Progression Of Hepatic Steatosis Research Articles

The role of inflammation induced by necroptosis in the development of fibrosis and liver cancer in novel knockin mouse models fed a western diet.

Non-resolving, chronic inflammation (inflammaging) is believed to play an important role in aging and age-related diseases. The goal of this study was to determine if inflammation induced by necroptosis arising from the liver plays a role in chronic liver disease (CLD) and liver cancer in mice fed a western diet (WD). Necroptosis was induced in liver using two knockin (KI) mouse models that overexpress genes involved in necroptosis (Ripk3 or Mlkl) specifically in liver (i.e., hRipk3-KI and hMlkl-KI mice). These mice and control mice (not overexpressing Ripk3 or Mlkl) were fed a WD (high in fat, sucrose, and cholesterol) starting at 2months of age for 3, 6, and 12months. Feeding the WD induced necroptosis in the control mice, which was further elevated in the hRipk3-KI and hMlkl-KI mice and was associated with a significant increase in inflammation in the livers of the hRipk3-KI and hMlkl-KI mice compared to control mice fed the WD. Overexpressing Ripk3 or Mlkl significantly increased steatosis and fibrosis compared to control mice fed the WD. Mice fed the WD for 12months developed liver tumors (hepatocellular adenomas): 28% of the control mice developing tumors compared to 62% of the hRipk3-KI and hMlkl-KI mice. The hRipk3-KI and hMlkl-KI mice showed significantly more and larger tumor nodules. Our study provides the first direct evidence that inflammation induced by necroptosis arising from hepatocytes can lead to the progression of hepatic steatosis to fibrosis in obese mice that eventually results in an increased incidence in hepatocellular adenomas.

Chemogenetic activation of hepatic G12 signaling ameliorates hepatic steatosis and obesity

ObjectiveHepatic steatosis, the early stage of nonalcoholic fatty liver disease (NAFLD), currently lacks targeted pharmacological treatments. G protein-coupled receptors (GPCRs) in hepatocytes differentially regulate lipid metabolism depending on their coupling profile of G protein subtypes. Unlike Gs, Gi, and Gq signaling, the role of G12 signaling in hepatic steatosis remains elusive. The objective of this study was to investigate the effect of G12 signaling on hepatic steatosis and obesity and its mechanisms. MethodsWe generated mice expressing a G12-coupled designer GPCR in a liver-specific manner. We performed phenotypic analysis in the mice under the condition of fasting (acute hepatic steatosis model) or high-fat diet feeding (chronic hepatic steatosis model). ResultsIn acute and chronic hepatic steatosis models, chemogenetic activation of hepatic G12 signaling suppressed the progression of hepatic steatosis. The treatment led to an increased triglyceride secretion with little effect on mitochondrial respiratory activity, fatty acid oxidation, de novo lipogenesis, and fatty acid uptake. Furthermore, in a high-fat-diet-induced obesity model, activation of the G12-coupled designer GPCR exerted anti-obesity effects with increased whole-body energy expenditure and fat oxidation. Anti-FGF21 antibody treatment showed that the anti-obesity effects of the hepatic G12D activation relied in part on the hepatokine FGF21. ConclusionsOur findings indicate that the activation of G12 signaling in the liver has the potential to prevent hepatic steatosis and obesity. This discovery provides a strong rationale for the development of drugs targeting G12-coupled GPCRs expressed in the liver.

Evaluating the efficacy of 8 non-invasive models in predicting MASLD and progression: a prospective study

