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Identification of potential therapeutic targets for nonischemic cardiomyopathy in European ancestry: an integrated multiomics analysis
Cardiovascular Diabetology volume 23, Article number: 338 (2024)
Abstract
Background
Nonischemic cardiomyopathy (NISCM) is a clinical challenge with limited therapeutic targets. This study aims to identify promising drug targets for NISCM.
Methods
We utilized cis-pQTLs from the deCODE study, which includes data from 35,559 Icelanders, and SNPs from the FinnGen study, which includes data from 1,754 NISCM cases and 340,815 controls of Finnish ancestry. Mendelian randomization (MR) analysis was performed to estimate the causal relationship between circulating plasma protein levels and NISCM risk. Proteins with significant associations underwent false discovery rate (FDR) correction, followed by Bayesian colocalization analysis. The expression of top two proteins, LILRA5 and NELL1, was further analyzed using various NISCM datasets. Descriptions from the Human Protein Atlas (HPA) validated protein expression. The impact of environmental exposures on LILRA5 was assessed using the Comparative Toxicogenomics Database (CTD), and molecular docking identified the potential small molecule interactions.
Results
MR analysis identified 255 circulating plasma proteins associated with NISCM, with 16 remaining significant after FDR correction. Bayesian colocalization analysis identified LILRA5 and NELL1 as significant, with PP.H4 > 0.8. LILRA5 has a protective effect (OR = 0.758, 95% CI, 0.670–0.857) while NELL1 displays the risk effect (OR = 1.290, 95% CI, 1.199–1.387) in NISCM. Decreased LILRA5 expression was found in NISCM such as diabetic, hypertrophic, dilated, and inflammatory cardiomyopathy, while NELL1 expression increased in hypertrophic cardiomyopathy. HPA data indicated high LILRA5 expression in neutrophils, macrophages and endothelial cells within normal heart and limited NELL1 expression. Immune infiltration analysis revealed decreased neutrophil in diabetic cardiomyopathy. CTD analysis identified several small molecules that affect LILRA5 mRNA expression. Among these, Estradiol, Estradiol-3-benzoate, Gadodiamide, Topotecan, and Testosterone were found to stably bind to the LILRA5 protein at the conserved VAL-15 or THR-133 residues in the Ig-like C2 domain.
Conclusion
Based on European Ancestry Cohort, this study reveals that LILRA5 and NELL1 are potential therapeutic targets for NISCM, with LILRA5 showing particularly promising prospects in diabetic cardiomyopathy. Several small molecules interact with LILRA5, implying potential clinical implication.
Introduction
Nonischemic cardiomyopathy (NISCM) encompasses a group of various myocardial diseases that are not related to coronary artery disease [1]. These diseases include hypertrophic cardiomyopathy, dilated cardiomyopathy, restrictive cardiomyopathy, diabetic cardiomyopathy, and other forms of cardiomyopathy. They have diverse and often unclear underlying causes, including genetic predisposition, autoimmune responses, and toxin exposure, ultimately leading to heart failure and arrhythmias [2]. Despite the significant incidence of NISCM and its considerable impact on morbidity and mortality, it remains a clinical challenge due to the limited availability of effective therapeutic targets. Current treatment approaches are typically symptomatic and do not address the underlying causes of the disease, highlighting the urgent need for precise and effective therapeutic interventions.
Advances in genomic technologies and bioinformatics have opened new avenues for understanding the molecular mechanisms of complex diseases such as NISCM. One promising approach is the use of circulating plasma proteins as biomarkers and potential drug targets [3]. Protein quantitative trait loci (pQTL) studies [4], which investigate the genetic regulation of protein levels in the blood, can provide valuable insights into the causal relationships between proteins and diseases. Cis-pQTLs are genetic loci located near or at the genes they regulate, offering insights into how genetic variations control protein levels and complementing genomic data with a functional perspective [5]. Mendelian randomization (MR) is a robust analytical method that uses genetic variation as an instrumental variable to infer causal relationships and identify potential therapeutic targets [6]. Recently, the strategy of combining MR and Bayesian colocalization for identifying causal biomarkers and therapeutic targets has been successfully proposed [7,8,9]. By integrating cis-pQTL data with disease phenotypes and using methods such as MR and Bayesian colocalization, causal relationships between specific proteins and disease outcomes have been discovered.
