Effect of chronic uremia on the transcriptional profile of the calcified aorta analyzed by RNA sequencing

Frontiers in Bone Metabolism and Disorder in Chronic Kidney Disease

Chronic Kidney Disease (CKD) is a progressive condition that affects 10-15% of the adult population, a prevalence expected to increase worldwide [...].

Updates in the chronic kidney disease-mineral bone disorder show the role of osteocytic proteins, a potential mechanism of the bone-Vascular paradox, a therapeutic target, and a biomarker

The chronic kidney disease-mineral bone disorder (CKD-MBD) is a complex multi-component syndrome occurring during kidney disease and its progression. Here, we update progress in the components of the syndrome, and synthesize recent investigations, which suggest a potential mechanism of the bone-vascular paradox. The discovery that calcified arteries in chronic kidney disease inhibit bone remodeling lead to the identification of factors produced by the vasculature that inhibit the skeleton, thus providing a potential explanation for the bone-vascular paradox. Among the factors produced by calcifying arteries, sclerostin secretion is especially enlightening. Sclerostin is a potent inhibitor of bone remodeling and an osteocyte specific protein. Its production by the vasculature in chronic kidney disease identifies the key role of vascular cell osteoblastic/osteocytic transdifferentiation in vascular calcification and renal osteodystrophy. Subsequent studies showing that inhibition of sclerostin activity by a monoclonal antibody improved bone remodeling as expected, but stimulated vascular calcification, demonstrate that vascular sclerostin functions to brake the Wnt stimulation of the calcification milieu. Thus, the target of therapy in the chronic kidney disease-mineral bone disorder is not inhibition of sclerostin function, which would intensify vascular calcification. Rather, decreasing sclerostin production by decreasing the vascular osteoblastic/osteocytic transdifferentiation is the goal. This might decrease vascular calcification, decrease vascular stiffness, decrease cardiac hypertrophy, decrease sclerostin production, reduce serum sclerostin and improve skeletal remodeling. Thus, the therapeutic target of the chronic kidney disease-mineral bone disorder may be vascular osteoblastic transdifferentiation, and sclerostin levels may be a useful biomarker for the diagnosis of the chronic kidney disease-mineral bone disorder and the progress of its therapy.

Klotho's impact on diabetic nephropathy and its emerging connection to diabetic retinopathy

Diabetic nephropathy (DN) is the leading cause of end-stage renal disease worldwide and is a significant burden on healthcare systems. α-klotho (klotho) is a protein known for its anti-aging properties and has been shown to delay the onset of age-related diseases. Soluble klotho is produced by cleavage of the full-length transmembrane protein by a disintegrin and metalloproteases, and it exerts various physiological effects by circulating throughout the body. In type 2 diabetes and its complications DN, a significant decrease in klotho expression has been observed. This reduction in klotho levels may indicate the progression of DN and suggest that klotho may be involved in multiple pathological mechanisms that contribute to the onset and development of DN. This article examines the potential of soluble klotho as a therapeutic agent for DN, with a focus on its ability to impact multiple pathways. These pathways include anti-inflammatory and oxidative stress, anti-fibrotic, endothelial protection, prevention of vascular calcification, regulation of metabolism, maintenance of calcium and phosphate homeostasis, and regulation of cell fate through modulation of autophagy, apoptosis, and pyroptosis pathways. Diabetic retinopathy shares similar pathological mechanisms with DN, and targeting klotho may offer new insights into the prevention and treatment of both conditions. Finally, this review assesses the potential of various drugs used in clinical practice to modulate klotho levels through different mechanisms and their potential to improve DN by impacting klotho levels.

Significant associations between bone mineral density and vascular calcification in patients with different stages of chronic kidney disease

Introduction

Chronic kidney disease—mineral and bone disorders (CKD-MBD) is characterised by generalised vascular calcification (VC) and impaired bone health. We aimed to investigate the relationship between VC and bone mineral density (BMD) in CKD patients.

Methods

We performed a cross-sectional study of patients with different stages of CKD. For assessment of VC of abdominal aorta lateral lumbar X-rays (Kauppila score), the ankle-brachial index (ABI) and echocardiography were used. Total body densitometry provided BMD.

