Neoagarotetraose Alleviates Atherosclerosis via Modulating Cholesterol and Bile Acid Metabolism in ApoE-/- Mice

Atherosclerosis is closely associated with metabolic disorders such as cholesterol accumulation, bile acid metabolism, and gut dysbiosis. Neoagarotetraose supplementation has been shown to inhibit obesity and alleviate type 2 diabetes, but its effects on modulating the development of atherosclerosis remain unexplored. Therefore, the present study was conducted to investigate the protective effects and potential mechanisms of neoagarotetraose on high-fat, high-cholesterol diet (HFHCD)-induced atherosclerosis in ApoE-/- mice. The results showed that neoagarotetraose supplementation decreased the atherosclerotic lesion area by 50.1% and the aortic arch lesion size by 80.4% compared to the HFHCD group. Furthermore, neoagarotetraose supplementation led to a significant reduction in hepatic lipid content, particularly non-high-density lipoprotein cholesterol. It also resulted in a substantial increase in total bile acid content in both urine and fecal samples by 3.0-fold and 38.7%, respectively. Moreover, neoagarotetraose supplementation effectively downregulated the intestinal farnesoid X receptor by 35.8% and modulated the expressions of its associated genes in both the liver and intestine. In addition, correlation analysis revealed strong associations between gut microbiota composition and fecal bile acid levels. These findings highlight the role of gut microbiota in neoagarotetraose-mitigating atherosclerosis in HFHCD-fed ApoE-/- mice. This study indicates the potential of neoagarotetraose as a functional dietary supplement for the prevention of atherosclerosis.

Effects of bile acid metabolism on intestinal health of livestock and poultry

Bile acids are synthesised in the liver and are essential amphiphilic steroids for maintaining the balance of cholesterol and energy metabolism in livestock and poultry. They can be used as novel feed additives to promote fat utilisation in the diet and the absorption of fat-soluble substances in the feed to improve livestock performance and enhance carcass quality. With the development of understanding of intestinal health, the balance of bile acid metabolism is closely related to the composition and growth of livestock intestinal microbiota, inflammatory response, and metabolic diseases. This paper systematically reviews the effects of bile acid metabolism on gut health and gut microbiology in livestock. In addition, our paper summarised the role of bile acid metabolism in performance and disease control.

Zearalenone Decreases Food Intake by Disrupting the Gut-Liver-Hypothalamus Axis Signaling via Bile Acids

Zearalenone (ZEN) is a mycotoxin that is harmful to humans and animals. In this study, female and male rats were exposed to ZEN, and the results showed that ZEN reduced the farnesoid X receptor (FXR) expression levels in the liver and disrupted the enterohepatic circulation of bile acids (BAs). A decrease in food intake induced by ZEN was negatively correlated with an increase in the level of total BAs. BA-targeted metabolomics revealed that ZEN increased glycochenodeoxycholic acid levels and decreased the ratio of conjugated BAs to unconjugated BAs, which further increased the hypothalamic FXR expression levels. Preventing the increase in total BA levels induced by ZEN via Lactobacillus rhamnosus GG intervention restored the appetite. In conclusion, ZEN disrupted the enterohepatic circulation of BAs to decrease the level of food intake. This study reveals a possible mechanism by which ZEN affects food intake and provides a new approach to decrease the toxic effects of ZEN.

Modulation of Gut Microbial Metabolism by Cyanidin-3-O-Glucoside in Mitigating Polystyrene-Induced Colonic Inflammation: Insights from 16S rRNA Sequencing and Metabolomics

Microplastics derived from plastic waste have emerged as a pervasive environmental pollutant with potential transfer and accumulation through the food chain, thus posing risks to both ecosystems and human health. The gut microbiota, tightly intertwined with metabolic processes, exert substantial influences on host physiology by utilizing dietary compounds and generating bacterial metabolites such as tryptophan and bile acid. Our previous studies have demonstrated that exposure to microplastic polystyrene (PS) disrupts the gut microbiota and induces colonic inflammation. Meanwhile, intervention with cyanidin-3-O-glucoside (C3G), a natural anthocyanin derived from red bayberry, could mitigate colonic inflammation by reshaping the gut bacterial composition. Despite these findings, the specific influence of gut bacteria and their metabolites on alleviating colonic inflammation through C3G intervention remains incompletely elucidated. Therefore, employing a C57BL/6 mouse model, this study aims to investigate the mechanisms underlying how C3G modulates gut bacteria and their metabolites to alleviate colonic inflammation. Notably, our findings demonstrated the efficacy of C3G in reversing the elevated levels of pro-inflammatory cytokines (IL-6, IL-1β, and TNF-α) and the upregulation of mRNA expression (Il-6, Il-1β, and Tnf-α) induced by PS exposure. Meanwhile, C3G effectively inhibited the reduction in levels (IL-22, IL-10, and IL-4) and the downregulation of mRNA expression (Il-22, Il-10, and Il-4) of anti-inflammatory cytokines induced by PS exposure. Moreover, PS-induced phosphorylation of the transcription factor NF-κB in the nucleus, as well as the increased level of protein expression of iNOS and COX-2 in the colon, were inhibited by C3G. Metabolisms of gut bacterial tryptophan and bile acids have been extensively implicated in the regulation of inflammatory processes. The 16S rRNA high-throughput sequencing disclosed that PS treatment significantly increased the abundance of pro-inflammatory bacteria (Desulfovibrio, norank_f_Oscillospiraceae, Helicobacter, and Lachnoclostridium) while decreasing the abundance of anti-inflammatory bacteria (Dubosiella, Akkermansia, and Alistipes). Intriguingly, C3G intervention reversed these pro-inflammatory changes in bacterial abundances and augmented the enrichment of bacterial genes involved in tryptophan and bile acid metabolism pathways. Furthermore, untargeted metabolomic analysis revealed the notable upregulation of metabolites associated with tryptophan metabolism (shikimate, l-tryptophan, indole-3-lactic acid, and N-acetylserotonin) and bile acid metabolism (3b-hydroxy-5-cholenoic acid, chenodeoxycholate, taurine, and lithocholic acid) following C3G administration. Collectively, these findings shed new light on the protective effects of dietary C3G against PS exposure and underscore the involvement of specific gut bacterial metabolites in the amelioration of colonic inflammation.

Navigating Perinatal Challenges: A Comprehensive Review of Cholestasis of Pregnancy and Its Impact on Maternal and Fetal Health

Cholestasis of pregnancy (CP), or intrahepatic CP (ICP), represents a condition peculiar to pregnancy, marked by impaired bile acid flow and consequent accumulation in the maternal bloodstream. Primarily emerging in the third trimester, CP is linked with considerable risks to both the mother and fetus, including heightened incidences of preterm birth, fetal distress, and stillbirth, alongside maternal complications such as intense pruritus and liver dysfunction. Despite its clinical significance, the etiology of CP, which involves genetic, hormonal, and environmental factors, remains partially understood. This comprehensive review delves into the physiology and pathophysiology of CP, outlines its clinical manifestations and diagnostic criteria, and discusses the associated maternal and fetal complications. Furthermore, it evaluates current management strategies, prognostic implications, and potential long-term effects on maternal and child health. It also explores future research directions, emphasizing the need for advancements in understanding the pathophysiology of CP, developing novel therapeutic interventions, and improving risk stratification models. By offering a thorough overview of CP, this review aims to enhance clinical awareness, guide management practices, and identify areas requiring further investigation, ultimately contributing to better health outcomes for affected women and their babies.

Ginsenoside Rb1, Compound K and 20(S)-Protopanaxadiol Attenuate High-Fat Diet-Induced Hyperlipidemia in Rats via Modulation of Gut Microbiota and Bile Acid Metabolism

Hyperlipidemia, characterized by elevated serum lipid concentrations resulting from lipid metabolism dysfunction, represents a prevalent global health concern. Ginsenoside Rb1, compound K (CK), and 20(S)-protopanaxadiol (PPD), bioactive constituents derived from Panax ginseng, have shown promise in mitigating lipid metabolism disorders. However, the comparative efficacy and underlying mechanisms of these compounds in hyperlipidemia prevention remain inadequately explored. This study investigates the impact of ginsenoside Rb1, CK, and PPD supplementation on hyperlipidemia in rats induced by a high-fat diet. Our findings demonstrate that ginsenoside Rb1 significantly decreased body weight and body weight gain, ameliorated hepatic steatosis, and improved dyslipidemia in HFD-fed rats, outperforming CK and PPD. Moreover, ginsenoside Rb1, CK, and PPD distinctly modified gut microbiota composition and function. Ginsenoside Rb1 increased the relative abundance of Blautia and Eubacterium, while PPD elevated Akkermansia levels. Both CK and PPD increased Prevotella and Bacteroides, whereas Clostridium-sensu-stricto and Lactobacillus were reduced following treatment with all three compounds. Notably, only ginsenoside Rb1 enhanced lipid metabolism by modulating the PPARγ/ACC/FAS signaling pathway and promoting fatty acid β-oxidation. Additionally, all three ginsenosides markedly improved bile acid enterohepatic circulation via the FXR/CYP7A1 pathway, reducing hepatic and serum total bile acids and modulating bile acid pool composition by decreasing primary/unconjugated bile acids (CA, CDCA, and β-MCA) and increasing conjugated bile acids (TCDCA, GCDCA, GDCA, and TUDCA), correlated with gut microbiota changes. In conclusion, our results suggest that ginsenoside Rb1, CK, and PPD supplementation offer promising prebiotic interventions for managing HFD-induced hyperlipidemia in rats, with ginsenoside Rb1 demonstrating superior efficacy.

