DGAT2 inhibition blocks SREBP-1 cleavage and improves hepatic steatosis by increasing phosphatidylethanolamine in the ER

Gut microbiota regulates hepatic ketogenesis and lipid accumulation in ketogenic diet-induced hyperketonemia by disrupting bile acid metabolism

The ketogenic diet (KD) induces prolonged hyperketonemia, characterized by elevated circulating level of β-hydroxybutyrate. However, the KD can negatively affect host metabolic health by altering the gut microbial community. Despite this, the regulatory effect of the gut microbiota on hepatic ketogenesis and triacylglycerol (TAG) accumulation during a KD remains poorly understood. Here, we hypothesized that the commensal bacterium regulates hepatic lipid metabolism in association with KD-induced hyperketonemia. The KD disrupts the remodeling of the gut microbiota following antibiotic-induced depletion. The capacity for ketogenesis and the severity of TAG accumulation in the liver closely correlated with changes in the gut microbial composition and the up-regulation of hepatic farnesoid X receptor (FXR), peroxisome proliferator-activated receptor alpha (PPARα), and diacylglycerol O-acyltransferase 2 (DGAT2), which were modulated by bile acid metabolism through the gut-liver axis. The commensal bacterium Clostridium perfringens type A is particularly implicated in prolonged hyperketonemia, exacerbating hepatic ketogenesis and steatosis by disrupting secondary bile acid metabolism. The increased conversion of deoxycholic acid to 12-ketolithocholic acid represents a critical microbial pathway during C. perfringens colonization. These findings illuminate the adverse effects of the gut microbiota on hepatic adaptation to a KD and highlight the regulatory role of C. perfringens in ketonic states.

Spatial lipidomics reveals sphingolipid metabolism as anti-fibrotic target in the liver

BACKGROUND AND AIMS

Steatotic liver disease (SLD), which encompasses various causes of fat accumulation in the liver, is a major cause of liver fibrosis. Understanding the specific mechanisms of lipotoxicity, dysregulated lipid metabolism, and the role of different hepatic cell types involved in fibrogenesis is crucial for therapy development.

METHODS

We analysed liver tissue from SLD patients and 3 mouse models. We combined bulk/spatial lipidomics, transcriptomics, imaging mass cytometry (IMC) and analysis of published spatial and single-cell RNA sequencing (scRNA-seq) data to explore the metabolic microenvironment in fibrosis. Pharmacological inhibition of sphingolipid metabolism with myriocin, fumonisin B1, miglustat and D-PDMP was carried out in hepatic stellate cells (HSCs) and human precision cut liver slices (hPCLSs).

RESULTS

Bulk lipidomics revealed increased glycosphingolipids, ether lipids and saturated phosphatidylcholines in fibrotic samples. Spatial lipidomics detected >40 lipid species enriched within fibrotic regions, notably sphingomyelin (SM) 34:1. Using bulk transcriptomics (mouse) and analysis of published spatial transcriptomics data (human) we found that sphingolipid metabolism was also dysregulated in fibrosis at transcriptome level, with increased gene expression for ceramide and glycosphingolipid synthesis. Analysis of human scRNA-seq data showed that sphingolipid-related genes were widely expressed in non-parenchymal cells. By integrating spatial lipidomics with IMC of hepatic cell markers, we found excellent spatial correlation between sphingolipids, such as SM(34:1), and myofibroblasts. Inhibiting sphingolipid metabolism resulted in anti-fibrotic effects in HSCs and hPCLSs.

CONCLUSIONS

Our spatial multi-omics approach suggests cell type-specific mechanisms of fibrogenesis involving sphingolipid metabolism. Importantly, sphingolipid metabolic pathways are modifiable targets, which may have potential as an anti-fibrotic therapeutic strategy.

Unlocking the lipid code: SREBPs as key drivers in gastrointestinal tumour metabolism

In recent years, metabolic reprogramming has emerged as a significant breakthrough in elucidating the onset and progression of gastrointestinal (GI) malignancies. As central regulatory hubs for lipid metabolism, sterol regulatory element binding proteins (SREBPs) integrate dietary metabolic signals and carcinogenic stimuli through subtype-specific mechanisms, thereby promoting malignant tumour phenotypes. In this review, we first present the molecular background, structural characteristics, and posttranscriptional regulatory networks associated with SREBPs. We subsequently describe a systematic analysis of the distinct activation patterns of SREBPs in liver, gastric, colorectal, and other gastrointestinal cancers. Furthermore, we explore targeted intervention strategies for different SREBP subtypes, including small molecule inhibitors (such as fatostatin, which inhibits SREBP cleavage), natural compounds (such as berberine, which modulates the AMPK/mTOR pathway), and statin-mediated inhibition of the mevalonic acid pathway. These strategies may enhance tumour cell sensitivity to chemotherapeutic agents (such as 5-FU, gezil, and tabine) and improve the response to synergistic chemoradiotherapy by reversing adaptive metabolic resistance driven by the tumour microenvironment. Through this review, we hope to provide new insights into precise interventions targeting various subtypes of the SREBP molecule.

