ET (Endothelin)-1 and Ischemic Heart Disease

Long-term dietary nitrate supplementation slows the progression of established atherosclerosis in ApoE-/- mice fed a high fat diet

BACKGROUND AND AIMS

Atherosclerosis is associated with a reduction in the bioavailability and/or bioactivity of endogenous nitric oxide (NO). Dietary nitrate has been proposed as an alternate source when endogenous NO production is reduced. Our previous study demonstrated a protective effect of dietary nitrate on the development of atherosclerosis in the apoE-/- mouse model. However most patients do not present clinically until well after the disease is established. The aims of this study were to determine whether chronic dietary nitrate supplementation can prevent or reverse the progression of atherosclerosis after disease is already established, as well as to explore the underlying mechanism of these cardiovascular protective effects.

METHODS

60 apoE-/- mice were given a high fat diet (HFD) for 12 weeks to allow for the development of atherosclerosis. The mice were then randomized to (i) control group (HFD + 1 mmol/kg/day NaCl), (ii) moderate-dose group (HFD +1 mmol/kg/day NaNO3), or (iii) high-dose group (HFD + 10 mmol/kg/day NaNO3) (20/group) for a further 12 weeks. A group of apoE-/- mice (n = 20) consumed a normal laboratory chow diet for 24 weeks and were included as a reference group.

RESULTS

Long-term supplementation with high dose nitrate resulted in ~ 50% reduction in plaque lesion area. Collagen expression and smooth muscle accumulation were increased, and lipid deposition and macrophage accumulation were reduced within atherosclerotic plaques of mice supplemented with high dose nitrate. These changes were associated with an increase in nitrite reductase as well as activation of the endogenous eNOS-NO pathway.

CONCLUSION

Long-term high dose nitrate significantly attenuated the progression of established atherosclerosis in the apoE-/- mice fed a HFD. This appears to be mediated in part through a XOR-dependent reduction of nitrate to NO, as well as enhanced eNOS activation via increased Akt and eNOS phosphorylation.

Causal association between mTOR-dependent EIF-4E and EIF-4A circulating protein levels and type 2 diabetes: a Mendelian randomization study

The mammalian Target of Rapamycin complex 1 (mTORC1) nutrient-sensing pathway is a central regulator of cell growth and metabolism and is dysregulated in diabetes. The eukaryotic translation initiation factor 4E (EIF-4E) protein, a key regulator of gene translation and protein function, is controlled by mTORC1 and EIF-4E Binding Proteins (EIF4EBPs). Both EIF4EBPs and ribosomal protein S6K kinase (RP-S6K) are downstream effectors regulated by mTORC1 but converge to regulate two independent pathways. We investigated whether the risk of type 2 diabetes varied with genetically predicted EIF-4E, EIF-4A, EIF-4G, EIF4EBP, and RP-S6K circulating levels using Mendelian Randomization. We estimated the causal role of EIF-4F complex, EIF4EBP, and S6K in the circulation on type 2 diabetes, based on independent single nucleotide polymorphisms strongly associated (p = 5 × 10^–6) with EIF-4E (16 SNPs), EIF-4A (11 SNPs), EIF-4G (6 SNPs), EIF4EBP2 (12 SNPs), and RP-S6K (16 SNPs). The exposure data were obtained from the INTERVAL study. We applied these SNPs for each exposure to publically available genetic associations with diabetes from the DIAbetes Genetics Replication And Meta-analysis (DIAGRAM) case (n = 26,676) and control (n = 132,532) study (mean age 57.4 years). We meta-analyzed SNP-specific Wald-estimates using inverse variance weighting with multiplicative random effects and conducted sensitivity analysis. Mendelian Randomization (MR-Base) R package was used in the analysis. The PhenoScanner curated database was used to identify disease associations with SNP gene variants. EIF-4E is associated with a lowered risk of type 2 diabetes with an odds ratio (OR) 0.94, 95% confidence interval (0.88, 0.99, p = 0.03) with similar estimates from the weighted median and MR-Egger. Similarly, EIF-4A was associated with lower risk of type 2 diabetes with odds ratio (OR) 0.90, 95% confidence interval (0.85, 0.97, p = 0.0003). Sensitivity analysis using MR-Egger and weighed median analysis does not indicate that there is a pleiotropic effect. This unbiased Mendelian Randomization estimate is consistent with a protective causal association of EIF-4E and EIF-4A on type 2 diabetes. EIF-4E and EIF-4A may be targeted for intervention by repurposing existing therapeutics to reduce the risk of type 2 diabetes.

