Kidney Week

Abstract: TH-OR044

Calciprotein Particle (CPP)-Inhibition Explains Magnesium-Mediated Protection Against Vascular Calcification

Session Information

• Bone and Mineral Metabolism: Basic Research
  November 07, 2019 | Location: 145, Walter E. Washington Convention Center
  Abstract Time: 05:06 PM - 05:18 PM

Category: Bone and Mineral Metabolism

• 401 Bone and Mineral Metabolism: Basic

Authors

• De Baaij, Jeroen H.F., Radboud University Medical Centre, Nijmegen, Netherlands

Jeroen H.F. De Baaij, PhD



Jeroen de Baaij (1987) is a physiologist interested in the molecular and genetic origin of renal electrolyte disorders, including hypomagnesemia. He works as assistant professor at the Radboud university medical center in Nijmegen. His research team is focused on the identification and characterization of new genes involved in renal magnesium reabsorption. Moreover, supported by NWO Rubicon and Veni Grants and a Dutch Kidney Foundation Kolff Grant, his team is examining the role of magnesium in the prevention of cardiovascular complications in the context of chronic kidney disease.

• Ter Braake, Anique D., Radboud University Medical Centre, Nijmegen, Netherlands

Anique D. Ter Braake,

• Eelderink, Coby, University Medical Center Groningen, Groningen, Netherlands

Coby Eelderink,

• Zeper, Lara W., Radboud University Medical Centre, Nijmegen, Netherlands

Lara W. Zeper,

• Pasch, Andreas, University Hospital Bern, Bern, Switzerland

Andreas Pasch,

• Bakker, Stephan J.L., University Medical Center Groningen, Groningen, Netherlands

Stephan J.L. Bakker,

• De Borst, Martin H., University Medical Center Groningen, Groningen, Netherlands

Martin H. De Borst,

• Hoenderop, Joost, Radboud University Medical Centre, Nijmegen, Netherlands

Joost Hoenderop,

Group or Team Name

• NIGRAM2+ consortium

Background

Phosphate (Pi) toxicity is a strong determinant of vascular calcification in chronic kidney disease (CKD). Pi induces the formation of calciprotein particles (CPP), which drive the calcification process. Magnesium (Mg²⁺) may prevent vascular calcification, but the mechanisms are poorly understood. Here, we investigated the role of Mg²⁺ in calcification and crystal maturation induced by Pi and secondary crystalline calciprotein particles (CPP2).

Methods

Vascular smooth muscle cells were treated with high Pi or CPP2 and supplemented with Mg²⁺ and calcification was analyzed by medium absorbance, electron microscopy and energy dispersive spectroscopy. Effects of increased dietary Mg²⁺ intake on aortic calcification were assessed in Klotho knock-out mice. The effects of Mg²⁺ on calcification propensity (T₅₀) were measured in sera from CKD patients and healthy controls.

Results

Mg²⁺ supplementation prevented Pi-induced calcification in vascular smooth muscle cells. In contrast, Mg²⁺ failed to inhibit CPP2-induced calcification, indicating that it acts before the formation of CPP2. Increased expression of the osteogenic genes osteopontin and alkaline phosphatase remained stable after Mg²⁺ supplementation. In CPP2 cultures, Mg²⁺ dose-dependently delayed the maturation of CPP2 by several days in vitro. Elemental analysis showed that CPP2 contain 37 % oxygen, 19% Pi and 39% Ca²⁺, all remaining stable upon Mg²⁺ supplementation in already matured CPP2. Furthermore, in Klotho knock-out mice, high dietary Mg²⁺ intake effectively prevented aortic calcification. In human serum, addition of 0.2 mmol/L Mg²⁺ increased T₅₀ in healthy controls from 371 ± 16 minutes to 422 ± 20 minutes and in CKD patients from 323 ± 19 minutes to 367 ± 23 minutes (both P < 0.05). Each further 0.2 mmol/L addition of Mg²⁺ led to increases of ~40 minutes in both groups, resulting in a T₅₀ of 566 ± 3 and 505 ± 21 minutes in healthy controls and CKD patients after addition of 1.0 mmol/L Mg²⁺, respectively.

Conclusion

Our results demonstrate CPP2 mediate Pi-induced calcification. Mg²⁺ prevents CPP2 formation and thereby prevents Pi toxicity leading to calcification. Mg²⁺ supplementation, even at low dosages, is a potential therapeutic strategy to reduce vascular calcification in CKD.

Funding

• Government Support - Non-U.S.