Research paperThe effects of Liuwei Dihuang on canonical Wnt/β-catenin signaling pathway in osteoporosis
Graphical abstract
Our results suggest that Liuwei Dihuang could alleviate osteoporosis induced by ovariectomy, in part, through up-regulation of canonical Wnt/β-catenin signaling pathway of osteoblast.
Introduction
Osteoporosis is the condition in which a low bone mass and altered bone microarchitecture leads to increased risk of fragility fracture (Collins et al., 2011, Rachner et al., 2011). Clinically, osteoporosis has been divided into two types: primary and secondary osteoporosis. The former usually results from aging and decreased gonadal function, such as decreased level of estrogen, while the latter is often the complication caused by other health problems and drugs, such as the prolonged corticosteroid therapy (Rachner et al., 2011). Osteoporosis is considered by the World Health Organization (WHO) to be an important health issue secondary to coronary heart disease. About 40% of postmenopausal women are affected by osteoporosis, and with an ageing population, this number is expected to steadily increase in the near future (Melton et al., 1992, Burge et al., 2007). In addition, about 18% of women and 6% of men worldwide will experience hip fragility fractures resulting from osteoporosis (Piscitelli et al., 2007). Current therapeutics in clinical use included bisphosphonates, anti-RANKL, parathyroid hormone, and strontium ranelate, which may reduce the risk of first and recurrent fractures (Das and Crockett, 2013). The direct and indirect costs of osteoporosis were estimated at $21.9 billion in American in 1998 (Max et al., 2002). However, these drugs remain costly and are not afford for the majority of Chinese. Therefore, there is an urgent and increasing need for effective but lower-cost pharmacotherapy.
The Liuwei Dihuang (LWDH), a classic traditional Chinese medicine formula, has been used clinically in the treatment of many types of diseases with signs of deficiency of Yin in the kidneys for more than thousand years in China. LWDH is most early recorded in the book of “Xiaoer YaoZheng ZhiJue”, and consists of six Chinese crude herbs: Rehmannia glutinosa Libosch. (family: Scrophulariaceae), Cornus officinalis Sieb. (family: Cornaceae), Dioscorea opposite Thunb. (family: Dioscoreaceae), Alisma orientale (G. Samuelsson) Juz (family: Alismataceae), Poria cocos (Schw.) Wolf (family: Polyporaceae) and Paeonia suffruticosa Andrews (family: Paeoniaceae) as a proportion of 8:4:4:3:3:3 (Wu et al., 2007, Zhao et al., 2007, Wang et al., 2010, Liu et al., 2013).
LWDH is orally administered as a decoction or in the form of pills, which is applied for the declined functions related to aging process and geriatric diseases, especially for diabetes, cognition and memory in china and Japan (Yokozawa et al., 2004, Wang et al., 2010, Liu et al., 2013). Recently, a number of studies have revealed that LWDH has therapeutic effects on osteoporosis and some possible mechanisms of action have been put forward (Chen et al., 1994, Sun et al., 2006, Peng, 2007); however, the precise mechanism has not yet been fully revealed.
The activation of different bone cells in bone remodeling process is regulated by multiple pathways and these pathways are exploited in the development of new therapies for osteoporosis. The canonical Wnt/β-catenin signaling pathway, which controls multiple developmental processes in skeletal and joint patterning also be involved in the progression of osteoporosis (Fei and Hurley, 2012, Brunetti et al., 2013, Kim et al., 2013, Xu et al., 2013).
Since genetic association studies suggest that the canonical Wnt/β-catenin signaling pathway plays a critical role in the pathogenesis of osteoporosis, we hypothesized that the benefit of LWDH on osteoporosis based on the regulation of the canonical Wnt/β-catenin signaling pathway. In our study, the key molecules involved in the canonical Wnt/β-catenin signaling pathway, including Lrp-5, β-catenin, Runx2 and Osx, were detected after treatment with LWDH both in vivo and in vitro experiments.
Section snippets
Preparation of LWDH
The method of preparation of LWDH was obtained from Yang et al. (2006). In brief, Rehmannia glutinosa Libosch. (family: Scrophulariaceae), Cornus officinalis Sieb. (family: Cornaceae), Dioscorea opposite Thunb. (family: Dioscoreaceae), Alisma orientale (G. Samuelsson) Juz (family: Alismataceae), Poria cocos (Schw.) Wolf (family: Polyporaceae) and Paeonia suffruticosa Andrews (family: Paeoniaceae) were mixed as a proportion of 8:4:4:3:3:3, and the total dry weight was 2 kg. The mixture of herbs
General condition of osteoporosis model
The success of osteoporosis model was confirmed by serum ALP, BGP, E2 and bone mineral density examination after twelve weeks of ovariectomy. When compared with control group, the level of ALP and BGP in serum were significantly increased in OVX group (P<0.05). Comparison of E2 and BMD, those in OVX group were significantly reduced than that of control group (P<0.05) (Fig. 1a–d). During the period of experiment, mean body weight of rat consistently increased in each group, while there was no
The model of osteoporosis
Setting up an appropriate animal model is very important in researches or studies. An ideal animal model should be similar to the prototype, and through analysis of models we could obtain partial information about prototypes. In our study, we used a well described, estrogen deficiency related model, which mimics features of postmenopausal osteoporosis women (Kalu, 1991, Aoyagi et al., 1996, Goss et al., 2004, French et al., 2008, Fathilah et al., 2013). This model, set up firstly by Saville
Acknowledgments
This publication was made possible by the National Natural Science Foundation of China (Grant no. 81202710), State Administration of Tradition Chinese Medicine of Zhejiang province (Grant no. 2009YA001), Zhejiang Provincial Natural Science Foundation of China (Grant no. Y2111184), and the Science Technology Department of Zhejiang province (Grant no. 2012R10064).
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