Energy Homeostasis

Obesity currently represents a major societal and health challenge worldwide. Its prevalence has reached epidemic proportions and trends continue to rise, reflecting the need for more effective preventive measures. Hypothalamic circuits that control energy homeostasis in response to food intake are interesting targets for body-weight management, for example, through interventions that reinforce the gut-to-brain nutrient signalling, whose malfunction contributes to obesity. Gut microbiota-diet interactions might interfere in nutrient sensing and signalling from the gut to the brain, where the information is processed to control energy homeostasis. This gut microbiota-brain crosstalk is mediated by metabolites, mainly short chain fatty acids, secondary bile acids or amino acids-derived metabolites and subcellular bacterial components. These activate gut-endocrine and/or neural-mediated pathways or pass to systemic circulation and then reach the brain. Feeding time and dietary composition are the main drivers of the gut microbiota structure and function. Therefore, aberrant feeding patterns or unhealthy diets might alter gut microbiota-diet interactions and modify nutrient availability and/or microbial ligands transmitting information from the gut to the brain in response to food intake, thus impairing energy homeostasis. Herein, we update the scientific evidence supporting that gut microbiota is a source of novel dietary and non-dietary biological products that may beneficially regulate gut-to-brain communication and, thus, improve metabolic health. Additionally, we evaluate how the feeding time and dietary composition modulate the gut microbiota and, thereby, the intraluminal availability of these biological products with potential effects on energy homeostasis. The review also identifies knowledge gaps and the advances required to clinically apply microbiome-based strategies to improve the gut-brain axis function and, thus, combat obesity.

Validation of Recombinant Chicken Liver Bile Acid Binding Protein as a Tool for Cholic Acid Hosting

Bile acids (BAs) are hydroxylated steroids derived from cholesterol that act at the intestinal level to facilitate the absorption of several nutrients and also play a role as signaling molecules. In the liver of various vertebrates, the trafficking of BAs is mediated by bile acid-binding proteins (L-BABPs). The ability to host hydrophobic or amphipathic molecules makes BABPs suitable for the distribution of a variety of physiological and exogenous substances. Thus, BABPs have been proposed as drug carriers, and more recently, they have also been employed to develop innovative nanotechnology and biotechnology systems. Here, we report an efficient protocol for the production, purification, and crystallization of chicken liver BABP (cL-BABP). By means of target expression as His⁶-tag cL-BABP, we obtained a large amount of pure and homogeneous proteins through a simple purification procedure relying on affinity chromatography. The recombinant cL-BABP showed a raised propensity to crystallize, allowing us to obtain its structure at high resolution and, in turn, assess the structural conservation of the recombinant cL-BABP with respect to the liver-extracted protein. The results support the use of recombinant cL-BABP for the development of drug carriers, nanotechnologies, and innovative synthetic photoswitch systems.

Structure of mouse cytosolic sulfotransferase SULT2A8 provides insight into sulfonation of 7α-hydroxyl bile acids

Cytosolic sulfotransferases (SULTs) catalyze the transfer of a sulfonate group from the cofactor 3'-phosphoadenosine 5'-phosphosulfate to a hydroxyl (OH) containing substrate and play a critical role in the homeostasis of endogenous compounds, including hormones, neurotransmitters, and bile acids. In human, SULT2A1 sulfonates the 3-OH of bile acids; however, bile acid metabolism in mouse is dependent on a 7α-OH sulfonating SULT2A8 via unknown molecular mechanisms. In this study, the crystal structure of SULT2A8 in complex with adenosine 3',5'-diphosphate and cholic acid was resolved at a resolution of 2.5 Å. Structural comparison with human SULT2A1 reveals different conformations of substrate binding loops. In addition, SULT2A8 possesses a unique substrate binding mode that positions the target 7α-OH of the bile acid close to the catalytic site. Furthermore, mapping of the critical residues by mutagenesis and enzyme activity assays further highlighted the importance of Lys44 and His48 for enzyme catalysis and Glu237 in loop 3 on substrate binding and stabilization. In addition, limited proteolysis and thermal shift assays suggested that the cofactor and substrates have protective roles in stabilizing SULT2A8 protein. Together, the findings unveil the structural basis of bile acid sulfonation targeting 7α-OH and shed light on the functional diversity of bile acid metabolism across species.