Molecular insights into human phosphatidylserine synthase 2 and its regulation of SREBP pathways

Homologous proteins share similar sequences, enabling them to work together in cells to support normal physiological functions. Phosphatidylserine synthases 1 and 2 (PSS1 and PSS2) are homologous enzymes that catalyze the synthesis of phosphatidylserine (PS) from different substrates. PSS2 shows a preference for phosphatidylethanolamine (PE) as its substrate, whereas PSS1 can utilize either PE or phosphatidylcholine. Previous studies showed that inhibiting PSS1 promotes SREBP-2 cleavage. Interestingly, despite their homology, our findings reveal that PSS2 exerts an opposing effect on the cleavage of both SREBP-1 and SREBP-2. We resolved the cryo-electron microscopy (cryo-EM) structure of human PSS2 at 3.3 Å resolution. Structural comparison of the catalytic cavities between PSS1 and PSS2 along with molecular dynamics simulations uncovers the molecular details behind the substrate preference of PSS2 for PE. The lipidomic analysis showed that PSS2 deficiency leads to PE accumulation in the endoplasmic reticulum, which has been shown to inhibit the cleavage of sterol regulatory element-binding proteins (SREBPs) in mice. Thus, our findings reveal the intricate network of intracellular phospholipid metabolism and underscore the distinct regulatory roles of homologous proteins in cellular activities.

Amyloid-β induces lipid droplet-mediated microglial dysfunction via the enzyme DGAT2 in Alzheimer's disease

Microglial phagocytosis genes have been linked to increased risk for Alzheimer's disease (AD), but the mechanisms translating genetic association to cellular dysfunction remain unknown. Here, we showed that microglia formed lipid droplets (LDs) upon amyloid-β (Aβ) exposure and that LD loads increased with proximity to amyloid plaques in brains from individuals with AD and the 5xFAD mouse model. LD-laden microglia exhibited defects in Aβ phagocytosis, and unbiased lipidomic analyses identified a parallel decrease in free fatty acids (FFAs) and increase in triacylglycerols (TGs) as the key metabolic transition underlying LD formation. Diacylglycerol O-acyltransferase 2 (DGAT2)-a key enzyme that converts FFAs to TGs-promoted microglial LD formation and was increased in mouse 5xFAD and human AD brains. Pharmacologically targeting DGAT2 improved microglial uptake of Aβ and reduced plaque load and neuronal damage in 5xFAD mice. These findings identify a lipid-mediated mechanism underlying microglial dysfunction that could become a therapeutic target for AD.

SREBP1-Dependent Metabolism as a Potential Target for Breast Cancer Risk Reduction

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Oroxylin A ameliorates non-alcoholic fatty liver disease by modulating oxidative stress and ferroptosis through the Nrf2 pathway

Non-alcoholic fatty liver disease (NAFLD) is a prevalent and progressive liver disorder posing a global health challenge. Oroxylin A, a naturally occurring flavonoid, with a broad spectrum of pharmacological activities. This study aimed to explore the therapeutic potential of oroxylin A and unravel its molecular mechanisms in mitigating high-fat diet (HFD)-induced NAFLD in murine models. Wild-type (WT) and nuclear factor erythroid 2-related factor 2 knockout (Nrf2-/-) mice were administered a HFD to generate in vivo models, while free fatty acids-treated HepG2 cells served as the in vitro model. To investigate the effects of oroxylin A, serum and liver biochemical markers, hepatic histology, lipid metabolism, and oxidative stress were assessed in a NAFLD mouse model. The underlying mechanisms of oroxylin A were further explored through Western blotting, immunohistochemistry, and immunofluorescence analysis. Oroxylin A mitigated hepatic steatosis and injury by reducing liver index, AST, ALT, TG, and TC levels, improving histology, and restoring lipid metabolism. Glucose and insulin tolerance tests demonstrated improved glucose homeostasis and insulin sensitivity. Moreover, oroxylin A suppressed inflammation, apoptosis, and fibrosis, while enhancing antioxidant defenses, and improving mitochondrial function. Mechanistically, oroxylin A activated the Keap1/Nrf2/GPX4/SLC7A11 axis, upregulating Nrf2 and HO-1. These effects were abolished in Nrf2-/- mice. In vitro results were consistent, and molecular docking, dynamics simulations, and CETSA confirmed its direct Keap1 binding. Oroxylin A protects against NAFLD by modulating the Nrf2 pathway, reducing oxidative stress and ferroptosis, making it a promising candidate for clinical NAFLD therapy.

Fu brick tea supplementation ameliorates non-alcoholic fatty liver disease and associated endotoxemia via maintaining intestinal homeostasis and remodeling hepatic immune microenvironment

Non-alcoholic fatty liver disease (NAFLD) is a prevalent disorder of excessive fat accumulation and inflammation in the liver that currently lacks effective therapeutic interventions. Fu brick tea (FBT) has been shown to ameliorate liver damage and modulate gut microbiota dysbiosis in NAFLD, but the potential mechanisms have not been comprehensively elucidated, especailly whether its hepatoprotective effects are determined to depend on the homeostasis of gut microbiota, intestinal barrier function and hepatic immune microenvironment. In this study, our results further demonstrated that FBT not only alleviated NAFLD symptoms and related endotoxemia in high-fat diet (HFD)-fed rats, but also attenuated intestinal barrier dysfunction and associated inflammation, also confirmed in Caco-2 cell experiment. Meanwhile, FBT intervention significantly relieved HFD-induced gut microbiota dysbiosis, characterized by increased diversity and composition, particularly facilitating beneficial microbes, including short chain fatty acids (SCFAs) and bile acids producers, such as Blautia and Fusicatenibacter, and inhibiting Gram-negative bacteria, such as Prevotella_9 and Phascolarctobacterium. Also, the gut microbiota-dependent hepatoprotective effects of FBT were verified by fecal microbiota transplantation (FMT) experiment. Thus, the beneficial moulation of gut microbiota altered by FBT in levels of SCFAs, bile acids and lipopolysaccharides, intestinal barrier function and TLR4/NF-κB pathway contributed to alleviate liver steatosis and inflammation. Additionally, the hepatoprotective effects of FBT was further demonstrated by suppressing Kupffer cell activation and regulating lipid metabolism using an ex vivo model of liver organoid. Therefore, FBT supplementation can maintain intenstinal homeostasis and remodel hepatic immune microenvironment to prevent NAFLD and associated endotoxemia.

