Bile salt biotransformations by human intestinal bacteria

Changes of bacterial communities and bile acid metabolism reveal the potential "intestine-hepatopancreas axis" in shrimp

The interaction between the gut and the liver plays a significant role in individual health and diseases. Mounting evidence supports that bile acids are important metabolites in the bidirectional communication between the gut and the liver. Most of the current studies on the "gut-liver axis" have focused on higher vertebrates, however, few was reported on lower invertebrates such as shrimp with an open circulatory system. Here, microbiomic and metabolomic analyses were conducted to investigate the bacterial composition and bile acid metabolism in intestine, hemolymph and hepatopancreas of Penaeus vannamei fed diets supplemented with octanoic acid and oleic acid. After six days of feeding, the bacterial composition in intestine, hemolymph and hepatopancreas changed at different stages, with significant increases in the relative abundance of several genera such as Pseudomonas and Rheinheimera in intestine and hepatopancreas. Notably, there was a more similar bacterial composition in intestine and hepatopancreas at the genus level, which indicated the close communication between shrimp intestine and hepatopancreas. Meanwhile, higher content of some bile acids such as lithocholic acid (LCA) and α-muricholic acid (α-MCA) in intestine and lower content of some bile acids such as taurohyocholic acids (THCA) and isolithocholic acid (IsoLCA) in hepatopancreas were detected. Furthermore, Spearman correlation analysis revealed a significant correlation between bacterial composition and bile acid metabolism in intestine and hepatopancreas. The microbial source tracking analysis showed that there was a high proportion of intestine and hepatopancreas bacterial community as the source of each other. Collectively, these results showed a strong crosstalk between shrimp intestine and hepatopancreas, which suggests a unique potential "intestine-hepatopancreas axis" in lower invertebrate shrimp with an open circulatory system. Our finding contributed to the understanding of the interplay between shrimp intestine and hepatopancreas in the view of microecology and provided new ideas for shrimp farming and disease control.

Berberine alleviates cholesterol and bile acid metabolism disorders induced by high cholesterol diet in mice

Berberine (BBR) is a traditional Chinese herb with broad antimicrobial activity. Gut microbiota plays an important role in the metabolism of bile acids and cholesterol. Our study investigated the effects of BBR on alleviating cholesterol and bile acid metabolism disorders induced by high cholesterol diet in mice. Adult male C57BL/6J mice fed with high cholesterol diet (HC) containing 1.25 % cholesterol (HC group) or fed with chow diet containing 0.02 % cholesterol (Chow group) served as controls. BBR50 and BBR100 group mice were fed with HC, and oral BBR daily at doses of 50 or 100 mg/kg respectively for 8 weeks. The results showed that BBR could reshape the homeostasis and composition of gut microbiota. The abundance of Clostridium genera was significantly inhibited by BBR, which resulted in a significant reduction of secondary bile acids within the enterohepatic circulation and a significant lower hydrophobic index of bile acids. The absorption of cholesterol in intestine, the deposition of cholesterol in liver and the excretion of cholesterol in biliary tract were significantly inhibited by BBR, which promoted the unsaturation of cholesterol in bile. These findings suggest the potential utility of BBR as a functional food to alleviate the negative effects of high cholesterol diet.

Ex vivo metabolism kinetics of primary to secondary bile acids via a physiologically relevant human faecal microbiota model

Bile acids (BA) are synthesized in the human liver and undergo metabolism by host gut bacteria. In diseased states, gut microbial dysbiosis may lead to high primary unconjugated BA concentrations and significant perturbations to secondary BA. Hence, it is important to understand the microbial-mediated formation kinetics of secondary bile acids using physiologically relevant ex vivo human faecal microbiota models. Here, we optimized an ex vivo human faecal microbiota model to recapitulate the metabolic kinetics of primary unconjugated BA and applied it to investigate the formation kinetics of novel secondary BA metabolites and their sequential pathways. We demonstrated (1) first-order depletion of primary BA, cholic acid (CA) and chenodeoxycholic acid (CDCA), under non-saturable conditions and (2) saturable Michaelis-Menten kinetics for secondary BA metabolite formation with increasing substrate concentration. Notably, relatively lower Michaelis constants (Km) were associated with the formation of deoxycholic acid (DCA, 14.3 μM) and lithocholic acid (LCA, 140 μM) versus 3-oxo CA (>1000 μM), 7-keto DCA (443 μM) and 7-keto LCA (>1000 μM), thereby recapitulating clinically observed saturation of 7α-dehydroxylation relative to oxidation of primary BA. Congruently, metagenomics revealed higher relative abundance of functional genes related to the oxidation pathway as compared to the 7α-dehydroxylation pathway. In addition, we demonstrated gut microbial-mediated hyocholic acid (HCA) and hyodeoxycholic acid (HDCA) formation from CDCA. In conclusion, we optimized a physiologically relevant ex vivo human faecal microbiota model to investigate gut microbial-mediated metabolism of primary BA and present a novel gut microbial-catalysed two-step pathway from CDCA to HCA and, subsequently, HDCA.

Breaking boundaries: Bacteria act as architects of host T cell modulators using bile acids

Bacteria act as architects of host T cell modulators using bile acids.

Unabsorbed Fecal Fat Content Correlates with a Reduction of Immunoglobulin a Coating of Gut Bacteria in High-Lard Diet-Fed Mice

SCOPE

Immunoglobulin A (IgA) selectively coats gut bacteria and contributes to regulatory functions in gastrointestinal inflammation and glucose metabolism. Excess intake of lard leads to decrease in the IgA coating of gut bacteria, although the underlying mechanisms remain unknown. This study validates how unabsorbed fat derived from a high-lard diet in the gut affects the IgA coating of bacteria, as assessed in mouse models using three types of dietary fat (lard, medium-, and long-chain triglycerides [MLCTs], and medium-chain triglycerides [MCTs]) exhibiting different digestibilities.

METHODS AND RESULTS

C57BL/6J mice are maintained on diets containing lard, MLCTs, or MCTs at 7% or 30% w/w for 10 weeks (n = 6 per group). The fecal fatty acid concentration is measured to quantify unabsorbed fat content. The ratio of IgA-coated bacteria to total bacteria (IgA coating ratio) in the feces is measured by flow cytometry. Compared to lard-fed mice, MLCT- and MCT-fed mice exhibit lower fecal concentrations of palmitic acid, stearic acid, and oleic acid and higher IgA coating ratios at both 7% and 30% dietary fat, and these parameters exhibit significant negative correlations.

CONCLUSION

Unabsorbed fat content in the gut may result in attenuated IgA coating of bacteria in high-lard diet-fed mice.

Altered Bile Acid and Pouch Microbiota Composition in Patients With Chronic Pouchitis

BACKGROUND

Patients with ulcerative colitis and total abdominal proctocolectomy with ileal pouch-anal anastomosis have a 50% risk of pouchitis and a 5% to 10% risk of chronic pouchitis.

AIMS

The goal of the study was to compare pouch microbiota and stool bile acid composition in patients with chronic pouchitis, chronic pouchitis and primary sclerosing cholangitis, and normal pouch.

METHODS

Patients with ulcerative colitis and ileal pouch-anal anastomosis were recruited from March 20, 2014, to August 6, 2019, and categorized into normal pouch, chronic pouchitis, and chronic pouchitis/primary sclerosing cholangitis groups. Stool samples were subjected to bile acid quantification and 16S rRNA gene sequencing. Statistical comparisons of absolute bile acid abundance and pouch microbiota α-diversity, β-diversity, and taxa abundance were performed among the patient groups.

RESULTS

A total of 51 samples were analyzed. Both α-diversity (P = .01, species richness) and β-diversity (P = .001) significantly differed among groups. Lithocholic acid was significantly lower in patients with chronic pouchitis/primary sclerosing cholangitis than in those with chronic pouchitis (P = .01) or normal pouch (P = .03). Decreased α-diversity was associated with an increased primary to secondary bile acid ratio (P = .002), which was also associated with changes in β-diversity (P = .006).

CONCLUSIONS

Pouch microbiota α- and β-diversity differed among patients with normal pouch, chronic pouchitis, and chronic pouchitis/primary sclerosing cholangitis. Lithocholic acid level and primary to secondary bile acid ratio were highly associated with pouch microbiota richness, structure, and composition. These findings emphasize the associations between pouch microbiota and bile acid composition in dysbiosis and altered metabolism, suggesting that secondary bile acids are decreased in chronic pouchitis.