Manipulating the Microbiome: An Alternative Treatment for Bile Acid Diarrhoea

Bile acid diarrhoea (BAD) is a widespread gastrointestinal disease that is often misdiagnosed as irritable bowel syndrome and is estimated to affect 1% of the United Kingdom (UK) population alone. BAD is associated with excessive bile acid synthesis secondary to a gastrointestinal or idiopathic disorder (also known as primary BAD). Current licensed treatment in the UK has undesirable effects and has been the same since BAD was first discovered in the 1960s. Bacteria are essential in transforming primary bile acids into secondary bile acids. The profile of an individual’s bile acid pool is central in bile acid homeostasis as bile acids regulate their own synthesis. Therefore, microbiome dysbiosis incurred through changes in diet, stress levels and the introduction of antibiotics may contribute to or be the cause of primary BAD. This literature review focuses on primary BAD, providing an overview of bile acid metabolism, the role of the human gut microbiome in BAD and the potential options for therapeutic intervention in primary BAD through manipulation of the microbiome.

Prevention of the rise in plasma cholesterol and glucose levels by kaki-tannin and characterization of its bile acid binding capacity

BACKGROUND

Bile acid-binding agents, such as cholestyramine and colesevelam, improve both cholesterol and glucose metabolism. Kaki-tannin, a polymerized condensed tannin derived from persimmon (Diospyros kaki), has been shown to have bile acid-binding capacity and a hypocholesterolemic effect. However, its effects on glucose metabolism have not been well studied, and the binding selectivity of kaki-tannin to bile acid molecules has not been reported.

RESULTS

In vivo experiments using mice with high-fat diet-induced obesity showed that kaki-tannin intake (20 g kg^-1 of the diet) increased fecal bile acid excretion by 2.3-fold and prevented a rise in plasma cholesterol levels and fasting plasma glucose levels. Kaki-tannin also suppressed the development of impaired glucose tolerance. To characterize the bile acid-binding capacity of kaki-tannin, we investigated its capacity to bind to eight types of bile acid and cholesterol in vitro. Kaki-tannin showed strong capacity to bind to lithocholic acid (85.5%), which has one hydroxy group. It also showed moderate capacity to bind to bile acids with two hydroxy groups (53.3%), followed by those with three hydroxy groups (39.0%), but kaki-tannin did not show binding capacity to cholesterol. These results suggest that the binding capacity of kaki-tannin to bile acids tends to decrease as the number of hydroxy groups increases. Interestingly, the binding capacity of kaki-tannin correlated with that of cholestyramine (correlation coefficient: r = 0.900).

CONCLUSION

Our findings indicate that kaki-tannin binds preferentially to bile acids with fewer hydroxy groups and has beneficial effects on glucose metabolism as well as cholesterol metabolism. © 2020 Society of Chemical Industry.

Administration of Cholic Acid Inhibits Equol Production from Daidzein in Mice

Equol (Eq) is a metabolite of soy isoflavone daidzein (De) produced by the intestinal microbiota. The clinical effectiveness of soy isoflavone is considered to depend on the individual ability of Eq production. Previous studies have demonstrated that habitual dietary patterns may influence the production of Eq. For example, high Eq producers consumed less fat as a percentage of energy than low Eq producers. However, the inhibitory factors of Eq production are unknown. Recently, it was reported that bile acids induced by high-fat diet consumption may be a host-related factor controlling the composition of the intestinal microbiota. In this study, we investigated the effect of cholic acid (CA) administration, a mimic of the microbiota altered by a high-fat diet, on Eq production in mice. CA administration significantly decreased the levels of the De metabolites Eq, dihydrodaidzein, and O-desmethylangolensin in the serum of mice. However, CA administration did not affect the total molar concentration of De and its metabolites. Moreover, CA administration increased the levels of secondary bile acids, particularly deoxycholic acid (DCA), which has strong antibacterial activity in the cecum contents of mice. Thus, CA administration may increase the levels of DCA, a secondary bile acid, resulting in inhibition of Eq production. These findings may help to reveal the factors inhibiting Eq production and enhance the clinical effectiveness of isoflavone intake.

