Deficiency of cholesterol 7α-hydroxylase in bile acid synthesis exacerbates alcohol-induced liver injury in mice

Blockade of the estrogen receptor alpha-pregnane X receptor axis protects ovariectomized mice against ethanol-induced hepatotoxicity

Women develop alcohol-associated liver disease (ALD) faster than men at any level of alcohol consumption, implicating estrogen as a contributing factor. However, the precise mechanism remains unknown. Therefore, 12-weeks-old female C57BL/6N mice were subjected to either bilateral ovariectomy (OVX) or sham surgery. After a three-week recovery period, the mice were fed either a 5% ethanol (EtOH)-containing liquid diet or paired-fed control diet for 10 days followed by a single gavage dose of EtOH (5 g/kg, 30% EtOH solution). The mice were examined for serum biochemical parameters, hepatotoxicity, histology, expression of xenobiotic nuclear receptors PXR and CAR, and their target gene mRNAs and proteins in hepatic and perigonadal white adipose tissues (pgWAT). While OVX mice on a control diet significantly gained weight, EtOH significantly increased hepatotoxicity, residual EtOH levels, lipid peroxidation, and oxidative stress in sham-operated mice but not in their OVX counterparts. Additionally, in the livers and pgWAT of the sham mice, EtOH significantly increased the mRNA and/or protein levels of the major estrogen receptor ERα, PXR, CAR, and their target genes, proinflammatory cytokines and chemokines, lipogenic genes, and FGF21 levels, a predictive biomarker for ALD severity in humans, but inhibited NRF2 and its targets genes encoding NQO1 and BHMT. Unexpectedly, all these changes were attenuated in the EtOH-fed OVX mice by the upregulation of NRF2 and aryl hydrocarbon receptor (AhR) and their downstream antioxidant target genes. Together these results suggest the existence of an estrogen-regulated ERα-PXR-NRF2-signaling axis in liver and pgWAT which contributes to sexual dimorphism in ALD.

Bile Acid Signaling in Metabolic and Inflammatory Diseases and Drug Development

Bile acids are the end products of cholesterol catabolism. Hepatic bile acid synthesis accounts for a major fraction of daily cholesterol turnover in humans. Biliary secretion of bile acids generates bile flow and facilitates biliary secretion of lipids, endogenous metabolites, and xenobiotics. In intestine, bile acids facilitate the digestion and absorption of dietary lipids and fat-soluble vitamins. Through activation of nuclear receptors and G protein-coupled receptors and interaction with gut microbiome, bile acids critically regulate host metabolism and innate and adaptive immunity and are involved in the pathogenesis of cholestasis, metabolic dysfunction-associated steatotic liver disease, alcohol-associated liver disease, type-2 diabetes, and inflammatory bowel diseases. Bile acids and their derivatives have been developed as potential therapeutic agents for treating chronic metabolic and inflammatory liver diseases and gastrointestinal disorders. SIGNIFICANCE STATEMENT: Bile acids facilitate biliary cholesterol solubilization and dietary lipid absorption, regulate host metabolism and immunity, and modulate gut microbiome. Targeting bile acid metabolism and signaling holds promise for treating metabolic and inflammatory diseases.

A new mechanism of thyroid hormone receptor β agonists ameliorating nonalcoholic steatohepatitis by inhibiting intestinal lipid absorption via remodeling bile acid profiles

Excessive dietary calories lead to systemic metabolic disorders, disturb hepatic lipid metabolism, and aggravate nonalcoholic steatohepatitis (NASH). Bile acids (BAs) play key roles in regulating nutrition absorption and systemic energy homeostasis. Resmetirom is a selective thyroid hormone receptor β (THRβ) agonist and the first approved drug for NASH treatment. It is well known that the THRβ activation could promote intrahepatic lipid catabolism and improve mitochondrial function, however, its effects on intestinal lipid absorption and BA compositions remain unknown. In the present study, the choline-deficient, L-amino acid defined, high-fat diet (CDAHFD) and high-fat diet plus CCl4 (HFD+CCl4)-induced NASH mice were used to evaluate the effects of resmetirom on lipid and BA composition. We showed that resmetirom administration (10 mg·kg-1·d-1, i.g.) significantly altered hepatic lipid composition, especially reduced the C18:2 fatty acyl chain-containing triglyceride (TG) and phosphatidylcholine (PC) in the two NASH mouse models, suggesting that THRβ activation inhibited intestinal lipid absorption since C18:2 fatty acid could be obtained only from diet. Targeted analysis of BAs showed that resmetirom treatment markedly reduced the hepatic and intestinal 12-OH to non-12-OH BAs ratio by suppressing cytochrome P450 8B1 (CYP8B1) expression in both NASH mouse models. The direct inhibition by resmetirom on intestinal lipid absorption was further verified by the BODIPY gavage and the oral fat tolerance test. In addition, disturbance of the altered BA profiles by exogenous cholic acid (CA) supplementation abolished the inhibitory effects of resmetirom on intestinal lipid absorption in both normal and CDAHFD-fed mice, suggesting that resmetirom inhibited intestinal lipid absorption by reducing 12-OH BAs content. In conclusion, we discovered a novel mechanism of THRβ agonists on NASH treatment by inhibiting intestinal lipid absorption through remodeling BAs composition, which highlights the multiple regulation of THRβ activation on lipid metabolism and extends the current knowledge on the action mechanisms of THRβ agonists in NASH treatment.

Sodium sulphate ameliorates hypercholesterolemia via the upregulation of Cyp7a1 in hepatocytes and alleviates hepatic insulin resistance via the downregulation of Trib3 in mice with high cholesterol diets

Amelioration of hypercholesterolemia is essential for the treatment of atherosclerotic cardiovascular disease. Sodium sulphate is the effective component of mirabilite, which has been used in traditional Chinese medicine for the treatment of various diseases. In the present study, C57BL/6 mice were fed with a high-cholesterol diet (HCD) for 7 weeks and were treated with sodium sulphate in the last three of those weeks. Sodium sulphate significantly reduced the total cholesterol level and the low-density lipoprotein cholesterol/high-density lipoprotein cholesterol ratio in the serum of mice fed the HCD. In addition, cytochrome P450 7a1 and 39a1 were significantly upregulated in the livers of mice treated with sodium sulphate. Furthermore, tribbles pseudokinase 3 expression was significantly increased in the livers of mice fed the HCD, but was significantly reduced by sodium sulphate treatment. In terms of the insulin signaling pathway, the ratio of phosphorylated AKT to total AKT in the livers of mice fed the HCD was significantly lower compared with that of control mice fed a normal diet, but was significantly increased by sodium sulphate treatment. Sodium sulphate treatment also reduced the levels of fibroblast growth factor (FGF)15 in the ileum and inhibited the FGF15/FGF receptor 4-Klotho β/c-Jun N-terminal kinase/c-Jun signaling pathway in the livers of mice fed the HCD. In addition, sodium sulphate changed the composition of the gut microbiota of mice fed the HCD. In conclusion, sodium sulphate may mitigate hypercholesterolemia and hepatic insulin resistance in mice fed an HCD.

Reversal of hepatic accumulation of nordeoxycholic acid underlines the beneficial effects of cholestyramine on alcohol-associated liver disease in mice

BACKGROUND

Dysregulation of bile acids (BAs) has been reported in alcohol-associated liver disease. However, the causal relationship between BA dyshomeostasis and alcohol-associated liver disease remains unclear. The study aimed to determine whether correcting BA perturbation protects against alcohol-associated liver disease and elucidate the underlying mechanism.

METHODS

BA sequestrant cholestyramine (CTM) was administered to C57BL/6J mice fed alcohol for 8 weeks to assess its protective effect and explore potential BA targets. The causal relationship between identified BA metabolite and cellular damage was examined in hepatocytes, with further manipulation of the detoxifying enzyme cytochrome p450 3A11. The toxicity of the BA metabolite was further validated in mice in an acute study.

