Gender Differences in Bile Acids and Microbiota in Relationship with Gender Dissimilarity in Steatosis Induced by Diet and FXR Inactivation

Pharmacological Mechanisms of Bile Acids Targeting the Farnesoid X Receptor

Bile acids (BAs), a category of amphiphilic metabolites synthesized by liver cells and released into the intestine via the bile duct, serve a vital role in the emulsification of ingested fats during the digestive process. Beyond their conventional emulsifying function, BAs, with their diverse structures, also act as significant hormones within the body. They are pivotal in facilitating nutrient absorption by interacting with the farnesoid X receptor (FXR), and they serve as key regulators of lipid and glucose metabolism, as well as immune system balance. Consequently, BAs contribute to the metabolism of glucose and lipids, enhance the digestion and absorption of lipids, and maintain the equilibrium of the bile pool. Their actions are instrumental in addressing obesity, managing cholestasis, and treating diabetes, and are involved in the onset and progression of cancer. This paper presents an updated systematic review of the pharmacological mechanisms by which BAs target the FXR, incorporating recent findings and discussing their signaling pathways in the context of novel research, including their distinct roles in various disease states and populations. The aim is to provide a theoretical foundation for the continued research and clinical application of BAs.

Sexual dimorphism of metabolic dysfunction-associated steatotic liver disease

Metabolic dysfunction-associated steatotic liver disease (MASLD) is the most common chronic liver condition. MASLD is a sexually dimorphic condition, with its development and progression influenced by sex chromosomes and hormones. Estrogens typically protect against, whereas androgens promote, MASLD. Therapeutic approaches for a sex-specific personalized medicine include estrogen replacement, androgen blockers, and novel drugs targeting hormonal pathways. However, the interactions between hormonal factors and inherited genetic variation impacts MASLD risk, necessitating more tailored therapies. Understanding sex disparities and the role of estrogens could improve MASLD interventions and management, whereas clinical trials addressing sex differences are crucial for advancing personalized treatment. This review explores the underappreciated impact of sexual dimorphism in MASLD and discusses the potential therapeutic application of sex-related hormones.

Noninvasive biomarkers implicated in urea and TCA cycles for metabolic liver disease

Bile acid (BA) and its receptor FXR play crucial roles in metabolism, and dysregulated BA synthesis regulated by hepatic and bacterial enzymes causes metabolic dysfunction-associated steatohepatitis (MASH) and hepatocellular carcinoma (HCC). Moreover, because ~ 75% of hepatic blood is from the gut, liver metabolism is influenced by intestinal bacteria and their metabolites. Thus, we used gut microbiota and metabolites from the urine and serum to uncover biomarkers for metabolic distress caused by Western diet (WD) intake, aging, and FXR inactivity. Hepatic transcriptomes were profiled to define liver phenotypes. There were 654 transcriptomes commonly altered by differential diet intake, ages, and FXR functional status, representing the signatures of liver dysfunction, and 76 of them were differentially expressed in healthy human livers and HCC. Machine learning approaches classified urine and serum metabolites for differential dietary intake and age difference. Additionally, the gut microbiota could predict FXR functional status. Furthermore, FXR was essential for differentiating dietary effects in colonizing age-related gut microbes. The integrated analysis established the relationships between the metabolites and gut microbiota correlated with hepatic transcripts commonly altered by diet, age, and FXR functionality. Remarkably, the changes in metabolites involved in the urea cycle, mitochondrial metabolism, and amino acid metabolism are associated with hepatic dysfunction (i.e. FXF deactivation). Taken together, noninvasive specimens and biomarkers are promising resources for identifying metabolic distress.

Temporal changes in the mouse gut bacteriota influenced by host sex, diet, and exercise

The gut microbiota plays an important role in host physiology. However, the effects of host sex, lifestyle, and temporal influences on the bacterial community within the gut remain ill-defined. To address this gap, we evaluated 56 male and female mice over a 10-wk study to assess the effects of sex, diet, and exercise on gut community dynamics. Mice were randomly assigned to high-fat or control diet feeding and had free access to running wheels or remained sedentary throughout the study period. The fecal bacterial community was characterized by rRNA operon profiling via nanopore sequencing. Differential abundance testing indicated that ∼200 bacterial taxa were significantly influenced by sex, diet, or exercise (4.2% of total community), which also changed over time (82 taxa, 1.7% of total community). Phylogenetic analysis of taxa closely related to Dysosmobacter welbionis, and several members of the family Muribaculaceae were examined more closely and demonstrated distinct species/strain level subclustering by host sex, diet, and exercise. Collectively, these data suggest that sex and lifestyle can alter the gut bacteriota at the species/strain level that may play a role in host health. These results also highlight the need for improved characterization methods to survey microbial communities at finer taxonomic resolution.NEW & NOTEWORTHY This study demonstrates that host sex, diet, and exercise can each modulate gut bacterial community structure, which may have consequences to host physiology. Our analysis shows selection of novel strains and genera for some members of the Oscillospiraceae and Muribaculaceae by host sex, diet, and activity status. Overall, these findings provide a framework for detecting the next generation of beneficial bacteria targeting obesity and associated metabolic diseases in a sex-specific manner.

Loss of the DNA-binding domain of the farnesoid X receptor gene causes severe liver and kidney injuries

Farnesoid X receptor (FXR) regulates bile acid synthesis, lipid metabolism, and glucose homeostasis in metabolic organs. FXR-knockout (FXR-KO) mice lacking the last exon of the FXR gene develop normally and display no prenatal and early postnatal lethality, whereas human patients with mutations in the DNA-binding domain of the FXR gene develop severe hepatic dysfunction. In this study, we generated novel FXR-KO mice lacking the DNA-binding domain of the FXR gene using CRISPR-Cas9 technology and evaluated their phenotypes. Similar to the aforementioned FXR-KO mice, our novel mice showed elevated serum levels of total bile acids and total cholesterol. However, they were obviously short-lived, showing severe liver and renal pathologies at an early age. These results indicate that FXR, including its unknown isoforms, has more significant functions in multiple organs than previously reported. Thus, the novel FXR-KO mice could lead to a new aspect that requires reworking of previous knowledge of FXR in the liver and renal function.

Early depletion of gut microbiota shape oligodendrocyte response after traumatic brain injury

White matter injury (WMI) is thought to be a major contributor to long-term cognitive dysfunctions after traumatic brain injury (TBI). This damage occurs partly due to apoptotic death of oligodendrocyte lineage cells (OLCs) after the injury, triggered directly by the trauma or in response to degenerating axons. Recent research suggests that the gut microbiota modulates the inflammatory response through the regulation of peripheral immune cell infiltration after TBI. Additionally, T-cells directly impact OLCs differentiation and proliferation. Therefore, we hypothesized that the gut microbiota plays a critical role in regulating the OLC response to WMI influencing T-cells differentiation and activation. Gut microbial depletion early after TBI chronically reduced re-myelination, acutely decreased OLCs proliferation, and was associated with increased myelin debris accumulation. Surprisingly, the absence of T-cells in gut microbiota depleted mice restored OLC proliferation and remyelination after TBI. OLCs co-cultured with T-cells derived from gut microbiota depleted mice resulted in impaired proliferation and increased expression of MHC-II compared with T cells from control-injured mice. Furthermore, MHC-II expression in OLCs appears to be linked to impaired proliferation under gut microbiota depletion and TBI conditions. Collectively our data indicates that depletion of the gut microbiota after TBI impaired remyelination, reduced OLCs proliferation with concomitantly increased OLC MHCII expression, and required the presence of T cells. This data suggests that T cells are an important mechanistic link by which the gut microbiota modulate the oligodendrocyte response and white matter recovery after TBI.

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.

