Overexpression of cholesterol 7α-hydroxylase promotes hepatic bile acid synthesis and secretion and maintains cholesterol homeostasis

The beneficial health effects of puerarin in the treatment of cardiovascular diseases: from mechanisms to therapeutics

Cardiovascular diseases (CVDs) are the leading causes of death globally that seriously threaten human health. Although novel western medicines have continued to be discovered over the past few decades to inhibit the progression of CVDs, new drug research and development for treating CVDs with less side effects and adverse reactions are continuously being desired. Puerarin is a natural product found in a variety of medicinal plants belonging to the flavonoid family with potent biological and pharmacological activities. Abundant research findings in the literature have suggested that puerarin possesses a promising prospect in treating CVDs. In recent years, numerous new molecular mechanisms of puerarin have been explored in experimental and clinical studies, providing new evidence for this plant metabolite to protect against CVDs. This article systematically introduces the history of use, bioavailability, and various dosage forms of puerarin and further summarizes recently published data on the major research advances and their underlying therapeutic mechanisms in treating CVDs. It may provide references for researchers in the fields of pharmacology, natural products, and internal medicine.

Multiomics Analysis Reveals Leucine Deprivation Promotes Bile Acid Synthesis by Upregulating Hepatic CYP7A1 and Intestinal Turicibacter sanguinis in Mice

BACKGROUND

Leucine, a branched-chain amino acid, participates in the regulation of lipid metabolism and the composition of the intestinal microbiota. However, the related mechanism remains unclear.

OBJECTIVES

Here, we aimed to reveal the potential mechanisms by which hepatic CYP7A1 (a rate-limiting enzyme for bile acid [BA] synthesis) and gut microbiota coregulate BA synthesis under leucine deprivation.

METHODS

To this end, 8-wk-old C57BL/6J mice were fed with either unpurified diets or leucine-free diets for 1 wk. Then, we investigated whether secondary BAs were synthesized by Turicibacter sanguinis in 7-wk-old C57BL/6J germ-free mice gavaged with T. sanguinis for 2 wk by determining BA concentrations in the plasma, liver, and cecum contents using liquid chromatography-tandem mass spectrometry.

RESULTS

The results showed that leucine deprivation resulted in a significant increase in total BA concentration in the plasma and an increase in the liver, but no difference in total BA was observed in the cecum contents before and after leucine deprivation. Furthermore, leucine deprivation significantly altered BA profiles such as taurocholic acid and ω-muricholic acid in the plasma, liver, and cecum contents. CYP7A1 expression was significantly upregulated in the liver under leucine deprivation. Leucine deprivation also regulated the composition of the gut microbiota; specifically, it significantly upregulated the relative abundance of T. sanguinis, thus enhancing the conversion of primary BAs into secondary BAs by intestinal T. sanguinis in mice.

CONCLUSIONS

Overall, leucine deprivation regulated BA profiles in enterohepatic circulation by upregulating hepatic CYP7A1 expression and increasing intestinal T. sanguinis abundance. Our findings reveal the contribution of gut microbiota to BA metabolism under dietary leucine deprivation.

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

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

Methylation changes of liver DNA during the formation of gallstones

Aim: To explore the overall methylation changes in liver tissues during the formation of gallstones, as well as the key pathways and genes involved in the process. Methods: Reduced-representation bisulfite sequencing and RNA sequencing were conducted on the liver tissues of mice with gallstones and control normal mice. Results: A total of 8705 differentially methylated regions in CpG and 1410 differentially expressed genes were identified. The joint analysis indicated that aberrant DNA methylation may be associated with dysregulated gene expression in key pathways such as cholesterol metabolism and bile secretion. Conclusion: We propose for the first time that methylation changes in some key pathway genes in liver tissue may be involved in the formation of gallstones.

CRISPR/Cas9-mediated knockout of the Vanin-1 gene in the Leghorn Male Hepatoma cell line and its effects on lipid metabolism

OBJECTIVE

Vanin-1 (VNN1) is a pantetheinase that catalyses the hydrolysis of pantetheine to produce pantothenic acid and cysteamine. Our previous studies have shown that the VNN1 is specifically expressed in chicken liver which negatively regulated by microRNA-122. However, the functions of the VNN1 in lipid metabolism in chicken liver haven't been elucidated.

METHODS

First, we detected the VNN1 mRNA expression in 4-week chickens which were fasted 24 hours. Next, knocked out VNN1 via CRISPR/Cas9 system in the chicken Leghorn Male Hepatoma cell line. Detected the lipid deposition via oil red staining and analysis the content of triglycerides (TG), low-density lipoprotein-C (LDL-C), and highdensity lipoprotein-C (HDL-C) after VNN1 knockout in Leghorn Male Hepatoma cell line. Then we captured various differentially expressed genes (DEGs) between VNN1-modified LMH cells and original LMH cells by RNA-seq.

RESULTS

Firstly, fasting-induced expression of VNN1. Meanwhile, we successfully used the CRISPR/Cas9 system to achieve targeted mutations of the VNN1 in the chicken LMH cell line. Moreover, the expression level of VNN1 mRNA in LMH-KO-VNN1 cells decreased compared with that in the wild-type LMH cells (p<0.0001). Compared with control, lipid deposition was decreased after knockout VNN1 via oil red staining, meanwhile, the contents of TG and LDL-C were significantly reduced, and the content of HDL-C was increased in LMH-KO-VNN1 cells. Transcriptome sequencing showed that there were 1,335 DEGs between LMH-KO-VNN1 cells and original LMH cells. Of these DEGs, 431 were upregulated, and 904 were downregulated. Gene ontology analyses of all DEGs showed that the lipid metabolism-related pathways, such as fatty acid biosynthesis and long-chain fatty acid biosynthesis, were enriched. KEGG pathway analyses showed that "lipid metabolism pathway", "energy metabolism", and "carbohydrate metabolism" were enriched. A total of 76 DEGs were involved in these pathways, of which 29 genes were upregulated (such as cytochrome P450 family 7 subfamily A member 1, ELOVL fatty acid elongase 2, and apolipoprotein A4) and 47 genes were downregulated (such as phosphoenolpyruvate carboxykinase 1) by VNN1 knockout in the LMH cells.

CONCLUSION

These results suggest that VNN1 plays an important role in coordinating lipid metabolism in the chicken liver.

Bidirectional effects of geniposide in liver injury: Preclinical evidence construction based on meta-analysis

ETHNOPHARMACOLOGICAL RELEVANCE

Gardenia jasminoides J.Ellis is widely used to treat liver diseases in traditional Chinese medicine. Geniposide, a major active constituent of Gardenia jasminoides J.Ellis, exerts therapeutic effects against liver injury, however, it also induces hepatotoxicity.

AIM OF THE STUDY

This meta-analysis was designed to determine the mechanisms of both the hepatoprotective and hepatotoxic effects of geniposide.

MATERIALS AND METHODS

The articles analysed in this meta-analysis were primarily obtained from five databases. The 10-item SYRCLE risk-of-bias tool was used to evaluate the quality of the included articles. STATA (version 15.1) was used to evaluate the total effect or toxicity sizes. In addition, three-dimensional (3D) dose/time-effect and mechanistic analyses were performed to assess the therapeutic and toxic effects of geniposide.

RESULTS

A total of 25 studies involving 479 animals were included. Meta-analysis revealed that geniposide not only significantly (P < 0.001) increased liver injury indices including ALT and AST levels but also improved liver function by decreasing the levels of ALT, AST and inflammatory factors in animal models of liver injury. The 3D dose/time-effect analysis revealed that geniposide administered at a dose of 20-150 mg/kg for 5-28 days effectively protected the liver without inducing toxicity. Mechanistically, geniposide exerts protective or toxic effects by regulating the TNF-α/NF-κB pathway to control oxidative stress and inflammatory responses.

CONCLUSION

Geniposide exhibits dual pharmacological activity in liver injury. It exerts potent hepatoprotective effects when administered at a dose of 20-150 mg/kg for 5-28 days.

Identifying hepatoprotective mechanism and effective components of Yinchenzhufu decoction in chronic cholestatic liver injury using a comprehensive strategy based on metabolomics, molecular biology, pharmacokinetics, and cytology

ETHNOPHARMACOLOGICAL RELEVANCE

In Traditional Chinese Medicine (TCM), cholestasis liver disease belongs to jaundice. Yinchenzhufu decoction (YCZFD) is a classic formula used for treating jaundice.

AIM OF THE STUDY

This study was aimed to investigate the potential mechanism and effective components of YCZFD in chronic cholestatic liver injury (CCLI).

MATERIALS AND METHODS

A chronic cholestatic mouse model induced by 3, 5-diethoxycarbonyl-1, 4-dihydroxychollidine was used to investigate the effect of YCZFD. Then, metabolomics was used to investigate the metabolites influenced by YCZFD. Serum and liver bile acid (BA) levels were measured using liquid chromatography coupled with triple quadruple mass spectrometry (LC-MS/MS), and the gene and protein expressions of BA transporters and metabolic enzymes were detected. Additionally, the pharmacokinetics of multiple components of YCZFD was explored to clarify the potential effective components. The effects of absorbed components of YCZFD on BA metabolism and transporter function, inflammation, and farnesoid X receptor (FXR) and pregnane X receptor (PXR) activation were analyzed using sandwich cultured rat hepatocytes, AML12 cells, and dual-luciferase receptor systems, respectively.

