Bile acids as regulatory molecules

Bile Acid Toxicity and Protein Kinases

If the bile acids reach to pathological concentrations due to cholestasis, accumulation of hydrophobic bile acids within the hepatocyte may result in cell death. Thus, hydrophobic bile acids induce apoptosis in hepatocytes, while hydrophilic bile acids increase intracellular adenosine 3',5'-monophosphate (cAMP) levels and activate mitogen-activated protein kinase (MAPK) and phosphoinositide 3-kinase (PI3K) pathways to protect hepatocytes from apoptosis.Two apoptotic pathways have been described in bile acids-induced death. Both are controlled by multiple protein kinase signaling pathways. In mitochondria-controlled pathway, caspase-8 is activated with death domain-independent manner, whereas, Fas-dependent classical pathway involves ligand-independent oligomerization of Fas.Hydrophobic bile acids dose-dependently upregulate the inflammatory response by further stimulating production of inflammatory cytokines. Death receptor-mediated apoptosis is regulated at the cell surface by the receptor expression, at the death-inducing signaling complex (DISC) by expression of procaspase-8, the death receptors Fas-associated death domain (FADD), and cellular FADD-like interleukin 1-beta (IL-1β)-converting enzyme (FLICE) inhibitory protein (cFLIP). Bile acids prevent cFLIP recruitment to the DISC and thereby enhance initiator caspase activation and lead to cholestatic apoptosis. At mitochondria, the expression of B-cell leukemia/lymphoma-2 (Bcl-2) family proteins contribute to apoptosis by regulating mitochondrial cytochrome c release via Bcl-2, Bcl-2 homology 3 (BH3) interacting domain death agonist (Bid), or Bcl-2 associated protein x (Bax). Fas receptor CD95 activation by hydrophobic bile acids is initiated by reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-dependent reactive oxygen species (ROS) signaling. However, activation of necroptosis by ligands of death receptors requires the kinase activity of receptor interacting protein1 (RIP1), which mediates the activation of RIP3 and mixed lineage kinase domain-like protein (MLKL). In this chapter, mainly the effect of protein kinases signal transduction on the mechanisms of hydrophobic bile acids-induced inflammation, apoptosis, necroptosis and necrosis are discussed.

Sterol sulfate alleviates atherosclerosis via mediating hepatic cholesterol metabolism in ApoE-/- mice

Compared with terrestrial organisms, the sterols in sea cucumber exhibit a sulfate group at the C-3 position. Our previous study demonstrated that dietary sterol sulfate was superior to phytosterol in alleviating metabolic syndrome by ameliorating inflammation and mediating cholesterol metabolism in high-fat-high-fructose diet mice, which indicated its potential anti-atherosclerosis bioactivity. In the present study, administration with sea cucumber-derived sterol sulfate (SCS) significantly decreased the cholesterol level in oleic acid/palmitic acid-treated HepG2 cells, while no significant changes were observed in the triacylglycerol level. RNA-seq analysis showed that the metabolic changes were mostly attributed to the steroid biosynthesis pathway. ApoE-/- mice were used as an atherosclerosis model to further investigate the regulation of SCS on cholesterol metabolism. The results showed that SCS supplementation dramatically reduced atherosclerotic lesions by 45% and serum low-density lipoprotein cholesterol levels by 59% compared with the model group. Dietary SCS inhibited hepatic cholesterol synthesis via downregulating SREBP-2 and HMGCR. Meanwhile, SCS administration increased cholesterol uptake via enhancing the expression of Vldlr and Ldlr. Noticeably, SCS supplementation altered bile acid profiles in the liver, serum, gallbladder and feces, which might cause the activation of FXR in the liver. These findings provided new evidence about the high bioactivity of sterols with the sulfate group on atherosclerosis.

Enterohepatic circulation of bile acids and their emerging roles on glucolipid metabolism

Bile acids (BAs) are amphiphilic molecules with a nonpolar steroid carbon skeleton and a polar carboxylate side chain. Recently, BAs have aroused the attention of scholars due to their potential roles on metabolic diseases. As important endogenous ligands, BAs are wildly active in the enterohepatic circulation, during which microbiota play a significant role in promoting the hydrolysis and dehydroxylation of BAs. Besides, many pathways initiated by BAs including glucolipid metabolism and inflammation signaling pathways have been reported to regulate the host metabolism and maintain immune homeostasis. Herein, the characteristics on the enterohepatic circulation and metabolism of BAs are systematically summarized. Moreover, the regulation mechanism of the glucolipid metabolism by BAs is intensively discussed. Worthily, FXR and TGR5, which are involved in glucolipid metabolism, are the prime candidates for targeted therapies of chronic metabolic diseases such as diabetes and hypercholesterolemia.

Deficiency of TGR5 exacerbates immune-mediated cholestatic hepatic injury by stabilizing the β-catenin destruction complex

Intrahepatic cholestasis induced by drug toxicity may cause cholestatic hepatic injury (CHI) leading to liver fibrosis and cirrhosis. The G protein-coupled bile acid receptor 1 (TGR5) is a membrane receptor with well-known roles in the regulation of glucose metabolism and energy homeostasis. However, the role and mechanism of TGR5 in the context of inflammation during CHI remains unclear. Wild-type (WT) and TGR5 knockout (TGR5^−/−) mice with CHI induced by bile duct ligation (BDL) were involved in vivo, and WT and TGR5^−/− bone marrow-derived macrophages (BMDMs) were used in vitro. TGR5 deficiency significantly exacerbated BDL-induced liver injury, inflammatory responses and hepatic fibrosis compared with WT mice in vivo. TGR5^−/− macrophages were more susceptible to lipopolysaccharide (LPS) stimulation than WT macrophages. TGR5 activation by its ligand suppressed LPS-induced pro-inflammatory responses in WT but not TGR5^−/− BMDMs. Notably, expression of β-catenin was effectively inhibited by TGR5 deficiency. Furthermore, TGR5 directly interacted with Gsk3β to repress the interaction between Gsk3β and β-catenin, thus disrupting the β-catenin destruction complex. The pro-inflammatory nature of TGR5-knockout was almost abolished by lentivirus-mediated β-catenin overexpression in BMDMs. BMDM migration in vitro was accelerated under TGR5-deficient conditions or supernatant from LPS-stimulated TGR5^−/− BMDMs. From a therapeutic perspective, TGR5^−/− BMDM administration aggravated BDL-induced CHI, which was effectively rescued by β-catenin overexpression. Our findings reveal that TGR5 plays a crucial role as a novel regulator of immune-mediated CHI by destabilizing the β-catenin destruction complex, with therapeutic implications for the management of human CHI.

A novel role for farnesoid X receptor in the bile acid-mediated intestinal glucose homeostasis

The farnesoid X receptor (FXR), as a bile acid (BA) sensor, plays an important role in the regulation of lipid metabolism. However, the effects and underlying molecular mechanisms of FXR on intestinal glucose homeostasis remain elusive. Herein, we demonstrated that FXR and glucose transporter 2 (GLUT2) are essential for BA‐mediated glucose homeostasis in the intestine. BA‐activated FXR enhanced glucose uptake in intestinal epithelial cells by increasing the expression of GLUT2, which depended on ERK1/2 phosphorylation via S1PR2. However, it also reduced the cell energy generation via inhibition of oxidative phosphorylation, which is crucial for intestinal glucose transport. Moreover, BA‐activated FXR signalling potently inhibited specific glucose flux through the intestinal epithelium to the circulation, which reduced the increase in blood glucose levels in mice following oral glucose administration. This trend was supported by the changed ratio of GLUT2 to SGLT1 in the brush border membrane (BBM), including especially decreased GLUT2 abundance in the BBM. Furthermore, impaired intestinal FXR signalling was observed in the patients with intestinal bile acid deficiency (IBAD). These findings uncover a novel function by which FXR sustains the intestinal glucose homeostasis and provide a rationale for FXR agonists in the treatment of IBAD‐related hyperglycaemia.

