Livers Of Non-alcoholic Fatty Liver Disease Patients Research Articles

Ubiquitin-specific peptidase 25 ameliorates hepatic steatosis by stabilizing peroxisome proliferator-activated receptor alpha

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease worldwide. USP25 in adipocytes has been proven to be involved in insulin resistance, a noteworthy characteristic of NAFLD. However, the roles of USP25 in NAFLD remain unclear. In this study, we aimed to elucidate the role of USP25 in NAFLD. Hepatic USP25 protein levels were measured in NAFLD patients and models. USP25 expression was manipulated in both mice and cells to evaluate its role in NAFLD. A downstream target of USP25 in NAFLD progression was identified through proteomic profiling analyses and confirmed. Additionally, a USP25 inhibitor was used to determine whether USP25 could be a viable treatment target for NAFLD. We found that USP25 protein levels were significantly decreased in the livers of NAFLD patients and NAFLD model mice. USP25 protein levels were also decreased in both mouse primary hepatocytes and Huh7 cells treated with free fatty acids (FFAs). We also found that Usp25 knockout mice presented much more severe hepatic steatosis when they were fed a high-fat diet. Similarly, knocking down USP25 in Huh7 cell lines aggravated FFA-induced steatosis, whereas USP25 overexpression ameliorated FFA-induced steatosis in Huh7 cell lines. Further proteomic profiling revealed that the PPARα signaling pathway was a downstream target of USP25, which was confirmed in both mice and cell lines. Moreover, USP25 could stabilize PPARα by promoting its deubiquitination. Finally, a USP25 inhibitor exacerbated diet-induced steatosis in mice. In conclusion, USP25 may play a role in NAFLD through the PPARα signaling pathway and could be a potential therapeutic target for NAFLD.

Are dietary factors associated with cardiometabolic risk factors in patients with non-alcoholic fatty liver disease?

Non-alcoholic fatty liver disease (NAFLD) is intricately linked with dietary patterns and metabolic homeostasis. Therefore, the present study focused to investigate the relation between dietary patterns and cardiometabolic risk factors related to fatty liver in NAFLD patients. This cross-sectional study included 117 individuals whose body mass index (BMI) threshold of 25 or above diagnosed with NAFLD by magnetic resonance imaging. The hospital database was used to review the patients' medical records such as lipid parameters, and fasting blood sugar. Anthropometric measurements and body composition were measured by researchers. Likewise, data from 24-h dietary recalls of individuals were collected to analyze their energy and nutrient intakes besides calculating dietary insulin index (DII), dietary insulin load (DIL), dietary glycemic index (DGI), and dietary glycemic load (DGL). Participants consuming diets with distinct levels of DII, DIL, DGI, and DGL exhibited variations in dietary energy and nutrient intake. Specifically, differences were noted in carbohydrate intake across quartiles of DII, DIL, DGI, and DGL, while fructose consumption showed variability in DGL quartiles (p ≤ 0.05). Moreover, sucrose intake demonstrated distinctions in both DII and DGL quartiles (p ≤ 0.05). No statistical difference was found in biochemical parameters and the fatty liver index among different levels of DII, DIL, DGI, and DGL (p > 0.05). After adjusting for potential confounders, participants with a higher DGI had four times greater odds of developing metabolic syndrome compared to those in the bottom quartile (OR, 4.32; 95% CI [1.42-13.11]). This study provides initial evidence of the intricate association between dietary factors and NAFLD, emphasizing the necessity for further research including prospective designs with larger sample sizes, to garner additional insights.

Identification of autophagy-related signatures in nonalcoholic fatty liver disease and correlation with non-parenchymal cells of the liver.

