Adiponectin and its receptors are expressed in bone-forming cells

Berner, Heidi S.; Lyngstadaas, Staale P.; Spahr, Axel; Monjo, Marta; Thommesen, Liv; Drevon, Christian A.; Syversen, Unni; Reseland, Janne E.

doi:10.1016/j.bone.2004.06.008

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Volume 35, Issue 4 , Pages 842-849, October 2004

Adiponectin and its receptors are expressed in bone-forming cells

Heidi S. Berner
- Corresponding author. Oral Research Laboratory, Institute for Clinical Dentistry, University of Oslo, PO Box 1109 Blindern, Oslo N-0317, Norway. Fax: +47-22-85-23-51.
- Oral Research Laboratory, Institute for Clinical Dentistry, University of Oslo, Norway
Staale P. Lyngstadaas
- Oral Research Laboratory, Institute for Clinical Dentistry, University of Oslo, Norway
Axel Spahr
- Department of Conservative Dentistry and Periodontology, University of Ulm, Germany
Marta Monjo
- Oral Research Laboratory, Institute for Clinical Dentistry, University of Oslo, Norway
Liv Thommesen
- Department of Cancer Research and Molecular Medicine, University of Science and Technology, Trondheim, Norway
Christian A. Drevon
- Department of Nutrition, Institute of Basic Medical Sciences, University of Oslo, Norway
Unni Syversen
- Department of Cancer Research and Molecular Medicine, University of Science and Technology, Trondheim, Norway
Janne E. Reseland
- Oral Research Laboratory, Institute for Clinical Dentistry, University of Oslo, Norway

Received 22 March 2004; received in revised form 11 June 2004; accepted 14 June 2004. published online 19 August 2004.

Abstract

Adiponectin has until now been considered to be synthesized and secreted exclusively by the adipose tissue, and is reported to influence energy homeostasis and insulin sensitivity. It is also known that body weight is positively correlated with increased bone mineral density and decreased fracture risk. The mechanisms explaining this relation, however, are not completely understood. We report a link between adiponectin and bone homeostasis by demonstrating transcription, translation, and secretion of adiponectin, as well as expression of its receptors, AdipoR1 and AdipoR2, in bone-forming cells. We show that adiponectin and the receptors are expressed in primary human osteoblasts from femur and tibia. The phenotype of bone cells was confirmed by the high expression levels of alkaline phosphatase, collagen type 1, osteocalcin, and CD44, and the formation of mineralization nodules. Immunostaining with monoclonal antibodies also demonstrated the presence of adiponectin in human osteosarcoma cells and normal osteoblasts. Both mRNA expression and secretion of adiponectin to the medium increased during differentiation of human osteoblasts in culture. The adiponectin mRNA level increases in osteoblasts cultured 3 and 7 days in the presence of dietary fatty acids and supplementation of culture medium with recombinant adiponectin enhances the proliferation of murine osteoblasts. The regulation and detailed function of adiponectin in bone still remains obscure, but our findings suggest a functional role in bone homeostasis. If so, adiponectin may provide an important signal linking fat and body weight to bone density.

Keywords: Adiponectin, Adipokines, Osteoblasts, Bone, Human