Investigating pleiotropic effects of statins on ischemic heart disease in the UK Biobank using Mendelian randomisation

We examined whether specifically statins, of the major lipid modifiers (statins, proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors and ezetimibe) have pleiotropic effects on ischemic heart disease (IHD) via testosterone in men or women. As a validation, we similarly assessed whether a drug that unexpectedly likely increases IHD also operates via testosterone. Using previously published genetic instruments we conducted a sex-specific univariable and multivariable Mendelian randomization study in the UK Biobank, including 179918 men with 25410 IHD cases and 212080 women with 12511 IHD cases. Of these three lipid modifiers, only genetically mimicking the effects of statins in men affected testosterone, which partly mediated effects on IHD. Correspondingly, genetically mimicking effects of anakinra on testosterone and IHD presented a reverse pattern to that for statins. These insights may facilitate the development of new interventions for cardiovascular diseases as well as highlighting the importance of sex-specific explanations, investigations, prevention and treatment.

Effects of blood lead on coronary artery disease and its risk factors: a Mendelian Randomization study

Lead is pervasive, although lead exposure has fallen in response to public health efforts. Observationally, lead is positively associated with cardiovascular disease and hypertension. We used separate-sample instrumental variable analysis with genetic instruments (Mendelian randomization) based on 13 single nucleotide polymorphisms (SNP), from a genome wide association study, strongly (p-value < 5 × 10^-6) and independently associated with blood lead. These SNPs were applied to a large extensively genotyped coronary artery disease (CAD) study (cases = <76014, controls = <264785) largely based on CARDIoGRAPMplusC4D 1000 Genomes and the UK Biobank SOFT CAD, to the UK Biobank (n = 361,194) for blood pressure and to the DIAGRAM 1000 genomes diabetes case (n = 26,676)-control (n = 132,532) study. SNP-specific Wald estimates were combined using inverse variance weighting, MR-Egger and MR-PRESSO. Genetically instrumented blood lead was not associated with CAD (odds ratio (OR) 1.01 per effect size of log transformed blood lead, 95% confidence interval (CI) 0.97, 1.05), blood pressure (systolic -0.18 mmHg, 95% CI -0.44 to 0.08 and diastolic -0.03 mmHg, 95% CI -0.09 to 0.15) or diabetes (OR 0.98, 95% CI 0.92 to 1.03) using MR-PRESSO estimates corrected for an outlier SNP (rs550057) from the highly pleiotropic gene ABO. Exogenous lead may have different effects from endogenous lead; nevertheless, this study raises questions about the role of blood lead in CAD.

Effect of glutamate and aspartate on ischemic heart disease, blood pressure, and diabetes: a Mendelian randomization study

BACKGROUND

Evolutionary biology suggests reproduction trades off against longevity. Genetic selection in favor of fertility and ischemic heart disease (IHD) exists in humans. Observationally, soy protects against IHD. Soy amino acids, glutamate and aspartate, may lower androgens. No large randomized controlled trials testing their health effects exist.

OBJECTIVE

Using Mendelian randomization, we assessed how genetically predicted glutamate and aspartate affected IHD, blood pressure, and diabetes.

METHODS

A separate sample instrumental variable analysis with genetic instruments was used to obtain unconfounded estimates using genetic variants strongly (P < 5 × 10(-8)) and solely associated with glutamate or aspartate applied to an IHD case (n ≤76,014)-control (n ≤ 264,785) study (based on a meta-analysis of CARDIoGRAMplusC4D 1000 Genomes, UK Biobank CAD SOFT GWAS and Myocardial Infarction Genetics and CARDIoGRAM Exome), blood pressure from the UK Biobank (n ≤ 361,194), and the DIAbetes Genetics Replication And Meta-analysis diabetes case (n = 26,676)-control (n = 132,532) study. A weighted median and MR-Egger were used for a sensitivity analysis.

RESULTS

Glutamate was not associated with IHD, blood pressure, or diabetes after correction for multiple comparisons. Aspartate was inversely associated with IHD (odds ratio (OR) 0.92 per log-transformed standard deviation (SD); 95% confidence interval (CI) 0.88, 0.96) and diastolic blood pressure (-0.03; 95% CI -0.04, -0.02) using inverse variance weighting, but not diabetes (OR 1.00; 95% CI 0.91, 1.09). Associations were robust to the sensitivity analysis.