The changing metabolic landscape of bile acids - keys to metabolism and immune regulation

Bile acids regulate nutrient absorption and mitochondrial function, they establish and maintain gut microbial community composition and mediate inflammation, and they serve as signalling molecules that regulate appetite and energy homeostasis. The observation that there are hundreds of bile acids, especially many amidated bile acids, necessitates a revision of many of the classical descriptions of bile acids and bile acid enzyme functions. For example, bile salt hydrolases also have transferase activity. There are now hundreds of known modifications to bile acids and thousands of bile acid-associated genes, especially when including the microbiome, distributed throughout the human body (for example, there are >2,400 bile salt hydrolases alone). The fact that so much of our genetic and small-molecule repertoire, in both amount and diversity, is dedicated to bile acid function highlights the centrality of bile acids as key regulators of metabolism and immune homeostasis, which is, in large part, communicated via the gut microbiome.

Bile acid metabolism in health and ageing-related diseases

Bile acids (BAs) have surpassed their traditional roles as lipid solubilizers and regulators of BA homeostasis to emerge as important signalling molecules. Recent research has revealed a connection between microbial dysbiosis and metabolism disruption of BAs, which in turn impacts ageing-related diseases. The human BAs pool is primarily composed of primary BAs and their conjugates, with a smaller proportion consisting of secondary BAs. These different BAs exert complex effects on health and ageing-related diseases through several key nuclear receptors, such as farnesoid X receptor and Takeda G protein-coupled receptor 5. However, the underlying molecular mechanisms of these effects are still debated. Therefore, the modulation of signalling pathways by regulating synthesis and composition of BAs represents an interesting and novel direction for potential therapies of ageing-related diseases. This review provides an overview of synthesis and transportion of BAs in the healthy body, emphasizing its dependence on microbial community metabolic capacity. Additionally, the review also explores how ageing and ageing-related diseases affect metabolism and composition of BAs. Understanding BA metabolism network and the impact of their nuclear receptors, such as farnesoid X receptor and G protein-coupled receptor 5 agonists, paves the way for developing therapeutic agents for targeting BA metabolism in various ageing-related diseases, such as metabolic disorder, hepatic injury, cardiovascular disease, renal damage and neurodegenerative disease.

Sex-specific effects of gut microbiome on shaping bile acid metabolism

Gut microbiome is a group of microorganisms that plays important roles in contributing to health and diseases. These bacterial compositions have been demonstrated to impact bile acids (BAs) profiles, either by directly metabolizing primary BAs to secondary BAs or indirect ways through host metabolism by influencing BAs synthesis, transportation and conjugation in liver. It has been observed sexually dimorphic gut microbiome and bile acids composition, with variations in expression levels of bile acid metabolizing genes in the liver. However, associations between sex-specific differences in gut microbiome and BAs profiles are not well understood. This study aimed to investigate whether gut microbiome could influence BAs profiles in host in a sexspecific manner. We transplanted cecum feces of male and female C57BL/6 mice to male mice and measured BAs concentrations in feces, serum and liver samples 7 days after fecal transplantation. We found different BAs profiles between mice with male and female gut microbiome, including altering levels and proportions of secondary BAs. We also observed varied expression levels of genes related to bile acid metabolism in the liver and distal ileum. Our results highlight sex-specific effects of gut microbiome on shaping bile acid metabolism through gut bacteria and regulation of host genes.

Bile acids and the gut microbiome are involved in the hyperthermia mediated by 3,4-methylenedioxymethamphetamine (MDMA)

Hyperthermia induced by phenethylamines, such as 3,4-methylenedioxymethamphetamine (MDMA), can lead to life-threatening complications and death. Activation of the sympathetic nervous system and subsequent release of norepinephrine and activation of uncoupling proteins have been demonstrated to be the key mediators of phenethylamine-induced hyperthermia (PIH). Recently, the gut microbiome was shown to also play a contributing role in PIH. Here, the hypothesis that bile acids (BAs) produced by the gut microbiome are essential to PIH was tested. Changes in the serum concentrations of unconjugated primary BAs cholic acid (CA) and chenodeoxycholic acid (CDCA) and secondary BA deoxycholic acid (DCA) were measured following MDMA (20 mg/kg, sc) treatment in antibiotic treated and control rats. MDMA-induced a significant hyperthermic response and reduced the serum concentrations of three BAs 60 min post-treatment. Pretreatment with antibiotics (vancomycin, bacitracin and neomycin) in the drinking water for five days resulted in the depletion of BAs and a hypothermic response to MDMA. Gut bacterial communities in the antibiotic-treated group were distinct from the MDMA or saline treatment groups, with decreased microbiome diversity and alteration in taxa. Metagenomic functions inferred using the bioinformatic tool PICRUSt2 on 16S rRNA gene sequences indicated that bacterial genes associated to BA metabolism are less abundant in the antibiotic-MDMA treated group. Overall, these findings suggest that gut bacterial produced BAs might play an important role in MDMA-induced hyperthermia.

Preservation of conjugated primary bile acids by oxygenation of the small intestinal microbiota in vitro

Bile acids play a critical role in the emulsification of dietary lipids, a critical step in the primary function of the small intestine, which is the digestion and absorption of food. Primary bile acids delivered into the small intestine are conjugated to enhance functionality, in part, by increasing aqueous solubility and preventing passive diffusion of bile acids out of the gut lumen. Bile acid function can be disrupted by the gut microbiota via the deconjugation of primary bile acids by bile salt hydrolases (BSHs), leading to their conversion into secondary bile acids through the expression of bacterial bile acid-inducible genes, a process often observed in malabsorption due to small intestinal bacterial overgrowth. By modeling the small intestinal microbiota in vitro using human small intestinal ileostomy effluent as the inocula, we show here that the infusion of physiologically relevant levels of oxygen, normally found in the proximal small intestine, reduced deconjugation of primary bile acids, in part, through the expansion of bacterial taxa known to have a low abundance of BSHs. Further recapitulating the small intestinal bile acid composition of the small intestine, limited conversion of primary into secondary bile acids was observed. Remarkably, these effects were preserved among four separate communities, each inoculated with a different small intestinal microbiota, despite a high degree of taxonomic variability under both anoxic and aerobic conditions. In total, these results provide evidence for a previously unrecognized role that the oxygenated environment of the small intestine plays in the maintenance of normal digestive physiology.

IMPORTANCE

Conjugated primary bile acids are produced by the liver and exist at high concentrations in the proximal small intestine, where they are critical for proper digestion. Deconjugation of these bile acids with subsequent transformation via dehydroxylation into secondary bile acids is regulated by the colonic gut microbiota and reduces their digestive function. Using an in vitro platform modeling the small intestinal microbiota, we analyzed the ability of this community to transform primary bile acids and studied the effect of physiological levels of oxygen normally found in the proximal small intestine (5%) on this metabolic process. We found that oxygenation of the small intestinal microbiota inhibited the deconjugation of primary bile acids in vitro. These findings suggest that luminal oxygen levels normally found in the small intestine may maintain the optimal role of bile acids in the digestive process by regulating bile acid conversion by the gut microbiota.

Antibiotic effects on gut microbiota modulate diet-induced metabolic dysfunction-associated steatohepatitis development in C57BL/6 mice

The potential involvement of the gut microbiota in metabolic dysfunction-associated steatohepatitis (MASH) pathogenesis has garnered increasing attention. In this study, we elucidated the link between high-fat/cholesterol/cholate-based (iHFC)#2 diet-induced MASH progression and gut microbiota in C57BL/6 mice using antibiotic treatments. Treatment with vancomycin (VCM), which targets gram-positive bacteria, exacerbated the progression of liver damage, steatosis, and fibrosis in iHFC#2-fed C57BL/6 mice. The expression levels of inflammation- and fibrosis-related genes in the liver significantly increased after VCM treatment for 8 weeks. F4/80+ macrophage abundance increased in the livers of VCM-treated mice. These changes were rarely observed in the iHFC#2-fed C57BL/6 mice treated with metronidazole, which targets anaerobic bacteria. A16S rRNA sequence analysis revealed a significant decrease in α-diversity in VCM-treated mice compared with that in placebo-treated mice, with Bacteroidetes and Firmicutes significantly decreased, while Proteobacteria and Verrucomicrobia increased markedly. Finally, VCM treatment dramatically altered the level and balance of bile acid (BA) composition in iHFC#2-fed C57BL/6 mice. Thus, the VCM-mediated exacerbation of MASH progression depends on the interaction between the gut microbiota, BA metabolism, and inflammatory responses in the livers of iHFC#2-fed C57BL/6 mice.

