Cytoplasmic SIRT6-mediated ACSL5 deacetylation impedes nonalcoholic fatty liver disease by facilitating hepatic fatty acid oxidation

Sirt6 deficiency exacerbates angiotensin II-induced lipid nephrotoxicity by affecting PLD6-derived cardiolipin metabolism in podocytes

BACKGROUND AND AIMS

Perturbation of cardiolipin (CL) metabolism is associated with lipid nephrotoxicity. Recent findings provide new insights into the roles of CL-modulating proteins as critical determinants of podocyte function in chronic kidney disease (CKD). We previously demonstrated that Sirtuin 6 (Sirt6) is a compelling target inhibiting Angiotensin II (Ang II)-induced lipid dysregulation in podocytes. However, whether Sirt6 regulates podocyte CL metabolism is unknown.

METHODS

Renal biopsy specimens of patients with hypertensive nephropathy (HN) were used in this study. Podocyte Sirt6-specific knockout mice were generated using the Cre-loxP system. The effect of Sirt6 on mitochondrial CL metabolism, especially the peroxidation and hydrolysis of CL, was investigated in Ang II-infusion mice and Ang II-induced cultured podocytes.

RESULTS

Sirt6 and outer mitochondrial membrane protein phospholipase D family member 6 (PLD6) were decreased in the glomeruli of patients with HN. Ang II downregulated Sirt6 and PLD6 expression in podocytes in vitro and in vivo. Podocyte-specific deletion of Sirt6 exacerbated lipid droplets formation, CL accumulation and peroxidation, aggravated Ang II-induced mitochondrial dysfunction and cell apoptosis. Mechanically, Sirt6 maintained podocyte CL homeostasis, at least in part through PLD6 signaling-mediated CL metabolism. In addition, cardiolipin antioxidant Szeto-Schiller Peptide 31 (SS-31) treatment inhibited Ang II-induced lipid accumulation and CL peroxidation in podocytes.

CONCLUSIONS

Our findings shed light on Sirt6's regulatory mechanisms on podocyte CL metabolism and suggest exploiting the Sirt6-PLD6 axis as a potential therapeutic target for protecting against lipid nephrotoxicity.

Senkyunolide A mitigates lipid deposition in hyperlipidemic hepatocytes through SIRT6-mediated suppression of oxidative stress and fetuin-A

Senkyunolide A (SenA), a phthalide compound isolated from celery seed essential oil, is known for its anti-inflammatory and antioxidant properties in various disease models. However, its impact on hepatic lipid metabolism and associated molecular mechanisms remain unclear. This study investigated the protective effects of SenA against lipotoxicity-induced hepatic steatosis and explored its underlying pathways. Lipid accumulation was assessed via Oil Red O staining, whereas protein expression was analyzed via Western blotting. Apoptosis was evaluated through TUNEL staining, caspase-3 activity, and cell viability assays. Oxidative stress was measured via DCFDA-based ROS detection and assays for MDA and H2O2. The role of SIRT6 was examined through siRNA-mediated knockdown. SenA treatment significantly reduced lipid deposition, apoptosis, oxidative stress, and fetuin-A expression in palmitate-treated hepatocytes. It also increased the expression of SIRT6 and Nrf2, two key regulators of metabolic and redox homeostasis. Silencing SIRT6 diminished these protective effects, indicating its essential role in mediating SenA activity. These findings suggest that SenA mitigates hepatic steatosis by modulating oxidative stress and metabolic dysfunction via SIRT6/Nrf2 signaling. As a natural bioactive compound, SenA offers promise for the development of safer therapeutic strategies for managing nonalcoholic fatty liver disease (NAFLD), which has broader relevance to metabolic health.

OTUB1 enhances fatty acid oxidation in APAP-induced liver injury by mediating ACSL5 deubiquitination

Overdosing on acetaminophen (APAP) is the primary cause of drug-induced liver injury. Recent studies have demonstrated that dysregulated lipid metabolism, particularly decreased fatty acid oxidation (FAO), is a key contributor to APAP-induced acute liver injury (AILI). OTU domain-containing ubiquitin aldehyde-binding protein 1 (OTUB1), a crucial member of the OTU deubiquitinase family, has been involved in the metabolic progression of multiple diseases. Nevertheless, its involvement in AILI as well as FAO remains unclear. Here, we aimed to elucidate the effects of OTUB1 on the regulation of FAO in AILI. Our investigation revealed decreased OTUB1 expression in AILI. OTUB1 overexpression not only alleviated liver injury but also improved FAO in vivo and in vitro. Conversely, opposite biochemical changes were observed in hepatocytes with OTUB1 knockdown. Mechanistically, long-chain acyl-CoA synthase 5 (ACSL5), which plays a crucial role in regulating FAO, was identified as a novel substrate of OTUB1 in AILI via mass spectrometry analysis. OTUB1 interacts with ACSL5 and promotes its deubiquitination and stability. Moreover, the protective effect of OTUB1 on FAO in AILI occurred via the deubiquitination of ACSL5. Overall, the present study revealed that the OTUB1-ACSL5 axis plays an essential role in regulating FAO during AILI progression and might be a novel target for therapeutic intervention.

Bisphenol AF induces lipid metabolism disorders, oxidative stress and upregulation of heat shock protein 70 in zebrafish

Bisphenol AF (BPAF) is a widespread endocrine disruptor in the environment, and the use of BPAF has been strongly associated with the development of several diseases. In this study, we investigated the effects of BPAF on growth, development, oxidative stress and lipid metabolism in zebrafish. We chose the concentrations based on the measured LC50 at 96 h post-fertilization (96 hpf), and the zebrafish embryos were exposed to three different concentrations (0.125, 0.5 and 2 μmol/L). The findings indicated that BPAF exposure in zebrafish leaded to alterations in heart rate, body length and hatching rate, as well as an accumulation of red blood cells in the heart. Additionally, BPAF exposure resulted in increased levels of neutrophils, reactive oxygen species (ROS) and malondialdehyde (MDA), and decreased activity of antioxidant enzymes (superoxide dismutase (SOD) and catalase (CAT)), thus disturbing the balance between oxidative and antioxidative systems. BPAF promoted fatty acid catabolism and inhibited fatty acid synthesis, ultimately leading to a reduction in fatty acid content. Mechanistically, RNA-seq analysis and RT-qPCR revealed a significant upregulation of heat shock protein 70 (hsp70) after BPAF exposure. Inhibition of hsp70 with VER-155008 ameliorated BPAF-induced oxidative stress. These data provided a novel approach to investigate BPAF-induced oxidative stress and suggested that regulation of hsp70 is a crucial target for alleviating this process.

Hederagenin promotes SIRT6 to attenuate epidural scar formation by aggravating PRMT1 deacetylation

Aims

The formation of a postoperative epidural scar induced by epidural fibrosis is the main reason for recurrence of lumbar disc herniation after laminectomy. Hederagenin (HE) has been found to be widely present in various medicinal plants and has various pharmacological functions. This study aimed to investigate the effect and regulatory mechanism of HE on epidural scar formation.

Methods

Transforming growth factor beta 1 (TGF-β1)-stimulated epidural scar fibroblasts were used as an in vitro cell model. Based on that, HE treatment was carried out along with sirtuin-6 (SIRT6) silence or protein arginine N-methyltransferase 1 (PRMT1) overexpression. The interaction between SIRT6 and PRMT1 was evaluated by pulldown and co-immunoprecipitation (CoIP) assays. Then, cell proliferation, apoptosis, and fibrosis were measured by Cell Counting Kit (CCK)-8, flow cytometry, and western blotting. Moreover, the effects of receptor activator of nuclear factor-κB ligand (RANKL) supplementation and endoplasmic reticulum (ER) stress were also evaluated by supplementing recombinant protein and specific inhibitor or activator.

Results

HE depressed cell proliferation and fibrosis, while inducing apoptosis of epidural fibroblasts. Meanwhile, HE promoted SIRT6 expression which suppressed PRMT1 acetylation and protein stability. Additionally, HE induced ER stress and upregulated RANKL in epidural fibroblasts via mediating SIRT6/PRMT1 axis.

Conclusion

Generally, the therapeutic role of HE treatment on epidural scar formation was exerted by regulating SIRT6/PRMT1 axis-mediated ER stress and RANKL pathway. This study provides evidence of a novel therapeutic measure for epidural scar formation.

Scutellariae Radix and Coptidis Rhizoma improve NAFLD via regulation of SIRT6/ACSL5 pathway and SCD1

ETHNOPHARMACOLOGICAL RELEVANCE

The herbal pair Scutellariae Radix-Coptidis Rhizoma (SR-CR) has been widely used in Traditional Chinese Medicine (TCM) for treating metabolic disorders, including nonalcoholic fatty liver disease (NAFLD) -related conditions. Its traditional use highlights its potential in addressing the multifaceted pathogenesis of NAFLD, though the underlying mechanisms remain unclear.

AIM OF THE STUDY

To evaluate the therapeutic efficacy of the SR-CR herbal pair in alleviating NAFLD and to elucidate its mechanisms of action, with a specific focus on lipid metabolism pathways.