RESULTS

YCZFD decreased the liver damage in chronic cholestatic mice. Serum metabolomics results indicated that the main pathways influenced by YCZFD involved primary BA biosynthesis and arachidonic acid metabolism. YCZFD upregulated the expression of FXR, PXR, and BA efflux transporters and the metabolic enzymes of liver tissues, promoting BA excretion and metabolism in cholestatic mice. Additionally, YCZFD downregulated the expression of genes and proteins of the toll-like receptor 4 (TLR4)/nuclear factor kappa-B (NF-κB) pathway and decreased liver inflammation. The pharmacokinetic study indicated that multiple components showed different pharmacokinetic properties. Among the absorbed components of YCZFD, multiple components activated the transcription of FXR and PXR, regulated BA transporters and metabolic enzyme function, and reduced the gene expression of TLR4 and NF-κB1.

CONCLUSION

YCZFD can ameliorate CCLI by promoting the excretion and metabolism of BAs and inhibiting inflammation via the TLR4/NF-κB signaling pathway. The multiple components of YCZFD could act on BA homeostasis regulation and anti-inflammation, exhibiting a combined effect against CCLI.

Combined transcriptome and metabolome analysis reveals breed-specific regulatory mechanisms in Dorper and Tan sheep

BACKGROUND

Dorper and Tan sheep are renowned for their rapid growth and exceptional meat quality, respectively. Previous research has provided evidence of the impact of gut microbiota on breed characteristics. The precise correlation between the gastrointestinal tract and peripheral organs in each breed is still unclear. Investigating the metabolic network of the intestinal organ has the potential to improve animal growth performance and enhance economic benefits through the regulation of intestinal metabolites.

RESULTS

In this study, we identified the growth advantage of Dorper sheep and the high fat content of Tan sheep. A transcriptome study of the brain, liver, skeletal muscle, and intestinal tissues of both breeds revealed 3,750 differentially expressed genes (DEGs). The genes PPARGC1A, LPL, and PHGDH were found to be highly expressed in Doper, resulting in the up-regulation of pathways related to lipid oxidation, glycerophospholipid metabolism, and amino acid anabolism. Tan sheep highly express the BSEP, LDLR, and ACHE genes, which up-regulate the pathways involved in bile transport and cholesterol homeostasis. Hindgut content analysis identified 200 differentially accumulated metabolites (DAMs). Purines, pyrimidines, bile acids, and fatty acid substances were more abundant in Dorper sheep. Based on combined gene and metabolite analyses, we have identified glycine, serine, and threonine metabolism, tryptophan metabolism, bile secretion, cholesterol metabolism, and neuroactive ligand-receptor interaction as key factors contributing to the differences among the breeds.

CONCLUSIONS

This study indicates that different breeds of sheep exhibit unique breed characteristics through various physiological regulatory methods. Dorper sheep upregulate metabolic signals related to glycine, serine, and threonine, resulting in an increase in purine and pyrimidine substances. This, in turn, promotes the synthesis of amino acids and facilitates body development, resulting in a faster rate of weight gain. Tan sheep accelerate bile transport, reduce bile accumulation in the intestine, and upregulate cholesterol homeostasis signals in skeletal muscles. This promotes the accumulation of peripheral and intramuscular fat, resulting in improved meat quality. This work adopts a joint analysis method of multi-tissue transcriptome and gut metabolome, providing a successful case for analyzing the mechanisms underlying the formation of various traits.

Divergence in aerobic capacity influences hepatic and systemic metabolic adaptations to bile acid sequestrant and short-term high-fat/sucrose feeding in rats

High versus low aerobic capacity significantly impacts the risk for metabolic diseases. Rats selectively bred for high or low intrinsic aerobic capacity differently modify hepatic bile acid metabolism in response to high-fat diets (HFDs). Here we tested if a bile acid sequestrant would alter hepatic and whole body metabolism differently in rats with high and low aerobic capacity fed a 1-wk HFD. Male rats (8 mo of age) that were artificially selected to be high (HCR) and low-capacity runners (LCR) with divergent intrinsic aerobic capacities were transitioned from a low-fat diet (LFD, 10% fat) to an HFD (45% fat) with or without a bile acid sequestrant (BA-Seq, 2% cholestyramine resin) for 7 days while maintained in an indirect calorimetry system. HFD + BA-Seq increased fecal excretion of lipids and bile acids and prevented weight and fat mass gain in both strains. Interestingly, HCR rats had increased adaptability to enhance fecal bile acid and lipid loss, resulting in more significant energy loss than their LCR counterpart. In addition, BA-Seq induced a greater expression of hepatic CYP7A1 gene expression, the rate-limiting enzyme of bile acid synthesis in HCR rats both on HFD and HFD + BA-Seq diets. HCR displayed a more significant reduction of RQ in response to HFD than LCR, but HFD + BA-Seq lowered RQ in both groups compared with HFD alone, demonstrating a pronounced impact on metabolic flexibility. In conclusion, BA-Seq provides uniform metabolic benefits for metabolic flexibility and adiposity, but rats with higher aerobic capacity display adaptability for hepatic bile acid metabolism.NEW & NOTEWORTHY The administration of bile acid sequestrant (BA-Seq) has uniform metabolic benefits in terms of metabolic flexibility and adiposity in rats with high and low aerobic capacity. However, rats with higher aerobic capacity demonstrate greater adaptability in hepatic bile acid metabolism, resulting in increased fecal bile acid and lipid loss, as well as enhanced fecal energy loss.

Interactions between dietary cholesterol and intestinal flora and their effects on host health

The interactions between dietary cholesterol and intestinal microbiota strongly affect host health. In recent years, relevant studies have greatly advanced this field and need to be summarized to deepen the understanding of dietary cholesterol-intestinal microbiota interactions and their effects on host health. This review covers the most recent frontiers on the effects of dietary cholesterol on the intestinal microbiota and its metabolites, the metabolism of cholesterol by the intestinal microbiota, and the effects of the interactions on host health. Several animal-feeding studies reported that dietary cholesterol altered different intestinal microbiota in the body, while mainly causing alterations in intestinal microbial metabolites such as bile acids, short-chain fatty acids, and tryptophan derivatives. Alterations in these metabolites may be a novel mechanism mediating cholesterol-related diseases. The cholesterol microbial metabolite, coprostanol, has a low absorption rate and is excreted in the feces. Thus, microbial conversion of cholesterol-to-coprostanol may be an important way of cholesterol-lowering by the organism. Cholesterol-3-sulfate is a recently discovered microbial metabolite of cholesterol, mainly metabolized by Bacteroides containing the Bt_0416 gene. Its effects on host health have been preliminarily characterized and are mainly related to immune modulation and repair of the intestinal epithelium.

Gallstone Disease and Its Correlation With Thyroid Disorders: A Narrative Review

Over the years, several studies have revealed an important link between thyroid disorders and gallstone disease. According to these studies, hypothyroidism and hyperthyroidism are associated with cholesterol gallstone disease. This association between thyroid hormone disorders and cholesterol gallstone disease is due to the importance of thyroid hormones on cholesterol synthesis, bile functioning and content, and gallbladder motility. Several genes and receptors have been found on the thyroid gland, liver, and gallbladder to verify this association. These genes affect thyroid hormone secretion, lipid metabolism, and bile secretion. Defects in these various gene expression and protein functions lead to bile duct diseases. Other causes that lead to cholesterol gallstone disease are supersaturation of the bile with cholesterol and impaired gallbladder motility, which leads to bile stasis. This article has discussed these factors in detail while highlighting the association between thyroid hormones and cholesterol gallstone disease.

Conferring liver selectivity to a thyromimetic using a novel nanoparticle increases therapeutic efficacy in a diet-induced obesity animal model

Optimization of metabolic regulation is a promising solution for many pathologies, including obesity, dyslipidemia, type 2 diabetes, and inflammatory liver disease. Synthetic thyroid hormone mimics-based regulation of metabolic balance in the liver showed promise but was hampered by the low biocompatibility and harmful effects on the extrahepatic axis. In this work, we show that specifically directing the thyromimetic to the liver utilizing a nanogel-based carrier substantially increased therapeutic efficacy in a diet-induced obesity mouse model, evidenced by the near-complete reversal of body weight gain, liver weight and inflammation, and cholesterol levels with no alteration in the thyroxine (T4) / thyroid stimulating hormone (TSH) axis. Mechanistically, the drug acts by binding to thyroid hormone receptor β (TRβ), a ligand-inducible transcription factor that interacts with thyroid hormone response elements and modulates target gene expression. The reverse cholesterol transport (RCT) pathway is specifically implicated in the observed therapeutic effect. Overall, the study demonstrates a unique approach to restoring metabolic regulation impacting obesity and related metabolic dysfunctions.

