SIRT1 as a potential therapeutic target for treatment of nonalcoholic fatty liver disease

Pharmacological and biochemical insights into lead-induced hepatotoxicity: Pathway interplay and the protective effects of arbutin via the oral and intraperitoneal routes in silico and in vivo

INTRODUCTION

Lead acetate (PbAc), a hazardous heavy metal, poses significant threats to human health and the environment because of widespread industrial exposure. PbAc exposure leads to liver injury primarily through oxidative stress and the disruption of key regulatory pathways. Understanding these mechanisms and exploring protective agents are vital for mitigating PbAc-induced hepatotoxicity. Therefore, we aimed to investigate the molecular pathways implicated in PbAc-induced liver damage, focusing on Sirt-1, Nrf2 (HO-1, NQO1, and SOD), Akt-1/GSK3β, m-TOR, and P53. Additionally, we aimed to assess the hepatoprotective effects of arbutin, which is administered orally and intraperitoneally, to determine the most effective delivery method.

METHODOLOGY

In silico analyses were conducted to identify relevant protein networks associated with Sirt-1 and AKT-1/GSK-3B pathways. The pharmacodynamic properties of arbutin were examined, followed by molecular docking studies to elucidate its interactions with the selected protein network. In vivo preclinical studies were carried out on adult male rats randomly assigned to 6 different treatment groups, including PbAc exposure and PbAc exposure treated with arbutin either orally or intraperitoneally.

RESULTS

PbAc exposure led to hepatic oxidative stress, as evidenced by elevated MDA levels and SIRT-1 inhibition, disrupting antioxidant pathways and activating antiautophagic and proapoptotic pathways, ultimately resulting in hepatocyte necrosis. Both oral and intraperitoneal arbutin administration effectively modifed these effects, with intraperitoneal delivery showing superior efficacy in mitigating PbAc-induced histological, immunological, and biochemical alterations.

CONCLUSION

This study provides insights into the molecular mechanisms underlying PbAc-induced liver injury and highlights the hepatoprotective potential of arbutin. These findings suggest that arbutin, particularly when administered intraperitoneally, holds promise as a therapeutic agent for combating PbAc-induced hepatotoxicity.

Elevated mir-141 in obesity: Insights into the interplay with sirtuin 1 and non-alcoholic fatty liver disease

Background

Changes in gene expression related to obesity are linked to microRNAs, such as miR-141, which play a crucial role in metabolic homeostasis. Sirtuin 1 (SIRT1), an enzyme that plays a crucial role in regulating various cellular functions and metabolism, is implicated in obesity and the ensuing non-alcoholic fatty liver disease (NAFLD). The aim of this research was to evaluate the levels of miR-141 and its relationship with SIRT1 and NAFLD.

Methods

A group of 100 adults (50 with obesity and 50 with normal-weight) were selected and underwent complete clinical evaluation and anthropometric measurements. Biochemical parameters were assessed in blood serum, and the levels of miR-141 in plasma were measured by real-time PCR. The expression of the SIRT1 gene was also evaluated in the peripheral blood mononuclear cells using Real-time PCR. The ELISA technique was used to determine insulin levels. Liver steatosis was assessed by ultrasound.

Results

The results showed that levels of miR-141 were significantly increased in participants with obesity compared with the control group. Conversely, the expression of the SIRT1 gene in individuals with obesity was lower than that in control participants. A strong negative correlation was observed between miR-141 and SIRT1 and a strong positive association was observed between miR-141 and metabolic parameters. Furthermore, participants with fatty liver had significantly elevated levels of miR-141 gene expression and lower expression of SIRT1 gene, compared to those without fatty liver.

Conclusion

elevated levels of miR-141 in individuals with obesity might be a contributing factor in the repression of SIRT1 in obesity and its consequences, including NAFLD. Therefore, miR-141 might serve as a suitable diagnostic and therapeutic target in obesity and NAFLD.

Effects of excess high-normal alanine aminotransferase levels in relation to new-onset metabolic dysfunction-associated fatty liver disease: Clinical implications

In this editorial, we comment on the article by Chen et al recently published in 2024. We focus the debate on whether reducing the upper limit of normal of alanine aminotransferase (ALT) would effectively identify cases of fibrosis in metabolic-dysfunction associated fatty liver disease (MAFLD). This is important given the increasing prevalence of MAFLD and obesity globally. Currently, a suitable screening test to identify patients in the general population does not exist and most patients are screened after the finding of an abnormal ALT. The authors of this paper challenge the idea of what a normal ALT is and whether that threshold should be lowered, particularly as their study found that 83.12% of their study population with a diagnosis of MAFLD had a normal ALT. The main advantages of screening would be to identify patients and provide intervention early, the mainstay of this being changing modifiable risk factors and monitoring for liver fibrosis. However, there is not enough suitable therapeutic options available as of yet although this is likely to change in the coming years with more targets for therapy being discovered. Semaglutide is one example of this which has demonstrated benefit with an acceptable side effect profile for those patients with MAFLD and obesity, although studies have not yet shown a significant improvement in fibrosis regression. It would also require a huge amount of resource if a reduced ALT level alone was used as criteria; it is more likely that current scoring systems such as fibrosis-4 may be amended to represent this additional risk. Currently, there is not a good argument to recommend widespread screening with a reduced ALT level as this is unlikely to be cost-effective. This is compounded by the fact that there is a significant heterogeneity in what is considered a normal ALT between laboratories. Although studies previously have suggested a more pragmatic approach in screening those over the age of 60, this is likely to change with the increasing incidence of obesity within the younger age groups. The main message from this study is that those who have hypercholesterolemia and high body metabolic index should have these risk factors modified to maintain a lower level of ALT to reduce the risk of progression to fibrosis and cirrhosis.

Oligonucleotide therapies for nonalcoholic steatohepatitis

Nonalcoholic steatohepatitis (NASH) represents a severe disease subtype of nonalcoholic fatty liver disease (NAFLD) that is thought to be highly associated with systemic metabolic abnormalities. It is characterized by a series of substantial liver damage, including hepatocellular steatosis, inflammation, and fibrosis. The end stage of NASH, in some cases, may result in cirrhosis and hepatocellular carcinoma (HCC). Nowadays a large number of investigations are actively under way to test various therapeutic strategies, including emerging oligonucleotide drugs (e.g., antisense oligonucleotide, small interfering RNA, microRNA, mimic/inhibitor RNA, and small activating RNA) that have shown high potential in treating this fatal liver disease. This article systematically reviews the pathogenesis of NASH/NAFLD, the promising druggable targets proven by current studies in chemical compounds or biological drug development, and the feasibility and limitations of oligonucleotide-based therapeutic approaches under clinical or pre-clinical studies.

Resveratrol attenuates against high-fat-diet-promoted non-alcoholic fatty liver disease in rats mainly by targeting the miR-34a/SIRT1 axis

This study evaluated if miR-34a/SIRT1 signalling mediates the anti-hepatosteatotic effect of resveratrol (RSV) in high-fat-diet (HFD)-fed rats. Rats were divided into seven groups (n = 6/each) as control, control + miR-34a agomir negative control, HFD, HFD + miR-34a, HFD + RSV, HFD + RSV + Ex-527 (a SIRT1 inhibitor), and HFD + RSV + miR-34a agomir. After 8 weeks, RSV suppressed dyslipidemia, lowered fasting glucose and insulin levels, improved insulin sensitivity, and prevented hepatic lipid accumulation. These effects were associated with hepatic downregulation of SREBP1 and SREBP2, upregulation of PPARα, and acetylation of Nrf2 (activation) and NF-κβ p65 (inhibition). Also, RSV reduced the transcription of miR-34a and increased the nuclear localisation of SIRT1 in the livers, muscles, and adipose tissues of HFD-fed rats. All these effects were prevented by EX-527 and miR-34a agmir. In conclusion, RSV prevents HFD-induced insulin resistance and hepatic steatosis by suppressing miR-34a-induced activation of SIRT1.