MATERIALS AND METHODS

The therapeutic effects of SR-CR were assessed using a high-fat diet (HFD)-induced NAFLD rat model and HepG2 cell model. Multi-omics analyses were employed to identify molecular targets and pathways, while affinity ultrafiltration-mass spectrometry characterized bioactive constituents. Findings were validated in vivo and in vitro via Western blot and immunofluorescence. Protein-constituent interactions were further characterized by surface plasmon resonance and molecular docking.

RESULTS

SR-CR significantly alleviated NAFLD symptoms in HFD-fed rats by reducing hepatic lipid accumulation, inflammation, and hepatocyte ballooning while normalizing biochemical indicators. Mechanistic studies revealed that SR-CR regulates the SIRT6/ACSL5 pathway and SCD1, both critical to lipid metabolism. Scutellariae Radix (SR) and its major constituent, baicalin, enhanced ACSL5 activity via SIRT6-mediated deacetylation, promoting fatty acid oxidation and intracellular lipid utilization. Coptidis Rhizoma (CR) and its primary component, berberine, inhibited SCD1, thereby reducing de novo lipogenesis. These complementary effects synergistically enhanced energy expenditure and reduced lipid synthesis.

CONCLUSION

The SR-CR herbal pair effectively alleviates HFD-induced NAFLD by synergistically modulating lipid metabolism, enhancing energy expenditure, and reducing de novo lipogenesis through the regulation of the SIRT6/ACSL5 pathway and SCD1. These findings provide molecular evidence for the traditional use of SR-CR in treating metabolic disorders and highlight its potential as a plant-based therapeutic for NAFLD.

Acetylation and deacetylation dynamics in stress response to cancer and infections

In response to stress stimuli, cells have evolved various mechanisms to integrate internal and external signals to achieve dynamic homeostasis. Lysine acetyltransferase (KATs) and deacetyltransferase (KDACs) are the key modulators of epigenetic modifications, enabling cells to modulate cellular responses through the acetylation and deacetylation of both histone and nonhistone proteins. Understanding the signaling pathways involved in cellular stress response, along with the roles of KATs and KDACs may pave the way for the development of novel therapeutic strategies. This review discusses the molecular mechanisms of acetylation and deacetylation in stress responses related to tumorigenesis, viral and bacterial infections. In tumorigenesis section, we focused on the tumor cells' intrinsic and external molecules and signaling pathways regulated by acetylation and deacetylation modification. In viral and bacterial infections, we summarized the update research on acetylation and deacetylation modification in viral and bacterial infections, which systematical introduction on this topic is not too much. Additionally, we provide an overview of current therapeutic interventions and clinical trials involving KAT and KDAC inhibitors in the treatment of cancer, as well as viral and bacterial infection-related diseases.

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.

Exploring Immune-Related Ferroptosis Genes in Thyroid Cancer: A Comprehensive Analysis

Background: The increasing incidence and poor outcomes of recurrent thyroid cancer highlight the need for innovative therapies. Ferroptosis, a regulated cell death process linked to the tumour microenvironment (TME), offers a promising antitumour strategy. This study explored immune-related ferroptosis genes (IRFGs) in thyroid cancer to uncover novel therapeutic targets. Methods: CIBERSORTx and WGCNA were applied to data from TCGA-THCA to identify hub genes. A prognostic model composed of IRFGs was constructed using LASSO Cox regression. Pearson correlation was employed to analyse the relationships between IRFGs and immune features. Single-cell RNA sequencing (scRNA-seq) revealed gene expression in cell subsets, and qRT-PCR was used for validation. Results: Twelve IRFGs were identified through WGCNA, leading to the classification of thyroid cancer samples into three distinct subtypes. There were significant differences in patient outcomes among these subtypes. A prognostic risk score model was developed based on six key IRFGs (ACSL5, HSD17B11, CCL5, NCF2, PSME1, and ACTB), which were found to be closely associated with immune cell infiltration and immune responses within the TME. The prognostic risk score was identified as a risk factor for thyroid cancer outcomes (HR = 14.737, 95% CI = 1.95-111.65; p = 0.009). ScRNA-seq revealed the predominant expression of these genes in myeloid cells, with differential expression validated using qRT-PCR in thyroid tumour and normal tissues. Conclusions: This study integrates bulk and single-cell RNA sequencing data to identify IRFGs and construct a robust prognostic model, offering new therapeutic targets and improving prognostic evaluation for thyroid cancer patients.

The Role and Molecular Pathways of SIRT6 in Senescence and Age-related Diseases

SIRT6 is a NAD+-dependent histone deacetylase with crucial roles in controlling DNA damage repair, telomere homeostasis, oxidative stress, autophagy, and other cellular processes, and it has long been recognized as a longevity-associated protein. This review details its anti-aging-related mechanisms. First, SIRT6 facilitates DNA repair pathways and maintains genome stability by deacetylating histone H3 at K56, K9, and K18 residues, in addition to participating in DNA damage repair through mono-ADP-ribosylation and other mechanisms. Second, SIRT6 preserves telomere integrity and mitigates cellular senescence by reducing oxidative stress-induced damage through the regulation of reactive oxygen species (ROS), inhibition of inflammation, and other pathways. Furthermore, SIRT6 promotes autophagy, slowing cellular senescence via the modulation of various signaling pathways, including AMPK, IGF-Akt-mTOR, H133Y, IL-1β, and mitochondrial autophagy-related proteins. Finally, SIRT6 regulates multiple signaling pathways, such asNF-κB, FOXO, and AMPK, to counteract the aging process. This review particularly delves into the interplay between SIRT6 and various diseases, including tumors, cardiovascular diseases (e.g., atherosclerosis, heart failure), metabolic diseases (e.g., type 2 diabetes, dyslipidemia, gluconeogenesis, osteoporosis), and neurodegenerative diseases (e.g., Alzheimer's disease). Moreover, recent advancements in SIRT6-regulated compounds (e.g., C3G, BZBS, Fisetin, FNDC5, Lycorine hydrochloride, and Ergothioneine) are discussed as potential therapeutic agents for these mediated diseases.

Targeting Histone Deacetylase 11 with a Highly Selective Inhibitor for the Treatment of MASLD

Metabolic dysfunction-associated steatotic liver disease (MASLD) represents the most prevalent chronic liver disorder globally. Due to its intricate pathogenesis and the current lack of efficacious pharmacological interventions, there is a pressing need to discover novel therapeutic targets and agents for MASLD treatment. Herein, it is found that histone deacetylase 11 (HDAC11), a subtype of HDAC family, is markedly overexpressed in both in vitro and in vivo models of MASLD. Furthermore, the knockdown of HDAC11 is observed to mitigate lipid accumulation in hepatic cells. A highly selective HDAC11 inhibitor, B6, which exhibits favorable pharmacokinetic property and liver distribution, is further designed and synthesized. Integrating RNA-seq data with in vivo and in vitro experiments, B6 is found to inhibit de novo lipogenesis (DNL) and promote fatty acid oxidation, thus mitigating hepatic lipid accumulation and pathological symptoms in MASLD mice. Further omics analysis and experiments reveal that B6 enhances the phosphorylation of AMPKα1 at Thr172 through the inhibition of HDAC11, consequently modulating DNL and fatty acid oxidation in the liver. In summary, this study identifies HDAC11 as a potential therapeutic target in MASLD and reports the discovery of a highly selective HDAC11 inhibitor with favorable drug-like properties for the treatment of MASLD.

Metabolic-Dysfunction-Associated Steatotic Liver Disease: Molecular Mechanisms, Clinical Implications, and Emerging Therapeutic Strategies

Metabolic-dysfunction-associated steatotic liver disease (MASLD), previously known as non-alcoholic fatty liver disease (NAFLD), is a highly prevalent metabolic disorder characterized by hepatic steatosis in conjunction with at least one cardiometabolic risk factor, such as obesity, type 2 diabetes, hypertension, or dyslipidemia. As global rates of obesity and metabolic syndrome continue to rise, MASLD is becoming a major public health concern, with projections indicating a substantial increase in prevalence over the coming decades. The disease spectrum ranges from simple steatosis to metabolic-dysfunction-associated steatohepatitis (MASH), fibrosis, cirrhosis, and hepatocellular carcinoma, contributing to significant morbidity and mortality worldwide. This review delves into the molecular mechanisms driving MASLD pathogenesis, including dysregulation of lipid metabolism, chronic inflammation, oxidative stress, mitochondrial dysfunction, and gut microbiota alterations. Recent advances in research have highlighted the role of genetic and epigenetic factors in disease progression, as well as novel therapeutic targets such as peroxisome proliferator-activated receptors (PPARs), fibroblast growth factors, and thyroid hormone receptor beta agonists. Given the multifaceted nature of MASLD, a multidisciplinary approach integrating early diagnosis, molecular insights, lifestyle interventions, and personalized therapies is critical. This review underscores the urgent need for continued research into innovative treatment strategies and precision medicine approaches to halt MASLD progression and improve patient outcomes.