FXR Friend-ChIPs in the Enterohepatic System

Chronic liver diseases encompass a wide spectrum of hepatic maladies that often result in cholestasis or altered bile acid secretion and regulation. Incidence and cost of care for many chronic liver diseases are rising in the United States with few Food and Drug Administration-approved drugs available for patient treatment. Farnesoid X receptor (FXR) is the master regulator of bile acid homeostasis with an important role in lipid and glucose metabolism and inflammation. FXR has served as an attractive target for management of cholestasis and fibrosis; however, global FXR agonism results in adverse effects in liver disease patients, severely affecting quality of life. In this review, we highlight seminal studies and recent updates on the FXR proteome and identify gaps in knowledge that are essential for tissue-specific FXR modulation. In conclusion, one of the greatest unmet needs in the field is understanding the underlying mechanism of intestinal versus hepatic FXR function.

High-cholesterol diet in combination with hydroxypropyl-beta-cyclodextrin induces NASH-like disorders in the liver of rats

Non-alcoholic fatty liver disease (NAFLD) is a general term for fatty liver disease not caused by viruses or alcohol. Fibrotic hepatitis, cirrhosis, and hepatocellular carcinoma can develop. The recent increase in NAFLD incidence worldwide has stimulated drug development efforts. However, there is still no approved treatment. This may be due in part to the fact that non-alcoholic steatohepatitis (NASH) pathogenesis is very complex, and its mechanisms are not well understood. Studies with animals are very important for understanding the pathogenesis. Due to the close association between the establishment of human NASH pathology and metabolic syndrome, several animal models have been reported, especially in the context of overnutrition. In this study, we investigated the induction of NASH-like pathology by enhancing cholesterol absorption through treatment with hydroxypropyl-beta-cyclodextrin (CDX). Female Sprague-Dawley rats were fed a normal diet with normal water (control group); a high-fat (60 kcal%), cholesterol (1.25 %), and cholic acid (0.5 %) diet with normal water (HFCC group); or HFCC diet with 2 % CDX water (HFCC+CDX group) for 16 weeks. Compared to the control group, the HFCC and HFCC+CDX groups showed increased blood levels of total cholesterol, aspartate aminotransferase, and alanine aminotransferase. At autopsy, parameters related to hepatic lipid synthesis, oxidative stress, inflammation, and fibrosis were elevated, suggesting the development of NAFLD/NASH. Elevated levels of endoplasmic reticulum stress-related genes were evident in the HFCC+CDX group. In the novel rat model, excessive cholesterol intake and accelerated absorption contributed to NAFLD/NASH pathogenesis.

Time-dependent effect of REV-ERBα agonist SR9009 on nonalcoholic steatohepatitis and gut microbiota in mice

The circadian clock is involved in the pathogenesis of nonalcoholic steatohepatitis (NASH), and the target pathways of many NASH candidate drugs are controlled by the circadian clock. However, the application of chronopharmacology in NASH is little considered currently. Here, the time-dependent effect of REV-ERBα agonist SR9009 on diet-induced NASH and microbiota was investigated. C57BL/6J mice were fed a high-cholesterol and high-fat diet (CL) for 12 weeks to induce NASH and then treated with SR9009 either at Zeitgeber time 0 (ZT0) or ZT12 for another 6 weeks. Pharmacological activation of REV-ERBα by SR9009 alleviated hepatic steatosis, insulin resistance, liver inflammation, and fibrosis in CL diet-induced NASH mice. These effects were accompanied by improved gut barrier function and altered microbial composition and function in NASH mice, and the effect tended to be stronger when SR9009 was injected at ZT0. Moreover, SR9009 treatment at different time points resulted in a marked difference in the composition of the microbiota, with a stronger effect on the enrichment of beneficial bacteria and the diminishment of harmful bacteria when SR9009 was administrated at ZT0. Therefore, the time-dependent effect of REV-ERBα agonist on NASH was partly associated with the microbiota, highlighting the potential role of microbiota in the chronopharmacology of NASH and the possibility of discovering new therapeutic strategies for NASH.

Transcriptome analysis reveals the host immune response upon LMBV infection in largemouth bass (Micropterus salmoides)

Largemouth bass (Micropterus salmoides) is one of the important economical freshwater aquaculture species in China. However, the outbreak of viral diseases always caused great economic losses in the largemouth bass aquaculture industry. Largemouth bass virus (LMBV), a double-stranded DNA (dsDNA) virus belonging to genus Ranavirus, family Iridoviridae causes high mortality in cultivated largemouth bass. However, host responses, especially the molecular events involved in LMBV infection still remained largely uncertain. Here, we established an in vivo model of LMBV infection, and systematically investigated the mRNA expression profiles of host genes in liver and spleen from infected largemouth bass using RNA sequencing (RNA-seq). Histopathological analysis indicated that necrotic cells and the formed necrotic focus were present in spleen, while numerous basophilic cells, hepatocytes volume shrinkage, nucleus pyknosis, and the disappeared boundary of hepatocytes were observed in the liver of infected largemouth bass. Transcriptomic analysis showed that transcription levels of 5128 genes (2804 up-regulated genes and 2324 down-regulated) in liver and 7008 genes (2603 up-regulated and 4405 down-regulated) in spleen were altered significantly. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis indicated that numerous co-regulated differentially expressed genes (DEGs) in liver and spleen were enriched in the pathways related to cell death and immune signaling, such as apoptosis, necroptosis, cytokine-cytokine receptor interaction and JAK-STAT signaling. Moreover, the DEGs specially regulated by LMBV infection in liver were significantly enriched in the KEGG pathways related to metabolism and cell death, while those in spleen were enriched in the immune related pathways. In addition, the expression changes of several randomly selected genes, such as SOCS1, IL-6, CXCL2, CASP8, CYC and TNF from qPCR were consistent with the transcriptomic data. Taken together, our findings will provide new insights into the fundamental patterns of molecular responses induced by LMBV in vivo, but also contribute greatly to understanding the host defense mechanisms against iridoviral pathogens.

Hepatic Energy Metabolism under the Local Control of the Thyroid Hormone System

The energy homeostasis of the organism is orchestrated by a complex interplay of energy substrate shuttling, breakdown, storage, and distribution. Many of these processes are interconnected via the liver. Thyroid hormones (TH) are well known to provide signals for the regulation of energy homeostasis through direct gene regulation via their nuclear receptors acting as transcription factors. In this comprehensive review, we summarize the effects of nutritional intervention like fasting and diets on the TH system. In parallel, we detail direct effects of TH in liver metabolic pathways with regards to glucose, lipid, and cholesterol metabolism. This overview on hepatic effects of TH provides the basis for understanding the complex regulatory network and its translational potential with regards to currently discussed treatment options of non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH) involving TH mimetics.

Pharmacological inhibition of MEK1/2 signaling disrupts bile acid metabolism through loss of Shp and enhanced Cyp7a1 expression

The RAS-MAPK signaling pathway is one of the most frequently dysregulated pathways in human cancer. Small molecule inhibitors directed against this pathway have clinical activity in patients with various cancer types and can improve patient outcomes. However, the use of these drugs is associated with adverse effects, which can result in dose reduction or treatment interruption. A better molecular understanding of on-target, off-tumor effects may improve toxicity management. In the present study, we aimed to identify early initiating biological changes in the liver upon pharmacological inhibition of the RAS-MAPK signaling pathway. To this end, we tested the effect of MEK inhibitor PD0325901 using mice and human hepatocyte cell lines. Male C57BL/6 mice were treated with either vehicle or PD0325901 for six days, followed by transcriptome analysis of the liver and phenotypic characterization. Pharmacological MEK inhibition altered the expression of 423 genes, of which 78 were upregulated and 345 were downregulated. We identified Shp, a transcriptional repressor, and Cyp7a1, the rate-limiting enzyme in converting cholesterol to bile acids, as the top differentially expressed genes. PD0325901 treatment also affected other genes involved in bile acid regulation, which was associated with changes in the composition of plasma bile acids and composition and total levels of fecal bile acids and elevated predictive biomarkers of early liver toxicity. In conclusion, short-term pharmacological MEK inhibition results in profound changes in bile acid metabolism, which may explain some of the clinical adverse effects of pharmacological inhibition of the RAS-MAPK pathway, including gastrointestinal complications and hepatotoxicity.

My lifelong dedication to bile acid research

It is a great honor to be invited to write a reflection of my lifelong bile acid research for the Journal of Biological Chemistry, the premier biochemistry journal in which I am proud to have published 24 manuscripts. I published 21 manuscripts in the Journal of Lipid Research, also a journal of American Society of Biochemistry and Molecular Biology. I started my reflection from my early education in Taiwan, my coming to America for graduate study, my postdoctoral training in cytochrome P450 research, and my lifelong bile acid research career at the not so "visible" Northeast Ohio Medical University. I have witnesses and help to transform this sleepy rural medical school to a well-funded powerhouse in liver research. Writing this reflection of my long, exciting, and rewarding journey in bile acid research brought back many good memories. I am proud of my scientific contribution. I attribute my lifelong academic success to working hard, perseverance, good mentoring, and networking. I hope that this reflection of my academic career may provide guidance to younger investigators who are pursuing academic teaching and research and might inspire the next generation of researchers in biochemistry and metabolic diseases.

