Hypomorphic ASGR1 modulates lipid homeostasis via INSIG1-mediated SREBP signaling suppression

Single-Cell Sequencing and Machine Learning Integration to Identify Candidate Biomarkers in Psoriasis: INSIG1

Background

Psoriasis represents a persistent, immune-driven inflammatory condition affecting the skin, characterized by a lack of well-established biologic treatments without adverse events. Consequently, the identification of novel targets and therapeutic agents remains a pressing priority in the field of psoriasis research.

Methods

We collected single-cell RNA sequencing (scRNA-seq) datasets and inferred T cell differentiation trajectories through pseudotime analysis. Bulk transcriptome and scRNA-seq data were integrated to identify differentially expressed genes (DEGs). Machine learning was employed to screen candidate genes. Correlation analysis was used to predict the interactions between cells expressing insulin-induced gene 1 (INSIG1) and other immune cells. Finally, drug docking was performed on INSIG1, and the expression levels of INSIG1 in psoriasis were verified through clinical and in vivo experiments, and further in vivo experiments established the efficacy of tetrandrine in the treatment of psoriasis.

Results

T cells were initially categorized into seven states, with differentially expressed genes in T cells (TDEGs) identified and their functions and signaling pathways. INSIG1 emerged as a characteristic gene for psoriasis and was found to be downregulated in psoriasis and potentially negatively associated with T cells, influencing psoriasis fatty acid metabolism, as inferred from enrichment and immunoinfiltration analyses. In the cellular communication network, cells expressing INSIG1 exhibited close interactions with other immune cells through multiple signaling channels. Furthermore, drug sensitivity showed that tetrandrine stably binds to INSIG1, could be a potential therapeutic agent for psoriasis.

Conclusion

INSIG1 emerges as a specific candidate gene potentially regulating the fatty acid metabolism of patients with psoriasis. In addition, tetrandrine shows promise as a potential treatment for the condition.

The low-density lipoprotein receptor: Emerging post-transcriptional regulatory mechanisms

Cholesterol is a vital component of cellular membranes and is an essential molecule in mammalian physiology. Yet dysregulation of hepatic cholesterol metabolism and an increase in plasma cholesterol is linked to development of atherosclerotic cardiovascular disease. Maintaining tight regulation of cholesterol homeostasis is therefore essential, elegantly highlighted by the control of hepatic low-density lipoprotein receptor (LDLR) abundance and associated lipoprotein clearance. The LDLR was discovered in the 1970's in the seminal work of Brown and Goldstein. This was followed by the development of statins, which promote hepatic clearance of LDL via the LDLR pathway. The discovery two decades ago of Proprotein Convertase Subtilisin-Kexin Type 9 (PCSK9), a secreted protein that binds to the LDLR ectodomain and promotes its degradation, and the clinical development of PCSK9 inhibitors has ushered an effort to uncover additional mechanisms that govern the function and abundance of the LDLR. In recent years this has led to the identification of novel post-transcriptional and post-translational mechanisms that govern the LDLR. This review focuses on these emerging regulatory mechanisms and specifically discusses: (1) Regulation of the LDLR mRNA by RNA-binding proteins and microRNAs, (2) Ubiquitin-dependent degradation of the LDLR protein by the E3 ubiquitin ligases inducible degrader of the LDLR (IDOL) and GOLIATH (RNF130), (3) Control of the LDLR pathway by the asialoglycoprotein receptor 1 (ASGR1), and (4) The role of LDLR ectodomain shedding mediated by membrane-type 1 matrix metalloprotease (MT1-MMP), Bone morphogenetic protein 1 (BMP1), and γ-secretase. Understanding the contribution of these emerging mechanisms to regulation of the LDLR is important for the development of novel LDLR-focused lipid-lowering strategies.