Competitive antagonism of KAT7 crotonylation against acetylation affects procentriole formation and colorectal tumorigenesis

Accurate procentriole formation is critical for centriole duplication. However, the holistic transcriptional regulatory mechanisms underlying this process remain elusive. Here, we show that KAT7 crotonylation, facilitated by the crotonyltransferase hMOF, competes against its acetylation regulated by the deacetylase HDAC2 at the K432 residue upon DNA damage stimulation. This competition diminishes its histone acetyltransferase activity, leading to the inhibition of procentriole formation in colorectal cancer cells. Mechanistically, the reduction of KAT7 histone acetyltransferase activity by the antagonistic effect of KAT7 crotonylation against its acetylation decreases the gene expression associated with procentriole formation by modulating the enrichment of H3K14ac at their promoters and plays an important role in colorectal tumorigenesis. Furthermore, KAT7 crotonylation and acetylation are associated with the prognosis in colorectal cancer patients. Collectively, our findings uncover a previously unidentified role of KAT7 in the regulation of procentriole formation and colorectal tumorigenesis via competitive antagonism of its crotonylation against acetylation.

Qige Decoction attenuated non-alcoholic fatty liver disease through regulating SIRT6-PPARα-mediated fatty acid oxidation

BACKGROUND

Sirtuin 6 (SIRT6), a potential therapeutic target for non-alcoholic fatty liver disease (NAFLD), has been shown to regulate fatty acid oxidation (FAO) by interacting with peroxisome proliferator-activated receptor α (PPARα). However, the impact of SIRT6-PPARα pathway on NAFLD phenotype has not yet been reported. Qige decoction (QG), a traditional Chinese medicine (TCM) formula, is widely applied to treat disorders of glycolipid metabolism. Our previous experiments showed that QG reduced hepatic steatosis and provided preliminary evidence that QG may promote FAO. However, a thorough understanding of molecular mechanisms by which QG regulates FAO requires further investigation.

PURPOSE

To investigate the role of SIRT6-PPARα signalling pathway on NAFLD phenotype and explore the mechanism by which QG improves NAFLD and its relationship with FAO regulated by SIRT6-PPARα signalling pathway.

METHODS

In vivo study, NAFLD mice induced by high fat diet (HFD) were divided into two parts. The first part involved four groups: control (CON), model (MOD), PPARα agonist (WY-14,643, WY), and SIRT6 inhibitor (OSS-128,167, OS) groups. The second part involved five groups: CON group, MOD group, positive drug (POS) group, low dose QG (QGL) group, and high dose QG (QGH) group. Widely-targeted lipidomic were performed by UHPLC-QTOF/MS to analyse differential lipids (DELs) in the liver, while differentially expressed genes (DEGs) were analysed by transcriptome analysis on the Illumina sequencing platform. In vitro study, co-immunoprecipitation and dual luciferase assay were employed to further identify the molecular mechanisms of SIRT6-PPARα interaction. The lentiviral vector, TG assay, and acetyl-CoA assay were used to clarify the indispensable role of the SIRT6-PPARα signalling pathway on QG amelioration of lipid accumulation in vitro.

RESULTS

Down-regulation of SIRT6 inhibited PPARα-mediated FAO and aggravated lipid accumulation in hepatocytes both in vivo and in vitro. SIRT6 bound to PPARα in HepG2 cells; however, SIRT6 activation of the PPARα promoter was not detected. Along with QG reduced hepatocyte lipid accumulation, SIRT6-PPARα signalling pathway was upregulated in vivo and in vitro. However, the alleviating effect of QG on lipid accumulation was blocked by SIRT6 silencing in vitro.

CONCLUSION

This study verified that SIRT6-PPARα signalling pathway inhibition exacerbated NAFLD dyslipidaemia and hepatic steatosis. In addition, this study provided the first in-depth analysis of the molecular mechanisms by which QG ameliorates NFALD, involving promotion of FAO through activation of the SIRT6-PPARα signalling pathway. Our study offers significant insights for the clinical application of QG.

hnRNPA2B1 deacetylation by SIRT6 restrains local transcription and safeguards genome stability

Repair of double strand breaks (DSBs) by RNA-binding proteins (RBPs) is vital for ensuring genome integrity. DSB repair is accompanied by local transcriptional repression in the vicinity of transcriptionally active genes, but the mechanism by which RBPs regulate transcriptional regulation is unclear. Here, we demonstrated that RBP hnRNPA2B1 functions as a RNA polymerase-associated factor that stabilizes the transcription complex under physiological conditions. Following a DSB, hnRNPA2B1 is released from damaged chromatin, reducing the efficiency of RNAPII complex assembly, leading to local transcriptional repression. Mechanistically, SIRT6 deacetylates hnRNPA2B1 at K113/173 residues, enforcing its rapid detachment from DSBs. This process disrupts the integrity of the RNAPII complex on active chromatin, which is a pre-requisite for transient but complete repression of local transcription. Functionally, the overexpression of an acetylation mimic stabilizes the transcription complex and facilitates the functioning of the transcription machinery. hnRNPA2B1 acetylation status was negatively correlated with SIRT6 expression, and acetylation mimic enhanced radio-sensitivity in vivo. Our findings demonstrate that hnRNPA2B1 is crucial for transcriptional repression. We have uncovered the missing link between DSB repair and transcriptional regulation in genome stability maintenance, highlighting the potential of hnRNPA2B1 as a therapeutic target.

Integrated bioinformatics and multi-omics to investigate the mechanism of Rhododendron molle Flos-induced hepatotoxicity

ETHNOPHARMACOLOGICAL RELEVANCE

Drug-induced liver injury (DILI) is an important and common adverse drug event. Rhododendron molle Flos (RMF), as one of toxic Traditional Chinese medicines (TCMs), holds a prominent position in clinical practice for treating rheumatoid arthritis. However, the toxicity of RMF limits its safe. Most of the concerns are about its rapid neurotoxicity and cardiotoxicity, with less attention paid to its hepatotoxicity, and the mechanism of which is still unclear.

AIM OF THE STUDY

To reveal the mechanism of RMF-induced hepatotoxicity by bioinformatics and multi-omics.

MATERIALS AND METHODS

Rats were intragastric administered RMF at doses of 0.8 g/kg, 0.4 g/kg, and 0.2 g/kg once daily for 2 weeks. Initially, hepatotoxicity was then evaluated using liver function enzymes, antioxidant enzymes, and histopathology. Subsequently, network toxicology, transcriptomics, and metabolomics were used to identify the genes and metabolites. In addition, molecular docking and Western blot were employed to verify toxic components and key targets.

RESULTS

RMF caused abnormal levels of ALT, γ-GT, TBIL, and TBA in the serum of rats, as well as abnormal levels of MDA, GSH-Px, and SOD in the liver, leading to inflammatory infiltration of liver cells, with a dose-dependent manner. RMF disordered the steroid hormone biosynthesis, pyruvate metabolism, fatty acid biosynthesis, and arachidonic acid metabolism. Six key targets were identified- UGT1A6, CYP2E1, ACOT1, ACSL5, CTH, and PKLR, along with their corresponding metabolites, namely 17β-estradiol, estriol, arachidonic acid, octadecanoic acid, and pyruvic acid. The hepatotoxicity could be attributed to five diterpenoid components, including grayanotoxin-III, rhodojaponin (RJ)-I, RJ-II, RJ-III, and RJ-V.

CONCLUSIONS

This study comprehensively identified the toxic components, upstream targets, and downstream metabolites of RMF-induced liver toxicity, providing a basis for evaluating and monitoring liver function in patients during clinical application.

Oral administration of astilbin mitigates acetaminophen-induced acute liver injury in mice by modulating the gut microbiota

Acetaminophen (APAP) overdose-induced acute liver injury (ALI) is characterized by extensive oxidative stress, and the clinical interventions for this adverse effect remain limited. Astilbin is an active compound found in the rhizome of Smilax glabra Roxb. with anti-inflammatory and antioxidant activities. Due to its low oral bioavailability, astilbin can accumulate in the intestine, which provides a basis for the interaction between astilbin and gut microbiota (GM). In the present study we investigated the protective effects of astilbin against APAP-induced ALI by focusing on the interaction between astilbin and GM. Mice were treated with astilbin (50 mg·kg-1·d-1, i.g.) for 7 days. After the last administration of astilbin for 2 h, the mice received APAP (300 mg/kg, i.g.) to induce ALI. We showed that oral administration of astilbin significantly alleviated APAP-induced ALI by altering the composition of GM and enriching beneficial metabolites including hydroxytyrosol (HT). GM depletion using an "antibiotics cocktail" or paraoral administration of astilbin abolished the hepatoprotective effects of astilbin. On the other hand, administration of HT (10 mg/kg, i.g.) caused similar protective effects in APAP-induced ALI mice. Transcriptomic analysis of the liver tissue revealed that HT inhibited reactive oxygen species and inflammation-related signaling in APAP-induced ALI; HT promoted activation of the Nrf2 signaling pathway to combat oxidative stress following APAP challenge in a sirtuin-6-dependent manner. These results highlight that oral astilbin ameliorates APAP-induced ALI by manipulating the GM and metabolites towards a more favorable profile, and provide an alternative therapeutic strategy for alleviating APAP-induced ALI.

