Common gene variants in ASGR1 gene locus associate with reduced cardiovascular risk in absence of pleiotropic effects

The emerging role of glycans and the importance of sialylation in cardiovascular disease

Glycosylation is the process by which glycans (i.e. 'sugars') are enzymatically attached to proteins or lipids to form glycoconjugates. Growing evidence points to glycosylation playing a central role in atherosclerosis. Glycosylation occurs in all human cells and post-translationally modifies many signalling molecules that regulate cardiovascular disease, affecting their binding and function. Glycoconjugates are present in abundance on the vascular endothelium and on circulating lipoproteins, both of which have well-established roles in atherosclerotic plaque development. Sialic acid is a major regulator of glycan function and therefore the process of sialylation, in which sialic acid is added to glycans, is likely to be entwined in any regulation of atherosclerosis. Glycans and sialylation regulators have the potential to present as new biomarkers that predict atherosclerotic disease or as targets for pharmacological intervention, as well as providing insights into novel cardiovascular mechanisms. Moreover, the asialoglycoprotein receptor 1 (ASGR1), a glycan receptor, is emerging as an exciting new regulator of lipid metabolism and coronary artery disease. This review summarises the latest advances in the growing body of evidence that supports an important role for glycosylation and sialylation in the regulation of atherosclerosis.

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.

Depression proteomic profiling in adolescents with transcriptome analyses in independent cohorts

Introduction

Depression is a major global burden with unclear pathophysiology and poor treatment outcomes. Diagnosis of depression continues to rely primarily on behavioral rather than biological methods. Investigating tools that might aid in diagnosing and treating early-onset depression is essential for improving the prognosis of the disease course. While there is increasing evidence of possible biomarkers in adult depression, studies investigating this subject in adolescents are lacking.

Methods

In the current study, we analyzed protein levels in 461 adolescents assessed for depression using the Development and Well-Being Assessment (DAWBA) questionnaire as part of the domestic Psychiatric Health in Adolescent Study conducted in Uppsala, Sweden. We used the Proseek Multiplex Neuro Exploratory panel with Proximity Extension Assay technology provided by Olink Bioscience, followed by transcriptome analyses for the genes corresponding to the significant proteins, using four publicly available cohorts.

Results

We identified a total of seven proteins showing different levels between DAWBA risk groups at nominal significance, including RBKS, CRADD, ASGR1, HMOX2, PPP3R1, CD63, and PMVK. Transcriptomic analyses for these genes showed nominally significant replication of PPP3R1 in two of four cohorts including whole blood and prefrontal cortex, while ASGR1 and CD63 were replicated in only one cohort.

Discussion

Our study on adolescent depression revealed protein-level and transcriptomic differences, particularly in PPP3R1, pointing to the involvement of the calcineurin pathway in depression. Our findings regarding PPP3R1 also support the role of the prefrontal cortex in depression and reinforce the significance of investigating prefrontal cortex-related mechanisms in depression.

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.

Plasma Proteomics to Identify Drug Targets for Ischemic Heart Disease

BACKGROUND

Integrated analyses of plasma proteomic and genetic markers in prospective studies can clarify the causal relevance of proteins and discover novel targets for ischemic heart disease (IHD) and other diseases.

OBJECTIVES

The purpose of this study was to examine associations of proteomics and genetics data with IHD in population studies to discover novel preventive treatments.

METHODS

We conducted a nested case-cohort study in the China Kadoorie Biobank (CKB) involving 1,971 incident IHD cases and 2,001 subcohort participants who were genotyped and free of prior cardiovascular disease. We measured 1,463 proteins in the stored baseline samples using the OLINK EXPLORE panel. Cox regression yielded adjusted HRs for IHD associated with individual proteins after accounting for multiple testing. Moreover, cis-protein quantitative loci (pQTLs) identified for proteins in genome-wide association studies of CKB and of UK Biobank were used as instrumental variables in separate 2-sample Mendelian randomization (MR) studies involving global CARDIOGRAM+C4D consortium (210,842 IHD cases and 1,378,170 controls).

