OPG/RANK/RANKL signaling axis in patients with type I diabetes: Associations with parathormone and vitamin D

BACKGROUND

Type 1 diabetes (T1D) has been associated with a higher fracture risk due to alterations in bone structure and metabolism. On the other hand, the important role of the RANKL/OPG/RANK signaling axis in bone physiology is well established. The aim of this study was to evaluate the levels of receptor activator of nuclear factor kappa-B ligand (RANKL), receptor activator of nuclear factor kappa-B (RANK) and plasma osteoprotegerin (OPG) levels, in T1D youngsters and to investigate factors that could influence the OPG/RANK/RANKL signaling axis such as 25-hydroxy vitamin D [25(OH) D], parathormone (PTH) and age.

METHODS

Serum RANKL, RANK, 25(OH) D, PTH levels and plasma OPG levels, were measured in 71 youngsters with T1D and 50 healthy controls matched for age and gender.

RESULTS

Plasma OPG levels were significantly lower (p = 0.025) in T1D patients compared to controls. Serum RANKL levels were significantly higher (p = 0.037), while no differences were observed in serum RANK levels (p = 0.946) between the two groups. Serum 25(OH) D levels found significantly decreased (p < 0.001) while serum PTH levels were significantly elevated (p < 0.001) in T1D patients than in controls.

CONCLUSIONS

Our results demonstrated that OPG and RANKL may be promising biomarkers for T1D patients. However, their circulating levels were associated with several factors including PTH, 25(OH) D and therefore, may represent an integrative biomarker for a variety of endocrine signaling disturbances observed in T1D.

Effect of caspases and RANKL induced by heavy force in orthodontic root resorption

Objective

Orthodontic root resorption (ORR) due to orthodontic tooth movement is a difficult treatment-related adverse event. Caspases are important effector molecules for apoptosis. At present, little is known about the mechanisms underlying ORR and apoptosis in the cementum. The aim of the present in vivo study was to investigate the expression of tartrate-resistant acid phosphatase (TRAP), caspase 3, caspase 8, and receptor activator of nuclear factor kappa-B ligand (RANKL) in the cementum in response to a heavy or an optimum orthodontic force.

Methods

The maxillary molars of male Wistar rats were subjected to an orthodontic force of 10 g or 50 g using a closed coil spring. The rats were sacrificed each experimental period on days 1, 3, 5, and 7 after orthodontic force application. And the rats were subjected to histopathological and immunohistochemical analyses.

Results

On day 7 for the 50-g group, hematoxylin and eosin staining revealed numerous root resorption lacunae with odontoclasts on the root, while immunohistochemistry showed increased TRAP- and RANKL-positive cells. Caspase 3- and caspase 8-positive cells were increased on the cementum surfaces in the 50-g group on days 3 and 5. Moreover, the number of caspase 3- and caspase 8-positive cells and RANKL-positive cells was significantly higher in the 50-g group than in the 10-g group.

Conclusions

In our rat model, ORR occurred after apoptosis was induced in the cementum by a heavy orthodontic force. These findings suggest that apoptosis of cementoblasts is involved in ORR.

Inhibition of the RANK/RANKL signaling with osteoprotegerin prevents castration-induced acceleration of bone metastasis in castration-insensitive prostate cancer

Androgen deprivation therapy (ADT) for patients with metastatic or locally advanced prostate cancer reduces bone mineral density by stimulating receptor activator of nuclear factor kappa-B (RANK) signaling in osteoclasts. The involvement of the RANK/RANKL signaling in ADT-induced acceleration of bone metastasis in castration-insensitive prostate cancer was examined in a murine model using osteoprotegerin (OPG). Male Balb/c nude mice were divided into three groups: the non-castration, castration, and castration + OPG groups. PC-3M-luc-C6 was injected into the left ventricle of the mice. Recombinant OPG was injected intravenously twice weekly in the castration + OPG group. In-vivo imaging system (IVIS^®) determined that the prevalence and photon counts of bone metastasis in the castration group were significantly higher than that in the non-castration and castration + OPG groups. The mean number of RANKL-positive osteoblasts and the mean serum RANKL level in the castration group were significantly higher than those in the non-castration group. RANKL-enhanced activation of osteoclasts was attenuated in the castration + OPG group. These results suggest that the mechanisms of RANK/RANKL signaling are involved in the ADT-induced acceleration of bone metastasis in castration-insensitive prostate cancer.

Immune mediators in the tumor microenvironment of prostate cancer

Prostate cancer tissue is composed of both cancer cells and host cells. The milieu of host components that compose the tumor is termed the tumor microenvironment (TME). Host cells can be those derived from the tissue in which the tumor originates (e.g., fibroblasts and endothelial cells) or those recruited, through chemotactic or other factors, to the tumor (e.g., circulating immune cells). Some immune cells are key players in the TME and represent a large proportion of non-tumor cells found within the tumor. Immune cells can have both anti-tumor and pro-tumor activity. In addition, crosstalk between prostate cancer cells and immune cells affects immune cell functions. In this review, we focus on immune cells and cytokines that contribute to tumor progression. We discuss T-regulatory and T helper 17 cells and macrophages as key modulators in prostate cancer progression. In addition, we discuss the roles of interleukin-6 and receptor activator of nuclear factor kappa-B ligand in modulating prostate cancer progression. This review highlights the concept that immune cells and cytokines offer a potentially promising target for prostate cancer therapy.