Cholestatic liver disease: Practice guidelines from the Saudi Association for the Study of Liver diseases and Transplantation

Cholestatic liver diseases (CLDs) are a group of diseases characterized by jaundice and cholestasis as the main presentation with different complications, which have considerable impact on the liver and can lead to end-stage liver disease, cirrhosis, and liver-related complications. In the last few years, tremendous progress has been made in understanding the pathophysiology, diagnosis, and treatment of patients with these conditions. However, several aspects related to the management of CLDs remain deficient and unclear. Due to the lack of recommendations that can help in the management, treatment of those conditions, the Saudi Association for the Study of Liver diseases and Transplantation (SASLT) has created a task force group to develop guidelines related to CLDs management in order to provide a standard of care for patients in need. These guidelines provide general guidance for health care professionals to optimize medical care for patients with CLDs for both adult and pediatric populations, in association with clinical judgments to be considered on a case-by-case basis. These guidelines describe common CLDs in Saudi Arabia, with recommendations on the best approach for diagnosis and management of different diseases based on the Grading of Recommendation Assessment (GRADE), combined with a level of evidence available in the literature.

Hepatocyte ATF3 protects against atherosclerosis by regulating HDL and bile acid metabolism

Activating transcription factor (ATF)3 is known to have an anti-inflammatory function, yet the role of hepatic ATF3 in lipoprotein metabolism or atherosclerosis remains unknown. Here we show that overexpression of human ATF3 in hepatocytes reduces the development of atherosclerosis in Western-diet-fed Ldlr^-/- or Apoe^-/- mice, whereas hepatocyte-specific ablation of Atf3 has the opposite effect. We further show that hepatic ATF3 expression is inhibited by hydrocortisone. Mechanistically, hepatocyte ATF3 enhances high-density lipoprotein (HDL) uptake, inhibits intestinal fat and cholesterol absorption and promotes macrophage reverse cholesterol transport by inducing scavenger receptor group B type 1 (SR-BI) and repressing cholesterol 12α-hydroxylase (CYP8B1) in the liver through its interaction with p53 and hepatocyte nuclear factor 4α, respectively. Our data demonstrate that hepatocyte ATF3 is a key regulator of HDL and bile acid metabolism and atherosclerosis.

β-Glucan Metabolic and Immunomodulatory Properties and Potential for Clinical Application

β-glucans are complex polysaccharides that are found in several plants and foods, including mushrooms. β-glucans display an array of potentially therapeutic properties. β-glucans have metabolic and gastro-intestinal effects, modulating the gut microbiome, altering lipid and glucose metabolism, reducing cholesterol, leading to their investigation as potential therapies for metabolic syndrome, obesity and diet regulation, gastrointestinal conditions such as irritable bowel, and to reduce cardiovascular and diabetes risk. β-glucans also have immune-modulating effects, leading to their investigation as adjuvant agents for cancers (solid and haematological malignancies), for immune-mediated conditions (e.g., allergic rhinitis, respiratory infections), and to enhance wound healing. The therapeutic potential of β-glucans is evidenced by the fact that two glucan isolates were licensed as drugs in Japan as immune-adjuvant therapy for cancer in 1980. Significant challenges exist to further clinical testing and translation of β-glucans. The diverse range of conditions for which β-glucans are in clinical testing underlines the incomplete understanding of the diverse mechanisms of action of β-glucans, a key knowledge gap. Furthermore, important differences appear to exist in the effects of apparently similar β-glucan preparations, which may be due to differences in sources and extraction procedures, another poorly understood issue. This review will describe the biology, potential mechanisms of action and key therapeutic targets being investigated in clinical trials of β-glucans and identify and discuss the key challenges to successful translation of this intriguing potential therapeutic.

