A high-cholesterol diet exacerbates liver fibrosis in mice via accumulation of free cholesterol in hepatic stellate cells

Delphinidin or α-amyrin attenuated liver steatosis and metabolic disarrangement in rats fed a high-fat diet

Non-alcoholic fatty liver disease (NAFLD) is a liver pathology concomitant with metabolic disarrangement. This study assessed the therapeutic impacts of delphinidin, an anthocyanin, or α-amyrin, a pentacyclic triterpenoid, on NAFLD in rats and the underlying mechanisms involved. NAFLD was established by feeding a high-fat diet (HFD) for 10 weeks, either alone or in combination with delphinidin (40 mg/kg, oral) or α-amyrin (20 mg/kg, oral). Delphinidin or α-amyrin ameliorated the metabolic and histopathological perturbations induced by HFD. These compounds markedly attenuated NAFLD-induced hepatic steatosis, as evidenced by a substantial decrease in body weight, insulin resistance, and liver and adipose tissue indices. Alongside normalization of the atherogenic index, both improved HFD-mediated abnormalities in serum lipids, liver enzymes, leptin, and ghrelin levels. Moreover, their intervention activated the NFE2 like bZIP transcription factor 2 and heme oxygenase 1 pathways and abrogated HFD-triggered activation of mitogen-activated protein kinase 1 signaling. These remedies inhibited hepatic apoptosis and modulated the gene expression of lipogenic enzymes. Furthermore, histological analysis corroborated the suppression of lipid accumulation and amelioration of hepatic architecture in the treated rats. Our findings highlight the hepatoprotective value of delphinidin or α-amyrin against NAFLD and related metabolic diseases through their insulin-sensitizing, anti-inflammatory, antioxidant, and antiapoptotic effects.

Female C57BL/6 mice exhibit protection against nonalcoholic fatty liver disease and diabesity accompanied by differential regulation of hepatic lipocalin prostaglandin D2 synthase

Nonalcoholic fatty liver disease (NAFLD) and its development into nonalcoholic steatohepatitis (NASH) are challenging health concerns globally. Clinically, the prevalence and severity of NAFLD/NASH are higher in men than in premenopausal women. NAFLD is strongly correlated with obesity, both of which are tied to high-fat/fructose-rich western diets. Therefore, we aimed to investigate sexual dimorphism in NAFLD pathogenesis in male and female C57BL/6 mice fed different diets. Male and female C57BL/67 mice were divided into four groups and kept on a chow (C), chow plus high fructose (CF), high fat (HF), and high fat plus high fructose (HFF) diet for 22 weeks. Liver tissues were collected at the end of the study and processed for NAFLD/NASH-related histology (H&E and trichrome staining), protein expression (SREBP1, SCAP, FABP4, α-SMA, TGF-β and L-PGDS), and biochemical parameters measurement. Our results displayed that female mice exhibited protection against NAFLD and diabesity on HF and HFF diets compared to male mice fed similar diets. Additionally, female mice showed protection from fibrosis compared to male mice. Both male and female mice fed HF and HFF diet groups displayed the cytosol-to-nuclear translocation of Lipocalin Prostaglandin D2 Synthase (L-PGDS). Cytoplasmic levels of L-PGDS were absent in females compared to low levels in males, revealing a possible sex-specific mechanism tied to fructose and fat metabolism. Collectively, female mice showed protection against NAFLD and diabesity relative to male mice, accompanied by differential regulation of hepatic lipocalin prostaglandin D2 synthase.

Cell metabolism-based therapy for liver fibrosis, repair, and hepatocellular carcinoma

Progression of chronic liver injury to fibrosis, abnormal liver regeneration, and HCC is driven by a dysregulated dialog between epithelial cells and their microenvironment, in particular immune, fibroblasts, and endothelial cells. There is currently no antifibrogenic therapy, and drug treatment of HCC is limited to tyrosine kinase inhibitors and immunotherapy targeting the tumor microenvironment. Metabolic reprogramming of epithelial and nonparenchymal cells is critical at each stage of disease progression, suggesting that targeting specific metabolic pathways could constitute an interesting therapeutic approach. In this review, we discuss how modulating intrinsic metabolism of key effector liver cells might disrupt the pathogenic sequence from chronic liver injury to fibrosis/cirrhosis, regeneration, and HCC.

Harnessing nuclear receptors to modulate hepatic stellate cell activation for liver fibrosis resolution

With the recent approval of Resmetirom as the first drug targeting nuclear receptors for metabolic dysfunction-associated steatohepatitis (MASH), there is promising way to treat MASH-associated liver fibrosis. However, liver fibrosis can arise from various pathogenic factors, and effective treatments for fibrosis due to other causes remain elusive. The activation of hepatic stellate cells (HSCs) represents a central link in the pathogenesis of hepatic fibrosis. Therefore, harnessing nuclear receptors to modulate HSC activation may be an effective approach to resolving the complex liver fibrosis caused by various factors. In this comprehensive review, we systematically explore the structure and physiological functions of nuclear receptors, shedding light on their multifaceted roles in HSC activation. Recent advancements in drug development targeting nuclear receptors are discussed, providing insights into their potential as rational and effective therapeutic targets for modulating HSC activation in the context of liver fibrosis. By elucidating the intricate interplay between nuclear receptors and HSC activation, this review contributes to the discovery of new nuclear receptor targets in HSCs for resolving hepatic fibrosis.

Cholesterol: The driving force behind the remodeling of tumor microenvironment in colorectal cancer

Essential membrane components and metabolites with a wide range of biological roles are both produced by cholesterol metabolism. Cell-intrinsic and cell-extrinsic stimuli alter cholesterol metabolism in the tumor microenvironment (TME), which in turn encourages colorectal carcinogenesis. Metabolites produced from cholesterol play intricate roles in promoting the development of colorectal cancer (CRC) and stifling immunological responses. By altering the extracellular matrix of the main tumor, redesigning its immunological environment, and altering its mechanical stiffness, cholesterol can encourage the epithelial-mesenchymal transition of the primary tumor, opening up a pathway for tumor metastasis. Its functions in TME remodeling and tumor prevention have been recently identified. In this review we address the function of cholesterol in TME remodeling and therapeutic techniques designed to block cholesterol metabolism, and discuss how combining these strategies with already available anti-CRC medicines can have combined effects and open up new therapeutic avenues.

Longitudinal evaluation of liver stiffness reveals hepatic cholesterol as the determinant of fibrosis progression in mice

AIMS

The metabolic dysfunction-associated steatotic liver disease (MASLD) affects approximately 30 % of the global population. While excessive consumption of dietary fat induces steatosis, it does not develop fibrosis, indicating that additional factors are required as "second hits" for further progression of MASLD. Here, based on shear wave elastography, we compared the longitudinal patterns of fibrogenesis induced by different diets and show the crucial role of cholesterol accumulation in fibrosis progression.

MATERIALS AND METHODS

Mice were fed chow, high-fat (HFD), high-fat high-cholesterol (HFHCD), choline-deficient, L-amino acid-defined high-fat (CDAHFD), or 3,5-Diethoxycarbonyl-1,4-Dihydrocollidine diets over 12 weeks.

KEY FINDINGS

Mice fed with HFD gained significant amounts of body weight but did not show an increase in liver stiffness. In contrast, the addition of cholesterol in the same diet robustly induced liver stiffening starting from the first week, which was comparable to the CDAHFD-induced fibrosis model. Longitudinal tracking of liver stiffness revealed a two-step progression of fibrosis after prolonged feeding of HFHCD and CDAHFD, likely due to cellular cholesterol accumulation over a certain threshold after the transition point. Biochemical analyses suggested the critical role of both total and hepatic cholesterol accumulation in liver fibrosis development.

SIGNIFICANCE

Collectively, our results underscore the significance of cholesterol in liver fibrosis development, also highlighting the benefit of monitoring liver stiffness to understand the pathogenesis of liver fibrosis.

Novel Choline-Deficient and 0.1%-Methionine-Added High-Fat Diet Induces Burned-Out Metabolic-Dysfunction-Associated Steatohepatitis with Inflammation by Rapid Immune Cell Infiltration on Male Mice

Background: Metabolic-dysfunction-associated steatotic liver disease (MASLD) is a progressive liver disorder that possesses metabolic dysfunction and shows steatohepatitis. Although the number of patients is globally increasing and many clinical studies have developed medicine for MASLD, most of the studies have failed due to low efficacy. One reason for this failure is the lack of appropriate animal disease models that reflect human MASLD to evaluate the potency of candidate drugs. Methods: We developed a novel choline-deficient and 0.11%-methionine-added high-fat diet (CDAHFD)-based (MASH) diet that can induce murine metabolic-dysfunction-associated steatohepatitis (MASH) without severe body weight loss. We performed kinetic analyses post-feeding and proposed an appropriate timing of MASH pathogenesis by quantitatively analyzing steatosis, inflammation, and fibrosis. Results: This MASH diet induced liver fibrosis earlier than the conventional CDAHFD model. In brief, lipid accumulation, inflammation, and fibrosis started after 1 week from feeding. Lipid accumulation increased until 8 weeks and declined thereafter; on the other hand, liver fibrosis showed continuous progression. Additionally, immune cells, especially myeloid cells, specifically accumulated and induced inflammation in the initiation stage of MASH. Conclusions: The novel MASH diet promotes the dynamics of lipid deposition and fibrosis in the liver, similar to human MASH pathophysiology. Furthermore, immune-cell-derived inflammation possibly contributes to the initiation of MASH pathogenesis. We propose this model can be the new pre-clinical MASH model to discover the drugs against human MASH by evaluating the interaction between parenchymal and non-parenchymal cells.

