LncRNA Linc-PINT inhibits miR-523-3p to hamper retinoblastoma progression by upregulating Dickkopf-1 (DKK1)

Emerging evidences indicated that long non-coding RNAs (LncRNAs) regulated the pathogenesis of retinoblastoma (RB). However, up until now, the role of LncRNA Linc-PINT in the regulation of RB progression is still largely unknown. The present study identified LncRNA Linc-PINT as a tumor suppressor to hinder RB development by regulating miR-523-3p/Dickkopf-1 (DKK1) axis. Mechanistically, Linc-PINT was low-expressed, while miR-523-3p was high-expressed in RB cells, compared to the normal retinal epithelial cells (ARPE-19). Further gain- and loss-function experiments verified that both upregulation of Linc-PINT and miR-523-3p downregulation slowed down cell growth, invasion and migration, and promoted cell apoptosis in RB cells, but Linc-PINT ablation and miR-523-3p overexpression promoted malignant phenotypes in RB cells. In addition, the dual-luciferase reporter gene system and RNA pull-down assay validated that Linc-PINT positively regulated DKK1 expressions by sponging miR-523-3p, and Linc-PINT inhibited RB progression by regulating miR-523-3p/DKK1 axis. Functionally, we found that both miR-523-3p overexpression and DKK1 silence abrogated the anti-cancer effects of overexpressed Linc-PINT on RB cells. Finally, Linc-PINT inhibited tumorigenicity of RB cells in xenograft mice models. In general, analysis of the data suggested that Linc-PINT inhibited miR-523-3p to upregulate DKK1, resulting in the inhibition of RB, and we demonstrated that Linc-PINT and miR-523-3p could be utilized as potential diagnostic and therapeutic biomarkers for RB in clinic.

Association between Serum Dickkopf-1 (DKK-1) Glycoprotein and Calcific Deposits on Cardiac Valves and Carotid Intimal-Medial Thickness in Hemodialysis Patients

BACKGROUND

Cardiac valve calcification (CVC) is common in hemodialysis (HD) patients, and associated with cardiovascular and all-cause mortality. Once believed to be a passive process, it is now understood that the Wnt signaling pathway has a major role. The aim of the current study was to assess the relationship between circulating DKK-1, a negative regulator of the Wnt signaling pathway, and CVC, as well as carotid intimal-medial thickness (CIMT) in HD patients.

METHODS

We enrolled 74 consecutive adults on maintenance HD. Echocardiographic calcification of the mitral valve (MV) and aortic valve (AV) were detected according to Wilkins score (range 0-4), and the study of Tenenbaum et al. [Int J Cardiol. 2004 Mar;94(1):7-13] (range 0-4), respectively. CVC severity was calculated by a supposed score (range 0-8) that represents the sum of calcification grade of MV and AV. CVC severity was classified into absent (CVC score = 0), mild (CVC score = 1-2), moderate (CVC score = 3-4), and severe (CVC score ≥5). Demographic and biochemical data were collected in addition to serum DKK-1 levels and CIMT.

RESULTS

CVC was present in 67 patients (91.0%). There was a highly significant negative correlation between serum DKK-1 level and CVC score (r = -0.492; p ≤ 0.001), as well as CIMT (r = -0.611; p ≤ 0.001). Age and CIMT were independent determinants of CVC.

CONCLUSIONS

CVC is almost present in all HD patients. DKK-1 seems to have a direct relation with CVC and CIMT in HD patients. Age is the strongest independent determinant of CVC.

Anti-DKK1 Enhances the Early Osteogenic Differentiation of Human Adipose-Derived Stem/Stromal Cells

Adipose-derived stem/stromal cells (ASCs) have been previously used for bone repair. However, significant cell heterogeneity exists within the ASC population, which has the potential to result in unreliable bone tissue formation and/or low efficacy. Although the use of cell sorting to lower cell heterogeneity is one method to improve bone formation, this is a technically sophisticated and costly process. In this study, we tried to find a simpler and more deployable solution-blocking antiosteogenic molecule Dickkopf-1 (DKK1) to improve osteogenic differentiation. Human adipose-derived stem cells were derived from = 5 samples of human lipoaspirate. In vitro, anti-DKK1 treatment, but not anti-sclerostin (SOST), promoted ASC osteogenic differentiation, assessed by alizarin red staining and real-time polymerase chain reaction (qPCR). Increased canonical Wnt signaling was confirmed after anti-DKK1 treatment. Expression levels of DKK1 peaked during early osteogenic differentiation (day 3). Concordantly, anti-DKK1 supplemented early (day 3 or before), but not later (day 7) during osteogenic differentiation positively regulated osteoblast formation. Finally, anti-DKK1 led to increased transcript abundance of the Wnt inhibitor SOST, potentially representing a compensatory cellular mechanism. In sum, DKK1 represents a targetable "molecular brake" on the osteogenic differentiation of human ASC. Moreover, release of this brake by neutralizing anti-DKK1 antibody treatment at least partially rescues the poor bone-forming efficacy of ASC.