Receptor activator of nuclear factor kappa-B ligand (RANKL) but not sclerostin or gene polymorphisms is related to joint destruction in early rheumatoid arthritis

The aim of this study was to analyze relationships between receptor activator of nuclear factor kappa-B (RANKL), sclerostin and their gene polymorphisms with radiological progression in patients with early rheumatoid arthritis (RA). Patients with early RA (n = 407, symptomatic <1 year) (ARA criteria) examined radiologically at inclusion and after 24 months were consecutively included. Disease activity score and C-reactive protein were regularly recorded. Sclerostin, RANKL, and anti-CCP2 antibodies were analyzed in plasma at baseline using ELISAs. Data on gene polymorphism for sclerostin and RANKL were extracted from Immunochip analysis. Sex- and age-matched controls (n = 71) were identified from the Medical Biobank of Northern Sweden. The concentration of RANKL was significantly higher in patients compared with controls, median (IQR) 0.56 (0.9) nmol/L and 0.20 (0.25) nmol/L (p < 0.001), and in anti-CCP2-positive patients compared with sero-negative individuals. Sclerostin was significantly increased in female patients 0.59 (0.47–0.65) ng/mL compared with female controls 0.49 (0.4–0.65) ng/mL (p < 0.02). RANKL concentration was related to the Larsen score at baseline (p < 0.01), after 24 months (p < 0.001), and to radiological progression at 24 months (p < 0.001). Positivity of RANKL and anti-CCP2 yielded significant risk for progression with negativity for both as reference. No single nucleotide polymorphism encoding TNFSF11 or SOST was associated with increased concentrations of the factors. The concentration of RANKL was related to the Larsen score at baseline, at 24 months, and radiological progression at 24 months particularly in anti-CCP2-positive patients, while the concentration of sclerostin was unrelated to radiological findings.

Osteoprotegerin and osteoprotegerin/TRAIL ratio are associated with cardiovascular dysfunction and mortality among patients with renal failure

PURPOSE

The high prevalence of cardiovascular morbidity and mortality among patients with chronic kidney disease (CKD) is observed especially in those undergoing dialysis. Osteoprotegerin (OPG) and its ligands, receptor activator of nuclear factor kappa-B ligand (RANKL) and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) have been associated with cardiovascular complications. Our aim was to study their role as cardiovascular risk factors in stage 5 CKD patients.

PATIENTS AND METHODS

OPG, RANKL and TRAIL concentrations were measured in 69 hemodialyzed CKD patients and 35 healthy volunteers. In CKD patients, cardiovascular dysfunction was assessed with aortic pulse wave velocity (AoPWV), carotid artery intima-media thickness (CCA-IMT), coronary artery calcium score (CACS) and N-terminal pro-B-type natriuretic peptide (NT-proBNP) serum concentrations. Cardiovascular and overall mortality data were collected during a 7-years follow-up.

RESULTS

OPG plasma concentrations were higher in CKD patients comparing to controls. Total soluble RANKL was lower and OPG/RANKL ratio higher in patients. Soluble TRAIL concentrations did not differ between the groups and OPG/TRAIL ratio was higher in CKD patients. OPG and OPG/TRAIL positively predicted long-term mortality (all-cause and cardiovascular) in CKD patients. OPG positively correlated with AoPWV, CCA-IMT and NT-proBNP whereas OPG/TRAIL with AoPWV and NT-proBNP. Described relationships were independent of classical and non-classical cardiovascular risk factors, with exception of age.

CONCLUSIONS

Our study confirmed the role of OPG as a biomarker of cardiovascular dysfunction and a predictor of mortality in stage 5 CKD. OPG/TRAIL ratio can be proposed as a predictor of cardiovascular dysfunction and mortality.

Bone health nutraceuticals alter microarray mRNA gene expression: A randomized, parallel, open-label clinical study

BACKGROUND AND OBJECTIVE

Dietary intake of fruits and vegetables has been suggested to have a role in promoting bone health. More specifically, the polyphenols they contain have been linked to physiological effects related to bone mineral density and bone metabolism. In this research, we use standard microarray analyses of peripheral whole blood from post-menopausal women treated with two fixed combinations of plant extracts standardized to polyphenol content to identify differentially expressed genes relevant to bone health.

