Sialoglycoproteins Isolated from the Eggs of Gadus morhua Inhibit Bone Resorption in Ovariectomized Rats by Suppressing the MAPK and NF-κB Pathways

The present study investigated the anti-osteoporosis function and the mechanism of sialoglycoproteins isolated from the eggs of Gadus morhua(Gm-SGP)on ovariectomized(OVX)rats.After 3 months of Gm-SGP treatment,OVX-induced bone loss was suppressed and uncoupling bone turnover was balanced,as indicated by systemic biomarkers of bone metabolism;no uterine estrogenicity was observed.Moreover,rats administered with Gm-SGP exhibited increased bone mineral density and biomechanical strength and significant restoration of the trabecular microarchitecture compared with rats in the control group.Gm-SGP significantly decreased bone resorption-related indicators in serum.Investigation of the associated mechanisms revealed that Gm-SGP significantly increases the OPG/RANKL ratio at the mRNA and protein levels.Further research suggested that Gm-SGP inhibits the mRNA and protein expressions of important transcription factors of the MAPK and NF-κB signaling pathways.It also attenuates the activation of related transduction signaling pathways by inhibiting phosphorylation of JNK,ERK,p38,and NF-κB,and ultimately suppresses the induction of c-Fos and NFATc1.Overall,these results demonstrate that Gm-SGP inhibits bone resorption by suppressing osteoclastogenesis-related MAPK and NF-κB pathways,thereby improving osteoporosis.