Secondary Sclerosing Cholangitis in Critically Ill Patients Alters the Gut-Liver Axis: A Case Control Study

Secondary sclerosing cholangitis in critically ill patients (SC-CIP) occurs after long-term intensive care treatment. This study aimed to assess the gut-liver axis in SC-CIP. Stool microbiome composition, gut permeability, bacterial translocation and serum bile acid profiles of 18 SC-CIP patients compared to 11 patients after critical illness without liver disease (CIP controls), 21 patients with cirrhosis and 21 healthy controls were studied. 16S rDNA was isolated from stool and sequenced using the Illumina technique. Diamine oxidase, zonulin, soluble CD14 (sCD14) and lipopolysaccharide binding protein were measured in serum and calprotectin in stool. Serum bile acids were analyzed by high-performance liquid chromatography-mass spectrometry (HPLC-MS). Reduced microbiome alpha diversity and altered beta diversity were seen in SC-CIP, CIP controls and cirrhosis compared to healthy controls. SC-CIP patients showed a shift towards pathogenic taxa and an oralization. SC-CIP, CIP controls and cirrhotic patients presented with impaired gut permeability, and biomarkers of bacterial translocation were increased in SC-CIP and cirrhosis. Total serum bile acids were elevated in SC-CIP and cirrhosis and the bile acid profile was altered in SC-CIP, CIP controls and cirrhosis. In conclusions, observed alterations of the gut-liver axis in SC-CIP cannot solely be attributed to liver disease, but may also be secondary to long-term intensive care treatment.

3β-Isoobeticholic acid efficiently activates the farnesoid X receptor (FXR) due to its epimerization to 3α-epimer by hepatic metabolism

Bile acids (BAs) are important signaling molecules acting via the farnesoid X nuclear receptor (FXR) and the membrane G protein-coupled bile acid receptor 1 (GPBAR1). Besides deconjugation of BAs, the oxidoreductive enzymes of colonic bacteria and hepatocytes enable the conversion of BAs into their epimers or dehydrogenated forms. Obeticholic acid (OCA) is the first-in-class BA-derived FXR agonist approved for the treatment of primary biliary cholangitis. Herein, a library of OCA derivatives, including 7-keto, 6-ethylidene derivatives and 3β-epimers, was synthetized and investigated in terms of interactions with FXR and GPBAR1 in transaction assays and evaluated for FXR target genes expression in human hepatocytes and C57BL/6 mice. The derivatives were further subjected to cell-free analysis employing in silico molecular docking and a TR-FRET assay. The conversion of the 3βhydroxy epimer and its pharmacokinetics in mice were studied using LC-MS. We found that only the 3β-hydroxy epimer of OCA (3β-isoOCA) possesses significant activity to FXR in hepatic cells and mice. However, in a cell-free assay, 3β-isoOCA had about 9-times lower affinity to FXR than did OCA. We observed that 3β-isoOCA readily epimerizes to OCA in hepatocytes and murine liver. This conversion was significantly inhibited by the hydroxy-Δ⁵-steroid dehydrogenase inhibitor trilostane. In addition, we found that 3,7-dehydroobeticholic acid is a potent GPBAR1 agonist. We conclude that 3β-isoOCA significantly activates FXR due to its epimerization to the more active OCA by hepatic metabolism. Other modifications as well as epimerization on the C3/C7 positions and the introduction of 6-ethylidene in the CDCA scaffold abrogate FXR agonism and alleviate GPBAR1 activation.

Metabolomics analysis of annual killifish (Austrofundulus limnaeus) embryos during aerial dehydration stress

The annual killifish, Austrofundulus limnaeus, survives in ephemeral ponds in the coastal deserts of Venezuela. Persistence through the dry season is dependent on drought-resistant eggs embedded in the pond sediments during the rainy season. The ability of these embryos to enter drastic metabolic dormancy (diapause) during normal development enables A. limnaeus to survive conditions lethal to most other aquatic vertebrates; critical to the survival of the species is the ability of embryos to survive months and perhaps years without access to liquid water. Little is known about the molecular mechanisms that aid in survival of the dry season. This study aims to gain insight into the mechanisms facilitating survival of dehydration stress due to aerial exposure by examining metabolite profiles of dormant and developing embryos. There is strong evidence for unique metabolic profiles based on developmental stage and length of aerial exposure. Actively developing embryos exhibit more robust changes; however, dormant embryos respond in an active manner and significantly alter their metabolic profile. A number of metabolites accumulate in aerial-exposed embryos that may play an important role in survival, including the identification of known antioxidants and neuroprotectants. In addition, a number of unique metabolites not yet discussed in the dehydration literature are identified, such as lanthionine and 2-hydroxyglutarate. Despite high oxygen availability, embryos accumulate the anaerobic end product lactate. This paper offers an overview of the metabolic changes occurring that may support embryonic survival during dehydration stress due to aerial incubation, which can be functionally tested using genetic and pharmacological approaches.

Volixibat in adults with non-alcoholic steatohepatitis: 24-week interim analysis from a randomized, phase II study

BACKGROUND & AIMS

Volixibat is an inhibitor of the apical sodium-dependent bile acid transporter (ASBT) that has been hypothesized to improve non-alcoholic steatohepatitis (NASH) by blocking bile acid reuptake and stimulating hepatic bile acid production. We studied the safety, tolerability and efficacy of volixibat in patients with NASH.

METHODS

In this double-blind, phase II dose-finding study, adults with ≥5% steatosis and NASH without cirrhosis (N = 197) were randomized to receive volixibat (5, 10 or 20 mg) or placebo once daily for 48 weeks. The endpoints of a predefined interim analysis (n = 80), at week 24, were: ≥5% reduction in MRI-proton density fat fraction and ≥20% reduction in serum alanine aminotransferase levels. The primary endpoint was a ≥2-point reduction in non-alcoholic fatty liver disease activity score without worsening fibrosis at week 48.

RESULTS

Volixibat did not meet either interim endpoint; the study was terminated owing to lack of efficacy. In participants receiving any volixibat dose, mean serum 7-alpha-hydroxy-4-cholesten-3-one (C4; a biomarker of bile acid synthesis) increased from baseline to week 24 (+38.5 ng/ml [SD 53.18]), with concomitant decreases in serum total cholesterol (-14.5 mg/dl [SD 28.32]) and low-density lipoprotein cholesterol (-16.1 mg/dl [SD 25.31]). These changes were generally dose-dependent. On histological analysis, a greater proportion of participants receiving placebo (38.5%, n = 5/13) than volixibat (30.0%, n = 9/30) met the primary endpoint. Treatment-emergent adverse events (TEAEs) were mainly mild or moderate. No serious TEAEs were related to volixibat. Diarrhoea was the most common TEAE overall and the most common TEAE leading to discontinuation.

CONCLUSIONS

Increased serum C4 and decreased serum cholesterol levels provide evidence of target engagement. However, inhibition of ASBT by volixibat did not elicit a liver-related therapeutic benefit in adults with NASH.

LAY SUMMARY

A medicine called volixibat has previously been shown to reduce cholesterol levels in the blood. This study investigated whether volixibat could reduce the amount of fat in the liver and reduce liver injury in adults with an advanced form of non-alcoholic fatty liver disease. Volixibat did not reduce the amount of fat in the liver, nor did it have any other beneficial effect on liver injury. Participants in the study generally tolerated the side effects of volixibat and, as in previous studies, the main side effect was diarrhoea. These results show that volixibat is not an effective treatment for people with fatty liver disease.