RESULTS

We found that CTM effectively reversed hepatic BA accumulation, leading to a reversal of alcohol-induced hepatic inflammation, cell death, endoplasmic reticulum stress, and autophagy dysfunction. Specifically, nordeoxycholic acid (NorDCA), a hydrophobic BA metabolite, was identified as predominantly upregulated by alcohol and reduced by CTM. Hepatic cytochrome p450 3A11 expression was in parallel with NorDCA levels, being upregulated by alcohol and reduced by CTM. Moreover, CTM reversed alcohol-induced gut barrier disruption and endotoxin translocation. Mechanistically, NorDCA was implicated in causing endoplasmic reticulum stress, suppressing autophagy flux, and inducing cell injury, and such deleterious effects could be mitigated by cytochrome p450 3A11 overexpression. Acute NorDCA administration in mice significantly induced hepatic inflammation and injury along with disrupting gut barrier integrity, leading to subsequent endotoxemia.

CONCLUSIONS

Our study demonstrated that CTM treatment effectively reversed alcohol-induced liver injury in mice. The beneficial effects of BA sequestrant involve lowering toxic NorDCA levels. NorDCA not only worsens hepatic endoplasmic reticulum stress and inhibits autophagy but also mediates gut barrier disruption and systemic translocation of pathogen-associated molecular patterns in mice.

Bile acids regulation of cellular stress responses in liver physiology and diseases

Bile acids are physiological detergents and signalling molecules that are critically implicated in liver health and diseases. Dysregulation of bile acid homeostasis alters cell function and causes cell injury in chronic liver diseases. Therapeutic agents targeting bile acid synthesis, transport and signalling hold great potential for treatment of chronic liver diseases. The broad cellular and physiological impacts of pharmacological manipulations of bile acid metabolism are still incompletely understood. Recent research has discovered new links of bile acid signalling to the regulation of autophagy and lysosome biology, redox homeostasis and endoplasmic reticulum stress. These are well-conserved mechanisms that allow cells to adapt to nutrient and organelle stresses and play critical roles in maintaining cellular integrity and promoting survival. However, dysregulation of these cellular pathways is often observed in chronic liver diseases, which exacerbates cellular dysfunction to contribute to disease pathogenesis. Therefore, identification of these novel links has significantly advanced our knowledge of bile acid biology and physiology, which is needed to understand the contributions of bile acid dysregulation in disease pathogenesis, establish bile acids as diagnostic markers and develop bile acid-based pharmacological interventions. In this review, we will first discuss the roles of bile acid dysregulation in the pathogenesis of chronic liver diseases, and then discuss the recent findings on the crosstalk of bile acid signalling and cellular stress responses. Future investigations are needed to better define the roles of these crosstalks in regulating cellular function and disease processes.

A Review: Cytochrome P450 in Alcoholic and Non-Alcoholic Fatty Liver Disease

Alcoholic fatty liver disease (FALD) and non-alcoholic fatty liver disease (NAFLD) have similar pathological spectra, both of which are associated with a series of symptoms, including steatosis, inflammation, and fibrosis. These clinical manifestations are caused by hepatic lipid synthesis and metabolism dysregulation and affect human health. Despite having been studied extensively, targeted therapies remain elusive. The Cytochrome P450 (CYP450) family is the most important drug-metabolising enzyme in the body, primarily in the liver. It is responsible for the metabolism of endogenous and exogenous compounds, completing biological transformation. This process is relevant to the occurrence and development of AFLD and NAFLD. In this review, the correlation between CYP450 and liver lipid metabolic diseases is summarised, providing new insights for the treatment of AFLD and NAFLD.

Regulation Mechanism and Potential Value of Active Substances in Spices in Alcohol-Liver-Intestine Axis Health

Excessive alcohol intake will aggravate the health risk between the liver and intestine and affect the multi-directional information exchange of metabolites between host cells and microbial communities. Because of the side effects of clinical drugs, people tend to explore the intervention value of natural drugs on diseases. As a flavor substance, spices have been proven to have medicinal value, but they are still rare in treating hepatointestinal diseases caused by alcohol. This paper summarized the metabolic transformation of alcohol in the liver and intestine and summarized the potential value of various perfume active substances in improving liver and intestine diseases caused by alcohol. It is also found that bioactive substances in spices can exert antioxidant activity in the liver and intestine environment and reduce the oxidative stress caused by diseases. These substances can interfere with fatty acid synthesis, promote sugar and lipid metabolism, and reduce liver injury caused by steatosis. They can effectively regulate the balance of intestinal flora, promote the production of SCFAs, and restore the intestinal microenvironment.

Fibroblast Growth Factor 19 Alters Bile Acids to Induce Dysbiosis in Mice With Alcohol-Induced Liver Disease

BACKGROUND & AIMS

Excessive alcohol consumption can lead to alcohol-associated liver disease, a spectrum of conditions ranging from steatosis to fibrosis and cirrhosis. Bile acids regulate metabolic pathways by binding to cellular and nuclear receptors, and they also interact with the gut microbiome to control microbial overgrowth. Fibroblast growth factor 19 (FGF-19) is an ileum-derived hormone induced and released in response to bile acid activation of the nuclear receptor farnesoid X receptor. FGF-19 signaling is dysregulated with ethanol consumption and is increased in patients with alcoholic hepatitis. Here, we examined the effects of FGF-19 in a mouse model of chronic + binge ethanol feeding.

METHODS

After injection of adeno-associated virus-green fluorescent protein or AAV-FGF-19, female C57BL/6J mice were pair-fed a Lieber DeCarli liquid diet (5% v/v) or control diet for 10 days and were given a bolus gavage of 5% ethanol or maltose control to represent a binge drinking episode. Tissues were collected for analysis 9 hours after the binge.

RESULTS

Chronic + binge ethanol feeding induced steatosis regardless of FGF-19 expression. Interestingly, FGF-19 and ethanol resulted in significantly increased liver inflammation, as measured by Il6, Tgfβ, and Tnfα, compared with ethanol alone. Both ethanol and FGF-19 decreased bile acid synthesis, and FGF-19 significantly reduced secondary bile acids, leading to overgrowth of specific pathogenic bacteria including Enterococcus faecalis, Escherichia coli, and Clostridium perfringens.

CONCLUSIONS

Dysregulation of FGF-19 and consequent changes in bile acid synthesis and composition during alcohol consumption may be a contributing factor to alcohol-induced liver disease and dysbiosis.

AMPD2 plays important roles in regulating hepatic glucose and lipid metabolism

Dysregulation of hepatic glucose and lipid metabolism can instigate the onset of various metabolic disorders including obesity, dyslipidemia, insulin resistance, type 2 diabetes, and fatty liver disease. Adenosine monophosphate (AMP) deaminase (AMPD), which converts AMP to inosine monophosphate, plays a key role in maintaining adenylate energy charge. AMPD2 is the major isoform present in the liver. However, the mechanistic link between AMPD2 and hepatic glucose and lipid metabolism remains elusive. In this study, we probed into the hepatic glucose and lipid metabolism in AMPD2-deficient (A2-/-) mice. These mice exhibited reduced body weight, fat accumulation, and blood glucose levels, coupled with enhanced insulin sensitivity while maintaining consistent calorie intake and spontaneous motor activity compared with wild type mice. Furthermore, A2-/- mice showed mitigated obesity and hyper-insulinemia induced by high-fat diet (HFD) but elevated levels of the serum triglyceride and cholesterol. The hepatic mRNA levels of several fatty acid and cholesterol metabolism-related genes were altered in A2-/- mice. RNA sequencing unveiled multiple alterations in lipid metabolic pathways due to AMPD2 deficiency. These mice were also more susceptible to fasting or HFD-induced hepatic lipid accumulation. The liver exhibited elevated AMP levels but unaltered AMP/ATP ratio. In addition, AMPD2 deficiency is not associated with the adenosine production. In summary, this study established a link between purine metabolism and hepatic glucose and lipid metabolism via AMPD2, providing novel insights into these metabolic pathways.

