Rubicon inhibits autophagy and accelerates hepatocyte apoptosis and lipid accumulation in nonalcoholic fatty liver disease in mice

Maternal protein restriction and postnatal sugar consumption increases inflammatory response and deregulates metabolic pathways in the liver of male offspring rats with aging

This study investigated the late effects of maternal protein restriction (MPR) and early postnatal sugar consumption on liver health in male Sprague-Dawley rat offspring, focusing on changes observed throughout the aging process. The animals were divided into the following groups: Control (CTR): Male offspring whose dams consumed a normal protein diet (NPD, 17% protein) and water ad libitum during gestation and lactation, and then fed a NPD and water until PND 540; Control + Sugar (CTR + SUG): The same treatment as CTR, but consuming a sugar solution (10% diluted in water) from postnatal day (PND) 21-90, and then fed a NPD and water until PND 540; Gestational and Lactational Low Protein (GLLP): Male offspring whose dams consumed a low-protein diet (LPD, 6% protein) during gestation and lactation and, then fed a NPD and water ad libitum until PND 540; Gestational and Lactational Low Protein + Sugar (GLLP + SUG): male offspring whose dams consumed a LPD during gestation and lactation, and then fed a NPD and a sugar solution (10% diluted in water) ad libitum from PND 21 to 90. On PND 540, the animals were anesthetized, weighed, and euthanized, and their livers were collected for morphological and molecular analyses. The GLLP and GLLP + SUG groups showed lower body weight and lower retroperitoneal fat weight compared to the CTR and CTR + SUG groups. Morphological analysis revealed inflammatory foci in the liver from the CTR + SUG, GLLP, and GLLP + SUG groups, compared to the CTR group. Hepatic activities of CAT, SOD, and GSH-Px were increased in the GLLP + SUG group and decreased in the GLLP group, compared to the CTR group. Immunohistochemistry showed a significant increase in occupied area per foci de hepatocytes positive for GSTpi (placental form) in the CTR + SUG, GLLP, and GLLP + SUG groups, compared to the CTR group. Proteomic analysis of the groups revealed significant changes in hepatic metabolic and inflammatory pathways. In the CTR + SUG group, upregulated pathways associated with non-alcoholic fatty liver disease (NAFLD) and downregulated pathways related to autophagy were observed. In the GLLP and GLLP + SUG groups, there was a significant impact on metabolic pathways, including glucose metabolism, gluconeogenesis, glycogenesis, and cellular stress responses. An upregulation of pathways associated with chemokine- and cytokine-mediated inflammatory processes was also identified, indicating activation of the immune system in the liver during aging. Therefore, MPR, with or without postnatal sugar consumption, resulted in hepatic changes in metabolism and the antioxidant defense in old male offspring.

Rubicon siRNA-encapsulated liver-targeting nanoliposome is a promising therapeutic for non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is a prevalent metabolic liver disorder worldwide, and effective therapeutic strategies for its treatment remains limited. In this article, we introduced Glipo-siRubi, a hepatocytes-targeting RNA interference (RNAi) nanoliposome for suppression of Rubicon expression, aiming to achieve precise regulation of autophagy in NAFLD. Autophagy activation induced by Rubicon suppression resulted in reduced endoplasmic reticulum stress and intracellular lipid accumulation in vitro. Moreover, Glipo-siRubi administration exhibited remarkable therapeutic efficacy, characterized by decreased liver lipid accumulation, ameliorated histopathology and improved insulin sensitivity in mice with western diet, indicating its notable potential against NAFLD. By inducing autophagy activation, the hepatocytes-targeting Glipo-siRubi provided a promising method for NAFLD treatment, addressing the limitations of current approaches. Our study highlighted the significance of Rubicon-specific suppression in NAFLD treatment, offering a specific, safe, and efficient approach to mitigate NAFLD.

DNA hypermethylation-induced suppression of ALKBH5 is required for folic acid to alleviate hepatic lipid deposition by enhancing autophagy in an ATG12-dependent manner

Nonalcoholic fatty liver disease (NAFLD) occurs when too much fat builds up in the liver. As a growing worldwide epidemic, NAFLD is strongly linked with multiple metabolic diseases including obesity, insulin resistance, and dyslipidemia. However, very few effective treatments are currently available. Folate, an essential B-group vitamin with important biological functions including DNA and RNA methylation regulation, has been shown to have a protective effect against NAFLD with its underlying mechanism remains largely unclear. Here, we show that administration of folic acid significantly improves glucose tolerance, insulin sensitivity, and dyslipidemia in high-fat diet (HFD) fed mice. Moreover, folic acid treatment significantly inhibits lipid deposition in hepatocytes both in vivo and in vitro. Mechanically, folic acid reduces the expression of m6A demethylase AlkB homolog 5 (ALKHB5) via promoter DNA hypermethylation. Decreased ALKBH5 causes increased m6A modification and increased expression of ATG12 in a demethylase activity-dependent manner, thereby promoting autophagy and preventing hepatic steatosis. Inhibition of ATG12 induced by overexpression of ALKBH5 could impair autophagy and the inhibitory effect of folic acid on lipid accumulation in hepatocytes. Together, these findings provide novel insights into understanding the protective role of folic acid in the treatment of NAFLD and suggest that folic acid may be a potential agent for combating NAFLD.

Maternal hyperglycemia and postnatal high-fat diet impair metabolic regulation and autophagy response in the liver of adult female rats

This study aimed to investigate the mechanisms by which the association between maternal hyperglycemia and postnatal high-fat diet (HFD) exposure compromises metabolic parameters and hepatic autophagy in adult female pups. For this, Sprague Dawley rats, female pups from nondiabetic (control = FC) or diabetic (FD) mothers, were fed a standard diet (SD) or HFD from weaning until adulthood (n minimum = 5 rats/group): FC/SD, FC/HFD, FD/SD, and FD/HFD. In adulthood, these rats were tested with the oral glucose tolerance test, euthanized, and serum biochemistry parameters were analyzed. Liver samples were collected to evaluate cytokines, redox status, and protein expression autophagy and apoptosis markers. Histomorphometric analyses and an assessment of lipofuscin accumulation were also performed to reflect incomplete autolysosomal digestion. The FC/HFD, FD/SD, and FD/HFD groups showed glucose intolerance and an increased number of hepatocytes. Furthermore, FD/SD and FD/HFD rats showed hyperlipidemia and insulin resistance. Adaptations in hepatic redox pathways were observed in the FD/SD group with increased antioxidant defense marker activity. The FD/SD group also exhibited increased autophagy protein expression, such as p-AMPK, LC3-II/LC3-I, and p62/SQSTM1, lipofuscin accumulation, and caspase-3 activation. After exposure to HFD, the adult female pups of diabetic rats had a reduced p-AMPK and LC3-II/LC3-I ratio, the presence of steatosis, oxidative stress, and inflammation. The reduction of autophagy, stimulated by HFD, may be of vital importance for the susceptibility to metabolic dysfunction-associated fatty liver disease induced by maternal diabetes.

Deciphering significances of autophagy in the development and metabolism of adipose tissue

The mechanisms of adipose tissue activation and inactivation have been a hot topic of research in the last decade, from which countermeasures have been attempted to be found against obesity as well as other lipid metabolism-related diseases, such as type 2 diabetes mellitus and non-alcoholic fatty liver disease. Autophagy has been shown to be closely related to the regulation of adipocyte activity, which is involved in the whole process including white adipocyte differentiation/maturation and brown or beige adipocyte generation/activation. Dysregulation of autophagy in adipose tissue has been demonstrated to be associated with obesity. On this basis, we summarize the pathways and mechanisms of autophagy involved in the regulation of lipid metabolism and present a review of its pathophysiological roles in lipid metabolism-related diseases, in the hope of providing ideas for the treatment of these diseases.

Therapeutic Targets and Approaches to Manage Inflammation of NAFLD

Non-alcoholic fatty liver disease (NAFLD) and its advanced form, non-alcoholic steatohepatitis (NASH), are the leading causes of chronic liver disease globally. They are driven by complex mechanisms where inflammation plays a pivotal role in disease progression. Current therapies, including lifestyle changes and pharmacological agents, are limited in efficacy, particularly in addressing the advanced stages of the disease. Emerging approaches targeting inflammation, metabolic dysfunction, and fibrosis offer promising new directions, though challenges such as treatment complexity and heterogeneity persist. This review concludes the main therapeutic targets and approaches to manage inflammation currently and emphasizes the critical need for future drug development and combination therapy for NAFLD/NASH management.

