Laura M. G. Meems

The vitamin D receptor activator paricalcitol prevents fibrosis and diastolic dysfunction in a murine model of pressure overload

BACKGROUND Activation of the vitamin D-vitamin D receptor (VDR) axis has been shown to reduce blood pressure and left ventricular (LV) hypertrophy. Besides cardiac hypertrophy, cardiac fibrosis is a key element of adverse cardiac remodeling. We hypothesized that activation of the VDR by paricalcitol would prevent fibrosis and LV diastolic dysfunction in an established murine model of cardiac remodeling. METHODS Mice were subjected to transverse aortic constriction (TAC) to induce cardiac hypertrophy. Mice were treated with paricalcitol, losartan, or a combination of both for a period of four consecutive weeks. RESULTS The fixed aortic constriction caused similar increase in blood pressure, both in untreated and paricalcitol- or losartan-treated mice. TAC significantly increased LV weight compared to sham operated animals (10.2±0.7 vs. 6.9±0.3 mg/mm, p<0.05). Administration of either paricalcitol (10.5±0.7), losartan (10.8±0.4), or a combination of both (9.2±0.6) did not reduce LV weight. Fibrosis was significantly increased in mice undergoing TAC (5.9±1.0 vs. sham 2.4±0.8%, p<0.05). Treatment with losartan and paricalcitol reduced fibrosis (paricalcitol 1.6±0.3% and losartan 2.9±0.6%, both p<0.05 vs. TAC). This reduction in fibrosis in paricalcitol treated mice was associated with improved indices of LV contraction and relaxation, e.g. dPdtmax and dPdtmin and lower LV end diastolic pressure, and relaxation constant Tau. Also, treatment with paricalcitol and losartan reduced mRNA expression of ANP, fibronectin, collagen III and TIMP-1. DISCUSSION Treatment with the selective VDR activator paricalcitol reduces myocardial fibrosis and preserves diastolic LV function due to pressure overload in a mouse model. This is associated with a reduced percentage of fibrosis and a decreased expression of ANP and several other tissue markers.

Vitamin D Biology in Heart Failure: Molecular Mechanisms and Systematic Review

Vitamin D has recently been suggested as an important mediator of blood pressure and cardiovascular disease, including heart failure. In patient with heart failure, low vitamin D levels are associated with adverse outcome and correlate with established clinical correlates and biomarkers. Many precursor states of heart failure, such as hypertension, atherosclerosis, and diabetes are more prevalent in subjects with low vitamin D levels. Recent experimental data have provided clues how vitamin D might exert cardioprotective effects. The steroid hormone vitamin D regulates gene expression of many genes that play a prominent role in the progression of heart failure, such as cytokines and hormones. Specifically, vitamin D is a negative regulator of the hormone renin, the pivotal hormone of the renin-angiotensin system. Mechanistic insights were gained by studying mice deficient for the vitamin D receptor, which develop hypertension and adverse cardiac remodeling mediated via the renin-angiotensin system. Furthermore, vitamin D receptor is expressed in the heart and regulated under pro-hypertrophic stimuli and vitamin D as receptor has been associated with the expression of other hypertrophic genes such as natriuretic peptides. So, epidemiological data and mechanistic studies have provided strong support for a potentially cardioprotective effect of vitamin D. It remains unclear if vitamin D supplementation is beneficial in preventing heart failure or if it could be a therapeutic addendum in the treatment of heart failure. This review summarizes current knowledge on vitamin D and its biology in heart failure.