ASGR1 Deficiency Inhibits Atherosclerosis in Western Diet-Fed ApoE-/- Mice by Regulating Lipoprotein Metabolism and Promoting Cholesterol Efflux

BACKGROUND

Atherosclerosis is the most common cause of cardiovascular diseases. Clinical studies indicate that loss-of-function ASGR1 (asialoglycoprotein receptor 1) is significantly associated with lower plasma cholesterol levels and reduces cardiovascular disease risk. However, the effect of ASGR1 on atherosclerosis remains incompletely understood; whether inhibition of ASGR1 causes liver injury remains controversial. Here, we comprehensively investigated the effects and the underlying molecular mechanisms of ASGR1 deficiency and overexpression on atherosclerosis and liver injury in mice.

METHODS

We engineered Asgr1 knockout mice (Asgr1-/-), Asgr1 and ApoE double-knockout mice (Asgr1-/-ApoE-/-), and ASGR1-overexpressing mice on an ApoE-/- background and then fed them different diets to assess the role of ASGR1 in atherosclerosis and liver injury.

RESULTS

After being fed a Western diet for 12 weeks, Asgr1-/-ApoE-/- mice exhibited significantly decreased atherosclerotic lesion areas in the aorta and aortic root sections, reduced plasma VLDL (very-low-density lipoprotein) cholesterol and LDL (low-density lipoprotein) cholesterol levels, decreased VLDL production, and increased fecal cholesterol contents. Conversely, ASGR1 overexpression in ApoE-/- mice increased atherosclerotic lesions in the aorta and aortic root sections, augmented plasma VLDL cholesterol and LDL cholesterol levels and VLDL production, and decreased fecal cholesterol contents. Mechanistically, ASGR1 deficiency reduced VLDL production by inhibiting the expression of MTTP (microsomal triglyceride transfer protein) and ANGPTL3 (angiopoietin-like protein 3)/ANGPTL8 (angiopoietin-like protein 8) but increasing LPL (lipoprotein lipase) activity, increased LDL uptake by increasing LDLR (LDL receptor) expression, and promoted cholesterol efflux through increasing expression of LXRα (liver X receptor-α), ABCA1 (ATP-binding cassette subfamily A member 1), ABCG5 (ATP-binding cassette subfamily G member 5), and CYP7A1 (cytochrome P450 family 7 subfamily A member 1). These underlying alterations were confirmed in ASGR1-overexpressing ApoE-/- mice. In addition, ASGR1 deficiency exacerbates liver injury in Western diet-induced Asgr1-/-ApoE-/- mice and high-fat diet-induced but not normal laboratory diet-induced and high-fat and high-cholesterol diet-induced Asgr1-/- mice, while its overexpression mitigates liver injury in Western diet-induced ASGR1-overexpressing ApoE-/- mice.

CONCLUSIONS

Inhibition of ASGR1 inhibits atherosclerosis in Western diet-fed ApoE-/- mice, suggesting that inhibiting ASGR1 may serve as a novel therapeutic strategy to treat atherosclerosis and cardiovascular diseases.

Beyond conventional treatment: ASGR1 Leading the new era of hypercholesterolemia management

Cardiovascular disease (CVD) remains a leading cause of mortality worldwide, with hypercholesterolemia being a major risk factor. Although various lipid-lowering therapies exist, many patients fail to achieve optimal cholesterol control, highlighting the need for novel therapeutic approaches. ASGR1 (asialoglycoprotein receptor 1), predominantly expressed on hepatocytes, has emerged as a key regulator of cholesterol metabolism and low-density lipoprotein (LDL) clearance. This receptor's ability to regulate lipid homeostasis positions it as a promising target for therapeutic intervention in hypercholesterolemia and related cardiovascular diseases. This review critically examines the biological functions and regulatory mechanisms of ASGR1 in cholesterol metabolism, with a focus on its potential as a therapeutic target for hypercholesterolemia and related cardiovascular diseases. By analyzing recent advances in ASGR1 research, this article explores its role in liver-specific pathways, the implications of ASGR1 variants in CVD risk, and the prospects for developing ASGR1-targeted therapies. This review aims to provide a foundation for future research and clinical applications in hypercholesterolemia management.

