Nicolas Verheyen

Aldosterone and parathyroid hormone interactions as mediators of metabolic and cardiovascular disease

Inappropriate aldosterone and parathyroid hormone (PTH) secretion is strongly linked with development and progression of cardiovascular (CV) disease. Accumulating evidence suggests a bidirectional interplay between parathyroid hormone and aldosterone. This interaction may lead to a disproportionally increased risk of CV damage, metabolic and bone diseases. This review focuses on mechanisms underlying the mutual interplay between aldosterone and PTH as well as their potential impact on CV, metabolic and bone health. PTH stimulates aldosterone secretion by increasing the calcium concentration in the cells of the adrenal zona glomerulosa as a result of binding to the PTH/PTH-rP receptor and indirectly by potentiating angiotensin 2 induced effects. This may explain why after parathyroidectomy lower aldosterone levels are seen in parallel with improved cardiovascular outcomes. Aldosterone mediated effects are inappropriately pronounced in conditions such as chronic heart failure, excess dietary salt intake (relative aldosterone excess) and primary aldosteronism. PTH is increased as a result of (1) the MR (mineralocorticoid receptor) mediated calciuretic and magnesiuretic effects with a trend of hypocalcemia and hypomagnesemia; the resulting secondary hyperparathyroidism causes myocardial fibrosis and disturbed bone metabolism; and (2) direct effects of aldosterone on parathyroid cells via binding to the MR. This adverse sequence is interrupted by mineralocorticoid receptor blockade and adrenalectomy. Hyperaldosteronism due to klotho deficiency results in vascular calcification, which can be mitigated by spironolactone treatment. In view of the documented reciprocal interaction between aldosterone and PTH as well as the potentially ensuing target organ damage, studies are needed to evaluate diagnostic and therapeutic strategies to address this increasingly recognized pathophysiological phenomenon.

Vitamin D and cardiovascular disease prevention

Vitamin D is a precursor of the steroid hormone calcitriol that is crucial for bone and mineral metabolism. Both the high prevalence of vitamin D deficiency in the general population and the identification of the vitamin D receptor in the heart and blood vessels raised interest in the potential cardiovascular effects of vitamin D. Experimental studies have demonstrated various cardiovascular protective actions of vitamin D, but vitamin D intoxication in animals is known to induce vascular calcification. In meta-analyses of epidemiological studies, vitamin D deficiency is associated with an increased cardiovascular risk. Findings from Mendelian randomization studies and randomized, controlled trials (RCTs) do not indicate significant effects of a general vitamin D supplementation on cardiovascular outcomes. Previous RCTs, however, were not adequately designed to address extraskeletal events, and did not focus on vitamin D-deficient individuals. Therefore, currently available evidence does not support cardiovascular benefits or harms of vitamin D supplementation with the commonly used doses, and whether vitamin D has cardiovascular effects in individuals with overt vitamin D deficiency remains to be evaluated. Here, we provide an update on clinical studies on vitamin D and cardiovascular risk, discuss ongoing vitamin D research, and consider the management of vitamin D deficiency from a cardiovascular health perspective.

Effects of vitamin D on blood pressure and cardiovascular risk factors: a randomized controlled trial.

Vitamin D deficiency is a risk factor for arterial hypertension, but randomized controlled trials showed mixed effects of vitamin D supplementation on blood pressure (BP). We aimed to evaluate whether vitamin D supplementation affects 24-hour systolic ambulatory BP monitoring values and cardiovascular risk factors. The Styrian Vitamin D Hypertension Trial is a single-center, double-blind, placebo-controlled study conducted from June 2011 to August 2014 at the endocrine outpatient clinic of the Medical University of Graz, Austria. We enrolled 200 study participants with arterial hypertension and 25-hydroxyvitamin D levels below 30 ng/mL. Study participants were randomized to receive either 2800 IU of vitamin D3 per day as oily drops (n=100) or placebo (n=100) for 8 weeks. Primary outcome measure was 24-hour systolic BP. Secondary outcome measures were 24-hour diastolic BP, N-terminal-pro-B-type natriuretic peptide, QTc interval, renin, aldosterone, 24-hour urinary albumin excretion, homeostasis model assessment-insulin resistance, triglycerides, high-density lipoprotein cholesterol, and pulse wave velocity. A total of 188 participants (mean [SD] age, 60.1 [11.3] years; 47% women; 25-hydroxyvitamin D, 21.2 [5.6] ng/mL) completed the trial. The mean treatment effect (95% confidence interval) for 24-hour systolic BP was −0.4 (−2.8 to 1.9) mm Hg (P=0.712). Triglycerides increased significantly (mean change [95% confidence interval], 17 [1–33] mg/dL; P=0.013), but no further significant effects were observed for secondary outcomes. Vitamin D supplementation in hypertensive patients with low 25-hydroxyvitamin D has no significant effect on BP and several cardiovascular risk factors, but it was associated with a significant increase in triglycerides. Clinical Trial Registration— URL: http://www.clinicaltrials.gov. Unique identifier: NCT02136771.