Gonadal sex and chromosome complement influence the gut microbiome in a mouse model of allergic airway inflammation

Evidence abounds that gut microbiome components are associated with sex disparities in the immune system. However, it remains unclear whether the observed sex disparity in asthma incidence is associated with sex-dependent differences in immune-modulating gut microbiota, and/or its influence on allergic airway inflammatory processes. Using a mouse model of house dust mite (HDM)-induced allergic inflammation and the four core genotypes (FCGs) model, we have previously reported sex differences in lung inflammatory phenotypes. Here, we investigated associations of gut microbiomes with these phenotypes by challenging FCG mice [mouse with female sex chromosome and male gonad (XXM), mouse with female sex chromosome and female gonad (XXF), mouse with male sex chromosome and male gonad (XYM), and mouse with male sex chromosome and female gonad (XYF); n = 7/group] with HDM (25 μg) or PBS intranasally for 5 wk and collecting fecal samples. We extracted fecal DNA and analyzed the 16S microbiome via Targeted Metagenomic Sequencing. We compared α and β diversity across genotypes and assessed the Firmicutes/Bacteroidetes (F/B) ratio. When comparing baseline and after exposure for the FCG, we found that the gut F/B ratio was only increased in the XXM genotype. We also found that α diversity was significantly increased in all FCG mice upon HDM challenge, with the highest increase in the XXF, and the lowest in the XXM genotypes. Similarly, β diversity of the microbial community was also affected by challenge in a gonad- and chromosome-dependent manner. In summary, our results indicated that HDM treatment, gonads, and sex chromosomes significantly influence the gut microbial community composition. We concluded that allergic lung inflammation may be affected by the gut microbiome in a sex-dependent manner involving both hormonal and genetic influences.NEW & NOTEWORTHY Recently, the gut microbiome and its role in chronic respiratory disease have been the subject of extensive research and the establishment of its involvement in immune functions. Using the FCG mouse model, our findings revealed the influence of gonads and sex chromosomes on the microbial community structure before and after exposure to HDM. Our data provide a potential new avenue to better understand mediators of sex disparities associated with allergic airway inflammation.

The Hepatokine Orosomucoid 2 Mediates Beneficial Metabolic Effects of Bile Acids

Bile acids (BAs) are pleiotropic regulators of metabolism. Elevated levels of hepatic and circulating BAs improve energy metabolism in peripheral organs, but the precise mechanisms underlying the metabolic benefits and harm still need to be fully understood. In the current study, we identified orosomucoid 2 (ORM2) as a liver-secreted hormone (i.e., hepatokine) induced by BAs and investigated its role in BA-induced metabolic improvements in mouse models of diet-induced obesity. Contrary to our expectation, under a high-fat diet (HFD), our Orm2 knockout (Orm2-KO) exhibited a lean phenotype compared with C57BL/6J control, partly due to the increased energy expenditure. However, when challenged with a HFD supplemented with cholic acid, Orm2-KO eliminated the antiobesity effect of BAs, indicating that ORM2 governs BA-induced metabolic improvements. Moreover, hepatic ORM2 overexpression partially replicated BA effects by enhancing insulin sensitivity. Mechanistically, ORM2 suppressed interferon-γ/STAT1 activities in inguinal white adipose tissue depots, forming the basis for anti-inflammatory effects of BAs and improving glucose homeostasis. In conclusion, our study provides new insights into the molecular mechanisms of BA-induced liver-adipose cross talk through ORM2 induction.

ARTICLE HIGHLIGHTS

Gut Microbiota Shape Oligodendrocyte Response after Traumatic Brain Injury

White matter injury (WMI) is thought to be a major contributor to long-term cognitive dysfunctions after traumatic brain injury (TBI). This damage occurs partly due to apoptotic death of oligodendrocyte lineage cells (OLCs) after the injury, triggered directly by the trauma or in response to degenerating axons. Recent research suggests that the gut microbiota modulates the inflammatory response through the modulation of peripheral immune cell infiltration after TBI. Additionally, T-cells directly impact OLCs differentiation and proliferation. Therefore, we hypothesized that the gut microbiota plays a critical role in regulating the OLC response to WMI influencing T-cells differentiation and activation. Gut microbial depletion early after TBI chronically reduced re-myelination, acutely decreased OLCs proliferation, and was associated with increased myelin debris accumulation. Surprisingly, the absence of T-cells in gut microbiota depleted mice restored OLC proliferation and remyelination after TBI. OLCs co-cultured with T-cells derived from gut microbiota depleted mice resulted in impaired proliferation and increased expression of MHC-II compared with T cells from control-injured mice. Furthermore, MHC-II expression in OLCs appears to be linked to impaired proliferation under gut microbiota depletion and TBI conditions. Collectively our data indicates that depletion of the gut microbiota after TBI impaired remyelination, reduced OLCs proliferation with concomitantly increased OLC MHCII expression and required the presence of T cells. This data suggests that T cells are an important mechanistic link by which the gut microbiota modulate the oligodendrocyte response and white matter recovery after TBI.

A study on the treatment effects of Crataegus pinnatifida polysaccharide on non-alcoholic fatty liver in mice by modulating gut microbiota

The objective of this study was to investigate the protective effect of Crataegus pinnatifida polysaccharide (CPP) on non-alcoholic fatty liver disease (NAFLD) induced by a high-fat diet (HFD) in mice. The findings demonstrated that CPP improved free fatty acid (FFA)-induced lipid accumulation in HepG2 cells and effectively reduced liver steatosis and epididymal fat weight in NAFLD mice, as well as decreased serum levels of TG, TC, AST, ALT, and LDL-C. Furthermore, CPP exhibited inhibitory effects on the expression of fatty acid synthesis genes FASN and ACC while activating the expression of fatty acid oxidation genes CPT1A and PPARα. Additionally, CPP reversed disturbances in intestinal microbiota composition caused by HFD consumption. CPP decreased the firmicutes/Bacteroidetes ratio, increased Akkermansia abundance, and elevated levels of total short-chain fatty acid (SCFA) content specifically butyric acid and acetic acid. Our results concluded that CPP may intervene in the development of NAFLD by regulating of intes-tinal microbiota imbalance and SCFAs production. Our study highlights that CPP has a potential to modulate lipid-related pathways via alterations to gut microbiome composition thereby ex-erting inhibitory effects on obesity and NAFLD development.

Calenduloside E ameliorates non-alcoholic fatty liver disease via modulating a pyroptosis-dependent pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Non-alcoholic fatty liver disease (NAFLD) is a prevalent chronic liver condition that can have multiple underlying causes. There are no satisfactory chemical or biological drugs for the treatment of NAFLD. Longyasongmu, the bark and root of Aralia elata (Miq.) Seem, is used extensively in traditional Chinese medicine (TCM) and has been used in treating diverse liver diseases including NAFLD. Based on Aralia elata (Miq.) Seem as the main ingredient, Longya Gantai Capsules have been approved for use in China for the treatment of acute hepatitis and chronic hepatitis. Calenduloside E (CE), a natural pentacyclic triterpenoid saponin, is a significant component of saponin isolated from the bark and root of Aralia elata (Miq.) Seem. However, the role and mechanism of anti-NAFLD effects of CE is still unclear.

AIM OF THE STUDY

The objective of this study was to examine the potential mechanisms underlying the protective effect of CE on NAFLD.

MATERIALS AND METHODS

In this study, an NAFLD model was established by Western diet in apoE-/- mice, followed by treatment with various doses of CE (5 mg/kg, 10 mg/kg). The anti-NAFLD effect of CE was assessed by the liver injury, lipid accumulation, inflammation, and pro-fibrotic phenotype. The mechanism of CE in ameliorating NAFLD was studied through transcriptome sequencing (RNA-seq). In vitro, the mouse hepatocytes (AML-12) were stimulated in lipid mixtures with CE and performed the exploration and validation of the relevant pathways using Western blot, immunofluorescence, etc. RESULTS: The findings revealed a significant improvement in liver injury, lipid accumulation, inflammation, and pro-fibrotic phenotype upon CE administration. Furthermore, RNAseq analysis indicated that the primary pathway through which CE alleviates NAFLD involves pyroptosis-related inflammatory cascade pathways. Furthermore, it was observed that CE effectively suppressed inflammasome-mediated pyroptosis both in vivo and in vitro. Remarkably, the functional enrichment analysis of RNA-seq data revealed that the PI3K-Akt signaling pathway is the primarily Signaling transduction pathway modulated by CE treatment. Subsequent experimental outcomes provided further validation of CE's ability to hinder inflammasome-mediated pyroptosis through the inhibition of PI3K/AKT/NF-κB signaling pathway.

CONCLUSIONS

These findings present a novel pharmacological role of CE in exerting anti-NAFLD effects by inhibiting pyroptosis signaling pathways.