The steroid hormone 20-hydroxyecdysone induces lipophagy via the brain-adipose tissue axis by promoting the adipokinetic hormone pathway

Lipophagy is a way to degrade lipids; however, the molecular mechanisms are not fully understood. Using the holometabolous lepidopteran insect Helicoverpa armigera, cotton bollworm, as a model, we revealed that the larval fat body undergoes lipophagy during metamorphosis, and lipophagy is essential for metamorphosis. The steroid hormone 20-hydroxyecdysone (20E) induced lipophagy by promoting the expression of the peptide hormone adipokinetic hormone (AKH, the insect analog of glucagon) and the adipokinetic hormone receptor (AKHR). Akh was highly expressed in the brain and Akhr was expressed in various tissues. The 20E upregulated the expression of Akh and Akhr by its nuclear receptor EcR during metamorphosis. AKH and AKHR increased glucose levels via gluconeogenesis and promoted lipophagy. The high glucose level induced acetylation of FOXO and nuclear localization to promote the expression of lipases and autophagy genes. Thus, the steroid hormone 20E induced lipophagy via the brain-adipose tissue axis by promoting the AKH pathway, which presented nutrients and energy to pupal and adult development during insect metamorphosis after feeding stops.

WSSV induces Rubicon expression to regulate innate immune response in Penaeus vannamei

Rubicon, the RUN domain Beclin-1-interacting and cysteine-rich domain-containing protein plays an important role in facilitating viral replication. In this study, an involvement of P. vannamei Rubicon or PvRUBCN during white spot syndrome virus (WSSV) infection and its roles in regulation of apoptosis and innate immune response were investigated. The full-length coding sequence of PvRUBCN was 3708 bp encoding the protein of 1235 amino acids. PvRUBCN contained three conserved domains including the RUN, the PI3K-binding, and the Rubicon homology domains. PvRUBCN was grouped with the closely related RUBCN from the Penaeid species with more than 95 % identity. It was highly expressed in nerve followed by intestine, and gill. Its expression was induced upon WSSV challenge at 12 and 48 hpi. Suppression of PvRUBCN by dsRNA upon WSSV challenge resulted in more than 80 % reduction in PvRUBCN mRNA expression. Knockdown of PvRUBCN mRNA significantly decreased the WSSV copy number and prolonged the survival rate of WSSV-infected shrimp. In addition, the caspase3, a key regulator of the apoptosis pathway was significantly down-regulated. The interferon like genes including Vago4 was dramatically decreased at 72 hpi whereas Vago5 demonstrated slight reduction at 24 hpi and increase at 72 and 120 hpi, respectively. On the other hand, the expressions of the genes involved in the prophenoloxidase pathway including PPO1 and PPO2 were not changed. Taken together, PvRUBCN played important roles in the antiviral immunity in response to WSSV infection.

Protective effects of PIK3CG knockdown against OGD/R-induced neuronal damage via inhibition of autophagy through the AMPK/mTOR pathway

BACKGROUND

Ischemic stroke represents an urgent need for more efficacious therapies owing to modest effectiveness of current treatment.

METHODS

Download data from stroke patients and collect blood samples from clinical patients to analyze phosphatidylinositol-3 kinase catalytic subunit γ (PIK3CG) expression. To establish a brain damage model, oxygen glucose deprivation/reperfusion (OGD/R) was applied to SH-SY5Y cells. Impact of PIK3CG on AMPK/mTOR autophagy pathway was verified treating cells with AMPK activator metformin. Proliferation and apoptosis were identified by CCK8 and flow cytometry.

RESULTS

Differential expression analysis and clinical testing show that PIK3CG is highly expressed in patients. Prolonged ODG/R exposure increased PIK3CG levels, supressed cell proliferation, and induced apoptosis. KEGG pathway analysis implicated PIK3CG in autophagy pathway. Knockdown of PIK3CG supressed OGD/R-induced reductions in cell proliferation and OGD/R-induced increases in apoptosis and expressions of Beclin 1 and LC3 II. Following OGD/R, AMPK phosphorylation was upregulated while mammalian target of rapamycin (mTOR) phosphorylation was downregulated, indicating AMPK/mTOR autophagy activation. Knockdown of PIK3CG opposed metformin-induced rises in Beclin 1, LC3 II and apoptosis along with decreases in proliferation.

CONCLUSION

PIK3CG knockdown protects neuronal cells by inhibiting AMPK/mTOR autophagy pathway and further inhibiting autophagy.

In Vivo CRISPR Activation Screening Reveals Chromosome 1q Genes VPS72, GBA1, and MRPL9 Drive Hepatocellular Carcinoma

BACKGROUND & AIMS

Hepatocellular carcinoma (HCC) frequently undergoes regional chromosomal amplification, resulting in elevated gene expression levels. We aimed to elucidate the role of these poorly understood genetic changes by using CRISPR activation (CRISPRa) screening in mouse livers to identify which genes within these amplified loci are cancer driver genes.

METHODS

We used data from The Cancer Genome Atlas to identify that frequently copy number-amplified and up-regulated genes all reside on human chromosomes 1q and 8q. We generated CRISPRa screening transposons that contain oncogenic Myc to drive tumor formation. We conducted CRISPRa screens in vivo in the liver to identify tumor driver genes. We extensively validated the findings in separate mice and performed RNA sequencing analysis to explore mechanisms driving tumorigenesis.

RESULTS

We targeted genes that frequently undergo amplification in human HCC using an in vivo CRISPRa screening system in mice, which induced extensive liver tumorigenesis. Human chromosome 1q genes Zbtb7b, Vps72, Gba1, and Mrpl9 emerged as drivers of liver tumorigenesis. In human HCC there is a trend in correlation between levels of MRPL9, VPS72, or GBA1 and poor survival. In validation assays, activation of Vps72, Gba1, or Mrpl9 resulted in extensive liver tumorigenesis and decreased survival in mice. RNA sequencing revealed different mechanisms driving HCC, with Mrpl9 activation altering genes functionally related to mitochondrial function, Vps72 levels altering phospholipid metabolism, and Gba1 activation enhancing endosomal-lysosomal activity, all leading to promotion of cellular proliferation. Analysis of human tumor tissues with high levels of MRPL9, VPS72, or GBA1 revealed congruent results, indicating conserved mechanisms driving HCC.

CONCLUSIONS

This study reveals chromosome 1q genes Vps72, Gba1, and Mrpl9 as drivers of HCC. Future efforts to prevent or treat HCC can focus on these new driver genes.

Hepatocyte HIF-2α aggravates NAFLD by inducing ferroptosis through increasing extracellular iron

Recent research has illuminated the pivotal role of the hypoxia-inducible factor-2α (HIF-2α)/peroxisome proliferator-activated receptor alpha (PPARα) pathway in the progression of nonalcoholic fatty liver disease (NAFLD). Meanwhile, it has been reported that HIF-2α is involved in iron regulation, and that aberrant iron distribution leads to liver lipogenesis. Therefore, we hypothesize that HIF-2α exacerbates fatty liver by affecting iron distribution. To substantiate this hypothesis, we utilized liver-specific HIF-2α knockout mice and the LO2 cell line with overexpressed HIF-2α. HIF-2α overexpression (OE) was induced via lentiviral infection, followed by exposure to free fatty acids (FFAs) and deferoxamine (DFO). In animal experiments, hepatic HIF-2α knockout resulted in lower liver lipid levels, lower liver weight, and higher serum iron levels. Enrichment in autophagy, ferroptosis, and the PI3K-AKT pathway was demonstrated through Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis in the liver of mice. In vitro experiments showed that HIF-2α increased supernatant iron. In the HIF-2α OE group, the addition of FFA led to decreased levels of reduced glutathione (GSH) and glutathione peroxidase 4 (GPX4) protein, along with increased lipid peroxidation (LPO), cellular lipid droplets, and triglyceride content. Impressively, DFO intervention decreased supernatant iron, reversed these changes by increasing GSH and GPX4 levels, and simultaneously reduced LPO levels, cellular lipid droplets, and triglyceride content. In addition, the expression of proteins related to β-oxidation increased, and lipid deposition in hepatocytes improved, which may be associated with the PI3K/AKT pathway. In summary, our findings suggest that HIF-2α-mediated iron flux enhances NAFLD cell susceptibility to ferroptosis, thereby impacting lipid metabolism-related genes and contributing to lipid accumulation.NEW & NOTEWORTHY The experiment demonstrated that HIF-2α increased extracellular iron. In LO2 cells overexpressing HIF-2α, FFAs not only increased cellular lipid and triglyceride levels but also induced key features of ferroptosis, such as reduced GSH and GPX4 levels and increased LPO, despite the absence of cellular iron overload. These effects were reversed by lowering extracellular iron with DFO. Furthermore, DFO treatment increased β-oxidation protein expression and improved lipid deposition in hepatocytes, potentially through the PI3K/AKT pathway.