Free Cholesterol-Induced Liver Injury in Non-Alcoholic Fatty Liver Disease: Mechanisms and a Therapeutic Intervention Using Dihydrotanshinone I

Build-up of free cholesterol (FC) substantially contributes to the development and severity of non-alcoholic fatty liver disease (NAFLD). Here, we investigate the specific mechanism by which FC induces liver injury in NAFLD and propose a novel therapeutic approach using dihydrotanshinone I (DhT). Rather than cholesterol ester (CE), we observed elevated levels of total cholesterol, FC, and alanine transaminase (ALT) in NAFLD patients and high-cholesterol diet-induced NAFLD mice compared to those in healthy controls. The FC level demonstrated a positive correlation with the ALT level in both patients and mice. Mechanistic studies revealed that FC elevated reactive oxygen species level, impaired the function of lysosomes, and disrupted lipophagy process, consequently inducing cell apoptosis. We then found that DhT protected mice on an HCD diet, independent of gut microbiota. DhT functioned as a potent ligand for peroxisome proliferator-activated receptor α (PPARα), stimulating its transcriptional function and enhancing catalase expression to lower reactive oxygen species (ROS) level. Notably, the protective effect of DhT was nullified in mice with hepatic PPARα knockdown. Thus, these findings are the first to report the detrimental role of FC in NAFLD, which could lead to the development of new treatment strategies for NAFLD by leveraging the therapeutic potential of DhT and PPARα pathway.

Diabetes as a risk factor for MASH progression

Non-alcoholic (now: metabolic) steatohepatitis (MASH) is the progressive inflammatory form of metabolic dysfunction-associated steatotic liver disease (MASLD), which often coexists and mutually interacts with type 2 diabetes (T2D), resulting in worse hepatic and cardiovascular outcomes. Understanding the intricate mechanisms of diabetes-related MASH progression is crucial for effective therapeutic strategies. This review delineates the multifaceted pathways involved in this interplay and explores potential therapeutic implications. The synergy between adipose tissue, gut microbiota, and hepatic alterations plays a pivotal role in disease progression. Adipose tissue dysfunction, particularly in the visceral depot, coupled with dysbiosis in the gut microbiota, exacerbates hepatic injury and insulin resistance. Hepatic lipid accumulation, oxidative stress, and endoplasmic reticulum stress further potentiate inflammation and fibrosis, contributing to disease severity. Dietary modification with weight reduction and exercise prove crucial in managing T2D-related MASH. Additionally, various well-known but also novel anti-hyperglycemic medications exhibit potential in reducing liver lipid content and, in some cases, improving MASH histology. Therapies targeting incretin receptors show promise in managing T2D-related MASH, while thyroid hormone receptor-β agonism has proven effective as a treatment of MASH and fibrosis.

Extracellular vesicles from mesenchymal stem cells alter gut microbiota and improve neuroinflammation and motor impairment in rats with mild liver damage

Gut microbiota perturbation and motor dysfunction have been reported in steatosis patients. Rats with mild liver damage (MLD) show motor dysfunction mediated by neuroinflammation and altered GABAergic neurotransmission in the cerebellum. The extracellular vesicles (EV) from mesenchymal stem cells (MSC) have emerged as a promising therapeutic proxy whose molecular basis relies partly upon TGFβ action. This study aimed to assess if MSC-EVs improve motor dysfunction in rats with mild liver damage and analyze underlying mechanisms, including the role of TGFβ, cerebellar neuroinflammation and gut microbiota. MLD in rats was induced by carbon tetrachloride administration and EVs from normal (C-EVs) or TGFβ-siRNA treated MSCs (T-EV) were injected. Motor coordination, locomotor gait, neuroinflammation and TNF-α-activated pathways modulating GABAergic neurotransmission in the cerebellum, microbiota composition in feces and microbial-derived metabolites in plasma were analyzed. C-EVs reduced glial and TNFα-P2X4-BDNF-TrkB pathway activation restoring GABAergic neurotransmission in the cerebellum and improving motor coordination and all the altered gait parameters. T-EVs also improved motor coordination and some gait parameters, but the mechanisms involved differed from those of C-EVs. MLD rats showed increased content of some Bacteroides species in feces, correlating with decreased kynurenine aside from motor alterations. These alterations were all normalized by C-EVs, whereas T-EVs only restored kynurenine levels. Our results support the value of MSC-EVs on improving motor dysfunction in MLD and unveil a possible mechanism by which altered microbiota may contribute to neuroinflammation and motor impairment. Some of the underlying mechanisms are TGFβ-dependent.

Comparison of the In Vivo Efficacy of Cuban (Raydel®) and Chinese (BOC Science) Policosanol in Alleviating Dyslipidemia and Inflammation via Safeguarding Major Organs and Reproductive Health in Hyperlipidemic Zebrafish: A Twelve-Week Consumption Study

Policosanol is a blend of long-chain aliphatic alcohols (LCAAs) and is well-known for several health-beneficial activities; however, the functionality of policosanol varied substantially based on the composition of LCAAs. In this study, two distinct policosanols, Raydel® (extracted from Cuban sugarcane wax) and BOC Sciences (extracted from Chinese sugarcane wax), were dietarily supplemented (0.1% w/w) for 12 weeks in hyperlipidemic zebrafish to examine their influence on the blood lipid profile and functionality of the liver, kidney, and reproductive organs. The results demonstrated a noteworthy impact of both policosanols on preventing high-cholesterol diet (HCD, 4% w/w)-induced dyslipidemia by decreasing total cholesterol (TC) and triglyceride (TG) levels in the plasma. However, compared to BOC Sciences, the Raydel® policosanol exhibited a significantly (p < 0.05) higher efficacy in reducing HCD-induced TC and TG levels. A substantial effect was observed exclusively with the Raydel® policosanol in mitigating HCD-impaired low-density-lipoprotein cholesterol (LDL-C) and high-density-lipoprotein cholesterol (HDL-C) levels. Hepatic histology and immunohistochemistry (IHC) analysis revealed the higher efficacy of Raydel® policosanol over BOC Sciences policosanol to prevent HCD-provoked fatty liver changes, cellular senescence, oxidative stress, and interleukin (IL)-6 production. Consistently, a significantly higher effect of Raydel® over BOC Sciences policosanol was observed on the protection of kidney, testis, and ovary morphology hampered by HCD consumption. In addition, Raydel® policosanol exhibited a notably stronger effect (~2-fold, p < 0.05) on the egg-laying ability of the zebrafish compared to policosanol from BOC Sciences. Furthermore, Raydel® policosanol plays a crucial role in improving embryo viability and mitigating developmental defects caused by the intake of an HCD. Conclusively, Raydel® policosanol displayed a substantially higher efficacy over BOC Sciences policosanol to revert HCD-induced dyslipidemia, the functionality of vital organs, and the reproductive health of zebrafish.

Fibrosis and Hepatocarcinogenesis: Role of Gene-Environment Interactions in Liver Disease Progression

The liver is a complex organ that performs vital functions in the body. Despite its extraordinary regenerative capacity compared to other organs, exposure to chemical, infectious, metabolic and immunologic insults and toxins renders the liver vulnerable to inflammation, degeneration and fibrosis. Abnormal wound healing response mediated by aberrant signaling pathways causes chronic activation of hepatic stellate cells (HSCs) and excessive accumulation of extracellular matrix (ECM), leading to hepatic fibrosis and cirrhosis. Fibrosis plays a key role in liver carcinogenesis. Once thought to be irreversible, recent clinical studies show that hepatic fibrosis can be reversed, even in the advanced stage. Experimental evidence shows that removal of the insult or injury can inactivate HSCs and reduce the inflammatory response, eventually leading to activation of fibrolysis and degradation of ECM. Thus, it is critical to understand the role of gene-environment interactions in the context of liver fibrosis progression and regression in order to identify specific therapeutic targets for optimized treatment to induce fibrosis regression, prevent HCC development and, ultimately, improve the clinical outcome.

