Fatty Acid Synthase-Suppressor Screening Identifies Sorting Nexin 8 as a Therapeutic Target for NAFLD

Membrane-associated ring-CH-type finger 2 protects against metabolic dysfunction-associated fatty liver disease by targeting fatty acid synthase

OBJECTIVE

Metabolic dysfunction-associated fatty liver disease (MAFLD) has emerged as an important public health concern that poses a significant threat to human health and imposes a substantial economic burden. Research has demonstrated that ubiquitin ligase-mediated substrate protein ubiquitination is a pivotal factor influencing liver lipid homeostasis and metabolic abnormalities in MAFLD. Nevertheless, the specific enzyme molecules implicated in this regulatory process remain to be elucidated. We have published a transcriptome-overexpressing ubiquitin ligase, membrane-associated ring-CH-type finger 2 (MARCH2), in HepG2 cells, and subsequent reanalysis of these transcriptome data revealed a close association between MARCH2 and lipid metabolism.

METHODS

By employing a range of methodologies, including recombinant adeno-associated virus (rAAV) transduction, lentiviral transduction, immunoblotting, quantitative PCR, tissue section staining, ubiquitination assays, serum biochemical analysis, immunoprecipitation, and mass spectrometry, this study investigated the functions and mechanisms of MARCH2 in the progression of MAFLD at the molecular, cellular, and organismal levels.

RESULTS

Overexpression of MARCH2, but not its catalytically inactive ligase variant, inhibited lipid accumulation in HepG2 cells. Additionally, MARCH2 undergoes K48-linked self-polyubiquitination and subsequent proteasomal degradation in response to oleic acid/palmitic acid stimulation. Furthermore, knockout of MARCH2 exacerbates the progression of MAFLD-related phenotypes, including increased body weight, impaired glucose tolerance, reduced insulin sensitivity, hypercholesterolemia, hepatic lipid accumulation, and steatosis, in high-fat diet-fed mice, irrespective of sex. Mechanistically, MARCH2 facilitates the polyubiquitination and degradation of fatty acid synthase (FASN) in the de novo lipogenesis pathway. And liver-specific overexpression of MARCH2 by rAAV effectively reduces FASN levels and further ameliorates MAFLD in ob/ob mice.

CONCLUSIONS

MARCH2 undergoes self-ubiquitination and plays an important role in maintaining the liver lipid homeostasis of MAFLD, and drug intervention in the MARCH2-FASN axis is a promising approach for treating systemic metabolic abnormalities in MAFLD.

The possible mechanisms of trans fatty acid effects on digestive disorders based on computational toxicology: a case study of elaidic acid

Trans fatty acids (TFAs) are potential health risk factors generated during food processing, and their mechanisms of association with digestive diseases remain incompletely elucidated. This study focused on elaidic acid (EA), integrating computational toxicology and molecular docking to systematically analyze its molecular mechanisms in regulating functional dyspepsia (FD), gastric cancer (GC), nonalcoholic fatty liver disease (NAFLD), and colorectal cancer (CRC) through multi-target networks. Protein Interaction Networks were constructed by screening EA and disease-intersecting targets, enriching and analyzing key pathways, and validating the binding ability of core targets. Results showed that EA shared 22, 67, 56, and 72 common targets with FD, GC, NAFLD, and CRC, respectively. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses indicated that EA acts through pathways including lipid metabolism dysregulation, inflammatory response, and chemical carcinogenesis-receptor activation. Molecular docking confirmed binding affinities between EA and core targets. The present study suggests that EA may promote the progression of digestive diseases through a multi-target-multi-pathway model, providing a new perspective for the study of the toxicity mechanism of TFA and food safety prevention and control.

Exosome-derived miR-548ag drives hepatic lipid accumulation via upregulating FASN through inhibition of DNMT3B

Metabolic dysfunction-associated steatotic liver disease (MASLD) is the leading cause of chronic liver disease worldwide. This study investigates the role of serum miR-548ag in regulating lipid metabolism and its contribution to MASLD in obesity. We found that miR-548ag levels were significantly elevated in the serum of both obese and MASLD patients, and positively correlated with body mass index (BMI), fasting plasma glucose (FPG), triglycerides (TG), total cholesterol (TC), LDL, HDL, aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels. Additionally, miR-548ag expression was significantly higher in the liver and abdominal adipose tissue of obese individuals compared to those of normal weight. In vitro studies in HepG2 and L02 cells, along with previous findings, demonstrated that miR-548ag promotes fatty acid synthase (FASN) expression by inhibiting DNA methyltransferase 3B (DNMT3B), thereby enhancing lipid synthesis. This was confirmed in two mouse models: one with tail vein injections of miR-548ag mimic/inhibitor adeno-associated viruses, and another with tail vein injections of exosomes from serum of normal-weight and obese individuals. Both models showed that miR-548ag upregulated FASN through DNMT3B inhibition, leading to increased lipid synthesis and larger hepatic lipid droplets, effects that were reversed by miR-548ag inhibition. Taken together, elevated miR-548ag expression in obesity enhances hepatic lipid synthesis by targeting DNMT3B to upregulate FASN, contributing to the development of MASLD.

The role of ubiquitination and deubiquitination in the pathogenesis of non-alcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is one of the most common chronic liver diseases and is closely associated with metabolic abnormalities. The causes of NAFLD are exceedingly complicated, and it is known that a variety of signaling pathways, endoplasmic reticulum stress, and mitochondrial dysfunction play a role in the pathogenesis of NAFLD. Recent studies have shown that ubiquitination and deubiquitination are involved in the regulation of the NAFLD pathophysiology. Protein ubiquitination is a dynamic and diverse post-translational alteration that affects various cellular biological processes. Numerous disorders, including NAFLD, exhibit imbalances in ubiquitination and deubiquitination. To highlight the significance of this post-translational modification in the pathogenesis of NAFLD and to aid in the development of new therapeutic approaches for the disease, we will discuss the role of enzymes involved in the processes of ubiquitination and deubiquitination, specifically E3 ubiquitin ligases and deubiquitinating enzymes that are important in the regulation of NAFLD.

The emerging role of E3 ubiquitin ligases and deubiquitinases in metabolic dysfunction-associated steatotic liver disease

Metabolic dysfunction-associated steatotic liver disease (MASLD) is the most common chronic liver disease worldwide, with a prevalence as high as 32.4%. MASLD encompasses a spectrum of liver pathologies, ranging from steatosis to metabolic dysfunction-associated steatohepatitis (MASH), fibrosis, and, in some cases, progression to end-stage liver disease (cirrhosis and hepatocellular carcinoma). A comprehensive understanding of the pathogenesis of this highly prevalent liver disease may facilitate the identification of novel targets for the development of improved therapies. E3 ubiquitin ligases and deubiquitinases (DUBs) are key regulatory components of the ubiquitin‒proteasome system (UPS), which plays a pivotal role in maintaining intracellular protein homeostasis. Emerging evidence implicates that aberrant expression of E3 ligases and DUBs is involved in the progression of MASLD. Here, we review abnormalities in E3 ligases and DUBs by (1) discussing their targets, mechanisms, and functions in MASLD; (2) summarizing pharmacological interventions targeting these enzymes in preclinical and clinical studies; and (3) addressing challenges and future therapeutic strategies. This review synthesizes current evidence to highlight the development of novel therapeutic strategies based on the UPS for MASLD and progressive liver disease.

Network pharmacology combined with untargeted metabolomics reveals the intervention mechanism and compatibility of chenpi-rougui herb pair in nonalcoholic fatty liver disease

Background

Chenpi (the dried mature peel of Citrus reticulata Blanco) and Rougui (the dried bark of Cinnamomum cassia Presl) are both edible and medicinal plants, which have therapeutic effects on nonalcoholic fatty liver disease (NAFLD). However, the underlying mechanisms necessitate further exploration. This study evaluated the prevention effect of Chenpi-Rougui herb pair (CRP) on NAFLD using an integrated strategy that combined network pharmacology with metabolomics.

Methods

Initially, the components in CRP decoction were characterized by UPLC-QTOF-MS/MS. Subsequently, a high-fat diet induced NAFLD mouse model was used to assess the efficacy of CRP and its individual constituent, Chenpi and Rougui. Additionally, synergetic pathways and crucial targets for CRP therapy in NAFLD were identified using network pharmacology and serum metabolomics. Finally, real-time polymerase chain reaction (RT-PCR) was utilized to validate relevant genes.

Results

CRP exerted a more extensive prevention effect on NAFLD mice compared to the individual herb of Chenpi and Rougui. A total of 105 compounds were characterized from CRP, which were linked to 70 potential therapeutic targets for NAFLD. Thirty-two differential metabolites were identified by metabolomics, which were co-regulated by Chenpi, Rougui and CRP. Pathways associated with the intervention of herb pair in NAFLD included energy metabolism, fatty acid metabolism, glycerophospholipid metabolism, sphingolipids metabolism, arachidonic acid metabolism, sterol and bile acid metabolism. Finally, eight targets were screened through conjoint analysis and experimental verification showed that six of them including FASN, AKT1, CASP3, F2, PTGS2 and PRKCA, could be modulated by CRP in NAFLD mice. Besides, Chenpi primarily regulated FASN, AKT1, CASP3 and PRKCA, which were associated with reducing apoptosis in hepatocytes, while Rougui exceled in regulating F2 and PTGS2, closely linked to its anti-inflammatory properties. The combination of Chenpi and Rougui resulted in a broader influence on metabolites, pathways, and primary targets compared to their individual application.