Cholesterol-Lowering Activity of Vitisin A Is Mediated by Inhibiting Cholesterol Biosynthesis and Enhancing LDL Uptake in HepG2 Cells

Pyranoanthocyanins have been reported to possess better chemical stability and bioactivities than monomeric anthocyanins in some aspects. The hypocholesterolemic activity of pyranoanthocyanins is unclear. In view of this, this study was conducted to compare the cholesterol-lowering activities of Vitisin A with the anthocyanin counterpart Cyanidin-3-O-glucoside(C3G) in HepG2 cells and to investigate the interaction of Vitisin A with the expression of genes and proteins associated with cholesterol metabolism. HepG2 cells were incubated with 40 μM cholesterol and 4 μM 25-hydroxycholeterol with various concentrations of Vitisin A or C3G for 24 h. It was found that Vitisin A decreased the cholesterol levels at the concentrations of 100 μM and 200 μM with a dose-response relationship, while C3G exhibited no significant effect on cellular cholesterol. Furthermore, Vitisin A could down-regulate 3-hydroxy-3-methyl-glutaryl coenzyme A reductase (HMGCR) to inhibit cholesterol biosynthesis through a sterol regulatory element-binding protein 2 (SREBP2)-dependent mechanism, and up-regulate low-density lipoprotein receptor (LDLR) and blunt the secretion of proprotein convertase subtilisin/kexin type 9 (PCSK9) protein to promote intracellular LDL uptake without LDLR degradation. In conclusion, Vitisin A demonstrated hypocholesterolemic activity, by inhibiting cholesterol biosynthesis and enhancing LDL uptake in HepG2 cells.

Astragaloside IV ameliorates diet-induced hepatic steatosis in obese mice by inhibiting intestinal FXR via intestinal flora remodeling

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is a major clinical and public health burden worldwide with no established pharmacological therapy. Changes in the intestinal flora and associated metabolite bile acids (BAs) have been described in NAFLD. Astragaloside IV (AS-IV) is a low drug permeability saponin with protective effects against multiple diseases. However, the specific mechanism underlying the involvement of AS-IV in the regulation of NAFLD is yet to be clarified.

PURPOSE

This study aimed to investigate the effect of AS-IV on NAFLD and explore whether intestinal flora was involved.

METHODS

The effect of AS-IV was evaluated on high-fat diet-fed mice. Real-time PCR, immunohistochemistry, immunofluorescence, and biochemical analyses were performed. 16S rRNA gene sequencing and UPLC-TQMS were used to determine the alterations in the intestinal flora and concentration of BAs. Fecal microbiota transplantation (FMT) and intestine-specific farnesoid X receptor (FXR) knockout were also performed.

RESULTS

AS-IV treatment alleviated diet-induced metabolic impairments, particularly hepatic steatosis. These changes occurred in the setting of decreased intestinal bile salt hydrolase (BSH)-expressing flora. Further analysis showed that the reduced BSH activity increased intestinal tauro-β-muricholic acid levels, an inhibitor of intestinal FXR. Inhibition of intestinal FXR signaling by AS-IV was accompanied by decreased expression of intestinal fibroblast growth factor 15 and subsequent hepatic FXR activation as well as increased glucagon-like peptide-1 and decreased ceramide production, all of which contribute to the inhibition of sterol regulatory element-binding protein-1c-mediated hepatic steatosis. Furthermore, intestine-specific Fxr knockout and FMT further demonstrated an FXR- and intestinal flora-dependent preventive effect of AS-IV on hepatic steatosis.

CONCLUSION

These results show that the changes in intestinal flora and BAs serve an essential role in the remission of hepatic steatosis by AS-IV, thereby suggesting that AS-IV may be used as a prebiotic agent to provide viable treatment for NAFLD.

UPLC-QTOF/MS Metabolomics and Biochemical Assays Reveal Changes in Hepatic Nutrition and Energy Metabolism during Sexual Maturation in Female Rainbow Trout (Oncorhynchus mykiss)

Mobilization and repartition of nutrients and energy are prerequisites for the normal sexual maturity of broodstock. However, there are few studies on the mechanisms of hepatic nutrients and energy metabolism during sexual maturation in female rainbow trout (Oncorhynchus mykiss). This study investigated hepatic metabolite changes and explored the potential nutritional regulation mechanism between mature and immature female rainbow trout by combining UPLC-QTOF/MS metabolomics and biochemical assays. It was observed that hepatic biochemical assays differed considerably between the two groups, such as glucose, triglycerides, hexokinase, lipase, and aspartate aminotransferase. Liver metabolomics showed that various differential metabolites involved in amino acid and lipid metabolism markedly increased, suggesting the enhancement of lipid metabolism and amino acid anabolism in the liver provides the necessary material basis for ovarian development. Meanwhile, glycogen catabolism and glycolysis hold the key to maintaining organismal energy homeostasis with normal sexual maturation of female rainbow trout. Overall, the results from this study suggested that the liver undergoes drastic reprogramming of the metabolic profile in response to mobilization and repartition of nutrients and energy during the sexual maturation of female rainbow trout. This study further deepened the understanding of the reproductive biology of rainbow trout, and provided the theoretical basis and practical ramifications for nutritional requirements of breeding high-quality broodstock in the artificial propagation of rainbow trout.

The Farnesoid X Receptor as a Master Regulator of Hepatotoxicity

The nuclear receptor farnesoid X receptor (FXR, NR1H4) is a bile acid (BA) sensor that links the enterohepatic circuit that regulates BA metabolism and elimination to systemic lipid homeostasis. Furthermore, FXR represents a real guardian of the hepatic function, preserving, in a multifactorial fashion, the integrity and function of hepatocytes from chronic and acute insults. This review summarizes how FXR modulates the expression of pathway-specific as well as polyspecific transporters and enzymes, thereby acting at the interface of BA, lipid and drug metabolism, and influencing the onset and progression of hepatotoxicity of varying etiopathogeneses. Furthermore, this review article provides an overview of the advances and the clinical development of FXR agonists in the treatment of liver diseases.

Di-(2-ethylhexyl) phthalate increases plasma glucose and induces lipid metabolic disorders via FoxO1 in adult mice

Di-(2-ethylhexyl) phthalate (DEHP), an endocrine-disrupting chemical (EDC) commonly used as a plasticizer, is responsible for widespread environmental pollution. Epidemiological and experimental data implicate DEHP and its metabolite mono(2-ethylhexyl) phthalate (MEHP) in the occurrence and development of metabolic syndrome. However, the specific effects and potential mechanisms of action of DEHP on glucose and lipid metabolism in adults are currently unclear. In the current study, adult male mice were continuously exposed to DEHP (0, 5, and 25 mg/kg/day) via oral administration and changes in glucose and lipid metabolism explored. Notably, exposure to DEHP led to a significant increase in plasma glucose and hepatic lipid accumulation but had no effect on insulin secretion. Western blot and real-time quantitative PCR showed that DEHP induced insulin resistance and promoted gluconeogenesis and lipid accumulation via overexpression of forkhead box protein O1 (FoxO1), in keeping with hepatic RNA sequencing data. Variations in gut microbiota aggravated these effects while inhibition of FoxO1 reversed the adverse effects of DEHP. Our findings support a key role of FoxO1 in disorders of glucose and lipid metabolism caused by DEHP.

G protein-coupled receptor 35 attenuates nonalcoholic steatohepatitis by reprogramming cholesterol homeostasis in hepatocytes

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease worldwide. Fat accumulation "sensitizes" the liver to insult and leads to nonalcoholic steatohepatitis (NASH). G protein-coupled receptor 35 (GPR35) is involved in metabolic stresses, but its role in NAFLD is unknown. We report that hepatocyte GPR35 mitigates NASH by regulating hepatic cholesterol homeostasis. Specifically, we found that GPR35 overexpression in hepatocytes protected against high-fat/cholesterol/fructose (HFCF) diet-induced steatohepatitis, whereas loss of GPR35 had the opposite effect. Administration of the GPR35 agonist kynurenic acid (Kyna) suppressed HFCF diet-induced steatohepatitis in mice. Kyna/GPR35 induced expression of StAR-related lipid transfer protein 4 (STARD4) through the ERK1/2 signaling pathway, ultimately resulting in hepatic cholesterol esterification and bile acid synthesis (BAS). The overexpression of STARD4 increased the expression of the BAS rate-limiting enzymes cytochrome P450 family 7 subfamily A member 1 (CYP7A1) and CYP8B1, promoting the conversion of cholesterol to bile acid. The protective effect induced by GPR35 overexpression in hepatocytes disappeared in hepatocyte STARD4-knockdown mice. STARD4 overexpression in hepatocytes reversed the aggravation of HFCF diet-induced steatohepatitis caused by the loss of GPR35 expression in hepatocytes in mice. Our findings indicate that the GPR35-STARD4 axis is a promising therapeutic target for NAFLD.