Pathogenic mechanisms and regulatory factors involved in alcoholic liver disease

Alcoholism is a widespread and damaging behaviour of people throughout the world. Long-term alcohol consumption has resulted in alcoholic liver disease (ALD) being the leading cause of chronic liver disease. Many metabolic enzymes, including alcohol dehydrogenases such as ADH, CYP2E1, and CATacetaldehyde dehydrogenases ALDHsand nonoxidative metabolizing enzymes such as SULT, UGT, and FAEES, are involved in the metabolism of ethanol, the main component in alcoholic beverages. Ethanol consumption changes the functional or expression profiles of various regulatory factors, such as kinases, transcription factors, and microRNAs. Therefore, the underlying mechanisms of ALD are complex, involving inflammation, mitochondrial damage, endoplasmic reticulum stress, nitrification, and oxidative stress. Moreover, recent evidence has demonstrated that the gut-liver axis plays a critical role in ALD pathogenesis. For example, ethanol damages the intestinal barrier, resulting in the release of endotoxins and alterations in intestinal flora content and bile acid metabolism. However, ALD therapies show low effectiveness. Therefore, this review summarizes ethanol metabolism pathways and highly influential pathogenic mechanisms and regulatory factors involved in ALD pathology with the aim of new therapeutic insights.

Tgr5-/- mice are protected from ethanol-induced metabolic alterations through enhanced leptin and Fgf21 signaling

BACKGROUND

Alcohol-associated liver disease (ALD) is caused by chronic use of alcohol and ranges from hepatic steatosis to fibrosis and cirrhosis. Bile acids are physiological detergents that also regulate hepatic glucose and lipid homeostasis by binding to several receptors. One such receptor, Takeda G protein-coupled receptor 5 (TGR5), may represent a therapeutic target for ALD. Here, we used a chronic 10-day + binge ethanol-feeding model in mice to study the role of TGR5 in alcohol-induced liver injury.

METHODS

Female C57BL/6J wild-type mice and Tgr5-/- mice were pair-fed Lieber-DeCarli liquid diet with ethanol (5% v/v) or isocaloric control diet for 10 days followed by a gavage of 5% ethanol or isocaloric maltose control, respectively, to represent a binge-drinking episode. Tissues were harvested 9 hours following the binge, and metabolic phenotypes were characterized through examination of liver, adipose, and brain mechanistic pathways.

RESULTS

Tgr5-/- mice were protected from alcohol-induced accumulation of hepatic triglycerides. Interestingly, liver and serum levels of Fgf21 were significantly increased during ethanol feeding in Tgr5-/- mice, as was phosphorylation of Stat3. Parallel to Fgf21 levels, increased leptin gene expression in white adipose tissue and increased leptin receptor in liver were detected in Tgr5-/- mice fed ethanol diet. Adipocyte lipase gene expression was significantly increased in Tgr5-/- mice regardless of diet, whereas adipose browning markers were also increased in ethanol-fed Tgr5-/- mice, indicating potential for enhanced white adipose metabolism. Lastly, hypothalamic mRNA targets of leptin, involved in the regulation of food intake, were significantly increased in Tgr5-/- mice fed ethanol diet.

CONCLUSIONS

Tgr5-/- mice are protected from ethanol-induced liver damage and lipid accumulation. Alterations in lipid uptake and Fgf21 signaling, and enhanced metabolic activity of white adipose tissue, may mediate these effects.

A review on the protective effect of active components in Antrodia camphorata against alcoholic liver injury

ETHNOPHARMACOLOGICAL RELEVANCE

Antrodia camphorata is a genus of wood-rot basidiomycete in the family Fomitopsidaceae. It is a valuable medicinal fungus in China that contains more than 78 kinds of active compounds. A. camphorata has good protection effects on the liver, especially on alcoholic liver injury (ALI).

AIM

This paper summarizes the complex occurrence and development of alcoholic liver disease (ALD). In addition, the effect of ALD on the intestine through the gut-liver axis is summarized. The protective mechanism of A. camphorata on ALI is reviewed to reveal its therapeutic potential, offering insights into future research.

MATERIALS AND METHODS

A comprehensive search in the literature was obtained from books and online databases such as Web of Science, Google Scholar, PubMed, Scopus, Science direct, ACS Publications and Baidu Scholar.

RESULTS

The pathogenesis of ALD mainly includes oxidative stress injury, intestinal microflora imbalance, inflammatory mediator injury and nutritional imbalance. A. camphorata contains rich active components (e.g. polysaccharides, triterpenoids, maleic and succinic acid derivatives, amino acids, superoxide dismutase, vitamins, lignin and sterols). These components have good antioxidant, anti-inflammatory and intestinal protection activities. Therefore, A. camphorata has a wide application in the prevention and treatment of ALI.

CONCLUSIONS

ALD develops from a mild disease to alcoholic hepatitis and cirrhosis, which is the main reason of global morbidity and mortality. At present, there is no effective drug for the treatment of ALD. A. camphorata, as a valuable medicinal fungus unique to Taiwan, has a great protective effect on the liver. It is expected to be an effective drug for ALI treatment. Although many studies have performed the protective effects of A. camphorata on ALI, its regulatory effects on the gut-liver axis of ALD patients need to be further explored.

A Role of Thyroid Hormones in Acute Myocardial Infarction: An Update

The acute coronary syndrome is one of the commonest life-threatening illnesses. It encompasses the clinical spectrum of acute myocardial ischemia and includes unstable angina and acute myocardial infarction both with and without ST segment elevation. The acute coronary syndrome can be attributed to a significant hemodynamic insult that leads to atherosclerosis of the epicardial coronary arteries. The main causative risk factors, such as obesity, smoking, and alcohol intake, increase the burden of acute coronary syndrome. Owing to an increase in the utilization of antioxidants, the antioxidant capacity decreases concerning the scavenging of lipid peroxides. Moreover, the thyroid hormones are important regulators of the expression of cardiac genes, and many of the cardiac manifestations of thyroid dysfunction are associated with alterations in triiodothyronine- mediated gene expression. Cardiovascular signs and symptoms of thyroid disease are among the most acute clinically relevant findings that occur in combination with both hypothyroidism and hyperthyroidism. By understanding the cellular mechanism of the action of thyroid hormones on the heart and cardiovascular system, it is possible to explain rhythm disturbances and alterations in cardiac output, blood pressure, cardiac contractility, and vascular resistance that result from thyroid dysfunction. Oxidative stress is thereby induced, together with a decrease in antioxidant capacity for overcoming oxidative stress, which leads to endothelial dysfunction, subsequent atherosclerosis, and, ultimately, acute myocardial infarction. The implications for the identification of the effects of thyroid disease on acute myocardial infarction include the observation that restoration of normal thyroid function repeatedly reverses abnormalities in cardiovascular hemodynamics.

Association between abnormal plasma metabolism and brain atrophy in alcohol-dependent patients

Objective

In this study, we aimed to characterize the plasma metabolic profiles of brain atrophy and alcohol dependence (s) and to identify the underlying pathogenesis of brain atrophy related to alcohol dependence.

Methods

We acquired the plasma samples of alcohol-dependent patients and performed non-targeted metabolomic profiling analysis to identify alterations of key metabolites in the plasma of BA-ADPs. Machine learning algorithms and bioinformatic analysis were also used to identify predictive biomarkers and investigate their possible roles in brain atrophy related to alcohol dependence.

