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PPAR Research
Volume 2007 (2007), Article ID 92501, 12 pages
doi:10.1155/2007/92501
Review Article

Energy Balance, Myostatin, and GILZ: Factors Regulating Adipocyte Differentiation in Belly and Bone

Xingming Shi,1,2 Mark Hamrick,1,3 and Carlos M. Isales1,4

1Institute of Molecular Medicine and Genetics, Medical College of Georgia, GA 30912, USA
2Department of Pathology, Medical College of Georgia Hospital, GA 30912, USA
3Department of Cellular Biology and Anatomy, Medical College of Georgia, GA 30912, USA
4Department of Orthopaedic Surgery, Medical College of Georgia, GA 30912, USA

Received 9 July 2007; Accepted 16 August 2007

Academic Editor: Z. Elizabeth Floyd

Copyright © 2007 Xingming Shi et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Peroxisome proliferator-activated receptor gamma (PPAR-γ) belongs to the nuclear hormone receptor subfamily of transcription factors. PPARs are expressed in key target tissues such as liver, fat, and muscle and thus they play a major role in the regulation of energy balance. Because of PPAR-γ's role in energy balance, signals originating from the gut (e.g., GIP), fat (e.g., leptin), muscle (e.g., myostatin), or bone (e.g., GILZ) can in turn modulate PPAR expression and/or function. Of the two PPAR-γ isoforms, PPAR-γ2 is the key regulator of adipogenesis and also plays a role in bone development. Activation of this receptor favors adipocyte differentiation of mesenchymal stem cells, while inhibition of PPAR-γ2 expression shifts the commitment towards the osteoblastogenic pathway. Clinically, activation of this receptor by antidiabetic agents of the thiazolidinedione class results in lower bone mass and increased fracture rates. We propose that inhibition of PPAR-γ2 expression in mesenchymal stem cells by use of some of the hormones/factors mentioned above may be a useful therapeutic strategy to favor bone formation.