Human fatty liver disease: old questions and new insights

Antioxidant action of xanthine oxidase inhibitor febuxostat protects the liver and blood vasculature in SHRSP5/Dmcr rats

BACKGROUND

Xanthine oxidase (XO) generates reactive oxygen species during uric acid production. Therefore, XO inhibitors, which suppress oxidative stress, may effectively treat non-alcoholic steatohepatitis (NASH) and atherosclerosis via uric acid reduction. In this study, we examined the antioxidant effect of the XO inhibitor febuxostat on NASH and atherosclerosis in stroke-prone spontaneously hypertensive 5 (SHRSP5/Dmcr) rats.

METHODS

SHRSP5/Dmcr rats were divided into three groups: SHRSP5/Dmcr + high-fat and high-cholesterol (HFC) diet [control group, n = 5], SHRSP5/Dmcr + HFC diet + 10% fructose (40 ml/day) [fructose group, n = 5], and SHRSP5/Dmcr + HFC diet + 10% fructose (40 ml/day) + febuxostat (1.0 mg/kg/day) [febuxostat group, n = 5]. Glucose and insulin resistance, blood biochemistry, histopathological staining, endothelial function, and oxidative stress markers were evaluated.

RESULTS

Febuxostat reduced the plasma uric acid levels. Oxidative stress-related genes were downregulated, whereas antioxidant factor-related genes were upregulated in the febuxostat group compared with those in the fructose group. Febuxostat also ameliorated inflammation, fibrosis, and lipid accumulation in the liver. Mesenteric lipid deposition decreased in the arteries, and aortic endothelial function improved in the febuxostat group.

CONCLUSIONS

Overall, the XO inhibitor febuxostat exerted protective effects against NASH and atherosclerosis in SHRSP5/Dmcr rats.

Taurine alleviated hepatic steatosis in oleic acid-treated-HepG2 cells and rats fed a high-fat diet

Taurine has been proven in many trials to alleviate the symptoms of metabolic associated fatty liver disease. Here its protective effect for hepatic steatosis and modulation of AMP-activated protein kinase and insulin signaling pathway were investigated. Steatotic HepG2 cell established with oleic acid (0.05 mmol/L), treated with taurine (5 mmol/L), dorsomorphin (10 μmol/L) for 24 h. Sprague Dawley rats were divided into regular and high-fat diet (HFD) groups, and their corresponding taurine (70 or 350 mg/kg BW/d) groups, fed for 8 weeks. In steatotic cell, taurine reduced the TG concentration and SREBP-1c, PPARγ, FAS, ACC, SCD1 protein levels, decreased phosphorylation of mTOR, IRS1 (Ser302), increased phosphorylation of AMPKα, LKB1, PI3K, Akt, ACC. While dorsomorphin eliminated taurine's TG-lowering effect. In HFD-fed rats, taurine reduced liver TG, serum TG, ALT, AST, IL-1β, IL-4, TNF-α. The effects of taurine on the main factors of fatty acid synthesis were mostly consistent with cell experiments, and the reduction of microRNAs (451, 33, 291b) was aligned with the improvement in LKB1 and AMPK expression in HFD rats. Taurine alleviated steatosis-induced inhibition of IRS1-PI3K-Akt pathway, but suppressed its positively regulated downstream factor mTOR. In parallel, taurine reduced steatosis by activating LKB1-AMPKα pathway via phosphorylation and no-phosphorylation manner, then inhibiting SREBP-1c directly or by suppressing mTOR phosphorylation.

GB1a Activates SIRT6 to Regulate Lipid Metabolism in Mouse Primary Hepatocytes

Lipid accumulation, oxidative stress, and inflammation in hepatocytes are features of nonalcoholic fatty liver disease (NAFLD). Garcinia biflavonoid 1a (GB1a) is a natural product capable of hepatic protection. In this study, the effect of GB1a on anti-inflammatory, antioxidant, and regulation of the accumulation in HepG2 cells and mouse primary hepatocytes (MPHs) was investigated, and its regulatory mechanism was further explored. The result showed that GB1a reduced triglyceride (TG) content and lipid accumulation by regulating the expression of SREBP-1c and PPARα; GB1a reduced reactive oxygen species (ROS) and improved cellular oxidative stress to protect mitochondrial morphology by regulating genes Nrf2, HO-1, NQO1, and Keap1; and GB1a reduced the damage of hepatocytes by inhibiting the expression of inflammatory cytokines interleukin-6 (IL-6), interleukin-1β (IL-1β), tumor necrosis factor-alpha (TNF-α), and nuclear factor kappa B (NF-κB) p65. The activities of GB1a were lost in liver SIRT6-specific knockout mouse primary hepatocytes (SIRT6-LKO MPHs). This indicated that activating SIRT6 was critical for GB1a to perform its activity, and GB1a acted as an agonist of SIRT6. It was speculated that GB1a may be a potential drug for NAFLD treatment.

Sulfosuccinimidyl oleate ameliorates the high-fat diet-induced obesity syndrome by reducing intestinal and hepatic absorption

Background: A high-fat Western diet is a risk factor for obesity and steatosis. Reducing intestinal absorption of a high-fat diet (HFD) is a feasible strategy to control obesity. Sulfosuccinimidyl oleate (SSO) inhibits intestinal fatty acid transport. Therefore, the aim of this study was to investigate the effects of SSO on HFD-induced glucose and lipid metabolism in mice and its possible underlying mechanisms. Methods: Male C57/BL were fed a HFD (60% calories) for 12 weeks and were administered an oral dose of SSO (50 mg/kg/day). The expression of lipid absorption genes (CD36, MTTP, and DGAT1) and the serum levels of triglycerides (TGs), total cholesterol (TC), and free fatty acids (FFAs) were detected. Lipid distribution in the liver was detected by oil red and hematoxylin and eosin staining. In addition, serum levels of inflammatory factors, alanine aminotransferase (ALT), and aspartate aminotransferase (AST) were measured to detect side effects. Results: SSO was effective in the treatment of obesity and metabolic syndrome induced by HFD in mice. It attenuated the assembly of intestinal epithelial chylomicrons by inhibiting intestinal epithelial transport and absorption of fatty acids, thereby reducing the gene expression levels of MTTP and DGAT1, resulting in decreased plasma TG and FFA levels. At the same time, it inhibited the transport of fatty acids in the liver and improved the steatosis induced by a HFD. The results of oil red staining showed that SSO treatment can reduce lipid accumulation in the liver by 70%, with no drug-induced liver injury detected on the basis of interleukin-6, C-reactive protein, ALT, and AST levels. In addition, SSO treatment significantly improved insulin resistance, decreased fasting blood glucose levels, and improved glucose tolerance in HFD-fed mice. Conclusion: SSO is effective in the treatment of obesity and metabolic syndrome induced by a HFD in mice. SSO reduces intestinal fatty acid absorption by reducing the inhibition of intestinal CD36 expression, followed by decreased TG and FFA levels, which attenuates HFD-induced fatty liver.

A new NASH model in aged mice with rapid progression of steatohepatitis and fibrosis

Non-alcoholic fatty liver disease (NAFLD) has a high prevalence worldwide, with a significant proportion of patients progressing into non-alcoholic steatohepatitis (NASH) and further into cirrhosis and hepatocellular carcinoma (HCC). Most of the current animal models of NASH have limitations, such as incompatibility with human pathogenesis characteristics or long induction periods, which severely limit the development of new drugs and preclinical studies for NASH. We investigated the progression of NASH and fibrosis, as well as metabolic indicators, at different time points in aged mice induced by the Gubra Amylin NASH (GAN) diet, a high-fat, high-sugar, high-cholesterol diet, and attempted to establish a rapid and useful mouse model of NASH. Young and aged C57BL/6 mice were induced on a normal chow or GAN diet for 12 and 21 weeks, respectively. After 12 weeks of induction, aged mice developed NASH, including hepatic steatosis, lobular inflammation and hepatic ballooning, and the phenotype was more severe compared with young mice. After 21 weeks of induction, aged mice developed hepatic fibrosis, which greatly shortened the induction time compared with young mice. Furthermore, analysis of immune cell infiltration in the liver by flow cytometry elucidated the changes of multiple immune cells during the pathogenesis of NASH. These findings suggest that aged mice may develop NASH and fibrosis more rapidly under GAN diet induction, which may significantly shorten the period for preclinical studies of NASH.

The role of pyroptosis in inflammatory diseases

Programmed cell death has crucial roles in the physiological maturation of an organism, the maintenance of metabolism, and disease progression. Pyroptosis, a form of programmed cell death which has recently received much attention, is closely related to inflammation and occurs via canonical, non-canonical, caspase-3-dependent, and unclassified pathways. The pore-forming gasdermin proteins mediate pyroptosis by promoting cell lysis, contributing to the outflow of large amounts of inflammatory cytokines and cellular contents. Although the inflammatory response is critical for the body's defense against pathogens, uncontrolled inflammation can cause tissue damage and is a vital factor in the occurrence and progression of various diseases. In this review, we briefly summarize the major signaling pathways of pyroptosis and discuss current research on the pathological function of pyroptosis in autoinflammatory diseases and sterile inflammatory diseases.