Bifidobacterium breve Protects the Intestinal Epithelium and Mitigates Inflammation in Colitis via Regulating the Gut Microbiota-Cholic Acid Pathway

In this study, we aimed to explore the protective effects of Bifidobacterium in colitis mice and the potential mechanisms. Results showed that Bifidobacterium breve (B. breve) effectively colonized the intestinal tract and alleviated colitis symptoms by reducing the disease activity index. Moreover, B. breve mitigated intestinal epithelial cell damage, inhibited the pro-inflammatory factors, and upregulated tight junction (TJ)-proteins. Gut microbiota and metabolome analysis found that B. breve boosted bile acid-regulating genera (such as Bifidobacterium and Clostridium sensu stricto 1), which promoted bile acid deconjugation in the intestine. Notably, cholic acid (CA) was closely associated with the expression levels of inflammatory factors and TJ-proteins (p < 0.05). Our in vitro cell experiments further confirmed that CA (20.24 ± 4.53 pg/mL) contributed to the inhibition of lipopolysaccharide-induced tumor necrosis factor-α expression (49.32 ± 5.27 pg/mL) and enhanced the expression of TJ-proteins (Occludin and Claudin-1) and MUC2. This study suggested that B. breve could be a probiotic candidate for use in infant foods.

Environmentally Relevant Concentrations of Microplastic Exposure Cause Cholestasis and Bile Acid Metabolism Dysregulation through a Gut-Liver Loop in Mice

The massive production of plastics causes the ubiquitous existence of microplastics (MPs) in the biota, therefore, posing exposure risks and potential health concerns to human beings. However, the exact mechanisms of MPs-induced toxicities and abnormalities are largely unknown. In this study, we developed a mouse model of gavage polystyrene microplastics (PS MPs) for 30 days. We found that PS MPs can damage the intestinal barrier, accumulate in the liver tissue, and cause injury. The liver and intestine are both highly associated with bile acid (BA) metabolism. Indeed, we found that PS MPs dysregulate BA synthesis and efflux-related gene expression in the liver, causing cholestasis. Tandemly, PS MPs alter the ratio of primary to secondary BA in the feces by affecting the composition of the intestinal flora. At last, PS MPs alter mice's fecal BA profile, which affects normal BA metabolism. Taken together, the present study provides robust data on the mechanism of toxicity of MPs causing the disturbance of BA metabolism via a 4-step gut-liver loop.

Therapeutic Role of Polyphenol Extract from Prunus cerasifera Ehrhart on Non-Alcoholic Fatty Liver

Prunus cerasifera Ehrhart (P. cerasifera) flourishes uniquely in the arid landscapes of Xinjiang, China. Preliminary studies have revealed the therapeutic potential of its polyphenol extract (PPE) in mitigating liver lipid accumulation in mice fed a high-fat diet. We established a mouse model that was subjected to a continuous high-fat diet for 24 weeks and administered PPE to investigate the effects of PPE on cholesterol and BA metabolism in NAFLD mice. The results showed that PPE administration (200 and 400 mg/kg/day, BW) led to a reduction in liver TC, an increase in liver T-BAs, and normalization of the disrupted fecal BA profile. Concurrently, it decreased levels of lipotoxic BAs and inhibited hepatic cholesterol synthesis (evidenced by reduced HMGCR activity) and intestinal cholesterol absorption (indicated by lower ACAT2 levels) while enhancing intestinal cholesterol efflux (via LXRα, ABCA1, ABCG5, and ABCG8) and stimulating hepatic BA synthesis (CYP7A1, CYP27A1) and secretion (BSEP). PPE thus led to a significant reduction in lipotoxic BAs metabolized by gut microbiota and a downregulation of the BA secretion pathway under its influence. Our findings reveal the therapeutic effect of PPE on NAFLD mice via regulating cholesterol and BA metabolism, providing a theoretical basis for exploring the potential functions of P. cerasifera.

Bile Acid Metabolic Profiles and Their Correlation with Intestinal Epithelial Cell Proliferation and Barrier Integrity in Suckling Piglets

Bile acids (BAs) are crucial for maintaining intestinal epithelial homeostasis. However, the metabolic changes in BAs and the communication between intestinal epithelial cells (IECs) in infants after birth remain unclear. This study aims to elucidate the BA profiles of newborn piglets (NPs) and suckling piglets (SPs), and to investigate their regulatory effects on IEC proliferation and barrier integrity, as well as the potential underlying mechanisms. In this study, compared with NPs, there were significant increases in serum triglycerides, total cholesterol, glucose, and albumin levels for SPs. The total serum BA content in SPs exhibited an obvious increase. Moreover, the expression of BA synthase cytochrome P450 27A1 (CYP27A1) was increased, and the ileal BA receptor Takeda G-coupled protein receptor 5 (TGR5) and proliferation marker Ki-67 were upregulated and showed a strong positive correlation through a Spearman correlation analysis, whereas the expression of farnesoid X receptor (FXR) and occludin was markedly downregulated in SPs and also revealed a strong positive correlation. These findings indicate that the increased synthesis and metabolism of BAs may upregulate TGR5 and downregulate FXR to promote IEC proliferation and influence barrier function; this offers a fresh perspective and evidence for the role of BAs and BA receptors in regulating intestinal development in neonatal pigs.

Correlation between Peptacetobacter hiranonis, the baiCD Gene, and Secondary Bile Acids in Dogs

Bile acid metabolism is a key pathway modulated by intestinal microbiota. Peptacetobacter (Clostridium) hiranonis has been described as the main species responsible for the conversion of primary into secondary fecal unconjugated bile acids (fUBA) in dogs. This multi-step biochemical pathway is encoded by the bile acid-inducible (bai) operon. We aimed to assess the correlation between P. hiranonis abundance, the abundance of one specific gene of the bai operon (baiCD), and secondary fUBA concentrations. In this retrospective study, 133 fecal samples were analyzed from 24 dogs. The abundances of P. hiranonis and baiCD were determined using qPCR. The concentration of fUBA was measured by gas chromatography-mass spectrometry. The baiCD abundance exhibited a strong positive correlation with secondary fUBA (ρ = 0.7377, 95% CI (0.6461, 0.8084), p < 0.0001). Similarly, there was a strong correlation between P. hiranonis and secondary fUBA (ρ = 0.6658, 95% CI (0.5555, 0.7532), p < 0.0001). Animals displaying conversion of fUBA and lacking P. hiranonis were not observed. These results suggest P. hiranonis is the main converter of primary to secondary bile acids in dogs.

Identification of Proteome-Based Immune Subtypes of Early Hepatocellular Carcinoma and Analysis of Potential Metabolic Drivers

Hepatocellular carcinoma (HCC) is a leading cause of cancer-related mortality worldwide, ranking fourth in frequency. The relationship between metabolic reprogramming and immune infiltration has been identified as having a crucial impact on HCC progression. However, a deeper understanding of the interplay between the immune system and metabolism in the HCC microenvironment is required. In this study, we used a proteomic dataset to identify three immune subtypes (IM1-IM3) in HCC, each of which has distinctive clinical, immune, and metabolic characteristics. Among these subtypes, IM3 was found to have the poorest prognosis, with the highest levels of immune infiltration and T-cell exhaustion. Furthermore, IM3 showed elevated glycolysis and reduced bile acid metabolism, which was strongly correlated with CD8 T cell exhaustion and regulatory T cell accumulation. Our study presents the proteomic immune stratification of HCC, revealing the possible link between immune cells and reprogramming of HCC glycolysis and bile acid metabolism, which may be a viable therapeutic strategy to improve HCC immunotherapy.

Integrated multi-omics reveal gut microbiota-mediated bile acid metabolism alteration regulating immunotherapy responses to anti-α4β7-integrin in Crohn's disease

Gut microbiota and related metabolites are both crucial factors that significantly influence how individuals with Crohn's disease respond to immunotherapy. However, little is known about the interplay among gut microbiota, metabolites, Crohn's disease, and the response to anti-α4β7-integrin in current studies. Our research utilized 2,4,6-trinitrobenzene sulfonic acid to induce colitis based on the humanized immune system mouse model and employed a combination of whole-genome shotgun metagenomics and non-targeted metabolomics to investigate immunotherapy responses. Additionally, clinical cases with Crohn's disease initiating anti-α4β7-integrin therapy were evaluated comprehensively. Particularly, 16S-rDNA gene high-throughput sequencing and targeted bile acid metabolomics were conducted at weeks 0, 14, and 54. We found that anti-α4β7-integrin therapy has shown significant potential for mitigating disease phenotypes in remission-achieving colitis mice. Microbial profiles demonstrated that not only microbial composition but also microbially encoded metabolic pathways could predict immunotherapy responses. Metabonomic signatures revealed that bile acid metabolism alteration, especially elevated secondary bile acids, was a determinant of immunotherapy responses. Especially, the remission mice significantly enriched the proportion of the beneficial Lactobacillus and Clostridium genera, which were correlated with increased gastrointestinal levels of BAs involving lithocholic acid and deoxycholic acid. Moreover, most of the omics features observed in colitis mice were replicated in clinical cases. Notably, anti-α4β7 integrin provided sustained therapeutic benefits in clinical remitters during follow-up, and long-lasting remission was linked to persistent changes in the microbial-related bile acids. In conclusion, gut microbiota-mediated bile acid metabolism alteration could play a crucial role in regulating immunotherapy responses to anti-α4β7-integrin in Crohn's disease. Therefore, the identification of prognostic microbial signals facilitates the advancement of targeted probiotics that activate anti-inflammatory bile acid metabolic pathways, thereby improving immunotherapy responses. The integrated multi-omics established in our research provide valuable insights into potential mechanisms that impact treatment responses in complex diseases.

