Vitamin E Attenuates the Progression of Non-Alcoholic Fatty Liver Disease Caused by Partial Hepatectomy in Mice

The Role of Antioxidants in the Treatment of Metabolic Dysfunction-Associated Fatty Liver Disease: A Systematic Review

Non-alcoholic fatty liver disease (NAFLD) is a global public health problem that causes liver-related morbidity and mortality. It is also an independent risk factor for non-communicable diseases. In 2020, a proposal was made to refer to it as "metabolic dysfunction-associated fatty liver disease (MAFLD)", with concise diagnostic criteria. Given its widespread occurrence, its treatment is crucial. Increased levels of oxidative stress cause this disease. This review aims to evaluate various studies on antioxidant therapies for patients with MAFLD. A comprehensive search for relevant research was conducted on the PubMed, SCOPUS, and ScienceDirect databases, resulting in the identification of 87 studies that met the inclusion criteria. In total, 31.1% of human studies used natural antioxidants, 53.3% used synthetic antioxidants, and 15.5% used both natural and synthetic antioxidants. In human-based studies, natural antioxidants showed 100% efficacy in the treatment of MAFLD, while synthetic antioxidants showed effective results in only 91% of the investigations. In animal-based research, natural antioxidants were fully effective in the treatment of MAFLD, while synthetic antioxidants demonstrated effectiveness in only 87.8% of the evaluations. In conclusion, antioxidants in their natural form are more helpful for patients with MAFLD, and preserving the correct balance of pro-oxidants and antioxidants is a useful way to monitor antioxidant treatment.

PCSK7: A novel regulator of apolipoprotein B and a potential target against non-alcoholic fatty liver disease

BACKGROUND

Epidemiological evidence links the proprotein convertase subtilisin/kexin 7 (PCSK7) to triglyceride (TG) metabolism. We associated the known PCSK7 gain-of-function non-coding SNP rs236918 with higher levels of plasma apolipoprotein B (apoB) and the loss-of-function coding variant p.Pro777Leu (SNP rs201598301) with lower apoB and TG. Herein, we aimed to unravel the in vivo role of liver PCSK7.

METHODS

We biochemically defined the functional role of PCSK7 in lipid metabolism using hepatic cell lines and Pcsk7-/- mice. Our findings were validated following subcutaneous administration of hepatocyte-targeted N-acetylgalactosamine (GalNAc)-antisense oligonucleotides (ASOs) against Pcsk7.

RESULTS

Independent of its proteolytic activity, membrane-bound PCSK7 binds apoB100 in the endoplasmic reticulum and enhances its secretion. Mechanistically, the loss of PCSK7/Pcsk7 leads to apoB100 degradation, triggering an unfolded protein response, autophagy, and β-oxidation, eventually reducing lipid accumulation in hepatocytes. Non-alcoholic fatty liver disease (NAFLD) was induced by a 12-week high fat/fructose/cholesterol diet in wild type (WT) and Pcsk7-/- mice that were then allowed to recover on a 4-week control diet. Pcsk7-/- mice recovered more effectively than WT mice from all NAFLD-related liver phenotypes. Finally, subcutaneous administration of GalNAc-ASOs targeting hepatic Pcsk7 to WT mice validated the above results.

CONCLUSIONS

Our data reveal hepatic PCSK7 as one of the major regulators of apoB, and its absence reduces apoB secretion from hepatocytes favoring its ubiquitination and degradation by the proteasome. This results in a cascade of events, eventually reducing hepatic lipid accumulation, thus supporting the notion of silencing PCSK7 mRNA in hepatocytes for targeting NAFLD.

α-Tocopherol reduces VLDL secretion through modulation of intracellular ER-to-Golgi transport of VLDL