Identification and Analysis of Phenolic Compounds in Vaccinium uliginosum L. and Its Lipid-Lowering Activity In Vitro

Vaccinium uliginosum L. (VU), rich in polyphenols, is an important wild berry resource primarily distributed in extremely cold regions. However, the detailed composition of Vaccinium uliginosum L. polyphenols (VUPs) has not been reported, which limits the development and utilization of VU. In this study, VU-free polyphenols (VUFPs) and VU-bound polyphenols (VUBPs) were, respectively, extracted using an ultrasonic, complex enzyme and alkali extraction method; the compositions were identified using ultra-performance liquid chromatography-electrospray ionization mass spectrometry, and lipid-lowering activity in vitro was evaluated. The results showed that 885 polyphenols and 47 anthocyanins were detected in the VUFPs and VUBPs, and 30 anthocyanin monomers were firstly detected in VU. Compared with the model group, the accumulation of lipid droplets and the total cholesterol and triglyceride contents in the high-concentration VUP group reduced by 36.95%, 65.82%, and 62.43%, respectively, and liver damage was also alleviated. It was also found that VUP can regulate the level of Asialoglycoprotein receptor 1, a new target for lipid lowering. In summary, this study provides a detailed report on VUP for the first time, confirming that VUP has lipid-lowering potential in vitro. These findings suggest new strategies and theoretical support for the development and utilization of VU, especially in the field of functional foods.

Recent progress in gene therapy for familial hypercholesterolemia treatment

Familial hypercholesterolemia (FH) is a genetic disorder that affects 1 in 300 people, leading to high cholesterol levels and significantly increased cardiovascular risk. The limitations of existing FH treatments underscore the need for innovative therapeutics, and gene therapy offers a promising alternative to address FH more effectively. In this review, we survey approved gene therapy drugs first and then delve into the landscape of gene addition, gene inactivation, and gene editing therapies for hypercholesterolemia, highlighting both approved interventions and those in various stages of development. We also discussed recent advancements in gene editing tools that are essential for their application in gene therapy. Safety considerations inherent to gene therapy are also discussed, emphasizing the importance of mitigating potential risks associated with such treatments. Overall, this review highlights the progress and prospects of gene therapies for FH treatments, underscoring their potential to revolutionize the management of this prevalent and challenging condition.

ASGR1 is a promising target for lipid reduction in pigs with PON2 as its inhibitor

Although the role of asialoglycoprotein receptor 1 (ASGR1) in lowering lipid levels is well established, recent studies indicate that ASGR1 inhibition can cause unexpected liver damage in pigs, raising a serious issue about whether ASGR1 can be a good target for treating ASCVD. Here, we utilized the CRISPR-Cas9 system to regenerate ASGR1-knockout pigs, who displayed decreased lipid profiles without observable liver damage. This was confirmed by the lower levels of serum ALT and AST, reduced expression of inflammation markers, and normal histological morphology. Also, we implemented immunoprecipitation combined with mass spectrometry (IP-MS) and discovered that paraoxonase-2 (PON2) can interact with and significantly degrade ASGR1 in a dose-dependent manner. This degradation reduced lipid levels in mice, accompanied by little inflammation. Our study highlights the effectiveness and safety of degrading ASGR1 to reduce lipid levels in pigs and provides a potential inhibitor of ASGR1.

Deficiency of ASGR1 Alleviates Diet-Induced Systemic Insulin Resistance via Improved Hepatic Insulin Sensitivity

BACKGRUOUND

Insulin resistance (IR) is the key pathological basis of many metabolic disorders. Lack of asialoglycoprotein receptor 1 (ASGR1) decreased the serum lipid levels and reduced the risk of coronary artery disease. However, whether ASGR1 also participates in the regulatory network of insulin sensitivity and glucose metabolism remains unknown.

METHODS

The constructed ASGR1 knockout mice and ASGR1-/- HepG2 cell lines were used to establish the animal model of metabolic syndrome and the IR cell model by high-fat diet (HFD) or drug induction, respectively. Then we evaluated the glucose metabolism and insulin signaling in vivo and in vitro.