Microbial products linked to steatohepatitis are reduced by deletion of nuclear hormone receptor SHP in mice

Deletion of the nuclear hormone receptor small heterodimer partner (Shp) ameliorates the development of obesity and nonalcoholic steatohepatitis (NASH) in mice. Liver-specific SHP plays a significant role in this amelioration. The gut microbiota has been associated with these metabolic disorders, and the interplay between bile acids (BAs) and gut microbiota contributes to various metabolic disorders. Since hepatic SHP is recognized as a critical regulator in BA synthesis, we assessed the involvement of gut microbiota in the antiobesity and anti-NASH phenotype of Shp-/- mice. Shp deletion significantly altered the levels of a few conjugated BAs. Sequencing the 16S rRNA gene in fecal samples collected from separately housed mice revealed apparent dysbiosis in Shp-/- mice. Cohousing Shp-/- mice with WT mice during a Western diet regimen impaired their metabolic improvement and effectively disrupted their distinctive microbiome structure, which became indistinguishable from that of WT mice. While the Western diet challenge significantly increased lipopolysaccharide and phenylacetic acid (PAA) levels in the blood of WT mice, their levels were not increased in Shp-/- mice. PAA was strongly associated with hepatic peroxisome proliferator-activated receptor gamma isoform 2 (Pparg2) activation in mice, which may represent the basis of the molecular mechanism underlying the association of gut bacteria and hepatic steatosis. Shp deletion reshapes the gut microbiota possibly by altering BAs. While lipopolysaccharide and PAA are the major driving forces derived from gut microbiota for NASH development, Shp deletion decreases these signaling molecules via dysbiosis, thereby partially protecting mice from diet-induced metabolic disorders.

The contributions of bacteria metabolites to the development of hepatic encephalopathy

Over 20% of mortality during acute liver failure is associated with the development of hepatic encephalopathy (HE). Thus, HE is a complication of acute liver failure with a broad spectrum of neuropsychiatric abnormalities ranging from subclinical alterations to coma. HE is caused by the diversion of portal blood into systemic circulation through portosystemic collateral vessels. Thus, the brain is exposed to intestinal-derived toxic substances. Moreover, the strategies to prevent advancement and improve the prognosis of such a liver-brain disease rely on intestinal microbial modulation. This is supported by the findings that antibiotics such as rifaximin and laxative lactulose can alleviate hepatic cirrhosis and/or prevent HE. Together, the significance of the gut-liver-brain axis in human health warrants attention. This review paper focuses on the roles of bacteria metabolites, mainly ammonia and bile acids (BAs) as well as BA receptors in HE. The literature search conducted for this review included searches for phrases such as BA receptors, BAs, ammonia, farnesoid X receptor (FXR), G protein-coupled bile acid receptor 1 (GPBAR1 or TGR5), sphingosine-1-phosphate receptor 2 (S1PR2), and cirrhosis in conjunction with the phrase hepatic encephalopathy and portosystemic encephalopathy. PubMed, as well as Google Scholar, was the search engines used to find relevant publications.

Variations in the Relative Abundance of Gut Bacteria Correlate with Lipid Profiles in Healthy Adults

The gut microbiome is a versatile system regulating numerous aspects of host metabolism. Among other traits, variations in the composition of gut microbial communities are related to blood lipid patterns and hyperlipidaemia, yet inconsistent association patterns exist. This study aims to assess the relationships between the composition of the gut microbiome and variations in lipid profiles among healthy adults. This study used data and samples from 23 adult participants of a previously conducted dietary intervention study. Circulating lipid measurements and whole-metagenome sequences of the gut microbiome were derived from 180 blood and faecal samples collected from eight visits distributed across an 11-week study. Lipid-related variables explained approximately 4.5% of the variation in gut microbiome compositions, with higher effects observed for total cholesterol and high-density lipoproteins. Species from the genera Odoribacter, Anaerostipes, and Parabacteroides correlated with increased serum lipid levels, whereas probiotic species like Akkermansia muciniphila were more abundant among participants with healthier blood lipid profiles. An inverse correlation with serum cholesterol was also observed for Massilistercora timonensis, a player in regulating lipid turnover. The observed correlation patterns add to the growing evidence supporting the role of the gut microbiome as an essential regulator of host lipid metabolism.

Xianglian Zhixie Tablet Antagonizes Dextran Sulfate Sodium-Induced Ulcerative Colitis by Attenuating Systemic Inflammation and Modulating Gut Microbiota

Purpose

Xianglian Zhixie Tablet (XLZXT), a classical traditional Chinese medicine formulation, is commonly used to treat Ulcerative Colitis (UC) in China. However, the therapeutic mechanisms of XLZXT for UC have yet to be fully understood. This study aimed to investigate the curative benefits of XLZXT and its associated mechanisms for healing UC in mice.

Methods

In the present study, the 1% dextran sulfate sodium (DSS) solution was used to establish the UC model in C57BL/6N mice. To investigate the therapeutic effects of XLZXT on DSS-induced UC mice, several parameters were measured, including DAI score, colon length, spleen index, pathological changes in colon tissue, and levels of inflammatory factors in plasma and colon tissue. By investigating the gut microbiota, assessing the levels of intestinal mucosal protein expression, and looking at the proteins involved in the TLR4/MyD88/NF-B p65 signaling pathway, the mechanisms of XLZXT impact on UC were investigated. Mouse feces were examined for patterns of gut microbiota expression using high-throughput sequencing of 16S rRNA.

Results

XLZXT effectively alleviated UC symptoms and colon pathological damage in DSS-induced UC mice. It improved body weight loss, stool consistency, and hematochezia, while also repairing colon damage. Moreover, it down-regulated pro-inflammatory cytokines (such as TNF-α, IL-1β, and IL-6), and up-regulated anti-inflammatory cytokines (such as IL-10). XLZXT also increased the expression of MUC-2, Occludin and ZO-1, while decreasing the expression of NF-κB, MyD88 and TLR4. Additionally, it regulated gut microbiota disorder by increasing the abundance of beneficial bacteria and reducing the adhesion of intestinal harmful bacteria.

Conclusion

XLZXT demonstrated therapeutic effects on DSS-induced UC mice. The mechanisms may be associated with repairing the intestinal mucosal barrier, regulating the TLR4/MyD88/NF-κB p65 signaling pathway, and restoring the balance of gut microbiota.

Plasma Bile Acid Profiling and Modulation of Secreted Mucin 5AC in Cholangiocarcinoma

Studies investigating the potential role of circulating bile acids (BAs) as diagnostic biomarkers for cholangiocarcinoma (CCA) are sparse and existing data do not adjust for confounding variables. Furthermore, the mechanism by which BAs affect the expression of the oncogenic mucin 5AC (MUC5AC) has never been investigated. We performed a case-control study to characterise the profile of circulating BAs in patients with CCA (n = 68) and benign biliary disease (BBD, n = 48) with a validated liquid chromatography-tandem mass spectrometry technique. Odd ratios (OR) for CCA associations were calculated with multivariable logistic regression models based on a directed acyclic graph structure learning algorithm. The most promising BAs were then tested in an in vitro study to investigate their interplay in modulating MUC5AC expression. The total concentration of BAs was markedly higher in patients with CCA compared with BBD controls and accompanied by a shift in BAs profile toward a higher proportion of primary conjugated BAs (OR = 1.50, CI: 1.14 to 1.96, p = 0.003), especially taurochenodeoxycholic acid (TCDCA, OR = 42.29, CI: 3.54 to 504.63, p = 0.003) after multiple adjustments. Western blot analysis of secreted MUC5AC in human primary cholangiocytes treated with primary conjugated BAs or with TCDCA alone allowed us to identify a novel 230 kDa isoform, possibly representing a post-translationally modified MUC5AC specie.

