Free fatty acids repress small heterodimer partner (SHP) activation and adiponectin counteracts bile acid-induced liver injury in superobese patients with nonalcoholic steatohepatitis

Animal models of NAFLD from a hepatologist's point of view

Non-alcoholic fatty liver disease (NAFLD) is a chronic liver disorder closely linked to obesity, hyperlipidemia and type 2 diabetes and is increasingly recognized as a major health problem in many parts of the world. While early stages of NAFLD are characterized by a bland accumulation of fat (steatosis) in hepatocytes, the disease can progress to non-alcoholic steatohepatitis (NASH) which involves chronic liver inflammation, tissue damage and fibrosis and can ultimately lead to end-stage liver disease including cirrhosis and cancer. As no approved pharmacological treatment for NAFLD exists today, there is an urgent need to identify promising pharmacological targets and develop future therapies. For this purpose, basic and translational research in NAFLD animal models is indispensable. While a large number of diverse animal models are currently used in the field, there is an ongoing challenge to identify those models that mirror human pathology the closest to allow good translation of obtained results into further clinical development. This review is meant to provide a concise overview of the most relevant NAFLD animal models currently available and will discuss the strengths and weaknesses of these models with regard to their comparability to human disease conditions.

Bile Acids and the Gut Microbiome as Potential Targets for NAFLD Treatment

Semisynthetic bile acid (BA) obeticholic acid, a potent farnesoid X receptor (FXR) agonist, exhibited beneficial effects on nonalcoholic fatty liver disease (NAFLD). Obeticholic acid, however, did not cause a resolution of nonalcoholic steatohepatitis. Here we discuss several prominent knowledge gaps in BA/FXR biology. Firstly, although many groups reported elevated serum BA levels, there are reports of decreased or normal serum BA levels in NAFLD, underlining the complexity of BA regulation by environmental and genetic factors. Secondly, conflicting data exist in animal studies regarding the effects of FXR signaling on obesity and associated metabolic abnormalities. Thirdly, it remains obscure how the gut microbiome and the BA pool interact and influence the pathogenesis of NAFLD. Lastly, it is not known how FXR-mediated signaling interact with G protein-coupled BA receptor 1-mediated signaling. Answering these questions may lead to an improved pharmaceutical intervention for NAFLD targeting the FXR signaling pathway.

Glycyrrhizin Alleviates Nonalcoholic Steatohepatitis via Modulating Bile Acids and Meta-Inflammation

Nonalcoholic steatohepatitis (NASH) is the progressive stage of nonalcoholic fatty liver disease that may ultimately lead to cirrhosis and liver cancer, and there are few therapeutic options for its treatment. Glycyrrhizin (GL), extracted from the traditional Chinese medicine liquorice, has potent hepatoprotective effects in both preclinical animal models and in humans. However, little is currently known about its effects and mechanisms in treating NASH. To explore the effects of GL on NASH, GL or its active metabolite glycyrrhetinic acid (GA) was administered to mice treated with a methionine- and choline-deficient (MCD) diet-induced NASH model, and histologic and biochemical analyses were used to measure the degree of lipid disruption, liver inflammation, and fibrosis. GL significantly improved MCD diet-induced hepatic steatosis, inflammation, and fibrosis and inhibited activation of the NLR family pyrin domain-containing 3 (NLRP3) inflammasome. GL significantly attenuated serum bile acid accumulation in MCD diet-fed mice partially by restoring inflammation-mediated hepatic farnesoid X receptor inhibition. In Raw 264.7 macrophage cells, both GL and GA inhibited deoxycholic acid-induced NLRP3 inflammasome-associated inflammation. Notably, both intraperitoneal injection of GL's active metabolite GA and oral administration of GL prevented NASH in mice, indicating that GL may attenuate NASH via its active metabolite GA. These results reveal that GL, via restoration of bile acid homeostasis and inhibition of inflammatory injury, can be a therapeutic option for treatment of NASH.

Hypoxic Signaling and Cholesterol Lipotoxicity in Fatty Liver Disease Progression

Cholesterol is the only lipid whose absorption in the gastrointestinal tract is limited by gate-keeping transporters and efflux mechanisms, preventing its rapid absorption and accumulation in the liver and blood vessels. In this review, I explored the current data regarding cholesterol accumulation in liver cells and key mechanisms in cholesterol-induced fatty liver disease associated with the activation of deleterious hypoxic and nitric oxide signal transduction pathways. Although nonalcoholic fatty liver disease (NAFLD) affects both obese and nonobese individuals, the mechanism of NAFLD progression in lean individuals with healthy metabolism is puzzling. Lean NAFLD individuals exhibit normal metabolic responses, implying that liver damage is not associated with impaired metabolism per se and that direct lipotoxic effects are crucial for disease progression. Several redox and oxidant signaling pathways involving cholesterol are at play in fatty liver disease development. These include impairment of the mitochondrial and lysosomal function by cholesterol loading of the inner-cell membranes; formation of cholesterol crystals and hepatocyte degradation; and crown-like structures surrounding degrading hepatocytes, activating Kupffer cells, and evoking inflammation. The current review focuses on the induction of liver inflammation, fibrosis, and steatosis by free cholesterol via the hypoxia-inducible factor 1α (HIF-1α), a main oxygen-sensing transcription factor involved in all stages of NAFLD. Cholesterol loading in hepatocytes can result in chronic HIF-1α activity because of the decreased oxygen availability and excessive production of nitric oxide and mitochondrial reactive oxygen species.

Endocrine Adiponectin-FGF15/19 Axis in Ethanol-Induced Inflammation and Alcoholic Liver Injury

Alcoholic liver disease (ALD) is the most prevalent form of liver disease, encompassing a spectrum of progressive pathological changes from steatosis to steatohepatitis to fibrosis/cirrhosis and hepatocellular carcinoma. Alcoholic steatosis/steatohepatitis is the initial stage of ALD and a major risk factor for advanced liver injuries. Adiponectin is a hormone secreted from adipocytes. Fibroblast growth factor (FGF) 15 (human homolog, FGF19) is an ileum-derived hormone. Adipocyte-derived adiponectin and gut-derived FGF15/19 regulate each other, share common signaling cascades, and exert similar beneficial functions. Emerging evidence has revealed that dysregulated adiponectin-FGF15/19 axis and impaired hepatic adiponectin-FGF15/19 signaling are associated with alcoholic liver damage in rodents and humans. More importantly, endocrine adiponectin-FGF15/19 signaling confers protection against ethanol-induced liver damage via fine tuning the adipose-intestine-liver crosstalk, leading to limited hepatic inflammatory responses, and ameliorated alcoholic liver injury. This review is focused on the recently discovered endocrine adiponectin-FGF15/19 axis that is emerging as an essential adipose-gut-liver coordinator involved in the development and progression of alcoholic steatohepatitis.

Hepatocyte nuclear receptor SHP suppresses inflammation and fibrosis in a mouse model of nonalcoholic steatohepatitis

Nonalcoholic fatty liver disease (NAFLD) is a burgeoning health problem worldwide, ranging from nonalcoholic fatty liver (NAFL, steatosis without hepatocellular injury) to the more aggressive nonalcoholic steatohepatitis (NASH, steatosis with ballooning, inflammation, or fibrosis). Although many studies have greatly contributed to the elucidation of NAFLD pathogenesis, the disease progression from NAFL to NASH remains incompletely understood. Nuclear receptor small heterodimer partner (Nr0b2, SHP) is a transcriptional regulator critical for the regulation of bile acid, glucose, and lipid metabolism. Here, we show that SHP levels are decreased in the livers of patients with NASH and in diet-induced mouse NASH. Exposing primary mouse hepatocytes to palmitic acid and lipopolysaccharide in vitro, we demonstrated that the suppression of Shp expression in hepatocytes is due to c-Jun N-terminal kinase (JNK) activation, which stimulates c-Jun-mediated transcriptional repression of Shp Interestingly, in vivo induction of hepatocyte-specific SHP in steatotic mouse liver ameliorated NASH progression by attenuating liver inflammation and fibrosis, but not steatosis. Moreover, a key mechanism linking the anti-inflammatory role of hepatocyte-specific SHP expression to inflammation involved SHP-induced suppression of NF-κB p65-mediated induction of chemokine (C-C motif) ligand 2 (CCL2), which activates macrophage proinflammatory polarization and migration. In summary, our results indicate that a JNK/SHP/NF-κB/CCL2 regulatory network controls communications between hepatocytes and macrophages and contributes to the disease progression from NAFL to NASH. Our findings may benefit the development of new management or prevention strategies for NASH.