Non-alcoholic fatty liver disease (NAFLD) is a chronic hepatic disease. The incidence and prevalence of NAFLD have increased greatly in recent years, and there is still a lack of effective drugs. Autophagy plays an important role in promoting liver metabolism and maintaining liver homeostasis, and defects in autophagy levels are considered to be related to the development of NAFLD. However, the molecular mechanisms of autophagy in NAFLD still remain unknown. In this study, we identified 6 autophagy-associated hub genes using gene expression profiles obtained from the GSE48452 and GSE89632 datasets. Biomarkers were screened according to gene significance (GS) and module membership (MM) using weighted gene co-expression network analysis (WGCNA), and the immune infiltration landscape of the liver in NAFLD patients was explored using the CIBERSORT algorithm. Subsequently, we analyzed the relationship between liver non-parenchymal cells and autophagy-related hub genes using scRNA-seq data (GSE129516). Finally, we separated the NAFLD patients into two groups based on 6 hub genes by consensus clustering and screened 10 potential autophagy-related small molecules based on the cMAP database.

256-LB: An OGT–TFF2 Axis in the Pathogenesis of Nonalcoholic Steatohepatitis

Nonalcoholic fatty liver disease (NAFLD) is a global metabolic disease that comprises a broad spectrum of liver dysfunction ranging from nonalcoholic fatty liver (NAFL) to nonalcoholic steatohepatitis (NASH) with fibrosis. It is largely unknown how the communication between hepatocytes and non-parenchymal cells dictates the disease progression from NAFL to NASH and fibrosis. Dysregulation of protein O-GlcNAcylation in hepatocytes has been implicated in a wide range of liver diseases. In this study, we demonstrate the role of O‑GlcNAc transferase (OGT) in mediating intercellular crosstalk between hepatocytes and immune cells in NASH-fibrosis development. RNA-sequencing analysis of wildtype and hepatocyte-specific OGT knockout mice was performed and trefoil factor 2 (TFF2) was identified as one of the highly induced genes encoding secreted proteins in OGT-deficient hepatocytes. Immunohistochemistry and western blot were performed to reveal decreased OGT and increased TFF2 expression in the liver of NAFLD patients. Mechanically, OGT was found to repress TFF2 transcription in hepatocytes by modifying forkhead box protein A2 (FOXA2). Recombinant TFF2 along with NASH stimuli was applied to a 3D spheroid culture system comprised of hepatocytes and non-parenchymal cells and TFF2 was shown to promote NASH stimuli-induced triglyceride secretion and elevate the expression of pro-inflammatory and fibrogenic genes. ELISA and RT-qPCR were performed to further show that TFF2 treatment induced the expression of Th1-type cytokines (IFN-γ and TNF-α) and Th17-type cytokine (IL17) in CD4 T cells, promoting Th1 and Th17 differentiation. Collectively, these results identify an OGT-TFF2 axis that mediates the crosstalk between hepatocytes and CD4 T cells during NASH pathogenesis, revealing a potential therapeutic target for the treatment of chronic liver disease. Disclosure L. Zhang: None. Q. Wang: None. R. Desrouleaux: None. X. Yang: None. Funding American Diabetes Association (1-19-IBS-119 to X.Y.); National Institutes of Health (R01DK089098, P30DK34989)

GAS5 protects against nonalcoholic fatty liver disease via miR-28a-5p/MARCH7/NLRP3 axis-mediated pyroptosis.

