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Genetic factors contribute to the risk of thrombotic diseases. Recent genome wide association studies have identified genetic loci including SLC44A2 which may regulate thrombosis. Here we show that Slc44a2 controls platelet activation and thrombosis by regulating mitochondrial energetics. We find that Slc44a2 null mice ( Slc44a2(KO)) have increased bleeding times and delayed thrombosis compared to wild-type ( Slc44a2 ( WT)) controls. Platelets from Slc44a2(KO) mice have impaired activation in response to thrombin. We discover that Slc44a2 mediates choline transport into mitochondria, where choline metabolism leads to an increase in mitochondrial oxygen consumption and ATP production. Platelets lacking Slc44a2 contain less ATP at rest, release less ATP when activated, and have an activation defect that can be rescued by exogenous ADP. Taken together, our data suggest that mitochondria require choline for maximum function, demonstrate the importance of mitochondrial metabolism to platelet activation, and reveal a mechanism by which Slc44a2 influences thrombosis. Genetic association studies have identified loci including the choline transporter SLC44A2 as a potential regulator of thrombosis. Here the authors report that loss of SLC44A2 impairs platelet activation and thrombosis in mice via a reduction of mitochondrial ATP production.

Observational studies have shown an association between obesity and venous thromboembolism (VTE) but it is not known if observed associations are causal, due to reverse causation or confounding bias. We conducted a Mendelian Randomization study of body mass index (BMI) and VTE. We identified 95 single nucleotide polymorphisms (SNPs) that have been previously associated with BMI and assessed the association between genetically predicted high BMI and VTE leveraging data from a previously conducted GWAS within the INVENT consortium comprising a total of 7507 VTE cases and 52,632 controls of European ancestry. Five BMI SNPs were associated with VTE at P < 0.05, with the strongest association seen for the FTO SNP rs1558902 (OR 1.07, 95% CI 1.02–1.12, P = 0.005). In addition, we observed a significant association between genetically predicted BMI and VTE (OR = 1.59, 95% CI 1.30–1.93 per standard deviation increase in BMI, P = 5.8 × 10−6). Our study provides evidence for a causal relationship between high BMI and risk of VTE. Reducing obesity levels will likely result in lower incidence in VTE.

Obstructive sleep apnea (OSA) has been associated with incidence of cardiovascular disease and with nocturnal angina, but evidence of a link with coronary atherosclerosis and myocardial ischemia is limited and previous studies may have been affected by selection bias or unmeasured confounding factors. We performed overnight polysomnography in 178 older male twins. The Apnea/Hypopnea Index (AHI) was calculated to assess OSA from the overnight sleep evaluation. AHI ≥15 was used as indicator of moderate/severe OSA. The following day, twins underwent myocardial perfusion imaging with [82Rb]-chloride positron emission tomography. Quantitative and semiquantitative measures of myocardial perfusion and absolute myocardial blood flow were obtained. The mean age was 68 years and 40% of the sample had an AHI≥15, which indicates moderate to severe OSA. Abnormal myocardial perfusion, both with stress and at rest, was more common in twins with elevated AHI. After adjusting for clinical, lifestyle and behavioral factors, and previous history of cardiovascular disease, twins with AHI ≥15 had 3.6 higher odds (95% CI, 1.5-8.9) of an abnormal total severity score, defined as a score ≥100, and for each 5-point increment in AHI, the odds of abnormality increased by 20% (95% CI, 7%-34%). Twin pairs where both twins had OSA exhibited the greatest risk. There were no differences in measures of ischemia and absolute myocardial blood flow and flow reserve by AHI status. OSA is associated with myocardial perfusion abnormalities that suggest prior subclinical myocardial scarring or infarction. Early environmental factors that affect both twins equally may play a role and should be further explored.

Oral contraceptive (OC) use increases venous thromboembolism risk 2-5-fold. Procoagulant changes can be detected in plasma from OC users even without thrombosis, but cellular mechanisms that provoke thrombosis have not been identified. Endothelial cell (EC) dysfunction is thought to initiate venous thromboembolism. It is unknown whether OC hormones provoke aberrant procoagulant activity in ECs. Characterize the effect of high-risk OC hormones (ethinyl estradiol [EE] and drospirenone) on EC procoagulant activity and the potential interplay with nuclear estrogen receptors ERα and ERβ and inflammatory processes. Human umbilical vein and dermal microvascular ECs (HUVEC and HDMVEC, respectively) were treated with EE and/or drospirenone. Genes encoding the estrogen receptors ERα and ERβ (ESR1 and ESR2, respectively) were overexpressed in HUVEC and HDMVEC via lentiviral vectors. EC gene expression was assessed by RT-qPCR. The ability of ECs to support thrombin generation and fibrin formation was measured by calibrated automated thrombography and spectrophotometry, respectively. Neither EE nor drospirenone, alone or together, changed expression of genes encoding anti- or procoagulant proteins (TFPI, THBD, F3), integrins (ITGAV, ITGB3), or fibrinolytic mediators (SERPINE1, PLAT). EE and/or drospirenone did not increase EC-supported thrombin generation or fibrin formation, either. Our analyses indicated a subset of individuals express ESR1 and ESR2 transcripts in human aortic ECs. However, overexpression of ESR1 and/or ESR2 in HUVEC and HDMVEC did not facilitate the ability of OC-treated ECs to support procoagulant activity, even in the presence of a pro-inflammatory stimulus. The OC hormones EE and drospirenone do not directly enhance thrombin generation potential of primary ECs in vitro.