Avoiding hepatic steatosis is crucial for preventing liver dysfunction, and one mechanism by which this is accomplished is through synchronization of the rate of very low density lipoprotein (VLDL) synthesis with its secretion. Endoplasmic reticulum (ER)-to-Golgi transport of nascent VLDL is the rate-limiting step in its secretion and is mediated by the VLDL transport vesicle (VTV). Recent in vivo studies have indicated that α-tocopherol (α-T) supplementation can reverse steatosis in nonalcoholic fatty liver disease, but its effects on hepatic lipoprotein metabolism are poorly understood. Here, we investigated the impact of α-T on hepatic VLDL synthesis, secretion, and intracellular ER-to-Golgi VLDL trafficking using an in vitro model. Pulse-chase assays using [3H]-oleic acid and 100 µmol/L α-T demonstrated a disruption of early VLDL synthesis, resulting in enhanced apolipoprotein B-100 expression, decreased expression in markers for VTV budding, ER-to-Golgi VLDL transport, and reduced VLDL secretion. Additionally, an in vitro VTV budding assay indicated a significant decrease in VTV production and VTV-Golgi fusion. Confocal imaging of lipid droplet (LD) localization revealed a decrease in overall LD retention, diminished presence of ER-associated LDs, and an increase in Golgi-level LD retention. We conclude that α-T disrupts ER-to-Golgi VLDL transport by modulating the expression of specific proteins and thus reduces VLDL secretion.

The portal vein in patients with cirrhosis is not an excessively inflammatory or hypercoagulable vascular bed, a prospective cohort study

BACKGROUND

A hypercoagulable state is not associated with development of portal vein thrombosis in cirrhosis, as we previously demonstrated. However, some groups demonstrated elevated levels of inflammatory markers and activation of hemostasis in the portal vein (PV) compared to posthepatic veins, but because the liver is involved in clearance of these markers, we hypothesize that interpretation of these data is not straightforward.

AIM

To determine whether the PV has particular proinflammatory/hypercoagulable characteristics by comparing plasma sampled in the PV, hepatic vein (HV), and the systemic circulation.

METHODS

Plasma samples from 51 cirrhotic patients with portal hypertension undergoing transjugular intrahepatic portosystemic shunt placement, were taken from the PV, HV, and jugular vein (JV). Markers of inflammation (lipopolysaccharide, tumor necrosis factor-α, interleukin-6, thiobarbituric acid-reactive substances), neutrophil-extracellular-traps (cfDNA, MPO-DNA), endothelial damage (von Willebrand factor [VWF]), and hemostasis were determined and compared among the three vascular beds.

RESULTS

Markers of inflammation were slightly, but significantly higher in the PV than in the HV and systemic circulation. VWF and markers of hemostasis were modestly elevated in the PV. Levels of multiple markers were lower in the HV compared with the PV and systemic circulation. Higher model for end-stage liver disease score was associated with a more prothrombotic state in all three sample sites.

CONCLUSION

In contrast to published studies, we did not detect a clear proinflammatory or prothrombotic environment in the PV of cirrhotic patients. Many markers are lowest in the HV, indicating that the low levels of these markers in the HV, at least in part, reflect clearance of those markers in the liver.

A Molecular Insight into the Role of Antioxidants in Nonalcoholic Fatty Liver Diseases

Nonalcoholic fatty liver disease (NAFLD) defines fat accumulation in the liver, and it is commonly associated with metabolic syndromes like diabetes and obesity. Progressive NAFLD leads to nonalcoholic steatohepatitis (NASH) and ultimately causes cirrhosis and hepatocellular carcinoma, and NASH is currently a frequent cause of liver transplantation. Oxidative stress is often contributed to the progression of NAFLD, and hence, antioxidants such as silymarin, silybin, or silibinin, pentoxifylline, resveratrol, and vitamins A, C, and E are used in clinical trials against NAFLD. Silymarin induces the peroxisome proliferator-activated receptor α (PPARα), a fatty acid sensor, which promotes the transcription of genes that are required for the enzymes involved in lipid oxidation in hepatocytes. Silybin inhibits sterol regulatory element-binding protein 1 and carbohydrate response element-binding protein to downregulate the expression of genes responsible for de novo lipogenesis by activating AMP-activated protein kinase phosphorylation. Pentoxifylline inhibits TNF-α expression and endoplasmic reticulum stress-mediated inflammatory nuclear factor kappa B (NF-κB) activation. Thus, it prevents NAFLD to NASH progression. Resveratrol inhibits methylation at Nrf-2 promoters and NF-κB activity via SIRT1 activation in NAFLD conditions. However, clinically, resveratrol has not shown promising beneficial effects. Vitamin C is beneficial in NAFLD patients. Vitamin E is not effectively regressing hepatic fibrosis. Hence, its combination with antifibrotic agents is used as an adjuvant to produce a synergistic antifibrotic effect. However, to date, none of these antioxidants have been used as a definite therapeutic agent in NAFLD patients. Further, these antioxidants should be studied in NAFLD patients with larger populations and multiple endpoints in the future.

