Elsevier

Life Sciences

Volume 233, 15 September 2019, 116706
Life Sciences

The influence of TRAIL, adiponectin and sclerostin alterations on bone loss in BDL-induced cirrhotic rats and the effect of opioid system blockade

https://doi.org/10.1016/j.lfs.2019.116706Get rights and content

Abstract

Aims

Osteoporosis is a common extra-hepatic complication in patients with chronic liver disease. Tumor necrosis factor related apoptosis-inducing ligand (TRAIL), sex hormones, adiponectin, and sclerostin are involved in the regulation of bone turnover but little is known about their role in the promotion of hepatic osteodystrophy. Endogenous opioids are reported to increase during cholestasis and may influence bone resorption. The purpose of this study was to investigate the circulating levels of these factors and their expression in the femur of bile duct ligated (BDL) rats, to evaluate the biomechanical bone strength, and the effect of naltrexone (NTX).

Materials and methods

BDL and sham-operated (SO) rats received 10 mg/kg NTX as an opioid-receptors antagonist or saline once daily for 28 days intraperitoneally. Three-point bending test was performed on the right femurs and, plasma bone alkaline phosphatase (BALP), sex hormones, TRAIL, adiponectin, sclerostin, as well as the mRNA expression levels of the latter three proteins, were measured in the femur tissues.

Key findings

Plasma TRAIL, estrogen, adiponectin, sclerostin and, BALP levels increased in BDL animals when compared to the related controls, whereas testosterone level decreased and NTX reversed these effects significantly. Femur strength decreased in cirrhotic animals and interestingly, blocking opioid-receptors by NTX improved it significantly (p ≤ 0.05).

Significance

High levels of TRAIL, adiponectin and, sclerostin after bile duct ligation, suggest that these factors may have some roles in bone loss after cirrhosis. Administration of NTX improved all the mentioned factors except for bone strength. Effect of NTX on bone loss in BDL rats needs more study to clarify.

Introduction

Osteoporosis is one of the most important extra-hepatic and liver disease-related complications which is associated with reduced bone mass and increased fracture risk, leading to what is termed hepatic osteodystrophy [1,2]. The exact pathophysiology of this complication is not completely understood [1]. Liver dysfunction probably causes alteration of several factors and hormones [3] which affect the bone tissue through RANK (receptor activator of nuclear factor-κB)/RANKL (RANK-ligand)/OPG (osteoprotegerin) system as a key regulator of bone turnover, resulting in increased bone resorption and decrease bone formation [4]. RANKL with binding to its receptor RANK stimulates osteoclastogenesis and activation of osteoclasts; the bone-resorbing cells. On the other hand, OPG as a decoy receptor deactivates this process [5]. However, several studies have shown elevated levels of OPG in liver diseases, contributing to bone loss [6,7].

Tumor necrosis factor related apoptosis-inducing ligand (TRAIL) is a glycoprotein, which belongs to the TNF family [8]. This protein plays a significant role in the formation and differentiation of osteoclasts [9,10] and by binding to OPG, prevents its inhibitory effect on osteoclastogenesis [8]. Also, the evidence presented has revealed the ability of sex hormones to stimulate OPG and reduce RANKL production in vitro and in vivo [11,12], and that cirrhosis is associated with impairment of the serum level of sex hormones [13]. Therefore, the observed increase levels of OPG in hepatic osteodystrophy may be related to changes in the level of TRAIL and sex hormones in this situation.

As mentioned above, following liver diseases bone loss is developed and is associated with increased bone resorption and decreased bone formation [14]. Adiponectin as an adipocyte-secreted hormone accelerates bone turnover and enhances bone resorption through regulating OPG/RANKL expression [15]. Moreover, sclerostin; a bone formation inhibitor, suppresses bone formation by preventing the Wnt signaling pathway [16]. The effect of these two factors may be considered as the same in mechanisms involved in hepatic osteodystrophy.

Increase in the level of endogenous opioids is important in bone quality during fibrosis and cirrhosis [17]. Binding of these opioids to their receptors inhibit the secretion of osteocalcin in osteoblasts [18] and believed to reduce bone density in animals and humans [19,20].

Up to now, the expression of TRAIL, adiponectin, and Sclerostin genes have not been analyzed in the bone tissue, although increased circulating levels of these factors have been described in chronic alcoholism and in liver cirrhosis [10,16,21]. Meanwhile, the role of these factors, along with opioid receptor antagonist (NTX) has not been studied in cholestatic liver cirrhosis; a disease clearly associated with bone loss.

This study aimed to measure the circulating levels of TRAIL, sex hormones, adiponectin and sclerostin in BDL-induced cirrhotic rats and their relationship with bone strength and bone turnover marker (BALP). The mRNA levels of some factors in the bone of BDL rats and their association with their circulating levels were assessed. Also, based on the effect of endogenous opioids on bone quality and density during fibrosis and cirrhosis [19,20,22,23], the influence of NTX (a non-specific opioid receptor blocker) on the above mentioned factors was investigated to find out the eventual role of endogenous opioids in the process.

Section snippets

Chemicals

Drugs and reagents; all with analytical grade, used in this study were as follows:

Naltrexone (non-specific opioid receptor antagonist) was obtained from Sigma (St Louis, MO, USA), ketamine hydrochloride, xylazine hydrochloride, were purchased from Daroupakhsh (Tehran, Iran) and formaldehyde was prepared from Merck (Darmstadt, Germany).

Animals

Male Sprague–Dawley rats (n = 38, weight 200–250 g) were purchased from the animal facility of the Institute of Biochemistry and Biophysics, (IBB, University of

Histological analysis

Results of histological evaluation of liver tissues by Masson's Trichrome staining revealed an elevated deposition of collagen fibers in BDL rats (Fig. 1C). Additionally, bile duct proliferation in the port space, thickening of the portal wall, and formation of communication septum known as biliary fibrosis were observed (arrow). Abnormality in liver tissues was expanded in NTX-treated BDL rats. Meanwhile, the liver of SO animals showed no abnormal histologic changes and the liver parenchyma

Discussion

It has been proposed that accumulation of endogenous opioid peptides in cholestasis affects many organs such as bone [17,18]. However, the effects of the receptors antagonists on bone quality have not been adequately studied. Meanwhile, although there is no direct evidence about the relationship between opioids and TRAIL, adiponectin, and sclerostin in the literature but, there is some evidence about the relationship between opioid receptors and bone loss [19,23,25]. So, to address this

Acknowledgement

This study was supported by Research Council of Tehran University of Medical Sciences and Health Services (Grant Numbers 34472 and 33605). The authors also wish to appreciate useful technical assistance and help of Prof. Iraj Ragerdi Kashani in fulfilment of this study.

Funding

This study was supported by Research Council of Tehran University of Medical Sciences (Grant Numbers 34472 and 33605).

Declaration of competing interest

The authors declare that they have no conflict of interest related to the data or interpretation of this study.

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