RESULTS

ASGR1 deficiency ameliorated systemic IR in mice fed with HFD, evidenced by improved insulin intolerance, serum insulin, and homeostasis model assessment of IR index, mainly contributed from increased insulin signaling in the liver, but not in muscle or adipose tissues. Meanwhile, the insulin signal transduction was significantly enhanced in ASGR1-/- HepG2 cells. By transcriptome analyses and comparison, those differentially expressed genes between ASGR1 null and wild type were enriched in the insulin signal pathway, particularly in phosphoinositide 3-kinase-AKT signaling. Notably, ASGR1 deficiency significantly reduced hepatic gluconeogenesis and glycogenolysis.

CONCLUSION

The ASGR1 deficiency was consequentially linked with improved hepatic insulin sensitivity under metabolic stress, hepatic IR was the core factor of systemic IR, and overcoming hepatic IR significantly relieved the systemic IR. It suggests that ASGR1 is a potential intervention target for improving systemic IR in metabolic disorders.

Faecal microbiota transplantation is better than probiotics for tissue regeneration of type 2 diabetes mellitus injuries in mice

CONTEXT

Western diet and unhealthy lifestyle have contributed to the continued growth of type 2 diabetes mellitus (T2DM). T2DM is associated with dysbacteriosis, and studies have found that altering the gut microbiota has a positive effect on treatment.

OBJECTIVE

In addition to hyperglycaemia, T2DM often causes damage to multiple organs. However, there are few studies on organ damage from faecal microbiota transplantation (FMT).

MATERIALS AND METHODS

T2DM mice were divided into four groups and were given phosphate buffered saline (PBS) (T2DM group), FMT (FMT group), Lactobacillus (LAB group), and Bifidobacterium (BIO group) by gavage for six weeks, respectively. Mice on a normal diet (control group) were gavaged with PBS for six weeks.

RESULTS

After gavage treatment, FMT, LAB, and BIO groups were similar in lowering glucose, endotoxemia was slightly reduced, and the colonic mucus layer and liver lobules developed towards normal tissue. Surprisingly, we found that the FMT group had unique effects on islet cell regeneration, increased functional β cells, and insulin sensitivity.

DISCUSSION AND CONCLUSION

Lactobacillus has the best glucose-lowering effect, but FMT has obvious advantages in β-cell regeneration, which provides new treatment ideas for tissue damage caused by T2DM.

Deficiency of ASGR1 promotes liver injury by increasing GP73-mediated hepatic endoplasmic reticulum stress

Liver injury is a core pathological process in the majority of liver diseases, yet the genetic factors predisposing individuals to its initiation and progression remain poorly understood. Here we show that asialoglycoprotein receptor 1 (ASGR1), a lectin specifically expressed in the liver, is downregulated in patients with liver fibrosis or cirrhosis and male mice with liver injury. ASGR1 deficiency exacerbates while its overexpression mitigates acetaminophen-induced acute and CCl4-induced chronic liver injuries in male mice. Mechanistically, ASGR1 binds to an endoplasmic reticulum stress mediator GP73 and facilitates its lysosomal degradation. ASGR1 depletion increases circulating GP73 levels and promotes the interaction between GP73 and BIP to activate endoplasmic reticulum stress, leading to liver injury. Neutralization of GP73 not only attenuates ASGR1 deficiency-induced liver injuries but also improves survival in mice received a lethal dose of acetaminophen. Collectively, these findings identify ASGR1 as a potential genetic determinant of susceptibility to liver injury and propose it as a therapeutic target for the treatment of liver injury.

Drug development advances in human genetics-based targets

Drug development is a long and costly process, with a high degree of uncertainty from the identification of a drug target to its market launch. Targeted drugs supported by human genetic evidence are expected to enter phase II/III clinical trials or be approved for marketing more quickly, speeding up the drug development process. Currently, genetic data and technologies such as genome-wide association studies (GWAS), whole-exome sequencing (WES), and whole-genome sequencing (WGS) have identified and validated many potential molecular targets associated with diseases. This review describes the structure, molecular biology, and drug development of human genetics-based validated beneficial loss-of-function (LOF) mutation targets (target mutations that reduce disease incidence) over the past decade. The feasibility of eight beneficial LOF mutation targets (PCSK9, ANGPTL3, ASGR1, HSD17B13, KHK, CIDEB, GPR75, and INHBE) as targets for drug discovery is mainly emphasized, and their research prospects and challenges are discussed. In conclusion, we expect that this review will inspire more researchers to use human genetics and genomics to support the discovery of novel therapeutic drugs and the direction of clinical development, which will contribute to the development of new drug discovery and drug repurposing.