The aim of this study is to discover new drug targets for NISCM by integrating genetic, proteomic, transcriptome and toxicogenomics. Relevant cis-pQTL and single nucleotide polymorphism (SNP) data from NISCM patients were extracted from public databases. By applying a stringent MR framework and performing FDR correction, we identified circulating plasma proteins that have a causal impact on NISCM. To eliminate biases caused by SNP linkage disequilibrium, we conducted Bayesian colocalization analysis on the identified circulating plasma proteins to facilitate precise drug target localization. In conclusion, this study identifies LILRA5 and NELL1 as potential therapeutic targets for NISCM, with LILRA5 ultimately showing particularly promising prospects in diabetic cardiomyopathy. Our investigation provides a strategy for identifying therapeutic target for NISCM.
Methods
Study design and data sources
A flowchart of the study design is provided in Fig. 1. Initially, we selected cis-pQTLs as instrumental variables from a comprehensive dataset of 4,907 distinct plasma protein pQTLs derived from the Ferkingstad study of 35,559 Icelanders, predominantly of European ancestry (deCODE study, https://www.decode.com/summarydata) [10]. Subsequently, we obtained SNP data associated with NISCM as the outcome variable from the FinnGen R10 dataset (https://storage.googleapis.com/finngen-public-data-r10). The FinnGen study includes 1,754 NISCM cases and 340,815 controls, all of Finnish ancestry, representing a significant European cohort for genome-wide association studies (GWAS). Then, we estimated the association between protein levels and patient outcomes using summary statistics from cis-pQTLs and GWAS data. Proteins with significant associations underwent FDR correction, followed by Bayesian colocalization analysis. The expression of the top two proteins, LILRA5 and NELL1, was further analyzed using various NISCM datasets. Then, using the Human Protein Atlas (HPA), we analyzed the expression of target proteins in normal heart tissue. Subsequently, using Comparative Toxicogenomics Database (CTD) databases, we curated the association of target proteins with environmental small molecule compounds. Finally, molecular docking with the potential small molecules was performed. The original studies, from which these datasets were derived, adhered to the principles of the Declaration of Helsinki and received ethical consent and approval. Consequently, no further ethical approval or informed consent was required for our current analysis.
Selection of instrumental variables
We selected (1) genetic variants associated with the target gene in cis positions (typically SNPs located at or near the target gene) within 1 Mb that can influence gene expression [11]; (2) variants that exhibited significant associations [12](p < 5 × 10−8); (3) variants situated outside the boundaries of the major histocompatibility complex region [11] (chromosome 6, 26–34 Mb); (4) variants that were independently associated through linkage disequilibrium clustering, with R2 < 0.1 [13]; (5) variants with F-statistic values > 10 [14]; and (6) variants with minor allele frequency > 0.01.
Mendelian randomization analysis
For two-sample MR, we used six regression models to validate the causal relationship between cis-pQTLs and NISCM: the Wald ratio method [15], MR‒Egger regression [16], random effects inverse-variance weighted regression [17], weighted median method [18], simple mode, and weighted mode. For single genetic instruments, the Wald ratio was calculated by dividing the effect size estimate of the variant–outcome association by the corresponding estimate of the variant–exposure association. When multiple SNPs were available, a meta-analysis of Wald estimates was performed using the inverse-variance weighted method. In the absence of pleiotropic heterogeneity or when heterogeneity is balanced, the inverse-variance weighted method provides an unbiased estimate. The MR‒Egger intercept test and Cochran’s Q statistic were used to detect the presence of heterogeneity or directional pleiotropy [19]. Visual inspection of forest plots, scatter plots, and leave-one-out plots was used to assess the MR assumption of “no pleiotropic heterogeneity”. MR analysis was performed using the TwoSampleMR R package (version 0.5.10;available at https://github.com/MRCIEU/TwoSampleMR/).
False discovery rate correction
To correct for multiple comparisons, the Benjamini‒Hochberg method was used for FDR correction, with the threshold set as 5% FDR. By controlling the FDR, we minimized the risk of falsely identifying significant results due to random variations in multiple comparisons, thus enhancing the reliability of our findings [20]. The analysis was conducted using R v4.3.3 software (https://cloud.r-project.org/).