Results

A total of 26 plasma metabolites were significantly altered in the BA-ADPs group when compared with a group featuring alcohol-dependent patients without brain atrophy (NBA-ADPs). Nine of these differential metabolites were further identified as potential biomarkers for BA-ADPs. Receiver operating characteristic curves demonstrated that these potential biomarkers exhibited good sensitivity and specificity for distinguishing BA-ADPs from NBA-ADPs. Moreover, metabolic pathway analysis suggested that glycerophospholipid metabolism may be highly involved in the pathogenesis of alcohol-induced brain atrophy.

Conclusion

This plasma metabolomic study provides a valuable resource for enhancing our understanding of alcohol-induced brain atrophy and offers potential targets for therapeutic intervention.

Complex impacts of gallstone disease on metabolic syndrome and nonalcoholic fatty liver disease

BACKGROUND

Patients with gallstone disease (GSD) often have highly co-occurrence with metabolic syndrome (MetS) and Nonalcoholic fatty liver disease (NAFLD) both associated with insulin resistance (IR). Meanwhile, highly prevalence of NAFLD was found in patients who received cholecystectomy. However, the associations of GSD with MetS, NAFLD is inconsistent in the published literature. And risk of cholecystectomy on NAFLD is unclear.

METHODS

We searched the Medline EMBASE and WOS databases for literature that met our study topic. To be specific, studies with focus on associations between GSD and MetS/NAFLD, and risk evaluation on cholecystectomy and NAFLD incidence were enrolled for further analysis. The random effect model was used to calculate the combined relative ratio (RR) and odds ratio (OR)and 95% confidence interval (CI).

RESULTS

Seven and six papers with focus on connections between GSD and NAFLD/MetS prevalence. Correspondingly, seven papers with focus on risk of cholecystectomy on NAFLD occurrence were also enrolled into meta-analysis. After pooling the results from individual study, patients with GSD had higher risk of MetS (OR:1.45, 95%CI: 1.23-1.67, I2 = 41.1%, P=0.165). Risk of GSD was increased by 52% in NAFLD patients (pooled OR:1.52, 95%CI:1.24-1.80). And about 32% of increment on NAFLD prevalence was observed in patients with GSD (pooled OR: 1.32, 95%CI:1.14-1.50). With regard to individual MetS components, patients with higher systolic blood pressure were more prone to develop GSD, with combined SMD of 0.29 (96%CI: 0.24-0.34, P<0.05). Dose-response analysis found the GSD incidence was significantly associated with increased body mass index (BMI) (pooled OR: 1.02, 95%CI:1.01-1.03) in linear trends. Patients who received cholecystectomy had a higher risk of post-operative NAFLD (OR:2.14, 95%CI: 1.43-2.85), P<0.05). And this impact was amplified in obese patients (OR: 2.51, 95%CI: 1.95-3.06, P<0.05).

CONCLUSION

Our results confirmed that controls on weight and blood pressure might be candidate therapeutic strategy for GSD prevention. And concerns should be raised on de-novo NAFLD after cholecystectomy.

The acute effect of thiamine on serum insulin levels and some biochemical parameters in excessive alcohol-consuming rats

There are studies that present metabolic disorders in alcohol drinkers are associated with thiamine deficiency. Therefore, in the present study, it was aimed to investigate the effectiveness of thiamine in rats with binge drinking model. For this purpose, total 21 spraque dawley rats were divided into three equal groups as control, alcohol and thiamine+alcohol groups. The thiamine+ethanol group was given thiamine at a daily dose of 100 mg/kg by oral gavage, starting 2 days before the ethanol administration. Alcohol and thiamine+alcohol groups were given 3.45g/kg/day ethanol as 20%. At the end of the study, while serum total bile acid, total bilirubin and insulin levels increased in rats in the alcohol group compared to the rats in the control group; total protein and albumin levels decreased (P&lt;0.05). In the thiamine + alcohol group, LDL-cholesterol, total cholesterol, bile acid levels and AST enzyme activity increased, while ALT enzyme activity and total protein levels decreased compared to the control group (P&lt;0.05). There was no statistically significant result in the values in the thiamine+alcohol group compared to the alcohol group. It has been concluded that acutely administered thiamine supplementation had no effect on alcohol-induced biochemical parameter changes in binge-drinking animals. In this sense, studies with longer-term thiamine use are needed.

Metabolic profiling of emodin drug-induced liver injury and silybin treatment in rats using UPLC-Q-TOF-MS: A metabolomic and mechanistic approach

Silybin, an active component in the plant Silybum marianum (L.) Gaertn. is commonly used to protect against liver disease. We investigated silybin's protective potential in rat liver against emodin-induced liver injury 4wk. Aspartate aminotransferase and direct bilirubin serum biomarkers for liver toxicity were significantly increased and liver histopathology revealed cholestasis and necrosis in rats given emodin only, whereas AST and total bile acid in rats given emodin and silybin simultaneously were changed compared to rats given emodin. Liver gene and protein levels of Cyp7a1 and Bsep for cholesterol metabolism, bile acid synthesis and transport were significantly altered with emodin, where cotreatment with silybin attenuated emodin's adverse effect. Metabolomic analysis with UPLC-Q-TOF-MS determined eight potential metabolite biomarkers in serum, urine, and liver tissue. Network analysis was conducted to conceptualize interplay of genes, metabolites, and metabolic pathways for cholesterol metabolism and bile acid synthesis for liver injury. Overall, rats given only emodin was shown to be a sound model to investigate fat-associated DILI and that cotreatment with silybin prevents fatty liver injury. This metabolomic study reveal that emodin-induced fatty liver injury has disrupted bile acid synthesis, vitamin B₆ and glycerophospholipid metabolism pathways, and that silybin ameliorates liver injury on these compromised pathways.

Recent advances on FXR-targeting therapeutics

The bile acid receptor FXR has emerged as a bona fide drug target for chronic cholestatic and metabolic liver diseases, ahead of all non-alcoholic fatty liver disease (NAFLD). FXR is highly expressed in the liver and intestine and activation at both sites differentially contributes to its desired metabolic effects. Unrestricted FXR activation, however, also comes along with undesired effects such as a pro-atherogenic lipid profile, pruritus and hepatocellular toxicity under certain conditions. Several pre-clinical studies have confirmed the potency of FXR activation for cholestatic and metabolic liver diseases, but overall it remains still open whether selective activation of intestinal FXR is advantageous over pan-FXR activation and whether restricted or modulated FXR activation can limit some of the side effects. Even more, FXR antagonist also bear the potential as intestinal-selective drugs in NAFLD models. In this review we will discuss the molecular prerequisites for FXR activation, pan-FXR activation and intestinal FXR in/activation from a therapeutic point of view, different steroidal and non-steroidal FXR agonists, ways to restrict FXR activation and finally what we have learned from pre-clinical models and clinical trials with different FXR therapeutics.

Key Signaling in Alcohol-Associated Liver Disease: The Role of Bile Acids

Alcohol-associated liver disease (ALD) is a spectrum of diseases, the onset and progression of which are due to chronic alcohol use. ALD ranges, by increasing severity, from hepatic steatosis to alcoholic hepatitis (AH) and alcohol-associated cirrhosis (AC), and in some cases, can lead to the development of hepatocellular carcinoma (HCC). ALD continues to be a significant health burden and is now the main cause of liver transplantations in the United States. ALD leads to biological, microbial, physical, metabolic, and inflammatory changes in patients that vary depending on disease severity. ALD deaths have been increasing in recent years and are projected to continue to increase. Current treatment centers focus on abstinence and symptom management, with little in the way of resolving disease progression. Due to the metabolic disruption and gut dysbiosis in ALD, bile acid (BA) signaling and metabolism are also notably affected and play a prominent role in disease progression in ALD, as well as other liver disease states, such as non-alcoholic fatty liver disease (NAFLD). In this review, we summarize the recent advances in the understanding of the mechanisms by which alcohol consumption induces hepatic injury and the role of BA-mediated signaling in the pathogenesis of ALD.