Sirtuins in kidney homeostasis and disease: where are we now?

Sirtuins, identified as (NAD+)- dependent class III histone deacetylases, engage in a spectrum of biological functions, encompassing DNA damage repair, oxidative stress, immune modulation, mitochondrial homeostasis, apoptosis and autophagy. Sirtuins play an apoptosis role in regulating cellular operations and overall organism health. Mounting data indicate that dysregulated sirtuin expression is linked to the onset of renal diseases. Effective modulation of sirtuins expression and activity has been shown to improve renal function and attenuate the advancement of kidney diseases. In this review, we present a comprehensive overview of the biological impacts of sirtuins and their molecular targets in regulating renal diseases. Additionally, we detail advancements in elucidating sirtuin roles in the pathophysiology of both chronic and acute renal disorders. We review compounds that modulate sirtuin activity through activation or inhibition, potentially improving outcomes in renal disease. In summary, strategic manipulation of sirtuin activity represents a prospective therapeutic approach for renal diseases.

Propofol Protects against Pyroptosis of Photoreceptors in Subretinal Hemorrhage via Regulating SIRT6/NLRP3 Signaling

Subretinal hemorrhage-induced neurotoxicity is a key cause of vision loss in age-related macular degeneration (AMD). The purpose of this study is to investigate the effects of Propofol on neurotoxicity. Oxygen glucose deprivation (OGD) was used to establish in vitro subretinal hemorrhage model. Gene expression was determined using reverse transcription-quantitative polymerase chain reaction and western blot. Cytokine release was determined using enzyme-linked immunosorbent assay. The interaction between sirtuin 6 (SIRT6) and NLR family pyrin domain containing 3 (NLRP3) was detected using co-immunoprecipitation assay. Cellular function was determined using cell counting kit-8 assay, lactate dehydrogenase assay, and terminal deoxynucleotidyl transferase dUTP nick end labeling assay. Propofol suppressed the inflammatory response induced by OGD. Moreover, Propofol inhibited the neurotoxicity and pyroptosis of photoreceptors. Propofol mediated the overexpression of SIRT6, which was downregulated in AMD. Inhibition of SIRT6 alleviated its deacetylation of NLRP3. Additionally, SIRT6 deficiency antagonized the effects of Propofol and promoted the neurotoxicity and pyroptosis of photoreceptors. Taken together, Propofol protects against subretinal hemorrhage-induced neurotoxicity and pyroptosis of photoreceptors via promoting SIRT6-mediated deacetylation of NLRP3.

USP29 alleviates the progression of MASLD by stabilizing ACSL5 through K48 deubiquitination

BACKGROUND/AIMS

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a chronic liver disease characterized by hepatic steatosis. Ubiquitin-specific protease 29 (USP29) plays pivotal roles in hepatic ischemiareperfusion injury and hepatocellular carcinoma, but its role in MASLD remains unexplored. Therefore, the aim of this study was to reveal the effects and underlying mechanisms of USP29 in MASLD progression.

METHODS

USP29 expression was assessed in liver samples from MASLD patients and mice. The role and molecular mechanism of USP29 in MASLD were assessed in high-fat diet-fed and high-fat/high-cholesterol diet-fed mice and palmitic acid and oleic acid treated hepatocytes.

RESULTS

USP29 protein levels were significantly reduced in mice and humans with MASLD. Hepatic steatosis, inflammation and fibrosis were significantly exacerbated by USP29 deletion and relieved by USP29 overexpression. Mechanistically, USP29 significantly activated the expression of genes related to fatty acid β-oxidation (FAO) under metabolic stimulation, directly interacted with long-chain acyl-CoA synthase 5 (ACSL5) and repressed ACSL5 degradation by increasing ACSL5 K48-linked deubiquitination. Moreover, the effect of USP29 on hepatocyte lipid accumulation and MASLD was dependent on ACSL5.

CONCLUSION

USP29 functions as a novel negative regulator of MASLD by stabilizing ACSL5 to promote FAO. The activation of the USP29-ACSL5 axis may represent a potential therapeutic strategy for MASLD.

Role of the histone deacetylase family in lipid metabolism: Structural specificity and functional diversity

Lipids play crucial roles in signal transduction. Lipid metabolism is associated with several transcriptional regulators, including peroxisome proliferator activated receptor γ, sterol regulatory element-binding protein 1, and acetyl-CoA carboxylase. In recent years, increasing evidence has suggested that members of the histone deacetylase (HDAC) family play key roles in lipid metabolism. However, the mechanisms by which each member of this family regulates lipid metabolism remain unclear. This review discusses the latest research on the roles played by HDACs in fat metabolism. The role of HDACs in obesity, diabetes, and atherosclerosis has also been discussed. In addition, the interaction of HDACs with the gut microbiome and circadian rhythm has been reviewed, and the future development trend in HDACs has been predicted, which may potentiate therapeutic application of targeted HDACs in related metabolic diseases.

Qiwei Jinggan Ling regulates oxidative stress and lipid metabolism in alcoholic liver disease by activating AMPK

BACKGROUND

Alcoholic liver disease (ALD) is a severe public health concern worldwide and there is still a lack of effective treatments. Qiwei Jinggan Ling (QJL) has protective effects against various liver injuries, but its pharmacological action on ALD has received little attention.

PURPOSE

To investigate the effect and mechanism of QJL on ALD in vivo and in vitro.

METHODS

In vivo, an ALD mouse model was established by alcohol combined with a high-fat diet (HFD) and treated with QJL. Biochemical indicators, HE staining, and Oil Red O staining were employed to assess hepatic oxidative stress, steatosis, and alcohol metabolism. RNA sequencing analysis was performed, and the results were verified by qRT-PCR and Western blot to elucidate the hepatoprotective mechanism of QJL. In vitro, HepG2 cells were co-stimulated with NaOA (sodium oleate) and EtOH (ethanol), followed by intervention with Compound C (CC, AMPK inhibitor) and QJL-containing serum. Oil Red O, BODIPY (boron-dipyrromethene), and ROS (reactive oxygen species) staining were applied to validate the efficacy and mechanism of QJL-containing serum. The expression of AMP-activated protein kinase (AMPK) pathway-related factors was analyzed through qRT-PCR and Western blot for additional corroboration. Moreover, the key pharmacodynamic components of QJL were identified by UPLC-MS/MS and molecular docking.

RESULTS

In vivo, QJL ameliorated liver structural disorders, steatosis, oxidative stress, and impaired alcohol metabolism, as indicated by biochemical indicators and histopathological assays. RNA sequencing analysis revealed that QJL reversed the expression of genes related to alcohol metabolism, fatty acid metabolism, and cholesterol metabolism. The results of qRT-PCR and Western blot were in line with those of RNA sequencing. Furthermore, it was discovered that QJL significantly upregulated the expression of p-AMPK and downregulated the expression of sterol regulatory element binding transcription factor 1 (SREBP-1c). In vitro, biochemical indicators and staining assays demonstrated that QJL-containing serum inhibited lipid accumulation and oxidative stress. The qRT-PCR and Western blot analysis revealed that QJL-containing serum markedly enhanced the expression of p-AMPK and carnitine palmitoyltransferase 1a (Cpt1a), while suppressing the expression of SREBP-1c, fatty acid synthase (Fasn), and acetyl-coenzyme A carboxylase 1 (ACC-1). However, CC inhibited the above pharmacological activities of QJL-containing serum. Additionally, (2S)-Liquiritigenin, Glycyrrhetinate, Isovitexin, Taxifolin, and Yohimbine were proved to be the key active components of QJL.

CONCLUSION

QJL had the potential to be a therapeutic drug for ALD by activating the AMPK pathway, thereby regulating lipid metabolism and inhibiting oxidative stress.

Mechanistic role of long non-coding RNAs in the pathogenesis of metabolic dysfunction-associated steatotic liver disease and fibrosis

Metabolic dysfunction-associated steatotic liver disease (MASLD), previously referred to as non-alcoholic fatty liver disease, encompasses a broad range of hepatic metabolic disorders primarily characterised by the disruption of hepatic lipid metabolism, hepatic lipid accumulation and steatosis. Severe cases of MASLD might progress to metabolic dysfunction-associated steatohepatitis, characterised by hepatic inflammation, hepatocyte ballooning degeneration, activation of hepatic stellate cells (HSCs) and fibrogenesis. It may further progress to hepatocellular carcinoma. In the liver, long non-coding RNAs (lncRNAs) target multiple metabolic pathways in hepatocytes, HSCs, and Kupffer cells at different stages of MASLD and liver fibrosis. In this study, we overview recent findings on the potential role of lncRNAs in the pathogenesis of MASLD and liver fibrosis via modulation of de novo lipid synthesis, fatty acid β-oxidation, lipotoxicity, oxidative stress, metabolic inflammation, mammalian target of rapamycin signalling, apoptosis, ubiquitination and fibrogenesis. We critically assess the literature reports that investigate the complex interplay between lncRNA, microRNA and key mediators in liver injury, in both human participants and animal models of MASLD and liver fibrosis. We also highlight the therapeutic potential of lncRNAs in chronic liver diseases.