Bayesian colocalization analysis
Bayesian statistical methods were used to estimate the probability that two or more phenotypes share the same causal SNPs [21]. To assess potential confounders, colocalization was assessed using the coloc R package (https://chr1swallace.github.io/coloc/). Visualization of the colocalization results was conducted using the LocusCompareR R package (https://github.com/boxiangliu/locuscomparer). To estimate the posterior probability that each genomic locus contains a single variant that affects both the protein and NISCM, all the SNPs within 1 Mb with minor allele frequency > 0.01 associated with cis-pQTLs were analyzed.
Access to GEO datasets
Using the GEO database (https://www.ncbi.nlm.nih.gov/geo/) with “cardiomyopathy” as the search keyword, the screening criteria were set as follows: (1) all samples tested must originate from human myocardial tissue; (2) the datasets must be related to NISCM and include a control group. Series Matrix File(s) and platform information that meet the above criteria were downloaded. These files contain all the statistical information for the GSE microarray and mRNA sequencing samples. The final selected datasets were GSE26887 (diabetic cardiomyopathy), GSE36961 (hypertrophic cardiomyopathy), GSE42955 (dilated cardiomyopathy), GSE4172 (inflammatory cardiomyopathy), GSE5406 (idiopathic cardiomyopathy), and GSE29819 (arrhythmogenic right ventricular cardiomyopathy). The GSE4172, GSE29819 series on the GPL570 platform (Affymetrix Human Genome U133 Plus 2.0 Array), the GSE5406 series on the GPL96 platform (Affymetrix Human Genome U133A Array), the GSE42955 and GSE26887 series on the GPL6244 platform (Affymetrix Human Gene 1.0 ST Array), and the GSE36961 series on the GPL15389 platform (Illumina HumanHT-12 V3.0 expression beadchip). Probe IDs were converted to homologous gene symbols using the platform’s annotation information.
Exploring target proteins expression and distribution in human protein atlas
The HPA (https://www.proteinatlas.org/) database was used to explore the transcriptome of LILRA5 and NELL1 in normal human heart tissues. And its expression in various cell types of normal heart was analyzed.
Comparison of differential gene expression and assessment of immune cell infiltration
The expression levels of target genes were screened across different groups. To assess the abundance of immune infiltration, the gene expression matrix data were uploaded to CIBERSORT (https://cibersort.stanford.edu/) to filter for the matrix of 22 immune cell types, obtaining the immune cell infiltration matrix. Visualization was performed using the R packages “ggplot2” or “reshape2”.
Exploring the chemical–protein interactions using comparative toxicogenomics database
Th CTD (https://ctdbase.org/) is a robust, publicly available database that aims to advance understanding about how environmental exposures affect human health. We used this database to curate information about chemical–protein interactions.
Molecular docking
Molecular docking was performed as described previously [22]. Briefly, compound structural files were downloaded from the PubChem website (https://pubchem.ncbi.nlm.nih.gov/) and converted from SDF to PDB files using Open Babel 2.3.2. Receptor proteins were obtained from the PDB database. The receptor proteins were prepared by removing water and ligands using PyMOL 2.3.4, and modifications such as adding hydrogens and balancing charges were performed using AutoDockTools. The receptor proteins and ligand molecules were converted to PDBQT format. Global molecular docking of the receptor proteins with the ligand molecules was conducted using AutoDock Vina 1.1.2. The docking results were analyzed using PLIP, and PyMol was used to visualize the docking results. The amino acid sequence LILRA5 was obtained from UniProt database (https://www.uniprot.org/). Finally, the binding sites and domains for each small molecule were identified.