CLINICAL TRIAL IDENTIFIER

NCT02787304.

Gut Microbiota and Cardiovascular Disease

Fecal microbial community changes are associated with numerous disease states, including cardiovascular disease (CVD). However, such data are merely associative. A causal contribution for gut microbiota in CVD has been further supported by a multitude of more direct experimental evidence. Indeed, gut microbiota transplantation studies, specific gut microbiota-dependent pathways, and downstream metabolites have all been shown to influence host metabolism and CVD, sometimes through specific identified host receptors. Multiple metaorganismal pathways (involving both microbe and host) both impact CVD in animal models and show striking clinical associations in human studies. For example, trimethylamine N-oxide and, more recently, phenylacetylglutamine are gut microbiota-dependent metabolites whose blood levels are associated with incident CVD risks in large-scale clinical studies. Importantly, a causal link to CVD for these and other specific gut microbial metabolites/pathways has been shown through numerous mechanistic animal model studies. Phenylacetylglutamine, for example, was recently shown to promote adverse cardiovascular phenotypes in the host via interaction with multiple ARs (adrenergic receptors)-a class of key receptors that regulate cardiovascular homeostasis. In this review, we summarize recent advances of microbiome research in CVD and related cardiometabolic phenotypes that have helped to move the field forward from associative to causative results. We focus on microbiota and metaorganismal compounds/pathways, with specific attention paid to short-chain fatty acids, secondary bile acids, trimethylamine N-oxide, and phenylacetylglutamine. We also discuss novel therapeutic strategies for directly targeting the gut microbiome to improve cardiovascular outcomes.

Altered Metabolome of Lipids and Amino Acids Species: A Source of Early Signature Biomarkers of T2DM

Diabetes mellitus, a disease of modern civilization, is considered the major mainstay of mortalities around the globe. A great number of biochemical changes have been proposed to occur at metabolic levels between perturbed glucose, amino acid, and lipid metabolism to finally diagnoe diabetes mellitus. This window period, which varies from person to person, provides us with a unique opportunity for early detection, delaying, deferral and even prevention of diabetes. The early detection of hyperglycemia and dyslipidemia is based upon the detection and identification of biomarkers originating from perturbed glucose, amino acid, and lipid metabolism. The emerging “OMICS” technologies, such as metabolomics coupled with statistical and bioinformatics tools, proved to be quite useful to study changes in physiological and biochemical processes at the metabolic level prior to an eventual diagnosis of DM. Approximately 300–400 such metabolites have been reported in the literature and are considered as predicting or risk factor-reporting metabolic biomarkers for this metabolic disorder. Most of these metabolites belong to major classes of lipids, amino acids and glucose. Therefore, this review represents a snapshot of these perturbed plasma/serum/urinary metabolic biomarkers showing a significant correlation with the future onset of diabetes and providing a foundation for novel early diagnosis and monitoring the progress of metabolic syndrome at early symptomatic stages. As most metabolites also find their origin from gut microflora, metabolism and composition of gut microflora also vary between healthy and diabetic persons, so we also summarize the early changes in the gut microbiome which can be used for the early diagnosis of diabetes.

Gut Microbiota and Heart, Vascular Injury

The gut microbiota plays an important role in maintaining human health. Accumulating evidence has indicated an intimate relationship between gut microbiota and cardiovascular diseases (CVD) which has become the leading cause of death worldwide. The alteration of gut microbial composition (gut dysbiosis) has been proven to contribute to atherosclerosis, the basic pathological process of CVD. In addition, the metabolites of gut microbiota have been found to be closely related to the development of CVD. For example, short-chain fatty acids are widely acclaimed beneficial effect against CVD, whereas trimethylamine-N-oxide is considered as a contributing factor in the development of CVD. In this chapter, we mainly discuss the gut microbial metabolite-involved mechanisms of CVD focusing on atherosclerosis, hypertension, diabetes, obesity, and heart failure. Targeting gut microbiota and related metabolites are novel and promising strategies for the treatment of CVD.

Genome-wide adaptive evolution to underground stresses in subterranean mammals: Hypoxia adaption, immunity promotion, and sensory specialization

Life underground has provided remarkable examples of adaptive evolution in subterranean mammals; however, genome-wide adaptive evolution to underground stresses still needs further research. There are approximately 250 species of subterranean mammals across three suborders and six families. These species not only inhabit hypoxic and dark burrows but also exhibit evolved adaptation to hypoxia, cancer resistance, and specialized sensory systems, making them an excellent model of evolution. The adaptive evolution of subterranean mammals has attracted great attention and needs further study. In the present study, phylogenetic analysis of 5,853 single-copy orthologous gene families of five subterranean mammals (Nannospalax galili, Heterocephalus glaber, Fukomys damarensis, Condylura cristata, and Chrysochloris asiatica) showed that they formed fou distinct clusters. This result is consistent with the traditional systematics of these species. Furthermore, comparison of the high-quality genomes of these five subterranean mammalian species led to the identification of the genomic signatures of adaptive evolution. Our results show that the five subterranean mammalian did not share positively selected genes but had similar functional enrichment categories, including hypoxia tolerance, immunity promotion, and sensory specialization, which adapted to the environment of underground stresses. Moreover, variations in soil hardness, climate, and lifestyles have resulted in different molecular mechanisms of adaptation to the hypoxic environment and different degrees of visual degradation. These results provide insights into the genome-wide adaptive evolution to underground stresses in subterranean mammals, with special focus on the characteristics of hypoxia adaption, immunity promotion, and sensory specialization response to the life underground.

Collision Cross Section Conformational Analyses of Bile Acids via Ion Mobility-Mass Spectrometry

Bile acids serve as one of the most important classes of biological molecules in the gastrointestinal system. Due to their structural similarity, bile acids have historically been difficult to accurately annotate in complex biological matrices using mass spectrometry. They often have identical or nominally similar mass-to-charge ratios and similar fragmentation patterns that make identification by mass spectrometry arduous, normally involving chemical derivatization and separation via liquid chromatography. Here, we demonstrate the use of drift tube ion mobility (DTIM) to derive collision cross section (CCS) values in nitrogen drift gas (DTCCSN2) for use as an additional descriptor to facilitate expedited bile acid identification. We also explore trends in DTIM measurements and detail structural characteristics for differences in DTCCSN2 values between subclasses of bile acid molecules.

Bile acids mediated potential functional interaction between FXR and FATP5 in the regulation of Lipid Metabolism

Perturbation in lipid homeostasis is one of the major bottlenecks in metabolic diseases, especially Non-alcoholic Fatty Liver Disease (NAFLD), which has emerged as a leading global cause of chronic liver disease. The bile acids (BAs) and their derivatives exert a variety of metabolic effects through complex and intertwined pathways, thus becoming the attractive target for metabolic syndrome treatment. To modulate the lipid homeostasis, the role of BAs, turn out to be paramount as it is essential for the absorption, transport of dietary lipids, regulation of metabolic enzymes and transporters that are essential for lipid modulation, flux, and excretion. The synthesis and transport of BAs (conjugated and unconjugated) is chiefly controlled by nuclear receptors and the uptake of long-chain fatty acids (LCFA) and BA conjugation via transporters. Among them, from in-vivo studies, farnesoid X receptor (FXR) and liver-specific fatty acid transport protein 5 (FATP5) have shown convincing evidence for their key roles in lipid homeostasis and reversal of fatty liver disease substantially. BAs have a wider range of biological effects as they are identified as modulators for FXR and FATP5 both and therefore hold a significant promise for altering the lipid content in the treatment of a metabolic disorder. BAs also have received noteworthy interest in drug delivery research due to its peculiar physicochemical properties and biocompatibility. Here, we are highlighting the connecting possibility of BAs as an agonist for FXR and antagonist for FATP5, paving an avenue to target them for designing synthetic small molecules for lipid homeostasis.