Discovery of Novel PROTAC SIRT6 Degraders with Potent Efficacy against Hepatocellular Carcinoma

Sirtuin 6 (SIRT6), a member of the SIRT family, plays essential roles in the regulation of metabolism, inflammation, aging, DNA repair, and cancer development, making it a promising anticancer drug target. Herein, we present our use of proteolysis-targeting chimera (PROTAC) technology to formulate a series of highly potent and selective SIRT6 degraders. One of the degraders, SZU-B6, induced the near-complete degradation of SIRT6 in both SK-HEP-1 and Huh-7 cell lines and more potently inhibited hepatocellular carcinoma (HCC) cell proliferation than the parental inhibitors. In preliminary mechanistic studies, SZU-B6 hampered DNA damage repair, promoting the cellular radiosensitization of cancer cells. Our SIRT6 degrader SZU-B6 displayed promising antitumor activity, particularly when combined with the well-known kinase inhibitor sorafenib or irradiation in an SK-HEP-1 xenograft mouse model. Our results suggest that these PROTACs might constitute a potent therapeutic strategy for HCC.

Protein posttranslational modifications in metabolic diseases: basic concepts and targeted therapies

Metabolism-related diseases, including diabetes mellitus, obesity, hyperlipidemia, and nonalcoholic fatty liver disease, are becoming increasingly prevalent, thereby posing significant threats to human health and longevity. Proteins, as the primary mediators of biological activities, undergo various posttranslational modifications (PTMs), including phosphorylation, ubiquitination, acetylation, methylation, and SUMOylation, among others, which substantially diversify their functions. These modifications are crucial in the physiological and pathological processes associated with metabolic disorders. Despite advancements in the field, there remains a deficiency in contemporary summaries addressing how these modifications influence processes of metabolic disease. This review aims to systematically elucidate the mechanisms through which PTM of proteins impact the progression of metabolic diseases, including diabetes, obesity, hyperlipidemia, and nonalcoholic fatty liver disease. Additionally, the limitations of the current body of research are critically assessed. Leveraging PTMs of proteins provides novel insights and therapeutic targets for the prevention and treatment of metabolic disorders. Numerous drugs designed to target these modifications are currently in preclinical or clinical trials. This review also provides a comprehensive summary. By elucidating the intricate interplay between PTMs and metabolic pathways, this study advances understanding of the molecular mechanisms underlying metabolic dysfunction, thereby facilitating the development of more precise and effective disease management strategies.

Impaired SUMOylation of FoxA1 promotes nonalcoholic fatty liver disease through down-regulation of Sirt6

Abnormal SUMOylation is implicated in non-alcoholic fatty liver disease (NAFLD) progression. Forkhead box protein A1 (FoxA1) has been shown to protect liver from steatosis, which was down-regulated in NAFLD. This study elucidated the role of FoxA1 deSUMOylation in NAFLD. NAFLD models were established in high-fat diet (HFD)-induced mice and palmitate acid (PAL)-treated hepatocytes. Hepatic steatosis was evaluated by biochemical and histological methods. Lipid droplet formation was determined by BODIPY and Oil red O staining. Target molecule levels were analyzed by RT-qPCR, Western blotting, and immunohistochemistry staining. SUMOylation of FoxA1 was determined by Ni-NTA pull-down assay and SUMOylation assay Ultra Kit. Protein interaction and ubiquitination were detected by Co-IP. Gene transcription was assessed by ChIP and dual luciferase reporter assays. Liver FoxA1 knockout mice developed severe liver steatosis, which could be ameliorated by sirtuin 6 (Sirt6) overexpression. Nutritional stresses reduced Sumo2/3-mediated FoxA1 SUMOylation at lysine residue K6, which promoted lipid droplet formation by repressing fatty acid β-oxidation. Moreover, Sirt6 was a target gene of FoxA1, and Sirt6 transcription activity was restrained by deSUMOylation of FoxA1 at site K6. Furthermore, nutritional stresses-induced deSUMOylation of FoxA1 promoted the ubiquitination and degradation of FoxA1 with assistance of murine double minute 2 (Mdm2). Finally, activating FoxA1 SUMOylation delayed the progression of NAFLD in mice. DeSUMOylation of FoxA1 at K6 promotes FoxA1 degradation and then inhibits Sirt6 transcription, thereby suppressing fatty acid β-oxidation and facilitating NAFLD development. Our findings suggest that FoxA1 SUMOylation activation might be a promising therapeutic strategy for NAFLD.

Inhibition of mitochondrial citrate shuttle alleviates metabolic syndromes induced by high-fat diet

The mitochondrial citrate shuttle, which relies on the solute carrier family 25 member 1 (SLC25A1), plays a pivotal role in transporting citrate from the mitochondria to the cytoplasm. This shuttle supports glycolysis, lipid biosynthesis, and protein acetylation. Previous research has primarily focused on SLC25A1 in pathological models, particularly high-fat diet (HFD)-induced obesity. However, the impact of SLC25A1 inhibition on nutrient metabolism under HFD remains unclear. To address this gap, we used zebrafish (Danio rerio) and Nile tilapia (Oreochromis niloticus) to evaluate the effects of inhibiting Slc25a1. In zebrafish, we administered Slc25a1-specific inhibitors (CTPI-2) for 4 wk, whereas Nile tilapia received intraperitoneal injections of dsRNA to knock down slc25a1b for 7 days. Inhibition of the mitochondrial citrate shuttle effectively protected zebrafish from HFD-induced obesity, hepatic steatosis, and insulin resistance. Of note, glucose tolerance was unaffected. Inhibition of Slc25a1 altered hepatic protein acetylation patterns, with decreased cytoplasmic acetylation and increased mitochondrial acetylation. Under HFD conditions, Slc25a1 inhibition promoted fatty acid oxidation and reduced hepatic triglyceride (TAG) accumulation by deacetylating carnitine palmitoyltransferase 1a (Cpt1a). In addition, Slc25a1 inhibition triggered acetylation-induced inactivation of Pdhe1α, leading to a reduction in glucose oxidative catabolism. This was accompanied by enhanced glucose uptake and storage in zebrafish livers. Furthermore, Slc25a1 inhibition under HFD conditions activated the SIRT1/PGC1α pathway, promoting mitochondrial proliferation and enhancing oxidative phosphorylation for energy production. Our findings provide new insights into the role of nonhistone protein acetylation via the mitochondrial citrate shuttle in the development of hepatic lipid deposition and hyperglycemia caused by HFD.NEW & NOTEWORTHY The mitochondrial citrate shuttle is a crucial physiological process for maintaining metabolic homeostasis. In the present study, we found that inhibition of mitochondrial citrate shuttle (Slc25a1) could alleviate metabolic syndromes induced by high-fat diet (HFD) through remodeling hepatic protein acetylation modification. Briefly, Slc25a1 inhibition reduces hepatic triglyceride deposition by deacetylating Cpt1a and reduces glucose oxidative catabolism by acetylating Pdhe1α. Our study provides new insights into the treatment of diet-induced metabolic syndromes.

Liver epigenomic signature associated with chronic oxidative stress in a mouse model of glutathione deficiency

Oxidative stress is intimately involved in the pathogenesis of fatty liver disease (FLD). A major factor contributing to oxidative stress is the depletion of the ubiquitous antioxidant glutathione (GSH). Unexpectedly, chronic GSH deficiency renders glutamate-cysteine ligase modifier subunit (Gclm)-null mice protected from fatty liver injuries. Epigenetic regulation serves as an important cellular mechanism in modulating gene expression and disease outcome in FLD, although it is not well understood how systemic redox imbalance modifies the liver epigenome. In the current study, utilizing the Gclm-null mouse model, we aimed to elucidate redox-associated epigenomic changes and their implications in liver stress response. We performed high-throughput array-based DNA methylation profiling (MeDIP array) in 22,327 gene promoter regions (from -1300 bp to +500 bp of the Transcription Start Sites) in the liver and peripheral blood cells. Results from the MeDIP array demonstrate that, although global methylation enrichment in gene promoters did not change, low GSH resulted in prevalent demethylation at the individual promoter level. Such an effect likely attributed to a declined availability of the methyl donor S-adenosyl methionine (SAM) in Gclm-null liver. Functional enrichment analysis of liver target genes is suggestive of a potential role of epigenetic mechanisms in promoting cellular survival and lipid homeostasis in Gclm-null liver. In comparison with the liver tissue, MeDIP array in peripheral blood cells revealed a panel of 19 gene promoters that are candidate circulating biomarkers for hepatic epigenomic changes associated with chronic GSH deficiency. Collectively, our results provided new insights into the in vivo interplay between liver redox state and DNA methylation status. The current study laid the groundwork for future epigenetic/epigenomic investigations in experimental settings or human populations under conditions of liver oxidative stress induced by environmental or dietary challenges.