The role of serum Dickkopf-1 in predicting 30-day death in severe traumatic brain injury

OBJECTIVE

Dickkopf-1 (DKK-1), an inhibitor of the canonical/-catenin cascade of the Wnt pathway, was upregulated in brain tissues of hemorrhagic stroke rats, and its rising circulating levels were associated with poor prognosis of acute ischemic stroke patients. We attempted to ascertain the relationship between serum DKK-1 levels and 30-day death after severe traumatic brain injury (sTBI).

MATERIALS AND METHODS

Serum DKK-1 levels were gauged in a total of 94 sTBI patients and 94 healthy controls. Trauma severity was assessed using Glasgow Coma Scale (GCS) and Rotterdam classification based on head computerized tomography scan. Prognostic variable was 30-day death.

RESULTS

Compared with controls, serum DKK-1 levels were substantially elevated in patients (median value, 3.7 versus 1.0 ng/ml). Area under receiver operating characteristic curve was 0.802 (95% confidence interval (CI), 0.708-0.877) for predicting 30-day death. Adjusted logistic regression showed that serum DKK-1 levels above 3.7 ng/ml remained as an independent marker of 30-day death (odds ratio, 8.573; 95% CI, 1.386-53.020) and overall survival (hazard ratio, 7.322; 95% CI, 1.320-40.622). An intimate correlation existed between DKK-1 levels and GCS scores (r = -.649) in addition to Rotterdam classification (r = .664).

CONCLUSIONS

High serum levels of DKK-1 are closely associated with increasing severity and rising short-term mortality of sTBI.

Study of Dickkopf-1 (DKK-1) in patients with chronic viral hepatitis C-related liver cirrhosis with and without hepatocellular carcinoma

Aim of the study

Dickkopf-1 (DKK-1) is a secreted protein which acts as an inhibitor of Wnt/β-catenin signaling. DKK-1 was found to be a helpful biomarker for many cancers including hepatocellular carcinoma (HCC). HCC is multifactorial in origin and its main etiology in Egypt is attributed to chronic hepatitis C virus (HCV) infection. Objectives: To assess the serum level and diagnostic performance of DKK-1 and α-fetoprotein (AFP) in Egyptian patients with chronic HCV-related liver cirrhosis with and without HCC.

Material and methods

80 subjects were divided into: a control group (group I, 20 healthy volunteers) and two patient groups: group II (HCV with liver cirrhosis, 30 patients), and group III, (HCV-related liver cirrhosis with HCC, 30 patients). Thorough physical examination, triphasic computed tomography, calculation of Child-Pugh score, laboratory investigations (complete blood picture, liver profile, hepatitis B surface antigen, anti-HCV antibodies, AFP (chemiluminometry) and DKK-1 (ELISA) were performed.

Results

There was a significant decrease in DKK-1 level in HCV patients with liver cirrhosis (group II) and HCV patients with HCC (group III) compared to the control group (group I) (p < 0.001). However, there was a significant increase in DKK-1 level in HCV patients with HCC (group III) compared to HCV patients with liver cirrhosis (group II) (p < 0.033). The ROC curve showed that DKK-1 has less sensitivity but higher specificity in HCV patients with HCC (group III) compared with HCV patients with liver cirrhosis (group II).

Conclusions

The combination of DKK-1 and AFP could further improve the diagnostic accuracy of HCV-related cirrhosis with or without HCC.

Circulating Myostatin Levels Decrease Transiently after Implantation of a Hip Hemi-Arthroplasty

INTRODUCTION

Muscle and bone metabolism are both important for the healing of fractures and the regeneration of injured muscle tissue. The aim of this investigation was to evaluate myostatin and other regulating factors in patients with hip fractures who underwent hemi-arthroplasty.

METHODS

Serum levels of myostatin (MSTN), follistatin (FSTN), dickkopf-1 (Dkk1), and periostin (PSTN) as well as markers of bone turnover were evaluated in patients with hip fractures before surgery and twice in the 2 weeks after surgery. These parameters were also evaluated in age- and gender-matched subjects without major musculoskeletal injury.

RESULTS

MSTN was transiently reduced; its opponent FSTN was transiently increased. Dkk1, the negative regulator of bone mass, and PSTN, a marker of subperiosteal bone formation, increased after surgery. With regard to markers of bone turnover, resorption was elevated during the entire period of observation whereas the early bone formation marker N-terminal propeptide of type I collagen was elevated 12 days after surgery.

CONCLUSIONS

Unexpectedly, MSTN, a negative regulator of muscle growth, was reduced after surgery compared with before surgery. As musculoskeletal markers are altered during bone healing, they do not reflect general bone metabolism after fracture or joint arthroplasty. This is important because many elderly patients receive treatment for osteoporosis.