Vitamin D and cardiovascular disease.

Vitamin D deficiency, as well as cardiovascular diseases (CVD) and related risk factors are highly prevalent worldwide and frequently co-occur. Vitamin D has long been known to be an essential part of bone metabolism, although recent evidence suggests that vitamin D plays a key role in the pathophysiology of other diseases, including CVD, as well. In this review, we aim to summarize the most recent data on the involvement of vitamin D deficiency in the development of major cardiovascular risk factors: hypertension, obesity and dyslipidemia, type 2 diabetes, chronic kidney disease and endothelial dysfunction. In addition, we outline the most recent observational, as well as interventional data on the influence of vitamin D on CVD. Since it is still an unresolved issue whether vitamin D deficiency is causally involved in the pathogenesis of CVD, data from randomized controlled trials (RCTs) designed to assess the impact of vitamin D supplementation on cardiovascular outcomes are awaited with anticipation. At present, we can only conclude that vitamin D deficiency is an independent cardiovascular risk factor, but whether vitamin D supplementation can significantly improve cardiovascular outcomes is still largely unknown.

Homoarginine in the renal and cardiovascular systems

Homoarginine (hArg) is an endogenous, nonproteinogenic amino acid which differs from arginine by an additional methylene (CH2) group in the backbone. In this brief narrative review, we summarize the current literature on hArg in the renal and cardiovascular systems. Epidemiological studies have identified low hArg levels as an independent risk marker for cardiovascular, cerebrovascular, and renal diseases as well as for mortality. The relatively low correlation of hArg with established cardiovascular risk factors underlines its great potential as an emerging biomarker to improve risk prediction because plasma hArg concentrations might reflect previously unrecognized pathophysiological processes. hArg may be involved in the pathogenesis of various diseases due to its effects on nitric oxide (NO) and energy metabolism. In view of its structural similarities with arginine, it has been proposed that hArg impacts on arginine metabolism and subsequently also on NO synthesis. The key enzyme for hArg synthesis, arginine:glycine amidinotransferase (AGAT), is involved in the synthesis of energy metabolites including guanidinoacetate, the precursor of creatine. Therefore, the involvement of hArg in energy metabolism could partially explain the close association between hArg and cardiovascular diseases such as heart failure. Whether hArg supplementation or modification of key enzymes of hArg metabolism such as AGAT activity is effective for the treatment of chronic diseases remains to be elucidated.

Effect of eplerenone on parathyroid hormone levels in patients with primary hyperparathyroidism: a randomized, double-blind, placebo-controlled trial

BackgroundIncreasing evidence suggests the bidirectional interplay between parathyroid hormone and aldosterone as an important mechanism behind the increased risk of cardiovascular damage and bone disease observed in primary hyperparathyroidism. Our primary object is to assess the efficacy of the mineralocorticoid receptor-blocker eplerenone to reduce parathyroid hormone secretion in patients with parathyroid hormone excess.Methods/designOverall, 110 adult male and female patients with primary hyperparathyroidism will be randomly assigned to eplerenone (25 mg once daily for 4 weeks and 4 weeks with 50 mg once daily after dose titration] or placebo, over eight weeks. Each participant will undergo detailed clinical assessment, including anthropometric evaluation, 24-h ambulatory arterial blood pressure monitoring, echocardiography, kidney function and detailed laboratory determination of biomarkers of bone metabolism and cardiovascular disease.The study comprises the following exploratory endpoints: mean change from baseline to week eight in (1) parathyroid hormone(1–84) as the primary endpoint and (2) 24-h systolic and diastolic ambulatory blood pressure levels, NT-pro-BNP, biomarkers of bone metabolism, 24-h urinary protein/albumin excretion and echocardiographic parameters reflecting systolic and diastolic function as well as cardiac dimensions, as secondary endpoints.DiscussionIn view of the reciprocal interaction between aldosterone and parathyroid hormone and the potentially ensuing target organ damage, the EPATH trial is designed to determine whether eplerenone, compared to placebo, will effectively impact on parathyroid hormone secretion and improve cardiovascular, renal and bone health in patients with primary hyperparathyroidism.Trial registrationISRCTN33941607

Cinacalcet hydrochloride for the treatment of hyperparathyroidism

Introduction: Effective therapeutic strategies are warranted to reduce the burden of parathyroid hormone excess related morbidity and mortality. The calcimimetic agent cinacalcet hydrochloride is a promising treatment strategy in hyperparathyroidism. Areas covered: This review provides an overview of the pharmacokinetics, clinical efficacy, cost-effectiveness, safety and the efficacy profile of cinacalcet in the setting of primary and secondary hyperparathyroidism (p/sHPT). The authors searched PubMed database for English language articles related to cinacalcet in human subjects, published till Dec 2012 – focusing on the period between 2008 and 2012. Expert opinion: The use of cinacalcet in pHPT can be considered on those hypercalcemic patients in whom parathyroidectomy is not performed. However, data on the impact of cinacalcet on hard clinical outcomes in pHPT are missing. Despite effective improvements of biochemical parameters of sHPT, the intention-to-treat-based analysis of the EVOLVE trial did not support the notion that cinacalcet significantly reduces the risk of death or major cardiovascular events in dialysis patients with moderate-to-severe sHPT. Considering the strong evidence indicating beneficial effects of cinacalcet in the setting of HPT, further randomized controlled trials are definitely warranted to evaluate whether calcimimetic treatment might improve mortality and cardiovascular risk in patients with parathyroid hormone excess over a broad spectrum of kidney function.