CONCLUSIONS

Our findings suggest aspartate may play a role in IHD and blood pressure, potentially underlying cardiovascular benefits of soy. Clarifying the mechanisms would be valuable for IHD prevention and for defining a healthy diet.

Association of genetically predicted testosterone with thromboembolism, heart failure, and myocardial infarction: mendelian randomisation study in UK Biobank

OBJECTIVE

To determine whether endogenous testosterone has a causal role in thromboembolism, heart failure, and myocardial infarction.

DESIGN

Two sample mendelian randomisation study using genetic variants as instrumental variables, randomly allocated at conception, to infer causality as additional randomised evidence.

SETTING

Reduction by Dutasteride of Prostate Cancer Events (REDUCE) randomised controlled trial, UK Biobank, and CARDIoGRAMplusC4D 1000 Genomes based genome wide association study.

PARTICIPANTS

3225 men of European ancestry aged 50-75 in REDUCE; 392 038 white British men and women aged 40-69 from the UK Biobank; and 171 875 participants of about 77% European descent, from CARDIoGRAMplusC4D 1000 Genomes based study for validation.

MAIN OUTCOME MEASURES

Thromboembolism, heart failure, and myocardial infarction based on self reports, hospital episodes, and death.

RESULTS

Of the UK Biobank participants, 13 691 had thromboembolism (6208 men, 7483 women), 1688 had heart failure (1186, 502), and 12 882 had myocardial infarction (10 136, 2746). In men, endogenous testosterone genetically predicted by variants in the JMJD1C gene region was positively associated with thromboembolism (odds ratio per unit increase in log transformed testosterone (nmol/L) 2.09, 95% confidence interval 1.27 to 3.46) and heart failure (7.81, 2.56 to 23.8), but not myocardial infarction (1.17, 0.78 to 1.75). Associations were less obvious in women. In the validation study, genetically predicted testosterone (based on JMJD1C gene region variants) was positively associated with myocardial infarction (1.37, 1.03 to 1.82). No excess heterogeneity was observed among genetic variants in their associations with the outcomes. However, testosterone genetically predicted by potentially pleiotropic variants in the SHBG gene region had no association with the outcomes.

CONCLUSIONS

Endogenous testosterone was positively associated with thromboembolism, heart failure, and myocardial infarction in men. Rates of these conditions are higher in men than women. Endogenous testosterone can be controlled with existing treatments and could be a modifiable risk factor for thromboembolism and heart failure.

Molecular mechanism involved in cyclophosphamide-induced cardiotoxicity: Old drug with a new vision

Cyclophosphamide (CP) is an important anticancer drug which belongs to the class of alkylating agent. Cyclophosphamide is mostly used in bone marrow transplantation, rheumatoid arthritis, lupus erythematosus, multiple sclerosis, neuroblastoma and other types of cancer. Dose-related cardiotoxicity is a limiting factor for its use. CP-induced cardiotoxicity ranges from 7 to 28% and mortality ranges from 11 to 43% at the therapeutic dose of 170-180 mg/kg, i.v. CP undergoes hepatic metabolism that results in the production of aldophosphamide. Aldophosphamide decomposes into phosphoramide mustard & acrolein. Phosphoramide is an active neoplastic agent, and acrolein is a toxic metabolite which acts on the myocardium and endothelial cells. This is the first review article that talks about cyclophosphamide-induced cardiotoxicity and the different signaling pathways involved in its pathogenicity. Based on the available literature, CP is accountable for cardiomyocytes energy pool alteration by affecting the heart fatty acid binding proteins (H-FABP). CP has been found associated with cardiomyocytes apoptosis, inflammation, endothelial dysfunction, calcium dysregulation, endoplasmic reticulum damage, and mitochondrial damage. Molecular mechanism of cardiotoxicity has been discussed in detail through crosstalk of Nrf2/ARE, Akt/GSK-3β/NFAT/calcineurin, p53/p38MAPK, NF-kB/TLR-4, and Phospholamban/SERCA-2a signaling pathway. Based on the available literature we support the fact that metabolites of CP are responsible for cardiotoxicity due to depletion of antioxidants/ATP level, altered contractility, damaged endothelium and enhanced pro-inflammatory/pro-apoptotic activities resulting into cardiomyopathy, myocardial infarction, and heart failure. Dose adjustment, elimination/excretion of acrolein and maintenance of endogenous antioxidant pool could be the therapeutic approach to mitigate the toxicities.