Nonalcoholic fatty liver disease (NAFLD) is characterised by hepatic steatosis, inflammation, and insulin resistance. The role of long noncoding RNA (lncRNA)-regulated pyroptosis in NAFLD development remains largely unknown. This study aimed to investigate whether NAFLD development is controlled by lncRNA growth-arrest specific transcript 5 (GAS5)/miR-28a-5p/membrane associated ring-CH-type finger 7 (MARCH7)-mediated pyroptosis using in vivo and in vitro models. First, GAS5 expression was decreased but miR-28a-5p expression was increased in the livers of NAFLD patients, high-fat diet (HFD)-fed mice and leptin-deficient obese (Ob/Ob) mice. Furthermore, GAS5 suppressed while miR-28a-5p promoted NAFLD development, and overexpression of miR-28a-5p reversed the GAS5 overexpression-induced attenuation of NAFLD. Mechanistically, GAS5 served as a sponge of miR-28a-5p, and miR-28a-5p enhanced pyroptosis by targeting the 3' untranslated region (UTR) of the E3 ligase MARCH7 during NAFLD development. MARCH7 interacted with the NOD-like receptor protein 3 (NLRP3) protein, resulting in proteasomal degradation of NLRP3 to inhibit pyroptosis. As expected, MARCH7 knockdown abolished the miR-28a-5p knockdown-induced inhibition of NAFLD development, and the ubiquitin E3 ligase-inactive mutant (W589A/I556A) of MARCH7 failed to inhibit NAFLD development. In conclusion, GAS5 protected against NAFLD development by binding to miR-28a-5p, miR-28a-5p promoted NAFLD development by targeting MARCH7, and MARCH7 ameliorated NAFLD by suppressing NLRP3-mediated pyroptosis. The GAS5/miR-28a-5p/MARCH7/NLRP3 axis plays an important role in NAFLD progression, and it might be a biomarker for NAFLD.

Detrimental role of SIX1 in hepatic lipogenesis and fibrosis of non-alcoholic fatty liver disease.

Nonalcoholic fatty liver disease (NAFLD) is the most common liver disease worldwide. Aberrant lipid metabolism and accumulation of extracellular matrix proteins are hallmarks of the disease, but the underlying mechanisms are largely unknown. This study aims to elucidate the key role of sine oculis homeobox homologue 1 (SIX1) in the development of NAFLD. Alb-Cre mice were administered the AAV9 vector for SIX1 liver-specific overexpression or knockdown. Metabolic disorders, hepatic steatosis, and inflammation were monitored in mice fed with HFHC or MCD diet. High throughput CUT&Tag analysis was employed to investigate the mechanism of SIX1 in diet-induced steatohepatitis. Here, we found increased SIX1 expression in the livers of NAFLD patients and animal models. Liver-specific overexpression of SIX1 using adeno-associated virus serotype 9 (AAV9) provoked more severe inflammation, metabolic disorders, and hepatic steatosis in the HFHC or MCD-induced mice model. Mechanistically, we demonstrated that SIX1 directly activated the expression of liver X receptor α (LXRα) and liver X receptor β (LXRβ), thus inducing de novo lipogenesis (DNL). In addition, our results also illustrated a critical role of SIX1 in regulating the TGF-β pathway by increasing the levels of type I and II TGF-β receptor (TGFβRI/TGFβRII) in hepatic stellate cells (HSCs). Finally, we found that liver-specific SIX1 deficiency could ameliorate diet-induced NAFLD pathogenesis. Our findings suggest a detrimental function of SIX1 in the progression of NAFLD. The direct regulation of LXRα/β and TGF-β signalling by SIX1 provides a new regulatory mechanism in hepatic steatosis and fibrosis.

The essential effect of mTORC1-dependent lipophagy in non-alcoholic fatty liver disease.

Non-alcoholic fatty liver disease (NAFLD) is a chronic progressive liver disease with increasing prevalence. Lipophagy is a type of programmed cell death that plays an essential role in maintaining the body's balance of fatty acid metabolism. However, the livers of NAFLD patients are abnormally dysregulated in lipophagy. mTORC1 is a critical negative regulator of lipophagy, which has been confirmed to participate in the process of lipophagy through various complex mechanisms. Therefore, targeting mTORC1 to restore failed autophagy may be an effective therapeutic strategy for NAFLD. This article reviews the main pathways through which mTORC1 participates in the formation of lipophagy and the intervention effect of mTORC1-regulated lipophagy in NAFLD, providing new therapeutic strategies for the prevention and treatment of NAFLD in the future.

Berberine alleviates non-alcoholic hepatic steatosis partially by promoting SIRT1 deacetylation of CPT1A in mice.