Glucocorticoids contribute to metabolic and liver impairments induced by lactation overnutrition in male adult rats

Introduction: Lactation overnutrition is a programming agent of energy metabolism, and litter size reduction leads to the early development of obesity, which persists until adulthood. Liver metabolism is disrupted by obesity, and increased levels of circulating glucocorticoids are pointed as a possible mediator for the obesity development, since bilateral adrenalectomy (ADX) can reduce obesity in different models of obesity. Methods: This study aimed to evaluate the effects of glucocorticoids on metabolic changes and liver lipogenesis and insulin pathway induced by lactation overnutrition. For this, on the postnatal day 3 (PND), 3 pups (small litter-SL) or 10 pups (normal litter-NL) were kept with each dam. On PND 60, male Wistar rats underwent bilateral adrenalectomy (ADX) or fictitious surgery (sham), and half of ADX animals received corticosterone (CORT- 25 mg/L) diluted in the drinking fluid. On PND 74, the animals were euthanized by decapitation for trunk blood collection, and liver dissection and storage. Results and Discussion: SL rats presented increased corticosterone, free fatty acids, total and LDL-cholesterol plasma levels, without changes in triglycerides (TG) and HDL-cholesterol. The SL group also showed increased content of liver TG, and expression of fatty acid synthase (FASN), but decreased expression of PI3K_p110 in the liver, compared to NL rats. In the SL group, the ADX decreased plasma levels of corticosterone, FFA, TG and HDL cholesterol, liver TG, and liver expression of FASN, and IRS2, compared to sham animals. In SL animals, CORT treatment increased plasma levels of TG and HDL cholesterol, liver TG, and expression of FASN, IRS1, and IRS2, compared with the ADX group. In summary, the ADX attenuated plasma and liver changes observed after lactation overnutrition, and CORT treatment could reverse most ADX-induced effects. Thus, increased circulating glucocorticoids are likely to play a pivotal role in liver and plasma impairments induced by lactation overnutrition in male rats.

Mitigating a Bioactivation Liability with an Azetidine-Based Inhibitor of Diacylglycerol Acyltransferase 2 (DGAT2) En Route to the Discovery of the Clinical Candidate Ervogastat

We recently disclosed SAR studies on systemically acting, amide-based inhibitors of diacylglycerol acyltransferase 2 (DGAT2) that addressed metabolic liabilities with the liver-targeted DGAT2 inhibitor PF-06427878. Despite strategic placement of a nitrogen atom in the dialkoxyaromatic ring in PF-06427878 to evade oxidative O-dearylation, metabolic intrinsic clearance remained high due to extensive piperidine ring oxidation as exemplified with compound 1. Piperidine ring modifications through alternate N-linked heterocyclic ring/spacer combination led to azetidine 2 that demonstrated lower intrinsic clearance. However, 2 underwent a facile cytochrome P450 (CYP)-mediated α-carbon oxidation followed by azetidine ring scission, resulting in the formation of ketone (M2) and aldehyde (M6) as stable metabolites in NADPH-supplemented human liver microsomes. Inclusion of GSH or semicarbazide in microsomal incubations led to the formation of Cys-Gly-thiazolidine (M3), Cys-thiazolidine (M5), and semicarbazone (M7) conjugates, which were derived from reaction of the nucleophilic trapping agents with aldehyde M6. Metabolites M2 and M5 were biosynthesized from NADPH- and l-cysteine-fortified human liver microsomal incubations with 2, and proposed metabolite structures were verified using one- and two-dimensional NMR spectroscopy. Replacement of the azetidine substituent with a pyridine ring furnished 8, which mitigated the formation of the electrophilic aldehyde metabolite, and was a more potent DGAT2 inhibitor than 2. Further structural refinements in 8, specifically introducing amide bond substituents with greater metabolic stability, led to the discovery of PF-06865571 (ervogastat) that is currently in phase 2 clinical trials for the treatment of nonalcoholic steatohepatitis.

Roles of the peroxisome proliferator-activated receptors (PPARs) in the pathogenesis of nonalcoholic fatty liver disease (NAFLD)

Non-alcoholic fatty liver disease (NAFLD) encompasses a spectrum of disease phenotypes which start with simple steatosis and lipid accumulation in the hepatocytes - a typical histological lesions characteristic. It may progress to non-alcoholic steatohepatitis (NASH) that is characterized by hepatic inflammation and/or fibrosis and subsequent onset of NAFLD-related cirrhosis and hepatocellular carcinoma (HCC). Due to the central role of the liver in metabolism, NAFLD is regarded as a result of and contribution to the metabolic abnormalities seen in the metabolic syndrome. Peroxisome proliferator-activated receptors (PPARs) has three subtypes, which govern the expression of genes responsible for energy metabolism, cellular development, inflammation, and differentiation. The agonists of PPARα, such as fenofibrate and clofibrate, have been used as lipid-lowering drugs in clinical practice. Thiazolidinediones (TZDs) - ligands of PPARγ, such as rosiglitazone and pioglitazone, are also used in the treatment of type 2 diabetes (T2D) with insulin resistance (IR). Increasing evidence suggests that PPARβ/δ agonists have potential therapeutic effects in improving insulin sensitivity and lipid metabolism disorders. In addition, PPARs ligands have been considered as potential therapeutic drugs for hypertension, atherosclerosis (AS) or diabetic nephropathy. Their crucial biological roles dictate the significance of PPARs-targeting in medical research and drug discovery. Here, it reviews the biological activities, ligand selectivity and biological functions of the PPARs family, and discusses the relationship between PPARs and the pathogenesis of NAFLD and metabolic syndrome. This will open new possibilities for PPARs application in medicine, and provide a new idea for the treatment of fatty liver and related diseases.

Adverse Maternal Environments Perturb Hepatic DNA Methylome and Transcriptome Prior to the Adult-Onset Non-Alcoholic Fatty Liver Disease in Mouse Offspring

Exposure to adverse early-life environments (AME) increases the incidence of developing adult-onset non-alcoholic fatty liver disease (NAFLD). DNA methylation has been postulated to link AME and late-onset diseases. This study aimed to investigate whether and to what extent the hepatic DNA methylome was perturbed prior to the development of NAFLD in offspring exposed to AME in mice. AME constituted maternal Western diet and late-gestational stress. Male offspring livers at birth (d0) and weaning (d21) were used for evaluating the DNA methylome and transcriptome using the reduced representation of bisulfite sequencing and RNA-seq, respectively. We found AME caused 5879 differentially methylated regions (DMRs) and zero differentially expressed genes (DEGs) at d0 and 2970 and 123, respectively, at d21. The majority of the DMRs were distal to gene transcription start sites and did not correlate with DEGs. The DEGs at d21 were significantly enriched in GO biological processes characteristic of liver metabolic functions. In conclusion, AME drove changes in the hepatic DNA methylome, which preceded perturbations in the hepatic metabolic transcriptome, which preceded the onset of NAFLD. We speculate that subtle impacts on dynamic enhancers lead to long-range regulatory changes that manifest over time as gene network alternations and increase the incidence of NAFLD later in life.

Applying Lipidomics to Non-Alcoholic Fatty Liver Disease: A Clinical Perspective

The prevalence of Non-alcoholic fatty liver disease (NAFLD) and associated complications, such as hepatocellular carcinoma (HCC), is growing worldwide, due to the epidemics of metabolic risk factors, such as obesity and type II diabetes. Among other factors, an aberrant lipid metabolism represents a crucial step in the pathogenesis of NAFLD and the development of HCC in this population. In this review, we summarize the evidence supporting the application of translational lipidomics in NAFLD patients and NAFLD associated HCC in clinical practice.

Effects of UBE3A on Cell and Liver Metabolism through the Ubiquitination of PDHA1 and ACAT1

Nonalcoholic fatty liver disease (NAFLD) is substantiated by the reprogramming of liver metabolic pathways that disrupts the homeostasis of lipid and glucose metabolism and thus promotes the progression of the disease. The metabolic pathways associated with NAFLD are regulated at different levels from gene transcription to various post-translational modifications including ubiquitination. Here, we used a novel orthogonal ubiquitin transfer platform to identify pyruvate dehydrogenase A1 (PDHA1) and acetyl-CoA acetyltransferase 1 (ACAT1), two important enzymes that regulate glycolysis and ketogenesis, as substrates of E3 ubiquitin ligase UBE3A/E6AP. We found that overexpression of UBE3A accelerated the degradation of PDHA1 and promoted glycolytic activities in HEK293 cells. Furthermore, a high-fat diet suppressed the expression of UBE3A in the mouse liver, which was associated with increased ACAT1 protein levels, while forced expression of UBE3A in the mouse liver resulted in decreased ACAT1 protein contents. As a result, the mice with forced expression of UBE3A in the liver exhibited enhanced accumulation of triglycerides, cholesterol, and ketone bodies. These results reveal the role of UBE3A in NAFLD development by inducing the degradation of ACAT1 in the liver and promoting lipid storage. Overall, our work uncovers an important mechanism underlying the regulation of glycolysis and lipid metabolism through UBE3A-mediated ubiquitination of PDHA1 and ACAT1 to regulate their stabilities and enzymatic activities in the cell.

