Effects of CYP7A1 overexpression on cholesterol and bile acid homeostasis

New insights into the regulation of bile acids synthesis during the early stages of liver regeneration: A human and experimental study

BACKGROUND AND AIMS

Liver regeneration is essential for the preservation of homeostasis and survival. Bile acids (BAs)-mediated signaling is necessary for liver regeneration, but BAs levels need to be carefully controlled to avoid hepatotoxicity. We studied the early response of the BAs-fibroblast growth factor 19 (FGF19) axis in healthy individuals undergoing hepatectomy for living donor liver transplant. We also evaluated BAs synthesis in mice upon partial hepatectomy (PH) and acute inflammation, focusing on the regulation of cytochrome-7A1 (CYP7A1), a key enzyme in BAs synthesis from cholesterol.

METHODS

Serum was obtained from twelve human liver donors. Mice underwent 2/3-PH or sham-operation. Acute inflammation was induced with bacterial lipopolysaccharide (LPS) in mice fed control or antoxidant-supplemented diets. BAs and 7α-hydroxy-4-cholesten-3-one (C4) levels were measured by HPLC-MS/MS; serum FGF19 by ELISA. Gene expression and protein levels were analyzed by RT-qPCR and western-blot.

RESULTS

Serum BAs levels increased after PH. In patients with more pronounced hypercholanemia, FGF19 concentrations transiently rose, while C4 levels (a readout of CYP7A1 activity) dropped 2 h post-resection in all cases. Serum BAs and C4 followed the same pattern in mice 1 h after PH, but C4 levels also dropped in sham-operated and LPS-treated animals, without marked changes in CYP7A1 protein levels. LPS-induced serum C4 decline was attenuated in mice fed an antioxidant-supplemented diet.

CONCLUSIONS

In human liver regeneration FGF19 upregulation may constitute a protective response from BAs excess during liver regeneration. Our findings suggest the existence of post-translational mechanisms regulating CYP7A1 activity, and therefore BAs synthesis, independent from CYP7A1/Cyp7a1 gene transcription.

A meta-analysis of the pooled impact of CYP7A1 single nucleotide polymorphisms on serum lipid responses to statins

Background and Aims: Various publications suggested that there is an association between CYP7A1 single nucleotide polymorphisms (SNP) and a reduced response to statin therapy, but the results were inconsistent. This study aimed to collectively review these publications to appraise the effect of statins on cholesterol control in carriers of CYP7A1 variant alleles. Methods: PUBMED, Cochrane and EMBASE were searched systematically to identify reported studies on the lipid responses to statin treatment between carriers of the variant allele versus the non-variant allele of CYP7A1 SNPs. The change from baseline in lipid responses for all included studies were calculated using weighted mean differences (WMD) (with 95% confidence interval (CI)). A meta-analysis was conducted to pool results using either the random-effects model or the fixed effects model. Results: A total of 6 publications comprising of 1,686 subjects for the assessment of total cholesterol, LDL-C and HDL-C and 1,156 subjects for the assessment of triglycerides were included in the meta-analyses. Subjects who were non-carriers of a CYP7A1 SNP (-204 A/C (rs3808607), -278 A/C (rs3808607) and rs8192875) had a greater reduction in total cholesterol (overall WMD -0.17, 95% CI -0.29, -0.06) and LDL-C levels (overall WMD -0.16, 95% CI -0.26, -0.05) as compared with subjects who borne the variant allele of CYP7A1 SNPs when administered a statin. Conclusion: The presence of variant allele of CYP7A1 SNPs may result in suboptimal control of total cholesterol and LDL-C levels as compared with individuals who do not carry the variant allele, when administered an equivalent dose of statin.

Reshaping the gut microbiome and bile acid composition by Gyejibongnyeong-hwan ameliorates western diet-induced dyslipidemia

Gyejibongnyeong-hwan (GBH), a traditional Chinese medicine, is used in clinical practice to treat blood stasis in metabolic diseases. Herein, we examined the effects of GBH on dyslipidemia and investigated the underlying mechanisms by focusing on modulation of the gut microbiota-bile acid axis by GBH. We utilized a Western diet-induced dyslipidemia mouse model and divided animals into the following four groups (n = 5 each): the normal chow diet, vehicle control (WD), simvastatin (Sim, 10 mg/kg/day simvastatin; positive control), and GBH (GBH, 300 mg/kg/day) groups. The drugs were administered for 10 weeks, and morphological changes in the liver and aorta were analyzed. The mRNA expression of genes related to cholesterol metabolism, gut microbiota, and bile acid profiles were also evaluated. The GBH group showed significantly lower levels of total cholesterol, accumulation of lipids, and inflammatory markers in the liver and aorta of Western diet-fed mice. Low-density lipoprotein cholesterol levels were significantly lower in the GBH group than in the WD group (P < 0.001). The expression of cholesterol excretion-associated genes such as liver X receptor alpha and ATP-binding cassette subfamily G member 8, as well as the bile acid synthesis gene cholesterol 7 alpha-hydroxylase, which lowers cholesterol in circulation, was increased. Furthermore, GBH inhibited the intestinal farnesoid X receptor (FXR)-fibroblast growth factor 15 signaling pathway through the interactions of gut microbiota with bile acids acting as FXR ligands, which included chenodeoxycholic acid and lithocholic acid. Overall, GBH improved dyslipidemia induced by a Western diet by modulating the gut microbiota-bile acid axis.

Role of Gut Microbiome in Atherosclerosis: Molecular and Therapeutic Aspects

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

Genetics, genomics, and diet interactions in obesity in the Latin American environment

Obesity is a chronic disease characterized by abnormal or excessive fat accumulation that could impact an individual's health; moreover, the World Health Organization (WHO) has declared obesity a global epidemic since 1997. In Latin America, in 2016, reports indicated that 24.2% of the adult population was obese. The environmental factor or specific behaviors like dietary intake or physical activity have a vital role in the development of a condition like obesity, but the interaction of genes could contribute to that predisposition. Hence, it is vital to understand the relationship between genes and disease. Indeed, genetics in nutrition studies the genetic variations and their effect on dietary response; while genomics in nutrition studies the role of nutrients in gene expression. The present review represents a compendium of the dietary behaviors in the Latin American environment and the interactions of genes with their single nucleotide polymorphisms (SNPs) associated with obesity, including the risk allele frequencies in the Latin American population. Additionally, a bibliographical selection of several studies has been included; these studies examined the impact that dietary patterns in Latin American environments have on the expression of numerous genes involved in obesity-associated metabolic pathways.

Dietary bile acids supplementation modulates immune response, antioxidant capacity, glucose, and lipid metabolism in normal and intrauterine growth retardation piglets

Intrauterine growth retardation (IUGR) results in intestinal dysfunction contributing to metabolic syndrome and growth lag of piglets. Bile acid (BA) presents various bioactivities, including regulation roles in antioxidant, anti-inflammation, and glucose and lipid metabolism. Forty-eight weaned piglets were allocated to four groups in a 2 × 2 factorial arrangement with the effects of BA supplementation and IUGR challenge. Twenty-four IUGR piglets and 24 normal birth weight (NBW) piglets were allocated into two groups, respectively, including the control group fed with a basal diet, and the treatment group fed a basal diet supplemented with 400 mg/kg BA. The experiment lasted 28 days. The results indicated that BA improved liver and spleen indexes in IUGR piglets, whereas decreased blood RDW-CV and RDW-SD regardless of IUGR (P < 0.05). Dietary BA supplementation decreased plasma CAT activity and liver GSH concentration regardless of IUGR, whereas increased plasma GSH and liver H₂O₂ and decreased liver T-AOC in weaned piglets (P < 0.05). In addition, IUGR downregulated liver Nrf1 and Nrf2 expression levels, while BA supplementation upregulated the Nrf2 expression of liver in weaned piglets (P < 0.05). Dietary BA decreased (P < 0.05) jejunal GSH concentration and ileal CAT activity regardless of IUGR. Furthermore, IUGR upregulated (P < 0.05) jejunal SOD and CAT expression levels; however, dietary BA upregulated ileal Nrf1 (P < 0.05) and Keap1 (P = 0.07) expression levels in piglets regardless of IUGR. Moreover, IUGR upregulated the liver lipid synthesis (FAS) and downregulated HSL and SCD1 expression levels, while dietary BA downregulated liver FAS and SCD1 expression levels (P < 0.05). However, BA supplementation could enhance liver gluconeogenesis by upregulating (P < 0.05) the liver G6PC and PCK1 expression levels in the NBW piglets but not in the IUGR piglets. Collectively, these findings suggest that BA could regulate the redox status of weaned piglets by regulating the Nrf2/Keap1 pathway and improving liver glucose and lipid metabolism of IUGR piglets. These findings will provide a reference for the application of BA in swine production; moreover, considering the physiological similarity between pigs and humans, these findings will provide a reference for IUGR research in humans.

