Abstract- Age-related bone loss has been associated with high levels of marrow adipogenesis. Estrogens (E2) are known to regulate the differentiation of marrow precursors into osteoblasts, however, their role in bone marrow adipogenesis remain unknown. E2 regulate adipocyte differentiation in subcutaneous and visceral fat through interaction with other nuclear receptors. This interaction has not been assessed in bone marrow adipocytes in vivo. In this study, we compared two groups of animals, young and old, after either oophorectomy (OVX) or oophorectomy plus E2 (OVX + E2) replacement. We found that absence of E2 was associated with higher levels of PPAR? and lower levels of Sirt1 most significantly in the old group. In addition, old mice responded better to E2 replacement in terms of reducing adipogenesis and PPAR? expression as well as increasing levels of Sirt1 expression. Our findings represent a new understanding of the role of E2 in age-related bone loss, which could be mediated through the regulation of Sirt1 expression within the bone marrow. In addition, this evidence suggests that old individuals may show a better response to E2 administration in terms of reverting the high levels of marrow fat seen in age-related bone loss.

Journal Biogerontology
Publisher Springer Netherlands
ISSN 1389-5729 (Print) 1573-6768 (Online)
Issue Volume 10, Number 6 / December, 2009
Category Research Article
DOI 10.1007/s10522-009-9221-7
Pages 747-755
Subject Collection Biomedical and Life Sciences

Alexander Elbaz1, Daniel Rivas1 and Gustavo Duque1, 2

(1) Lady Davis Institute for Medical Research, McGill University, Montreal, QC, H3T 1E2, Canada
(2) Aging Bone Research Program, Nepean Clinical School, Nepean Hospital, University of Sydney, Level 5, South Block, Penrith, NSW, 2750, Australia