Lauric acid attenuates hepato-metabolic complications and molecular alterations in high-fat diet-induced nonalcoholic fatty liver disease in rats

Nonalcoholic fatty liver disease (NAFLD) has emerged as a major chronic liver illness characterized by increase of lipid content in the liver. This study investigated the role of lauric acid to treat NAFLD in male adult Sprague Dawley rats. In this study, to induce NAFLD in the rats, a high-fat diet (HFD) was administered for eight consecutive weeks. Lauric acid groups received lauric acid (250 and 500 mg/kg; orally), concurrently with HFD for eight consecutive weeks. Lauric acid could ameliorate the serum levels of TG, TC, ALT, AST, blood glucose, and insulin. Moreover, lauric acid significantly elevated the levels of SOD, GSH, catalase, and IL-10. Additionally, it lowered the hepatic levels of MDA, ROS, MPO, 4-HNE, interleukin (IL)-1β, and tumor necrosis factor (TNF-α). Furthermore, lauric acid significantly up-regulated the hepatic expression of IRS1, AMPK, PI3K, and SIRT1 genes. In parallel, lauric acid could improve the histopathological picture of the liver and reduce the liver apoptosis via decreasing the expression of annexin V (Anx V). Finally, our data proposed that lauric acid could be an effective candidate for the NAFLD treatment.

CDK4/6 inhibitors in drug-induced liver injury: a pharmacovigilance study of the FAERS database and analysis of the drug-gene interaction network

Objective

The aim of this study was to investigate the potential risk of drug-induced liver injury (DILI) caused by the CDK4/6 inhibitors (CDK4/6is abemaciclib, ribociclib, and palbociclib by comprehensively analyzing the FDA Adverse Event Reporting System (FAERS) database. Moreover, potential toxicological mechanisms of CDK4/6is-related liver injury were explored via drug-gene network analysis.

Methods

In this retrospective observational study, we collected reports of DILI associated with CDK4/6i use from the FAERS dated January 2014 to March 2023. We conducted disproportionality analyses using the reporting odds ratio (ROR) with a 95% confidence interval (CI). Pathway enrichment analysis and drug-gene network analyses were subsequently performed to determine the potential mechanisms underlying CDK4/6i-induced liver injury.

Results

We found positive signals for DILI with ribociclib (ROR = 2.60) and abemaciclib (ROR = 2.37). DILIs associated with liver-related investigations, signs, and symptoms were confirmed in all three reports of CDK4/6is. Moreover, ascites was identified as an unlisted hepatic adverse effect of palbociclib. We isolated 189 interactive target genes linking CDK4/6 inhibitors to hepatic injury. Several key genes, such as STAT3, HSP90AA1, and EP300, were revealed via protein-protein analysis, emphasizing their central roles within the network. KEGG pathway enrichment of these genes highlighted multiple pathways.

Conclusion

Our study revealed variations in hepatobiliary toxicity among the different CDK4/6 inhibitors, with ribociclib showing the highest risk of liver injury, followed by abemaciclib, while palbociclib appeared relatively safe. Our findings emphasize the need for cautious use of CDK4/6 inhibitors, and regular liver function monitoring is recommended for long-term CDK4/6 inhibitor use.

Low sirtuin-1 levels are associated with gestational diabetes mellitus

BACKGROUND

The aim of this study was to determine whether sirtuin-1 (SIRT1), which has a regulatory role in glucose and lipid metabolism with its deacetylase activity, has a decisive role in predicting gestational diabetes (GDM).

METHODS

This study was performed at the antenatal outpatient clinic of Ankara City Hospital between January 2021 and May 2021. A total of 525 women with low-risk pregnancy underwent the 75 g oral glucose tolerance test (OGTT) between 24th-28th weeks of pregnancy during the study period. Fasting serum SIRT1 levels of patients diagnosed with GDM according to OGTT results were compared some of those without GDM.

RESULTS

Of the 525 pregnant women who underwent 75 g OGTT, 50 (9.6%) were diagnosed with GDM. The data of pregnant women with GDM were compared with age and Body Mass Index matched 122 controls. While serum SIRT1 levels were 22.0 (19.9-24.3) ng/mL in the GDM group, it was 34.7 (28.8-54.6) ng/mL in the control group (P<0.001). ROC curve analysis showed that a threshold level for serum SIRT1 equal to or greater than 27.3 ng/mL may predict GDM with a sensitivity of 86% and specificity of 80%.

CONCLUSIONS

Second-trimester low serum SIRT1 levels are associated with GDM. It may be a diagnostic marker for GDM.

Dihydrotrichodimerol Purified from the Marine Fungus Acremonium citrinum Prevents NAFLD by Targeting PPARα

The pathogenesis of nonalcoholic fatty liver disease (NAFLD) is closely linked to the imbalance of lipid and glucose metabolism, in which peroxisome proliferator-activated receptors (PPARs) play essential roles. The clinical trials have shown the beneficial effects of the PPARs' ligands on NAFLD. In this study, we screen the extracts from the marine fungus Acremonium citrinum and identify the natural compounds dihydrotrichodimerol (L1A) and trichodimerol (L1B) as the ligands of PPARs, of which L1A is a dual PPARα/γ agonist, whereas L1B is a selective PPARγ agonist. L1A but not L1B significantly prevents hepatic lipid accumulation in an oleic acid-induced NAFLD cell model as well as in a high-fat-diet-induced NAFLD mouse model. Moreover, L1A potently inhibits hepatic steatosis in a PPARα-dependent manner in another NAFLD mouse model constructed by using a choline-deficient and amino acid-defined diet. Mechanistically, L1A transcriptionally up-regulates the expression of SIRT1 in a PPARα-dependent manner, followed by the activation of AMPK and inactivation of ACC, resulting in the inhibition of lipid anabolism and the increase of lipid catabolism. Taken together, our study reveals a dual ligand of PPARα/γ with a distinct structure and therapeutic effect on NAFLD, providing a potential drug candidate bridging the currently urgent need for the management of NAFLD.

Mechanisms of Action of Mesenchymal Stem Cells in Metabolic-Associated Fatty Liver Disease

Metabolic-associated fatty liver disease (MAFLD) is currently the most common chronic liver disease worldwide. However, its pathophysiological mechanism is complicated, and currently, it has no FDA-approved pharmacological therapies. In recent years, mesenchymal stem cell (MSC) therapy has attracted increasing attention in the treatment of hepatic diseases. MSCs are multipotent stromal cells that originated from mesoderm mesenchyme, which have self-renewal and multipotent differentiation capability. Recent experiments and studies have found that MSCs have the latent capacity to be used for MAFLD treatment. MSCs have the potential to differentiate into hepatocytes, which could be induced into hepatocyte-like cells (HLCs) with liver-specific morphology and function under appropriate conditions to promote liver tissue regeneration. They can also reduce liver tissue injury and reverse the development of MAFLD by regulating immune response, antifibrotic activities, and lipid metabolism. Moreover, several advantages are attributed to MSC-derived exosomes (MSC-exosomes), such as targeted delivery, reliable reparability, and poor immunogenicity. After entering the target cells, MSC-exosomes help regulate cell function and signal transduction; thus, it is expected to become an emerging treatment for MAFLD. In this review, we comprehensively discussed the roles of MSCs in MAFLD, main signaling pathways of MSCs that affect MAFLD, and mechanisms of MSC-exosomes on MAFLD.

Screening for MAFLD: who, when and how?

Metabolic-associated fatty liver disease (MAFLD) is a highly prevalent disease with increasing prevalence worldwide. Currently, no universal screening methods have been standardized, even when this disease poses a major health burden. MAFLD as a spectrum of diseases can range from simple steatosis, and steatohepatitis to fibrosis and hepatocellular carcinoma. Its extra-hepatic manifestations are vast and include cardiovascular diseases, extra-hepatic malignancies, cognitive and respiratory alterations. Given its extensive damage targets as well as its high prevalence, timely identification of the high-risk population presenting metabolic dysfunction should undergo universal non-invasive screening methods, which can be carried out through blood tests, easy and effective imaging techniques, such as ultrasound, score calculation and general clinical information brought together from primary patient-physician contact.

Detangling the interrelations between MAFLD, insulin resistance, and key hormones

Metabolic dysfunction-associated fatty liver disease (MAFLD) has increasingly become a significant and highly prevalent cause of chronic liver disease, displaying a wide array of risk factors and pathophysiologic mechanisms of which only a few have so far been clearly elucidated. A bidirectional interaction between hormonal discrepancies and metabolic-related disorders, including obesity, type 2 diabetes mellitus (T2DM), and polycystic ovarian syndrome (PCOS) has been described. Since the change in nomenclature from non-alcoholic fatty liver disease (NAFLD) to MAFLD is based on the clear impact of metabolic elements on the disease, the reciprocal interactions of hormones such as insulin, adipokines (leptin and adiponectin), and estrogens have strongly pointed to the intrinsic links that lead to the heterogeneous epidemiology, clinical presentations, and risk factors involved in MAFLD in different populations. The objective of this work is twofold. Firstly, there is a brief discussion regarding the change in nomenclature as well as epidemiology, risk factors, and pathophysiologic mechanisms other than hormonal effects, which include nutrition and the gut microbiome, as well as genetic and epigenetic influences. Secondly, we review the basis of the most important hormonal factors involved in the development and progression of MAFLD that act both independently and in an interrelated manner.

