Green tea extract suppresses osteoclastogenesis and opposes glucocorticoid-induced osteoporosis in rats

Abstract

Background/aim Glucocorticoids-induced osteoporosis (GIO) through suppression of osteoblast activity, induction of receptor activator of nuclear factor-κB ligand (RANKL), and downregulation of osteoprotegerin (OPG). Green tea has antioxidant and anti-inflammatory properties. This study aims to evaluate the effects of green tea extract (GTE) supplementation on bone proteins, mineralization, and markers in GIO. Materials and methods The study was performed on 30 adult male Wistar rats, which were divided into three groups: control (C, n=10); GIO (n=10), which received dexamethasone 7 mg/kg body weight intramuscular once/week for 4 weeks; and GTE-supplemented osteoporotic (GT-GIO, n=10), which received dexamethasone, followed by 300 mg/kg per day of GTE by gavage for 4 weeks, with continuation of the dexamethasone. Serum calcium, phosphate, alkaline phosphatase activity, parathyroid hormone, deoxypyridinoline, osteocalcin, OPG, and RANKL were determined. Samples of left tibia were used for histopathological examination of bone. Results A significant decrease in serum Ca++, PO4, osteocalcin, and OPG, accompanied by a significant increase in serum bone-specific alkaline phosphatase, deoxypyridinoline, and RANKL was detected in the GIO group compared with the control group. GT-GIO group showed a significant increase in serum Ca++, PO4, osteocalcin, and OPG, with a significant decrease in serum bone-specific alkaline phosphatase, deoxypyridinoline, and RANKL compared with the GIO group. Bone examination of GIO rats revealed thinning, loss of architecture, erosions, and increased osteoclasts. Bone sections of the GT-GIO group revealed significant improvement, regain of normal architecture, and decreased osteoclast number. Conclusion GTE had an antiosteoporotic effect in GIO, and its effects are much more than its antioxidant characteristics.