Effects of standardized quassinoid-rich Eurycoma longifolia extract in a rat model of osteoporosis due to testosterone deficiency: A densitometric, morphometric and biomechanical study

BACKGROUND

Eurycoma longifolia (EL) is a well-known aphrodisiac herb for men. Recently, the crude extract of EL was reported to possess anti-osteoporotic activities.

OBJECTIVE

This study aims to determine the bone protective effects of the standardized quassinoid-rich EL extract in testosterone-deficient rat model.

METHODS

Ninety-six intact male Sprague-Dawley rats were randomized into baseline, sham, orchidectomized, and chemically castrated groups. Chemical castration was performed via subcutaneous injection of degarelix at 2 mg/kg. The orchidectomized and degarelix-induced rats were administered with vehicle, intramuscularly injected with testosterone once a week, or orally supplemented with EL extract at doses of 25 mg/kg, 50 mg/kg or 100 mg/kg daily for 10 weeks. Bone mass, microarchitecture and strength were analyzed by dual-energy x-ray absorptiometry (DEXA), micro-CT and three-point bending test.

RESULTS

Whole body bone mineral density and femoral bone mineral content significantly increased in testosterone groups (p <  0.05). Micro-CT analysis revealed that trabecular bone volume, number, separation and connectivity density were significantly improved by testosterone administration. However, the structural model index was only improved in degarelix group supplemented with 100 mg/kg EL extract (P <  0.05). The improvement of cortical thickness by EL extract was similar to that of testosterone groups (p <  0.05). Biomechanically, EL extract supplementation was able to improve stiffness, strain and modulus of elasticity in degarelix-induced groups, while stress parameter was significantly improved in orchidectomized groups (p <  0.05).

CONCLUSION

Quassinoid-rich EL extract enables to protect against bone loss due to testosterone deficiency. The protective effect on cortical thickness and biomechanical parameters is comparable to testosterone group.

Effect of Combined Teriparatide and Monthly Risedronate Therapy on Cancellous Bone Mass in Orchidectomized Rats: A Bone Histomorphometry Study

This study investigated the effects of combined teriparatide (an anabolic agent) and monthly risedronate (an anti-resorptive agent) therapy on cancellous bone mass in orchidectomized (ORX) rats. Fifty 14-week-old male Sprague-Dawley rats were randomized into five groups of ten animals each: sham-operation + vehicle; ORX + vehicle; ORX + risedronate (90 μg/kg subcutaneous, every 4 weeks); ORX + teriparatide (30 μg/kg subcutaneous, three times per week); and ORX + risedronate + teriparatide. After the 12-week experimental period, cancellous bone in the tibial proximal metaphysis was examined by static and dynamic histomorphometric analyses. ORX decreased bone volume per total volume (BV/TV) and trabecular number (Tb.N), and increased trabecular separation (Tb.Sp). Risedronate increased BV/TV and Tb.N above the sham control values, while teriparatide prevented the ORX-induced decrease in BV/TV and increased trabecular width (Tb.Wi) above sham control levels. Risedronate decreased Tb.Sp below control values, while teriparatide prevented the ORX-induced increase in Tb.Sp. The combination of teriparatide and risedronate further increased BV/TV and Tb.N and decreased Tb.Sp as a result of suppression of bone remodeling, compared with teriparatide alone. These results suggest that teriparatide and monthly risedronate exert different effects on cancellous bone structure and thus have additive effects on cancellous bone mass in ORX rats.

Eurycoma longifolia upregulates osteoprotegerin gene expression in androgen- deficient osteoporosis rat model

BACKGROUND

Eurycoma longifolia (EL) has been shown recently to protect against bone calcium loss in orchidectomised rats, the model for androgen-deficient osteoporosis. The mechanism behind this is unclear but it may be related to its ability to elevate testosterone levels or it may directly affect bone remodeling. The aim of this study is to determine the mechanism involved by investigating the effects of EL extract on serum testosterone levels, bone biomarkers, biomechanical strength and gene expression of Receptor Activator of Nuclear Factor kappa-B ligand (RANKL), Osteoprotegerin (OPG) and Macrophage-Colony Stimulating Factor (MCSF) in orchidectomised rats.

METHODS

Thirty-two male Sprague-Dawley rats were divided into: Sham-operated group (SHAM); orchidectomised-control group (ORX); orchidectomised and given 15 mg/kg EL extract (ORX + EL) and orchidectomised and given 8 mg/kg testosterone (ORX + T). The rats were treated for 6 weeks. The serum levels of testosterone, osteocalcin and C-terminal telopeptide of type I collagen (CTX) were measured using the ELISA technique. The femoral bones were subjected to biomechanical testing. The tibial bone gene expressions of RANKL, OPG and MCSF were measured using the branch DNA technique.

RESULTS

The post-treatment level of testosterone was found to be significantly reduced by orchiectomy (p < 0.05). Both ORX + EL and ORX + T groups have significantly higher post-treatment testosterone levels compared to their pre-treatment levels (p < 0.05). The bone resorption marker (CTx) was elevated after orchiectomy but was suppressed after treatment in the ORX + EL and ORX + T groups (p < 0.05). There was no significant finding for the femoral biomechanical parameters. The tibial OPG gene expression in the ORX group was significantly lower compared to the SHAM and ORX + EL groups (p < 0.05).