Uncovering the Gut-Liver Axis Biomarkers for Predicting Metabolic Burden in Mice

Western diet (WD) intake, aging, and inactivation of farnesoid X receptor (FXR) are risk factors for metabolic and chronic inflammation-related health issues ranging from metabolic dysfunction-associated steatotic liver disease (MASLD) to dementia. The progression of MASLD can be escalated when those risks are combined. Inactivation of FXR, the receptor for bile acid (BA), is cancer prone in both humans and mice. The current study used multi-omics including hepatic transcripts, liver, serum, and urine metabolites, hepatic BAs, as well as gut microbiota from mouse models to classify those risks using machine learning. A linear support vector machine with K-fold cross-validation was used for classification and feature selection. We have identified that increased urine sucrose alone achieved 91% accuracy in predicting WD intake. Hepatic lithocholic acid and serum pyruvate had 100% and 95% accuracy, respectively, to classify age. Urine metabolites (decreased creatinine and taurine as well as increased succinate) or increased gut bacteria (Dorea, Dehalobacterium, and Oscillospira) could predict FXR deactivation with greater than 90% accuracy. Human disease relevance is partly revealed using the metabolite-disease interaction network. Transcriptomics data were also compared with the human liver disease datasets. WD-reduced hepatic Cyp39a1 (cytochrome P450 family 39 subfamily a member 1) and increased Gramd1b (GRAM domain containing 1B) were also changed in human liver cancer and metabolic liver disease, respectively. Together, our data contribute to the identification of noninvasive biomarkers within the gut-liver axis to predict metabolic status.

Sex different effect of antibiotic and probiotic treatment on intestinal microbiota composition in chemically induced liver injury rats

Differences in the gut microbiota and metabolic processes between males and females may explain differences in the risk of liver injury; however, the sex-specific effects of antibiotics and probiotics on these relationships are not clear. We evaluated differences in the gut microbiota and the risk of liver injury between male and female rats after the oral administration of antibiotics or probiotics followed by a period of diethylnitrosamine treatment to chemically induce liver injuryusing high-throughput sequencing of fecal microbiota combined with histological analyses of liver and colon tissues. Our results suggest that the ratio of gram-positive to gram-negative bacteria in kanamycin-treated rats was significantly higher than that of other groups, and this difference persisted for the duration of the experiment. Antibiotics significantly changed the composition of the gut microbiota of experimental rats. Clindamycin caused more diethylnitrosamine-induced damage to livers of male rats. Probiotics did not influencethe gut microbiota; however, they hadprotective effects against liver injury induced by diethylnitrosamine, especially in female rats. These results strengthen our understanding of sex differences in the indirect effects of antibiotics or probiotics on metabolism and liver injury in hosts via the gut microbiota.

Commensal microbiota regulate renal gene expression in a sex-specific manner

The gut microbiome impacts host gene expression not only in the colon but also at distal sites including the liver, white adipose tissue, and spleen. The gut microbiome also influences the kidney and is associated with renal diseases and pathologies; however, a role for the gut microbiome to modulate renal gene expression has not been examined. To determine if microbes modulate renal gene expression, we used whole organ RNA sequencing to compare gene expression in C57Bl/6 mice that were germ free (lacking gut microbiota) versus conventionalized (gut microbiota reintroduced using an oral gavage of a fecal slurry composed of mixed stool). 16S sequencing showed that male and female mice were similarly conventionalized, although Verrucomicrobia was higher in male mice. We found that renal gene expression was differentially regulated in the presence vs. absence of microbiota and that these changes were largely sex specific. Although microbes also influenced gene expression in the liver and large intestine, most differentially expressed genes (DEGs) in the kidney were not similarly regulated in the liver or large intestine. This demonstrates that the influence of the gut microbiota on gene expression is tissue specific. However, a minority of genes (n = 4 in males and n = 6 in females) were similarly regulated in all three tissues examined, including genes associated with circadian rhythm (period 1 in males and period 2 in females) and metal binding (metallothionein 1 and metallothionein 2 in both males and females). Finally, using a previously published single-cell RNA-sequencing dataset, we assigned a subset of DEGs to specific kidney cell types, revealing clustering of DEGs by cell type and/or sex.NEW & NOTEWORTHY It is unknown whether the microbiome influences host gene expression in the kidney. Here, we utilized an unbiased, bulk RNA-sequencing approach to compare gene expression in the kidneys of male and female mice with or without gut microbiota. This report demonstrates that renal gene expression is modulated by the microbiome in a sex- and tissue-specific manner.

Apigenin Alleviated High-Fat-Diet-Induced Hepatic Pyroptosis by Mitophagy-ROS-CTSB-NLRP3 Pathway in Mice and AML12 Cells

Apigenin is considered the most-known natural flavonoid and is abundant in a wide variety of fruits and vegetables. A high fat diet (HFD) can induce liver injury and hepatocyte death in multiple ways. Pyroptosis is an innovative type of programmed cell death. Moreover, excessive pyroptosis of hepatocytes leads to liver injury. We used HFD to induce liver cell pyroptosis in C57BL/6J mice in this work. After gavage of apigenin, apigenin can significantly reduce the level of lactate dehydrogenase (LDH) in liver tissue ignited by HFD and reduce the levels of NLRP3 (NOD-like receptor family pyrin domain containing 3), the N-terminal domain of GSDMD (GSDMD-N), cleaved-caspase 1, cathepsin B (CTSB), interleukin-1β (IL-1β) and interleukin-18 (IL-18) protein expression and the colocalization of NLRP3 and CTSB and increase the level of lysosomal associated membrane protein-1 (LAMP-1) protein expression, thus alleviating cell pyroptosis. In a further in vitro mechanism study, we find that palmitic acid (PA) can induce pyroptosis in AML12 cells. After adding apigenin, apigenin can clear the damaged mitochondria through mitophagy and reduce the generation of intracellular reactive oxygen species (ROS), thus alleviating CTSB release caused by lysosomal membrane permeabilization (LMP), reducing the LDH release caused by PA and reducing the levels of NLRP3, GSDMD-N, cleaved-caspase 1, CTSB, IL-1β, and IL-18 protein expression. By adding the mitophagy inhibitor cyclosporin A (CsA), LC3-siRNA, the CTSB inhibitor CA-074 methyl ester (CA-074 Me), and the NLRP3 inhibitor MCC950, the aforementioned results were further confirmed. Therefore, our results show that HFD-fed and PA can damage mitochondria, promote the production of intracellular ROS, enhance the lysosomal membrane permeabilization (LMP), and cause the leakage of CTSB, thus activating the NLRP3 inflammatory body and inducing pyroptosis in C57BL/6J mice and AML12 cells, while apigenin alleviates this phenomenon through the mitophagy-ROS-CTSB-NLRP3 pathway.

The essential roles of FXR in diet and age influenced metabolic changes and liver disease development: a multi-omics study

BACKGROUND

Aging and diet are risks for metabolic diseases. Bile acid receptor farnesoid X receptor (FXR) knockout (KO) mice develop metabolic liver diseases that progress into cancer as they age, which is accelerated by Western diet (WD) intake. The current study uncovers the molecular signatures for diet and age-linked metabolic liver disease development in an FXR-dependent manner.

METHODS

Wild-type (WT) and FXR KO male mice, either on a healthy control diet (CD) or a WD, were euthanized at the ages of 5, 10, or 15 months. Hepatic transcriptomics, liver, serum, and urine metabolomics as well as microbiota were profiled.

RESULTS

WD intake facilitated hepatic aging in WT mice. In an FXR-dependent manner, increased inflammation and reduced oxidative phosphorylation were the primary pathways affected by WD and aging. FXR has a role in modulating inflammation and B cell-mediated humoral immunity which was enhanced by aging. Moreover, FXR dictated neuron differentiation, muscle contraction, and cytoskeleton organization in addition to metabolism. There were 654 transcripts commonly altered by diets, ages, and FXR KO, and 76 of them were differentially expressed in human hepatocellular carcinoma (HCC) and healthy livers. Urine metabolites differentiated dietary effects in both genotypes, and serum metabolites clearly separated ages irrespective of diets. Aging and FXR KO commonly affected amino acid metabolism and TCA cycle. Moreover, FXR is essential for colonization of age-related gut microbes. Integrated analyses uncovered metabolites and bacteria linked with hepatic transcripts affected by WD intake, aging, and FXR KO as well as related to HCC patient survival.

CONCLUSION

FXR is a target to prevent diet or age-associated metabolic disease. The uncovered metabolites and microbes can be diagnostic markers for metabolic disease.