A novel differentiated HuH-7 cell model to examine bile acid metabolism, transport and cholestatic hepatotoxicity

Hepatic cell lines serve as economical and reproducible alternatives for primary human hepatocytes. However, the utility of hepatic cell lines to examine bile acid homeostasis and cholestatic toxicity is limited due to abnormal expression and function of bile acid-metabolizing enzymes, transporters, and the absence of canalicular formation. We discovered that culturing HuH-7 human hepatoma cells with dexamethasone (DEX) and 0.5% dimethyl sulfoxide (DMSO) for two weeks, with Matrigel overlay after one week, resulted in a shorter and improved differentiation process. These culture conditions increased the expression and function of the major bile acid uptake and efflux transporters, sodium taurocholate co-transporting polypeptide (NTCP) and the bile salt export pump (BSEP), respectively, in two-week cultures of HuH-7 cells. This in vitro model was further characterized for expression and function of bile acid-metabolizing enzymes, transporters, and cellular bile acids. Differentiated HuH-7 cells displayed a marked shift in bile acid composition and induction of cytochrome P450 (CYP) 7A1, CYP8B1, CYP3A4, and bile acid-CoA: amino acid N-acyltransferase (BAAT) mRNAs compared to control. Inhibition of taurocholate uptake and excretion after a 24-h treatment with prototypical cholestatic drugs suggests that differentiated HuH-7 cells are a suitable model to examine cholestatic hepatotoxicity.

Metabolites of gut microbiota fermenting Poria cocos polysaccharide alleviates chronic nonbacterial prostatitis in rats

Chronic nonbacterial prostatitis (CNP) is a common urology disease. Our previous research found Poria cocos polysaccharides (PPs) alleviated CNP and suggested the effect was related to gut bacteria. We investigated the crucial bacteria and their metabolites responsible for the anti-CNP effect to discover possible mechanisms. The results showed that after the fermentation of PPs by human fecal microbiota, Parabacteroides, Fusicatenibacter, and Parasutterella were significantly enriched. Haloperidol glucuronide and 7-ketodeoxycholic acid generated by these bacteria could be responsible for the increased expression of Alox15 and Pla2g2f and the reduced expression of Cyp1a1 and Hsd17b7 in colon epithelium. The ratio of dihydrotestosterone to estradiol in serum was regulated, and CNP was alleviated. Our results suggested that Parabacteroides, Fusicatenibacter, and Parasutterella could be the essential bacteria in CNP alleviation and their metabolites of PPs 7-ketodeoxycholic acid and haloperidol glucuronide could be the signal molecules of the "gut-prostate axis".

Effect of Lactobacillus fermentum HFY06 Combined with Arabinoxylan on Reducing Lipid Accumulation in Mice Fed with High-Fat Diet

In this experiment, a high-fat diet was used to induce hyperlipidemia in mice to determine the synergistic effect of AX and L. fermentum HFY06 on the prevention of hyperlipidemia and its potential regulatory mechanism. The results of this study showed that after the AX and L. fermentum HFY06 synergistic intervention, the body weight, epididymal fat index, blood lipid level, and liver function indexes of mice were improved. In addition, the synbiotics comprising AX and L. fermentum HFY06 increased the CAT activity in the serum of mice on a high-fat diet, reduced NO and MDA levels, and improved the body's oxidative stress. From the perspective of molecular biology, on the one hand, AX and L. fermentum HFY06 synergistic intervention activated the AMPK pathway to regulate body lipid metabolism; up-regulated the mRNA expressions of CPT-1, PPAR-α, CYP7A1, and HSL; and down-regulated the mRNA expressions of ACC, C/EBPα, and LPL. On the other hand, the synergistic effect of AX and HFY06 enhanced the mRNA expressions of ZO-1, occludin, and claudin-1 in the small intestine of mice, increased the strength of the intestinal barrier, and optimized the composition of the intestinal microbiota. From the above results, it can be concluded that AX and L. fermentum HFY06 have a synergistic effect in improving hyperlipidemia. However, this study was only performed using animal models, and the lipid synthesis and metabolism mechanism are complicated; hence, further clinical studies are needed.

Sex-specific alterations in hepatic cholesterol metabolism in low birth weight adult guinea pigs

BACKGROUND

Intrauterine growth restriction and low birth weight (LBW) have been widely reported as an independent risk factor for adult hypercholesterolaemia and increased hepatic cholesterol in a sex-specific manner. However, the specific impact of uteroplacental insufficiency (UPI), a leading cause of LBW in developed world, on hepatic cholesterol metabolism in later life, is ill defined and is clinically relevant in understanding later life liver metabolic health trajectories.

METHODS

Hepatic cholesterol, transcriptome, cholesterol homoeostasis regulatory proteins, and antioxidant markers were studied in UPI-induced LBW and normal birth weight (NBW) male and female guinea pigs at 150 days.

RESULTS

Hepatic free and total cholesterol were increased in LBW versus NBW males. Transcriptome analysis of LBW versus NBW livers revealed that "cholesterol metabolism" was an enriched pathway in LBW males but not in females. Microsomal triglyceride transfer protein and cytochrome P450 7A1 protein, involved in hepatic cholesterol efflux and catabolism, respectively, and catalase activity were decreased in LBW male livers. Superoxide dismutase activity was reduced in LBW males but increased in LBW females.

CONCLUSIONS

UPI environment is associated with a later life programed hepatic cholesterol accumulation via impaired cholesterol elimination in a sex-specific manner. These programmed alterations could underlie later life cholesterol-induced hepatic lipotoxicity in LBW male offspring.

IMPACT

Low birth weight (LBW) is a risk factor for increased hepatic cholesterol. Uteroplacental insufficiency (UPI) resulting in LBW increased hepatic cholesterol content, altered hepatic expression of cholesterol metabolism-related genes in young adult guinea pigs. UPI-induced LBW was also associated with markers of a compromised hepatic cholesterol elimination process and failing antioxidant system in young adult guinea pigs. These changes, at the current age studied, were sex-specific, only being observed in LBW males and not in LBW females. These programmed alterations could lead to further hepatic damage and greater predisposition to liver diseases in UPI-induced LBW male offspring as they age.

Novel Bile Acid-Dependent Mechanisms of Hepatotoxicity Associated with Tyrosine Kinase Inhibitors

Drug-induced liver injury (DILI) is the leading cause of acute liver failure and a major concern in drug development. Altered bile acid homeostasis via inhibition of the bile salt export pump (BSEP) is one mechanism of DILI. Dasatinib, pazopanib, and sorafenib are tyrosine kinase inhibitors (TKIs) that competitively inhibit BSEP and increase serum biomarkers for hepatotoxicity in ∼25-50% of patients. However, the mechanism(s) of hepatotoxicity beyond competitive inhibition of BSEP are poorly understood. This study examined mechanisms of TKI-mediated hepatotoxicity associated with altered bile acid homeostasis. Dasatinib, pazopanib, and sorafenib showed bile acid-dependent toxicity at clinically relevant concentrations, based on the C-DILI assay using sandwich-cultured human hepatocytes (SCHH). Among several bile acid-relevant genes, cytochrome P450 (CYP) 7A1 mRNA was specifically upregulated by 6.2- to 7.8-fold (dasatinib) and 5.7- to 9.3-fold (pazopanib), compared with control, within 8 hours. This was consistent with increased total bile acid concentrations in culture medium up to 2.3-fold, and in SCHH up to 1.4-fold, compared with control, within 24 hours. Additionally, protein abundance of sodium taurocholate co-transporting polypeptide (NTCP) was increased up to 2.0-fold by these three TKIs. The increase in NTCP protein abundance correlated with increased function; dasatinib and pazopanib increased hepatocyte uptake clearance (CL_uptake) of taurocholic acid, a probe bile acid substrate, up to 1.4-fold. In conclusion, upregulation of CYP7A1 and NTCP in SCHH constitute novel mechanisms of TKI-associated hepatotoxicity. SIGNIFICANCE STATEMENT: Understanding the mechanisms of hepatotoxicity associated with tyrosine kinase inhibitors (TKIs) is fundamental to development of effective and safe intervention therapies for various cancers. Data generated in sandwich-cultured human hepatocytes, an in vitro model of drug-induced hepatotoxicity, revealed that TKIs upregulate bile acid synthesis and alter bile acid uptake and excretion. These findings provide novel insights into additional mechanisms of bile acid-mediated drug-induced liver injury, an adverse effect that limits the use and effectiveness of TKI treatment in some cancer patients.

α-globulin-rich rice cultivar, low glutelin content-1 (LGC-1), decreases serum cholesterol concentration in exogenously hypercholesterolemic rats

BACKGROUND

Rice α-globulin has been reported to have serum cholesterol-lowering activity in rats. However, it is still unclear whether α-globulin exerts this effect when taken as one of the dietary components. In the present study, we investigated the effect of two cultivars of rice, low glutelin content (LGC)-1 and LGC-Jun, on reducing serum cholesterol in exogenously hypercholesterolemic (ExHC) rats. LGC-1 is enriched in α-globulin (10.6 mg g^-1 rice flour, which is an approximately 1.5 times higher α-globulin content than in Koshihikari a predominant rice cultivar in Japan), whereas LGC-Jun is a globulin-negative cultivar.

