Vitamin D depletion aggravates hypertension and target-organ damage

Abstract

Background: We tested the controversial hypothesis that vitamin D depletion aggravates hypertension and target-organ damage by influencing renin.

Methods and results: Four-week-old double-transgenic rats (dTGR) with excess angiotensin (Ang) II production due to overexpression of the human renin (hREN) and angiotensinogen (hAGT) genes received vitamin D-depleted (n=18) or standard chow (n=15) for 3 weeks. The depleted group had very low serum 25-hydroxyvitamin D levels (mean±SEM; 3.8±0.29 versus 40.6±1.19 nmol/L) and had higher mean systolic BP at week 5 (158±3.5 versus 134.6±3.7 mm Hg, P<0.001), week 6 (176.6±3.3 versus 162.3±3.8 mm Hg, P<0.01), and week 7 (171.6±5.1 versus 155.9±4.3 mm Hg, P<0.05). Vitamin D depletion led to increased relative heart weights and increased serum creatinine concentrations. Furthermore, the mRNAs of natriuretic peptides, neutrophil gelatinase-associated lipocalin, hREN, and rRen were increased by vitamin D depletion. Regulatory T cells in the spleen and in the circulation were not affected. Ang metabolites, including Ang II and the counter-regulatory breakdown product Ang 1 to 7, were significantly up-regulated in the vitamin D-depleted groups, while ACE-1 and ACE-2 activities were not affected.

Conclusions: Short-term severe vitamin D depletion aggravated hypertension and target-organ damage in dTGR. Our data suggest that even short-term severe vitamin D deficiency may directly promote hypertension and impacts on renin-angiotensin system components that could contribute to target-organ damage. The findings add to the evidence that vitamin D deficiency could also affect human hypertension.

Keywords: hypertension; renin; vitamin D.

Figure 1.

Serum 25(OH)D₃ concentration and systolic blood pressure. A, Vitamin D‐depleted rats had a significant decrease in serum 25‐hydroxyvitamin D3 after 3 weeks on vitamin D‐depleted chow. Results are expressed as mean±SEM of at least 6 animals per group. B, Systolic BP increased progressively in vehicle‐treated dTGR from week 5 to week 7. Vitamin D depletion increased BP from week 5 to 7. BP indicates blood pressure; ctl‐dTGR, controls double‐transgenic rats; VDd, vitamin D‐depleted.

Figure 2.

Effect of vitamin D depletion on cardiac hypertrophy, BNP, and ANP expression. Vitamin D depletion‐induced cardiac hypertrophy (A) expressed as ratio of heart weight to body weight. Cardiac hypertrophy indices of VDd‐dTGR were significantly higher compared with ctl‐dTGR. B, With RT‐PCR, we examined BNP (left) and ANP (right) mRNA expression in the heart. ANP and BNP mRNA expression were significantly higher in VDd‐dTGR compared with ctl‐dTGR. mRNA levels of BNP and ANP were normalized for the housekeeping gene GAPDH. Results are expressed as arbitrary units (AU) with mean±SEM of at least 7 animals per group. ANP indicates atrial natriuretic peptide; BNP, brain natriuretic peptide; ctl‐dTGR, controls double‐transgenic rats; RT‐PCR, real‐time polymerase chain reaction; VDd, vitamin D‐depleted.

Figure 3.

Effect of vitamin D depletion on renal function. A, dTGR developed progressive increased 24 hours urinary albumin excretion, which was not changed by vitamin D depletion. B, Left to right: Plasma creatinine was significantly higher in VDd‐dTGR. Serum cystatin C concentration was higher in VDd‐dTGR, but this was only a trend (P=0.1). The expression of NGAL mRNA kidney tissue was significantly higher in VDd‐dTGR compared with ctl‐dTGR. mRNA levels of NGAL were normalized for the housekeeping gene 18S. Results are expressed as arbitrary units (AU) with mean±SEM of at least 7 animals per group. ctl‐dTGR indicates controls double‐transgenic rats; VDd, vitamin D‐depleted.

Figure 4.

A and B, Masson Goldner staining for fibrosis in formalin fixed paraffin‐embedded kidney sections (top: lower magnification, middle: higher magnification). C, Macrophage immunofluorescent staining (ED1) in formalin‐fixed paraffin‐embedded Kidney Sections and quantification of ED1‐positive Cells. All measurements were performed in double transgenic rats with normal diet (VDs‐dTGR) and after vitamin D depletion (VDd‐dTGR). dTGR indicates double‐transgenic rats; VDd, vitamin D‐depleted.

Figure 5.

A and B, Picro Sirius Red staining for fibrosis in formalin fixed paraffin‐embedded heart Sections (top: lower magnification, middle: higher magnification). Quantification of Fibrosis in Picro Sirius Red staining (C) Immunofluoresence staining of macrophages (ED1) in formalin‐fixed paraffin‐embedded heart sections and quantification (% Area Measured as Area related to whole LV). All measurements were performed in double transgenic rats with normal diet (VDs‐dTGR) and after vitamin D depletion (VDd‐dTGR). dTGR indicates double‐transgenic rats; LV, left ventricule; VDd, vitamin D‐depleted.

Figure 6.

Renin and angiotensinogen expression. A, Vitamin D depletion resulted in a significant increase in mRNA expression of human renin (left) and rat renin (right) in the kidney. B, mRNA expression of human angiotensinogen (left) and rat angiotensinogen (right) were similar between VDd‐ and ctl‐dTGR. mRNA levels of the target genes were normalized for the housekeeping gene 18S. Results are expressed as arbitrary units (AU) with mean±SEM of at least 7 animals per group. ctl‐dTGR indicates controls double‐transgenic rats; hAGT, human angiotensinogen; VDd, vitamin D‐depleted.

Figure 7.

Effect of vitamin D depletion on regulatory T‐cells. A, Percentage of FoxP3+ cells, calculated relative to CD4+ cells in spleen (left) and peripheral blood (right) are shown. Results are expressed with mean±SEM of at least 7 animals per group (spleen) or 3 animals per group (peripheral blood). Vitamin D depletion did not alter regulatory T‐cells compared to control dTGR. B, representative example of a FACS in spleen and peripheral blood. ctl‐dTGR indicates controls double‐transgenic rats; VDd, vitamin D‐depleted.