Evolving functions of Dickkopf-1 in cancer and immunity

Dickkopf-1 (DKK-1) is a well-established inhibitor of canonical Wnt-signaling that critically participates in the regulation of bone formation and has been implicated in the development and progression of bone metastases. While the skeleton was originally considered the sole site of DKK-1 synthesis, it has now become clear that the molecule is also highly expressed in T-cells, platelets and multiple cancer cells. In the past years, several new functions of DKK-1 in angiogenesis, cancer cell biology, immune homeostasis and inflammation have been revealed. These novel insights have paved the way for clinical trials investigating the efficacy of anti-DKK-1 antibodies in a variety of different malignancies, most of which are currently still ongoing. In this review, we discuss the evolution and recent advances in DKK-1 research and highlight clinical implications of the available knowledge on the molecule, especially in cancer. Finally, we emphasize outstanding questions and provide an outlook on potential future studies that will aid in further improving our understanding of the pleiotropic roles of DKK-1 in health and disease.

Serum Sclerostin But Not DKK-1 Correlated with Central Arterial Stiffness in End Stage Renal Disease Patients

Sclerostin and dickkopf-1 (DKK1) played a role in the development of cardiovascular diseases and arterial stiffness in chronic kidney disease (CKD) patients but with controversial results of patients in end-stage renal disease (ESRD) including hemodialysis (HD) and peritoneal dialysis (PD). This study aimed to examine the association between the mode of dialysis or the values of sclerostin or DKK1 and carotid-femoral pulse wave velocity (cfPWV) in ESRD patients. There were 122 HD and 72 PD patients enrolled in this study. By a validated tonometry system, cfPWV was measured and then segregated patients into values of >10 m/s as the high central arterial stiffness (AS) group and values ≤ 10 m/s as the control group. Serum levels of sclerostin and DKK1 were measured using a commercial enzyme-linked immunosorbent assay kit. Possible risk factors for the development of AS were analyzed by logistic regression analysis. There were 21 (29.2%) of PD and 53 (43.4%) of HD in the high AS group. Compared to patients in the control group, those in the high AS group were older, had more comorbidities, had higher systolic blood pressure, and had higher serum levels of fasting glucose, C-reactive protein, and sclerostin. Levels of sclerostin (adjusted OR 1.012, 95% CI. 1.006–1.017, p = 0.0001) was found to be an independent predictor of high AS in ESRD patients by multivariate logistic regression analysis. Furthermore, receiver operating characteristic curve analysis showed the optimal cut-off values of sclerostin for predicting AS was 208.64 pmol/L (Area under the curve 0.673, 95% CI: 0.603–0.739, p < 0.001). This study showed that serum levels of sclerostin, but not DKK1 or mode of dialysis, to be a predictor for high central AS in ESRD patients.

Angiotensin II inhibits osteogenic differentiation of isolated synoviocytes by increasing DKK-1 expression

The renin-angiotensin system contributes to the pathogenesis of rheumatoid arthritis, but that the mechanism is unclear. This study aims to investigate the effect of angiotensin II (Ang II) on osteogenic differentiation of synoviocytes and the underlying mechanism. Ang II was showed to inhibite osteogenic differentiation of synoviocytes, which was mitigated by a Dickkopf-1 (DKK-1) inhibitor. DKK-1 was upregulated by Ang II, which was weakened by the Ang II type 1 receptor (AT1R) blocker, reactive oxygen species (ROS) scavenger, and p38 inhibitor. Ang II increased the levels of AT1R, ROS, and NADPH oxidase (NOX), and the upregulations were mitigated by the AT1R blocker or NOX inhibitor. Furthermore, Ang II activated the p38 pathway, which was blocked by the AT1R blocker, ROS scavenger, or siRNA-MKK3. In brief, these results indicate that Ang II upregulates NOX expression and ROS production via AT1R, activates the MKK3/p38 signaling, and in turn upregulates DKK-1 expression, participating in the inhibition of osteogenic differentiation of synoviocytes.

Dickkopf-1 Overexpression in vitro Nominates Candidate Blood Biomarkers Relating to Alzheimer's Disease Pathology

BACKGROUND

Previous studies suggest that Dickkopf-1 (DKK1), an inhibitor of Wnt signaling, plays a role in amyloid-induced toxicity and hence Alzheimer's disease (AD). However, the effect of DKK1 expression on protein expression, and whether such proteins are altered in disease, is unknown.

OBJECTIVE

We aim to test whether DKK1 induced protein signature obtained in vitro were associated with markers of AD pathology as used in the amyloid/tau/neurodegeneration (ATN) framework as well as with clinical outcomes.

METHODS

We first overexpressed DKK1 in HEK293A cells and quantified 1,128 proteins in cell lysates using aptamer capture arrays (SomaScan) to obtain a protein signature induced by DKK1. We then used the same assay to measure the DKK1-signature proteins in human plasma in two large cohorts, EMIF (n = 785) and ANM (n = 677).