Results
Causal effect estimation of plasma proteins on NISCM
We conducted a two-sample MR analysis to identify circulating plasma proteins causally associated with NISCM. We sourced cis-pQTLs from the deCODE study and, on the basis of cis-pQTL selection criteria, 58,304 SNPs representing 1,796 circulating plasma proteins were identified (Additional file 1: Table S1). NISCM data from the FinnGen R10 study (cases n = 1,754; controls n = 340,815) were evaluated as outcomes, with exposure information extracted and reverse structures removed, resulting in 55,410 SNPs (Additional file 1: Table S2). The MR analysis identified 255 plasma proteins related to NISCM (Additional file 1: Table S3 and Table S4). After FDR correction, 16 plasma proteins were found to be significantly associated with NISCM, namely, HIBCH, SAA1, BTD, SAA2, UROD, GMPR2, CNTN1, NME2, ASPN, NELL1, LCT, ACVRL1, TP53I3, C5, F7, and LILRA5 (Fig. 2). Furthermore, each instrumental variable linked to NISCM had an F-statistic value > 10 (Additional file 1 Table S2), confirming the relatively strong effect estimates of the instrumental variables. We applied Cochran’s Q statistic and MR–Egger intercept tests to detect pleiotropy [19]; neither test showed heterogeneity or pleiotropy for the 16 plasma proteins (Additional file 1: Table S5, Additional file 2: Fig. S1). Therefore, these 16 circulating plasma proteins were considered to have significant association with NISCM. Specifically, a positive correlation between genetically predicted plasma protein levels and NISCM risk was detected for 11 of the plasma proteins: HIBCH (OR: 1.282, 95% CI: 1.130–1.455, p = 1.178 × 10−4), SAA1 (OR: 1.280, 95% CI: 1.149–1.425, p = 6.99 × 10−6), BTD (OR: 1.194, 95% CI: 1.097–1.301, p = 4.59 × 10−5), SAA2 (OR: 1.297, 95% CI: 1.170–1.438, p = 7.44 × 10−7), UROD (OR: 1.741, 95% CI: 1.486–2.040, p = 6.71 × 10−12), GMPR2 (OR: 1.491, 95% CI: 1.211–1.835, p = 1.69 × 10−4), CNTN1 (OR: 1.459, 95% CI: 1.289–1.651, p = 2.33 × 10−9), NME2 (OR: 2.070, 95% CI: 1.466–2.922, p = 3.52 × 10−5), ASPN (OR: 1.203, 95% CI: 1.098–1.319, p = 7.73 × 10−5), NELL1 (OR: 1.290, 95% CI: 1.199–1.387, p = 8.15 × 10−12), and LCT (OR: 1.095, 95% CI: 1.055–1.136, p = 1.52 × 10−6). The other five plasma proteins showed a negative correlation with NISCM risk: ACVRL1 (OR: 0.642, 95% CI: 0.511–0.806, p = 1.372 × 10−4), TP53I3 (OR: 0.823, 95% CI: 0.743–0.912, p = 2.07 × 10−4), C5 (OR: 0.479, 95% CI: 0.342–0.670, p = 1.82 × 10−5), F7 (OR: 0.906, 95% CI: 0.860–0.954, p = 2.032 × 10−4), and LILRA5 (OR: 0.758, 95% CI: 0.670–0.857, p = 1.04 × 10−5) (Fig. 3).
Genetic colocalization analysis of cis-pQTLs with NISCM
To eliminate biases caused by SNP linkage disequilibrium, we conducted Bayesian colocalization analysis of the 16 circulating plasma proteins with NISCM, which also aids in precisely targeting drug candidates. The results consistently supported strong colocalization evidence for two of the circulating plasma proteins (LILRA5 and NELL1) with NISCM (PP.H4 > 0.8) as shown in Fig. 4; the 14 other plasma proteins had PP.H4 values < 0.8 (Table 1 and Additional file 3: Fig. S2).
Differential expression analysis and protein distribution
Additionally, differential expression analysis of various NISCM datasets provided further context for the roles of LILRA5 and NELL1. We screened the GEO public database and selected the following datasets: GSE26887 (diabetic cardiomyopathy), GSE36961 (hypertrophic cardiomyopathy), GSE42955 (dilated cardiomyopathy), GSE5406 (idiopathic cardiomyopathy), GSE4172 (inflammatory cardiomyopathy), and GSE29819 (arrhythmogenic right ventricular cardiomyopathy). We found that LILRA5 expression was decreased in cardiac tissues from diabetic cardiomyopathy, hypertrophic cardiomyopathy, dilated cardiomyopathy, and inflammatory cardiomyopathy (Fig. 5A), while no significant differences were observed in idiopathic cardiomyopathy and arrhythmogenic right ventricular cardiomyopathy. In contrast, NELL1 expression was increased in cardiac tissues from hypertrophic cardiomyopathy, with no significant differences observed in other cardiomyopathies (Fig. 5A). Further validation of protein expression levels was conducted using data from the HPA. This resource confirmed the high expression of LILRA5 in neutrophils, macrophages and endothelial cells within cardiac tissue (Fig. 5B), underscoring its potential importance in cardiac immune responses. On the other hand, NELL1 could not be retrieved in normal cardiac tissue (data not shown).