Mechanisms and therapeutic implications of selective autophagy in nonalcoholic fatty liver disease

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) has become the most common chronic liver disease worldwide, whereas there is no approved drug therapy due to its complexity. Studies are emerging to discuss the role of selective autophagy in the pathogenesis of NAFLD, because the specificity among the features of selective autophagy makes it a crucial process in mitigating hepatocyte damage caused by aberrant accumulation of dysfunctional organelles, for which no other pathway can compensate.

AIM OF REVIEW

This review aims to summarize the types, functions, and dynamics of selective autophagy that are of particular importance in the initiation and progression of NAFLD. And on this basis, the review outlines the therapeutic strategies against NAFLD, in particular the medications and potential natural products that can modulate selective autophagy in the pathogenesis of this disease.

KEY SCIENTIFIC CONCEPTS OF REVIEW

The critical roles of lipophagy and mitophagy in the pathogenesis of NAFLD are well established, while reticulophagy and pexophagy are still being identified in this disease due to the insufficient understanding of their molecular details. As gradual blockage of autophagic flux reveals the complexity of NAFLD, studies unraveling the underlying mechanisms have made it possible to successfully treat NAFLD with multiple pharmacological compounds that target associated pathways. Overall, it is convinced that the continued research into selective autophagy occurring in NAFLD will further enhance the understanding of the pathogenesis and uncover novel therapeutic targets.

Lipophagy and epigenetic alterations are related to metabolic dysfunction-associated steatotic liver disease progression in an experimental model

BACKGROUND

Genetic and epigenetic alterations are related to metabolic dysfunction-associated steatotic liver disease (MASLD) pathogenesis.

AIM

To evaluate micro (mi)RNAs and lipophagy markers in an experimental model of metabolic dysfunction-associated steatohepatitis (MASH).

METHODS

Adult male Sprague Dawley rats were randomized into two groups: Control group (n = 10) fed a standard diet; and intervention group (n = 10) fed a high-fat-choline-deficient diet for 16 weeks. Molecular evaluation of lipophagy markers in liver tissue [sirtuin-1, p62/sequestosome-1, transcription factor-EB, perilipin-2 (Plin2), Plin3, Plin5, lysosome-associated membrane proteins-2, rubicon, and Cd36], and serum miRNAs were performed.

RESULTS

Animals in the intervention group developed MASH and showed a significant decrease in sirtuin-1 (P = 0.020) and p62/sequestosome-1 (P < 0.001); the opposite was reported for transcription factor-EB (P = 0.020), Plin2 (P = 0.003), Plin3 (P = 0.031), and Plin5 (P = 0.005) compared to the control group. There was no significant difference between groups for lysosome-associated membrane proteins-2 (P = 0.715), rubicon (P = 0.166), and Cd36 (P = 0.312). The intervention group showed a significant increase in miR-34a (P = 0.005) and miR-21 (P = 0.043) compared to the control. There was no significant difference between groups for miR-375 (P = 0.905), miR-26b (P = 0.698), and miR-155 (P = 0.688).

CONCLUSION

Animals with MASH presented expression changes in markers related to lysosomal stress and autophagy as well as in miRNAs related to inflammation and fibrogenesis, processes that promote MASLD progression.

Sesamin alleviates lipid accumulation induced by elaidic acid in L02 cells through TFEB regulated autophagy

Introduction

Non-alcoholic fatty liver disease (NAFLD) is a common chronic disease seriously threatening human health, with limited treatment means, however. Sesamin, a common lignan in sesame seed oil, exhibits anti-inflammatory, antioxidant, and anticancer properties. Our previous studies have shown an ameliorative effect of sesamin on lipid accumulation in human hepatocellular carcinoma (HePG2) induced by oleic acid, with its protective effects unclear in the case of 9-trans-C18:1 elaidic acid (9-trans-C18,1).

Methods

L02 cells, an important tool in scientific researches due to its high proliferation ability, preserved hepatocyte function, and specificity in response to exogenous factors, were incubated with 9-trans-C18:1 to establish an in vitro model of NAFLD in our study. The lipid accumulation in cells and the morphology of mitochondria and autolysosomes were observed by Oil Red O staining and transmission electron microscopy. The effects of sesamin on oxidative stress, apoptosis, mitochondrial function, autophagy as well as related protein levels in L02 cells were also investigated in the presence of 9-trans-C18:1.

Results

The results showed that sesamin significantly accelerated the autophagy flux of L02 cells induced by 9-trans-C18:1 as well as elevated protein levels of transcription factor EB (TFEB) and its downstream target lysosome-associated membrane protein 1(LAMP1), along with up-regulated levels of TFEB and LAMP1 in the nucleus indicated by Immunofluorescence. In addition, PTEN-induced putative kinase 1 and Parkin mediated mitophagy was activated by sesamin. The direct inhibitor Eltrombopag and indirect inhibitor MHY1485 of TFEB reversed the protective effect of sesamin, suggesting the involvement of autophagy in the lipid-lowering process of sesamin.

Discussion

This work suggests that sesamin regulates autophagy through TFEB to alleviate lipid accumulation in L02 cells induced by 9-trans-C18:1, providing a potential target for the prevention and treatment of NAFLD.

Potential mechanism of perillaldehyde in the treatment of nonalcoholic fatty liver disease based on network pharmacology and molecular docking

Non-alcoholic fatty liver disease (NAFLD) is one of the most common chronic metabolic liver diseases worldwide. Perillaldehyde (4-propyl-1-en-2-ylcyclohexene-1-aldehyde, PA) is a terpenoid compound extracted from Perilla, which has effective pharmacological activities such as anti-inflammatory, antidepressant, and anticancer. This study aimed to explore the pharmacological effects of PA in intervening with NAFLD and reveal its potential mechanisms. Firstly, we identified the core targets of PA intervention therapy for NAFLD through network pharmacology and molecular docking techniques. After that, in vitro animal experiments such as H&E and Masson staining, immunofluorescence, immunohistochemistry, and Western blot were conducted to validate the results network effectively pharmacology predicted. Network pharmacology analysis suggested that PPAR-α may be the core target of PA intervention in NAFLD. H&E and Masson staining showed that after low-dose (50 mg/kg) PA administration, there was a noticeable improvement in fat deposition in the livers of NAFLD mice, and liver tissue fibrosis was alleviated. Immunohistochemical and immunofluorescence analysis showed that low dose (50 mg/kg) PA could reduce hepatocyte apoptosis, decrease the content of pro-apoptosis protein Bax, and increase the expression of anti-apoptosis protein Bcl-2 in NAFLD mice. Western blot results confirmed that low-dose (50 mg/kg) PA could increase the expression of PPAR-α and inhibit the expression of NF-κB in NAFLD mice. Our study indicated that PA could enhance the activity of PPAR-α and reduce the level of NF-κB in NAFLD mice, which may positively affect the prevention of NAFLD.

The Effect of Quercetin on Non-Alcoholic Fatty Liver Disease (NAFLD) and the Role of Beclin1, P62, and LC3: An Experimental Study

Background/Objectives: Non-alcoholic fatty liver disease (NAFLD) is a major metabolic disorder with no established pharmacotherapy. Quercetin, a polyphenolic flavonoid, demonstrates potential hepatoprotective effects but has limited bioavailability. This study evaluates the impact of quercetin on NAFLD and assesses the roles of autophagy-related proteins in disease progression. Methods: Forty-seven male C57BL/6J mice were fed a high-fat diet (HFD) for 12 weeks to induce NAFLD, followed by quercetin treatment for 4 weeks. Mice were divided into baseline, control, and two quercetin groups, receiving low (10 mg/kg) and high (50 mg/kg) doses. Liver histology was scored using the NAFLD Activity Score (NAS). Immunohistochemistry and immunoblotting were performed to analyze autophagy markers. Results: Quercetin-treated groups showed significant reductions in NAS compared to controls (p = 0.011), mainly in steatosis and steatohepatitis. Immunohistochemistry indicated increased expression of autophagy markers LCA and p62 in quercetin groups. Western blot analysis revealed significant elevations in LC3A in the treated groups, suggesting improved autophagic activity and lipid degradation. Conclusions: Quercetin effectively reduces NAFLD severity and modulates autophagy-related proteins. These findings suggest that quercetin enhances autophagic flux, supporting its therapeutic potential for NAFLD. Additional research is needed to clarify the molecular mechanisms of quercetin and to determine the optimal dosing for clinical application.