Results

Ninety patients (41% male, median age 64 years (range 29–87)) were included, of whom 41.1% had a Kauppila score > 1. Evidence of peripheral VC as measured by ABI was detected in 23.3% of cases. Lesions of the heart valves were found in 46.7% of patients. There was a significant association between high ABI and lesions of the heart valves. In the multivariate regression model to analyse the independent determinants of abdominal aorta calcification (AAC) and ABI, the BMD of the femoral neck was identified as significant for both (p = 0.001, p = 0.001). The total spine BMD was found to be significant for AAC (p = 0.001), and the BMD of spine L1-L4 and the ribs were found to be significant for ABI (p = 0.01, p = 0.002 respectively). In factorial regression analysis, where BMD was independent determinant, valvular calcification was significant for BMD of femur, femoral neck and total BMD. Age and tALP were inversely correlated with the BMD of femur and femoral neck.

Conclusions

Our work highlighted clinically important relationships between VC and bone mineral density (BMD) in CKD patients. We detected inverse relationships between AAC, high ABI and BMD. Secondly, BMD at certain bone sites (femur, femoral neck) and total BMD were associated with important lesions of heart valves. Thirdly, a significant association between a high ABI and lesions of the heart valves. We believe that the results of our study will help in the planning of future research and in current clinical practice for the early diagnosis, further monitoring and management of CKD-MBD. Additionally, these results may have treatment implications on use of different CKD-MBD medications.

Distinct role of mitochondrial function and protein kinase C in intimal and medial calcification in vitro

Introduction

Vascular calcification (VC) is a major risk factor for cardiovascular morbidity and mortality. Depending on the location of mineral deposition within the arterial wall, VC is classified as intimal and medial calcification. Using in vitro mineralization assays, we developed protocols triggering both types of calcification in vascular smooth muscle cells (SMCs) following diverging molecular pathways.

Materials and methods and results

Human coronary artery SMCs were cultured in osteogenic medium (OM) or high calcium phosphate medium (CaP) to induce a mineralized extracellular matrix. OM induces osteoblast-like differentiation of SMCs–a key process in intimal calcification during atherosclerotic plaque remodeling. CaP mimics hyperphosphatemia, associated with chronic kidney disease–a risk factor for medial calcification. Transcriptomic analysis revealed distinct gene expression profiles of OM and CaP-calcifying SMCs. OM and CaP-treated SMCs shared 107 differentially regulated genes related to SMC contraction and metabolism. Real-time extracellular efflux analysis demonstrated decreased mitochondrial respiration and glycolysis in CaP-treated SMCs compared to increased mitochondrial respiration without altered glycolysis in OM-treated SMCs. Subsequent kinome and in silico drug repurposing analysis (Connectivity Map) suggested a distinct role of protein kinase C (PKC). In vitro validation experiments demonstrated that the PKC activators prostratin and ingenol reduced calcification triggered by OM and promoted calcification triggered by CaP.

Conclusion

Our direct comparison results of two in vitro calcification models strengthen previous observations of distinct intracellular mechanisms that trigger OM and CaP-induced SMC calcification in vitro. We found a differential role of PKC in OM and CaP-calcified SMCs providing new potential cellular and molecular targets for pharmacological intervention in VC. Our data suggest that the field should limit the generalization of results found in in vitro studies using different calcification protocols.

Identification of potential biomarkers of vascular calcification using bioinformatics analysis and validation in vivo

Background

Vascular calcification (VC) is the most widespread pathological change in diseases of the vascular system. However, we know poorly about the molecular mechanisms and effective therapeutic approaches of VC.

Methods

The VC dataset, GSE146638, was downloaded from the Gene Expression Omnibus (GEO) database. Using the edgeR package to screen Differentially expressed genes (DEGs). Gene set enrichment analysis (GSEA) and gene set variation analysis (GSVA) were used to find pathways affecting VC. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) were performed on the DEGs. Meanwhile, using the String database and Cytoscape software to construct protein-protein interaction (PPI) networks and identify hub genes with the highest module scores. Correlation analysis was performed for hub genes. Receiver operating characteristic (ROC) curves, expression level analysis, GSEA, and subcellular localization were performed for each hub gene. Expression of hub genes in normal and calcified vascular tissues was verified by quantitative reverse transcription PCR (RT-qPCR) and immunohistochemistry (IHC) experiments. The hub gene-related miRNA-mRNA and TF-mRNA networks were constructed and functionally enriched for analysis. Finally, the DGIdb database was utilized to search for alternative drugs targeting VC hub genes.