Prebiotic mechanisms of resistant starches from dietary beans and pulses on gut microbiome and metabolic health in a humanized murine model of aging

Dietary pulses, being a rich source of fiber and proteins, offer an ideal and inexpensive food choice for older adults to promote gut and metabolic health. However, the prebiotic effects of dietary pulses-derived resistant starches (RS), compared to RS from cereals and tubers, remain relatively underexplored, particularly in context to their gut modulatory potential in old age. We herein investigate the prebiotic effects of pulses-derived RS on the gut microbiome and intestinal health in aged (60-week old) mice colonized with human microbiota. C57B6/J mice were fed for 20 weeks with either a western-style high-fat diet (control; CTL) or CTL diet supplemented (5% w/w) with RS from pinto beans (PTB), black-eyed-peas (BEP), lentils (LEN), chickpeas (CKP), or inulin (INU; reference control). We find that the RS supplementation modulates gut microbiome in a sex-dependent manner. For instance, CKP enriched α-diversity only in females, while β-diversity deviated for both sexes. Further, different RS groups exhibited distinct microbiome differences at bacterial phyla and genera levels. Notably, LEN fostered Firmicutes and depleted Proteobacteria abundance, whereas Bacteroidota was promoted by CKP and INU. Genus Dubosiella increased dominantly in males for all groups except PTB, whilst Faecalibaculum decreased in females by CKP and INU groups. Linear discriminant analysis effect size (LEfSe) and correlational analyzes reveal RS-mediated upregulation of key bacterial genera associated with short-chain fatty acids (butyrate) production and suppression of specific pathobionts. Subsequent machine-learning analysis validate decreased abundance of notorious genera, namely, Enterococcus, Odoribacter, Desulfovibrio, Alistipes and Erysipelatoclostridium among RS groups. CKP and LEN groups partly protected males against post-prandial glycemia. Importantly, RS ameliorated high-fat diet-induced gut hyperpermeability and enhanced expression of tight-junction proteins (claudin-1 and claudin-4), which were more pronounced for LEN. In addition, IL10 upregulation was more prominent for LEN, while TNF-α was downregulated by LEN, CKP, and INU. Together, these findings demonstrate that RS supplementation beneficially modulates the gut microbiome with a reduction in gut leakiness and inflammation, indicating their prebiotic potential for functional food and nutritional applications.

Gestation and lactation triphenyl phosphate exposure disturbs offspring gut microbiota in a sex-dependent pathway

Triphenyl phosphate (TPhP) is an Organophosphate flame retardant (OPFR) that has been widely used in many commercial products. Following its widely usage, its health risk has been concerned. In this study, mice were exposed to TPhP (1 mg/kg) during pregnancy and lactation (E0-PND21), the effect of TPhP on gut microbiota and its role in TPhP mediated lipid metabolism disturbance of offspring was investigated. Our results showed that TPhP disturbed the gut microbiota in dam or offspring at different extent, with male offspring experiencing major effects. Both the composition, abundance or network of gut microbiome was affected in male offspring. In male offspring, expression of genes along gut-liver axis including FXR, CYP7A1, SREBP-1c and ChREBP was significantly up-regulated, and expression of SHP, FGF15 and ASBT was significantly down-regulated. Consistent with this, lipid accumulation in the liver, and increased level of triglyceride, total cholestrol and total bile acid in the serum was observed. The changed abundance of Ruminococcaceae, Clostridiaceae, and Bacteroidaceae shows strong correlation with disturbed lipid metabolism in male offspring. Our research showed that indirect TPhP exposure during early life stage could affect the gut microbiota and gene expression along gut-liver axis in offspring at sex-dependent pathways, with males experiencing more effects.

Sex, puberty, and the gut microbiome

In brief

Sex differences in the gut microbiome may impact multiple aspects of human health and disease. In this study, we review the evidence for microbial sex differences in puberty and adulthood and discuss potential mechanisms driving differentiation of the sex-specific gut microbiome.

Abstract

In humans, the gut microbiome is strongly implicated in numerous sex-specific physiological processes and diseases. Given this, it is important to understand how sex differentiation of the gut microbiome occurs and how these differences contribute to host health and disease. While it is commonly believed that the gut microbiome stabilizes after 3 years of age, our review of the literature found considerable evidence that the gut microbiome continues to mature during and after puberty in a sex-dependent manner. We also review the intriguing, though sparse, literature on potential mechanisms by which host sex may influence the gut microbiome, and vice versa, via sex steroids, bile acids, and the immune system. We conclude that the evidence for the existence of a sex-specific gut microbiome is strong but that there is a dearth of research on how host-microbe interactions lead to this differentiation. Finally, we discuss the types of future studies needed to understand the processes driving the maturation of sex-specific microbial communities and the interplay between gut microbiota, host sex, and human health.

Potential biological contributers to the sex difference in multiple sclerosis progression

Multiple sclerosis (MS) is an immune-mediated disease that targets the myelin sheath of central nervous system (CNS) neurons leading to axon injury, neuronal death, and neurological progression. Though women are more highly susceptible to developing MS, men that develop this disease exhibit greater cognitive impairment and accumulate disability more rapidly than women. Magnetic resonance imaging and pathology studies have revealed that the greater neurological progression seen in males correlates with chronic immune activation and increased iron accumulation at the rims of chronic white matter lesions as well as more intensive whole brain and grey matter atrophy and axon loss. Studies in humans and in animal models of MS suggest that male aged microglia do not have a higher propensity for inflammation, but may become more re-active at the rim of white matter lesions as a result of the presence of pro-inflammatory T cells, greater astrocyte activation or iron release from oligodendrocytes in the males. There is also evidence that remyelination is more efficient in aged female than aged male rodents and that male neurons are more susceptible to oxidative and nitrosative stress. Both sex chromosome complement and sex hormones contribute to these sex differences in biology.

Urolithin A Attenuates Helicobacter pylori-Induced Damage In Vivo

Urolithin A (UA) is a metabolite produced in the gut following the consumption of ellagic acid (EA) rich foods. EA has shown anti-inflammatory, antioxidant, and anticancer properties. Because EA is poorly absorbed in the gastrointestinal tract, urolithins are considered to play a major role in bioactivity. Helicobacter pylori (H. pylori) infection is the most common chronic bacterial infection all over the world. It is potentially hazardous to humans because of its relationship to various gastrointestinal diseases. In this study, we investigated the effect of UA on inflammation by H. pylori. The results indicated that UA attenuated H. pylori-induced inflammation in vitro and in vivo. UA also reduced the secretion of H. pylori virulence factors and tissue injuries in mice. Furthermore, UA decreased the relative abundance of Helicobacteraceae in feces of H. pylori-infected mice. In summary, taking UA effectively inhibited the injury caused by H. pylori.

Abnormal bile acid metabolism is an important feature of gut microbiota and fecal metabolites in patients with slow transit constipation

Destructions in the intestinal ecosystem are implicated with changes in slow transit constipation (STC), which is a kind of intractable constipation characterized by colonic motility disorder. In order to deepen the understanding of the structure of the STC gut microbiota and the relationship between the gut microbiota and fecal metabolites, we first used 16S rRNA amplicon sequencing to evaluate the gut microbiota in 30 STC patients and 30 healthy subjects. The α-diversity of the STC group was changed to a certain degree, and the β-diversity was significantly different, which indicated that the composition of the gut microbiota of STC patients was inconsistent with healthy subjects. Among them, Bacteroides, Parabacteroides, Desulfovibrionaceae, and Ruminiclostridium were significantly upregulated, while Subdoligranulum was significantly downregulated. The metabolomics showed that different metabolites between the STC and the control group were involved in the process of bile acids and lipid metabolism, including taurocholate, taurochenodeoxycholate, taurine, deoxycholic acid, cyclohexylsulfamate, cholic acid, chenodeoxycholate, arachidonic acid, and 4-pyridoxic acid. We found that the colon histomorphology of STC patients was significantly disrupted, and TGR5 and FXR were significantly downregulated. The differences in metabolites were related to changes in the abundance of specific bacteria and patients’ intestinal dysfunction. Analysis of the fecal genomics and metabolomics enabled separation of the STC from controls based on random forest model prediction [STC vs. control (14 gut microbiota and metabolite biomarkers)—Sensitivity: 1, Specificity: 0.877]. This study provided a perspective for the diagnosis and intervention of STC related with abnormal bile acid metabolism.