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

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

Danger signals in liver injury and restoration of homeostasis

Damage-associated molecular patterns are signalling molecules involved in inflammatory responses and restoration of homeostasis. Chronic release of these molecules can also promote inflammation in the context of liver disease. Herein, we provide a comprehensive summary of the role of damage-associated molecular patterns as danger signals in liver injury. We consider the role of reactive oxygen species and reactive nitrogen species as inducers of damage-associated molecular patterns, as well as how specific damage-associated molecular patterns participate in the pathogenesis of chronic liver diseases such as alcohol-related liver disease, non-alcoholic steatohepatitis, liver fibrosis and liver cancer. In addition, we discuss the role of damage-associated molecular patterns in ischaemia reperfusion injury and liver transplantation and highlight current studies in which blockade of specific damage-associated molecular patterns has proven beneficial in humans and mice.

May dexpanthenol, platelet-rich plasma, and thymoquinone provide new hope to maintain liver regeneration after partial hepatectomy?

BACKGROUND/AIMS

Complete liver regeneration may not always be possible after liver injuries and/or partial liver resection. The present study investigated the effects of dexpanthenol, platelet-rich plasma (PRP), and thymoquinone on liver regeneration in rats after partial hepatectomy (PH).

MATERIALS AND METHODS

A total of 34 Wistar albino rats, each weighing 250-280 g, were randomly separated into four groups. PH was performed, and except for the control group, intraperitoneal dexpanthenol, PRP, or thymoquinone was administered to the relevant groups for 7 days. All rats were then sacrificed, and the liver tissues were examined histopathologically and biochemically.

RESULTS

PRP reduced all oxidant-antioxidant parameters in rats that experienced liver regeneration, but did not create histopathological improvement in the liver tissue. Dexpanthenol had a histopathological improving effect on the liver tissue, but had no effect on biochemical parameters. Thymoquinone showed no histopathological or biochemical effects on liver regeneration.

CONCLUSION

Although dexpanthenol did not affect biochemical oxidative parameters, it was considered to have improving effects on liver regeneration histopathologically. In addition, it was thought that PRP may be used for treatment of ischemia-reperfusion injury and cholestatic damage of the liver. Nevertheless, further studies are required on these subjects.

Pharmacokinetics and Pharmacodynamics of Ursodeoxycholic Acid in an Overweight Population With Abnormal Liver Function

Ursodeoxycholic acid (UDCA) is a secondary bile acid that is used to treat primary biliary cholangitis. Although UDCA has a hepatoprotective effect in some diseases, its benefit in nonalcoholic fatty liver disease (NAFLD) remains controversial. We aimed to evaluate the pharmacokinetics (PK) and pharmacodynamics (PD) of UDCA in overweight subjects with elevated liver enzymes after multiple administrations of UDCA and compare these changes with vitamin E treatment. Overweight subjects (body mass index, 25-30 kg/m² ) with elevated alanine aminotransferase (ALT) level (40-200 IU/L) were enrolled. Subjects received one of the following three 8-week treatments: UDCA 300 mg twice daily UDCA 300 mg twice daily for 4 weeks followed by UDCA 300 mg twice daily and metformin 500 mg twice daily for 4 weeks, and vitamin E 400 IU twice daily. PK and PD (liver function, lipid profiles, insulin sensitivity, and miR-122) analyses were performed. Thirty subjects were enrolled; 1 subject withdrew his consent during the study. The PK characteristics were similar to those of healthy volunteers. The ALT and miR-122 levels decreased in the UDCA groups, whereas the ALT and aspartate aminotransferase levels decreased in the vitamin E group. The lipid profiles and insulin sensitivity did not show significant changes among the groups. There was no serious adverse event, and the safety profiles were similar among the treatment groups. The liver enzyme and miR-122 levels were decreased by UDCA. Considering UDCA and vitamin E have a hepatoprotective effect and different mechanisms of action, combination therapy could be an option for NAFLD.

Plasma levels of circulating DNA are associated with outcome, but not with activation of coagulation in decompensated cirrhosis and ACLF

Acute-on-chronic liver failure (ACLF) is a recently (re)defined syndrome of acute decompensation of cirrhosis that presents with extrahepatic organ failure(s) and poor outcome. Given the prominent role of inflammation and activation of coagulation in ACLF, we hypothesized that ACLF might be characterized by the generation of neutrophil extracellular traps (NETs), that could drive both activation of coagulation and progression of organ failure.