Chemoproteomic profiling of substrate specificity in gut microbiota-associated bile salt hydrolases

The gut microbiome possesses numerous biochemical enzymes that biosynthesize metabolites that impact human health. Bile acids comprise a diverse collection of metabolites that have important roles in metabolism and immunity. The gut microbiota-associated enzyme that is responsible for the gateway reaction in bile acid metabolism is bile salt hydrolase (BSH), which controls the host's overall bile acid pool. Despite the critical role of these enzymes, the ability to profile their activities and substrate preferences remains challenging due to the complexity of the gut microbiota, whose metaproteome includes an immense diversity of protein classes. Using a systems biochemistry approach employing activity-based probes, we have identified gut microbiota-associated BSHs that exhibit distinct substrate preferences, revealing that different microbes contribute to the diversity of the host bile acid pool. We envision that this chemoproteomic approach will reveal how secondary bile acid metabolism controlled by BSHs contributes to the etiology of various inflammatory diseases.

The Gut Microbiome and Symptom Burden After Kidney Transplantation: An Overview and Research Opportunities

Many kidney transplant recipients continue to experience high symptom burden despite restoration of kidney function. High symptom burden is a significant driver of quality of life. In the post-transplant setting, high symptom burden has been linked to negative outcomes including medication non-adherence, allograft rejection, graft loss, and even mortality. Symbiotic bacteria (microbiota) in the human gastrointestinal tract critically interact with the immune, endocrine, and neurological systems to maintain homeostasis of the host. The gut microbiome has been proposed as an underlying mechanism mediating symptoms in several chronic medical conditions including irritable bowel syndrome, chronic fatigue syndrome, fibromyalgia, and psychoneurological disorders via the gut-brain-microbiota axis, a bidirectional signaling pathway between the enteric and central nervous system. Post-transplant exposure to antibiotics, antivirals, and immunosuppressant medications results in significant alterations in gut microbiota community composition and function, which in turn alter these commensal microorganisms' protective effects. This overview will discuss the current state of the science on the effects of the gut microbiome on symptom burden in kidney transplantation and future directions to guide this field of study.

Prevention and treatment of antibiotics-associated adverse effects through the use of probiotics: A review

BACKGROUND

The human gut hosts a diverse microbial community, essential for maintaining overall health. However, antibiotics, commonly prescribed for infections, can disrupt this delicate balance, leading to antibiotic-associated diarrhea, inflammatory bowel disease, obesity, and even neurological disorders. Recognizing this, probiotics have emerged as a promising strategy to counteract these adverse effects.

AIM OF REVIEW

This review aims to offer a comprehensive overview of the latest evidence concerning the utilization of probiotics in managing antibiotic-associated side effects.

KEY SCIENTIFIC CONCEPTS OF REVIEW

Probiotics play a crucial role in preserving gut homeostasis, regulating intestinal function and metabolism, and modulating the host immune system. These mechanisms serve to effectively alleviate antibiotic-associated adverse effects and enhance overall well-being.

Impact of High-Fat Diet and Exercise on Bone and Bile Acid Metabolism in Rats

Bile acids help facilitate intestinal lipid absorption and have endocrine activity in glucose, lipid and bone metabolism. Obesity and exercise influence bile acid metabolism and have opposite effects in bone. This study investigates if regular exercise helps mitigate the adverse effects of obesity on bone, potentially by reversing alterations in bile acid metabolism. Four-month-old female Sprague Dawley rats either received a high-fat diet (HFD) or a chow-based standard diet (lean controls). During the 10-month study period, half of the animals performed 30 min of running at moderate speed on five consecutive days followed by two days of rest. The other half was kept inactive (inactive controls). At the study's end, bone quality was assessed by microcomputed tomography and biomechanical testing. Bile acids were measured in serum and stool. HFD feeding was related to reduced trabecular (-33%, p = 1.14 × 10-7) and cortical (-21%, p = 2.9 × 10-8) bone mass and lowered femoral stiffness (12-41%, p = 0.005). Furthermore, the HFD decreased total bile acids in serum (-37%, p = 1.0 × 10-6) but increased bile acids in stool (+2-fold, p = 7.3 × 10-9). These quantitative effects were accompanied by changes in the relative abundance of individual bile acids. The concentration of serum bile acids correlated positively with all cortical bone parameters (r = 0.593-0.708), whilst stool levels showed inverse correlations at the cortical (r = -0.651--0.805) and trabecular level (r = -0.656--0.750). Exercise improved some trabecular and cortical bone quality parameters (+11-31%, p = 0.043 to 0.001) in lean controls but failed to revert the bone loss related to the HFD. Similarly, changes in bile acid metabolism were not mitigated by exercise. Prolonged HFD consumption induced quantitative and qualitative alterations in bile acid metabolism, accompanied by bone loss. Tight correlations between bile acids and structural indices of bone quality support further functional analyses on the potential role of bile acids in bone metabolism. Regular moderate exercise improved trabecular and cortical bone quality in lean controls but failed in mitigating the effects related to the HFD in bone and bile acid metabolism.

Unique bile acid profiles in the bile ducts of patients with primary sclerosing cholangitis

BACKGROUND

The relationship between primary sclerosing cholangitis (PSC) and biliary bile acids (BAs) remains unclear. Although a few studies have compared PSC biliary BAs with other diseases, they did not exclude the influence of cholestasis, which affects the composition of BAs. We compared biliary BAs and microbiota among patients with PSC, controls without cholestasis, and controls with cholestasis, based on the hypothesis that alterations in BAs underlie the pathophysiology of PSC.

METHODS

Bile samples were obtained using endoscopic retrograde cholangiopancreatography from patients with PSC (n = 14), non-hepato-pancreato-biliary patients without cholestasis (n = 15), and patients with cholestasis (n = 13).

RESULTS

The BA profiles showed that patients with PSC and cholestasis controls had significantly lower secondary BAs than non-cholestasis controls, as expected, whereas the ratio of cholic acid/chenodeoxycholic acid in patients with PSC was significantly lower despite cholestasis, and the ratio of (cholic acid + deoxycholic acid)/(chenodeoxycholic acid + lithocholic acid) in patients with PSC was significantly lower than that in the controls with or without cholestasis. The BA ratio in the bile of patients with PSC showed a similar trend in the serum. Moreover, there were correlations between the alteration of BAs and clinical data that differed from those of the cholestasis controls. Biliary microbiota did not differ among the groups.

CONCLUSIONS

Patients with PSC showed characteristic biliary and serum BA compositions that were different from those in other groups. These findings suggest that the BA synthesis system in patients with PSC differs from that in controls and patients with other cholestatic diseases. Our approach to assessing BAs provides insights into the pathophysiology of PSC.

The alteration of fecal microbial and metabolic profile of gallstone patients in Taiwan: Single-center study

BACKGROUND

Gallstone disease is a common health problem worldwide. The role of the gut microbiota in gallstone pathogenesis remains obscure. Our aim was to evaluate the association and crosstalk between gut microbiota, gut metabolomic, and metabolic parameters in cholesterol gallstone patients, pigmented gallstone patients, and controls.

METHODS

We collected stool samples from healthy individuals and patients with gallstones in our hospital from March 2019 to February 2021. 16s rRNA sequencing was performed, followed by differential abundance analyses. Measurement of bile acids and short-chain fatty acids was conducted via targeted metabolomics.

RESULT

Thirty healthy individuals and 20 gallstone patients were recruited. The intergroup difference of microbial composition was significant between control and gallstone patients. The control group had more abundant Faecalibacterium , Prevotella 9 , and Bacteroides plebeius DSM 17135 . The cholesterol stones group had higher Desulfovibrionaceae and Bacteroides uniformis than the other two groups, while the pigment stone group had more abundant Escherichia-Shigella . In the analysis of metabolites, only n-butyric acid had a significantly higher concentration in the controls than in the gallstone group ( p < 0.01). The level of 3α-hydroxy-12 ketolithocholic acid, deoxycholic acid, and cholic acid showed no intergroup differences but was correlated to the serum cholesterol level and bacterial richness and evenness.

CONCLUSION

Our study revealed the key taxa that can discriminate between individuals with or without gallstones. We also identified metabolites that are possibly associated with metabolic parameter and bacterial diversity. However, the correlation of the metabolites to certain clusters of bacteria should be analyzed in a larger cohort.