Metabolic dysfunction-associated fatty liver disease increased the risk of subclinical carotid atherosclerosis in China

BACKGROUND AND AIMS

Metabolic dysfunction-associated fatty liver disease (MAFLD) was proposed to substitute NAFLD in 2020. This new term highlights the systematic metabolic disturbances that accompany fatty liver. We evaluated the correlations between MAFLD and subclinical carotid atherosclerosis (SCA) based on a nationwide health examination population in China.

METHODS

We performed a nationwide cross-sectional population and a Beijing retrospective cohort from 2009 to 2017. SCA was defined as elevated carotid intima-media thickness. The multivariable logistic and Cox models were used to analyze the association between MAFLD and SCA.

RESULTS

153,482 participants were included in the cross-sectional study. MAFLD was significantly associated with SCA in fully adjusted models, with an odds ratio of 1.66; 95% confidence interval (CI): 1.62-1.70. This association was consistent in the cohort, with a hazard ratio (HR) of 1.31. The association between baseline MAFLD and incident SCA increased with hepatic steatosis severity. Subgroup analysis showed an interaction between age and MAFLD, with a higher risk in younger groups (HR:1.67, 95% CI: 1.17-2.40).

CONCLUSION

In this large cross-section and cohort study, MAFLD was significantly associated with the presence and development of SCA. Further, the risk was higher among MAFLD individuals with high hepatic steatosis index and young adults.

Sustained oral intake of nano-iron oxide perturbs the gut-liver axis

Nanomaterial have shown excellent properties in the food industry. Although iron oxides are often considered safe and widely used as food additives, the toxicity of nano‑iron oxide remains unclear. Here we established a subchronic exposure mouse model by gavage, tested the biodistribution of nano‑iron oxide, and explored the mechanism of liver injury caused by it through disturbance of the gut-liver axis. Oral intake of nano‑iron oxide will likely disrupt the small intestinal epithelial barrier, induce hepatic lipid metabolism disorders through the gut-liver axis, and cause hepatic damage accompanied with hepatic iron deposition. Nano‑iron oxide mainly caused hepatic lipid metabolism disorder by perturbing glycerophospholipid metabolism and the sphingolipid metabolism pathways, with the total abundance of phosphatidylcholine (PC) and phosphatidylethanolamine (PE) tending to decrease while that of triglyceride tended to increase, in a time- and dose-dependent manner. The imbalanced lipid homeostasis could cause damage via membrane disruption, lipid accumulation, and lipotoxicity. This data provides information about the subchronic toxicity of nano‑iron oxide, highlights the importance of gut-liver axis in the hepatotoxicity.

Therapeutic potential of bioactive phytoconstituents found in fruits in the treatment of non-alcoholic fatty liver disease: A comprehensive review

Nonalcoholic fatty liver disease (NAFLD), a chronic liver condition affects a large number of people around the world with a frequency of 25% of all the chronic liver disease worldwide. Several targets viz. anti-inflammatory, anti-apoptotic and, anti-fibrotic factors, anti-oxidant and insulin-sensitizing pathways, metabolic regulators as well as repurposing traditional medications have been studied for the pharmacologic therapy of NAFLD. Newer pharmacotherapies like caspases blockade, agonists of PPAR and farnesoid X receptor agonists are currently being investigated in treating human NAFLD. However, NAFLD has no FDA-approved pharmacological therapy, therefore there is a considerable unmet therapy need. Apart from the conventional treatment regime, the current approaches to treating NAFLD include lifestyle interventions including healthy diet with adequate nutrition and physical activity. Fruits are known to play a key role in the well-being of human health. Fruits are loaded with a repertoire of bioactive phytoconstituents like catechins, phytosterols, proanthocyanidin, genestin, daidzen, resveratrol, magiferin found in fruits like pear, apricot, strawberries, oranges, apples, bananas, grapes, kiwi, pineapple, watermelon, peach, grape seed and skin, mango, currants, raisins, dried dates, passion fruit and many more. These bioactive phytoconstituents are reported to demonstrate promising pharmacological efficacy like reduction in fatty acid deposition, increased lipid metabolism, modulation of insulin signaling pathway, gut microbiota and hepatic inflammation, inhibition of histone acetyltransferase enzymatic activity to name a few. Not only fruits, but their derivatives like oils, pulp, peel, or their preparations are also found to be equally beneficial in various liver diseases like NAFLD, NASH. Although most of the fruits contains potent bioactive phytoconstituents, however, the presence of sugar in fruits put a question mark on the ameliorative property of the fruits and there has been contrasting reports on the glycemic control post fruit consumption in type 2 diabetic patients. This review is an attempt to summarize the beneficial effects of fruit phytoconstituents on NAFLD based on epidemiological, clinical and experimental evidence, focusing especially on their mechanisms of action.

Betulin prevents high fat diet-induced non-alcoholic fatty liver disease by mitigating oxidative stress and upregulating Nrf2 and SIRT1 in rats

Non-alcoholic fatty liver disease (NAFLD) is a common chronic hepatic disorder characterized by hepatic lipid accumulation. This study explored the effect of betulin (BE), a terpenoid with promising antioxidant, anti-inflammatory and insulin sensitizing effects, on NAFLD induced by high fat diet (HFD). Rats received HFD and BE (15 and 30 mg/kg) for 12 weeks and blood and liver samples were collected for analyses. HFD caused hyperlipidemia, cholesterol and triglycerides accumulation in the liver, hepatocellular ballooning, fibrosis, insulin resistance (IR), lipid peroxidation (LPO), and NF-kB p65 upregulation. BE ameliorated serum and liver lipids, blood glucose, and insulin, liver LPO, prevented steatosis and fibrosis, suppressed NF-kB p65 and enhanced antioxidants in HFD-fed rats. BE downregulated ACC1 and FAS, and upregulated Nrf2, HO-1 and SIRT1 in the liver of HFD-fed rats. In silico investigations revealed the binding affinity of BE towards NF-kB, Keap1, HO-1 and SIRT1. In conclusion, BE attenuated HFD-induced NAFLD by ameliorating hyperlipidemia, IR, lipogenesis, liver lipid accumulation, and oxidative stress. The protective effect of BE was associated with enhanced Nrf2/HO-1 signaling and SIRT1.

Steatosis in metabolic diseases: A focus on lipolysis and lipophagy

Fatty acids (FAs), as part of lipids, are involved in cell membrane composition, cellular energy storage, and cell signaling. FAs can also be toxic when their concentrations inside and/or outside the cell exceed physiological levels, which is called "lipotoxicity", and steatosis is a form of lipotoxity. To facilitate the storage of large quantities of FAs in cells, they undergo a process called lipolysis or lipophagy. This review focuses on the effects of lipolytic enzymes including cytoplasmic "neutral" lipolysis, lysosomal "acid" lipolysis, and lipophagy. Moreover, the impact of related lipolytic enzymes on lipid metabolism homeostasis and energy conservation, as well as their role in lipid-related metabolic diseases. In addition, we describe how they affect lipid metabolism homeostasis and energy conservation in lipid-related metabolic diseases with a focus on hepatic steatosis and cancer and the pathogenesis and therapeutic targets of AMPK/SIRTs/FOXOs, PI3K/Akt, PPARs/PGC-1α, MAPK/ERK1/2, TLR4/NF-κB, AMPK/mTOR/TFEB, Wnt/β-catenin through immune inflammation, oxidative stress and autophagy-related pathways. As well as the current application of lipolytic enzyme inhibitors (especially Monoacylglycerol lipase (MGL) inhibitors) to provide new strategies for future exploration of metabolic programming in metabolic diseases.

MBOAT7-driven lysophosphatidylinositol acylation in adipocytes contributes to systemic glucose homeostasis

We previously demonstrated that antisense oligonucleotide-mediated knockdown of Mboat7, the gene encoding membrane bound O-acyltransferase 7, in the liver and adipose tissue of mice promoted high fat diet-induced hepatic steatosis, hyperinsulinemia, and systemic insulin resistance. Thereafter, other groups showed that hepatocyte-specific genetic deletion of Mboat7 promoted striking fatty liver and NAFLD progression in mice but does not alter insulin sensitivity, suggesting the potential for cell autonomous roles. Here, we show that MBOAT7 function in adipocytes contributes to diet-induced metabolic disturbances including hyperinsulinemia and systemic insulin resistance. We generated Mboat7 floxed mice and created hepatocyte- and adipocyte-specific Mboat7 knockout mice using Cre-recombinase mice under the control of the albumin and adiponectin promoter, respectively. Here, we show that MBOAT7 function in adipocytes contributes to diet-induced metabolic disturbances including hyperinsulinemia and systemic insulin resistance. The expression of Mboat7 in white adipose tissue closely correlates with diet-induced obesity across a panel of ∼100 inbred strains of mice fed a high fat/high sucrose diet. Moreover, we found that adipocyte-specific genetic deletion of Mboat7 is sufficient to promote hyperinsulinemia, systemic insulin resistance, and mild fatty liver. Unlike in the liver, where Mboat7 plays a relatively minor role in maintaining arachidonic acid-containing PI pools, Mboat7 is the major source of arachidonic acid-containing PI pools in adipose tissue. Our data demonstrate that MBOAT7 is a critical regulator of adipose tissue PI homeostasis, and adipocyte MBOAT7-driven PI biosynthesis is closely linked to hyperinsulinemia and insulin resistance in mice.