Assessment of serum bile acid profiles as biomarkers of liver injury and liver disease in humans

To assess the potential of individual bile acids (IBA) and their profiles as mechanistic biomarkers of liver injury for humans in real world situations, we interrogated samples collected under minimum controlled conditions (ie subjects were not fasted). Total bile acids (TBA) have been considered to be biomarkers of liver injury for decades, and more recently, monitoring of IBA has been proposed for differentiation of variety of etiologies of liver injury. We established a LC-MS/MS methodology to analyze nine IBA, generated reference ranges, and examined effects of age, gender, and ethnicity for each IBA. Furthermore, we evaluated the ability of IBA and their profiles to detect hepatic injury in subjects with a broad range of liver impairments. To date, our study utilized the largest total cohort of samples (N = 645) that were divided into 2 groups, healthy or liver impaired, to evaluate IBA as biomarkers. The TBA serum levels in the Asian ethnic group trended higher when compared to other ethnic groups, and the serum concentrations of IBA, such as glycocholic acid (GCA), glycochenodeoxycholic acid (GCDCA), chenodeoxycholic acid (CDCA), and taurochenoxycholic acid (TCDCA) were significantly increased. To our knowledge, this report is the first to describe ethnic differences in serum concentrations of IBAs. In patients with hepatic impairments, with the exception of deoxycholic acid (DCA), the concentrations of IBAs were significantly elevated when compared with healthy subjects. The conjugated bile acids displayed greater differences between healthy subjects and subjects with hepatic impairments than non-conjugated bile acids. Furthermore, the subjects with hepatic impairments exhibited distinct profiles (signatures) of IBAs that clustered subjects according the nature of their liver impairments. Although additional studies are needed, our data suggested that the analysis of IBA has the potential to become useful for differentiation of various forms of liver injury.

Protective effects of yangonin from an edible botanical Kava against lithocholic acid-induced cholestasis and hepatotoxicity

Accumulation of toxic bile acids in liver could cause cholestasis and liver injury. The purpose of the current study is to evaluate the hepatoprotective effect of yangonin, a product isolated from an edible botanical Kava against lithocholic acid (LCA)-induced cholestasis, and further to elucidate the involvement of farnesoid X receptor (FXR) in the anticholestatic effect using in vivo and in vitro experiments. The cholestatic liver injury model was established by intraperitoneal injections of LCA in C57BL/6 mice. Serum biomarkers and H&E staining were used to identify the amelioration of cholestasis after yangonin treatment. Mice hepatocytes culture, gene silencing experiment, real-time PCR and Western blot assay were used to elucidate the mechanisms underlying yangonin hepatoprotection. The results indicated that yangonin promoted bile acid efflux and reduced hepatic uptake via an induction in FXR-target genes Bsep, Mrp2 expression and an inhibition in Ntcp, all of which are responsible for bile acid transport. Furthermore, yangonin reduced bile acid synthesis through repressing FXR-target genes Cyp7a1 and Cyp8b1, and increased bile acid metabolism through an induction in gene expression of Sult2a1, which are involved in bile acid synthesis and metabolism. In addition, yangonin suppressed liver inflammation through repressing inflammation-related gene NF-κB, TNF-α and IL-1β. In vitro evidences showed that the changes in transporters and enzymes induced by yangonin were abrogated when FXR was silenced. In conclusions, yangonin produces protective effect against LCA-induced hepatotoxity and cholestasis due to FXR-mediated regulation. Yangonin may be an effective approach for the prevention against cholestatic liver diseases.

The presence and severity of nonalcoholic steatohepatitis is associated with specific changes in circulating bile acids

The histologic spectrum of nonalcoholic fatty liver disease (NAFLD) includes fatty liver (NAFL) and steatohepatitis (NASH), which can progress to cirrhosis in up to 20% of NASH patients. Bile acids (BA) are linked to the pathogenesis and therapy of NASH. We (1) characterized the plasma BA profile in biopsy-proven NAFL and NASH and compared to controls and (2) related the plasma BA profile to liver histologic features, disease activity, and fibrosis. Liquid chromatography/mass spectrometry quantified BAs. Descriptive statistics, paired and multiple group comparisons, and regression analyses were performed. Of 86 patients (24 controls, 25 NAFL, and 37 NASH; mean age 51.8 years and body mass index 31.9 kg/m² ), 66% were women. Increased total primary BAs and decreased secondary BAs (both P < 0.05) characterized NASH. Total conjugated primary BAs were significantly higher in NASH versus NAFL (P = 0.047) and versus controls (P < 0.0001). NASH had higher conjugated to unconjugated chenodeoxycholate (P = 0.04), cholate (P = 0.0004), and total primary BAs (P < 0.0001). The total cholate to chenodeoxycholate ratio was significantly higher in NAFLD without (P = 0.005) and with (P = 0.02) diabetes. Increased key BAs were associated with higher grades of steatosis (taurocholate), lobular (glycocholate) and portal inflammation (taurolithocholate), and hepatocyte ballooning (taurocholate). Conjugated cholate and taurocholate directly and secondary to primary BA ratio inversely correlated to NAFLD activity score. A higher ratio of total secondary to primary BA decreased (odds ratio, 0.57; P = 0.004) and higher conjugated cholate increased the likelihood of significant fibrosis (F≥2) (P = 0.007). Conclusion: NAFLD is associated with significantly altered circulating BA composition, likely unaffected by type 2 diabetes, and correlated with histological features of NASH; these observations provide the foundation for future hypothesis-driven studies of specific effects of BAs on specific aspects of NASH. (Hepatology 2018;67:534-548).

Role of Bile Acids in Metabolic Control

Bile acids are endocrine molecules that in addition to facilitating the absorption of fat-soluble nutrients regulate numerous metabolic processes, including glucose, lipid, and energy homeostasis. The signaling actions of bile acids are mediated through specific bile-acid-activated nuclear and membrane-bound receptors. These receptors are not only expressed by tissues within the enterohepatic circulation such as the liver and the intestine, but also in other organs where bile acids mediate their systemic actions. In this review, we discuss bile acid signaling and the interplay with the gut microbiota in the pathophysiology of obesity, type 2 diabetes, and non-alcoholic fatty liver disease, and the role of surgical and pharmacological interventions on bile acid profiles and metabolism.

Changes in Bile Acid Profile After Laparoscopic Sleeve Gastrectomy are Associated with Improvements in Metabolic Profile and Fatty Liver Disease

BACKGROUND

Bile acids (BA) modulate lipid and glucose metabolism in a feedback loop through production of fibroblast growth factor (FGF) 19 in the terminal ileum. Changes in BA after bariatric surgery may lead to improvements in the metabolic syndrome, including fatty liver disease. This study investigated the relationship between BA and metabolic and inflammatory profiles after laparoscopic sleeve gastrectomy (LSG).

METHODS

Patients undergoing LSG had fasting blood samples taken pre-operatively and 6 months post-surgery. Liver injury was measured using cytokeratin (CK) 18 fragments. BA were measured using liquid chromatography tandem-mass spectrometry. FGF-19 was measured using enzyme-linked immunosorbent assay.

RESULTS

The study included 18 patients (12 females), with mean age 46.3 years (SEM ± 2.9) and BMI 60.1 kg/m(2) (±2.6). After 6 months, patients lost 39.8 kg (±3.1; p < 0.001). Fourteen patients (78 %) had steatosis. FGF-19 increased from median 128.1 (IQR 89.4-210.1) to 177.1 (121.8-288.9, p = 0.045) at 6 months. Although total BA did not change, primary glycine- and taurine-conjugated BA, cholic acid decreased, and secondary BA, glycine-conjugated urodeoxycholic acid increased over the study period. These changes are associated with reduction in insulin resistance, pro-inflammatory cytokines and CK-18 levels.