Ferulic acid attenuates high-fat diet-induced hypercholesterolemia by activating classic bile acid synthesis pathway

Ferulic acid (FA), a natural phenolic phytochemical abundantly present in whole grains, displays promising therapeutic effects on hypercholesterolemia while its underlying mechanism not fully elucidated. This study aimed to investigate the cholesterol-lowering effect of FA in high-fat diet (HFD)-fed mice and its potential molecular mechanism. FA supplementation alleviated HFD-induced hypercholesterolemia (–13.2%, p < 0.05), along with increased excretion of bile acids (BAs) in feces (37.0%, p < 0.05). Mechanism studies showed that FA activated the expression of cholesterol 7α hydroxylase (CYP7A1), a rate-limiting enzyme in BA biosynthesis in the liver, which increased the BAs biosynthesis from cholesterol. Surprisingly, increased excretion of BAs in feces is a consequence, not a cause, of CYP7A1 activation. Furthermore, enterohepatic farnesoid X receptor (FXR) signaling is not involved in the activation of hepatic CYP7A1 by FA. In conclusion, FA activates CYP7A1 through non-FXR signaling, which on the one hand effectively prevents hypercholesterolemia, and on the other hand leads to secondary BAs elevation in plasma. The latter may be the key to the anti-obesity and hypoglycemic effects of FA.

Transcription factor Klf9 controls bile acid reabsorption and enterohepatic circulation in mice via promoting intestinal Asbt expression

Bile acid (BA) homeostasis is regulated by the extensive cross-talk between liver and intestine. Many bile-acid-activated signaling pathways have become attractive therapeutic targets for the treatment of metabolic disorders. In this study we investigated the regulatory mechanisms of BA in the intestine. We showed that the BA levels in the gallbladder and faeces were significantly increased, whereas serum BA levels decreased in systemic Krüppel-like factor 9 (Klf9) deficiency (Klf9-/-) mice. These phenotypes were also observed in the intestine-specific Klf9-deleted (Klf9vil-/-) mice. In contrast, BA levels in the gallbladder and faeces were reduced, whereas BA levels in the serum were increased in intestinal Klf9 transgenic (Klf9Rosa26+/+) mice. By using a combination of biochemical, molecular and functional assays, we revealed that Klf9 promoted the expression of apical sodium-dependent bile acid transporter (Asbt) in the terminal ileum to enhance BA absorption in the intestine. Reabsorbed BA affected liver BA synthetic enzymes by regulating Fgf15 expression. This study has identified a previously neglected transcriptional pathway that regulates BA homeostasis.

Effect of caloric intake and macronutrient composition on intestinal cholesterol absorption and bile acids in patients with obesity

Obesity is associated with alterations in cholesterol and bile acid (BA) metabolism. However, the interaction among dietary intake, cholesterol absorption, and BA metabolism in patients with obesity remains unclear. We conducted a 4-wk nutritional intervention nonrandomized clinical trial with three different sequential diets for a week in the following order: regular diet (RD); high calorie, high-fat diet (HCHF), washout period on RD; and low-calorie, low-fat diet (LCLF). We provided participants with meal replacements during HCHF and LCLF diets. A total of 16 participants completed the study [n = 8 normal weight (NW); n = 8 with obesity (OB)]. Overall, there was a significant increase in intestinal cholesterol uptake when changing from RD to HCHF and a reduction in intestinal cholesterol uptake from HCHF to LCLF. When analyzing by BMI groups, these findings were similar in patients with NW (RD to HCHF: P < 0.007; HCHF to LCLF: P = 0.02); however, in patients with obesity, the change in intestinal cholesterol uptake was only observed when changing from RD to HCHF (P = 0.006). There was no correlation between cholesterol absorption and fecal bile acids or other markers of BA metabolism in all patients or the subgroups. Dietary caloric content had a significant effect on cholesterol absorption, however, this effect is blunted in patients with obesity. These data are consistent with the impaired effect of a low-fat diet on cholesterol absorption in obesity.NEW & NOTEWORTHY We show how switching from a regular diet to an HCHF increases cholesterol absorption in patients with normal weight and obesity. The decrease in cholesterol absorption from an HCHF to an LCLF, on the other hand, was only seen in normal-weight controls, underlining the importance of body weight in this regulation. In addition, changes in caloric and fat content had an immediate and direct effect on hepatic bile acid production.

Spermidine Ameliorates Nonalcoholic Steatohepatitis through Thyroid Hormone-Responsive Protein Signaling and the Gut Microbiota-Mediated Metabolism of Bile Acids

Spermidine, a natural polyamine and physiological autophagy inducer, is involved in various physiological processes. However, the impact and mechanism of spermidine on nonalcoholic steatohepatitis (NASH) remains unclarified. We found that daily spermidine intake was significantly lower in volunteers with liver dysfunction than the healthy controls, and the serum and fecal spermidine levels were negatively correlated with the NASH phenotypes. Spermidine supplementation significantly attenuated hepatic lipid accumulation, insulin resistance, hepatic inflammation, and fibrosis in NASH mice induced by a western diet. The ameliorating effect of spermidine on lipid accumulation might be partly regulated by thyroid hormone-responsive protein (THRSP) signaling and autophagy. Moreover, spermidine altered the profile of hepatic bile acids (BAs) and microbial composition and function. Furthermore, spermidine reversed the progression of hepatic steatosis, inflammation, and fibrosis in mice with preexisting NASH. Therefore, spermidine ameliorates NASH partly through the THRSP signaling and the gut microbiota-mediated metabolism of BAs, suggesting that spermidine might be a viable therapy for NASH.

Obeticholic Acid Induces Hepatoxicity Via FXR in the NAFLD Mice

Objective: Obeticholic acid (OCA), a potent farnesoid X receptor (FXR) agonist, is a promising drug for nonalcoholic fatty liver disease (NAFLD); however, it can cause liver injury, especially at high doses. Here, we investigated the role of FXR in the high-dose OCA-induced hepatoxicity in the condition of the NAFLD mouse model.

Methods: Wild-type (WT) mice and FXR^−/− mice were administered with over-dose OCA (0.40%) and high-dose OCA (0.16%), in a high-fat diet. RNA-seq on liver samples of mice fed with high-dose OCA was performed to dig out the prominent biological events contributing to hepatic fibrosis.

Results: Over-dose OCA induced liver injury and shortened survival in WT mice, but not FXR^−/− mice. High-dose OCA caused hepatic stellate cell activation and liver fibrosis in the presence of FXR. Furthermore, high-dose OCA induced cholesterol accumulation in livers via the upregulation of genes involved in cholesterol acquisition and downregulation of genes regulating cholesterol degradation in liver, leading to the production of interleukin -1β and an FXR-mediated inflammatory response.

Conclusion: The high-dose OCA induced FXR-dependent hepatic injury via cholesterol accumulation and interleukin -1β pathway in the NAFLD mice.

Pharmacologic activation of hepatic farnesoid X receptor prevents parenteral nutrition-associated cholestasis in mice

BACKGROUND AND AIMS

Parenteral nutrition (PN)-associated cholestasis (PNAC) complicates the care of patients with intestinal failure. In PNAC, phytosterol containing PN synergizes with intestinal injury and IL-1β derived from activated hepatic macrophages to suppress hepatocyte farnesoid X receptor (FXR) signaling and promote PNAC. We hypothesized that pharmacological activation of FXR would prevent PNAC in a mouse model.

APPROACH AND RESULTS

To induce PNAC, male C57BL/6 mice were subjected to intestinal injury (2% dextran sulfate sodium [DSS] for 4 days) followed by central venous catheterization and 14-day infusion of PN with or without the FXR agonist GW4064. Following sacrifice, hepatocellular injury, inflammation, and biliary and sterol transporter expression were determined. GW4064 (30 mg/kg/day) added to PN on days 4-14 prevented hepatic injury and cholestasis; reversed the suppressed mRNA expression of nuclear receptor subfamily 1, group H, member 4 (Nr1h4)/FXR, ATP-binding cassette subfamily B member 11 (Abcb11)/bile salt export pump, ATP-binding cassette subfamily C member 2 (Abcc2), ATP binding cassette subfamily B member 4(Abcb4), and ATP-binding cassette subfamily G members 5/8(Abcg5/8); and normalized serum bile acids. Chromatin immunoprecipitation of liver showed that GW4064 increased FXR binding to the Abcb11 promoter. Furthermore, GW4064 prevented DSS-PN-induced hepatic macrophage accumulation, hepatic expression of genes associated with macrophage recruitment and activation (ll-1b, C-C motif chemokine receptor 2, integrin subunit alpha M, lymphocyte antigen 6 complex locus C), and hepatic macrophage cytokine transcription in response to lipopolysaccharide in vitro. In primary mouse hepatocytes, GW4064 activated transcription of FXR canonical targets, irrespective of IL-1β exposure. Intestinal inflammation and ileal mRNAs (Nr1h4, Fgf15, and organic solute transporter alpha) were not different among groups, supporting a liver-specific effect of GW4064 in this model.

CONCLUSIONS

GW4064 prevents PNAC in mice through restoration of hepatic FXR signaling, resulting in increased expression of canalicular bile and of sterol and phospholipid transporters and suppression of macrophage recruitment and activation. These data support augmenting FXR activity as a therapeutic strategy to alleviate or prevent PNAC.

Dietary emulsifier glycerol monodecanoate affects gut microbiota contributing to regulating lipid metabolism, insulin sensitivity and inflammation

Glycerol monodecanoate (GMD) is a medium-chain monoacylglycerol that possesses emulsifying and antibacterial properties. Common emulsifiers carboxymethylcellulose and polysorbate-80 have been reported to cause intestinal microbiota dysbiosis and metabolic disturbances. While...