BackgroundSelecting the optimal non-invasive diagnostic model for MASLD (Metabolic Dysfunction-Associated Steatosis Liver Disease) and steatosis progression is a critical issue given the variety of available models. We aimed to compare the performance of eight clinical prediction models for diagnosing and predicting the progression of hepatic steatosis using MRI-PDFF (Magnetic Resonance Imaging-Derived Proton Density Fat Fraction), and validate the findings with FibroScan and histopathological results.MethodsIn this study, 846 participants were initially enrolled, with 108 undergoing liver biopsy and 706 completing one-year follow-up, including 26 who underwent repeat biopsy. We calculated scores for eight clinical prediction models (FAST, KNAFLD, HSI, FLI, Liver Fat Score, Liver Fat Equation, BAAT, LAP) using collected clinical data and defined steatosis progression as a 30% relative increase in liver fat content (LFC) measured by MRI-PDFF. CAP(Controlled Attenuation Parameter) and LSM (Liver Stiffness Measurement) were obtained by Fibroscan. MRI-PDFF served as the reference standard for evaluating model accuracy, and sensitivity analyses were performed using liver biopsy and Fibroscan results.ResultsAmong the eight clinical models, NAS (nonalcoholic fatty liver disease activity score) showed higher correlation with the FAST and KNAFLD models (r: 0.62 and 0.52, respectively). Among the whole cohort (N = 846), KNAFLD was the best model for predicting different degrees of hepatic steatosis (AUC = 0.84). When the KNAFLD score was above 2.935, LFC was significantly higher (4.4% vs. 19.7%, P < 0.001). After 1 year of follow-up (N = 706), FAST performed best in predicting MASLD progression (AUC = 0.84); with dFAST > -0.02, LFC increased (8.6–10.9%, P < 0.05), mean LSM increased by 0.51 kPa, and with dFAST < -0.02, LFC significantly decreased (11.5–8.5%, P < 0.05), mean LSM and NAS decreased by 0.87 kPa and 0.76, respectively (both P < 0.05).ConclusionsMost models demonstrated good diagnostic and prognostic capabilities for hepatic steatosis, with FAST and KNAFLD showing particular promise as primary non-invasive tools in clinical practice.Trail RegistrationChinese Clinical Trial Registry NO: ChiCTR2100054743, Registered December 26, 2021.

Integrator complex subunit 6 promotes hepatocellular steatosis via β-catenin-PPARγ axis

Hepatic adipogenesis has common mechanisms with adipocyte differentiation such as PPARγ involvement and the induction of adipose tissue-specific molecules. A previous report demonstrated that integrator complex subunit 6 (INTS6) is required for adipocyte differentiation. This study aimed to investigate INTS6 expression and its role in hepatic steatosis progression. The expression of INTS6 and PPARγ was examined in the liver of a mouse model of steatohepatitis and in paired liver biopsy samples from 11 patients with severe obesity and histologically proven metabolic dysfunction associated steatohepatitis (MASH) before and one year after bariatric surgery. To induce hepatocellular steatosis in vitro, an immortalized human hepatocyte cell line Hc3716 was treated with free fatty acids. In the steatohepatitis mouse model, we observed hepatic induction of INTS6, PPARγ, and adipocyte-specific genes. In contrast, β-catenin which negatively regulates PPARγ was reduced. Biopsied human livers demonstrated a strong positive correlation (r2 = 0.8755) between INTS6 and PPARγ mRNA levels. After bariatric surgery, gene expressions of PPARγ, FABP4, and CD36 were mostly downregulated. In our in vitro experiments, we observed a concentration-dependent increase in Oil Red O staining in Hc3716 cells after treatment with the free fatty acids. Alongside this change, the expression of INTS6, PPARγ, and adipocyte-specific genes was induced. INTS6 knockdown using siRNA significantly suppressed cellular lipid accumulation together with induction of β-catenin and PPARγ downregulation. Collectively, INTS6 expression closely correlates with PPARγ. INTS6 suppression significantly reduced hepatocyte steatosis via β-catenin-PPARγ axis, indicating that INTS6 could be a novel therapeutic target for treating MASH.

O-GlcNAcylation promotes the progression of nonalcoholic fatty liver disease by upregulating the expression and function of CD36