Endothelin-1 Measurement in Patients Undergoing Diagnostic Coronary Angiography—Results from the Catheter Sampled Blood Archive in Cardiovascular Diseases (CASABLANCA) Study

BACKGROUND

Endothelin-1 (ET-1) is a vasoconstrictor produced by vascular endothelial cells and may play a role in risk for development of coronary artery disease (CAD) and heart failure (HF). In a cohort of 1084 patients referred for coronary angiography, we investigated cross-sectional associations between ET-1 concentrations and prevalent CAD, as well as value of ET-1 for prognostication of future cardiovascular events.

METHODS

Associations between ET-1 and presence/severity of CAD were assessed. Patients were followed for a median of 4 years for outcomes including incident HF, myocardial infarction (MI), cardiovascular mortality, and all-cause mortality.

RESULTS

The median concentration of ET-1 was 2.57 ng/L. Patients with ET-1 concentrations above the median were more likely to have higher risk clinical features. Among those without prevalent MI at presentation, ET-1 concentrations were not associated with presence or severity of CAD. In adjusted Cox proportional hazards analyses, log-transformed ET-1 concentrations predicted incident HF [hazard ratio (HR) = 1.51 per increase in log-SD; 95% CI, 1.06–2.15; P = 0.02] and all-cause mortality (HR = 1.61 per increase in log-SD; 95% CI, 1.03–2.53; P = 0.04). Concentrations of ET-1 above the median were associated with shorter time to incident HF, MI, cardiovascular mortality, all-cause mortality, and the composite of incident HF/MI/cardiovascular mortality (all log-rank P &lt; 0.001).

CONCLUSIONS

Despite epidemiologic links to CAD, we found no cross-sectional association between biologically active ET-1 and prevalent coronary atherosclerosis in an at-risk population referred for coronary angiography. Increased ET-1 concentrations independently predict incident HF and death and are associated with more near-term cardiovascular events.

Genetic predictors of testosterone and their associations with cardiovascular disease and risk factors: A Mendelian randomization investigation

Background

Testosterone supplementation has been linked to increased cardiovascular disease risk in some observational studies. The causal role of testosterone can be investigated using a Mendelian randomization approach.

Methods and results

We assessed genetic associations of variants in two gene regions (SHBG and JMJD1C) with several cardiovascular risk factors (lipids, adiponectin, blood pressure, anthropometric traits) plus male pattern baldness, including control outcomes and potential mediators. We assessed genetic associations with coronary artery disease (CAD) risk in the CARDIoGRAMplusC4D consortium (171,191 individuals including 60,801 cases), and associations with CAD and ischaemic stroke risk in the UK Biobank (367,643 individuals including 25,352 CAD cases and 3650 ischaemic stroke cases).

Genetic predictors of increased serum testosterone were associated with lipids, blood pressure, and height. There was some evidence of an association with risk of CAD (SHBG gene region: odds ratio (OR) 0.95 per 1 unit increase in log-transformed testosterone [95% confidence interval: 0.81–1.12, p = 0.55]; JMJD1C gene region: OR 1.24 [1.01–1.51, p = 0.04]) and ischaemic stroke both overall (SHBG: OR 1.05 [0.64, 1.73, p = 0.83]; JMJD1C: OR 2.52 [1.33, 4.77, p = 0.005]) and in men. However, associations with some control outcomes were in the opposite direction to that expected.

Conclusions

Sex hormone-related mechanisms appear to be relevant to cardiovascular risk factors and for stroke (particularly for men). However, the extent that these findings are specifically informative about endogenous testosterone or testosterone supplementation is unclear. These findings underline a fundamental limitation for the use of Mendelian randomization where biological knowledge about the function of genetic variants is uncertain.

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Genetic predictors of testosterone were associated with cardiovascular risk factors, such as lipids and blood pressure.

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However, associations were not consistent between the two gene regions considered in this analysis.

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Some genetic predictors of increased testosterone associated with higher coronary artery disease and ischaemic stroke risk.

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This suggests that some sex hormone-related mechanisms are implicated in cardiovascular disease.

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However, the extent to which these analyses are predictive of the effects of testosterone supplementation is unclear.