Anti-apoptotic properties of N-Acetyl cysteine and its effects on of Liver X receptor and Sirtuin 1 expression in the liver of rats exposed to Lead

BACKGROUND

This study aimed to evaluate the expression of Liver X receptor (Lxr), Sirtuin 1 (Sirt1), apoptotic-related genes, and the protective role of N-acetylcysteine (NAC) in the liver of rats treated with Lead (Pb).

METHODS

Rats were randomly divided into 5 groups, including G1 (control), G2 (single dose of Pb), G3 (continuous dose of Pb), G4 (single dose of Pb + NAC), and G5 (continuous dose of Pb + NAC). Lipid profiles and liver specific enzymes were assessed. Expression of Lxr, Sirt1, Bax and Caspase-3 genes was considered using RT-PCR.

RESULTS

Exposure to Pb caused a significant accumulation of Pb in the blood and liver tissue, increase in serum AST, ALT and ALP enzymes, as well as lipid profiles. Chronic exposure to Pb caused a significant decrease in Lxr (3.15-fold; p < 0.001) and Sirt1 (2.78-fold; p = 0.009), but significant increase in expression of Bax (4.49-fold; p < 0.001) and Caspase-3 (4.10-fold; p < 0.001) genes when compared to the control. Combined therapy with Pb + NAC in rats caused a significant decrease in AST, ALT and ALP values (28.93%, 20.80% and 28.86%, respectively) in the blood as compared to rats treated with Pb alone. Co-treated with Pb + NAC significantly increased the expression of Lxr (1.72-fold; p = 0.043) and Sirt1 (2.45-fold; p = 0.008), but decreased the expression of Bax (1.96-fold; p = 0.03) and Caspase 3 (2.22-fold; p = 0.029) genes when compared to rats treated with Pb alone.

CONCLUSION

Chronic exposure to Pb is strongly associated with accumulation of Pb in the blood and liver, hepatic cells apoptosis, down-expression of Lxr and Sirt1 genes and consequently liver injury and abnormal lipid profiles. NAC reversed the Pb-induced toxicity on the liver tissue.

All Roads Lead to Cathepsins: The Role of Cathepsins in Non-Alcoholic Steatohepatitis-Induced Hepatocellular Carcinoma

Cathepsins are lysosomal proteases that are essential to maintain cellular physiological homeostasis and are involved in multiple processes, such as immune and energy regulation. Predominantly, cathepsins reside in the lysosomal compartment; however, they can also be secreted by cells and enter the extracellular space. Extracellular cathepsins have been linked to several pathologies, including non-alcoholic steatohepatitis (NASH) and hepatocellular carcinoma (HCC). NASH is an increasingly important risk factor for the development of HCC, which is the third leading cause of cancer-related deaths and poses a great medical and economic burden. While information regarding the involvement of cathepsins in NASH-induced HCC (NASH-HCC) is limited, data to support the role of cathepsins in either NASH or HCC is accumulating. Since cathepsins play a role in both NASH and HCC, it is likely that the role of cathepsins is more significant in NASH-HCC compared to HCC derived from other etiologies. In the current review, we provide an overview on the available data regarding cathepsins in NASH and HCC, argue that cathepsins play a key role in the transition from NASH to HCC, and shed light on therapeutic options in this context.

Progress in Nonalcoholic Fatty Liver Disease: SIRT Family Regulates Mitochondrial Biogenesis

Nonalcoholic fatty liver disease (NAFLD) is characterized by hepatic steatosis, insulin resistance, mitochondrial dysfunction, inflammation, and oxidative stress. As a group of NAD+-dependent III deacetylases, the sirtuin (SIRT1-7) family plays a very important role in regulating mitochondrial biogenesis and participates in the progress of NAFLD. SIRT family members are distributed in the nucleus, cytoplasm, and mitochondria; regulate hepatic fatty acid oxidation metabolism through different metabolic pathways and mechanisms; and participate in the regulation of mitochondrial energy metabolism. SIRT1 may improve NAFLD by regulating ROS, PGC-1α, SREBP-1c, FoxO1/3, STAT3, and AMPK to restore mitochondrial function and reduce steatosis of the liver. Other SIRT family members also play a role in regulating mitochondrial biogenesis, fatty acid oxidative metabolism, inflammation, and insulin resistance. Therefore, this paper comprehensively introduces the role of SIRT family in regulating mitochondrial biogenesis in the liver in NAFLD, aiming to further explain the importance of SIRT family in regulating mitochondrial function in the occurrence and development of NAFLD, and to provide ideas for the research and development of targeted drugs. Relatively speaking, the role of some SIRT family members in NAFLD is still insufficiently clear, and further research is needed.

Amelioration of high-fat diet (HFD) + CCl4 induced NASH/NAFLD in CF-1 mice by activation of SIRT-1 using cinnamoyl sulfonamide hydroxamate derivatives: in-silico molecular modelling and in-vivo prediction

Non-alcoholic fatty liver disease (NAFLD) is one of the major hepatic metabolic disorders that occurs because of the accumulation of lipids in hepatocytes in the form of free fatty acids (FFA) and triglycerides (TG) which become non-alcoholic steatohepatitis (NASH). NOTCH-1 receptors act as novel targets for the development of NAFLD/NASH, where overexpression of NOTCH-1 receptor alters the lipid metabolism in hepatocytes leading to NAFLD. SIRT-1 deacetylates the NOTCH-1 receptor and inhibits NAFLD. Hence, computer-aided drug design (CADD) was used to check the SIRT-1 activation ability of cinnamic sulfonyl hydroxamate derivatives (NMJ 1–8), resveratrol, and vorinostat. SIRT-1 (PDB ID: 5BTR) was docked with eight hydroxamate derivatives and vorinostat using Schrödinger software. Based on binding energy obtained (– 26.31 to – 47.34 kcal/mol), vorinostat, NMJ-2, NMJ-3, NMJ-5 were selected for induced-fit docking (IFD) and results were within – 750.70 to – 753.22 kcal/mol. Qikprop tool was used to analyse the pre pharmacokinetic parameters (ADME analysis) of all hydroxamate compounds. As observed in the molecular dynamic (MD) study, NMJ-2, NMJ-3 were showing acceptable results for activation of SIRT-1. Based on these predictions, in-vivo studies were conducted in CF1 mice, where NMJ-3 showed significant (p < 0.05) changes in lipid profile and anti-oxidant parameters (Catalase, SOD, GSH, nitrite, and LPO) and plasma insulin levels. NMJ-3 treatment also reduced inflammation, fibrosis, and necrosis in liver samples.

Corn peptides improved obesity-induced non-alcoholic fatty liver disease through relieving lipid metabolism, insulin resistance and oxidative stress

Non-alcoholic fatty liver disease (NAFLD) is increasingly threatening human health. The remarkable effects of corn peptides (CPs) as bioactive peptides on liver protection have attracted much attention. Nevertheless, the specific effect of CPs on NAFLD remains unclear. The present study was designed to investigate the efficacy of CPs in the prevention and auxiliary treatment of high-fat diet (HFD)-induced NAFLD in SD rats, and puerarin was used as the positive control. SD rats were fed a high-fat diet to establish the NAFLD rat model, and LO2 cells were treated with a high concentration of fructose to simulate the NAFLD cell model. NAFLD was comprehensively examined in terms of body weight, liver function markers, serum biochemistry and liver histology. Protein expression was determined using western blot analysis. The results of animal experiments showed that CPs could effectively inhibit the rate of weight gain, reduce the blood lipid level and liver index, and enhance glucose tolerance. The results of cell experiments showed that CPs could effectively reduce the accumulation of lipids in LO2 cells and inhibit the accumulation of reactive oxygen species (ROS). In addition, CPs could markedly reduce liver lipid accumulation in the liver cell and liver tissue, as further evidenced by the reduced expression of SREBP-1c in human non-tumour hepatic (LO2) cells. Meanwhile, the increased expression of SIRT1/PPAR-α and Nrf2/HO-1 pathways under the pretreatment of CPs in LO2 cells indicated that CPs could markedly relieve high fat-induced fatty liver injury, regulate insulin sensitivity, and reduce production of ROS. The results of in vivo and in vitro experiments demonstrated that CPs provided potential prevention and auxiliary treatment for NAFLD through reducing lipid accumulation, alleviating insulin resistance, and inhibiting oxidative stress. This study investigated the biological activity of CPs and laid the theoretical basis for the development of CP-based functional foods and dietary supplements.