Transcriptional landscape and chromatin accessibility reveal key regulators for liver regenerative initiation and organoid formation

Liver regeneration is a well-organized and phase-restricted process that involves chromatin remodeling and transcriptional alterations. However, the specific transcription factors (TFs) that act as key "switches" to initiate hepatocyte regeneration and organoid formation remain unclear. Comprehensive integration of RNA sequencing and ATAC sequencing reveals that ATF3 representing "Initiation_on" TF and ONECUT2 representing "Initiation_off" TF transiently modulate the occupancy of target promoters to license liver cells for regeneration. Knockdown of Atf3 or overexpression of Onecut2 not only reduces organoid formation but also delays tissue-damage repair after PHx or CCl4 treatment. Mechanistically, we demonstrate that ATF3 binds to the promoter of Slc7a5 to activate mTOR signals while the Hmgcs1 promoter loses ONECUT2 binding to facilitate regenerative initiation. The results identify the mechanism for initiating regeneration and reveal the remodeling of transcriptional landscapes and chromatin accessibility, thereby providing potential therapeutic targets for liver diseases with regenerative defects.

Targeting PNPLA3 to Treat MASH and MASH Related Fibrosis and Cirrhosis

Metabolic dysfunction-associated steatotic liver disease (MASLD) is caused by metabolic triggers and genetic predisposition. Among the genetic MASLD risk variants identified today, the common PNPLA3 148M variant exerts the largest effect size of MASLD heritability. The PNPLA3 148M protein is causatively linked to the development of liver steatosis, inflammation and fibrosis in experimental studies and is therefore an appealing target for therapeutic approaches to treat this disease. Several PNPLA3 targeted approaches are currently being evaluated in clinical trials for the treatment of metabolic dysfunction-associated steatohepatitis (MASH), the most severe form of MASLD and promising proof of principle data with reduced liver fat content in homozygous PNPLA3 148M risk allele carriers has been reported from phase 1 trials following hepatic silencing of PNPLA3. Thus, targeting PNPLA3, the strongest genetic determinant of MASH may hold promise as the first precision medicine for the treatment of this disease. A histological endpoint-based phase 2b study has been initiated and several more are expected to be initiated to evaluate treatment effects on histological MASH and liver fibrosis in participants being homozygous for the PNPLA3 148M risk allele variant. The scope of this mini-review is to briefly describe the PNPLA3 148M genetics, function and preclinical experimental evidence with therapeutic approaches targeting PNPLA3 as well as to summarise the PNPLA3 based therapies currently in clinical development.

Liver gene expression and its rewiring in hepatic steatosis are controlled by PI3Kα-dependent hepatocyte signaling

Insulin and other growth factors are key regulators of liver gene expression, including in metabolic diseases. Most of the phosphoinositide 3-kinase (PI3K) activity induced by insulin is considered to be dependent on PI3Kα. We used mice lacking p110α, the catalytic subunit of PI3Kα, to investigate its role in the regulation of liver gene expression in health and in metabolic dysfunction-associated steatotic liver disease (MASLD). The absence of hepatocyte PI3Kα reduced maximal insulin-induced PI3K activity and signaling, promoted glucose intolerance in lean mice and significantly regulated liver gene expression, including insulin-sensitive genes, in ad libitum feeding. Some of the defective regulation of gene expression in response to hepatocyte-restricted insulin receptor deletion was related to PI3Kα signaling. In addition, though PI3Kα deletion in hepatocytes promoted insulin resistance, it was protective against steatotic liver disease in diet-induced obesity. In the absence of hepatocyte PI3Kα, the effect of diet-induced obesity on liver gene expression was significantly altered, with changes in rhythmic gene expression in liver. Altogether, this study highlights the specific role of p110α in the control of liver gene expression in physiology and in the metabolic rewiring that occurs during MASLD.

Curcumin inhibits pancreatic steatosis in mice with a high-fat diet through the YAP/p53 pathway and confirmed through ultrasonic imaging

AIMS

To investigate the mechanism by which curcumin inhibits pancreatic steatosis (PS), and the diagnostic value of ultrasonography in the pancreas of mice with obesity.

MATERIALS AND METHODS

Male mice were randomly divided into normal chow diet (NC), high-fat diet (HFD), and HFD + 80 mg/kg curcumin groups (HC) and maintained for 12 weeks to induce PS. Weight and fasting blood glucose (FBG) were collected biweekly and oral glucose tolerance test and insulin levels were measured in the final week. The morphology and fat infiltration of pancreas were observed by ultrasonography and histology. The level of blood lipid was detected, and the expression of genes and proteins related to lipid metabolism in pancreatic tissues was analyzed.

RESULTS

Compared to the NC and HC groups, the HFD group had higher body weight, cholesterol, triglycerides, and LDL and HDL levels, along with increased inflammation and fat deposits in the pancreas. The HC group had milder inflammation and lower glucose intolerance and insulin resistance (P<0.05). The gray value, steatosis scores, immunohistochemical results, and ORO staining were significantly correlated (P<0.05). Correlations were found between gray values, steatosis scores, and ORO staining (P<0.05). In comparison to the HFD, expression of LATS2, FAS, YAP, and SREBP2 were downregulated and p53 was upregulated in the HC group.