RESULTS

We identified a 100-protein signature induced by DKK1 in vitro. Subsets of proteins, along with age and apolipoprotein E ɛ4 genotype distinguished amyloid pathology (A + T-N-, A+T+N-, A+T-N+, and A+T+N+) from no AD pathology (A-T-N-) with an area under the curve of 0.72, 0.81, 0.88, and 0.85, respectively. Furthermore, we found that some signature proteins (e.g., Complement C3 and albumin) were associated with cognitive score and AD diagnosis in both cohorts.

CONCLUSIONS

Our results add further evidence for a role of DKK regulation of Wnt signaling in AD and suggest that DKK1 induced signature proteins obtained in vitro could reflect theATNframework as well as predict disease severity and progression in vivo.

Improved carotid intima-media thickness-induced high-intensity interval training associated with decreased serum levels of Dkk-1 and sclerostin in type 2 diabetes

AIMS

Carotid intima-media thickness (cIMT) is a validated surrogate marker of atherosclerosis. Dickkopf-1 (Dkk-1) and sclerostin modulate wingless signaling, which is involved in atherosclerosis. The purpose of this study was to investigate whether 12 weeks of high-intensity interval training (HIIT) would improve cIMT and serum Dkk-1 and sclerostin levels in patients with type 2 diabetes.

METHODS

Seventy-four sedentary patients with type 2 diabetes were randomly divided into HIIT and control groups. The HIIT group intervention was 6 intervals (4 min) at 85%-90% HR_max separated by 3 min at 45%-50% HR_max in 3 sessions/week for 12 weeks. Before and after the intervention, cIMT, artery diameter and wall/lm ratio were recorded with high-resolution ultrasound. Serum sclerostin and Dkk-1 were measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

cIMT decreased significantly in the HIIT group (0.83 ± 0.17 baseline, 0.71 ± 0.14 follow-up) compared to the control group (0.84 ± 0.20 baseline, 0.85 ± 0.19 follow-up) (P < .05). Dkk-1 and sclerostin decreased significantly after 12 weeks of HIIT (P < .01). In addition, VO_2peak was increased in the HIIT group than the control group (by 6.2 mL/kg/min) (P < .05). There was a positive correlation between percent changes in cIMT and percent changes in Dkk-1 and sclerostin (both P < .01). Additionally, there were a negative correlation between percent changes VO2peak and cIMT (r = - 0.740, P = .003), Dkk-1 (r = - 0.844, P < .001) and sclerostin (r = - 0.575, P = .001) in HIIT group.

CONCLUSION

Our results indicate that HIIT decreases cIMT, serum levels of Dkk-1 and sclerostin and improves VO_2peak in patients with type 2 diabetes.

Dkk1 Controls Cell-Cell Interaction through Regulation of Non-nuclear β-Catenin Pools

Dickkopf-1 (Dkk1) is a secreted Wnt antagonist with a well-established role in head induction during development. Numerous studies have emerged implicating Dkk1 in various malignancies and neurodegenerative diseases through an unknown mechanism. Using zebrafish gastrulation as a model for collective cell migration, we unveil such a mechanism, identifying a role for Dkk1 in control of cell connectivity and polarity in vivo, independent of its known function. We find that Dkk1 localizes to adhesion complexes at the plasma membrane and regions of concentrated actomyosin, suggesting a direct involvement in regulation of local cell adhesion. Our results show that Dkk1 represses cell polarization and integrity of cell-cell adhesion, independently of its impact on β-catenin protein degradation. Concurrently, Dkk1 prevents nuclear localization of β-catenin by restricting its distribution to a discrete submembrane pool. We propose that redistribution of cytosolic β-catenin by Dkk1 concomitantly drives repression of cell adhesion and inhibits β-catenin-dependent transcriptional output.

Elevations in Serum Dickkopf-1 and Disease Progression in Community-Dwelling Older Adults With Mild Cognitive Impairment and Mild-to-Moderate Alzheimer's Disease

Background: Disruption of Wnt signaling has been implicated in dysfunctional synaptic plasticity, the degree of which correlates with Alzheimer's disease severity. We sought to examine whether serum levels of Dickkopf-1 (Dkk-1), a Wnt antagonist, are associated with global disease progression in older adults with mild cognitive impairment (MCI) and mild-to-moderate AD. Methods: We prospectively followed 88 older adults with MCI and mild-to-moderate AD attending a Memory Clinic. Cognitive performance, functional performance and neuropsychological symptoms were assessed at baseline and after 1 year. We reviewed neuroimaging for white matter changes and medial temporal atrophy, and performed ApoE genotyping at baseline. Serum Dkk-1 was assayed at baseline and 1 year, along with blood biomarkers of inflammation and endocrine dysfunction. We defined global disease progression ("progressors") as an increase in Clinical Dementia Rating Sum-of-Boxes (CDR-SB) score by >2 points at 1 year. Results: Fifteen (17.0%) participants had global disease progression. At baseline, there was no difference in cognitive performance and neuropsychiatric symptoms between groups, although progressors were more impaired in instrumental activities of daily living (p = 0.008). Progressors had significantly greater deterioration in cognitive performance (p = 0.002), with significantly worse functional performance and more severe neuropsychiatric symptoms (p = 0.042) at follow-up. Serum inflammatory and endocrine biomarkers at baseline and 1 year were similar between progressors and non-progressors. Serum Dkk-1 had increased significantly from baseline amongst progressors, while non-progressors exhibited decremental Dkk-1 over time (Dkk-1_change: 354.304 ± 670.467 vs. -173.582 ± 535.676 ng/ml, p = 0.001). Adjusting for age, gender and baseline cognitive performance, incremental Dkk-1 independently predicted global cognitive decline (p = 0.012). Conclusion: Our results suggest progressively dysfunctional Wnt signaling through Dkk-1 antagonism contributes to disease progression amongst older adults with MCI and mild-moderate AD.

