Acute cardiovascular effect of 1,25-dihydroxycholecalciferol in essential hypertension

Plasma total calcium concentration is associated with blood pressure and systemic vascular resistance in normotensive and never-treated hypertensive subjects

Purpose: The underlying causes of primary hypertension are not fully understood. Evidence on the relation of plasma calcium concentration with blood pressure (BP) is inconsistent and relies largely on studies utilizing office BP measurements in populations using cardiovascular drugs. In many studies adjustment for confounders was not optimal. In this cross-sectional study we examined the association of plasma total calcium concentration with the haemodynamic determinants of blood pressure.Subjects and methods: Supine haemodynamics were recorded using pulse wave analysis, whole-body impedance cardiography, and heart rate variability analysis in 618 normotensive or never-treated hypertensive subjects (aged 19-72 years) without diabetes, cardiovascular or renal disease, or cardiovascular medications. Linear regression analysis was used to investigate factors associated with haemodynamic variables.Results: Mean age was 45.0 years, body mass index 26.8 kg/m², seated office BP 141/89 mmHg, and 307 subjects (49.7%) were male. Mean values of routine blood and plasma chemistry analyses were within the reference limits of the tests except for low-density lipoprotein cholesterol (3.05 mmol/l). In the laboratory, mean supine radial BP was 131/75 mmHg, and both systolic and diastolic BP correlated directly with plasma total calcium concentration (r = 0.25 and r = 0.22, respectively, p < 0.001 for both). In regression analysis plasma total calcium concentration was an independent explanatory variable for radial and aortic systolic and diastolic BP, and systemic vascular resistance, but not for cardiac output, pulse wave velocity, or any of the heart rate variability parameters.Conclusion: Plasma total calcium concentration was directly associated with systolic and diastolic BP and systemic vascular resistance in normotensive or never-treated hypertensive subjects without comorbidities and cardiovascular medications. Higher plasma calcium concentration potentially plays a role in primary hypertension via an effect on vascular resistance.

Modulation of the sympathetic nervous system in youngsters by vitamin-D supplementation

The level of circulating vitamin D is known to be associated with the ejection fraction in heart failure patients and studies in rats have shown that vitamin D depletion leads to increased levels of circulating norepinephrine and decreased atrial contractility. We elucidated the effects of vitamin D supplementation on the autonomous nervous system in healthy youngsters. Thirty healthy subjects aged 18–25 years were recruited based on their serum 25‐hydroxyvitamin D (25[OH]D): 15 vitamin D insufficient (25[OH]D < 50 nmol/L) and 15 vitamin D sufficient (25[OH]D > 80 nmol/L) subjects. Both groups had vitamin D supplementation (30 microg/day) and were tested at baseline and after 30, 90, and 180 days. At each visit the serum 25‐hydroxyvitamin D was measured and the head‐up tilt test performed. Serum 25[OH]D remained stable in the vitamin D sufficient group, while the insufficient group had a significant increase (32.0–64.5 nmol/L), P < 0.0001. Despite the increase, the insufficient group did not reach the level of the vitamin D sufficient group within the 6 months observational period (96.1 vs 64.5 nmol/L), P < 0.01. Serum norepinephrine at baseline was higher in the insufficient group (mean = 1.61 nmol/L) than in the vitamin D sufficient group (mean = 0.94 nmol/L), P < 0.01, whereas the response to tilt was lower in the insufficient group (mean = 0.69 nmol/L) compared to the sufficient group (mean = 1.17 nmol/L), P < 0.01. The heart rate at rest was higher in the insufficient group (mean = 67.7 bpm) than in the vitamin D sufficient group (mean = 56.6 bpm), P < 0.01, for the three first visits. At the last visit no difference was found. The systolic and diastolic blood pressure differed between the groups after a month, with higher pressures in the insufficient group than in the sufficient group. Vitamin D supplementation modulates the sympathetic nervous system in healthy youngsters with low serum vitamin D. The observation might lead to a greater focus on possible prevention of cardiac disease later on in life by vitamin D supplementation early in life.

Vitamin d therapy and cardiovascular health

Vitamin D belongs to the family of nuclear steroid hormones, which has pleiotropic effects on several organ systems. Different vitamin D compounds have been studied as potential cardioprotective agents over the past 20 years. The results of these clinical studies vary based on the form and dosage of vitamin D administered during the trial. In the past 5 years, many have described an association of vitamin D compounds and cardiovascular health through reduction in blood pressure, reduction in inflammatory biomarkers, improved insulin sensitivity, and reduction in cardiovascular disease complications and death. Because there are several vitamin D compounds, it is important to consider the full breadth of the literature when examining vitamin D and cardiovascular health, to assist in hypothesis generation and understanding of the current state of the science. Although a growing body of evidence suggests that nutritional vitamin D supplementation and potentially even treatment with synthetic analogues of vitamin D may be cardioprotective, relatively few studies have examined either of these compounds in a randomized, controlled fashion. Studies examining the benefit of vitamin D supplementation are now beginning, but future studies considering calcitriol and analogue therapy also seem warranted.

