Cross-talk between bile acids and intestinal microbiota in host metabolism and health

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.

Microbiome and metabolome analyses reveal significant alterations of gut microbiota and bile acid metabolism in ETEC-challenged weaned piglets by dietary berberine supplementation

This study mainly investigated the effects of berberine (BBR) on the bile acid metabolism in gut-liver axis and the microbial community in large intestine of weaned piglets challenged with enterotoxigenic Escherichia coli (ETEC) by microbiome and metabolome analyses. Sixty-four piglets were randomly assigned to four groups including Control group, BBR group, ETEC group, and BBR + ETEC group. Dietary BBR supplementation upregulated the colonic mRNA expression of Occludin, Claudin-5, trefoil factor 3 (TFF3), and interleukin (IL)-10, and downregulated colonic IL-1β and IL-8 mRNA expression in piglets challenged with ETEC K88 (p < 0.05). The hepatic non-targeted metabolome results showed that dietary BBR supplementation enriched the metabolic pathways of primary bile acid biosynthesis, tricarboxylic acid cycle, and taurine metabolism. The hepatic targeted metabolome analyses showed that BBR treatment increased the hepatic concentrations of taurocholic acid (TCA) and taurochenodeoxycholic acid (TDCA), but decreased the hepatic cholic acid (CA) concentration (p < 0.05). Further intestinal targeted metabolome analyses indicated that the deoxycholic acid (DCA), hyocholic acid (HCA), 7-ketodeoxycholic acid (7-KDCA), and the unconjugated bile acid concentrations in ileal mucosa was decreased by dietary BBR treatment (p < 0.05). Additionally, BBR treatment significantly upregulated the hepatic holesterol 7 α-hydroxylase (CYP7A1) and sterol 27-hydroxylase (CYP27A1) mRNA expression, and upregulated the ileal mRNA expression of farnesoid X receptor (FXR) and apical sodium-dependent bile acid transporter (ASBT) as well as the colonic mRNA expression of FXR, fibroblast growth factor19 (FGF19), takeda G protein-coupled receptor 5 (TGR5) and organic solute transporters beta (OST-β) in piglets (p < 0.05). Moreover, the microbiome analysis showed that BBR significantly altered the composition and diversity of colonic and cecal microbiota community, with the abundances of Firmicutes (phylum), and Lactobacillus and Megasphaera (genus) significantly increased in the large intestine of piglets (p < 0.05). Spearman correlation analysis showed that the relative abundances of Megasphaera (genus) were positively correlated with Claudin-5, Occludin, TFF3, and hepatic TCDCA concentration, but negatively correlated with hepatic CA and glycocholic acid (GCA) concentration (p < 0.05). Moreover, the relative abundances of Firmicute (phylum) and Lactobacillus (genus) were positively correlated with hepatic TCDCA concentration (p < 0.05). Collectively, dietary BBR supplementation could regulate the gut microbiota and bile acid metabolism through modulation of gut-liver axis, and attenuate the decreased intestinal tight junction expression caused by ETEC, which might help maintain intestinal homeostasis in weaned piglets.

Altered bile acid and correlations with gut microbiome in transition dairy cows with different glucose and lipid metabolism status

The transition from pregnancy to lactation is critical in dairy cows. Among others, dairy cows experience a metabolic stress due to a large change in glucose and lipid metabolism. Recent studies revealed that bile acids (BA), besides being involved in both the emulsification and solubilization of fats during intestinal absorption, can also affect the metabolism of glucose and lipids, both directly or indirectly by affecting the gut microbiota. Thus, we used untargeted and targeted metabolomics and 16S rRNA sequencing approaches to investigate the concentration of plasma metabolites and BA, the composition of the rectum microbial community, and assess their interaction in transition dairy cows. In Experiment 1, we investigated BA and other blood parameters and gut microbiota in dairy cows without clinical diseases during the transition period, which can be seen as well adapted to the challenge of changed glucose and lipid metabolism. As expected, we detected an increased plasma concentration of β-hydroxybutyrate (BHBA) and nonesterified fatty acids (NEFA) but decreased concentration of glucose, cholesterol, and triglycerides (TG). Untargeted metabolomic analysis of the plasma revealed primary BA biosynthesis was one of the affected pathways, and was consistent with the increased concentration of BA in the plasma. A correlation approach revealed a complex association between BA and microbiota with the host plasma concentration of glucose and lipid metabolites. Among BA, chenodeoxycholic acid derivates such as glycolithocholic acid, taurolithocholic acid, lithocholic acid, taurochenodeoxycholic acid, and taurodeoxycholic acid were the main hub nodes connecting microbe and blood metabolites (such as glucose, TG, and NEFA). In Experiment 2, we investigated early postpartum dairy cows with or without hyperketonemia (HPK). As expected, HPK cows had increased concentration of NEFA and decreased concentrations of glucose and triglycerides. The untargeted metabolomic analysis of the plasma revealed that primary BA biosynthesis was also one of the affected pathways. Even though the BA concentration was similar among the 2 groups, the profiles of taurine conjugated BA changed significantly. A correlation analysis also revealed an association between BA and microbiota with the concentration in plasma of glucose and lipid metabolites (such as BHBA). Among BA, cholic acid and its derivates such as taurocholic acid, tauro α-muricholic acid, and taurodeoxycholic acid were the main hub nodes connecting microbe and blood metabolites. Our results indicated an association between BA, intestinal microbe, and glucose and lipid metabolism in transition dairy cows. These findings provide new insight into the adaptation mechanisms of dairy cows during the transition period.

Impacts of pancreatic exocrine insufficiency on gut microbiota

Pancreatic exocrine insufficiency (PEI) can be induced by various kinds of diseases, including chronic pancreatitis, acute pancreatitis, and post-pancreatectomy. The main pathogenetic mechanism of PEI involves the decline of trypsin synthesis, disorder of pancreatic fluid flow, and imbalance of secretion feedback. Animal studies have shown that PEI could induce gut bacterial overgrowth and dysbiosis, with the abundance of Lactobacillus and Bifidobacterium increasing the most, which could be partially reversed by pancreatic enzyme replacement therapy. Clinical studies have also confirmed the association between PEI and the dysbiosis of gut microbiota. Pancreatic exocrine secretions and changes in duodenal pH as well as bile salt malabsorption brought about by PEI may affect and shape the abundance and composition of gut microbiota. In turn, the gut microbiota may impact the pancreatic exocrine acinus through potential bidirectional crosstalk. Going forward, more and higher-quality studies are needed that focus on the mechanism underlying the impact of PEI on the gut microbiota.

Targeting mitochondria with antioxidant nutrients for the prevention and treatment of postweaning diarrhea in piglets

Post-weaning diarrhea (PWD) in piglets poses a significant challenge and presents a grave threat to the global swine industry, resulting in considerable financial losses and compromising the welfare of animals. PWD is commonly associated with gut homeostatic imbalance, including oxidative stress, excessive inflammation, and microbiota dysbiosis. Antibiotic use has historically been a common initiative to combat PWD, but concerns about the development of antibiotic resistance have led to increased interest in alternative strategies. Mitochondria are key players in maintaining cellular homeostasis, and their dysfunction is intricately linked to the onset and progression of PWD. Accumulating evidence suggests that targeting mitochondrial function using antioxidant nutrients, such as vitamins, minerals and polyphenolic compounds, may represent a promising approach for preventing and treating PWD. Moreover, nutrients based on antioxidant strategies have been shown to improve mitochondrial function, restore intestinal redox balance, and reduce oxidative damage, which is a key driver of PWD. The present review begins with an overview of the potential interplay between mitochondria and gut homeostasis in the pathogenesis of PWD in piglets. Subsequently, alternative strategies to prevent and treat PWD using antioxidant nutrients to target mitochondria are described and discussed. Ultimately, we delve into potential limitations and suggest future research directions in this field for further advancement. Overall, targeting mitochondria using antioxidant nutrients may be a promising approach to combat PWD and provides a potential nutrition intervention strategy for regulating gut homeostasis of weaned piglets.

Alterations in gut microbiota and metabolite profiles in patients with infantile cholestasis

BACKGROUND

Infantile cholestasis (IC) is the most common hepatobiliary disease in infants, resulting in elevated direct bilirubin levels. Indeed, hepatointestinal circulation impacts bile acid and bilirubin metabolism. This study evaluates changes in the gut microbiota composition in children with IC and identifies abnormal metabolite profiles associated with microbial alterations.