Total alkaloids of Sophora alopecuroides L. ameliorated murine colitis by regulating bile acid metabolism and gut microbiota

ETHNOPHARMACOLOGICAL RELEVANCE

Sophora alopecuroides L. is one of the most commonly used plants in traditional medicine for the management conditions including inflammatory and gastrointestinal disease. However, the therapeutic mechanism of Sophora alopecuroides L.particularly in inflammatory bowel disease (IBD) remains unclear.

AIM OF THE STUDY

To evaluate the treatment effects of total alkaloids of Sophora alopecuroides L. in ulcerative colitis (UC) mice model and explore the therapeutic mechanism of KDZ on UC based on bile acid metabolism and gut microbiota.

MATERIALS AND METHODS

Colitis were induced in BALB/c mice by administering 3.5% dextran sulfate sodium (DSS) in drinking water for 7 days. The mice were then given KDZ (300, 150 and 75 mg/kg) and the positive drug sulfasalazine (SASP, 450 mg/kg) via oral administration for 7 days. The levels of 23 bile acids in the liver, bile, serum, cecum content and colon were determined through ultra-performance liquid chromatography/tandem mass spectrometry (UPLC-MS/MS). The cecum microbiota was characterized through high-throughput Illumina MiSeq sequencing.

RESULTS

KDZ treatment significantly decreased the disease activity index (DAI) scores and ameliorated colonic injury in DSS-treated mice. The expression of IL-1β and TGF-β1 were suppressed, yet, IL-10 was up-regulated by KDZ and SASP treatment compared with those in the model group. Meanwhile, the serum contents of total bile acid and total cholesterol in the DSS group increased significantly compared with those in the control group, but reversed by SASP and KDZ. The relative abundance of Firmicutes increased after KDZ was administration, whereas the abundance of Bacteroidetes decreased. αMCA, βMCA, ωMCA and CA in the SASP and KDZ groups did not differ from those in the control group, whereas these parameters significantly increased in the DSS group.

CONCLUSIONS

KDZ had a protective effect on DSS-induced colitis by mitigating colonic injury, preventing gut microbiota dysbiosis and regulating bile acid metabolism.

Paroxetine Administration Affects Microbiota and Bile Acid Levels in Mice

Recent interest in the role of microbiota in health and disease has implicated gut microbiota dysbiosis in psychiatric disorders including major depressive disorder. Several antidepressant drugs that belong to the class of selective serotonin reuptake inhibitors have been found to display antimicrobial activities. In fact, one of the first antidepressants discovered serendipitously in the 1950s, the monoamine-oxidase inhibitor Iproniazid, was a drug used for the treatment of tuberculosis. In the current study we chronically treated DBA/2J mice for 2 weeks with paroxetine, a selective serotonin reuptake inhibitor, and collected fecal pellets as a proxy for the gut microbiota from the animals after 7 and 14 days. Behavioral testing with the forced swim test revealed significant differences between paroxetine- and vehicle-treated mice. Untargeted mass spectrometry and 16S rRNA profiling of fecal pellet extracts showed several primary and secondary bile acid level, and microbiota alpha diversity differences, respectively between paroxetine- and vehicle-treated mice, suggesting that microbiota functions are altered by the drug. In addition to their lipid absorbing activities bile acids have important signaling activities and have been associated with gastrointestinal diseases and colorectal cancer. Antidepressant drugs like paroxetine should therefore be used with caution to prevent undesirable side effects.

Association between 12α-hydroxylated bile acids and hepatic steatosis in rats fed a high-fat diet

High-fat (HF) diet induces hepatic steatosis that is a risk factor for noncommunicable diseases such as obesity, type 2 diabetes and cardiovascular disease. Previously, we found that HF feeding in rats increases the excretion of fecal bile acids (BAs), specifically 12α-hydroxylated (12αOH) BAs. Although the liver is the metabolic center in our body, the association between hepatic steatosis and 12αOH BAs in HF-fed rats is unclear. Thus, we investigated extensively BA composition in HF-fed rats and evaluated the association between hepatic steatosis and 12αOH BAs. Acclimated male inbred WKAH/HkmSlc rats were divided into two groups and fed either control or HF diet for 8 weeks. Feeding HF diet increased hepatic triglyceride and total cholesterol concentrations, which correlated positively with 12αOH BAs concentrations but not with non-12αOH BAs in the feces, portal plasma and liver. Accompanied by the increase in 12αOH BAs, the rats fed HF diet showed increased fat absorption and higher mRNA expression of liver Cidea. The enhancement of 12αOH BA secretion may contribute to hepatic steatosis by the promotion of dietary fat absorption and hepatic Cidea mRNA expression. The increase in 12αOH BAs was associated with enhanced liver cholesterol 7α-hydroxylase (Cyp7a1) and sterol 12α-hydroxylase (Cyp8b1) mRNA expression. There was a significant increase in 7α-hydroxycholesterol, a precursor of BAs, in the liver of HF-fed rats. Altogether, these data suggest that the HF diet increases preferentially 12αOH BAs synthesis by utilizing the accumulated hepatic cholesterol and enhancing mRNA expression of Cyp7a1 and Cyp8b1 in the liver.

Gut microbiota and metabolites in the pathogenesis of endocrine disease

Type 1 diabetes (T1D) and Hashimoto's thyroiditis (HT) are the two most common autoimmune endocrine diseases that have rising global incidence. These diseases are caused by the immune-mediated destruction of hormone-producing endocrine cells, pancreatic beta cells and thyroid follicular cells, respectively. Both genetic predisposition and environmental factors govern the onset of T1D and HT. Recent evidence strongly suggests that the intestinal microbiota plays a role in accelerating or preventing disease progression depending on the compositional and functional profile of the gut bacterial communities. Accumulating evidence points towards the interplay between the disruption of gut microbial homeostasis (dysbiosis) and the breakdown of host immune tolerance at the onset of both diseases. In this review, we will summarize the major recent findings about the microbiome alterations associated with T1D and HT, and the connection of these changes to disease states. Furthermore, we will discuss the potential mechanisms by which gut microbial dysbiosis modulates the course of the disease, including disruption of intestinal barrier integrity and microbial production of immunomodulatory metabolites. The aim of this review is to provide broad insight into the role of gut microbiome in the pathophysiology of these diseases.

Eicosapentaenoic Acid-Enriched Phosphoethanolamine Plasmalogens Alleviated Atherosclerosis by Remodeling Gut Microbiota to Regulate Bile Acid Metabolism in LDLR-/- Mice

Eicosapentaenoic acid (EPA)-enriched phosphoethanolamine plasmalogens (EPA-PlsEtns) might be retained in the intestine rich in gut microbiota for a long time after treatment. It reminded us that EPA-PlsEtns might affect intestinal microbiota composition and its metabolites, which have been identified as a contributing factor in the development of cardiovascular diseases. In the present study, EPA-PlsEtn administration for 8 weeks significantly reduced the atherosclerotic lesion area in low-density lipoprotein receptor deficient (LDLR^-/-) mice. Notably, the serum total cholesterol and low-density lipoprotein cholesterol levels were significantly reduced by 33.6 and 38.2%, respectively, by EPA-PlsEtns instead of EPA in the form of ethyl ester (EPA-EE) treatment compared with the model group. EPA-PlsEtn administration also increased total neutral sterol and bile acids in feces by 92 and 39%, respectively, rather than EPA-EE. Mechanistically, EPA-PlsEtns might affect the abundance of gut microbiota contributing to the alteration of bile acid profiles, which might further accelerate bile acid synthesis via increasing cholesterol 7 α-hydroxylase expression induced by the inhibition of farnesoid X receptor activation.