The LifeLines Cohort Study: Prevalence and treatment of cardiovascular disease and risk factors

BACKGROUND The LifeLines Cohort Study is a large three-generation prospective study and Biobank. Recruitment and data collection started in 2006 and follow-up is planned for 30years. The central aim of LifeLines is to understand healthy ageing in the 21st century. Here, the study design, methods, baseline and major cardiovascular phenotypes of the LifeLines Cohort Study are presented. METHODS AND RESULTS Baseline cardiovascular phenotypes were defined in 9700 juvenile (8-18years) and 152,180 adult (≥18years) participants. Cardiovascular disease (CVD) was defined using ICD-10 criteria. At least one cardiovascular risk factor was present in 73% of the adult participants. The prevalence, adjusted for the Dutch population, was determined for risk factors (hypertension (33%), hypercholesterolemia (19%), diabetes (4%), overweight (56%), and current smoking (19%)) and CVD (myocardial infarction (1.8%), heart failure (1.0%), and atrial fibrillation (1.3%)). Overall CVD prevalence increased with age from 9% in participants<65years to 28% in participants≥65years. Of the participants with hypertension, hypercholesterolemia and diabetes, respectively 75%, 96% and 41% did not receive preventive pharmacotherapy. CONCLUSIONS The contemporary LifeLines Cohort Study provides researchers with unique and novel opportunities to study environmental, phenotypic, and genetic risk factors for CVD and is expected to improve our knowledge on healthy ageing. In this contemporary Western cohort we identified a remarkable high percentage of untreated CVD risk factors suggesting that not all opportunities to reduce the CVD burden are utilised.

Low levels of vitamin D are associated with multimorbidity: results from the LifeLines Cohort Study.

Background. The prevalence of multimorbidity (≥ 1 disease within an individual) is rapidly increasing. So far, studies on the relationship between vitamin D and morbidity are mainly focusing on effects on single disease domains only, while vitamin D biology is associated with several diseases throughout the human body. Methods. We studied 8,726 participants from the LifeLines Cohort Study (a cross-sectional, population-based cohort study) and used the self-developed composite morbidity score to study the association between vitamin D levels and multimorbidity. Results. Study participants (mean age 45 ± 13 years, 73% females) had a mean plasma vitamin D level of 59 ± 22 nmol/L. In participants aged between 50 and 60 years, 58% had ≥ 2 affected disease domains, while morbidity score increased with age (70–80 years: 82% morbidity score > 1; > 80 years: 89% morbidity score > 1). Each incremental reduction by 1 standard deviation (SD) of vitamin D level was associated with an 8% higher morbidity score (full model OR 0.92, 95% CI 0.88–0.97, P = 0.001). Participants with vitamin D levels < 25 nmol/L were at highest risk for increasing morbidity prevalence (versus > 80 nmol/L, OR 1.34, 95% CI 1.07–1.67, P = 0.01). Conclusions. Low levels of vitamin D are associated with higher prevalence of multimorbidity, especially in participants with vitamin D levels < 25 nmol/L. Collectively, our results favor a general, rather than an organ-specific, approach when assessing the impact of vitamin D deficiency.

Parental vitamin D deficiency during pregnancy is associated with increased blood pressure in offspring via Panx1 hypermethylation

Vitamin D deficiency is one of the most common nutritional deficiencies worldwide. Maternal vitamin D deficiency is associated with increased susceptibility to hypertension in offspring, but the reasons for this remain unknown. The aim of this study was to determine if parental vitamin D deficiency leads to altered DNA methylation in offspring that may relate to hypertension. Male and female Sprague-Dawley rats were fed a standard or vitamin D-depleted diet. After 10 wk, nonsibling rats were mated. The conceived pups received standard chow. We observed an increased systolic and diastolic blood pressure in the offspring from depleted parents (F1-depl). Genome-wide methylation analyses in offspring identified hypermethylation of the promoter region of the Pannexin-1 (Panx1) gene in F1-depl rats. Panx1 encodes a hemichannel known to be involved in endothelial-dependent relaxation, and we demonstrated that in F1-depl rats the increase in blood pressure was associated with impaired endothelial relaxation of the large vessels, suggesting an underlying biological mechanism of increased blood pressure in children from parents with vitamin deficiency. Parental vitamin D deficiency is associated with epigenetic changes and increased blood pressure levels in offspring.