Gender Differences in Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) has currently emerged as the most common liver disorder in both developed and developing countries. It has been observed that NAFLD exhibits sexual dimorphism, and there is limited understanding on the sex differences in adults with NAFLD. Nonalcoholic fatty liver disease shows marked differences in prevalence and severity with regards to gender. There are considerable biological disparities between males and females attributed to differences in the chromosomal makeup and sex hormone levels, distinct from the gender differences resulting from the sociocultural influences that lead to differences in lifestyle, which have a significant impact on the pathogenesis of this complex disorder. A multitude of factors contributes to the gender disparities seen and need to be researched in-depth to better understand the mechanisms behind them and the therapeutic measures that can be taken. In this article, we will review the gender disparities seen in NAFLD, as well as recent studies highlighting certain gender-specific factors contributing to its varying prevalence and severity.

HOW TO CITE THIS ARTICLE

Nagral A, Bangar M, Menezes S, et al. Gender Differences in Nonalcoholic Fatty Liver Disease. Euroasian J Hepato-Gastroenterol 2022;12(Suppl 1):S19-S25.

Mini-Review: Gut-Microbiota and the Sex-Bias in Autoimmunity - Lessons Learnt From Animal Models

It is well appreciated that there is a female preponderance in the development of most autoimmune diseases. Thought to be due to a complex interplay between sex chromosome complement and sex-hormones, however, the exact mechanisms underlying this sex-bias remain unknown. In recent years, there has been a focus on understanding the central pathogenic role of the bacteria that live in the gut, or the gut-microbiota, in the development of autoimmunity. In this review, we discuss evidence from animal models demonstrating that the gut-microbiota is sexually dimorphic, that there is a bidirectional relationship between the production of sex-hormones and the gut-microbiota, and that this sexual dimorphism within the gut-microbiota may influence the sex-bias observed in autoimmune disease development. Collectively, these data underline the importance of considering sex as a variable when investigating biological pathways that contribute to autoimmune disease risk.

Short-Term High-Fat Diet Fuels Colitis Progression in Mice Associated With Changes in Blood Metabolome and Intestinal Gene Expression

Clinical cases and animal experiments show that high-fat (HF) diet is involved in inflammatory bowel disease (IBD), but the specific mechanism is not fully clear. A close association between long-term HF-induced obesity and IBD has been well-documented. However, there has been limited evaluation of the impact of short-term HF feeding on the risk of intestinal inflammation, particularly on the risk of disrupted metabolic homeostasis. In this study, we analyzed the metabolic profile and tested the vulnerability of 2,4,6-trinitrobenzenesulfonic acid (TNBS)-induced colitis after short-term HF feeding in mice. The results showed that compared with the control diet (CD), the fatty acid (FA), amino acid (AA), and bile acid (BA) metabolisms of mice in the HF group were significantly changed. HF-fed mice showed an increase in the content of saturated and unsaturated FAs and a decrease in the content of tryptophan (Trp). Furthermore, the disturbed spatial distribution of taurocholic acid (TCA) in the ileum and colon was identified in the HF group using matrix-assisted laser desorption/ionization-mass spectrometry imaging (MALDI-MSI). After HF priming, mice on TNBS induction were subjected to more severe colonic ulceration and histological damage compared with their CD counterparts. In addition, TNBS enema induced higher gene expressions of mucosal pro-inflammatory cytokines under HF priming conditions. Overall, our results show that HF may promote colitis by disturbing lipid, AA, and BA metabolic homeostasis and inflammatory gene expressions.

Dietary nutrients mediate crosstalk between bile acids and gut microbes in animal host metabolism

Bile acids (BAs) are synthesized by liver, then gut microbes embellish primary BAs into secondary BAs with diverse and biological functions. Over the past few decades, amounts of evidences demonstrated the importance of gut microbes in BA metabolism. There is also significant evidence that BAs are regarded as cell signals in gut-liver, gut-brain, and gut-testis axis. Moreover, the interaction between BAs and gut microbes plays a key role not only in the absorption and metabolism of nutrients, but the regulation of immune function. Herein, we collected the major information of the BA metabolism-related bacteria, nutrients, and cell signals, focused on the possible molecular mechanisms by "Microbes-Bile acids" crosstalk, highlighted the gut-liver, gut-brain, and gut-testis axis, and discussed the possibility and application of the regulation of BA metabolism by nutrients.

Non-alcoholic fatty liver disease: a multi-system disease influenced by ageing and sex, and affected by adipose tissue and intestinal function

In recent years, a wealth of factors are associated with increased risk of developing non-alcoholic fatty liver disease (NAFLD) and NAFLD is now thought to increase the risk of multiple extra-hepatic diseases. The aim of this review is first to focus on the role of ageing and sex as key, poorly understood risk factors in the development and progression of NAFLD. Secondly, we aim to discuss the roles of white adipose tissue (WAT) and intestinal dysfunction, as producers of extra-hepatic factors known to further contribute to the pathogenesis of NAFLD. Finally, we aim to summarise the role of NAFLD as a multi-system disease affecting other organ systems beyond the liver. Both increased age and male sex increase the risk of NAFLD and this may be partly driven by alterations in the distribution and function of WAT. Similarly, changes in gut microbiota composition and intestinal function with ageing and chronic overnutrition are likely to contribute to the development of NAFLD both directly (i.e. by affecting hepatic function) and indirectly via exacerbating WAT dysfunction. Consequently, the presence of NAFLD significantly increases the risk of various extra-hepatic diseases including CVD, type 2 diabetes mellitus, chronic kidney disease and certain extra-hepatic cancers. Thus changes in WAT and intestinal function with ageing and chronic overnutrition contribute to the development of NAFLD – a multi-system disease that subsequently contributes to the development of other chronic cardiometabolic diseases.

Gender dimorphism in IgA subclasses in T2-high asthma

Immunoglobulin A (Chan in J Allergy Clin Immunol 134:1394-14014e4, 2014), the second most abundant immunoglobulin in serum, plays an important role in mucosal homeostasis. In human serum, there are two subclasses of IgA, IgA1 (≅ 90%) and IgA2 (≅ 10%), transcribed from two distinct heavy chain constant regions. This study evaluated the serum concentrations of total IgA, IgA1, and IgA2, and total IgG, IgG1, IgG2, IgG3, and IgG4 in T2-high asthmatics compared to healthy controls and the presence of gender-related variations of immunoglobulins. Total IgA levels were increased in asthmatics compared to controls. Even more marked was the increase in total IgA in male asthmatics compared to healthy male donors. IgA1 were increased only in male, but not in female asthmatics, compared to controls. Concentrations of IgG2, but not IgG1, IgG3, and IgG4, were reduced in asthmatics compared to controls. IgG4 levels were reduced in female compared to male asthmatics. In female asthmatics, IgA and IgA1 levels were increased in postmenopause compared to premenopause. IgA concentrations were augmented in mild, but not severe asthmatics. A positive correlation was found between IgA levels and the age of patients and an inverse correlation between serum concentrations of IgA2 and IgE in asthmatics. A positive correlation between total IgA or IgA2 and IgG2 was found in asthmatics. These results highlight a gender dimorphism in IgA subclasses in male and female T2-high asthmatics. More adequate consideration of immunological gender disparity in asthma may open new opportunities in personalized medicine by optimizing diagnosis and targeted therapy.

Identification and Spatial Visualization of Dysregulated Bile Acid Metabolism in High-Fat Diet-Fed Mice by Mass Spectral Imaging

Changes in overall bile acid (BA) levels and specific BA metabolites are involved in metabolic diseases, gastrointestinal, and liver cancer. BAs have become established as important signaling molecules that enable fine-tuned inter-tissue communication within the enterohepatic circulation. The liver, BAs site of production, displayed physiological and functional zonal differences in the periportal zone versus the centrilobular zone. In addition, BA metabolism shows regional differences in the intestinal tract. However, there is no available method to detect the spatial distribution and molecular profiling of BAs within the enterohepatic circulation. Herein, we demonstrated the application in mass spectrometry imaging (MSI) with a high spatial resolution (3 μm) plus mass accuracy matrix-assisted laser desorption ionization (MALDI) to imaging BAs and N-1-naphthylphthalamic acid (NPA). Our results could clearly determine the zonation patterns and regional difference characteristics of BAs on mouse liver, ileum, and colon tissue sections, and the relative content of BAs based on NPA could also be ascertained. In conclusion, our method promoted the accessibility of spatial localization and quantitative study of BAs on gastrointestinal tissue sections and demonstrated that MALDI-MSI was a valuable tool to investigate and locate several BA molecules in different tissue types leading to a better understanding of the role of BAs behind the gastrointestinal diseases.

