Article abstract
Nature Medicine 15, 674 - 681 (2009)
Published online: 17 May 2009 | doi:10.1038/nm.1963
Impaired gastric acidification negatively affects calcium homeostasis and bone mass
Thorsten Schinke1,11, Arndt F Schilling1,11, Anke Baranowsky1, Sebastian Seitz1, Robert P Marshall1, Tilman Linn1, Michael Blaeker2, Antje K Huebner1, Ansgar Schulz3, Ronald Simon4, Matthias Gebauer1, Matthias Priemel1, Uwe Kornak5, Sandra Perkovic1, Florian Barvencik1, F Timo Beil1, Andrea Del Fattore6, Annalisa Frattini7,8, Thomas Streichert9, Klaus Pueschel10, Anna Villa7,8, Klaus-Michael Debatin3, Johannes M Rueger1, Anna Teti6, Jozef Zustin4, Guido Sauter4 & Michael Amling1
Abstract
Activation of osteoclasts and their acidification-dependent resorption of bone is thought to maintain proper serum calcium levels. Here we show that osteoclast dysfunction alone does not generally affect calcium homeostasis. Indeed, mice deficient in Src, encoding a tyrosine kinase critical for osteoclast activity, show signs of osteopetrosis, but without hypocalcemia or defects in bone mineralization. Mice deficient in Cckbr, encoding a gastrin receptor that affects acid secretion by parietal cells, have the expected defects in gastric acidification but also secondary hyperparathyroidism and osteoporosis and modest hypocalcemia. These results suggest that alterations in calcium homeostasis can be driven by defects in gastric acidification, especially given that calcium gluconate supplementation fully rescues the phenotype of the Cckbr-mutant mice. Finally, mice deficient in Tcirg1, encoding a subunit of the vacuolar proton pump specifically expressed in both osteoclasts and parietal cells, show hypocalcemia and osteopetrorickets. Although neither Src- nor Cckbr-deficient mice have this latter phenotype, the combined deficiency of both genes results in osteopetrorickets. Thus, we find that osteopetrosis and osteopetrorickets are distinct phenotypes, depending on the site or sites of defective acidification (pages 610–612).
- Center for Biomechanics and Skeletal Biology, Department of Trauma, Hand, and Reconstructive Surgery, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
- Department of Internal Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
- Department of Pediatrics, University Medical Center Ulm, Ulm, Germany.
- Institute of Pathology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
- Institute of Medical Genetics, Charite University Medical Center, Berlin, Germany.
- Department of Experimental Medicine, University of L'Aquila, L'Aquila, Italy.
- Human Genome Department, Istituto di Tecnologie Biomediche, Italian National Research Council (CNR), Segrate, Italy.
- Istituto Clinico Humanitas, IRCCS, Rozzano, Italy.
- Institute of Clinical Chemistry, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
- Institute of Forensic Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
- These authors contributed equally to this work.
Correspondence to: Michael Amling1 e-mail: amling@uke.uni-hamburg.de
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