The Role of Bile Acids in Cardiovascular Diseases: from Mechanisms to Clinical Implications

Bile acids (BAs), key regulators in the metabolic network, are not only involved in lipid digestion and absorption but also serve as potential therapeutic targets for metabolic disorders. Studies have shown that cardiac dysfunction is associated with abnormal BA metabolic pathways. As ligands for several nuclear receptors and membrane receptors, BAs systematically regulate the homeostasis of metabolism and participate in cardiovascular diseases (CVDs), such as myocardial infarction, diabetic cardiomyopathy, atherosclerosis, arrhythmia, and heart failure. However, the molecular mechanism by which BAs trigger CVDs remains controversial. Therefore, the regulation of BA signal transduction by modulating the synthesis and composition of BAs is an interesting and novel direction for potential therapies for CVDs. Here, we mainly summarized the metabolism of BAs and their role in cardiomyocytes and noncardiomyocytes in CVDs. Moreover, we comprehensively discussed the clinical prospects of BAs in CVDs and analyzed the clinical diagnostic and application value of BAs. The latest development prospects of BAs in the field of new drug development are also prospected. We aimed to elucidate the underlying mechanism of BAs treatment in CVDs, and the relationship between BAs and CVDs may provide new avenues for the prevention and treatment of these diseases.

LKB1 in Intestinal Epithelial Cells Regulates Bile Acid Metabolism by Modulating FGF15/19 Production

BACKGROUND & AIMS

Liver kinase B1 (LKB1) is a master upstream protein kinase involved in nutrient sensing and glucose and lipid metabolism in many tissues; however, its metabolic role in intestinal epithelial cells (IEC) remains unclear. In this study, we investigated the regulatory role of LKB1 on bile acid (BA) homeostasis.

METHODS

We generated mice with IEC-specific deletion of LKB1 (LKB1^ΔIEC) and analyzed the characteristics of IEC development and BA level. In vitro assays with small interfering RNA, liquid chromatography/mass spectrometry, metagenomics, and RNA-sequencing were used to elucidate the regulatory mechanisms underlying perturbed BA homeostasis.

RESULTS

LKB1 deletion resulted in abnormal differentiation of secretory cell lineages. Unexpectedly, BA pool size increased substantially in LKB1^ΔIEC mice. A significant reduction of the farnesoid X receptor (FXR) target genes, including fibroblast growth factor 15/19 (FGF15/19), known to inhibit BA synthesis, was found in the small intestine (SI) ileum of LKB1^ΔIEC mice. We observed that LKB1 depletion reduced FGF15/19 protein level in human IECs in vitro. Additionally, a lower abundance of bile salt hydrolase-producing bacteria and elevated levels of FXR antagonist (ie, T-βMCA) were observed in the SI of LKB1^ΔIEC mice. Moreover, LKB1^ΔIEC mice showed impaired conversion of retinol to retinoic acids in the SI ileum. Subsequently, vitamin A treatment failed to induce FGF15 production. Thus, LKB1^ΔIEC mice fed with a high-fat diet showed improved glucose tolerance and increased energy expenditure.

CONCLUSIONS

LKB1 in IECs manages BA homeostasis by controlling FGF15/19 production.

Dietary Phospholipids Prepared From Scallop Internal Organs Attenuate the Serum and Liver Cholesterol Contents by Enhancing the Expression of Cholesterol Hydroxylase in the Liver of Mice

In this study, we successfully prepared scallop oil (SCO), which contains high levels of phospholipids (PL) and eicosapentaenoic acid (EPA), from the internal organs of the Japanese giant scallop (Patinopecten yessoensis), one of the most important underutilized fishery resources in Japan. The intake of SCO lowers the serum and liver cholesterol contents in mice; however, whether the fatty acids (FA) composition or PL of SCO exhibits any cholesterol-lowering effect remains unknown. To elucidate whether the cholesterol-lowering function is due to FA composition or PL of SCO, and investigate the cholesterol-lowering mechanism by SCO, in the present study, mice were fed SCO's PL fraction (SCO-PL), triglyceride (TG)-type oil with almost the same FA composition as SCO-PL, called SCO's TG fraction (SCO-TG), soybean oil (SOY-TG), and soybean's PL fraction (SOY-PL). Male C57BL/6J mice (5-week-old) were fed high-fat and cholesterol diets containing 3% (w/w) experimental oils (SOY-TG, SOY-PL, SCO-TG, and SCO-PL) for 28 days. The SCO-PL diet significantly decreased the serum and liver cholesterol contents compared with the SOY-TG diet, but the intake of SOY-PL and SCO-TG did not show this effect. This result indicated that the serum and liver cholesterol-lowering effect observed in the SCO intake group was due to the effect of SCO-PL. The cholesterol-lowering effect of SCO-PL was in part related to the promotion of liver cholesterol 7α-hydroxylase (CYP7A1) expression, which is the rate-limiting enzyme for bile acid synthesis. In contrast, the expression levels of the ileum farnesoid X receptor (Fxr) and fibroblast growth factor 15 (Fgf15), which inhibit the expression of liver CYP7A1, were significantly reduced in the SCO-PL group than the SOY-TG group. From these results, the increase in the liver CYP7A1 expression by dietary SCO-PL was in part through the reduction of the ileum Fxr/Fgf15 regulatory pathway. Therefore, this study showed that SCO-PL may be a health-promoting component as it lowers the serum and liver cholesterol contents by increasing the liver CYP7A1 expression, which is not seen in SOY-PL and SCO-TG.

A Novel Sialoglycopeptide from Gadus morhua Eggs Prevents Liver Fibrosis Induced by CCl4 via Downregulating FXR/FGF15 and TLR4/TGF-β/Smad Pathways

Liver fibrosis plays a critical role in liver disease progression. A sialoglycopeptide from the Gadus morhua eggs (Gm-SGPP) was identified having a 7000 Da molecular weight with a core pentasaccharide structure and osteogenesis activity. However, whether Gm-SGPP is beneficial to liver fibrosis remains unknown. In this study, mice with liver fibrosis were intraperitoneally injected with 2.5% CCl₄ (10 mL/kg) and orally administered with Gm-SGPP (500 mg/kg) for 30 days. Results showed that Gm-SGPP alleviated oxidative liver damage and lipid metabolism disorder and reduced hepatocyte necrosis and lipid droplet accumulation. Notably, we found that Gm-SGPP increased the number and changed the composition of bile acids via increasing cholesterol 7a-hydroxylase (CYP7A1) and sterol 27-hydroxylase (CYP27A1) expression, which caused inhibition of ileum farnesoid X receptor (FXR) expression and accelerated the cholesterol conversion. Cholesterol accumulation is a risk factor for liver fibrosis. Masson staining showed that Gm-SGPP significantly reduced the degree of collagen deposition. Western blotting further suggested that Gm-SGPP downregulated the key gene of the toll-like receptor 4 (TLR4)-mediated transforming growth factor-β (TGF-β)/Smad pathway. To our best knowledge, this is the first report that Gm-SGPP prevented liver fibrosis via attenuating cholesterol accumulation. Our present results provide new ideas for the Gadus morhua egg's high-value utilization.

Heukcha, naturally post-fermented green tea extract, ameliorates diet-induced hypercholesterolemia and NAFLD in hamster

Hypercholesterolemia, characterized by an increase in plasma low-density lipoprotein (LDL) cholesterol and total cholesterol (TC), is the leading cause of non-alcoholic fatty liver disease (NAFLD). The present study examined the effect of Heukcha extract (HCE), a naturally post-fermented green tea extract, on diet-induced hypercholesterolemia and related NAFLD in hamsters that metabolize lipids in a similar fashion to humans. The 10-week-old golden Syrian hamsters were fed a normal diet (ND) or a high cholesterol diet (HCD) containing 0.2% cholesterol and 10% lard, and some were also given HCE (200 or 500 mg/kg/day) orally for 12 weeks. The HCE did not affect the body weight gain, food intake, or the calorie intake. HCD significantly (p < 0.05) increased LDL (0.9 to 2.1 mmol/L), TC (2.7 to 7.8 mmol/L), and triglyceride (TG; 2.3 to 4.0 mmol/L), which was significantly decreased by 27.7%, 17.3%, and 60%, respectively, by HCE. HDL was significantly increased by HCD (0.6 to 1.6 mmol/L), but it was not affected by HCE administration. Furthermore, HCE suppressed HCD-induced liver oxidative stress, fibrosis, and lipid accumulation almost to control levels. Interestingly, HCE significantly increased the protein level of cholesterol 7 alpha-hydroxylase (CYP7A1), the rate-limiting enzyme for bile acid synthesis, by 1.5-fold in the liver. The present data suggest that HCE could be a functional food ingredient that can suppress the occurrence of diet-induced hypercholesterolemia and NAFLD, possibly by increasing the expression of CYP7A1.