CONCLUSION

Curcumin is a potential modulator of insulin resistance and SREBP2 expression, with its underlying mechanism possibly mediated through the YAP/p53 signaling pathway. Pancreatic steatosis exhibits distinct ultrasonographic features, making ultrasound an effective diagnostic tool for identifying the condition.

SOX9 Overexpression Ameliorates Metabolic Dysfunction-associated Steatohepatitis Through Activation of the AMPK Pathway

Background and Aims

The transcription factor sex-determining region Y-related high-mobility group-box gene 9 (SOX9) plays a critical role in organ development. Although SOX9 has been implicated in regulating lipid metabolism in vitro, its specific role in metabolic dysfunction-associated steatohepatitis (MASH) remains poorly understood. This study aimed to investigate the role of SOX9 in MASH pathogenesis and explored the underlying mechanisms.

Methods

MASH models were established using mice fed either a methionine- and choline-deficient (MCD) diet or a high-fat, high-fructose diet. To evaluate the effects of SOX9, hepatocyte-specific SOX9 deletion or overexpression was performed. Lipidomic analyses were conducted to assess how SOX9 influences hepatic lipid metabolism. RNA sequencing was employed to identify pathways modulated by SOX9 during MASH progression. To elucidate the mechanism further, HepG2 cells were treated with an adenosine monophosphate-activated protein kinase (AMPK) inhibitor to test whether SOX9 acts via AMPK activation.

Results

SOX9 expression was significantly elevated in hepatocytes of MASH mice. Hepatocyte-specific SOX9 deletion exacerbated MCD-induced MASH, whereas overexpression of SOX9 mitigated high-fat, high-fructose-induced MASH. Lipidomic and RNA sequencing analyses revealed that SOX9 suppresses the expression of genes associated with lipid metabolism, inflammation, and fibrosis in MCD-fed mice. Furthermore, SOX9 deletion inhibited AMPK pathway activation, while SOX9 overexpression enhanced it. Notably, administration of an AMPK inhibitor negated the protective effects of SOX9 overexpression, leading to increased lipid accumulation in HepG2 cells.

Conclusions

Our findings demonstrate that SOX9 overexpression alleviates hepatic lipid accumulation in MASH by activating the AMPK pathway. These results highlight SOX9 as a promising therapeutic target for treating MASH.

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.

Regulation of lipid dysmetabolism and neuroinflammation linked with Alzheimer's disease through modulation of Dgat2

Alzheimer's disease (AD) is a progressive neurodegenerative disorder marked by amyloid-β (Aβ) plaque accumulation, cognitive decline, lipid dysregulation, and neuroinflammation. While mutations in the Amyloid Precursor Protein (APP) and Aβ42 accumulation contribute to AD, the mechanisms linking Aβ to lipid metabolism and neuroinflammation remain unclear. Using Drosophila models, we show that App NLG and Aβ42 expression causes locomotor deficits, disrupted sleep, memory impairments, lipid accumulation, synaptic loss, and neuroinflammation. Similar lipid and inflammatory changes are observed in the App NLG-F knock-in mouse model, reinforcing their role in AD pathogenesis. We identify diacylglycerol O-acyltransferase 2 (Dgat2), a key lipid metabolism enzyme, as a modulator of AD phenotypes. In Drosophila and mouse AD models, Dgat2 levels and its transcription factors are altered. Dgat2 knockdown in Drosophila reduced lipid accumulation, restored synaptic integrity, improved locomotor and cognitive function, and mitigated neuroinflammation. Additionally, Dgat2 modulation improved sleep and circadian rhythms. In App NLG-F mice, Dgat2 inhibition decreased neuroinflammation and reduced AD risk gene expression. These findings highlight the intricate link between amyloid pathology, lipid dysregulation, and neuroinflammation, suggesting that targeting Dgat2 may offer a novel therapeutic approach for AD. Conserved lipid homeostasis mechanisms across species provide valuable translational insights.

Exploration of Novel Metabolic Mechanisms Underlying Primary Biliary Cholangitis Using Hepatic Metabolomics, Lipidomics, and Proteomics Analysis

Metabolic reprogramming is important in primary biliary cholangitis (PBC) development. However, studies investigating the metabolic signature within the liver of PBC patients are limited. In this study, liver biopsies from 31 PBC patients and 15 healthy controls were collected, and comprehensive metabolomics, lipidomics, and proteomics analysis were conducted to characterize the metabolic landscape in PBC. We observed distinct lipidome remodeling in PBC with increased polyunsaturated fatty acid levels and augmented fatty acid β-oxidation (FAO), evidenced by the increased acylcarnitine levels and upregulated expression of proteins involved in FAO. Notably, PBC patients exhibited an increase in glucose-6-phosphate (G6P) and purines, alongside a reduction in pyruvate, suggesting impaired glycolysis and increased purines biosynthesis in PBC. Additionally, the accumulation of bile acids as well as a decrease in branched chain amino acids and aromatic amino acids were observed in PBC liver. We also observed an aberrant upregulation of proteins associated with ductular reaction, apoptosis, and autophagy. In conclusion, our study highlighted substantial metabolic reprogramming in glycolysis, fatty acid metabolism, and purine biosynthesis, coupled with aberrant upregulation of proteins associated with apoptosis and autophagy in PBC patients. Targeting the specific metabolic reprogramming may offer potential targets for the therapeutic intervention of PBC.