Circulating CD40 ligand, Dickkopf-1 and P-selectin in HIV-infected patients

OBJECTIVES

The aim of this study was to evaluate the circulating levels of CD40 ligand (CD40 L), Dickkopf-1 (DKK-1) and P-selectin, their relationships and their contributions to cardiovascular risk in subjects with HIV infection.

METHODS

The study population included 80 HIV-infected patients, 14 (17.5%) of whom had diabetes mellitus (DM) and 32 (40.0%) of whom had arterial hypertension (AH). The HIV-infected patients were compared with a control group with similar demographic and clinical features. CD40L, DKK-1 and P-selectin levels were measured using an enzyme-linked immunosorbent assay.

RESULTS

The HIV-infected patients showed higher levels of all the cardiovascular disease (CVD) markers. Both serum CD40L and DKK-1 were significantly higher in HIV-infected patients than in the HIV-negative controls (P < 0.001), while soluble P-selectin showed no significant between-group difference (P = 0.133), reflecting the role of HIV infection in CVD. In the HIV-infected group, patients with DM showed lower levels of CD40L and DKK-1 in comparison with the nondiabetic patients and patients with AH (P < 0.05, with Bonferroni correction). In contrast, patients with AH showed higher levels of CD40L and DKK-1 in comparison to patients without DM or AH (P < 0.05, with Bonferroni correction). Patients with AH showed higher levels of CD40L and DKK-1 than patients with DM (P < 0.05, with Bonferroni correction).

CONCLUSIONS

In this study, we found that HIV-infected patients displayed significantly higher circulating levels of both CD40L and DKK-1, which were linearly and directly correlated, when compared to HIV-negative patients. The presence of diabetes was associated with lower levels of both CD40L and DKK-1, whereas the presence of hypertension was associated with higher levels of CD40L.

Minocycline Preserves the Integrity and Permeability of BBB by Altering the Activity of DKK1-Wnt Signaling in ICH Model

Disruption of the blood-brain barrier (BBB) and subsequent neurological deficits are the most severe consequence of intracerebral hemorrhage (ICH). Minocycline has been wildly used clinically as a neurological protective agent in clinical practice. However, the underlying mechanisms by which minocycline functions remain unclear. Therefore, we assessed the influence of minocycline on BBB structure, neurological function, and inflammatory responses in a collagenase-induced ICH model, and elucidated underlying molecular mechanisms as well. Following a single injection of collagenase VII-S into the basal ganglia, BBB integrity was assessed by Evans blue extravasation while neurological function was assessed using an established neurologic function scoring system. Minocycline treatment significantly alleviated the severity of BBB disruption, brain edema, and neurological deficits in ICH model. Moreover, minocycline decreased the production of inflammatory mediators including TNF, IL-6, and MMP-9, by microglia. Minocycline treatment decreased DKK1 expression but increased Wnt1, β-catenin and Occludin, a phenomenon mimicked by DKK1 silencing. These data suggest that minocycline improves the consequences of ICH by preserving BBB integrity and attenuating neurologic deficits in a DKK1-related manner that involves enhancement of the Wnt1-β-catenin activity.

Dickkopf-1 and Amphiregulin as Novel Biomarkers and Potential Therapeutic Targets in Hepatocellular Carcinoma

Background: Hepatocellular carcinoma (HCC) is a highly fatal tumor which represents a major health problem worldwide. Due to asymptomatic nature of HCC, most patients present with the progressive stage of disease, so, unfortunately, there are no effective therapies. Existing techniques for HCC surveillance and diagnosis lack the required accuracy. Therefore, searching for new diagnostic and/or therapeutic tools could improve patient survival. This study aimed to estimate the diagnostic role of Dickkopf-1 (DKK1) and amphiregulin (AREG) and to find out their correlation with different clinicopathological parameters in HCC patients. Materials and Methods: Serum levels of DKK1 and AREG in 55 HCC patients, 20 cirrhotic patients, and 15 healthy subjects as control group were measured using the ELISA technique. Results: Both of DKK1 and AREG showed a significant increase in the HCC group compared to cirrhotic and healthy groups. DKK1 at a cutoff point of 8.92 ng/ml showed that the area under the curve (AUC) was 0.826 with 87.3% sensitivity and 82.9% specificity. DKK1 showed a significant correlation with tumor size, liver dysfunction, and poor performance status in HCC patients. AREG at a cutoff point of 8.74 pg/ml showed a sensitivity of 74.5% but low specificity (47.1%). AREG showed a significant correlation with portal vein thrombosis and tumor metastasis in HCC patients. Conclusion: Serum DKK1 could be a diagnostic biomarker for HCC. Both of DKK1 and AREG may play significant roles in tumor progression and may offer promising therapeutic targets in HCC patients.

