Calciprotein particles: mineral behaving badly?

Current Opinion in Nephrology & Hypertension, vol. 29, pp. 378–386

Abstract

PURPOSE OF REVIEW: Calciprotein particles (CPP) are formed in supersaturated solutions of calcium, phosphate and the mineral-binding protein fetuin-A. CPP have garnered considerable interest as potential mediators of mineral stress, but little consideration has been given to their origin, clearance and role in metabolism. RECENT FINDINGS: CPP are made whilst buffering the mineral absorbed from the intestine after a meal or during remodelling of bone matrix. The postprandial rise in circulating CPP rise may be sensed by osteoblasts/osteocytes in bone, stimulating the secretion of the master phosphatonin fibroblast growth factor 23. Amorphous calcium phosphate-containing CPP are rapidly cleared by endothelial cells in the liver whereas crystalline apatite-containing CPP are filtered by phagocytic cells of the reticuloendothelial system. Impaired excretory function in kidney disease may lead to accumulation of CPP and its precursors with possible pathological sequalae. Inability to stabilize CPP in fetuin-A-deficiency states can result in intraluminal precipitation and inflammatory cascades if other mineralisation regulatory networks are compromised. SUMMARY: CPP allow efficient transport and clearance of bulk calcium phosphate as colloids without risk of precipitation. As circulating factors, CPP may couple dietary mineral exposure with endocrine control of mineral metabolism in bone, signalling the need to dispose of excess phosphate from the body.

Authors 3

1. Edward R. Smith corresponding

   The Royal Melbourne Hospital · The University of Melbourne

   Affiliation as printed

   Department of Medicine, University of Melbourne, Parkville, Australia

   Department of Nephrology, The Royal Melbourne Hospital, Melbourne

   fax: +61 39342 8440

   to Edward R. Smith, Kincaid-Smith Renal Laboratories, Department of Nephrology, The Royal Melbourne Hospital, Grattan Street, Parkville, VIC 3050, Australia. Tel: +61 39342 3065

2. Tim D. Hewitson

   The Royal Melbourne Hospital · The University of Melbourne

   Affiliation as printed

   Department of Medicine, University of Melbourne, Parkville, Australia

   Department of Nephrology, The Royal Melbourne Hospital, Melbourne

3. Willi Jahnen‐Dechent Aachen

   RWTH Aachen University · Universitätsklinikum Aachen

   Affiliation as printed

   Helmholtz-Institute for Biomedical Engineering, RWTH Aachen University Hospital, Aachen, Germany