Modulation of Oxidative Stress-Induced Senescence during Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease is characterized by disturbed lipid metabolism and increased oxidative stress. These conditions lead to the activation of different cellular response mechanisms, including senescence. Cellular senescence constitutes an important response to injury in the liver. Recent findings show that chronic oxidative stress can induce senescence, and this might be a driving mechanism for NAFLD progression, aggravating the disturbance of lipid metabolism, organelle dysfunction, pro-inflammatory response and hepatocellular damage. In this context, the modulation of cellular senescence can be beneficial to ameliorate oxidative stress-related damage during NAFLD progression. This review focuses on the role of oxidative stress and senescence in the mechanisms leading to NAFLD and discusses the possibilities to modulate senescence as a therapeutic strategy in the treatment of NAFLD.

The Ameliorating Effects of Apple Polyphenol Extract on High-Fat-Diet-Induced Hepatic Steatosis Are SIRT1-Dependent: Evidence from Hepatic-Specific SIRT1 Heterozygous Mutant C57BL/6 Mice

Apple polyphenol extract (APE) has been reported to possess protective effects against hepatic steatosis. To explore whether APE-induced alleviation of hepatic steatosis is SIRT1-dependent, the present study was carried out using wild-type and hepatic SIRT1 heterozygous mutant (Sirt1^+/-) C57BL/6 mice. On consideration of the sex disparity related to hepatic steatosis morbidity, both male and female mice were included in the study. Six to eight week old mice were fed a high-fat diet (HFD) and randomly assigned to one of the following groups: (1) wild-type mice (wt+HFD), (2) Sirt1^+/- mice (Sirt1^+/-+HFD), and (3) Sirt1^+/- mice with 500 mg/(kg·bw·d) APE intragastric administration (Sirt1^+/-+HAP). HFD-induced weight gain and triglyceride accumulation was more prominent in Sirt1^+/- mice in comparison to wild-type mice. Following APE treatment, these effects were significantly reduced along with the alleviation of hepatic steatosis via upregulated expression of SIRT1 at the protein and mRNA levels in both male and female mice. However, APE differentially regulated the genes related to lipid metabolism (Lkb1, Ampk, Hsl, Srebp-1c, Abcg1, and Cd36) in a sex-specific manner. Moreover, APE treatment altered gut microbiota composition, with an increased relative abundance of Akkermansia and a decreased Firmicutes/Bacterodetes ratio. Thus, our study provided new evidence supporting our hypothesis that APE-induced alleviation of hepatic steatosis is SIRT1-dependent.

Pharmacotherapy for Non-Alcoholic Fatty Liver Disease: Emerging Targets and Drug Candidates

Non-alcoholic fatty liver disease (NAFLD), or metabolic (dysfunction)-associated fatty liver disease (MAFLD), is characterized by high global incidence and prevalence, a tight association with common metabolic comorbidities, and a substantial risk of progression and associated mortality. Despite the increasingly high medical and socioeconomic burden of NAFLD, the lack of approved pharmacotherapy regimens remains an unsolved issue. In this paper, we aimed to provide an update on the rapidly changing therapeutic landscape and highlight the major novel approaches to the treatment of this disease. In addition to describing the biomolecules and pathways identified as upcoming pharmacological targets for NAFLD, we reviewed the current status of drug discovery and development pipeline with a special focus on recent evidence from clinical trials.

SIRT2 regulates mitochondrial dynamics and reprogramming via MEK1-ERK-DRP1 and AKT1-DRP1 axes

During somatic reprogramming, cellular energy metabolism fundamentally switches from predominantly mitochondrial oxidative phosphorylation toward glycolysis. This metabolic reprogramming, also called the Warburg effect, is critical for the induction of pluripotency, but its molecular mechanisms remain poorly defined. Notably, SIRT2 is consistently downregulated during the reprogramming process and regulates glycolytic switch. Here, we report that downregulation of SIRT2 increases acetylation of mitogen-activated protein kinase (MAPK) kinase-1 (MEK1) at Lys175, resulting in activation of extracellular signal-regulated kinases (ERKs) and subsequent activation of the pro-fission factor dynamin-related protein 1 (DRP1). In parallel, downregulation of SIRT2 hyperacetylates the serine/threonine protein kinase AKT1 at Lys20 in a non-canonical way, activating DRP1 and metabolic reprogramming. Together, our study identified two axes, SIRT2-MEK1-ERK-DRP1 and SIRT2-AKT1-DRP1, that critically link mitochondrial dynamics and oxidative phosphorylation to the somatic reprogramming process. These upstream signals, together with SIRT2’s role in glycolytic switching, may underlie the Warburg effect observed in human somatic cell reprogramming.

Mitochondrial remodeling has critical roles for the somatic cell reprogramming process. Cha et al. report the functional role of SIRT2 in mitochondrial dynamics and remodeling during the human somatic cell reprogramming process. They identify two axes, SIRT2-MEK1-ERK-DRP1 and SIRT2-AKT1-DRP1, that link SIRT2 downregulation to mitochondrial remodeling and somatic cell reprogramming.

Exercise Intervention Mitigates Pathological Liver Changes in NAFLD Zebrafish by Activating SIRT1/AMPK/NRF2 Signaling

Non-alcoholic fatty liver disease (NAFLD) is a common disease that causes serious liver damage. Exercise is recognized as a non-pharmacological tool to improve the pathology of NAFLD. However, the antioxidative effects and mechanisms by which exercise ameliorates NAFLD remain unclear. The present study conducted exercise training on zebrafish during a 12-week high-fat feeding period to study the antioxidant effect of exercise on the liver. We found that swimming exercise decreased lipid accumulation and improved pathological changes in the liver of high-fat diet-fed zebrafish. Moreover, swimming alleviated NOX4-derived reactive oxygen species (ROS) overproduction and reduced methanedicarboxylic aldehyde (MDA) levels. We also examined the anti-apoptotic effects of swimming and found that it increased the expression of antiapoptotic factor bcl2 and decreased the expression of genes associated with apoptosis (caspase3, bax). Mechanistically, swimming intervention activated SIRT1/AMPK signaling-mediated lipid metabolism and inflammation as well as enhanced AKT and NRF2 activation and upregulated downstream antioxidant genes. In summary, exercise attenuates pathological changes in the liver induced by high-fat diets. The underlying mechanisms might be related to NRF2 and mediated by SIRT1/AMPK signaling.

Resveratrol reverses the programmed high-susceptibility to non-alcoholic fatty liver disease by targeting the hepatic SIRT1-SREBP1c pathway in prenatal ethanol-exposed rat offspring

An increased susceptibility to non-alcoholic fatty liver disease (NAFLD) in female rat offspring that experienced prenatal ethanol exposure (PEE) has been previously demonstrated. The present study further investigated the potential mechanism. Based on the results from both fetal and adult studies of offspring rats that experienced PEE (4 g/kg/day), the fetal weight, serum glucose and triglyceride levels decreased significantly and hepatocellular ultra-structure was altered. Fetal livers exhibited inhibited expression and activity of sirtuin 1 (SIRT1), enhanced expression of lipogenic genes: sterol regulatory element binding protein 1c (SREBP1c), fatty acid synthase (FASN), acetyl-coenzyme A carboxylase α (ACCα), stearyl-coenzyme A desaturase 1 (SCD1). In adult offspring fed with high-fat diet, the PEE offspring revealed obviously catch-up growth, increased food intake, elevated serum metabolic phenotypes, suppressed hepatic SIRT1-SREBP1c pathway, and formation of NAFLD. Resveratrol (the chemical activator of SIRT1) could remarkably reverse the serum metabolic phenotypes and alleviate the hepatocyte steatosis in relation to the PEE offspring through activating the hepatic SIRT1-SREBP1c pathway. Therefore, increased susceptibility to diet-induced NAFLD in PEE offspring appears to be mediated by intrauterine programming of hepatic lipogenesis via the SIRT1-SREBP1c pathway. This altered programming effect could partially be reversed by resveratrol intervention after birth in PEE offspring rats.