Crosstalk in extrahepatic and hepatic system in NAFLD/NASH

Non-alcoholic fatty liver disease (NAFLD) has emerged as the most prevalent chronic liver disease globally. Non-alcoholic steatohepatitis (NASH) represents an extremely progressive form of NAFLD, which, without timely intervention, may progress to cirrhosis or hepatocellular carcinoma. Presently, a definitive comprehension of the pathogenesis of NAFLD/NASH eludes us, and pharmacological interventions targeting NASH specifically remain constrained. The aetiology of NAFLD encompasses a myriad of external factors including environmental influences, dietary habits and gender disparities. More significantly, inter-organ and cellular interactions within the human body play a role in the development or regression of the disease. In this review, we categorize the influences affecting NAFLD both intra- and extrahepatically, elaborating meticulously on the mechanisms governing the onset and progression of NAFLD/NASH. This exploration delves into progress in aetiology and promising therapeutic targets. As a metabolic disorder, the development of NAFLD involves complexities related to nutrient metabolism, liver-gut axis interactions and insulin resistance, among other regulatory functions of extraneous organs. It further encompasses intra-hepatic interactions among hepatic cells, Kupffer cells (KCs) and hepatic stellate cells (HSCs). A comprehensive understanding of the pathogenesis of NAFLD/NASH from a macroscopic standpoint is instrumental in the formulation of future therapies for NASH.

Exploring Fibrosis Pathophysiology in Lean and Obese Metabolic-Associated Fatty Liver Disease: An In-Depth Comparison

While obesity-related nonalcoholic fatty liver disease (NAFLD) is linked with metabolic dysfunctions such as insulin resistance and adipose tissue inflammation, lean NAFLD more often progresses to liver fibrosis even in the absence of metabolic syndrome. This review aims to summarize the current knowledge regarding the mechanisms of liver fibrosis in lean NAFLD. The most commonly used lean NAFLD models include a methionine/choline-deficient (MCD) diet, a high-fat diet with carbon tetrachloride (CCl4), and a high-fructose and high-cholesterol diet. The major pro-fibrogenic mechanisms in lean NAFLD models include increased activation of the extracellular signal-regulated kinase (ERK) pathway, elevated expression of α-smooth muscle actin (α-SMA), collagen type I, and TGF-β, and modulation of fibrogenic markers such as tenascin-X and metalloproteinase inhibitors. Additionally, activation of macrophage signaling pathways promoting hepatic stellate cell (HSC) activation further contributes to fibrosis development. Animal models cannot cover all clinical features that are evident in patients with lean or obese NAFLD, implicating the need for novel models, as well as for deeper comparisons of clinical and experimental studies. Having in mind the prevalence of fibrosis in lean NAFLD patients, by addressing specific pathways, clinical studies can reveal new targeted therapies along with novel biomarkers for early detection and enhancement of clinical management for lean NAFLD patients.

Metabolic reprogramming in liver fibrosis

Chronic liver diseases, primarily metabolic dysfunction-associated steatotic liver disease (MASLD), harmful use of alcohol, or viral hepatitis, may result in liver fibrosis, cirrhosis, and cancer. Hepatic fibrogenesis is a complex process with interactions between different resident and non-resident heterogeneous liver cell populations, ultimately leading to deposition of extracellular matrix and organ failure. Shifts in cell phenotypes and functions involve pronounced transcriptional and protein synthesis changes that require metabolic adaptations in cellular substrate metabolism, including glucose and lipid metabolism, resembling changes associated with the Warburg effect in cancer cells. Cell activation and metabolic changes are regulated by metabolic stress responses, including the unfolded protein response, endoplasmic reticulum stress, autophagy, ferroptosis, and nuclear receptor signaling. These metabolic adaptations are crucial for inflammatory and fibrogenic activation of macrophages, lymphoid cells, and hepatic stellate cells. Modulation of these pathways, therefore, offers opportunities for novel therapeutic approaches to halt or even reverse liver fibrosis progression.

Alcohol-induced epigenetic changes prevent fibrosis resolution after alcohol cessation in miceresolution

BACKGROUND AND AIMS

Alcohol-associated liver disease is a major cause of alcohol-associated mortality. Recently, we identified hepatic demethylases lysine demethylase (KDM)5B and KDM5C as important epigenetic regulators of alcohol response in the liver. In this study, we aimed to investigate the role of KDM5 demethylases in alcohol-associated liver disease resolution.

APPROACH AND RESULTS

We showed that alcohol-induced liver steatosis rapidly resolved after alcohol cessation. In contrast, fibrosis persisted in the liver for up to 8 weeks after the end of alcohol exposure. Defects in fibrosis resolution were in part due to alcohol-induced KDM5B and KDM5C-dependent epigenetic changes in hepatocytes. Using cell-type-specific knockout mice, we found that adeno-associated virus-mediated knockout of KDM5B and KDM5C demethylases in hepatocytes at the time of alcohol withdrawal promoted fibrosis resolution. Single-cell ATAC sequencing analysis showed that during alcohol-associated liver disease resolution epigenetic cell states largely reverted to control conditions. In addition, we found unique epigenetic cell states distinct from both control and alcohol states and identified associated transcriptional regulators, including liver X receptor (LXR) alpha (α). In vitro and in vivo analysis confirmed that knockout of KDM5B and KDM5C demethylases promoted LXRα activity, likely through regulation of oxysterol biosynthesis, and this activity was critical for the fibrosis resolution process. Reduced LXR activity by small molecule inhibitors prevented fibrosis resolution in KDM5-deficient mice.

CONCLUSIONS

In summary, KDM5B and KDM5C demethylases prevent liver fibrosis resolution after alcohol cessation in part through suppression of LXR activity.

Unraveling the hepatic stellate cells mediated mechanisms in aging's influence on liver fibrosis

Aging enhances numerous processes that compromise homeostasis and pathophysiological processes. Among these, activated HSCs play a pivotal role in advancing liver fibrosis. This research delved into how aging impacts liver fibrosis mechanisms. The study involved 32 albino rats categorized into four groups: Group I (young controls), Group II (young with liver fibrosis), Group III (old controls), and Group IV (old with liver fibrosis). Various parameters including serum ALT, adiponectin, leptin, and cholesterol levels were evaluated. Histopathological analysis was performed, alongside assessments of TGF-β, FOXP3, and CD133 gene expressions. Markers of fibrosis and apoptosis were the highest in group IV. Adiponectin levels significantly decreased in Group IV compared to all other groups except Group II, while cholesterol levels were significantly higher in liver fibrosis groups than their respective control groups. Group III displayed high hepatic expression of desmin, α-SMA, GFAP and TGF- β and in contrast to Group I. Increased TGF-β and FOXP3 gene expressions were observed in Group IV relative to Group II, while CD133 gene expression decreased in Group IV compared to Group II. In conclusion, aging modulates immune responses, impairs regenerative capacities via HSC activation, and influences adipokine and cholesterol levels, elevating the susceptibility to liver fibrosis.

Efficacy Assessment of Five Policosanol Brands and Damage to Vital Organs in Hyperlipidemic Zebrafish by Six-Week Supplementation: Highlighting the Toxicity of Red Yeast Rice and Safety of Cuban Policosanol (Raydel®)

Policosanol is a mixture of long-chain aliphatic alcohols (LCAAs) derived from various plant and insect origins that are marketed by various companies with distinct formulations and brand names. Policosanols offer several beneficial effects to treat dyslipidemia and hypertension; however, a comprehensive functionality comparison of various policosanol brands has yet to be thoroughly explored. In the present study five distinct policosanol brands from different origins and countries, Raydel-policosanol, Australia (PCO1), Solgar-policosanol, USA (PCO2), NutrioneLife-monacosanol, South Korea (PCO3), Mothernest-policosanol, Australia (PCO4), and Peter & John-policosanol, New Zealand (PCO5) were compared via dietary supplementation (1% in diet, final wt/wt) to zebrafish for six weeks to investigate their impact on survivability, blood lipid profile, and functionality of vital organs under the influence of a high-cholesterol diet (HCD, final 4%, wt/wt). The results revealed that policosanol brands (PCO1-PCO5) had a substantial preventive effect against HCD-induced zebrafish body weight elevation and hyperlipidemia by alleviating total cholesterol (TC) and triglycerides (TG) in blood. Other than PCO3, all the brands significantly reduced the HCD's elevated low-density lipoprotein cholesterol (LDL-C). On the contrary, only PCO1 displayed a significant elevation in high-density lipoprotein cholesterol (HDL-C) level against the consumption of HCD. The divergent effect of PCO1-PCO5 against HCD-induced hepatic damage biomarkers, aspartate aminotransferase (AST) and alanine aminotransferase (ALT), was observed. PCO1, PCO2, and PCO4 efficiently curtailed the AST and ALT levels; however, PCO3 and PCO5 potentially aggravated the HCD's elevated plasma AST and ALT levels. Consistently, the hepatic histology outcome revealed the least effectiveness of PCO3 and PCO5 against HCD-induced liver damage. On the contrary, PCO1 exhibited a substantial hepatoprotective role by curtailing HCD-induced fatty liver changes, cellular senescent, reactive oxygen species (ROS), and interleukin-6 (IL-6) production. Likewise, the histological outcome from the kidney, testis, and ovary revealed the significant curative effect of PCO1 against the HCD-induced adverse effects. PCO2-PCO5 showed diverse and unequal results, with the least effective being PCO3, followed by PCO5 towards HCD-induced kidney, testis, and ovary damage. The multivariate interpretation based on principal component analysis (PCA) and hierarchical cluster analysis (HCA) validated the superiority of PCO1 over other policosanol brands against the clinical manifestation associated with HCD. Conclusively, different brands displayed distinct impacts against HCD-induced adverse effects, signifying the importance of policosanol formulation and the presence of aliphatic alcohols on the functionality of policosanol products.