Rosmarinic Acid Exhibits a Lipid-Lowering Effect by Modulating the Expression of Reverse Cholesterol Transporters and Lipid Metabolism in High-Fat Diet-Fed Mice

Hyperlipidemia is a potent risk factor for the development of cardiovascular diseases. The reverse cholesterol transport (RCT) process has been shown to alleviate hyperlipidemia and protect against cardiovascular diseases. Recently, rosmarinic acid was reported to exhibit lipid-lowering effects. However, the underlying mechanism is still unclear. This study aims to investigate whether rosmarinic acid lowers lipids by modulating the RCT process in high-fat diet (HFD)-induced hyperlipidemic C57BL/6J mice. Our results indicated that rosmarinic acid treatment significantly decreased body weight, blood glucose, and plasma total cholesterol and triglyceride levels in HFD-fed mice. Rosmarinic acid increased the expression levels of cholesterol uptake-associated receptors in liver tissues, including scavenger receptor B type 1 (SR-B1) and low-density lipoprotein receptor (LDL-R). Furthermore, rosmarinic acid treatment notably increased the expression of cholesterol excretion molecules, ATP-binding cassette G5 (ABCG5) and G8 (ABCG8) transporters, and cholesterol 7 alpha-hydroxylase A1 (CYP7A1) as well as markedly reduced cholesterol and triglyceride levels in liver tissues. In addition, rosmarinic acid facilitated fatty acid oxidation through AMP-activated protein kinase (AMPK)-mediated carnitine palmitoyltransferase 1A (CPT1A) induction. In conclusion, rosmarinic acid exhibited a lipid-lowering effect by modulating the expression of RCT-related proteins and lipid metabolism-associated molecules, confirming its potential for the prevention or treatment of hyperlipidemia-derived diseases.

Role of Cholesterol-Associated Steatohepatitis in the Development of NASH

The rising prevalence of nonalcoholic fatty liver disease (NAFLD) and NAFLD-related cirrhosis in the United States and globally highlights the need to better understand the mechanisms causing progression of hepatic steatosis to fibrosing steatohepatitis and cirrhosis in a small proportion of patients with NAFLD. Accumulating evidence suggests that lipotoxicity mediated by hepatic free cholesterol (FC) overload is a mechanistic driver for necroinflammation and fibrosis, characteristic of nonalcoholic steatohepatitis (NASH), in many animal models and also in some patients with NASH. Diet, lifestyle, obesity, key genetic polymorphisms, and hyperinsulinemia secondary to insulin resistance are pivotal drivers leading to aberrant cholesterol signaling, which leads to accumulation of FC within hepatocytes. FC overload in hepatocytes can lead to ER stress, mitochondrial dysfunction, development of toxic oxysterols, and cholesterol crystallization in lipid droplets, which in turn lead to hepatocyte apoptosis, necrosis, or pyroptosis. Activation of Kupffer cells and hepatic stellate cells by hepatocyte signaling and cholesterol loading contributes to this inflammation and leads to hepatic fibrosis. Cholesterol accumulation in hepatocytes can be readily prevented or reversed by statins. Observational studies suggest that use of statins in NASH not only decreases the substantially increased cardiovascular risk, but may ameliorate liver pathology. Conclusion: Hepatic FC loading may result in cholesterol-associated steatohepatitis and play an important role in the development and progression of NASH. Statins appear to provide significant benefit in preventing progression to NASH and NASH-cirrhosis. Randomized controlled trials are needed to demonstrate whether statins or statin/ezetimibe combination can effectively reverse steatohepatitis and liver fibrosis in patients with NASH.

Deletion of Intestinal SHP Impairs Short-term Response to Cholic Acid Challenge in Male Mice

Small heterodimer partner (SHP) is a crucial regulator of bile acid (BA) transport and synthesis; however, its intestine-specific role is not fully understood. Here, we report that male intestine-specific Shp knockout (IShpKO) mice exhibit higher intestinal BA but not hepatic or serum BA levels compared with the f/f Shp animals when challenged with an acute (5-day) 1% cholic acid (CA) diet. We also found that BA synthetic genes Cyp7a1 and Cyp8b1 are not repressed to the same extent in IShpKO compared with control mice post-CA challenge. Loss of intestinal SHP did not alter Fxrα messenger RNA (mRNA) but increased Asbt (BA ileal uptake transporter) and Ostα (BA ileal efflux transporter) expression even under chow-fed conditions. Surprisingly, the acute CA diet in IShpKO did not elicit the expected induction of Fgf15 but was able to maintain the suppression of Asbt, and Ostα/β mRNA levels. At the protein level, apical sodium-dependent bile acid transporter (ASBT) was downregulated, while organic solute transporter-α/β (OSTα/β) expression was induced and maintained regardless of diet. Examination of ileal histology in IShpKO mice challenged with acute CA diet revealed reduced villi length and goblet cell numbers. However, no difference in villi length, and the expression of BA regulator and transporter genes, was seen between f/f Shp and IShpKO animals after a chronic (14-day) CA diet, suggesting a potential adaptive response. We found the upregulation of the Pparα-Ugt axis after 14 days of CA diet may reduce the BA burden and compensate for the ileal SHP function. Thus, our study reveals that ileal SHP expression contributes to both overall intestinal structure and BA homeostasis.

Bicyclol Alleviates Signs of BDL-Induced Cholestasis by Regulating Bile Acids and Autophagy-Mediated HMGB1/p62/Nrf2 Pathway

Cholestasis is a liver disease characterized by the accumulation of toxic bile salts, bilirubin, and cholesterol, resulting in hepatocellular damage. Recent findings have revealed several key steps of cholestasis liver injury including the toxicity of bile acids and accumulation of proinflammatory mediator. In this study, we investigated the protective effect of bicyclol in cholestasis caused by bile duct ligation (BDL), as well as relevant mechanisms. Bicyclol attenuated liver damage in BDL mice by increasing the levels of hydrophilic bile acid such as α-MCA and β-MCA, regulating bile acid-related pathways and improving histopathological indexes. High-mobility group box 1 (HMGB1) is an extracellular damage-associated molecular pattern molecule which can be used as biomarkers of cells and host defense. Bicyclol treatment decreased extracellular release of HMGB1. In addition, HMGB1 is also involved in regulating autophagy in response to oxidative stress. Bicyclol promoted the lipidation of LC3 (microtubule-associated protein 1 light chain 3)-Ⅱ to activate autophagy. The nuclear factor, E2-related factor 2 (Nrf2) and its antioxidant downstream genes were also activated. Our results indicate that bicyclol is a promising therapeutic strategy for cholestasis by regulating the bile acids and autophagy-mediated HMGB1/p62/Nrf2 pathway.

Hepatic cholesterol transport and its role in non-alcoholic fatty liver disease and atherosclerosis

Non-alcoholic fatty liver disease (NAFLD) is a quickly emerging global health problem representing the most common chronic liver disease in the world. Atherosclerotic cardiovascular disease represents the leading cause of mortality in NAFLD patients. Cholesterol metabolism has a crucial role in the pathogenesis of both NAFLD and atherosclerosis. The liver is the major organ for cholesterol metabolism. Abnormal hepatic cholesterol metabolism not only leads to NAFLD but also drives the development of atherosclerotic dyslipidemia. The cholesterol level in hepatocytes reflects the dynamic balance between endogenous synthesis, uptake, esterification, and export, a process in which cholesterol is converted to neutral cholesteryl esters either for storage in cytosolic lipid droplets or for secretion as a major constituent of plasma lipoproteins, including very-low-density lipoproteins, chylomicrons, high-density lipoproteins, and low-density lipoproteins. In this review, we describe decades of research aimed at identifying key molecules and cellular players involved in each main aspect of hepatic cholesterol metabolism. Furthermore, we summarize the recent advances regarding the biological processes of hepatic cholesterol transport and its role in NAFLD and atherosclerosis.

Estradiol treatment or modest exercise improves hepatic health and mitochondrial outcomes in female mice following ovariectomy

We recently reported that compared with males, female mice have increased hepatic mitochondrial respiratory capacity and are protected against high-fat diet-induced steatosis. Here, we sought to determine the role of estrogen in hepatic mitochondrial function, steatosis, and bile acid metabolism in female mice and investigate potential benefits of exercise in the absence or presence of estrogen via ovariectomy (OVX). Female C57BL mice (n = 6 per group) were randomly assigned to sham surgery (sham), ovariectomy (OVX), or OVX plus estradiol replacement therapy (OVX + Est). Half of the mice in each treatment group were sedentary (SED) or had access to voluntary wheel running (VWR). All mice were fed a high-fat diet (HFD) and were housed at thermoneutral temperatures. We assessed isolated hepatic mitochondrial respiratory capacity using the Oroboros O2k with both pyruvate and palmitoylcarnitine as substrates. As expected, OVX mice presented with greater hepatic steatosis, weight gain, and fat mass gain compared with sham and OVX + Est animals. Hepatic mitochondrial coupling (basal/state 3 respiration) with pyruvate was impaired following OVX, but both VWR and estradiol treatment rescued coupling to levels greater than or equal to sham animals. Estradiol and exercise also had different effects on liver electron transport chain protein expression depending on OVX status. Markers of bile acid metabolism and excretion were also impaired by ovariectomy but rescued with estradiol add-back. Together our data suggest that estrogen depletion impairs hepatic mitochondrial function and liver health, and that estradiol replacement and modest exercise can aid in rescuing this phenotype.NEW & NOTEWORTHY OVX induces hepatic steatosis in sedentary mice which can be prevented by modest physical activity (VWR) and/or estradiol treatment. Estrogen impacts hepatic mitochondrial coupling in a substrate-specific manner. OVX mice have impaired fecal bile acid excretion, which was rescued with estradiol treatment.