Ethanol extract of Pueraria lobata improve acute myocardial infarction in rats via regulating gut microbiota and bile acid metabolism

BACKGROUND AND AIM

Acute myocardial infarction (AMI) is a multifactorial disease with high mortality rate worldwide. Ethanol extract of Pueraria lobata (EEPL) has been widely used in treating cardiovascular diseases in China. This study aimed to explore the underlying therapeutic mechanism of EEPL in AMI rats.

EXPERIMENTAL PROCEDURE

We first evaluated the anti-AMI efficacy of EEPL through immunohistochemistry staining and biochemical indexes. Then, UPLC-MS/MS, 16S rDNA, and shotgun metagenomic sequencing were used to analyze the alterations in bile acid metabolism and intestinal flora. Finally, the influence of EEPL on ilem bile acid metabolism, related enzymes expression, and transporter proteins expression in rats were verified by mass spectrometry image and ELISA.

KEY RESULTS

The results showed that EEPL can reduce cardiac impairment in AMI rats. Besides, EEPL effectively increased bile acid levels and regulated gut microbiota disturbance in AMI rats via increasing CYP7A1 expression and restoring intestinal microbiota diversity, separately. Moreover, it can increase bile acids reabsorption and fecal excretion through inhibiting FXR-FGF15 signaling pathway and increasing OST-α expression, which associated with Lachnoclostridium.

CONCLUSIONS AND IMPLICATIONS

Our findings demonstrated that EEPL alleviated AMI partially by remediating intestinal dysbiosis and promoting bile acid biosynthesis, which provided new targets for AMI treatment.

Saikosaponin a ameliorates diet-induced fatty liver via regulating intestinal microbiota and bile acid profile in laying hens

Fatty liver hemorrhagic syndrome is a widespread metabolic disease in laying hens that decreases egg production and even causes death in severe cases. Many traditional Chinese medicine ingredients, such as saikosaponin a (SSa), have been shown to alleviate fatty liver, but the underlying mechanisms remain unclear. In this study, we aimed to explore the alleviation of dietary SSa on excessive hepatic lipid deposition and the interactions between intestinal microbiota and bile acid (BA) in laying hens. Fifty-four 35-wk-old laying hens were randomly allocated into 3 treatment groups with 6 replicates (3 birds per replicate) and fed with a basal diet (CON), high-energy and low-protein diet (HELP), and HELP diet with 30 mg/kg SSa (HELP + SSa). SSa reversed diet-induced egg production rate decrease (P < 0.05). SSa could potently ameliorate HELP-induced accumulation of hepatic cholesterol and liver injury via the increase (P < 0.05) of mRNA expression of BA synthesis gene, such as cholesterol 7 alpha-hydroxylase 1. SSa treatment alleviated gut dysbiosis, especially reducing (P < 0.05) the relative abundance of bile salt hydrolase (BSH)-producing bacteria such as Lactobacillus, Bifidobacterium, and Turicibacter. Ileal BA metabolomic analysis revealed that SSa increased (P < 0.05) the content of tauro-conjugated BAs, mainly taurochenodeoxycholic acid and tauro-α-muricholic acid. The mRNA expression of farnesoid X receptor (FXR) and fibroblast growth factor 19 were decreased (P < 0.05) in intestine, which was associated with increased gene expression of enzymes in the BA synthesis that reduced the levels of cholesterol. Moreover, SSa treatment inhibited intestinal BA reabsorption via decreasing (P < 0.05) the mRNA expression of apical sodium-dependent bile acid transporter. Our findings indicated that SSa reduced liver cholesterol accumulation and alleviated fatty liver in laying hens through microbiota-BA-intestinal FXR crosstalk.

Mitochondrial GpC and CpG DNA Hypermethylation Cause Metabolic Stress-Induced Mitophagy and Cholestophagy

Metabolic dysfunction-associated steatotic liver disease (MASLD) is characterized by a constant accumulation of lipids in the liver. This hepatic lipotoxicity is associated with a dysregulation of the first step in lipid catabolism, known as beta oxidation, which occurs in the mitochondrial matrix. Eventually, this dysregulation will lead to mitochondrial dysfunction. To evaluate the possible involvement of mitochondrial DNA methylation in this lipid metabolic dysfunction, we investigated the functional metabolic effects of mitochondrial overexpression of CpG (MSssI) and GpC (MCviPI) DNA methyltransferases in relation to gene expression and (mito)epigenetic signatures. Overall, the results show that mitochondrial GpC and, to a lesser extent, CpG methylation increase bile acid metabolic gene expression, inducing the onset of cholestasis through mito-nuclear epigenetic reprogramming. Moreover, both increase the expression of metabolic nuclear receptors and thereby induce basal overactivation of mitochondrial respiration. The latter promotes mitochondrial swelling, favoring lipid accumulation and metabolic-stress-induced mitophagy and autophagy stress responses. In conclusion, both mitochondrial GpC and CpG methylation create a metabolically challenging environment that induces mitochondrial dysfunction, which may contribute to the progression of MASLD.

Non-12α-Hydroxylated Bile Acids Improve Piglet Growth Performance by Improving Intestinal Flora, Promoting Intestinal Development and Bile Acid Synthesis

As an emulsifier and bioactive substance, bile acids (BAs) participate in the absorption of nutrients and in various physiological processes. The objective of this experiment was to investigate the effects of non-12α-hydroxylated BAs (including hyocholic acid, hyodeoxycholic acid and chenodeoxycholic acid, from now on referred to as NBAs) on growth performance, BAs metabolism and the intestinal flora of piglets. The experiment included four groups, with eight piglets per group. The four groups of pigs were fed 0, 60, 120 and 180 mg/kg of NBAs, respectively. The results show that adding NBAs significantly increased the final weight (FW), average daily feed intake (ADFI), average daily gain (ADG), and digestibility of crude fat (EE) and organic matter (OM) in piglets (p < 0.05). Adding NBAs significantly increased the villus height (VH) of the jejunum and ileum (p < 0.05). In addition, NBAs supplementation increased the content of urea nitrogen (BUN) and creatinine (CREA) as well as the ratio of urea nitrogen to creatinine (BUN/CREA) in serum (p < 0.05). Adding NBAs can affect the genes related to BAs enterohepatic circulation. Specifically, adding NBAs significantly decreased the relative mRNA abundance of FXR in the liver (p < 0.05), significantly increased the relative mRNA abundance of CYP27A1 (p < 0.05), and significantly increased the relative mRNA abundance of NTCP (p < 0.05). Adding NBAs also significantly decreased the relative mRNA abundance of FXR in the ileum (p < 0.05). In the full-length 16S rDNA sequencing analysis, ten biomarkers were found from the gate to the species level. NBAs mainly enriched Lactobacillus_Johnsonii and decreased the abundance of Streptococcus_alactolyticus. Short-chain fatty acids (SCFAs) content in the colon was significantly increased (p < 0.05). These results indicate that NBAs supplementation can improve the growth performance of piglets, promote the development of the bile acid replacement pathway and improve intestinal flora.

Gut commensal Parabacteroides distasonis alleviates inflammatory arthritis

OBJECTIVE

Gut microbiota dysbiosis is closely linked to the pathogenesis of rheumatoid arthritis (RA). We aimed to identify potential probiotic gut microbes that can ameliorate the development of RA.

DESIGN

Microbiota profiling in patients with RA and healthy individuals was investigated via 16S rDNA bacterial gene sequencing and shotgun metagenomics. Collagen-induced arthritic mice and TNF-α transgenic mice were used to evaluate the roles of the gut commensal Parabacteroides distasonis in RA. The effects of P. distasonis-derived microbial metabolites on the differentiation of CD4+ T cells and macrophage polarisation were also investigated.

RESULTS

The relative abundance of P. distasonis in new-onset patients with RA and patients with RA with history of the disease was downregulated and this decrease was negatively correlated with Disease Activity Score-28 (DAS28). Oral treatment of arthritic mice with live P. distasonis (LPD) considerably ameliorated RA pathogenesis. LPD-derived lithocholic acid (LCA), deoxycholic acid (DCA), isolithocholic acid (isoLCA) and 3-oxolithocholic acid (3-oxoLCA) had similar and synergistic effects on the treatment of RA. In addition to directly inhibiting the differentiation of Th17 cells, 3-oxoLCA and isoLCA were identified as TGR5 agonists that promoted the M2 polarisation of macrophages. A specific synthetic inhibitor of bile salt hydrolase attenuated the antiarthritic effects of LPD by reducing the production of these four bile acids. The natural product ginsenoside Rg2 exhibited its anti-RA effects by promoting the growth of P. distasonis.

CONCLUSIONS

P. distasonis and ginsenoside Rg2 might represent probiotic and prebiotic agents in the treatment of RA.

Altered bile acid metabolism in skin tissues in response to ionizing radiation: deoxycholic acid (DCA) as a novel treatment for radiogenic skin injury

OBJECTIVE

Radiogenic skin injury (RSI) is a common complication during cancer radiotherapy or accidental exposure to radiation. The aim of this study is to investigate the metabolism of bile acids (BAs) and their derivatives during RSI.

METHODS

Rat skin tissues were irradiated by an X-ray linear accelerator. The quantification of BAs and their derivatives were performed by liquid chromatography-mass spectrometry (LC-MS)-based quantitative analysis. Key enzymes in BA biosynthesis were analyzed from single-cell RNA sequencing (scRNA-Seq) data of RSI in the human patient and animal models. The in vivo radioprotective effect of deoxycholic acid (DCA) was detected in irradiated SD rats.