Polygenic risk score values vary with genetic ancestry due to differences in population-specific allele frequencies and linkage disequilibrium patterns. We present a framework to calibrate polygenic risk scores based on ancestral makeup. We propose the “expected polygenic risk score” or ePRS, defined as the expected value of a polygenic risk score based on one’s global or local admixture patterns. We further define the “residual polygenic risk score” or rPRS as measuring the deviation of the polygenic risk score from the ePRS. The ePRS reflects the baseline ancestry-driven component of genetic risk, whereas the rPRS isolates an ancestry-agnostic measure of genetic liability. Simulation studies confirm that it suffices to adjust for ePRS to obtain nearly unbiased estimates of the polygenic risk score-outcome association without further adjusting for principal components. Using the TOPMed and the All of Us datasets, effect size estimates for the rPRS (adjusted for ePRS) are similar to those obtained from polygenic risk scores adjusting for genetic principal components. The ePRS framework can protect from population stratification in association analysis and provide an equitable strategy to interpret genetic risk across diverse populations. Polygenic risk scores vary with genetic ancestry. Here, the authors develop a framework to calibrate for genetic ancestry in these scores that leverages admixture analysis, separating out the ancestry-specific component of polygenic risk scores.

Sickle cell disease (SCD) is the most common monogenic-hemolytic disorder affecting people of African ancestry. Adenosine diphosphate (ADP) released following intravascular hemolysis activates platelets by stimulating purinergic receptors to promote thrombosis. Despite brisk intravascular hemolysis, which releases high levels of ADP into plasma, and evidence of platelet and hemostatic activation, it remains elusive why only a subset of SCD patients develop lung thrombosis. Using real-time in vivo lung microscopy, we report a surprising finding that humanized SCD mice are protected from ADP-induced lung thrombosis, which is secondary to the degradation of ADP by CD39 present in circulating extracellular vesicles released by the lung endothelium. ADP-induced platelet aggregation is also impaired in the blood of SCD patients with elevated levels of CD39 + extracellular vesicles. CD39 polymorphism rs3176891A→G is associated with the incidence of lung thrombosis in SCD patients but not healthy humans of African ancestry. Remarkably, CD39 + extracellular vesicles are fewer and ADP-induced platelet aggregation is higher in the blood of SCD patients with rs3176891G allele. This study identifies a novel extracellular vesicle-dependent mechanism preventing lung thrombosis in SCD and reveals how CD39 polymorphisms may impair this protection to increase the risk for lung thrombosis in a subset of SCD patients. It remains unknown why only some sickle cell disease (SCD) patients develop lung thrombosis. Here, the authors show that an extracellular vesicle-dependent mechanism prevents lung thrombosis in SCD and how a CD39 polymorphism impairs this protection to promote lung thrombosis in subset of patients.

BackgroundU.S. Veterans experience a high burden of COVID-19; characterizing immune responses associated with COVID-19 outcomes could help improve treatment. Changes in peripheral blood cytokines over time may predict both acute outcomes and long COVID symptoms.MethodsCytokine concentrations were quantified from peripheral blood collected 0–7 days (early) and 14–42 days (post-acute) after enrollment from SARS-CoV-2 positive participants in the EPIC3 study, a prospective, longitudinal cohort following U.S. Veterans. Responses were correlated with Veterans Affairs Severity Index for COVID-19 criteria and chronic symptoms with the modified Medical Research Council Dyspnea scale, Patient-Reported Outcomes Measurement Information System (PROMIS) Cognitive function, and PROMIS Fatigue scores 3 months after enrollment (60–135 days). Trends in cytokine concentration with COVID-19 severity were assessed. Odds of COVID-19 severity and long-term symptoms were estimated with logistic regression adjusted for sex, age, and morbidity. Longitudinal changes in cytokine concentration were examined for participants sampled during both time periods, by severity and long-term symptom group.ResultsEarly HGF, IL-18, IL-1RA, IP-10, and VEGF-A and post-acute MIP-1α and VEGF-A concentrations trended positively with increasing COVID-19 severity (q-values < 0.05, Jonckheere-Terpstra trend test). Increases in EGF, MIP-1β, and RANTES concentration and decreases in MIP-1α concentration over time were associated with mild rather than moderate or severe disease. Increases in MIP-1β and RANTES concentration and decreases in Eotaxin concentration over time were associated with the absence of long-term symptoms.ConclusionsWorse COVID-19 severity by 30 days was associated with higher early and post-acute period cytokine concentrations. Participants with long-term symptoms did not see resolution of cytokine responses over time.