Immune cell infiltration analysis
Considering LILRA5 is mainly expressed in immune cells within normal human heart tissues (Fig. 5B), we further analyzed the immune cell infiltration in these NISCM subtypes. By estimating the relative proportions of 22 immune cell types in blood samples from different groups compared to controls, the analysis identified notable alterations. In diabetic cardiomyopathy, neutrophil expression was found to be downregulated (Fig. 6A). In hypertrophic cardiomyopathy, there was an increase in native B cells, regulatory T cells, gamma delta T cells, resting NK cells, and M2 macrophages, alongside a decrease in monocytes and activated dendritic cells (Fig. 6B). In dilated cardiomyopathy, a reduction in activated NK cell expression was observed (Fig. 6C). No significant differences in immune cell expression were noted in inflammatory cardiomyopathy (Fig. 6D).
Potential drug target analysis
Through the CTD, we identified the effects of environmental exposures (small molecules) on LILRA5 expression (Table 2). We selected some small molecules that could upregulate LILRA5 expression and have been shown cardiovascular protection for further molecular docking experiments, and these molecules include Estradiol, Estradiol 3-benzoate, Gardiquimod, Genistein, Testosterone, Topotecan, N,N, N’,N’-tetrakis (2-pyridylmethyl)ethylenediamine(TPEN) and Methimazole. Some molecules with binding energies less than − 5 kcal/mol, including Estradiol 3-benzoate, Estradiol, Gardiquimod, Genistein, TPEN, Testosterone, and Topotecan, were found to stably bind to LILRA5 (Fig. 7A). Methimazole exhibited a binding energy of only − 2.9 kcal/mol with LILRA5 and thus was not shown in the results. To further analyze the specific amino acid sites where these small molecules bind to LILRA5 protein, the sites obtained by molecular docking are shown in Fig. 7B, as indicated by red color. It can be seen that the VAL-15 (V, purple background) and THR-133(T, green background) sites of LILRA5 protein are relative conserved binding sites. To further clarify the potential impact of small molecule binding sites on the function of LILRA5 protein, we further constructed the topology and domain of LILRA5 protein and found that these conserved binding sites of small molecules are mainly located on the immunoglobulin-like domains (Ig-like C2-type 1 and Ig-like C2-type 2) (Fig. 7C). The function of biological processes (BP) for LILRA5 indicates that LILRA5 plays a significant regulatory role in various biological processes, particularly in immune response and inflammation regulation (Additional file 4: Fig. S3).
Discussion
NISCM includes myocardial diseases not caused by coronary artery disease and presents significant challenges in cardiovascular medicine. Due to improved detection and aging populations, its prevalence is increasing [23]. Studies indicate a rise in NISCM among younger individuals due to genetic predisposition and lifestyle factors [24]. Clinically, its complexity and diversity pose numerous challenges. Integrating emerging technologies and interdisciplinary research is key to new therapeutic potentials and improving patient outcomes. Research into the genetic foundations of NISCM has identified multiple critical genes involved in cardiac structure and function [25, 26]. This study identified LILRA5 and NELL1 as potential therapeutic targets, highlighting LILRA5’s role in diabetic cardiomyopathy.
We conducted MR analysis on the circulating plasma proteome to identify proteins causally related to NISCM. Using multiple cis-pQTLs as instrumental variables, we performed a comprehensive analysis. After FDR correction, we identified proteins closely associated with NISCM pathology. Eleven proteins (HIBCH, SAA1, BTD, SAA2, UROD, GMPR2, CNTN1, NME2, ASPN, NELL1, LCT) were positively correlated with NISCM risk, while five (ACVRL1, TP53I3, C5, F7, LILRA5) were negatively correlated. Drug development and clinical translation often require significant time and financial investment, leading to lower success rates. Population-based genetic studies have successfully identified new drug targets or repurposed existing drugs; two-thirds of FDA-approved drugs in 2021 had genetic evidence support [27]. Next-generation sequencing of 208 patients identified NISCM-related genes [28], broadening our understanding of NISCM. RNA sequencing described the transcriptome of 880,000 nuclei from NISCM hearts, identifying genotype-related pathways, cell interactions, and gene expression differences at the single-cell level [29]. Although circulating plasma proteins do not have a direct histological relationship with NISCM like atrial or ventricular tissues, they are valuable for drug target screening due to their detectability and accessibility. Bayesian colocalization analysis of the 16 proteins identified by MR showed strong colocalization of LILRA5 and NELL1 with NISCM (PP.H4 > 0.8). High posterior probabilities indicate a shared genetic architecture between protein expression and NISCM risk, suggesting a direct role in disease pathogenesis. This strong genetic association highlights the potential of LILRA5 and NELL1 as therapeutic targets. Utilizing MR and colocalization analysis minimizes confounders and enhances the reliability of causal relationship identification, providing a solid foundation for subsequent therapeutic strategies.