The Protective Effects of Ganoderic Acids from Ganoderma lucidum Fruiting Body on Alcoholic Liver Injury and Intestinal Microflora Disturbance in Mice with Excessive Alcohol Intake

This study aimed to investigate the protective effects of ganoderic acids (GA) from Ganoderma lucidum against liver injury and intestinal microbial disorder in mice with excessive alcohol intake. Results showed GA supplement significantly inhibited the abnormal elevation of the liver index, serum lipid parameters, aspartate aminotransferase and alanine aminotransferase in mice exposed to alcohol intake, and also significantly protected the excessive lipid accumulation and pathological changes. Alcohol-induced oxidative stress in the liver was significantly ameliorated by GA intervention through reducing the levels of maleic dialdehyde and lactate dehydrogenase and increasing the levels of glutathione, catalase, superoxide dismutase and alcohol dehydrogenase. Intestinal microbiota profiling demonstrated GA intervention modulated the composition of intestinal microflora by increasing the levels of Lactobacillus, Faecalibaculum, Romboutsia, Bifidobacterium and decreasing the Helicobacter level. Furthermore, liver metabolomic profiling suggested GA intervention had a remarkable regulatory effect on liver metabolism with excessive alcohol consumption. Moreover, GA intervention regulated mRNA levels of alcohol metabolism, fatty lipid metabolism, oxidative stress, bile acid biosynthesis and metabolism-related genes in the liver. Conclusively, these findings demonstrate GA intervention can significantly relieve alcoholic liver injury and it is hopeful to become a new functional food ingredient for the prevention of alcoholic liver injury.

Influence of Oral Intaking Habit on Tongue Coating Microbiota in Patients with Esophageal Precancerous Lesions

Background: Esophageal cancer (EC) is a common digestive tract tumor in China, and oral intaking habit has a great influence on the development of EC. The present study explored the correlation between oral intaking habit and tongue coating (TC) microbiota in patients with esophageal precancerous lesions (EPL) to provide a reasonable interpretation of the influence of oral intaking habit on microbial alterations in the EPL. Methods: A case-control study was designed with 123 EPL patients and 176 volunteers with mild esophagitis, and they were well matched using sex, age, and body mass index. The TC microbiota was profiled using high-throughput sequencing of the V3-V4 region of the 16S rRNA gene, and the serum levels of total bile acid (TBA) and interleukin-17α (IL-17α) were measured using enzyme-linked immunosorbent assay. Alpha diversity, community structure, and linear discriminant analysis were conducted, and Spearman correlation analysis was used to build the symbiotic network. Results: No significant differences were observed in the diversity and richness of the TC microbiota between the cases and controls (P > 0.05). TC Peptostreptococcus and Capnocytophaga were enriched in EPL patients. Stratified analysis showed that TC microbial composition was affected by both EPL and oral intaking habit; for example, Atopobium and Actinomyces were positively related to oral intaking habit scores in both the cases and controls, while Simonsiella was negatively correlated with oral intaking habit status in cases but positively correlated with oral intaking habit status in controls. Although serum TBA and IL-17α were not associated with EPL (P > 0.05), the daily-drinking cases had a higher level of serum TBA than the nondrinking cases (P < 0.05), and Helicobacter pylori (Hp) negative controls had a higher level of serum TBA than the Hp-positive controls (P < 0.05). The symbiotic networks were comprised of 71 significant correlations in the controls and 52 significant correlations in the cases. Conclusions: The development of EPL changed the TC microbiota and decreased the symbiotic complexity of the TC bacteria, which were also influenced by the cancer-related oral intaking habit. Bile acid may be a key factor mediating changes in TC microbiota.

Bile Acid-Mediated Activation of Brown Fat Protects From Alcohol-Induced Steatosis and Liver Injury in Mice

BACKGROUND & AIMS

Alcohol-associated liver disease (AALD) is one of the most common causes of liver injury and failure. Limited knowledge of the mechanisms underlying AALD impedes the development of efficacious therapies. Bile acid (BA) signaling was shown to participate in the progression of AALD. However, the mechanisms remain poorly understood.

METHODS

C57BL/6J wild-type (WT), Takeda G-protein-coupled bile acid receptor 5 (TGR5) knockout (KO) and brown adipose tissue (BAT)-specific TGR5 knockdown mice were subjected to ethanol feeding-induced AALD. Liver samples from alcoholic hepatitis patients were used to examine the BA circulation signaling. Human Embryonic Kidney Cells 293 were used for the TGR5 reporter assay. 23(S)-methyl-lithocholic acid was used as a molecular tool to confirm the regulatory functions of BAT in the AALD mouse model.

RESULTS

Ethanol feeding increased the expression of the thermogenesis genes downstream of TGR5 in BAT of WT, but not TGR5 KO, mice. TGR5 deficiency significantly blocked BAT activity and energy expenditure in mice after ethanol feeding. Alcohol increased serum BA levels in mice and human beings through altering BA transportation, and the altered BAs activated TGR5 signaling to regulate metabolism. Compared with ethanol-fed WT mice, ethanol-fed TGR5 KO mice showed less free fatty acid (FFA) β-oxidation in BAT, leading to higher levels of FFA in the circulation, increased liver uptake of FFAs, and exacerbated AALD. BAT-specific TGR5 knockdown mice showed similar results with TGR5 KO mice in AALD. Agonist treatment significantly activated TGR5 signaling in BAT, increased thermogenesis, reduced serum FFA level, and ameliorated hepatic steatosis and injury in AALD mice, while these effects were lost in TGR5 KO mice.

CONCLUSIONS

BA signaling plays a protective role in AALD by enhancing BAT thermogenesis. Targeting TGR5 in BAT may be a promising approach for the treatment of AALD.

Fibroblast Growth Factor 21 Response in a Preclinical Alcohol Model of Acute-on-Chronic Liver Injury

BACKGROUND AND AIMS

Fibroblast growth factor (FGF) 21 has recently been shown to play a potential role in bile acid metabolism. We aimed to investigate the FGF21 response in an ethanol-induced acute-on-chronic liver injury (ACLI) model in Abcb4-/- mice with deficiency of the hepatobiliary phospholipid transporter.

METHODS

Total RNA was extracted from wild-type (WT, C57BL/6J) and Abcb4-/- (KO) mice, which were either fed a control diet (WT-Cont and KO-Cont groups; n = 28/group) or ethanol diet, followed by an acute ethanol binge (WT-EtOH and KO-EtOH groups; n = 28/group). A total of 58 human subjects were recruited into the study, including patients with alcohol-associated liver disease (AALD; n = 31) and healthy controls (n = 27). The hepatic and ileal expressions of genes involved in bile acid metabolism, plasma FGF levels, and bile acid and its precursors 7α- and 27-hydroxycholesterol (7α- and 27-OHC) concentrations were determined. Primary mouse hepatocytes were isolated for cell culture experiments.

RESULTS

Alcohol feeding significantly induced plasma FGF21 and decreased hepatic Cyp7a1 levels. Hepatic expression levels of Fibroblast growth factor receptor 1 (Fgfr1), Fgfr4, Farnesoid X-activated receptor (Fxr), and Small heterodimer partner (Shp) and plasma FGF15/FGF19 levels did not differ with alcohol challenge. Exogenous FGF21 treatment suppressed Cyp7a1 in a dose-dependent manner in vitro. AALD patients showed markedly higher FGF21 and lower 7α-OHC plasma levels while FGF19 did not differ.

CONCLUSIONS

The simultaneous upregulation of FGF21 and downregulation of Cyp7a1 expressions upon chronic plus binge alcohol feeding together with the invariant plasma FGF15 and hepatic Shp and Fxr levels suggest the presence of a direct regulatory mechanism of FGF21 on bile acid homeostasis through inhibition of CYP7A1 by an FGF15-independent pathway in this ACLI model. Lay Summary: Alcohol challenge results in the upregulation of FGF21 and repression of Cyp7a1 expressions while circulating FGF15 and hepatic Shp and Fxr levels remain constant both in healthy and pre-injured livers, suggesting the presence of an alternative FGF15-independent regulatory mechanism of FGF21 on bile acid homeostasis through the inhibition of Cyp7a1.