The Detection of Bile Acids in the Lungs of Paediatric Cystic Fibrosis Patients Is Associated with Altered Inflammatory Patterns

Background: Cystic fibrosis (CF) is a hereditary disorder in which persistent unresolved inflammation and recurrent airway infections play major roles in the initiation and progression of the disease. Little is known about triggering factors modulating the transition to chronic microbial infection and inflammation particularly in young children. Cystic fibrosis respiratory disease starts early in life, with the detection of inflammatory markers and infection evident even before respiratory symptoms arise. Thus, identifying factors that dysregulate immune responsiveness at the earliest stages of the disease will provide novel targets for early therapeutic intervention. Methods: We evaluated the clinical significance of bile acid detection in the bronchoalveolar lavage fluid of clinically stable preschool-aged children diagnosed with CF. Results: We applied an unbiased classification strategy to categorize these specimens based on bile acid profiles. We provide clear associations linking the presence of bile acids in the lungs with alterations in the expression of inflammatory markers. Using multiple regression analysis, we also demonstrate that clustering based on bile acid profiles is a meaningful predictor of the progression of structural lung disease. Conclusions: Altogether, our work has identified a clinically relevant host-derived factor that may participate in shaping early events in the aetiology of CF respiratory disease.

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.

Lipidomics perturbations in the brain of adult zebrafish (Danio rerio) after exposure to chiral ibuprofen

The stereoselective effects of chiral ibuprofen (IBU) were studied using lipidomics by exposing adult zebrafish (Danio rerio) to an environmental concentration of 5 μg/L for 28 days. After treatment with rac-/R-(-)-/S-(+)-IBU, the brain tissue of the zebrafish was harvested to analyze for lipid metabolites by using ultra-performance liquid chromatography-quadrupole time-of-flight mass spectrometry. Results showed that the six classes of lipids, namely, glycerophospholipids, sterol lipids, prenol lipids, fatty acyls, glycerolipids, and sphingolipids, including 46 biomarkers, were affected after exposure. The different influences on metabolites were observed in the rac-/R-(-)-/S-(+)-IBU-treated samples. The rac-IBU treatment remarkably affected nine lipids. The R-(-)-IBU and S-(+)-IBU treatments had remarkably effects on six and four lipids, respectively. According to the HMDB database and KEGG pathways, nine important lipids were successfully matched to the involved biochemical pathways, such as glycerophospholipid metabolism, arachidonic acid metabolism, and linoleic acid metabolism. Therefore, IBU can cause disorders in the metabolism of the brain lipids of adult zebrafish and affect the composition of biological membranes, inflammatory responses, and cardiovascular and cerebrovascular diseases. The significant difference in the effects of R-(-)-IBU and S-(+)-IBU on lipidomics indicated that chiral IBU has stereoselective toxicity to aquatic organisms. Our study provided new insights into the environmental toxicology and highlighted the hazard of pharmaceutical and personal care product pollution in aquatic environments.

Long Non-Coding RNA (lncRNA) SNHG5 Participates in Vertical Sleeve Gastrectomy for Type II Diabetes Mellitus by Regulating TGR5

BACKGROUND Due to its remarkable effect in controlling glycometabolism, relatively simple operation, and low risk of complications, sleeve gastrectomy (SG) has become the preferred surgical treatment for type II diabetes mellitus. Increased blood glucose in the body can cause damage to functional cells. MATERIAL AND METHODS Long non-coding RNA SNHG5 expression and TGR5 in serum were analyzed by real-time PCR. A diabetic cell model was established by culturing normal human intestinal epithelial cells NCM460 and DLD-1 with high-glucose and high-fat medium. CCK-8 assay, TUNEL assay, and flow cytometry were used to assess cell growth and apoptosis, respectively. The secretion of lactate dehydrogenase (LDH) was detected using the LDH Cytotoxicity Kit. lncRNA SNHG5 was downregulated by siRNA. The changes in expression of SNHG5, TGR5, Akt, p65, and Bcl-2 were analyzed by real-time PCR assay or Western blot. RESULTS In 40 type II diabetes patients who underwent sleeve gastrectomy, the expression of SNHG5 decreased and the expression of TGR5 increased compared with that before the operation. After high-glucose and high-fat culture, cell growth was inhibited and cell apoptosis increased significantly. The expression of SNHG5 was increased and TGR5 was decreased with high-glucose and high-fat culture. However, high glucose and high fat showed an opposite trend for cell growth, apoptosis, and LDH release under inhibition of SNHG5. The expression levels of TGR5 and Akt, p65, and Bcl-2 were also returned to normal by SNHG5 inhibition. CONCLUSIONS By downregulating expression of the SNHG5 gene and then altering expression of the TGR5 gene, the damage to colorectal cells induced by high glucose was alleviated. This may be one of the mechanisms underlying the effect of sleeve gastric surgery in treatment of diabetes mellitus.

Treatment with Anaerobutyricum soehngenii: a pilot study of safety and dose-response effects on glucose metabolism in human subjects with metabolic syndrome

Dysbiosis of the intestinal microbiota has been implicated in insulin resistance, although evidence regarding causality in humans is scarce. We performed a phase I/II dose-finding and safety study on the effect of oral intake of the anaerobic butyrogenic strain Anaerobutyricum soehngenii on glucose metabolism in 24 subjects with metabolic syndrome. We found that treatment with A. soehngenii was safe and observed a significant correlation between the measured fecal abundance of administered A. soehngenii and improvement in peripheral insulin sensitivity after 4 weeks of treatment. This was accompanied by an altered microbiota composition and a change in bile acid metabolism. Finally, we show that metabolic response upon administration of A. soehngenii (defined as improved insulin sensitivity 4 weeks after A. soehngenii intake) is dependent on microbiota composition at baseline. These data in humans are promising, but additional studies are needed to reproduce our findings and to investigate long-term effects, as well as other modes of delivery.

Benzene exposure induces gut microbiota dysbiosis and metabolic disorder in mice

The gut microbiota comprises a multispecies microbial community and is essential for maintaining health. Benzene is a widespread environmental and occupational pollutant that mainly causes blood and bone marrow abnormalities. However, the effects of benzene on gut microbiota and metabolism have not yet been investigated. In this study, C57BL/6 mice were exposed to 0, 6, 30 and 150 mg/kg benzene by subcutaneous injection for 30 days. We observed that white blood cell levels significantly decreased in the three benzene exposure groups, while red blood cell and hemoglobin levels were only changed remarkably in 30 and 150 mg/kg benzene-treated mice. The results of 16S rRNA sequencing showed that benzene exposure altered the overall structure of the gut microbial communities. In addition, significant enrichments of Actinobacteria (p < .05) at the phylum level and Helicobacter at the genus level were observed in the cecal contents and feces of mice exposed to 150 mg/kg benzene. Moreover, there was a significant negative correlation between Actinobacteria abundance and basic blood indicators, including white blood cell, red blood cell, and hemoglobin levels. Furthermore, according to LC-MS analysis, a total of 42 cecal metabolites were significantly altered by 150 mg/kg benzene. Several metabolic pathways were significantly influenced by benzene exposure, including cysteine and methionine metabolism, porphyrin and chlorophyll metabolism, steroid biosynthesis, aminoacyl-tRNA biosynthesis, and arginine and proline metabolism. In summary, this study demonstrated that benzene exposure causes dysbiosis of the gut microbiota and metabolic disorder in mice.

Effect of the Ileum and Colon on Liver Regeneration

PURPOSE

The colon and ileum play significant roles on liver physiology. Studies about simultaneous hepatectomy and colectomy or enterectomy are scarce and controversial. We investigated and compared the effects of ileum and colon resection on liver regeneration.