Milk products, dietary patterns and blood pressure management

High blood pressure (BP) is a major risk factor for heart disease, stroke, congestive heart failure, and kidney disease. Inverse associations between dairy product consumption and systolic blood pressure (SBP) and diastolic blood pressure (DBP) have been observed in cross-sectional studies; some studies, however, have reported an inverse association with only one BP parameter, predominantly SBP. Randomized clinical trials examining the effect of calcium and the combination of calcium, potassium and magnesium provide evidence for causality. In these studies, reductions in BP were generally modest (-1.27 to -4.6 mmHg for SBP, and -0.24 to -3.8 mmHg for DBP). Dairy nutrients, most notably calcium, potassium and magnesium, have been shown to have a blood pressure lowering effect. A low calcium intake increases intracellular calcium concentrations which increases 1,25-dihydroxyvitamin D(3) and parathyroid hormone (PTH), causing calcium influx into vascular smooth muscle cells, resulting in greater vascular resistance. New research indicates that dairy peptides may act as angiotensin converting enzyme (ACE) inhibitors, thereby inhibiting the renin angiotensin system with consequent vasodilation. A growing evidence base shows that dairy product consumption is involved in the regulation of BP. Consequently, inclusion of dairy products in a heart healthy diet is an important focal point to attain BP benefits.

Vitamin D status and arterial hypertension: a systematic review

Vitamin D deficiency is common and is primarily caused by a lack of ultraviolet-B (UVB) radiation from reduced sun exposure, and the consequent limiting of vitamin D production in the skin. The vitamin D endocrine system regulates about 3% of the human genome. Observational data support the concept that vitamin D is involved in the pathogenesis of cardiovascular diseases and arterial hypertension. The antihypertensive properties of vitamin D include renoprotective effects, suppression of the renin-angiotensin-aldosterone system, direct effects on vascular cells, and effects on calcium metabolism, including prevention of secondary hyperparathyroidism. The results of clinical studies largely, but not consistently, favor the hypothesis that vitamin D sufficiency promotes lowering of arterial blood pressure. Randomized, placebo-controlled trials are greatly needed to clarify and definitively prove the effect of vitamin D on blood pressure. In general, the antihypertensive effects of vitamin D seem to be particularly prominent in vitamin-D-deficient patients with elevated blood pressure. Thus, in view of the relatively safe and inexpensive way in which vitamin D can be supplemented, we believe that vitamin D supplementation should be prescribed to patients with hypertension and 25-hydroxyvitamin D levels below target values.

Vitamin D and the vasculature: can we teach an old drug new tricks?

BACKGROUND

Vitamin D is a steroid hormone known for its role in regulating levels of calcium and phosphorus. Vitamin D has important autocrine/paracrine roles and it is involved in vascular biology. Clinical studies have shown a relationship between vitamin D levels and cardiovascular health, and low levels of vitamin D metabolites have been associated with higher incidence of congestive heart failure and increases in mortality.

OBJECTIVE

To summarise the effect of vitamin D on cardiovascular pathology, the leading cause of death in chronic kidney disease patients.

CONCLUSIONS

All results indicate a potential effect of vitamin D on cardiovascular health. Therefore, maintaining optimum levels of circulating vitamin D is critical for a healthy cardiovascular system. In patients with low vitamin D status, like renal patients, supplementation with vitamin D metabolites has shown beneficial cardiovascular effects.

Differential effects of vitamin D analogs on vascular calcification

We tested the effects of calcitriol and its analog paricalcitol on VSMC calcification in vitro and in vivo. For that reason, cells and animals with five-sixths nephrectomy were treated with both compounds. Calcitriol, but not paricalcitol, increased VSMC calcification in vitro and in vivo independently of calcium and phosphate levels. This increase in calcification was parallel to an increase in the RANKL/OPG ratio.

INTRODUCTION

Vascular calcification is a common finding in patients with endstage renal disease. Furthermore, those patients often present secondary hyperparathyroidism, partly because of a decrease of calcitriol synthesis on the kidney. Thus, one of the main therapeutic options is to treat those patients with calcitriol or analogs. However, this treatment presents unwanted side effects, such as increases in vascular calcification.

MATERIALS AND METHODS

We tested the effect on vascular smooth muscle cell (VSMC) calcification of calcitriol and one of its analogs, paricalcitol, in vitro and in vivo in animals with endstage renal disease.