Conclusion

These results provided valuable insights into the compatibility mechanism of CRP for treating NAFLD, and could also improve the value of its forthcoming application and development as a natural liver protective agent.

Mechanisms by which SNX-BAR subfamily controls the fate of SNXs' cargo

The SNX-BAR subfamily is a component of the sorting nexins (SNXs) superfamily. Distinct from other SNXs, which feature a PX domain for phosphoinositide binding, the SNX-BAR subfamily includes a BAR domain that induces membrane curvature. Members of the SNX-BAR subfamily work together to recognize and select specific cargo, regulate receptor signaling, and manage cargo sorting both with and without the involvement of sorting complexes. They play a crucial role in maintaining cellular homeostasis by directing intracellular cargo to appropriate locations through endo-lysosomal, autophagolysosomal, and ubiquitin-proteasome pathways. This subfamily thus links various protein homeostasis pathways. This review examines the established and hypothesized functions of the SNX-BAR subfamily, its role in intracellular protein sorting and stability, and explores the potential involvement of subfamily dysfunction in the pathophysiology of cardiovascular and neurodegenerative diseases.

The ubiquitin-proteasome system: A potential target for the MASLD

Metabolic dysfunction-associated steatotic liver disease (MASLD), the most prevalent chronic liver condition globally, lacks adequate and effective therapeutic remedies in clinical practice. Recent studies have increasingly highlighted the close connection between the ubiquitin-proteasome system (UPS) and the progression of MASLD. This relationship is crucial for understanding the disease's underlying mechanism. As a sophisticated process, the UPS govern protein stability and function, maintaining protein homeostasis, thus influencing a multitude of elements and biological events of eukaryotic cells. It comprises four enzyme families, namely, ubiquitin-activating enzymes (E1), ubiquitin-conjugating enzymes (E2), ubiquitin-protein ligases (E3), and deubiquitinating enzymes (DUBs). This review aims to delve into the array of pathways and therapeutic targets implicated in the ubiquitination within the pathogenesis of MASLD. Therefore, this review unveils the role of ubiquitination in MASLD while spotlighting potential therapeutic targets within the context of this disease.

Gallstones in the Era of Metabolic Syndrome: Pathophysiology, Risk Prediction, and Management

Gallstone disease (GSD) and metabolic syndrome (MetS) are increasingly prevalent conditions with significant global health implications. Recent evidence highlights a strong epidemiological association between these disorders, driven by shared pathophysiological mechanisms. This review provides a comprehensive analysis of the intricate relationship between MetS and GSD, focusing on the role of insulin resistance, dyslipidemia, obesity, and gut microbiota dysbiosis in gallstone formation. An integrated pathophysiological model is proposed, linking metabolic disturbances to bile cholesterol supersaturation, gallbladder dysmotility, and chronic inflammation. The review also explores clinical implications, including risk prediction models based on metabolic parameters, early detection biomarkers, and targeted interventions such as lifestyle modifications, pharmacological therapies, and microbiome modulation. By addressing the metabolic underpinnings of GSD, this synthesis offers a foundation for developing preventive and therapeutic strategies to mitigate the burden of these interconnected conditions. Future research directions are outlined to refine mechanistic insights and improve clinical outcomes.

Stable Transmission of DNA Methylation Epimutations from Germlines to the Liver and Their Association with Fatty Liver Disease in Medaka

Background

Environmental stressors can induce heritable traits in organisms across phyla, with distinct epigenetic alterations in gametes and phenotypic outcomes across several generations. However, the mechanisms underlying such intergenerational inheritance, mainly from the germline to the germline and from the germline to the soma, are enigmatic, given that postfertilization embryos and germline cells reprogram the epigenome in each generation to gain their cellular identity. Here, we report stable germline transmission of differential DNA methylation alterations (epimutations) and their associations with nonalcoholic fatty liver disease (NAFLD) in medaka exposed to a model estrogenic chemical but a ubiquitous environmental contaminant, bisphenol A (BPA).

Results

Ancestral BPA exposure in the F0 generation led to advanced NAFLD in the unexposed grandchildren generation (F2) of medaka. The F2 liver transcriptome and histopathology revealed a severe NAFLD phenotype in females. Whole-genome bisulfite sequencing of the sperm and liver revealed a gradual shift in promoter methylation from F0 sperm (hypomethylated) to F1 sperm (mix of hypo- and hypermethylated) and F2 liver (predominantly hypermethylated). Many differentially methylated promoters (DMPs) overlapped in F0 sperm, F1 sperm, and F2 liver, regardless of sex. In females, stable transmission of 1511 DMPs was found across three generations, which are associated with protein-coding genes, miRNAs, and others and linked to NAFLD and nonalcoholic steatohepatitis (NASH). Among them, 27 canonical genes maintained consistently hypermethylated promoters across three generations, with significant downregulation of their expression and enrichment in NAFLD-related pathways, mainly fat digestion, glycerolipid metabolism, and steroid biosynthesis.

Conclusions

The present results demonstrate stable inter- and transgenerational germline-to-germline and germline-to-soma transmission of environmentally induced DNA epimutations with F0 and F1 gametic epimutations, predicting the F2 liver phenotype-a clear transgenerational passage of the disease phenotype in medaka.

Integrating larval zebrafish model and network pharmacology for screening and identification of edible herbs with therapeutic potential for MAFLD: A promising drug Smilax glabra Roxb

Metabolic-associated fatty liver disease (MAFLD) is becoming a prevalent chronic liver disease. Many medicinal and edible herbs exhibit remarkable biological activities in ameliorating MAFLD but lack a comprehensive assessment of their therapeutic efficacy. This study determined total phenolic and flavonoid contents and in vitro antioxidant properties of 34 edible herbs. Smilax glabra Roxb. (SGR), Coreopsis tinctoria Nutt., and Smilax china L. were obtained with the best bioactivity and antioxidant capacity. The high-cholesterol diet-induced larval zebrafish model was established to compare the anti-MAFLD activity of the three herb extracts mentioned above. In vivo experiments revealed that SGR intervention significantly decreased lipid accumulation, alleviated oxidative stress, and modulated intestinal microbiota composition in zebrafish. Furthermore, three potential active components in SGR and their possible mechanisms were explored through network pharmacology and molecular docking. Our study suggested that SGR is a potential candidate for developing new drugs or dietary supplements for MAFLD therapy.

Identification and Validation of Lipid Metabolism Gene FASN-Associated miRNA in Wilms Tumor

miRNA has been a research hotspot in recent years and its scope of action is very wide, involving the regulation of cell proliferation, differentiation, apoptosis, and other biological behaviors. This study intends to explore the role of miRNA in the lipid metabolism and development of Wilms tumor (WT) by detecting and analyzing the differences in the expression profiles of miRNAs between the tumor and adjacent normal tissue. Gene detection was performed in tumor tissues and adjacent normal tissues of three cases of WT to screen differentially expressed miRNAs (DEMs). According to our previous research, FASN, which participates in the lipid metabolism pathway, may be a target of WT. The starBase database was used to predict FASN-targeted miRNAs. The above two groups of miRNAs were intersected to obtain FASN-targeted DEMs and then GO Ontology (GO) functional enrichment analysis of FASN-targeted DEMs was performed. Finally, the FASN-targeted DEMs were compared and further verified by qRT‒PCR. Through gene sequencing and differential analysis, 287 DEMs were obtained, including 132 upregulated and 155 downregulated miRNAs. The top ten DEMs were all downregulated. Fourteen miRNAs targeted by the lipid metabolism-related gene FASN were predicted by starBase. After intersection with the DEMs, three miRNAs were finally obtained, namely, miR-107, miR-27a-3p, and miR-335-5p. GO enrichment analysis was mainly concentrated in the Parkin-FBXW7-Cul1 ubiquitin ligase complex and response to prostaglandin E. Further experimental verification showed that miR-27a-3p was significantly correlated with WT (P = 0.0018). Imbalanced expression of miRNAs may be involved in the occurrence and development of WT through lipid metabolism. The expression of miR-27a-3p is related to the malignant degree of WT, and it may become the target of diagnosis, prognosis, and treatment of WT in the later stage.

Lipid nanosystems for fatty liver therapy and targeted medication delivery: a comprehensive review

Fatty liver is considered to be the most common chronic liver disease with a high global incidence, which can lead to cirrhosis and liver cancer in severe cases, and there is no specific drug for the treatment of fatty liver in the clinic. The use of lipid nanosystems has the potential to be an effective means of fatty liver treatment. The pathogenesis and intervening factors associated with the development of fatty liver are reviewed, and the advantages and the disadvantages of different lipid nanosystems for the treatment of fatty liver are comprehensively discussed, including liposomes, solid lipid nanoparticles, nanostructured lipid carriers, nanoemulsions, microemulsions, and phospholipid complexes. The composition and characterisation of these lipid nanosystems are highlighted and summarised with a view to improving the efficiency of lipid nanosystems for the treatment of fatty liver. In addition, active targeting and passive targeting strategies used for fatty liver therapy are discussed in detail.