Methods

We measured markers of circulating DNA, activation of coagulation, inflammation, and oxidative stress in 52 patients with acute decompensation (AD) of cirrhosis and 57 patients with ACLF on admission, and compared levels with 40 healthy controls.

Results

All analytes were higher in patients compared to controls. Plasma levels of cell-free DNA, but not of the specific NET marker myeloperoxidase-DNA complexes were higher in patients with ACLF compared to AD cirrhosis. In addition, TAT complexes (coagulation), IL-6 (inflammation), and TBARS (oxidative stress) were higher in ACLF compared to AD. Markers for activation of coagulation were not associated with circulating DNA, IL-6, or TBARS. In contrast, levels of circulating DNA, IL-6, and TBARS were higher in patients with more severe disease, higher in patients with organ failure, and higher in patients that died within 30 days of admission. Importantly, myeloperoxidase-DNA levels did not differ between patients with complications and poor outcome.

Conclusions

Collectively, we show that cell-free DNA, inflammation, and oxidative stress are associated with outcomes in AD and ACLF, but not with activation of coagulation. Our data argue against a role of NETs in activation of coagulation and in progression of organ failure in patients with AD and ACLF.

Lay summary

Acute-on-chronic liver failure is a devastating syndrome that can follow acute decompensation of chronic liver disease. Herein, we demonstrate that these patients accumulate DNA released from dying cells in their blood, and that the quantity of this DNA is related to the outcome of disease. We also show that outcome of disease is not related to recently described neutrophil extracellular traps, which have been shown in animal models to play vital roles in the progression of liver diseases.

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Levels of circulating DNA, IL6, and TBARS are higher in patients with ACLF than in patients with AD

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Circulating DNA, IL6, and TBARS are higher in patients with organ failure and those who died

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Circulating DNA, IL6, and TBARS are not correlated with markers of activation of coagulation

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The neutrophil extracellular trap marker MPO-DNA was not related to coagulation or outcome

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DNA- or NET-related coagulation does not appear to drive ACLF progression

Vitamin E alleviates non-alcoholic fatty liver disease in phosphatidylethanolamine N-methyltransferase deficient mice

Phosphatidylethanolamine N-methyltransferase (PEMT) converts phosphatidylethanolamine (PE) to phosphatidylcholine (PC), mainly in the liver. Pemt^-/- mice are protected from high-fat diet (HFD)-induced obesity and insulin resistance, but develop severe non-alcoholic fatty liver disease (NAFLD) when fed a HFD, mostly due to impaired VLDL secretion. Oxidative stress is thought to be an essential factor in the progression from simple steatosis to steatohepatitis. Vitamin E is an antioxidant that has been clinically used to improve NAFLD pathology. Our aim was to determine whether supplementation of the diet with vitamin E could attenuate HFD-induced hepatic steatosis and its progression to NASH in Pemt^-/- mice. Treatment with vitamin E (0.5 g/kg) for 3 weeks improved VLDL-TG secretion and normalized cholesterol metabolism, but failed to reduce hepatic TG content. Moreover, vitamin E treatment was able to reduce hepatic oxidative stress, inflammation and fibrosis. We also observed abnormal ceramide metabolism in Pemt^-/- mice fed a HFD, with elevation of ceramides and other sphingolipids and higher expression of mRNAs for acid ceramidase (Asah1) and ceramide kinase (Cerk). Interestingly, vitamin E supplementation restored Asah1 and Cerk mRNA and sphingolipid levels. Together this study shows that vitamin E treatment efficiently prevented the progression from simple steatosis to steatohepatitis in mice lacking PEMT.