Multidrug resistance-associated protein 4 (Mrp4) is a novel genetic factor in the pathogenesis of obesity and diabetes

Multidrug resistance protein 4 (Mrp4) is an efflux transporter known to transport several xenobiotics and endogenous molecules. We recently identified that the lack of Mrp4 increases adipose tissue and body weights in mice. However, the role of Mrp4 in adipose tissue physiology are unknown. The current study aimed at characterizing these specific roles of Mrp4 using wild-type (WT) and knockout (Mrp4^-/- ) mice. Our studies determined that Mrp4 is expressed in mouse adipose tissue and that the lack of Mrp4 expression is associated with adipocyte hypertrophy. Furthermore, the lack of Mrp4 increased blood glucose and leptin levels, and impaired glucose tolerance. Additionally, in 3T3-L1 cells and human pre-adipocytes, pharmacological inhibition of Mrp4 increased adipogenesis and altered expression of adipogenic genes. Lack of Mrp4 activity in both of our in vivo and in vitro models leads to increased activation of adipose tissue cAMP response element-binding protein (Creb) and decreased plasma prostaglandin E (PGE) metabolite levels. These changes in Creb activation, coupled with decreased PGE levels, together promoted the observed metabolic phenotype in Mrp4^-/- mice. In conclusion, our results indicate that Mrp4 as a novel genetic factor involved in the pathogenesis of metabolic diseases, such as obesity and diabetes.

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.

Gut-restricted apical sodium-dependent bile acid transporter inhibitor attenuates alcohol-induced liver steatosis and injury in mice

BACKGROUND

Recent studies have shown that human and experimental alcohol-related liver disease (ALD) is robustly associated with dysregulation of bile acid homeostasis, which may in turn modulate disease severity. Pharmacological agents targeting bile acid metabolism and signaling may be potential therapeutics for ALD.

METHODS

The potential beneficial effects of a gut-restricted apical sodium-dependent bile acid transporter (ASBT) inhibitor were studied in a chronic-plus-binge ALD mouse model.

RESULTS

Blocking intestinal bile acid reabsorption by the gut-restricted ASBT inhibitor GSK2330672 attenuated hepatic steatosis and liver injury in a chronic-plus-binge ALD mouse model. Alcohol feeding is associated with intestinal bile acid accumulation but paradoxically impaired ileal farnesoid × receptor (FXR) function, and repressed hepatic cholesterol 7α-hydrolase (CYP7A1) expression despite decreased hepatic small heterodimer partner (SHP) and ileal fibroblast growth factor 15 (FGF15) expression. ASBT inhibitor treatment decreased intestinal bile acid accumulation and increased hepatic CYP7A1 expression, but further decreased ileal FXR activity. Alcohol feeding induces serum bile acid concentration that strongly correlates with a liver injury marker. However, alcohol-induced serum bile acid elevation is not due to intrahepatic bile acid accumulation but is strongly and positively associated with hepatic multidrug resistance-associated protein 3 (MRP4) and MRP4 induction but poorly associated with sodium-taurocholate cotransporting peptide (NTCP) expression. ASBT inhibitor treatment decreases serum bile acid concentration without affecting hepatocyte basolateral bile acid uptake and efflux transporters.

CONCLUSION

ASBT inhibitor treatment corrects alcohol-induced bile acid dysregulation and attenuates liver injury in experimental ALD.

A metabolomic-based study on disturbance of bile acids metabolism induced by intratracheal instillation of nickel oxide nanoparticles in rats

Nickel oxide nanoparticles (Nano NiO) evoke hepatotoxicity, while whether it affects the hepatic metabolism remains unclear. The aim of this study was to explore the differential metabolites and their metabolic pathways in rat serum and to further verify the potential mechanism of bile acids' (BAs) metabolism dysregulation after Nano NiO exposure. Sixteen male Wistar rats were intratracheally instilled with Nano NiO (0.24 mg/kg body weight) twice a week for 9 weeks. Liquid chromatography/mass spectrometry was applied to filter the differentially expressed metabolites in rat serum. Western blot was employed to detect the protein contents. Twenty-one differential metabolites that associated with BAs, lipid and phospholipid metabolism pathways were identified in rat serum after Nano NiO exposure. Decreased cholic acid and deoxycholic acid implied that the BAs metabolism was disturbed. The nickel content increased in liver after Nano NiO exposure. The protein expression of cholesterol 7α-hydroxylase (CYP7A1) was down-regulated, and the bile salt export pump was up-regulated after Nano NiO administration in rat liver. Moreover, dehydroepiandrosterone sulphotransferase (SULT2A1) and cytochrome P450 (CYP) 3A4 were elevated in the exposure group. In conclusion, Nano NiO might trigger the disturbances of BAs, lipid and phospholipid metabolism pathways in rats. The diminished serum BAs induced by Nano NiO might be related to the down-regulation of synthetase and to the overexpression of transmembrane protein and detoxification enzymes in BAs metabolism.

Antrodin A from Antrodia camphorata modulates the gut microbiome and liver metabolome in mice exposed to acute alcohol intake

This study aimed to investigate the protective effect of Antrodin A (AdA) from Antrodia camphorata (A. camphorata) mycelium on alcohol-induced gut microbiota and liver metabolomic disorders. In acute alcoholic liver injury mice, AdA ameliorated alcoholic exposure-induced hepatic lipid deposition (TC and TG), oxidative stress (MDA), inflammation (TNF-α, IL-1β, IL-6, IL-17 and IFN-γ), and liver damage via modulating microbiome and metabolomic responses. AdA restored the composition of intestinal flora with an increase in the relative abundance of Lactobacillus and Dubosiella and a decrease in Clostridium_sensu_stricto_1, Lachnospiraceae_NK4A136_group, Prevotellaceae_NK3B31_group, and Prevotellaceae_UCG-001. Besides, AdA favorably regulated alcohol-induced metabolic disorders, including glutathione metabolism (S-(2-hydroxyethyl)glutathione and glutathione oxidized), ascorbate and aldarate metabolism (l-ascorbic acid), and taurine and hypotaurine metabolism (taurine). In conclusion, AdA in A. camphorata is a beneficial active ingredient to treat the microbiomic and metabolic disturbance induced by alcohol intake.

Bile acid metabolism and circadian rhythms

Circadian rhythms are biological systems that synchronize cellular circadian oscillators with the organism's daily feeding-fasting or rest-activity cycles in mammals. Circadian rhythms regulate nutrient absorption and utilization at the cellular level and are closely related to obesity and metabolic disorders. Bile acids are important modulators that facilitate nutrient absorption and regulate energy metabolism. Here, we provide an overview of the current connections and future perspectives between the circadian clock and bile acid metabolism as well as related metabolic diseases. Feeding and fasting cycles influence bile acid pool size and composition, and bile acid signaling can respond to acute lipid and glucose utilization and mediate energy balance. Disruption of circadian rhythms such as shift work, irregular diet, and gene mutations can contribute to altered bile acid metabolism and heighten obesity risk. High-fat diets, alcohol, and gene mutations related to bile acid signaling result in desynchronized circadian rhythms. Gut microbiome also plays a role in connecting circadian rhythms with bile acid metabolism. The underlying mechanism of how circadian rhythms interact with bile acid metabolism has not been fully explored. Sustaining bile acid homeostasis based on circadian rhythms may be a potential therapy to alleviate metabolic disturbance.

Metabolomics study of the hepatoprotective effect of Phellinus igniarius in chronic ethanol-induced liver injury mice using UPLC-Q/TOF-MS combined with ingenuity pathway analysis

BACKGROUND

Phellinus igniarius (L.) Quèl as a potential medicinal mushroom possesses multiple biological activities including hepatoprotection, but the hepatoprotective mechanism is not clear.