Phytotherapy as Multi-Hit Therapy to Confront the Multiple Pathophysiology in Non-Alcoholic Fatty Liver Disease: A Systematic Review of Experimental Interventions

Non-alcoholic fatty liver disease (NAFLD), or metabolic dysfunction-associated fatty liver disease (MAFLD), is a metabolic condition distinguished by fat deposition in the hepatocytes. It has a prevalence of about 25% worldwide and is associated with other conditions such as diabetes mellitus, obesity, hypertension, etc. Background and Objectives: There is currently no approved drug therapy for NAFLD. Current measures in the management of NAFLD include lifestyle modification such as an increase in physical activity or weight loss. Development of NAFLD involves a number of parallel hits: including genetic predisposition, insulin resistance, disordered lipid metabolism, mitochondrial dysfunction, lipotoxicity, oxidative stress, etc. Herbal therapy may have a role to play in the treatment of NAFLD, due to their numerous bioactive constituents and the multiple pharmacological actions they exhibit. Therefore, this systematic review aims to investigate the potential multi-targeting effects of plant-derived extracts in experimental models of NAFLD. Materials and Methods: We performed a systematic search on databases and web search engines from the earliest available date to 30 April 2021, using relevant keywords. The study included articles published in English, assessing the effects of plant-derived extracts, fractions, or polyherbal mixtures in the treatment of NAFLD in animal models. These include their effects on at least disordered lipid metabolism, insulin resistance/type 2 diabetes mellitus (T2DM), and histologically confirmed steatosis with one or more of the following: oxidative stress, inflammation, hepatocyte injury, obesity, fibrosis, and cardiometabolic risks factors. Results: Nine articles fulfilled our inclusion criteria and the results demonstrated the ability of phytomedicines to simultaneously exert therapeutic actions on multiple targets related to NAFLD. Conclusions: These findings suggest that herbal extracts have the potential for effective treatment or management of NAFLD.

Pathogenetic mechanisms of nonalcoholic fatty liver disease and inhibition of the inflammasome as a new therapeutic target

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease worldwide, and its incidence is increasing. Nonalcoholic steatohepatitis (NASH), the progressive form of the disease, can lead to end-stage liver disease. The pathogenesis of the disease is not fully understood, and there is currently no specific treatment. Therefore, an effective and reliable treatment modality is needed. In recent years, the inflammasome has been shown to play a vital role in many stages of NAFLD pathogenesis. In particular, the detection, by toll-like receptors, of pathogen-associated molecular patterns induced by the gut-liver axis triggers the formation of the NLRP3 (NLR family pyrin domain-containing protein 3) inflammasome. Stimulation of damage-associated molecular patterns also activates the NLRP3 inflammasome. The activated inflammasome has caspase-1 activity, which leads to the release of interleukin (IL)-1 and IL-18 and formation of pores in the cell wall. This process spreads the inflammatory process to the outside of the cell and induces inflammatory cell death (pyroptosis). Subsequent progression of the inflammatory process leads to fibrosis. Recent evidence suggests that the NLRP3 inflammasome may be a potential target for the treatment of NASH. The discovery of specific NLRP3 inflammasome blockers in recent years and evidence of their positive effects in experimental models support this therapeutic approach. In this article, we discuss recent evidence on the pathogenesis of NAFLD, the role of the inflammasome in the pathogenesis of NAFLD, and the potential effects of inhibition of the inflammasome.

Role of Endocrine-Disrupting Chemicals in the Pathogenesis of Non-Alcoholic Fatty Liver Disease: A Comprehensive Review

Non-alcoholic fatty liver disease (NAFLD) is considered the most common liver disorder, affecting around 25% of the population worldwide. It is a complex disease spectrum, closely linked with other conditions such as obesity, insulin resistance, type 2 diabetes mellitus, and metabolic syndrome, which may increase liver-related mortality. In light of this, numerous efforts have been carried out in recent years in order to clarify its pathogenesis and create new prevention strategies. Currently, the essential role of environmental pollutants in NAFLD development is recognized. Particularly, endocrine-disrupting chemicals (EDCs) have a notable influence. EDCs can be classified as natural (phytoestrogens, genistein, and coumestrol) or synthetic, and the latter ones can be further subdivided into industrial (dioxins, polychlorinated biphenyls, and alkylphenols), agricultural (pesticides, insecticides, herbicides, and fungicides), residential (phthalates, polybrominated biphenyls, and bisphenol A), and pharmaceutical (parabens). Several experimental models have proposed a mechanism involving this group of substances with the disruption of hepatic metabolism, which promotes NAFLD. These include an imbalance between lipid influx/efflux in the liver, mitochondrial dysfunction, liver inflammation, and epigenetic reprogramming. It can be concluded that exposure to EDCs might play a crucial role in NAFLD initiation and evolution. However, further investigations supporting these effects in humans are required.

Epigenetics in NAFLD/NASH: Targets and therapy

Recently non-alcoholic fatty liver disease (NAFLD) has grabbed considerable scientific attention, owing to its rapid increase in prevalence worldwide and growing burden on end-stage liver diseases. Metabolic syndrome including obesity, diabetes, and hypertension poses a grave risk to NAFLD etiology and progression. With no drugs available, the mainstay of NAFLD management remains lifestyle changes with exercise and dietary modifications. Nonselective drugs such as metformin, thiazolidinediones (TZDs), ursodeoxycholic acid (UDCA), silymarin, etc., are also being used to target the interrelated pathways for treating NAFLD. Considering the enormous disease burden and the unmet need for drugs, fresh insights into pathogenesis and drug discovery are required. The emergence of the field of epigenetics offers a convincing explanation for the basis of lifestyle, environmental, and other risk factors to influence NAFLD pathogenesis. Therefore, understanding these epigenetic modifications to target the primary cause of the disease might prove a rational strategy to prevent the disease and develop novel therapeutic interventions. Apart from describing the role of epigenetics in the pathogenesis of NAFLD as in other reviews, this review additionally provides an elaborate discussion on exploiting the high plasticity of epigenetic modifications in response to environmental cues, for developing novel therapeutics for NAFLD. Besides, this extensive review provides evidence for epigenetic mechanisms utilized by several potential drugs for NAFLD.

Sirtuins and the circadian clock interplay in cardioprotection: focus on sirtuin 1

Chronic disruption of circadian rhythms which include intricate molecular transcription-translation feedback loops of evolutionarily conserved clock genes has serious health consequences and negatively affects cardiovascular physiology. Sirtuins (SIRTs) are nuclear, cytoplasmic and mitochondrial histone deacetylases that influence the circadian clock with clock-controlled oscillatory protein, NAMPT, and its metabolite NAD+. Sirtuins are linked to the multi-organ protective role of melatonin, particularly in acute kidney injury and in cardiovascular diseases, where melatonin, via upregulation of SIRT1 expression, inhibits the apoptotic pathway. This review focuses on SIRT1, an NAD+-dependent class III histone deacetylase which counterbalances the intrinsic histone acetyltransferase activity of one of the clock genes, CLOCK. SIRT1 is involved in the development of cardiomyocytes, regulation of voltage-gated cardiac sodium ion channels via deacetylation, prevention of atherosclerotic plaque formation in the cardiovascular system, protection against oxidative damage and anti-thrombotic actions. Overall, SIRT1 has a see-saw effect on cardioprotection, with low levels being cardioprotective and higher levels leading to cardiac hypertrophy.

The effect of N-Acetyl cysteine on the expression of Fxr (Nr1h4), LXRα (Nr1h3) and Sirt1 genes, oxidative stress, and apoptosis in the liver of rats exposed to different doses of cadmium

The aim of this study was to consider the expression of farnesoid X receptor (Fxr), liver X receptor (LXRα) and sirtuin 1 (Sirt1), oxidative stress, inflammation, apoptosis, and the protective role of N-acetylcysteine (NAC) in the liver of rats treated with cadmium (Cd). 30 Wistar rats were divided into 5 groups: G1 (control), G2 (single dose of Cd), G3 (continuous dose of Cd), G4 (single dose of Cd + continuous dose of NAC), and G5 (continuous dose of Cd + continuous dose of NAC). The apoptosis of hepatic cells was measured using the TUNEL assay. Levels of malondialdehyde (MDA), IL-10, TNF-α, and total antioxidant capacity (TAC) were measured by specific kits. The expression of Fxr, LXRα, and Sirt1 genes and ratio of Bax/Bcl2 was considered using RT-PCR. While NAC treatment improved TAC and IL-10 values, it decreased MDA and TNF-α levels in the liver of rats exposed to Cd (P < 0.001). NAC decreased Bax/Bcl2 in the liver of G4 and G5 groups (P < 0.001). Exposure to a continuous dose of Cd decreased Fxr, LXRα, and Sirt1 expression by 36.65- (P < 0.001), 12.52- (P < 0.001) and 11.34-fold (P < 0.001) compared to control, respectively. NAC increased Fxr, LXRα, and Sirt1 expression (P < 0.01) and decreased Cd concentrations in both serum and tissue samples in G4 and G5 groups. Our results suggested that NAC protects liver tissue against Cd toxicity by elevating antioxidant capacity, mitigating oxidative stress, inflammation, apoptosis and up-regulation of FXR, LXR, and SIRT1 genes.