Results

By comparing the genes with normal vessels, there were 64 DEGs in mildly calcified vessels and 650 DEGs in severely calcified vessels. Spp1, Sost, Col1a1, Fn1, and Ibsp were central in the progression of the entire VC by the MCODE plug-in. These hub genes are primarily enriched in ossification, extracellular matrix, and ECM-receptor interactions. Expression level results showed that Spp1, Sost, Ibsp, and Fn1 were significantly highly expressed in VC, and Col1a1 was incredibly low. RT-qPCR and IHC validation results were consistent with bioinformatic analysis. We found multiple pathways of hub genes acting in VC and identified 16 targeting drugs.

Conclusions

This study perfected the molecular regulatory mechanism of VC. Our results indicated that Spp1, Sost, Col1a1, Fn1, and Ibsp could be potential novel biomarkers for VC and promising therapeutic targets.

New Insights to the Crosstalk between Vascular and Bone Tissue in Chronic Kidney Disease-Mineral and Bone Disorder

Vasculature plays a key role in bone development and the maintenance of bone tissue throughout life. The two organ systems are not only linked in normal physiology, but also in pathophysiological conditions. The chronic kidney disease–mineral and bone disorder (CKD-MBD) is still the most serious complication to CKD, resulting in increased morbidity and mortality. Current treatment therapies aimed at the phosphate retention and parathyroid hormone disturbances fail to reduce the high cardiovascular mortality in CKD patients, underlining the importance of other factors in the complex syndrome. This review will focus on vascular disease and its interplay with bone disorders in CKD. It will present the very late data showing a direct effect of vascular calcification on bone metabolism, indicating a vascular-bone tissue crosstalk in CKD. The calcified vasculature not only suffers from the systemic effects of CKD but seems to be an active player in the CKD-MBD syndrome impairing bone metabolism and might be a novel target for treatment and prevention.

Cardiovascular Safety of Anti-Sclerostin Therapy in Chronic Kidney Disease

The significance of sclerostin for bone and cardiovascular health in patients with chronic kidney disease (CKD) is complex and incompletely understood. Experimental evidence suggests that anti-sclerostin therapy shows diminished efficacy on bone in the setting of CKD. Limited clinical evidence suggests that the osteoanabolic and anti-resorptive activity is attenuated, but hypocalcemia is more prevalent in patients with advanced CKD (eGFR < 30 mL/min) treated with anti-sclerostin (romosozumab) therapy as compared to patients without kidney disease. Furthermore, sclerostin is prominently expressed in uremic arteries. Whether the inhibition of sclerostin has adverse effects on cardiovascular health in CKD is currently unknown. This review summarizes the current understanding of the physiology and pathophysiology of sclerostin in CKD, with a focus on the cardiovascular safety of anti-sclerostin therapy in patients with or without CKD.

Paraoxonase 1 gene (PON1) variants concerning hepatitis C virus (HCV) spontaneous clearance in hemodialysis individuals: a case-control study

BACKGROUND

To explore associations between PON1 rs854560, rs662, 705,379, HCV clearance, and interactions between tested PON1 single nucleotide variants (SNVs) and interferon-λ4 gene (IFNL4) rs368234815 variant in hemodialyzed individuals.

METHODS

The study included 83 HD individuals who spontaneously resolved HCV infection (all had known IFNL4 rs368234815 variant) and 104 individuals with persistently positive blood tests for HCV RNA (102 were IFNL4 rs368234815 variant successfully genotyped). We genotyped PON1 by high-resolution melt analysis (rs662) or predesigned TaqMan SNV Genotyping Assay (rs854560, rs705379). We used a logistic regression model to assess the association between genetic data and HCV outcome while adjusting for clinical confounding variables. Epistatic interactions between tested PON1 SNVs and IFNL4 rs368234815 were analyzed by the multifactor dimensionality reduction method.

