PPARG in osteocytes is essential for sclerostin expression, bone mass, marrow adiposity and TZD-induced bone loss

Abstract

PPARG role in regulation of osteocyte function is largely unknown. We report that PPARG is essential for sclerostin production, a recently approved target to treat osteoporosis. There is an excellent correlation in osteocytes between Sost/sclerostin and PPARG at the transcript and protein levels, and increased bone mass in mice with osteocyte-specific deletion of PPARG ({gamma}OTKO) correlated with increased WNT signaling and bone forming activity of endosteal osteoblasts and decreased marrow fat. The 8 kb sequence upstream of Sost gene transcription start site possesses multiple PPARG binding elements (PPREs) with at least two of them binding PPARG with dynamics reflecting its activation and the levels of Sost transcript and sclerostin protein expression. Older {gamma}OTKO female mice are largely protected from TZD-induced bone loss providing proof of concept that PPARG in osteocytes can be pharmacologically targeted. Our study opens the possibility to consider repurposing PPARG as a target for treatment of osteoporosis.