Establishment of a Steatosis Model in LMH Cells, Chicken Embryo Hepatocytes, and Liver Tissues Based on a Mixture of Sodium Oleate and Palmitic Acid

Research on hepatic steatosis in animal husbandry has been a prominent area of study. Developing an appropriate in vitro cellular steatosis model is crucial for comprehensively investigating the mechanisms involved in liver lipid deposition in poultry and for identifying potential interventions to address abnormalities in lipid metabolism. The research on the methods of in vitro liver steatosis in chickens, particularly the effects of different fat mixtures, is still lacking. In this study, LMH cells were utilized to investigate the effects of OA, SO, PA, SP, and their pairwise combinations on steatosis development, with the aim of identifying the optimal conditions for inducing steatosis. Analysis of triglyceride (TG) content in LMH cells revealed that OA and SP had limited efficacy in increasing TG content, while a combination of SO and PA in a 1:2 ratio exhibited the highest TG content. Moreover, Oil Red O staining results in LMH cells demonstrated that the combination treatment had a more pronounced induction effect compared to 0.375 mM SO. Additionally, RNA-seq analysis showed that 0.375 mM SO significantly influenced the expression of genes associated with fatty acid metabolism compared to the control group, whereas the combination of SO and PA led to an enrichment of key GO terms associated with programmed cell death. These findings suggest that varying conditions of cellular steatosis could lead to distinct disruptions in gene expression. The optimal conditions for inducing steatosis in LMH cells were also tested on chicken embryonic liver cells and embryos. TG detection and Oil Red O staining assays showed that the combination of SO and PA successfully induced steatosis. However, the gene expression pattern differed from that of LMH cells. This study lays the foundations for further investigations into avian hepatic steatosis.

MAPKAP1 orchestrates macrophage polarization and lipid metabolism in fatty liver-enhanced colorectal cancer

Various factors, including fatty liver and macrophage alterations, influence colorectal cancer (CRC). This study explores the mechanistic role of fatty liver in CRC progression, focusing on macrophage polarization and lipid metabolism. A murine fatty liver model was created with a high-fat diet (HFD), and CRC was induced using AOM and DSS. Single-cell transcriptome sequencing (scRNA-seq) identified MAPKAP1 as a critical gene promoting CRC via M2 macrophage polarization and lipid metabolism reprogramming. Prognosis analysis on the TCGA-CRC dataset confirmed MAPKAP1's significance. In vitro and in vivo experiments demonstrated that EVs from fatty liver cells enhanced MAPKAP1 expression, accelerating CRC development and metastasis. HFD exacerbated CRC, but fatty acid inhibitors delayed progression. Fatty liver upregulates MAPKAP1, driving M2 macrophage polarization and lipid metabolism changes, worsening CRC. These findings suggest potential therapeutic strategies for CRC, particularly targeting lipid metabolism and macrophage-mediated tumor promotion.

Si-Wu-Tang alleviates metabolic dysfunction-associated fatty liver disease by inhibiting ACSL4-mediated arachidonic acid metabolism and ferroptosis in MCD diet-fed mice

BACKGROUND

Metabolic dysfunction-associated fatty liver disease (MAFLD) is a prevalent chronic liver disease worldwide. Si-Wu-Tang (SWT), a traditional Chinese medicine decoction has shown therapeutic effects on various liver diseases. However, the hepatoprotective effects and underlying mechanism of SWT on MAFLD remain unclear.

METHODS

First, a methionine-choline-deficient (MCD) diet-fed mice model was used and lipidomic analysis and transcriptomic analysis were performed. The contents of total iron ions, ferrous ions, and lipid peroxidation were detected and Prussian blue staining was performed to confirm the protective effects of SWT against ferroptosis. Finally, chemical characterization and network pharmacological analysis were employed to identify the potential active ingredients.

RESULTS

Serological and hepatic histopathological findings indicated SWT's discernible therapeutic impact on MCD diet-induced MAFLD. Lipidomic analysis revealed that SWT improved intrahepatic lipid accumulation by inhibiting TG synthesis and promoting TG transport. Transcriptomic analysis suggested that SWT ameliorated abnormal FA metabolism by inhibiting FA synthesis and promoting FA β-oxidation. Then, ferroptosis phenotype experiments revealed that SWT could effectively impede hepatocyte ferroptosis, which was induced by long-chain acyl-CoA synthetase 4 (ACSL4)-mediated esterification of arachidonic acid (AA). Finally, chemical characterization and network pharmacological analysis identified that paeoniflorin and other active ingredients might be responsible for the regulative effects against ferroptosis and MAFLD.

CONCLUSION

In conclusion, our study revealed the intricate mechanism through which SWT improved MCD diet-induced MAFLD by targeting FA metabolism and ferroptosis in hepatocytes, thus offering a novel therapeutic approach for the treatment of MAFLD and its complications.

SIRT1: Harnessing multiple pathways to hinder NAFLD

Non-alcoholic fatty liver disease (NAFLD) encompasses hepatic steatosis, non-alcoholic steatohepatitis (NASH), fibrosis, cirrhosis, and hepatocellular carcinoma. It is the primary cause of chronic liver disorders, with a high prevalence but no approved treatment. Therefore, it is indispensable to find a trustworthy therapy for NAFLD. Recently, mounting evidence illustrates that Sirtuin 1 (SIRT1) is strongly associated with NAFLD. SIRT1 activation or overexpression attenuate NAFLD, while SIRT1 deficiency aggravates NAFLD. Besides, an array of therapeutic agents, including natural compounds, synthetic compounds, traditional Chinese medicine formula, and stem cell transplantation, alleviates NALFD via SIRT1 activation or upregulation. Mechanically, SIRT1 alleviates NAFLD by reestablishing autophagy, enhancing mitochondrial function, suppressing oxidative stress, and coordinating lipid metabolism, as well as reducing hepatocyte apoptosis and inflammation. In this review, we introduced the structure and function of SIRT1 briefly, and summarized the effect of SIRT1 on NAFLD and its mechanism, along with the application of SIRT1 agonists in treating NAFLD.

Examining the Pathogenesis of MAFLD and the Medicinal Properties of Natural Products from a Metabolic Perspective

Metabolic-associated fatty liver disease (MAFLD), characterized primarily by hepatic steatosis, has become the most prevalent liver disease worldwide, affecting approximately two-fifths of the global population. The pathogenesis of MAFLD is extremely complex, and to date, there are no approved therapeutic drugs for clinical use. Considerable evidence indicates that various metabolic disorders play a pivotal role in the progression of MAFLD, including lipids, carbohydrates, amino acids, and micronutrients. In recent years, the medicinal properties of natural products have attracted widespread attention, and numerous studies have reported their efficacy in ameliorating metabolic disorders and subsequently alleviating MAFLD. This review aims to summarize the metabolic-associated pathological mechanisms of MAFLD, as well as the natural products that regulate metabolic pathways to alleviate MAFLD.

Dietary elaidic acid boosts tumoral antigen presentation and cancer immunity via ACSL5

Immunomodulatory effects of long-chain fatty acids (LCFAs) and their activating enzyme, acyl-coenzyme A (CoA) synthetase long-chain family (ACSL), in the tumor microenvironment remain largely unknown. Here, we find that ACSL5 functions as an immune-dependent tumor suppressor. ACSL5 expression sensitizes tumors to PD-1 blockade therapy in vivo and the cytotoxicity mediated by CD8+ T cells in vitro via regulation of major histocompatibility complex class I (MHC-I)-mediated antigen presentation. Through screening potential substrates for ACSL5, we further identify that elaidic acid (EA), a trans LCFA that has long been considered harmful to human health, phenocopies to enhance MHC-I expression. EA supplementation can suppress tumor growth and sensitize PD-1 blockade therapy. Clinically, ACSL5 expression is positively associated with improved survival in patients with lung cancer, and plasma EA level is also predictive for immunotherapy efficiency. Our findings provide a foundation for enhancing immunotherapy through either targeting ACSL5 or metabolic reprogramming of antigen presentation via dietary EA supplementation.

SIRT6 activates PPARα to improve doxorubicin-induced myocardial cell aging and damage

The Sirtuins family, formally known as the Silent Information Regulator Factors, constitutes a highly conserved group of histone deacetylases. Recent studies have illuminated SIRT6's role in doxorubicin (DOX)-induced oxidative stress and apoptosis within myocardial cells. Nevertheless, the extent of SIRT6's impact on DOX-triggered myocardial cell aging and damage remains uncertain, with the associated mechanisms yet to be fully understood. In our research, we examined the influence of SIRT6 on DOX-induced cardiomyocyte senescence using β-galactosidase and γ-H2AX staining. Additionally, we gauged the mRNA expression of senescence-associated genes, namely p16, p21, and p53, through Real-time PCR. Employing ELISA assay kits, MDA, and total SOD activity assay kits, we measured inflammatory factors TNF-α, IL-6, and IL-1β, alongside oxidative stress-related indicators. The results unequivocally indicated that SIRT6 overexpression robustly inhibited DOX-induced cardiomyocyte senescence. Furthermore, we established that SIRT6 overexpression suppressed the inflammatory response and oxidative stress induced by DOX in cardiomyocytes. Conversely, silencing SIRT6 exacerbated DOX-induced cardiomyocyte injury. Our investigations further unveiled that SIRT6 upregulated the expression of genes CD36, CPT1, LCAD, MCAD associated with fatty acid oxidation through its interaction with PPARα, thereby exerting anti-aging effects. In vivo, the overexpression of SIRT6 was observed to restore DOX-induced declines in EF and FS to normal levels in mice. Echocardiography and HE staining revealed the restoration of cardiomyocyte alignment, affording protection against DOX-induced myocardial senescence and injury. The findings from this study suggest that SIRT6 holds significant promise as a therapeutic target for mitigating DOX-induced cardiomyopathy.