RESULTS

The gut microbiota in the IC group exhibits the higher abundance of Veillonella, Streptococcus and Clostridium spp. (P < 0.05), compared to healthy infants (CON) group. Moreover, the abundance of Ruminococcus, Vibrio butyricum, Eubacterium coprostanogenes group, Intestinibacter, and Faecalibacterium were lower (P < 0.05). In terms of microbiota-derived metabolites, the levels of fatty acids (palmitoleic, α-linolenic, arachidonic, and linoleic) (P < 0.05) increased and the levels of amino acids decreased in IC group. Furthermore, the abundances of Ruminococcus, Eubacterium coprostanoligenes group, Intestinibacter and Butyrivibrio are positively correlated with proline, asparagine and aspartic acid, but negatively correlated with the α-linolenic acid, linoleic acid, palmitoleic acid and arachidonic acid. For analysis of the relationship between the microbiota and clinical index, it was found that the abundance of Veillonella and Streptococcus was positively correlated with serum bile acid content (P < 0.05), while APTT, PT and INR were negatively correlated with Faecalibalum and Ruminococcus (P < 0.05).

CONCLUSION

Microbiota dysbiosis happened in IC children, which also can lead to the abnormal metabolism, thus obstructing the absorption of enteral nutrition and aggravating liver cell damage. Veillonella, Ruminococcus and Butyrivibrio may be important microbiome related with IC and need further research.

Trans-Anethole Alleviates DSS-Induced Ulcerative Colitis by Remodeling the Intestinal Flora to Regulate Immunity and Bile Acid Metabolism

Ulcerative colitis (UC) is the most common inflammatory bowel disease (IBD); it is incurable, and the treatment is expensive. Trans-anethole (TA), the main component of fennel, exhibits various biological activities. An increasing number of studies have demonstrated the efficacy of herbal active ingredients in the treatment of UC. This study aimed to investigate the effect and mechanism of TA in UC. In this study, we have experimented on mice with dextran sulfate sodium salt (DSS)-induced UC. The TA group was gavaged with 62.5 mg/kg TA by gavage once daily on days 8-14. To observe the effect of TA on the colon tissue, various investigations were performed, including western blot and immunohistochemistry for intestinal barrier protein expression, TUNEL staining for apoptosis, western blot, and ELISA for inflammation level, flow cytometry for Th17/Treg, LC-MS for blood bile acid content, GC-MS for blood fatty acid content, and 16s RNA for intestinal contents. TA alleviated weight loss in mice with UC; increased colon length; alleviated intestinal mucosal damage; upregulated claudin-1, occludin, and ZO-1 protein expression levels; reduced inflammatory factors in the colon and serum; and alleviated apoptosis. TA reduced fatty acid and bile acid levels by inhibiting colony abundance and reducing Th17/Treg cell differentiation in the colon. We found that TA alleviates DSS-induced UC by remodeling the intestinal flora to regulate immunity and bile acid metabolism.

Lactobacillus gasseri LA39 promotes hepatic primary bile acid biosynthesis and intestinal secondary bile acid biotransformation

A growing body of evidence has linked the gut microbiota to liver metabolism. The manipulation of intestinal microflora has been considered as a promising avenue to promote liver health. However, the effects of Lactobacillus gasseri LA39, a potential probiotic, on liver metabolism remain unclear. Accumulating studies have investigated the proteomic profile for mining the host biological events affected by microbes, and used the germ-free (GF) mouse model to evaluate host-microbe interaction. Here, we explored the effects of L. gasseri LA39 gavage on the protein expression profiles of the liver of GF mice. Our results showed that a total of 128 proteins were upregulated, whereas a total of 123 proteins were downregulated by treatment with L. gasseri LA39. Further bioinformatics analyses suggested that the primary bile acid (BA) biosynthesis pathway in the liver was activated by L. gasseri LA39. Three differentially expressed proteins (cytochrome P450 family 27 subfamily A member 1 (CYP27A1), cytochrome P450 family 7 subfamily B member 1 (CYP7B1), and cytochrome P450 family 8 subfamily B member 1 (CYP8B1)) involved in the primary BA biosynthesis pathway were further validated by western blot assay. In addition, targeted metabolomic analyses demonstrated that serum and fecal β‍-muricholic acid (a primary BA), dehydrolithocholic acid (a secondary BA), and glycolithocholic acid-3-sulfate (a secondary BA) were significantly increased by L. gasseri LA39. Thus, our data revealed that L. gasseri LA39 activates the hepatic primary BA biosynthesis and promotes the intestinal secondary BA biotransformation. Based on these findings, we suggest that L. gasseri LA39 confers an important function in the gut‒liver axis through regulating BA metabolism.

Revisited role of the placenta in bile acid homeostasis

To date, the discussion concerning bile acids (BAs) during gestation is almost exclusively linked to pregnancy complications such as intrahepatic cholestasis of pregnancy (ICP) when maternal serum BA levels reach very high concentrations (>100 μM). Generally, the placenta is believed to serve as a protective barrier avoiding exposure of the growing fetus to excessive amounts of maternal BAs that might cause detrimental effects (e.g., intrauterine growth restriction and/or increased vulnerability to metabolic diseases). However, little is known about the precise role of the placenta in BA biosynthesis, transport, and metabolism in healthy pregnancies when serum BAs are at physiological levels (i.e., low maternal and high fetal BA concentrations). It is well known that primary BAs are synthesized from cholesterol in the liver and are later modified to secondary BA species by colonic bacteria. Besides the liver, BA synthesis in extrahepatic sites such as the brain elicits neuroprotective actions through inhibition of apoptosis as well as oxidative and endoplasmic reticulum stress. Even though historically BAs were thought to be only "detergent molecules" required for intestinal absorption of dietary fats, they are nowadays acknowledged as full signaling molecules. They modulate a myriad of signaling pathways with functional consequences on essential processes such as gluconeogenesis -one of the principal energy sources of the fetus- and cellular proliferation. The current manuscript discusses the potential multipotent roles of physiologically circulating BAs on developmental processes during gestation and provides a novel perspective in terms of the importance of the placenta as a previously unknown source of BAs. Since the principle "not too much, not too little" applicable to other signaling molecules may be also true for BAs, the risks associated with fetal exposure to excessive levels of BAs are discussed.

Ameliorative effect of Aconite aqueous extract on diarrhea is associated with modulation of the gut microbiota and bile acid metabolism

Introduction: Aconite is a form of traditional Chinese medicine (TCM) that has been widely used to treat diarrhea for thousands of years. However, it is not clear whether the anti-diarrhea role of aconite aqueous extract (AA) is associated with regulation of the gut microbiota or with bile acid (BA) metabolism. This study aimed to confirm whether AA exerts its anti-diarrhea effects by regulating the gut microbiota and BA metabolism. Methods: The therapeutic effect of AA in a mouse model of diarrhea was measured based on analysis of body weight, fecal water content, diarrhea scores, intestinal propulsion rate, colonic pathology, and colonic immunohistochemistry. In addition, 16S rRNA high-throughput sequencing was conducted to analyze the effect of AA on the gut microbiota, and targeted metabolomics was employed to analyze the effect of AA on metabolism of BAs. Results: The results showed that treatment with AA reduced fecal water content and diarrhea scores, inhibited intestinal propulsion rate and pathological changes in the colon, and increased AQP3 and AQP4 content in the colon. In addition, AA was found to be capable of regulating the gut microbiota. Effects included increasing its richness (according to the ACE and Chao1 indices); altering the gut microbiota community structure (PCA, PCoA, and NMDS); increasing the relative abundance of norank_f_Muribaculaceae, Ruminococcus, Lachnospiraceae_NK4A136_group, Prevotellaceae_UCG-001, and norank_f_norank_o_Clostridia_UCG-014; and decreasing the relative abundance of Escherichia-Shigella, unclassified_f_Ruminococcaceae, Ruminococcus_torques_group, and Parasutterella. More importantly, AA significantly increased fecal TCA (a primary BA) and DCA, LCA, GDCA, dehydro-LCA, and 12-keto-LCA (secondary BAs), thus restoring BA homeostasis. Moreover, AA increased the ratios of DCA/CA, DCA/TCA, and LCA/CDCA and decreased the ratios of TLCA/LCA, GLCA/LCA, and TUDCA/UDCA. Conclusion: The anti-diarrhea effect of AA was associated with restoration of the gut microbiota and BA metabolism-related homeostasis. The results of this study provide insights into the application of AA and the treatment of diarrhea.