Bone Matrix Levels of Dickkopf and Sclerostin are Positively Correlated with Bone Mass and Strength in Postmenopausal Osteoporosis

Wnt signaling plays a pivotal role in maintaining bone mass. Secreted pathway modulators such as sclerostin (SOST) and Dickkopfs (DKKs) may influence bone mass inhibiting the canonical Wnt pathway. We evaluated whether bone protein content of secreted Wnt antagonists is related to age, bone mass, and strength in postmenopausal osteoporosis. We measured cortical and trabecular bone contents of SOST and Dickkopf-1 (DKK1) in combined extracts obtained after ethylenediaminetetraacetic acid and guanidine hydrochloride extraction in 56 postmenopausal women aged 47–74 (mean, 63) yr with a previous distal forearm fracture and a hip or spine Z-score less than 0. Our findings were (i) SOST and DKK1 protein levels were higher in trabecular bone, (ii) cortical and trabecular DKK1 and trabecular SOST correlated positively with bone matrix levels of osteocalcin (r between 0.28 and 0.45, p < 0.05), (iii) cortical DKK1 correlated with lumbar spine bone mineral density (BMD) (r = 0.32, p < 0.05) and femoral neck BMD (r = 0.41, p < 0.01), and (iv) cortical DKK1 and SOST correlated with apparent bone volumetric density and compressive strength (r between 0.34 and 0.51, p < 0.01). In conclusion, cortical bone matrix levels of DKK1 and SOST were positively correlated with bone mass and bone strength in postmenopausal osteoporotic women.

In Silico Structural Prediction and Production of a Chimeric Recombinant Dickkopf-1 (DKK-1) Antigen

Dickkopf (DKK) family of proteins are known as antagonists for the Wnt-β-catenin signaling pathway. It is suggested that the Dickkopf-1 (DKK-1) has a role in several diseases such as hepatocellular carcinomas, hepatoblastomas, Wilms' tumors, lung cancer and Myeloma bone disease. The aim of the present study was to produce a chimeric-recombinant DKK-1 protein in order to induce immune response against the antigen. The recombinant Dickkopf-1 (rDKK-1) protein was designed using bioinformatics analysis. The standard methods were used for cloning, expression and purification. The structure of recombinant protein was analyzed by spectroscopy methods. Enzyme-linked immunosorbent assay (ELISA) and Western blotting were performed to confirm the recombinant protein using a commercial anti-DKK-1 (whole protein) polyclonal antibody. The immunogenicity of the recombinant DKK-1 was assessed by immunizing, intraperitoneally, BALB/C mice four times with the 31-kDa and 45-kDa purified rDKK-1 cloned in pET28a and pET32a vectors respectively. The antibody titer was measured in due course of time. Stronger immunogenic parts of the protein were selected based on in-silico predictions and recombinant protein was successfully designed. The chimeric gene was sub-cloned, expressed, purified and refolded. The purified protein was confirmed by Western blotting and ELISA. The three dimensional structural was confirmed by CD spectrum and predicted structures by bioinformatics tools, revealed the stability of helix structures. rDKK-1 protein was capable of inducing immune response with high titer antibody and  excessive humoral immune response. No significant difference was observed between immunization by 31-kDa and 45-kDa antigen.

Correlation between sclerostin and Dickkopf-1 with aortic arterial stiffness in patients with type 2 diabetes: A prospective, cross-sectional study

BACKGROUND

Sclerostin and Dickkopf-1 are extracellular inhibitors of the canonical Wnt/β-catenin signalling pathway, which is implicated in the development of arterial stiffness. However, the correlation between aortic stiffness and sclerostin or Dickkopf-1 levels in patients with type 2 diabetes mellitus is unknown.

METHODS

Fasting blood samples were collected from 125 patients with type 2 diabetes mellitus. Aortic stiffness was measured by carotid-femoral pulse wave velocity, and high aortic stiffness was defined by a carotid-femoral pulse wave velocity of >10 m/s. The serum sclerostin and Dickkopf-1 concentrations were determined using commercially available enzyme-linked immunosorbent assays.

RESULTS

In total, 46 patients with type 2 diabetes mellitus (36.8%) had high levels of aortic stiffness. Compared to the control group without aortic stiffness, this group was significantly older, had higher systolic and diastolic blood pressures, had higher blood urea nitrogen, creatinine, urinary albumin-to-creatinine ratio and serum sclerostin levels, and had significantly lower high-density lipoprotein cholesterol levels and estimated glomerular filtration rates. After adjusting for confounders, serum sclerostin [odds ratio = 1.005 (1.002-1.007), p = 0.002] levels remained an independent predictor of aortic stiffness. Multivariate analysis showed that the serum sclerostin level ( β = 0.374, adjusted R² change = 0.221, p < 0.001) was positively associated with carotid-femoral pulse wave velocity.