Berberine effectively alleviates non-alcoholic fatty liver disease (NAFLD). Nevertheless, the mechanism is incompletely comprehended. It has been reported that SIRT1 mediates lipid metabolism in liver and berberine promotes the expression of SIRT1 in hepatocytes. We hypothesized that SIRT1 mediated the effect of berberine on NAFLD. The effects of berberine on NAFLD were evaluated in C57BL/6J mice fed a high-fat diet (HFD) and in mouse primary hepatocytes and cell lines exposed to palmitate. The change of fatty acid oxidation (FAO) and the activity of CPT1A were observed in HepG2 cells. Quantitative real-time polymerase chain reaction and Western blot were employed to observe the expression of SIRT1 and lipid metabolism-related molecules. The interaction between SIRT1 and CPT1A was investigated by using co-immunoprecipitation assay in HEK293T cells. Berberine treatment attenuated hepatic steatosis, reduced triglyceride (190.1 ± 11.2 μmol/g liver vs 113.6 ± 7.6 μmol/g liver, P < 0.001) and cholesterol (11.3 ± 2.5 μmol/g liver vs 6.3 ± 0.4 μmol/g liver, P < 0.001) concentration in the liver, and improved lipid and glucose metabolism disorders compared with the HFD group. The expression of SIRT1 was reduced in the liver of NAFLD patients and mouse models. Berberine increased the expression of SIRT1 and promoted the protein level of CPT1A and its activity in HepG2 cells. SIRT1 overexpression mimicked the effect of berberine on reducing triglyceride levels in HepG2 cells, whereas SIRT1 knock-down attenuated the effect of berberine. Mechanistically, berberine increased the expression of SIRT1. SIRT1 deacetylated CPT1A at the Lys675 site, which suppressed its ubiquitin-dependent degradation, thereby promoting FAO and alleviating non-alcoholic liver steatosis. Berberine promoted SIRT1 deacetylation of CPT1A at the Lys675 site, which reduced the ubiquitin-dependent degradation of CPT1A and ameliorated non-alcoholic liver steatosis.

RGS7-ATF3-Tip60 Complex Promotes Hepatic Steatosis and Fibrosis by Directly Inducing TNFα.

Aims: The pathophysiological mechanism(s) underlying non-alcoholic fatty liver disease (NAFLD) have yet to be fully delineated and only a single drug, peroxisome proliferator-activated receptor (PPAR) α/γ agonist saroglitazar, has been approved. Here, we sought to investigate the role of Regulator of G Protein Signaling 7 (RGS7) in hyperlipidemia-dependent hepatic dysfunction. Results: RGS7 is elevated in the livers of NAFLD patients, particularly those with severe hepatic damage, pronounced insulin resistance, and high inflammation. In the liver, RGS7 forms a unique complex with transcription factor ATF3 and histone acetyltransferase Tip60, which is implicated in NAFLD. The removal of domains is necessary for ATF3/Tip60 binding compromises RGS7-dependent reactive oxygen species generation and cell death. Hepatic RGS7 knockdown (KD) prevented ATF3/Tip60 induction, and it provided protection against fibrotic remodeling and inflammation in high-fat diet-fed mice translating to improvements in liver function. Hyperlipidemia-dependent oxidative stress and metabolic dysfunction were largely reversed in RGS7 KD mice. Interestingly, saroglitazar failed to prevent RGS7/ATF3 upregulation but it did partially restore Tip60 levels. RGS7 drives the release of particularly tumor necrosis factor α (TNFα) from isolated hepatocytes, stellate cells and its depletion reverses steatosis, oxidative stress by direct TNFα exposure. Conversely, RGS7 overexpression in the liver is sufficient to trigger oxidative stress in hepatocytes that can be mitigated via TNFα inhibition. Innovation: We discovered a novel non-canonical function for an R7RGS protein, which usually functions to regulate G protein coupled receptor (GPCR) signaling. This is the first demonstration for a functional role of RGS7 outside the retina and central nervous system. Conclusion: RGS7 represents a potential novel target for the amelioration of NAFLD. Antioxid. Redox Signal. 38, 137-159.