Effects of Probiotics Supplementation on the Intestinal Metabolites, Muscle Fiber Properties, and Meat Quality of Sunit Lamb

The development of animal husbandry is closely related to the meat quality of small ruminants. Intestinal metabolites and the muscle fiber types of lambs are important factors that affect their meat quality, but few studies have examined the regulation of the "intestinal muscle axis" by probiotics. In this study, 12 Sunit lambs were divided into a control group (C) and a probiotics group (P). The gene expressions of the myosin heavy chain, metabolic enzyme activity, and short-chain fatty acids in the intestines were analyzed using gas chromatography-mass spectrometry (GC-MS) and quantitative real-time PCR. The results showed that levels of propionic acid and butyric acid in the intestines of group P were significantly higher than in group C (p < 0.05). In addition, probiotics increased the number and area ratio of type I muscle fibers. They also increased the mRNA expression of MyHC IIA and the activity of malate dehydrogenase (MDH) and succinate dehydrogenase (SDH). Propionic acid was negatively correlated with the number ratio of type IIB muscle fibers. Butyric acid was found to be significantly positively correlated with the number ratio of type IIA muscle fibers. Cooking loss, pH_24h, and shear force decreased significantly in group P. In conclusion, intestinal metabolites (SCFAs) altered the activity of oxidative-myofibril-metabolizing enzymes and the expression of myosin heavy-chain type IIA, reduced the meat shear values, and improved meat tenderness. This study provides a new basis for improving the production and meat quality of small ruminants.

Cholestasis: exploring the triangular relationship of gut microbiota-bile acid-cholestasis and the potential probiotic strategies

Cholestasis is a condition characterized by the abnormal production or excretion of bile, and it can be induced by a variety of causes, the factors of which are extremely complex. Although great progress has been made in understanding cholestasis pathogenesis, the specific mechanisms remain unclear. Therefore, it is important to understand and distinguish cholestasis from different etiologies, which will also provide indispensable theoretical support for the development of corresponding therapeutic drugs. At present, the treatment of cholestasis mainly involves several bile acids (BAs) and their derivatives, most of which are in the clinical stage of development. Multiple lines of evidence indicate that ecological disorders of the gut microbiota are strongly related to the occurrence of cholestasis, in which BAs also play a pivotal role. Recent studies indicate that probiotics seem to have certain effects on cholestasis, but further confirmation from clinical trials is required. This paper reviews the etiology of and therapeutic strategies for cholestasis; summarizes the similarities and differences in inducement, symptoms, and mechanisms of related diseases; and provides information about the latest pharmacological therapies currently available and those under research for cholestasis. We also reviewed the highly intertwined relationship between gut microbiota-BA-cholestasis, revealing the potential role and possible mechanism of probiotics in the treatment of cholestasis.

Role of Gut Microbiome in Atherosclerosis: Molecular and Therapeutic Aspects

Atherosclerosis is one of the most relevant and prevalent cardiovascular diseases of our time. It is one of the pathological entities that increases the morbidity and mortality index in the adult population. Pathophysiological connections have been observed between atherosclerosis and the gut microbiome (GM), represented by a group of microorganisms that are present in the gut. These microorganisms are vital for metabolic homeostasis in humans. Recently, direct and indirect mechanisms through which GM can affect the development of atherosclerosis have been studied. This has led to research into the possible modulation of GM and metabolites as a new target in the prevention and treatment of atherosclerosis. The goal of this review is to analyze the physiopathological mechanisms linking GM and atherosclerosis that have been described so far. We also aim to summarize the recent studies that propose GM as a potential target in atherosclerosis management.

Gut-Liver Axis and Non-Alcoholic Fatty Liver Disease: A Vicious Circle of Dysfunctions Orchestrated by the Gut Microbiome

Non-alcoholic fatty liver disease (NAFLD) is a prevalent, multifactorial, and poorly understood liver disease with an increasing incidence worldwide. NAFLD is typically asymptomatic and coupled with other symptoms of metabolic syndrome. The prevalence of NAFLD is rising in tandem with the prevalence of obesity. In the Western hemisphere, NAFLD is one of the most prevalent causes of liver disease and liver transplantation. Recent research suggests that gut microbiome dysbiosis may play a significant role in the pathogenesis of NAFLD by dysregulating the gut-liver axis. The so-called "gut-liver axis" refers to the communication and feedback loop between the digestive system and the liver. Several pathological mechanisms characterized the alteration of the gut-liver axis, such as the impairment of the gut barrier and the increase of the intestinal permeability which result in endotoxemia and inflammation, and changes in bile acid profiles and metabolite levels produced by the gut microbiome. This review will explore the role of gut-liver axis disruption, mediated by gut microbiome dysbiosis, on NAFLD development.

Farnesoid-X receptor as a therapeutic target for inflammatory bowel disease and colorectal cancer

Farnesoid-X receptor (FXR), as a nuclear receptor activated by bile acids, is a vital molecule involved in bile acid metabolism. Due to its expression in immune cells, FXR has a significant effect on the function of immune cells and the release of chemokines when immune cells sense changes in bile acids. In addition to its regulation by ligands, FXR is also controlled by post-translational modification (PTM) activities such as acetylation, SUMOylation, and methylation. Due to the high expression of FXR in the liver and intestine, it significantly influences intestinal homeostasis under the action of enterohepatic circulation. Thus, FXR protects the intestinal barrier, resists bacterial infection, reduces oxidative stress, inhibits inflammatory reactions, and also acts as a tumor suppressor to impair the multiplication and invasion of tumor cells. These potentials provide new perspectives on the treatment of intestinal conditions, including inflammatory bowel disease (IBD) and its associated colorectal cancer (CRC). Moreover, FXR agonists on the market have certain organizational heterogeneity and may be used in combination with other drugs to achieve a greater therapeutic effect. This review summarizes current data on the role of FXR in bile acid metabolism, regulation of immune cells, and effects of the PTM of FXR. The functions of FXR in intestinal homeostasis and potential application in the treatment of IBD and CRC are discussed.

A Novel Gene Alignment in Dorea sp. AM58-8 Produces 7-Dehydroxy-3β Bile Acids from Primary Bile Acids

Bile acids are essential metabolites and signaling molecules in mammals. Primary bile acids are synthesized from cholesterol in the liver. At the same time, the microbiota in the mammalian gut has many interactions with bile acid, including various biotransformation processes such as 7-dehydroxylation and 3-epimerization. 7-Dehydroxylation is mediated by a bile acid-inducible (bai) operon, while 7-dehydroxylation and 3-epimerization are independently observed in only a few strains. Herein, we describe a novel microbe, Dorea sp. AM58-8, that can accomplish a two-step transformation and turn primary bile acids into both 3α secondary bile acids like deoxycholic acid and lithocholic acid, and 3β secondary bile acids like isodeoxycholic acid and isolithocholic acid. We subsequently characterized BaiA, BaiB, BaiE, and their substrate profiles biochemically. The potential bai gene clusters in the metagenomes were further mined. Their evolution, potential functions, and possible regulatory pathways were predicted using bioinformatics based on our understanding of the 7-dehydroxylation pathway in Dorea sp. AM58-8. This study of Dorea sp. AM58-8 also helps us distinguish the inactive bacteria that seem to have the 7-dehydroxylation pathway proteins and discover the 7-dehydroxylation pathway in other mammalian gut microbes.

Mitochondrial Function and Microbial Metabolites as Central Regulators of Intestinal Immune Responses and Cancer

Energy and anabolic metabolism are essential for normal cellular homeostasis but also play an important role in regulating immune responses and cancer development as active immune and cancer cells show an altered metabolic profile. Mitochondria take a prominent position in these metabolic reactions. First, most key energetic reactions take place within or in conjunction with mitochondria. Second, mitochondria react to internal cues from within the cell but also to external cues originating from the microbiota, a vast diversity of associated microorganisms. The impact of the microbiota on host physiology has been largely investigated in the last decade revealing that the microbiota contributes to the extraction of calories from the diet, energy metabolism, maturation of the immune system and cellular differentiation. Thus, changes in the microbiota termed dysbiosis have been associated with disease development including metabolic diseases, inflammation and cancer. Targeting the microbiota to modulate interactions with the mitochondria and cellular metabolism to delay or inhibit disease development and pathogenesis appears an attractive therapeutic approach. Here, we summarize recent advances in developing the therapeutic potential of microbiota-mitochondria interactions for inflammation and cancer.