Addressing the interaction of stem bromelain with different anionic surfactants, below, at and above the critical micelle concentration (cmc) in phosphate buffer at pH 7: Physicochemical, spectroscopic, & molecular docking study

The structural stability and therapeutic activity of Stem Bromelain (BM) have been explored by unravelling the interaction of stem BM in presence of two different types of anionic surfactants namely, bile salts, NaC and NaDC and the conventional anionic surfactants, SDDS and SDBS, below, at and above the critical micelle concentration (cmc) in aqueous phosphate buffer of pH 7. Different physicochemical parameters like, surface excess (Γcmc), minimum area of surfactants at air water interface (Amin) etc. are calculated from tensiometry both in absence and presence of BM. Several inflection points (C1, C2 and C3) have been found in tensiometry profile of surfactants in presence of BM due to the conformational change of BM assisted by surfactants. Similar observation also found in isothermal titration calorimetry (ITC) profiles where the enthalpy of micellization (ΔH0obs) of surfactants in absence and presence of BM have calculated. Further, steady state absorption and fluorescence spectra monitoring the tryptophan (Trp) emission of free BM and in presence of all the surfactants at three different temperatures (288.15 K, 298.15 K, and 308.15 K) reveal the nature of fluorescence quenching of BM in presence of bile salts/surfactants. Time resolved fluorescence studies at room temperature also support to determine the several quenching parameters. The binding constant (Kb) of BM with all the surfactants and free energy of binding (∆G0 of bile salts/surfactants with BM at different temperatures have been calculated exploiting steady state fluorescence technique. It is observed that, the binding of NaC with BM is greater as compared to other surfactants while Stern-Volmer quenching constant (KSV) is found greater in presence of SDBS as compared with others which supports the surface tension and ITC data with the fact that surface activity of surfactant(s) is decreasing with the binding of the surfactants at the core or binding pocket of BM. Circular Dichroism (CD) study shows the stability of secondary structure of BM in presence of NaC and NaDC below C3, while BM lost its structural stability even at very low surfactant concentration of SDDS and SDBS which also supports the more involvement of bile salts in binding rather than surfactants. The molecular docking studies have also been substantiated for better understanding the several experimental investigations interaction of BM with the bile salts/surfactants.

Exploring the significance of microbiota metabolites in rheumatoid arthritis: uncovering their contribution from disease development to biomarker potential

Rheumatoid arthritis (RA) is a multifaceted autoimmune disorder characterized by chronic inflammation and joint destruction. Recent research has elucidated the intricate interplay between gut microbiota and RA pathogenesis, underscoring the role of microbiota-derived metabolites as pivotal contributors to disease development and progression. The human gut microbiota, comprising a vast array of microorganisms and their metabolic byproducts, plays a crucial role in maintaining immune homeostasis. Dysbiosis of this microbial community has been linked to numerous autoimmune disorders, including RA. Microbiota-derived metabolites, such as short-chain fatty acids (SCFAs), tryptophan derivatives, Trimethylamine-N-oxide (TMAO), bile acids, peptidoglycan, and lipopolysaccharide (LPS), exhibit immunomodulatory properties that can either exacerbate or ameliorate inflammation in RA. Mechanistically, these metabolites influence immune cell differentiation, cytokine production, and gut barrier integrity, collectively shaping the autoimmune milieu. This review highlights recent advances in understanding the intricate crosstalk between microbiota metabolites and RA pathogenesis and also discusses the potential of specific metabolites to trigger or suppress autoimmunity, shedding light on their molecular interactions with immune cells and signaling pathways. Additionally, this review explores the translational aspects of microbiota metabolites as diagnostic and prognostic tools in RA. Furthermore, the challenges and prospects of translating these findings into clinical practice are critically examined.

Colchicine disrupts bile acid metabolic homeostasis by affecting the enterohepatic circulation in mice

Although the medicinal properties of colchicine (COL) have been widely known for centuries, its toxicity has been the subject of controversy. The narrow therapeutic window causes COL to induce gastrointestinal adverse effects even when taken at recommended doses, mainly manifested as nausea, vomiting, and diarrhea. However, the mechanism of COL-induced gastrointestinal toxic reactions remains obscure. In the present study, the mice were dosed with COL (2.5 mg/kg b.w./day) for a week to explore the effect of COL on bile acid metabolism and the mechanism of COL-induced diarrhea. The results showed that COL treatment affected liver biochemistry in mice, resulting in a significant down-regulation of the mRNA expression levels of bile acid biosynthesis regulators Cyp7a1, Cyp8b1, Cyp7b1, and Cyp27a1 in liver tissues. The mRNA expression levels of bile acid transporters Ntcp, Oatp1, Mrp2, Ibabp, Mrp3, Osta, and Ostb in liver and ileum tissues were also significantly down-regulated. In addition, COL treatment significantly inhibited the mRNA expression levels of Fxr and its downstream target genes Shp, Lrh1, and Fgf15 in liver and ileum tissues, affecting the feedback regulation of bile acid biosynthesis. More importantly, the inhibition of COL on bile acid transporters in ileal and hepatic tissues affected bile acid recycling in the ileum as well as their reuptake in the liver, leading to a significantly increased accumulation of bile acids in the colon, which may be an important cause of diarrhea. In conclusion, our study revealed that COL treatment affected bile acid biosynthesis and enterohepatic circulation, thereby disrupting bile acid metabolic homeostasis in mice.

Recombinant Bile Salt Hydrolase Enhances the Inhibition Efficiency of Taurodeoxycholic Acid against Clostridium perfringens Virulence

Clostridium perfringens is the main pathogen of chicken necrotic enteritis (NE) causing huge economic losses in the poultry industry. Although dietary secondary bile acid deoxycholic acid (DCA) reduced chicken NE, the accumulation of conjugated tauro-DCA (TDCA) raised concerns regarding DCA efficacy. In this study, we aimed to deconjugate TDCA by bile salt hydrolase (BSH) to increase DCA efficacy against the NE pathogen C. perfringens. Assays were conducted to evaluate the inhibition of C. perfringens growth, hydrogen sulfide (H2S) production, and virulence gene expression by TDCA and DCA. BSH activity and sequence alignment were conducted to select the bsh gene for cloning. The bsh gene from Bifidobacterium longum was PCR-amplified and cloned into plasmids pET-28a (pET-BSH) and pDR111 (pDR-BSH) for expressing the BSH protein in E. coli BL21 and Bacillus subtilis 168 (B-sub-BSH), respectively. His-tag-purified BSH from BL21 cells was evaluated by SDS-PAGE, Coomassie blue staining, and a Western blot (WB) assays. Secretory BSH from B. subtilis was analyzed by a Dot-Blot. B-sub-BSH was evaluated for the inhibition of C. perfringens growth. C. perfringens growth reached 7.8 log10 CFU/mL after 24 h culture. C. perfringens growth was at 8 vs. 7.4, 7.8 vs. 2.6 and 6 vs. 0 log10 CFU/mL in 0.2, 0.5, and 1 mM TDCA vs. DCA, respectively. Compared to TDCA, DCA reduced C. perfringens H2S production and the virulence gene expression of asrA1, netB, colA, and virT. BSH activity was observed in Lactobacillus johnsonii and B. longum under anaerobe but not L. johnsonii under 10% CO2 air. After the sequence alignment of bsh from ten bacteria, bsh from B. longum was selected, cloned into pET-BSH, and sequenced at 951 bp. After pET-BSH was transformed in BL21, BSH expression was assessed around 35 kDa using Coomassie staining and verified for His-tag using WB. After the subcloned bsh and amylase signal peptide sequence was inserted into pDR-BSH, B. subtilis was transformed and named B-sub-BSH. The transformation was evaluated using PCR with B. subtilis around 3 kb and B-sub-BSH around 5 kb. Secretory BSH expressed from B-sub-BSH was determined for His-tag using Dot-Blot. Importantly, C. perfringens growth was reduced greater than 59% log10 CFU/mL in the B-sub-BSH media precultured with 1 vs. 0 mM TDCA. In conclusion, TDCA was less potent than DCA against C. perfringens virulence, and recombinant secretory BSH from B-sub-BSH reduced C. perfringens growth, suggesting a new potential intervention against the pathogen-induced chicken NE.

Lycium barbarum polysaccharide remodels colon inflammatory microenvironment and improves gut health

Aim

Disturbed intestinal microbiota has been implicated in the inflammatory microenvironment of the colon, which usually results in ulcerative colitis (UC). Given the limitations of these drugs, it is important to explore alternative means of protecting the gut health from UC. This study aimed to investigate the potential of polysaccharides as beneficial nutrients in the regulation of the gut microbiota, which determines the inflammatory microenvironment of the colon.

Materials and methods

Mice were treated with dextran sulfate sodium (DSS) to evaluate the effects and mechanisms of Lycium barbarum polysaccharide (LBP) in remodeling the inflammatory microenvironment and improving gut health. Body weight and disease activity indices were monitored daily. Hematoxylin and eosin staining was used to analyze colon dynamics. The levels of inflammatory indicators and expression of MUC-2, claudin-1, ZO-1, and G-protein-coupled receptor 5 (TGR5) were determined using assay kits and immunohistochemistry, respectively. 16S rRNA high-throughput sequencing of the intestinal microbiota and liquid chromatography-tandem mass spectrometry for related bile acids were used.