CONCLUSIONS

The profile of individual BA is altered after LSG. These changes occur in the presence of reductions in inflammatory cytokines and markers of liver injury. This study supports evidence from recent animal models that LSG may have an effect on fatty liver through changes in BA metabolism.

Bile Acids in Nonalcoholic Fatty Liver Disease: New Concepts and therapeutic advances

Nonalcoholic liver disease (NAFLD) is a major emerging health burden that is a common cause of illness and death worldwide. NAFLD can progress into nonalcoholic steatohepatitis (NASH) which is a severe form of liver disease characterized by inflammation and fibrosis. Further progression leads to cirrhosis, which predisposes patients to hepatocellular carcinoma or liver failure. The mechanism of the progression from simple steatosis to NASH is unclear. However, there are theories and hypothesis which support the link between disruption of the bile acids homeostasis and the progression of this disorder. Previous studies have been demonstrated that alterations to these pathways can lead to dysregulation of energy balance and increased liver inflammation and fibrosis. In this review, we summarized the current knowledge of the interaction between BA and the process related to the development of NAFLD, besides, the potential targets for novel therapies.

Engineered fibroblast growth factor 19 protects from acetaminophen-induced liver injury and stimulates aged liver regeneration in mice

The liver displays a remarkable regenerative capacity triggered upon tissue injury or resection. However, liver regeneration can be overwhelmed by excessive parenchymal destruction or diminished by pre-existing conditions hampering repair. Fibroblast growth factor 19 (FGF19, rodent FGF15) is an enterokine that regulates liver bile acid and lipid metabolism, and stimulates hepatocellular protein synthesis and proliferation. FGF19/15 is also important for liver regeneration after partial hepatectomy (PH). Therefore recombinant FGF19 would be an ideal molecule to stimulate liver regeneration, but its applicability may be curtailed by its short half-life. We developed a chimaeric molecule termed Fibapo in which FGF19 is covalently coupled to apolipoprotein A-I. Fibapo retains FGF19 biological activities but has significantly increased half-life and hepatotropism. Here we evaluated the pro-regenerative activity of Fibapo in two clinically relevant models where liver regeneration may be impaired: acetaminophen (APAP) poisoning, and PH in aged mice. The only approved therapy for APAP intoxication is N-acetylcysteine (NAC) and no drugs are available to stimulate liver regeneration. We demonstrate that Fibapo reduced liver injury and boosted regeneration in APAP-intoxicated mice. Fibapo improved survival of APAP-poisoned mice when given at later time points, when NAC is ineffective. Mechanistically, Fibapo accelerated recovery of hepatic glutathione levels, potentiated cell growth-related pathways and increased functional liver mass. When Fibapo was administered to old mice prior to PH, liver regeneration was markedly increased. The exacerbated injury developing in these mice upon PH was attenuated, and the hepatic biosynthetic capacity was enhanced. Fibapo reversed metabolic and molecular alterations that impede regeneration in aged livers. It reduced liver steatosis and downregulated p21 and hepatocyte nuclear factor 4 α (Hnf4α) levels, whereas it stimulated Foxm1b gene expression. Together our findings indicate that FGF19 variants retaining the metabolic and growth-promoting effects of this enterokine may be valuable for the stimulation of liver regeneration.

Bile Acid Alterations Are Associated With Insulin Resistance, but Not With NASH, in Obese Subjects

CONTEXT

Bile acids (BAs) are signaling molecules controlling energy homeostasis that can be both toxic and protective for the liver. BA alterations have been reported in obesity, insulin resistance (IR), and nonalcoholic steatohepatitis (NASH). However, whether BA alterations contribute to NASH independently of the metabolic status is unclear.

OBJECTIVE

To assess BA alterations associated with NASH independently of body mass index and IR.

DESIGN AND SETTING

Patients visiting the obesity clinic of the Antwerp University Hospital (a tertiary referral facility) were recruited from 2006 to 2014.

PATIENTS

Obese patients with biopsy-proven NASH (n = 32) and healthy livers (n = 26) were matched on body mass index and homeostasis model assessment of IR.

MAIN OUTCOME MEASURES

Transcriptomic analyses were performed on liver biopsies. Plasma concentrations of 21 BA species and 7α-hydroxy-4-cholesten-3-one, a marker of BA synthesis, were determined by liquid chromatography-tandem mass spectrometry. Plasma fibroblast growth factor 19 was measured by enzyme-linked immunosorbent assay.

RESULTS

Plasma BA concentrations did not correlate with any hepatic lesions, whereas, as previously reported, primary BA strongly correlated with IR. Transcriptomic analyses showed unaltered hepatic BA metabolism in NASH patients. In line, plasma 7α-hydroxy-4-cholesten-3-one was unchanged in NASH. Moreover, no sign of hepatic BA accumulation or activation of BA receptors-farnesoid X, pregnane X, and vitamin D receptors-was found. Finally, plasma fibroblast growth factor 19, secondary-to-primary BA, and free-to-conjugated BA ratios were similar, suggesting unaltered intestinal BA metabolism and signaling.

CONCLUSIONS

In obese patients, BA alterations are related to the metabolic phenotype associated with NASH, especially IR, but not liver necroinflammation.

Analyzing the hepatoprotective effect of the Swertia cincta Burkillextract against ANIT-induced cholestasis in rats by modulating the expression of transporters and metabolic enzymes

ETHNOPHARMACOLOGICAL RELEVANCE

Swertia cincta Burkill was traditionally used for treating jaundice and various types of chronic and acute hepatitis in Yunnan and Tibet in China for hundreds of years. This study aims to investigate the protective effect of S. cincta Burkill (ESC) extract on alpha-naphthylisothiocyanate (ANIT)-induced hepatotoxicity and cholestasis in rats.

MATERIALS AND METHODS

Crude extracts were prepared using 90% ethanol and by vacuum drying. We utilized an ultra-high-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight tandem mass spectrometry (UHPLC/Q-TOF-MS) system to conduct a phytochemical analysis of the active components of ESC. Liver function was evaluated by measuring the serum levels of enzymes and components and by analyzing the liver histology. We also measured the expression of bile metabolism-related transporters and metabolic enzymes at both protein and mRNA levels to elucidate the underlying mechanisms.

RESULTS

ESC analysis using an UHPLC/Q-TOF-MS revealed eight compounds. Oral administration of ESC to ANIT-treated rats can significantly reduce the increases in serum levels of ALT, AST, ALP, TBIL, and TBA. It can also improve liver pathology and bile flow. Western blot and qRT-PCR analyses showed that ESC upregulated the protein and mRNA expression of Fxr, Ntcp, Bsep, Cyp7a1, Mrp2, and Mdr2.

CONCLUSION

ESC could alleviate liver injury by reducing enzyme activities of serums, improving liver pathology and bile flow. The protective mechanism was associated with regulation of the expression of hepatic transporters and metabolic enzymes.

Free fatty acids profile among lean, overweight and obese non-alcoholic fatty liver disease patients: a case - control study

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) given its association with obesity and diabetes may perhaps exert distinct free fatty acids (FFA) pattern, but the understanding of this phenomenon is limited. To this effect, we evaluated FFA profiles among healthy subjects and NAFLD patients stratified by body weight, to identify FFA valuable for early diagnosis of NAFLD.

METHODS

Serum FFA profiles of healthy and NAFLD (lean, overweight and obese) subjects was determined using gas chromatography-mass spectrometry (GC-MS) and distinctions in FFA patterns were evaluated using one-way ANOVA while Receiver operating characteristics (ROC) and logistic regression models were used to explore FFA significant for diagnosing NAFLD.