Non-Invasive Liver Fibrosis Scores Are Associated With Contrast-Associated Acute Kidney Injury in Patients Undergoing Elective Percutaneous Coronary Intervention

Previous studies have demonstrated that non-invasive liver fibrosis scores (LFSs) are associated with kidney function deterioration. This study aimed to assess the predictive performance of LFSs in contrast-associated acute kidney injury (CA-AKI) in coronary artery disease (CAD) patients undergoing elective percutaneous coronary intervention (PCI). This retrospective study involved 5627 patients. The frequency of CA-AKI was 6.3% (n = 353). In a multivariate logistic analysis after adjustment, non-invasive LFSs, including fibrosis-5 score (FIB-5), fibrosis-4 score (FIB-4), aspartate aminotransferase to alanine aminotransferase ratio (AAR), and aspartate aminotransferase to platelet ratio index were independent risk factors for CA-AKI (all P < .05), whereas the Forns score was not (P > .05). The highest predictive performance was observed for FIB-5 (area under the curve [AUC] = .644) compared to other LFSs. A restricted cubic spline analysis confirmed approximately linear relationships between LFSs and risks of CA-AKI. Furthermore, adding FIB-5 (AUC = .747; net reclassification improvement [NRI] = .441, P < .001; integrated discrimination improvement [IDI] = .008, P < .001) or AAR (AUC = .747; NRI = .419, P < .001; IDI = .006, P = .010) to an established clinical risk model could significantly improve the prediction of CA-AKI. The LFSs were significantly associated with CA-AKI, possibly serving as predictive tools for early identification of CAD patients undergoing elective PCI that are at high risk of CA-AKI.

Uncarboxylated Osteocalcin Decreases SCD1 by Activating AMPK to Alleviate Hepatocyte Lipid Accumulation

Uncarboxylated osteocalcin (GluOC), a small-molecule protein specifically synthesized and secreted by osteoblasts, is important in the regulation of energy metabolism. In our previous study, GluOC was shown to be effective in ameliorating dyslipidemia and hepatic steatosis in KKAy mice. However, the underlying mechanism of GluOC action on hepatocytes has not been well validated. In this study, oleic acid/palmitic acid (OA/PA)-induced HepG2 and NCTC 1469 cells were used as non-alcoholic fatty liver disease (NAFLD) cell models, and triacylglycerol (TG) levels were measured by oil red O staining, Nile Red staining, and ELISA. The fatty acid synthesis-related protein expression was detected by real-time quantitative polymerase chain reaction, Western blotting, and immunofluorescence. The results show that GluOC reduced triglyceride levels, and decreased the expression of sterol regulatory element-binding protein-1c (SREBP-1c) and stearyl-coenzyme A desaturase 1 (SCD1). si-SCD1 mimicked the lipid accumulation-reducing effect of GluOC, while overexpression of SCD1 attenuated the effect of GluOC. In addition, GluOC activated AMP-activated protein kinase (AMPK) phosphorylation to affect lipid metabolism in hepatocytes. Overall, the results of this study suggest that GluOC decreases SCD1 by activating AMPK to alleviate hepatocyte lipid accumulation, which provides a new target for improving NAFLD in further research.

MicroRNA-483-5p Inhibits Hepatocellular Carcinoma Cell Proliferation, Cell Steatosis, and Fibrosis by Targeting PPARα and TIMP2

MicroRNAs (miRNAs) are small non-coding RNA molecules that bind with the 3′ untranslated regions (UTRs) of genes to regulate expression. Downregulation of miR-483-5p (miR-483) is associated with the progression of hepatocellular carcinoma (HCC). However, the significant roles of miR-483 in nonalcoholic fatty liver disease (NAFLD), alcoholic fatty liver diseases (AFLD), and HCC remain elusive. In the current study, we investigated the biological significance of miR-483 in NAFLD, AFLD, and HCC in vitro and in vivo. The downregulation of miR-483 expression in HCC patients’ tumor samples was associated with Notch 3 upregulation. Overexpression of miR-483 in a human bipotent progenitor liver cell line HepaRG and HCC cells dysregulated Notch signaling, inhibited cell proliferation/migration, induced apoptosis, and increased sensitivity towards antineoplastic agents sorafenib/regorafenib. Interestingly, the inactivation of miR-483 upregulated cell steatosis and fibrosis signaling by modulation of lipogenic and fibrosis gene expression. Mechanistically, miR-483 targets PPARα and TIMP2 gene expression, which leads to the suppression of cell steatosis and fibrosis. The downregulation of miR-483 was observed in mice liver fed with a high-fat diet (HFD) or a standard Lieber-Decarli liquid diet containing 5% alcohol, leading to increased hepatic steatosis/fibrosis. Our data suggest that miR-483 inhibits cell steatosis and fibrogenic signaling and functions as a tumor suppressor in HCC. Therefore, miR-483 may be a novel therapeutic target for NAFLD/AFLD/HCC management in patients with fatty liver diseases and HCC.

TUBB2B facilitates progression of hepatocellular carcinoma by regulating cholesterol metabolism through targeting HNF4A/CYP27A1

Cholesterol metabolism plays a critical role in the progression of hepatocellular carcinoma (HCC), but it is not clear how cholesterol metabolism is regulated. The tubulin beta class I genes (TUBBs) are associated with the prognosis of many different cancers. To confirm the function of TUBBs in HCC, the Kaplan-Meier method and Cox analyses were performed using TCGA and GSE14520 datasets. A higher expression of TUBB2B is an independent prognostic factor for shorter over survival in HCC patients. Deletion of TUBB2B in hepatocytes inhibits proliferation and promotes tumor cell apoptosis, while over-expression of TUBB2B has the opposite function. This result was confirmed in a mouse xenograft tumor model. Mechanistically, TUBB2B induces the expression of CYP27A1, an enzyme responsible for the conversion of cholesterol to 27-hydroxycholesterol, which leads to the up-regulation of cholesterol and the progression of HCC. In addition, TUBB2B regulates CYP27A1 via human hepatocyte nuclear factor 4alpha (HNF4A). These findings indicated that TUBB2B functions as an oncogene in HCC, and plays a role in promoting cell proliferation and anti-apoptosis through targeting HNF4A/CYP27A1/cholesterol.

Thymoquinone attenuates hepatic lipid accumulation by inducing autophagy via AMPK/mTOR/ULK1-dependent pathway in nonalcoholic fatty liver disease

Thymoquinone (TQ) has been proved to exert wide-ranging pharmacological activities, with anti-inflammatory, antioxidant, anticonvulsant, antimicrobial, anti-tumor, and antidiabetic properties. In this study, we investigated the beneficial effects of TQ on a high-fat diet (HFD)-induced nonalcoholic fatty liver disease (NAFLD) in C57BL/6 N mice in vivo and free fatty acid (FFA)-induced human hepatocellular carcinoma HepG2 cells in vitro. Further, the underlying mechanisms of TQ to promote hepatic autophagy were also discovered. Data showed that TQ caused (p < 0.01) body weight reduction, improved glucose homeostasis, alleviated hepatosteatosis, and decreased hepatic lipid accumulation related to the induction of autophagy in HFD-fed mice. In vitro, TQ obviously increased (p < 0.01) autophagic flux in FFA-induced HepG2 cells and consequently reduced the lipid accumulation in combination with activation of AMPK/mTOR/ULK1 signaling pathways. Moreover, pharmacological inhibition of the AMPK pathway by addition with AMPK inhibitor Compound C (CC) or silence of ULK1 by transfection with siRNA(ULK1) into HepG2 cells reversed these beneficial effects of TQ on triggering hepatic autophagy and reducing lipid accumulation (p < 0.01). Taken together, these results suggested that TQ alleviated hepatic lipid accumulation by triggering autophagy through the AMPK/mTOR/ULK1-dependent signaling pathway. Our study supports a potential role for TQ in ameliorating NAFLD.

Gut-Microbiota Dysbiosis in Stroke-Prone Spontaneously Hypertensive Rats with Diet-Induced Steatohepatitis

Metabolic-dysfunction-associated fatty-liver disease (MAFLD) is the principal worldwide cause of liver disease. Individuals with nonalcoholic steatohepatitis (NASH) have a higher prevalence of small-intestinal bacterial overgrowth (SIBO). We examined gut-microbiota isolated from 12-week-old stroke-prone spontaneously hypertensive-5 rats (SHRSP5) fed on a normal diet (ND) or a high-fat- and high-cholesterol-containing diet (HFCD) and clarified the differences between their gut-microbiota. We observed that the Firmicute/Bacteroidetes (F/B) ratio in both the small intestines and the feces of the SHRSP5 rats fed HFCD increased compared to that of the SHRSP5 rats fed ND. Notably, the quantities of the 16S rRNA genes in small intestines of the SHRSP5 rats fed HFCD were significantly lower than those of the SHRSP5 rats fed ND. As in SIBO syndrome, the SHRSP5 rats fed HFCD presented with diarrhea and body-weight loss with abnormal types of bacteria in the small intestine, although the number of bacteria in the small intestine did not increase. The microbiota of the feces in the SHRSP5 rats fed HFCD was different from those in the SHRP5 rats fed ND. In conclusion, there is an association between MAFLD and gut-microbiota alteration. Gut-microbiota alteration may be a therapeutic target for MAFLD.

