Isorhamnetin ameliorates ovariectomy-induced osteoporosis in female rats by regulating the receptor activator of nuclear factor kappa B ligand, osteoprotegerin, bone morphogenetic protein 2 and runt-related transcription factor 2 signaling pathway.

Osteoporosis is characterized by reduced bone density and increased fracture risk. The present study assessed anti-osteoporotic effects of isorhamnetin on ovariectomy (OVX)-induced osteoporosis in female rats. Osteoporosis was induced in OVXX-female Sprague-Dawley rats by using Freund's Complete Adjuvant and randomly divided into the following groups (n=15): OVX control, alendronate (3 mg/kg, subcutaneous), and isorhamnetin (10, 20, and 40 mg/kg, p.o.), and received treatment for five weeks after OVX. In results following OVX, significant alterations in behavioral, biochemical, and histological parameters were observed. Conversely, isorhamnetin (20 and 40 mg/kg) treatment significantly improved (P<0.05) OVX-induced alterations in body, femur, and uterine weight, bone mineral content and density, but also effectively mitigated (P<0.05) elevated allodynia and hyperalgesia. It notably improved (P<0.05) changes in serum alkaline phosphatase, osteocalcin, C-terminal telopeptide of type I collagen (CTX-I), serum and urinary calcium, and phosphorus levels. Isorhamnetin markedly attenuated elevated (P<0.05) serum TNF-α, IL-1β, IL-6 levels but increased (P<0.05) serum IL-4 and IL-10 levels. Furthermore, mRNA expression of osteoprotegerin (OPG), runt-related transcription factor 2 (Runx2), and bone morphogenetic protein 2 (BMP-2) was upregulated (P<0.05), whereas receptor activator of nuclear factor kappa B ligand (RANKL) was downregulated (P<0.05). Histological analysis demonstrated that isorhamnetin effectively improved (P<0.05) OVX-induced inflammation, thereby preventing cellular infiltration, synovial hyperplasia, cartilage erosion, and pannus formation in bone specimens. In conclusion, isorhamnetin exerts its anti-osteoporotic potential by modulating pain (allodynia and hyperalgesia), serum biomarkers (osteocalcin, CTX-I, TNF-α, ILs), and bone signaling pathways (RANKL, OPG, BMP-2, Runx2).