Results

LBP significantly improved the colonic tissue structure by upregulating MUC-2, claudin-1, and ZO-1 protein expression. The bacterial genus Dubosiella was dominant in healthy mice, but significantly decreased in mice treated with DSS. LBP rehabilitated Dubosiella in the sick guts of DSS mice to a level close to that of healthy mice. The levels of other beneficial bacterial genera Akkermansia and Bifidobacterium were also increased, whereas those of the harmful bacterial genera Turicibacter, Clostridium_sensu_stricto_1, Escherichia-Shigella, and Faecalibaculum decreased. The activity of beneficial bacteria promoted the bile acids lithocholic and deoxycholic acids in mice with UC, which improved the gut barrier function through the upregulation of TGR5.

Conclusion

The inflammatory microenvironment in the gut is determined by the balance of the gut microbiota. LBP showed great potential as a beneficial nutrient for rehabilitating Dubosiella which is dominant in the gut of healthy mice. Nutrient-related LBP may play an important role in gut health management.

Comparative profiling of serum, urine, and feces bile acids in humans, rats, and mice

Bile acids (BAs) play important pathophysiological roles in both humans and mammalian animals. Laboratory rats and mice are widely used animal models for assessing pharmacological effects and their underlying molecular mechanisms. However, substantial physiological differences exist in BA composition between humans and murine rodents. Here, we comprehensively compare BA profiles, including primary and secondary BAs, along with their amino acid conjugates, and sulfated metabolites in serum, urine, and feces between humans and two murine rodents. We further analyze the capabilities in gut microbial transform BAs among three species and compare sex-dependent variations within each species. As a result, BAs undergo amidation predominately with glycine in humans and taurine in mice but are primarily unamidated in rats. BA sulfation is a unique characteristic in humans, whereas rats and mice primarily perform multiple hydroxylations during BA synthesis and metabolism. For gut microbial transformed BA capabilities, humans are comparable to those of rats, stronger than those of mice in deconjugation and 7α-dehydroxylation, while humans are weak than those of rats or mice in oxidation and epimerization. Such differences enhance our understanding of the divergent experimental outcomes observed in humans and murine rodents, necessitating caution when translating findings from these rodent species to humans.

Fecal microbiota transplantation in the treatment of hepatic encephalopathy: A perspective

Due to its complex pathogenesis, treatment of hepatic encephalopathy (HE) continues to be a therapeutic challenge. Of late, gut microbiome has garnered much attention for its role in the pathogenesis of various gastrointestinal and liver diseases and its potential therapeutic use. New evidence suggests that gut microbiota plays a significant role in cerebral homeostasis. Alteration in the gut microbiota has been documented in patients with HE in a number of clinical and experimental studies. Research on gut dysbiosis in patients with HE has opened newer therapeutic avenues in the form of probiotics, prebiotics and the latest fecal microbiota transplantation (FMT). Recent studies have shown that FMT is safe and could be effective in improving outcomes in advanced liver disease patients presenting with HE. However, questions over the appropriate dose, duration and route of administration for best treatment outcome remains unsettled.

Gut Epithelial Barrier Function is Impacted by Hyperglycemia and Secondary Bile Acids in Vitro: Possible Rescuing Effects of Specific Pectins

Gut epithelial barrier disruption is commonly observed in Western diseases like diabetes and inflammatory bowel disease (IBD). Enhanced epithelial permeability triggers inflammatory responses and gut microbiota dysbiosis. Reduced bacterial diversity in IBD affects gut microbiota metabolism, altering microbial products such as secondary bile acids (BAs), which potentially play a role in gut barrier regulation and immunity. Dietary fibers such as pectin may substitute effects of these BAs. The study examines transepithelial electrical resistance of gut epithelial T84 cells and the gene expression of tight junctions after exposure to (un)sulfated secondary BAs. This is compared to the impact of the dietary fiber pectin with different degrees of methylation (DM) and blockiness (DB), with disruption induced by calcium ionophore A23187 under both normal and hyperglycemic conditions. Unsulfated lithocholic acid (LCA) and deoxycholic acid (DCA) show a stronger rescuing effect, particularly evident under 20 mM glucose levels. DM19 with high DB (HB) and DM43HB pectin exhibit rescuing effects under both glucose conditions. Notably, DM19HB and DM43HB display higher rescue effects under 20 mM glucose compared to 5 mM glucose. The study demonstrates that specific pectins such as DM19HB and DM43HB may serve as alternatives for preventing barrier disruption in the case of disturbed DCA metabolism.

The bacterial metabolite, lithocholic acid, has antineoplastic effects in pancreatic adenocarcinoma

Lithocholic acid (LCA) is a secondary bile acid. LCA enters the circulation after bacterial synthesis in the gastrointestinal tract, reaches distantly located cancer cells, and influences their behavior. LCA was considered carcinogenic, but recent studies demonstrated that LCA has antitumor effects. We assessed the possible role of LCA in pancreatic adenocarcinoma. At the serum reference concentration, LCA induced a multi-pronged antineoplastic program in pancreatic adenocarcinoma cells. LCA inhibited cancer cell proliferation and induced mesenchymal-to-epithelial (MET) transition that reduced cell invasion capacity. LCA induced oxidative/nitrosative stress by decreasing the expression of nuclear factor, erythroid 2-like 2 (NRF2) and inducing inducible nitric oxide synthase (iNOS). The oxidative/nitrosative stress increased protein nitration and lipid peroxidation. Suppression of oxidative stress by glutathione (GSH) or pegylated catalase (pegCAT) blunted LCA-induced MET. Antioxidant genes were overexpressed in pancreatic adenocarcinoma and decreased antioxidant levels correlated with better survival of pancreatic adenocarcinoma patients. Furthermore, LCA treatment decreased the proportions of cancer stem cells. Finally, LCA induced total and ATP-linked mitochondrial oxidation and fatty acid oxidation. LCA exerted effects through the farnesoid X receptor (FXR), vitamin D receptor (VDR), and constitutive androstane receptor (CAR). LCA did not interfere with cytostatic agents used in the chemotherapy of pancreatic adenocarcinoma. Taken together, LCA is a non-toxic compound and has antineoplastic effects in pancreatic adenocarcinoma.

Production of deoxycholic acid by low-abundant microbial species is associated with impaired glucose metabolism

Alterations in gut microbiota composition are suggested to contribute to cardiometabolic diseases, in part by producing bioactive molecules. Some of the metabolites are produced by very low abundant bacterial taxa, which largely have been neglected due to limits of detection. However, the concentration of microbially produced metabolites from these taxa can still reach high levels and have substantial impact on host physiology. To explore this concept, we focused on the generation of secondary bile acids by 7α-dehydroxylating bacteria and demonstrated that addition of a very low abundant bacteria to a community can change the metabolic output dramatically. We show that Clostridium scindens converts cholic acid into the secondary bile acid deoxycholic acid (DCA) very efficiently even though the abundance of C. scindens is low, but still detectable by digital droplet PCR. We also show that colonization of germ-free female mice with a community containing C. scindens induces DCA production and affects host metabolism. Finally, we show that DCA correlates with impaired glucose metabolism and a worsened lipid profile in individuals with type 2 diabetes, which implies that this metabolic pathway may contribute to the development of cardiometabolic disease.

Bile Salt Hydrolase Activity-Based Probes for Monitoring Gut Microbial Bile Acid Metabolism

Bile acids are bioactive metabolites that are biotransformed into secondary bile acids by the gut microbiota, a vast consortium of microbes that inhabit the intestines. The first step in intestinal secondary bile acid metabolism is carried out by a critical enzyme, bile salt hydrolase (BSH), that catalyzes the gateway reaction that precedes all subsequent microbial metabolism of these important metabolites. As gut microbial metabolic activity is difficult to probe due to the complex nature of the gut microbiome, approaches are needed to profile gut microbiota-associated enzymes such as BSH. Here, we develop a panel of BSH activity-based probes (ABPs) to determine how changes in diurnal rhythmicity of gut microbiota-associated metabolism affects BSH activity and substrate preference. This panel of covalent probes enables determination of BSH activity and substrate specificity from multiple gut anerobic bacteria derived from the human and mouse gut microbiome. We found that both gut microbiota-associated BSH activity and substrate preference is rhythmic, likely due to feeding patterns of the mice. These results indicate that this ABP-based approach can be used to profile changes in BSH activity in physiological and disease states that are regulated by circadian rhythms.

Surgery for Crohn's Disease Is Associated With a Dysbiotic Microbiome and Metabolome: Results From Two Prospective Cohorts

BACKGROUND & AIMS

Crohn's disease is associated with alterations in the gut microbiome and metabolome described as dysbiosis. We characterized the microbial and metabolic consequences of ileal resection, the most common Crohn's disease surgery.