Drug Advances in NAFLD: Individual and Combination Treatment Strategies of Natural Products and Small-Synthetic-Molecule Drugs

Non-alcoholic fatty liver disease (NAFLD) has become the most common chronic liver disease and is closely associated with metabolic diseases such as obesity, type 2 diabetes mellitus (T2DM), and metabolic syndrome. However, effective treatment strategies for NAFLD are still lacking. In recent years, progress has been made in understanding the pathogenesis of NAFLD, identifying multiple therapeutic targets and providing new directions for drug development. This review summarizes the recent advances in the treatment of NAFLD, focusing on the mechanisms of action of natural products, small-synthetic-molecule drugs, and combination therapy strategies. This review aims to provide new insights and strategies in treating NAFLD.

Casz1 and Znf101/Zfp961 differentially regulate apolipoproteins A1 and B, alter plasma lipoproteins, and reduce atherosclerosis

High apolipoprotein B-containing (apoB-containing) low-density lipoproteins (LDLs) and low apoA1-containing high-density lipoproteins (HDLs) are associated with atherosclerotic cardiovascular diseases. In search of a molecular regulator that could simultaneously and reciprocally control both LDL and HDL levels, we screened a microRNA (miR) library using human hepatoma Huh-7 cells. We identified miR-541-3p that both significantly decreases apoB and increases apoA1 expression by inducing mRNA degradation of 2 different transcription factors, Znf101 and Casz1. We found that Znf101 enhances apoB expression, while Casz1 represses apoA1 expression. The hepatic knockdown of Casz1 in mice increased plasma apoA1, HDL, and cholesterol efflux capacity. The hepatic knockdown of Zfp961, an ortholog of Znf101, reduced lipogenesis and production of triglyceride-rich lipoproteins and atherosclerosis, without causing hepatic lipid accumulation. This study identifies hepatic Znf101/Zfp961 and Casz1 as potential therapeutic targets to alter plasma lipoproteins and reduce atherosclerosis without causing liver steatosis.

Silybin A from Silybum marianum reprograms lipid metabolism to induce a cell fate-dependent class switch from triglycerides to phospholipids

Rationale: Silybum marianum is used to protect against degenerative liver damage. The molecular mechanisms of its bioactive component, silybin, remained enigmatic, although membrane-stabilizing properties, modulation of membrane protein function, and metabolic regulation have been discussed for decades. Methods: Experiments were performed with hepatocyte cell lines and primary monocytes in vitro under both basal and stressed conditions, and in mice in vivo. Quantitative lipidomics was used to detect changes in phospholipids and triglycerides. Key findings were confirmed by Western blotting, quantitative PCR, microscopy, enzyme activity assays, metabolic flux studies, and functional relationships were investigated using selective inhibitors. Results: We show that specifically the stereoisomer silybin A decreases triglyceride levels and lipid droplet content, while enriching major phospholipid classes and maintaining a homeostatic phospholipid composition in human hepatocytes in vitro and in mouse liver in vivo under normal and pre-disease conditions. Conversely, in cell-based disease models of lipid overload and lipotoxic stress, silybin treatment primarily depletes triglycerides. Mechanistically, silymarin/silybin suppresses phospholipid-degrading enzymes, induces phospholipid biosynthesis to varying degrees depending on the conditions, and down-regulates triglyceride remodeling/biosynthesis, while inducing complex changes in sterol and fatty acid metabolism. Structure-activity relationship studies highlight the importance of the 1,4-benzodioxane ring configuration of silybin A in triglyceride reduction and the saturated 2,3-bond of the flavanonol moiety in phospholipid accumulation. Enrichment of hepatic phospholipids and intracellular membrane expansion are associated with a heightened biotransformation capacity. Conclusion: Our study deciphers the structural features of silybin contributing to hepatic lipid remodeling and suggests that silymarin/silybin protects the liver in individuals with mild metabolic dysregulation, involving a lipid class switch from triglycerides to phospholipids, whereas it may be less effective in disease states associated with severe metabolic dysregulation.

Z-Ligustilide: A Potential Therapeutic Agent for Atherosclerosis Complicating Cerebrovascular Disease

Atherosclerosis (AS) is one of the major catalysts of ischemic cerebrovascular disease, and the death and disease burden from AS and its cerebrovascular complications are increasing. Z-ligustilide (Z-LIG) is a key active ingredient in Angelica sinensis (Oliv.) Diels and Ligusticum chuanxiong Hort. In this paper, we first introduced LIG's physicochemical properties and pharmacokinetics. Then, we reviewed Z-LIG's intervention and therapeutic mechanisms on AS and its cerebrovascular complications. The mechanisms of Z-LIG intervention in AS include improving lipid metabolism, antioxidant and anti-inflammatory effects, protecting vascular endothelium, and inhibiting vascular endothelial fibrosis, pathological thickening, and plaque calcification. In ischemic cerebrovascular diseases complicated by AS, Z-LIG exerts practical neuroprotective effects in ischemic stroke (IS), transient ischemic attack (TIA), and vascular dementia (VaD) through anti-neuroinflammatory, anti-oxidation, anti-neuronal apoptosis, protection of the blood-brain barrier, promotion of mitochondrial division and angiogenesis, improvement of cholinergic activity, inhibition of astrocyte proliferation, and endoplasmic reticulum stress. This paper aims to provide a basis for subsequent studies of Z-LIG in the prevention and treatment of AS and its cerebrovascular complications and, thus, to promote the development of interventional drugs for AS.