Dasatinib and Quercetin as Senolytic Drugs Improve Fat Deposition and Exhibit Antifibrotic Effects in the Medaka Metabolic Dysfunction-Associated Steatotic Liver Disease Model

Metabolic dysfunction-associated steatotic liver disease (MASLD) causes cellular senescence due to oxidative stress, endoplasmic reticulum stress, and ectopic fat deposition in the liver. Recently, dasatinib, an antitumor agent, and quercetin, a dietary supplement, were combined as a senolytic drug to eliminate senescent cells. Thus, this study aimed to examine the effects of dasatinib and quercetin administration on removing senescent cells and their therapeutic effects on MASLD in a medaka MASLD model. Dasatinib and quercetin were administered to a medaka MASLD model, which was fed a high-fat diet by dissolving them in aquarium water. The results revealed that senescent cells in the liver were increased in the HFD group but improved in the treatment group. Hematoxylin and eosin staining also showed that treatment improved fat deposition in hepatocytes. In addition, TGFβ1, a driver factor of fibrosis, was reduced in the treatment group. Dasatinib and quercetin eliminated senescent cells in MASLD, attenuated fat deposition, and suppressed fibrosis gene expression. The results indicate that dasatinib and quercetin as senolytic drugs are novel therapeutic agents that reduce MASLD.

Quercetin's Potential in MASLD: Investigating the Role of Autophagy and Key Molecular Pathways in Liver Steatosis and Inflammation

Metabolic dysfunction-associated fatty liver disease (MASLD) is a widespread liver disorder characterized by excessive fat accumulation in the liver, commonly associated with metabolic syndrome components such as obesity, diabetes, and dyslipidemia. With a global prevalence of up to 30%, MASLD is projected to affect over 100 million people in the U.S. and 20 million in Europe by 2030. The disease ranges from Steatotic Lived Disease (SLD) to more severe forms like metabolic dysfunction-associated steatohepatitis (MASH), which can progress to cirrhosis and hepatocellular carcinoma. Autophagy, a cellular process crucial for lipid metabolism and homeostasis, is often impaired in MASLD, leading to increased hepatic lipid accumulation and inflammation. Key autophagy-related proteins, such as Beclin1, LC3A, SQSTM1 (p62), CD36, and Perilipin 3, play significant roles in regulating this process. Disruption in these proteins contributes to the pathogenesis of MASLD. Quercetin, a natural polyphenolic flavonoid with antioxidant and anti-inflammatory properties, has promising results in mitigating MASLD. It may reduce hepatic lipid accumulation, improve mitochondrial function, and enhance autophagy. However, further research is needed to elucidate its mechanisms and validate its therapeutic potential in clinical settings. This underscores the need for continued investigation into autophagy and novel treatments for MASLD.

LC3-associated phagocytosis and human diseases: Insights from mechanisms to therapeutic potential

LC3-associated phagocytosis (LAP) is a distinct type of autophagy that involves the sequestration of extracellular material by phagocytes. Beyond the removal of dead cells and cellular debris from eukaryotic cells, LAP is also involved in the removal of a variety of pathogens, including bacteria, fungi, and viruses. These events are integral to multiple physiological and pathological processes, such as host defense, inflammation, and tissue homeostasis. Dysregulation of LAP has been associated with the pathogenesis of several human diseases, including infectious diseases, autoimmune diseases, and neurodegenerative diseases. Thus, understanding the molecular mechanisms underlying LAP and its involvement in human diseases may provide new insights into the development of novel therapeutic strategies for these conditions. In this review, we summarize and highlight the current consensus on the role of LAP and its biological functions in disease progression to propose new therapeutic strategies. Further studies are needed to illustrate the precise role of LAP in human disease and to determine new therapeutic targets for LAP-associated pathologies.

Uvaol ameliorates lipid deposition in hyperlipidemic hepatocytes by suppressing protein-tyrosine phosphatase 1B/ER stress signaling

Uvaol (UV), a pentacyclic triterpene found in olives and virgin olive oil, is known for its anti-inflammatory and antioxidant effects in various disease models. While olive oil is reported to reduce obesity and insulin resistance, the specific impact of UV on liver lipid metabolism and its molecular mechanisms are not fully understood. In this study, hepatic lipid accumulation was measured using oil red O staining, and protein expression levels in liver cells were assessed via Western blot analysis. Apoptosis was evaluated through cell viability and caspase 3 activity assays. UV treatment reduced lipid accumulation, fatty acid uptake, apoptosis, and ER stress in palmitate-treated liver cells. Additionally, UV enhanced fatty acid oxidation. Mechanistically, increased SIRT6 expression and autophagy were observed in UV-treated cells. SIRT6-targeted siRNA or 3-methyladenine blocked the effects of UV in hyperlipidemic cells. In conclusion, UV improves SIRT6/autophagy signaling, reducing lipid deposition and apoptosis in liver cells under high lipid conditions. This in vitro study provides strong evidence for potential therapeutic strategies for hepatic steatosis.

Hepatocyte-specific GDF15 overexpression improves high-fat diet-induced obesity and hepatic steatosis in mice via hepatic FGF21 induction

GDF15 and FGF21, stress-responsive cytokines primarily secreted from the liver, are promising therapeutic targets for metabolic dysfunction-associated steatotic liver disease (MASLD). However, the interaction between GDF15 and FGF21 remains unclear. We examined the effects of hepatocyte-specific GDF15 or FGF21 overexpression in high-fat diet (HFD)-fed mice for 8 weeks. Hydrodynamic injection of GDF15 or FGF21 sustained high circulating levels of GDF15 or FGF21, respectively, resulting in marked reductions in body weight, epididymal fat mass, insulin resistance, and hepatic steatosis. In addition, GDF15 treatment led to early reduction in body weight despite no change in food intake, indicating the role of GDF15 other than appetite loss. GDF15 treatment increased liver-derived serum FGF21 levels, whereas FGF21 treatment did not affect GDF15 expression. GDF15 promoted eIF2α phosphorylation and XBP1 splicing, leading to FGF21 induction. In murine AML12 hepatocytes treated with free fatty acids (FFAs), GDF15 overexpression upregulated Fgf21 mRNA levels and promoted eIF2α phosphorylation and XBP1 splicing. Overall, continuous exposure to excess FFAs resulted in a gradual increase of β-oxidation-derived reactive oxygen species and endoplasmic reticulum stress, suggesting that GDF15 enhanced this pathway and induced FGF21 expression. GDF15- and FGF21-related crosstalk is an important pathway for the treatment of MASLD.

The novel TFEB agonist desloratadine ameliorates hepatic steatosis by activating the autophagy-lysosome pathway

The autophagy-lysosome pathway plays an essential role in promoting lipid catabolism and preventing hepatic steatosis in non-alcoholic fatty liver disease (NAFLD). Transcription factor EB (TFEB) enhances the autophagy-lysosome pathway by regulating the expression of genes related to autophagy and lysosome biogenesis. Therefore, targeting TFEB provides a novel strategy for the treatment of lipid metabolic diseases. In this study, the antiallergic drug desloratadine was screened and identified as a novel TFEB agonist. Desloratadine effectively induced translocation of TFEB to the nucleus and promoted autophagy and lysosome biogenesis. Desloratadine-induced TFEB activation was dependent on AMPK rather than mTORC1. Moreover, desloratadine treatment enhanced clearance of lipid droplets in cells induced by fatty acids oleate and palmitate. Furthermore, high-fat diet (HFD) induced obesity mouse model experiments indicated treatment with desloratadine markedly reduced the body weight of HFD-fed mice, as well as the levels of hepatic triglycerides and total cholesterol, serum glutamic pyruvic transaminase and glutamic-oxaloacetic transaminase. Oil red O staining showed the liver fat was significantly reduced after desloratadine treatment, and H&E staining analysis demonstrated hepatocellular ballooning was improved. In addition, autophagy and lysosomal biogenesis was stimulated in the liver of desloratadine treated mice. Altogether, these findings demonstrate desloratadine ameliorates hepatic steatosis through activating the TFEB-mediated autophagy-lysosome pathway, thus desloratadine has an exciting potential to be used to treat fatty liver disease.

Autophagy and hepatic lipid metabolism: mechanistic insight and therapeutic potential for MASLD

Metabolic dysfunction-associated steatotic liver disease (MASLD) originates from a homeostatic imbalance in hepatic lipid metabolism. Increased fat deposition in the liver of people suffering from MASLD predisposes them to develop further metabolic derangements, including diabetes mellitus, metabolic dysfunction-associated steatohepatitis (MASH), and other end-stage liver diseases. Unfortunately, only limited pharmacological therapies exist for MASLD to date. Autophagy, a cellular catabolic process, has emerged as a primary mechanism of lipid metabolism in mammalian hepatocytes. Furthermore, preclinical studies with autophagy modulators have shown promising results in resolving MASLD and mitigating its progress into deleterious liver pathologies. In this review, we discuss our current understanding of autophagy-mediated hepatic lipid metabolism, its therapeutic modulation for MASLD treatment, and current limitations and scope for clinical translation.