LILRA5, a member of the leukocyte immunoglobulin-like receptor A subfamily, may trigger innate immune responses [30, 31]. GO enrichment analysis indicates LILRA5 plays a crucial role in immune response and inflammation regulation. It may influence the pathophysiology of NISCM through cytokine production, calcium ion transport, and protein tyrosine phosphorylation, supporting further research on its function and therapeutic potential. NELL1, a protein kinase C-binding protein involved in cell growth and differentiation, is a biomarker for idiopathic pulmonary fibrosis and is consistently expressed in both rats and humans [32]. Differential expression analysis shows LILRA5 is significantly reduced in diabetic, hypertrophic, dilated, and inflammatory cardiomyopathies, suggesting its broad involvement in these diseases. Interestingly, a recent study has also reported a negative correlation between LILRA5 and severe insulin-resistant diabetes with relative insulin deficiency; furthermore, this study suggests a significant association between LILRA5 and heart failure [33], which is highly consistent with our current findings. Conversely, NELL1 expression increases in hypertrophic cardiomyopathy, indicating a role in hypertrophic remodeling. HPA validation revealed high LILRA5 expression in neutrophils, macrophages and endothelial cells within cardiac tissue, highlighting its importance in cardiac immune responses. Limited NELL1 expression suggests a specific role in hypertrophic remodeling. Future research should establish multicenter cohorts and use large-scale proteomics and clinical samples to validate these proteins’ roles in NISCM.
Further immune infiltration analysis revealed significant changes in immune cell populations in NISCM. In diabetic cardiomyopathy, downregulation of neutrophils correlates with reduced LILRA5 expression, suggesting a link between neutrophil activity and LILRA5 [30]. In hypertrophic cardiomyopathy, increased activation of native B cells, regulatory T cells, gamma delta T cells, resting NK cells, and M2 macrophages, along with decreased in monocytes and activated dendritic cells, highlights a complex immune environment, aligning with recent findings [34]. In dilated cardiomyopathy, activated NK cell expression is reduced. No significant immune cell changes were observed in inflammatory cardiomyopathy. Studies show immune cells play a critical role in NISCM [33,34,35], consistent with our findings. Different NISCM subtypes exhibit distinct immune characteristics, suggesting precise immunomodulatory therapies as a potential treatment approach, highlighting the potential of immune-targeted therapies.
CTD analysis identified several small molecules affecting LILRA5 mRNA expression. Due to the negative correlation between LILRA5 and NISCM, we screened small molecules that upregulate LILRA5 and conducted molecular docking. Results showed that Benzoate estradiol, Estradiol, Gadodiamide, Genistein, TPEN, Testosterone, and Topotecan stably bind to LILRA5, mainly at its Ig-like domain, suggesting the domain’s role in binding and function. Conserved sites VAL-15 and THR-133 are crucial for these interactions. Pan-assay interference compounds (PAINs) are known to hinder drug development [35, 36]. Among our candidates, Genistein is a PAINs molecule due to nonspecific binding and false positives. TPEN, while not typically a PAINs molecule, may cause nonspecific interference due to metal-chelation. Other molecules (Topotecan, Estradiol-3-benzoate, Estradiol, Gadodiamide, and Testosterone) did not exhibit PAINs characteristics, making their binding to LILRA5 more reliable. Our findings suggest the Ig-like domain is key for ligand binding. Despite Genistein and TPEN’s potential nonspecific binding, other small molecules showed high specificity and stability. Studies have indicated these molecules benefit the cardiovascular system [37,38,39,40,41,42,43]. Our current findings provide a foundation for further research on LILRA5 function and LILRA5-targeted drug development. Considering the fact that these small molecules have the capacity to upregulate the expression of LILRA5 mRNA on the one hand, and on the other, they are able to interact with LILRA5 protein, thereby influencing its crucial domains, it implies that these molecules modulate the expression and functionality of LILRA5 via multifaceted mechanisms, but the precise mechanisms still need further research.