Role of sirtuins in epigenetic regulation and aging control

Advances in modern healthcare in developed countries make it possible to extend the human lifespan, which is why maintaining active longevity is becoming increasingly important. After the sirtuin (SIRT) protein family was discovered, it started to be considered as a significant regulator of the physiological processes associated with aging. SIRT has deacetylase, deacylase, and ADP-ribosyltransferase activity and modifies a variety of protein substrates, including chromatin components and regulatory proteins. This multifactorial regulatory system affects many processes: cellular metabolism, mitochondrial functions, epigenetic regulation, DNA repair and more. As is expected, the activity of sirtuin proteins affects the manifestation of classic signs of aging in the body, such as cellular senescence, metabolic disorders, mitochondrial dysfunction, genomic instability, and the disruption of epigenetic regulation. Changes in the SIRT activity in human cells can also be considered a marker of aging and are involved in the genesis of various age-dependent disorders. Additionally, experimental data obtained in animal models, as well as data from population genomic studies, suggest a SIRT effect on life expectancy. At the same time, the diversity of sirtuin functions and biochemical substrates makes it extremely complicated to identify cause-and-effect relationships and the direct role of SIRT in controlling the functional state of the body. However, the SIRT influence on the epigenetic regulation of gene expression during the aging process and the development of disorders is one of the most important aspects of maintaining the homeostasis of organs and tissues. The presented review centers on the diversity of SIRT in humans and model animals. In addition to a brief description of the main SIRT enzymatic and biological activity, the review discusses its role in the epigenetic regulation of chromatin structure, including the context of the development of genome instability associated with aging. Studies on the functional connection between SIRT and longevity, as well as its effect on pathological processes associated with aging, such as chronic inflammation, fibrosis, and neuroinflammation, have been critically analyzed.

GBA3 promotes fatty acid oxidation and alleviates non-alcoholic fatty liver by increasing CPT2 transcription

BACKGROUND

Excessive lipids accumulation and hepatocytes death are prominent characteristics of non-alcoholic fatty liver disease (NAFLD). Nonetheless, the precise pathophysiological mechanisms are not fully elucidated.

METHODS

HepG2 cells stimulated with palmitic acids and rats fed with high-fat diet were used as models for NAFLD. The impact of Glucosylceramidase Beta 3 (GBA3) on fatty acid oxidation (FAO) was assessed using Seahorse metabolic analyzer. Lipid content was measured both in vitro and in vivo. To evaluate NAFLD progression, histological analysis was performed along with measurements of inflammatory factors and liver enzyme levels. Western blot and immunohistochemistry were employed to examine the activity levels of necroptosis. Flow cytometry and reactive oxygen species (ROS) staining were utilized to assess levels of oxidative stress.

RESULTS

GBA3 promoted FAO and enhanced the mitochondrial membrane potential without affecting glycolysis. These reduced the lipid accumulation. Rats supplemented with GBA3 exhibited lower levels of inflammatory factors and liver enzymes, resulting in a slower progression of NAFLD. GBA3 overexpression reduced ROS and the ratio of cell apoptosis. Phosphorylation level was reduced in the essential mediator, MLKL, implicated in necroptosis. Mechanistically, as a transcriptional coactivator, GBA3 promoted the expression of Carnitine Palmitoyltransferase 2 (CPT2), which resulted in enhanced FAO.

CONCLUSIONS

Increased FAO resulting from GBA3 reduced oxidative stress and the production of ROS, thereby inhibiting necroptosis and delaying the progression of NAFLD. Our research offers novel insights into the potential therapeutic applications of GBA3 and FAO in the management and treatment of NAFLD.

Dysregulated palmitic acid metabolism promotes the formation of renal calcium-oxalate stones through ferroptosis induced by polyunsaturated fatty acids/phosphatidic acid

The pathogenesis of renal calcium-oxalate (CaOx) stones is complex and influenced by various metabolic factors. In parallel, palmitic acid (PA) has been identified as an upregulated lipid metabolite in the urine and serum of patients with renal CaOx stones via untargeted metabolomics. Thus, this study aimed to mechanistically assess whether PA is involved in stone formation. Lipidomics analysis of PA-treated renal tubular epithelial cells compared with the control samples revealed that α-linoleic acid and α-linolenic acid were desaturated and elongated, resulting in the formation of downstream polyunsaturated fatty acids (PUFAs). In correlation, the levels of fatty acid desaturase 1 and 2 (FADS1 and FADS2) and peroxisome proliferator-activated receptor α (PPARα) in these cells treated with PA were increased relative to the control levels, suggesting that PA-induced upregulation of PPARα, which in turn upregulated these two enzymes, forming the observed PUFAs. Lipid peroxidation occurred in these downstream PUFAs under oxidative stress and Fenton Reaction. Furthermore, transcriptomics analysis revealed significant changes in the expression levels of ferroptosis-related genes in PA-treated renal tubular epithelial cells, induced by PUFA peroxides. In addition, phosphatidyl ethanolamine binding protein 1 (PEBP1) formed a complex with 15-lipoxygenase (15-LO) to exacerbate PUFA peroxidation under protein kinase C ζ (PKC ζ) phosphorylation, and PKC ζ was activated by phosphatidic acid derived from PA. In conclusion, this study found that the formation of renal CaOx stones is promoted by ferroptosis of renal tubular epithelial cells resulting from PA-induced dysregulation of PUFA and phosphatidic acid metabolism, and PA can promote the renal adhesion and deposition of CaOx crystals by injuring renal tubular epithelial cells, consequently upregulating adhesion molecules. Accordingly, this study provides a new theoretical basis for understanding the correlation between fatty acid metabolism and the formation of renal CaOx stones, offering potential targets for clinical applications.

Sirtuins in kidney diseases: potential mechanism and therapeutic targets

Sirtuins, which are NAD+-dependent class III histone deacetylases, are involved in various biological processes, including DNA damage repair, immune inflammation, oxidative stress, mitochondrial homeostasis, autophagy, and apoptosis. Sirtuins are essential regulators of cellular function and organismal health. Increasing evidence suggests that the development of age-related diseases, including kidney diseases, is associated with aberrant expression of sirtuins, and that regulation of sirtuins expression and activity can effectively improve kidney function and delay the progression of kidney disease. In this review, we summarise current studies highlighting the role of sirtuins in renal diseases. First, we discuss sirtuin family members and their main mechanisms of action. We then outline the possible roles of sirtuins in various cell types in kidney diseases. Finally, we summarise the compounds that activate or inhibit sirtuin activity and that consequently ameliorate renal diseases. In conclusion, targeted modulation of sirtuins is a potential therapeutic strategy for kidney diseases. Video Abstract.

Loss of PPARα function promotes epigenetic dysregulation of lipid homeostasis driving ferroptosis and pyroptosis lipotoxicity in metabolic dysfunction associated Steatotic liver disease (MASLD)

Metabolic Dysfunction Associated Steatotic Liver Disease (MASLD) is a growing epidemic with an estimated prevalence of 20%-30% in Europe and the most common cause of chronic liver disease worldwide. The onset and progression of MASLD are orchestrated by an interplay of the metabolic environment with genetic and epigenetic factors. Emerging evidence suggests altered DNA methylation pattern as a major determinant of MASLD pathogenesis coinciding with progressive DNA hypermethylation and gene silencing of the liver-specific nuclear receptor PPARα, a key regulator of lipid metabolism. To investigate how PPARα loss of function contributes to epigenetic dysregulation in MASLD pathology, we studied DNA methylation changes in liver biopsies of WT and hepatocyte-specific PPARα KO mice, following a 6-week CDAHFD (choline-deficient, L-amino acid-defined, high-fat diet) or chow diet. Interestingly, genetic loss of PPARα function in hepatocyte-specific KO mice could be phenocopied by a 6-week CDAHFD diet in WT mice which promotes epigenetic silencing of PPARα function via DNA hypermethylation, similar to MASLD pathology. Remarkably, genetic and lipid diet-induced loss of PPARα function triggers compensatory activation of multiple lipid sensing transcription factors and epigenetic writer-eraser-reader proteins, which promotes the epigenetic transition from lipid metabolic stress towards ferroptosis and pyroptosis lipid hepatoxicity pathways associated with advanced MASLD. In conclusion, we show that PPARα function is essential to support lipid homeostasis and to suppress the epigenetic progression of ferroptosis-pyroptosis lipid damage associated pathways towards MASLD fibrosis.