RESULTS

Calcitriol increased calcification of VSMCs cultured in calcification media. This effect was not present when cells were incubated with paricalcitol. Furthermore, only cells incubated with calcitriol showed an increased RANKL/osteoprotegerin (OPG) expression. Animals with renal failure treated with hypercalcemic doses of calcitriol and paricalcitol showed an increase in systolic blood pressure. However, diastolic blood pressure only raised significantly in those animals treated with paricalcitol. This effect led to a significant increase in pulse pressure in animals treated with calcitriol. The increase in pulse pressure was likely caused by the extensive calcification observed in arteries of animals treated with calcitriol. This increase in calcification was not seen in arteries of animals treated with paricalcitol, despite having similar levels of serum calcium and phosphorus as animals treated with calcitriol. Furthermore, the decreases in serum PTH levels were similar in both treatments.

CONCLUSIONS

We conclude that paricalcitol has a different effect than calcitriol in VSMC calcification and that this could explain part of the differences observed in the clinical settings.

Less calcemic Vitamin D analogs enhance creatine kinase specific activity and modulate responsiveness to gonadal steroids in the vasculature

Vitamin D receptors are widely expressed in the cardiovascular system, in which Vitamin D and its metabolites exert a variety of biological activities such as regulation of cellular proliferation and differentiation, cell calcium transients and cell energy metabolism in vitro. The latter is mediated through the control of the brain type creatine kinase specific activity (CK), which serves to provide a readily available reservoir for ATP generation under increased work-load. In the present study we undertook to assess the role of Vitamin D on energy metabolism in the rat heart and aorta in vivo by using CK, which is a key energy metabolizing enzyme and compare Vitamin D depleted and repleted animals. Vascular tissues from female or male Vitamin D-depleted rats showed 61-80% lower CK activity in the aorta (Ao) and left ventricle of the heart (Lv) than control, Vitamin D-replete rats. Moreover, neither estradiol-17beta (E2) nor dihydrotestosterone (DHT), which increases CK specific activity in Ao and Lv of intact female or male rats, respectively, were able to stimulate CK in Vitamin D-depleted rats. Treatment of intact female rats for 2 weeks or 2 months with the less-calcemic Vitamin D analogs JKF 1624F2-2 (JKF) or QW 1624F2-2 (QW) (Fig. 1), did not significantly affect CK specific activity. However, after pretreatment with these analogs, there was an up regulation of the E2-induced CK response in Ao and Lv. In intact female rats, all Vitamin D analogs also potentiated the in vivo CK response to the SERMs raloxifene (Ral) and tamoxifen (TAM) in Ao and Lv. However the inhibitory effect of Ral or TAM on E2-induced CK activity was lost after pretreatment with Vitamin D analogs. The non-calcemic analog CB 1093 (CB) induced a significant increase in estradiol receptor alpha (ERalpha) protein in both myocardial and aortic tissue from intact and from ovariectomized female rats. Collectively, these results indicate that Vitamin D analogs modulate cell energy homeostasis in vascular tissues through induction of CK and up regulation of the response and sensitivity of CK in vascular tissues to E2 and to SERMs, possibly through via an increase in ERalpha protein in female derived organs. These results corroborate our previous in vitro studies in human vascular cells and further suggest that the Vitamin D system plays an important physiological role in maintaining normal cell energy reservoir in the vasculature.

Relationship between high consumption of marine fatty acids in early pregnancy and hypertensive disorders in pregnancy

OBJECTIVE

To investigate whether there is a relationship between maternal intake of cod-liver oil in early and late pregnancy and hypertensive disorders in pregnancy.

DESIGN

An observational prospective study.

SETTING

Free-living conditions in a community with traditional fish and cod-liver oil consumption.

POPULATION

Four hundred and eighty-eight low-risk pregnant Icelandic women.

METHODS

Maternal use of cod-liver oil, foods and other supplements was estimated with a semiquantitative food frequency questionnaire covering food intake together with lifestyle factors for the previous 3 months. Questionnaires were filled out twice, between 11 and 15 weeks of gestation and between 34 and 37 weeks of gestation. Supplements related to hypertensive disorders in pregnancy, i.e. gestational hypertension and pre-eclampsia, were presented, with logistic regression controlling for potential confounding.

MAIN OUTCOME MEASURES

Gestational hypertension, pre-eclampsia, cod-liver oil and multivitamins.

RESULTS

The odds ratio for developing hypertensive disorders in pregnancy for women consuming liquid cod-liver oil was 4.7 (95% CI 1.8-12.6, P= 0.002), after adjusting for confounding factors. By dividing the amount of n-3 long-chain polyunsaturated fatty acids (n-3 LCPUFA) into centiles, the odds ratio for hypertensive disorders across groups for n-3 LCPUFA suggested a u-shaped curve (P = 0.008). Similar results were found for gestational hypertension alone. Further, the use of multivitamin supplements without vitamins A and D in late pregnancy doubled the odds of hypertensive disorders (OR 2.4, 95% CI 1.0-5.4, P= 0.044).