MATERIALS AND METHODS

Twenty four Wistar rats were allocated in group I-(sham), group II-70% hepatectomy; group III-70% hepatectomy + ileal resection, and group IV-70% hepatectomy + partial colectomy. On the sixth day, serum hepatic enzymes, albumin, hepatocyte growth-factor (HGF) and transforming growth factor-alpha (TGF-α) were measured. The hepatic regeneration rate was estimated. Ki-67 immunohistochemical analysis was done in remnant liver.

RESULTS

Hepatic enzymes levels were significantly higher in group III rats comparing to the other groups (p < 0.001). In group IV, the levels were significantly lower than in groups II and III (p < 0.001). Albuminemia was significantly lower in group III rats comparing with the other groups (p < 0.001). Albuminemia was not different comparing groups I and IV (p > 0.05). Cytokines HGF and TGF-α levels in group IV were significantly higher than in the other groups (p < 0.001). Liver regeneration rate was higher group IV than in groups II and III, and the difference was statistically significant (p = 0.002). The hepatocytes expression of Ki-67 was significantly higher in the remnant liver of group IV than in group III (p = 0.002). There was no difference in Ki-67 expression between groups II and IV (p > 0.05).

CONCLUSION

Ileum and colon resection have different effects on liver regeneration. Colon resection positively influences liver regeneration, while ileum resection negatively influences the regenerative process, in a rat model.

Glycochenodeoxycholate promotes the metastasis of gallbladder cancer cells by inducing epithelial to mesenchymal transition via activation of SOCS3/JAK2/STAT3 signaling pathway

The incidence of gallbladder cancer (GBC) is relatively rare but a high degree of malignancy. The migration and invasion potential of GBC severely affects the prognosis of patients with GBC. Glycochenodeoxycholate (GCDC) is one of the most important components in GBC-associated microenvironment. However, the role of GCDC in the metastatic feature of GBC cells is not fully understood. First, the results of this study found that GCDC could effectively enhance the metastasis of GBC cells. Furthermore, GCDC could lead to the enhancement of epithelial to mesenchymal transition (EMT) phenotype in GBC cells, which is concerned to be an important mechanism of tumor metastasis. Further studies showed that GCDC treatment induced the upregulation of matrix metalloproteinase-3 (MMP3), MMP9, and SOCS3/JAK2/p-STAT3 signal pathway in GBC cells, which could regulate the level of EMT. Beside that, we also found the positive expression of farnesoid X receptor (FXR) in GBC cells and inhibition of FXR could significantly block the effect of GCDC on the metastasis of GBC cells. These results indicated that GCDC promoted GBC cells metastasis by enhancing the level of EMT and inhibition of FXR could significantly block the effect of GCDC. On one hand, FXR might be an indicator for predicting the metastasis of patient with GBC. On the other hand, FXR might serve as a potential antimetastasis target in GBC therapy.

Nerve growth factor induced farnesoid X receptor upregulation modulates autophagy flux and protects hepatocytes in cholestatic livers

Upregulation of nerve growth factor (NGF) in parenchymal hepatocytes has been shown to exert hepatoprotective function during cholestatic liver injury. However, the modulatory role of NGF in regulation of liver autophagy remains unclear. This study aimed to scrutinize the regulatory role of NGF in hepatic expression of farnesoid X receptor (FXR), a bile acid (BA)-activated nuclear receptor, and to determine its cytoprotective effect on BA-induced autophagy and cytotoxicity. Livers of human hepatolithiasis and bile duct ligation (BDL)-induced mouse cholestasis were used for histopathological and molecular detection. The regulatory roles of NGF in autophagy flux and FXR expression, as well as its hepatoprotection against BA cytotoxicity were examined in cultured hepatocytes. FXR downregulation in human hepatolithiasis livers showed positive correlation with hepatic NGF levels. NGF administration upregulated hepatic FXR levels, while neutralization of NGF decreased FXR expression in BDL-induced cholestatic mouse livers. In vitro studies demonstrated that NGF upregulated FXR expression, increased cellular LC3 levels, and exerted hepatoprotective effect in cultured primary rat hepatocytes. Conversely, autophagy inhibition abrogated NGF-driven cytoprotection under BA exposure, suggesting involvement of NGF-modulated auophagy flux. Although FXR agonistic GW4064 stimulation did not affect auophagic LC3 levels, FXR activity inhibition significantly potentiated BA-induced cytotoxicity and increased cellular p62/SQSTM1 and Rab7 protein in SK-Hep1 hepatocytes. Moreover, FXR gene silencing abolished the protective effect of NGF under BA exposure. These findings support that NGF modulates autophagy flux via FXR upregulation and protects hepatocytes against BA-induced cytotoxicity. NGF/FXR axis is a novel therapeutic target for treatment of cholestatic liver diseases.

Intersection of the Gut Microbiome and Circadian Rhythms in Metabolism

The gut microbiome and circadian rhythms (CRs) both exhibit unique influence on mammalian hosts and have been implicated in the context of many diseases, particularly metabolic disorders. It has become increasingly apparent that these systems also interact closely to alter host physiology and metabolism. However, the mechanisms that underlie these observations remain largely unknown. Recent findings have implicated microbially derived mediators as potential signals between the gut microbiome and host circadian clocks; two specific mediators are discussed in this review: short-chain fatty acids (SCFAs) and bile acids (BAs). Key gaps in knowledge and major challenges that remain in the circadian and microbiome fields are also discussed, including animal versus human models and the need for precise timed sample collection.

Gut microbiota: a promising target against cardiometabolic diseases

Introduction: Cardiometabolic diseases (CMD) are a group of interrelated disorders such as metabolic syndrome, type 2 diabetes mellitus and cardiovascular diseases (CVD). As the prevalence of these diseases increases globally, efficient new strategies are necessary to target CMD and modifiable risk factors. In the past decade, evidence has accumulated regarding the influence of gut microbiota (GM) on CMD, providing new targets for therapeutic interventions.Areas covered: This narrative review discusses the pathophysiologic link between CMD, GM, and potential microbiota-based targets against atherosclerosis and modifiable risk factors for atherosclerosis. Low-grade inflammation can be induced through GM and its derived metabolites. CMD are influenced by GM and microbiota-derived metabolites such as short-chain fatty acids (SCFA), secondary bile acids, trimethylamine N-oxide (TMAO), and the composition of GM can modulate host metabolism. All of the above can lead to promising therapeutic targets.Expert opinion: Most data are derived from animal models or human association studies; therefore, more translational and interventional research in humans is necessary to validate these promising findings. Reproduced findings such as aberrant microbiota patterns or circulating biomarkers could be targeted depending on individual metabolic profiles, moving toward personalized medicine in CMD.

[Non - alcoholic fatty liver disease and enteral insufficiency: comorbidity of their development]

The article reflects current literature data on the epidemiology and risk factors of non - alcoholic fatty liver disease. An important aspect is the description of the modern views of combined lesions of the hepatobiliary tract and small intestine. Disorders of the intestinal microbiota play a special role in the development of non - alcoholic fatty liver disease. The value of enterohepatic circulation of bile acids in the development of intestinal and liver diseases was shown. It seems relevant to further study the comorbidity of the development of non - alcoholic fatty liver disease and enteropathy for the development of pathogenetically substantiated therapy.