The Essential Role of IL-17 as the Pathogenetic Link between Psoriasis and Metabolic-Associated Fatty Liver Disease

Interleukin 17 (IL-17) is an effector cytokine that plays a key role in the pathogenesis of both psoriasis and metabolic-associated fatty liver disease (MAFLD), a condition that is more prevalent and severe in patients with psoriasis. In liver inflammation, IL-17 is mainly produced by CD4+ T (TH17) and CD8+ T cells (Tc17), although numerous other cells (macrophages, natural killer cells, neutrophils and Tγδ cells) also contribute to the production of IL-17. In hepatocytes, IL-17 mediates systemic inflammation and the recruitment of inflammatory cells to the liver, and it is also implicated in the development of fibrosis and insulin resistance. IL-17 levels have been correlated with progression from MAFLD to steatohepatitis, cirrhosis, and even hepatocellular carcinoma. Clinical trials have shown that inhibiting IL-17A in patients with psoriasis could potentially contribute to the improvement of metabolic and liver parameters. A better understanding of the key factors involved in the pathogenesis of these chronic inflammatory processes could potentially lead to more efficient treatment for both psoriasis and MAFLD, and help to develop holistic strategies to improve the management of these patients.

Liver Organoids, Novel and Promising Modalities for Exploring and Repairing Liver Injury

The past decades have witnessed great advances in organoid technology. Liver is the biggest solid organ, performing multifaceted physiological functions. Nowadays, liver organoids have been applied in many fields including pharmaceutical research, precision medicine and disease models. Compared to traditional 2-dimensional cell line cultures and animal models, liver organoids showed the unique advantages. More importantly, liver organoids can well model the features of the liver and tend to be novel and promising modalities for exploring liver injury, thus finding potential treatment targets and repairing liver injury. In this review, we reviewed the history of the development of liver organoids and summarized the application of liver organoids and recent studies using organoids to explore and further repair the liver injury. These novel modalities could provide new insights about the process of liver injury.

Down regulation of NDUFS1 is involved in the progression of parenteral-nutrition-associated liver disease by increasing Oxidative stress

Parenteral nutrition (PN)-associated liver disease (PNALD) is a common and life-threatening complication of patients receiving PN. However, its definitive pathology remains unclear. Ubiquinone oxidoreductase core subunit S1 (NDUFS1), which is the largest core subunit of mitochondrial complex I, could alter the mitochondrial reactive oxygen species (ROS) formation. The purpose of this study was to investigate the role of NDUFS1 in the pathogenesis of PNALD and its underlying mechanism. We performed hepatic proteomics analysis of PNALD patients, and established a PNALD rat model to verify the role of oxidative stress, NDUFS1, pyrin inflammasome, and IL-1β in the progression of PNALD. Proteomics analysis revealed the NDUFS1 expression was decreased in PNALD patients, and the differentially espressed proteins were involved in mitochondrial respiratory chain complex Ⅰ. Treatment with MitoQ or overexpression of NDUFS1 can alleviate the progression of PNALD by reducing oxidative stress. The expression of pyrin, caspase-1, and IL-1β was increased in PN rats. Pharmacological antagonism of pyrin by colchicine can alleviate liver injury and hepatic steatosis. NDUFS1 prevents PNALD pathogenesis by regulating oxidative stress. Pyrin inflammasome and IL-1β may participate in the process of PNALD development by suppressing the transcription of MTTP and impairing the secretion of VLDL. Oxidative stress reduction may be employed as a strategy in the prevention and treatment of PNALD.

Investigating dual inhibition of ACC and CD36 for the treatment of nonalcoholic fatty liver disease in mice

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease worldwide. Dysregulation in hepatic lipid metabolism, including increased fatty acid uptake and de novo lipogenesis (DNL), is a hallmark of NAFLD. Here, we investigated dual inhibition of the fatty acid transporter fatty acid translocase (FAT/CD36), and acetyl-CoA carboxylase (ACC), the rate-limiting enzyme in DNL, for the treatment of NAFLD in mice. Mice with hepatic CD36 deletion (Cd36^LKO) and wild-type littermates were fed a high-fat diet for 12 wk and treated daily with either oral administration of an ACC inhibitor (GS-834356, Gilead Sciences; ACCi) or vehicle for 8 wk. Neither CD36 deletion or ACC inhibition impacted body composition, energy expenditure, or glucose tolerance. Cd36^LKO mice had elevated fasting plasma insulin, suggesting mild insulin resistance. Whole body fatty acid oxidation was significantly decreased in Cd36^LKO mice. Liver triglyceride content was significantly reduced in mice treated with ACCi; however, CD36 deletion caused an unexpected increase in liver triglycerides. This was associated with upregulation of genes and proteins of DNL, including ACC, and decreased liver triglyceride secretion ex vivo. Overall, these data confirm the therapeutic utility of ACC inhibition for steatosis resolution but indicate that inhibition of CD36 is not an effective treatment for NAFLD in mice.NEW & NOTEWORTHY Dysregulation of hepatic lipid metabolism is a hallmark of nonalcoholic fatty liver disease. Here, we show that dual inhibition of the de novo lipogenesis enzyme, ACC, and hepatic deletion of the fatty acid transporter, CD36, was ineffective for the treatment of NAFLD in mice. This was due to a paradoxical increase in liver triglycerides with CD36 deletion resulting from decreased hepatic triglyceride secretion and increased lipogenic gene expression.

Unlocking life-threatening COVID-19 through two types of inborn errors of type I IFNs

Since 2003, rare inborn errors of human type I IFN immunity have been discovered, each underlying a few severe viral illnesses. Autoantibodies neutralizing type I IFNs due to rare inborn errors of autoimmune regulator (AIRE)-driven T cell tolerance were discovered in 2006, but not initially linked to any viral disease. These two lines of clinical investigation converged in 2020, with the discovery that inherited and/or autoimmune deficiencies of type I IFN immunity accounted for approximately 15%-20% of cases of critical COVID-19 pneumonia in unvaccinated individuals. Thus, insufficient type I IFN immunity at the onset of SARS-CoV-2 infection may be a general determinant of life-threatening COVID-19. These findings illustrate the unpredictable, but considerable, contribution of the study of rare human genetic diseases to basic biology and public health.

Emerging role of aging in the progression of NAFLD to HCC

With the aging of global population, the incidence of nonalcoholic fatty liver disease (NAFLD) has surged in recent decades. NAFLD is a multifactorial disease that follows a progressive course, ranging from simple fatty liver, nonalcoholic steatohepatitis (NASH) to liver cirrhosis and hepatocellular carcinoma (HCC). It is well established that aging induces pathological changes in liver and potentiates the occurrence and progression of NAFLD, HCC and other age-related liver diseases. Studies of senescent cells also indicate a pivotal engagement in the development of NAFLD via diverse mechanisms. Moreover, nicotinamide adenine dinucleotide (NAD⁺), silence information regulator protein family (sirtuins), and mechanistic target of rapamycin (mTOR) are three vital and broadly studied targets involved in aging process and NAFLD. Nevertheless, the crucial role of these aging-associated factors in aging-related NAFLD remains underestimated. Here, we reviewed the current research on the roles of aging, cellular senescence and three aging-related factors in the evolution of NAFLD to HCC, aiming at inspiring promising therapeutic targets for aging-related NAFLD and its progression.

Cancer-Associated Fibroblasts in Hepatocellular Carcinoma and Cholangiocarcinoma

Primary liver cancer (PLC) includes hepatocellular carcinoma and intrahepatic cholangiocarcinoma and is the sixth most common cancer worldwide with poor prognosis. PLC is characterized by an abundant stromal reaction in which cancer-associated fibroblasts (CAFs) are one of the major stromal components. Solid evidence has demonstrated the crucial role of CAFs in tumor progression, and CAF abundance is often correlated with poor clinical outcomes. Although CAFs are regarded as an attractive and promising target for PLC treatment, a poor understanding of CAF origins and heterogeneity and a lack of specific CAF markers are the major hurdles to efficient CAF-specific therapy. In this review, we examine recent advances in the understanding of CAF diversity in the context of biomarkers, subtypes, and functions in PLC. The regulatory roles of CAFs in extracellular matrix remodeling, metastasis, cancer stemness, and therapeutic resistance are summarized. With an increasing link between CAF abundance and reduced antitumor immune responses, we provide updated knowledge on the crosstalk between CAFs and immune cells within the tumor microenvironment, which leads to immune resistance. In addition, we present current CAF-targeted therapies and describe some future perspectives. A better understanding of CAF biology will shed light on a novel therapeutic strategy against PLC.