Mechanistic Insights into the Link between Gut Dysbiosis and Major Depression: An Extensive Review

Depression is a highly common mental disorder, which is often multifactorial with sex, genetic, environmental, and/or psychological causes. Recent advancements in biomedical research have demonstrated a clear correlation between gut dysbiosis (GD) or gut microbial dysbiosis and the development of anxiety or depressive behaviors. The gut microbiome communicates with the brain through the neural, immune, and metabolic pathways, either directly (via vagal nerves) or indirectly (via gut- and microbial-derived metabolites as well as gut hormones and endocrine peptides, including peptide YY, pancreatic polypeptide, neuropeptide Y, cholecystokinin, corticotropin-releasing factor, glucagon-like peptide, oxytocin, and ghrelin). Maintaining healthy gut microbiota (GM) is now being recognized as important for brain health through the use of probiotics, prebiotics, synbiotics, fecal microbial transplantation (FMT), etc. A few approaches exert antidepressant effects via restoring GM and hypothalamus–pituitary–adrenal (HPA) axis functions. In this review, we have summarized the etiopathogenic link between gut dysbiosis and depression with preclinical and clinical evidence. In addition, we have collated information on the recent therapies and supplements, such as probiotics, prebiotics, short-chain fatty acids, and vitamin B12, omega-3 fatty acids, etc., which target the gut–brain axis (GBA) for the effective management of depressive behavior and anxiety.

A designed self-microemulsion delivery system for dihydromyricetin and its dietary intervention effect on high-fat-diet fed mice

The present study aims to design a self-microemulsion delivery system (d-α-tocopheryl polyethylene glycol 1000 succinate - quillaja saponin) to enhance the absorptivity of dihydromyricetin (DMY-S), and to investigate its dietary intervention effect on high-fat-diet (HFD) fed mice. We find DMY-S can inhibit the increase of body weight and fat mass, preventing non-alcoholic fatty liver disease. Compared to the model group, the abundance of mice intestinal flora is mainly changed in certain bacterial genera of Firmicutes and Bacteroides, including norank_f_Muribaculaceae and Blautia. The result of metabolism analysis indicated that the expression levels of cincassiol B, creatine, pantothenic acid and aminobutyric acid in the liver tissues of mice treated with DMY-S showed a down-regulation. The DMY-S prevented hyperlipidemia in HFD mice mainly by affecting different pathways including glycerophospholipid metabolism, sphingolipid metabolism and pantothenate and CoA biosynthesis.

Intertwined Relationship of Mitochondrial Metabolism, Gut Microbiome and Exercise Potential

The microbiome has emerged as a key player contributing significantly to the human physiology over the past decades. The potential microbial niche is largely unexplored in the context of exercise enhancing capacity and the related mitochondrial functions. Physical exercise can influence the gut microbiota composition and diversity, whereas a sedentary lifestyle in association with dysbiosis can lead to reduced well-being and diseases. Here, we have elucidated the importance of diverse microbiota, which is associated with an individual's fitness, and moreover, its connection with the organelle, the mitochondria, which is the hub of energy production, signaling, and cellular homeostasis. Microbial by-products, such as short-chain fatty acids, are produced during regular exercise that can enhance the mitochondrial capacity. Therefore, exercise can be employed as a therapeutic intervention to circumvent or subside various metabolic and mitochondria-related diseases. Alternatively, the microbiome-mitochondria axis can be targeted to enhance exercise performance. This review furthers our understanding about the influence of microbiome on the functional capacity of the mitochondria and exercise performance, and the interplay between them.

Role of the Gut Microbiota in Parenteral Nutrition-Associated Liver Disease: From Current Knowledge to Future Opportunities

Parenteral nutrition-associated liver disease (PNALD) refers to a spectrum of conditions that can develop cholestasis, steatosis, fibrosis, and cirrhosis in the setting of parenteral nutrition (PN) use. Patient risk factors include short bowel syndrome, bacterial overgrowth and translocation, disturbance of hepatobiliary circulation, and lack of enteral feeding. A growing body of evidence suggests an intricate linkage between the gut microbiota and the pathogenesis of PNALD. In this review, we highlight current knowledge on the taxonomic and functional changes in the gut microbiota that might serve as noninvasive biomarkers. We also discuss the function of microbial metabolites and associated signaling pathways in the pathogenesis of PNALD. By providing the perspectives of microbiota-host interactions in PNALD for basic and translational research and summarizing current limitations of microbiota-based approaches, this review paves the path for developing novel and precise microbiota-based therapies in PNALD.

Reductions in Intestinal Taurine-Conjugated Bile Acids and Short-Chain Fatty Acid-Producing Bacteria Might be Novel Mechanisms of Type 2 Diabetes Mellitus in Otsuka Long-Evans Tokushima Fatty Rats

BACKGROUND

The pathogenesis of spontaneously diabetic Otsuka Long-Evans Tokushima Fatty (OLETF) rats, among the best models for human type 2 diabetes mellitus (T2DM), remains poorly defined. Therefore, we investigated the dynamic changes in taurine-conjugated bile acids (T-BAs) and intestinal microbiota during T2DM development in OLETF rats.

METHODS

OLETF rats and corresponding diabetes-resistant Long Evans Tokushima Otsuka (LETO) rats were fed a normal baseline diet. The progress of T2DM was divided into four phases, including normal glycemia-normal insulinemia (baseline), normal glycemia-hyperinsulinemia, impaired glucose tolerance, and DM. Body weight, liver function, blood lipids, fasting plasma glucose, fasting plasma insulin, fasting plasma glucagon-like peptide (GLP)-1 and GLP-2, serum and fecal T-BAs, and gut microbiota were analyzed during the entire course of T2DM development.

RESULTS

There were reductions in fecal T-BAs and short-chain fatty acids (SCFAs)-producing bacteria including Phascolarctobacterium and Lactobacillus in OLETF rats compared with those in LETO rats at baseline, and low levels of fecal T-BAs and SCFAs-producing bacteria were maintained throughout the whole course of the development of T2DM among OLETF rats compared with those in corresponding age-matched LETO rats. Fecal taurine-conjugated chenodeoxycholic acid correlated positively with Phascolarctobacterium. Fecal taurine-conjugated deoxycholic acid correlated positively with Lactobacillus and fasting plasma GLP-1 and inversely with fasting plasma glucose.

CONCLUSION

The fecal BAs profiles and microbiota structure among OLETF rats were different from those of LETO rats during the entire course of T2DM development, indicating that reductions in intestinal T-BAs and specific SCFA-producing bacteria may be potential mechanisms of T2DM in OLETF rats.

Emodin Improves Intestinal Health and Immunity through Modulation of Gut Microbiota in Mice Infected by Pathogenic Escherichia coli O1

The effect of emodin on the intestinal mucosal barrier of a mouse E. coli O₁-induced diarrhea model was observed. Following successful establishment of a diarrhea model, the mice were treated with drugs for seven days. Intestinal lesions and the shape and the number of goblet cells were assessed via hematoxylin-eosin and periodic-acid-Schiff staining, while changes in inflammatory factors, ultrastructure of the small intestine, expression of MUC-2, and changes in the intestinal microbiota were analyzed via RT-PCR, electron microscopy, immunofluorescence, and 16S rRNA sequencing. Examination showed that emodin ameliorated pathological damage to the intestines of diarrheic mice. RT-PCR indicated that emodin reduced TNF-α, IL-β, IL-6, MPO, and COX-2 mRNA levels in duodenal tissues and increased the levels of sIgA and MUC-2 and the number of goblet cells. Microbiome analysis revealed that Escherichia coli O₁ reduced bacterial richness and altered the distribution pattern of bacterial communities at the phylum and order levels in cecum contents. Notably, pathogenic Clostridiales and Enterobacteriales were significantly increased in diarrheic mice. However, emodin reversed the trend. Thus, emodin protected against intestinal damage induced by E. coli O₁ and improved intestinal mucosal barrier function in mice by increasing the abundance of beneficial intestinal microbiota and inhibiting the abundance of harmful bacteria, thereby alleviating diarrhea.