RESULTS

Twelve BA metabolites showed significant differences during the progression of RSI. Among them, the levels of cholic acid (CA), DCA, muricholic acid (MCA), chenodeoxycholic acid (CDCA), glycocholic acid (GCA), glycohyodeoxycholic acid (GHCA), 12-ketolithocholic acid (12-ketoLCA) and ursodeoxycholic acid (UDCA) were significantly elevated in irradiated skin, whereas lithocholic acid (LCA), tauro-β-muricholic acid (Tβ-MCA) and taurocholic acid (TCA) were significantly decreased. Additionally, the results of scRNA-Seq indicated that genes involved in 7a-hydroxylation process, the first step in BA synthesis, showed pronounced alterations in skin fibroblasts or keratinocytes. The alternative pathway of BA synthesis is more actively altered than the classical pathway after ionizing radiation. In the model of rat radiogenic skin damage, DCA promoted wound healing and attenuated epidermal hyperplasia.

CONCLUSIONS

Ionizing radiation modulates the metabolism of BAs. DCA is a prospective therapeutic agent for the treatment of RSI.

Butyrate Protects against Clostridium difficile Infection by Regulating Bile Acid Metabolism

Clostridium difficile infection (CDI) is caused by a prevalent nosocomial enteric pathogen, leading to high morbidity and mortality. CDI recurrence after antibiotic treatment is high; therefore, it is necessary to develop novel therapeutics against this enteric pathogen. Butyrate is used to treat many diseases because it provides energy, has anti-inflammatory properties, and maintains intestinal barrier function. An anti-CDI effect for butyrate has been reported; however, the specific mechanism remains elusive. This study aimed to explore the potential role and mechanism of butyrate in the treatment of CDI. Using a CDI mouse model, we found that butyrate significantly inhibited CDI development by regulating bile acid metabolism. Dysregulation of fecal bile acid was significantly higher, and levels of short-chain fatty acids were significantly lower in patients with CDI than those in controls. In CDI mice, butyrate exhibited a protective role by enhancing barrier protection, exerting anti-inflammatory effects, and regulating bile acid metabolism. Butyrate treatment also regulated the production of bile salt hydrolase (BSH) flora and activated farnesoid X receptor (FXR), and its therapeutic effects were reduced in CDI mice treated with BSH or FXR inhibitors. Thus, butyrate treatment may serve as a novel therapeutic approach for patients with CDI. IMPORTANCE Here, we show that levels of fecal short-chain fatty acids (SCFAs), particularly butyrate, are reduced, and normal colon structure is damaged in patients with CDI compared with those in healthy individuals. Bile acid (BA) metabolic disorder in patients with CDI is characterized by increased primary BA levels and decreased secondary BAs. In mice, butyrate alters BA metabolism in CDI and may play a vital role in CDI treatment by promoting secondary BA metabolism. Lastly, butyrate-mediated therapeutic effects in CDI require FXR. Our findings demonstrate that butyrate treatment significantly decreases the severity of CDI-induced colitis in mice and affects BA metabolism and FXR activation, which provides a potential alternative treatment for CDI.

The Potential of Bile Acids as Biomarkers for Metabolic Disorders

Bile acids (BAs) are well known to facilitate the absorption of dietary fat and fat-soluble molecules. These unique steroids also function by binding to the ubiquitous cell membranes and nuclear receptors. As chemical signals in gut-liver axis, the presence of metabolic disorders such as nonalcoholic fatty liver disease (NAFLD), type 2 diabetes mellitus (T2DM), and even tumors have been reported to be closely related to abnormal levels of BAs in the blood and fecal metabolites of patients. Thus, the gut microbiota interacting with BAs and altering BA metabolism are critical in the pathogenesis of numerous chronic diseases. This review intends to summarize the mechanistic links between metabolic disorders and BAs in gut-liver axis, and such stage-specific BA perturbation patterns may provide clues for developing new auxiliary diagnostic means.

Distinct profiles of bile acid metabolism caused by gut microbiota in kidney transplantation recipients revealed by 16S rRNA gene sequencing

The present study sought to characterise the gut microbiota of subjects with kidney transplantation and healthy control to identify the distinct gut microbiota and analyse their potential function. We found that gut microbiota abundance had significant differences in subjects between the two groups. Line Discriminant Analysis (LDA) Effect Size (LEfSe) analysis showed that the bacterial taxa were differentially represented between the two groups, and the potential biomarkers at different taxonomic levels in kidney transplant recipients were Streptococcus, Enterococcaceae, and Ruminococcus. Phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt) Functional Inference analyses suggested that the difference in gut microbiota between the two groups was correlated with bile acid metabolism. In conclusion, gut microbiota abundance is different between the two groups, which is related to bile acid metabolism, and may influence the metabolic homeostasis of allograft recipients.

Corrigendum: Effects of Poria cocos extract on metabolic dysfunction-associated fatty liver disease via the FXR/PPARα-SREBPs pathway

[This corrects the article DOI: 10.3389/fphar.2022.1007274.].

Prevention of High-Fat-Diet-Induced Dyslipidemia by Lactobacillus plantarum LP104 through Mediating Bile Acid Enterohepatic Axis Circulation and Intestinal Flora

This work aimed to investigate the alleviative mechanism of Lactobacillus plantarum LP104 (LP104) isolated from kimchi on high-fat-diet-induced dyslipidemia by targeting the intestinal flora and bile acid (BA) metabolism. Oral administration of LP104 over 8 weeks reduced body weight gain and body fat, as well as ameliorating serum and hepatic dyslipidemia in HFD-fed C57BL/6N mice significantly. LP104 intervention also increased the ileal tauro-α/β-muricholic acid sodium salt (T-α-MCA or T-β-MCA) and tauroursodeoxycholic acid (TUDCA) concentrations to suppress the enterohepatic farnesoid X receptor/fibroblast growth factor 15-fibroblast growth factor receptor 4 (FXR/FGF15-FGFR4) signaling pathway, which stimulated the hepatic cholic acid (CA) and chenodeoxycholic acid (CDCA) de novo synthesis through using cholesterol. Then, LP104 treatment accelerated BA excretion with the feces and cholesterol efflux to improve HFD-caused hyperlipidemia effectively. The 16S rRNA gene high-throughput sequencing revealed that LP104 promoted intestinal flora rebalance by increasing the abundances of Bacteroides, Akkermansia, Lactobacillus, and Clostridium and decreasing the abundance of Oscillospira and Coprococcus. Meanwhile, Spearman correlation analysis demonstrated that the differential flora were closely related to BA signaling molecules including CA, CDCA, T-α-MCA, T-β-MCA, and TUDCA after LP104 intervention. These findings provided new evidence that LP104 had the potential to be used as a naturally functional food for the prevention of dyslipidemia.

Bacillus cereus Alters Bile Acid Composition and Alleviates High-Carbohydrate Diet-Induced Hepatic Lipid Accumulation in Nile Tilapia (Oreochromis niloticus)

A high-carbohydrate diet (HCD) can induce excessive fat accumulation in fish, and intestinal microbiota are thought to play important roles in host metabolism. Whether and how intestinal bacteria alleviate the HCD-induced metabolic disorders in fish have attracted more attention. Bacillus cereus was isolated from the intestine content of Nile tilapia. The control diet, high-carbohydrate diet (HC), and HC supplemented with B. cereus Su1 (HCS) were used to feed juvenile Nile tilapia for 8 weeks. The results of the present study showed that B. cereus Su1 supplementation decreased the serum glucose, triglycerides (TG), and reduced hepatic lipid accumulation compared with the HC group. The intestinal bacterial composition analysis suggested that HCS elevated bacterial diversity and the enriched bacteria were closely related to bile acid (BA) metabolism. Higher bile salt hydrolase (BSH) activity was found in the HCS group and B-targeted metabolomic analysis revealed that HCS increased BA content in the intestine and liver compared with HC, including unconjugated BAs (CA and CDCA) and conjugated BAs (TCA, GCA, TCDCA, GCDCA, TDCA, and TUDCA). Furthermore, a high-carbohydrate diet supplemented with B. cereus Su1 significantly enhanced the protein expression of the BA receptor farnesoid X receptor in the liver and decreased significantly the expression level of lipid synthesis-related genes and proteins, while it had no significant effect on lipolysis-related genes and proteins. This study found that B. cereus Su1 altered the intestinal microbiota and bile acid content and composition to regulate the lipid metabolism, revealing the function of the crosstalk among probiotics, intestinal microbiota, and BAs in ameliorating lipid accumulation induced by a high-carbohydrate diet in fish.

6α-hydroxylated bile acids mediate TGR5 signalling to improve glucose metabolism upon dietary fiber supplementation in mice

OBJECTIVE

Dietary fibres are essential for maintaining microbial diversity and the gut microbiota can modulate host physiology by metabolising the fibres. Here, we investigated whether the soluble dietary fibre oligofructose improves host metabolism by modulating bacterial transformation of secondary bile acids in mice fed western-style diet.

DESIGN

To assess the impact of dietary fibre supplementation on bile acid transformation by gut bacteria, we fed conventional wild-type and TGR5 knockout mice western-style diet enriched or not with cellulose or oligofructose. In addition, we used germ-free mice and in vitro cultures to evaluate the activity of bacteria to transform bile acids in the caecal content of mice fed with western-style diet enriched with oligofructose. Finally, we treated wild-type and TGR5 knockout mice orally with hyodeoxycholic acid to assess its antidiabetic effects.

RESULTS

We show that oligofructose sustains the production of 6α-hydroxylated bile acids from primary bile acids by gut bacteria when fed western-style diet. Mechanistically, we demonstrated that the effects of oligofructose on 6α-hydroxylated bile acids were microbiota dependent and specifically required functional TGR5 signalling to reduce body weight gain and improve glucose metabolism. Furthermore, we show that the 6α-hydroxylated bile acid hyodeoxycholic acid stimulates TGR5 signalling, in vitro and in vivo, and increases GLP-1R activity to improve host glucose metabolism.