RESULTS

NAFLD patients presented significantly higher (P < 0.05) serum FFA profiles compared to healthy controls (HC). While total FFA profiles were insignificantly different between lean (2093.33 ± 558.11 μg/ml) and overweight (2420.81 ± 555.18 μg/ml) NAFLD patients, obese NAFLD (2739.01 ± 810.35 μg/ml) presented most significantly elevated (P < 0.05) total FFA profiles compared with HC. Of the four FFA; myristic acid (14:0), palmitoleic acid (16:1), γ-linolenic acid (γ-18:3) and cis-7,10,13,16,19-docosapentaenoic acid (22:5), selected in ROC analysis given their high Youden's index and AUC, only 14:0; 5.58(1.37, 22.76) and 16:1; 4.36(1.34, 14.13) had statistical significant odd ratios.

CONCLUSION

Our findings suggest 14:0 and 16:1 are promising for early diagnosis of NAFLD.

Osteopontin regulates the cross-talk between phosphatidylcholine and cholesterol metabolism in mouse liver

Osteopontin (OPN) is involved in different liver pathologies in which metabolic dysregulation is a hallmark. Here, we investigated whether OPN could alter liver, and more specifically hepatocyte, lipid metabolism and the mechanism involved. In mice, lack of OPN enhanced cholesterol 7α-hydroxylase (CYP7A1) levels and promoted loss of phosphatidylcholine (PC) content in liver; in vivo treatment with recombinant (r)OPN caused opposite effects. rOPN directly decreased CYP7A1 levels through activation of focal adhesion kinase-AKT signaling in hepatocytes. PC content was also decreased in OPN-deficient (OPN-KO) hepatocytes in which de novo FA and PC synthesis was lower, whereas cholesterol (CHOL) synthesis was higher, than in WT hepatocytes. In vivo inhibition of cholesterogenesis normalized liver PC content in OPN-KO mice, demonstrating that OPN regulates the cross-talk between liver CHOL and PC metabolism. Matched liver and serum samples showed a positive correlation between serum OPN levels and liver PC and CHOL concentration in nonobese patients with nonalcoholic fatty liver. In conclusion, OPN regulates CYP7A1 levels and the metabolic fate of liver acetyl-CoA as a result of CHOL and PC metabolism interplay. The results suggest that CYP7A1 is a main axis and that serum OPN could disrupt liver PC and CHOL metabolism, contributing to nonalcoholic fatty liver disease progression in nonobese patients.

A longitudinal study of whole body, tissue, and cellular physiology in a mouse model of fibrosing NASH with high fidelity to the human condition

The sequence of events that lead to inflammation and fibrosing nonalcoholic steatohepatitis (NASH) is incompletely understood. Hence, we investigated the chronology of whole body, tissue, and cellular events that occur during the evolution of diet-induced NASH. Male C57Bl/6 mice were assigned to a fast-food (FF; high calorie, high cholesterol, high fructose) or standard-chow (SC) diet over a period of 36 wk. Liver histology, body composition, mitochondrial respiration, metabolic rate, gene expression, and hepatic lipid content were analyzed. Insulin resistance [homeostasis model assessment-insulin resistance (HOMA-IR)] increased 10-fold after 4 wk. Fibrosing NASH was fully established by 16 wk. Total hepatic lipids increased by 4 wk and remained two- to threefold increased throughout. Hepatic triglycerides declined from sixfold increase at 8 wk to threefold increase by 36 wk. In contrast, hepatic cholesterol levels steadily increased from baseline at 8 wk to twofold by 36 wk. The hepatic immune cell population altered over time with macrophages persisting beyond 16 wk. Mitochondrial oxygen flux rates of FF mice diet were uniformly lower with all the tested substrates (13-276 pmol·s^-1·ml^-1 per unit citrate synthase) than SC mice (17-394 pmol·s^-1·ml^-1 per unit citrate synthase) and was accompanied by decreased mitochondrial:nuclear gene copy number ratios after 4 wk. Metabolic rate was lower in FF mice. Mitochondrial glutathione was significantly decreased at 24 wk in FF mice. Expression of dismutases and catalase was also decreased in FF mice. The evolution of NASH in the FF diet-induced model is multiphasic, particularly in terms of hepatic lipid composition. Insulin resistance precedes hepatic inflammation and fibrosis. Mitochondrial dysfunction and depletion occur after the histological features of NASH are apparent. Collectively, these observations provide a unique overview of the sequence of changes that coevolve with the histological evolution of NASH.NEW & NOTEWORTHY This study demonstrates in a first of kind longitudinal analysis, the evolution of nonalcoholic steatohepatitis (NASH) on a fast-food diet-induced model. Key findings include 1) hepatic lipid composition changes in a multiphasic fashion as NASH evolves; 2) insulin resistance precedes hepatic inflammation and fibrosis, answering a longstanding chicken-and-egg question regarding the relationship of insulin resistance to liver histology in NASH; and 3) mitochondrial dysfunction and depletion occur after the histological features of NASH are apparent.

The role of bile acids in nonalcoholic fatty liver disease and nonalcoholic steatohepatitis

Nonalcoholic fatty liver disease is growing in prevalence worldwide. It is marked by the presence of macrosteatosis on liver histology but is often clinically asymptomatic. However, it can progress into nonalcoholic steatohepatitis which is a more severe form of liver disease characterized by inflammation and fibrosis. Further progression leads to cirrhosis, which predisposes patients to hepatocellular carcinoma or liver failure. The mechanism by which simple steatosis progresses to steatohepatitis is not entirely clear. However, multiple pathways have been proposed. A common link amongst many of these pathways is disruption of the homeostasis of bile acids. Other than aiding in the absorption of lipids and lipid-soluble vitamins, bile acids act as ligands. For example, they bind to farnesoid X receptor, which is critically involved in many of the pathways responsible for maintaining bile acid, glucose, and lipid homeostasis. Alterations to these pathways can lead to dysregulation of energy balance and increased inflammation and fibrosis. Repeated insults over time may be the key to development of steatohepatitis. For this reason, current drug therapies target aspects of these pathways to try to reduce and halt inflammation and fibrosis. This review will focus on the role of bile acids in these various pathways and how changes in these pathways may result in steatohepatitis. While there is no approved pharmaceutical treatment for either hepatic steatosis or steatohepatitis, this review will also touch upon the multitude of potential therapies.

Changes in drug transport and metabolism and their clinical implications in non-alcoholic fatty liver disease

INTRODUCTION

The incidence of non-alcoholic fatty liver disease (NAFLD) is rising, especially in Western countries. Drug treatment in patients with NAFLD is common since it is linked to other conditions like diabetes, obesity, and cardiovascular disease. Consequently, changes in drug metabolism may have serious clinical implications. Areas covered: A literature search for studies in animal models or patients with obesity, fatty liver, non-alcoholic steatohepatitis (NASH) or NASH cirrhosis published before November 2016 was performed. After discussing epidemiology and animal models for NAFLD, we summarized both basic as well as clinical studies investigating changes in drug transport and metabolism in NAFLD. Important drug groups were assessed separately with emphasis on clinical implications for drug treatment in patients with NAFLD. Expert opinion: Given the frequency of NAFLD even today, a high degree of drug treatment in NAFLD patients appears safe and well-tolerated despite considerable changes in hepatic uptake, distribution, metabolism and transport of drugs in these patients. NASH causes changes in biliary excretion, systemic concentrations, and renal handling of drugs leading to alterations in drug efficacy or toxicity under specific circumstances. Future clinical drug studies should focus on this special patient population in order to avoid serious adverse events in NAFLD patients.

Effect of prebiotics of Agave salmiana fed to healthy Wistar rats

BACKGROUND

Inulin and other fructans are synthesized and stored in mezcal agave (Agave salmiana). Fructans provide several health benefits and have excellent technological properties, but only few data report their physiological effect when added in the diet.

RESULTS

Here, we studied the physiological effects of fructans obtained from A. salmiana when added in the diet of Wistar rats. Results showed favorable changes on Wistar rats when the fructans was added to their diet, including the decrease of the pH in the feces and the increase of the number of lactic acid bacteria (CFU g^-1 ) (Lactobacillus spp. and Bifidobacterium spp.), even these changes were enhanced with the synbiotic diet (fructans plus B. animalis subsp. lactis). Synbiotic diet, developed changes in the reduction of cholesterol and triglycerides concentrations in serum, with statistical differences (P < 0.05). Histological analysis of colon sections showed that synbiotic diet promoted colon cells growth suggesting that fructans from A. salmiana confer beneficial health effects through gut microbiota modulation.