Contribution of gut microbiota to hepatic steatosis following F-53B exposure from the perspective of glucose and fatty acid metabolism

Altered gut microbiota is a pathogenic mechanism of 6:2 Cl-PFESA (F-53B)-induced hepatic steatosis, indicated by correlations between gut microbiota and lipid indices. However, the detailed mechanism remains unknown. In this study, adult zebrafish were exposed to 0.25, 5 and 100 μg/L F-53B for 28 days to explore how microbiota regulate hepatic lipid metabolism from the perspective of glucose and fatty acid metabolism. Results showed glucose and fatty acids were transported from blood into liver after 100 μg/L F-53B exposure, in which glucose was further transformed into acetyl-CoA and fatty acid. The accumulated fatty acids were then converted into triglycerides (TGs), inducing hepatic steatosis. Changes in the abundances of certain gut microbiota contributed to the above processes, which was verified by the fact that the levels of g_Crenobacter, g_Shewanella, and g_Vibrio restored to control levels after Lactobacillus rhamnosus GG intervention, and the levels of their related lipid indicators recovered partially towards the control levels. 0.25 and 5 μg/L F-53B had no effect on the hepatic lipid profile due to the few changed TG synthesis related indicators. Our findings provide novel insights into lipid metabolic disorders caused by F-53B exposure, highlighting the health risks linked to gut microbial dysbiosis.

Glycerol Kinase Drives Hepatic de novo Lipogenesis and Triglyceride Synthesis in Nonalcoholic Fatty Liver by Activating SREBP-1c Transcription, Upregulating DGAT1/2 Expression, and Promoting Glycerol Metabolism

Glycerol kinase (GK) participates in triglyceride (TG) synthesis by catalyzing glycerol metabolism. Whether GK contributes to nonalcoholic fatty liver (NAFL) is unclear. The expression of hepatic Gk is found to be increased in diet-induced and genetic mouse models of NAFL and is positively associated with hepatic SREBP-1c expression and TG levels. Cholesterol and fatty acids stimulate GK expression in hepatocytes. In HFD-induced NAFL mice, knockdown of hepatic Gk decreases expression of SREBP-1c and its target lipogenic genes as well as DGAT1/2, increases serum glycerol levels, decreases serum TG levels, and attenuates hepatic TG accumulation. Overexpression of GK in hepatocytes in mice or in culture produces opposite results. Mechanistic studies reveal that GK stimulates SREBP-1c transcription directly by binding to its gene promoter and indirectly by binding to SREBP-1c protein, thereby increasing lipogenic gene expression and de novo lipogenesis. Studies with truncated GK and mutant GKs indicate that GK induces SREBP-1c transcription independently of its enzyme activity. GK contributes to lipid homeostasis under physiological conditions by catalyzing glycerol metabolism rather than by regulating SREBP-1c transcription. Collectively, these results demonstrate that increased hepatic GK promotes de novo lipogenesis and TG synthesis in NAFL by stimulating SREBP-1c transcription and DGAT1/2 expression and catalyzing glycerol metabolism.

Apolipoprotein E Induces Lipid Accumulation Through Dgat2 That Is Prevented with Time-Restricted Feeding in Drosophila

Background: Apolipoprotein E (ApoE) is the leading genetic risk factor for late-onset Alzheimer's disease (AD), which is the leading cause of dementia worldwide. Most people have two ApoE-ε3 (ApoE3) alleles, while ApoE-ε2 (ApoE2) is protective from AD, and ApoE-ε4 (ApoE4) confers AD risk. How these alleles modulate AD risk is not clearly defined, and ApoE's role in lipid metabolism is also not fully known. Lipid droplets increase in AD. However, how ApoE contributes to lipid accumulation in the brain remains unknown. Methods: Here, we use Drosophila to study the effects of ApoE alleles on lipid accumulation in the brain and muscle in a cell-autonomous and non-cell-autonomous manner. Results: We report that pan-neuronal expression of each ApoE allele induces lipid accumulation specifically in the brain, but not in the muscle. However, this was not the case when expressed with muscle-specific drivers. ApoE2- and ApoE3-induced lipid accumulation is dependent on the expression of Dgat2, a key regulator of triacylglycerol production, while ApoE4 still induces lipid accumulation even with knock-down of Dgat2. Additionally, we find that implementation of time-restricted feeding (TRF), a dietary intervention in which food access only occurs in the active period (day), prevents ApoE-induced lipid accumulation in the brain of flies and modulates lipid metabolism genes. Conclusions: Altogether, our results demonstrate that ApoE induces lipid accumulation in the brain, that ApoE4 is unique in causing lipid accumulation independent of Dgat2, and that TRF prevents ApoE-induced lipid accumulation. These results support the idea that lipid metabolism is critical in AD, and that TRF could be a promising therapeutic approach to prevent ApoE-associated dysfunction in lipid metabolism.

Molecular Regulation and Therapeutic Targeting of VLDL Production in Cardiometabolic Disease

There exists a complex relationship between steatotic liver disease (SLD) and atherosclerotic cardiovascular disease (CVD). CVD is a leading cause of morbidity and mortality among individuals with SLD, particularly those with metabolic dysfunction-associated SLD (MASLD), a significant proportion of whom also exhibit features of insulin resistance. Recent evidence supports an expanded role of very low-density lipoprotein (VLDL) in the pathogenesis of CVD in patients, both with and without associated metabolic dysfunction. VLDL represents the major vehicle for exporting neutral lipid from hepatocytes, with each particle containing one molecule of apolipoproteinB100 (APOB100). VLDL production becomes dysregulated under conditions characteristic of MASLD including steatosis and insulin resistance. Insulin resistance not only affects VLDL production but also mediates the pathogenesis of atherosclerotic CVD. VLDL assembly and secretion therefore represents an important pathway in the setting of cardiometabolic disease and offers several candidates for therapeutic targeting, particularly in metabolically complex patients with MASLD at increased risk of atherosclerotic CVD. Here we review the clinical significance as well as the translational and therapeutic potential of key regulatory steps impacting VLDL initiation, maturation, secretion, catabolism, and clearance.