Liver Transcriptome Changes of Hyla Rabbit in Response to Chronic Heat Stress

Simple Summary

It has been widely acknowledged in farm animals that environmental heat stress would have comprehensive influences on many kinds of physiological aspects, including the metabolic characteristics, production performances, welfare concerns, etc. The rabbit is a small herbivore and needs to regulate the body temperature in a fine mechanism. Little is known, however, about the genes and pathways that are involved in the regulatory responses under chronic heat stress conditions. In the present study, we investigated the liver transcriptome changes in response to chronic heat stress for Hyla rabbit, that is a commercial meat breed recently introduced into China. We successfully revealed the differentially expressed genes that were significantly enriched in heat stress related biological processes. The results would help us for better understanding the molecular mechanisms underlying physiological responses against heat stress in rabbits.

Abstract

Rabbit is an economically important farm animal in China and also is a widely used animal model in biological researches. Rabbits are very sensitive to the environmental conditions, therefore we investigated the liver transcriptome changes in response to chronic heat stress in the present study. Six Hyla rabbits were randomly divided into two groups: chronic heat stress (HS) and controls without heat stress (CN). Six RNA-Seq libraries totally yielded 380 million clean reads after the quality filtering. Approximately 85.07% of reads were mapped to the reference genome. After assembling transcripts and quantifying gene expression levels, we detected 51 differentially expressed genes (DEGs) between HS and CN groups with thresholds of the adjusted p-value < 0.05 and |log2(FoldChange)| > 1. Among them, 33 and 18 genes were upregulated and downregulated, respectively. Gene ontology analyses further revealed that these DEGs were mainly associated with metabolism of lipids, thyroid hormone metabolic process, and cellular modified amino acid catabolic process. The upregulated ACACB, ACLY, LSS, and CYP7A1 genes were found to be inter-related through biological processes of thioester biosynthetic process, acyl-CoA biosynthetic process, acetyl-CoA metabolic process, and others. Six DEGs were further validated by quantitative real-time PCR analysis. The results revealed the candidate genes and biological processes that will potentially be considered as important regulatory factors involved in the heat stress response in rabbits.

Saxagliptin alters bile acid profiles and yields metabolic benefits in drug-naïve overweight or obese type 2 diabetes patient

BACKGROUND

The aim of the present study was to investigate the metabolic benefits of saxagliptin and its effects on serum bile acids (BAs) in normal weight and overweight/obese drug-naïve type 2 diabetes (T2D) patients.

METHODS

In all, 282 drug-naïve T2D patients (123 normal weight [NW], with body mass index [BMI] between 19.0 and <25.0 kg/m² ; 159 overweight/obese [OW/OB], with BMI ≥25.0 kg/m² ) were enrolled in the study and treated with saxagliptin 5 mg daily for 24 weeks. Serum BAs were assayed by liquid chromatography with tandem mass spectrometry.

RESULTS

At 24 weeks, HbA1c was significantly reduced in both groups, but the HbA1c levels were lower in the OW/OB than NW group. Moreover, significant decreases were seen at 24 weeks in C-reactive protein (CRP), aspartate aminotransferase, alanine aminotransferase, waist circumference, and systolic blood pressure in the OW/OB group. Interestingly, cholic acid, glycocholic acid, glycochenodeoxycholic acid, glycodeoxycholic acid (GDCA), and glycoursodeoxycholic acid (GUDCA) were increased in both groups after treatment, whereas chenodeoxycholic acid and deoxycholic acid (DCA) were specifically increased in the OW/OB group. Increased DCA and GDCA concentrations were significantly associated with decreased HbA1c or fasting blood glucose and CRP levels, whereas increased GDCA and GUDCA concentrations were associated with decreased waist circumference in the OW/OB group during treatment. In the NW group, increased GUDCA concentrations were significantly associated with a decrease in HbA1c.

CONCLUSIONS

Type 2 diabetes patients with OW/OB exhibited greater improvement in glycemic control and additional metabolic benefits after saxagliptin treatment. Saxagliptin significantly increased the BA pool, and DCA and GDCA were associated with metabolic improvements in OW/OB T2D patients.

Tauroursodeoxycholate-Bile Acid with Chaperoning Activity: Molecular and Cellular Effects and Therapeutic Perspectives

Tauroursodeoxycholic acid (TUDCA) is a naturally occurring hydrophilic bile acid that has been used for centuries in Chinese medicine. Chemically, TUDCA is a taurine conjugate of ursodeoxycholic acid (UDCA), which in contemporary pharmacology is approved by Food and Drug Administration (FDA) for treatment of primary biliary cholangitis. Interestingly, numerous recent studies demonstrate that mechanisms of TUDCA functioning extend beyond hepatobiliary disorders. Thus, TUDCA has been demonstrated to display potential therapeutic benefits in various models of many diseases such as diabetes, obesity, and neurodegenerative diseases, mostly due to its cytoprotective effect. The mechanisms underlying this cytoprotective activity have been mainly attributed to alleviation of endoplasmic reticulum (ER) stress and stabilization of the unfolded protein response (UPR), which contributed to naming TUDCA as a chemical chaperone. Apart from that, TUDCA has also been found to reduce oxidative stress, suppress apoptosis, and decrease inflammation in many in-vitro and in-vivo models of various diseases. The latest research suggests that TUDCA can also play a role as an epigenetic modulator and act as therapeutic agent in certain types of cancer. Nevertheless, despite the massive amount of evidence demonstrating positive effects of TUDCA in pre-clinical studies, there are certain limitations restraining its wide use in patients. Here, molecular and cellular modes of action of TUDCA are described and therapeutic opportunities and limitations of this bile acid are discussed.

Antibiotic-modulated microbiome suppresses lethal inflammation and prolongs lifespan in Treg-deficient mice

BACKGROUND

Regulatory T cell (Treg) deficiency leads to IPEX syndrome, a lethal autoimmune disease, in Human and mice. Dysbiosis of the gut microbiota in Treg-deficient scurfy (SF) mice has been described, but to date, the role of the gut microbiota remains to be determined.

RESULTS

To examine how antibiotic-modified microbiota can inhibit Treg deficiency-induced lethal inflammation in SF mice, Treg-deficient SF mice were treated with three different antibiotics. Different antibiotics resulted in distinct microbiota and metabolome changes and led to varied efficacy in prolonging lifespan and reducing inflammation in the liver and lung. Moreover, antibiotics altered plasma levels of several cytokines, especially IL-6. By analyzing gut microbiota and metabolome, we determined the microbial and metabolomic signatures which were associated with the antibiotics. Remarkably, antibiotic treatments restored the levels of several primary and secondary bile acids, which significantly reduced IL-6 expression in RAW macrophages in vitro. IL-6 blockade prolonged lifespan and inhibited inflammation in the liver and lung. By using IL-6 knockout mice, we further identified that IL-6 deletion provided a significant portion of the protection against inflammation induced by Treg dysfunction.

CONCLUSION

Our results show that three antibiotics differentially prolong survival and inhibit lethal inflammation in association with a microbiota-IL-6 axis. This pathway presents a potential avenue for treating Treg deficiency-mediated autoimmune disorders.

Serum Bile Acids in Patients With Primary Open-angle Glaucoma

PURPOSE

To measure the serum bile acids (SBA) in patients with primary open-angle glaucoma (POAG) and to compare with nonglaucomatous controls.

PATIENTS AND METHODS

A hospital-based case control study of 90 patients above the age of 40 years was conducted. Patients with POAG formed the study group and individuals without glaucoma in the same age group formed the control group. SBA estimation was done using ELISA kit enzymatic assay technique and the median value was compared between the 2 groups.

RESULTS

The median of SBA level was found to be more in POAG patients when compared with the control group. The difference was statistically significant (P<0.001). Median SBA level was not affected by the age or sex of the participants in the study.

CONCLUSIONS

"Bile acids" may have a role in the oxidative stress and apoptosis involved in the pathophysiology of POAG.

