Sex-specific Mendelian randomisation to assess the causality of sex differences in the effects of risk factors and treatment: spotlight on hypertension

Hypertension is a key modifiable risk factor for cardiovascular disease. Several observational studies have found a stronger association of blood pressure and cardiovascular disease risk in women compared to men. Since observational studies can be affected by sex-specific residual confounding and reverse causation, it remains unclear whether these differences reflect actual differential effects. Other study designs are needed to uncover the causality of sex differences in the strength of risk factor and treatment effects. Mendelian randomisation (MR) uses genetic variants as instrumental variables to provide evidence about putative causal relations between risk factors and outcomes. By exploiting the random allocation of genes at gamete forming, MR is unaffected by confounding and results in more reliable causal effect estimates. In this review, we discuss why and how sex-specific MR and cis-MR could be used to study sex differences in risk factor and drug target effects. Sex-specific MR can be helpful to strengthen causal inferences in the field of sex differences, where it is often challenging to distinguish nature from nurture. The challenge of sex-specific (drug target) MR lays in leveraging robust genetic instruments from sex-specific GWAS studies which are not commonly available. Knowledge on sex-specific causal effects of hypertension, or other risk factors, could improve clinical practice and health policies by tailoring interventions based on personalised risk. Drug target MR can help to determine the anticipated on-target effects of a drug compound and to identify targets to pursue in drug developmen

Age-specific sex differences in intravascular ultrasound based coronary atherosclerotic plaque characteristics

Insights in age- and sex-specific coronary atherosclerotic plaque characteristics may contribute to a better understanding of coronary artery disease and, ultimately, to its prevention and treatment. In 307 women and 406 men aged 20 to 90 years undergoing intravascular ultrasound imaging, sex-based differences in coronary atherosclerotic plaque characteristics were mainly present in younger patients, while these differences were less pronounced at advanced age.</p

Sex-specific Mendelian randomisation to assess the causality of sex differences in the effects of risk factors and treatment: spotlight on hypertension

Hypertension is a key modifiable risk factor for cardiovascular disease. Several observational studies have found a stronger association of blood pressure and cardiovascular disease risk in women compared to men. Since observational studies can be affected by sex-specific residual confounding and reverse causation, it remains unclear whether these differences reflect actual differential effects. Other study designs are needed to uncover the causality of sex differences in the strength of risk factor and treatment effects. Mendelian randomisation (MR) uses genetic variants as instrumental variables to provide evidence about putative causal relations between risk factors and outcomes. By exploiting the random allocation of genes at gamete forming, MR is unaffected by confounding and results in more reliable causal effect estimates. In this review, we discuss why and how sex-specific MR and cis-MR could be used to study sex differences in risk factor and drug target effects. Sex-specific MR can be helpful to strengthen causal inferences in the field of sex differences, where it is often challenging to distinguish nature from nurture. The challenge of sex-specific (drug target) MR lays in leveraging robust genetic instruments from sex-specific GWAS studies which are not commonly available. Knowledge on sex-specific causal effects of hypertension, or other risk factors, could improve clinical practice and health policies by tailoring interventions based on personalised risk. Drug target MR can help to determine the anticipated on-target effects of a drug compound and to identify targets to pursue in drug development

A diet rich in unsaturated fatty acids prevents progression toward heart failure in a rabbit model of pressure and volume overload

Background-During heart failure (HF), cardiac metabolic substrate preference changes from fatty acid (FA) toward glucose oxidation. This change may cause progression toward heart failure. We hypothesize that a diet rich in FAs may prevent this process, and that dietary 3-FAs have an added antiarrhythmic effect based on action potential (AP) shortening in animals with HF. Methods and Results-Rabbits were fed a diet containing 1.25% (w/w) high oleic sunflower oil (HF-9, N 11), 1.25% fish oil (HF-3, N11), or no supplement (HF-control, N8). Subsequently, HF was induced by volume and pressure overload. After 4 months, HF-parameters were assessed, electrocardiograms were recorded, and blood and ventricular tissue were collected. Myocytes were isolated for patch clamp or intracellular Ca2-recordings to study electrophysiologic remodeling and arrhythmogenesis. Both the HF-9 and the HF-3 groups had larger myocardial FA oxidation capacity than HF control. The HF-3 group had significantly lower mean ( SEM) relative heart and lung weight (3.3-0.13 and 3.2-0.12 g kg 1, respectively) than HF control (4.8-0.30 and 4.5-0.23), and shorter QTc intervals (167-2.6 versus 182-6.4). The HF-9 also displayed a significantly reduced relative heart weight (3.6-0.26), but had similar QTc (179-4.3) compared with HF control. AP duration in the HF-3 group was 20% shorter due to increased Ito1 and IK1 and triggered activity, and Ca2-aftertransients were less than in the HF-9 group. Conclusions-Dietary unsaturated FAs started prior to induction of HF prevent hypertrophy and HF. In addition, fish oil FAs prevent HF-induced electrophysiologic remodeling and arrhythmias. © 2012 American Heart Association, Inc