CONCLUSIONS

Consumption of high doses of n-3 LCPUFA in early pregnancy, or other nutrients found in liquid cod-liver oil, may increase the risk of developing hypertensive disorders in pregnancy.

Regulation of parathyroid hypertensive factor secretion by vitamin D3 analogs in parathyroid cells derived from spontaneously hypertensive rats

Parathyroid hypertensive factor (PHF) is a novel substance secreted by the parathyroid gland (PTG), which is elevated in 30-40% of all hypertensive patients; specifically, the low-renin subset. However, very little is known about the regulation of PHF secretion. Since the classical parathyroid regulator, 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3), may be elevated concurrent with or preceding the development of low-renin hypertension and elevated plasma PHF, we hypothesized that 1,25-(OH)2D3 would stimulate PHF release. To test this hypothesis, PTG organ and cell cultures, derived from spontaneously hypertensive rats (SHR) and the normotensive genetic control Wistar Kyoto (WKY) rats, were exposed to various vitamin D3 metabolites and PHF release measured by ELISA. 1,25-(OH)2D3 rapidly stimulated PHF release with enhanced sensitivity in SHR versus WKY cultures indicated by a leftward shift in the dose-response curve, whereas 24,25-dihydroxyvitamin D3 (24,25-(OH)2D3) had the converse effect. Vitamin D3 analog "BT," an agonist for the classical nuclear vitamin D receptor (1,25VDR(nuc)), was without effect suggesting a 1,25VDR(nuc)-independent mechanism and potential involvement of the plasma membrane-bound vitamin D receptor (1,25 D3-MARRS). Interestingly, protein expression of the 1,25 D3-MARRS was increased in SHR versus WKY parathyroid cells. In conclusion, these results support the idea that 1,25-(OH)2D3 may contribute to elevated plasma PHF in the SHR.

Vitamin D, Shedding Light on the Development of Disease in Peripheral Arteries

Vitamin D is generally associated with calcium metabolism, especially in the context of uptake in the intestine and the formation and maintenance of bone. However, vitamin D influences a wide range of metabolic systems through both genomic and nongenomic pathways that have an impact on the properties of peripheral arteries. The genomic effects have wide importance for angiogenesis, elastogenesis, and immunomodulation; the nongenomic effects have mainly been observed in the presence of hypertension. Although some vitamin D is essential for cardiovascular health, excess may have detrimental effects, particularly on elastogenesis and inflammation of the arterial wall. Vitamin D is likely to have a role in the paradoxical association between arterial calcification and osteoporosis. This review explores the relationship between vitamin D and a range of physiological and pathological processes relevant to peripheral arteries.

Blood pressure is correlated with vitamin d(3) serum levels in dialysis patients

BACKGROUND/AIMS

The blood pressure, the most influencing factor in cardiovascular disease in end-stage renal failure patients, follows a seasonal variation during the year. Since vitamin D(3) is known to be related to sun exposure, we wanted to evaluate the putative participation of the vitamin D(3) metabolism in blood pressure modifications.

METHODS

We studied 22 stable hemodialysis patients (11 females and 11 males, mean age +/- SD 56 +/- 1 year) who had been continuously treated in our dialysis unit for more than 1 year between 1994 and 1997 and did not receive pulse vitamin D(3) treatment. Supine systolic and diastolic blood pressures were measured before every dialysis session (>12,000 measurements) and the intact parathormone (iPTH), 25-hydroxyvitamin D(3) [25(OH)D(3)], and 1,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)] levels every 3 months (>300 determinations). The mean values of blood pressure per season and per patient were taken for analysis using a 4-year longitudinal study design.

RESULTS

The blood pressure varied during the years studied following a seasonal trend. It was highest during autumn and tended to decrease during spring and warmer months. Systolic as well as diastolic blood pressures were significantly correlated with the 25(OH)D(3) levels (p = 0.0291 and p = 0.0327, respectively). No correlation was observed between blood pressure and 1,25(OH)(2)D(3) or iPTH levels.

CONCLUSION

There is a link between blood pressure and 25(OH)D(3) level. This interrelation is not secondary to a iPTH modulation. Although it cannot be excluded that vitamin D(3) and blood pressure vary following a third factor with seasonal variations, since vitamin D(3) varies during the year, mainly following sun exposure, we suggest that vitamin D(3) is one of the factors participating in the seasonal variation of the blood pressure. Other factors known to control the blood pressure and particularly the extracellular volume overload may also participate.