The role of DGAT1 and DGAT2 in tumor progression via fatty acid metabolism: A comprehensive review

Fatty acid metabolism is a complex biochemical process, including the production, breakdown and application of fatty acids. Not only is it an important component of lipid metabolism, fatty acid metabolism is also connected to the energy metabolism pathways of cells and plays a vital role in maintaining the energy balance of organisms. Diacylglycerol-O-acyltransferase 1 (DGAT1) and Diacylglycerol-O-acyltransferase 2 (DGAT2) are key components in regulating lipid metabolism, which provide energy for cell proliferation and growth. Recent studies have shown that DGAT1 and DGAT2 influence tumor progression through fatty acid metabolism in cancer. Although DGAT1 and DGAT2 have similar names, they differ significantly in various aspects and play distinct roles in individual tumors. A comparative analysis of the physiological roles of these enzymes and their differential expressions in different types of tumors will enhance our understanding of their unique characteristics. This article summarizes the characteristics of tumor fatty acid metabolism and explains how DGAT1 and DGAT2 specifically promote tumor progression. In addition, this review discusses the potential of lipid-lowering drugs in tumor treatment, providing a new perspective on targeting fatty acid metabolism to inhibit tumor progression in the future, while emphasizing the importance of DGAT1 and DGAT2 as potential targets for tumor treatment.

The emerging role of ethanolamine phosphate phospholyase in regulating hepatic phosphatidylethanolamine and plasma lipoprotein metabolism in mice

Ethanolamine phosphate phospholyase (ETNPPL) is an enzyme that irreversibly degrades phospho-ethanolamine (p-ETN), an intermediate in the Kennedy pathway of phosphatidylethanolamine (PE) biosynthesis. PE is the second most abundant phospholipid in mammalian membranes. Disturbance of hepatic phospholipid homeostasis has been linked to the development of metabolic dysfunction-associated steatotic liver disease (MASLD). We generated whole-body Etnppl knockout mice to investigate the impact of genetic deletion of Etnppl on hepatic lipid metabolism. Primary hepatocytes isolated from Etnppl-/- mice showed increased conversion of [3H]ethanolamine to [3H]p-ETN and [3H]PE compared to Etnppl+/+ mice. Male and female Etnppl+/+ and Etnppl-/- mice were fed either a chow or a western-type diet (WTD). Irrespective of diet, Etnppl-/- mice had elevated fasting levels of total plasma cholesterol, triglyceride (TG) and apolipoprotein B100 (VLDL particles). Interestingly, hepatic TG secretion was unchanged between groups. Although hepatic lipids (phosphatidylcholine (PC), PE, TG, and cholesterol) were not different between mice, RNA sequencing analysis showed downregulation in genes related to cholesterol biosynthesis in Etnppl-/- mice. Furthermore, hepatic low-density lipoprotein receptor-related protein1 (LRP1) protein level was lower in female Etnppl-/- mice, which may indicate reduced uptake of remnant VLDL particles from circulation. Hepatic PE levels were only increased in WTD-fed female Etnppl-/- mice, not chow diet-fed mice. However, hepatic lipid accumulation and metabolic dysfunction-associated steatohepatitis (MASH) development were unchanged between Etnppl+/+ and Etnppl-/- mice. To conclude, ETNPPL has a role in regulating plasma lipoprotein metabolism independent of hepatic TG levels.

Mendelian randomization analysis of the causal relationship between serum metabolites and thoracic aortic aneurysm

Thoracic aortic aneurysm (TAA) is associated with changes in the levels of metabolites; however, the exact causal relationships remain unclear. Identifying this complex relationship may provide new insights into the pathogenesis of TAA. We used genome-wide association studies to investigate the relationship between metabolites and TAA in this study. A total of 1400 serum metabolites were investigated for their potential causal effects on the risk of TAA. We performed bidirectional and 2-sample Mendelian randomization (MR) analysis using 5 MR tests: MR-Egger, weighted mode, weighted median, inverse variance weighted (IVW), and simple mode. We also performed sensitivity analysis to verify our findings, including heterogeneity analysis using IVW and MR-Egger tests and pleiotropy analysis using the MR-Egger test. Multiple metabolites were identified as having a causal effect on the risk of TAA, particularly those related to lipid metabolites; the top 2 risk factors identified using the IVW test were 3-carboxy-4-methyl-5-pentyl-2-furanpropionate (P = .019) and 5alpha-androstan-3alpha,17alpha-diol (P = .021), whereas the 2 top protective factors were 1-stearoyl-2-docosahexaenoyl-gpc (P = .023) and 1-oleoyl-2-docosahexaenoyl-GPC (P = .005). Sensitivity analysis verified the lack of heterogeneity (P = .499, .584, .232, and .624, respectively; IVW test) or pleiotropy (P = .621, .483, .598, and .916, respectively; Egger test). Our study provides new evidence of a causal relationship between metabolites and the risk of TAA, thus providing new insights into the pathogenesis of this disease. These findings suggest a promising approach for metabolite-based therapeutic interventions.