Strengths and limitations
A key advantage of this study is the use of the most comprehensive and high-quality pQTL database for circulating plasma proteins. Using cis-pQTLs as instrumental variables reduces the impact of environmental confounders typical in observational studies, minimizing pleiotropy. This strengthens causal inferences between gene expression and disease outcomes, helping identify genetic mechanisms and pathways in disease pathogenesis. The cis-pQTL data used SomaLogic SOMAscan technology, ensuring high selectivity, specificity, and sensitivity, which reduces false pQTL results. This enables large-scale pQTL studies to explore genetic variations in protein levels and their disease associations comprehensively. We also applied multiple testing corrections (FDR control) to minimize false positives from multiple comparisons.
There are some limitations in our study. This study is restricted to individuals of European ancestry and a single cohort, which may limit the generalizability of the findings. Integrating more databases would enhance the credibility of our conclusions. We used the GEO database to analyze and validate LILRA5 and NELL1 expression in different NISCM subtypes, future research should involve multicenter collaborations and large-scale proteomics data to further validate these proteins’ roles in NISCM. Finally, we used an R²<0.1 threshold for instrumental variable selection, increasing sample size and improving detection of causal relationships but introducing potential collinearity.
Conclusion
This study identifies LILRA5 and NELL1 as potential therapeutic targets for NISCM based on a European ancestry cohort, with LILRA5 particularly promising for diabetic cardiomyopathy. Integrating genetic, proteomic, transcriptomic, and toxicogenomic data provides a comprehensive understanding of NISCM pathogenesis and potential treatments. These findings underscore the importance of personalized medicine in NISCM treatment, targeting specific molecular profiles based on patients’ unique genetic and molecular characteristics.
Data availability
The datasets used in MR analyses and supported the conclusions of this article are included within the article and its additional files. The main R scripts and code have been made publicly available on GitHub and archived on Zenodo (DOI: 10.5281/zenodo.12977418). If further code is required, please contact the authors.
Abbreviations
- CTD:
-
Comparative toxicogenomics database
- FDR:
-
False discovery rate
- HPA:
-
Human protein atlas
- MR:
-
Mendelian randomization
- NISCM:
-
Nonischemic cardiomyopathy
- PAINs:
-
Pan-assay interference compounds
- pQTL:
-
Protein quantitative trait loci
- SNP:
-
Single nucleotide polymorphism
- TPEN:
-
N, N,N’,N’-tetrakis (2-pyridylmethyl)ethylenediamine
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Acknowledgements
We appreciate all the participants in the study. We thank Margaret Biswas, PhD, from Liwen Bianji (Edanz) (www.liwenbianji.cn/) for editing the English text of a draft of this manuscript.
Funding
This work was supported by the Hainan Key Research and Development Project (ZDYF2020122, ZDYF2022SHFZ038), the Innovational Fund for Scientific and Technological Personnel of Hainan Province (KJRC2023B07). the National Natural Science Foundation of China (82060053, 82260083, U220A20270), the Cardiovascular Disease Research Science Innovation Group of Hainan Medical University, and the Innovative Research Projects for Graduate Students in Hainan Province (Qhyb2022-140).
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K.S. and X.C. significantly contributed to the conceptualization, investigation, visualization, formal analysis, data curation, and methodology development of the study. Y.Z., J.C., P.L. and J.Q. assisted in enhancing the visualization, optimizing software utilization, and managing data curation. K.S. and X.C. were primarily responsible for drafting the manuscript. Additionally, Z.S., J.G., and W.J. were involved in project administration and provided supervision. They also played a critical role in reviewing and editing the manuscript to ensure its academic rigor and coherence. Moreover, K.S., J.G., and W.J. secured the funding necessary to support this project. All authors critically reviewed the manuscript.
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Shi, K., Chen, X., Zhao, Y. et al. Identification of potential therapeutic targets for nonischemic cardiomyopathy in European ancestry: an integrated multiomics analysis. Cardiovasc Diabetol 23, 338 (2024). https://doi.org/10.1186/s12933-024-02431-8
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DOI: https://doi.org/10.1186/s12933-024-02431-8