CONCLUSION

Serum levels of sclerostin, but not Dickkopf-1, are positively correlated with carotid-femoral pulse wave velocity and independently predict aortic stiffness in patients with type 2 diabetes mellitus.

The Role of the Wnt Signaling Pathway in Upper Jaw Development of Chick Embryo

Cleft lip with or without cleft palate (CLP) usually results from a failure of the medial nasal prominences to fuse with the lateral and maxillary prominences. This failure inhibits facial morphogenesis regulated by several major morphogenetic signaling pathways. We hypothesized that CLP results from the failure of the Wnt signaling pathway. To examine whether Wnt signaling can influences upper jaw development, we applied beads soaked with Dickkopf-1 (Dkk-1), Alsterpaullone (AL) or Wnt3a to the right side of the maxillary prominence of the chick embryo. The embryo showed a defect of the maxilla on the treated side, and skeletal staining revealed hypoplasia of the premaxilla and palatine bone as a result of Dkk-1-soaked bead implantation. 5-bromo-2'-deoxyuridine (BrdU)-positive cell numbers in the treated maxillary prominence were significantly lower at both 24 and 48 hr after implantation. Down-regulation of the expression of Bmp4, Tbx22, Sox9, and Barx1 was confirmed in the maxillary prominence treated with Dkk-1, which indicated that the deformity of the maxillary bone was controlled by gene targets of the Wnt signaling pathway. Expression of N-cadherin was seen immunohistochemically in the maxillary prominences of embryos at 6 hr and increased at 24 hr after AL treatment. Wnt signaling enhanced by AL or Wnt3a up-regulated the expression levels of Msx1, Bmp4, Tbx22, Sox9, and Barx1. Our data suggest that the Wnt signaling pathway regulates maxillary morphogenesis and growth through Bmp4, Tbx22, Sox9, and Barx1. Wnt signaling might regulate N-cadherin expression via Msx1, resulting in cell aggregation for osteochondrogenesis.

Dickkopf-1 (DKK1) promotes tumor growth via Akt-phosphorylation and independently of Wnt-axis in Barrett's associated esophageal adenocarcinoma

Esophageal adenocarcinoma (EAC) is still associated with poor prognosis, despite modern multi-modal therapies. New molecular markers, which control cell cycle and promote lymph node metastases or tumor growth, may introduce novel target therapies. Dickkopf-1 (DKK1) is a secreted glycoprotein that blocks the oncogenic Wnt/β-catenin signaling and its aberrant expression has been observed in many malignancies, including EAC. In this study, we investigated the biological role of DKK1 in EAC. Analysis of DKK1 and active β-catenin expression in human esophageal tissues confirmed a simultaneous DKK1-overexpression together with aberrant activation of β-catenin signaling in EAC in comparison with Barrett's and healthy mucosa. To elucidate the molecular role of DKK1, the OE33 adenocarcinoma cells, which were found to overexpress DKK1, were subjected to functional and molecular assays following siRNA-mediated DKK1-knockdown. At the functional level, OE33 cell viability, proliferation, migration and invasion were significantly attenuated by the absence of DKK1. At the molecular level, neither DKK1-knockdown nor application of exogenous recombinant DKK1 were found to alter the baseline β-catenin signaling in OE33 cells. However, DKK1-knockdown significantly abrogated downstream Akt-phosphorylation. On the other hand, the Wnt-agonist, Wnt3a, restored the Akt-phorphorylation in the absence of DKK1, without, however, being able to further stimulate β-catenin transcription. These findings suggest that the β-catenin transcriptional activity in EAC is independent of Wnt3a/DKK1 site-of-action and define an oncogenic function for DKK1 in this type of malignancy via distinct activation of Akt-mediated intracellular pathways and independently of Wnt-axis inhibition. Taken together, DKK1 may present a novel therapeutic target in EAC.

Mechanisms Underlying Normal Fracture Healing and Risk Factors for Delayed Healing

PURPOSE OF REVIEW

Substantial advances have been made in understanding the biological basis of fracture healing. Yet, it is unclear whether the presence of osteoporosis or prior or current osteoporosis therapy influences the healing process or is associated with impaired healing. This review discusses the normal process of fracture healing and the role of osteoporosis and patient-specific factors in relation to fracture repair.

RECENT FINDINGS

The definitive association of osteoporosis to impaired fracture healing remains inconclusive because of limited evidence addressing this point. eStudies testing anabolic agents in preclinical models of ovariectomized animals with induced fractures have produced mostly positive findings showing enhanced fracture repair. Prospective human clinical trials, although few in number and limited in design and to testing only one anabolic agent, have similarly yielded modestly favorable results. Interest is high for exploring currently available osteoporosis therapies for efficacy in fracture repair. Definitive data supporting their efficacy are essential in achieving approval for this indication.