Background and aimsNonalcoholic fatty liver disease (NAFLD) and its progressive variant, nonalcoholic steatohepatitis (NASH), constitute a burgeoning worldwide epidemic with no FDA-approved pharmacotherapies. The multifunctional immunometabolic receptor, fatty acid translocase CD36 (CD36), plays an important role in the progression of hepatic steatosis. O-GlcNAcylation is a crucial posttranslational modification that mediates the distribution and function of CD36, but its involvement in NAFLD remains poorly understood. MethodsO-GlcNAcylation and CD36 expression were evaluated in human liver tissues obtained from NASH patients and normal control. Mice with hepatocyte-specific CD36 knockout were administered adeno-associated viral vectors expressing wild-type CD36 (WT-CD36) or CD36 O-GlcNAcylation site mutants (S468A&T470A-CD36) and were provided with a high-fat/high-cholesterol (HFHC) diet for 3 months. RT–qPCR analysis, immunoblotting, dual-luciferase reporter assays, chromatin immunoprecipitation, and coimmunoprecipitation were performed to explore the mechanisms by which O-GlcNAcylation regulates CD36 expression. Membrane protein extraction, immunofluorescence analysis, site-directed mutagenesis, and fatty acid uptake assays were conducted to elucidate the impact of O-GlcNAcylation on CD36 function. ResultsO-GlcNAcylation and CD36 expression were significantly increased in patients with NASH, mouse models of NASH, and palmitic acid-stimulated hepatocytes. Mechanistically, the increase in O-GlcNAcylation facilitated the transcription of CD36 via the NF-κB signalling pathway and stabilized the CD36 protein by inhibiting its ubiquitination, thereby promoting CD36 expression. On the other hand, O-GlcNAcylation facilitated the membrane localization of CD36, fatty acid uptake, and lipid accumulation. However, site-directed mutagenesis of residues S468 and T470 of CD36 reversed these effects. Furthermore, compared with their WT-CD36 counterparts, HFHC-fed S468A&T470A-CD36 mice exhibited decreases in systemic insulin resistance, steatosis severity, inflammation and fibrosis. Pharmacological inhibition of O-GlcNAcylation and CD36 also mitigated the progression of NASH. ConclusionsO-GlcNAcylation promotes the progression of NAFLD by upregulating CD36 expression and function. Inhibition of CD36 O-GlcNAcylation protects against NASH, highlighting a potentially effective therapeutic approach for individuals with NASH.

Dietary inflammatory index in relation to the progression of hepatic steatosis and liver fibrosis: evaluation by elastography/Fibroscan

One of the proposed mechanisms by which nutrition influences the progression of hepatic steatosis to fibrosis is inflammation. The study investigated how the inflammatory potential of the diet affects the risk of liver damage in patients with nonalcoholic fatty liver disease (NAFLD), a condition where fat accumulates in the liver. This cross-sectional study included 170 outpatients with newly diagnosed NAFLD. This study used a device called Fibroscan® to measure the degree of liver fibrosis, which is the scarring of the liver tissue due to chronic inflammation. The study also used a tool called the Dietary Inflammatory Index (DII) to measure the inflammatory potential of the diet based on the intake of different foods and nutrients. In the findings of the study, patients with more severe fat accumulation in the liver (hepatic steatosis) had higher DII scores, meaning they had more inflammatory diets. The study also found that higher DII scores were associated with higher weight and body mass index (BMI). One standard deviation (SD) increase in DII scores was associated with a 0.29 kilopascal (95% CI: 0.10–0.44; P-value 0.001) increase in the mean liver stiffness, an indicator of liver fibrosis. The study concluded that patients with higher DII scores had a higher risk of developing liver fibrosis than those with lower DII scores, even after adjusting for confounding factors (odds ratio: 5.89; P-value: 0.001). The study suggested that eating less inflammatory foods may help prevent or slow down the progression of hepatic steatosis and liver in patients with NAFLD.

Probiotic consumption and hepatic steatosis: results from the NHANES 2011-2016 and Mendelian randomization study.

Recent research showed that probiotics treatment may reduce insulin resistance, regulate lipid metabolism, raise liver enzyme levels, and ameliorate inflammation in individuals with metabolic associated fatty liver disease (MAFLD). However, the possible effects of probiotic use on the progression of hepatic steatosis (HS) have not been identified. The purpose of this study was to investigate this in a large population database. The cross-sectional research was conducted among adults with complete data on probiotic yogurt consumption and HS in the 2011-2016 National Health and Nutrition Examination Survey (NHANES). Probiotic yogurt consumption was assessed using a dietary supplement questionnaire, while HS was evaluated with HS index (HSI). To explore their relationship, weighted univariate regression analysis, subgroup analysis, and interaction analysis were conducted. To evaluate the causal association between yogurt consumption and NAFLD, mendelian randomization analysis (MR) were performed. A restricted cubic spline (RCS) was used to analyze the relationship curve between the leves of yogurt consumption and hepatic steatosis. A total of 7,891 participants were included in the study represented 146.7 million non-institutionalized residents of the United States, of whom 4,322 (54.77%) were diagnosed with HS. Multivariable logistic regression showed probiotic yogurt consumption had significantly inverse relationship for HS (OR = 0.84, 95% CI: 0.72-0.97, p = 0.02) after adjusting for all covariates. Once more, the independent relationship between probiotic yogurt consumption and HS was verified by subgroup analysis and interaction analysis. The MR analysis results indicate that there is no causal relationship between yogurt consumption and NAFLD. The RCS model demonstrated a robust J-shaped link between yogurt consumption and HS, revealing a significant decrease in risk within the lower range of yogurt consumption, which attained the lowest risk close to 0.4 cup. According to the NHANES data, the consumption of probiotics and yogurt has a beneficial effect on HS, whereas the MR results indicated it was not related to NAFLD. The RCS analysis indicates a J-shaped relationship between yogurt consumption and HS, which may account for the inconsistency in the results. Based on these findings, we recommend that adults take half a cup of yogurt daily.