Voluntary exercise improves sperm parameters in high fat diet receiving rats through alteration in testicular oxidative stress, mir-34a/SIRT1/p53 and apoptosis

OBJECTIVES

High fat diet can lead to testicular structural and functional disturbances, spermatogenesis disorders as well as infertility. So, the present investigation was proposed to clarify whether voluntary exercise could prevent high fat diet induced reproductive complications in rats through testicular stress oxidative and apoptosis.

METHODS

Forty male Wistar rats were randomly divided into four groups; control (C), voluntary exercise (VE), high fat diet (HFD) and high fat diet and voluntary exercise (VE + HFD) groups. The rats in the VE and VE + HFD groups were accommodated in apart cages that had running wheels and the running distance was assessed daily for 10 weeks. In VE + HFD group, animals were fed with HFD for five weeks before commencing exercise. The sperm parameters, the expressions of testicular miR-34a gene, and P53 and SIRT1 proteins as well as testicular apoptosis were analyzed in all groups.

RESULTS

The results indicated that voluntary exercise in VE + HFD group led to significantly increased GPX and SOD activities, SIRT1 protein expression, sperm parameters, and decreased the expression of miR34a gene and Acp53 protein, and cellular apoptosis index compared to HFD group (p<0.001 to p<0.05). The SOD and catalase activities, SIRT1 protein expression, sperm parameters in VE + HFD group were lower than of those of VE group, however, MDA content, expression of Acp53 protein, apoptosis indexes in VE + HFD group was higher than that of VE group (p<0.001 to p<0.05).

CONCLUSION

This study revealed that voluntary exercise improved spermatogenesis, in part by decreasing the testicular oxidative stress status, apoptosis through alteration in miR-34a/SIRT1/p53 pathway.

Le Carbone prevents liver damage in non-alcoholic steatohepatitis-hepatocellular carcinoma mouse model via AMPKα-SIRT1 signaling pathway activation

Le Carbone (LC), a fiber-enriched activated charcoal dietary supplement, claimed to be effective against inflammation associated with colitis, trimethylaminuria, and sclerosis. The study aimed to investigate the underlying mechanisms of LC to protect liver damage and its progression in non-alcoholic steatohepatitis-hepatocellular carcinoma (NASH-HCC) mice. To induce this model, C57BL/6J male baby mice were injected with a low-dose of streptozotocin and fed with a high-fat diet (HFD) 32 during 4 weeks–16 weeks of age. The LC suspension was administered orally at a dose of 5 mg/mouse/day started at the age of 6 weeks and continued until 16 weeks of age along with HFD32 feeding. At the end of the experiment, serum and liver tissues were collected for the biochemical, histological, and molecular analysis. We found that LC suspension improved the histopathological changes, serum aminotransferases in NASH mice. The hepatic expression of metabolic proteins, p-AMPKα and sirtuin 1, and proteins responsible for β-oxidation of fatty acids, peroxisome proliferator-activated receptor (PPAR) γ coactivator-α, PPARα were significantly repressed in NASH mice. LC treatment markedly restored these expressions. LC treatment significantly reduced the hepatic proteins expressions of PPARγ, tissue inhibitor of metalloproteinases 4, p47phox, p-JNK, p-ERK1/2, glypican-3, and prothrombin in NASH mice. Our findings demonstrate that LC prevents the liver damage and progression of NASH, possibly by enhancing the AMPK-SIRT1 signaling pathway.

Ferulic acid alleviates lipotoxicity-induced hepatocellular death through the SIRT1-regulated autophagy pathway and independently of AMPK and Akt in AML-12 hepatocytes

Background

Lipotoxicity-induced cell death plays a detrimental role in the pathogenesis of metabolic diseases. Ferulic acid, widespread in plant-based food, is a radical scavenger with multiple bioactivities. However, the benefits of ferulic acid against hepatic lipotoxicity are largely unclear. Here, we investigated the protective effect of ferulic acid against palmitate-induced lipotoxicity and clarified its potential mechanisms in AML-12 hepatocytes.

Methods

AML-12 mouse hepatocytes were exposed to palmitate to mimic lipotoxicity. Different doses (25, 50, and 100 μM) of ferulic acid were added 2 h before palmitate treatment. Cell viability was detected by measuring lactate dehydrogenase release, nuclear staining, and the expression of cleaved-caspase-3. Intracellular reactive oxygen species content and mitochondrial membrane potential were analysed by fluorescent probes. The potential mechanisms were explored by molecular biological methods, including Western blotting and quantitative real-time PCR, and were further verified by siRNA interference.

Results

Our data showed that ferulic acid significantly inhibited palmitate-induced cell death, rescued mitochondrial membrane potential, reduced reactive oxygen species accumulation, and decreased inflammatory factor activation, including IL-6 and IL-1beta. Ferulic acid significantly stimulated autophagy in hepatocytes, whereas autophagy suppression blocked the protective effect of ferulic acid against lipotoxicity. Ferulic acid-activated autophagy, which was triggered by SIRT1 upregulation, was mechanistically involved in its anti-lipotoxicity effects. SIRT1 silencing blocked most beneficial changes induced by ferulic acid.

Conclusions

We demonstrated that the phytochemical ferulic acid, which is found in plant-based food, protected against hepatic lipotoxicity, through the SIRT1/autophagy pathway. Increased intake of ferulic acid-enriched food is a potential strategy to prevent and/or improve metabolic diseases with lipotoxicity as a typical pathological feature.

Renoprotective effects of estrogen on acute kidney injury: the role of SIRT1

Acute kidney injury (AKI) is a common syndrome associated with high morbidity and mortality, despite progress in medical care. Many studies have shown that there are sex differences and different role of sex hormones particularly estrogens in kidney injury. In this regard, the incidence and rate of progression of kidney diseases are higher in men compared with women. These observations suggest that female sex hormone may be renoprotective. Silent information regulator 2 homolog 1 (SIRT1) is a histone deacetylase, which is implicated in multiple biologic processes in several organisms. In the kidneys, SIRT1 inhibits renal cell apoptosis, inflammation, and fibrosis. Studies have reported a link between SIRT1 and estrogen. In addition, SIRT1 regulates ERα expression and inhibition of SIRT1 activity suppresses ERα expression. This effect leads to inhibition of estrogen-responsive gene expression. In this text, we review the role of SIRT1 in mediating the protective effects of estrogen in the onset and progression of AKI.

Non-alcoholic fatty liver disease: molecular and cellular interplays of the lipid metabolism in a steatotic liver

INTRODUCTION

Non-alcoholic fatty liver disease (NAFLD) affects ~25% of world population and cases have increased in recent decades. These anomalies have several etiologies; however, obesity and metabolic dysfunctions are the most relevant causes. Despite being considered a public health problem, no effective therapeutic approach to treat NAFLD is available. For that, a deep understanding of metabolic routes that support hepatic diseases is needed.

AREAS COVERED

This review covers aspects of the onset of NAFLD. Thereby, biochemistry routes as well as cellular and metabolic effects of the gut microbiota in body's homeostasis and epigenetics are contextualized.

EXPERT OPINION

Recently, the development of biological sciences has generated innovative knowledge, bringing new insights and perspectives to clarify the systems biology of liver diseases. A detailed comprehension of epigenetics mechanisms will offer possibilities to develop new therapeutic and diagnostic strategies for NAFLD. Different epigenetic processes have been reported that are modulated by the environment such as gut microbiota, suggesting strong interplays between cellular behavior and pathology. Thus, a more complete description of such mechanisms in hepatic diseases will help to clarify how to control the establishment of fatty liver, and precisely describe molecular interplays that potentially control NAFLD.