ZDHHC20 mediated S-palmitoylation of fatty acid synthase (FASN) promotes hepatocarcinogenesis

BACKGROUND

Protein palmitoylation is a reversible fatty acyl modification that undertakes important functions in multiple physiological processes. Dysregulated palmitoylations are frequently associated with the formation of cancer. How palmitoyltransferases for S-palmitoylation are involved in the occurrence and development of hepatocellular carcinoma (HCC) is largely unknown.

METHODS

Chemical carcinogen diethylnitrosamine (DEN)-induced and DEN combined CCl4 HCC models were used in the zinc finger DHHC-type palmitoyltransferase 20 (ZDHHC20) knockout mice to investigate the role of ZDHHC20 in HCC tumourigenesis. Palmitoylation liquid chromatography-mass spectrometry analysis, acyl-biotin exchange assay, co-immunoprecipitation, ubiquitination assays, protein half-life assays and immunofluorescence microscopy were conducted to explore the downstream regulators and corresponding mechanisms of ZDHHC20 in HCC.

RESULTS

Knocking out of ZDHHC20 significantly reduced hepatocarcinogenesis induced by chemical agents in the two HCC mouse models in vivo. 97 proteins with 123 cysteine sites were found to be palmitoylated in a ZDHHC20-dependent manner. Among these, fatty acid synthase (FASN) was palmitoylated at cysteines 1471 and 1881 by ZDHHC20. The genetic knockout or pharmacological inhibition of ZDHHC20, as well as the mutation of the critical cysteine sites of FASN (C1471S/C1881S) accelerated the degradation of FASN. Furthermore, ZDHHC20-mediated FASN palmitoylation competed against the ubiquitin-proteasome pathway via the E3 ubiquitin ligase complex SNX8-TRIM28.

CONCLUSIONS

Our findings demonstrate the critical role of ZDHHC20 in promoting hepatocarcinogenesis, and a mechanism underlying a mutual restricting mode for protein palmitoylation and ubiquitination modifications.

Establishment of a non-alcoholic fatty liver disease model by high fat diet in adult zebrafish

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) has become the most common chronic liver disease in recent years, but the pathogenesis is not fully understood. Therefore, it is important to establish an effective animal model for studying NAFLD.

METHODS

Adult zebrafish were fed a normal diet or a high-fat diet combined with egg yolk powder for 30 days. Body mass index (BMI) was measured to determine overall obesity. Serum lipids were measured using triglyceride (TG) and total cholesterol (TC) kits. Liver lipid deposition was detected by Oil Red O staining. Liver injury was assessed by measuring glutathione aminotransferase (AST) and glutamic acid aminotransferase (ALT) levels. Reactive oxygen species (ROS) and malondialdehyde (MDA) were used to evaluate oxidative damage. The level of inflammation was assessed by qRT-PCR for pro-inflammatory factors. H&E staining was used for pathological histology. Caspase-3 immunofluorescence measured apoptosis. Physiological disruption was assessed via RNA-seq analysis of genes at the transcriptional level and validated by qRT-PCR.

RESULTS

The high-fat diet led to significant obesity in zebrafish, with elevated BMI, hepatic TC, and TG. Severe lipid deposition in the liver was observed by ORO and H&E staining, accompanied by massive steatosis and ballooning. Serum AST and ALT levels were elevated, and significant liver damage was observed. The antioxidant system in the body was severely imbalanced. Hepatocytes showed massive apoptosis. RNA-seq results indicated that several physiological processes, including endoplasmic reticulum stress, and glucolipid metabolism, were disrupted.

CONCLUSION

Additional feeding of egg yolk powder to adult zebrafish for 30 consecutive days can mimic the pathology of human nonalcoholic fatty liver disease.

Roles of posttranslational modifications in lipid metabolism and cancer progression

Lipid metabolism reprogramming has emerged as a hallmark of malignant tumors. Lipids represent a complex group of biomolecules that not only compose the essential components of biological membranes and act as an energy source, but also function as messengers to integrate various signaling pathways. In tumor cells, de novo lipogenesis plays a crucial role in acquiring lipids to meet the demands of rapid growth. Increasing evidence has suggested that dysregulated lipid metabolism serves as a driver of cancer progression. Posttranslational modifications (PTMs), which occurs in most eukaryotic proteins throughout their lifetimes, affect the activity, abundance, function, localization, and interactions of target proteins. PTMs of crucial molecules are potential intervention sites and are emerging as promising strategies for the cancer treatment. However, there is limited information available regarding the PTMs that occur in cancer lipid metabolism and the potential treatment strategies associated with these PTMs. Herein, we summarize current knowledge of the roles and regulatory mechanisms of PTMs in lipid metabolism. Understanding the roles of PTMs in lipid metabolism in cancer could provide valuable insights into tumorigenesis and progression. Moreover, targeting PTMs in cancer lipid metabolism might represent a promising novel therapeutic strategy.

H3K9me3 demethylation by JMJD2B is regulated by pirfenidone resulting in improved NASH

NASH is characterized by hepatic lipid accumulation and inflammation; and JMJD2B-a histone demethylase-upregulation has been linked to its progression. Pirfenidone (PFD) is an antifibrotic agent with anti-inflammatory and antioxidant effects recognized to decrease NASH symptoms. Herein, our aim was to investigate PFD-induced epigenetics mechanisms involving JMJD2B and histone modifications in experimental NASH. Male C57BL/6J mice were fed with normo-diet, or high fat/carbohydrate diet (HF) for 16 weeks. A HF-subgroup was treated with PFD 300 mg/kg/d from week 8th to the end of protocol. Insulin tolerance test and liver and fat histological and biochemical analyses were carried out. Hepatic transcriptome was examined. Liver proteins were studied by western blot (WB) and Chromatin immunoprecipitation. In vitro, lipotoxicity was induced in HepG2 cells and proteins were evaluated using WB. Molecular docking was used to explore binding of PFD to JMJD2B. Mice treated with PFD reduced weight gain, epididymal fat and inflammatory nodules, and steatosis in liver tissue, as well as, improved biochemical test. PFD modified the expression of Jmjd2b, Pparg, Fasn and Srebp1, and restored JMJD2B protein and H3K9me3 repressive mark, both in animal and cell models. PFD increased hepatic enrichment of H3K9me2 and H3K9me3 at the promoter region of Fasn and Srebp1, and Pparg. In HepG2 cells, PFD reduced lipid vacuole accumulation. In silico, PFD interacted with JMJD2B catalytic site. PFD is an epigenetic regulator modifying JMJD2B activity, resulting in reduced NASH traits.

Comparison of the effects of three sourdough postbiotics on high-fat diet-induced intestinal damage

There is significant interest in using postbiotics as an intervention strategy to address obesity. This study assesses the efficacy of postbiotics derived from different sourdough strains (Lactiplantibacillus plantarum LP1, LP25, and Pediococcus pentosaceus PP18) in mitigating intestinal injury in zebrafish fed on a high-fat diet. We screened postbiotics for their anti-colon cancer cell effects and compared various preparation methods applied to live bacterial strains, including heat-killing at different temperatures, pH adjustments, and ultraviolet radiation exposure. Heat-killing at 120 °C proved to be the most effective preparation method. A marked variation in health effects was observed in the heat-killed microbial cells, as evidenced by their hydrophobicity and self-aggregation ability. A five-week high-fat dietary intervention study in zebrafish demonstrated that diets supplemented with 108 CFU g-1 K-LP25 significantly attenuated weight gain and body fat, along with reductions in FASN, Leptin, and SREBF1 mRNA expression. However, diets supplemented with 107 CFU g-1 K-PP18 only reduced Leptin and SREBF1 mRNA expression. K-PP18 was more effective at mitigating gut barrier damage, promoting colonic Occludin, ZO-1, and Claudin-1 levels. Additionally, K-LP25 supplementation markedly downregulated the pro-inflammatory cytokines TNF-α, IL-6, and IL-1β, reducing intestinal inflammation. Supplementation with K-LP1 and K-PP18 increased the abundance of Acinetobacter spp., whereas K-LP25 increased the abundance of Cetobacterium and Plesiomonas. Collectively, these findings suggest that inactivated strains confer protective effects against high-fat diet-induced intestinal damage in zebrafish, with variation observed across different species. Studying the effects of sourdough-derived postbiotics on gut health may open new avenues for dietary interventions to manage gut-related diseases.