CONCLUSION

Our data underline the advantage of targeting the gut microbiota by colonic nutrients like specific structure of fructans from A. salmiana, with their beneficial effects. More studies are necessary to define the role of fructans to develop more solid therapeutic solutions in humans. © 2016 Society of Chemical Industry.

Myeloid Cell-Specific Lipin-1 Deficiency Stimulates Endocrine Adiponectin-FGF15 Axis and Ameliorates Ethanol-Induced Liver Injury in Mice

Lipin-1 is a phosphatidate phosphohydrolase (PAP) required for the generation of diacylglycerol during glycerolipid synthesis, and exhibits dual functions in the regulation of lipid metabolism. Lipin-1 has been implicated in the pathogenesis of alcoholic liver disease (ALD). In the present study, we assessed lipin-1 function in myeloid cells in ALD using a myeloid cell-specific lipin-1 knockout (mLipin-1KO) mouse model. Utilizing the Gao-binge ethanol feeding protocol, matched mLipin-1KO mice and littermate loxP control (WT) mice were pair-fed with either an ethanol-containing diet or an ethanol-free diet (control). Surprisingly, deletion of lipin-1 in myeloid cells dramatically attenuated liver inflammatory responses and ameliorated liver injury that would normally occur following the ethanol feeding protocol, but slightly exacerbated the ethanol-induced steatosis in mice. Mechanistically, myeloid cell-specific lipin-1 deficiency concomitantly increased the fat-derived adiponectin and ileum-derived fibroblast growth factor (FGF) 15. In concordance with concerted elevation of circulating adiponectin and FGF15, myeloid cell-specific lipin-1 deficiency diminished hepatic nuclear factor kappa B (NF-κB) activity, limited liver inflammatory responses, normalized serum levels of bile acids, and protected mice from liver damage after ethanol challenge. Our novel data demonstrate that myeloid cell-specific deletion of lipin-1 ameliorated inflammation and alcoholic hepatitis in mice via activation of endocrine adiponectin-FGF15 signaling.

MitoNEET Deficiency Alleviates Experimental Alcoholic Steatohepatitis in Mice by Stimulating Endocrine Adiponectin-Fgf15 Axis

MitoNEET (mNT) (CDGSH iron-sulfur domain-containing protein 1 or CISD1) is an outer mitochondrial membrane protein that donates 2Fe-2S clusters to apo-acceptor proteins. In the present study, using a global mNT knock-out (mNTKO) mouse model, we investigated the in vivo functional role of mNT in the development of alcoholic steatohepatitis. Experimental alcoholic steatohepatitis was achieved by pair feeding wild-type (WT) and mNTKO mice with Lieber-DeCarli ethanol-containing diets for 4 weeks. Strikingly, chronically ethanol-fed mNTKO mice were completely resistant to ethanol-induced steatohepatitis as revealed by dramatically reduced hepatic triglycerides, decreased hepatic cholesterol level, diminished liver inflammatory response, and normalized serum ALT levels. Mechanistic studies demonstrated that ethanol administration to mNTKO mice induced two pivotal endocrine hormones, namely, adipose-derived adiponectin and gut-derived fibroblast growth factor 15 (Fgf15). The elevation in circulating levels of adiponectin and Fgf15 led to normalized hepatic and serum levels of bile acids, limited hepatic accumulation of toxic bile, attenuated inflammation, and amelioration of liver injury in the ethanol-fed mNTKO mice. Other potential mechanisms such as reduced oxidative stress, activated Sirt1 signaling, and diminished NF-κB activity also contribute to hepatic improvement in the ethanol-fed mNTKO mice. In conclusion, the present study identified adiponectin and Fgf15 as pivotal adipose-gut-liver metabolic coordinators in mediating the protective action of mNT deficiency against development of alcoholic steatohepatitis in mice. Our findings may help to establish mNT as a novel therapeutic target and pharmacological inhibition of mNT may be beneficial for the prevention and treatment of human alcoholic steatohepatitis.

Simple steatosis sensitizes cholestatic rats to liver injury and dysregulates bile salt synthesis and transport

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disorder. It is uncertain if simple steatosis, the initial and prevailing form of NAFLD, sensitizes the liver to cholestasis. Here, we compared the effects of obstructive cholestasis in rats with a normal liver versus rats with simple steatosis induced by a methionine/choline-deficient diet. We found that plasma liver enzymes were higher and hepatic neutrophil influx, inflammation, and fibrosis were more pronounced in animals with combined steatosis and cholestasis compared to cholestasis alone. Circulating bile salt levels were markedly increased and hepatic bile salt composition shifted from hydrophilic tauro-β-muricholate to hydrophobic taurocholate. This shift was cytotoxic for HepG2 hepatoma cells. Gene expression analysis revealed induction of the rate-limiting enzyme in bile salt synthesis, cytochrome P450 7a1 (CYP7A1), and modulation of the hepatic bile salt transport system. In conclusion, simple steatosis sensitizes the liver to cholestatic injury, inflammation, and fibrosis in part due to a cytotoxic shift in bile salt composition. Plasma bile salt levels were elevated, linked to dysregulation of bile salt synthesis and enhanced trafficking of bile salts from the liver to the systemic circulation.

Elevated cholesterol levels have a poor prognosis in a cholestasis scenario

Cholestasis results from defective bile flow through the biliary ducts leading to the accumulation of bile acids (BAs) in hepatocytes and serum. It has been seen that cholestasis is associated with hypercholesterolemia, which is a prerequisite for gallstone formation and primary biliary cirrhosis, being some of the most common gastrointestinal disorders in Western societies. Cytotoxic BAs induce proinflammatory mediators, oxidative stress, and apoptosis in hepatocytes, whereas cytoprotective BAs prevent them; they can also modify the plasmatic membrane structure of cells or mitochondrial outer membrane properties as well as the distribution of cholesterol, altering various proteins involved in BAs homeostasis.

The intrahepatic expression levels of bile acid transporters are inversely correlated with the histological progression of nonalcoholic fatty liver disease

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) presents as a spectrum ranging from simple steatosis to nonalcoholic steatohepatitis (NASH). The latter is progressive, and its pathogenesis remains poorly understood. Recently, bile acid (BA) metabolism has become a therapeutic focus in NASH patients. The aim of the present study was to explore changes in bile acid metabolism in NAFLD patients in the context of disease progression.

METHODS

We prospectively enrolled patients with clinically suspected NAFLD. Patients taking ursodeoxycholic acid were excluded. The intrahepatic expression levels of genes associated with BA metabolism were determined by quantitative PCR and immunohistochemistry.

RESULTS

Seventy-eight patients (male:female = 49:29) histologically diagnosed with NAFLD were analyzed. The expression levels of farnesoid X receptor, liver receptor homolog 1, and small heterodimer partner, key proteins in BA synthesis, significantly decreased as the NAFLD activity score (NAS) increased in either males or females. The levels of cholesterol 7 alpha-hydroxylase, the rate-limiting enzyme of BA synthesis, were not changed. Notably, the expression levels of a main export transporter, bile salt export pump (BSEP), significantly decreased as the NAS and the each NAS component increased in both genders. The decreases of BSEP levels were also observed by immunohistochemistry, particularly in areas with pronounced fatty changes in cases with high NAS.

CONCLUSIONS

The expression levels of the BA export transporter BSEP were inversely correlated with NAS in NAFLD patients. Such down-regulation may cause excessive BA levels in hepatocytes, leading to cell injury. Our findings may afford new insights into the pathogenesis of NASH.