Exploring the molecular mechanism of Gan Shuang granules for the treatment of non-alcoholic steatohepatitis using network pharmacology, molecular docking, and experimental verification

Background: With the gradual increase in prevalence in recent years, non-alcoholic steatohepatitis (NASH) has become one of the significant health problems that urgently needs to be addressed worldwide. GanShuang Granules (GSG) is derived from the classical Chinese formula Xiaoyao San and mainly used in the clinical treatment of chronic liver diseases. Objective: In this study, we aim to gain a deeper insight into the inhibiting effects of GSG on non-alcoholic fatty liver disease (NAFLD) rats and preliminarily elucidate the underlying intervention mechanisms. Methods: First, High performance liquid chromatography (UHPLC-Q/Orbitrap-MS/MS) was used for the active compounds prediction in GSG. Then the data was mapped to mzCloud database. The targets corresponding to GSG compounds were collected from public databases, along with disease genes for NAFLD. The core targets and molecular mechanisms of GSG for NAFLD treatment were predicted by protein-protein interaction (PPI) network, Gene Ontology (GO), and Kyoto Encyclopedia of Genes and Genomes (KEGG) functional enrichment analyses. Molecular docking of the core target-component interactions was simulated using AutoDock Vina software. The effect of GSG on NASH rats was evaluated by pathological staining and analysis of various index results. Finally, the candidate targets were further validated by ELISA and western blot (WB) analyses. Results: Combining UHPLC-Q/Orbitrap-MS/MS data analysis and public database data, a total of 346 cross-targets were obtained, corresponding to 81 compounds. The subnetwork with an MCODE score of 53.623 is a potential core target group for this study. GO and KEGG enrichment analyses showed that the targets of GSG in NAFLD were mostly related to oxidative stress, the NF-κB signaling pathway, and the apoptosis signaling pathway. By integrating the results of network pharmacology analysis, the core objectives of this study mainly include AKT1, CASP9, TNF, and CASP8. The core ingredients are related to resveratrol and fisetin. The molecular docking results indicated key binding activity between AKT1-fisetin, AKT1-Resveratrol, and CASP8-fisetin. Moreover, GSG could improve the inflammatory status and restore the abnormal lipid accumulation of NAFLD/NASH liver, and these levels are further verified by pathological staining and detection of related indicators. Mechanistically, GSG could regulate protein expression levels in the liver for P65, p-P65, IKB, p-IKB, IKK, caspase-3, -8, -9, and cytochrome C, etc. It reflects the inhibitory effect of GSG on the NF-κB/IκB signaling pathway. Conclusion: Our results suggested that GSG demonstrated therapeutic effects on NAFLD/NASH rats, and these may be mainly reflected in the inhibitory effects on the NF-κB/IκB signaling pathway and its downstream inflammation and apoptosis signals.

Ellagic Acid and Its Metabolites as Potent and Selective Allosteric Inhibitors of Liver Pyruvate Kinase

Liver pyruvate kinase (PKL) has recently emerged as a new target for non-alcoholic fatty liver disease (NAFLD), and inhibitors of this enzyme could represent a new therapeutic option. However, this breakthrough is complicated by selectivity issues since pyruvate kinase exists in four different isoforms. In this work, we report that ellagic acid (EA) and its derivatives, present in numerous fruits and vegetables, can inhibit PKL potently and selectively. Several polyphenolic analogues of EA were synthesized and tested to identify the chemical features responsible for the desired activity. Molecular modelling studies suggested that this inhibition is related to the stabilization of the PKL inactive state. This unique inhibition mechanism could potentially herald the development of new therapeutics for NAFLD.

Hyperphosphorylation of hepatic proteome characterizes nonalcoholic fatty liver disease in S-adenosylmethionine deficiency

Methionine adenosyltransferase 1a (MAT1A) is responsible for hepatic S-adenosyl-L-methionine (SAMe) biosynthesis. Mat1a ^-/- mice have hepatic SAMe depletion, develop nonalcoholic steatohepatitis (NASH) which is reversed with SAMe administration. We examined temporal alterations in the proteome/phosphoproteome in pre-disease and NASH Mat1a ^-/- mice, effects of SAMe administration, and compared to human nonalcoholic fatty liver disease (NAFLD). Mitochondrial and peroxisomal lipid metabolism proteins were altered in pre-disease mice and persisted in NASH Mat1a ^-/- mice, which exhibited more progressive alterations in cytoplasmic ribosomes, ER, and nuclear proteins. A common mechanism found in both pre-disease and NASH livers was a hyperphosphorylation signature consistent with casein kinase 2α (CK2α) and AKT1 activation, which was normalized by SAMe administration. This was mimicked in human NAFLD with a metabolomic signature (M-subtype) resembling Mat1a ^-/- mice. In conclusion, we have identified a common proteome/phosphoproteome signature between Mat1a ^-/- mice and human NAFLD M-subtype that may have pathophysiological and therapeutic implications.

Peonidin-3-O-Glucoside from Purple Corncob Ameliorates Nonalcoholic Fatty Liver Disease by Regulating Mitochondrial and Lysosome Functions to Reduce Oxidative Stress and Inflammation

A frequent chronic liver condition across the world is nonalcoholic fatty liver disease (NAFLD). Oxidative stress caused by lipid accumulation is generally considered to be the main cause of NAFLD. Anthocyanins can effectively inhibit the production of reactive oxygen species and improve oxidative stress. In this work, six major anthocyanins were separated from purple corncob by semi-preparative liquid chromatography. The effects of the 6 kinds of anthocyanins against NAFLD were investigated using a free fatty acid (FFA)-induced cell model. The results showed that peonidin 3-O-glucoside (P3G) can significantly reduce lipid accumulation in the NAFLD cell model. The treatment with P3G also inhibited oxidative stress via inhibiting the excessive production of reactive oxygen species and superoxide anion, increasing glutathione levels, and enhancing the activities of SOD, GPX, and CAT. Further studies unveiled that treatment with P3G not only alleviated inflammation but also improved the depletion of mitochondrial content and damage of the mitochondrial electron transfer chain developed concomitantly in the cell model. P3G upregulated transcription factor EB (TFEB)-mediated lysosomal function and activated the peroxisome proliferator-activated receptor alpha (PPARα)-mediated peroxisomal lipid oxidation by interacting with PPARα possibly. Overall, this study added to our understanding of the protective effects of purple corn anthocyanins against NAFLD and offered suggestions for developing functional foods containing these anthocyanins.

Alterations in circulating lipidomic profile in patients with type 2 diabetes with or without non-alcoholic fatty liver disease

Objective: Non-alcoholic fatty liver disease (NAFLD) and Type 2 diabetes mellitus (T2DM) often coexist and drive detrimental effects in a synergistic manner. This study was designed to understand the changes in circulating lipid and lipoprotein metabolism in patients with T2DM with or without NAFLD. Methods: Four hundred thirty-four T2DM patients aged 18-60 years were included in this study. Fatty liver was assessed by FibroScan. The comprehensive metabolic lipid profiling of serum samples was assessed by using high-throughput proton NMR metabolomics. Results: Our data revealed a significant association between steatosis and serum total lipids in VLDL and LDL lipoprotein subclasses, while total lipids in HDL subclasses were negatively associated. A significant positive association was found between steatosis and concentration of lipids, phospholipids, cholesterol, and triglycerides in VLDL and LDL subclasses, while HDL subclasses were negatively associated. Furthermore, a significant, association was observed between fibrosis and concentrations of lipids, phospholipids, cholesterol, and triglycerides in very small VLDL, large, and very large HDL subclasses. Subgroup analysis revealed a decrease in the concentrations of lipids, phospholipids, cholesterol, and other lipid biomolecules in patients using antilipemic medications. Conclusion: The metabolomics results provide evidence that patients with T2DM with higher steatosis grades have altered lipid metabolomics compared to patients without steatosis. Increased lipid, phospholipids, cholesterol, and triglycerides concentration of VLDL and LDL subclasses are associated with steatosis in patients with T2DM.

Association between smoking cessation and non-alcoholic fatty liver disease using NAFLD liver fat score

Background

Smoking is well known to be associated with a higher prevalence and incidence of liver diseases such as advanced fibrosis. However, the impact of smoking on developing nonalcoholic fatty liver disease remains controversial, and clinical data on this is limited. Therefore, this study aimed to investigate the association between smoking history and nonalcoholic fatty liver disease (NAFLD).

Methods

Data from the Korea National Health and Nutrition Examination Survey 2019-2020 were used for the analysis. NAFLD was diagnosed according to an NAFLD liver fat score of >-0.640. Smoking status was classified as into nonsmokers, ex-smokers, and current smokers. Multiple logistic regression analysis was conducted to examine the association between smoking history and NAFLD in the South Korean population.

Results

In total, 9,603 participants were enrolled in this study. The odds ratio (OR) for having NAFLD in ex-smokers and current smokers in males was 1.12 (95% confidence interval [CI]: 0.90-1.41) and 1.38 (95% CI: 1.08-1.76) compared to that in nonsmokers, respectively. The OR increased in magnitude with smoking status. Ex-smokers who ceased smoking for <10 years (OR: 1.33, 95% CI: 1.00-1.77) were more likely to have a strong correlation with NAFLD. Furthermore, NAFLD had a dose-dependent positive effect on pack-years, which was 10 to 20 (OR: 1.39, 95% CI: 1.04-1.86) and over 20 (OR: 1.51, 95% CI: 1.14-2.00).