β-patchoulene improves lipid metabolism to alleviate non-alcoholic fatty liver disease via activating AMPK signaling pathway

Non-alcoholic fatty liver disease (NAFLD) has been a leading cause of chronic metabolic disease, seriously posing healthy burdens to the public, whereas interventions available for it are limited to date. Patchouli oil had been reported to attenuate hepatic steatosis in our previous study. β-patchoulene (β-PAE) is a representative component separated from patchouli oil with multiple activities, but its effect against NAFLD is still unknown. To investigate the effect and potential mechanism of β-PAE on NAFLD, we used high fat diet (HFD) in vivo and free fatty acid (FFA) in vitro to induce hepatic steatosis in rats and L02 cells, respectively. Histological examination was evaluated via Hematoxylin-eosin and oil red O staining. The parameters for hepatic steatosis were estimated via biochemical kits, western blotting and quantitative real-time PCR. Compound C, the inhibitor of AMPK, was applied further to examine the precise mechanism of β-PAE on NAFLD. Our results indicated that β-PAE significantly attenuated HFD-induced weight gain, hepatic injury, lipid deposition in serum and hepatic tissue as well as FFA induced-lipid accumulation. Besides, β-PAE markedly improved the expression of AMP-activated protein kinase (AMPK) and its downstream factors which correlate with hepatic lipid synthesis and oxidation in vivo and in vitro. Nevertheless, Compound C abrogated the benefits derived from β-PAE in L02 cells. In conclusion, these results suggest that β-PAE exerts AMPK agonist-like effect to regulate hepatic lipid synthesis and oxidation, eventually prevent NAFLD progression.

Hepatoprotective Effect and Molecular Mechanisms of Hengshun Aromatic Vinegar on Non-Alcoholic Fatty Liver Disease

Aromatic vinegar with abundant bioactive components can be used as a food additive to assist the treatment of various diseases. However, its effect on non-alcoholic fatty liver disease (NAFLD) is still unknown. The purpose of this study was to investigate the mechanism of Hengshun aromatic vinegar in preventing NAFLD in vivo and in vitro. Aromatic vinegar treatment was applied to rats fed with a high-fat diet (HFD) and HepG2 cells challenged with palmitic acid (PA). Our results showed that aromatic vinegar markedly improved cell viabilities and attenuated cell damage in vitro. The levels of TC, TG, FFA, AST, ALT, and malondialdehyde (MDA) in HFD-induced rats were significantly decreased by aromatic vinegar. Mechanism investigation revealed that aromatic vinegar markedly up-regulated the level of silent information regulator of transcription 1 (Sirt1), and thereby inhibited inflammation of the pathway through down-regulating the expressions of high mobility group box 1, toll-likereceptor-4, nuclear transcription factor-κB, tumor necrosis factor receptor-associated factor-6, and inflammatory factors. Aromatic vinegar simultaneously increased the expression of farnesoid X receptor and suppressed expressions of lipogenesis related proteins, including fatty acid synthase, acetyl-CoA carboxylase-1, sterol regulatory element binding transcription factor 1, and stearoyl-CoA desaturase-1. These results were further validated by knockdown of Sirt1 using siRNAs silencing in vitro. In conclusion, Hengshun aromatic vinegar showed protective effects against NAFLD by enhancing the activity of SIRT1 and thereby inhibiting lipogenesis and inflammation pathways, which is expected to become a new assistant strategy for NAFLD therapy in the future.

The Role of Histone Acetylation-/Methylation-Mediated Apoptotic Gene Regulation in Hepatocellular Carcinoma

Epigenetics, an inheritable phenomenon, which influences the expression of gene without altering the DNA sequence, offers a new perspective on the pathogenesis of hepatocellular carcinoma (HCC). Nonalcoholic steatohepatitis (NASH) is projected to account for a significant share of HCC incidence due to the growing prevalence of various metabolic disorders. One of the major molecular mechanisms involved in epigenetic regulation, post-translational histone modification seems to coordinate various aspects of NASH which will further progress to HCC. Mounting evidence suggests that the orchestrated events of cellular and nuclear changes during apoptosis can be regulated by histone modifications. This review focuses on the current advances in the study of acetylation-/methylation-mediated histone modification in apoptosis and the implication of these epigenetic regulations in HCC. The reversibility of epigenetic alterations and the agents that can target these alterations offers novel therapeutic approaches and strategies for drug development. Further molecular mechanistic studies are required to enhance information governing these epigenetic modulators, which will facilitate the design of more effective diagnosis and treatment options.

Diphlorethohydroxycarmalol Attenuates Palmitate-Induced Hepatic Lipogenesis and Inflammation

Non-alcoholic fatty liver disease (NAFLD) is a common cause of chronic liver disease, encompassing a range of conditions caused by lipid deposition within liver cells, and is also associated with obesity and metabolic diseases. Here, we investigated the protective effects of diphlorethohydroxycarmalol (DPHC), which is a polyphenol isolated from an edible seaweed, Ishige okamurae, on palmitate-induced lipotoxicity in the liver. DPHC treatment repressed palmitate-induced cytotoxicity, triglyceride content, and lipid accumulation. DPHC prevented palmitate-induced mRNA and protein expression of SREBP (sterol regulatory element-binding protein) 1, C/EBP (CCAAT-enhancer-binding protein) α, ChREBP (carbohydrate-responsive element-binding protein), and FAS (fatty acid synthase). In addition, palmitate treatment reduced the expression levels of phosphorylated AMP-activated protein kinase (AMPK) and sirtuin (SIRT)1 proteins, and DPHC treatment rescued this reduction. Moreover, DPHC protected palmitate-induced liver toxicity and lipogenesis, as well as inflammation, and enhanced AMPK and SIRT1 signaling in zebrafish. These results suggest that DPHC possesses protective effects against palmitate-induced toxicity in the liver by preventing lipogenesis and inflammation. DPHC could be used as a potential therapeutic or preventive agent for fatty liver diseases.

Role of acetylation in nonalcoholic fatty liver disease: a focus on SIRT1 and SIRT3

Nonalcoholic fatty liver disease (NAFLD) has become the most prevalent liver chronic disease worldwide. The pathogenesis of NAFLD is complex and involves many metabolic enzymes and multiple pathways. Posttranslational modifications of proteins (PMPs) added another layer of complexity to the pathogenesis of NAFLD. PMPs change protein properties and regulate many biological functions, including cellular localization, stability, intracellular signaling, and protein function. Lysine acetylation is a common reversible PMP that consists of the transfer of an acetyl group from acetyl-coenzyme A (CoA) to a lysine residue on targeted proteins. The deacetylation reaction is catalyzed by deacetylases called sirtuins. This review summarizes the role of acetylation in NAFLD with a focus on sirtuins 1 and 3.

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

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

Enhanced GIP Secretion in Obesity Is Associated with Biochemical Alteration and miRNA Contribution to the Development of Liver Steatosis

Nutrient excess enhances glucose-dependent insulinotropic polypeptide (GIP) secretion, which may in turn contribute to the development of liver steatosis. We hypothesized that elevated GIP levels in obesity may affect markers of liver injury through microRNAs. The study involved 128 subjects (body mass index (BMI) 25–40). Fasting and postprandial GIP, glucose, insulin, and lipids, as well as fasting alanine aminotransferase (ALT), γ-glutamyltransferase (GGT), cytokeratin-18, fibroblast growth factor (FGF)-19, and FGF-21 were determined. TaqMan low density array was used for quantitative analysis of blood microRNAs. Fasting GIP was associated with ALT [β = 0.16 (confidence interval (CI): 0.01–0.32)], triglycerides [β = 0.21 (95% CI: 0.06–0.36], and FGF-21 [β = 0.20 (95%CI: 0.03–0.37)]; and postprandial GIP with GGT [β = 0.17 (95%CI: 0.03–0.32)]. The odds ratio for elevated fatty liver index (>73%) was 2.42 (95%CI: 1.02–5.72) for high GIP versus low GIP patients. The miRNAs profile related to a high GIP plasma level included upregulated miR-136-5p, miR-320a, miR-483-5p, miR-520d-5p, miR-520b, miR-30e-3p, and miR-571. Analysis of the interactions of these microRNAs with gene expression pathways suggests their potential contribution to the regulation of the activity of genes associated with insulin resistance, fatty acids metabolism, and adipocytokines signaling. Exaggerated fasting and postprandial secretion of GIP in obesity are associated with elevated liver damage markers as well as FGF-21 plasma levels. Differentially expressed microRNAs suggest additional, epigenetic factors contributing to the gut–liver cross-talk.

Chinese Herbal Medicine Formula Shenling Baizhu San Ameliorates High-Fat Diet-Induced NAFLD in Rats by Modulating Hepatic MicroRNA Expression Profiles

Objective

The purpose of present study was to investigate the potential mechanism underlying the protective effect of Shenling Baizhu San (SLBZS) on nonalcoholic fatty liver disease (NAFLD) by microRNA (miRNA) sequencing.