Molecular mechanisms of lipotoxicity and glucotoxicity in nonalcoholic fatty liver disease

The exposure of hepatocytes to high concentrations of lipids and carbohydrates and the ensuing hepatocellular injury are termed lipotoxicity and glucotoxicity, respectively. A common denominator is metabolic derangement, especially in regards to intracellular energy homeostasis, which is brought on by glucose intolerance and insulin resistance in tissues. In this review, we highlight the lipids and carbohydrates that provoke hepatocyte injury and the mechanisms involved in lipotoxicity and glucotoxicity, including endoplasmic reticulum stress, oxidative stress and mitochondrial impairment. Through upregulation of proteins involved in various pathways including PKR-like ER kinase (PERK), CCAAT/enhancer-binding homologous protein (CHOP), c-Jun NH2-terminal kinase-1 (JNK), Bcl-2 interacting mediator (BIM), p53 upregulated modulator of apoptosis (PUMA), and eventually caspases, hepatocytes in lipotoxic states ultimately undergo apoptosis. The protective role of certain lipids and possible targets for pharmacological therapy are explored. Finally, we discuss the role of high fructose and glucose diets in contributing to organelle impairment and poor glucose transport mechanisms, which perpetuate hyperglycemia and hyperlipidemia by shunting of excess carbohydrates into lipogenesis.

Free Fatty Acids Differentially Downregulate Chemokines in Liver Sinusoidal Endothelial Cells: Insights into Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease is a prevalent problem throughout the western world. Liver sinusoidal endothelial cells (LSEC) have been shown to play important roles in liver injury and repair, but their role in the underlying pathogenetic mechanisms of non-alcoholic fatty liver disease remains undefined. Here, we evaluated the effects of steatosis on LSEC gene expression in a murine model of non-alcoholic fatty liver disease and an immortalized LSEC line. Using microarray we identified distinct gene expression profiles following exposure to free fatty acids. Gene pathway analysis showed a number of differentially expressed genes including those involved in lipid metabolism and signaling and inflammation. Interestingly, in contrast to hepatocytes, fatty acids led to decreased expression of pro-inflammatory chemokines including CCL2 (MCP-1), CXCL10 and CXCL16 in both primary and LSEC cell lines. Chemokine downregulation translated into a significant inhibition of monocyte migration and LSECs isolated from steatotic livers demonstrated a similar shift towards an anti-inflammatory phenotype. Overall, these pathways may represent a compensatory mechanism to reverse the liver damage associated with non-alcoholic fatty liver disease.

Nuclear receptor FXR: A potential therapeutic target for non-alcoholic steatohepatitis

Non-alcoholic fatty liver disease (NAFLD) has become a very common chronic liver disease all over the world. The high incidence of NAFLD is closely related to obesity, diabetes and metabolic disorders. Insulin resistance and dyslipidemia following the hepatic proinflammatory response and fibrosis are the primary features of NAFLD deterioration. Nuclear receptor farnesoid X receptor (FXR) regulates lipid metabolism and homeostasis. Clarification of FXR function and features can provide a better understanding of the pathophysiological characteristics of non-alcoholic steatohepatitis (NASH) and illuminate the mechanism of NAFLD/NASH potential therapeutic targets. FXR activation can inhibit the de novo hepatic lipogenesis, improve insulin sensitivity and protect against bile acid-induced cytotoxicity. Clinical studies indicated that FXR agonists or modulators are very promising for the clinical treatment of NAFLD and NASH. This review focuses on the important regulatory role of FXR in NASH.

Thymoquinone alleviates nonalcoholic fatty liver disease in rats via suppression of oxidative stress, inflammation, apoptosis

Nonalcoholic steatohepatitis (NAFLD) is a progressive form of liver disease that leads to advanced fibrosis. The present study was designed to assess the hepatoprotective effect of thymoquinone (TQ) on liver functions, insulin resistance, and PPAR-γ expression in NAFLD. Rats were divided into two main groups: one fed with normal rat chow diet and the other with high-fat high-cholesterol diet group for 6 weeks. Every group was subdivided into three subgroups (n = 8): treated with saline, low dose TQ (10 mg/kg), high dose TQ (20 mg/kg). High fat high cholesterol diet caused marked liver damage as noted in histopathology and significant increase in liver index, liver enzymes. There was significant increase in the insulin resistance, serum cholesterol, triglyceride, PPAR-γ gene overexpression with significant decrease in HDL. Additionally, oxidative stress increased by measuring MDA associated with significant decrease in serum total antioxidant capacity. As markers of inflammation, hepatic TNF-α was significantly increased with decrease in IL10. Further, there was increase in BAX protein with decrease in Bcl as compared to control group. This model of 6 weeks high-fat high-cholesterol diet showed minimal fibrosis as noticed by increase MMP2 and Masson trichrome satin. Co-treatment with TQ improved all previous parameters. High dose was more effective, although mostly non-statistically significant. TQ may have a promising agent to improve hepatic steatosis, oxidative stress; inflammatory, apoptotic status, fibrosis and so prevent liver damage in patients with NAFLD. Although PPAR-γ was significantly under-expressed by TQ, insulin resistance was improved significantly suggesting a role of liver damage.

Liver transcriptomic networks reveal main biological processes associated with feed efficiency in beef cattle

BACKGROUND

The selection of beef cattle for feed efficiency (FE) traits is very important not only for productive and economic efficiency but also for reduced environmental impact of livestock. Considering that FE is multifactorial and expensive to measure, the aim of this study was to identify biological functions and regulatory genes associated with this phenotype.

RESULTS

Eight genes were differentially expressed between high and low feed efficient animals (HFE and LFE, respectively). Co-expression analyses identified 34 gene modules of which 4 were strongly associated with FE traits. They were mainly enriched for inflammatory response or inflammation-related terms. We also identified 463 differentially co-expressed genes which were functionally enriched for immune response and lipid metabolism. A total of 8 key regulators of gene expression profiles affecting FE were found. The LFE animals had higher feed intake and increased subcutaneous and visceral fat deposition. In addition, LFE animals showed higher levels of serum cholesterol and liver injury biomarker GGT. Histopathology of the liver showed higher percentage of periportal inflammation with mononuclear infiltrate.

CONCLUSION

Liver transcriptomic network analysis coupled with other results demonstrated that LFE animals present altered lipid metabolism and increased hepatic periportal lesions associated with an inflammatory response composed mainly by mononuclear cells. We are now focusing to identify the causes of increased liver lesions in LFE animals.

Liver cell injury caused by bad habits

Apoptosis and necrosis of liver cells induced by environmental or genetic factors are the main features of liver injury. Liver injury is usually caused by apoptosis of liver cells, which is controlled by a complex regulatory system involved in liver damage and secondary inflammation. This article aims to review liver injury caused by bad habits and the underlying molecular mechanisms.

Boldine Attenuates Cholestasis Associated With Nonalcoholic Fatty Liver Disease in Hereditary Hypertriglyceridemic Rats Fed by High-Sucrose Diet

The aim of the current study was to clarify the effect of high sucrose diet (HSD) on bile formation (BF) in rats with hereditary hypertriglyceridemia (HHTg). Potentially positive effects were studied for boldine, a natural choleretic agent. Administration of HSD to HHTg rats led to increased triglyceride deposition in the liver. HSD reduced BF as a consequence of decreased biliary secretion of bile acids (BA) and glutathione. Responsible mechanism was down-regulation of hepatic transporters for BA and glutathione, Bsep and Mrp2, respectively. Moreover, gene expressions of transporters for other constituents of bile, namely Abcg5/8 for cholesterol, Abcb4 for phospholipids, and Oatp1a4 for xenobiotics, were also reduced by HSD. Boldine partially attenuated cholestatic effect of HSD by promotion of biliary secretion of BA through up-regulation of Bsep and Ntcp, and by increase in biliary secretion of glutathione as a consequence of its increased hepatic disposition. This study demonstrates mechanisms of impaired BF during nonalcoholic fatty liver disease induced by HSD. Altered function of responsible transporters suggests also potential for changes in kinetics of drugs, which may complicate pharmacotherapy in subjects with high intake of sucrose, and with fatty liver disease. Sucrose induced alterations in BF may be alleviated by administration of boldine.

Altered Bile Acid Metabolome in Patients with Nonalcoholic Steatohepatitis

BACKGROUND AND AIMS

The prevalence of nonalcoholic fatty liver disease (NAFLD) and steatohepatitis (NASH) is increasing at an alarming rate. The role of bile acids in the development and progression of NAFLD to NASH and cirrhosis is poorly understood. This study aimed to quantify the bile acid metabolome in healthy subjects and patients with non-cirrhotic NASH under fasting conditions and after a standardized meal.