All-trans retinoic acid induces lipophagy by reducing Rubicon in Hepa1c1c7 cells

All-trans retinoic acid (atRA), a metabolite of vitamin A, reduces hepatic lipid accumulation in liver steatosis model animals. Lipophagy, a new lipolysis pathway, degrades a lipid droplet (LD) via autophagy in adipose tissue and the liver. We recently found that atRA induces lipophagy in adipocytes. However, it remains unclear whether atRA induces lipophagy in hepatocytes. In this study, we investigated the effects of atRA on lipophagy in Hepa1c1c7 cells and the liver of mice fed a high-fat diet (HFD). First, we confirmed that atRA induced autophagy in Hepa1c1c7 cells by Western blotting and the GFP-LC3-mCherry probe. Next, we evaluated the lipolysis in fatty Hepa1c1c7 cells treated with the knockdown of Atg5, an essential gene in autophagy induction. Atg5-knockdown partly suppressed the atRA-induced lipolysis in fatty Hepa1c1c7 cells. We also found that atRA reduced the protein, but not mRNA, expression of Rubicon, a negative regulator of autophagy, in Hepa1c1c7 cells and the liver of HFD-fed mice. Rubicon-knockdown partly inhibited the atRA-induced lipolysis in fatty Hepa1c1c7 cells. In addition, atRA reduced hepatic Rubicon expression in young mice, but the effect of atRA on it diminished in aged mice. Finally, we investigated the mechanism underlying reduced Rubicon protein expression by atRA in hepatocytes. A protein synthesis inhibitor, but not proteasome or lysosomal inhibitors, significantly blocked the reduction of Rubicon protein expression by atRA in Hepa1c1c7 cells. These results suggest that atRA may promote lipophagy in fatty hepatocytes by reducing hepatic Rubicon expression via inhibiting protein synthesis.

Lipid Nanoparticle-Mediated Delivery of CRISPR-Cas9 Against Rubicon Ameliorates NAFLD by Modulating CD36 Along with Glycerophospholipid Metabolism

Non-alcoholic fatty liver disease (NAFLD) is a prominent cause of various chronic metabolic hepatic diseases with limited therapeutics. Rubicon, an essential regulator in lysosomal degradation, is reported to exacerbate hepatic steatosis in NAFLD mice and patients, indicating its probability of being a therapeutic target for NAFLD treatment. In this study, the therapeutic potential of Rubicon blockage is investigated. Lipid nanoparticles carrying Rubicon-specific CRISPR-Cas9 components exhibited liver accumulation, cell internalization, and Rubicon knockdown. A single administration of the nanoparticles results in attenuated lipid deposition and hepatic steatosis, with lower circulating lipid levels and decreased adipocyte size in NAFLD mice. Furthermore, the increase of phosphatidylcholine and phosphatidylethanolamine levels can be observed in the NAFLD mice livers after Rubicon silencing, along with regulatory effects on metabolism-related genes such as CD36, Gpcpd1, Chka, and Lpin2. The results indicate that knockdown of Rubicon improves glycerophospholipid metabolism and thereby ameliorates the NAFLD progression, which provides a potential strategy for NAFLD therapy via the restoration of Rubicon.

Roles of lipid droplets and related proteins in metabolic diseases

Lipid droplets (LDs), which are active organelles, derive from the monolayer membrane of the endoplasmic reticulum and encapsulate neutral lipids internally. LD-associated proteins like RAB, those in the PLIN family, and those in the CIDE family participate in LD formation and development, and they are active players in various diseases, organelles, and metabolic processes (i.e., obesity, non-alcoholic fatty liver disease, and autophagy). Our synthesis on existing research includes insights from the formation of LDs to their mechanisms of action, to provide an overview needed for advancing research into metabolic diseases and lipid metabolism.

The marine-derived compound TAG alleviates Parkinson's disease by restoring RUBCN-mediated lipid metabolism homeostasis

Parkinson's disease (PD) is the second most common neurodegenerative disease, and its prevalence is increasing. Currently, no effective therapies for PD exist. Marine-derived natural compounds are considered important resources for the discovery of new drugs due to their distinctive structures and diverse activities. In this study, tetrahydroauroglaucin (TAG), a polyketide isolated from a marine sponge, was found to have notable neuroprotective effects on MPTP/MPP+-induced neurotoxicity. RNA sequencing analysis and metabolomics revealed that TAG significantly improved lipid metabolism disorder in PD models. Further investigation indicated that TAG markedly decreased the accumulation of lipid droplets (LDs), downregulated the expression of RUBCN, and promoted autophagic flux. Moreover, conditional knockdown of Rubcn notably attenuated PD-like symptoms and the accumulation of LDs, accompanied by blockade of the neuroprotective effect of TAG. Collectively, our results first indicated that TAG, a promising PD therapeutic candidate, could suppress the accumulation of LDs through the RUBCN-autophagy pathway, which highlighted a novel and effective strategy for PD treatment.

A RAB7A phosphoswitch coordinates Rubicon Homology protein regulation of Parkin-dependent mitophagy

Activation of PINK1 and Parkin in response to mitochondrial damage initiates a response that includes phosphorylation of RAB7A at Ser72. Rubicon is a RAB7A binding negative regulator of autophagy. The structure of the Rubicon:RAB7A complex suggests that phosphorylation of RAB7A at Ser72 would block Rubicon binding. Indeed, in vitro phosphorylation of RAB7A by TBK1 abrogates Rubicon:RAB7A binding. Pacer, a positive regulator of autophagy, has an RH domain with a basic triad predicted to bind an introduced phosphate. Consistent with this, Pacer-RH binds to phosho-RAB7A but not to unphosphorylated RAB7A. In cells, mitochondrial depolarization reduces Rubicon:RAB7A colocalization whilst recruiting Pacer to phospho-RAB7A-positive puncta. Pacer knockout reduces Parkin mitophagy with little effect on bulk autophagy or Parkin-independent mitophagy. Rescue of Parkin-dependent mitophagy requires the intact pRAB7A phosphate-binding basic triad of Pacer. Together these structural and functional data support a model in which the TBK1-dependent phosphorylation of RAB7A serves as a switch, promoting mitophagy by relieving Rubicon inhibition and favoring Pacer activation.

Dietary Chitosan Attenuates High-Fat Diet-Induced Oxidative Stress, Apoptosis, and Inflammation in Nile Tilapia (Oreochromis niloticus) through Regulation of Nrf2/Kaep1 and Bcl-2/Bax Pathways

Fatty liver injury is a prevalent condition in most farmed fish, yet the molecular mechanisms underpinning this pathology remain largely elusive. A comprehensive feeding trial spanning eight weeks was conducted to discern the potential of dietary chitosan in mitigating the deleterious effects of a high-fat diet (HFD) while concurrently exploring the underlying mechanism. Growth performance, haemato-biochemical capacity, antioxidant capacity, apoptotic/anti-apoptotic gene expression, inflammatory gene expression, and histopathological changes in the liver, kidney, and intestine were meticulously assessed in Nile tilapia. Six experimental diets were formulated with varying concentrations of chitosan. The first three groups were administered a diet comprising 6% fat with chitosan concentrations of 0%, 5%, and 10% and were designated as F6Ch0, F6Ch5, and F6Ch10, respectively. Conversely, the fourth, fifth, and sixth groups were fed a diet containing 12% fat with chitosan concentrations of 0%, 5%, and 10%, respectively, for 60 days and were termed F12Ch0, F12Ch5, and F12Ch10. The results showed that fish fed an HFD demonstrated enhanced growth rates and a significant accumulation of fat in the perivisceral tissue, accompanied by markedly elevated serum hepatic injury biomarkers and serum lipid levels, along with upregulation of pro-apoptotic and inflammatory markers. In stark contrast, the expression levels of nrf2, sod, gpx, and bcl-2 were notably decreased when compared with the control normal fat group. These observations were accompanied by marked diffuse hepatic steatosis, diffuse tubular damage, and shortened intestinal villi. Intriguingly, chitosan supplementation effectively mitigated the aforementioned findings and alleviated intestinal injury by upregulating the expression of tight junction-related genes. It could be concluded that dietary chitosan alleviates the adverse impacts of an HFD on the liver, kidney, and intestine by modulating the impaired antioxidant defense system, inflammation, and apoptosis through the variation in nrf2 and cox2 signaling pathways.

Hepatocytes and the art of killing Plasmodium softly

The Plasmodium parasites that cause malaria undergo asymptomatic development in the parenchymal cells of the liver, the hepatocytes, prior to infecting erythrocytes and causing clinical disease. Traditionally, hepatocytes have been perceived as passive bystanders that allow hepatotropic pathogens such as Plasmodium to develop relatively unchallenged. However, now there is emerging evidence suggesting that hepatocytes can mount robust cell-autonomous immune responses that target Plasmodium, limiting its progression to the blood and reducing the incidence and severity of clinical malaria. Here we discuss our current understanding of hepatocyte cell-intrinsic immune responses that target Plasmodium and how these pathways impact malaria.

