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Nephrol Dial Transplant. 2019 Jun 1;34(6):934-941. doi: 10.1093/ndt/gfy287.

High-serum phosphate and parathyroid hormone distinctly regulate bone loss and vascular calcification in experimental chronic kidney disease.

Author information

1
Bone and Mineral Research Unit, Hospital Universitario Central de Asturias, Instituto de Investigación Sanitaria del Principado de Asturias (ISPA), REDinREN-ISCIII, Oviedo, Spain.
2
Laboratorio de Medicina, Hospital Universitario Central de Asturias, Oviedo, Spain.
3
Departamento de Biología de Sistemas, Universidad de Alcalá, REDinREN-ISCIII, Alcalá de Henares, Spain.
4
Departamento de Medicina, Universidad de Oviedo, Oviedo, Spain.

Abstract

BACKGROUND:

In chronic kidney disease (CKD), increases in serum phosphate and parathyroid hormone (PTH) aggravate vascular calcification (VC) and bone loss. This study was designed to discriminate high phosphorus (HP) and PTH contribution to VC and bone loss.

METHODS:

Nephrectomized rats fed a HP diet underwent either sham operation or parathyroidectomy and PTH 1-34 supplementation to normalize serum PTH.

RESULTS:

In uraemic rats fed a HP diet, parathyroidectomy with serum PTH 1-34 supplementation resulted in (i) reduced aortic calcium (80%) by attenuating osteogenic differentiation (higher α-actin; reduced Runx2 and BMP2) and increasing the Wnt inhibitor Sclerostin, despite a similar degree of hyperphosphataemia, renal damage and serum Klotho; (ii) prevention of bone loss mostly by attenuating bone resorption and increases in Wnt inhibitors; and (iii) a 70% decrease in serum calcitriol levels despite significantly reduced serum Fgf23, calcium and renal 24-hydroxylase, which questions that Fgf23 is the main regulator of renal calcitriol production. Significantly, when vascular smooth muscle cells (VSMCs) were exposed exclusively to high phosphate and calcium, high PTH enhanced while low PTH attenuated calcium deposition through parathyroid hormone 1 receptor (PTH1R) signalling.

CONCLUSIONS:

In hyperphosphataemic CKD, a defective suppression of high PTH exacerbates HP-mediated osteogenic VSMC differentiation and reduces vascular levels of anti-calcifying sclerostin.

KEYWORDS:

gene expression; mineral metabolism; parathyroidectomy; renal osteodystrophy; vascular calcification

PMID:
30189026
DOI:
10.1093/ndt/gfy287

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