METHODS

Liquid chromatography tandem mass spectroscopy was used to quantify 30 serum and 16 urinary bile acids from 15 healthy volunteers and 7 patients with biopsy-confirmed NASH. Bile acid concentrations were measured at two fasting and four post-prandial time points following a high-fat meal to induce gallbladder contraction and bile acid reabsorption from the intestine.

RESULTS

Patients with NASH had significantly higher total serum bile acid concentrations than healthy subjects under fasting conditions (2.2- to 2.4-fold increase in NASH; NASH 2595-3549 µM and healthy 1171-1458 µM) and at all post-prandial time points (1.7- to 2.2-fold increase in NASH; NASH 4444-5898 µM and healthy 2634-2829 µM). These changes were driven by increased taurine- and glycine-conjugated primary and secondary bile acids. Patients with NASH exhibited greater variability in their fasting and post-prandial bile acid profile.

CONCLUSIONS

Results indicate that patients with NASH have higher fasting and post-prandial exposure to bile acids, including the more hydrophobic and cytotoxic secondary species. Increased bile acid exposure may be involved in liver injury and the pathogenesis of NAFLD and NASH.

Screening for biomarkers of liver injury induced by Polygonum multiflorum: a targeted metabolomic study

Heshouwu (HSW), the dry roots of Polygonum multiflorum, a classical traditional Chinese medicine is used as a tonic for a wide range of conditions, particularly those associated with aging. However, it tends to be taken overdose or long term in these years, which has resulted in liver damage reported in many countries. In this study, the indicative roles of nine bile acids (BAs) were evaluated to offer potential biomarkers for HSW induced liver injury. Nine BAs including cholic acid (CA) and chenodeoxycholic acid (CDCA), taurocholic acid (TCA), glycocholic acid (GCA), glycochenodeoxycholic acid (GCDCA), deoxycholic acid (DCA), glycodeoxycholic acid (GDCA), ursodeoxycholic acid (UDCA), and hyodeoxycholic acid (HDCA) in rat bile and serum were detected by a developed LC-MS method after 42 days treatment. Partial least square-discriminate analysis (PLS-DA) was applied to evaluate the indicative roles of the nine BAs, and metabolism of the nine BAs was summarized. Significant change was observed for the concentrations of nine BAs in treatment groups compared with normal control; In the PLS-DA plots of nine BAs in bile, normal control and raw HSW groups were separately clustered and could be clearly distinguished, GDCA was selected as the distinguished components for raw HSW overdose treatment group. In the PLS-DA plots of nine BAs in serum, the normal control and raw HSW overdose treatment group were separately clustered and could be clearly distinguished, and HDCA was selected as the distinguished components for raw HSW overdose treatment group. The results indicated the perturbation of nine BAs was associated with HSW induced liver injury; GDCA in bile, as well as HDCA in serum could be selected as potential biomarkers for HSW induced liver injury; it also laid the foundation for the further search on the mechanisms of liver injury induced by HSW.

The hepatitis B virus receptor

Hepatitis B virus (HBV) infection affects 240 million people worldwide. A liver-specific bile acid transporter named the sodium taurocholate cotransporting polypeptide (NTCP) has been identified as the cellular receptor for HBV and its satellite, the hepatitis D virus (HDV). NTCP likely acts as a major determinant for the liver tropism and species specificity of HBV and HDV at the entry level. NTCP-mediated HBV entry interferes with bile acid transport in cell cultures and has been linked with alterations in bile acid and cholesterol metabolism in vivo. The human liver carcinoma cell line HepG2, complemented with NTCP, now provides a valuable platform for studying the basic biology of the viruses and developing treatments for HBV infection. This review summarizes critical findings regarding NTCP's role as a viral receptor for HBV and HDV and discusses important questions that remain unanswered.

Persistent organic pollutants and non-alcoholic fatty liver disease in morbidly obese patients: a cohort study

BACKGROUND

In animal experiments persistent organic pollutants (POPs) cause hepatosteatosis. In epidemiological studies POPs have positive associations with serum markers of nonalcoholic fatty liver disease (NAFLD) and together with obesity synergistic association with insulin resistance. Because insulin resistance and obesity are critical in NAFLD pathogenesis, we investigated the association of serum pollutant levels with liver histology and alanine aminotransferase (ALT) in morbidly obese.

METHODS

Liver biopsies were from 161 participants of the Kuopio Obesity Surgery Study (KOBS) who underwent bariatric surgery 2005-2011. Liver histology was categorized as normal, steatosis and non-alcoholic steatohepatitis (NASH). Liver phenotype at baseline and ALT at baseline and 12 months post-surgery were correlated to serum POP concentrations at respective time points. As lipophilic POPs concentrate to smaller fat volume during weight loss, serum levels before and 12 months after bariatric surgery were compared.

RESULTS

Baseline serum concentration of PCB-118, β-HCH and several PFAAs had an inverse association with lobular inflammation possibly due to changes in bile acid metabolism. ALT had negative associations with many POPs at baseline that turned positive at 12 months after major clinical improvements. There was an interaction between some POPs and sex at 12 months, and in stratified data positive associations were observed mainly in females but not in males.

CONCLUSIONS

We found a negative association between serum concentrations of PCB-118, β-HCH and several PFAAs with lobular inflammation at baseline. Positive POPs-ATL associations at 12 months among women suggest that increased POP concentrations may decrease the degree of liver recovery.

Normal liver enzymes are correlated with severity of metabolic syndrome in a large population based cohort

Key features of the metabolic syndrome are insulin resistance and diabetes. The liver as central metabolic organ is not only affected by the metabolic syndrome as non-alcoholic fatty liver disease (NAFLD), but may contribute to insulin resistance and metabolic alterations. We aimed to identify potential associations between liver injury markers and diabetes in the population-based Heinz Nixdorf RECALL Study. Demographic and laboratory data were analyzed in participants (n = 4814, age 45 to 75y). ALT and AST values were significantly higher in males than in females. Mean BMI was 27.9 kg/m² and type-2-diabetes (known and unkown) was present in 656 participants (13.7%). Adiponectin and vitamin D both correlated inversely with BMI. ALT, AST, and GGT correlated with BMI, CRP and HbA1c and inversely correlated with adiponectin levels. Logistic regression models using HbA1c and adiponectin or HbA1c and BMI were able to predict diabetes with high accuracy. Transaminase levels within normal ranges were closely associated with the BMI and diabetes risk. Transaminase levels and adiponectin were inversely associated. Re-assessment of current normal range limits should be considered, to provide a more exact indicator for chronic metabolic liver injury, in particular to reflect the situation in diabetic or obese individuals.

Association of serum retinoic acid with hepatic steatosis and liver injury in nonalcoholic fatty liver disease

BACKGROUND

Retinoic acid (RA), an active metabolite of vitamin A (retinol), has been implicated in the regulation of lipid metabolism and hepatic steatosis in animal models. However, the relation between RA and liver histology in patients with nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH) is unknown.

OBJECTIVE

This study aimed at examining the association of RA with NAFLD and NASH in Chinese subjects.

DESIGN

Serum RA concentration was determined by ELISA in 41 control subjects, 45 patients with NAFLD, and 38 patients with NASH. The associations of RA with adiposity, serum glucose, lipid profiles, and markers of liver damage were studied. Moreover, both mRNA and protein levels of retinoic X receptor α (RXRα) in the liver were analyzed in subjects with different degrees of hepatic steatosis.

RESULTS

Serum RA concentrations in patients with NAFLD (1.42 ± 0.47 ng/mL) and NASH (1.14 ± 0.26 ng/mL) were significantly lower than those in control subjects (2.70 ± 0.52 ng/mL) (P < 0.01). Furthermore, serum RA concentrations were significantly different between subjects with normal glucose tolerance and those with type 2 diabetes in control [2.87 ± 0.52 (n = 28) vs. 2.32 ± 0.44 ng/mL (n = 13)], NAFLD [1.61 ± 0.37 (n = 29) vs. 1.28 ± 0.41 ng/mL (n = 16)], and NASH [1.35 ± 0.34 (n = 24) vs. 1.07 ± 0.29 ng/mL (n = 14)] groups. In human liver tissue, RXRα mRNA expression was inversely correlated with the exacerbation of hepatic steatosis. Both serum RA concentrations and RXRα mRNA levels were inversely correlated with intrahepatic triglyceride content (r = -0.700, P < 0.001, and r = -0.611, P = 0.002, respectively). Compared with grade 0 severity, the concentration of RXRα protein was lower in more severe grades in patients with NAFLD.