MondoA and AKI and AKI-to-CKD Transition

Key Points

Background

Elderly individuals and patients with CKD are at a higher risk of AKI. The transcription factor MondoA is downregulated in the kidneys of aged individuals or patients with AKI; however, its roles in AKI development and the AKI-to-CKD transition remain unknown.

Methods

We investigated the expression of MondoA in human kidney biopsy samples, ischemia-reperfusion–injured (IRI) mouse kidneys, and cultured proximal tubular epithelial cells under hypoxia/reoxygenation. The role of MondoA during the initial and recovery phases after IRI was evaluated using proximal tubule–specific MondoA knockout mice and MondoA-deficient proximal tubular epithelial cells. Furthermore, we explored the involvement of Rubicon and transcription factor EB (TFEB), both of which are downstream factors of MondoA.

Results

MONDOA expression was decreased in the renal tubules of patients with CKD. In mouse kidneys, MondoA expression was decreased under ischemia, whereas its expression was increased during reperfusion. Genetic ablation of MondoA in proximal tubular epithelial cells inhibited autophagy and increased vulnerability to AKI through increased expression of Rubicon. Ablation of Rubicon in MondoA-deficient IRI kidneys activated autophagy and protected mitochondrial function. MondoA ablation during the recovery phase after ischemia-reperfusion aggravated kidney injury through downregulation of the TFEB-peroxisome proliferator-activated receptor-γ coactivator-1α axis. Pharmacological upregulation of TFEB contributed to maintaining mitochondrial biogenesis and increased peroxisome proliferator-activated receptor-γ coactivator-1α transcription.

Conclusions

Our findings demonstrate that MondoA protected against vulnerability to AKI by maintaining autophagy and subsequently supporting mitochondrial function to prevent progression to CKD.

Sesamin alleviates lipid accumulation induced by oleic acid via PINK1/Parkin-mediated mitophagy in HepG2 cells

Sesamin, a special compound present in sesame and sesame oil, has been reported a role in regulating lipid metabolism, while the underlying mechanisms remain unclear. Autophagy has been reported associated with lipid metabolism and regarded as a key modulator in liver steatosis. The present work aimed to investigate whether sesamin could exert its protective effects against lipid accumulation via modulating autophagy in HepG2 cells stimulated with oleic acid (OA). Cell viability was evaluated using the CCK-8 method, and triglycerides (TG), total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein, cholesterol (LDL-C), alanine aminotransferase (ALT), along with aspartate aminotransferase (AST) were assessed by oil red O staining, transmission electron microscopy (TEM), and biochemical kits to investigate the lipid-lowering effects of sesamin. Differentially expressed genes were screened by RNA sequencing and validated using real-time quantitative PCR and Western blot. Autophagy and mitophagy related molecules were analyzed employing TEM, Western blot, and immunofluorescence. The data shows that in HepG2 cells stimulated by OA, sesamin reduces levels of TG, TC, LDL-C, ALT, and AST while elevating HDL-C, alleviates the lipid accumulation and improves fatty acid metabolism through modulating the levels of fat metabolism related genes including PCSK9, FABP1, CD36, and SOX4. Sesamin restores the suppressed autophagy in HepG2 cells caused by OA, which could be blocked by autophagy inhibitors. This indicates that sesamin improves fatty acid metabolism by enhancing autophagy levels, thereby mitigating the intracellular lipid accumulation. Furthermore, sesamin significantly enhances the mitophagy and improves mitochondrial homeostasis via activating the PINK/Parkin pathway. These data suggest that sesamin alleviates the excessive lipid accumulation in HepG2 caused by OA by restoring the impaired mitophagy via the PINK1/Parkin pathway, probably playing a preventive or therapeutic role in hepatic steatosis.

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.

Vitamin D and Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD): Novel Mechanistic Insights

Metabolic dysfunction-associated steatotic liver disease (MASLD) is an increasingly prevalent condition characterized by abnormal fat accumulation in the liver, often associated with metabolic disorders. Emerging evidence suggests a potential link between vitamin D deficiency and the development and progression of MASLD. The current review provides a concise overview of recent studies uncovering novel mechanistic insights into the interplay between vitamin D and MASLD. Several epidemiological studies have highlighted a significant association between low vitamin D levels and an increased risk of MASLD. Vitamin D, traditionally known for its role in bone health, has now been recognized as a key player in various physiological processes, including immune regulation and inflammation. Experimental studies using animal models have demonstrated that vitamin D deficiency exacerbates liver steatosis and inflammation, suggesting a potential protective role against MASLD. Mechanistically, vitamin D appears to modulate MASLD through multiple pathways. Firstly, the vitamin D receptor (VDR) is abundantly expressed in liver cells, indicating a direct regulatory role in hepatic function. Activation of the VDR has been shown to suppress hepatic lipid accumulation and inflammation, providing a mechanistic basis for the observed protective effects. Additionally, vitamin D influences insulin sensitivity, a critical factor in MASLD pathogenesis. Improved insulin sensitivity may mitigate the excessive accumulation of fat in the liver, thus attenuating MASLD progression. In parallel, vitamin D exhibits anti-inflammatory properties by inhibiting pro-inflammatory cytokines implicated in MASLD pathophysiology. Experimental evidence suggests that the immunomodulatory effects of vitamin D extend to the liver, reducing inflammation and oxidative stress, key drivers of MASLD, and the likelihood of hepatocyte injury and fibrosis. Understanding the complex interplay between vitamin D and MASLD provides a basis for exploring targeted therapeutic strategies and preventive interventions. As vitamin D deficiency is a modifiable risk factor, addressing this nutritional concern may prove beneficial in mitigating the burden of MASLD and associated metabolic disorders.

RAMP1 Protects Hepatocytes against Ischemia-reperfusion Injury by Inhibiting the ERK/YAP Pathway

Background and Aims

Hepatic ischemia-reperfusion injury (HIRI) is a prevalent complication of liver transplantation, partial hepatectomy, and severe infection, necessitating the development of more effective clinical strategies. Receptor activity-modifying protein 1 (RAMP1), a member of the G protein-coupled receptor adapter family, has been implicated in numerous physiological and pathological processes. The study aimed to investigate the pathogenesis of RAMP1 in HIRI.

Methods

We established a 70% liver ischemia-reperfusion model in RAMP1 knockout (KO) and wild-type mice. Liver and blood samples were collected after 0, 6, and 24 h of hypoxia/reperfusion. Liver histological and serological analyses were performed to evaluate liver damage. We also conducted in-vitro and in-vivo experiments to explore the molecular mechanism underlying RAMP1 function.

Results

Liver injury was exacerbated in RAMP1-KO mice compared with the sham group, as evidenced by increased cell death and elevated serum transaminase and inflammation levels. HIRI was promoted in RAMP1-KO mice via the induction of hepatocyte apoptosis and inhibition of proliferation. The absence of RAMP1 led to increased activation of the extracellular signal-regulated kinase (ERK)/mitogen-activated protein kinase (MAPK) pathway and yes-associated protein (YAP) phosphorylation, ultimately promoting apoptosis. SCH772984, an ERK/MAPK phosphorylation inhibitor, and PY-60, a YAP phosphorylation inhibitor, reduced apoptosis in in-vitro and in-vivo experiments.

Conclusions

Our findings suggest that RAMP1 protects against HIRI by inhibiting ERK and YAP phosphorylation signal transduction, highlighting its potential as a therapeutic target for HIRI and providing a new avenue for intervention.

All-trans retinoic acid induces lipophagy through the activation of the AMPK-Beclin1 signaling pathway and reduces Rubicon expression in adipocytes

Lipophagy is defined as a lipolysis pathway that degrades lipid droplet (LD) via autophagy. All-trans retinoic acid (atRA), a metabolite of vitamin A, stimulates lipolysis through hormone-sensitive lipase and β-oxidation. However, the regulation of lipolysis by atRA-induced autophagy in adipocytes remains unclear. In this study, we investigated the effect of atRA on autophagy in epididymal fat of mice and the molecular mechanisms of autophagy in 3T3-L1 adipocytes. Western blotting showed that atRA decreased the expression of p62, a cargo receptor for autophagic degradation, and increased the expression of the lipidated LC3B (LC3B-II), an autophagy marker, in epididymal fat. Next, we confirmed that atRA increased autophagic flux in differentiated 3T3-L1 cells using the GFP-LC3-RFP-LC3ΔG probe. Immunofluorescent staining revealed that the colocalization of LC3B with perilipin increased in differentiated 3T3-L1 cells treated with atRA. The knockdown of Atg5, an essential gene in autophagy induction, partly suppressed the atRA-induced release of non-esterified fatty acid (NEFA) from LDs in differentiated 3T3-L1 cells. atRA time-dependently elicited the phosphorylation of AMPK and Beclin1, autophagy-inducing factors, in mature 3T3-L1 adipocytes. Inversely, atRA decreased the protein expression of Rubicon, an autophagy repressor, in differentiated 3T3-L1 cells and epididymal fat. Interestingly, the expression of ALDH1A1, atRA-synthesizing enzymes, increased in epididymal fat with decreased protein expression of Rubicon in aged mice. These results suggest that atRA may partially induce lipolysis through lipophagy by activating the AMPK-Beclin1 signaling pathway in the adipocytes and increased atRA levels may contribute to decreased Rubicon expression in the epididymal fat of aged mice. (248/250 words).