The impact of alteration in gut microbiome in the pathogenesis of nonalcoholic fatty liver disease

PURPOSE OF REVIEW

We have increasing evidence that alterations of the intestinal microbiome have a strong influence on human health. Previous work has demonstrated the association between changes in the microbiome and metabolic risk factors. One related area of interest is the relationship between dysbiosis and nonalcoholic fatty liver disease (NAFLD), as the global prevalence of NAFLD, and its resultant complications, increases.

RECENT FINDINGS

In this review, we summarize the hypothesized pathophysiology of dysbiosis-mediated progression of NAFLD, including promotion of an inflammatory intestinal environment, increased intestinal permeability, endogenous ethanol production, short-chain fatty acid production, secondary bile acid metabolism, and choline depletion. We also review potential therapeutic interventions of the microbiome to slow or prevent NAFLD progression, including antibiotics, probiotics, prebiotics, fecal microbiota transplant, and farnesoid × receptor agonism.

SUMMARY

Much of the evidence supporting dysbiosis-mediated NAFLD progression has been gathered in high-quality animal trials. There remains a need for additional observational and randomized controlled trials in humans to establish causality between the suspected factors and pathogenesis of NAFLD.

The Role of Gut Microbiota and Gut-Brain Interplay in Selected Diseases of the Central Nervous System

The gut microbiome has attracted increasing attention from researchers in recent years. The microbiota can have a specific and complex cross-talk with the host, particularly with the central nervous system (CNS), creating the so-called “gut–brain axis”. Communication between the gut, intestinal microbiota, and the brain involves the secretion of various metabolites such as short-chain fatty acids (SCFAs), structural components of bacteria, and signaling molecules. Moreover, an imbalance in the gut microbiota composition modulates the immune system and function of tissue barriers such as the blood–brain barrier (BBB). Therefore, the aim of this literature review is to describe how the gut–brain interplay may contribute to the development of various neurological disorders, combining the fields of gastroenterology and neuroscience. We present recent findings concerning the effect of the altered microbiota on neurodegeneration and neuroinflammation, including Alzheimer’s and Parkinson’s diseases, as well as multiple sclerosis. Moreover, the impact of the pathological shift in the microbiome on selected neuropsychological disorders, i.e., major depressive disorders (MDD) and autism spectrum disorder (ASD), is also discussed. Future research on the effect of balanced gut microbiota composition on the gut–brain axis would help to identify new potential opportunities for therapeutic interventions in the presented diseases.

The Intestinal Microbiota: Impacts of Antibiotics Therapy, Colonization Resistance, and Diseases

Trillions of microbes exist in the human body, particularly the gastrointestinal tract, coevolved with the host in a mutually beneficial relationship. The main role of the intestinal microbiome is the fermentation of non-digestible substrates and increased growth of beneficial microbes that produce key antimicrobial metabolites such as short-chain fatty acids, etc., to inhibit the growth of pathogenic microbes besides other functions. Intestinal microbiota can prevent pathogen colonization through the mechanism of colonization resistance. A wide range of resistomes are present in both beneficial and pathogenic microbes. Giving antibiotic exposure to the intestinal microbiome (both beneficial and hostile) can trigger a resistome response, affecting colonization resistance. The following review provides a mechanistic overview of the intestinal microbiome and the impacts of antibiotic therapy on pathogen colonization and diseases. Further, we also discuss the epidemiology of immunocompromised patients who are at high risk for nosocomial infections, colonization and decolonization of multi-drug resistant organisms in the intestine, and the direct and indirect mechanisms that govern colonization resistance to the pathogens.

Ligustrum robustum Alleviates Atherosclerosis by Decreasing Serum TMAO, Modulating Gut Microbiota, and Decreasing Bile Acid and Cholesterol Absorption in Mice

SCOPE

Atherosclerosis (AS) is closely related to gut microbiota. Previous studies demonstrates that Ligustrum robustum (LR), a flavonoid-rich tea like plant, can mitigate several AS-related risk factors and modulate gut microbiota in animal models and human subjects. But its anti-AS effect and mechanisms remain unclear. Therefore, in this study, impacts of LR on AS development are investigated and the potential underlying mechanisms in C57BL/6J and Apoe^-/- mice are explored.

METHODS AND RESULTS

Female C57BL/6J and Apoe^{-/ -} mice are fed a chow diet or high-choline diet, supplemented with vehicle (water) or LR water extract (700 mg kg^-1 ) by gavage for 17 weeks. It is found that LR attenuates diet-induced AS by reducing serum trimethylamine and trimethylamine-N-oxide (TMAO) levels likely by modulating gut microbiota. Moreover, LR increases the abundance of the genus Bifidobacterium, which generates bile salt hydrolase, and thus presumably enhances bile acid (BA) deconjugation and increases fecal BA excretion. Meanwhile, LR increases fecal cholesterol excretion, decreases the levels of serum and hepatic cholesterol, but did not affect short-chain fatty acids in feces.

CONCLUSION

LR attenuates AS development presumably by decreasing serum TMAO levels and increasing fecal BA excretion likely via gut microbial modulation. These effects are accompanied by increases in fecal cholesterol excretion and decreases in serum and hepatic cholesterol.

Mechanism of deoxynivalenol mediated gastrointestinal toxicity: Insights from mitochondrial dysfunction

Deoxynivalenol (DON) is a mycotoxin predominantly produced by Fusarium genus, and widely contaminates cereals and associated products all over the world. The intestinal toxicity of DON is well established. However, intestinal homeostasis involves mitochondria, which has rarely been considered in the context of DON exposure. We summarize the recent knowledge on mitochondria as a key player in maintaining intestinal homeostasis based on their functions in cellular energy metabolism, redox homeostasis, apoptosis, intestinal immune responses, and orchestrated bidirectional cross-talk with gut microbe. In addition, we discuss the pivotal roles of mitochondrial dysfunction in the intestinal toxicity of DON and highlight promising mitochondrial-targeted therapeutics for DON-induced intestinal injury. Recent studies support that the intestinal toxicity of DON is attributed to mitochondrial dysfunction as a critical factor. Mitochondrial dysfunction characterized by failure in respiratory capacities and ROS overproduction has been demonstrated in intestinal cells exposed to DON. Perturbation of mitochondrial respiration leading to ROS accumulation is implicated in the early initiation of apoptosis. DON-induced intestinal inflammatory response is tightly linked to the mitochondrial ROS, whereas immunosuppression is intimately associated with mitophagy inhibition. DON perturbs the orchestrated bidirectional cross-talk between gut microbe and host mitochondria, which may be involved in DON-induced intestinal toxicity.

Effect of Lactylate and Bacillus subtilis on Growth Performance, Peripheral Blood Cell Profile, and Gut Microbiota of Nursery Pigs

To evaluate the effects of lactylate and Bacillus subtilis on growth performance, complete blood cell count, and microbial changes, 264 weaning pigs were assigned to four treatments (1) control (Con) basal diets that met the nutrient requirement for each phase, (2) 0.2% lactylate (LA), (3) 0.05% Bacillus subtilis strains mixtures (BM), or (4) the combination of LA and BM (LA+BM) added to the control basal diet at their respective inclusion rates in each of the three phases. Dietary lactylate tended to increase weight gain, significantly increased feed intake, and reduced fecal total E. coli and enterotoxigenic E. coli counts during Phase 1. Pigs fed Bacillus subtilis had a greater gain to feed ratio (G:F) during Phases 1 and 2. Pigs fed lactylate had an increased peripheral absolute neutrophil count on D14 but a decreased eosinophil percentage. Pigs fed Bacillus subtilis had an elevated peripheral total white blood cell count at study completion. The addition of lactylate increased microbiota richness, reduced E. coli, and increased Prevotella, Christensenellaceae, and Succinivibrio. Bacillus subtilis supplementation-enriched f_Ruminococcaceae_unclassified and S24-7_ unclassified had positive relationships with feed efficiency. Collectively, these findings suggested that lactylate can be added to diets to balance gut microbiota and improve growth performance during the early postweaning period. The combination of lactylate and Bacillus subtilis strains exerted a synergic effect on the growth performance of nursery pigs.

