Calciprotein Particle Inhibition Explains Magnesium‐mediated Protection against Vascular Calcification

Abstract

Phosphate toxicity is a strong determinant of vascular calcification development in chronic kidney disease (CKD). Phosphate induces the formation of calciprotein particles (CPP), which were identified to drive the calcification process. Epidemiological data of suggests that magnesium may improve cardiovascular risk by inhibiting vascular calcification. However, the mechanism by which magnesium counteracts vascular calcification is poorly understood. Here, we investigated the effects of magnesium on phosphate and secondary crystalline calciprotein particles (CPP2) induced calcification and crystal maturation.Vascular smooth muscle cells were treated with high phosphate or CPP2 and supplemented with magnesium to study cellular calcification. The effect of magnesium on CPP maturation, morphology and composition was studied by medium absorbance, electron microscopy and energy dispersive spectroscopy. Effects of magnesium intake on aortic calcification was assessed in Klotho knock‐out mice. To translate our findings to CKD patients, the effects of magnesium on calcification propensity (T50) was measured in sera from CKD patients and healthy controls.Magnesium supplementation prevented phosphate‐induced calcification in vascular smooth muscle cells. In contrast, magnesium failed to inhibit CPP2‐induced calcification, indicating it acts before the formation of CPP2. Increased expression of osteogenic genes osteopontin and alkaline phosphatase were unchanged after magnesium supplementation. Furthermore, in a Klotho knock‐out mouse model for vascular calcification, high dietary magnesium intake prevented aortic calcification effectively. Showing the potential of magnesium in patients, magnesium dose‐dependently delayed the maturation of CPP2 by several days. In human serum, addition of 0.2 mmol/L magnesium increased T50 from healthy controls by 51 ± 5 minutes (P < 0.05) and CKD patients by 44 ± 4 minutes (P < 0.05). Each further 0.2 mmol/L addition of magnesium led to further increases in both groups.Our results demonstrate crystalline CPP2 mediate phosphate‐induced calcification. Magnesium prevents crystalline CPP2 formation and thereby prevents phosphate toxicity leading to calcification. Magnesium supplementation, even at low dosages, is a potential therapeutic strategy to reduce vascular calcification in CKD.Support or Funding InformationThis research was funded by grants from the Netherlands Organization for Scientific Research (NWO Veni 016.186.012 and VICI 016.130.668) and the Dutch Kidney Foundation (Kolff 14OKG17 and 15OP02). This work was furthermore supported by the NIGRAM2+ consortium funded by Health Holland (LSHM17034) and the Dutch Kidney Foundation (16TKI02).