Recent Molecular Mechanisms and Beneficial Effects of Phytochemicals and Plant-Based Whole Foods in Reducing LDL-C and Preventing Cardiovascular Disease

Abnormal lipid metabolism leads to the development of hyperlipidemia, a common cause of multiple chronic disorders, including cardiovascular disease (CVD), obesity, diabetes, and cerebrovascular disease. Low-density lipoprotein cholesterol (LDL-C) currently remains the primary target for treatment of hyperlipidemia. Despite the advancement of treatment and prevention of hyperlipidemia, medications used to manage hyperlipidemia are limited to allopathic drugs, which present certain limitations and adverse effects. Increasing evidence indicates that utilization of phytochemicals and plant-based whole foods is an alternative and promising strategy to prevent hyperlipidemia and CVD. The current review focuses on phytochemicals and their pharmacological mode of actions for the regulation of LDL-C and prevention of CVD. The important molecular mechanisms illustrated in detail in this review include elevation of reverse cholesterol transport, inhibition of intestinal cholesterol absorption, acceleration of cholesterol excretion in the liver, and reduction of cholesterol synthesis. Moreover, the beneficial effects of plant-based whole foods, such as fresh fruits, vegetables, dried nuts, flax seeds, whole grains, peas, beans, vegan diets, and dietary fibers in LDL-C reduction and cardiovascular health are summarized. This review concludes that phytochemicals and plant-based whole foods can reduce LDL-C levels and lower the risk for CVD.

Glucagon-like peptide 1 analogue prevents cholesterol gallstone formation by modulating intestinal farnesoid X receptor activity

BACKGROUND & AIMS

Cholesterol gallstone disease (CGD) is a common gastrointestinal disease. Liraglutide, an analogue of glucagon-like peptide 1, has been approved to treat type 2 diabetes. Clinical studies have suggested a potential role of liraglutide in CGD.

METHODS

Mice were subcutaneously injected with liraglutide, then fed a lithogenic diet. Bile duct cannulation was performed to collect bile output in mice. Intestinal-specific ablation or pharmacological inhibition of farnesoid X receptor (FXR) was used to study its functions in CGD.

RESULTS

Liraglutide could protect mice against CGD. Liraglutide treatment increased the biliary concentration of cholesterol, phospholipids and bile acids and thereby decreased the cholesterol saturation index. The resistance to CGD conferred by liraglutide is likely a result of increased bile acid synthesis and efficient bile acid transport. The expression of a key bile acid synthetic enzyme, Cyp7a1, was significantly increased in liraglutide-treated mice. The increased expression of Cyp7a1 resulted from a relieved suppression signal of Fgf15 from the ileum. Mechanistically, liraglutide treatment altered bile acid composition and suppressed FXR activity in the ileum. Genetic ablation or pharmacological inhibition of FXR in the intestine protected mice against CGD. More importantly, intestinal FXR was required for liraglutide-mediated regulation of hepatic expression of Cyp7a1.

CONCLUSION

Liraglutide improved CGD by increasing bile acid secretion and decreasing cholesterol saturation index. Liraglutide attenuates the negative feedback inhibition of bile acids through inhibiting intestinal FXR activity. Our results suggest that liraglutide may represent a novel way for treating or preventing cholesterol gallstones in individuals with high risk of CGD.

The pathophysiological function of non-gastrointestinal farnesoid X receptor

Farnesoid X receptor (FXR) influences bile acid homeostasis and the progression of various diseases. While the roles of hepatic and intestinal FXR in enterohepatic transport of bile acids and metabolic diseases were reviewed previously, the pathophysiological functions of FXR in non-gastrointestinal cells and tissues have received little attention. Thus, the roles of FXR in the liver, immune system, nervous system, cardiovascular system, kidney, and pancreas beyond the gastrointestinal system are reviewed herein. Gain of FXR function studies in non-gastrointestinal tissues reveal that FXR signaling improves various experimentally-induced metabolic and immune diseases, including non-alcoholic fatty liver disease, type 2 diabetes, primary biliary cholangitis, sepsis, autoimmune diseases, multiple sclerosis, and diabetic nephropathy, while loss of FXR promotes regulatory T cells production, protects the brain against ischemic injury, atherosclerosis, and inhibits pancreatic tumor progression. The downstream pathways regulated by FXR are diverse and tissue/cell-specific, and FXR has both ligand-dependent and ligand-independent activities, all of which may explain why activation and inhibition of FXR signaling could produce paradoxical or even opposite effects in some experimental disease models. FXR signaling is frequently compromised by diseases, especially during the progressive stage, and rescuing FXR expression may provide a promising strategy for boosting the therapeutic effect of FXR agonists. Tissue/cell-specific modulation of non-gastrointestinal FXR could influence the treatment of various diseases. This review provides a guide for drug discovery and clinical use of FXR modulators.

Sitosterolemia: Twenty Years of Discovery of the Function of ABCG5ABCG8

Sitosterolemia is a lipid disorder characterized by the accumulation of dietary xenosterols in plasma and tissues caused by mutations in either ABCG5 or ABCG8. ABCG5 ABCG8 encodes a pair of ABC half transporters that form a heterodimer (G5G8), which then traffics to the surface of hepatocytes and enterocytes and promotes the secretion of cholesterol and xenosterols into the bile and the intestinal lumen. We review the literature from the initial description of the disease, the discovery of its genetic basis, current therapy, and what has been learned from animal, cellular, and molecular investigations of the transporter in the twenty years since its discovery. The genomic era has revealed that there are far more carriers of loss of function mutations and likely pathogenic variants of ABCG5 ABCG8 than previously thought. The impact of these variants on G5G8 structure and activity are largely unknown. We propose a classification system for ABCG5 ABCG8 mutants based on previously published systems for diseases caused by defects in ABC transporters. This system establishes a framework for the comprehensive analysis of disease-associated variants and their impact on G5G8 structure-function.

Pentoxifylline Attenuates Arsenic Trioxide-Induced Cardiac Oxidative Damage in Mice

This study was undertaken to evaluate the therapeutic potential effect of pentoxifylline (PTX) against arsenic trioxide (ATO)-induced cardiac oxidative damage in mice. Thirty-six male albino mice were divided into six groups and treated intraperitoneally with normal saline (group 1), ATO (5 mg/kg; group 2), PTX (100 mg/kg; group 3), and different doses of PTX (25, 50, and 100 mg/kg; groups 4, 5, and 6, respectively) with ATO. After four weeks, the blood sample was collected for biochemical experiments. In addition, cardiac tissue was removed for assessment of oxidative stress markers and histopathological changes (such as hemorrhage, necrosis, infiltration of inflammatory cells, and myocardial degeneration). The findings showed that ATO caused a significant raise in serum biochemical markers such as lactate dehydrogenase (LDH), creatine phosphokinase (CPK) and troponin-I (cTnI), glucose, total cholesterol (TC), and triglyceride (TG) levels. In addition to histopathological changes in cardiac tissue, ATO led to the significant increase in cardiac lipid peroxidation (LPO) and nitric oxide (NO); remarkable decrease in the activity of cardiac antioxidant enzymes such as catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx); and the depletion of the total antioxidant capacity (TAC) and total thiol groups (TTGs). PTX was able to reduce the increased levels of serum cardiac markers (LDH, CPK, cTnI, TC, and TG), cardiac LPO, and improve antioxidant markers (TAC, TTGs, CAT, SOD, and GPx) alongside histopathologic changes. However, no significant changes were observed in elevated serum glucose and cardiac NO levels. In conclusion, the current study showed the potential therapeutic effect of PTX in the prevention of ATO-induced cardiotoxicity via reversing the oxidative stress.

Hypolipidemic and Hepatoprotective Effects of Polysaccharides Extracted from Liriope spicata Var. Prolifera in C57BL/6J Mice with High-Fat Diet-Induced Hyperlipidemia

In this study, C57BL/6J mice with high-fat diet- (HFD-) induced hyperlipidemia were treated with total Liriope spicata var. prolifera polysaccharides (TLSP: 200, 400, and 800 mg/kg body weight), simvastatin (3 mg/kg body weight), or saline for 8 weeks, respectively. The results showed that TLSP had strong lipid-lowering and hepatoprotective effects on C57BL/6J mice with HFD-induced hyperlipidemia. TLSP administration significantly reduced serum total cholesterol (TC), triglyceride (TG), and low-density lipoprotein cholesterol (LDL-C) levels and downregulated the expressions of peroxisome proliferator-activated receptor (PPAR)γ and fatty acid synthase (FAS) in the adipose and liver tissues of the mice. TLSP exerted hypolipidemic and hepatoprotective effects by activating lipid/bile acid metabolism via the FXH-SHP/CYP7A1 and SEBP-1c/FAC/ACC signaling pathways. Thus, TLPS is a promising natural polymer with hepatoprotective and hypolipidemic properties.