RESULTS

Overall 361 proteins were significantly associated at false discovery rate <0.05 with risk of IHD (349 positively, 12 inversely) in CKB, including N-terminal prohormone of brain natriuretic peptide and proprotein convertase subtilisin/kexin type 9. Of these 361 proteins, 212 had cis-pQTLs in CKB, and MR analyses of 198 variants in CARDIOGRAM+C4D identified 13 proteins that showed potentially causal associations with IHD. Independent MR analyses of 307 cis-pQTLs identified in Europeans replicated associations for 4 proteins (FURIN, proteinase-activated receptor-1, Asialoglycoprotein receptor-1, and matrix metalloproteinase-3). Further downstream analyses showed that FURIN, which is highly expressed in endothelial cells, is a potential novel target and matrix metalloproteinase-3 a potential repurposing target for IHD.

CONCLUSIONS

Integrated analyses of proteomic and genetic data in Chinese and European adults provided causal support for FURIN and multiple other proteins as potential novel drug targets for treatment of IHD.

Genetically mimicked effects of ASGR1 inhibitors on all-cause mortality and health outcomes: a drug-target Mendelian randomization study and a phenome-wide association study

BACKGROUND

Asialoglycoprotein receptor 1 (ASGR1) is emerging as a potential drug target to reduce low-density lipoprotein (LDL)-cholesterol and coronary artery disease (CAD) risk. Here, we investigated genetically mimicked ASGR1 inhibitors on all-cause mortality and any possible adverse effects.

METHODS

We conducted a drug-target Mendelian randomization study to assess genetically mimicked effects of ASGR1 inhibitors on all-cause mortality and 25 a priori outcomes relevant to lipid traits, CAD, and possible adverse effects, i.e. liver function, cholelithiasis, adiposity and type 2 diabetes. We also performed a phenome-wide association study of 1951 health-related phenotypes to identify any novel effects. Associations found were compared with those for currently used lipid modifiers, assessed using colocalization, and replicated where possible.

RESULTS

Genetically mimicked ASGR1 inhibitors were associated with a longer lifespan (3.31 years per standard deviation reduction in LDL-cholesterol, 95% confidence interval 1.01 to 5.62). Genetically mimicked ASGR1 inhibitors were inversely associated with apolipoprotein B (apoB), triglycerides (TG) and CAD risk. Genetically mimicked ASGR1 inhibitors were positively associated with alkaline phosphatase, gamma glutamyltransferase, erythrocyte traits, insulin-like growth factor 1 (IGF-1) and C-reactive protein (CRP), but were inversely associated with albumin and calcium. Genetically mimicked ASGR1 inhibitors were not associated with cholelithiasis, adiposity or type 2 diabetes. Associations with apoB and TG were stronger for ASGR1 inhibitors compared with currently used lipid modifiers, and most non-lipid effects were specific to ASGR1 inhibitors. The probabilities for colocalization were > 0.80 for most of these associations, but were 0.42 for lifespan and 0.30 for CAD. These associations were replicated using alternative genetic instruments and other publicly available genetic summary statistics.

CONCLUSIONS

Genetically mimicked ASGR1 inhibitors reduced all-cause mortality. Beyond lipid-lowering, genetically mimicked ASGR1 inhibitors increased liver enzymes, erythrocyte traits, IGF-1 and CRP, but decreased albumin and calcium.

Glutaredoxin 1 regulates cholesterol metabolism and gallstone formation by influencing protein S-glutathionylation

OBJECTIVE

Cholesterol gallstone disease (CGD) is closely related to cholesterol metabolic disorder. Glutaredoxin-1 (Glrx1) and Glrx1-related protein S-glutathionylation are increasingly being observed to drive various physiological and pathological processes, especially in metabolic diseases such as diabetes, obesity and fatty liver. However, Glrx1 has been minimally explored in cholesterol metabolism and gallstone disease.