Gut feelings: the microbiota-gut-brain axis on steroids

The intricate connection between central and enteric nervous systems is well established with emerging evidence linking gut microbiota function as a significant new contributor to gut-brain axis signaling. Several microbial signals contribute to altered gut-brain communications, with steroids representing an important biological class that impacts central and enteric nervous system function. Neuroactive steroids contribute pathologically to neurological disorders, including dementia and depression, by modulating the activity of neuroreceptors. However, limited information is available on the influence of neuroactive steroids on the enteric nervous system and gastrointestinal function. In this review, we outline how steroids can modulate enteric nervous system function by focusing on their influence on different receptors that are present in the intestine in health and disease. We also highlight the potential role of the gut microbiota in modulating neuroactive steroid signaling along the gut-brain axis.

Influence of Three Probiotics Strains, Lactobacillus rhamnosus GG, Bifidobacterium animalis subsp. Lactis BB-12 and Saccharomyces boulardii CNCM I-745 on the Biochemical and Haematological Profiles and Body Weight of Healthy Rabbits

Simple Summary

Currently, probiotics are used as growth promoters on a large scale to improve the productivity of several animals’ species within the aim of reducing the presence of antibiotic residues in animal products consumed by humans. Several reports evidenced the positive effect of probiotic supplementation on the growth performances and health of rabbits, mainly through the balance of the intestinal microbiota of the host animal. Therefore, certain probiotics, including Lactobacilli, Bifidobacteria, Saccharomyces, can improve the biochemical and haematological profiles, especially in production animals. In this context, this study was performed on rabbits for the economic importance they play as a source of meat proteins in developing countries and their use as experimental models in research and biomedicine. This study then aimed to evaluate the effect of three strains of probiotics: Lactobacillus rhamnosus GG Bifidobacterium animalis subsp. Lactis BB-12 and Saccharomyces boulardii CNCM I-745, on the biochemical and haematological parameters and their influence on the rabbit’s weight of the ITELV2006 strain. The findings evidenced that the probiotic strain affected the biochemical and haematological parameters. Further, the strains showed a positive effect on the weight gain of the rabbits.

Abstract

This study aimed to investigate the effects of three strains of probiotics, these being Lactobacillus rhamnosus GG, Bifidobacterium animalis subsp. Lactis BB-12 and Saccharomyces boulardii CNCM I-745, on the body weight, animal performances and blood parameters of rabbits (male and female) of the ITELV2006 strain. The supplementation of the feed of the rabbits with the three probiotic strains allowed observing positive effects on most of the biochemical and haematological parameters investigated during a period of 60 days (30 days of supplementation and 30 days without treatment). Further, there was a significant improvement in the body weight of the rabbits at the end of the experiment. The effect of the three probiotics investigated in this trial was found to be related to the sex of the rabbits and to the intake period (duration). Ultimately, these findings raise the possibility of using probiotics to investigate in an in-depth and specific manner based on fixed factors such as the strain, the gender and age of the animals, the main underlying mechanisms and effects, which would allow achieving optimal and adapted health benefits and sustainable production. In the context of animal production, it is worth investigating in a targeted study the effect of the three strains on muscle growth and development and finding evidence of the possible consequences on meat quality traits of the rabbits supplemented with probiotics.

Probiotics Improve Gastrointestinal Function and Life Quality in Pregnancy

We studied whether probiotics were beneficial for hormonal change-associated dysbiosis, which may influence the enteric nervous system and GI function during early pregnancy. The study was 16 days consisting of two cycles of six daily probiotics mainly Lactobacillus and 2 days without probiotics. Daily surveys were conducted to monitor GI function and life quality. A subset of the participants who contributed fecal specimens was used for microbiota metagenomic sequencing, metabolomics, and quantification of bacterial genes to understand potential underlying mechanisms. Statistical analyses were done by generalized linear mixed-effects models. Thirty-two obstetric patients and 535 daily observations were included. The data revealed that probiotic supplementation significantly reduced the severity of nausea, vomiting, constipation, and improved life quality. Moreover, a low copy number of fecal bsh (bile salt hydrolase), which generates free bile acids, was associated with high vomiting scores and probiotic intake increased fecal bsh. In exploratory analysis without adjusting for multiplicity, a low fecal α-tocopherol, as well as a high abundance of Akkemansia muciniphila, was associated with high vomiting scores and times, respectively. The potential implications of these biomarkers in pregnancy and GI function are discussed. Probiotics likely produce free bile acids to facilitate intestinal mobility and metabolism.

Hepatic sexual dimorphism - implications for non-alcoholic fatty liver disease

The liver is often thought of as a single functional unit, but both its structural and functional architecture make it highly multivalent and adaptable. In any given physiological situation, the liver can maintain metabolic homeostasis, conduct appropriate inflammatory responses, carry out endobiotic and xenobiotic transformation and synthesis reactions, as well as store and release multiple bioactive molecules. Moreover, the liver is a very resilient organ. This resilience means that chronic liver diseases can go unnoticed for decades, yet culminate in life-threatening clinical complications once the adaptive capacity of the liver is overwhelmed. Non-alcoholic fatty liver disease (NAFLD) predisposes individuals to cirrhosis and increases liver-related and cardiovascular disease-related mortality. This Review discusses the accumulating evidence of sexual dimorphism in NAFLD, which is currently rarely considered in preclinical and clinical studies. Increased awareness of the mechanistic causes of hepatic sexual dimorphism could lead to improved understanding of the biological processes that are dysregulated in NAFLD, to the identification of relevant therapeutic targets and to improved risk stratification of patients with NAFLD undergoing therapeutic intervention.

Aldehyde Dehydrogenase Mutation Exacerbated High-Fat-Diet-Induced Nonalcoholic Fatty Liver Disease with Gut Microbiota Remodeling in Male Mice

Simple Summary

ALDH2, mitochondrial aldehyde dehydrogenase 2, is a critical enzyme involved in ethanol clearance in acetaldehyde metabolism. The prevalence of the ALDH2*2 variant is 45% in the Taiwanese population. ALDH2 reportedly has protective properties on myocardial damage, stroke, and diabetic retina damage. However, the effects of ALDH2 in modulation of metabolic syndromes remain unclear. The study evaluated the roles of ALDH2 in a high-fat-diet-induced metabolic syndrome in mice. We explored the effects of ALDH2 gene on NAFLD and potential association with gut microbiota.

Abstract

Mitochondrial aldehyde dehydrogenase 2 (ALDH2) is a critical enzyme involved in ethanol clearance in acetaldehyde metabolism and plays a key role in protecting the liver. The ALDH2*2 mutation causes a significant decrease in acetaldehyde scavenging capacity, leading to the accumulation of acetaldehyde after consuming alcohol. The prevalence of the ALDH2*2 variant is in 45% of Taiwanese individuals. ALDH2 reportedly has protective properties on myocardial damage, stroke, and diabetic retina damage. However, the effects of ALDH2 in the modulation of metabolic syndromes remain unclear. This study evaluates the roles of ALDH2 in a high-fat-diet-induced metabolic syndrome in mice. Male (M) and female (F) wild-type (WT) and ALDH2 knock-in C57BL/6J mice (4–5 weeks old) were fed a high-fat diet for 16 weeks. Results showed that the body and white-adipose-tissue weights were significantly increased in ALDH2-M compared to those in the other groups. We observed markedly elevated serum levels of alanine transaminase and glucose. Oral glucose-tolerance test and homeostasis-model assessment of insulin resistance (HOMA-IR) values were significantly higher in ALDH2-M mice than those in WT-M mice, with no observable differences in female mice. Abundant steatosis and inflammatory cells were observed in ALDH2-M, with significantly decreased expression of hepatic genes IRS2, GLUT4, and PGC-1α compared to that in WT-M. ALDH2 gene mutation also affected the β-diversity of gut microbiota in ALDH2-M resulting in the decreased abundance of Actinobacteria and an increase in Deferribacteres. Our results suggest that potential changes in gut microbiota may be associated with the defective ALDH2 exacerbation of high-fat-diet-induced liver diseases in male mice. However, female mice were not affected, and sex hormones may be an important factor that requires further investigation.