An Update on the Chemokine System in the Development of NAFLD.

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease in the world. Sustained hepatic inflammation is a key driver of the transition from simple fatty liver to nonalcoholic steatohepatitis (NASH), the more aggressive form of NAFLD. Hepatic inflammation is orchestrated by chemokines, a family of chemoattractant cytokines that are produced by hepatocytes, Kupffer cells (liver resident macrophages), hepatic stellate cells, endothelial cells, and vascular smooth muscle cells. Over the last three decades, accumulating evidence from both clinical and experimental investigations demonstrated that chemokines and their receptors are increased in the livers of NAFLD patients and that CC chemokine ligand (CCL) 2 and CCL5 in particular play a pivotal role in inducing insulin resistance, steatosis, inflammation, and fibrosis in liver disease. Cenicriviroc (CVC), a dual antagonist of these chemokines’ receptors, CCR2 and CCR5, has been tested in clinical trials in patients with NASH-associated liver fibrosis. Additionally, recent studies revealed that other chemokines, such as CCL3, CCL25, CX3C chemokine ligand 1 (CX3CL1), CXC chemokine ligand 1 (CXCL1), and CXCL16, can also contribute to the pathogenesis of NAFLD. Here, we review recent updates on the roles of chemokines in the development of NAFLD and their blockade as a potential therapeutic approach.

Down-Regulating the High Level of 17-Beta-Hydroxysteroid Dehydrogenase 13 Plays a Therapeutic Role for Non-Alcoholic Fatty Liver Disease.

Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease worldwide, and there is no specific drug to treat it. Recent results showed that 17-beta-hydroxysteroid dehydrogenase type 13 (HSD17B13) is associated with liver diseases, but these conclusions are controversial. Here, we showed that HSD17B13 was more highly expressed in the livers of NAFLD patients, and high expression was induced in the livers of murine NAFLD models and cultural hepatocytes treated using various etiologies. The high HSD17B13 expression in the hepatocytes facilitated the progression of NAFLD by directly stabilizing the intracellular lipid drops and by indirectly activating hepatic stellate cells. When HSD17B13 was overexpressed in the liver, it aggravated liver steatosis and fibrosis in mice fed with a high-fat diet, while down-regulated the high expression of HSD17B13 by short hairpin RNAs produced a therapeutic effect in the NAFLD mice. We concluded that high HSD17B13 expression is a good target for the development of drugs to treat NAFLD.

Pemafibrate Ameliorates Liver Dysfunction and Fatty Liver in Patients with Non-Alcoholic Fatty Liver Disease with Hypertriglyceridemia: A Retrospective Study with the Outcome after a Mid-Term Follow-Up.

Non-alcoholic fatty liver disease (NAFLD) is a chronic liver disease related to metabolic syndrome. No standard pharmacological treatment has yet been established. We retrospectively evaluated the efficacy of pemafibrate in 16 NAFLD patients (11 men and 5 women; median age, 59 years; range, 27–81 years) who had taken pemafibrate for at least one year. They were all diagnosed with fatty liver according to imaging and clinical criteria. They were administered pemafibrate from October 2018 to October 2021 (median, 94 weeks; range, 56–157 weeks). Serum triglyceride was significantly decreased by −41.9% (342.3 ± 54.0 to 198.9 ± 20.4 mg/dL, p < 0.001). Aspartate aminotransferase (AST), alanine aminotransferase, and gamma-glutamyl transferase levels significantly decreased by −42.1% (49.6 ± 7.0 to 28.7 ± 3.4 U/L, p < 0.001), −57.1% (65.1 ± 10.8 to 27.9 ± 3.7 U/L, p < 0.001), and −43.2% (68.9 ± 10.9 to 39.1 ± 5.3 U/L, p < 0.05), respectively. The AST to platelet ratio (APRI) (0.8 ± 0.1 to 0.4 ± 0.1, p < 0.001) and fibrosis based on four factors (FIB-4) index (1.8 ± 0.3 to 1.4 ± 0.2, p < 0.05) also significantly decreased. Liver attenuation (39.1 ± 1.2 to 57.8 ± 2.7 HU, p = 0.028) and liver/spleen ratio (0.76 ± 0.04 to 1.18 ± 0.02, p = 0.012) significantly improved in three patients, as assessed by computed tomography. In conclusion, pemafibrate significantly improves serum triglyceride levels, liver function, FIB-4 index, APRI, and fatty liver in NAFLD patients with hypertriglyceridemia.