Dietary macro and micronutrients associated with MASLD: Analysis of a national US cohort database

INTRODUCTION AND OBJECTIVES

Our objective was to measure and compare the intake of macro and micronutrients in a cohort of individuals with Metabolic Syndrome Associated Steatotic Liver Disease (MASLD) compared with matched controls to identify areas of further research in this area; we identified nutrition-associated associations with MASLD in the United States general population.

MATERIALS AND METHODS

We used the 2017 - 2018 NHANES dataset. Elastography Controlled Attenuation Parameter (CAP score>280) in the absence of other liver disease was defined as MASLD in adults (>18). Advanced fibrosis was defined by transient elastography >10 kPa. Controls were adults without liver disease.

RESULTS

1648 MASLD cases (11.4 % advanced fibrosis) and 2527 controls were identified. MASLD cases were older (P<0.001), more likely males (P = 0.01), less likely to have a college education (P = 0.04) and more likely married (P = 0.002). MASLD cases were more likely to be of Mexican American or Hispanic ethnicity (P = 0.002), have higher BMI, and have higher prevalence of diabetes, hyperlipidemia and hypertension (P<0.001 for all). MASLD cases had higher hs-CRP (P = 0.02) and ferritin (P = 0.02). MASLD cases had lower total (P = 0.004) and added vitamin E in their diet (P = 0.002), lower vitamin K intake (P = 0.005), and higher selenium intake (P = 0.03). Caloric intake (P = 0.04), carbohydrate intake (P = 0.02), cholesterol intake (P = 0.03) and saturated fatty acid intake (P = 0.05) were higher in MASLD. Individuals with MASLD were more likely to be on a diet (P<0.001), sedentary (P = 0.008) and less likely to participate in moderate or vigorous recreational activities (P<0.001).

CONCLUSIONS

The deficiencies of micronutrients and excess of macronutrients point to oxidative stress, pro-inflammatory state, and lipotoxicity as pathways linking the US diet to MASLD. MASLD patients are more often on special diets, which may reflect prior provider counseling on diet changes to improve health.

Effects of multiple metals exposure on abnormal liver function: The mediating role of low-density lipoprotein cholesterol

Equilibration of metal metabolism is critical for normal liver function. Most epidemiological studies have only concentrated on the influence of limited metals. However, the single and synergistic impact of multiple-metal exposures on abnormal liver function (ALF) are still unknown. A cross-sectional study involving 1493 Chinese adults residing in Shenzhen was conducted. Plasma concentrations of 13 metals, including essential metals (calcium, copper, cobalt, iron, magnesium, manganese, molybdenum, zinc, and selenium) and toxic metals (aluminum, cadmium, arsenic, and thallium) were detected by the inductively coupled plasma spectrometry (ICP-MS). ALF was ascertained as any observed abnormality from albumin, alanine transaminase, aspartate transaminase, γ-glutamyl transpeptidase, and direct bilirubin. Diverse statistical methods were used to evaluate the single and mixture effect of metals, as well as the dose-response relationships with ALF risk, respectively. Mediation analysis was conducted to evaluate the role of blood lipids in the relation of metal exposure with ALF. The average age of subjects was 59.7 years, and 56.7 % were females. Logistic regression and the least absolute shrinkage and selection operator (LASSO) penalized regression model consistently suggested that increased levels of arsenic, aluminum, manganese, and cadmium were related to elevated risk of ALF; while magnesium and zinc showed protective effects on ALF (all p-trend < 0.05). The grouped weighted quantile sum (GWQS) regression revealed that the WQS index of essential metals and toxic metals showed significantly negative or positive relationship with ALF, respectively. Aluminum, arsenic, cadmium, and manganese showed linear whilst magnesium and zinc showed non-linear dose-response relationships with ALF risk. Mediation analysis showed that LDL-c mediated 4.41 % and 14.74 % of the relationship of plasma cadmium and manganese with ALF, respectively. In summary, plasma aluminum, arsenic, manganese, cadmium, magnesium, and zinc related with ALF, and LDL-c might underlie the pathogenesis of ALF associated with cadmium and manganese exposure. This study may provide critical public health significances in liver injury prevention and scientific evidence for the establishment of environmental standard.

Notoginsenoside R1 targets PPAR-γ to inhibit hepatic stellate cell activation and ameliorates liver fibrosis

BACKGROUND

Hepatic fibrosis, a common pathological process that occurs in end-stage liver diseases, is a serious public health problem and lacks effective therapy. Notoginsenoside R1 (NR1) is a small molecule derived from the traditional Chinese medicine Sanqi, exhibiting great potential in treating diverse metabolie disorders. Here we aimed to enquired the role of NR1 in liver fibrosis and its underlying mechanism in hepatoprotective effects.

METHODS

We investigated the anti-fibrosis effect of NR1 using CCl4-induced mouse mode of liver fibrosis as well as TGF-β1-activated JS-1, LX-2 cells and primary hepatic stellate cell. Cell samples treated by NR1 were collected for transcriptomic profiling analysis. PPAR-γ mediated TGF-β1/Smads signaling was examined using PPAR-γ selective inhibitors and agonists intervention, immunofluorescence staining and western blot analysis. Additionally, we designed and studied the binding of NR1 to PPAR-γ using molecular docking.

RESULTS

NR1 obviously attenuated liver histological damage, reduced serum ALT, AST levels, and decreased liver fibrogenesis markers in mouse mode. Mechanistically, NR1 elevated PPAR-γ and decreased TGF-β1, p-Smad2/3 expression. The TGF-β1/Smads signaling pathway and fibrotic phenotype were altered in JS-1 cells after using PPAR-γ selective inhibitors and agonists respectively, confirming PPAR-γ played a pivotal protection role inNR1 treating liver fibrosis. Further molecular docking indicated NR1 had a strong binding tendency to PPAR-γ with minimum free energy.

CONCLUSIONS

NR1 attenuates hepatic stellate cell activation and hepatic fibrosis by elevating PPAR-γ to inhibit TGF-β1/Smads signalling. NR1 may be a potential candidate compound for reliving liver fibrosis.

Non-Necroptotic Roles of MLKL in Diet-Induced Obesity, Liver Pathology, and Insulin Sensitivity: Insights from a High-Fat, High-Fructose, High-Cholesterol Diet Mouse Model

Chronic inflammation is a key player in metabolic dysfunction-associated fatty liver disease (MAFLD) progression. Necroptosis, an inflammatory cell death pathway, is elevated in MAFLD patients and mouse models, yet its role is unclear due to the diverse mouse models and inhibition strategies. In our study, we inhibited necroptosis by targeting mixed lineage kinase domain-like pseudokinase (MLKL), the terminal effector of necroptosis, in a high-fat, high-fructose, high-cholesterol (HFHFrHC) mouse model of diet-induced MAFLD. Despite the HFHFrHC diet upregulating MLKL (2.5-fold), WT mice livers showed no increase in necroptosis markers or associated proinflammatory cytokines. Surprisingly, Mlkl-/- mice experienced exacerbated liver inflammation without protection from diet-induced liver damage, steatosis, or fibrosis. In contrast, Mlkl+/- mice showed a significant reduction in these parameters that was associated with elevated Pparα and Pparγ levels. Both Mlkl-/- and Mlkl+/- mice on the HFHFrHC diet resisted diet-induced obesity, attributed to the increased beiging, enhanced oxygen consumption, and energy expenditure due to adipose tissue, and exhibited improved insulin sensitivity. These findings highlight the tissue-specific effects of MLKL on the liver and adipose tissue, and they suggest a dose-dependent effect of MLKL on liver pathology.

27-Hydroxycholesterol induces liver fibrosis via down-regulation of trimethylation of histone H3 at lysine 27 by activating oxidative stress; effect of nutrient interventions

BACKGROUND

Chronic liver injury caused by activation of hepatic stellate cells (HSCs) is a key event in the development of liver fibrosis (LF). A high-cholesterol diet can prompt accumulation of free cholesterol in HSCs, which promotes HSC activation and progression of LF.

OBJECTIVE

27-Hydroxycholesterol (27HC) is the most abundant cholesterol metabolite. Here, we investigated whether the HSC activation and LF induced by high cholesterol is caused by its metabolite 27HC, and whether TGFβ classical signaling were involved in these processes.

METHODS

In vitro, LX2 and HSC-T6 cells were used to explore the effects of 27HC on activation of HSCs, while LSECs were used to observe the effects of 27HC on capillarization. In vivo, zebrafish were used to assess the effect of 27HC on LF.