Conclusion

This study found that smoking may contribute to NAFLD. Our study suggests cessation of smoking may help management of NAFLD.

Effect of ammonia stress on AMPK regulating-carbohydrate and lipid metabolism in Chinese striped-neck turtle (Mauremys sinensis)

In aquatic organisms, ammonia is one of the major factors that affect energy levels when it exceeds its optimal concentration. Numerous studies have examined the effects of ammonia on aquatic animals, but its effect on metabolism is still unknown. The effect of ammonia on carbohydrates and lipid metabolism in the Chinese striped neck turtle (Mauremys sinensis) was investigated in this study by exposing the turtle to two different ammonia concentrations (A100: 1.53 mg L^-1) and (A200: 2.98 mg L^-1) for 24 and 48 h, respectively. Our results showed that the mRNA expression of adenosine monophosphate-activated protein kinase α1 (AMPKα1) significantly increased only in A100 at 24 h, whereas its activity increased in both ammonia-exposed groups. The two AMPK-regulated transcription factors responsible for carbohydrate metabolism also exhibited changes in ammonia-treated groups, as hepatocyte nuclear factor-4-alpha (HNF4α) increased and forkhead box protein O1 (FoxO1) decreased. The expression of phosphofructokinase (PFK) and glucose-6-phosphatase (G-6-PAS) was subsequently downregulated. In addition, transcription factors, carbohydrate-responsive element-binding protein (ChREBP), and sterol regulatory element-binding protein 1c (SREBP-1c), which are known to be involved in lipogenesis, were suppressed. These downstream genes include fatty acid synthase, stearoyl CoA desaturase, and acetyl-CoA carboxylase (FAS, SCD-1 and ACC). Moreover, the glucose content decreased, whereas the triglyceride content increased significantly in A200 at 24 h. We concluded that AMPK signaling inhibits gluconeogenesis and lipogenesis, and promotes glycolysis to meet energy demand under stressful conditions in M. sinensis.

Preclinical models of non-alcoholic steatohepatitis leading to hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the third leading cause of cancer related deaths worldwide and its incidence is increasing due to endemic obesity and the growing burden of non-alcoholic steatohepatitis (NASH) associated liver cancer. Although much is known about the clinical and histological pathology of NASH-driven HCC in humans, its etiology remains unclear and there is a lack of reliable biomarkers and limited effective therapies. Progress has been hampered by the scarcity of standardized animal models that recapitulate the gradual progression of NASH towards HCC observed in humans. Here we review existing mouse models and their suitability for studying NASH-driven HCC with special emphasis on a preclinical model that we recently developed that faithfully mimics all the clinical endpoints of progression of the human disease. Moreover, it is highly translatable, allows the use of gene-targeted mice, and is suitable for gaining knowledge of how NASH progresses to HCC and development of new targets for treatment.

Bifidobacterium-derived short-chain fatty acids and indole compounds attenuate nonalcoholic fatty liver disease by modulating gut-liver axis

Emerging evidences about gut-microbial modulation have been accumulated in the treatment of nonalcoholic fatty liver disease (NAFLD). We evaluated the effect of Bifidobacterium breve and Bifidobacterium longum on the NAFLD pathology and explore the molecular mechanisms based on multi-omics approaches. Human stool analysis [healthy subjects (n = 25) and NAFLD patients (n = 32)] was performed to select NAFLD-associated microbiota. Six-week-old male C57BL/6 J mice were fed a normal chow diet (NC), Western diet (WD), and WD with B. breve (BB) or B. longum (BL; 109 CFU/g) for 8 weeks. Liver/body weight ratio, histopathology, serum/tool analysis, 16S rRNA-sequencing, and metabolites were examined and compared. The BB and BL groups showed improved liver histology and function based on liver/body ratios (WD 7.07 ± 0.75, BB 5.27 ± 0.47, and BL 4.86 ± 0.57) and NAFLD activity scores (WD 5.00 ± 0.10, BB 1.89 ± 1.45, and BL 1.90 ± 0.99; p < 0.05). Strain treatment showed ameliorative effects on gut barrier function. Metagenomic analysis showed treatment-specific changes in taxonomic composition. The community was mainly characterized by the significantly higher composition of the Bacteroidetes phylum among the NC and probiotic-feeding groups. Similarly, the gut metabolome was modulated by probiotics treatment. In particular, short-chain fatty acids and tryptophan metabolites were reverted to normal levels by probiotics, whereas bile acids were partially normalized to those of the NC group. The analysis of gene expression related to lipid and glucose metabolism as well as the immune response indicated the coordinative regulation of β-oxidation, lipogenesis, and systemic inflammation by probiotic treatment. BB and BL attenuate NAFLD by improving microbiome-associated factors of the gut-liver axis.

Hepatic PTP4A1 ameliorates high-fat diet-induced hepatosteatosis and hyperglycemia by the activation of the CREBH/FGF21 axis

Precise regulation of kinases and phosphatases is crucial for human metabolic homeostasis. This study aimed to investigate the roles and molecular mechanisms of protein tyrosine phosphatase type IVA1 (PTP4A1) in regulating hepatosteatosis and glucose homeostasis. Method: Ptp4a1^-/- mice, adeno-associated virus encoding Ptp4a1 under liver-specific promoter, adenovirus encoding Fgf21, and primary hepatocytes were used to evaluate PTP4A1-mediated regulation in the hepatosteatosis and glucose homeostasis. Glucose tolerance test, insulin tolerance test, 2-deoxyglucose uptake assay, and hyperinsulinemic-euglycemic clamp were performed to estimate glucose homeostasis in mice. The staining, including oil red O, hematoxylin & eosin, and BODIPY, and biochemical analysis for hepatic triglycerides were performed to assess hepatic lipids. Luciferase reporter assays, immunoprecipitation, immunoblots, quantitative real-time polymerase chain reaction, and immunohistochemistry staining were conducted to explore the underlying mechanism. Results: Here, we found that deficiency of PTP4A1 aggravated glucose homeostasis and hepatosteatosis in mice fed a high-fat (HF) diet. Increased lipid accumulation in hepatocytes of Ptp4a1^-/- mice reduced the level of glucose transporter 2 on the plasma membrane of hepatocytes leading to a diminution of glucose uptake. PTP4A1 prevented hepatosteatosis by activating the transcription factor cyclic adenosine monophosphate-responsive element-binding protein H (CREBH)/fibroblast growth factor 21 (FGF21) axis. Liver-specific PTP4A1 or systemic FGF21 overexpression in Ptp4a1^-/- mice fed an HF diet restored the disorder of hepatosteatosis and glucose homeostasis. Finally, liver-specific PTP4A1 expression ameliorated an HF diet-induced hepatosteatosis and hyperglycemia in wild-type mice. Conclusions: Hepatic PTP4A1 is critical for regulating hepatosteatosis and glucose homeostasis by activating the CREBH/FGF21 axis. Our current study provides a novel function of PTP4A1 in metabolic disorders; hence, modulating PTP4A1 may be a potential therapeutic strategy against hepatosteatosis-related diseases.

Pemafibrate improves liver dysfunction and non-invasive surrogates for liver fibrosis in patients with non-alcoholic fatty liver disease with hypertriglyceridemia: a multicenter study

BACKGROUND

This retrospective, multicenter study evaluated the effect of pemafibrate treatment on liver function and fibrosis by liver function tests (LFTs) and various fibrotic biomarkers including FibroScan in non-alcoholic fatty liver disease (NAFLD) with hypertriglyceridemia.

METHODS

A total of 138 NAFLD patients treated with pemafibrate at three hospitals between September 2018 and April 2021 were included. To evaluate the effect of pemafibrate treatment, FibroScan-aspartate aminotransferase (FAST) score, a novel index of steatohepatitis that can be calculated based on the aspartate aminotransferase (AST) value, controlled attenuation parameter (CAP), and liver stiffness measurement (LSM) was used.

RESULTS

Serum TG levels were significantly decreased 4 weeks after pemafibrate treatment (p = 0.003). The levels of AST (p = 0.038), alanine aminotransferase (ALT) (p = 0.003), and gamma-glutamyl transferase (GGT) (p = 0.047) also significantly diminished 12 weeks after pemafibrate administration compared to before administration (p < 0.05). However, serum HDL-cholesterol (p = 0.193), LDL-cholesterol (p = 0.967), and eGFR (p = 0.909) levels were not significantly altered 12 weeks after pemafibrate administration. In addition, the fibrosis biomarkers' Type IV collagen (p = 0.753) and FIB-4 index (p = 0.333) did not significantly differ, while Autotaxin (p = 0.006) and the AST-to-platelet ratio index (APRI) (p = 0.003) significantly decreased 48 weeks after pemafibrate administration. No significant reductions in LSM (p = 0.959) and CAP (p = 0.266) were detected using FibroScan 48 weeks after pemafibrate administration. FAST score was significantly improved (p = 0.0475).

CONCLUSION

Pemafibrate improved LFTs, including fibrotic biomarkers and FAST score, due to the hepatic anti-inflammatory effect, suggesting that pemafibrate may prevent disease progression in NAFLD patients with hypertriglyceridemia.