Adenosine deaminase 2 produced by infiltrative monocytes promotes liver fibrosis in nonalcoholic fatty liver disease.

SUMMARYElevated circulating activity of adenosine deaminase 2 (ADA2) is associated with liver fibrosis in nonalcoholic fatty liver disease (NAFLD). In the liver of NAFLD patients, ADA2-positive portal macrophages are significantly associated with the degree of liver fibrosis. These liver macrophages are CD14- and CD16-positive and co-express chemokine receptors CCR2, CCR5, and CXCR3, indicating infiltrative monocyte origin. Human circulatory monocytes release ADA2 upon macrophage differentiation in vitro. When stimulated by recombinant human ADA2 (rhADA2), human monocyte-derived macrophages demonstrate upregulation of pro-inflammatory and pro-fibrotic genes, including PDGF-B, a key pro-fibrotic cytokine. This PDGF-B upregulation is reproduced by inosine, the enzymatic product of ADA2, but not adenosine, and is abolished by E359N, a loss-of-function mutation in ADA2. Finally, rhADA2 also stimulates PDGF-B production from Kupffer cells in primary human liver spheroids. Together, these data suggest that infiltrative monocytes promote fibrogenesis in NAFLD via ADA2-mediated autocrine/paracrine signaling culminating in enhanced PDGF-B production.

GADD45β stabilized by direct interaction with HSP72 ameliorates insulin resistance and lipid accumulation

Growth arrest and DNA damage-inducible 45β (GADD45β) belongs to the GADD45 family which is small acidic proteins in response to cellular stress. GADD45β has already been reported to have excellent capabilities against cancer, innate immunity and neurological diseases. However, there is little information regard GADD45β and non-alcoholic fatty liver disease (NAFLD). In the current work, we found that the expression of GADD45β was markedly decreased in the livers of NAFLD patients via analyzing Gene Expression Omnibus (GEO) dataset and in mouse model through detecting its mRNA in high-fat-high-fructose diet (HFHFr)-fed mice. Moreover, the results from in vivo experiment demonstrated that overexpression of GADD45β by AAV8-mediated gene transfer in HFHFr-fed mouse model could reduce the level of serum and hepatic triglyceride (TG), and alleviate insulin resistance. Subsequently, by combining immunoprecipitation (IP) and mass spectrometry, we identified that HSP72 directly interacted with GADD45β to prevent GADD45β from being degraded by the proteasome pathway. Finally, the benefits of GADD45β in regulating key factors of TG synthesis and insulin signaling pathway were abolished after HSP72 knockdown. In conclusion, GADD45β stabilized by the interaction with HSP72 could alleviate the NAFLD-related pathologies, suggested it might be a potential target for the treatment of NAFLD.

The Role of Fatty Acids in Non-Alcoholic Fatty Liver Disease Progression: An Update.