RESULTS

The cholesterol metabolite 27HC promoted the proliferation of HSCs and up-regulated expression of COL-1 and α-SMA as well as CTGF and TIMP1. Also, 27HC up-regulated expression of Smad2/3 and phosphorylated Smad2/3 in HSCs. Furthermore, 27HC-induced up-regulation of COL-1, α-SMA, CTGF, and TIMP1 protein levels was inhibited by Smad2/3 knockout. In addition, 27HC down-regulated H3K27me3 by inhibition of EZH2 and promotion of UTX and JMJD3 expression via the TGFβ signaling, thereby inducing activation of HSCs. Notably, 27HC significantly aggravated the pathological damage induced by DEN, and induced deposition of collagen fibers in zebrafish liver. Folic acid (FA) and resveratrol (RES) both reduced 27HC-induced production of reactive oxygen species (ROS) and inhibited the effects of TGFβ signaling on EZH2, UTX, and JMJD3, thereby increasing H3K27me3, and finally jointly inhibiting LF.

CONCLUSION

Cholesterol is metabolized to 27HC, which mediates activation of HSCs and onset of LF. Reduced expression of H3k27me3 by TGFβ signaling is crucial to 27HC-induced LF. FA and RES ameliorated activation of HSCs and LF by reducing 27HC-induced production of ROS and regulating of H3K27me3.

Lysosomal cholesterol overload in macrophages promotes liver fibrosis in a mouse model of NASH

Accumulation of lipotoxic lipids, such as free cholesterol, induces hepatocyte death and subsequent inflammation and fibrosis in the pathogenesis of nonalcoholic steatohepatitis (NASH). However, the underlying mechanisms remain unclear. We have previously reported that hepatocyte death locally induces phenotypic changes in the macrophages surrounding the corpse and remnant lipids, thereby promoting liver fibrosis in a murine model of NASH. Here, we demonstrated that lysosomal cholesterol overload triggers lysosomal dysfunction and profibrotic activation of macrophages during the development of NASH. β-cyclodextrin polyrotaxane (βCD-PRX), a unique supramolecule, is designed to elicit free cholesterol from lysosomes. Treatment with βCD-PRX ameliorated cholesterol accumulation and profibrotic activation of macrophages surrounding dead hepatocytes with cholesterol crystals, thereby suppressing liver fibrosis in a NASH model, without affecting the hepatic cholesterol levels. In vitro experiments revealed that cholesterol-induced lysosomal stress triggered profibrotic activation in macrophages predisposed to the steatotic microenvironment. This study provides evidence that dysregulated cholesterol metabolism in macrophages would be a novel mechanism of NASH.

Mechanism for FXR to regulate bile acid and glycolipid metabolism to improve NAFLD

Nonalcoholic fatty liver disease (NAFLD) is the main cause of chronic liver disease, with liver metabolic disorders as major pathological changes, manifested as abnormal lipid accumulation, liver cell oxidative stress, etc., but its etiology is still unclear. The farnesol X receptor (FXR) is a major bile acid receptor in the "gut-liver axis", via which FXR regulates metabolism and affects the pathophysiological status of various substances through different pathways, thus contributing to the occurrence and development of NAFLD. Therefore, FXR has become a potential therapeutic target for NAFLD. This article reviews the relationship between FXR regulation of bile acid, glucose, and lipid metabolism through the "gut-liver axis" and the occurrence and development of NAFLD, to provide new insights and clues for further research about FXR-based pharmaceutical treatments.

Found in translation-Fibrosis in metabolic dysfunction-associated steatohepatitis (MASH)

Metabolic dysfunction-associated steatohepatitis (MASH) is a severe form of liver disease that poses a global health threat because of its potential to progress to advanced fibrosis, leading to cirrhosis and liver cancer. Recent advances in single-cell methodologies, refined disease models, and genetic and epigenetic insights have provided a nuanced understanding of MASH fibrogenesis, with substantial cellular heterogeneity in MASH livers providing potentially targetable cell-cell interactions and behavior. Unlike fibrogenesis, mechanisms underlying fibrosis regression in MASH are still inadequately understood, although antifibrotic targets have been recently identified. A refined antifibrotic treatment framework could lead to noninvasive assessment and targeted therapies that preserve hepatocellular function and restore the liver's architectural integrity.

Cellular heterogeneity and plasticity during NAFLD progression

Nonalcoholic fatty liver disease (NAFLD) is a progressive liver disease that can progress to nonalcoholic steatohepatitis (NASH), NASH-related cirrhosis, and hepatocellular carcinoma (HCC). NAFLD ranges from simple steatosis (or nonalcoholic fatty liver [NAFL]) to NASH as a progressive form of NAFL, which is characterized by steatosis, lobular inflammation, and hepatocellular ballooning with or without fibrosis. Because of the complex pathophysiological mechanism and the heterogeneity of NAFLD, including its wide spectrum of clinical and histological characteristics, no specific therapeutic drugs have been approved for NAFLD. The heterogeneity of NAFLD is closely associated with cellular plasticity, which describes the ability of cells to acquire new identities or change their phenotypes in response to environmental stimuli. The liver consists of parenchymal cells including hepatocytes and cholangiocytes and nonparenchymal cells including Kupffer cells, hepatic stellate cells, and endothelial cells, all of which have specialized functions. This heterogeneous cell population has cellular plasticity to adapt to environmental changes. During NAFLD progression, these cells can exert diverse and complex responses at multiple levels following exposure to a variety of stimuli, including fatty acids, inflammation, and oxidative stress. Therefore, this review provides insights into NAFLD heterogeneity by addressing the cellular plasticity and metabolic adaptation of hepatocytes, cholangiocytes, hepatic stellate cells, and Kupffer cells during NAFLD progression.

Inhibition of microRNA-33b in humanized mice ameliorates nonalcoholic steatohepatitis

Nonalcoholic steatohepatitis (NASH) can lead to cirrhosis and hepatocellular carcinoma in their advanced stages; however, there are currently no approved therapies. Here, we show that microRNA (miR)-33b in hepatocytes is critical for the development of NASH. miR-33b is located in the intron of sterol regulatory element-binding transcription factor 1 and is abundantly expressed in humans, but absent in rodents. miR-33b knock-in (KI) mice, which have a miR-33b sequence in the same intron of sterol regulatory element-binding transcription factor 1 as humans and express miR-33b similar to humans, exhibit NASH under high-fat diet feeding. This condition is ameliorated by hepatocyte-specific miR-33b deficiency but unaffected by macrophage-specific miR-33b deficiency. Anti-miR-33b oligonucleotide improves the phenotype of NASH in miR-33b KI mice fed a Gubra Amylin NASH diet, which induces miR-33b and worsens NASH more than a high-fat diet. Anti-miR-33b treatment reduces hepatic free cholesterol and triglyceride accumulation through up-regulation of the lipid metabolism-related target genes. Furthermore, it decreases the expression of fibrosis marker genes in cultured hepatic stellate cells. Thus, inhibition of miR-33b using nucleic acid medicine is a promising treatment for NASH.

Establishment of Novel Mouse Model of Dietary NASH Rapidly Progressing into Liver Cirrhosis and Tumors

Non-alcoholic steatohepatitis (NASH), which is the most severe manifestation of non-alcoholic fatty liver disease (NAFLD), has been recognized as a major hepatocellular carcinoma (HCC) catalyst. However, the molecular mechanism of NASH-liver fibrosis-HCC sequence remains unclear and a specific and effective treatment for NASH has not yet been established. The progress in this field depends on the availability of reliable preclinical models which show the steady progression to NASH, liver cirrhosis, and HCC. However, most of the NASH mouse models that have been described to date develop NASH generally for more than 24 weeks and there is an uncertainty of HCC development. To overcome such shortcomings of experimental NASH studies, we established a novel NASH-HCC mouse model with very high reproducibility, generality, and convenience. We treated male C57BL/6J mice with a newly developed choline-deficient and methionine-restricted high-fat diet, named OYC-NASH2 diet, for 60 weeks. Treatment of OYC-NASH2 diet for 3 weeks revealed marked steatosis, lobular inflammation, and fibrosis, histologically diagnosed as NASH. Liver cirrhosis was observed in all mice with 48-week treatment. Liver nodules emerged at 12 weeks of the treatment, > 2 mm diameter liver tumors developed in all mice at 24 weeks of the treatment and HCC appeared after 36-week treatment. In conclusion, our rapidly progressive and highly reproducible NASH-liver cirrhosis-HCC model is helpful for preclinical development and research on the pathogenesis of human NAFLD-NASH-HCC. Our mouse model would be useful for the development of novel chemicals for NASH-HCC-targeted therapies.

Immune microenvironment changes of liver cirrhosis: emerging role of mesenchymal stromal cells

Cirrhosis is a progressive and diffuse liver disease characterized by liver tissue fibrosis and impaired liver function. This condition is brought about by several factors, including chronic hepatitis, hepatic steatosis, alcohol abuse, and other immunological injuries. The pathogenesis of liver cirrhosis is a complex process that involves the interaction of various immune cells and cytokines, which work together to create the hepatic homeostasis imbalance in the liver. Some studies have indicated that alterations in the immune microenvironment of liver cirrhosis are closely linked to the development and prognosis of the disease. The noteworthy function of mesenchymal stem cells and their paracrine secretion lies in their ability to promote the production of cytokines, which in turn enhance the self-repairing capabilities of tissues. The objective of this review is to provide a summary of the alterations in liver homeostasis and to discuss intercellular communication within the organ. Recent research on MSCs is yielding a blueprint for cell typing and biomarker immunoregulation. Hopefully, as MSCs researches continue to progress, novel therapeutic approaches will emerge to address cirrhosis.