METHODS

We first investigated whether Glrx1 plays a role in gallstone formation in lithogenic diet-fed mice using immunoblotting and quantitative real-time PCR. Then a whole-body Glrx1-deficient (Glrx1^-/-) mice and hepatic-specific Glrx1-overexpressing (AAV8-TBG-Glrx1) mice were generated, in which we analyzed the effects of Glrx1 on lipid metabolism upon LGD feeding. Quantitative proteomic analysis and immunoprecipitation (IP) of glutathionylated proteins were performed.

RESULTS

We found that protein S-glutathionylation was markedly decreased and the deglutathionylating enzyme Glrx1 was greatly increased in the liver of lithogenic diet-fed mice. Glrx1^-/- mice were protected from gallstone disease induced by a lithogenic diet because their biliary cholesterol and cholesterol saturation index (CSI) were reduced. Conversely, AAV8-TBG-Glrx1 mice showed greater gallstone progression with increased cholesterol secretion and CSI. Further studies showed that Glrx1-overexpressing greatly induced bile acid levels and/or composition to increase intestinal cholesterol absorption by upregulating Cyp8b1. In addition, liquid chromatography-mass spectrometry and IP analysis revealed that Glrx1 also affected the function of asialoglycoprotein receptor 1 (ASGR1) by mediating its deglutathionylation, thereby altering the expression of LXRα and controlling cholesterol secretion.

CONCLUSION

Our findings present novel roles of Glrx1 and Glrx1-regulated protein S-glutathionylation in gallstone formation through the targeting of cholesterol metabolism. Our data advises Glrx1 significantly increased gallstone formation by simultaneously increase bile-acid-dependent cholesterol absorption and ASGR1- LXRα-dependent cholesterol efflux. Our work suggests the potential effects of inhibiting Glrx1 activity to treat cholelithiasis.

Circulating platelet count and glycans

PURPOSE OF THE REVIEW

This review highlights recent advancements in understanding the regulation of platelet numbers, focusing on mechanisms by which carbohydrates (glycans) link platelet removal with platelet production in the bone marrow in health and disease.

RECENT FINDINGS

This review is focused on the role of carbohydrates, specifically sialic acid moieties, as a central mediator of platelet clearance. We discuss recently identified novel mechanisms of carbohydrate-mediated platelet removal and carbohydrate-binding receptors that mediate platelet removal.

SUMMARY

The platelet production rate by megakaryocytes and removal kinetics controls the circulating platelet count. Alterations in either process can lead to thrombocytopenia (low platelet count) or thrombocytosis (high platelet count) are associated with the risk of bleeding or overt thrombus formation and serious complications. Thus, regulation of a steady-state platelet count is vital in preventing adverse events. There are few mechanisms delineated that shed light on carbohydrates' role in the complex and massive platelet removal process. This review focuses on carbohydrate-related mechanisms that contribute to the control of platelet numbers.

Impact of protein glycosylation on lipoprotein metabolism and atherosclerosis

Protein glycosylation is a post-translational modification consisting in the enzymatic attachment of carbohydrate chains to specific residues of the protein sequence. Several types of glycosylation have been described, with N-glycosylation and O-glycosylation being the most common types impacting on crucial biological processes, such as protein synthesis, trafficking, localization, and function. Genetic defects in genes involved in protein glycosylation may result in altered production and activity of several proteins, with a broad range of clinical manifestations, including dyslipidaemia and atherosclerosis. A large number of apolipoproteins, lipoprotein receptors, and other proteins involved in lipoprotein metabolism are glycosylated, and alterations in their glycosylation profile are associated with changes in their expression and/or function. Rare genetic diseases and population genetics have provided additional information linking protein glycosylation to the regulation of lipoprotein metabolism.