Evolutive Models, Algorithms and Predictive Parameters for the Progression of Hepatic Steatosis.

The utilization of evolutive models and algorithms for predicting the evolution of hepatic steatosis holds immense potential benefits. These computational approaches enable the analysis of complex datasets, capturing temporal dynamics and providing personalized prognostic insights. By optimizing intervention planning and identifying critical transition points, they promise to revolutionize our approach to understanding and managing hepatic steatosis progression, ultimately leading to enhanced patient care and outcomes in clinical settings. This paradigm shift towards a more dynamic, personalized, and comprehensive approach to hepatic steatosis progression signifies a significant advancement in healthcare. The application of evolutive models and algorithms allows for a nuanced characterization of disease trajectories, facilitating tailored interventions and optimizing clinical decision-making. Furthermore, these computational tools offer a framework for integrating diverse data sources, creating a more holistic understanding of hepatic steatosis progression. In summary, the potential benefits encompass the ability to analyze complex datasets, capture temporal dynamics, provide personalized prognostic insights, optimize intervention planning, identify critical transition points, and integrate diverse data sources. The application of evolutive models and algorithms has the potential to revolutionize our understanding and management of hepatic steatosis, ultimately leading to improved patient outcomes in clinical settings.

FoxO6-Mediated TXNIP Induces Lipid Accumulation in the Liver through NLRP3 Inflammasome Activation.

Hepatic steatosis, which involves the excessive accumulation of lipid droplets in hepatocytes, presents a significant global health concern due to its association with obesity and metabolic disorders. Inflammation plays a crucial role in the progression of hepatic steatosis; however, the precise molecular mechanisms responsible for this process remain unknown. This study investigated the involvement of the nucleotide-binding oligomerization domain-like receptor pyrin domain-containing-3 (NLRP3) inflammasome and the forkhead box O6 (FoxO6) transcription factor in the pathogenesis of hepatic steatosis. We monitored the NLRP3 inflammasome and lipogenesis in mice overexpressing the constitutively active (CA)-FoxO6 allele and FoxO6-null mice. In an in vitro study, we administered palmitate to liver cells overexpressing CA-FoxO6 and measured changes in lipid metabolism. We administered palmitate treatment to clarify the mechanisms through which FoxO6 activates cytokine interleukin (IL)-1β through the NLRP3 inflammasome. The initial experiments revealed that dephosphorylation led to palmitate-induced FoxO6 transcriptional activity. Further palmitate experiments showed increased expression of IL-1β and the hepatic NLRP3 inflammasome complex, including adaptor protein apoptotic speck protein containing a caspase recruitment domain (ASC) and pro-caspase-1. Furthermore, thioredoxin-interacting protein (TXNIP), a key regulator of cellular redox conditions upstream of the NLRP3 inflammasome, was induced by FoxO6 in the liver and HepG2 cells. The findings of this study shed light on the molecular mechanisms underpinning the FoxO6-NLRP3 inflammasome axis in promoting inflammation and lipid accumulation in the liver.

The Role of SCAP/SREBP as Central Regulators of Lipid Metabolism in Hepatic Steatosis.