Plasma calcidiol, calcitriol, and parathyroid hormone and risk of new onset heart failure in a population‐based cohort study

Heart failure (HF) is a major problem in the Western world, with increasing prevalence and incidence. Because HF cannot be cured, prevention of HF is of utter importance. Calcidiol, calcitriol, and parathyroid hormone (PTH) have been identified as risk factors for cardiovascular disease. However, their association with new onset HF remains to be established. We investigated whether calcidiol, calcitriol, and PTH could be used to identify those subjects at risk for new onset HF, and if they had additive predictive value over established risk predictors like N‐terminal‐pro Brain‐type natriuretic peptide and highly sensitive Troponin‐T.Abstract Background Heart failure (HF) is a major problem in the Western world, with increasing prevalence and incidence. Because HF cannot be cured, prevention of HF is of utter importance. Calcidiol, calcitriol, and parathyroid hormone (PTH) have been identified as risk factors for cardiovascular disease. However, their association with new onset HF remains to be established. We investigated whether calcidiol, calcitriol, and PTH could be used to identify those subjects at risk for new onset HF, and if they had additive predictive value over established risk predictors like N‐terminal‐pro Brain‐type natriuretic peptide and highly sensitive Troponin‐T. Methods and results We examined 7470 HF‐free participants in Prevention of Renal and Vascular End‐stage Disease, a community‐based cohort study in Groningen, the Netherlands (latitude 53°N, mean age: 49 years, 48% male). During follow‐up time of 12.6 years (interquartile range: 12.3–12.9), 281 participants (4%) developed HF: 181 (66%) HF with reduced and 94 (34%) HF with preserved ejection fraction (HFrEF [left ventricular ejection fraction ≤ 40%], and HFpEF [left ventricular ejection fraction ≥ 50%], respectively). Mean (±SD) of calcidiol was 58 (±24) nmol/L, mean calcitriol 145 (±48) pmol/L, and median (interquartile range) PTH was 3.7 (3.0–4.6) pmol/L. Calcidiol levels were univariately associated with new onset HF [hazard ratio (HR) 0.82 (95% CI 0.69–0.96)], but calcitriol levels were not [HR 0.85 (95% CI 0.71–1.03)]. PTH levels kept their predictive value after adjustment for age, sex, and day of blood withdrawal (HR 1.26 [95% CI 1.04–1.53]). However, in our full model this association was lost [HR 1.10 (95% CI 0.92–1.32)]. Calcidiol, calcitriol, and PTH could not differentiate between new onset HFrEF or HFpEF. Conclusions After adjustment for confounding factors, a single measurement of plasma calcidiol, calcitriol, or PTH was not associated with risk of developing HF. Screening for these markers to identify subjects at risk for new onset HF cannot be advocated.

Vitamin D supplementation in heart failure: case closed?