METHODS

Patients with and without intestinal resection were identified from the Diet to Induce Remission in Crohn's Disease and Study of a Prospective Adult Research Cohort with Inflammatory Bowel Disease studies. Stool samples were analyzed with shotgun metagenomics sequencing. Fecal butyrate was measured with 1H nuclear magnetic resonance spectroscopy. Fecal bile acids and plasma 7α-hydroxy-4-cholesten-3-one (C4) was measured with mass spectrometry.

RESULTS

Intestinal resection was associated with reduced alpha diversity and altered beta diversity with increased Proteobacteria and reduced Bacteroidetes and Firmicutes. Surgery was associated with higher representation of genes in the KEGG pathway for ABC transporters and reduction in genes related to bacterial metabolism. Surgery was associated with reduced concentration of the But gene but this did not translate to reduced fecal butyrate concentration. Surgery was associated with decreased abundance of bai operon genes, with increased plasma C4 concentration, increased primary bile acids and reduced secondary bile acids, including isoLCA. Additionally, Egerthella lenta, Adlercreutzia equalofaciens, and Gordonibacter pamelaeae were lower in abundance among patients with prior surgery in both cohorts.

CONCLUSIONS

In 2 different populations, prior surgery in Crohn's disease is associated with altered fecal microbiome. Patients who had undergone ileal resection had reduction in the potentially beneficial bacteria E lenta and related actinobacteria and secondary bile acids, including isoLCA, suggesting that these could be biomarkers of patients at higher risk for disease progression.

Mitochondrial function and gastrointestinal diseases

Mitochondria are dynamic organelles that function in cellular energy metabolism, intracellular and extracellular signalling, cellular fate and stress responses. Mitochondria of the intestinal epithelium, the cellular interface between self and enteric microbiota, have emerged as crucial in intestinal health. Mitochondrial dysfunction occurs in gastrointestinal diseases, including inflammatory bowel diseases and colorectal cancer. In this Review, we provide an overview of the current understanding of intestinal epithelial cell mitochondrial metabolism, function and signalling to affect tissue homeostasis, including gut microbiota composition. We also discuss mitochondrial-targeted therapeutics for inflammatory bowel diseases and colorectal cancer and the evolving concept of mitochondrial impairment as a consequence versus initiator of the disease.

Shifts in the functional capacity and metabolite composition of the gut microbiome during recovery from enteric infection

While enteric pathogens have been widely studied for their roles in causing foodborne infection, their impacts on the gut microbial community have yet to be fully characterized. Previous work has identified notable changes in the gut microbiome related to pathogen invasion, both taxonomically and genetically. Characterization of the metabolic landscape during and after enteric infection, however, has not been explored. Consequently, we investigated the metabolome of paired stools recovered from 60 patients (cases) during and after recovery from enteric bacterial infections (follow-ups). Shotgun metagenomics was applied to predict functional microbial pathways combined with untargeted metametabolomics classified by Liquid Chromatography Mass Spectrometry. Notably, cases had a greater overall metabolic capacity with significantly higher pathway richness and evenness relative to the follow-ups (p<0.05). Metabolic pathways related to central carbon metabolism, amino acid metabolism, and lipid and fatty acid biosynthesis were more highly represented in cases and distinct signatures for menaquinone production were detected. By contrast, the follow-up samples had a more diverse metabolic landscape with enhanced richness of polar metabolites (p<0.0001) and significantly greater richness, evenness, and overall diversity of nonpolar metabolites (p<0.0001). Although many metabolites could not be annotated with existing databases, a marked increase in certain clusters of metabolites was observed in the follow-up samples when compared to the case samples and vice versa. These findings suggest the importance of key metabolites in gut health and recovery and enhance understanding of metabolic fluctuations during enteric infections.

Antibiotic-Induced Gut Microbiota Dysbiosis Modulates Host Transcriptome and m6A Epitranscriptome via Bile Acid Metabolism

Gut microbiota can influence host gene expression and physiology through metabolites. Besides, the presence or absence of gut microbiome can reprogram host transcriptome and epitranscriptome as represented by N6-methyladenosine (m6A), the most abundant mammalian mRNA modification. However, which and how gut microbiota-derived metabolites reprogram host transcriptome and m6A epitranscriptome remain poorly understood. Here, investigation is conducted into how gut microbiota-derived metabolites impact host transcriptome and m6A epitranscriptome using multiple mouse models and multi-omics approaches. Various antibiotics-induced dysbiotic mice are established, followed by fecal microbiota transplantation (FMT) into germ-free mice, and the results show that bile acid metabolism is significantly altered along with the abundance change in bile acid-producing microbiota. Unbalanced gut microbiota and bile acids drastically change the host transcriptome and the m6A epitranscriptome in multiple tissues. Mechanistically, the expression of m6A writer proteins is regulated in animals treated with antibiotics and in cultured cells treated with bile acids, indicating a direct link between bile acid metabolism and m6A biology. Collectively, these results demonstrate that antibiotic-induced gut dysbiosis regulates the landscape of host transcriptome and m6A epitranscriptome via bile acid metabolism pathway. This work provides novel insights into the interplay between microbial metabolites and host gene expression.

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

BACKGROUND AND AIMS

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

APPROACH AND RESULTS

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

CONCLUSIONS

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

Proanthocyanidin B2 derived metabolites may be ligands for bile acid receptors S1PR2, PXR and CAR: an in silico approach

Bile acids (BAs) act as signaling molecules via their interactions with various nuclear (FXR, VDR, PXR and CAR) and G-protein coupled (TGR5, M3R, S1PR2) BA receptors. Stimulation of these BA receptors influences several processes, including inflammatory responses and glucose and xenobiotic metabolism. BA profiles and BA receptor activity are deregulated in cardiometabolic diseases; however, dietary polyphenols were shown to alter BA profile and signaling in association with improved metabolic phenotypes. We previously reported that supplementing mice with a proanthocyanidin (PAC)-rich grape polyphenol (GP) extract attenuated symptoms of glucose intolerance in association with changes to BA profiles, BA receptor gene expression, and/or downstream markers of BA receptor activity. Exact mechanisms by which polyphenols modulate BA signaling are not known, but some hypotheses include modulation of the BA profile via changes to gut bacteria, or alteration of ligand-availability via BA sequestration. Herein, we used an in silico approach to investigate putative binding affinities of proanthocyanidin B2 (PACB2) and PACB2 metabolites to nuclear and G-protein coupled BA receptors. Molecular docking and dynamics simulations revealed that certain PACB2 metabolites had stable binding affinities to S1PR2, PXR and CAR, comparable to that of known natural and synthetic BA ligands. These findings suggest PACB2 metabolites may be novel ligands of S1PR2, CAR, and PXR receptors.Communicated by Ramaswamy H. Sarma.

Changes in bile acid subtypes and improvements in lipid metabolism and atherosclerotic cardiovascular disease risk: the Preventing Overweight Using Novel Dietary Strategies (POUNDS Lost) trial

BACKGROUND

Distinct circulating bile acid (BA) subtypes may play roles in regulating lipid homeostasis and atherosclerosis.

OBJECTIVES

We investigated whether changes in circulating BA subtypes induced by weight-loss dietary interventions were associated with improved lipid profiles and atherosclerotic cardiovascular disease (ASCVD) risk estimates.

METHODS

This study included adults with overweight or obesity (n = 536) who participated in a randomized weight-loss dietary intervention trial. Circulating primary and secondary unconjugated BAs and their taurine-/glycine-conjugates were measured at baseline and 6 mo after the weight-loss diet intervention. The ASCVD risk estimates were calculated using the validated equations.

RESULTS

At baseline, higher concentrations of specific BA subtypes were related to higher concentrations of atherogenic very low-density lipoprotein lipid subtypes and ASCVD risk estimates. Weight-loss diet-induced decreases in primary BAs were related to larger reductions in triglycerides and total cholesterol [every 1 standard deviation (SD) decrease of glycocholate, glycochenodeoxycholate, or taurochenodeoxycholate was related to β (standard error) -3.3 (1.3), -3.4 (1.3), or -3.8 (1.3) mg/dL, respectively; PFDR < 0.05 for all]. Greater decreases in specific secondary BA subtypes were also associated with improved lipid metabolism at 6 mo; there was β -4.0 (1.1) mg/dL per 1-SD decrease of glycoursodeoxycholate (PFDR =0.003) for changes in low-density lipoprotein cholesterol. We found significant interactions (P-interaction < 0.05) between dietary fat intake and changes in BA subtypes on changes in ASCVD risk estimates; decreases in primary and secondary BAs (such as conjugated cholate or deoxycholate) were significantly associated with improved ASCVD risk after consuming a high-fat diet, but not after consuming a low-fat diet.

CONCLUSIONS

Decreases in distinct BA subtypes were associated with improved lipid profiles and ASCVD risk estimates, highlighting the importance of changes in circulating BA subtypes as significant factors linked to improved lipid metabolism and ASCVD risk estimates in response to weight-loss dietary interventions. Habitual dietary fat intake may modify the associations of changes in BAs with ASCVD risk. This trial was registered at clinicaltrials.gov as NCT00072995.