The prevalence of metabolic dysfunction-associated steatotic liver disease (MASLD) is rapidly increasing worldwide at an alarming pace, due to an increase in obesity, sedentary and unhealthy lifestyles, and unbalanced dietary habits. MASLD is a unique, multi-factorial condition with several phases of progression including steatosis, steatohepatitis, fibrosis, cirrhosis, and hepatocellular carcinoma. Sterol element binding protein 1c (SREBP1c) is the main transcription factor involved in regulating hepatic de novo lipogenesis. This transcription factor is synthesized as an inactive precursor, and its proteolytic maturation is initiated in the membrane of the endoplasmic reticulum upon stimulation by insulin. SREBP cleavage activating protein (SCAP) is required as a chaperon protein to escort SREBP from the endoplasmic reticulum and to facilitate the proteolytic release of the N-terminal domain of SREBP into the Golgi. SCAP inhibition prevents activation of SREBP and inhibits the expression of genes involved in triglyceride and fatty acid synthesis, resulting in the inhibition of de novo lipogenesis. In line, previous studies have shown that SCAP inhibition can resolve hepatic steatosis in animal models and intensive research is going on to understand the effects of SCAP in the pathogenesis of human disease. This review focuses on the versatile roles of SCAP/SREBP regulation in de novo lipogenesis and the structure and molecular features of SCAP/SREBP in the progression of hepatic steatosis. In addition, recent studies that attempt to target the SCAP/SREBP axis as a therapeutic option to interfere with MASLD are discussed.

6-Gingerol regulates triglyceride and cholesterol biosynthesis to improve hepatic steatosis in MAFLD by activating the AMPK-SREBPs signaling pathway

Excessive synthesis of triglycerides and cholesterol accelerates the progression of hepatic steatosis in metabolic-associated fatty liver disease (MAFLD). However, the precise mechanism by which 6-gingerol mitigates hepatic steatosis in MAFLD model mice has yet to be fully understood. The present study observed that 6-gingerol administration exhibited significant protective effects against obesity, insulin resistance, and hepatic steatosis in mice subjected to a high-fat diet (HFD), and mitigated lipid accumulation in HepG2 cells treated with palmitate (PA). Following the hepatic lipidomic analysis, we confirmed that the AMPK-SREBPs signaling pathway as the underlying molecular mechanism by which 6-gingerol inhibited triglyceride and cholesterol biosynthesis, both in vivo and in vitro, through Western blot and immunofluorescence assay. Additionally, the application of an AMPK agonist/inhibitor further validated that 6-gingerol promoted AMPK activation by increasing the phosphorylation level of AMPK in vitro. Notably, the inhibitory effect of 6-gingerol on cholesterol biosynthesis, rather than triglyceride biosynthesis, was significantly diminished after silencing SREBP2 using a lentiviral plasmid shRNA in HepG2 cells. Our study demonstrates that 6-gingerol mitigates hepatic triglyceride and cholesterol biosynthesis to alleviate hepatic steatosis by activating the AMPK-SREBPs signaling pathway, indicating that 6-gingerol may be a potential candidate in the therapy of MAFLD.

NME4 mediates metabolic reprogramming and promotes nonalcoholic fatty liver disease progression

Nonalcoholic fatty liver disease (NAFLD) is mainly characterized by excessive fat accumulation in the liver, and it is associated with liver-related complications and adverse systemic diseases. NAFLD has become the most prevalent liver disease; however, effective therapeutic agents for NAFLD are still lacking. We combined clinical data with proteomics and metabolomics data, and found that the mitochondrial nucleoside diphosphate kinase NME4 plays a central role in mitochondrial lipid metabolism. Nme4 is markedly upregulated in mice fed with high-fat diet, and its expression is positively correlated with the level of steatosis. Hepatic deletion of Nme4 suppresses the progression of hepatic steatosis. Further studies demonstrated that NME4 interacts with several key enzymes in coenzyme A (CoA) metabolism and increases the level of acetyl-CoA and malonyl-CoA, which are the major lipid components of the liver in NAFLD. Increased level of acetyl-CoA and malonyl-CoA lead to increased triglyceride levels and lipid accumulation in the liver. Taken together, these findings reveal that NME4 is a critical regulator of NAFLD progression and a potential therapeutic target for NAFLD.

Perilipin 5 protects the mitochondrial oxidative functions and improves the alcoholic liver injury in mice.