METHODS

ExHC rats, the model strain of diet-induced hypercholesterolemia, were fed 50% LGC-1 or LGC-Jun and 0.5% cholesterol-containing diets for 2 weeks, followed by measurement of cholesterol metabolism parameters in serum and tissues.

RESULTS

Serum cholesterol and non-high-density lipoprotein cholesterol levels were significantly lower in the LGC-1 group compared to the LGC-Jun group. Cholesterol intestinal absorption markers, hepatic and serum levels of campesterol and β-sitosterol, and lymphatic cholesterol transport were not different between the two groups. Levels of 7α-hydroxycholesterol, an intermediate of bile acid synthesis, showed a downward trend in the livers of rats that were fed LGC-1 (P = 0.098). There was a significant decrease in the hepatic mRNA expression of Cyp7a1 (a synthetic enzyme for 7α-hydroxycholesterol) in the LGC-1 group compared to the LGC-Jun group.

CONCLUSION

Dietary LGC-1 significantly decreased serum cholesterol levels in ExHC rats. The possible mechanism for the cholesterol-lowering activity of LGC-1 is partial inhibition of bile acid and cholesterol synthesis in the liver. © 2021 Society of Chemical Industry.

Effects of Xylooligosaccharides on Lipid Metabolism, Inflammation, and Gut Microbiota in C57BL/6J Mice Fed a High-Fat Diet

Xylooligosaccharide (XOS) is a source of prebiotics with multiple biological activities. The present study aimed to investigate the effects of XOS on mice fed a high-fat diet. Mice were fed either a normal diet or a high-fat diet supplemented without or with XOS (250 and 500 mg/kg), respectively, for 12 weeks. The results showed that the XOS inhibited mouse weight gain, decreased the epididymal adipose index, and improved the blood lipid levels, including triglyceride (TG), total cholesterol (TC), and low-density lipoprotein cholesterol (LDL-C) levels. Moreover, XOS reduced the activity of alanine aminotransferase (ALT) and aspartate aminotransferase (AST), and alleviated the damage to the liver caused by the high-fat diet. XOS also reduced hyperlipidemia-associated inflammatory responses. Additionally, quantitative real-time polymerase chain reaction results showed that XOS intervention activated the AMP-activated protein kinase (AMPK) pathway to regulate the fat synthesis, decomposition, and β oxidation; upregulated the mRNA expression levels of carnitine palmitoyl transferase 1 (CPT-1), peroxisome proliferator-activated receptors α (PPAR-α), and cholesterol 7-alpha hydroxylase (CYP7A1); and downregulated the mRNA expression levels of acetyl-CoA carboxylase (ACC), CCAAT/enhancer-binding protein alpha (C/EBPα), and lipoprotein lipase (LPL). On the other hand, XOS enhanced the mRNA expression levels of zonula occludens-1 (ZO-1), occludin, and claudin-1 in the small intestine; increased the strength of the intestinal barrier; and optimized the composition of the intestinal microbiota. Therefore, it was concluded that XOS regulated the intestinal barrier, changed the intestinal microecology, and played an important role in preventing hyperlipidemia through the unique anatomical advantages of the gut-liver axis.

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.

High-throughput toxicogenomic screening of chemicals in the environment using metabolically competent hepatic cell cultures

The ToxCast in vitro screening program has provided concentration-response bioactivity data across more than a thousand assay endpoints for thousands of chemicals found in our environment and commerce. However, most ToxCast screening assays have evaluated individual biological targets in cancer cell lines lacking integrated physiological functionality (such as receptor signaling, metabolism). We evaluated differentiated HepaRGTM cells, a human liver-derived cell model understood to effectively model physiologically relevant hepatic signaling. Expression of 93 gene transcripts was measured by quantitative polymerase chain reaction using Fluidigm 96.96 dynamic arrays in response to 1060 chemicals tested in eight-point concentration-response. A Bayesian framework quantitatively modeled chemical-induced changes in gene expression via six transcription factors including: aryl hydrocarbon receptor, constitutive androstane receptor, pregnane X receptor, farnesoid X receptor, androgen receptor, and peroxisome proliferator-activated receptor alpha. For these chemicals the network model translates transcriptomic data into Bayesian inferences about molecular targets known to activate toxicological adverse outcome pathways. These data also provide new insights into the molecular signaling network of HepaRGTM cell cultures.

Cholesterol Metabolites 25-Hydroxycholesterol and 25-Hydroxycholesterol 3-Sulfate Are Potent Paired Regulators: From Discovery to Clinical Usage

Oxysterols have long been believed to be ligands of nuclear receptors such as liver × receptor (LXR), and they play an important role in lipid homeostasis and in the immune system, where they are involved in both transcriptional and posttranscriptional mechanisms. However, they are increasingly associated with a wide variety of other, sometimes surprising, cell functions. Oxysterols have also been implicated in several diseases such as metabolic syndrome. Oxysterols can be sulfated, and the sulfated oxysterols act in different directions: they decrease lipid biosynthesis, suppress inflammatory responses, and promote cell survival. Our recent reports have shown that oxysterol and oxysterol sulfates are paired epigenetic regulators, agonists, and antagonists of DNA methyltransferases, indicating that their function of global regulation is through epigenetic modification. In this review, we explore our latest research of 25-hydroxycholesterol and 25-hydroxycholesterol 3-sulfate in a novel regulatory mechanism and evaluate the current evidence for these roles.

A review of the processed Polygonum multiflorum (Thunb.) for hepatoprotection: Clinical use, pharmacology and toxicology

ETHNOPHARMACOLOGICAL RELEVANCE

Polygonum multiflorum (Thunb.) (PMT) is a member of Polygonaceae. Traditional Chinese medicine considers that the processed PMT can tonify liver, nourish blood and blacken hair. In recent years, the processed PMT and its active ingredients have significant therapeutic effects on nonalcoholic fatty liver disease, alcoholic fatty liver disease, viral hepatitis, liver fibrosis and liver cancer.

AIM OF THE STUDY

The main purpose of this review is to provide a critical appraisal of the existing knowledge on the clinical application, hepatoprotective pharmacology and hepatotoxicity, it provides a comprehensive evaluation of the liver function of the processed PMT.

MATERIALS AND METHODS

A detailed literature search was conducted using various online search engines, such as Pubmed, Google Scholar, Mendeley, Web of Science and China National Knowledge Infrastructure (CNKI) database. The main active components of the processed PMT and the important factors in the occurrence and development of liver diseases are used as key words to carry out detailed literature retrieval.

RESULTS

In animal and cell models, the processed PMT and active components can treat various liver diseases, such as fatty liver induced by high-fat diet, liver injury and fibrosis induced by drugs, viral transfected hepatitis, hepatocellular carcinoma, etc. They can protect liver by regulating lipid metabolism related enzymes, resisting insulin resistance, decreasing the expression of inflammatory cytokines, inhibiting the activation of hepatic stellate cells, reducing generation of extracellular matrix, promoting cancer cell apoptosis and controlling the growth of tumor cells, etc. However, improperly using of the processed PMT can cause liver injury, which is associated with the standardization of processing, the constitution of the patients, the characteristics of the disease, and the administration of dosage and time.

CONCLUSION

The processed PMT can treat various liver diseases via reasonably using, and the active compounds (2,3,5,4'-tetrahydroxystilbene-2-O-β-D-glucoside, emodin, physcion, etc.) are promising candidate drugs for developing new liver protective agents. However, some components have a "toxic-effective" bidirectional effect, which should be used cautiously.

Insulin resistance dysregulates CYP7B1 leading to oxysterol accumulation: a pathway for NAFL to NASH transition

NAFLD is an important public health issue closely associated with the pervasive epidemics of diabetes and obesity. Yet, despite NAFLD being among the most common of chronic liver diseases, the biological factors responsible for its transition from benign nonalcoholic fatty liver (NAFL) to NASH remain unclear. This lack of knowledge leads to a decreased ability to find relevant animal models, predict disease progression, or develop clinical treatments. In the current study, we used multiple mouse models of NAFLD, human correlation data, and selective gene overexpression of steroidogenic acute regulatory protein (StarD1) in mice to elucidate a plausible mechanistic pathway for promoting the transition from NAFL to NASH. We show that oxysterol 7α-hydroxylase (CYP7B1) controls the levels of intracellular regulatory oxysterols generated by the "acidic/alternative" pathway of cholesterol metabolism. Specifically, we report data showing that an inability to upregulate CYP7B1, in the setting of insulin resistance, results in the accumulation of toxic intracellular cholesterol metabolites that promote inflammation and hepatocyte injury. This metabolic pathway, initiated and exacerbated by insulin resistance, offers insight into approaches for the treatment of NAFLD.