Metabolic networks of the human gut microbiota

The human gut microbiota controls factors that relate to human metabolism with a reach far greater than originally expected. Microbial communities and human (or animal) hosts entertain reciprocal exchanges between various inputs that are largely controlled by the host via its genetic make-up, nutrition and lifestyle. The composition of these microbial communities is fundamental to supply metabolic capabilities beyond those encoded in the host genome, and contributes to hormone and cellular signalling that support the dynamic adaptation to changes in food availability, environment and organismal development. Poor functional exchange between the microbial communities and their human host is associated with dysbiosis, metabolic dysfunction and disease. This review examines the biology of the dynamic relationship between the reciprocal metabolic state of the microbiota-host entity in balance with its environment (i.e. in healthy states), the enzymatic and metabolic changes associated with its imbalance in three well-studied diseases states such as obesity, diabetes and atherosclerosis, and the effects of bariatric surgery and exercise.

[Gut microbiota is a factor of risk for obesity and type 2 diabetes]

Gut microbiota (GM) is a set of bacteria which colonize the gastrointestinal tract. GM and its active metabolites take part in intestinal and hepatic gluconeogenesis, in the synthesis of incretin hormones, and affect the regulation of appetite. Thus, GM and its metabolites participate in the homeostasis of carbohydrates and fats. An imbalance in the set of the intestinal flora and a disturbance of the production of active metabolites sharply increases the risk of developing obesity and type 2 diabetes. There are conflicting data in the literature on the role of specific microorganisms in the development of metabolic disorders. Research is needed to identify specific types of bacteria and their active metabolites which affect the development of obesity and type 2 diabetes.

Circulating Bile Acids Profiles in Obese Children and Adolescents: A Possible Role of Sex, Puberty and Liver Steatosis

Background. Childhood obesity is becoming a major health issue and contributes to increasing the risk of cardiovascular disease in adulthood. Since dysregulated metabolism of bile acids (BAs) plays a role in progression of obesity-related disorders, including steatosis and hypertension, this study aimed to investigate BAs profiles in obese children with and without steatosis and hypertension, as well as exploring the interplay between BAs profile and vascular function. Methods. BAs concentrations were quantified with liquid chromatography-tandem mass spectrometry in 69 overweight/obese children and adolescents (mean age, 11.6 ± 2.5 years; 30 females). Liver steatosis was defined with abdomen ultrasonography, whilst hypertension was defined according to the current European guidelines. Vascular function was assessed with ultrasound technique, by measuring carotid intima media thickness (cIMT) and common carotid artery distensibility (cDC). Results. Total and individual glycine-conjugated BAs concentrations were found to be significantly higher in males compared to females, as well as in pre-pubertal compared to pubertal stage (p < 0.05 for both). No difference in BAs concentration was observed between hypertensive and normotensive subjects. Total BAs and glycine conjugated BAs were significantly higher in participants with steatosis compared to those without (p = 0.004 for both). The values of total glycine-conjugate acids were positively correlated with cDC and this association remained significant in linear regression after adjusting for sex, age, pubertal stage, body mass index and aspartate aminotransferase. Conclusion. The results suggest a possible role of BAs in the pathogenesis of liver and/or vascular damage in children and adolescent. Further studies are hence needed to validate these preliminary findings.

Metabolic Network Analysis Reveals Altered Bile Acid Synthesis and Metabolism in Alzheimer's Disease

Increasing evidence suggests Alzheimer's disease (AD) pathophysiology is influenced by primary and secondary bile acids, the end product of cholesterol metabolism. We analyze 2,114 post-mortem brain transcriptomes and identify genes in the alternative bile acid synthesis pathway to be expressed in the brain. A targeted metabolomic analysis of primary and secondary bile acids measured from post-mortem brain samples of 111 individuals supports these results. Our metabolic network analysis suggests that taurine transport, bile acid synthesis, and cholesterol metabolism differ in AD and cognitively normal individuals. We also identify putative transcription factors regulating metabolic genes and influencing altered metabolism in AD. Intriguingly, some bile acids measured in brain tissue cannot be explained by the presence of enzymes responsible for their synthesis, suggesting that they may originate from the gut microbiome and are transported to the brain. These findings motivate further research into bile acid metabolism in AD to elucidate their possible connection to cognitive decline.