Non-alcoholic fatty liver disease (NAFLD) is a major public health problem worldwide. NAFLD (both simple steatosis and steatohepatitis) is characterized by alterations in hepatic lipid metabolism, which may lead to the development of severe liver complications including cirrhosis and hepatocellular carcinoma. Thus, an exhaustive examination of lipid disorders in the liver of NAFLD patients is much needed. Mass spectrometry-based lipidomics platforms allow for in-depth analysis of lipid alterations in a number of human diseases, including NAFLD. This review summarizes the current research on lipid alterations associated with NAFLD and related complications, with special emphasis on the changes in long-chain and short-chain fatty acids levels in both serum and liver tissue, as well as in the hepatic expression of genes encoding the enzymes catalyzing lipid interconversions.

Impact of vitamin E on redox biomarkers in non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is the most common liver disorder in Western nations and characterized by excessive accumulation of lipids in the liver. In this narrative review, we summarize the evidence from human trials that free radical-induced oxidation of macromolecules, in particular of lipids, is a characteristic feature of NAFLD and non-alcoholic steatohepatitis (NASH). We further synthesize the data in the scientific literature describing the impact of vitamin E (mainly α-tocopherol) on concentrations of redox biomarkers in liver biopsies from patients with NAFLD as well as animal experiments. In summary, the available evidence from clinical trials suggests that reactive species-mediated damage to macromolecules, predominantly lipids, occurs in NAFLD and NASH and that daily supplementation with at least 200 I.U. α-tocopherol may alleviate oxidative stress in the liver of NAFLD patients. We propose α-tocopherol as a useful model substance to identify and validate suitable redox biomarkers that may be employed in future clinical trials of new therapeutics for NAFLD.

Silencing hepatic MCJ attenuates non-alcoholic fatty liver disease (NAFLD) by increasing mitochondrial fatty acid oxidation

Nonalcoholic fatty liver disease (NAFLD) is considered the next major health epidemic with an estimated 25% worldwide prevalence. No drugs have yet been approved and NAFLD remains a major unmet need. Here, we identify MCJ (Methylation-Controlled J protein) as a target for non-alcoholic steatohepatitis (NASH), an advanced phase of NAFLD. MCJ is an endogenous negative regulator of the respiratory chain Complex I that acts to restrain mitochondrial respiration. We show that therapeutic targeting of MCJ in the liver with nanoparticle- and GalNAc-formulated siRNA efficiently reduces liver lipid accumulation and fibrosis in multiple NASH mouse models. Decreasing MCJ expression enhances the capacity of hepatocytes to mediate β-oxidation of fatty acids and minimizes lipid accumulation, which results in reduced hepatocyte damage and fibrosis. Moreover, MCJ levels in the liver of NAFLD patients are elevated relative to healthy subjects. Thus, inhibition of MCJ emerges as an alternative approach to treat NAFLD.

Hypoxia-inducible factor 2α drives hepatosteatosis through the fatty acid translocase CD36.

Background & AimsMolecular mechanisms by which hypoxia might contribute to hepatosteatosis, the earliest stage in non‐alcoholic fatty liver disease (NAFLD) pathogenesis, remain still to be elucidated. We aimed to assess the impact of hypoxia‐inducible factor 2α (HIF2α) on the fatty acid translocase CD36 expression and function in vivo and in vitro.MethodsCD36 expression and intracellular lipid content were determined in hypoxic hepatocytes, and in hypoxic CD36‐ or HIF2α ‐silenced human liver cells. Histological analysis, and HIF2α and CD36 expression were evaluated in livers from animals in which von Hippel‐Lindau (Vhl) gene is inactivated (Vhlf/f‐deficient mice), or both Vhl and Hif2a are simultaneously inactivated (Vhlf/fHif2α/f‐deficient mice), and from 33 biopsy‐proven NAFLD patients and 18 subjects with histologically normal liver.ResultsIn hypoxic hepatocytes, CD36 expression and intracellular lipid content were augmented. Noteworthy, CD36 knockdown significantly reduced lipid accumulation, and HIF2A gene silencing markedly reverted both hypoxia‐induced events in hypoxic liver cells. Moreover livers from Vhlf/f‐deficient mice showed histologic characteristics of non‐alcoholic steatohepatitis (NASH) and increased CD36 mRNA and protein amounts, whereas both significantly decreased and NASH features markedly ameliorated in Vhlf/fHif2αf/f‐deficient mice. In addition, both HIF2α and CD36 were significantly overexpressed within the liver of NAFLD patients and, interestingly, a significant positive correlation between hepatic transcript levels of CD36 and erythropoietin (EPO), a HIF2α ‐dependent gene target, was observed in NAFLD patients.ConclusionsThis study provides evidence that HIF2α drives lipid accumulation in human hepatocytes by upregulating CD36 expression and function, and could contribute to hepatosteatosis setup.