Phocaeicola vulgatus alleviates diet-induced metabolic dysfunction-associated steatotic liver disease progression by downregulating histone acetylation level via 3-HPAA

Diet-induced metabolic dysfunction-associated steatotic liver disease (MASLD) is a prevalent metabolic disorder with limited effective interventions available. A novel approach to address this issue is through gut microbiota-based therapy. In our study, we utilized multi-omics analysis to identify Phocaeicola vulgatus (P. vulgatus) as a potential probiotic for the treatment of MASLD. Our findings from murine models clearly illustrate that the supplementation of P. vulgatus mitigates the development of MASLD. This beneficial effect is partly attributed to the metabolite 3-Hydroxyphenylacetic acid (3-HPAA) produced by P. vulgatus, which reduces the acetylation levels of H3K27 and downregulates the transcription of Squalene Epoxidase (SQLE), a rate-limiting enzyme in steroid biosynthesis that promotes lipid accumulation in liver cells. This study underscores the significant role of P. vulgatus in the development of MASLD and the critical importance of its metabolite 3-HPAA in regulating lipid homeostasis. These findings offer a promising avenue for early intervention therapy in the context of MASLD.

Roles of immune dysregulation in MASLD

Metabolic dysfunction-associated steatotic liver disease (MASLD) is the most common chronic liver disease worldwide. Its occurrence and progression involve the process from simple hepatic steatosis to metabolic dysfunction associated steatohepatitis (MASH), which could develop into advanced liver fibrosis, cirrhosis, or hepatocellular carcinoma (HCC). Growing evidences support that the pathogenesis and progression of MASLD are closely related to immune system dysfunction. This review aims to summarize the association of MASLD with immune disorders and the prospect of using immunotherapy for MASLD.

Epithelial SIRT6 governs IL-17A pathogenicity and drives allergic airway inflammation and remodeling

Dysregulation of IL-17A is closely associated with airway inflammation and remodeling in severe asthma. However, the molecular mechanisms by which IL-17A is regulated remain unclear. Here we identify epithelial sirtuin 6 (SIRT6) as an epigenetic regulator that governs IL-17A pathogenicity in severe asthma. Mice with airway epithelial cell-specific deletion of Sirt6 are protected against allergen-induced airway inflammation and remodeling via inhibiting IL-17A-mediated inflammatory chemokines and mesenchymal reprogramming. Mechanistically, SIRT6 directly interacts with RORγt and mediates RORγt deacetylation at lysine 192 via its PPXY motifs. SIRT6 promotes RORγt recruitment to the IL-17A gene promoter and enhances its transcription. In severe asthma patients, high expression of SIRT6 positively correlates with airway remodeling and disease severity. SIRT6 inhibitor (OSS_128167) treatment significantly attenuates airway inflammation and remodeling in mice. Collectively, these results uncover a function for SIRT6 in regulating IL-17A pathogenicity in severe asthma, implicating SIRT6 as a potential therapeutic target for severe asthma.

PARylated PDHE1α generates acetyl-CoA for local chromatin acetylation and DNA damage repair

Chromatin relaxation is a prerequisite for the DNA repair machinery to access double-strand breaks (DSBs). Local histones around the DSBs then undergo prompt changes in acetylation status, but how the large demands of acetyl-CoA are met is unclear. Here, we report that pyruvate dehydrogenase 1α (PDHE1α) catalyzes pyruvate metabolism to rapidly provide acetyl-CoA in response to DNA damage. We show that PDHE1α is quickly recruited to chromatin in a polyADP-ribosylation-dependent manner, which drives acetyl-CoA generation to support local chromatin acetylation around DSBs. This process increases the formation of relaxed chromatin to facilitate repair-factor loading, genome stability and cancer cell resistance to DNA-damaging treatments in vitro and in vivo. Indeed, we demonstrate that blocking polyADP-ribosylation-based PDHE1α chromatin recruitment attenuates chromatin relaxation and DSB repair efficiency, resulting in genome instability and restored radiosensitivity. These findings support a mechanism in which chromatin-associated PDHE1α locally generates acetyl-CoA to remodel the chromatin environment adjacent to DSBs and promote their repair.

SIRT6's function in controlling the metabolism of lipids and glucose in diabetic nephropathy

Diabetic nephropathy (DN) is a complication of diabetes mellitus (DM) and the main cause of excess mortality in patients with type 2 DM. The pathogenesis and progression of DN are closely associated with disorders of glucose and lipid metabolism. As a member of the sirtuin family, SIRT6 has deacetylation, defatty-acylation, and adenosine diphosphate-ribosylation enzyme activities as well as anti-aging and anticancer activities. SIRT6 plays an important role in glucose and lipid metabolism and signaling, especially in DN. SIRT6 improves glucose and lipid metabolism by controlling glycolysis and gluconeogenesis, affecting insulin secretion and transmission and regulating lipid decomposition, transport, and synthesis. Targeting SIRT6 may provide a new therapeutic strategy for DN by improving glucose and lipid metabolism. This review elaborates on the important role of SIRT6 in glucose and lipid metabolism, discusses the potential of SIRT6 as a therapeutic target to improve glucose and lipid metabolism and alleviate DN occurrence and progression of DN, and describes the prospects for future research.

Histone Modifications in NAFLD: Mechanisms and Potential Therapy

Nonalcoholic fatty liver disease (NAFLD) is a progressive condition that encompasses a spectrum of liver disorders, beginning with the simple steatosis, progressing to nonalcoholic steatohepatitis (NASH), and possibly leading to more severe diseases, including liver cirrhosis and hepatocellular carcinoma (HCC). In recent years, the prevalence of NAFLD has increased due to a shift towards energy-dense dietary patterns and a sedentary lifestyle. NAFLD is also strongly associated with metabolic disorders such as obesity and hyperlipidemia. The progression of NAFLD could be influenced by a variety of factors, such as diet, genetic factors, and even epigenetic factors. In contrast to genetic factors, epigenetic factors, including histone modifications, exhibit dynamic and reversible features. Therefore, the epigenetic regulation of the initiation and progression of NAFLD is one of the directions under intensive investigation in terms of pathogenic mechanisms and possible therapeutic interventions. This review aims to discuss the possible mechanisms and the crucial role of histone modifications in the framework of epigenetic regulation in NAFLD, which may provide potential therapeutic targets and a scientific basis for the treatment of NAFLD.

Protocol to purify the histone deacetylase SIRT6 and assess its activity in vitro

The histone deacetylase known as sirtuin 6 (SIRT6) deacetylates both histone and non-histone proteins but has low deacetylase activity in vitro. Here, we present a protocol to monitor SIRT6-mediated deacetylation of long-chain acyl-CoA synthase 5 in the presence of palmitic acid. We describe the purification of His-SIRT6 and a Flag-tagged substrate. We then detail a deacetylation assay protocol that can be widely applied to study other SIRT6-mediated deacetylation events and the effect of SIRT6 mutations on its activity. For complete details on the use and execution of this protocol, please refer to Hou et al. (2022).¹.

Association between abnormal lipid metabolism and tumor

Metabolic Reprogramming is a sign of tumor, and as one of the three major substances metabolism, lipid has an obvious impact. Abnormal lipid metabolism is related to the occurrence of various diseases, and the proportion of people with abnormal lipid metabolism is increasing year by year. Lipid metabolism is involved in the occurrence, development, invasion, and metastasis of tumors by regulating various oncogenic signal pathways. The differences in lipid metabolism among different tumors are related to various factors such as tumor origin, regulation of lipid metabolism pathways, and diet. This article reviews the synthesis and regulatory pathways of lipids, as well as the research progress on cholesterol, triglycerides, sphingolipids, lipid related lipid rafts, adipocytes, lipid droplets, and lipid-lowering drugs in relation to tumors and their drug resistance. It also points out the limitations of current research and potential tumor treatment targets and drugs in the lipid metabolism pathway. Research and intervention on lipid metabolism abnormalities may provide new ideas for the treatment and survival prognosis of tumors.

Comprehensive Proteome and Acetyl-Proteome Atlas Reveals Hepatic Lipid Metabolism in Layer Hens with Fatty Liver Hemorrhagic Syndrome

The feeding of high-energy and low-protein diets often induces fatty liver hemorrhagic syndrome (FLHS) in laying hens. However, the mechanism of hepatic fat accumulation in hens with FLHS remains uncertain. In this research, a comprehensive hepatic proteome and acetyl-proteome analysis was performed in both normal and FLHS-affected hens. The results indicated that the upregulated proteins were primarily associated with fat digestion and absorption, the biosynthesis of unsaturated fatty acids, and glycerophospholipid metabolism, while the downregulated proteins were mainly related to bile secretion and amino acid metabolism. Furthermore, the significant acetylated proteins were largely involved in ribosome and fatty acid degradation, and the PPAR signaling pathway, while the significant deacetylated proteins were related to valine, leucine, and isoleucine degradation in laying hens with FLHS. Overall, these results demonstrate that acetylation inhibits hepatic fatty acid oxidation and transport in hens with FLHS, and mainly exerts its effects by affecting protein activity rather than expression. This study provides new nutritional regulation options to alleviate FLHS in laying hens.