Cistanche acteoside improves bone strength to anti-osteoporosis

Contact: emily.li@wecistanche.com

There is a growing recognition and approval of Traditional Chinese Medicine (TCM) for the treatment of complicated ailments based on extensive experience which has been accumulated over thousands of years in China. More remarkably, TCM (Traditional Chinese Medicine) theory points out that the bone development system is governed and dominated by the kidney which means the kidney is an essential organ for nourishing bone development during growth. Thus TCM (Traditional Chinese Medicine) materials that possess properties for invigorating the kidney function can be used as an anti-osteoporotic agent for clinical purposes.

Cistanche deserticola, a traditional TCM (Traditional Chinese Medicine) material herb and also a common natural health food ingredient that have long been used as a tonic agent in China and Japan. C. deserticola (Cistanche deserticola) is also called “desert ginseng" due to its traditional uses of nourishing the kidney as well as its excellent curative effects including anti-oxidative, anti-nociceptive, anti-inflammatory, anti-fatigue, and neuroprotective activity. Furthermore, previous studies have discovered that C. deserticola (Cistanche deserticola) dose-dependently improved bone quality in animals with osteoporosis induced by ovariectomy.

Cistanche is good for bone development

Based on the TCM (Traditional Chinese Medicine) theory of “kidney dominates bone" as well as published data, C. deserticola (Cistanche deserticola) indeed possessed potent anti-osteoporotic activity; however, the corresponding compounds and the underlying molecular mechanisms are still unclear. According to Chinese pharmacopeia, the compound of phenylethanoid glycoside including echinacoside and acteoside are the main and effective chemical compositions of C. deserticola (Cistanche deserticola), and acteoside is a well-studied natural component that is widely distributed in dozens of medicinal plants. Given the detailed anti-osteoporosis mechanisms of C. deserticola (Cistanche deserticola), including acteoside, are still unclear, the present study was designed to systematically evaluate the therapeutic effect of acteoside as well as underlying molecular mechanisms. As expected, our research demonstrated that acteoside could enhance the bone mineral density and biomechanical properties as well as improve the microarchitecture of bone trabecular, and finally prevent bone loss in osteoporotic mice induced by ovariectomy.

There is no doubt that estrogen plays an important role in stimulating bone metabolism, and postmenopausal osteoporosis, a sex-steroid deficiency state characterized by decreased bone mineral density and increased risk of fracture, is believed to be mainly caused by estrogen deficiency. According to previous data from the literature, after ovariectomy (OVX )surgery and during the process of postmenopausal osteoporosis, uterine and vaginal weights of OVX animals were significantly decreased, whereas the body weight was obviously increased. In the present study, as expected, postmenopausal osteoporosis caused an excess of whole-body weight and a sharp decline of uterine and vaginal weights of OVX mice. When complemented with positive drug EV, an estrogen agent that has been proved effective in the treatment of postmenopausal osteoporosis in clinical conditions, the gained bodyweight and atrophied uterine and vaginal weights were significantly reversed. In contrast, acteoside did not prevent the induced body weight gain as well as uterine and vaginal weight loss in the OVX mice, which implied that the stimulation of unwanted proliferation of body growth and atrophy of uterine and vaginal tissues in the OVX mice were not influenced by acteoside but reversed by EV treatment. All the above results indicate that acteoside improved the bone microarchitecture and biomechanics through another mechanism rather than the phytoestrogen characteristic such as EV.

As well as BMD as one of the major markers for the diagnosis of osteoporosis, micro-CT and biochemical detection was also used to provide additional direct information of trabecular microarchitecture to assess bone fragility. The micro-CT technology, instead of histological staining, can give us both the intuitive and quantitative data of the microarchitecture of trabecular bone, and the 3D image of trabecular bone supplied by the micro-CT method was very intuitive. The area of the trabecular bone can be observed, and quantitative data including BVF, BMD, BMC, TMC, TMD, Tb.N, Tb.Th, Tb. Sp etc. were also obtained. Therefore, the data obtained from the micro-CT and biochemical detection were believed to be more meaningful and comprehensive for the diagnosis of osteoporosis. In the present study, acteoside dose-dependently (20,40, and 80 mg/kg/day) improved the BMD in OVX mice, and most of the variables in the micro-CT experiment were significantly ameliorated, including the reduction of BMC, TMC, BVF, Tb. N, and Tb.Th in OVX mice, which was consistent with the published data, whereas the increment of Tb. Sp was totally reversed; moreover, in parallel with the micro-CT findings, the biomechanical parameters, including the maximal load and stiffness, were also significantly enhanced by acteoside treatment. Therefore, our data implied the therapeutic effect of acteoside on the bone microarchitecture of OVX mice.

During the process of postmenopausal osteoporosis, the reduction of BMD and deterioration of the bone microarchitecture in the femur were always accompanied by significant changes in the bone remodeling markers including ALP, BGP, TRAP, cathepsin K and DPD. It is well known that TRAP, cathepsin K, and DPD are regarded as typical markers for bone resorption, while ALP and BGP are widely considered to be bone formation indexes. Treatment with acteoside prevented any significant increase in TRAP, cathepsin K, and DPD activities, and the level of BGP was also up-regulated in OVX mice, which means acteoside could both suppress bone resorption and enhance bone formation and thus exhibited anti-osteoporotic properties.

To the best of our knowledge, bone reconstruction and remodeling is a complicated physiological process that requires the function of osteoclasts. It was confirmed that the activity and differentiation of osteoclasts were significantly increased during menopause because of the sharply declined estrogen levels. RANKL and its receptor, RANK, two key differentiation factors of osteoclast progenitors that belong to the TNF family, were believed to be able to stimulate osteoclast differentiation and then mediate osteoclastogenesis. Furthermore, it was determined that the binding of RANKL to RANK could activate a variety of downstream signal pathways including NF-kB and PI3K/AKT, as well as some transcription factors including NFAT2 and c-Fos, and thus stimulated the development of osteoclasts and osteoclastogenesis. Nevertheless, the RANK receptor protein lacked intrinsic enzymatic activity unless the TNF-receptor-associated factors (TRAFs) were recruited and were followed by the downstream signal cascades being transduced. TRAF6 was believed to be the primary adaptor molecule which was potentially useful for the function and differentiation of osteoclasts. Hence, the RANKL/RANK/TRAF6 system was considered to be an important mechanism to explain osteoclastogenesis. In the present study, a hypothesized schematic mechanism by which acteoside suppressed osteoclastogenesis is depicted. Concisely, acteoside decreased RANKL, RANK, and TRAF6 expressions and therefore inhibited the system of RANKL/RANK/TRAF6, and consequently, the downstream pathway of NF-kB was inactivated and PI3K/AKT was activated, and ultimately, the level of NFAT2 decreased and the expression of c-Fos increased, Previous published data also showed that acteoside inhibited osteoclast differentiation by suppressing RANKL-induced activation of transcription factors such as-KB and NFATc1, which is consistent with our results. Overall, the targeted modulation of the RANKL/RANK/TRAF6 system can be useful in the explanation of the therapeutic effects of acteoside on the bone metabolism in OVX mice, However, there are several limitations that should be considered in further studies, including the differences hf bone cellular parameters and dynamic parameters in OVX mice, which should be detected using histomorphometric methods; it is more appropriate to induce postmenopausal osteoporosis in aged mice than young mice.