Abstract 12552: Causal Effect of Exposure to Elevated Lipoprotein(a) Levels on the Blood Transcriptome : A Mendelian Randomization Study

INTRODUCTION: Lipoprotein(a) [Lp(a)] is one of the strongest genetic risk factors for atherosclerotic cardiovascular diseases (ASCVD). Several ex vivo studies have revealed a pro-inflammatory and pro-atherogenic role of Lp(a) in the etiology of ASCVD, mainly through induction of inflammation, metabolic processes, and apoptosis. However, whether Lp(a) causally influences the human transcriptome is unknown. Here, we aimed at identifying whether genetically-predicted Lp(a) levels could also affect the whole blood expression of genes involved in metabolic- and inflammatory-related pathways. Methods: We performed a series of inverse-variance weighted mendelian randomization analyses using single-nucleotide polymorphisms located in the LPA locus (±500kb; p<5x10 -8 ) from the UK Biobank GWAS on Lipoprotein(a) quantiles as exposure (n=377,590 and whole blood expression levels of 14,288 coding gene from eQTLGen as outcomes (n=31,684 from 37 studies). We then used the Functional Mapping and Annotation of Genome-Wide Association Studies tool (FUMA) to identify gene sets for cardiometabolic- and inflammatory-related pathways from gene ontology biological processes. Results: The MR analyses identified 1363 genes that may be causally influenced by exposure to high Lp(a) levels (with p<0.05). The 10 most strongly associated genes with genetically-predicted Lp(a) levels are FSTL3 , PRKC1 , PDE6C , PLXNB3 , SESN1 , SASH1 , CD1D , CCDC102A , SS18L1 and TCF12 . These genes are also differentially expressed in the heart. We identified 16 cardiometabolic-related pathways, mostly related to immune response, signaling, apoptosis, cardiovascular and vasculature development, cell proliferation, metabolic process, and catalytic activity. The 5 most significant pathways are regulation of cell population proliferation, regulation of intracellular signal transduction, positive regulation of cell population proliferation, cardiovascular system development and TOR signaling. Conclusions: Results of this study highlight a potentially causal effect of exposure to elevated Lp(a) levels on several key genes involved in metabolic processes and inflammation and provide mechanistic insight on the pathobiological role of Lp(a) in the etiology of ASCVD.