Manipulating the Microbiome: An Alternative Treatment for Bile Acid Diarrhoea

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

Secondary bile acid ursodeoxycholic acid alters weight, the gut microbiota, and the bile acid pool in conventional mice

Ursodeoxycholic acid (commercially available as ursodiol) is a naturally occurring bile acid that is used to treat a variety of hepatic and gastrointestinal diseases. Ursodiol can modulate bile acid pools, which have the potential to alter the gut microbiota community structure. In turn, the gut microbial community can modulate bile acid pools, thus highlighting the interconnectedness of the gut microbiota-bile acid-host axis. Despite these interactions, it remains unclear if and how exogenously administered ursodiol shapes the gut microbial community structure and bile acid pool in conventional mice. This study aims to characterize how ursodiol alters the gastrointestinal ecosystem in conventional mice. C57BL/6J wildtype mice were given one of three doses of ursodiol (50, 150, or 450 mg/kg/day) by oral gavage for 21 days. Alterations in the gut microbiota and bile acids were examined including stool, ileal, and cecal content. Bile acids were also measured in serum. Significant weight loss was seen in mice treated with the low and high dose of ursodiol. Alterations in the microbial community structure and bile acid pool were seen in ileal and cecal content compared to pretreatment, and longitudinally in feces following the 21-day ursodiol treatment. In both ileal and cecal content, members of the Lachnospiraceae Family significantly contributed to the changes observed. This study is the first to provide a comprehensive view of how exogenously administered ursodiol shapes the healthy gastrointestinal ecosystem in conventional mice. Further studies to investigate how these changes in turn modify the host physiologic response are important.

Gut microbiota of animals living in polluted environments are a potential resource of anticancer molecules

Cancer is a prominent cause of morbidity and mortality worldwide, in spite of advances in therapeutic interventions and supportive care. In 2018 alone, there were 18·1 million new cancer cases and 9·6 million deaths indicating the need for novel anticancer agents. Plant-based products have often been linked with protective effects against communicable and non-communicable diseases. Recently, we have shown that animals such as crocodiles thrive in polluted environments and are often exposed to carcinogenic agents, but still benefit from prolonged lifespan. The protective mechanisms shielding them from cancer could be attributed to the immune system, and/or it is possible that their gut microbiota produce anticancer molecules. In support, several lines of evidence suggest that gut microbiota plays a critical role in the physiology of its host. Here, we reviewed the available literature to assess whether the gut microbiota of animals thriving in polluted environment possess anticancer molecules.

Effect of different bile acids on the intestine through enterohepatic circulation based on FXR

Farnesoid X receptor (FXR) is a nuclear receptor for bile acids (BAs) that is widely expressed in the intestine, liver and kidney. FXR has important regulatory impacts on a wide variety of metabolic pathways (such as glucose, lipid, and sterol metabolism) and has been recognized to ameliorate obesity, liver damage, cholestasis and chronic inflammatory diseases. The types of BAs are complex and diverse. BAs link the intestine with the liver through the enterohepatic circulation. BAs derivatives have entered clinical trials for liver disease. In addition to the liver, the intestine is also targeted by BAs. This article reviews the effects of different BAs on the intestinal tract through the enterohepatic circulation from the perspective of FXR, aiming to elucidate the effects of different BAs on the intestinal tract and lay a foundation for new treatment methods.

Bile Acids as Key Modulators of the Brain-Gut-Microbiota Axis in Alzheimer's Disease

Recently, the concept of the brain-gut-microbiota (BGM) axis disturbances in the pathogenesis of Alzheimer's disease (AD) has been receiving growing attention. At the same time, accumulating data revealing complex interplay between bile acids (BAs), gut microbiota, and host metabolism have shed new light on a potential impact of BAs on the BGM axis. The crosstalk between BAs and gut microbiota is based on reciprocal interactions since microbiota determines BA metabolism, while BAs affect gut microbiota composition. Secondary BAs as microbe-derived neuroactive molecules may affect each of three main routes through which interactions within the BGM axis occur including neural, immune, and neuroendocrine pathways. BAs participate in the regulation of multiple gut-derived molecule release since their receptors are expressed on various cells. The presence of BAs and their receptors in the brain implies a direct effect of BAs on the regulation of neurological functions. Experimental and clinical data confirm that disturbances in BA signaling are present in the course of AD. Disturbed ratio of primary to secondary BAs as well as alterations in BA concertation in serum and brain samples have been reported. An age-related shift in the gut microbiota composition associated with its decreased diversity and stability observed in AD patients may significantly affect BA metabolism and signaling. Given recent evidence on BA neuroprotective and anti-inflammatory effects, new therapeutic targets have been explored including gut microbiota modulation by probiotics and dietary interventions, ursodeoxycholic acid supplementation, and use of BA receptor agonists.

Lactobacillus rhamnosus GG Reduces β-conglycinin-Allergy-Induced Apoptotic Cells by Regulating Bacteroides and Bile Secretion Pathway in Intestinal Contents of BALB/c Mice

Allergy can cause intestinal damage, including through cell apoptosis. In this study, intestinal cell apoptosis was first observed in the β-conglycinin (β-CG) allergy model, and the effect of Lactobacillus rhamnosus GG (LGG) on reducing apoptosis of cells in the intestine and its underlying mechanisms were further investigated. Allergic mice received oral LGG daily, and intestinal tissue apoptotic cells, gut microbiota, and metabolites were evaluated six and nine days after intervention. Terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) analysis revealed that LGG intervention could reduce the incidence of cell apoptosis more effectively than natural recovery (NR). The results of 16S rRNA analysis indicated that LGG intervention led to an increase in the relative abundance of Bacteroides. Metabolite analysis of intestinal contents indicated that histamine, N-acetylhistamine, N(α)-γ-glutamylhistamine, phenylalanine, tryptophan, arachidonic acid malate, and xanthine were significantly decreased, and deoxycholic acid, lithocholic acid were significantly increased after the LGG intervention on β-CG allergy; the decreases in histamine and N(α)-γ-glutamylhistamine were significant compared with those of NR. In conclusion, LGG reduces apoptosis of cells induced by β-CG allergy, which may be related to regulation of Bacteroides and the bile secretion pathway.

The Gut Microbiota: How Does It Influence the Development and Progression of Liver Diseases

The gut–liver axis plays important roles in both the maintenance of a healthy liver and the pathogenesis of liver diseases, where the gut microbiota acts as a major determinant of this relationship. Gut bacteria-derived metabolites and cellular components are key molecules that affect the function of the liver and modulate the pathology of liver diseases. Accumulating evidence showed that gut microbiota produces a myriad of molecules, including lipopolysaccharide, lipoteichoic acid, peptidoglycan, and DNA, as well as short-chain fatty acids, bile acids, trimethylamine, and indole derivatives. The translocation of these components to the liver exerts beneficial or pathogenic effects by interacting with liver immune cells. This is a bidirectional relationship. Therefore, the existence of crosstalk between the gut and liver and its implications on host health and diseases are essential for the etiology and treatment of diseases. Several mechanisms have been proposed for the pathogenesis of liver diseases, but still, the mechanisms behind the pathogenic role of gut-derived components on liver pathogenesis remain elusive and not understandable. This review discusses the current progress on the gut microbiota and its components in terms of the progression of liver diseases, and in turn, how liver diseases indirectly affect the intestinal function and induce intestinal inflammation. Moreover, this paper highlights the current therapeutic and preventive strategies used to restore the gut microbiota composition and improve host health.

Nutrition and the gut microbiome during critical illness: A new insight of nutritional therapy

Changes in the microbiome in response to environmental influences can affect the overall health. Critical illness is considered one of the major environmental factors that can potentially influence the normal gut homeostasis. It is associated with pathophysiological effects causing damage to the intestinal microbiome. Alteration of intestinal microbial composition during critical illness may subsequently compromise the integrity of the intestinal epithelial barrier and intestinal mucosa absorptive function. Many factors can impact the microbiome of critically ill patients including ischemia, hypoxia and hypotension along with the iatrogenic effects of therapeutic agents and the lack of enteral feeds. Factors related to disease state and medication are inevitable and they are part of the intensive care unit (ICU) exposure. However, a nutritional intervention targeting gut microbiota might have the potential to improve clinical outcomes in the critically ill population given the extensive vascular and lymphatic links between the intestines and other organs. Although nutrition is considered an integral part of the treatment plan of critically ill patients, still the role of nutritional intervention is restricted to improve nitrogen balance. What is dismissed is whether the nutrients we provide are adequate and how they are processed and utilised by the host and the microbiota. Therefore, the goal of nutrition therapy during critical illness should be extended to provide good quality feeds with balanced macronutrient content to feed up the entire body including the microbiota and host cells. The main aim of this review is to examine the current literature on the effect of critical illness on the gut microbiome and to highlight the role of nutrition as a factor affecting the intestinal microbiome-host relationship during critical illness.