The role of sclerostin and dickkopf-1 in oral tissues - A review from the perspective of the dental disciplines

Wnt signaling is of high relevance in the development, homeostasis, and regeneration of oral tissues. Therefore, Wnt signaling is considered to be a potential target for therapeutic strategies. The action of Wnt is tightly controlled by the inhibitors sclerostin (SOST) and Dickkopf (DKK)-1. Given the impact of SOST and DKK-1 in hard tissue formation, related diseases and healing, it is of high relevance to understand their role in oral tissues. The clinical relevance of this knowledge is further underlined by systemic and local approaches which are currently in development for treating a variety of diseases such as osteoporosis and inflammatory hard tissue resorption. In this narrative review, we summarize the current knowledge and understanding on the Wnt signaling inhibitors SOST and DKK-1, and their role in physiology, pathology, and regeneration in oral tissues. We present this role from the perspective of the different specialties in dentistry, including endodontics, orthodontics, periodontics, and oral surgery.

The serum sclerostin level is positively associated with the aortic augmentation index in patients on peritoneal dialysis

OBJECTIVE

Sclerostin is a canonical Wingless (Wnt)/β-catenin signaling pathway inhibitor and had been associated with high arterial stiffness in patients with chronic kidney disease. The aortic augmentation index (AIx), a noninvasive method of assessing central hemodynamics/wave reflections, has been widely used as a clinical index of arterial stiffness. The aim of this study was to evaluate the relationship between fasting serum sclerostin levels and AIx values in peritoneal dialysis (PD) patients.

MATERIALS AND METHODS

Fasting blood samples were obtained from 75 PD patients. The aortic AIx value was measured using a validated tonometry system (SphygmoCor, AtCor Medical, Sydney, New South Wales, Australia). Serum sclerostin and dickkopf-1 (DKK1) levels were quantified using commercial enzyme-linked immunosorbent assay kits.

RESULTS

Women PD patients had higher aortic AIx values than men (P = 0.039), while lower aortic AIx values were found in PD patients who used statins (P = 0.004). Univariate linear analysis of the aortic AIx values in PD patients showed that systolic blood pressure (P = 0.001), diastolic blood pressure (P = 0.018), and serum sclerostin levels (P = 0.001) were positively correlated, while height (P = 0.018), body weight (P = 0.001), body mass index (P = 0.043), and weekly total creatinine clearance (P = 0.015) were negatively correlated with aortic AIx values in PD patients. Multivariate linear regression analysis of the factors significantly associated with the aortic AIx values showed that serum sclerostin levels (adjusted R ² = 0.057, P = 0.011) and systolic blood pressure (adjusted R ² = 0.125, P = 0.004) were positively associated, while body weight (adjusted R ² = 0.113, P = 0.002) was inversely associated with aortic AIx values in PD patients.

CONCLUSION

In this study, the serum sclerostin level, but not DKK1, was positively associated with aortic AIx values in PD patients.

Serum levels of sclerostin as a potential biomarker in central arterial stiffness among hypertensive patients

BACKGROUND

Sclerostin is known to be a canonical Wnt/β-catenin signaling pathway inhibitor, while the Wnt/β-catenin signaling pathway is proposed to be involved in the development of arterial stiffness. This study aims to investigate the relationship between serum sclerostin levels and carotid-femoral pulse wave velocity (cfPWV) among hypertensive patients.

METHODS

Fasting blood samples were obtained from 105 hypertensive patients. Patients with cfPWV values of > 10 m/s were classified in the high arterial stiffness group, whereas those with cfPWV values of ≤10 m/s were assigned to the low arterial stiffness group. Serum sclerostin and Dickkopf-1 (DKK1) levels were quantified using commercially available enzyme-linked immunosorbent assays.

RESULTS

Thirty-six hypertensive patients (34.3%) who belonged to the high arterial stiffness group were generally older (p < 0.001), presented with lower estimated glomerular filtration rates (eGFR, p = 0.014), higher incidence of diabetes mellitus (p = 0.030), average systolic blood pressures (SBP, p = 0.013), pulse pressure (p = 0.026), serum creatinine levels (p = 0.013), intact parathyroid hormone levels (iPTH, p = 0.003), and sclerostin levels (p < 0.001) than their counterparts in the low arterial stiffness group. A multivariable logistic regression analysis identified sclerostin as an independent predictor of arterial stiffness in hypertensive patients (odds ratio, 1.042; 95% confidence interval (CI), 1.017-1.068; p = 0.001). Multivariable forward stepwise linear regression analysis also showed that serum sclerostin level (β = 0.255, adjusted R2 change: 0.146, p = 0.003) was positively associated with cfPWV values in patients with hypertension.

CONCLUSIONS

In this study, serum sclerostin level, but not DKK1, is found to be positively correlated with cfPWV values and is identified as an independent predictor of arterial stiffness in hypertensive patients after adjusting for significant confounders.