Disruption of Plin5 degradation by CMA causes lipid homeostasis imbalance in NAFLD.

The pathological hallmark of nonalcoholic fatty liver disease (NAFLD) is an imbalance in hepatic lipid homeostasis, in which lipophagy has been found to play a vital role. However, the underlying molecular mechanisms remain unclear. We investigated the role of chaperone-mediated autophagy (CMA) in the pathogenesis of NAFLD. CMA activity was evaluated in liver tissues from NAFLD patients and high-fat diet (HFD)-fed mice. Liver-specific LAMP2A-knockout mice and HepG2 cells lacking LAMP2A [L2A(-) cells] were used to investigate the influence of CMA on lipolysis in hepatocytes. The expression of Plin5, a lipid droplet (LD)-related protein, was also evaluated in human and mouse liver tissues and in [L2A(-)] cells. Here, we found disrupted CMA function in the livers of NAFLD patients and animal models, displaying obvious reduction of LAMP2A and concurrent with decreased levels of CMA-positive regulators. More LDs and higher serum triglycerides accumulated in liver-specific LAMP2A-knockout mice and L2A(-) cells under high-fat challenge. Meanwhile, deleting LAMP2A hindered LD breakdown but not increased LD formation. In addition, the LD-associated protein Plin5 is a CMA substrate, and its degradation through CMA is required for LD breakdown. We propose that the disruption of CMA-induced Plin5 degradation obstacles LD breakdown, explaining the lipid homeostasis imbalance in NAFLD.

EX-527 Prevents the Progression of High-Fat Diet-Induced Hepatic Steatosis and Fibrosis by Upregulating SIRT4 in Zucker Rats.

Sirtuin (SIRT) is known to prevent nonalcoholic fatty liver disease (NAFLD); however, the role of SIRT4 in the progression of hepatic fibrosis remains unknown. We hypothesize that EX-527, a selective SIRT1 inhibitor, can inhibit the progression of high-fat diet (HFD)-induced hepatic fibrosis. We found that SIRT4 expression in the liver of NAFLD patients is significantly lower than that in normal subjects. In this study, EX-527 (5 µg/kg), administered to HFD rats twice a week for ten weeks, reduced the serum levels of triglyceride (TG), total cholesterol, alanine aminotransferase (ALT), and aspartate aminotransferase (AST) and attenuated hepatic fibrosis evidenced by Masson’s trichrome and hepatic fat by oil red-O staining. EX-527 upregulated SIRT2, SIRT3, and SIRT4 expression in the liver of HFD fed rats but downregulated transforming growth factor-β1 (TGF-β1) and α-smooth muscle actin (α-SMA) expression. It decreased proinflammatory cytokine production and hydroxyproline levels in the serum and SMAD4 expression and restored apoptotic protein (Bcl-2, Bax, and cleaved caspase-3) expression. These data propose a critical role for the SIRT4/SMAD4 axis in hepatic fibrogenesis. SIRT4 upregulation has the potential to counter HFD-induced lipid accumulation, inflammation, and fibrogenesis. We demonstrate that EX-527 is a promising candidate in inhibiting the progression of HFD-induced liver fibrosis.