Alcohol consumption is a well-established risk factor for the onset and progression of hepatic steatosis. Perilipin 5 (Plin5), a lipid droplet protein, is an important protective factor against hepatic lipotoxicity induced by excessive lipolysis, but its role and molecular mechanism in alcoholic liver disease (ALD) are not fully elucidated. The optimized National Institute on Alcohol Abuse and Alcoholism model was used to construct ALD model mice. Automatic biochemical analyser was used for Biochemical Parameters. The primary hepatocytes and Plin5-overexpressed HepG2 cells (including full-length Plin5 and Plin5 deleting 444-464 aa) were used for invitro experiment. Haematoxylin and Eosin staining, Oil Red O staining, Bodipy 493/503 staining, Periodic Acid-Schiff staining, immunohistochemistry and JC-1 staining were used to evaluate cell morphology, lipids, glycogen, inflammation and membrane potential. Commercially kits are used to detect glycolipid metabolites, such as triglycerides, glycogen, glucose, reactive oxygen species, lactic acids, ketone bodies. Fluorescently labelled deoxyglucose, NBDG, was used for glucose intake. An XF96 extracellular flux analyser was used to determinate oxygen consumption rate in hepatocytes. The morphological and structural damage of mitochondria was evaluated by electron microscopy. Classical ultracentrifugation is used to separate the subcellular organelles of tissues and cells. Immunoblotting and qPCR were used to detect changes in mRNA and protein levels of related genes. Our results showed that the expression of Plin5 in mouse livers was enhanced by alcohol intake, and Plin5 deficiency aggravated the alcohol-induced liver injury. To clarify the mechanism, we found that Plin5 deficiency significantly elevated the hepatic NADH levels and ketone body production in the alcohol-treated mice. As NADH elevation could promote the reduction of pyruvate into lactate and then inhibit the gluconeogenesis, alcohol-treated Plin5-deficient mice exhibited more lactate production and severer hypoglycemia. These results implied that Plin5 deficiency impaired the mitochondrial oxidative functions in the presence of alcohol. In addition, we demonstrated that Plin5 could be recruited onto mitochondria by alcohol, while Plin5 without mitochondrial targeting sequences lost its mitochondrial protection functions. Collectively, this study demonstrated that the mitochondrial Plin5 could protect the alcohol-induced mitochondrial injury, which provides an important new insight on the roles of Plin5 in highly oxidative tissues.

DNMT3B Alleviates Liver Steatosis Induced by Chronic Low-grade LPS via Inhibiting CIDEA Expression

Nonalcoholic fatty liver disease is the most prevalent chronic liver disease and threats to human health. Gut dysbiosis caused by lipopolysaccharide (LPS) leakage has been strongly related to nonalcoholic fatty liver disease progression, although the underlying mechanisms remain unclear. Previous studies have shown that low-grade LPS administration to mice on a standard, low-fat chow diet is sufficient to induce symptoms of fatty liver. This study confirmed these findings and supported LPS as a lipid metabolism regulator in the liver. Mechanically, LPS induced dysregulated lipid metabolism by inhibiting the expression of DNA methyltransferases 3B (DNMT3B). Genetic overexpression of DNMT3B alleviated LPS-induced lipid accumulation, whereas its knockdown increased steatosis in mice and human hepatocytes. LPS-induced lower expression of DNMT3B led to hypomethylation in promoter region of CIDEA, resulting in increased binding of SREBP-1c to its promoter and activated CIDEA expression. Hepatic interference of CIDEA reversed the effect of LPS on lipogenesis. These effects were independent of a high-fat diet or high fatty acid action. Overall, these findings sustain the conclusion that LPS is a lipogenic factor and could be involved in hepatic steatosis progression.

Interleukin-13 (IL-13)-A Pleiotropic Cytokine Involved in Wound Healing and Fibrosis.

The liver, as a central metabolic organ, is systemically linked to metabolic-inflammatory diseases. In the pathogenesis of the metabolic syndrome, inflammatory and metabolic interactions between the intestine, liver, and adipose tissue lead to the progression of hepatic steatosis to metabolic-dysfunction-associated steatohepatitis (MASH) and consecutive MASH-induced fibrosis. Clinical and animal studies revealed that IL-13 might be protective in the development of MASH through both the preservation of metabolic functions and Th2-polarized inflammation in the liver and the adipose tissue. In contrast, IL-13-associated loss of mucosal gut barrier function and IL-13-associated enhanced hepatic fibrosis may contribute to the progression of MASH. However, there are only a few publications on the effect of IL-13 on metabolic diseases and possible therapies to influence them. In this review article, different aspects of IL-13-associated effects on the liver and metabolic liver diseases, which are partly contradictory, are summarized and discussed on the basis of the recent literature.