Tissue engineering of the biliary tract and modelling of cholestatic disorders

Our insight into the pathogenesis of cholestatic liver disease remains limited, partly owing to challenges in capturing the multitude of factors that contribute to disease pathogenesis in vitro. Tissue engineering could address this challenge by combining cells, materials and fabrication strategies into dynamic modelling platforms, recapitulating the multifaceted aetiology of cholangiopathies. Herein, we review the advantages and limitations of platforms for bioengineering the biliary tree, looking at how these can be applied to model biliary disorders, as well as exploring future directions for the field.

Vaginal progesterone treatment for the prevention of preterm birth and intrahepatic cholestasis of pregnancy: A case-control study

INTRODUCTION

Intrahepatic cholestasis of pregnancy (ICP) is associated with a distinctive maternal pruritus, abnormal liver function tests, raised serum total bile acids, and increased rates of adverse fetal outcomes, including intrauterine fetal death. Progesterone has been implicated in the pathogenesis of ICP. We aimed to evaluate whether the incidence of ICP is altered in women receiving long-term daily vaginal progesterone, indicated for a short cervical length.

STUDY DESIGN

A matched 1:3 case-control study of pregnant women between January 2014 and January 2019. Study cases included pregnant women with the diagnosis of ICP. Control cases were women without ICP. The primary outcome was the rate of vaginal progesterone treatment among the groups.

RESULTS

The use of vaginal progesterone throughout pregnancy was higher in the ICP group compared with the control group (8/174 [4.6 %] versus 6/522 [1.1 %], respectively, P = 0.03, odds ratio 4 [95 % confidence interval 1.4-11.7]).

CONCLUSIONS

Pregnant women treated with long-term vaginal progesterone preparations for the prevention of preterm birth are at increased risk of developing ICP. In the presence of pruritus during pregnancy, we recommend an early consultation and diagnostic test to confirm or rule-out ICP.

Open-label phase II study evaluating safety and efficacy of the non-steroidal farnesoid X receptor agonist PX-104 in non-alcoholic fatty liver disease

Background

The PX-104 is an oral non-steroidal agonist for the farnesoid X receptor (FXR), a key regulator of bile acid (BA), glucose and lipid homeostasis.

Aims and methods

This single center, proof of concept study evaluated the efficacy, safety and tolerability of PX-104 in non-diabetic NAFLD patients. 12 individuals were treated daily with 5 mg of PX-104 orally for 4 weeks. Serum liver enzymes, insulin sensitivity by clamp like index (CLIX) and hepatic fat by proton ¹H‑MRS, MRI-PDFF and CAP were assessed. Hepatic energy metabolism and Kupffer cell function were evaluated by phosphorus ³¹P‑MRS and superparamagnetic iron oxide MRI (SPIO-MRI). Other readouts included serum lipids and markers of BA metabolism/signaling besides fecal microbiome and BA analysis.

Results

A significant decrease in ALT (p = 0.027; 1‑tailed) and GGT (p = 0.019) was observed, without changes in serum alkaline phosphatase or serum lipids. Insulin sensitivity improved in 92% of patients (p = 0.02). However, hepatic steatosis measured by PDFF-MRI, ¹H‑MRS and CAP besides extended serum lipoprotein and BA profiles did not change. NADPH/γATP ratios at ³¹P‑MRS significantly decreased (p = 0.022) possibly reflecting reduced hepatic inflammatory stress, but SPIO-MRI remained unchanged. Reduced preponderance of Coriobacteriaceae (p = 0.036) correlated with a relative reduction of total fecal BAs. There were no serious adverse events but short intervals of cardiac arrhythmia recorded in 2 patients led to termination of the study.