PNPLA3-I148M Variant Promotes the Progression of Liver Fibrosis by Inducing Mitochondrial Dysfunction

Patatin-like phospholipase domain-containing 3 (PNPLA3) rs738409 polymorphism (I148M) is strongly associated with non-alcoholic steatohepatitis and advanced fibrosis; however, the underlying mechanisms remain largely unknown. In this study, we investigated the effect of PNPLA3-I148M on the activation of hepatic stellate cell line LX-2 and the progression of liver fibrosis. Immunofluorescence staining and enzyme-linked immunosorbent assay were used to detect lipid accumulation. The expression levels of fibrosis, cholesterol metabolism, and mitochondria-related markers were measured via real-time PCR or western blotting. Electron microscopy was applied to analyze the ultrastructure of the mitochondria. Mitochondrial respiration was measured by a Seahorse XFe96 analyzer. PNPLA3-I148M significantly promoted intracellular free cholesterol aggregation in LX-2 cells by decreasing cholesterol efflux protein (ABCG1) expression; it subsequently induced mitochondrial dysfunction characterized by attenuated ATP production and mitochondrial membrane potential, elevated ROS levels, caused mitochondrial structural damage, altered the oxygen consumption rate, and decreased the expression of mitochondrial-function-related proteins. Our results demonstrated for the first time that PNPLA3-I148M causes mitochondrial dysfunction of LX-2 cells through the accumulation of free cholesterol, thereby promoting the activation of LX-2 cells and the development of liver fibrosis.

Mechanisms of liver fibrosis in metabolic syndrome

The understanding of the mechanisms of liver fibrosis has been dominated by models in which chronic hepatocellular injury is the initiating step as is seen with viral infections. The increased prevalence of the metabolic syndrome, and the increases in liver fibrosis due to metabolic syndrome driven non-alcoholic steatohepatitis (NASH), has made it a priority to understand how this type of liver fibrosis is similar to, and different from, pure hepatocellular injury driven liver fibrosis. Both types of liver fibrosis have the transformation of the hepatic stellate cell (HSC) into a myofibroblast as a key step. In metabolic syndrome, there is little evidence that metabolite changes such as high levels of glucose and free fatty acids are directly inducing HSC transdifferentiation, however, metabolite changes may lead to reductions in immunomodulatory and hepatoprotective molecules such as lipoxins, resolvins and Interleukin (IL)-22. Cells of the innate immune system are known to be important intermediaries between hepatocellular damage and HSC transdifferentiation, primarily by producing cytokines such as transforming growth factor-β (TGF-β) and platelet derived growth factor (PDGF). Resident and infiltrating macrophages are the dominant innate immune cells, but others (dendritic cells, neutrophils, natural killer T cells and mucosal-associated invariant T cells) also have important roles in inducing and resolving liver fibrosis. CD8+ and CD4+ T cells of the adaptive immune system have been identified to have greater profibrotic roles than previously realised by inducing hepatocyte death (auto-aggressive CD8+T) cells and cytokines producing (TH17 producing CD4+T) cells. Finally, the cellular networks present in NASH fibrosis are being identified and suggest that once fibrosis has developed cell-to-cell communication is dominated by myofibroblasts autocrine signalling followed by communication with cholangiocytes and endothelial cells, with myofibroblast-hepatocyte, and myofibroblast-macrophage signalling having minor roles. Such information is essential to the development of antifibrotic strategies for different stages of fibrosis.

Simvastatin inhibits hepatic stellate cells activation by regulating the ferroptosis signaling pathway

BACKGROUND & AIMS

Ferroptosis is a form of regulated cell death and its promotion in hepatic stellate cells (HSCs) attenuates liver fibrosis. Statins, which are 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors, may induce ferroptosis via the downregulation of glutathione peroxidase 4 (GPX4) by inhibiting the mevalonate pathway. However, little evidence is available regarding the association between statins and ferroptosis. Therefore, we investigated the association between statins and ferroptosis in HSCs.

METHODS

Two human HSC cell lines, LX-2 and TWNT-1, were treated with simvastatin, an HMG-CoA reductase inhibitor. Mevalonic acid (MVA), farnesyl pyrophosphate (FPP), and geranylgeranyl pyrophosphate (GGPP) were used to determine the involvement of the mevalonate pathway. We performed a detailed analysis of the ferroptosis signaling pathway. We also investigated human liver tissue samples from patients with nonalcoholic steatohepatitis to clarify the effect of statins on GPX4 expression.

RESULTS

Simvastatin reduced cell mortality and inhibited HSCs activation, accompanied by iron accumulation, oxidative stress, lipid peroxidation, and reduced GPX4 protein expression. These results indicate that simvastatin inhibits HSCs activation by promoting ferroptosis. Furthermore, treatment with MVA, FPP, or GGPP attenuated simvastatin-induced ferroptosis. These results suggest that simvastatin promotes ferroptosis in HSCs by inhibiting the mevalonate pathway. In human liver tissue samples, statins downregulated the expression of GPX4 in HSCs without affecting hepatocytes.

CONCLUSIONS

Simvastatin inhibits the activation of HSCs by regulating the ferroptosis signaling pathway.

Mitochondrial cholesterol: Metabolism and impact on redox biology and disease

Cholesterol is a crucial component of membrane bilayers by regulating their structural and functional properties. Cholesterol traffics to different cellular compartments including mitochondria, whose cholesterol content is low compared to other cell membranes. Despite the limited availability of cholesterol in the inner mitochondrial membrane (IMM), the metabolism of cholesterol in the IMM plays important physiological roles, acting as the precursor for the synthesis of steroid hormones and neurosteroids in steroidogenic tissues and specific neurons, respectively, or the synthesis of bile acids through an alternative pathway in the liver. Accumulation of cholesterol in mitochondria above physiological levels has a negative impact on mitochondrial function through several mechanisms, including the limitation of crucial antioxidant defenses, such as the glutathione redox cycle, increased generation of reactive oxygen species and consequent oxidative modification of cardiolipin, and defective assembly of respiratory supercomplexes. These adverse consequences of increased mitochondrial cholesterol trafficking trigger the onset of oxidative stress and cell death, and, ultimately, contribute to the development of diverse diseases, including metabolic liver diseases (i.e. fatty liver disease and liver cancer), as well as lysosomal disorders (i.e. Niemann-Pick type C disease) and neurodegenerative diseases (i.e. Alzheimer's disease). In this review, we summarize the metabolism and regulation of mitochondrial cholesterol and its potential impact on liver and neurodegenerative diseases.

Targeting Liver X Receptors for the Treatment of Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) refers to a range of conditions in which excess lipids accumulate in the liver, possibly leading to serious hepatic manifestations such as steatohepatitis, fibrosis/cirrhosis and cancer. Despite its increasing prevalence and significant impact on liver disease-associated mortality worldwide, no medication has been approved for the treatment of NAFLD yet. Liver X receptors α/β (LXRα and LXRβ) are lipid-activated nuclear receptors that serve as master regulators of lipid homeostasis and play pivotal roles in controlling various metabolic processes, including lipid metabolism, inflammation and immune response. Of note, NAFLD progression is characterized by increased accumulation of triglycerides and cholesterol, hepatic de novo lipogenesis, mitochondrial dysfunction and augmented inflammation, all of which are highly attributed to dysregulated LXR signaling. Thus, targeting LXRs may provide promising strategies for the treatment of NAFLD. However, emerging evidence has revealed that modulating the activity of LXRs has various metabolic consequences, as the main functions of LXRs can distinctively vary in a cell type-dependent manner. Therefore, understanding how LXRs in the liver integrate various signaling pathways and regulate metabolic homeostasis from a cellular perspective using recent advances in research may provide new insights into therapeutic strategies for NAFLD and associated metabolic diseases.

Impact of Sex and Gender on Clinical Management of Patients with Advanced Chronic Liver Disease and Type 2 Diabetes

Gender differences in the epidemiology, pathophysiological mechanisms and clinical features in chronic liver diseases that may be associated with type 2 diabetes (T2D) have been increasingly reported in recent years. This sexual dimorphism is due to a complex interaction between sex- and gender-related factors, including biological, hormonal, psychological and socio-cultural variables. However, the impact of sex and gender on the management of T2D subjects with liver disease is still unclear. In this regard, sex-related differences deserve careful consideration in pharmacology, aimed at improving drug safety and optimising medical therapy, both in men and women with T2D; moreover, low adherence to and persistence of long-term drug treatment is more common among women. A better understanding of sex- and gender-related differences in this field would provide an opportunity for a tailored diagnostic and therapeutic approach to the management of T2D subjects with chronic liver disease. In this narrative review, we summarized available data on sex- and gender-related differences in chronic liver disease, including metabolic, autoimmune, alcoholic and virus-related forms and their potential evolution towards cirrhosis and/or hepatocarcinoma in T2D subjects, to support their appropriate and personalized clinical management.