Dickkopf-1 promotes vascular smooth muscle cell foam cell formation and atherosclerosis development through CYP4A11/SREBP2/ABCA1

Vascular smooth muscle cells (VSMCs) are considered to be a crucial source of foam cells in atherosclerosis due to their low expression level of cholesterol exporter ATP-binding cassette transporter A1 (ABCA1) intrinsically. While the definite regulatory mechanisms are complicated and have not yet been fully elucidated, we previously reported that Dickkopf-1 (DKK1) mediates endothelial cell (EC) dysfunction, thereby aggravating atherosclerosis. However, the role of smooth muscle cell (SMC) DKK1 in atherosclerosis and foam cell formation remains unknown. In this study, we established SMC-specific DKK1-knockout (DKK1SMKO ) mice by crossbreeding DKK1flox/flox mice with TAGLN-Cre mice. Then, DKK1SMKO mice were crossed with APOE-/- mice to generate DKK1SMKO /APOE-/- mice, which exhibited milder atherosclerotic burden and fewer SMC foam cells. In vitro loss- and gain-of-function studies of DKK1 in primary human aortic smooth muscle cells (HASMCs) have proven that DKK1 prevented oxidized lipid-induced ABCA1 upregulation and cholesterol efflux and promoted SMC foam cell formation. Mechanistically, RNA-sequencing (RNA-seq) analysis of HASMCs as well as chromatin immunoprecipitation (ChIP) experiments showed that DKK1 mediates the binding of transcription factor CCAAT/enhancer-binding protein delta (C/EBPδ) to the promoter of cytochrome P450 epoxygenase 4A11 (CYP4A11) to regulate its expression. In addition, CYP4A11 as well as its metabolite 20-HETE-promoted activation of transcription factor sterol regulatory element-binding protein 2 (SREBP2) mediated the DKK1 regulation of ABCA1 in SMC. Furthermore, HET0016, the antagonist of CYP4A11, has also shown an alleviating effect on atherosclerosis. In conclusion, our results demonstrate that DKK1 promotes SMC foam cell formation during atherosclerosis via a reduction in CYP4A11-20-HETE/SREBP2-mediated ABCA1 expression.

Receptors and Cofactors That Contribute to SARS-CoV-2 Entry: Can Skin Be an Alternative Route of Entry?

To prevent the spread of SARS-CoV-2, all routes of entry of the virus into the host must be mapped. The skin is in contact with the external environment and thus may be an alternative route of entry to transmission via the upper respiratory tract. SARS-CoV-2 cell entry is primarily dependent on ACE2 and the proteases TMPRSS2 or cathepsin L but other cofactors and attachment receptors have been identified that may play a more important role in specific tissues such as the skin. The continued emergence of new variants may also alter the tropism of the virus. In this review, we summarize current knowledge on these receptors and cofactors, their expression profile, factors modulating their expression and their role in facilitating SARS-CoV-2 infection. We discuss their expression in the skin and their possible involvement in percutaneous infection since the presence of the virus has been detected in the skin.

Cooked pork-derived exosome nanovesicles mediate metabolic disorder-microRNA could be the culprit

In this study, exosomes from cooked meat were extracted by ultra-high-speed centrifugation. Approximately 80% of exosome vesicles were within 20-200 nm. In addition, the surface biomarkers of isolated exosomes were evaluated using flow cytometry. Further studies showed the exosomal microRNA profiles were different among cooked porcine muscle, fat and liver. Cooked pork-derived exosomes were chronically administered to ICR mice by drinking for 80 days. The mice plasma levels of miR-1, miR-133a-3p, miR-206 and miR-99a were increased to varying degrees after drinking exosome enriched water. Furthermore, GTT and ITT results confirmed an abnormal glucose metabolism and insulin resistance in mice. Moreover, the lipid droplets were significantly increased in the mice liver. A transcriptome analysis performed with mice liver samples identified 446 differentially expressed genes (DEGs). Functional enrichment analysis found that DEGs were enriched in metabolic pathways. Overall, the results suggest that microRNAs derived form cooked pork may function as a critical regulator of metabolic disorder in mice.