Conclusion

The non-steroidal FXR agonist PX-104 improved insulin sensitivity and liver enzymes after 4 weeks of treatment in non-diabetic NAFLD patients. Changes in fecal BAs and gut microbiota deserve more extensive investigations.

Electronic supplementary material

The online version of this article (10.1007/s00508-020-01735-5) contains supplementary material, which is available to authorized users.

Two highly related odorant receptors specifically detect α-bile acid pheromones in sea lamprey (Petromyzon marinus)

Pheromones play critical roles in habitat identification and reproductive behavior synchronization in the sea lamprey (Petromyzon marinus). The bile acid 3-keto petromyzonol sulfate (3kPZS) is a major component of the sex pheromone mixture from male sea lamprey that induces specific olfactory and behavioral responses in conspecific individuals. Olfactory receptors interact directly with pheromones, which is the first step in their detection, but identifying the cognate receptors of specific pheromones is often challenging. Here, we deorphanized two highly related odorant receptors (ORs), OR320a and OR320b, of P. marinus that respond to 3kPZS. In a heterologous expression system coupled to a cAMP-responsive CRE-luciferase, OR320a and OR320b specifically responded to C24 5α-bile acids, and both receptors were activated by the same set of 3kPZS analogs. OR320a displayed larger responses to all 3kPZS analogs than did OR320b. This difference appeared to be largely determined by a single amino acid residue, Cys-792.56, the C-terminal sixth residue relative to the most conserved residue in the second transmembrane domain (2.56) of OR320a. This region of TM2 residues 2.56-2.60 apparently is critical for the detection of steroid compounds by odorant receptors in lamprey, zebrafish, and humans. Finally, we identified OR320 orthologs in Japanese lamprey (Lethenteron camtschaticum), suggesting that the OR320 family may be widely present in lamprey species and that OR320 may be under purifying selection. Our results provide a system to examine the origin of olfactory steroid detection in vertebrates and to define a highly conserved molecular mechanism for steroid-ligand detection by G protein-coupled receptors.

Molecular Physiology of Bile Acid Signaling in Health, Disease, and Aging

Over the past two decades, bile acids (BAs) have become established as important signaling molecules that enable fine-tuned inter-tissue communication from the liver, their site of production, over the intestine, where they are modified by the gut microbiota, to virtually any organ, where they exert their pleiotropic physiological effects. The chemical variety of BAs, to a large extent determined by the gut microbiome, also allows for a complex fine-tuning of adaptive responses in our body. This review provides an overview of the mechanisms by which BA receptors coordinate several aspects of physiology and highlights new therapeutic strategies for diseases underlying pathological BA signaling.

Integrated omics analysis reveals the alteration of gut microbe-metabolites in obese adults

Obesity, a risk to health, is a global problem in modern society. The prevalence of obesity was approximately 13% among world's adult population. Recently, several reports suggested that the interference of gut microbiota composition and function is associated with metabolic disorders, including obesity. Gut microbiota produce a board range of metabolites involved in energy and glucose homeostasis, leading to the alteration in host metabolism. However, systematic evaluation of the relationship between gut microbiota, gut metabolite and host metabolite profiles in obese adults is still lacking. In this study, we used comparative metagenomics and metabolomics analysis to determine the gut microbiota and gut-host metabolite profiles in six normal and obese adults of Chinese origin, respectively. Following the functional and pathway analysis, we aimed to understand the possible impact of gut microbiota on the host metabolites via the change in gut metabolites. The result showed that the change in gut microbiota may result in the modulation of gut metabolites contributing to glycolysis, tricarboxylic acid cycle and homolactic fermentation. Furthermore, integrated metabolomic analysis demonstrated a possible positive correlation of dysregulated metabolites in the gut and host, including l-phenylalanine, l-tyrosine, uric acid, kynurenic acid, cholesterol sulfate and glucosamine, which were reported to contribute to metabolic disorders such as obesity and diabetes. The findings of this study provide the possible association between gut microbiota-metabolites and host metabolism in obese adults. The identified metabolite changes could serve as biomarkers for the evaluation of obesity and metabolic disorders.