Hepatic Stellate Cells: Dictating Outcome in Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is a fast growing, chronic liver disease affecting ∼25% of the global population. Nonalcoholic fatty liver disease severity ranges from the less severe simple hepatic steatosis to the more advanced nonalcoholic steatohepatitis (NASH). The presence of NASH predisposes individuals to liver fibrosis, which can further progress to cirrhosis and hepatocellular carcinoma. This makes hepatic fibrosis an important indicator of clinical outcomes in patients with NASH. Hepatic stellate cell activation dictates fibrosis development during NASH. Here, we discuss recent advances in the analysis of the profibrogenic pathways and mediators of hepatic stellate cell activation and inactivation, which ultimately determine the course of disease in nonalcoholic fatty liver disease/NASH.

Lipidomic profiling of rat hepatic stellate cells during activation reveals a two-stage process accompanied by increased levels of lysosomal lipids

Hepatic stellate cells (HSCs) are liver-resident cells best known for their role in vitamin A storage under physiological conditions. Upon liver injury, HSCs activate into myofibroblast-like cells, a key process in the onset of liver fibrosis. Lipids play an important role during HSC activation. Here, we provide a comprehensive characterization of the lipidomes of primary rat HSCs during 17 days of activation in vitro. For lipidomic data interpretation, we expanded our previously described Lipid Ontology (LION) and associated web application (LION/Web) with the LION-PCA heatmap module, which generates heatmaps of the most typical LION-signatures in lipidomic datasets. Furthermore, we used LION to perform pathway analysis to determine the significant metabolic conversions in lipid pathways. Together, we identify two distinct stages of HSC activation. In the first stage, we observe a decrease of saturated phosphatidylcholine, sphingomyelin, and phosphatidic acid and an increase in phosphatidylserine and polyunsaturated bis(monoacylglycero)phosphate (BMP), a lipid class typically localized at endosomes and lysosomes. In the second activation stage, BMPs, hexosylceramides, and ether-linked phosphatidylcholines are elevated, resembling a lysosomal lipid storage disease profile. The presence of isomeric structures of BMP in HSCs was confirmed ex vivo in MS-imaging datasets of steatosed liver sections. Finally, treatment with pharmaceuticals targeting the lysosomal integrity led to cell death in primary HSCs but not in HeLa cells. In summary, our combined data suggest that lysosomes play a critical role during a two-stage activation process of HSCs.

Expression and Function of BMP and Activin Membrane-Bound Inhibitor (BAMBI) in Chronic Liver Diseases and Hepatocellular Carcinoma

BAMBI (bone morphogenetic protein and activin membrane-bound inhibitor) is a transmembrane pseudoreceptor structurally related to transforming growth factor (TGF)-β type 1 receptors (TGF-β1Rs). BAMBI lacks a kinase domain and functions as a TGF-β1R antagonist. Essential processes such as cell differentiation and proliferation are regulated by TGF-β1R signaling. TGF-β is the best-studied ligand of TGF-βRs and has an eminent role in inflammation and fibrogenesis. Liver fibrosis is the end stage of almost all chronic liver diseases, such as non-alcoholic fatty liver disease, and at the moment, there is no effective anti-fibrotic therapy available. Hepatic BAMBI is downregulated in rodent models of liver injury and in the fibrotic liver of patients, suggesting that low BAMBI has a role in liver fibrosis. Experimental evidence convincingly demonstrated that BAMBI overexpression is able to protect against liver fibrosis. Chronic liver diseases have a high risk of hepatocellular carcinoma (HCC), and BAMBI was shown to exert tumor-promoting as well as tumor-protective functions. This review article aims to summarize relevant studies on hepatic BAMBI expression and its role in chronic liver diseases and HCC.

Beneficial Effects of Moderate Hepatic Activin A Expression on Metabolic Pathways, Inflammation, and Atherosclerosis

BACKGROUND

Atherosclerosis is an inflammatory vascular disease marked by hyperlipidemia and hematopoietic stem cell expansion. Activin A, a member of the Activin/GDF/TGFβ/BMP (growth/differentiation factor/transforming growth factor beta/bone morphogenetic protein) family is broadly expressed and increases in human atherosclerosis, but its functional effects in vivo in this context remain unclear.

METHODS

We studied LDLR^-/- mice on a Western diet for 12 weeks and used adeno-associated viral vectors with a liver-specific TBG (thyroxine-binding globulin) promoter to express Activin A or GFP (control). Atherosclerotic lesions were analyzed by oil red staining. Blood lipid profiling was performed by high-performance liquid chromatography, and immune cells were evaluated by flow cytometry. Liver RNA-sequencing was performed to explore the underlying mechanisms.

RESULTS

Activin A expression decreased in both livers and aortae from LDLR^-/- mice fed a Western diet compared with standard laboratory diet. Adenoassociated virus-TBG-Activin A increased Activin A hepatic expression ≈10-fold at 12 weeks; P<0.001) and circulating Activin A levels ≈2000 pg/ml versus ≈50 pg/ml; P<0.001, compared with controls). Hepatic Activin A expression decreased plasma total and LDL (low-density lipoprotein) cholesterol ≈60% and ≈40%, respectively), reduced inflammatory cells in aortae and proliferating hematopoietic stem cells in bone marrow, and reduced atherosclerotic lesion and necrotic core area in aortae. Activin A also attenuated liver steatosis and expression of the lipogenesis genes, Srebp1 and Srebp2. RNA sequencing revealed Activin A not only blocked expression of genes involved in hepatic de novo lipogenesis but also fatty acid uptake and liver inflammation. In addition, Activin A expressed in the liver also reduced white fat tissue accumulation, decreased adipocyte size, and improved glucose tolerance.

CONCLUSIONS

Our studies reveal hepatic Activin A expression reduces inflammation, hematopoietic stem cell expansion, liver steatosis, circulating cholesterol, and fat accumulation, which likely all contribute to the observed protection against atherosclerosis. The reduced Activin A observed in LDLR^-/- mice on a Western diet seems maladaptive and deleterious for atherogenesis.

Immune and metabolic cross-links in the pathogenesis of comorbid non-alcoholic fatty liver disease

In recent years, there has been a steady growth of interest in non-alcoholic fatty liver disease (NAFLD), which is associated with negative epidemiological data on the prevalence of the disease and its clinical significance. NAFLD is closely related to the metabolic syndrome and these relationships are the subject of active research. A growing body of evidence shows cross-linkages between metabolic abnormalities and the innate immune system in the development and progression of NAFLD. These links are bidirectional and largely still unclear, but a better understanding of them will improve the quality of diagnosis and management of patients. In addition, lipid metabolic disorders and the innate immune system link NAFLD with other diseases, such as atherosclerosis, which is of great clinical importance.

The protective roles of augmenter of liver regeneration in hepatocytes in the non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) occurs in 25% of the global population and manifests as lipid deposition, hepatocyte injury, activation of Kupffer and stellate cells, and steatohepatitis. Predominantly expressed in hepatocytes, the augmenter of liver regeneration (ALR) is a key factor in liver regulation that can alleviate fatty liver disease and protect the liver from abnormal liver lipid metabolism. ALR has three isoforms (15-, 21-, and 23-kDa), amongst which 23-kDa ALR is the most extensively studied. The 23-kDa ALR isoform is a sulfhydryl oxidase that resides primarily in the mitochondrial intermembrane space (IMS), whereby it protects the liver against various types of injury. In this review, we describe the role of ALR in regulating hepatocytes in the context of NAFLD. We also discuss questions about ALR that remain to be explored in the future. In conclusion, ALR appears to be a promising therapeutic target for treating NAFLD.

ChemPert: mapping between chemical perturbation and transcriptional response for non-cancer cells

Prior knowledge of perturbation data can significantly assist in inferring the relationship between chemical perturbations and their specific transcriptional response. However, current databases mostly contain cancer cell lines, which are unsuitable for the aforementioned inference in non-cancer cells, such as cells related to non-cancer disease, immunology and aging. Here, we present ChemPert (https://chempert.uni.lu/), a database consisting of 82 270 transcriptional signatures in response to 2566 unique perturbagens (drugs, small molecules and protein ligands) across 167 non-cancer cell types, as well as the protein targets of 57 818 perturbagens. In addition, we develop a computational tool that leverages the non-cancer cell datasets, which enables more accurate predictions of perturbation responses and drugs in non-cancer cells compared to those based onto cancer databases. In particular, ChemPert correctly predicted drug effects for treating hepatitis and novel drugs for osteoarthritis. The ChemPert web interface is user-friendly and allows easy access of the entire datasets and the computational tool, providing valuable resources for both experimental researchers who wish to find datasets relevant to their research and computational researchers who need comprehensive non-cancer perturbation transcriptomics datasets for developing novel algorithms. Overall, ChemPert will facilitate future in silico compound screening for non-cancer cells.