Vitamin D deficiency is one of the most common nutritional deficiencies, affecting hundreds of millions of people in western societies, but also in Africa, the Middle East, and Asia. Although mostly denoted as a vitamin, vitamin D in fact is a pleiotropic hormone that acts as a transcription factor, with global effects on gene transcription; it has been suggested that up to 3% of the entire humane genome is regulated by vitamin D. Transcriptional activity is regulated by the vitamin D–vitamin D receptor (VDR) complex which, in concert with a complex set of co-repressors and co-activators, switches on or off downstream genes. As a result, vitamin D deficiency has been associated with multiple conditions and diseases, in almost all organ systems. More specifically, a low vitamin D concentration appeared to be associated with a poor prognosis in patients with heart failure. Mechanistic studies have provided potential mechanisms that may explain this relationship: vitamin D directly inhibits renin transcription, and regulates genes and pro-inflammatory cytokines involved in tissue fibrosis. Other, indirect, effects may also define why vitamin D deficiency is associated with increased cardiovascular morbidity and mortality: low vitamin D levels directly increase parathyroid hormone (PTH) levels, inducing deleterious effects on cardiac function and structure. Additionally, vitamin D deficiency in parents has been associated with hypertension in (vitamin D-sufficient) offspring via epigenetic modifications. The effects of vitamin D on the cardiovascular system are thus multifold and strongly suggest that restoration of vitamin D levels may improve cardiac function and outcome. Associative studies, however, cannot prove causality. In order to prove causality, it is essential to embark on interventional studies. In the current issue of the journal, Zittermann and colleagues have examined the effects of long-term vitamin D supplementation on hard cardiovascular outcomes in a moderately large sized randomized placebo controlled trial in patients with heart failure. This trial is important since it shows that vitamin D supplementation does not improve such outcomes, and, more importantly, suggests that safety may potentially be an issue. The study by Zittermann et al. is methodologically sound: it has a relatively large sample size and adequate long-term follow up of 3 years. Therefore, in our opinion, these findings should carry substantial weight as they allow evaluation of hard outcomes such as death and hospitalizations. Vitamin D supplementation boosted vitamin D levels quite readily, and patients on supplementation remained vitamin D sufficient for the entire study period. Patient recruitment, however, was an issue: although the study initially was powered to recruit 934 patients, recruitment had to be stopped after 31 months at a total of 400 patients because too many patients were already using vitamin D supplements, vitamin D levels were >75 nmol/L (which was the cut-off point for inclusion), or patients declined to participate in the study. Besides all-cause mortality, this study also considered mechanical circulatory support (MCS) as an (secondary) outcome parameter, since heart transplantation remains scarce because of lack of donors. Interestingly, it was observed that vitamin D supplementation may be associated with more frequent need for MCS. Although this additional analysis provides potentially important and valuable information, we question the importance of this relatively rare event; EVITA was not powered for this secondary outcome analysis, and the result may very well be a chance finding. The overall numbers of MCS systems were low (28/199 in the vitamin D group vs. 15/201 in the placebo group), with a reported P-value of 0.031. Given the number of endpoints evaluated, we would have corrected for multiple testing, resulting in a P-value exceeding 0.05. We nevertheless agree with the authors that this finding certainly warrants caution; supplementing vitamin D either chronically or in mega dosages, as done in some countries, has (again) not been proven to be efficacious, while safety issues cannot be accepted in this light. Furthermore, a recent intervention trial in the general population also did not provide any

Rodent heart failure models do not reflect the human circulating microRNA signature in heart failure

Introduction We recently identified a set of plasma microRNAs (miRNAs) that are downregulated in patients with heart failure in comparison with control subjects. To better understand their meaning and function, we sought to validate these circulating miRNAs in 3 different well-established rat and mouse heart failure models, and correlated the miRNAs to parameters of cardiac function. Methods The previously identified let-7i-5p, miR-16-5p, miR-18a-5p, miR-26b-5p, miR-27a-3p, miR-30e-5p, miR-199a-3p, miR-223-3p, miR-423-3p, miR-423-5p and miR-652-3p were measured by means of quantitative real time polymerase chain reaction (qRT-PCR) in plasma samples of 8 homozygous TGR(mREN2)27 (Ren2) transgenic rats and 8 (control) Sprague-Dawley rats, 6 mice with angiotensin II-induced heart failure (AngII) and 6 control mice, and 8 mice with ischemic heart failure and 6 controls. Circulating miRNA levels were compared between the heart failure animals and healthy controls. Results Ren2 rats, AngII mice and mice with ischemic heart failure showed clear signs of heart failure, exemplified by increased left ventricular and lung weights, elevated end-diastolic left ventricular pressures, increased expression of cardiac stress markers and reduced left ventricular ejection fraction. All miRNAs were detectable in plasma from rats and mice. No significant differences were observed between the circulating miRNAs in heart failure animals when compared to the healthy controls (all P>0.05) and no robust associations with cardiac function could be found. Conclusions The previous observation that miRNAs circulate in lower levels in human patients with heart failure could not be validated in well-established rat and mouse heart failure models. These results question the translation of data on human circulating miRNA levels to experimental models, and vice versa the validity of experimental miRNA data for human heart failure.