Bile acid and nonalcoholic steatohepatitis: Molecular insights and therapeutic targets

BACKGROUND

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

AIMS

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

KEY SCIENTIFIC CONCEPTS OF REVIEW

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

Role of the microbiota-gut-heart axis between bile acids and cardiovascular disease

Bile acid (BA) receptors (e.g., farnesoid X-activated receptor, muscarinic receptor) are expressed in cardiomyocytes, endothelial cells, and vascular smooth muscle cells, indicating the relevance of BAs to cardiovascular disease (CVD). Hydrophobic BAs are cardiotoxic, while hydrophilic BAs are cardioprotective. For example, fetal cardiac insufficiency in maternal intrahepatic cholestasis during pregnancy, and the degree of fetal cardiac abnormality, is closely related to the level of hydrophobic BAs in maternal blood and infant blood. However, ursodeoxycholic acid (the most hydrophilic BA) can reverse/prevent these detrimental effects of increased levels of hydrophobic BAs on the heart. The gut microbiota (GM) and GM metabolites (especially secondary BAs) have crucial roles in hypertension, atherosclerosis, unstable angina, and heart failure. Herein, we describe the relationship between CVD and the GM at the BA level. We combine the concept of the "microbiota-gut-heart axis" (MGHA) and postulate the role and mechanism of BAs in CVD development. In addition, the strategies for treating CVD with BAs under the MGHA are proposed.

Bile acid metabolism and signaling in health and disease: molecular mechanisms and therapeutic targets

Bile acids, once considered mere dietary surfactants, now emerge as critical modulators of macronutrient (lipid, carbohydrate, protein) metabolism and the systemic pro-inflammatory/anti-inflammatory balance. Bile acid metabolism and signaling pathways play a crucial role in protecting against, or if aberrant, inducing cardiometabolic, inflammatory, and neoplastic conditions, strongly influencing health and disease. No curative treatment exists for any bile acid influenced disease, while the most promising and well-developed bile acid therapeutic was recently rejected by the FDA. Here, we provide a bottom-up approach on bile acids, mechanistically explaining their biochemistry, physiology, and pharmacology at canonical and non-canonical receptors. Using this mechanistic model of bile acids, we explain how abnormal bile acid physiology drives disease pathogenesis, emphasizing how ceramide synthesis may serve as a unifying pathogenic feature for cardiometabolic diseases. We provide an in-depth summary on pre-existing bile acid receptor modulators, explain their shortcomings, and propose solutions for how they may be remedied. Lastly, we rationalize novel targets for further translational drug discovery and provide future perspectives. Rather than dismissing bile acid therapeutics due to recent setbacks, we believe that there is immense clinical potential and a high likelihood for the future success of bile acid therapeutics.

Untargeted metabolomics based on ultra-high performance liquid chromatography-mass spectrometry/MS reveals the lipid-lowering mechanism of taurine in hyperlipidemia mice

Introduction

Taurine has a prominent lipid-lowering effect on hyperlipidemia. However, a comprehensive analysis of the effects of taurine on endogenous metabolites in hyperlipidemia has not been documented. This study aimed to explore the impact of taurine on multiple metabolites associated with hyperlipidemia.

Methods

The hyperlipidemic mouse model was induced by high-fat diet (HFD). Taurine was administered via oral gavage at doses of 700  mg/kg/day for 14  weeks. Evaluation of body weight, serum lipid levels, and histopathology of the liver and adipose tissue was performed to confirm the lipid-lowering effect of taurine. Ultra-high performance liquid chromatography-mass spectrometry (UPLC-MS)-based metabonomics analyses of serum, urine, feces, and liver, coupled with multivariate data analysis, were conducted to assess changes in the endogenous metabolites.

Results and discussion

Biochemical and histological examinations demonstrated that taurine administration prevented weight gain and dyslipidemia, and alleviated lipid deposition in the liver and adipose tissue in hyperlipidemic mice. A total of 76 differential metabolites were identified by UPLC-MS-based metabolomics approach, mainly involving BAs, GPs, SMs, DGs, TGs, PUFAs and amino acids. Taurine was found to partially prevent HFDinduced abnormalities in the aforementioned metabolites. Using KEGG database and MetaboAnalyst software, it was determined that taurine effectively alleviates metabolic abnormalities caused by HFD, including fatty acid metabolism, sphingolipid metabolism, glycerophospholipid metabolism, diacylglycerol metabolism, amino acid metabolism, bile acid and taurine metabolism, taurine and hypotaurine metabolism. Moreover, DGs, GPs and SMs, and taurine itself may serve as active metabolites in facilitating various anti-hyperlipidemia signal pathways associated with taurine. This study provides new evidence for taurine to prevent hyperlipidemia.

Probiotic Mixture Ameliorates a Diet-Induced MASLD/MASH Murine Model through the Regulation of Hepatic Lipid Metabolism and the Gut Microbiome

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a prevalent metabolic disease that has no effective treatment. Our proprietary probiotic mixture, Prohep, has been proven in a previous study to be helpful in reducing hepatocellular carcinoma (HCC) in vivo. However, its prospective benefits on the treatment of other liver diseases such as MASLD, which is one of the major risk factors in the development of HCC, are unclear. To investigate the potential of Prohep in modulating the development and progression of MASLD, we first explored the effect of Prohep supplementation via voluntary intake in a high-fat diet (HFD)-induced MASLD/metabolic dysfunction-associated steatohepatitis (MASH) murine model. Our results indicated that Prohep alleviated HFD-induced liver steatosis and reduced excessive hepatic lipid accumulation and improved the plasma lipid profile when compared with HFD-fed control mice through suppressing hepatic de novo lipogenesis and cholesterol biosynthesis gene expressions. In addition, Prohep was able to modulate the gut microbiome, modify the bile acid (BA) profile, and elevate fecal short-chain fatty acid (SCFA) levels. Next, in a prolonged HFD-feeding MASLD/MASH model, we observed the effectiveness of Prohep in preventing the transition from MASLD to MASH via amelioration in hepatic steatosis, inflammation, and fibrosis. Taken together, Prohep could ameliorate HFD-induced MASLD and control the MASLD-to-MASH progression in mice. Our findings provide distinctive insights into the development of novel microbial therapy for the management of MASLD and MASH.

Bile acids modified by the intestinal microbiota promote colorectal cancer growth by suppressing CD8+ T cell effector functions

Concentrations of the secondary bile acid, deoxycholic acid (DCA), are aberrantly elevated in colorectal cancer (CRC) patients, but the consequences remain poorly understood. Here, we screened a library of gut microbiota-derived metabolites and identified DCA as a negative regulator for CD8+ T cell effector function. Mechanistically, DCA suppressed CD8+ T cell responses by targeting plasma membrane Ca2+ ATPase (PMCA) to inhibit Ca2+-nuclear factor of activated T cells (NFAT)2 signaling. In CRC patients, CD8+ T cell effector function negatively correlated with both DCA concentration and expression of a bacterial DCA biosynthetic gene. Bacteria harboring DCA biosynthetic genes suppressed CD8+ T cells effector function and promoted tumor growth in mice. This effect was abolished by disrupting bile acid metabolism via bile acid chelation, genetic ablation of bacterial DCA biosynthetic pathway, or specific bacteriophage. Our study demonstrated causation between microbial DCA metabolism and anti-tumor CD8+ T cell response in CRC, suggesting potential directions for anti-tumor therapy.

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

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

Susceptibility to febrile malaria is associated with an inflammatory gut microbiome

Malaria is a major public health problem, but many of the factors underlying the pathogenesis of this disease are not well understood. Here, we demonstrate in Malian children that susceptibility to febrile malaria following infection with Plasmodium falciparum is associated with the composition of the gut microbiome prior to the malaria season. Gnotobiotic mice colonized with the fecal samples of malaria-susceptible children had a significantly higher parasite burden following Plasmodium infection compared to gnotobiotic mice colonized with the fecal samples of malaria-resistant children. The fecal microbiome of the susceptible children was enriched for bacteria associated with inflammation, mucin degradation, gut permeability and inflammatory bowel disorders (e.g., Ruminococcus gauvreauii, Ruminococcus torques, Dorea formicigenerans, Dorea longicatena, Lachnoclostridium phocaeense and Lachnoclostridium sp. YL32). However, the susceptible children also had a greater abundance of bacteria known to produce anti-inflammatory short-chain fatty acids and those associated with favorable prognosis and remission following dysbiotic intestinal events (e.g., Anaerobutyricum hallii, Blautia producta and Sellimonas intestinalis). Metabolomics analysis of the human fecal samples corroborated the existence of inflammatory and recovery-associated features within the gut microbiome of the susceptible children. There was an enrichment of nitric oxide-derived DNA adducts (deoxyinosine and deoxyuridine) and long-chain fatty acids, the absorption of which has been shown to be inhibited by inflamed intestinal epithelial cells, and a decrease in the abundance of mucus phospholipids. Nevertheless, there were also increased levels of pseudouridine and hypoxanthine, which have been shown to be regulated in response to cellular stress and to promote recovery following injury or hypoxia. Overall, these results indicate that the gut microbiome may contribute malaria pathogenesis and suggest that therapies targeting intestinal inflammation could decrease malaria susceptibility.