Exercise and/or Genistein Treatment Impact Gut Microbiota and Inflammation after 12 Weeks on a High-Fat, High-Sugar Diet in C57BL/6 Mice

Genistein (Gen) and exercise (Exe) have been postulated as potential strategies to ameliorate obesity, inflammation, and gut microbiota (GM) with promising results. However, the impact of the combination of both Exe and Gen is yet to be investigated. We aimed to analyze the impacts of Exe, Gen, and their combined effects on GM and inflammation in mice after a 12-week high-fat, high-sugar diet (HFD). Eighty-three C57BL/6 mice were randomized to control, HFD, HFD + Exe, HFD + Gen, or HFD + Exe + Gen. The V4 region of the 16S rRNA gene was analyzed with Illumina MiSeq. Serum samples were used to analyze interleukin (Il)-6 and Tumor Necrosis Factor alpha (TNF-alpha). The HFD + Exe and HFD + Exe + Gen treatments resulted in significantly greater microbial richness compared to HFD. All the treatments had a significantly different impact on the GM community structure. Ruminococcus was significantly more abundant after the HFD + Exe + Gen treatment when compared to all the other HFD groups. Exe + Gen resulted in serum Il-6 concentrations similar to that of controls. TNF-alpha concentrations did not differ by treatment. Overall, Exe had a positive impact on microbial richness, and Ruminococcus might be the driving bacteria for the GM structure differences. Exe + Gen may be an effective treatment for preventing HFD-induced inflammation.

Microbiota-Mitochondria Inter-Talk: A Potential Therapeutic Strategy in Obesity and Type 2 Diabetes

The rising prevalence of obesity and type 2 diabetes (T2D) is a growing concern worldwide. New discoveries in the field of metagenomics and clinical research have revealed that the gut microbiota plays a key role in these metabolic disorders. The mechanisms regulating microbiota composition are multifactorial and include resistance to stress, presence of pathogens, diet, cultural habits and general health conditions. Recent evidence has shed light on the influence of microbiota quality and diversity on mitochondrial functions. Of note, the gut microbiota has been shown to regulate crucial transcription factors, coactivators, as well as enzymes implicated in mitochondrial biogenesis and metabolism. Moreover, microbiota metabolites seem to interfere with mitochondrial oxidative/nitrosative stress and autophagosome formation, thus regulating the activation of the inflammasome and the production of inflammatory cytokines, key players in chronic metabolic disorders. This review focuses on the association between intestinal microbiota and mitochondrial function and examines the mechanisms that may be the key to their use as potential therapeutic strategies in obesity and T2D management.

The Intestinal Microbiome Restricts Alphavirus Infection and Dissemination through a Bile Acid-Type I IFN Signaling Axis

Chikungunya virus (CHIKV), an emerging alphavirus, has infected millions of people. However, the factors modulating disease outcome remain poorly understood. Here, we show in germ-free mice or in oral antibiotic-treated conventionally housed mice with depleted intestinal microbiomes that greater CHIKV infection and spread occurs within 1 day of virus inoculation. Alteration of the microbiome alters TLR7-MyD88 signaling in plasmacytoid dendritic cells (pDCs) and blunts systemic production of type I interferon (IFN). Consequently, circulating monocytes express fewer IFN-stimulated genes and become permissive for CHIKV infection. Reconstitution with a single bacterial species, Clostridium scindens, or its derived metabolite, the secondary bile acid deoxycholic acid, can restore pDC- and MyD88-dependent type I IFN responses to restrict systemic CHIKV infection and transmission back to vector mosquitoes. Thus, symbiotic intestinal bacteria modulate antiviral immunity and levels of circulating alphaviruses within hours of infection through a bile acid-pDC-IFN signaling axis, which affects viremia, dissemination, and potentially transmission.

Fecal Microbiota Transplantation for Chronic Liver Diseases: Current Understanding and Future Direction

Chronic liver disease is a major cause of morbidity and mortality worldwide. Even though effective treatments are now available for most chronic viral hepatitis, treatment options for other causes of chronic liver disease remain inadequate. Recent research has revealed a previously unappreciated role that the human intestinal microbiome plays in mediating the development and progression of chronic liver diseases. The recent remarkable success of fecal microbiota transplantation (FMT) in treating Clostridioides difficile demonstrates that the intestinal microbiota can be manipulated to obtain favorable therapeutic benefits and that FMT may become an important component of a total therapeutic approach to effectively treat hepatic disorders.

Regulation of bile acid metabolism-related signaling pathways by gut microbiota in diseases

Over the past decade, there has been increasing attention on the interaction between microbiota and bile acid metabolism. Bile acids are not only involved in the metabolism of nutrients, but are also important in signal transduction for the regulation of host physiological activities. Microbial-regulated bile acid metabolism has been proven to affect many diseases, but there have not been many studies of disease regulation by microbial receptor signaling pathways. This review considers findings of recent research on the core roles of farnesoid X receptor (FXR), G protein-coupled bile acid receptor (TGR5), and vitamin D receptor (VDR) signaling pathways in microbial-host interactions in health and disease. Studying the relationship between these pathways can help us understand the pathogenesis of human diseases, and lead to new solutions for their treatments.

Long-term Proton Pump Inhibitor Administration Caused Physiological and Microbiota Changes in Rats

Proton pump inhibitors (PPIs) are used for the long-term treatment of gastroesophageal disorders and the non-prescription medicines for acid reflux. However, there is growing concerns about PPI misuse, overuse and abuse. This study aimed to develop an animal model to examine the effects of long-term use of PPI in vivo. Twenty one Wistar rats were given omeprazole orally or intravenously for 30 days, and caerulein as a positive control. After euthanization, the serum and stool were collected to perform MS-based quantitative analysis of metabolites. We carried out 16S-based profiling of fecal microbiota, assessed the expression of bile acid metabolism regulators and examined the immunopathological characteristics of bile ducts. After long-term PPI exposure, the fecal microbial profile was altered and showed similarity to those observed in high-fat diet studies. The concentrations of several metabolites were also changed in various specimens. Surprisingly, morphological changes were observed in the bile duct, including ductal epithelial proliferation, micropapillary growth of biliary epithelium, focal bile duct stricture formation and bile duct obstruction. These are characteristics of precancerous lesions of bile duct. FXR and RXRα expressions were significantly reduced, which were similar to that observed in cholangiocarcinoma in TCGA and Oncomine databases. We established a novel animal model to examine the effects of long-term use of omeprazole. The gut microbes and metabolic change are consequences of long-term PPI exposure. And the results showed the environment in vivo tends to a high-fat diet. More importantly, we observed biliary epithelial hyperplasia, which is an indicator of a high-fat diet.

The mitochondrial negative regulator MCJ modulates the interplay between microbiota and the host during ulcerative colitis

Recent evidences indicate that mitochondrial genes and function are decreased in active ulcerative colitis (UC) patients, in particular, the activity of Complex I of the electron transport chain is heavily compromised. MCJ is a mitochondrial inner membrane protein identified as a natural inhibitor of respiratory chain Complex I. The induction of experimental colitis in MCJ-deficient mice leads to the upregulation of Timp3 expression resulting in the inhibition of TACE activity that likely inhibits Tnf and Tnfr1 shedding from the cell membrane in the colon. MCJ-deficient mice also show higher expression of Myd88 and Tlr9, proinflammatory genes and disease severity. Interestingly, the absence of MCJ resulted in distinct microbiota metabolism and composition, including a member of the gut community in UC patients, Ruminococcus gnavus. These changes provoked an effect on IgA levels. Gene expression analyses in UC patients showed decreased levels of MCJ and higher expression of TIMP3, suggesting a relevant role of mitochondrial genes and function among active UC. The MCJ deficiency disturbs the regulatory relationship between the host mitochondria and microbiota affecting disease severity. Our results indicate that mitochondria function may be an important factor in the pathogenesis. All together support the importance of MCJ regulation during UC.