Tetrahydropalmatine ameliorates hepatic steatosis in nonalcoholic fatty liver disease by switching lipid metabolism via AMPK-SREBP-1c-Sirt1 signaling axis

BackgroundNonalcoholic fatty liver disease (NAFLD) is becoming a global epidemic without effective treatment currently available. NAFLD is characterized by an increase in hepatic de novo lipogenesis (DNL) and inadequate compensatory enhancement in fatty acid oxidation (FAO), which disturbs lipid homeostasis. In NAFLD, lipid metabolism relies heavily on metabolic reprogramming. Moreover, lipid metabolism plays an essential role in switching between lipogenesis and FAO, which is beneficial for the anti-NAFLD therapy. Our recent study demonstrated that the phytochemical tetrahydropalmatine (THP) has positive efficacy in hepatocellular carcinoma (HCC). However, it remains unclear whether the therapeutic benefits of THP are primarily due to delaying the progression of hepatic steatosis to HCC. PurposeThis work aimed to systemically evaluate the pharmacological functions and underlying mechanisms of THP in NAFLD using both in vitro and in vivo models. MethodsNAFLD models were established using high-fat diet (HFD)-fed mice in vivo and palmitic acid- and oleic acid-challenged hepatocytes in vitro. Metabonomics analysis concomitant with biochemical indices and computational biology assays were performed comprehensively to reveal the key link between the treatment of NAFLD and the AMPK-SREBP-1c-Sirt1 signaling axis. ResultsHepatic metabolomics analysis revealed that THP altered lipid metabolism by enhancing FAO and inhibiting glycolysis, tricarboxylic acid cycle, and urea cycle in HFD-fed mice. Analysis of gene expression showed that THP profoundly suppressed hepatic DNL and promoted FAO. THP supplementation not only significantly decreased body/liver weight gain and serum indices but also ameliorated hepatic steatosis. Simultaneously, impaired lipotoxicity was observed in vivo and in vitro after THP supplementation, protecting against steatosis-driven injury. Metabolic phenotype assays showed that THP promoted switching from glycolysis inhibition to FAO enhancement in steatotic cells, resulting in reprogramming lipid metabolism. Mechanistically, THP accelerated lipid oxidation by activating AMPK-SREBP-1c-Sirt1 axis signaling. Applying molecular docking combined with surface plasmon resonance and cellular thermal shift assay target engagement, as well as siRNA assays, AMPKα was confirmed as a direct molecular target of THP. ConclusionIn summary, THP ameliorates hepatic steatosis in NAFLD by switching lipid metabolism via the AMPK-SREBP-1c-Sirt1 pathway. This work provides an attractive phytochemical component for therapy against hepatic steatosis in NAFLD.

Hepatic Krüppel-like factor 14 regulates lipid metabolism in nonalcoholic steatohepatitis mice.

Excessive lipid accumulation is a critical characteristic in the development of nonalcoholic steatohepatitis (NASH). The underlying molecular mechanism, however, is unclear. In this study, we explored whether and how Krüppel-like factor 14 (KLF14) affects hepatic lipid metabolism in NASH. KLF14 expression was detected in NASH patients and mice fed a choline-deficient, L-amino acid-defined, high-fat diet (CDAHFD). Adeno-associated viruses and adenoviruses were used to alter hepatic KLF14 expression in vivo or in vitro to investigate how KLF14 functions in lipid regulation. The molecular mechanisms were explored using RNA-seq, luciferase reporter, and ChIP assays. The fatty liver phenotype was analyzed histopathologically, and serum and hepatocyte biochemical parameters were measured. The NASH mouse model developed quickly in C57BL/6J mice fed a CDAHFD for 8 weeks. We found that KLF14 expression was decreased in NASH patients and CDAHFD mice. Oleic acid and palmitic acid treatment also reduced KLF14 levels in hepatocytes. KLF14 knockdown downregulated the genes involved in fatty acid oxidation, promoting the progression of hepatic steatosis. In contrast, hepatic KLF14 overexpression alleviated lipid accumulation and oxidative stress in CDAHFD mice. These effects resulted from direct activation of the PPARα signaling pathway. PPARα inhibition diminished the KLF14 overexpression-reduced protective effects against steatosis in OA&PA-treated MPHs and AAV-KLF14-infected CDAHFD mice. These data reveal that hepatic KLF14 regulates lipid accumulation and oxidative stress through the KLF14-PPARα pathway as NASH progresses. KLF14 may be a novel therapeutic target for hepatic steatosis.