CONCLUSION

Modulation of the gut microbiota with oligofructose enriches bacteria involved in 6α-hydroxylated bile acid production and leads to TGR5-GLP1R axis activation to improve body weight and metabolism under western-style diet feeding in mice.

Bifidobacterium pseudocatenulatum-Mediated Bile Acid Metabolism to Prevent Rheumatoid Arthritis via the Gut-Joint Axis

Early intervention in rheumatoid arthritis (RA) is critical for optimal treatment, but initiation of pharmacotherapy to prevent damage remains unsatisfactory currently. Manipulation of the gut microbiome and microbial metabolites can be effective in protecting against RA. Thus, probiotics can be utilized to explore new strategies for preventing joint damage. The aim of this study was to explore the metabolites and mechanisms by which Bifidobacterium pseudocatenulatum affects RA. Based on 16S rRNA sequencing and UPLC-MS/MS assays, we focused on bile acid (BA) metabolism. In a collagen-induced arthritis (CIA) mouse model, B. pseudocatenulatum prevented joint damage by protecting the intestinal barrier and reshaped gut microbial composition, thereby elevating bile salt hydrolase (BSH) enzyme activity and increasing the levels of unconjugated secondary BAs to suppress aberrant T-helper 1/17-type immune responses; however, these benefits were eliminated by the Takeda G protein-coupled receptor 5 (TGR5) antagonist SBI-115. The results suggested that a single bacterium, B. pseudocatenulatum, can prevent RA, indicating that prophylactic administration of probiotics may be an effective therapy.

Dietary supplementation with garcinol during late gestation alleviates disorders of bile acid metabolism and improves the performance of sows and newborn piglets

The present study was conducted to evaluate the effects of dietary garcinol supplementation during late gestation on bile acid metabolism and performance of sows. Sixty sows (Duroc × Yorkshire × Landrace; second- or third-parity; n = 20) with disorder of bile acid metabolism were randomly divided into three groups: control diet (CON; basal diet), basal diet with 200 mg garcinol (Low Gar), and basal diet with 600 mg garcinol (High Gar) per kg of feed. The body weight (BW); backfat thickness and litter size of the sows; and birth weight, weaning weight, and mortality of piglets were recorded. Sows' blood was collected for the measurements of hematological parameters and antioxidative and immune indexes, and indicators related to bile acid metabolism, respectively. The colostrum and fecal samples of the sows were also collected for analysis of colostrum composition and apparent total tract nutrient digestibility. Garcinol had no effect on the BW and backfat thickness of the sows but significantly decreased the mortality and number of weak litter (P < 0.05). Moreover, the white blood cell counts, superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase (CAT) activity in the plasma of the sows were increased more significantly (P < 0.05) in the garcinol groups than that in the CON group, whereas the malondialdehyde (MDA) content was decreased (P < 0.05). Dietary supplementation with garcinol significantly reduced TBA concentrations (P < 0.05). The content of immunoglobulin A (IgA) and immunoglobulin G (IgG) in the plasma and in colostrum of sows were increased more significantly (P < 0.05) in the garcinol groups than that in the CON group. In addition, dry matter (DM), Ash, and EE in the colostrum were similar between groups (P > 0.05), whereas the garcinol significantly increased the crude protein (CP) in the colostrum. The apparent total tract nutrient digestibility was similar between treatments. Garcinol treatment induced a gradually decreased (P > 0.05) the expression of genes involved in BA synthesis (CYP7A1, CYP8B1), BA uptake (NTCP, OATP1A2), BA secretion (BSEP and MRP2), BA detoxification (SULT2A1), and BA efflux into the blood circulation (OSTβ). Collectively, this study indicates that sows fed with garcinol in late gestation showed relieved bile acid metabolism disorder and improved sows performance, antioxidative status, colostrum protein content, showing promise in natural plant extract nutrition for sows with disorder of bile acid metabolism.

Resveratrol Modulates the Redox Response and Bile Acid Metabolism to Maintain the Cholesterol Homeostasis in Fish Megalobrama amblycephala Offered a High-Carbohydrate Diet

This study aimed to characterize the effects of resveratrol on the redox balance, cholesterol homeostasis and bile acid metabolism of Megalobrama amblycephala offered a high-carbohydrate diet. Fish (35.0 ± 0.15 g) were fed four diets including one control diet (32% nitrogen-free extract), one high-carbohydrate diet (45% nitrogen-free extract, HC), and the HC diet supplemented with different levels (0.04%, HCR1; 0.08%, HCR2) of resveratrol for 12 weeks. The HC diet-induced redox imbalance is characterized by increased MDA content and decreased T-SOD and CAT activities in the liver. Resveratrol attenuated this by up-regulating the transcription of Cu/Zn-sod, and increasing the activities of T-SOD, CAT, and GPX. The HC diet enhanced the cholesterol synthesis, but decreased the bile acid synthesis via up-regulating both hmgcr and acat2, and down-regulating cyp7a1, thus resulting in excessive cholesterol accumulation. Resveratrol supplement decreased cholesterol synthesis, and increased cholesterol uptake in the liver by down-regulating both hmgcr and acat2, and up-regulating ldlr. It also increased bile acid synthesis and biliary excretion by up-regulating cyp7a1, and down-regulating mrp2, oatp1, and oatp4 in the hindgut, thereby decreasing cholesterol accumulation. In conclusion, resveratrol improves the cholesterol homeostasis of Megalobrama amblycephala fed a high-carbohydrate diet by modulating the redox response and bile acid metabolism.

Effect of nicotine on cholesterol gallstone formation in C57BL/6J mice fed on a lithogenic diet

Gallstones are diseases of the biliary system caused by cholesterol supersaturation and/or deficiency in bile salts in bile. Early studies have shown that symptomatic gallstones are primarily a disease of non-smokers, raising the possibility that nicotine can prevent gallstone formation. The present study investigated the effect of nicotine on the formation of cholesterol gallstone in C57BL/6J mice. C57BL/6J mice (eight-weeks-old) were fed a normal or lithogenic diet (basic feed 82.45%, fat 15.8%, cholesterol 1.25% and sodium cholate 0.5%) and divided into five groups: normal diet (ND); ND + high dose nicotine (H); lithogenic diet (LD); LD + low dose nicotine (L) and LD + nicotine (H). They were treated with or without nicotine injection for 10 weeks. Nicotine treatment did not change the rate of cholesterol gallstone formation. There was no difference in TNFα, IL-1β and IL-6 among the five groups. The LD group showed the highest cholesterol levels and there was significant suppression of the total cholesterol, low-density lipoprotein-cholesterol and total bile acid levels in the serum of the nicotine-treated mice. Quantitative PCR showed nicotine altered few bile acid metabolism-related genes expression in liver tissue and significantly altered cholesterol-metabolism genes in gallbladder tissue. Hematoxylin and eosin staining and western blotting showed that protein levels of farnesoid X receptor (FXR) and megalin in the gallbladder increased in the lithogenic-diet mice, which was significantly suppressed in the nicotine-treated mice. In vitro studies using gallbladder epithelial cells showed that chenodeoxycholic acids increased megalin expression, which could be attenuated by nicotine. Nicotine could regulate bile acid metabolism via the FXR-megalin/cubilin pathways, which potentially contribute to cholesterol nucleation and subsequent gallstone formation.

High-grain diet feeding alters ileal microbiota and disrupts bile acid metabolism in lactating dairy cows

Bile acids (BAs) play an important role in the regulation of lipid metabolic homeostasis, but little is known about their metabolism in dairy cows fed a high-grain (HG) diet. In the present study, we examined the bacterial community, BA profile, and the FXR/FGF19 signaling pathway in the ileum and liver to investigate the gut microbe-BA metabolism interactions response to HG diet and the changes in the subsequent enterohepatic circulation of dairy cows. The results showed that the ileal bacterial community was altered, with an increase of Paraclostridium, Anaerobutyricum, Shuttleworthia, and Stomatobaculum in the relative abundance in the HG group. Moreover, real-time polymerase chain reaction (PCR) showed that the abundance of total bacteria and bacterial bile-salt hydrolase (BSH) genes was increased in the ileal digesta in the HG group. Meanwhile, HG feeding also decreased the total BA content in the digesta of jejunum and ileum and in feces. HG feeding altered the BA profile in the ileal digesta by increasing unconjugated BAs and decreasing conjugated BAs. In addition, the intestinal FXR/FGF19 signaling pathway was activated. The expression of CYP7A1 (cholesterol 7α-hydroxylase) was depressed, which inhibited BAs synthesis in the liver of cows fed HG. Overall, HG feeding altered the ileal bacterial community and BA profile, and activated FXR/FGF19 signaling pathway, resulting in a decrease of BA level in the ileal digesta via the inhibition of hepatic BA synthesis. The findings provided novel insights into understanding the relationship between gut microbiota and the homeostasis of BAs in dairy cows fed a HG diet.