A Candidate Drug for Nonalcoholic Fatty Liver Disease: A Review of Pharmacological Activities of Polygoni Multiflori Radix

Nonalcoholic fatty liver disease, a type of metabolic syndrome, continues to rise globally. Currently, there is no approved drug for its treatment. Improving lifestyle and exercise can alleviate symptoms, but patients' compliance is poor. More and more studies have shown the potential of Polygoni Multiflori Radix (PMR) in the treatment of NAFLD and metabolic syndrome. Therefore, this paper reviews the pharmacological effects of PMR and its main chemical components (tetrahydroxystilbene glucoside, emodin, and resveratrol) on NAFLD. PMR can inhibit the production of fatty acids and promote the decomposition of triglycerides, reduce inflammation, and inhibit the occurrence of liver fibrosis. At the same time, it maintains an oxidation equilibrium status in the body, to achieve the therapeutic purpose of NAFLD and metabolic syndrome. Although more standardized studies and clinical trials are needed to confirm its efficacy, PMR may be a potential drug for the treatment of NAFLD and its complications. However, the occurrence of adverse reactions of PMR has affected its extensive clinical application. Therefore, it is necessary to further study its toxicity mechanism, enhance efficacy and control toxicity, and even reduce toxicity, which will contribute to the safe clinical use of PMR.

Wild Melon Seed Oil Reduces Plasma Cholesterol and Modulates Gut Microbiota in Hypercholesterolemic Hamsters

Wild melon (Cucumis melo var. agrestis) seed oil (CO) contains 71.3% polyunsaturated fatty acids. The present study investigated the effects of CO on blood cholesterol and gut microbiota. Hamsters (n = 32) were randomly divided into four groups and given one of four diets, namely noncholesterol diet (NCD), high-cholesterol diet containing 0.1% cholesterol (HCD), HCD containing 4.75% CO (COL), and HCD containing 9.5% CO (COH) for 6 weeks. CO supplementation at 9.5% in the diet reduced plasma cholesterol by 24% and enhanced the excretion of fecal bile acids by 150%. CO supplementation upregulated the gene expression of hepatic cholesterol 7α-hydroxylase (CYP7A1). In addition, supplementation of CO in the diet remarkably increased the production of fecal short-chain fatty acids and favorably altered the relative abundances of Eubacteriaceae, Clostridiales_vadinBB60_group, Ruminococcaceae, Streptococcaceae, and Desulfovibrionaceae at a family level. It was concluded that CO could reduce plasma cholesterol via promoting the excretion of fecal acidic sterols and modulating gut microbiota.

Lipid and Cholesterol Homeostasis after Arsenic Exposure and Antibiotic Treatment in Mice: Potential Role of the Microbiota

BACKGROUND

Arsenic-induced liver X receptor/retinoid X receptor (LXR/RXR) signaling inhibition is a potential mechanism underlying the cardiovascular effects caused by arsenic. The gut microbiota can influence arsenic toxic effects.

OBJECTIVE

We aimed to explore whether gut microbiota play a role in arsenic-induced LXR/RXR signaling inhibition and the subsequent lipid and cholesterol dysbiosis.

METHODS

Conventional and antibiotic-treated mice (AB-treated mice) were exposed to 0.25   ppm and 1   ppm arsenic for 2 wk. Hepatic mRNAs were extracted and sequenced. The expression levels of genes associated with LXR/RXR signaling were quantified by quantitative real-time polymerase chain reaction (qPCR), and serum and hepatic cholesterol levels were measured. Liquid chromatography-mass spectrometry (LC-MS)-based lipidomics were used to examine serum and hepatic lipids.

RESULTS

Pathway analysis indicated that arsenic exposure differentially influenced the hepatic signaling pathways in conventional and AB-treated mice. The expression of sterol regulatory element-binding protein 1 (Srebp1c), 3-hydroxy-3-methylglutaryl-CoA reductase (Hmgcr), and cytochrome P450 family 7 subfamily A member 1 (Cyp7a1), as well as cholesterol efflux genes, including ATP binding cassette subfamily G member 5/8 (Abcg5/8) and cluster of differentiation 36 (Cd36), was lower in arsenic-exposed conventional mice but not in AB-treated mice. Similarly, under arsenic exposure, the hepatic expression of scavenger receptor class B member 1 (Scarb1), which is involved in reverse cholesterol transport (RCT), was lower in conventional mice, but was higher in AB-treated animals compared with controls. Correspondingly, arsenic exposure exerted opposite effects on the serum cholesterol levels in conventional and AB-treated mice, i.e., higher serum cholesterol levels in conventional mice but lower levels in AB-treated mice than in respective controls. Serum lipid levels, especially triglyceride (TG) levels, were higher in conventional mice exposed to 1   ppm arsenic, while arsenic exposure did not significantly affect the serum lipids in AB-treated mice. Liver lipid patterns were also differentially perturbed in a microbiota-dependent manner.

CONCLUSIONS

Our results suggest that in mice, the gut microbiota may be a critical factor regulating arsenic-induced LXR/RXR signaling perturbation, suggesting that modulation of the gut microbiota might be an intervention strategy to reduce the toxic effects of arsenic on lipid and cholesterol homeostasis. https://doi.org/10.1289/EHP4415.

Polydatin attenuates atherosclerosis in apolipoprotein E-deficient mice: Role of reverse cholesterol transport

BACKGROUND

Polydatin has been recently shown to possess extensive cardiovascular pharmacological activities. However, its protective effect against atherosclerosis in vivo remains poorly understood. The aim of the present study was to evaluate the potential effects of polydatin on high fat diet (HFD)-induced atherosclerosis using ApoE^-/- mice, and explore the underlying mechanisms involved, especially focusing on reverse cholesterol transport (RCT) regulation.

METHODS

after 12 weeks treatment, serum samples, mouse aorta, liver, peritoneal macrophages were collected to determine lipid profiles, atherosclerotic lesions, hepatic steatosis, foam cell formation and expression of related molecules. RAW264.7 macrophages were used to study cholesterol efflux.

RESULTS

Polydatin improved serum lipid profiles, attenuated atherosclerosis and hepatic steatosis. Furthermore, polydatin may facilitate RCT by stimulating cholesterol efflux through ATP-binding cassette transporters (ABC) A1, ABCG1 and scavenger receptor class B type I (SR-BI) in macrophages, increasing serum levels of high density lipoprotein and apolipoprotein A-I, promoting of SR-BI-mediated cholesterol uptake of liver, increasing secretion of cholesterol into bile by ABCG5/ABCG8 and improving cholesterol metabolism by CYP7A1 pathway. Polydatin also regulated the protein expressions of hepatic fatty acid synthase and peroxisome proliferator-activated receptor-α. Additionally, polydatin reduced hepatic and aortic reactive oxygen species generation, normalized activities of antioxidant enzymes and increased protein expressions of NADPH-oxidase (NOX) 2 and NOX4 in liver. Polydatin also prevented hepatic and aortic inflammation as evidenced by the reduced macrophage infiltration and mRNA expressions of tumor necrosis factor-α and interleukin-6 in both aorta and liver.

CONCLUSION

These findings indicated that polydatin can inhibit atherosclerosis through enhancement of overall RCT. In addition, anti-oxidative and anti-inflammatory effect of polydatin may also contribute to its inhibitory effects on atherosclerosis.

2, 3, 4', 5-tetrahydroxystilbene-2-0-β-d Glycoside Attenuates Age- and Diet-Associated Non-Alcoholic Steatohepatitis and Atherosclerosis in LDL Receptor Knockout Mice and Its Possible Mechanisms

The compound, 2,3,5,4'-tetrahydroxystilbene-2-O-β-d-glucoside (TSG), a primary bioactive polyphenolic component of Polygonum multiflorum exerts numerous pharmacological activities. However, its protective effect against non-alcoholic steatohepatitis (NASH), in the context of metabolic syndrome, remains poorly understood. The aim of the present study is to evaluate the effects of TSG treatment on middle-aged (12-mo-old) male LDLr^-/- mice, which were fed a high fat diet for 12 weeks to induce metabolic syndrome and NASH. At the end of the experiment, the blood samples of mice were collected for determination of metabolic parameters. Liver and aorta tissues were collected for analysis, such as histology, immunofluorescence, hepatic lipid content, real-time PCR, and western blot. Our data show that TSG treatment improved the different aspects of NASH (steatosis, inflammation, and fibrosis) and atherosclerosis, as well as some of the metabolic basal characteristics. These modulatory effects of TSG are mediated, at least in part, through regulating key regulators of lipid metabolism (SREBP1c, PPARα and their target genes, ABCG5 and CYP7A1), inflammation (CD68, TNF-α, IL-6 and ICAM), fibrosis (α-SMA and TNFβ) and oxidative stress (NADPH-oxidase 2/4, CYP2E1 and antioxidant enzymes). These results suggest that TSG may be a promising candidate for preventing and treating the progression of NASH.