Age-specific sex differences in intravascular ultrasound based coronary atherosclerotic plaque characteristics

Insights in age- and sex-specific coronary atherosclerotic plaque characteristics may contribute to a better understanding of coronary artery disease and, ultimately, to its prevention and treatment. In 307 women and 406 men aged 20 to 90 years undergoing intravascular ultrasound imaging, sex-based differences in coronary atherosclerotic plaque characteristics were mainly present in younger patients, while these differences were less pronounced at advanced age

The age- and sex-specific composition of atherosclerotic plaques in vascular surgery patients

BACKGROUND AND AIMS: The sex- and age-related differences in the composition of iliofemoral atherosclerotic plaques are largely unknown. Therefore, the aim of the current study is to gain insight into plaque composition across strata of age and sex in a large cohort of vascular surgery patients. METHODS: Peripheral atherosclerotic plaques of patients who underwent iliofemoral endarterectomy (n = 790) were harvested between 2002 and 2014. The plaques were semi-quantitatively analyzed for the presence of lipid cores, calcifications, plaque hemorrhages (PH), collagen, macrophage and smooth muscle cell (SMC) content, and quantitatively for microvessel density. Patients were stratified by age tertiles and sex. RESULTS: Ageing was independently associated with rupture-prone iliofemoral plaque characteristics, such as higher prevalence of plaque calcifications (OR 1.52 (95%CI:1.03-2.24) p = 0.035) and PH (OR 1.46 (95%CI:1.01-2.09) p = 0.042), and lower prevalence of collagen (OR 0.52 (95%CI:0.31-0.86) p = 0.012) and SMCs (OR 0.59 (95%CI:0.39-0.90) p = 0.015). Sex-stratified data showed that men had a higher prevalence of lipid cores (OR 1.62 (95%CI:1.06-2.45) p = 0.025) and PH (OR 1.62 (95%CI:1.16-2.54) p = 0.004) compared to women. These sex-differences attenuated with increasing age, with women showing an age-related increase in calcifications (p = 0.002), PH (p = 0.015) and decrease in macrophages (p = 0.005). In contrast, men only showed a decrease in collagen (p = 0.043). CONCLUSIONS: Atherosclerotic iliofemoral plaques derived from men display more rupture-prone characteristics compared to women. Yet, this difference is attenuated with an increase in age, with older women having more rupture-prone characteristics compared to younger women

Preventing unnecessary imaging in patients suspect of coronary artery disease through machine learning of electronic health records

Aims With the ageing European population, the incidence of coronary artery disease (CAD) is expected to rise. This will likely result in an increased imaging use. Symptom recognition can be complicated, as symptoms caused by CAD can be atypical, particularly in women. Early CAD exclusion may help to optimize use of diagnostic resources and thus improve the sustainability of the healthcare system. To develop sex-stratified algorithms, trained on routinely available electronic health records (EHRs), raw electrocardiograms, and haematology data to exclude CAD in patients upfront. Methods and results We trained XGBoost algorithms on data from patients from the Utrecht Patient-Oriented Database, who underwent coronary computed tomography angiography (CCTA), and/or stress cardiac magnetic resonance (CMR) imaging, or stress single-photon emission computerized tomography (SPECT) in the UMC Utrecht. Outcomes were extracted from radiology reports. We aimed to maximize negative predictive value (NPV) to minimize the false negative risk with acceptable specificity. Of 6808 CCTA patients (31% female), 1029 females (48%) and 1908 males (45%) had no diagnosis of CAD. Of 3053 CMR/SPECT patients (45% female), 650 females (47%) and 881 males (48%) had no diagnosis of CAD. On the train and test set, the CCTA models achieved NPVs and specificities of 0.95 and 0.19 (females) and 0.96 and 0.09 (males). The CMR/SPECT models achieved NPVs and specificities of 0.75 and 0.041 (females) and 0.92 and 0.026 (males). Conclusion Coronary artery disease can be excluded from EHRs with high NPV. Our study demonstrates new possibilities to reduce unnecessary imaging in women and men suspected of CAD

Increased circulating IgG levels, myocardial immune cells and IgG deposits support a role for an immune response in pre- and end-stage heart failure