Nonalcoholic Fatty Liver Disease and Cardiovascular Disease: Causation or Association

Nonalcoholic fatty liver disease (NAFLD) is a disease process that is gaining increasing recognition. The global prevalence of NAFLD is increasing in parallel with growing rates of risk factors for NAFLD such as hypertension, obesity, diabetes, and metabolic syndrome. NAFLD has been referred to as a risk factor for cardiovascular disease (CVD). As CVD is the leading cause of morbidity and mortality worldwide, there are constant efforts to describe and alleviate its risk factors. Although there is conflicting data supporting NAFLD as a causative or associative factor for CVD, NAFLD has been shown to be associated with structural, electrical, and atherosclerotic disease processes of the heart. Shared risk factors and pathophysiologic mechanisms between NAFLD and CVD warrant further explication. Pathologic mechanisms such as endothelial dysfunction, oxidative stress, insulin resistance, genetic underpinnings, and gut microbiota dysregulation have been described in both CVD and NAFLD. The mainstay of treatment for NAFLD is lifestyle intervention including physical exercise and hypocaloric intake in addition to bariatric surgery. Investigations into various therapeutic targets to alleviate hepatic steatosis and fibrosis by way of maintaining the balance between lipid synthesis and breakdown. A major obstacle preventing the success of many pharmacologic approaches has been the effects of these medications on CVD risk. The future of pharmacologic treatment of NAFLD is promising as effective medications with limited CVD harm are being investigated.

The Role of Tripartite Motif Family Proteins in Chronic Liver Diseases: Molecular Mechanisms and Therapeutic Potential

The worldwide impact of liver diseases is increasing steadily, with a consistent upswing evidenced in incidence and mortality rates. Chronic liver diseases (CLDs) refer to the liver function's progressive deterioration exceeding six months, which includes abnormal clotting factors, detoxification failure, and hepatic cholestasis. The most common etiologies of CLDs are mainly composed of chronic viral hepatitis, MAFLD/MASH, alcoholic liver disease, and genetic factors, which induce inflammation and harm to the liver, ultimately resulting in cirrhosis, the irreversible final stage of CLDs. The latest research has shown that tripartite motif family proteins (TRIMs) function as E3 ligases, which participate in the progression of CLDs by regulating gene and protein expression levels through post-translational modification. In this review, our objective is to clarify the molecular mechanisms and potential therapeutic targets of TRIMs in CLDs and provide insights for therapy guidelines and future research.

Polyphenols alleviate metabolic disorders: the role of ubiquitin-proteasome system

Metabolic disorders include obesity, nonalcoholic fatty liver disease, insulin resistance and type 2 diabetes. It has become a major health issue around the world. Ubiquitin-proteasome system (UPS) is essential for nearly all cellular processes, functions as a primary pathway for intracellular protein degradation. Recent researches indicated that dysfunctions in the UPS may result in the accumulation of toxic proteins, lipotoxicity, oxidative stress, inflammation, and insulin resistance, all of which contribute to the development and progression of metabolic disorders. An increasing body of evidence indicates that specific dietary polyphenols ameliorate metabolic disorders by preventing lipid synthesis and transport, excessive inflammation, hyperglycemia and insulin resistance, and oxidative stress, through regulation of the UPS. This review summarized the latest research progress of natural polyphenols improving metabolic disorders by regulating lipid accumulation, inflammation, oxidative stress, and insulin resistance through the UPS. In addition, the possible mechanisms of UPS-mediated prevention of metabolic disorders are comprehensively proposed. We aim to provide new angle to the development and utilization of polyphenols in improving metabolic disorders.

Estrogen Induces LCAT to Maintain Cholesterol Homeostasis and Suppress Hepatocellular Carcinoma Development

Hepatocellular carcinoma (HCC) is an aggressive disease that occurs predominantly in men. Estrogen elicits protective effects against HCC development. Elucidation of the estrogen-regulated biological processes that suppress HCC could lead to improved prevention and treatment strategies. Here, we performed transcriptomic analyses on mouse and human liver cancer and identified lecithin cholesterol acyltransferase (LCAT) as the most highly estrogen-upregulated gene and a biomarker of favorable prognosis. LCAT upregulation inhibited HCC in vitro and in vivo and mediated estrogen-induced suppression of HCC in an ESR1-dependent manner. LCAT facilitated high-density lipoprotein cholesterol production and uptake via the LDLR and SCARB1 pathways. Consistently, high HDL-C levels corresponded to a favorable prognosis in HCC patients. The enhanced HDL-C absorption induced by LCAT impaired SREBP2 maturation, which ultimately suppressed cholesterol biosynthesis and dampened HCC cell proliferation. HDL-C alone inhibited HCC growth comparably to the cholesterol-lowering drug lovastatin, and SREBF2 overexpression abolished the inhibitory activity of LCAT. Clinical observations and cross-analyses of multiple databases confirmed the correlation of elevated LCAT and HDL-C levels to reduced cholesterol synthesis and improved HCC patient prognosis. Furthermore, LCAT deficiency mimicked whereas LCAT overexpression abrogated the tumor growth-promoting effects of ovariectomy in HCC-bearing female mice. Most importantly, HDL-C and LCAT delayed the development of subcutaneous tumors in nude mice, and HDL-C synergized with lenvatinib to eradicate orthotopic liver tumors. Collectively, this study reveals that estrogen upregulates LCAT to maintain cholesterol homeostasis and to dampen hepatocarcinogenesis. LCAT and HDL-C represent potential prognostic and therapeutic biomarkers for targeting cholesterol homeostasis as a strategy for treating HCC. Significance: Estrogen mediates the sex differences in hepatocellular carcinoma development by reducing cholesterol biosynthesis through activation of an LCAT/HDL-C axis, providing strategies for improving liver cancer prevention, prognosis, and treatment.

Emerging Roles and Therapeutic Applications of Arachidonic Acid Pathways in Cardiometabolic Diseases

Cardiometabolic disease has become a major health burden worldwide, with sharply increasing prevalence but highly limited therapeutic interventions. Emerging evidence has revealed that arachidonic acid derivatives and pathway factors link metabolic disorders to cardiovascular risks and intimately participate in the progression and severity of cardiometabolic diseases. In this review, we systemically summarized and updated the biological functions of arachidonic acid pathways in cardiometabolic diseases, mainly focusing on heart failure, hypertension, atherosclerosis, nonalcoholic fatty liver disease, obesity, and diabetes. We further discussed the cellular and molecular mechanisms of arachidonic acid pathway-mediated regulation of cardiometabolic diseases and highlighted the emerging clinical advances to improve these pathological conditions by targeting arachidonic acid metabolites and pathway factors.

Aryl Hydrocarbon Receptor Activation Limits the Fatty Acid Synthesis and Subsequent "miR-193a-3p-HDAC3-FASN" Signals to Alleviate Intestinal Fibrosis

Intestinal fibrosis is a common complication of Crohn's disease and characterized by excessive extracellular matrix (ECM) deposition. The aryl hydrocarbon receptor (AhR) detects micronutrients and microbial metabolites in diet and can attenuate intestinal fibrosis with unclear mechanisms. In this study, AhR activation was demonstrated to downregulate the transcription of collagen I and fibronectin in a Sp1- but not Sp3- or AP-1-dependent manner. A suppressed fatty acid synthesis was highlighted using untargeted metabolomics analyses, and synthetic products, palmitic acid (PA), were used as the intermediary agent. After a screening study, fatty acid synthase (FASN) was identified as the main targeted protein, and AhR activation regulated "HDAC3-acetylation" signals but not glycosylation to enhance FASN degradation. Furthermore, results of bioinformatics analysis and others showed that after being activated, AhR targeted miR-193a-3p to control HDAC3 transcription. Collectively, AhR activation inhibited ECM deposition and alleviated intestinal fibrosis by limiting fatty acid synthesis subsequent to the inhibition of "miR-193a-3p-HDAC3-FASN" signals.

Exploring the dynamic three-dimensional chromatin architecture and transcriptional landscape in goose liver tissues underlying metabolic adaptations induced by a high-fat diet

BACKGROUND

Goose, descendants of migratory ancestors, have undergone extensive selective breeding, resulting in their remarkable ability to accumulate fat in the liver and exhibit a high tolerance for significant energy intake. As a result, goose offers an excellent model for studying obesity, metabolic disorders, and liver diseases in mammals. Although the impact of the three-dimensional arrangement of chromatin within the cell nucleus on gene expression and transcriptional regulation is widely acknowledged, the precise functions of chromatin architecture reorganization during fat deposition in goose liver tissues still need to be fully comprehended.

RESULTS

In this study, geese exhibited more pronounced changes in the liver index and triglyceride (TG) content following the consumption of the high-fat diet (HFD) than mice without significant signs of inflammation. Additionally, we performed comprehensive analyses on 10 goose liver tissues (5 HFD, 5 normal), including generating high-resolution maps of chromatin architecture, conducting whole-genome gene expression profiling, and identifying H3K27ac peaks in the livers of geese and mice subjected to the HFD. Our results unveiled a multiscale restructuring of chromatin architecture, encompassing Compartment A/B, topologically associated domains, and interactions between promoters and enhancers. The dynamism of the three-dimensional genome architecture, prompted by the HFD, assumed a pivotal role in the transcriptional regulation of crucial genes. Furthermore, we identified genes that regulate chromatin conformation changes, contributing to the metabolic adaptation process of lipid deposition and hepatic fat changes in geese in response to excessive energy intake. Moreover, we conducted a cross-species analysis comparing geese and mice exposed to the HFD, revealing unique characteristics specific to the goose liver compared to a mouse. These chromatin conformation changes help elucidate the observed characteristics of fat deposition and hepatic fat regulation in geese under conditions of excessive energy intake.