The effect of ursodeoxycholic acid on the relative expression of the lipid metabolism genes in mouse cholesterol gallstone models

BACKGROUND

Many studies indicate that gallstone formation has genetic components. The abnormal expression of lipid-related genes could be the basis for particular forms of cholesterol gallstone disease. The aim of this study was to obtain insight into lipid metabolism disorder during cholesterol gallstone formation and to evaluate the effect of ursodeoxycholic acid (UDCA) on the improvement of bile lithogenicity and its potential influence on the transcription of lipid-related genes.

METHODS

Gallstone-susceptible mouse models were induced by feeding with a lithogenic diet (LD) for 8 weeks. Bile and liver tissues were obtained from these mouse models after 0, 4 and 8 weeks. Bile lipids were measured enzymatically, and the cholesterol saturation index (CSI) was calculated to evaluate the bile lithogenicity by using Carey's critical tables. Real-time polymerase chain reaction (RT-PCR) was used to detect the mRNA expression levels of farnesoid X receptor (FXR), liver X receptor (LXR), adenosine triphosphate-binding cassette subfamily G member 5/8 (ABCG5/8), cholesterol 7-α hydroxylase (CYP7A1), oxysterol 7-α hydroxylase (CYP7B1), sterol 27-α hydroxylase (CYP27A1), peroxisome proliferator-activated receptor alpha (PPAR-α) and adenosine triphosphate-binding cassette subfamily B member 11 (ABCB11).

RESULTS

The rate of gallstone formation was 100% in the 4-week group but only 30% in the UDCA-treated group. The UDCA-treated group had a significantly lower CSI compared with other groups. Of special note, the data on the effects of UDCA showed higher expression levels of ABCG8, ABCB11 and CYP27A1, as well as lower expression levels of LXR and PPAR-α, compared to the model control group.

CONCLUSIONS

UDCA exhibits tremendously potent activity in restraining lipid accumulation, thus reversing the lithogenic effect and protecting hepatocytes from serious pathological damage. The abnormal expression of ABCG8, CYP7A1, CYP27A1, LXR and PPAR-α might lead to high lithogenicity of bile. These results are helpful in exploring new lipid metabolism pathways and potential targets for the treatment of cholesterol stones and for providing some basis for the study of the pathogenesis and genetic characteristics of cholelithiasis. Research on the mechanism of UDCA in improving lipid metabolism and bile lithogenicity may be helpful for clinical treatment and for reducing the incidence of gallstones.

Deoxycholic acid modulates the progression of gallbladder cancer through N6-methyladenosine-dependent microRNA maturation

Bile acids (BAs), well-defined signaling molecules with diverse metabolic functions, play important roles in cellular processes associated with many cancers. As one of the most common BAs, deoxycholic acid (DCA) is originally synthesized in the liver, stored in the gallbladder, and processed in the gut. DCA plays crucial roles in various tumors; however, functions and molecular mechanisms of DCA in gallbladder cancer (GBC) still remain poorly characterized. Here, we analyzed human GBC samples and found that DCA was significantly downregulated in GBC, and reduced levels of DCA was associated with poor clinical outcome in patients with GBC. DCA treatment impeded tumor progression by halting cell proliferation. DCA decreased miR-92b-3p expression in an m⁶A-dependent posttranscriptional modification manner by facilitating dissociation of METTL3 from METTL3–METTL14–WTAP complex, which increased the protein level of the phosphatase and tensin homolog, a newly identified target of miR-92b-3p, and subsequently inactivated the PI3K/AKT signaling pathway. Our findings revealed that DCA might function as a tumor suppressive factor in GBC at least by interfering with miR-92b-3p maturation, and suggested that DCA treatment could provide a new therapeutic strategy for GBC.