Uteroplacental Insufficiency Impairs Cholesterol Elimination in Adult Female Growth-Restricted Rat Offspring Fed a High-Fat Diet

Uteroplacental insufficiency (UPI) causes intrauterine growth restriction (IUGR) and increases the risk of hypercholesterolemia and cardiovascular disease, which are leading causes of morbidity and mortality worldwide. Little is known about the mechanism through which UPI increases cholesterol. Hepatic Cholesterol 7 alpha-hydroxylase (Cyp7a1) is the rate-limiting and most highly regulated step of cholesterol catabolism to bile acids. Cholesterol 7 alpha-hydroxylase is regulated by transcription factor liver X receptor α (Lxrα) and by microRNA-122. We previously showed that microRNA-122 inhibition of Cyp7a1 translation decreased cholesterol catabolism to bile acids in female IUGR rats at the time of weaning. We hypothesized that UPI would increase cholesterol and microRNA-122 and decrease Cyp7a1 protein and hepatic bile acids in young adult female IUGR rats. To test our hypothesis, we used a rat model of IUGR induced by bilateral uterine artery ligation. Both control and IUGR offspring were exposed to a maternal high-fat diet from before conception through lactation, and all offspring were weaned to a high-fat diet on postnatal day 21. At postnatal day 60, IUGR female rats had increased total and low-density lipoprotein serum cholesterol and hepatic cholesterol, decreased Lxrα and Cyp7a1 protein, and decreased hepatic bile acids. Hepatic microRNA-122 was not changed by UPI. Our findings suggest that UPI decreased cholesterol catabolism to bile acids in young adult female rats through a mechanism independent of microRNA-122.

Prenatal Exposure to a Maternal High Fat Diet Increases Hepatic Cholesterol Accumulation in Intrauterine Growth Restricted Rats in Part Through MicroRNA-122 Inhibition of Cyp7a1

Intrauterine growth restriction (IUGR) and consumption of a high saturated fat diet (HFD) increase the risk of hypercholesterolemia, a leading cause of morbidity and mortality. The mechanism through which the cumulative impact of IUGR and in utero exposure to a maternal HFD increase cholesterol levels remains unknown. Cholesterol 7α hydroxylase (Cyp7a1) initiates catabolism of cholesterol to bile acids for elimination from the body, and is regulated by microRNA-122 (miR-122). We hypothesized that IUGR rats exposed to a maternal HFD would have increased cholesterol and decreased Cyp7a1 protein levels in juvenile rats, findings which would be normalized by administration of a miR-122 inhibitor. To test our hypothesis we used a rat model of surgically induced IUGR and fed the dams a regular diet or a HFD from prior to conception through lactation. At the time of weaning, IUGR female rats exposed to a maternal HFD had increased hepatic cholesterol, decreased hepatic Cyp7a1 protein and hepatic bile acids, and increased hepatic miR-122 compared to non-IUGR rats exposed to the same HFD. In vivo inhibition of miR-122 increased hepatic Cyp7a1 protein and decreased hepatic cholesterol. Our findings suggest that IUGR combined with a maternal HFD decreased cholesterol catabolism to bile acids, in part, via miR-122 inhibition of Cyp7a1.

Salusin-α attenuates hepatic steatosis and atherosclerosis in high fat diet-fed low density lipoprotein receptor deficient mice

Salusin-α is an endogenous bioactive peptide and likely to prevent atherosclerosis. But its protective effect against atherosclerosis in vivo remains poorly understood. The aim of the present study was to determine the potential effects of salusin-α on atherosclerosis and its associated metabolic disorders in high fat diet (HFD)-fed low density lipoprotein receptor deficient (LDLr^-/-) mice, and also explore the possible underlying mechanisms involved. Our data showed that after 12 weeks treatment, salusin-α ameliorated HFD-induced weight gain, hyperlipidemia, and serum levels of interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α). Salusin-α suppressed HFD-induced hepatic steatosis and regulated gene expression of fatty acid synthase, acetyl coenzyme A carboxylase-α, peroxisome proliferator-activated receptor-α, camitine palmitoyltransferase-1α and CYP7A1 in liver. Salusin-α reduced atherosclerotic plaque area and macrophage foam cell formation. Salusin-α prevented hepatic and aortic inflammation as evidenced by the reduced macrophage recruitment and mRNA expression of IL-6 and TNF-α in both liver and aorta. Salusin-α also reduced hepatic and aortic oxidative stress by normalizing activities of antioxidant enzymes in liver and suppressing reactive oxygen species generation and protein expressions of NADPH-oxidase (NOX) 2 and NOX4 in both liver and aorta. Our present data suggest that salusin-α could reduce hepatic steatosis and atherosclerosis via its pleiotropic effects, including amelioration of lipid profiles, regulation of some key molecules involved in lipid metabolism in liver, anti-oxidative effect and anti-inflammatory action.

Combined toxicity of endosulfan and phenanthrene mixtures and induced molecular changes in adult Zebrafish (Danio rerio)

Individual and combined toxicities of endosulfan (ENDO) with phenanthrene (PHE) were evaluated using zebrafish (Danio rerio) adults. The 96-h LC₅₀ values for ENDO and PHE were 4.6 μg L^-1 and 920 μg L^-1, respectively. To evaluate the mixture toxicity, LC₁₀ and LC₅₀ concentrations were grouped into four combinations as ENDO-LC₁₀ + PHE-LC₁₀, ENDO-LC₁₀ + PHE-LC₅₀, ENDO-LC₅₀ + PHE-LC₁₀, and ENDO-LC₅₀ + PHE-LC₅₀, and their acute toxicities were determined. The combination of LC₅₀-ENDO and LC₁₀-PHE exhibited a synergistic effect. In addition, acetylcholinesterase activity decreased in zebrafish bodies exposed to ENDO with or without PHE. Combined treatments induced higher glutathione S-transferase activity compared to individual treatments. Carboxylesterase activity increased in both heads and bodies of ENDO-treated fishes compared with PHE-treated fishes. Using RT-qPCR technique, CYP1A gene expression significantly up-regulated in all combinations, whereas CYP3A was unchanged, suggesting that enzymes involved in defense may play different roles in the detoxification. CYP7A1 gene responsible for bile acid biosynthesis is dramatically down-regulated after exposure to the synergistic combination exposure, referring that the synergistic effect may be resulted from the reduction of bile production in zebrafishes. Among gender-related genes, CYP11A1 and CYP17A1 genes in female zebrafish decreased after treatment with ENDO alone and combination of LC₅₀-ENDO and LC₁₀-PHE. This might be related to a reduction in cortisol production. The overall results indicated that ENDO and PHE were toxic to zebrafish adults both individually and in combination, and that their co-presence induced changes in the expression of genes responsible for metabolic processes and defense mechanisms.

2,3,4′,5-tetrahydroxystilbene-2-O-β-d-glycoside attenuates atherosclerosis in apolipoprotein E-deficient mice: role of reverse cholesterol transport

The aim of this study was to evaluate the potential effects of 2,3,4′,5-tetrahydroxystilbene-2-O-β-d-glucoside (TSG) on the development of atherosclerotic plaque in ApoE−/− mice, and explore the mechanisms involved. Our data showed that after 8 weeks of treatment, TSG ameliorated serum levels of total cholesterol, triglyceride, and low density lipoprotein cholesterol, and increased serum levels of high density lipoprotein cholesterol in ApoE−/− mice. TSG suppressed hepatic steatosis, the formation of atherosclerotic lesions, and the formation of macrophage foam cells in ApoE−/− mice. Moreover, TSG improved the expressions of hepatic SR-BI, ABCG5, and CYP7A1, and up-regulated the protein expressions of aortic ABCA1 and ABCG1. An in-vitro study showed that TSG promoted macrophage cholesterol efflux and increased the protein expressions of ABCA1 and ABCG1. Our findings provide evidence for a positive role of TSG in preventing atherosclerosis by promoting reverse cholesterol transport. These effects may be achieved by stimulating cholesterol efflux through ABCA1 and ABCG1, promoting SR-BI-mediated cholesterol uptake in the liver, increasing secretion of cholesterol into bile by ABCG5, and improving cholesterol metabolism by the CYP7A1 pathway. In addition, antioxidative and anti-inflammatory effects of TSG may also contribute to its inhibitory effects on atherosclerosis. Further study is needed to investigate whether other potential mechanisms are involved in TSG-mediated atheroprotection.

Dietary daidzein, but not genistein, has a hypocholesterolemic effect in non-ovariectomized and ovariectomized female Sprague-Dawley rats on a cholesterol-free diet

We compared the effects of two major isoflavones, daidzein and genistein, on lipid metabolism in rats. Daidzein (150 mg/kg diet), genistein (150 mg/kg diet), daidzein and genistein (1:1, 300 mg/kg diet), or control diets were fed to 4 groups of 6-week-old ovariectomized (Ovx) and non-Ovx Sprague Dawley rats for 4 weeks. Dietary daidzein, but not genistein, reduced serum and hepatic total cholesterol levels significantly relative to that by the control group, regardless of whether the rats had undergone ovariectomy. Genistein did not exhibit any physiological effects on lipid levels, but did affect genes involved in cholesterol metabolism. These results indicate that daidzein and genistein may influence lipid regulation via differing modes of action.