METHODS

In this 28-day open-label study, healthy post-menopausal women were randomized into three groups, each receiving one of three investigational fixed combinations of plant extracts: an anti-resorptive (AR) combination of pomegranate fruit (Punica granatum L.) and grape seed (Vitis vinifera L.) extracts; a bone formation (BF) combination of quercetin (Dimorphandra mollis Benth) and licorice (Glycyrrhiza glabra L.) extracts; and a fixed combination of all four plant extracts (AR plus BF). Standard microarray analysis was performed on peripheral whole blood samples taken before and after each treatment. Annotated genes were analyzed for their association to bone health by comparison to a gene library.

RESULTS

The AR combination down-regulated a number of genes involved in reduction of bone resorption including cathepsin G (CTSG) and tachykinin receptor 1 (TACR1). The AR combination also up-regulated genes associated with formation of extracellular matrix including heparan sulfate proteoglycan 2 (HSPG2) and hyaluronoglucosaminidase 1 (HYAL1). In contrast, treatment with the BF combination resulted in up-regulation of bone morphogenetic protein 2 (BMP-2) and COL1A1 (collagen type I α1) genes which are linked to bone and collagen formation while down-regulating genes linked to osteoclastogenesis. Treatment with a combination of all four plant extracts had a distinctly different effect on gene expression than the results of the AR and BF combinations individually. These results could be due to multiple feedback systems balancing activities of osteoblasts and osteoclasts.

CONCLUSION

In summary, this ex-vivo microarray study indicated that the pomegranate, grape seed, quercetin and licorice combinations of plant extracts modulated gene expression for both osteoclastic and osteogenic processes.

Influence of Palmatine on Bone Metabolism in Ovariectomized Mice and Cytokine Secretion of Osteoblasts

BACKGROUND/AIM

Receptor activator of nuclear factor-κB ligand (RANKL) and osteoprotegerin (OPG), regulate the cognate receptor RANK on osteoclast precursor cells. Herein we examined the inhibitory effects of palmatine on bone metabolism using ovariectomized (OVX) mice.

MATERIALS AND METHODS

The first experimentaI set was designed to histologically and biochemically examine mice randomly divided into four groups: sham-operated, OVX, and OVX-palmatine intake groups (1 mg/kg and 10 mg/kg). The second experimental set examined the influence of palmatine on osteoblast-like cells in vitro.

RESULTS

Palmatine caused significant suppression of osteoclast numbers in tissues. In palmatine-treated mice, RANKL and OPG expression decreased. In the culture supernatant of MC3T3-E1 cells, RANKL and OPG levels were significantly reduced by palmatine addition.

CONCLUSION

Palmatine may attenuate osteoclast differentiation through inhibition of RANKL and OPG expression by osteoblasts. Therefore, palmatine might be a candidate anti-resorptive agent for osteoporosis therapy.

Ginseng saponins and the treatment of osteoporosis: mini literature review

The ginseng plant (Panax ginseng Meyer) has a large number of active ingredients including steroidal saponins with a dammarane skeleton as well as protopanaxadiol and protopanaxatriol, commonly known as ginsenosides, which have antioxidant, anticancer, antidiabetic, anti-adipocyte, and sexual enhancing effects. Though several discoveries have demonstrated that ginseng saponins (ginsenosides) as the most important therapeutic agent for the treatment of osteoporosis, yet the molecular mechanism of its active metabolites is unknown. In this review, we summarize the evidence supporting the therapeutic properties of ginsenosides both in vivo and in vitro, with an emphasis on the different molecular agents comprising receptor activator of nuclear factor kappa-B ligand, receptor activator of nuclear factor kappa-B, and matrix metallopeptidase-9, as well as the bone morphogenetic protein-2 and Smad signaling pathways.

Uncoupling of osteoblast-osteoclast regulation in a chemical murine model of Gaucher disease

Gaucher disease (GD) is caused by mutations in the GBA gene that confer a deficient level of activity of glucocerebrosidase (GCase). This deficiency leads to accumulation of the glycolipid glucocerebroside in the lysosomes of cells of monocyte/macrophage system. Type I GD is the mildest form and is characterized by the absence of neuronopathic affection. Bone compromise in Gaucher disease patients is the most disabling aspect of the disease. However, pathophysiological aspects of skeletal alterations are still poorly understood. The homeostasis of bone tissue is maintained by the balanced processes of bone resorption by osteoclasts and formation by osteoblasts. We decided to test whether bone resorption and/or bone formation could be altered by the use of a chemical in vitro murine model of Gaucher disease. We used two sources of cells from monocyte/macrophages lineage isolated from normal mice, splenocytes (S) and peritoneal macrophages (PM), and were exposed to CBE, the inhibitor of GCase (S-CBE and PM-CBE, respectively). Addition of both conditioned media (CM) from S-CBE and PM-CBE induced the differentiation of osteoclasts precursors from bone marrow to mature and functional osteoclasts. TNF-α could be one of the factors responsible for this effect. On the other hand, addition of CM to an osteoblast cell culture resulted in a reduction in expression of alkaline phosphatase and mineralization process. In conclusion, these results suggest implication of changes in both bone formation and bone resorption and are consistent with the idea that both sides of the homeostatic balance are affected in GD.