Haptoglobin Genotype and Vitamin E Versus Placebo for the Treatment of Nondiabetic Patients with Nonalcoholic Steatohepatitis in China: A Multicenter, Randomized, Placebo-Controlled Trial Design

INTRODUCTION

Vitamin E is one of the most promising agents for nonalcoholic steatohepatitis (NASH) treatment, and its drug responsiveness may be closely associated with haptoglobin (Hp) genotype. However, its efficacy and safety remain unknown in China. This clinical trial of vitamin E versus placebo for the treatment of nondiabetic patients with nonalcoholic steatohepatitis (VENS) is conducted to evaluate (a) the efficacy and safety of treatment with vitamin E softgel (300 mg/day) determined from standardized histologic scoring of liver biopsies, (b) whether treatment with vitamin E improves biochemical parameters, cytokines, anthropometric parameters, controlled attenuation parameter (CAP), and transient elastography (TE) values determined by Fibroscan and health-related quality of life (SF-36), (c) whether the efficacy of vitamin E treatment is associated with the Hp genotype in nondiabetic adults with NASH.

METHODS

VENS is a multicenter, randomized, double-masked, placebo parallel controlled trial to evaluate the efficacy and safety of treatment with vitamin E softgel in nondiabetic adults with NASH versus treatment with placebo in China. Liver biopsies are read by a pathological evaluation committee independently according to the NASH Clinical Research Network (CRN) scoring system. The NAFLD activity score (NAS) represents the sum of scores for steatosis, lobular inflammation, and hepatocyte ballooning. The definition of histologic improvement requires all three of the following criteria to be met: (a) either improvement in NAS by at least 2 points or post-treatment NAS score no higher than 3, (b) at least 1-point improvement in the score for ballooning, and (c) no worsening of fibrosis stages. We plan to recruit 120 biopsy-proven NASH patients from13 centers in China. Participants will be randomly assigned to groups treated with either with vitamin E (100 mg, tid) or placebo for 96 weeks then followed by 24 weeks of post-treatment observation. Biochemical parameters, cytokines, anthropometric parameters, CAP and TE values, Hp genotype, and several questionnaires will be collected as per the schedule. This protocol was approved by the Ethics Committee of Hangzhou Normal University Affiliated Hospital to ensure patients safety, and R&G Pharmastudies Co., Ltd. was established for monitoring the accumulated interim data to review efficacy and quality of data collection and overall study management.

RESULTS

As a preliminary study, a mobile phone application (app) for lifestyle modification and database recording ( http://laiyivens.365hy.com ) was exploited for every participant. The percentage of NAFLD patients with Hp 2-2 allele is much higher than that of Western patients (65.71% vs 36%, respectively), which suggests that the Chinese benefit more from vitamin E treatment.

CONCLUSION

VENS is the first randomized controlled trial (RCT) to evaluate the efficacy of Vitamin E in treating nondiabetic NASH patients in China.

TRIAL REGISTRATION

This study registered at https://clinicaltrials.gov (registration number: NCT02962297).

FUNDING

Zhejiang Medicine Co., Ltd.

Vitamin E as a Treatment for Nonalcoholic Fatty Liver Disease: Reality or Myth?

Obesity is one of the major epidemics of this millennium, and its incidence is growing worldwide. Following the epidemics of obesity, nonalcoholic fatty liver disease (NAFLD) has become a disease of increasing prevalence and a leading cause of morbidity and mortality closely related to cardiovascular disease, malignancies, and cirrhosis. It is believed that oxidative stress is a main player in the development and progression of NAFLD. Currently, a pharmacological approach has become necessary in NAFLD because of a failure to modify lifestyle and dietary habits in most patients. Vitamin E is a potent antioxidant that has been shown to reduce oxidative stress in NAFLD. This review summarizes the biological activities of vitamin E, with a primary focus on its therapeutic efficacy in NAFLD.

Alternative treatment methods attenuate the development of NAFLD: A review of resveratrol molecular mechanisms and clinical trials

Nonalcoholic fatty liver disease (NAFLD) is considered to be one of the most common liver pathologies that occur widely among societies with a predominance of the Western dietary pattern. NAFLD may progress from hepatic steatosis to nonalcoholic steatohepatitis (NASH), subsequently leading to cirrhosis and becoming a major cause of hepatocellular carcinoma. Thus its prevention and therapy play an important role in hepatology. To our knowledge, there is no effective treatment for patients with NAFLD. The aim of this review was to summarize the results of recent alternative treatment studies conducted both on cell cultures and in vivo that concern molecular effects of resveratrol (3,5,4'-trihydroxystilbene) in the treatment of NAFLD. The precise metabolism, pharmacology, and clinical trials with different concentrations of resveratrol were described. The review also presents a brief summary of other alternative treatment methods of NAFLD and their mechanisms compared with current clinical understanding.