Effects of Karela (Bitter Melon; Momordica charantia) on genes of lipids and carbohydrates metabolism in experimental hypercholesterolemia: biochemical, molecular and histopathological study

Background

Hypercholesterolemia is a serious diseases associated with type-2 diabetes, atherosclerosis, cardiovascular disorders and liver diseases. Humans seek for safe herbal medication such as karela (Momordica charantia/bitter melon) to treat such disorders to avoid side effect of pharmacotherapies widely used.

Methods

Forty male Wistar rats were divided into four equal groups; control group with free access to food and water, cholesterol administered group (40 mg/kg BW orally); karela administered group (5 g /kg BW orally) and mixture of cholesterol and karela. The treatments continued for 10 weeks. Karela was given for hypercholesterolemic rats after 6 weeks of cholesterol administration. Serum, liver and epididymal adipose tissues were taken for biochemical, histopathological and genetic assessments.

Results

Hypercholesterolemia induced a decrease in serum superoxide dismutase (SOD), catalase, reduced glutathione (GSH) and an increase in malondialdehyde (MDA) levels that were ameliorated by karela administration. Hypercholesterolemia up regulated antioxidants mRNA expression and altered the expression of carbohydrate metabolism genes. In parallel, hypercholesterolemic groups showed significant changes in the expression of PPAR-alpha and gamma, lipolysis, lipogenesis and cholesterol metabolism such as carnitine palmitoyltransferase-1 (CPT-1). Acyl CoA oxidase (ACO), fatty acids synthase (FAS), sterol responsible element binding protein-1c (SREBP1c), 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG-CoAR) and cholesterol 7α-hydroxylase (CYP7A1) at hepatic and adipose tissue levels. Interestingly, Karela ameliorated all altered genes confirming its hypocholesterolemic effect. Histopathological and immunohistochemical findings revealed that hypercholesterolemia induced hepatic tissue changes compared with control. These changes include cholesterol clefts, necrosis, karyolysis and sever congestion of portal blood vessel. Caspase-3 immunoreactivity showed positive expression in hepatic cells of hypercholesterolemic rats compared to control. All were counteracted and normalized after Karela administration to hypercholesterolemic group.

Conclusion

Current findings confirmed that karela is a potential supplement useful in treatment of hypercholesterolemia and its associated disorders and is good for human health.

Gene co-expression network analysis identifies porcine genes associated with variation in metabolizing fenbendazole and flunixin meglumine in the liver

Identifying individual genetic variation in drug metabolism pathways is of importance not only in livestock, but also in humans in order to provide the ultimate goal of giving the right drug at the right dose at the right time. Our objective was to identify individual genes and gene networks involved in metabolizing fenbendazole (FBZ) and flunixin meglumine (FLU) in swine liver. The population consisted of female and castrated male pigs that were sired by boars represented by 4 breeds. Progeny were randomly placed into groups: no drug (UNT), FLU or FBZ administered. Liver transcriptome profiles from 60 animals with extreme (i.e. fast or slow drug metabolism) pharmacokinetic (PK) profiles were generated from RNA sequencing. Multiple cytochrome P450 (CYP1A1, CYP2A19 and CYP2C36) genes displayed different transcript levels across treated versus UNT. Weighted gene co-expression network analysis identified 5 and 3 modules of genes correlated with PK parameters and a portion of these were enriched for biological processes relevant to drug metabolism for FBZ and FLU, respectively. Genes within identified modules were shown to have a higher transcript level relationship (i.e. connectivity) in treated versus UNT animals. Investigation into the identified genes would allow for greater insight into FBZ and FLU metabolism.

Altered systemic bile acid homeostasis contributes to liver disease in pediatric patients with intestinal failure

Intestinal failure (IF)-associated liver disease (IFALD), as a major complication, contributes to significant morbidity in pediatric IF patients. However, the pathogenesis of IFALD is still uncertain. We here investigate the roles of bile acid (BA) dysmetabolism in the unclear pathogenesis of IFALD. It found that the histological evidence of pediatric IF patients exhibited liver injury, which was characterized by liver bile duct proliferation, inflammatory infiltration, hepatocyte apoptosis and different stages of fibrosis. The BA compositions were altered in serum and liver of pediatric IF patients, as reflected by a primary BA dominant composition. In IF patients, the serum FGF19 levels decreased significantly, and were conversely correlated with ileal inflammation grades (r = −0.50, p < 0.05). In ileum, the inflammation grades were inversely associated with farnesoid X receptor (FXR) expression (r = −0.55, p < 0.05). In liver, the expression of induction of the rate-limiting enzyme in bile salt synthesis, cytochrome P450 7a1 (CYP7A1) increased evidently. In conclusion, ileum inflammation decreases FXR expression corresponding to reduce serum FGF19 concentration, along with increased hepatic bile acid synthesis, leading to liver damages in IF patients.

Targeting the Enterohepatic Bile Acid Signaling Induces Hepatic Autophagy via a CYP7A1-AKT-mTOR Axis in Mice

BACKGROUND & AIMS

Hepatic cholesterol accumulation and autophagy defects contribute to hepatocyte injury in fatty liver disease. Bile acid synthesis is a major pathway for cholesterol catabolism in the liver. This study aims to understand the molecular link between cholesterol and bile acid metabolism and hepatic autophagy activity.

METHODS

The effects of cholesterol and cholesterol 7α-hydroxylase (CYP7A1) expression on autophagy and lysosome function were studied in cell models. The effects and mechanism of disrupting enterohepatic bile acid circulation on hepatic autophagy were studied in mice.

RESULTS

The results first showed differential regulation of hepatic autophagy by free cholesterol and cholesterol ester, whereby a modest increase of cellular free cholesterol, but not cholesterol ester, impaired lysosome function and caused marked autolysosome accumulation. We found that CYP7A1 induction, either by cholestyramine feeding in mice or adenovirus-mediated CYP7A1 expression in hepatocytes, caused strong autophagy induction. Mechanistically, we showed that CYP7A1 expression markedly attenuated growth factor/AKT signaling activation of mechanistic target of rapamycin (mTOR), but not amino acid signaling to mTOR in vitro and in vivo. Metabolomics analysis further found that CYP7A1 induction not only decreased hepatic cholesterol but also altered phospholipid and sphingolipid compositions. Collectively, these results suggest that CYP7A1 induction interferes with growth factor activation of AKT/mTOR signaling possibly by altering membrane lipid composition. Finally, we showed that cholestyramine feeding restored impaired hepatic autophagy and improved metabolic homeostasis in Western diet-fed mice.

CONCLUSIONS

This study identified a novel CYP7A1-AKT-mTOR signaling axis that selectively induces hepatic autophagy, which helps improve hepatocellular integrity and metabolic homeostasis.

Farnesoid X receptor activation increases reverse cholesterol transport by modulating bile acid composition and cholesterol absorption in mice

Activation of farnesoid X receptor (FXR) markedly attenuates development of atherosclerosis in animal models. However, the underlying mechanism is not well elucidated. Here, we show that the FXR agonist, obeticholic acid (OCA), increases fecal cholesterol excretion and macrophage reverse cholesterol transport (RCT) dependent on activation of hepatic FXR. OCA does not increase biliary cholesterol secretion, but inhibits intestinal cholesterol absorption. OCA markedly inhibits hepatic cholesterol 7α-hydroxylase (Cyp7a1) and sterol 12α-hydroxylase (Cyp8b1) partly through inducing small heterodimer partner, leading to reduced bile acid pool size and altered bile acid composition, with the α/β-muricholic acid proportion in bile increased by 2.6-fold and taurocholic acid (TCA) level reduced by 71%. Overexpression of Cyp8b1 or concurrent overexpression of Cyp7a1 and Cyp8b1 normalizes TCA level, bile acid composition, and intestinal cholesterol absorption.

CONCLUSION

Activation of FXR inhibits intestinal cholesterol absorption by modulation of bile acid pool size and composition, thus leading to increased RCT. Targeting hepatic FXR and/or bile acids may be useful for boosting RCT and preventing the development of atherosclerosis. (Hepatology 2016;64:1072-1085).

Oxysterols: From cholesterol metabolites to key mediators

Oxysterols are cholesterol metabolites that can be produced through enzymatic or radical processes. They constitute a large family of lipids (i.e. the oxysterome) involved in a plethora of physiological processes. They can act through GPCR (e.g. EBI2, SMO, CXCR2), nuclear receptors (LXR, ROR, ERα) and through transporters or regulatory proteins. Their physiological effects encompass cholesterol, lipid and glucose homeostasis. Additionally, they were shown to be involved in other processes such as immune regulatory functions and brain homeostasis. First studied as precursors of bile acids, they quickly emerged as interesting lipid mediators. Their levels are greatly altered in several pathologies and some oxysterols (e.g. 4β-hydroxycholesterol or 7α-hydroxycholestenone) are used as biomarkers of specific pathologies. In this review, we discuss the complex metabolism and molecular targets (including binding properties) of these bioactive lipids in human and mice. We also discuss the genetic mouse models currently available to interrogate their effects in pathophysiological settings. We also summarize the levels of oxysterols reported in two key organs in oxysterol metabolism (liver and brain), plasma and cerebrospinal fluid. Finally, we consider future opportunities and directions in the oxysterol field in order to gain a better insight and understanding of the complex oxysterol system.