Advances in the Pathogenesis of Metabolic Liver Disease-Related Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is the sixth most common cancer globally and the primary cause of death in cancer cases, with significant public health concern worldwide. Despite the overall decline in the incidence and mortality rates of HCC in recent years in recent years, the emergence of metabolic liver disease-related HCC is causing heightened concern, especially in countries like the United States, the United Kingdom, and P.R. China. The escalation of metabolic liver disease-related HCC is attributed to a combination of factors, including genetic predisposition, lifestyle choices, and changes in the living environment. However, the pathogenesis of metabolic liver disease-associated HCC remains imperfect. In this review, we encapsulate the latest advances and essential aspects of the pathogenesis of metabolic liver disease-associated HCC, including alcoholic liver disease (ALD), metabolic dysfunction-associated steatotic liver disease (MASLD), and inherited metabolic liver diseases.

Decoding m6A mRNA methylation by reader proteins in liver diseases

N6-methyladenosine (m6A) is a dynamic and reversible epigenetic regulation. As the most prevalent internal post-transcriptional modification in eukaryotic RNA, it participates in the regulation of gene expression through various mechanisms, such as mRNA splicing, nuclear export, localization, translation efficiency, mRNA stability, and structural transformation. The involvement of m6A in the regulation of gene expression depends on the specific recognition of m6A-modified RNA by reader proteins. In the pathogenesis and treatment of liver disease, studies have found that the expression levels of key genes that promote or inhibit the development of liver disease are regulated by m6A modification, in which abnormal expression of reader proteins determines the fate of these gene transcripts. In this review, we introduce m6A readers, summarize the recognition and regulatory mechanisms of m6A readers on mRNA, and focus on the biological functions and mechanisms of m6A readers in liver cancer, viral hepatitis, non-alcoholic fatty liver disease (NAFLD), hepatic fibrosis (HF), acute liver injury (ALI), and other liver diseases. This information is expected to be of high value to researchers deciphering the links between m6A readers and human liver diseases.

Dysfunction of autophagy in high-fat diet-induced non-alcoholic fatty liver disease

ABBREVIATIONS

ACOX1: acyl-CoA oxidase 1; ADH5: alcohol dehydrogenase 5 (class III), chi polypeptide; ADIPOQ: adiponectin, C1Q and collagen domain containing; ATG: autophagy related; BECN1: beclin 1; CRTC2: CREB regulated transcription coactivator 2; ER: endoplasmic reticulum; F2RL1: F2R like trypsin receptor 1; FA: fatty acid; FOXO1: forkhead box O1; GLP1R: glucagon like peptide 1 receptor; GRK2: G protein-coupled receptor kinase 2; GTPase: guanosine triphosphatase; HFD: high-fat diet; HSCs: hepatic stellate cells; HTRA2: HtrA serine peptidase 2; IRGM: immunity related GTPase M; KD: knockdown; KDM6B: lysine demethylase 6B; KO: knockout; LAMP2: lysosomal associated membrane protein 2; LAP: LC3-associated phagocytosis; LDs: lipid droplets; Li KO: liver-specific knockout; LSECs: liver sinusoidal endothelial cells; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MAP3K5: mitogen-activated protein kinase kinase kinase 5; MED1: mediator complex subunit 1; MTOR: mechanistic target of rapamycin kinase; MTORC1: mechanistic target of rapamycin complex 1; NAFLD: non-alcoholic fatty liver disease; NASH: non-alcoholic steatohepatitis; NFE2L2: NFE2 like bZIP transcription factor 2; NOS3: nitric oxide synthase 3; NR1H3: nuclear receptor subfamily 1 group H member 3; OA: oleic acid; OE: overexpression; OSBPL8: oxysterol binding protein like 8; PA: palmitic acid; RUBCNL: rubicon like autophagy enhancer; PLIN2: perilipin 2; PLIN3: perilipin 3; PPARA: peroxisome proliferator activated receptor alpha; PRKAA2/AMPK: protein kinase AMP-activated catalytic subunit alpha 2; RAB: member RAS oncogene family; RPTOR: regulatory associated protein of MTOR complex 1; SCD: stearoyl-CoA desaturase; SIRT1: sirtuin 1; SIRT3: sirtuin 3; SNARE: soluble N-ethylmaleimide-sensitive factor attachment protein receptor; SQSTM1/p62: sequestosome 1; SREBF1: sterol regulatory element binding transcription factor 1;SREBF2: sterol regulatory element binding transcription factor 2; STING1: stimulator of interferon response cGAMP interactor 1; STX17: syntaxin 17; TAGs: triacylglycerols; TFEB: transcription factor EB; TP53/p53: tumor protein p53; ULK1: unc-51 like autophagy activating kinase 1; VMP1: vacuole membrane protein 1.

Nobiletin Alleviated Epithelial-Mesenchymal Transition of Hepatocytes in Liver Fibrosis Based on Autophagy-Hippo/YAP Pathway

SCOPE

The current researches indicated that the epithelial-mesenchymal transition (EMT) of hepatocytes plays a crucial role in the development of liver fibrosis. To date, there is a paucity of literature regarding the impact of nobiletin (NOB) on liver fibrosis. This study investigates the inhibitory effect of NOB on EMT in hepatocytes during the progression of liver fibrosis and its underlying mechanism.

METHODS AND RESULTS

The findings demonstrated that NOB significantly suppresses liver fibrosis in carbon tetrachloride (CCl4 )-induced mice by reducing inflammation and fiber deposition in the liver. Moreover, NOB mitigates EMT in hepatocytes, concurrently alleviating inflammatory status and reducing the production of reactive oxygen species (ROS) generation. The comprehensive investigation reveals that the hepatoprotective effect of NOB in liver fibrosis is attributed to autophagy activation, as evidenced by a significant increase in LC3 II expression and p62 degradation upon NOB treatment. Additionally, NOB activates the Hippo/YAP pathway by downregulating YAP and its downstream targets in liver fibrosis, which is regulated by autophagy based on experiments with chloroquine (CQ), 3-methyladenine (3-MA), and siYAP intervention.

CONCLUSION

Therefore, this study provides evidences that NOB can protect hepatocytes from undergoing EMT during liver fibrosis by inducing autophagy and subsequently modulating the Hippo/YAP pathway.

Regulation of Benzo[a]pyrene-Induced Hepatic Lipid Accumulation through CYP1B1-Induced mTOR-Mediated Lipophagy

Metabolic dysfunction-associated steatotic liver disease (MASLD) is caused by lipid accumulation within the liver. The pathogenesis underlying its development is poorly understood. Benzo[a]pyrene (B[a]P) is a polycyclic aromatic hydrocarbon and a group 1 carcinogen. The aryl hydrocarbon receptor activation by B[a]P induces cytochrome P450 (CYP) enzymes, contributing to hepatic lipid accumulation. However, the molecular mechanism through which the B[a]P-mediated induction of CYP enzymes causes hepatic lipid accumulation is unknown. This research was conducted to elucidate the role of CYP1B1 in regulating B[a]P-induced lipid accumulation within hepatocytes. B[a]P increased hepatic lipid accumulation, which was mitigated by CYP1B1 knockdown. An increase in the mammalian target of rapamycin (mTOR) by B[a]P was specifically reduced by CYP1B1 knockdown. The reduction of mTOR increased the expression of autophagic flux-related genes and promoted phagolysosome formation. Both the expression and translocation of TFE3, a central regulator of lipophagy, were induced, along with the expression of lipophagy-related genes. Conversely, enhanced mTOR activity reduced TFE3 expression and translocation, which reduced the expression of lipophagy-related genes, diminished phagolysosome production, and increased lipid accumulation. Our results indicate that B[a]P-induced hepatic lipid accumulation is caused by CYP1B1-induced mTOR and the reduction of lipophagy, thereby introducing novel targets and mechanisms to provide insights for understanding B[a]P-induced MASLD.

Effects of riboflavin deficiency and high dietary fat on hepatic lipid accumulation: a synergetic action in the development of non-alcoholic fatty liver disease

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is characterized by excessive lipid accumulation in the liver. Riboflavin, one of water soluble vitamins, plays a role in lipid metabolism and antioxidant function. However, the effects of riboflavin deficiency on NAFLD development have not yet to be fully explored.