PURPOSE

To elucidate the hepatoprotective effect and potential target of P. igniarius.

METHODS

The male C57BL/6 mice were fed with the Lieber-DeCarli diet containing alcohol or isocaloric maltose dextrin as control diet with or without P. igniarius decoction (PID) in the dosage of 0.65 g/kg and 2.6 g/kg. The levels of serum biomarkers were detected by an automatic biochemistry analyser. The histopathological changes of liver were observed by hematoxylin and eosin (H&E) staining. Ultra performance liquid chromatography-quadrupole/time-of-flight mass spectrometry (UPLC-Q/TOF-MS) was applied for investigating the dynamic changes of serum metabolites in chronic ethanol-induced liver injury mice and after treatment with PID. Ingenuity pathway analysis (IPA) was employed to identify the potential target of PID.

RESULTS

PID could significantly reduce the levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), triglyceride (TG) and total bile acid (TBA) in serum and improved hepatic steatosis and inflammation. In terms of metabolism, a total of 36 serum differential metabolites were identified, and PID intervention regulated 24 of them, involving the key metabolic pathways such as the biosynthesis of unsaturated fatty acids, primary bile acid biosynthesis, glycerophospholipid metabolism, fatty acids biosynthesis, ether lipid metabolism and arachidonic acid metabolism. On the mechanism, IPA showed that farnesol X receptor (FXR) was the major potential target for PID, and PID could improve chronic alcohol intake induced by the inhibition of mRNA expression of FXR in the liver and the activation of mRNA expression of FXR in the intestine in mice.

CONCLUSION

The present study for the first time systematically illustrated the hepatoprotective effect of P. igniarius and preliminarily explored its potential target FXR. P. igniarius might be exploited as a promising therapeutic option for alcoholic liver injury.

Bile acid-based therapies for non-alcoholic steatohepatitis and alcoholic liver disease

Bile acids are synthesized from cholesterol only in hepatocytes. Bile acids circulating in the enterohepatic system act as physiological detergent molecules to help solubilize biliary cholesterol and emulsify dietary lipids and fat-soluble vitamins in small intestine. Bile acids are signaling molecules that activate nuclear receptor farnesoid X receptor (FXR) and cell surface G protein-coupled receptor TGR5. FXR critically regulates bile acid homeostasis by mediating bile acid feedback inhibition of hepatic bile acid synthesis. In addition, bile acid-activated cellular signaling pathways regulate metabolic homeostasis, immunity, and cell proliferation in various metabolically active organs. In the small and large intestine, gut bacterial enzymes modify primary bile acids to generate secondary bile acids to help shape the bile acid pool composition and subsequent biological effects. In turn, bile acids exhibit anti-microbial properties and modulate gut microbiota to influence host metabolism and immunity. Currently, bile acid-based therapies including systemic and intestine-restricted FXR agonists, TGR5 agonists, fibroblast growth factor 19 analogue, intestine FXR antagonists, and intestine apical sodium-bile acid transporter (ASBT) inhibitors have been developed as promising treatments for non-alcoholic steatohepatitis (NASH). These pharmacological agents improved metabolic and inflammatory disorders via distinct mechanisms of action that are subjects of extensive research interest. More recently, human and experimental alcoholic liver disease (ALD) has been associated with disrupted bile acid homeostasis. In additional, new findings showed that targeting bile acid metabolism and signaling may be promising therapeutic approaches for treating ALD.

Bile acid receptors FXR and TGR5 signaling in fatty liver diseases and therapy

Bile acid synthesis is the most significant pathway for catabolism of cholesterol and for maintenance of whole body cholesterol homeostasis. Bile acids are physiological detergents that absorb, distribute, metabolize, and excrete nutrients, drugs, and xenobiotics. Bile acids also are signal molecules and metabolic integrators that activate nuclear farnesoid X receptor (FXR) and membrane Takeda G protein-coupled receptor 5 (TGR5; i.e., G protein-coupled bile acid receptor 1) to regulate glucose, lipid, and energy metabolism. The gut-to-liver axis plays a critical role in the transformation of primary bile acids to secondary bile acids, in the regulation of bile acid synthesis to maintain composition within the bile acid pool, and in the regulation of metabolic homeostasis to prevent hyperglycemia, dyslipidemia, obesity, and diabetes. High-fat and high-calorie diets, dysbiosis, alcohol, drugs, and disruption of sleep and circadian rhythms cause metabolic diseases, including alcoholic and nonalcoholic fatty liver diseases, obesity, diabetes, and cardiovascular disease. Bile acid-based drugs that target bile acid receptors are being developed for the treatment of metabolic diseases of the liver.

High Dietary Kuding Tea Extract Supplementation Induces Hepatic Xenobiotic-Metabolizing Enzymes-A 6-Week Feeding Study in Mice

Kuding tea (KT) is a traditional Chinese beverage rich in plant bioactives that may exhibit various health benefits. However, little is known about the safety of KT extract (KTE) when consumed long term at high doses as a dietary supplement. Therefore, in this study, we investigated aspects of the safety of KTE. Male C57BL/6 mice were fed a high-fat, high-fructose, Western-type diet (control) supplemented with either 12.88% γ-cyclodextrin (γCD), 7.12% KTE (comprising 0.15% ursolic acid, UA) encapsulated in 12.88% γCD (KTE-γCD), or 0.15% UA over a 6-week experimental period. The dietary treatments did not affect food intake, body weight or body composition. However, treatment with KTE-γCD, but not γCD and UA, increased liver weight and hepatic fat accumulation, which was accompanied by increased hepatic PPARγ and CD36 mRNA levels. KTE-γCD treatment elevated plasma cholesterol and CYP7A1 mRNA and protein levels compared to those in control mice. KTE-γCD substantially increased the mRNA and protein levels of hepatic CYP3A and GSTA1, which are central to the detoxification of drugs and xenobiotics. Furthermore, we observed a moderate elevation in hepatic CYP3A (5-fold change) and GSTA1 (1.7-fold change) mRNA levels in UA-fed mice. In vitro data collected in HepG2 cells indicated a dose-dependent increase in hepatic cytotoxicity in response to KTE treatment, which may have been partly mediated by UA. Overall, the present data may contribute to the safety assessment of KTE and suggest that KTE encapsulated in γCD affects liver fat storage and the hepatic phase I and phase II responses in mice.

Decreased ω-6:ω-3 PUFA ratio attenuates ethanol-induced alterations in intestinal homeostasis, microbiota, and liver injury

Ethanol (EtOH)-induced alterations in intestinal homeostasis lead to multi-system pathologies, including liver injury. ω-6 PUFAs exert pro-inflammatory activity, while ω-3 PUFAs promote anti-inflammatory activity that is mediated, in part, through specialized pro-resolving mediators [e.g., resolvin D1 (RvD1)]. We tested the hypothesis that a decrease in the ω-6:ω-3 PUFA ratio would attenuate EtOH-mediated alterations in the gut-liver axis. ω-3 FA desaturase-1 (fat-1) mice, which endogenously increase ω-3 PUFA levels, were protected against EtOH-mediated downregulation of intestinal tight junction proteins in organoid cultures and in vivo. EtOH- and lipopolysaccharide-induced expression of INF-γ, Il-6, and Cxcl1 was attenuated in fat-1 and WT RvD1-treated mice. RNA-seq of ileum tissue revealed upregulation of several genes involved in cell proliferation, stem cell renewal, and antimicrobial defense (including Alpi and Leap2) in fat-1 versus WT mice fed EtOH. fat-1 mice were also resistant to EtOH-mediated downregulation of genes important for xenobiotic/bile acid detoxification. Further, gut microbiome and plasma metabolomics revealed several changes in fat-1 versus WT mice that may contribute to a reduced inflammatory response. Finally, these data correlated with a significant reduction in liver injury. Our study suggests that ω-3 PUFA enrichment or treatment with resolvins can attenuate the disruption in intestinal homeostasis caused by EtOH consumption and systemic inflammation with a concomitant reduction in liver injury.

