Sialoglycoproteins isolated from the eggs of Carassius auratus prevents osteoporosis by suppressing the activation of osteoclastogenesis related NF-κB and MAPK pathways

A sialoglycoprotein was isolated from the eggs of Carassius auratus (Ca-SGP) and its anti-osteoporotic activities were first investigated in in vitro and in vivo systems. In vitro experiments using osteoclast precursors showed that Ca-SGP significantly decreased the formation of tartrate-resistant acid phosphatase (TRAP)-positive multinucleated osteoclasts, bone resorption pits and the expression of osteoclastic marker genes, indicating its inhibitory effect on RANKL-induced osteoclastogenesis. qRT-PCR and western blotting results suggested that Ca-SGP significantly decreased mRNA and protein expressions of NFATc1 and c-Fos, two key transcription factors of osteoclastogenesis regulated by NF-κB and MAPK pathways. Further investigation revealed that Ca-SGP suppressed the activation of NF-κB and MAPK signaling pathways by diminishing the mRNA expression and phosphorylation of p38, ERK, JNK, IκB, NF-κB. In vivo experiment using ovariectomized (OVX)-induced osteoporotic model rats indicated that Ca-SGP prominently declined the levels of serum TRAP, CSTK, MMP-9, urine DPD and ameliorated the damaged trabecular. These results suggest that Ca-SGP can improve osteoporosis by inhibiting bone resorption via suppressing the activation of osteoclastogenesis related NF-κB and MAPK pathways.