MetGENE: gene-centric metabolomics information retrieval tool

BACKGROUND

Biomedical research often involves contextual integration of multimodal and multiomic data in search of mechanisms for improved diagnosis, treatment, and monitoring. Researchers need to access information from diverse sources, comprising data in various and sometimes incongruent formats. The downstream processing of the data to decipher mechanisms by reconstructing networks and developing quantitative models warrants considerable effort.

RESULTS

MetGENE is a knowledge-based, gene-centric data aggregator that hierarchically retrieves information about the gene(s), their related pathway(s), reaction(s), metabolite(s), and metabolomic studies from standard data repositories under one dashboard to enable ease of access through centralization of relevant information. We note that MetGENE focuses only on those genes that encode for proteins directly associated with metabolites. All other gene-metabolite associations are beyond the current scope of MetGENE. Further, the information can be contextualized by filtering by species, anatomy (tissue), and condition (disease or phenotype).

CONCLUSIONS

MetGENE is an open-source tool that aggregates metabolite information for a given gene(s) and presents them in different computable formats (e.g., JSON) for further integration with other omics studies. MetGENE is available at https://bdcw.org/MetGENE/index.php.

Integrated analysis of effect of daisaikoto, a traditional Japanese medicine, on the metabolome and gut microbiome in a mouse model of nonalcoholic fatty liver disease

Dysregulation of lipid metabolism and diabetes are risk factors for nonalcoholic fatty liver disease (NAFLD), and the gut-liver axis and intestinal microbiome are known to be highly associated with the pathogenesis of this disease. In Japan, the traditional medicine daisaikoto (DST) is prescribed for individuals affected by hepatic dysfunction. Herein, we evaluated the therapeutic potential of DST for treating NAFLD through modification of the liver and stool metabolome and microbiome by using STAM mice as a model of NAFLD. STAM mice were fed a high-fat diet with or without 3 % DST for 3 weeks. Plasma and liver of STAM, STAM with DST, and C57BL/6J ("Normal") mice were collected at 9 weeks, and stools at 4, 6, and 9 weeks of age. The liver pathology, metabolome and stool microbiome were analyzed. DST ameliorated the NAFLD activity score of STAM mice and decreased the levels of several liver lipid mediators such as arachidonic acid and its derivatives. In normal mice, nine kinds of family accounted for 94.1 % of microbiome composition; the total percentage of these family was significantly decreased in STAM mice (45.6 %), and DST administration improved this imbalance in microbiome composition (65.2 %). In stool samples, DST increased ursodeoxycholic acid content and altered several amino acids, which were correlated with changes in the gut microbiome and liver metabolites. In summary, DST ameliorates NAFLD by decreasing arachidonic acid metabolism in the liver; this amelioration seems to be associated with crosstalk among components of the liver, intestinal environment, and microbiome.

Sympathetic blockage attenuates fasting-induced hepatic steatosis

Although the central nervous system coordinates whole-body metabolism, the neural mechanism for hepatic steatosis remains unclear. This study is aimed to explore the neural mechanism of fasting-induced hepatic steatosis. Mice were pretreated with 6-hydroxydopamine to block sympathetic nerve activity before fasting, and to explore the potential effects of chemical sympathectomy on fasting-induced hepatic steatosis and transcriptional changes. Twenty-four hours fasting led to obvious hepatic steatosis, low-core temperature, and similar effects to cold-induced white adipose lipolysis. The alterations in hepatic mRNA expression revealed that the hepatic lipid accumulation did not result from an increase in hepatic lipogenesis or a decrease in fatty acid oxidation but from enhanced fatty acid uptake as indicated by upregulation of CD36. Blockage of the sympathetic nervous system via chemical sympathectomy attenuated fasting-induced hepatic steatosis and suppressed CD36 upregulation in the liver, but did not obviously alter the expression of genes associated with lipogenesis or fatty acid oxidation. These findings indicate that the sympathetic nervous system orchestrates the mechanism for fasting-induced hepatic steatosis via modulating CD36 expression and adipose fat trafficking into the liver, which provides clues to reveal new targets for fatty liver diseases.

The hepatic integrated stress response suppresses the somatotroph axis to control liver damage in nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) can be ameliorated by calorie restriction, which leads to the suppressed somatotroph axis. Paradoxically, the suppressed somatotroph axis is associated with patients with NAFLD and is correlated with the severity of fibrosis. How the somatotroph axis becomes dysregulated and whether the repressed somatotroph axis impacts liver damage during the progression of NAFLD are unclear. Here, we identify a regulatory branch of the hepatic integrated stress response (ISR), which represses the somatotroph axis in hepatocytes through ATF3, resulting in enhanced cell survival and reduced cell proliferation. In mouse models of NAFLD, the ISR represses the somatotroph axis, leading to reduced apoptosis and inflammation but decreased hepatocyte proliferation and exacerbated fibrosis in the liver. NAD+ repletion reduces the ISR, rescues the dysregulated somatotroph axis, and alleviates NAFLD. These results establish that the hepatic ISR suppresses the somatotroph axis to control cell fate decisions and liver damage in NAFLD.

Canagliflozin Attenuates Hepatic Steatosis and Atherosclerosis Progression in Western Diet-Fed ApoE-Knockout Mice

Purpose

To investigate the effect of canagliflozin (20 mg/kg) on hepatic steatosis and atherosclerosis, and further to explore its possible mechanism.

Methods

Blood glucose, blood lipid, oxidative stress response and inflammatory cytokines were examined by intraperitoneal glucose tolerance test and ELISA assay. HE and Oil Red O staining were used to estimate the extent of hepatic steatosis and atherosclerosis. RNA-seq and qRT-PCR were used to further investigate the potential mechanism. The effects of canagliflozin on autophagy were detected using transmission electron microscopy and Western blotting. The endothelial function-related markers were determined by qRT-PCR.

Results

Canagliflozin notably alleviated the elevation in blood glucose and insulin resistance in western diet-fed ApoE-/- mice. In ApoE-/-+Cana group, ApoE-/- mice had lower levels of TG, TC, LDL-C, TNF-α, IL-6, IL-1β, and MCP-1. HE and Oil Red O staining presented that canagliflozin restrained the atherosclerotic plaque development and lipid accumulation. RNA-seq showed that 87 DEGs were relevant to improvement of hepatic steatosis and atherosclerosis by canagliflozin. Among them, CPS1, ASS1, ASL, ARG1, MATLA, GLS2, GOT1, SREBP1, Plin5, Retreg1, and C/EBPβ were verified. KEGG enrichment analysis indicated that DEGs were mainly involved in amino acid metabolism. Besides, we observed that canagliflozin reduced the contents of aspartic acid and citrulline in liver. Western blotting showed that ASS1 and p-AMPK/AMPK was remarkably elevated after administration of canagliflozin. Correspondingly, canagliflozin down-regulated SREBP1, FAS, ACC1, HMGCR, p-mTOR/m-TOR, p-ULK1/ULK1 and p62, but up-regulated CPT1, Beclin 1 and LC3 II/LC3I. TEM showed that canagliflozin reduced the number of lipid droplets and increased the autophagosomes. Moreover, we found that canagliflozin elevated the aortic endothelial function-associated markers including ASS1, ASL and eNOS.

Conclusion

Canagliflozin may attenuate hepatic steatosis by improving lipid metabolism, enhancing autophagy, and reducing inflammatory response through ASS1/AMPK pathway. Besides, canagliflozin further effectively improves the aortic endothelial function, thereby suppressing atherosclerosis development.

Ferulic Acid and P-Coumaric Acid Synergistically Attenuate Non-Alcoholic Fatty Liver Disease through HDAC1/PPARG-Mediated Free Fatty Acid Uptake

Non-alcoholic fatty liver disease (NAFLD) is the most common liver disease and has become a growing public health concern worldwide. Polyphenols may improve high-fat diet (HFD)-related NAFLD. Our previous study found that ferulic acid (FA) and p-coumaric acid (p-CA) were the polyphenols with the highest content in foxtail millet. In this study, we investigated the mechanism underlying the impact of ferulic acid and p-coumaric acid (FA/p-CA) on non-alcoholic fatty liver (NAFLD). The association of FA and p-CA with fatty liver was first analyzed by network pharmacology. Synergistic ameliorating of NAFLD by FA and p-CA was verified in oleic acid (OA) and palmitic acid (PA) (FFA)-treated hepatocytes. Meanwhile, FA/p-CA suppressed final body weight and TG content and improved liver dysfunction in HFD-induced NAFLD mice. Mechanistically, our data indicated that FA and p-CA bind to histone deacetylase 1 (HDAC1) to inhibit its expression. The results showed that peroxisome proliferator activated receptor gamma (PPARG), which is positively related to HDAC1, was inhibited by FA/p-CA, and further suppressed fatty acid binding protein (FABP) and fatty acid translocase (CD36). It suggests that FA/p-CA ameliorate NAFLD by inhibiting free fatty acid uptake via the HDAC1/PPARG axis, which may provide potential dietary supplements and drugs for prevention of NAFLD.