Vitamin-D concentrations, cardiovascular risk and events - a review of epidemiological evidence

Vitamin D has long been established as an elemental factor of bone physiology. Beyond mineral metabolism, the expression of the vitamin D receptor has been identified throughout the cardiovascular (CV) system. Experimental studies showed beneficial effects of vitamin D on heart and vessels, but vitamin D intoxication in animals also led to hypercalcemia and vascular calcification. Our knowledge has been extended by epidemiological studies that showed that 25-hydroxyvitamin D (25(OH)D) levels are inversely associated with an increased CV risk itself, but also with established CV risk factors, such as arterial hypertension, endothelial dysfunction and atherosclerosis. Conversely, randomized controlled trials could not document significant and consistent effects of vitamin D supplementation on CV risk or events. Potential explanations may lie in differences in reference ranges or the possibility that low vitamin D in CV disease is only an epiphenomenon. In the latter case, the key question is why low 25(OH)D levels are such a strong predictor of health. While we wait for new data, the current conclusion is that vitamin D is a strong risk marker for CV risk factors and for CV diseases itself.

Effects of Vitamin D Supplementation on Plasma Aldosterone and Renin—A Randomized Placebo-Controlled Trial

Increasing evidence describes a possible interplay between vitamin D insufficiency with increased aldosterone. The authors sought to evaluate the effect of vitamin D supplementation on plasma aldosterone concentration (PAC) in patients with hypertension and 25‐hydroxyvitamin D[25(OH)D] insufficiency. The Styrian Vitamin D Hypertension Trial was a single‐center, double‐blind, placebo‐controlled randomized clinical trial conducted from 2011 to 2014. Two hundred patients with arterial hypertension and 25(OH)D levels <30 ng/mL were enrolled. Study participants were randomized to receive either 2800 IU of vitamin D3 or placebo. The present investigation is a post hoc analysis using analysis of covariance adjusting for baseline differences. A total of 188 participants (mean±standard deviation age, 60.1±11.3 years; 47% women; 25(OH)D, 21.2±5.6 ng/mL) completed the trial. Mean differences between baseline and follow‐up PAC in the control and intervention arm were +3.3 ng/dL and +0.9 ng/dL, respectively (P=.04). The findings indicate that vitamin D3 supplementation significantly decreases PAC in patients with arterial hypertension and 25(OH)D insufficiency.

Effect of eplerenone on parathyroid hormone levels in patients with primary hyperparathyroidism: results from the EPATH randomized, placebo-controlled trial

Background: Accumulating evidence points toward mutual interaction between parathyroid hormone (PTH) and aldosterone as potential mechanism for increasing cardiovascular risk in primary hyperparathyroidism (pHPT). Methods: The Eplerenone on parathyroid hormone levels in patients with primary hyperparathyroidism (EPATH) trial is a single-center, randomized, double-blind, parallel-group, placebo-controlled trial. The primary aim is to evaluate the effects of the mineralocorticoid receptor antagonist eplerenone on plasma intact PTH (iPTH) concentration in patients with pHPT. Secondary end points comprised surrogate parameters of cardiovascular health [24-h ambulatory SBP and DBP and echocardiographic parameters related to systolic/diastolic function as well as to cardiac dimensions]. Results: We enrolled 110 study participants with pHPT, 25-hydroxyvitamin D at least 20 ng/ml and estimated glomerular filtration rate more than 50 ml/min per 1.73 m2. Patients were 1 : 1 randomly assigned to receive either 25 mg eplerenone once daily (up-titration after 4 weeks to 50 mg/day) or matching placebo for a treatment period of 8 weeks. The study was completed by 97 participants [mean (SD) age: 67.5 ± 9.5 years; 78.4% women). The mean treatment effect (95% confidence interval) for iPTH was 1.0 (0.9–1.1; P = 0.777) pg/ml. Mean 24-h ambulatory SBP and DBP decreased significantly [mean change (95% confidence interval) −6.3 (−9.4 to −3.3) and −3.7 (−5.7 to −1.7) mmHg, respectively; P < 0.001]. No differences were seen in any further secondary outcomes or frequency of adverse events. Conclusion: In pHPT, treatment with eplerenone compared with placebo had no effect on circulating iPTH levels. Eplerenone treatment was well tolerated and safe and followed by significant decrease of ambulatory blood pressure.