Inhibition of ASGR1 decreases lipid levels by promoting cholesterol excretion

High cholesterol is a major risk factor for cardiovascular disease¹. Currently, no drug lowers cholesterol through directly promoting cholesterol excretion. Human genetic studies have identified that the loss-of-function Asialoglycoprotein receptor 1 (ASGR1) variants associate with low cholesterol and a reduced risk of cardiovascular disease². ASGR1 is exclusively expressed in liver and mediates internalization and lysosomal degradation of blood asialoglycoproteins³. The mechanism by which ASGR1 affects cholesterol metabolism is unknown. Here, we find that Asgr1 deficiency decreases lipid levels in serum and liver by stabilizing LXRα. LXRα upregulates ABCA1 and ABCG5/G8, which promotes cholesterol transport to high-density lipoprotein and excretion to bile and faeces⁴, respectively. ASGR1 deficiency blocks endocytosis and lysosomal degradation of glycoproteins, reduces amino-acid levels in lysosomes, and thereby inhibits mTORC1 and activates AMPK. On one hand, AMPK increases LXRα by decreasing its ubiquitin ligases BRCA1/BARD1. On the other hand, AMPK suppresses SREBP1 that controls lipogenesis. Anti-ASGR1 neutralizing antibody lowers lipid levels by increasing cholesterol excretion, and shows synergistic beneficial effects with atorvastatin or ezetimibe, two widely used hypocholesterolaemic drugs. In summary, this study demonstrates that targeting ASGR1 upregulates LXRα, ABCA1 and ABCG5/G8, inhibits SREBP1 and lipogenesis, and therefore promotes cholesterol excretion and decreases lipid levels.

Modeling MEN1 with Patient-Origin iPSCs Reveals GLP-1R Mediated Hypersecretion of Insulin

Multiple endocrine neoplasia type 1 (MEN1) is an inherited disease caused by mutations in the MEN1 gene encoding a nuclear protein menin. Among those different endocrine tumors of MEN1, the pancreatic neuroendocrine tumors (PNETs) are life-threatening and frequently implicated. Since there are uncertainties in genotype and phenotype relationship and there are species differences between humans and mice, it is worth it to replenish the mice model with human cell resources. Here, we tested whether the patient-origin induced pluripotent stem cell (iPSC) lines could phenocopy some defects of MEN1. In vitro β-cell differentiation revealed that the percentage of insulin-positive cells and insulin secretion were increased by at least two-fold in MEN1-iPSC derived cells, which was mainly resulted from significantly higher proliferative activities in the pancreatic progenitor stage (Day 7-13). This scenario was paralleled with increased expressions of prohormone convertase1/3 (PC1/3), glucagon-like peptide-1 (GLP-1), GLP-1R, and factors in the phosphatidylinositol 3-kinase (PI3K)/AKT signal pathway, and the GLP-1R was mainly expressed in β-like cells. Blockages of either GLP-1R or PI3K significantly reduced the percentages of insulin-positive cells and hypersecretion of insulin in MEN1-derived cells. Furthermore, in transplantation of different stages of MEN1-derived cells into immune-deficient mice, only those β-like cells produced tumors that mimicked the features of the PNETs from the original patient. To the best of our knowledge, this was the first case using patient-origin iPSCs modeling most phenotypes of MEN1, and the results suggested that GLP-1R may be a potential therapeutic target for MEN1-related hyperinsulinemia.