Polygoni Multiflori Radix interferes with bile acid metabolism homeostasis by inhibiting Fxr transcription, leading to cholestasis

Objective: To explore the possible mechanisms of cholestasis induced by Polygoni Multiflori Radix (PM). Methods: Low and high doses of water extract of PM were given to mice by gavage for 8 weeks. The serum biochemical indexes of aspartate aminotransferase (AST), alanine aminotransferase (ALT), glutamyltransferase (GGT) alkaline phosphatase (ALP) and so on were detected in the second, fourth, sixth, and eighth weeks after administration. At the end of the eighth week of administration, the bile acid metabolic profiles of liver and bile were screened by high-performance liquid chromatography tandem triple quadrupole mass spectrometry (HPLC-QQQ-MS/MS). Liver pathological changes were observed by hematoxylin and eosin staining. Real-time quantitative polymerase chain reaction (RT-qPCR) was used to detect the mRNA transcription of the target genes and Western blotting (WB) was used to the detect target protein expression. Results: Biochemical tests results showed the values of ALP and GGT were two and three times greater than the normal values respectively, and the value of R was less than 2. Histopathology also showed that PM caused lymphocyte infiltration, a small amount of hepatocyte necrosis and nuclear fragmentation in mouse liver. The proliferation of bile duct epithelial cells was observed in the high group. These results indicated that PM may lead to cholestatic liver injury. HPLC-QQQ-MS/MS analysis with the multivariate statistical analysis revealed significant alterations of individual bile acids in liver and gallbladder as compared to those of the control group. RT-qPCR showed that the transcription of Fxr, Shp, Bsep, Bacs, Mdr2, and Ugt1a1 were downregulated and that of Cyp7a1, Mrp3, and Cyp3a11 was significantly upregulated in the treatment group. WB demonstrated that PM also markedly downregulated the protein expression of FXR, BSEP, and MDR2, and upregulated CYP7A1. Conclusion: PM inhibited the expression of FXR, which reduced the expression of MDR2 and BSEP, leading to the obstruction of bile acids outflow, and increased the expression of CYP7A1, resulting in an increase of intrahepatic bile acid synthesis, which can lead to cholestasis.

Fucoidan Ameliorated Dextran Sulfate Sodium-Induced Ulcerative Colitis by Modulating Gut Microbiota and Bile Acid Metabolism

Gut dysbiosis and bile acid (BA) metabolism disturbance are involved in the pathogenesis of ulcerative colitis. This study aimed to investigate the effect of fucoidan on BA metabolism and gut microbiota in dextran sulfate sodium-induced colitis mice. Our results showed that fucoidan effectively suppressed colonic inflammation and repaired the gut barrier. In addition, fucoidan increased the relative abundance of the Lachnospiraceae family, such as Turicibacter, Muribaculum, Parasutterella, and Colidextribacter, followed by an increase in short-chain fatty acids, especially in butyrate. Moreover, fucoidan modulated bile acid metabolism by elevating cholic acid, ursodeoxycholic acid, deoxycholic acid, and lithocholic acid and decreasing β-muricholic acid, which led to activation of FXR and TGR5 and further enhanced the gut barrier and suppressed colonic inflammation. Our results revealed that the effect of fucoidan alleviating colitis was largely mediated by gut microbiota, which was confirmed by the fecal transplantation experiment. Collectively, these findings provided the basis for fucoidan as a potential functional food for colitis.

Gut dysbiosis in nonalcoholic fatty liver disease: pathogenesis, diagnosis, and therapeutic implications

The incidence of nonalcoholic fatty liver disease (NAFLD) is increasing recently and has become one of the most common clinical liver diseases. Since the pathogenesis of NAFLD has not been completely elucidated, few effective therapeutic drugs are available. As the "second genome" of human body, gut microbiota plays an important role in the digestion, absorption and metabolism of food and drugs. Gut microbiota can act as an important driver to advance the occurrence and development of NAFLD, and to accelerate its progression to cirrhosis and hepatocellular carcinoma. Growing evidence has demonstrated that gut microbiota and its metabolites directly affect intestinal morphology and immune response, resulting in the abnormal activation of inflammation and intestinal endotoxemia; gut dysbiosis also causes dysfunction of gut-liver axis via alteration of bile acid metabolism pathway. Because of its composition diversity and disease-specific expression characteristics, gut microbiota holds strong promise as novel biomarkers and therapeutic targets for NAFLD. Intervening intestinal microbiota, such as antibiotic/probiotic treatment and fecal transplantation, has been a novel strategy for preventing and treating NAFLD. In this article, we have reviewed the emerging functions and association of gut bacterial components in different stages of NAFLD progression and discussed its potential implications in NAFLD diagnosis and therapy.

Serum Bile Acid Profiling and Mixed Model Analysis Reveal Biomarkers Associated with Pruritus Reduction in Maralixibat-Treated Patients with BSEP Deficiency

Progressive familial intrahepatic cholestasis (PFIC) is a debilitating disease manifest by severe cholestasis, intractable pruritus and growth delay that ultimately leads to liver failure or transplantation. Maralixibat (MRX) was recently approved for the treatment of cholestatic pruritus in patients with Alagille syndrome. The aim of this study was to determine whether specific changes in the composition of the serum bile acid metabolome could predict pruritus response to treatment. Serum BAs (sBA) and 7α-hydroxy-4-cholesten-3-one (7α-C4), a surrogate marker of BA synthesis, were monitored by ultrahigh-performance liquid chromatography coupled with tandem mass spectrometry over 72 weeks in PFIC patients with mild to moderate non-truncating bile salt export pump (BSEP) mutations (n = 19) treated with MRX. The weekly itch reported outcome observer (ItchRO[Obs]) score measured pruritus severity. Linear mixed models (LMM) were applied to explore the effects of individual sBA profiles and their relationship to pruritus response. Changes in the composition of sBA correlated with pruritus improvement. Notably, the trajectory of serum total and individual BA species and 7α-C4 were significantly associated with ItchRO[Obs] score (p < 0.05). These results reveal that beyond simple total sBA concentrations, specific changes to the BA metabolome are associated with pruritus reduction in patients with BSEP deficiency, thus providing further insight into causal relationship of bile acids and pruritus.

Nuciferine Protects Against High-Fat Diet-Induced Hepatic Steatosis via Modulation of Gut Microbiota and Bile Acid Metabolism in Rats

Our previous study showed that nuciferine (NF) attenuated non-alcoholic fatty liver disease (NAFLD), which is attributed to a high-fat diet (HFD) through reinforcing intestinal barrier functions, regulating lipid metabolism, and improving inflammation. To clarify whether other mechanisms contribute to the anti-NAFLD efficacy of NF, the present study investigated the influence of NF on bile acid (BA) metabolism and gut microbiota in HFD-fed rats. The data demonstrated that NF changed the composition of colonic BA, particularly elevating conjugated BA and non-12OH BA levels. As shown by downregulated protein levels of FXR, FGF15, FGFR4, and ASBT and upregulated protein levels of CYP7A1 and CYP27A1, NF inhibited ileal FXR signaling, promoted BA synthesis, suppressed BA reabsorption, and facilitated fecal BA excretion. NF might affect hepatic FXR signaling, BA conjugation, and enterohepatic circulation by the changed mRNA levels of Fxr, Shp, Baat, Bacs, Bsep, Ntcp, Ibabp, and Ostα/β. Meanwhile, NF regulated the gut microbiota, characterized by decreased BSH-producing genus, 7α-dehydroxylation genus, and increased taurine metabolism-related genus. Spearman rank correlation analysis implied that Colidextribacter, Adlercreutzia, Family_XIII_AD3011_group, Lachnospiraceae_UCG-010, Eisenbergiella, and UCG-005 were robustly associated with particular BA monomers. In conclusion, our experiment results suggested that NF could exert a mitigating effect on NAFLD via regulating BA metabolism and modulating the gut microbiota.

Intestinal transgene delivery with native E. coli chassis allows persistent physiological changes

Live bacterial therapeutics (LBTs) could reverse diseases by engrafting in the gut and providing persistent beneficial functions in the host. However, attempts to functionally manipulate the gut microbiome of conventionally raised (CR) hosts have been unsuccessful because engineered microbial organisms (i.e., chassis) have difficulty in colonizing the hostile luminal environment. In this proof-of-concept study, we use native bacteria as chassis for transgene delivery to impact CR host physiology. Native Escherichia coli bacteria isolated from the stool cultures of CR mice were modified to express functional genes. The reintroduction of these strains induces perpetual engraftment in the intestine. In addition, engineered native E. coli can induce functional changes that affect physiology of and reverse pathology in CR hosts months after administration. Thus, using native bacteria as chassis to “knock in” specific functions allows mechanistic studies of specific microbial activities in the microbiome of CR hosts and enables LBT with curative intent.

Native E. coli strains isolated from mouse stool are genetically engineered for long-term engraftment in the conventional mouse gut and enable long-term systemic effects on the host, such as improvements in insulin sensitivity in mouse models of type 2 diabetes.

Oyster (Crassostrea gigas) Polysaccharide Ameliorates High-Fat-Diet-Induced Oxidative Stress and Inflammation in the Liver via the Bile Acid-FXR-AMPKα Pathway

Oyster polysaccharides (OPS) have a variety of biological activities. In this study, we aimed to investigate the potential mechanisms of OPS to ameliorate hepatic oxidative stress and inflammation in mice induced by a high-fat diet (HFD). The results showed that OPS reduced the HFD-induced increases in serum transaminase levels and alleviated hepatic oxidative stress and inflammation. Moreover, OPS regulated bile acid metabolism and increased bile acid content in the liver, serum, and feces. Serum bile acid profile results indicated that OPS reduced levels of chenodeoxycholic acid, deoxycholic acid, and lithocholic acid associated with high-affinity agonists of Farnesol X receptor (FXR). Western blot analysis showed that OPS accelerated bile acid metabolism by downregulating hepatic FXR expression and promoting its downstream CYP7A1, CYP27A1, and CYP8B1 protein expression. Meanwhile, OPS ameliorated oxidative stress and inflammation in the liver by modulating FXR-AMPKα-Nrf2/NF-κB signaling to reduce p-IκBα/IκBα, p-NF-κB p65/NF-κB p65, IL-1β, and TNF-α expression and increase p-Nrf2/Nrf2, HO-1, and NQO-1 expression. This study was the first to explore the possible mechanism of OPS in improving liver oxidative stress and inflammation from the perspective of bile acid metabolism, providing a theoretical basis for OPS as a new source of functional food.