Roles of Sex Hormones and Gender in the Gut Microbiota

The distribution of gut microbiota varies according to age (childhood, puberty, pregnancy, menopause, and old age) and sex. Gut microbiota are known to contribute to gastrointestinal (GI) diseases such as irritable bowel syndrome, inflammatory bowel disease, and colon cancer; however, the exact etiology remains elusive. Recently, sex and gender differences in GI diseases and their relation to gut microbiota has been suggested. Furthermore, the metabolism of estrogen and androgen was reported to be related to the gut microbiome. As gut microbiome is involved in the excretion and circulation process of sex hormones, the concept of “microgenderome” indicating the role of sex hormone on the gut microbiota has been suggested. However, further research is needed for this concept to be universally accepted. In this review, we summarize sex- and gender-differences in gut microbiota and the interplay of microbiota and GI diseases, focusing on sex hormones. We also describe the metabolic role of the microbiota in this regard. Finally, current subjects, such as medication including probiotics, are briefly discussed.

Sex differences feed into nuclear receptor signaling along the digestive tract

Sex differences in physiology are noted in clinical and animal studies. However, mechanisms underlying these observed differences between males and females remain elusive. Nuclear receptors control a wide range of physiological pathways and are expressed in the gastrointestinal tract, including the mouth, stomach, liver and intestine. We investigated the literature pertaining to ER, AR, FXR, and PPAR regulation and highlight the sex differences in nutrient metabolism along the digestive system. We chose these nuclear receptors based on their metabolic functions, and hormonal actions. Intriguingly, we noted an overlap in target genes of ER and FXR that modulate mucosal integrity and GLP-1 secretion, whereas overlap in target genes of PPARα with ER and AR modulate lipid metabolism. Sex differences were seen not only in the basal expression of nuclear receptors, but also in activation as their endogenous ligand concentrations fluctuate depending on nutrient availability. Finally, in this review, we speculate that interactions between the nuclear receptors may influence overall metabolic decisions in the gastrointestinal tract in a sex-specific manner.

Bile Acids, Their Receptors, and the Gut Microbiota

Bile acids (BAs) are a family of hydroxylated steroids secreted by the liver that aid in the breakdown and absorption of dietary fats. BAs also function as nutrient and inflammatory signaling molecules, acting through cognate receptors, to coordinate host metabolism. Commensal bacteria in the gastrointestinal tract are functional modifiers of the BA pool, affecting composition and abundance. Deconjugation of host BAs creates a molecular network that inextricably links gut microtia with their host. In this review we highlight the roles of BAs in mediating this mutualistic relationship with a focus on those events that impact host physiology and metabolism.

Fxr signaling and microbial metabolism of bile salts in the zebrafish intestine

Bile salt synthesis, secretion into the intestinal lumen, and resorption in the ileum occur in all vertebrate classes. In mammals, bile salt composition is determined by host and microbial enzymes, affecting signaling through the bile salt-binding transcription factor farnesoid X receptor (Fxr). However, these processes in other vertebrate classes remain poorly understood. We show that key components of hepatic bile salt synthesis and ileal transport pathways are conserved and under control of Fxr in zebrafish. Zebrafish bile salts consist primarily of a C27 bile alcohol and a C24 bile acid that undergo multiple microbial modifications including bile acid deconjugation that augments Fxr activity. Using single-cell RNA sequencing, we provide a cellular atlas of the zebrafish intestinal epithelium and uncover roles for Fxr in transcriptional and differentiation programs in ileal and other cell types. These results establish zebrafish as a nonmammalian vertebrate model for studying bile salt metabolism and Fxr signaling.

Gut microbiome responses in the metabolism of human dietary components: Implications in health and homeostasis

The gut microbiome and its link with human health and disease have gained a lot of attention recently. The microbiome executes its functions in the host by carrying out the transformation of dietary components and/or de novo synthesis of various essential nutrients. The presence of complex microbial communities makes it difficult to understand the host-microbiome interplay in the metabolism of dietary components. This review attempts to uncover the incredible role of the gut microbiome in the metabolism of dietary components, diet-microbiome interplay, and restoration of the microbiome. The in silico analysis performed in this study elucidates the functional description of essential/hub genes involved in the amino acid degradation pathway, which are mutually present in the host and its gut microbiome. Hence, the computational model helps comprehend the inter-and intracellular molecular networks between humans and their microbial partners.

Xanthohumol ameliorates Diet-Induced Liver Dysfunction via Farnesoid X Receptor-Dependent and Independent Signaling

The farnesoid X receptor (FXR) plays a critical role in the regulation of lipid and bile acid (BA) homeostasis. Hepatic FXR loss results in lipid and BA accumulation, and progression from hepatic steatosis to nonalcoholic steatohepatitis (NASH). This study aimed to evaluate the effects of xanthohumol (XN), a hop-derived compound mitigating metabolic syndrome, on liver damage induced by diet and FXR deficiency in mice. Wild-type (WT) and liver-specific FXR-null mice (FXR^Liver−/−) were fed a high-fat diet (HFD) containing XN or the vehicle formation followed by histological characterization, lipid, BA and gene profiling. HFD supplemented with XN resulted in amelioration of hepatic steatosis and decreased BA concentrations in FXR^Liver−/− mice, the effect being stronger in male mice. XN induced the constitutive androstane receptor (CAR), pregnane X receptor (PXR) and glucocorticoid receptor (GR) gene expression in the liver of FXR^Liver−/− mice. These findings suggest that activation of BA detoxification pathways represents the predominant mechanism for controlling hydrophobic BA concentrations in FXR^Liver−/− mice. Collectively, these data indicated sex-dependent relationship between FXR, lipids and BAs, and suggest that XN ameliorates HFD-induced liver dysfunction via FXR-dependent and independent signaling.

Dietary anthocyanins as potential natural modulators for the prevention and treatment of non-alcoholic fatty liver disease: A comprehensive review

Nonalcoholic fatty liver disease (NAFLD) refers to a metabolic syndrome linked with type 2 diabetes mellitus, obesity, and cardiovascular diseases. It is characterized by the accumulation of triglycerides in the hepatocytes in the absence of alcohol consumption. The prevalence of NAFLD has abruptly increased worldwide, with no effective treatment yet available. Anthocyanins (ACNs) belong to the flavonoid subclass of polyphenols, are commonly present in various edible plants, and possess a broad array of health-promoting properties. ACNs have been shown to have strong potential to combat NAFLD. We critically assessed the literature regarding the pharmacological mechanisms and biopharmaceutical features of the action of ACNs on NAFLD in humans and animal models. We found that ACNs ameliorate NAFLD by improving lipid and glucose metabolism, increasing antioxidant and anti-inflammatory activities, and regulating gut microbiota dysbiosis. In conclusion, ACNs have potential to attenuate NAFLD. However, further mechanistic studies are required to confirm these beneficial impacts of ACNs on NAFLD.

Age-specific microbiota in altering host inflammatory and metabolic signaling as well as metabolome based on the sex

Background

Metabolism is sex-different, and the direct link between gut microbiota and aging-associated metabolic changes needs to be established in both sexes.

Methods

Gene expression, metabolic and inflammatory signaling, gut microbiota profile, and metabolome were studied during aging and after fecal microbiota transplantation (FMT) in mice of both sexes.

Results

Our data revealed young female mice and aged male mice were the most insulin sensitive and resistant group, respectively. In addition, aging reduced sex difference in insulin sensitivity. Such age- and sex-dependent metabolic phenotypes were accompanied by shifted gut microbiota profile and altered abundance of bacterial genes that produce butyrate, propionate, and bile acids. After receiving feces from the aged males (AFMT), the most insulin-resistant group, recipients of both sexes had increased hepatic inflammation and serum endotoxin. However, AFMT only increased insulin resistance in female mice and abolished sex difference in insulin sensitivity. Additionally, such changes were accompanied by narrowed sex difference in metabolome. Metabolomics data revealed that age-associated insulin resistance in males was accompanied by increased sugar alcohols and dicarboxylic acids as well as reduced aromatic and branched-chain amino acids. Further, receiving feces from the young females (YFMT), the most insulin-sensitive group, reduced body weight and fasting blood glucose in male recipients and improved insulin sensitivity in females, leading to enhanced sex differences in insulin sensitivity and metabolome.

Conclusions

Aging systemically affected inflammatory and metabolic signaling based on the sex. Gut microbiome is age and sex-specific, which affects inflammation and metabolism in a sex-dependent manner.