CONCLUSIONS

We examined the dynamic modifications in three-dimensional chromatin architecture and gene expression induced by an HFD in goose liver tissues. We conducted a cross-species analysis comparing that of mice. Our results contribute significant insights into the chromatin architecture of goose liver tissues, offering a novel perspective for investigating mammal liver diseases.

Regulation of lipid metabolism by E3 ubiquitin ligases in lipid-associated metabolic diseases

Previous studies have progressively elucidated the involvement of E3 ubiquitin (Ub) ligases in regulating lipid metabolism. Ubiquitination, facilitated by E3 Ub ligases, modifies critical enzymes in lipid metabolism, enabling them to respond to specific signals. In this review, we aim to present a comprehensive analysis of the role of E3 Ub ligases in lipid metabolism, which includes lipid synthesis and lipolysis, and their influence on cellular lipid homeostasis through the modulation of lipid uptake and efflux. Furthermore, it explores how the ubiquitination process governs the degradation or activation of pivotal enzymes, thereby regulating lipid metabolism at the transcriptional level. Perturbations in lipid metabolism have been implicated in various diseases, including hepatic lipid metabolism disorders, atherosclerosis, diabetes, and cancer. Therefore, this review focuses on the association between E3 Ub ligases and lipid metabolism in lipid-related diseases, highlighting enzymes critically involved in lipid synthesis and catabolism, transcriptional regulators, lipid uptake translocators, and transporters. Overall, this review aims to identify gaps in current knowledge, highlight areas requiring further research, offer potential targeted therapeutic approaches, and provide a comprehensive outlook on clinical conditions associated with lipid metabolic diseases.

SNX8 enables lysosome reformation and reverses lysosomal storage disorder

Lysosomal Storage Disorders (LSDs), which share common phenotypes, including enlarged lysosomes and defective lysosomal storage, are caused by mutations in lysosome-related genes. Although gene therapies and enzyme replacement therapies have been explored, there are currently no effective routine therapies against LSDs. During lysosome reformation, which occurs when the functional lysosome pool is reduced, lysosomal lipids and proteins are recycled to restore lysosome functions. Here we report that the sorting nexin protein SNX8 promotes lysosome tubulation, a process that is required for lysosome reformation, and that loss of SNX8 leads to phenotypes characteristic of LSDs in human cells. SNX8 overexpression rescued features of LSDs in cells, and AAV-based delivery of SNX8 to the brain rescued LSD phenotypes in mice. Importantly, by screening a natural compound library, we identified three small molecules that enhanced SNX8-lysosome binding and reversed LSD phenotypes in human cells and in mice. Altogether, our results provide a potential solution for the treatment of LSDs.

Exosomes derived from impaired liver aggravate alveolar bone loss via shuttle of Fasn in type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) exacerbates irreversible bone loss in periodontitis, but the mechanism of impaired bone regeneration caused by the abnormal metabolic process of T2DM remains unclear. Exosomes are regarded as the critical mediator in diabetic impairment of regeneration via organ or tissue communication. Here, we find that abnormally elevated exosomes derived from metabolically impaired liver in T2DM are significantly enriched in the periodontal region and induced pyroptosis of periodontal ligament cells (PDLCs). Mechanistically, fatty acid synthase (Fasn), the main differentially expressed molecule in diabetic exosomes results in ectopic fatty acid synthesis in PDLCs and activates the cleavage of gasdermin D. Depletion of liver Fasn effectively mitigates pyroptosis of PDLCs and alleviates bone loss. Our findings elucidate the mechanism of exacerbated bone loss in diabetic periodontitis and reveal the exosome-mediated organ communication in the "liver-bone" axis, which shed light on the prevention and treatment of diabetic bone disorders in the future.

Hepatic regulator of G protein signaling 14 ameliorates NAFLD through activating cAMP-AMPK signaling by targeting Giα1/3

OBJECTIVE

Nonalcoholic fatty liver disease (NAFLD) is an emerging public health threat as the most common chronic liver disease worldwide. However, there remains no effective medication to improve NAFLD. G protein-coupled receptors (GPCRs) are the most frequently investigated drug targets family. The Regulator of G protein signaling 14 (RGS14), as an essential negative modulator of GPCR signaling, plays important regulatory roles in liver damage and inflammatory responses. However, the role of RGS14 in NAFLD remains largely unclear.

METHODS AND RESULTS

In this study, we found that RGS14 was decreased in hepatocytes in NAFLD individuals in a public database. We employed genetic engineering technique to explore the function of RGS14 in NAFLD. We demonstrated that RGS14 overexpression ameliorated lipid accumulation, inflammatory response and liver fibrosis in hepatocytes in vivo and in vitro. Whereas, hepatocyte specific Rgs14-knockout (Rgs14-HKO) exacerbated high fat high cholesterol diet (HFHC) induced NASH. Further molecular experiments demonstrated that RGS14 depended on GDI activity to attenuate HFHC-feeding NASH. More importantly, RGS14 interacted with Guanine nucleotide-binding protein (Gi) alpha 1 and 3 (Giα1/3, gene named GNAI1/3), promoting the generation of cAMP and then activating the subsequent AMPK pathways. GNAI1/3 knockdown abolished the protective role of RGS14, indicating that RGS14 binding to Giα1/3 was required for prevention against hepatic steatosis.

CONCLUSIONS

RGS14 plays a protective role in the progression of NAFLD. RGS14-Giα1/3 interaction accelerated the production of cAMP and then activated cAMP-AMPK signaling. Targeting RGS14 or modulating the RGS14-Giα1/3 interaction may be a potential strategy for the treatment of NAFLD in the future.

Corydalis saxicola Bunting total alkaloids improve NAFLD by suppressing de novo lipogenesis through the AMPK-SREBP1 axis

ETHNOPHARMACOLOGICAL RELEVANCE

Along with the gradually increasing incidence, nonalcoholic fatty liver disease (NAFLD) has already been influencing the health of more and more people in the world. Corydalis saxicola Bunting (CSB), a valuable folk medicine, is the dried whole grass of a perennial herb, Yanhuanglian (Papaveraceae), which has significant effects on various hepatitis, liver fibrosis, cirrhosis and other liver diseases. Corydalis saxicola Bunting total alkaloids (CSBTA), a mixture of alkaloids extracted from CSB, exhibit widely-accepted hepatoprotective effects.

AIM OF THE STUDY

This study aimed to explore the therapeutic potential of CSBTA on NAFLD and the underlying mechanism.

MATERIALS AND METHODS

A mice model was established by high fat and high cholesterol diet (HFHCD) to study the benefits of CSBTA on the progression of NAFLD. The efficacy of CSBTA on NAFLD was revealed systematically via RNA-sequencing analysis. Further efficacy and molecular mechanism study were explored in mouse primary hepatocytes and HepG2 cells stimulated with high energy with or without pharmacological inhibition or gene silencing.

RESULTS

CSBTA effectively improved the major hallmarks of NAFLD including liver lipid accumulation, liver injury, inflammation and fibrosis in HFHCD-fed mice. RNA sequencing and targeted qPCR analysis jointly evidenced CSBTA significantly suppressed the expression of Srebf1, Acc1 and Fasn which are the genes responsible for fatty acid biosynthesis. Moreover, stable isotope tracer test denoted CSBTA reduced lipid accumulation via interrupting fatty acid biosynthesis in hepatocytes or the liver. Mechanistically, CSBTA could impede SREBP1 maturation via AMPK activation, thereby reducing DNL-derived lipid accumulation in hepatocytes.

CONCLUSIONS

CSBTA protected against hepatic steatosis and other hallmarks of NAFLD induced by HFHCD via suppressing DNL, through modulating the AMPK-SREBP1 axis. CSBTA may therefore have a therapeutic potential for NAFLD treatment.

Non-alcoholic fatty liver disease promotes liver metastasis of colorectal cancer via fatty acid synthase dependent EGFR palmitoylation

Liver metastasis is the major reason for most of colorectal cancer (CRC) related deaths. Accumulating evidence indicates that CRC patients with non-alcoholic fatty liver disease (NAFLD) are at a greater risk of developing liver metastasis. With the growing prevalence of NAFLD, a better understanding of the molecular mechanism in NAFLD-driven CRC liver metastasis is needed. In this study, we demonstrated that NAFLD facilitated CRC liver metastasis as a metabolic disorder and promoted the stemness of metastatic CRC cells for their colonization and outgrowth in hepatic niches. Metabolically, the lipid-rich microenvironment in NAFLD activated de novo palmitate biosynthesis in metastatic CRC cells via upregulating fatty acid synthase (FASN). Moreover, increased intracellular palmitate bioavailability promoted EGFR palmitoylation to enhance its protein stability and plasma membrane localization. Furthermore, we demonstrated that the FDA-approved FASN inhibitor orlistat could reduce NAFLD-activated endogenous palmitate production, thus inhibiting palmitoylation of EGFR to suppress CRC cell stemness and restrict liver metastasis in synergy with conventional chemotherapy. These findings reveal that the NAFLD metabolic microenvironment boosts endogenous palmitate biosynthesis in metastatic CRC cells and promotes cell stemness via EGFR palmitoylation, and FASN inhibitor orlistat could be a candidate adjuvant drug to suppress liver metastasis in CRC patients with NAFLD.