CONCLUSION

Supplementation with EL extract elevated the testosterone levels, reduced the bone resorption marker and upregulated OPG gene expression of the orchidectomised rats. These actions may be responsible for the protective effects of EL extract against bone resorption due to androgen deficiency.

Combined Effects of Eurycoma longifolia and Testosterone on Androgen-Deficient Osteoporosis in a Male Rat Model

Androgen-deficient osteoporosis in men is treated with testosterone therapy, which is associated with side effects. Eurycoma longifolia (EL) is known to possess androgenic properties and has been reported to protect bone from androgen-deficient osteoporosis in experimental animal models. The present study aimed to determine the effectiveness of combination therapy of EL and testosterone (T) in treating androgen-deficient osteoporosis. Forty male Sprague-Dawley rats were divided into: sham-operated (SHAM), orchidectomized-control (ORX), orchidectomized with testosterone (ORX + T), orchidectomized with EL (ORX + EL), and orchidectomized with combined T and EL therapy (ORX + T + EL). EL was administered via oral gavages daily at the dose of 15 mg/kg. T was injected intramuscularly at 8 mg/kg and 4 mg/kg for the ORX + T and ORX + T + EL groups, respectively. Following 6 weeks of treatment, the osteocalcin levels of ORX + T and ORX + T + EL groups were significantly lower than the SHAM group (P < 0.05). The posttreatment CTX levels of ORX + T and ORX + T + EL groups were significantly lower than their pretreatment levels (P < 0.05). Biomechanically, the strain parameter of the ORX + T + EL group was significantly higher than the ORX group (P < 0.05). Thus, the combination therapy of EL and low-dose T has potential for treatment of androgen-deficient osteoporosis. The lower T dose is beneficial in reducing the sideeffects of testosterone therapy.

Modulation of bone turnover in orchidectomized rats treated with raloxifene and risedronate

Osteoporosis is a reduction in bone mineral density (BMD). It develops less often in men than in women. This study aimed to evaluate the bone protective effects of raloxifene (RAL), risedronate (RIS), and their combination on osteoporotic male rats. Forty male Wister rats (12 weeks) were randomly divided into five groups: sham-operated group (n = 8), orchidectomized (ORX) group (n = 7), RAL group (n = 9), RIS group (n = 7) and RAL + RIS group (n = 7). RAL was orally administered at 3 mg/kg three times/week, and RIS was given subcutaneously at 5 μg/kg, twice weekly. After 6 weeks of treatment, serum cathepsin-K, alkaline (ALP) and acid phosphatase activities, serum osteocalcin, serum Ca²⁺, and Pi were determined. Urinary Ca²⁺ and deoxypyridinoline levels, BMD, and Ca²⁺ content of femur ash were estimated. Histochemical localization of ALP activity of tibia and histomorphometry was examined. As compared to sham, ORX rats showed a significant increase in bone turnover markers, and histochemical activity of ALP was increased markedly in proximal tibia of ORX rats, whereas BMD and Ca²⁺ content of femur ash were reduced after ORX. These changes were modulated after treatment with RAL and RIS or both to ORX rats; BMD of femur was improved by each treatment, and bone turnover markers were reduced as compared to ORX vehicle group. We concluded that orchidectomy induced osteoporosis and increased bone turnover in male rats because of withdrawal of sex hormones. Both RAL and RIS could treat osteoporosis in ORX rats; they reduced bone turnover markers and maintained BMD.

Increased prevalence of bisphosphonate-related osteonecrosis of the jaw with vitamin D deficiency in rats

Necrotic bone exposure in the oral cavity has recently been reported in patients treated with nitrogen-containing bisphosphonates as part of their therapeutic regimen for multiple myeloma or metastatic cancers to bone. It has been postulated that systemic conditions associated with cancer patients combined with tooth extraction may increase the risk of osteonecrosis of the jaw (ONJ). The objective of this study was to establish an animal model of bisphosphonate-related ONJ by testing the combination of these risk factors. The generation of ONJ lesions in rats resembling human disease was achieved under the confluence of intravenous injection of zoledronate (ZOL; 35 microg/kg every 2 weeks), maxillary molar extraction, and vitamin D deficiency [VitD(-)]. The prevalence of ONJ in the VitD(-)/ZOL group was 66.7%, which was significantly higher (p < .05, Fisher exact test) than the control (0%), VitD(-) (0%), and ZOL alone (14.3%) groups. Similar to human patients, rat ONJ lesions prolonged the oral exposure of necrotic bone sequestra and were uniquely associated with pseudoepitheliomatous hyperplasia. The number of terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick-end label-positive (TUNEL(+)) osteoclasts significantly increased on the surface of post-tooth extraction alveolar bone of the VitD(-)/ZOL group, where sustained inflammation was depicted by [(18)F]fluorodeoxyglucose micro-positron emission tomography (microPET). ONJ lesions were found to be associated with dense accumulation of mixed inflammatory/immune cells. These cells, composed of neutrophils and lymphocytes, appeared to juxtapose apoptotic osteoclasts. It is suggested that the pathophysiologic mechanism(s) underpinning ONJ may involve the interaction between bisphosphonates and compromised vitamin D functions in the realm of skeletal homeostasis and innate immunity.