Abstract
Dysregulated blood lipids are a major predictor of cardiovascular events. A recent genome-wide association study (GWAS) with five clinically relevant lipid traits in 1.65 million individuals implicated over 770 genomic regions in regulating blood lipid metabolism. To translate these associations into clinical applications, a functional understanding of their roles in lipoprotein metabolism, transport and remodeling (LPmtr) is required. Here, we report the deep molecular fine-mapping of 554 of these lipid risk loci using 168 lipoprotein-related traits and all possible ratios between them in over 273,000 participants of the UK Biobank. We identified new ratio-based markers of pathways shared by multiple LPmtr genes, such as the linoleic acid fraction of the polyunsaturated fatty acid pool to reveal potential causal genes at poorly characterized lipid risk loci, the percentage of esterified cholesterol moieties in LDL particles as a proxy for soluble LDL receptor levels, and the HDL fraction of total lipoprotein particle number as a predictor of incident myocardial infarction. We demonstrate how lipoprotein fine-mapping can generate new hypotheses for drug target development while uncovering new mechanisms relevant to hyperlipidemia. Ratio-driven clustering further implicated miR-148 in TG secretion, linking ER-stress responses at postprandial state to VLDL metabolism via mTORC1, shown through series of integrated cellular assays and mouse studies. Moreover, consistent with its regulatory influence on lipid flux we identify miR-148a a previously unrecognized determinat of Lp(a) levels. Our study implements a novel approach of using metabolomic data to follow-up on genetic evidence from GWAS with clinical traits and generates new insights into the biology of lipoprotein particles, supporting the emerging view that assessing lipoprotein size and composition is essential for the understanding, prevention, and treatment of lipid-related disorders.