Effect of fosfomycin, Cynara scolymus extract, deoxynivalenol and their combinations on intestinal health of weaned piglets

Weaning is a challenging stage of pig farming. Animals undergo environmental, social and dietary changes leading to weaning stress syndrome. In order to compensate for the detrimental effects of weaning stress, antibiotics and natural extracts are used as feed additives, sometimes without fully understanding the interactions between them or even with low concentrations of mycotoxins that are frequently present in feed. The aim of this study was to evaluate the effect of fosfomycin (FOS), Cynara scolymus extract (CSE), deoxynivalenol (DON) and their combined administration on intestinal health of weaned piglets. The experiment was designed as a 2 × 2 × 2 factorial arrangement with 3 factors (FOS, CSE and DON treatments), 2 levels each (presence and absence) and 3 repeats. Weaned piglets (n = 24) were randomly divided in groups to receive the different treatments, namely DON administered in diet (50 μg/kg BW), FOS administered into the drinking water (30 mg/kg BW), CSE administered in diet (15 mg/kg BW) and all their combinations. After 15 d, the animals were euthanized and gastrointestinal tract samples were immediately taken to evaluate gastrointestinal pH, Enterobacteriaceae to lactic acid bacteria (E:L) ratio, volatile fatty acid (VFA) concentrations, disaccharidase (lactase, sucrase and maltase) activity, histology (intestinal absorptive area [IAA] and goblet cells count) and mucus ability to adhere pathogenic Escherichia coli. From our results, FOS and CSE treatments, individually or combined, produced a lower E:L ratio, an enhanced production of butyrate, increased disaccharidase activity (particularly maltase), and a greater IAA and goblet cells count along with an increase in pathogenic bacteria adherence to intestinal mucus. Deoxynivalenol did not show interactions with the other factors and its administration produced decreases on VFA, disaccharidase activity and goblet cells count. In conclusion, weaning piglets receiving diets containing FOS, CSE or both exhibited evident beneficial intestinal effects compared to animals receiving diets free from these compounds. On the contrary, the presence of DON at sub-toxic concentrations produced detrimental effects on intestinal health. The knowledge of the physiological and pathological gut changes produced by these compounds contributes to understand their potential productive consequences.

Evolutionary Analysis of Bile Acid-Conjugating Enzymes Reveals a Complex Duplication and Reciprocal Loss History

To fulfill their physiological functions, bile acids are conjugated with amino acids. In humans, conjugation is catalyzed by bile acid coenzyme A: amino acid N-acyltransferase (BAAT), an enzyme with a highly conserved catalytic triad in its active site. Interestingly, the conjugated amino acids are highly variable among mammals, with some species conjugating bile acids with both glycine and taurine, whereas others conjugate only taurine. The genetic origin of these bile acid conjugation differences is unknown. Here, we tested whether mutations in BAAT’s catalytic triad could explain bile acid conjugation differences. Our comparative analysis of 118 mammals first revealed that the ancestor of placental mammals and marsupials possessed two genes, BAAT and BAATP1, that arose by a tandem duplication. This duplication was followed by numerous gene losses, including BAATP1 in humans. Losses of either BAAT or BAATP1 largely happened in a reciprocal fashion, suggesting that a single conjugating enzyme is generally sufficient for mammals. In intact BAAT and BAATP1 genes, we observed multiple changes in the catalytic triad between Cys and Ser residues. Surprisingly, although mutagenesis experiments with the human enzyme have shown that replacing Cys for Ser greatly diminishes the glycine-conjugating ability, across mammals we found that this residue provides little power in predicting the experimentally measured amino acids that are conjugated with bile acids. This suggests that the mechanism of BAAT’s enzymatic function is incompletely understood, despite relying on a classic catalytic triad. More generally, our evolutionary analysis indicates that results of mutagenesis experiments may not easily be extrapolatable to other species.

Can tailored nanoceria act as a prebiotic? Report on improved lipid profile and gut microbiota in obese mice

Background

Microbiome modulation is a pillar intervention to treat metabolic syndrome, prestages, and cascade of related pathologies such as atherosclerosis, among others. Lactobacillus and Bifidobacterium probiotic strains demonstrate efficacy to reduce obesity, dyslipidemia, and improve metabolic health. Novel prebiotic substances composed with known probiotics may strongly synergize health benefits to the host. The aim of this study was to evaluate beneficial effects of Lactobacillus and Bifidobacterium strains (probiotics) if composed with nanoceria (potential prebiotic) to reduce cholesterol levels and restore gut microbiota in obese mice.

Materials and Methods

Two lines of mice were used in the study: BALB/c mice (6-8 weeks, 18-24 g) and CBA mice (11-12 months, 20-26 g); experimental animals were fed by fat-enriched diet 3 weeks before the evaluation. Animals were divided into groups to test probiotic strains and nanoceria. All groups received probiotic strains orally and cerium dioxide orally or intravenously in various composition. A group of untreated animals was used as a control. Cholesterol level and gut microbiota of mice were studied.

Results

Cerium dioxide nanoparticles, probiotic strain L. casei ІМV В-7280, and composition B. animalis VKB/B. animalis VKL applied separately and in different combinations all reduced at different levels free and bound cholesterol in blood serum of mice fed by fat-enriched diet. The combination of 0.01 M nanoceria and probiotic strain L. casei ІМV В-7280 resulted in the fastest cholesterol level decrease in both young and mature animals. Oral administration of CeO₂ applied alone reduced the number of microscopic fungi in the gut of mice and Gram-positive cocci (staphylococci and/or streptococci). Application of L. casei IMV B-7280 as a probiotic strain increased most significantly the number of lactobacilli and bifidobacteria in the gut of mice. The most significant normalization of gut microbiota was observed after oral administration of alternatively either L. casei IMV B-7280 + 0.1 M CeO₂ or L. casei IMV B-7280 + 0.01 M CeO₂.

Conclusion

Dietary application of nanoceria combined with probiotic strains L. casei IMV B-7280, B. animalis VKB, and B. animals VKL has significantly reduced both free and bound cholesterol levels in serum. Simultaneous administration of probiotics and cerium nanoparticles as a prebiotic, in various combinations, significantly enhanced positive individual effects of them on the gut microbiota spectrum. The presented results provide novel insights into mechanisms behind nutritional supplements and open new perspectives for application of probiotics combined with substances demonstrating prebiotic qualities benefiting, therefore, the host health. Follow-up translational measures are discussed to bring new knowledge from lab to the patient. If validated in a large-scale clinical study, this approach might be instrumental for primary and secondary prevention in obese individual and patients diagnosed with diabetes. To this end, individualized prediction and treatments tailored to the person are strongly recommended to benefit the health condition of affected individuals.

Diversification of host bile acids by members of the gut microbiota

Bile acid biotransformation is a collaborative effort by the host and the gut microbiome. Host hepatocytes synthesize primary bile acids from cholesterol. Once these host-derived primary bile acids enter the gastrointestinal tract, the gut microbiota chemically modify them into secondary bile acids. Interest into the gut-bile acid-host axis is expanding in diverse fields including gastroenterology, endocrinology, oncology, and infectious disease. This review aims to 1) describe the physiologic aspects of collaborative bile acid metabolism by the host and gut microbiota; 2) to evaluate how gut microbes influence bile acid pools, and in turn how bile acid pools modulate the gut microbial community structure; 3) to compare species differences in bile acid pools; and lastly, 4) discuss the effects of ursodeoxycholic acid (UDCA) administration, a common therapeutic bile acid, on the gut microbiota-bile acid-host axis.

Obesity and cancer: A mechanistic overview of metabolic changes in obesity that impact genetic instability

Obesity, defined as a state of positive energy balance with a body mass index exceeding 30 kg/m2 in adults and 95th percentile in children, is an increasing global concern. Approximately one-third of the world's population is overweight or obese, and in the United States alone, obesity affects one in six children. Meta-analysis studies suggest that obesity increases the likelihood of developing several types of cancer, and with poorer outcomes, especially in children. The contribution of obesity to cancer risk requires a better understanding of the association between obesity-induced metabolic changes and its impact on genomic instability, which is a major driving force of tumorigenesis. In this review, we discuss how molecular changes during adipose tissue dysregulation can result in oxidative stress and subsequent DNA damage. This represents one of the many critical steps connecting obesity and cancer since oxidative DNA lesions can result in cancer-associated genetic instability. In addition, the by-products of the oxidative degradation of lipids (e.g., malondialdehyde, 4-hydroxynonenal, and acrolein), and gut microbiota-mediated secondary bile acid metabolites (e.g., deoxycholic acid and lithocholic acid), can function as genotoxic agents and tumor promoters. We also discuss how obesity can impact DNA repair efficiency, potentially contributing to cancer initiation and progression. Finally, we outline obesity-related epigenetic changes and identify the gaps in knowledge to be addressed for the development of better therapeutic strategies for the prevention and treatment of obesity-related cancers.