METHODS

In the present study, an animal model of NAFLD was induced by high fat diet feeding in mice and a cellular model of NAFLD was developed in HepG2 cells by palmitic acid (PA) exposure. The effects of riboflavin deficiency on lipid metabolism and antioxidant function were investigated both in vivo and in vitro. In addition, the possible role of peroxisome proliferator-activated receptor gamma (PPARγ) was studied in HepG2 cells using gene silencing technique.

RESULTS

The results showed that riboflavin deficiency led to hepatic lipid accumulation in mice fed high fat diet. The expressions of fatty acid synthase (FAS) and carnitine palmitoyltransferase 1 (CPT1) were up-regulated, whereas that of adipose triglyceride lipase (ATGL) down-regulated. Similar changes in response to riboflavin deficiency were demonstrated in HepG2 cells treated with PA. Factorial analysis revealed a significant interaction between riboflavin deficiency and high dietary fat or PA load in the development of NAFLD. Hepatic PPARγ expression was significantly upregulated in mice fed riboflavin deficient and high fat diet or in HepG2 cells treated with riboflavin deficiency and PA load. Knockdown of PPARγ gene resulted in a significant reduction of lipid accumulation in HepG2 cells exposed to riboflavin deficiency and PA load.

CONCLUSIONS

There is a synergetic action between riboflavin deficiency and high dietary fat on the development of NAFLD, in which PPARγ may play an important role.

The promotion of fatty acid β-oxidation by hesperidin via activating SIRT1/PGC1α to improve NAFLD induced by a high-fat diet

Reducing fat deposits in hepatocytes is a direct treatment for nonalcoholic fatty liver disease (NAFLD) and the fatty acid metabolic processes mediated by fatty acid β-oxidation are important for the prevention of NAFLD. In this study, we established high-fat-diet models in vitro and in vivo to investigate the mechanism by which hesperidin (HDN) prevents NAFLD by modulating fatty acid β oxidation. Based on LC-MS screening of differential metabolites, many metabolites involved in phospholipid and lipid metabolism were found to be significantly altered and closely associated with fatty acid β-oxidation. The results from COIP experiments indicated that HDN increased the deacetylation of PGC1α by SIRT1. In addition, the results of CETSA and molecular docking experiments suggest that HDN targeting of SIRT1 plays an important role in their stable binding. Meanwhile, it was found that HDN reduced fatty acid uptake and synthesis and promoted the expression of SIRT1/PGC1α and fatty acid β-oxidation, and the latter process was inhibited after transfection to knockdown SIRT1. The results suggest that HDN improves NAFLD by promoting fatty acid β-oxidation through activating SIRT1/PGC1α. Thus, the findings indicate that HDN may be a potential drug for the treatment of NAFLD.

Emerging role of lipophagy in liver disorders

Lipophagy is a selective degradation of lipids by a lysosomal-mediated pathway, and dysregulation of lipophagy is linked with the pathological hallmark of many liver diseases. Downregulation of lipophagy in liver cells results in abnormal accumulation of LDs (Lipid droplets) in hepatocytes which is a characteristic feature of several liver pathologies such as nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH). Contrarily, upregulation of lipophagy in activated hepatic stellate cells (HSCs) is associated with hepatic fibrosis and cirrhosis. Lipid metabolism reprogramming in violent cancer cells contributes to the progression of liver cancer. In this review, we have summarized the recent studies focusing on various components of the lipophagic machinery that can be modulated for their potential role as therapeutic agents against a wide range of liver diseases.

Targeting DGAT1 inhibits prostate cancer cells growth by inducing autophagy flux blockage via oxidative stress

Impaired macroautophagy/autophagy flux has been implicated in the treatment of prostate cancer (PCa). However, the mechanism underlying autophagy dysregulation in PCa remains unknown. In the current study, we investigated the role of diacylglycerol acyltransferases 1 (DGAT1) and its potential effects on cellular energy homeostasis and autophagy flux in PCa. The results of immunohistochemical staining suggested that DGAT1 expression was positively corrected with tumor stage and node metastasis, indicating DGAT1 is an important factor involved in the development and progression of PCa. Furthermore, targeting DGAT1 remarkably inhibited cell proliferation in vitro and suppressed PCa growth in xenograft models by triggering severe oxidative stress and subsequently autophagy flux blockage. Mechanically, DGAT1 promoted PCa progression by maintaining cellular energy homeostasis, preserving mitochondrial function, protecting against reactive oxygen species, and subsequently promoting autophagy flux via regulating lipid droplet formation. Moreover, we found that fenofibrate exhibits as an upstream regulator of DGAT1. Fenofibrate performed its anti-PCa effect involved the aforementioned mechanisms, and partially dependent on the regulation of DGAT1. Collectively. These findings indicate that DGAT1 regulates PCa lipid droplets formation and is essential for PCa progression. Targeting DGAT1 might be a promising method to control the development and progression of PCa. Schematic representation of DGAT1 affects autophagy flux by regulating lipid homeostasis and maintaining mitochondrial function in prostate cancer (PCa). PCa is characterized up-regulation of DGAT1, leading to the translocation of free fatty acids into lipid droplets, thereby preventing PCa cell from lipotoxicity. Inhibition of DGAT1 suppresses growth of PCa by inducing oxidative stress and subsequently autophagy flux blockage. Further, the current results revealed that fenofibrate exhibits as an upstream regulator of DGAT1, and fenofibrate plays an anti-PCa role partially dependent on the regulation of DGAT1, suggesting a potential therapeutic approach to ameliorate this refractory tumor.

Cell-type specific role of autophagy in the liver and its implications in non-alcoholic fatty liver disease

Autophagy, a cellular degradative process, has emerged as a key regulator of cellular energy production and stress mitigation. Dysregulated autophagy is a common phenomenon observed in several human diseases, and its restoration offers curative advantage. Non-alcoholic fatty liver disease (NAFLD), more recently renamed metabolic dysfunction-associated steatotic liver disease, is a major metabolic liver disease affecting almost 30% of the world population. Unfortunately, NAFLD has no pharmacological therapies available to date. Autophagy regulates several hepatic processes including lipid metabolism, inflammation, cellular integrity and cellular plasticity in both parenchymal (hepatocytes) and non-parenchymal cells (Kupffer cells, hepatic stellate cells and sinusoidal endothelial cells) with a profound impact on NAFLD progression. Understanding cell type-specific autophagy in the liver is essential in order to develop targeted treatments for liver diseases such as NAFLD. Modulating autophagy in specific cell types can have varying effects on liver function and pathology, making it a promising area of research for liver-related disorders. This review aims to summarize our present understanding of cell-type specific effects of autophagy and their implications in developing autophagy centric therapies for NAFLD.

Distinct Types of Cell Death and Implications in Liver Diseases: An Overview of Mechanisms and Application

Cell death is associated with a variety of liver diseases, and hepatocyte death is a core factor in the occurrence and progression of liver diseases. In recent years, new cell death modes have been identified, and certain biomarkers have been detected in the circulation during various cell death modes that mediate liver injury. In this review, cell death modes associated with liver diseases are summarized, including some cell death modes that have emerged in recent years. We described the mechanisms associated with liver diseases and summarized recent applications of targeting cell death in liver diseases. It provides new ideas for the diagnosis and treatment of liver diseases. In addition, multiple cell death modes can contribute to the same liver disease. Different cell death modes are not isolated, and they interact with each other in liver diseases. Future studies may focus on exploring the regulation between various cell death response pathways in liver diseases.

Potential mechanisms underlying the effect of hepatocyte growth factor on liver injury in short bowel syndrome model rats

PURPOSE

The purpose of this study was to investigate the autophagy associated with apoptosis in hepatic damage in the short bowel syndrome rat model.

METHODS

SD rats underwent jugular vein catheterization for continuous total parenteral nutrition (TPN) and 90% small bowel resection. Animals were divided into two groups: TPN plus SBS (Control group) or TPN plus SBS plus intravenous administration of HGF (HGF group). On day 7, the rats were harvested, and hepatocellular injury was evaluated.

RESULTS

In an SBS rat model, hepatic steatosis and lobular inflammation were histologically suppressed in the HGF group (p < 0.01). The expression of tumor necrosis factor-α in the HGF group tend to be higher than that in the control group (p = 0.13). The gene expression of transforming Growth Factor-β in the HGF group was suppressed compared to the control group (p < 0.01). HGF treatment may have an antiapoptotic effect via the intrinsic pathway by caspase 9. Protein expressions of Rubicon (p = 0.03) and p62 (p < 0.01) in the HGF group were found to have increased compared to those in the control group.

CONCLUSION

The inhibitory effect of HGF on hepatic steatosis remains unclear, and further studies focusing on the mechanisms of fat accumulation are needed.