NSC48160 targets AMPKα to ameliorate nonalcoholic steatohepatitis by inhibiting lipogenesis and mitochondrial oxidative stress

Hepatic steatosis, which is triggered by dysregulation of lipid metabolism and redox equilibrium in the liver, is regarded as a risk factor in the non-alcoholic fatty liver disease (NAFLD). However, pharmacologic engagement of this process is difficult. We identified the small molecule NSC48160 as an effective agent against nonalcoholic steatohepatitis (NASH). We found that NSC48160 significantly lowered hepatic lipid levels in vitro and in vivo by activating the AMPKα-dependent pathway. AMPKα regulated its downstream pathway involved in lipogenesis (SREBP-1c/FASN pathway) and fatty acid oxidation (PPARα pathway). Metabonomics analysis combined with RNA-sequencing profiling revealed that NSC48160-induced lipogenesis is modulated by lipid metabolism. Moreover, NSC48160 dramatically reduces reactive oxygen species (ROS) production, restores the levels of the membrane potential and NAD+/NADH ratio, and improves mitochondrial respiration. These findings suggest that NSC48160 is a promising hit compound in the pursuit of a pharmacological approach in the treatment of NASH.

Chaihu Shugan powder influences nonalcoholic fatty liver disease in rats in remodeling microRNAome and decreasing fatty acid synthesis

ETHNOPHARMACOLOGICAL RELEVANCE

Chaihu Shugan powder (CSP) plays an important role in the prevention and treatment of nonalcoholic fatty liver disease (NAFLD) through a variety of biological mechanisms. However, whether the mechanism involves microRNA (miRNA) regulation remains unknown.

AIM OF THE STUDY

To investigate the effects of CSP on the miRNA expression profile of rats with NAFLD induced by high-fat diet (HFD), and to explore the mechanism of CSP in the treatment of NAFLD.

METHODS

NAFLD rat models were established by an 8-week HFD. The therapeutic effects of CSP on NAFLD were evaluated by physiological, biochemical and pathological analysis and hepatic surface microcirculation perfusion test. MicroRNA sequencing was used to study the effect of CSP on the miRNA expression profile of NAFLD rats, and the target genes of differentially expressed (DE) miRNAs were predicted for further function enrichment analysis. Next, targets of CSP and NAFLD were collected by a network pharmacological approach, and Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) analysis were performed for the common target genes of CSP, NAFLD and DE miRNAs, and the expression levels of key genes and proteins were verified by quantitative Real-time PCR and Western blot. Finally, a network among formula-herb-compound-miRNA-target-biological processes-disease was established to explained the complex regulation mechanism of CSP on NAFLD.

RESULTS

The results showed that CSP significantly improved liver lipid accumulation, serum lipid and transaminase levels and liver surface microcirculation disturbance in HFD-induced NAFLD rats. The intervention of CSP reversed the high expression of 15 miRNAs in liver tissues induced by HFD, including miR-34a-5p, miR-146a-5p, miR-20b-5p and miR-142-3p. The results of pathway and functional enrichment analysis showed that, CSP might play an anti-NAFLD role via regulating DE miRNAs related to fatty acid metabolic process. Combined with the network pharmacological analysis, it was found that the DE miRNAs might affected the fatty acid biosynthesis pathway in the treatment of NAFLD by CSP. Molecular biology experiments have conformed the decreased the gene and protein levels of acetyl-CoA carboxylase alpha (ACACA), fatty acid synthase (FASN) and other fatty acid biosynthesis related enzymes on NAFLD rats after intervention of CSP.

CONCLUSIONS

CSP can significantly reduce hepatic lipid accumulation of NAFLD rat model induced by HFD, and its mechanism may be through the action of 15 miRNAs such as miR-34a-5p, miR-146a-5p, miR-20b-5p and miR-142-3p. Reduce the gene and protein expression levels of ACACA, FASN and other fatty acid biosynthesis related enzymes, thus reducing fatty acid biosynthesis. Based on an epigenetic perspective, this study explains the key anti-NAFLD mechanism of CSP via combination of microRNA sequencing and network pharmacological analysis, providing a new reference for the modernization of traditional Chinese medicine.

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.

Emerging Role of Sorting Nexin 17 in Human Health and Disease

The distortion of the cellular membrane transport pathway has a profound impact on cell dynamics and can drive serious physiological consequences during the process of cell sorting. SNX17 is a member of the Sorting Nexin (SNX) family and plays a crucial role in protein sorting and transport in the endocytic pathway. SNX17, SNX27, and SNX31 belong to the SNX-FERM subfamily and possess the FERM domain, which can assist in endocytic transport and lysosomal degradation. The binding partners of SNX27 have been discovered to number over 100, and SNX27 has been linked to the development of Alzheimer's disease progression, tumorigenesis, cancer progression, and metastasis. However, the role and potential mechanisms of SNX17 in human health and disease remain poorly understood, and the function of SNX17 has not been fully elucidated. In this review, we summarize the structure and basic functions of SNX protein, focusing on providing current evidence of the role and possible mechanism of SNX17 in human neurodegenerative diseases and cardiovascular diseases.

Si-Ni-San inhibits hepatic Fasn expression and lipid accumulation in MAFLD mice through AMPK/p300/SREBP-1c axis

BACKGROUND

Soothing the liver and regulating qi is one of the core ideas of traditional Chinese medicine (TCM) in the treatment of fatty liver. Si-Ni-San (SNS) is a well-known herbal formula in TCM for liver soothing and qi regulation in fatty liver treatment. However, its efficacy lacks modern scientific evidence.

PURPOSE

This study was aimed to investigate the impact of SNS on metabolic associated fatty liver disease (MAFLD) in mice and explore the underlying molecular mechanisms, particularly its effects on lipid metabolism in hepatocytes.

METHODS

The therapeutic effect of SNS was evaluated using in vivo and in vitro models of high-fat/high-cholesterol (HFHC) diet-induced mice and palmitic acid (PA)-induced hepatocytes, respectively. Molecular biological techniques such as RNA-sequencing (RNA-seq), co-immunoprecipitation (co-IP), and western blotting were employed to elucidate the molecular mechanism of SNS in regulating lipid metabolism in hepatocytes.

RESULTS

Our findings revealed that SNS effectively reduced lipid accumulation in the livers of HFHC diet-induced mice and PA-induced hepatocytes. RNA-seq analysis demonstrated that SNS significantly down-regulated the expression of fatty acid synthase (Fasn) in the livers of HFHC-fed mice. Mechanistically, SNS inhibited Fasn expression and lipid accumulation by activating adenosine monophosphate (AMP)-activated protein kinase (AMPK). Activation of AMPK suppressed the activity of the transcriptional coactivator p300 and modulated the protein stability of sterol regulatory element-binding protein-1c (SREBP-1c). Importantly, p300 was required for the inhibition of Fasn expression and lipid accumulation by SNS. Furthermore, SNS activated AMPK by decreasing adenosine triphosphate (ATP) production in hepatocytes.

CONCLUSION

This study provided novel evidence on the regulatory mechanisms underlying the effects of SNS on Fasn expression. Our findings demonstrate, for the first time, that SNS exerts suppressive effects on Fasn expression through modulation of the AMPK/p300/SREBP-1c axis. Consequently, this regulatory pathway mitigates excessive lipid accumulation and ameliorates MAFLD in mice.

Role of the tripartite motif-containing (TRIM) family of proteins in insulin resistance and related disorders

Emerging evidence suggests that the ubiquitin-mediated degradation of insulin-signalling-related proteins may be involved in the development of insulin resistance and its related disorders. Tripartite motif-containing (TRIM) proteins, a superfamily belonging to the E3 ubiquitin ligases, are capable of controlling protein levels and function by ubiquitination, which is essential for the modulation of insulin sensitivity. Recent research has indicated that some of these TRIMs act as key regulatory factors of metabolic disorders such as type 2 diabetes mellitus, obesity, nonalcoholic fatty liver disease, and atherosclerosis. This review provides a comprehensive overview of the latest evidence linking TRIMs to the regulation of insulin resistance and its related disorders, their roles in regulating multiple signalling pathways or cellular processes, such as insulin signalling pathways, peroxisome proliferator-activated receptor signalling pathways, glucose and lipid metabolism, the inflammatory response, and cell cycle control, as well as recent advances in the development of TRIM-targeted drugs.