CONCLUSION

These results show that circulating RA concentrations were lower in subjects with NAFLD and were associated with hepatic lipid metabolism and insulin resistance. This trial was registered at clinicaltrials.gov as NCT01940263.

Ketone body production is differentially altered in steatosis and non-alcoholic steatohepatitis in obese humans

BACKGROUND & AIMS

Levels of ketone bodies have been reported to be both increased and decreased in individuals with non-alcoholic fatty liver disease. We investigated whether the metabolism of ketone bodies is different in simple steatosis and in non-alcoholic steatohepatitis (NASH).

METHODS

Serum low molecular weight molecules including ketone bodies were measured using high-throughput proton (1H) nuclear magnetic resonance in 116 (76 categorized unequivocally to those with normal liver, simple steatosis or NASH) morbidly obese individuals [age 47.3 ± 8.7 (mean ± SD) years, body mass index 45.1 ± 6.1 kg/m(2) , 39 men and 77 women] with histological assessment of NASH and analysis of gene expression in the liver. Finally, we correlated β-hydroxybutyrate (β-OHB) levels with NASH predicting score in Metabolic Syndrome in Men Study (METSIM) population study (n = 8749 non-diabetic men).

RESULTS

Levels of ketone bodies were lower in individuals with NASH compared to individuals with simple steatosis (P = 0.004 and P = 0.018 for β-OHB and acetoacetate respectively). Lower levels of β-OHB were associated with the NASH predicting score in the METSIM study (P = 0.001). Liver inflammation correlated with mRNA expression of genes regulating ketolysis in the liver (Spearman correlation 0.379-0.388, P < 0.0006 for ACAT1, ACSS2 and BDH1).

CONCLUSION

Lower levels of ketone bodies in individuals with NASH compared to individuals with simple steatosis suggest a decrease in ketone body metabolism in NASH.

Liver steatosis in hepatitis C patients

There is controversy regarding some aspects of hepatitis C virus (HCV) infection-associated liver steatosis, and their relationship with body fat stores. It has classically been found that HCV, especially genotype 3, exerts direct metabolic effects which lead to liver steatosis. This supports the existence of a so called viral steatosis and a metabolic steatosis, which would affect HCV patients who are also obese or diabetics. In fact, several genotypes exert metabolic effects which overlap with some of those observed in the metabolic syndrome. In this review we will analyse the pathogenic pathways involved in the development of steatosis in HCV patients. Several cytokines and adipokines also become activated and are involved in “pure” steatosic effects, in addition to inflammation. They are probably responsible for the evolution of simple steatosis to steatohepatitis, making it difficult to explain why such alterations only affect a proportion of steatosic patients.

Vitamin D counteracts fibrogenic TGF-β signalling in human hepatic stellate cells both receptor-dependently and independently

OBJECTIVE

Non-alcoholic fatty liver disease (NAFLD) is closely linked to obesity and constitutes part of the metabolic syndrome, which have been associated with low serum vitamin D (VD). Due to known crosstalk between VD and transforming growth factor (TGF)-β signalling, VD has been proposed as an antifibrotic treatment.

DESIGN

We evaluated the association between VD, the vitamin D receptor (VDR) and liver fibrosis in primary human hepatic stellate cells (phHSC) and 106 morbidly obese patients with NAFLD.

RESULTS

Treating phHSC with VD ameliorated TGF-β-induced fibrogenesis via both VDR-dependent and VDR-independent mechanisms. Reduction of fibrogenic response was abolished in cells homozygous for GG at the A1012G single nucleotide polymorphisms within the VDR gene. Compared with healthy livers, NAFLD livers expressed higher levels of VDR mRNA and VDR fragments. VDR mRNA was lower in patients homozygous for GG at A1012G and expression of pro-fibrogenic genes was higher in patients carrying the G allele.

CONCLUSIONS

VD may be an antifibrotic treatment option early in the onset of fibrosis in specific genotypes for VDR. Known polymorphisms of the VDR may influence the response to VD treatment.

Chlorpromazine-induced perturbations of bile acids and free fatty acids in cholestatic liver injury prevented by the Chinese herbal compound Yin-Chen-Hao-Tang

BACKGROUNDS

Yin-Chen-Hao-Tang (YCHT), a commonly used as a traditional chinese medicine for liver disease. Several studies indicated that YCHT may improving hepatic triglyceride metabolism and anti-apoptotic response as well as decreasing oxidative stress .However, little is known about the role of YCHT in chlorpromazine (CPZ) -induced chlolestatic liver injury. Therefore, we aimed to facilitate the understanding of the pathogenesis of cholestatic liver injury and evaluate the effect of Yin-Chen-Hao-Tang (YCHT) on chlorpromazine (CPZ)-induced cholestatic liver injury in rats based on the change of bile acids (BAs) and free fatty acids (FFAs) alone with the biochemical indicators and histological examination.

METHODS

We conducted an experiment on CPZ-induced cholestatic liver injury in Wistar rats with and without YCHT for nine consecutive days. Serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), albumin (ALB), total bilirubin (TBIL), total cholesterol (TC), triglycerides (TG), low density lipoprotein-cholesterol (LDL-C) were measured to evaluate the protective effect of YCHT against chlorpromazine (CPZ)-induced cholestatic liver injury. Histopathology of the liver tissue showed that pathological injuries were relieved after YCHT pretreatment. In addition, ultra-performance lipid chromatography coupled with quadrupole mass spectrometry (UPLC-MS) and gas chromatography coupled with mass spectrometry (GC-MS) was applied to determine the content of bile acids, free fatty acids, respectively.

RESULTS

Obtained data showed that YCHT attenuated the effect of CPZ-induced cholestatic liver injury, which was manifested by the serum biochemical parameters and histopathology of the liver tissue. YCHT regulated the lipid levels as indicated by the reversed serum levels of TC, TG, and LDL-C. YCHT also regulated the disorder of BA and FFA metabolism by CPZ induction.

CONCLUSIONS

Results indicated that YCHT exerted a protective effect on CPZ-induced cholestasis liver injury. The variance of BA and FFA concentrations can be used to evaluate the cholestatic liver injury caused by CPZ and the hepatoprotective effect of YCHT.

Quercetin ameliorates dysregulation of lipid metabolism genes via the PI3K/AKT pathway in a diet-induced mouse model of nonalcoholic fatty liver disease

SCOPE

Flavonoids and related compounds seem to have favorable effects on nonalcoholic fatty liver disease (NAFLD) progression, although the exact mechanisms implicated are poorly understood. In this study, we aimed to investigate the effect of the flanovol quercetin on gene expression deregulation involved in the development of NAFLD, as well as the possible implication of phosphatidylinositol 3-kinase (PI3K)/AKT pathway modulation.

METHODS AND RESULTS

We used an in vivo model based on methionine- and choline-deficient (MCD) diet-fed mice and an in vitro model consisting of Huh7 cells incubated with MCD medium. MCD-fed mice showed classical pathophysiological characteristics of nonalcoholic steatohepatitis, associated with altered transcriptional regulation of fatty acid uptake- and trafficking-related gene expression, with increased lipoperoxidation. PI3K/AKT pathway was activated by MCD and triggered gene deregulation causing either activation or inhibition of all studied genes as demonstrated through cell incubation with the PI3K-inhibitor LY294002. Treatment with quercetin reduced AKT phosphorylation, and oxidative/nitrosative stress, inflammation and lipid metabolism-related genes displayed a tendency to normalize in both in vivo and in vitro models.

CONCLUSION

These results place quercetin as a potential therapeutic strategy for preventing NAFLD progression by attenuating gene expression deregulation, at least in part through PI3K/AKT pathway inactivation.