Methods

Thirty male Wistar rats were randomly divided into a normal control (NC) group, a high-fat diet (HFD) group, and an SLBZS group. After 12 weeks, the biochemical parameters and liver histologies of the rats were assessed. The Illumina HiSeq 2500 sequencing platform was used to analyse the hepatic miRNA expression profiles. Representative differentially expressed miRNAs were further validated by qRT-PCR. The functions of the differentially expressed miRNAs were analysed by bioinformatics.

Results

Our results identified 102 miRNAs that were differentially expressed in the HFD group compared with the NC group. Among those differentially expressed miRNAs, the expression levels of 28 miRNAs were reversed by SLBZS administration, suggesting the modulation effect of SLBZS on hepatic miRNA expression profiles. The qRT-PCR results confirmed that the expression levels of miR-155-5p, miR-146b-5p, miR-132-3p, and miR-34a-5p were consistent with those detected by sequencing. Bioinformatics analyses indicated that the target genes of the differentially expressed miRNAs reversed by SLBZS were mainly related to metabolic pathways.

Conclusion

This study provides novel insights into the mechanism of SLBZS in protecting against NAFLD; this mechanism may be partly related to the modulation of hepatic miRNA expression and their target pathways.

DHA Protects Against Hepatic Steatosis by Activating Sirt1 in a High Fat Diet-Induced Nonalcoholic Fatty Liver Disease Mouse Model

AIM

Docosahexaenoic acid (DHA; C22; n-3) shows beneficial effects on Non-alcoholic fatty liver disease (NAFLD). Deacetylase Sirtuin1 (Sirt1) was reported to increase energy metabolism and decrease lipogenesis. Here, we investigated whether DHA plays a role in protecting against hepatic steatosis via Sirt1.

MAIN METHODS

Both in vivo and in vitro hepatic steatosis models were used: diet-induced obesity (DIO) model (middle-aged C57BL/6 mice fed a high-fat diet (HFD)) and palmitic acid (PA)-induced lipid accumulation cell model (HepG2 cells).

KEY FINDINGS

In DIO mice, treatment with DHA (gavage supplementation) for 8 weeks not only inhibited the lipid accumulation, but also increased fatty acids (FA) oxidation and induced triglyceride export in liver. These changes were accompanied by attenuation of inflammation. Moreover, DHA reversed the HFD-induced reduction of Sirt1 in liver. Interestingly, the beneficial effects of DHA were reversed by lentivirus-mediated Sirt1 knockdown, accompanied with increased expression of markers of lipogenesis, inflammation and reduced FA oxidation. In HepG2 cells, DHA prevented the accumulation of PA-induced lipid droplets, the decrease of FA oxidation and the reduction of Sirt1 level. Inhibition of Sirt1 by sirtinol partially reversed the beneficial effects of DHA on PA-treated cells.

SIGNIFICANCE

DHA alleviated hepatic steatosis and reduced inflammation of liver in obese middle-aged mice by mechanisms involving Sirt1 activation.

Berberine chloride ameliorated PI3K/Akt-p/SIRT-1/PTEN signaling pathway in insulin resistance syndrome induced in rats

The liver is the main organ involved in lipid metabolism process and it helps in drug detoxification. Insulin resistance is considered one of risk reasons which lead to several metabolic diseases. Currently, berberine (BER) occupies a huge challenge against multiple diseases with no toxic effect. The present work was aimed to identify, does BER-chloride has a poisonous influence on the liver? and investigating the outcome of BER-chloride on PI3K/Akt-p/SIRT-1/PTEN pathway during insulin resistance syndrome. The insulin resistance model was achieved in experimental female rats via high-fat diet (HFD). Glucose, insulin, lipid profiles, and hepatic oxidative stress parameters were assessed. PI3K, AKt-p, SIRT-1, and PTEN levels in hepatic tissue were determined at genome and protein levels. Further adiponectin concentration was performed in serum, hepatic, and white adipose tissues. Molecular study of fold alteration in insulin, insulin receptor, and retinol binding protein-4 (RBP4) in liver was done. PRACTICAL APPLICATIONS: Obesity syndrome causes multiple obstacles in modern years. The current results revealed elevation the body weight of rats, plasma glucose, homeostatic model assessment, glycated hemoglobin, insulin, and lipid profiles concentrations in a group of rats, which nourished HFD for 8 weeks and this rise, was diminished after 2 weeks from BER-chloride administration. Further, BER-chloride improved transaminases enzymes, pro-oxidant, and antioxidant defense system, PI3K, AKt-p, SIRT-1, and PTEN in the liver, with downregulation of hepatic RBP4. Hence, these data provide a crucial message that BER-chloride enhanced both hepatic function and insulin signaling pathways that might be of therapeutic importance to insulin resistance with no harmful effect on the liver. BER-chloride is predicted to be a drug of choice for obesity complications cure.

Effect of resveratrol on non-alcoholic fatty liver disease

The aim of the present study was to investigate the effect of a micronized formulation of trans-resveratrol in humans with non-alcoholic fatty liver disease (NAFLD). Trans-Resveratrol has been used in the form of micronized formulation, which is better absorbed, has strong antioxidants effects, is more effective than plain resveratrol formulations and is circulated on the market as a food supplement. Resveratrol (3,5,4′-trihydroxy-trans-stilbene) is a stilbenoid and a phytoalexin produced by several plants. NAFLD is an increasing clinical problem involving the liver for which effective treatments are required. The present study was based on two patient groups. The study, which commenced on April 2013 and finished on April 2015, included 44 patients, aged 29–70 years, with an average weight of 84.6 kg (n=22 per group; 28 men and 16 women) who were randomly assigned to groups and given 50 mg Evelor capsule (n=22) and 200 mg Evelor H tablet (n=22) correspondingly on a daily basis. The patients were followed up for 6 months. Quantity fat measurements, with ultrasound on the liver and kidney, were carried out. There was an initial measurement (time 1) and one after six months (time 2). The study results showed the effects of Trans-resveratrol micronized formulation in reducing the liver fat, as well as decreasing hepatic enzymes, serum glutamate pyruvic transaminase (SGPT) and gamma-glutamyl transpeptidase (g-GT) and insulin resistance. At the end of the study, the statistical analysis showed a statistically significant reduction on the liver fat. These data demonstrate that use of Trans-resveratrol micronized formulation improves features of NAFLD, and prevents liver damage. Thus, Trans-resveratrol micronized formulation can be a new treatment method for NAFLD.

Effect of sodium-glucose cotransporter 2 inhibitor, empagliflozin, and α-glucosidase inhibitor, voglibose, on hepatic steatosis in an animal model of type 2 diabetes

OBJECTIVE

We investigated the effects of sodium-glucose cotransporter 2 inhibitor, empagliflozin, and α-glucosidase inhibitor, voglibose, on hepatic steatosis in an animal model of type 2 diabetes (T2DM).

METHODS

Empagliflozin (OLETF-EMPA) or voglibose (OLETF-VOG) was administered to Otsuka Long-Evans Tokushima fatty (OLETF) rats once daily for 12 weeks. Control Long-Evans Tokushima Otsuka (LETO) and OLETF (OLETF-C) rats received saline.

RESULTS

Blood glucose levels were significantly suppressed in OLETF-EMPA and OLETF-VOG compared with the OLETF-C group. The liver fat content was significantly higher in the OLETF-C group than in the OLETF-EMPA and OLETF-VOG. Hepatic gene expressions involved in gluconeogenesis (glucose 6-phosphatase [G6Pase], fructose-1,6-bisphosphatase [FBP1], and phosphoenolpyruvate carboxykinase [PEPCK]) and lipogenesis (acetyl-CoA carboxylase [ACC], fatty acid synthase [FAS], and sterol regulatory element-binding transcription factor 1c [SREBP-1c]) were significantly decreased in the OLETF-EMPA group compared with other OLETF groups (OLETF-C and OLETF-VOG). Sirtuin 1 (SIRT1) expression level and SIRT1 activity were markedly reduced in OLETF-C rats; however, its expression increased in the OLETF-EMPA and OLETF-VOG. AMP-activated protein kinase (AMPK) phosphorylation level was remarkably increased by empagliflozin treatment in OLETF rats compared with other OLETF groups. Long-term empagliflozin and voglibose treatment reduced hepatic steatosis with suppression of gluconeogenesis and lipogenesis pathway in OLETF rats.

CONCLUSION

We suggest that this metabolic improvement might be related to SIRT1 and AMPK pathway in T2DM. But empagliflozin is thought to have more advantage to prevent hepatic steatosis than voglibose in T2DM.