E3 ubiquitin ligase Siah1 aggravates NAFLD through Scp2 ubiquitination

Nonalcoholic fatty liver disease (NAFLD) is one of the most common liver disorders and accompanied by multiple metabolic dysfunctions. Although excessive lipid accumulation in hepatocytes has been identified as a crucial mediator of NAFLD development, the underlying mechanisms are very complicated and remain largely unknown. In this study, we reported that upregulated expression of the seven in absentia homolog 1 (Siah1) in the liver exacerbated NAFLD progression. Conversely, Siah1 downregulation markedly alleviated the high fat diet-induced accumulation of hepatic fat and expression of genes related to lipid metabolism in vitro and in vivo. The mechanistic study revealed that Siah1 interacted with sterol carrier protein 2 (Scp2) and promotes its ubiquitination and degradation, suggesting that Siah1 is an important activator of Scp2 ubiquitination in the context of NAFLD. Our results demonstrated that Siah1 regulated the lipid accumulation in NAFLD by interacting with Scp2. Thus, this study presents Siah1 as a promising therapeutic target in the development of NAFLD.

Long-term and liver-selected ginsenoside C-K nanoparticles retard NAFLD progression by restoring lipid homeostasis

Non-alcoholic fatty liver disease (NAFLD) is the most prevalent hepatic disease characterized as lipid accumulation, yet without any approved drug. And development of therapeutic molecules is obstructed by low efficiency and organ toxicity. Herein, we develop a long-term, low-toxic and liver-selected nano candidate, nabCK, to alleviate NAFLD. NabCK is simply composed by natural compound ginsenoside compound K (CK) and albumin. As a major metabolite of ginseng, ginsenoside CK has excellently modulating functions for lipid metabolism, but accompanied by an extremely poor bioavailability <1%. Albumin is a key lipid carrier secreted and metabolized by livers. Thereby, it can improve solubility and liver-localization of CK. In adipocytes and hepatocytes, nabCK prevents lipid deposition and eliminates lipid droplets. Transcriptomic analysis reveals that nabCK rectifies various pathways that involved in steatosis development, including lipid absorption, lipid export, fatty acid biosynthesis, lipid storage and inflammation. All these pathways are modulated by mTOR, the pivotal feedback sensor that is hyperactive in NAFLD. NabCK suppresses mTOR activation to restores lipid homeostasis. In high-fat diet (HFD) induced NAFLD mice, nabCK retards development of steatosis and fibrosis, coupling a protective effect on cardiac tissues from lipotoxicity. Together, nabCK is a safe and potent candidate to offer benefits for NAFLD treatment.

The Different Mechanisms of Lipid Accumulation in Hepatocytes Induced by Oleic Acid/Palmitic Acid and High-Fat Diet

Non-alcoholic fatty liver disease (NAFLD) is the primary chronic liver disease worldwide, mainly manifested by hepatic steatosis. Hepatic lipids may be derived from dietary intake, plasma free fatty acid (FFA) uptake, or hepatic de novo lipogenesis (DNL). Currently, cellular and animal models of hepatocellular steatosis are widely used to study the pathogenesis of NAFLD and to investigate therapeutic agents. However, whether there are differences between the in vivo and in vitro models of the mechanisms that cause lipid accumulation has not been reported. We used OA/PA-induced NCTC 1469 cells and high-fat-diet-fed C57BL/6J mice to simulate a hepatocyte steatosis model of NAFLD and to detect indicators related to FFA uptake and DNL. In addition, when serological indicators were analysed in the mouse model, it was found that serum FASN levels decreased. The results revealed that, in the cellular model, indicators related to DNL were decreased, FASN enzyme activity was unchanged, and indicators related to FFA uptake were increased, including the high expression of CD36; while, in the animal model, indicators related to both FFA uptake and de novo synthesis were increased, including the high expression of CD36 and the increased protein levels of FASN with enhanced enzyme activity. In addition, after an analysis of the serological indicators in the mouse model, it was found that the serum levels of FASN were reduced. In conclusion, the OA/PA-induced cellular model can be used to study the mechanism of FFA uptake, whereas the high-fat-diet-induced mouse model can be used to study the mechanism of FFA uptake and DNL. Combined treatment with CD36 and FASN may be more effective against NAFLD. FASN in the serum can be used as one of the indicators for the clinical diagnosis of NAFLD.

Preventive and therapeutic effects of natural products and herbal extracts on nonalcoholic fatty liver disease/nonalcoholic steatohepatitis

Nonalcoholic fatty liver disease (NAFLD) is a common condition that is prevalent in patients who consume little or no alcohol, and is characterized by excessive fat accumulation in the liver. The disease is becoming increasingly common with the rapid economic development of countries. Long-term accumulation of excess fat can lead to NAFLD, which represents a global health problem with no effective therapeutic approach. NAFLD is a complex, multifaceted pathological process that has been the subject of extensive research over the past few decades. Herbal medicines have gained attention as potential therapeutic agents to prevent and treat NAFLD due to their high efficacy and low risk of side effects. Our overview is based on a PubMed and Web of Science database search as of Dec 22 with the keywords: NAFLD/NASH Natural products and NAFLD/NASH Herbal extract. In this review, we evaluate the use of herbal medicines in the treatment of NAFLD. These natural resources have the potential to inform innovative drug research and the development of treatments for NAFLD in the future.

TAF15 exacerbates nonalcoholic steatohepatitis progression by regulating lipid metabolism and inflammation via FASN and p65 NF-κB

BACKGROUND & AIMS

Nonalcoholic fatty liver disease (NAFLD) consists of a broad spectrum of conditions, and nonalcoholic steatohepatitis (NASH) is the advanced form of NAFLD. TAF15 is a DNA and RNA binding protein and is involved in crucial inflammatory signalling pathways. We aimed to investigate the role of TAF15 in the progression of NASH and the underlying molecular mechanism.

METHODS

We generated mice with hepatocyte-specific knockdown and overexpression of TAF15 using a specific adeno-associated virus (AAV). NASH models were established by feeding mice high-fat and high-cholesterol diets and methionine- and choline-deficient diets. Cleavage under targets and tagmentation and dual-luciferase reporter assays were performed to investigate the effect of TAF15 on FASN transcription. Coimmunoprecipitation and immunofluorescence assays were conducted to explore the interaction of TAF15 and p65. In vitro coculture systems were established to study the interactions of hepatocytes, macrophages and HSCs.

RESULTS

TAF15 was significantly increased in the livers of mouse NASH models and primary hepatocyte NASH model. Knockdown of TAF15 inhibited steatosis, inflammation and fibrosis, while overexpression of TAF15 promoted NASH phenotypes. Mechanistically, TAF15 bound directly to the promoter region of FASN to facilitate its expression, thereby promoting steatosis. Moreover, TAF15 interacted with p65 and activated the NF-κB signalling pathway, increasing the secretion of proinflammatory cytokines and triggering M1 macrophage polarization. Treatment with the FASN inhibitor orlistat partially reversed the phenotypes.

CONCLUSIONS

These results suggested that TAF15 exacerbated NASH progression by regulating lipid metabolism and inflammation via transcriptional activation of FASN and interacting with p65 to activate the NF-κB signalling pathway.

CircRREB1 mediates lipid metabolism related senescent phenotypes in chondrocytes through FASN post-translational modifications

Osteoarthritis is a prevalent age-related disease characterized by dysregulation of extracellular matrix metabolism, lipid metabolism, and upregulation of senescence-associated secretory phenotypes. Herein, we clarify that CircRREB1 is highly expressed in secondary generation chondrocytes and its deficiency can alleviate FASN related senescent phenotypes and osteoarthritis progression. CircRREB1 impedes proteasome-mediated degradation of FASN by inhibiting acetylation-mediated ubiquitination. Meanwhile, CircRREB1 induces RanBP2-mediated SUMOylation of FASN and enhances its protein stability. CircRREB1-FASN axis inhibits FGF18 and FGFR3 mediated PI3K-AKT signal transduction, then increased p21 expression. Intra-articular injection of adenovirus-CircRreb1 reverses the protective effects in CircRreb1 deficiency mice. Further therapeutic interventions could have beneficial effects in identifying CircRREB1 as a potential prognostic and therapeutic target for age-related OA.

Cullin-associated and neddylation-dissociated protein 1 (CAND1) alleviates NAFLD by reducing ubiquitinated degradation of ACAA2

Nonalcoholic fatty liver disease (NAFLD) is the most common liver disorder with high morbidity and mortality. The current study aims to explore the role of Cullin-associated and neddylation-dissociated protein 1 (CAND1) in the development of NAFLD and the underlying mechanisms. CAND1 is reduced in the liver of NAFLD male patients and high fat diet (HFD)-fed male mice. CAND1 alleviates palmitate (PA) induced lipid accumulation in vitro. Hepatocyte-specific knockout of CAND1 exacerbates HFD-induced liver injury in HFD-fed male mice, while hepatocyte-specific knockin of CAND1 ameliorates these pathological changes. Mechanistically, deficiency of CAND1 enhances the assembly of Cullin1, F-box only protein 42 (FBXO42) and acetyl-CoA acyltransferase 2 (ACAA2) complexes, and thus promotes the ubiquitinated degradation of ACAA2. ACAA2 overexpression abolishes the exacerbated effects of CAND1 deficiency on NAFLD. Additionally, androgen receptor binds to the -187 to -2000 promoter region of CAND1. Collectively, CAND1 mitigates NAFLD by inhibiting Cullin1/FBXO42 mediated ACAA2 degradation.