Lactobacillus casei SYF-08 Protects Against Pb-Induced Injury in Young Mice by Regulating Bile Acid Metabolism and Increasing Pb Excretion

Pb poisoning affects infant growth and development. However, dimercaptosuccinic acid (DMSA) as the current therapy for Pb poisoning exerts relatively significant toxic side effects in infants. Therefore, identifying a non-toxic treatment in this regard is particularly important. In this study, we aimed to investigate the therapeutic effect of an infant feces-derived probiotic strain, Lactobacillus casei SYF-08 (SYF-08), on Pb poisoning in young mice. The Pb levels in the organisms were detected via inductively coupled plasma mass spectrometry, while the therapeutic effect of SYF-08 on Pb-induced neural system damage was explored via the Morris water maze test, hematoxylin-eosin staining, and immunohistochemistry. Additionally, the molecular mechanisms underlying the protective effects of SYF-08 against Pb-induced intestinal damage were also explored via histological staining, 16S rRNA sequencing, untargeted metabolomics, qRT-PCR, and western blotting. In vivo experiments revealed that SYF-08 reduced blood and bone Pb levels and increased urinary Pb excretion. Additionally, SYF-08 alleviated Pb-induced pathological damage to the brain and ultimately improved the learning and cognitive abilities of the young mice. This treatment also restored intestinal microflora dysbiosis, regulated bile acid metabolism, and inhibited the FXR-NLRP3 signaling pathway. It also resulted in fewer adverse events than the DMSA treatment. In conclusion, our results provided valuable insights into the therapeutic role of SYF-08 in Pb poisoning and also suggested that its administration can significantly alleviate the Pb-induced damage.

Dietary Exposure to Antibiotic Residues Facilitates Metabolic Disorder by Altering the Gut Microbiota and Bile Acid Composition

Antibiotics used as growth promoters in livestock and animal husbandry can be detected in animal-derived food. Epidemiological studies have indicated that exposure to these antibiotic residues in food may be associated with childhood obesity. Herein, the effect of exposure to a residual dose of tylosin—an antibiotic growth promoter—on host metabolism and gut microbiota was explored in vivo. Theoretical maximal daily intake (TMDI) doses of tylosin were found to facilitate high-fat-diet-induced obesity, induce insulin resistance, and perturb gut microbiota composition in mice. The obesity-related phenotypes were transferrable to germfree recipient mice, indicating that the effects of a TMDI dose of tylosin on obesity and insulin resistance occurred mainly via alteration of the gut microbiota. Tylosin TMDI exposure restricted to early life, the critical period of gut microbiota development, altered the abundance of specific bacteria related to host metabolic homeostasis later in life. Moreover, early-life exposure to tylosin TMDI doses was sufficient to modify the ratio of primary to secondary bile acids, thereby inducing lasting metabolic consequences via the downstream FGF15 signaling pathway. Altogether, these findings demonstrate that exposure to very low doses of antibiotic residues, whether continuously or in early life, could exert long-lasting effects on host metabolism by altering the gut microbiota and its metabolites.

IMPORTANCE This study demonstrates that even with limited exposure in early life, a residual dose of tylosin might cause long-lasting metabolic disturbances by altering the gut microbiota and its metabolites. Our findings reveal that the gut microbiota is susceptible to previously ignored environmental factors.

Longitudinal 16S rRNA Sequencing Reveals Relationships among Alterations of Gut Microbiota and Nonalcoholic Fatty Liver Disease Progression in Mice

Nonalcoholic fatty liver disease (NAFLD) is a prevalent and progressive disease spectrum ranging from nonalcoholic fatty liver (NAFL) to nonalcoholic steatohepatitis (NASH), yet there is no effective treatment and efficient noninvasive diagnostic method for NASH. The present study investigated the longitudinal alternations of gut microbiota in the Western diet (WD) induced murine NAFLD model using 16S rRNA sequencing. Evident steatosis and inflammation were detected in the liver at the 8th and 12th week, while prompted hepatic oxidative injury and fibrosis were found at the 16th week. In this progressive process, impaired bile acid (BA) metabolism plays a vital part. Long-term WD intervention alters microbial richness and composition in the intestine, shaping characteristic microbial feature correspondence to each NAFLD stage. Descending abundances of Clostridia and Ruminococcaceae were found in NAFLD progression, while inflammation-related microbes [Eubacterium]_fissicatena_group, Romboutsia, and Erysipelatoclostridium were verified to identify borderline NASH at 8th and 12th week, and BA-associated taxa Dubosiella, Bosea, Helicobacter, and Alistipes were recognized as special symbols reflecting the state of oxidative damage and fibrosis in NASH at 16th week. Further, feces and colon abundances of Akkermansia were verified to be depleted in the process of borderline NASH progressed to NASH, and exhibited substantial correlations with NAFLD indexes ALT, AST, TC, and TBA. These characteristic taxa were effective to identify NAFLD and NASH, and microbiota-derived predictive models for NAFLD and NASH exhibited great potential (AUC 0.983 and 0.784). These findings demonstrate that a core set of gut microbiome especially BA-related taxa may be adopted as a noninvasive diagnostic tool for NAFLD and NASH.

IMPORTANCE This study concentrates on longitudinal alternations of gut microbiota in NAFLD progression and discovers the interrelationships between them. These findings may uncover the role of gut microbiota in NAFLD progression and identify novel noninvasive diagnostic tools for NAFLD based on microbial biomarkers.

Different typical dietary lipid consumption affects the bile acid metabolism and the gut microbiota structure: an animal trial using Sprague-Dawley rats

BACKGROUND

The palm oil (PO), leaf lard oil (LO), rapeseed oil (RO), sunflower oil (SO) and linseed oil (LN) are five of the most typical dietary lipids in most Asian countries. However, their influences on gut health, and the connections between the fatty acid composition, the gut microbiota, and the bile acid metabolism are not fully understood.

RESULTS

In the present study, results showed that compared with polyunsaturated fatty acid (PUFA)-rich SO and LN, the saturated fatty acid (SFA)-rich and monounsaturated fatty acid (MUFA)-rich PO, LO and RO were more likely to decrease the re-absorption of bile acid in the colon, which was probably caused by their different role in modulating the gut microbiota structure. LO consumption significantly up-regulated the Cyp27a1, FXR and TGR5 gene expression level (P < 0.05). The correlation results suggested that the C18:0 was significantly positive correlated with these three genes, indicating that intake of SFA-rich dietary lipids, especially for the C18:0, could specifically increase the bile acid production by stimulating the bile acid alternative synthesis pathway. Although the bile acid receptor expression in the colon was increased, the re-absorption of bile acid did not show a significant increase (P > 0.05) as compared with other dietary lipids. Moreover, the C18:2-rich SO maintained the bile acid metabolic balance probably by decreasing the Romboutsia, while increasing the Bifidobacterium abundance in the colon.

CONCLUSIONS

The different dietary lipids showed different effects on the bile acid metabolism, which was probably connected with the alterations in the gut microbiota structure. The present study could provide basic understandings about the influences of the different dietary lipids consumption on gut homeostasis and bile acid metabolism. © 2021 Society of Chemical Industry.

Exposure to GenX and Its Novel Analogs Disrupts Hepatic Bile Acid Metabolism in Male Mice

Due to its wide usage and recent detection in environmental matrices, hexafluoropropylene oxide dimer acid (HFPO-DA, commercial name GenX) has attracted considerable attention. Here, we explored and compared the toxicity of GenX and its novel analogs with that of perfluorooctanoic acid (PFOA) to provide guidance on the structural design and optimization of novel alternatives to poly- and perfluoroalkyl substances (PFASs). Adult male BALB/c mice were continuously exposed to PFOA, GenX, perfluoro-2-methyl-3,6-dioxo-heptanoic acid (PFMO2HpA), and perfluoro-2-methyl-3,6,8-trioxo-nonanoic acid (PFMO3NA; 0, 0.4, 2, or 10 mg/kg/d) via oral gavage for 28 days. The PFOA, GenX, and PFMO3NA treatment groups showed an increase in relative liver weight, and bile acid metabolism was the most significantly affected pathway in all treatment groups, as shown via weighted gene coexpression network analysis. The highest total bile acid levels were observed in the 2 and 10 mg/kg/d PFMO3NA groups. The ratios of primary bile acids to all bile acids increased in the high-dose groups, while the ratios of secondary bile acids showed a downward trend. Thus, bile acid metabolism disorder may be a prominent adverse effect induced by exposure to GenX, its analogs, and PFOA. Results also showed that the hepatotoxicity of PFMO2HpA was lower than that of GenX, whereas the hepatotoxicity of PFMO3NA was stronger, suggesting that PFMO2HpA may be a potential alternative to GenX.

Maternal obesogenic diet enhances cholestatic liver disease in offspring

Human and animal model data show that maternal obesity promotes nonalcoholic fatty liver disease in offspring and alters bile acid (BA) homeostasis. Here we investigated whether offspring exposed to maternal obesogenic diets exhibited greater cholestatic injury. We fed female C57Bl6 mice conventional chow (CON) or high fat/high sucrose (HF/HS) diet and then bred them with lean males. Offspring were fed 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) for 2 weeks to induce cholestasis, and a subgroup was then fed CON for an additional 10 days. Additionally, to evaluate the role of the gut microbiome, we fed antibiotic-treated mice cecal contents from CON or HF/HS offspring, followed by DDC for 2 weeks. We found that HF/HS offspring fed DDC exhibited increased fine branching of the bile duct (ductular reaction) and fibrosis but did not differ in BA pool size or intrahepatic BA profile compared to offspring of mice fed CON. We also found that after 10 days recovery, HF/HS offspring exhibited sustained ductular reaction and periportal fibrosis, while lesions in CON offspring were resolved. In addition, cecal microbiome transplant from HF/HS offspring donors worsened ductular reaction, inflammation, and fibrosis in mice fed DDC. Finally, transfer of the microbiome from HF/HS offspring replicated the cholestatic liver injury phenotype. Taken together, we conclude that maternal HF/HS diet predisposes offspring to increased cholestatic injury after DDC feeding and delays recovery after returning to CON diets. These findings highlight the impact of maternal obesogenic diet on hepatobiliary injury and repair pathways during experimental cholestasis.