The chronic inflammatory response plays an important role in adverse cardiac remodelling and the development of heart failure (HF). There is also evidence that in the pathogenesis of several cardiovascular diseases, chronic inflammation is accompanied by antibody and complement deposits in the heart, suggestive of a true autoimmune response. However, the role of antibody-mediated immune responses in HF progression is less clear. We assessed whether immune cell infiltration and immunoglobulin levels are associated with HF type and disease stage, taking sex differences into account. We found IgG deposits and increased infiltration of immune cells in the affected myocardium of patients with end-stage HF with reduced ejection fraction (HFrEF, n = 20). Circulating levels of IgG1 and IgG3 were elevated in these patients. Furthermore, the percentage of transitional/regulatory B cells was decreased (from 6.9% to 2.4%) compared with healthy controls (n = 5). Similarly, increased levels of circulating IgG1 and IgG3 were observed in men with left ventricular diastolic dysfunction (LVDD, n = 5), possibly an early stage of HF with preserved EF (HFpEF). In conclusion, IgG deposits and infiltrates of immune cells are present in end-stage HFrEF. In addition, both LVDD patients and end-stage HFrEF patients show elevated levels of circulating IgG1 and IgG3, suggesting an antibody-mediated immune response upon cardiac remodelling, which in the early phase of remodelling appear to differ between men and women. These immunoglobulin subclasses might be used as marker for pre-stage HF and its progression. Future identification of auto-antigens might open possibilities for new therapeutic interventions

Tobacco smoking is associated with sex- and plaque-type specific upregulation of CRLF1 in atherosclerotic lesions

Background and aims: Tobacco smoking is a known risk factor for atherosclerotic disease, with more elevated risks in women compared to men. We hypothesized that atherosclerotic plaques from smokers show different gene expression patterns compared to non-smokers, in a sex-specific manner. Methods: Gene expression data of 625 carotid plaques (151 females and 474 males) were analyzed for differential gene expression between current smokers (n = 226) and non-smokers (n = 399). All analyses were stratified by sex and by molecular plaque characteristics. Finally, we projected the activity of gene regulatory networks and utilized single-cell transcriptomics from 38 plaques (26 males and 12 females) to interpret the sex- and plaque-type specific signals. Results: We observed higher expression levels of CRLF1 gene in atherosclerotic plaques from smokers compared to non-smokers (log2FC = 0.48, FDR = 0.012). CRLF1 upregulation was interacting with sex (p = 0.01) and was more pronounced in females (log2FC = 0.93, p = 1.53E-05) compared to males (log2FC = 0.35, p = 0.0018). Through single-cell RNA-seq analysis, we identified the highest CRLF1 expression within the transitioning and synthetic smooth muscle cell populations. CRLF1 expression was increased in fibro-inflammatory and fibro-cellular plaque types. Gene annotations pointed to increased expression of CRLF1 in networks with extracellular matrix related genes. Conclusions: Atherosclerotic plaques from current smokers show sex-dependent upregulation of smooth muscle cell gene CRLF1. This may explain the different contributions of smoking to cardiovascular risk in females

X chromosome inactivation skewing is common in advanced carotid atherosclerotic lesions in females and predicts secondary peripheral artery events

BACKGROUND AND AIM: Sex differences in atherosclerosis have been described with female plaques being mostly perceived as stable and fibrous. Sex-specific mechanisms such as mosaic loss of the Y chromosome in men have been linked to cardiovascular health. In women, X-linked mechanisms such as X chromosome inactivation (XCI) skewing is common in several tissues. Yet, information on the role of XCI in female atherosclerotic plaques is lacking. Here, we investigated the presence of XCI skewing in advanced atherosclerotic lesions and its association with cardiovascular risk factors, histological plaque data, and clinical data. METHODS: XCI skewing was quantified in 154 atherosclerotic plaque and 55 blood DNA samples of women included in the Athero-Express study. The skewing status was determined performing the HUMARA assay. Then, we studied the relationship of XCI skewing in female plaque and cardiovascular risk factors using regression models. In addition, we studied if plaque XCI predicted plaque composition, and adverse events during 3-years follow-up using Cox proportional hazard models. RESULTS: XCI skewing was detected in 76 of 154 (49.4%) plaques and in 27 of 55 (67%) blood samples. None of the clinical risk factors were associated with plaque skewing. Plaque skewing was more often detected in plaques with a plaque hemorrhage (OR [95% CI]: 1.44 [1.06-1.98], P = 0.02). Moreover, skewed plaques were not associated with a higher incidence of composite and major events but were specifically associated with peripheral artery events during a 3-year follow-up period in a multivariate model (HR [95%CI]: 1.46 [1.09-1.97]; P = 0.007). CONCLUSIONS: XCI skewing is common in carotid plaques of females and is predictive for the occurrence of peripheral artery events within 3 years after carotid endarterectomy