Abstract:
Osteoclasts are the sole bone resorbing cell in the body and their over activity is key in
the development of osteoporosis. Osteoclastogenesis is mediated by receptor activator of nuclear
factor B ligand (RANKL) signalling pathways. Unsaturated fatty acids (UFA) are known to inhibit
osteoclastogenesis by targeting RANKL signalling. However, the mechanisms of action remain
unclear. Peroxisome proliferator activated receptors (PPARs) are a family of nuclear receptors,
with three known isoforms (PPAR- , PPAR- / and PPAR-
), that are known to bind UFAs and
are expressed in osteoclasts. In this study, we aimed to determine how di erent families of UFAs
activate PPARs and how PPAR activation influences osteoclast signalling. Human CD14+ monocytes
were seeded into cluster plates with RANKL and macrophage colony stimulating factor (M-CSF)
in the presence of PPAR agonists or di erent types of UFAs. All the PPAR agonists were shown to
upregulate the activity of their respective receptors. Polyunsaturated fatty acids increased PPAR- to
a greater extent than monounsaturated fatty acids (MUFAs), which favoured PPAR- / activation.
All PPAR agonists inhibited osteoclastogenesis. The activation of RANKL signalling pathways and
expression of key osteoclast genes were downregulated by PPAR agonists. This study reveals that
PPAR activation can inhibit osteoclastogenesis through modulation of RANKL signalling.