Prediagnostic alterations in circulating bile acid profiles in the development of hepatocellular carcinoma

Bile acids (BAs) play different roles in cancer development. Some are carcinogenic and BA signaling is also involved in various metabolic, inflammatory and immune-related processes. The liver is the primary site of BA synthesis. Liver dysfunction and microbiome compositional changes, such as during hepatocellular carcinoma (HCC) development, may modulate BA metabolism increasing concentration of carcinogenic BAs. Observations from prospective cohorts are sparse. We conducted a study (233 HCC case-control pairs) nested within a large observational prospective cohort with blood samples taken at recruitment when healthy with follow-up over time for later cancer development. A targeted metabolomics method was used to quantify 17 BAs (primary/secondary/tertiary; conjugated/unconjugated) in prediagnostic plasma. Odd ratios (OR) for HCC risk associations were calculated by multivariable conditional logistic regression models. Positive HCC risk associations were observed for the molar sum of all BAs (ORdoubling  = 2.30, 95% confidence intervals [CI]: 1.76-3.00), and choline- and taurine-conjugated BAs. Relative concentrations of BAs showed positive HCC risk associations for glycoholic acid and most taurine-conjugated BAs. We observe an association between increased HCC risk and higher levels of major circulating BAs, from several years prior to tumor diagnosis and after multivariable adjustment for confounders and liver functionality. Increase in BA concentration is accompanied by a shift in BA profile toward higher proportions of taurine-conjugated BAs, indicating early alterations of BA metabolism with HCC development. Future studies are needed to assess BA profiles for improved stratification of patients at high HCC risk and to determine whether supplementation with certain BAs may ameliorate liver dysfunction.

Untargeted Metabolomics of Slc13a5 Deficiency Reveal Critical Liver-Brain Axis for Lipid Homeostasis

Though biallelic variants in SLC13A5 are known to cause severe encephalopathy, the mechanism of this disease is poorly understood. SLC13A5 protein deficiency reduces citrate transport into the cell. Downstream abnormalities in fatty acid synthesis and energy generation have been described, though biochemical signs of these perturbations are inconsistent across SLC13A5 deficiency patients. To investigate SLC13A5-related disorders, we performed untargeted metabolic analyses on the liver, brain, and serum from a Slc13a5-deficient mouse model. Metabolomic data were analyzed using the connect-the-dots (CTD) methodology and were compared to plasma and CSF metabolomics from SLC13A5-deficient patients. Mice homozygous for the Slc13a5^tm1b/tm1b null allele had perturbations in fatty acids, bile acids, and energy metabolites in all tissues examined. Further analyses demonstrated that for several of these molecules, the ratio of their relative tissue concentrations differed widely in the knockout mouse, suggesting that deficiency of Slc13a5 impacts the biosynthesis and flux of metabolites between tissues. Similar findings were observed in patient biofluids, indicating altered transport and/or flux of molecules involved in energy, fatty acid, nucleotide, and bile acid metabolism. Deficiency of SLC13A5 likely causes a broader state of metabolic dysregulation than previously recognized, particularly regarding lipid synthesis, storage, and metabolism, supporting SLC13A5 deficiency as a lipid disorder.

Maternal obesogenic diet regulates offspring bile acid homeostasis and hepatic lipid metabolism via the gut microbiome in mice

Mice exposed in gestation to maternal high-fat/high-sucrose (HF/HS) diet develop altered bile acid (BA) homeostasis. We hypothesized that these reflect an altered microbiome and asked if microbiota transplanted from HF/HS offspring change hepatic BA and lipid metabolism to determine the directionality of effect. Female mice were fed HF/HS or chow (CON) for 6 wk and bred with lean males. 16S sequencing was performed to compare taxa in offspring. Cecal microbiome transplantation (CMT) was performed from HF/HS or CON offspring into antibiotic-treated mice fed chow or high fructose. BA, lipid metabolic, and gene expression analyses were performed in recipient mice. Gut microbiomes from HF/HS offspring segregated from CON offspring, with increased Firmicutes to Bacteriodetes ratios and Verrucomicrobial abundance. After CMT was performed, HF/HS-recipient mice had larger BA pools, increased intrahepatic muricholic acid, and decreased deoxycholic acid species. HF/HS-recipient mice exhibited downregulated hepatic Mrp2, increased hepatic Oatp1b2, and decreased ileal Asbt mRNA expression. HF/HS-recipient mice exhibited decreased cecal butyrate and increased hepatic expression of Il6. HF/HS-recipient mice had larger livers and increased intrahepatic triglyceride versus CON-recipient mice after fructose feeding, with increased hepatic mRNA expression of lipogenic genes including Srebf1, Fabp1, Mogat1, and Mogat2. CMT from HF/HS offspring increased BA pool and shifted the composition of the intrahepatic BA pool. CMT from HF/HS donor offspring increased fructose-induced liver triglyceride accumulation. These findings support a causal role for vertical transfer of an altered microbiome in hepatic BA and lipid metabolism in HF/HS offspring.NEW & NOTEWORTHY We utilized a mouse model of maternal obesogenic diet exposure to evaluate the effect on offspring microbiome and bile acid homeostasis. We identified shifts in the offspring microbiome associated with changes in cecal bile acid levels. Transfer of the microbiome from maternal obesogenic diet-exposed offspring to microbiome-depleted mice altered bile acid homeostasis and increased fructose-induced hepatic steatosis.

Genetic manipulation of gut microbes enables single-gene interrogation in a complex microbiome

Hundreds of microbiota genes are associated with host biology/disease. Unraveling the causal contribution of a microbiota gene to host biology remains difficult because many are encoded by nonmodel gut commensals and not genetically targetable. A general approach to identify their gene transfer methodology and build their gene manipulation tools would enable mechanistic dissections of their impact on host physiology. We developed a pipeline that identifies the gene transfer methods for multiple nonmodel microbes spanning five phyla, and we demonstrated the utility of their genetic tools by modulating microbiome-derived short-chain fatty acids and bile acids in vitro and in the host. In a proof-of-principle study, by deleting a commensal gene for bile acid synthesis in a complex microbiome, we discovered an intriguing role of this gene in regulating colon inflammation. This technology will enable genetically engineering the nonmodel gut microbiome and facilitate mechanistic dissection of microbiota-host interactions.

Changes in bile acid subtypes and long-term successful weight-loss in response to weight-loss diets: The POUNDS lost trial

BACKGROUND AND AIMS

Primary bile acids (BAs) are synthesized in the liver and secondary BAs result from intestinal microbial activity. Different subtypes of BAs may be involved in regulating adiposity and energy homeostasis. We examined how changes in circulating BA subtypes induced by weight-loss diets were associated with improvements in adiposity, regional fat deposition and energy metabolism among overweight and obese adults.

METHODS

The study included 551 subjects who participated in a 2-year weight-loss diet intervention trial. Circulating 14 BA subtypes (primary and secondary unconjugated BAs and their taurine-/glycine-conjugates) were measured at baseline and 6 months. Associations of changes in BAs with changes in weight, waist circumference, resting energy expenditure (REE), body fat composition and fat distribution were evaluated.

RESULTS

Greater decreases in primary BAs (cholate and chenodeoxycholate) and secondary BAs (deoxycholate and lithocholate) and their conjugates (except for glycolithocholate) were associated with more decreases in weight and waist circumference at 6 months (P_{-after-false-discovery-rate-correction} [P_FDR ] < .05). We found that changes in glycocholate and glycoursodeoxycholate were consistently associated with reductions of general and central adiposity, REE, whole-body fat and visceral adipose tissue (P_FDR  < .05). Further, the initial (6-month) changes in BA subtypes were differently predictive of successful weight loss over 2 years.

CONCLUSIONS

The decreases in primary and secondary BA subtypes after eating low-calorie weight-loss diets were significantly associated with improving adiposity, fat accumulation and energy metabolism, suggesting that specific BA subtypes would be predictive of long-term successful weight loss and individuals' response to the treatment of weight-loss diets.

Suppression of Bile Acid Synthesis in a Preterm Infant Receiving Prolonged Parenteral Nutrition

Bile acid metabolism is altered in neonates on parenteral nutrition (PN), predisposing them to parenteral nutrition-associated liver disease. Cholesterol 7α-hydroxylase (CYP7A1), the rate-limiting enzyme in the bile acid synthesis pathway, is repressed by fibroblast growth factor 19 (FGF19) and phytosterols (PS). We describe a case of a preterm infant who developed necrotizing enterocolitis (NEC) and received exclusive PN for over 2 months. Our objective was to serially assess CYP7A1 activity and plasma FGF19 and PS concentrations in this infant case compared to five healthy preterm infants. We found that CYP7A1 activity increased during the first 2 weeks of life in control infants but was undetectable in the infant case. FGF19 concentrations were high at birth in all infants and subsequently declined and did not differ between the case and control infants. As expected, PS concentrations were elevated in the infant case and continued to increase despite lipid minimization. In conclusion, CYP7A1 activity was gradually upregulated in healthy preterm infants but remained suppressed in the infant requiring prolonged PN. Preterm infants also had elevated FGF19 concentrations at birth, which decreased with advancing postnatal age.