Camellia (Camellia oleifera bel.) seed oil reprograms gut microbiota and alleviates lipid accumulation in high fat-fed mice through the mTOR pathway

Camellia (Camellia oleifera bel.) seed oil (CO) is extensively used as an edible oil in China and Asian countries owing to its high nutritional and medicinal values. It has been shown that a high-fat diet enhances lipid accumulation and induces intestinal microbiota imbalance in mice. However, it is still to be learned whether CO prevents dyslipidemia through gut microbiota. Here, using 16S rRNA gene sequencing analysis of the gut microbiota, we found that oral CO relieved lipid accumulation and reversed gut microbiota dysbiosis. Compared to mice (C57BL/6J male mice) fed a high-fat diet, treatment with CO regulated the composition and functional profiling communities related to the lipid metabolism of gut microbiota. The abundances of Dubosiella, Lactobacillus, and Alistipes were markedly increased in CO supplementation mice. In addition, the colon levels of isobutyric acid, pentanoic acid, and isovaleric acid were similar between the control and CO supplementation mice. Besides, the results indicated that CO supplementation in mice alleviated lipid droplet accumulation in the hepatocytes and subcutaneous adipose tissue, although the liver index did not show a difference. Notably, CO supplementation for 6 weeks significantly reduced the levels of LDL, TC, and TG, while enhancing the level of HDL in serum and liver. Meanwhile, we also identified that CO supplementation suppressed the mammalian target of rapamycin (mTOR) signaling pathway in high fat-fed (HF-fed) mice. Taken together, our results suggest that CO improved dyslipidemia and alleviated lipid accumulation in HF-fed mice, the molecular mechanisms possibly associated with the reorganization of gut microbiota, in particular, Alistipes and Dubosiella, mediated the inhibition of the mTOR pathway.

LncRNA NEAT1 Potentiates SREBP2 Activity to Promote Inflammatory Macrophage Activation and Limit Hantaan Virus Propagation

As the global prototypical zoonotic hantavirus, Hantaan virus (HTNV) is prevalent in Asia and is the leading causative agent of severe hemorrhagic fever with renal syndrome (HFRS), which has profound morbidity and mortality. Macrophages are crucial components of the host innate immune system and serve as the first line of defense against HTNV infection. Previous studies indicated that the viral replication efficiency in macrophages determines hantavirus pathogenicity, but it remains unknown which factor manipulates the macrophage activation pattern and the virus-host interaction process. Here, we performed the transcriptomic analysis of HTNV-infected mouse bone marrow-derived macrophages and identified the long noncoding RNA (lncRNA) nuclear enriched abundant transcript 1 (NEAT1), especially the isoform NEAT1-2, as one of the lncRNAs that is differentially expressed at the early phase. Based on coculture experiments, we revealed that silencing NEAT1-2 hinders inflammatory macrophage activation and facilitates HTNV propagation, while enhancing NEAT1-2 transcription effectively restrains viral replication. Furthermore, sterol response element binding factor-2 (SREBP2), which controls the cholesterol metabolism process, was found to stimulate macrophages by promoting the production of multiple inflammatory cytokines upon HTNV infection. NEAT1-2 could potentiate SREBP2 activity by upregulating Srebf1 expression and interacting with SREBP2, thus stimulating inflammatory macrophages and limiting HTNV propagation. More importantly, we demonstrated that the NEAT1-2 expression level in patient monocytes was negatively correlated with viral load and HFRS disease progression. Our results identified a function and mechanism of action for the lncRNA NEAT1 in heightening SREBP2-mediated macrophage activation to restrain hantaviral propagation and revealed the association of NEAT1 with HFRS severity.

Lipoprotein sialylation in atherosclerosis: Lessons from mice

Sialylation is a dynamically regulated modification, which commonly occurs at the terminal of glycan chains in glycoproteins and glycolipids in eukaryotic cells. Sialylation plays a key role in a wide array of biological processes through the regulation of protein-protein interactions, intracellular localization, vesicular trafficking, and signal transduction. A majority of the proteins involved in lipoprotein metabolism and atherogenesis, such as apolipoproteins and lipoprotein receptors, are sialylated in their glycan structures. Earlier studies in humans and in preclinical models found a positive correlation between low sialylation of lipoproteins and atherosclerosis. More recent works using loss- and gain-of-function approaches in mice have revealed molecular and cellular mechanisms by which protein sialylation modulates causally the process of atherosclerosis. The purpose of this concise review is to summarize these findings in mouse models and to provide mechanistic insights into lipoprotein sialylation and atherosclerosis.