F-box only protein 2 exacerbates non-alcoholic fatty liver disease by targeting the hydroxyl CoA dehydrogenase alpha subunit

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is a major health burden with an increasing global incidence. Unfortunately, the unavailability of knowledge underlying NAFLD pathogenesis inhibits effective preventive and therapeutic measures.

AIM

To explore the molecular mechanism of NAFLD.

METHODS

Whole genome sequencing (WGS) analysis was performed on liver tissues from patients with NAFLD (n = 6) and patients with normal metabolic conditions (n = 6) to identify the target genes. A NAFLD C57BL6/J mouse model induced by 16 wk of high-fat diet feeding and a hepatocyte-specific F-box only protein 2 (FBXO2) overexpression mouse model were used for in vivo studies. Plasmid transfection, co-immunoprecipitation-based mass spectrometry assays, and ubiquitination in HepG2 cells and HEK293T cells were used for in vitro studies.

RESULTS

A total of 30982 genes were detected in WGS analysis, with 649 up-regulated and 178 down-regulated. Expression of FBXO2, an E3 ligase, was upregulated in the liver tissues of patients with NAFLD. Hepatocyte-specific FBXO2 overexpression facilitated NAFLD-associated phenotypes in mice. Overexpression of FBXO2 aggravated odium oleate (OA)-induced lipid accumulation in HepG2 cells, resulting in an abnormal expression of genes related to lipid metabolism, such as fatty acid synthase, peroxisome proliferator-activated receptor alpha, and so on. In contrast, knocking down FBXO2 in HepG2 cells significantly alleviated the OA-induced lipid accumulation and aberrant expression of lipid metabolism genes. The hydroxyl CoA dehydrogenase alpha subunit (HADHA), a protein involved in oxidative stress, was a target of FBXO2-mediated ubiquitination. FBXO2 directly bound to HADHA and facilitated its proteasomal degradation in HepG2 and HEK293T cells. Supplementation with HADHA alleviated lipid accumulation caused by FBXO2 overexpression in HepG2 cells.

CONCLUSION

FBXO2 exacerbates lipid accumulation by targeting HADHA and is a potential therapeutic target for NAFLD.

Integrated serum pharmacochemistry, 16S rRNA sequencing and metabolomics to reveal the material basis and mechanism of Yinzhihuang granule against non-alcoholic fatty liver disease

ETHNOPHARMACOLOGICAL RELEVANCE

Yinzhihuang granule (YZHG) has liver protective effect and can be used for clinical treatment of non-alcoholic fatty liver disease (NAFLD), but its material basis and mechanism need to be further clarified.

AIM OF THE STUDY

This study aims to reveal the material basis and mechanism of YZHG treating NAFLD.

MATERIALS AND METHODS

Serum pharmacochemistry were employed to identify the components from YZHG. The potential targets of YZHG against NAFLD were predicted by system biology and then preliminarily verified by molecular docking. Furthermore, the functional mechanism of YZHG in NAFLD mice was elucidated by 16S rRNA sequencing and untargeted metabolomics.

RESULTS

From YZHG, 52 compounds were identified, of which 42 were absorbed into the blood. Network pharmacology and molecular docking showed that YZHG treats NAFLD with multi-components and multi-targets. YZHG can improve the levels of blood lipids, liver enzymes, lipopolysaccharide (LPS), and inflammatory factors in NAFLD mice. YZHG can also significantly improve the diversity and richness of intestinal flora and regulate glycerophospholipid and sphingolipid metabolism. Moreover, Western Blot experiment showed that YZHG can regulate liver lipid metabolism and enhance intestinal barrier function.

CONCLUSIONS

YZHG may treat NAFLD by improving the disruption of intestinal flora and enhancing the intestinal barrier. This will reduce the invasion of LPS into the liver subsequently regulate liver lipid metabolism and reduce liver inflammation.

HECT, UBA and WWE domain containing 1 represses cholesterol efflux during CD4+ T cell activation in Sjögren's syndrome

Introduction: Sjögren's syndrome (SS) is a chronic autoimmune disorder characterized by exocrine gland dysfunction, leading to loss of salivary function. Histological analysis of salivary glands from SS patients reveals a high infiltration of immune cells, particularly activated CD4⁺ T cells. Thus, interventions targeting abnormal activation of CD4⁺ T cells may provide promising therapeutic strategies for SS. Here, we demonstrate that Hect, uba, and wwe domain containing 1 (HUWE1), a member of the eukaryotic Hect E3 ubiquitin ligase family, plays a critical role in CD4⁺ T-cell activation and SS pathophysiology. Methods: In the context of HUWE1 inhibition, we investigated the impact of the HUWE1 inhibitor BI8626 and sh-Huwe1 on CD4⁺ T cells in mice, focusing on the assessment of activation levels, proliferation capacity, and cholesterol abundance. Furthermore, we examined the therapeutic potential of BI8626 in NOD/ShiLtj mice and evaluated its efficacy as a treatment strategy. Results: Inhibition of HUWE1 reduces ABCA1 ubiquitination and promotes cholesterol efflux, decreasing intracellular cholesterol and reducing the expression of phosphorylated ZAP-70, CD25, and other activation markers, culminating in the suppressed proliferation of CD4⁺ T cells. Moreover, pharmacological inhibition of HUWE1 significantly reduces CD4⁺ T-cell infiltration in the submandibular glands and improves salivary flow rate in NOD/ShiLtj mice. Conclusion: These findings suggest that HUWE1 may regulate CD4⁺ T-cell activation and SS development by modulating ABCA1-mediated cholesterol efflux and presents a promising target for SS treatment.

Targeting protein modifications in metabolic diseases: molecular mechanisms and targeted therapies

The ever-increasing prevalence of noncommunicable diseases (NCDs) represents a major public health burden worldwide. The most common form of NCD is metabolic diseases, which affect people of all ages and usually manifest their pathobiology through life-threatening cardiovascular complications. A comprehensive understanding of the pathobiology of metabolic diseases will generate novel targets for improved therapies across the common metabolic spectrum. Protein posttranslational modification (PTM) is an important term that refers to biochemical modification of specific amino acid residues in target proteins, which immensely increases the functional diversity of the proteome. The range of PTMs includes phosphorylation, acetylation, methylation, ubiquitination, SUMOylation, neddylation, glycosylation, palmitoylation, myristoylation, prenylation, cholesterylation, glutathionylation, S-nitrosylation, sulfhydration, citrullination, ADP ribosylation, and several novel PTMs. Here, we offer a comprehensive review of PTMs and their roles in common metabolic diseases and pathological consequences, including diabetes, obesity, fatty liver diseases, hyperlipidemia, and atherosclerosis. Building upon this framework, we afford a through description of proteins and pathways involved in metabolic diseases by focusing on PTM-based protein modifications, showcase the pharmaceutical intervention of PTMs in preclinical studies and clinical trials, and offer future perspectives. Fundamental research defining the mechanisms whereby PTMs of proteins regulate metabolic diseases will open new avenues for therapeutic intervention.

Tripartite motif 38 alleviates the pathological process of NAFLD/NASH by promoting TAB2 degradation

Nonalcoholic fatty liver disease (NAFLD) has become the most prevalent chronic liver disease worldwide, without any FDA-approved pharmacological intervention in clinic. The TRIM (tripartite motif-containing) family plays essential roles in innate immune and hepatic inflammation. TRIM38, as one of the important members in TRIM family, was largely reported to be involved in the regulation of innate immune and inflammatory responses. However, the functional roles of TRIM38 in NAFLD remains largely unknown. Here, the expression of TRIM38 was first detected in liver samples of both NAFLD mice model and patients diagnosed with NAFLD. We found TRIM38 expression was downregulated in NAFLD liver tissues compared with normal liver tissues. Genetic TRIM38 knockout in vivo showed that TRIM38 depletion deteriorated the HFD and HFHC diet-induced hepatic steatosis and HFHC diet-induced liver inflammation and fibrosis. In particular, we found that the effects of hepatocellular lipid accumulation and inflammation induced by palmitic acid and oleic acid (PA+OA) was aggravated by TRIM38 depletion but mitigated by TRIM38 overexpression in vitro. Mechanically, RNA-seq analysis demonstrated that TRIM38 ameliorated NASH progression by attenuating the activating of mitogen-activated protein kinase (MAPK) signaling pathway. We further found that TRIM38 interacted with TGF-β-activated kinase 1 (TAK1) binding protein 2 (TAB2) and promoted its protein degradation, thus inhibiting the TAK1-MAPK signal cascades. In summary, our study revealed that TRIM38 could suppress hepatic steatosis, inflammatory and fibrosis in NAFLD via promoting TAB2 degradation. TRIM38 could be a potential target for NAFLD treatment.