Genome-wide association studies have identified multiple novel genomic loci associated with vascular diseases. Many of these loci are common non-coding variants that affect the expression of disease-relevant genes within coronary vascular cells. To identify such genes on a genome-wide level, we performed deep transcriptomic analysis of genotyped primary human coronary artery smooth muscle cells (HCASMCs) and coronary endothelial cells (HCAECs) from the same subjects, including splicing Quantitative Trait Loci (sQTL), allele-specific expression (ASE), and colocalization analyses. We identified sQTLs for TARS2, YAP1, CFDP1, and STAT6 in HCASMCs and HCAECs, and 233 ASE genes, a subset of which are also GTEx eGenes in arterial tissues. Colocalization of GWAS association signals for coronary artery disease (CAD), migraine, stroke and abdominal aortic aneurysm with GTEx eGenes in aorta, coronary artery and tibial artery discovered novel candidate risk genes for these diseases. At the CAD and stroke locus tagged by rs2107595 we demonstrate colocalization with expression of the proximal gene TWIST1. We show that disrupting the rs2107595 locus alters TWIST1 expression and that the risk allele has increased binding of the NOTCH signaling protein RBPJ. Finally, we provide data that TWIST1 expression influences vascular SMC phenotypes, including proliferation and calcification, as a potential mechanism supporting a role for TWIST1 in CAD. Genome-wide association studies (GWAS) have identified hundreds of genetic variants that are associated with human vascular disease including coronary artery disease. These are predominantly common single nucleotide polymorphisms (SNPs) in non-coding regions, which makes the identification of the causal genes and their underlying connection to pathophysiology challenging. Mapping of expression quantitative trait loci (eQTLs) has been performed to associate GWAS SNPs with risk genes in vascular cells and tissues. However, atherosclerotic vascular tissues contain multiple cell types. We perform deep transcriptomic profiling of genotyped human-derived vascular cells–endothelial cells and smooth muscle cells–and use splicing quantitative trait locus, allele-specific expression, and colocalization analyses to annotate genetic variants associated with vascular diseases and gain insight into their potential function in a cell-type specific manner. Based on these analyses, we identified computationally and then validate experimentally an association between the CAD risk locus rs2107595 and the gene TWIST1. We propose that the minor allele for this locus can affect transcription factor binding and provide data supporting a role for TWIST1 in modulating smooth muscle cell phenotype.

Cardiac perfusion PET is increasingly used to assess ischemia and cardiovascular risk and can also provide quantitative myocardial blood flow (MBF) and flow reserve (MBFR) values. These have been shown to be prognostic biomarkers of adverse outcomes, yet MBF and MBFR quantification remains underutilized in clinical settings. We compare MBFR to traditional cardiovascular risk factors in a large and diverse clinical population (60% African-American, 35.3% Caucasian) to rank its relative contribution to cardiovascular outcomes. Major adverse cardiovascular events (MACE), including unstable angina, non-ST and ST-elevation myocardial infarction, stroke, and death, were assessed for consecutive patients who underwent rest-dipyridamole stress 82Rb PET cardiac imaging from 2012–2015 at the Hospital of the University of Pennsylvania (n = 1283, mean follow-up 2.3 years). Resting MBF (1.1 ± 0.4 ml/min/g) was associated with adverse cardiovascular outcomes. MBFR (2.1 ± 0.8) was independently and inversely associated with MACE. Furthermore, MBFR was more strongly associated with MACE than both traditional cardiovascular risk factors and the presence of perfusion defects in regression analysis. Decision tree analysis identified MBFR as superior to established cardiovascular risk factors in predicting outcomes. Incorporating resting MBF and MBFR in CAD assessment may improve clinical decision making.

Non-alcoholic fatty liver disease (NAFLD) is characterised by the accumulation of lipid droplets (LDs) within hepatocytes. Perilipin 2 (PLIN2) is the most abundant protein in hepatic LDs and its expression correlates with intracellular lipid accumulation. A recently discovered PLIN2 coding variant, Ser251Pro (rs35568725), was found to promote the accumulation of small LDs in embryonic kidney cells. In this study, we investigate the role of PLIN2-Ser251Pro (PLIN2-Pro251) on hepatic LD metabolism in vivo and research the metabolic phenotypes associated with this variant in humans. For our animal model, we used Plin2 knockout mice in which we expressed either human PLIN2-Pro251 (Pro251 mice) or wild-type human PLIN2-Ser251 (Ser251 mice) in a hepatocyte-specific manner. We fed both cohorts a lipogenic high-fat, high-cholesterol, high-fructose diet for 12 weeks. Pro251 mice were associated with reduced liver triglycerides (TGs) and had lower mRNA expression of fatty acid synthase and diacylglycerol O-acyltransferase-2 compared with Ser251 mice. Moreover, Pro251 mice had a reduction of polyunsaturated fatty acids-TGs and reduced expression of epoxygenase genes. For our human study, we analysed the Penn Medicine BioBank, the Million Veteran Program, and UK Biobank. Across these databases, the minor allele frequency of PLIN2-Pro251 was approximately 5%. There was no association with the clinical diagnosis of NAFLD, however, there was a trend toward reduced liver fat in PLIN2-Pro251 carriers by MRI-spectroscopy in UK Biobank subjects. In mice lacking endogenous Plin2, expression of human PLIN2-Pro251 attenuated high-fat, high-fructose, high-cholesterol, diet-induced hepatic steatosis compared with human wild-type PLIN2-Ser251. Moreover, Pro251 mice had lower polyunsaturated fatty acids-TGs and epoxygenase genes expression, suggesting less liver oxidative stress. In humans, PLIN2-Pro251 is not associated with NAFLD. Lipid droplet accumulation in hepatocytes is the distinctive characteristic of non-alcoholic fatty liver disease. Perilipin 2 (PLIN2) is the most abundant protein in hepatic lipid droplets; however, little is known on the role of a specific polymorphism PLIN2-Pro251 on hepatic lipid droplet metabolism. PLIN2-Pro251 attenuates liver triglycerides accumulation after a high-fat-high-glucose-diet. PLIN2-Pro251 may be a novel lipid droplet protein target for the treatment of liver steatosis.

Coronary microvascular disease (CMVD) affects the coronary pre‐arterioles, arterioles, and capillaries and can lead to blood supply–demand mismatch and cardiac ischemia. CMVD can present clinically as ischemia or myocardial infarction with no obstructive coronary arteries (INOCA or MINOCA, respectively). Currently, therapeutic options for CMVD are limited, and there are no targeted therapies. Genetic studies have emerged as an important tool to gain rapid insights into the molecular mechanisms of human diseases. For example, coronary artery disease (CAD) genome‐wide association studies (GWAS) have enrolled hundreds of thousands of patients and have identified > 320 loci, elucidating CAD pathogenic pathways and helping to identify therapeutic targets. Here, we review the current landscape of genetic studies of CMVD, consisting mostly of genotype‐first approaches. We then present the hypothesis that CAD GWAS have enrolled heterogenous populations and may be better characterized as ischemic heart disease (IHD) GWAS. We discuss how several of the genetic loci currently associated with CAD may be involved in the pathogenesis of CMVD. Genetic studies could help accelerate progress in understanding CMVD pathophysiology and identifying putative therapeutic targets. Larger phenotype‐first genomic studies into CMVD with adequate sex and ancestry representation are needed. Given the extensive CAD genetic and functional validation data, future research should leverage these loci as springboards for CMVD genomic research.