Application of seaweeds to develop new food products with enhanced shelf-life, quality and health-related beneficial properties

Edible seaweeds are a good source of antioxidants, dietary fibers, essential amino acids, vitamins, phytochemicals, polyunsaturated fatty acids, and minerals. Many studies have evaluated the gelling, thickening and therapeutic properties of seaweeds when they are used individually. This review gives an overview on the nutritional, textural, sensorial, and health-related properties of food products enriched with seaweeds and seaweed extracts. The effect of seaweed incorporation on properties of meat, fish, bakery, and other food products were highlighted in depth. Moreover, the positive effects of foods enriched with seaweeds and seaweed extracts on different lifestyle diseases such as obesity, dyslipidemia, hypertension, and diabetes were also discussed. The results of the studies demonstrated that the addition of seaweeds, in powder or extract form, can improve the nutritional and textural properties of food products. Additionally, low-fat products with less calories and less saturated fatty acids can be prepared using seaweeds. Moreover, the addition of seaweeds also affected the health properties of food products. The results of these studies demonstrated that the health value, shelf-life and overall quality of foods can be improved through the addition of either seaweeds or seaweed extracts.

Cholesterol 7α-hydroxylase protects the liver from inflammation and fibrosis by maintaining cholesterol homeostasis

Cholesterol 7α-hydroxylase (CYP7A1) plays a critical role in control of bile acid and cholesterol homeostasis. Bile acids activate farnesoid X receptor (FXR) and Takeda G protein-coupled receptor 5 (TGR5) to regulate lipid, glucose, and energy metabolism. However, the role of bile acids in hepatic inflammation and fibrosis remains unclear. In this study, we showed that adenovirus-mediated overexpression of Cyp7a1 ameliorated lipopolysaccharide (LPS)-induced inflammatory cell infiltration and pro-inflammatory cytokine production in WT and TGR5-deficient (Tgr5^-/-) mice, but not in FXR-deficient (Fxr^-/-) mice, suggesting that bile acid signaling through FXR protects against hepatic inflammation. Nuclear factor κ light-chain enhancer of activated B cells (NF-κB)-luciferase reporter assay showed that FXR agonists significantly inhibited TNF-α-induced NF-κB activity. Furthermore, chromatin immunoprecipitation and mammalian two-hybrid assays showed that ligand-activated FXR interacted with NF-κB and blocked recruitment of steroid receptor coactivator-1 to cytokine promoter and resulted in inhibition of NF-κB activity. Methionine/choline-deficient (MCD) diet increased hepatic inflammation, free cholesterol, oxidative stress, apoptosis, and fibrosis in CYP7A1-deficient (Cyp7a1^-/-) mice compared with WT mice. Remarkably, adenovirus-mediated overexpression of Cyp7a1 effectively reduced hepatic free cholesterol and oxidative stress and reversed hepatic inflammation and fibrosis in MCD diet-fed Cyp7a1^-/- mice. Current studies suggest that increased Cyp7a1 expression and bile acid synthesis ameliorate hepatic inflammation through activation of FXR, whereas reduced bile acid synthesis aggravates MCD diet-induced hepatic inflammation and fibrosis. Maintaining bile acid and cholesterol homeostasis is important for protecting against liver injury and nonalcoholic fatty liver disease.

Transcriptome Profiles Using Next-Generation Sequencing Reveal Liver Changes in the Early Stage of Diabetes in Tree Shrew (Tupaia belangeri chinensis)

Determining the liver changes during the early stages of diabetes is critical to understand the nature of the disease and development of novel treatments for it. Advances in the use of animal models and next-generation sequencing technologies offer a powerful tool in connection between liver changes and the diabetes. Here, we created a tree shrew diabetes model akin to type 1 diabetes by using streptozotocin to induce hyperglycemia and hyperlipidemia. Using RNA-seq, we compiled liver transcriptome profiles to determine the differentially expressed genes and to explore the role of hyperglycemia in liver changes. Our results, respectively, identified 14,060 and 14,335 genes in healthy tree shrews and those with diabetes, with 70 genes differentially expressed between the two groups. Gene orthology and KEGG annotation revealed that several of the main biological processes of these genes were related to translational processes, steroid metabolic processes, oxidative stress, inflammation, and hypertension, all of which are highly associated with diabetes and its complications. These results collectively suggest that STZ induces hyperglycemia in tree shrew and that hyperglycemia induced oxidative stress led to high expression of aldose reductase, inflammation, and even cell death in liver tissues during the early stage of diabetes.

Alpinumisoflavone and abyssinone V 4'-methylether derived from Erythrina lysistemon (Fabaceae) promote HDL-cholesterol synthesis and prevent cholesterol gallstone formation in ovariectomized rats

OBJECTIVES

Erythrina lysistemon was found to improve lipid profile in ovariectomized rats. Alpinumisoflavone (AIF) and abyssinone V 4'-methylether (AME) derived from this plant induced analogous effects on lipid profile and decreased atherogenic risks. To highlight the molecular mechanism of action of these natural products, we evaluated their effects on the expression of some estrogen-sensitive genes associated with cholesterol synthesis (Esr1 and Apoa1) and cholesterol clearance (Ldlr, Scarb1 and Cyp7a1).

METHODS

Ovariectomized rats were subcutaneously treated for three consecutive days with either compound at the daily dose of 0.1, 1 and 10 mg/kg body weight (BW). Animals were sacrificed thereafter and their liver was collected. The mRNA of genes of interest was analysed by quantitative real-time polymerase chain reaction.

KEY FINDINGS

Both compounds downregulated the mRNA expression of Esr1, a gene associated with cholesterogenesis and cholesterol gallstone formation. AME leaned the Apoa1/Scarb1 balance in favour of Apoa1, an effect promoting high-density lipoprotein (HDL)-cholesterol formation. It also upregulated the mRNA expression of Ldlr at 1 mg/kg/BW per day (25%) and 10 mg/kg/BW per day (133.17%), an effect favouring the clearance of low-density lipoprotein (LDL)-cholesterol. Both compounds may also promote the conversion of cholesterol into bile acids as they upregulated Cyp7a1 mRNA expression.

CONCLUSION

AIF and AME atheroprotective effects may result from their ability to upregulate mechanisms promoting HDL-cholesterol and bile acid formation.

Combination of intrauterine growth restriction and a high-fat diet impairs cholesterol elimination in rats

BACKGROUND

Intrauterine growth restriction (IUGR) increases the risk of adult-onset hypercholesterolemia. High-fat diet (HFD) consumption potentiates IUGR-induced increased cholesterol. Cholesterol is converted to bile acids by Cyp7a1 in preparation for excretion. We hypothesized that IUGR rats fed a HFD will have increased cholesterol, decreased Cyp7a1 protein levels, and decreased bile acids compared to control rats fed a HFD.

METHODS

At day 21, IUGR and control pups were placed on one of three diets: a regular chow or one of two HFDs containing 1% or 2% cholesterol. Cholesterol levels and hepatic Cyp7a1 protein levels were quantified a postnatal week 28.

RESULTS

Both HFDs increased serum cholesterol levels in control rats, and HFD fed IUGR rats had further increased serum cholesterol up to 35-fold. Both HFDs increased hepatic cholesterol levels, and IUGR further increased hepatic cholesterol levels up to fivefold. IUGR decreased hepatic Cyp7a1 protein up to 75%, and hepatic bile acids up to 54%.

CONCLUSION

IUGR increased cholesterol and bile acids and decreased Cyp7a1 protein in rats fed a HFD without changing food intake. These findings suggest that IUGR increases the vulnerability of HFD fed rats to hypercholesterolemia via decreased cholesterol conversion to bile acids.

Identification of novel regulatory cholesterol metabolite, 5-cholesten, 3β,25-diol, disulfate

Oxysterol sulfation plays an important role in regulation of lipid metabolism and inflammatory responses. In the present study, we report the discovery of a novel regulatory sulfated oxysterol in nuclei of primary rat hepatocytes after overexpression of the gene encoding mitochondrial cholesterol delivery protein (StarD1). Forty-eight hours after infection of the hepatocytes with recombinant StarD1 adenovirus, a water-soluble oxysterol product was isolated and purified by chemical extraction and reverse-phase HPLC. Tandem mass spectrometry analysis identified the oxysterol as 5-cholesten-3β, 25-diol, disulfate (25HCDS), and confirmed the structure by comparing with a chemically synthesized compound. Administration of 25HCDS to human THP-1-derived macrophages or HepG2 cells significantly inhibited cholesterol synthesis and markedly decreased lipid levels in vivo in NAFLD mouse models. RT-PCR showed that 25HCDS significantly decreased SREBP-1/2 activities by suppressing expression of their responding genes, including ACC, FAS, and HMG-CoA reductase. Analysis of lipid profiles in the liver tissues showed that administration of 25HCDS significantly decreased cholesterol, free fatty acids, and triglycerides by 30, 25, and 20%, respectively. The results suggest that 25HCDS inhibits lipid biosynthesis via blocking SREBP signaling. We conclude that 25HCDS is a potent regulator of lipid metabolism and propose its biosynthetic pathway.