A lipidomic study: Nobiletin ameliorates hepatic steatosis through regulation of lipid alternation

Hepatic lipidome has been given emphasis for years since hepatic steatosis is the most remarkable character of nonalcoholic fatty liver diseases, an increasingly serious health issue worldwide. Nobiletin (NOB), one of the citrus flavonoids, exerted outstanding effect on lipid metabolism disorder. However, the underlying mechanism of NOB exerting effect on hepatic lipid alternation remains unclear. In this study, the animal model was built by feeding APOE−/− mice with high fat diet (HFD). The results of Oil Red O-stained liver section and the biochemical assay of lipid parameters confirmed the protective effect of NOB on hepatic steatosis and global lipid metabolism disorder in APOE−/− mice. The hepatic lipidomic study revealed a total of 958 lipids significantly altered by HFD and a total of 86, 116, 212 lipid metabolites changed by L-NOB (50 mg/kg/d NOB), M-NOB (100 mg/kg/d NOB) and H-NOB (200 mg/kg/d NOB) respectively. In the further screening analysis, an amount of 60 lipids were identified as the potential lipid markers of NOB treatment, most of which belonged to glycerophospholipids lipid categories and exhibited obvious correlation with each other and the lipid parameters related to hepatic steatosis. Taken together, our data demonstrated that glycerophospholipids metabolism played an indispensable role in the progression of hepatic steatosis and the protective effect of NOB. Besides, the modulation towards genes involved in lipid synthesis was observed after NOB administration in this study. These finding illustrated the antihepatic steatosis effect of NOB based on altering hepatic lipidome, particularly the glycerophospholipids metabolism, and provided a new insight in the pathogenesis of hepatic steatosis.

Cyanotoxin exposure and hepatocellular carcinoma

Cyanobacteria are ubiquitous in aquatic and terrestrial environments worldwide and include a number of species producing tumor-promoting hepatotoxins. Human exposure to cyanobacteria and cyanotoxins primarily occurs though ingestion of contaminated drinking water and food sources. In a Northeast U.S. population, we recently reported an independent association of oral cyanobacteria with risk of hepatocellular carcinoma (HCC). In a cross-sectional study of 55 HCC patients in Hawaii, U.S.A., serum microcystin/nodularin (MC/NOD), cylindrospermopsin (CYN), and anabaenopeptin (AB) were measured by ELISA. In a subset of 16 patients, cyanotoxin levels were compared by tumor expression of over 700 genes analyzed via the Nanostring nCounter Fibrosis panel. MC/NOD, CYN, and AB were detected in all HCC patients. MC/NOD and CYN levels significantly varied by etiology with the highest levels in cases attributed to metabolic risk factors, specifically, hyperlipidemia, type 2 diabetes, and non-alcoholic fatty liver disease/non-alcoholic steatohepatitis. Cyanotoxin levels were significantly positively correlated with tumor expression of genes functioning in PPAR signaling and lipid metabolism. Our study provides novel albeit limited evidence that cyanotoxins may a role in the pathogenesis of HCC through the dysregulation of lipid metabolism and progression of hepatic steatosis.

Lambda-cyhalothrin induces lipid accumulation in mouse liver is associated with AMPK inactivation.

Lambda-cyhalothrin (LCT) is a critical synthetic Type II pyrethroid insecticide widely applied. Several studies suggest pyrethroids could induce fat accumulation, promote adipogenesis, and impair liver function. Now, the influences of LCT on the hepatic lipid metabolism and the cellular mechanism is still unknown. AMPK has important function in regulating cellular energy balance. To indicate the potential pathogenesis of liver injury caused by LCT exposure, ICR mice were orally administrated with LCT at a dose of 0.4mg/kg and 2mg/kg. The results suggest that LCT induced obesity, dyslipidemia and hepatic steatosis. In addition, LCT also induced oxidative stress, liver function injury, and disorganized structure of the liver. Furthermore, upregulation of PPARγ, FASN, and SREBP1c expression, as well as reduction of PPARα and FGF21 expression, bringing with decreases of phosphorylated ratios of AMPK and ACC were found in LCT-L group. These results indicate that LCT at 0.4mg/kg could result in dyslipidemia and hepatic steatosis in mice. In addition, activation of AMPK in hepatocytes effectively attenuated the effects of LCT. The detailed mechanism of LCT-induced hepatic steatosis is associated with AMPK and its downsteam genes. Activation of AMPK might be a novel protection against the progression of hepatic steatosis induced by LCT.