Testosterone treatment of men with low testosterone is common and, although relatively short-term, has raised concern regarding an increased risk of prostate cancer (CaP). We investigated the association between modest-duration testosterone treatment and incident aggressive CaP. Retrospective inception cohort study of male Veterans aged 40 to 89 years with a laboratory-defined low testosterone measurement from 2002 to 2011 and recent prostate specific antigen (PSA) testing; excluding those with recent testosterone treatment, prostate or breast cancer, high PSA or prior prostate biopsy. Histologically-confirmed incident aggressive prostate cancer or any prostate cancer were the primary and secondary outcomes, respectively. Of the 147,593 men included, 58,617 were treated with testosterone. 313 aggressive CaPs were diagnosed, 190 among untreated men (incidence rate (IR) 0.57 per 1000 person years, 95% CI 0.49-0.65) and 123 among treated men (IR 0.58 per 1000 person years; 95% CI 0.48-0.69). After adjusting for age, race, hospitalization during year prior to cohort entry, geography, BMI, medical comorbidities, repeated testosterone and PSA testing, testosterone treatment was not associated with incident aggressive CaP (HR 0.89; 95% CI 0.70-1.13) or any CaP (HR 0.90; 95% CI 0.81-1.01). No association between cumulative testosterone dose or formulation and CaP was observed. Among men with low testosterone levels and normal PSA, testosterone treatment was not associated with an increased risk of aggressive or any CaP. The clinical risks and benefits of testosterone treatment can only be fully addressed by large, longer-term randomized controlled trials.

Christopher Newton-Cheh and colleagues from the QTGEN consortium report genetic associations to the QT interval duration, a measure of cardiac repolarization which is a risk factor for sudden cardiac death, in three genome-wide association studies from the Framingham Heart Study, the Rotterdam Study and the Cardiovascular Health Study. QT interval duration, reflecting myocardial repolarization on the electrocardiogram, is a heritable risk factor for sudden cardiac death and drug-induced arrhythmias. We conducted a meta-analysis of three genome-wide association studies in 13,685 individuals of European ancestry from the Framingham Heart Study, the Rotterdam Study and the Cardiovascular Health Study, as part of the QTGEN consortium. We observed associations at P < 5 × 10 −8 with variants in NOS1AP , KCNQ1, KCNE1 , KCNH2 and SCN5A , known to be involved in myocardial repolarization and mendelian long-QT syndromes. Associations were found at five newly identified loci, including 16q21 near NDRG4 and GINS3 , 6q22 near PLN , 1p36 near RNF207 , 16p13 near LITAF and 17q12 near LIG3 and RFFL . Collectively, the 14 independent variants at these 10 loci explain 5.4–6.5% of the variation in QT interval. These results, together with an accompanying paper, offer insights into myocardial repolarization and suggest candidate genes that could predispose to sudden cardiac death and drug-induced arrhythmias.

Background Limited information is available on how DNA methylation of cytosine-phosphate-guanine (CpG) sites across the genome regulate circulating von Willebrand Factor (VWF) and factor VIII (FVIII) levels. Methods We performed an epigenome-wide association study to examine the association of leukocyte DNA methylation levels at 483,735 CpG sites with VWF antigen plasma levels and FVIII activity in 2,597 Black and 1,011 White participants from the Atherosclerosis Risk in Communities (ARIC) study. VWF antigen levels and FVIII activity were measured at the baseline exam, while DNA methylation was measured with the Infinium HumanMethylation450 BeadChip array at visit 2 or 3. Discovery analysis was performed in the Black population, with replication in the White population. Results We identified 55 and 46 significant CpG sites associated with VWF and FVIII ( P  < 1.03 × 10 –7 ) in the discovery analysis, respectively. Among these, for VWF, 13 were replicated, mapping to one novel ( NBEAL2 ) and one known ( ABO ) locus. For FVIII, 12 associations were replicated which mapped to 1 novel locus ( B3GALT4 ) and 2 known but previously unreplicated loci ( ABO and CORO1A ). When we adjusted for the variants previously identified as independently associated with VWF and FVIII at the ABO locus, all attenuated at least 10% towards the null after adjustment for genetic variants. Conclusion We identified novel epigenetic associations with VWF and FVIII levels at the NBEAL2 and B3GALT4 loci. NBEAL2 is critical for the biosynthesis of platelet alpha granules, which store proteins that enable platelet adhesion initiation, including VWF while B3GALT4 is involved in glycosylation of glycoproteins like VWF and FVIII.