Gut bacterial microbiome composition and statin intake-A systematic review

Recently, the gut microbiome has become an important field of interest. Indeed, the microbiome has been associated to numerous drug interactions and it is thought to influence the efficacy of pharmacologic treatments. Although statins are widely prescribed medications, there remains considerable variability in its therapeutic response. In this context, we aimed to investigate how statins modulate the gut microbiome and, reversely, how can the microbiome influence the course of anti-hypercholesterolemic treatment. We conducted a systematic review by searching four online databases, in accordance with PRISMA guidelines. Studies addressing gut microbiome changes following statin treatment and those assessing statins' response and associating it with patients' microbiome were included. Due to the limited number of results, we decided to include studies enrolling both humans and animals. We summarized information from three human and seven animal studies and aimed to assess the influence of gut microbiome composition on statin response (Outcome 1) and to evaluate the impact of statin treatment on the gut microbiome (Outcome 2). An association between a certain microbiome composition that promoted the lipid-lowering effect of statins was found. However, what kind of microorganisms and how they can exert this effect remains uncertain. Furthermore, statins might have a role in the modulation of the gut microbiome, but then again, it is still unknown whether this change is directly caused by the drug or another metabolic mechanism. Even though gut microbiota may have several potential therapeutic implications, its use as a personalized predictive biomarker requires further studies.

Alternate-day fasting alleviates diabetes-induced glycolipid metabolism disorders: roles of FGF21 and bile acids

Glycolipid metabolism disorder is one of the causes of type 2 diabetes (T2D). Alternate-day fasting (ADF) is an effective dietary intervention to counteract T2D. The present study is aimed to determine the underlying mechanisms of the benefits of ADF metabolic on diabetes-induced glycolipid metabolism disorders in db/db mice. Here, leptin receptor knock-out diabetic mice were subjected to 28 days of isocaloric ADF. We found that ADF prevented insulin resistance and bodyweight gain in diabetic mice. ADF promoted glycogen synthesis in both liver and muscle. ADF also activated recombinant insulin receptor substrate-1 (IRS-1)/protein kinase B (AKT/PKB) signaling，inactivated inflammation related AMP-activated protein kinase (AMPK) and the inflammation-regulating nuclear factor kappa-B (NF-κB) signaling in the liver. ADF also suppressed lipid accumulation by inactivating the expression of peroxisome proliferator-activated receptor gamma (PPAR-γ) and sterol regulatory element-binding protein-1c (SREBP-1c). Furthermore, ADF elevated the expression of fibroblast growth factor 21 (FGF21) and down-stream signaling AMPK/silent mating type information regulation 2 homolog 1 (SIRT1)/peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α) in the liver of diabetic mice. The mitochondrial biogenesis and autophagy were also stimulated by ADF. Interestingly, ADF also enhanced the bile acids (BAs) metabolism by generating more cholic acid (CA), deoxycholic acid (DCA) and tauroursodeoxycholic acid (TUDCA) in db/db mice. In conclusion, ADF could significantly inhibit T2D induced insulin resistance and obesity, promote insulin signaling，reduce inflammation, as well as promote glycogen synthesis and lipid metabolism. It possibly depends on FGF21 and BA metabolism to enhance mitochondrial biosynthesis and energy metabolism.

Preference for dietary fat: From detection to disease

Recent advances in the field of taste physiology have clarified the role of different basic taste modalities and their implications in health and disease and proposed emphatically that there might be a distinct cue for oro-sensory detection of dietary long-chain fatty acids (LCFAs). Hence, fat taste can be categorized as a taste modality. During mastication, LCFAs activate tongue lipid sensors like CD36 and GPR120 triggering identical signaling pathways as the basic taste qualities do; however, the physico-chemical perception of fat is not as distinct as sweet or bitter or other taste sensations. The question arises whether "fat taste" is a basic or "alimentary" taste. There is compelling evidence that fat-rich dietary intervention modulates fat taste perception where an increase or a decrease in lipid contents in the diet results, respectively, in downregulation or upregulation of fat taste sensitivity. Evidently, a decrease in oro-sensory detection of LCFAs leads to high fat intake and, consequently, to obesity. In this article, we discuss recent relevant advances made in the field of fat taste physiology with regard to dietary fat preference and lipid sensors that can be the target of anti-obesity strategies.