The effect of exposure to a high-fat diet on microRNA expression in the liver of blunt snout bream (Megalobrama amblycephala)

Blunt snout bream (Megalobrama amblycephala) are susceptible to hepatic steatosis when maintained in modern intensive culture systems. The aim of this study was to investigate the potential roles of microRNAs (miRNAs) in diet-induced hepatic steatosis in this species. MiRNAs, small non-coding RNAs that regulate gene expression at the posttranscriptional level, are involved in diverse biological processes, including lipid metabolism. Deep sequencing of hepatic small RNA libraries from blunt snout bream fed normal-fat and high-fat diets identified 202 (193 known and 9 novel) miRNAs, of which 12 were differentially expressed between the normal-fat and high-fat diet groups. Quantitative stem-loop reverse transcriptase-polymerase chain reaction analyses confirmed the upregulation of miR-30c and miR-30e-3p and the downregulation of miR-145 and miR-15a-5p in high-fat diet-fed fish. Bioinformatics tools were used to predict the targets of these verified miRNAs and to explore potential downstream gene ontology biological process categories and Kyoto Encyclopedia of Genes and Genomes pathways. Six putative lipid metabolism-related target genes (fetuin-B, Cyp7a1, NADH dehydrogenase (ubiquinone) 1 beta subcomplex subunit 2, 3-oxoacid CoA transferase 1b, stearoyl-CoA desaturase, and fatty-acid synthase) were identified as having potential important roles in the development of diet-induced hepatic steatosis in blunt snout bream. The results presented here are a foundation for future studies of miRNA-controlled lipid metabolism regulatory networks in blunt snout bream.

Increased plasma corticosterone contributes to the development of alcoholic fatty liver in mice

Ethanol ingestion increases endogenous glucocorticoid levels in both humans and rodents. The present study aimed to define a mechanistic link between the increased glucocorticoids and alcoholic fatty liver in mice. Plasma corticosterone levels were not affected in mice on a 2-wk ethanol diet regimen but significantly increased upon 4 wk of ethanol ingestion. Accordingly, hepatic triglyceride levels were not altered after 2 wk of ethanol ingestion but were elevated at 4 wk. Based on the observation that 2 wk of ethanol ingestion did not significantly increase endogenous corticosterone levels, we administered exogenous glucocorticoids along with the 2-wk ethanol treatment to determine whether the elevated glucocorticoid contributes to the development of alcoholic fatty liver. Mice were subjected to ethanol feeding for 2 wk with or without dexamethasone administration. Hepatic triglyceride contents were not affected by either ethanol or dexamethasone alone but were significantly increased by administration of both. Microarray and protein level analyses revealed two distinct changes in hepatic lipid metabolism in mice administered with both ethanol and dexamethasone: accelerated triglyceride synthesis by diacylglycerol O-acyltransferase 2 and suppressed fatty acid β-oxidation by long-chain acyl-CoA synthetase 1, carnitine palmitoyltransferase 1a, and acyl-CoA oxidase 1. A reduction of hepatic peroxisome proliferation activator receptor-α (PPAR-α) was associated with coadministration of ethanol and dexamethasone. These findings suggest that increased glucocorticoid levels may contribute to the development of alcoholic fatty liver, at least partially, through hepatic PPAR-α inactivation.

Lipid-lowering and antioxidant activities of Jiang-Zhi-Ning in Traditional Chinese Medicine

ETHNOPHARMACOLOGICAL RELEVANCE

Jiang-Zhi-Ning (JZN) is composed of four Chinese herbs, i.e., Fleeceflower Root, Fructus Crataegi, Folium Nelumbinis and Semen Cassiae. It was used to strengthen blood circulation of coronary artery, arrhythmia and hyperlipidemia.

AIM OF THE STUDY

The main objective of this paper is to evaluate lipid-lowering and antioxidant activities of extract and effective fraction of JZN by using in vitro experiments on hyperlipidemic rats. Moreover, in vivo experiments on cells were performed to investigate lipid-lowering and antioxidant activities of effective fraction and active constituents of JZN.

MATERIALS AND METHOD

Wistar rats with high fat diet-induced hyperlipidemia were used as in vitro models to study biological effects of lipid-lowering and antioxidant activities of extract and effective fraction of JZN. Serum total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), Coronary Index and Atherogenic Index were investigated to evaluate lipid-lowering effects of extract and effective fraction of JZN. Serum total nitric oxide synthase (NOS), nitric oxide (NO), endothelin-1 (ET-1), malondialdehyde (MDA), superoxide dismutase (SOD) and total antioxidant capacity (T-AOC) were detected to measure antioxidant effects of extract and effective fraction of JZN. Furthermore, oxidized low-density lipoprotein (Ox-LDL) injured human umbilical vein endothelial cell (HUVEC) model was employed as in vivo experiment to study lipid-lowering and antioxidant effects of effective fraction and active constituents of JZN. NO, ET-1, MDA SOD and T-AOC in HUVECs or culture media were investigated to evaluate antioxidant activity of effective fraction and active constituents of JZN. Using human hepatoma cell line Bel-7402, reverse transcription polymerase chain reaction (RT-PCR) technology was performed to investigate cholesterol metabolism effects of effective fraction and active constituents of JZN. Expressions of low density lipoprotein receptor (LDL-R), 3-hydroxy-3-methyl-HMG-coenzyme A reductase (HMG-CoAR), and cholesterol 7α-hydroxylase (CYP7A1) mRNA of the liver cells were investigated to evaluate JZN on associated receptor and enzymes of cholesterol metabolism. High-performance liquid chromatography (HPLC) and spectrophotometry were used to study the impact of effective fraction and active constituents of JZN on synthesis and translation of cholesterol during the process of metabolism by measuring inside and extracellular contents of total bile acid (TBA) of Bel-7402.

RESULTS

Extract and effective fraction of JZN significantly reduced contents of TC, TG and LDL-C, CRI and AI in hyperlipidemic rats as well as significantly increased contents of HDL-C in the rats. Moreover, they significantly enhanced the activity of NOS and increased contents of NO. They also caused significant reductions in contents of ET-1 and MDA as well as significant increase in SOD activity and T-AOC in the hyperlipidemic rats. Several indicators were found to be concentration-dependent. As far as in vivo experiments to investigate biological activities of effective fraction and active constituents of JZN were concerned, it was found that they restored and enhanced the vitality of HUVECs with a concentration-dependent manner as well as content of NO in the culture media of HUVEC. They caused reductions in the contents of ET-1 in the culture media of HUVEC and contents of MDA in HUVECs. They also caused an increase in the vitality of SOD and T-AOC in HUVECs. Furthermore, they enhanced LDL-RmRNA expression, with a concentration-dependent manner. Low and medium concentrations of effective fraction and active constituents of JZN could inhibit expression of HMG-CoAR mRNA. High concentration counterpart could enhance expression of the HMG-CoAR mRNA. They enhanced expression of CYP7A1 mRNA in a concentration-dependent manner. Finally, they caused reductions in the contents of cholesterol in Bel-7402. They also increased intercellular content of total bile acid as well as lowered extracellular contents of TBA in the cells in a concentration-dependent manner.

CONCLUSION

We demonstrated for the first time lipid-lowering and antioxidant activities of extract and effective fractions as well as active constituents of JZN. Active constituents of JZN had the same biological effects with effective fraction and extract of JZN. Therefore, this study supports its ethnopharmacological use in Traditional Chinese Medicine to manage hyperlipidemia and paves a basis for establishing quality control method of Chinese medicine.

Expressions of genes encoding drug-metabolizing enzymes are altered after sevoflurane, isoflurane, propofol or dexmedetomidine anesthesia

We previously showed that sevoflurane anesthesia affected the expression ratios of 177 of 10,000 genes in multiple organs of rats by microarray analyses. The maximum number of altered genes was detected in the liver, and included several genes characterized as encoding drug-metabolizing enzymes (DMEs). Here, we investigated whether alterations of pharmacokinetic gene expressions after anesthesia differed between inhalation and intravenous anesthesia, and how long the alterations persisted after awakening from anesthesia. Livers were obtained from rats (n = 6 per group) anesthetized with sevoflurane, isoflurane, propofol or dexmedetomidine for 0 or 6 h, and rats awakened for 24 h after anesthesia for 6 h. The mRNA expression ratios of eight genes encoding DMEs that showed the greatest alterations in the previous study, namely Cyp7a1, Cyp2b15, Por, Nr1i2, Ces2, Ugt1a7, Abcb1a and Abcc2, were measured by quantitative real-time reverse transcriptase-polymerase chain reaction. The expression ratios were mostly increased after 6 h of anesthesia and returned to their control levels at 24 h after awakening from anesthesia. However, the expression ratios of some genes remained elevated for 24 h after awakening from anesthesia. There were differences between inhalation and intravenous anesthesia, and interestingly, between sevoflurane and isoflurane and between propofol and dexmedetomidine.