Gut instincts: Unveiling the connection between gut microbiota and Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative disorder marked by neuroinflammation and gradual cognitive decline. Recent research has revealed that the gut microbiota (GM) plays an important role in the pathogenesis of AD through the microbiota-gut-brain axis. However, the mechanism by which GM and microbial metabolites alter brain function is not clearly understood. GM dysbiosis increases the permeability of the intestine, alters the blood-brain barrier permeability, and elevates proinflammatory mediators causing neurodegeneration. This review article introduced us to the composition and functions of GM along with its repercussions of dysbiosis in relation to AD. We also discussed the importance of the gut-brain axis and its role in communication. Later we focused on the mechanism behind gut dysbiosis and the progression of AD including neuroinflammation, oxidative stress, and changes in neurotransmitter levels. Furthermore, we highlighted recent developments in AD management, such as microbiota-based therapy, dietary interventions like prebiotics, probiotics, and fecal microbiota transplantation. Finally, we concluded with challenges and future directions in AD research based on GM.

Probiotics Influence Gut Microbiota and Tumor Immune Microenvironment to Enhance Anti-Tumor Efficacy of Doxorubicin

Probiotics have been reported to influence the gut microbiota and immune system in various diseases. Now, the potential impacts of probiotics on tumor treatment still need to be investigated. In this study, three strains of probiotics, Bifidobacterium breve BBr60 (BBr60), Pediococcus pentosaceus PP06 (PP06), and Bifidobacterium longum subsp. longum BL21 (BL21) were investigated for their combination with chemotherapeutic drugs doxorubicin (DOX). Our study showed that PP06 and BL21 have good performance in gastric acid, bile salt, and intestinal fluid tolerance, antimicrobial activity to pathogenic Staphylococcus aureus, and adhesion to Caco-2 cells. Besides, the probiotics all exhibited antioxidant effect, especially BL21. In vitro cytotoxicity and in vivo animal studies revealed that probiotics used alone could not directly induce anti-tumor effects, but the combination of PP06/BL21 and DOX exhibits a higher inhibition rate than DOX alone, via recruitment and infiltration of immune cells in the tumor region. After 16S rRNA analysis of fecal samples from animal models, it was found that BL21 could increase the abundance of Akkermansia, which may also play a role in regulating the tumor microenvironment to improve immune response. In conclusion, BL21 and PP06 in this study could enhance the anti-tumor efficacy by influencing the gut microbiota and tumor immune microenvironment.

The microbiome: an integral player in immune homeostasis and inflammation in the respiratory tract

The last decade of microbiome research has highlighted its fundamental role in systemic immune and metabolic homeostasis. The microbiome plays a prominent role during gestation and into early life, when maternal lifestyle factors shape immune development of the newborn. Breast milk further shapes gut colonization, supporting the development of tolerance to commensal bacteria and harmless antigens while preventing outgrowth of pathogens. Environmental microbial and lifestyle factors that disrupt this process can dysregulate immune homeostasis, predisposing infants to atopic disease and childhood asthma. In health, the low-biomass lung microbiome, together with inhaled environmental microbial constituents, establishes the immunological set point that is necessary to maintain pulmonary immune defense. However, in disease perturbations to immunological and physiological processes allow the upper respiratory tract to act as a reservoir of pathogenic bacteria, which can colonize the diseased lung and cause severe inflammation. Studying these host-microbe interactions in respiratory diseases holds great promise to stratify patients for suitable treatment regimens and biomarker discovery to predict disease progression. Preclinical studies show that commensal gut microbes are in a constant flux of cell division and death, releasing microbial constituents, metabolic by-products, and vesicles that shape the immune system and can protect against respiratory diseases. The next major advances may come from testing and utilizing these microbial factors for clinical benefit and exploiting the predictive power of the microbiome by employing multiomics analysis approaches.

A Probiotic Targets Bile Acids Metabolism to Alleviate Ulcerative Colitis by Reducing Conjugated Bile Acids

SCOPE

Gut microbiota (GM) dysbiosis and dysregulated bile acids (BAs) metabolism have been linked to ulcerative colitis (UC) pathogenesis. The possibility of utilizing live probiotics with a defined BAs-metabolizing capability to modify the composition BAs for UC treatment remains unexplored.

METHODS AND RESULTS

In this study, Strain GR-4 is sourced from traditional Chinese fermented food, "Jiangshui," and demonstrated the ability to deconjugate two common conjugated BAs by over 69% and 98.47%, respectively. It administers strain GR-4 to dextran sulfate sodium (DSS)-induced UC mice, and observes an overall alleviation of UC symptoms, as evidence by improved colon morphology, reduces inflammation and oxidative stress, and restores intestinal barrier function. Importantly, these effects are reliant on an intact commensal microbiota, as depletion of GM mitigated GR-4s efficacy. Metabolomics analysis unveils a decline in conjugated BAs and an increase in secondary BAs following GR-4 administration. GM analysis indicates that GR-4 selectively enriches bacterial taxa linked to BAs metabolism, enhancing GM's capacity to modify BAs.

CONCLUSION

This research demonstrates the potential for natural fermented foods and probiotics to effectively manipulate BAs composition, including conjugated and secondary BAs, to alleviate UC symptoms, underscoring the benefits of these approaches for gut health.

Effects of pork sausage on intestinal microecology and metabolism in mice

BACKGROUND

Processed meat, as an important part of the human diet, has been recognized as a carcinogen by the International Agency for Research on Cancer (IARC). Although numerous epidemiological reports supported the IARC's view, the relevant evidence of a direct association between processed meat and carcinogenicity has been insufficient and the mechanism has been unclear. This study aims to investigate the effects of pork sausage (as a representative example of processed meat) intake on gut microbial communities and metabolites of mice. Microbial communities and metabolites from all groups were analyzed using 16S rRNA gene sequencing and Ultra performance liquid chromatography-quadrupole-time of flight-mass spectrometer (UPLC-Q-TOF/MS), respectively.

RESULTS

The levels of Bacteroidetes, Bacteroides, Alloprevotella, Lactobacillus, Prevotella_9, Lachnospiraceae_NK4A136_group, Alistipes, Blautia, Proteobacteria, Firmicutes, Allobaculum, Helicobacter, Desulfovibrio, Clostridium_sensu_stricto_1, Ruminococcaceae_UCG-014, Lachnospiraceae_UCG-006 and Streptococcus (P < 0.05) were obviously altered in the mice fed a pork sausage diet. Twenty-seven metabolites from intestinal content samples and fourteen matabolites from whole blood samples were identified as potential biomarkers from multivariate analysis, including Phosphatidic acid (PA), Sphingomyelin (SM), Lysophosphatidylcholine (LysoPC), Diglyceride (DG), D-maltose, N-acylamides and so forth. The significant changes in these biomarkers demonstrate metabonomic variations in pork sausage treated rats, especially carbohydrate metabolism, lipid metabolism, and amino acid metabolism.

CONCLUSION

The present study provided evidence that a processed meat diet can increase the risk of colorectal cancer and other diseases significantly by altering the microbial community structure and disrupting the body's metabolic pathways. © 2023 Society of Chemical Industry.

Chemoproteomic profiling of substrate specificity in gut microbiota-associated bile salt hydrolases

The gut microbiome possesses numerous biochemical enzymes that biosynthesize metabolites that impact human health. Bile acids comprise a diverse collection of metabolites that have important roles in metabolism and immunity. The gut microbiota-associated enzyme that is responsible for the gateway reaction in bile acid metabolism is bile salt hydrolase (BSH), which controls the host's overall bile acid pool. Despite the critical role of these enzymes, the ability to profile their activities and substrate preferences remains challenging due to the complexity of the gut microbiota, whose metaproteome includes an immense diversity of protein classes. Using a systems biochemistry approach employing activity-based probes, we have identified gut microbiota-associated BSHs that exhibit distinct substrate preferences, revealing that different microbes contribute to the diversity of the host bile acid pool. We envision that this chemoproteomic approach will reveal how secondary bile acid metabolism controlled by BSHs contributes to the etiology of various inflammatory diseases.