Microbial Metabolites Determine Host Health and the Status of Some Diseases

The gastrointestinal (GI) tract is a highly complex organ composed of the intestinal epithelium layer, intestinal microbiota, and local immune system. Intestinal microbiota residing in the GI tract engages in a mutualistic relationship with the host. Different sections of the GI tract contain distinct proportions of the intestinal microbiota, resulting in the presence of unique bacterial products in each GI section. The intestinal microbiota converts ingested nutrients into metabolites that target either the intestinal microbiota population or host cells. Metabolites act as messengers of information between the intestinal microbiota and host cells. The intestinal microbiota composition and resulting metabolites thus impact host development, health, and pathogenesis. Many recent studies have focused on modulation of the gut microbiota and their metabolites to improve host health and prevent or treat diseases. In this review, we focus on the production of microbial metabolites, their biological impact on the intestinal microbiota composition and host cells, and the effect of microbial metabolites that contribute to improvements in inflammatory bowel diseases and metabolic diseases. Understanding the role of microbial metabolites in protection against disease might offer an intriguing approach to regulate disease.

A Physiology-Based Model of Human Bile Acid Metabolism for Predicting Bile Acid Tissue Levels After Drug Administration in Healthy Subjects and BRIC Type 2 Patients

Drug-induced liver injury (DILI) is a matter of concern in the course of drug development and patient safety, often leading to discontinuation of drug-development programs or early withdrawal of drugs from market. Hepatocellular toxicity or impairment of bile acid (BA) metabolism, known as cholestasis, are the two clinical forms of DILI. Whole-body physiology-based modelling allows a mechanistic investigation of the physiological processes leading to cholestasis in man. Objectives of the present study were: (1) the development of a physiology-based model of the human BA metabolism, (2) population-based model validation and characterisation, and (3) the prediction and quantification of altered BA levels in special genotype subgroups and after drug administration. The developed physiology-based bile acid (PBBA) model describes the systemic BA circulation in humans and includes mechanistically relevant active and passive processes such as the hepatic synthesis, gallbladder emptying, transition through the gastrointestinal tract, reabsorption into the liver, distribution within the whole body, and excretion via urine and faeces. The kinetics of active processes were determined for the exemplary BA glycochenodeoxycholic acid (GCDCA) based on blood plasma concentration-time profiles. The robustness of our PBBA model was verified with population simulations of healthy individuals. In addition to plasma levels, the possibility to estimate BA concentrations in relevant tissues like the intracellular space of the liver enhance the mechanistic understanding of cholestasis. We analysed BA levels in various tissues of Benign Recurrent Intrahepatic Cholestasis type 2 (BRIC2) patients and our simulations suggest a higher susceptibility of BRIC2 patients toward cholestatic DILI due to BA accumulation in the liver. The effect of drugs on systemic BA levels were simulated for cyclosporine A (CsA). Our results confirmed the higher risk of DILI after CsA administration in healthy and BRIC2 patients. The presented PBBA model enhances our mechanistic understanding underlying cholestasis and drug-induced alterations of BA levels in blood and organs. The developed PBBA model might be applied in the future to anticipate potential risk of cholestasis in patients.

Gut microbial metabolites in depression: understanding the biochemical mechanisms

Gastrointestinal and central function are intrinsically connected by the gut microbiota, an ecosystem that has co-evolved with the host to expand its biotransformational capabilities and interact with host physiological processes by means of its metabolic products. Abnormalities in this microbiota-gut-brain axis have emerged as a key component in the pathophysiology of depression, leading to more research attempting to understand the neuroactive potential of the products of gut microbial metabolism. This review explores the potential for the gut microbiota to contribute to depression and focuses on the role that microbially-derived molecules – neurotransmitters, short-chain fatty acids, indoles, bile acids, choline metabolites, lactate and vitamins – play in the context of emotional behavior. The future of gut-brain axis research lies is moving away from association, towards the mechanisms underlying the relationship between the gut bacteria and depressive behavior. We propose that direct and indirect mechanisms exist through which gut microbial metabolites affect depressive behavior: these include (i) direct stimulation of central receptors, (ii) peripheral stimulation of neural, endocrine, and immune mediators, and (iii) epigenetic regulation of histone acetylation and DNA methylation. Elucidating these mechanisms is essential to expand our understanding of the etiology of depression, and to develop new strategies to harness the beneficial psychotropic effects of these molecules. Overall, the review highlights the potential for dietary interventions to represent such novel therapeutic strategies for major depressive disorder.

The association between gut microbiota development and maturation of intestinal bile acid metabolism in the first 3 y of healthy Japanese infants

The gut microbial community greatly changes in early life, influencing infant health and subsequent host physiology, notably through its collective metabolism, including host-microbiota interplay of bile acid (BA) metabolism. However, little is known regarding how the development of the intestinal microbial community is associated with maturation of intestinal BA metabolism. To address this, we monitored the succession of gut bacterial community and its association with fecal BA profile in the first 3 y of ten healthy Japanese infants. The BA profiles were classified into four types, defined by high content of conjugated primary BA (Con type), unconjugated primary BA (chenodeoxycholic acid and cholic acid) (Pri type), ursodeoxycholic acid (Urs type), and deoxycholic and lithocholic acid (Sec type). Most subjects begun with Con type or Pri type profiles during lactation and eventually transited to Sec type through Urs type after the start of solid food intake. Con type and Pri type were associated with Enterobacteriaceae-dominant microbiota corresponding to the neonatal type or Bifidobacterium-dominant microbiota corresponding to lactation type, respectively. Urs type subjects were strongly associated with Ruminococcus gnavus colonization, mostly occurring between Pri type and Sec type. Sec type was associated with adult-type complex microbiota dominated by a variety of Firmicutes and Bacteroidetes species. Addressing the link of the common developmental passage of intestinal BA metabolism with infant's health and subsequent host physiology requires further study.

Improved infrared spectroscopic discrimination between gall bladder (GB) polyps and GB cancer using component-descriptive spectral features of separated phases from bile

This study demonstrates a unique strategy for enhancing infrared (IR) spectroscopic discrimination between gall bladder (GB) polyps and cancer. This strategy includes the separation of raw bile juice into three sections of organic, aqueous, and amphiphilic phases and a cooperative combination of all IR spectral features of each separated phase for the discrimination. Raw bile juice is viscous and complex in composition because it contains fatty acids, cholesterol, proteins, phospholipids, bilirubin, and other components; therefore, the acquisition of IR spectra providing more component-discernible information is fundamental for improving discrimination. For this purpose, raw bile juice was separated into an aqueous phase, mostly containing bile salts, an organic phase with isolated lipids, and an amphiphilic phase, mainly containing proteins. The subsequent IR spectra of each separated phase were mutually characteristic and complementary to each other. When all the IR spectral features were combined, the discrimination was improved compared to that using the spectra of raw bile juice with no separation. The cooperative integration of more component-specific spectra obtained from each separated phase enhanced the discrimination. In addition, the IR spectra of the major constituents in bile juice, such as bile acids, conjugated bile salts, lecithin, and cholesterol, were recorded to explain the IR features of each separated phase.

The role of the gut microbiome in chronic liver disease: the clinical evidence revised

Recent research has suggested a role for the intestinal microbiota in the pathogenesis and potential treatment of a wide range of liver diseases. The intestinal microbiota and bacterial products may contribute to the development of liver diseases through multiple mechanisms including increased intestinal permeability, chronic systemic inflammation, production of short-chain fatty acids and changes in metabolism. This suggests a potential role for pre-, pro- and synbiotic products in the prevention or treatment of some liver diseases. In addition, there is emerging evidence on the effects of faecal microbial transplant. Herein, we discuss the relationship between the intestinal microbiota and liver diseases, as well as reviewing intestinal microbiota-based treatment options that are currently being investigated.