Cholesterol accumulation in hepatocytes mediates IRE1/p38 branch of endoplasmic reticulum stress to promote nonalcoholic steatohepatitis

Non-alcoholic fatty liver disease (NAFLD), based on the elevating obesity incidence, is one of the major health issue worldwide. Transition from NAFLD to non-alcoholic steatohepatitis (NASH) is driven by increased apoptosis and is relevant to higher morbidity rates. In regard to limited understanding on cholesterol mediated hepatocyte alterations in NALFD/NASH transition, we investigated endoplasmic reticulum (ER) stress and related apoptosis. Our findings suggest that cholesterol upregulates ER stress and enhances C/EBP homologous protein (CHOP) either in hypercholesterolemic rabbits or in hepatocytes treated with liposome-cholesterol complex. Mechanistically, cholesterol accumulation in hepatocytes activates IRE1/p38 branch of ER stress, stimulating CHOP levels. In liver tissues of cholesterol fed rabbits, α-tocopherol supplementation decreased IRE1/p38/CHOP activation and prevented NASH development. Thus, our study provides a critical role of hepatocyte cholesterol in inducing IRE1/p38/CHOP pathway and suggests novel candidates for therapeutic targets against NASH.

Metformin, pioglitazone, dapagliflozin and their combinations ameliorate manifestations associated with NAFLD in rats via anti-inflammatory, anti-fibrotic, anti-oxidant and anti-apoptotic mechanisms

Non-alcoholic fatty liver disease (NAFLD) is an important health threat that is strongly linked to components of metabolic syndrome, particularly the low-grade inflammatory changes. Significantly, several of the available anti-diabetic drug classes demonstrate a considerable anti-inflammatory effect, and hence might be of benefit for NAFLD patients. In this study, we used a rat model of diet-induced NAFLD to examine the potential effect of metformin, pioglitazone, dapagliflozin and their combinations on NAFLD manifestations. Rats were fed an atherogenic diet containing 1.25 % cholesterol, 0.5 % cholic acid and 60 % cocoa butter for 6 weeks causing a number of metabolic and hepatic alterations including insulin resistance, dyslipidemia, systemic inflammation, increased hepatic oxidative stress and lipid peroxidation, hepatic steatosis, lobular inflammation, as well as increased markers of liver inflammation and hepatocyte apoptosis. Drug treatment, which started at the third week of NAFLD induction and continued for three weeks, not only ameliorated the observed metabolic impairment, but also functional and structural manifestations of NAFLD. Specifically, anti-diabetic drug treatment reversed markers of systemic and hepatic inflammation, oxidative stress, hepatic fibrosis, and hepatocyte apoptosis. Our findings propose that anti-diabetic drugs with a potential anti-inflammatory effect can ameliorate the manifestations of NAFLD, and thus may provide a therapeutic option for such a condition that is closely associated with metabolic diseases. The detailed pharmacology of these classes in aspects linked to the observed impact on NAFLD requires to be further investigated and translated into clinical studies for tailored therapy specifically targeting NAFLD.

Dietary Cholic Acid Exacerbates Liver Fibrosis in NASH Model of Sprague–Dawley Rats Fed a High-Fat and High-Cholesterol Diet

Background: Recently, we established a novel rodent model of nonalcoholic steatohepatitis (NASH) with advanced fibrosis induced by a high-fat and high-cholesterol (HFC) diet containing cholic acid (CA), which is known to cause hepatotoxicity. The present study aimed to elucidate the direct impact of dietary CA on the progression of NASH induced by feeding the HFC diet. Methods: Nine-week-old male Sprague–Dawley rats were randomly assigned to receive a normal, HFC, or CA-supplemented (0.1%, 0.5% or 2.0%, w/w) HFC diet for 9 weeks. Results: Histopathological assessment revealed that the supplementation of CA dose-dependently aggravated hepatic steatosis, inflammation, and fibrosis, reaching stage 4 cirrhosis in the 2.0% CA diet group. In contrast, the rats that were fed the HFC diet without any added CA developed mild steatosis and inflammation without fibrosis. The hepatic cholesterol content and mRNA expression involved in inflammatory response and fibrogenesis was higher in a CA dose-dependent manner. The hepatic chenodeoxycholic acid levels were higher in 2.0% CA diet group than in the control, although hepatic levels of total bile acid and CA did not increase dose-dependently with CA intake. Conclusion: Adding CA to the HFC diet altered bile acid metabolism and inflammatory response and triggered the development of fibrosis in the rat liver.

Gut microbiota combined with metabolomics reveal the mechanism of curcumol on liver fibrosis in mice

OBJECTIVE

Liver fibrosis is a reversible pathological process, and its prevention and treatment hold great significance for patients with chronic liver disease. This study combined 16S rRNA analysis of gut microbiota and serum metabolomics to explore the mechanism of curcumol's effect on liver fibrosis in mice. The results clarified the relationship between the gut microbiota and metabolites in the process of liver fibrosis.

MATERIALS AND METHODS

In this study, we randomly divided mice into a control group, a model group, and a curcumol treatment group to analyze the pathological changes in the liver tissue as well as the activities of the toll-like receptor 4 (TLR4)/nuclear factory kappa B (NF-κB) signaling pathway and inflammatory factors, such as tumor necrosis factor (TNF), interleukin 6 (IL-6), and IL-8. The gut microbiota were analyzed by 16 S rRNA sequencing, and serum metabolites were examined by liquid chromatography-mass spectrometry (LC-MS) metabolomic analysis.

RESULTS

Molecular biological testing found that curcumol could significantly improve the pathological changes of the liver tissue and inhibit the occurrence of liver inflammation. Intestinal flora testing found that curcumol could significantly change the abundances of Veillonellaceae, Prerotella_oulorum, and Alistipes_finegoldii. Metabolomics analysis found that curcumol's antihepatic fibrosis effect may be related to its regulation of arachidonic acid metabolism. Correlation analysis suggested that curcumol regulated the abundances of Bacteroidota and Bacteroides and participated in the metabolism of Prostaglandin B2.

CONCLUSIONS

When liver fibrosis occurs, the intestinal flora and metabolic network are altered. The effect of curcumol on liver fibrosis may be related to its regulation of intestinal flora and the resulting interference with metabolic pathways, thereby reducing liver inflammation.

The Crosstalk Between Liver Sinusoidal Endothelial Cells and Hepatic Microenvironment in NASH Related Liver Fibrosis

Chronic liver injury can be caused by many factors, including virus infection, alcohol intake, cholestasis and abnormal fat accumulation. Nonalcoholic steatohepatitis (NASH) has become the main cause of liver fibrosis worldwide. Recently, more and more evidences show that hepatic microenvironment is involved in the pathophysiological process of liver fibrosis induced by NASH. Hepatic microenvironment consists of various types of cells and intercellular crosstalk among different cells in the liver sinusoids. Liver sinusoidal endothelial cells (LSECs), as the gatekeeper of liver microenvironment, play an irreplaceable role in the homeostasis and alterations of liver microenvironment. Many recent studies have reported that during the progression of NASH to liver fibrosis, LSECs are involved in various stages mediated by a series of mechanisms. Therefore, here we review the key role of crosstalk between LSECs and hepatic microenvironment in the progression of NASH to liver fibrosis (steatosis, inflammation, and fibrosis), as well as promising therapeutic strategies targeting LSECs.

Fibrogenic Pathways in Metabolic Dysfunction Associated Fatty Liver Disease (MAFLD)

The prevalence of nonalcoholic fatty liver disease (NAFLD), recently also re-defined as metabolic dysfunction associated fatty liver disease (MAFLD), is rapidly increasing, affecting ~25% of the world population. MALFD/NAFLD represents a spectrum of liver pathologies including the more benign hepatic steatosis and the more advanced non-alcoholic steatohepatitis (NASH). NASH is associated with enhanced risk for liver fibrosis and progression to cirrhosis and hepatocellular carcinoma. Hepatic stellate cells (HSC) activation underlies NASH-related fibrosis. Here, we discuss the profibrogenic pathways, which lead to HSC activation and fibrogenesis, with a particular focus on the intercellular hepatocyte–HSC and macrophage–HSC crosstalk.

Very-low-density lipoprotein receptor-enhanced lipid metabolism in pancreatic stellate cells promotes pancreatic fibrosis

Lipoprotein disorder is a common feature of chronic pancreatitis (CP); however, the relationship between lipoprotein disorder and pancreatic fibrotic environment is unclear. Here, we investigated the occurrence and mechanism of pancreatic stellate cell (PSC) activation by lipoprotein metabolites and the subsequent regulation of type 2 immune responses, as well as the driving force of fibrotic aggressiveness in CP. Single-cell RNA sequencing revealed the heterogeneity of PSCs and identified very-low-density lipoprotein receptor (VLDLR)⁺ PSCs that were characterized by a higher lipid metabolism. VLDLR promoted intracellular lipid accumulation, followed by interleukin-33 (IL-33) expression and release in PSCs. PSC-derived IL-33 strongly induced pancreatic group 2 innate lymphoid cells (ILC2s) to trigger a type 2 immune response accompanied by the activation of PSCs, eventually leading to fibrosis during pancreatitis. Our findings indicate that VLDLR-enhanced lipoprotein metabolism in PSCs promotes pancreatic fibrosis and highlight a dominant role of IL-33 in this pro-fibrotic cascade.