DGAT1 and DGAT2 Inhibitors for Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD) Management: Benefits for Their Single or Combined Application

Inhibiting diacylglycerol acetyltransferase (DGAT1, DGAT2) enzymes (iDGAT1, iDGAT2), involved in triglyceride (TG) synthesis, improves hepatic steatosis in metabolic dysfunction-associated steatotic liver disease (MASLD) patients. However, their potential synergism in disease onset (SLD) and progression (metabolic dysfunction-associated steatohepatitis, fibrosis) has been poorly explored. We investigated iDGAT1 and iDGAT2 efficacy, alone or combined (iDGAT1/2) on fat accumulation and hepatocellular injury in hepatocytes (HepG2) and on fibrogenic processes in hepatic stellate cells (LX2). We further tested whether the addition of MitoQ antioxidant to iDGAT1/2 would enhance their effects. SLD and MASH conditions were reproduced in vitro by supplementing Dulbecco's Modified Eagle's Medium (DMEM) with palmitic/oleic acids (PAOA) alone (SLD-medium), or plus Lipopolisaccaride (LPS), fructose, and glucose (MASH-medium). In SLD-medium, iDGAT1 and iDGAT2 individually, and even more in combination, reduced TG synthesis in HepG2 cells. Markers of hepatocellular damage were slightly decreased after single iDGAT exposure. Conversely, iDGAT1/2 counteracted ER/oxidative stress and inflammation and enhanced mitochondrial Tricarboxylic acid cycle (TCA) and respiration. In HepG2 cells under a MASH-like condition, only iDGAT1/2 effectively ameliorated TG content and oxidative and inflammatory mediators, further improving bioenergetic balance. LX2 cells, challenged with SLD/MASH media, showed less proliferation and slower migration rates in response to iDGAT1/2 drugs. MitoQ combined with iDGAT1/2 improved cell viability and dampened free fatty acid release by stimulating β-oxidation. Dual DGAT inhibition combined with antioxidants open new perspectives for MASLD management.

Effects of emulsifiers on lipid metabolism and performance of yellow-feathered broilers

BACKGROUND

Reducing production costs while producing high-quality livestock and poultry products is an ongoing concern in the livestock industry. The addition of oil to livestock and poultry diets can enhance feed palatability and improve growth performance. Emulsifiers can be used as potential feed supplements to improve dietary energy utilization and maintain the efficient productivity of broilers. Therefore, further investigation is warranted to evaluate whether dietary emulsifier supplementation can improve the efficiency of fat utilization in the diet of yellow-feathered broilers. In the present study, the effects of adding emulsifier to the diet on lipid metabolism and the performance of yellow-feathered broilers were tested. A total of 240 yellow-feasted broilers (21-day-old) were randomly divided into 4 groups (6 replicates per group, 10 broilers per replicate, half male and half female within each replicate). The groups were as follows: the control group (fed with basal diet), the group fed with basal diet supplemented with 500 mg/kg emulsifier, the group fed with a reduced oil diet (reduced by 1%) supplemented with 500 mg/kg emulsifier, and the group fed with a reduced oil diet supplemented with 500 mg/kg emulsifier. The trial lasted for 42 days, during which the average daily feed intake, average daily gain, and feed-to-gain ratio were measured. Additionally, the expression levels of lipid metabolism-related genes in the liver, abdominal fat and each intestinal segment were assessed.

RESULTS

The results showed that compared with the basal diet group, (1) The average daily gain of the basal diet + 500 mg/kg emulsifier group significantly increased (P < 0.05), and the half-even-chamber rate was significantly increased (P < 0.05); (2) The mRNA expression levels of Cd36, Dgat2, Apob, Fatp4, Fabp2, and Mttp in the small intestine were significantly increased (P < 0.05). (3) Furthermore, liver TG content significantly decreased (P < 0.05), and the mRNA expression level of Fasn in liver was significantly decreased (P < 0.05), while the expression of Apob, Lpl, Cpt-1, and Pparα significantly increased (P < 0.05). (4) The mRNA expression levels of Lpl and Fatp4 in adipose tissue were significantly increased (P < 0.05), while the expression of Atgl was significantly decreased (P < 0.05). (5) Compared with the reduced oil diet group, the half-evading rate and abdominal fat rate of broilers in the reduced oil diet + 500 mg/kg emulsifier group were significantly increased (P < 0.05), and the serum level of LDL-C increased significantly (P < 0.05)0.6) The mRNA expression levels of Cd36, Fatp4, Dgat2, Apob, and Mttp in the small intestine were significantly increased (P < 0.05). 7) The mRNA expression levels of Fasn and Acc were significantly decreased in the liver (P < 0.05), while the mRNA expression levels of Lpin1, Dgat2, Apob, Lpl, Cpt-1, and Pparα were significantly increased (P < 0.05).

CONCLUSIONS

These results suggest that dietary emulsifier can enhance the fat utilization efficiency of broilers by increasing the small intestinal fatty acid uptake capacity, inhibiting hepatic fatty acid synthesis and promoting hepatic TG synthesis and transport capacity. This study provides valuable insights for the potential use of emulsifier supplementation to improve the performance of broiler chickens.

Role of lipid metabolism in hepatocellular carcinoma

Hepatocellular carcinoma (HCC), an aggressive malignancy with a dismal prognosis, poses a significant public health challenge. Recent research has highlighted the crucial role of lipid metabolism in HCC development, with enhanced lipid synthesis and uptake contributing to the rapid proliferation and tumorigenesis of cancer cells. Lipids, primarily synthesized and utilized in the liver, play a critical role in the pathological progression of various cancers, particularly HCC. Cancer cells undergo metabolic reprogramming, an essential adaptation to the tumor microenvironment (TME), with fatty acid metabolism emerging as a key player in this process. This review delves into intricate interplay between HCC and lipid metabolism, focusing on four key areas: de novo lipogenesis, fatty acid oxidation, dysregulated lipid metabolism of immune cells in the TME, and therapeutic strategies targeting fatty acid metabolism for HCC treatment.