Microbiome dysbiosis and alcoholic liver disease☆

Microbiome dysbiosis is strongly associated with alcoholic liver disease (ALD). Recent studies on comprehensive analyses of microbiome compositional and functional changes have begun to uncover the mechanistic relation between microbiome and the pathogenesis of ALD. Importantly, targeting the microbiome has become a potential strategy for the prevention and treatment of ALD. In this review, we summarize the clinical evidence of microbiome dysbiosis in ALD patients, and experimental advances in microbiome and metabolomic functional changes in animals with different species and genetic backgrounds in ALD. We also summarize the studies in humanized intestinal microbiome and fecal microbiota transplantation in mice. We introduce new developments in the studies on the role of the circulating bacterial microbiome, oral bacterial microbiome and fungal microbiome in the development of ALD. We highlight the potential mechanisms by which microbiome dysbiosis contributes to ALD, including short chain fatty acid changes, bile acid metabolism, intestinal barrier function, release of bacterial and fungal products, and inflammation. In addition, we summarize the recent developments targeting the microbiome in prevention and treatment of ALD, including dietary nutrient interference, herbal medicine, antibiotics, anti-fungal agents, probiotics, engineered bacterial therapy, fecal transplantation and oral hygiene. Although recent preclinical studies have advanced our understanding of the microbiome and ALD, clinical studies, especially prospective studies with large samples, are needed to better understand the cause-effect of microbiome dysbiosis in ALD. Identifying new precision-based strategies targeting the microbiome are expected to be developed as more effective therapies in ALD.

Understanding Bile Acid Signaling in Diabetes: From Pathophysiology to Therapeutic Targets

Diabetes and obesity have reached an epidemic status worldwide. Diabetes increases the risk for cardiovascular disease and non-alcoholic fatty liver disease. Primary bile acids are synthesized in hepatocytes and are transformed to secondary bile acids in the intestine by gut bacteria. Bile acids are nutrient sensors and metabolic integrators that regulate lipid, glucose, and energy homeostasis by activating nuclear farnesoid X receptor and membrane Takeda G protein-coupled receptor 5. Bile acids control gut bacteria overgrowth, species population, and protect the integrity of the intestinal barrier. Gut bacteria, in turn, control circulating bile acid composition and pool size. Dysregulation of bile acid homeostasis and dysbiosis causes diabetes and obesity. Targeting bile acid signaling and the gut microbiome have therapeutic potential for treating diabetes, obesity, and non-alcoholic fatty liver disease.

Bile Acids as Metabolic Regulators and Nutrient Sensors

Bile acids facilitate nutrient absorption and are endogenous ligands for nuclear receptors that regulate lipid and energy metabolism. The brain-gut-liver axis plays an essential role in maintaining overall glucose, bile acid, and immune homeostasis. Fasting and feeding transitions alter nutrient content in the gut, which influences bile acid composition and pool size. In turn, bile acid signaling controls lipid and glucose use and protection against inflammation. Altered bile acid metabolism resulting from gene mutations, high-fat diets, alcohol, or circadian disruption can contribute to cholestatic and inflammatory diseases, diabetes, and obesity. Bile acids and their derivatives are valuable therapeutic agents for treating these inflammatory metabolic diseases.

Alcohol Induces More Severe Fatty Liver Disease by Influencing Cholesterol Metabolism

Objectives. Fatty liver disease (FLD) is a major cause of morbidity and mortality worldwide. Dietary cholesterol and alcohol consumption are important risk factors for the progression of FLD, but whether and how alcohol induces more severe FLD with cholesterol ingestion remain unclear. Herein, we mainly used the Lieber-DeCarli diet to establish the FLD mouse model to investigate the synergistic effects of alcohol and cholesterol metabolism on liver damage. The indices of aspartate transaminase (AST), alanine transaminase (ALT), low-density lipoprotein cholesterol (LDL-c), and total cholesterol (TC) levels, inflammation foci, and pathogenesis by hematoxylin and eosin (H&E) and Oil Red O staining revealed that alcohol induces more severe liver damage by influencing cholesterol metabolism, which might be primarily related to the influence of cholesterol absorption, synthesis, and excretion on the liver or small intestine. Moreover, inhibition of absorption of intestinal cholesterol, but not of fat, sucrose, and alcohol, absorption into the body's metabolism by Ezetimibe, significantly improved FLD in rats fed with the high fat-cholesterol-sucrose and alcohol diet. These results showed that alcohol plays an important role in cholesterol metabolism in FLD.

In vivo antioxidant activity of mackerel (Scomber japonicus) muscle protein hydrolysate

Pacific chub mackerel (Scomber japonicus) is an important fish throughout the world, especially in East Asian countries, including Korea, China, and Japan. Protein hydrolysates from marine sources are commonly used as nutritional supplements, functional ingredients, and flavor enhancers in the food, beverage, and pharmaceutical industries. Antioxidants isolated from fish are relatively easy to prepare, are cost effective, and have no reported side effects. Hence, the present study aimed to investigate the in vivo antioxidant activities of mackerel muscle protein hydrolysate (MMPH) prepared using Protamex. The in vivo bioactivities of MMPH were investigated in alcoholic fatty liver mice (C57BL/6). Serum alanine aminotransferase and aspartate aminotransferase levels were comparable in test and control mice, whereas serum triglyceride and lipid peroxidation levels significantly (p < 0.05; p < 0.001) decreased after administration of MMPH (100-500 mg kg^-1), especially at a concentration of 100 mg kg^-1. A significant (p < 0.05) reduction in xanthine oxidase activity was observed in all groups treated with MMPH (100-500 mg kg^-1), as compared with the control group. Significantly (p < 0.05) higher superoxide dismutase (SOD) activity/protein expression and regulated catalase (CAT) activity/protein expression levels were observed in groups administered MMPH (100-500 mg kg^-1), especially at a concentration of 100 mg kg^-1. These results show that the abundant amino acids of S. japonicus play an important role in the cytosol of the liver cells by directly participating in the expression of xanthine oxidase and the detoxifying SOD and CAT proteins, thereby enhancing antioxidant ability and ultimately, inhibiting lipid peroxidation. This study demonstrated that muscle protein hydrolysate from S. japonicus has strong antioxidant activities.

New insights in the multiple roles of bile acids and their signaling pathways in metabolic control

PURPOSE OF REVIEW

There is a growing awareness that individual bile acid species exert different physiological functions, beyond their classical roles in bile formation and fat absorption, due to differential stimulatory effects on the bile-acid-activated receptors farnesoid X receptor (FXR) and takeda G receptor 5 (TGR5). This review integrates recent findings on the role of individual bile acids and their receptors in metabolic control, with special emphasis on cholesterol homeostasis.

RECENT FINDINGS

The consequences of altered bile acid metabolism, for example, in type 2 diabetes and during aging, on metabolic control is increasingly recognized but full impact hereof remains to be elucidated. These effects interact with those of newly developed pharmacological FXR and TGR5 modulators that aim to improve metabolic health. Studies in genetically modified mice have provided important new insights, for example, establishment of the role of intestinal FXR in control of the transintestinal cholesterol excretion pathway. However, translation from mice to men is hampered by the presence of rodent-specific bile acid species with special features.

SUMMARY

Specific bile acids and their signaling pathways play important roles in control of (cholesterol) metabolism. Deeper insight into the interactions between endogenous (i.e., bile acids) and pharmacological modulators of FXR and TGR5 is needed to optimize therapeutic benefit of the latter. The recent identification of cytochrome P450 2C70 as key enzyme in the formation of rodent-specific hydrophilic muricholic acids allows for the development of adequate mouse models for this purpose.