RESULTS

In the recessive inheritance model, PON1 rs662 GG (OR 9.94, 95% CI 1.20-82.7, P = 0.022) and rs854560 TT (OR 4.31, 95% CI 1.62-11.5, P = 0.003) genotypes were associated with a higher probability for HCV clearance. The haplotype composed of rs662A_rs854560A_rs705379 was not associated with spontaneous HCV clearance. The IFNL4 rs368234815 TT/TT variant was equally distributed among individuals bearing different PON1 SNVs. The epistatic gene-gene analysis did not reveal the interaction between tested PON1 SNVs and IFNL4 rs368234815 (P = 0.094). Regression model, including the PON1 rs662 GG genotype, the PON1 rs854560 genotype, the IFNL4 rs368234815 TT/TT genotype, age at RRT onset, RRT duration, and chronic glomerulonephritis as possible explanatory variables for spontaneous HCV clearance, showed that significant predictors of spontaneous HCV clearance were the IFNL4 rs368234815 TT/TT genotype (OR 2.607, 95% CI 1.298-5.235, P = 0.007), PON1 rs854560 TT (OR 6.208, 1.962-19.644, P = 0.002), PON1 rs662 GG (OR 10.762, 1.222-94.796, P = 0.032), and RRT duration (OR 0.930, 95% CI 0.879-0.984, P = 0.011).

CONCLUSION

In HD individuals, PON1 rs662 GG and rs854560 TT are associated with a higher frequency of spontaneous HCV clearance.

Correlation Between Soluble Klotho and Vascular Calcification in Chronic Kidney Disease: A Meta-Analysis and Systematic Review

Background: The correlation between soluble Klotho (sKlotho) level and vascular calcification (VC) in patients with chronic kidney disease (CKD) remains controversial. Using meta-analysis, we aimed to address this controversy and assess the feasibility of applying sKlotho as a biomarker for VC. Methods: Medical electronic databases were thoroughly searched for eligible publications on the association between sKlotho level and VC in CKD patients. Effectors, including correlation coefficients (r), odds ratios (ORs), hazard ratio (HR) or β-values, and 95% confidence intervals (CIs) were extracted and combined according to study design or effector calculation method. Pooled effectors were generated using both random-effects models and fixed-effects models according to I 2-value. Origin of heterogeneity was explored by sensitivity analysis and subgroup analysis. Results: Ten studies with 1,204 participants from a total of 1,199 publications were eligible and included in this meta-analysis. The combined correlation coefficient (r) was [-0.33 (-0.62, -0.04)] with significant heterogeneity (I 2 = 89%, p < 0.001) based on Spearman correlation analysis, and this significant association was also demonstrated in subgroups. There was no evidence of publication bias. The combined OR was [3.27 (1.70, 6.30)] with no evidence of heterogeneity (I 2 = 0%, p = 0.48) when sKlotho was treated as a categorical variable or [1.05 (1.01, 1.09)] with moderate heterogeneity (I 2 = 63%, p = 0.10) when sKlotho was treated as a continuous variable based on multivariate logistic regression. No significant association was observed and the pooled OR was [0.29 (0.01, 11.15)] with high heterogeneity (I 2 = 96%, p < 0.001) according to multivariate linear regression analysis. There was an inverse association between sKlotho and parathyroid hormone levels. The combined coefficient (r) was [-0.20 (-0.40, -0.01)] with significant heterogeneity (I 2 = 86%, p < 0.001), and without obvious publication bias. No significant association was found between sKlotho and calcium or phosphate levels. Conclusion: There exists a significant association between decreased sKlotho level and increased risk of VC in CKD patients. This raises the possibility of applying sKlotho as a biomarker for VC in CKD populations. Large, prospective, well-designed studies or interventional clinical trials are required to validate our findings.

Extrarenal expression of α-klotho, the kidney related longevity gene, in Heterocephalus glaber, the long living Naked Mole Rat

The Naked Mole Rat (NMR), Heterocephalus glaber, provides an interesting model for studying biomarkers of longevity due to its long lifespan of more than 30 years, almost ten times longer than that of mice and rats. α-Klotho (klotho) is an aging-suppressor gene, and overexpression of klotho is associated with extended lifespan in mice. Klotho is predominantly expressed in the kidney. The expression profile of klotho in the NMR has not previously been reported. The present investigation studied the expression of klotho in the kidney of NMR with that of Rattus Norvegicus (RN) and demonstrated that klotho was expressed in the kidney of NMR at the same level as found in RN. Besides, a significant expression of Kl mRNA was found in the liver of NMR, in contrast to RN, where no hepatic expression was detected. The Klotho expression was further confirmed at the protein level. Thus, the results of the present comparative study indicate a differential tissue expression of klotho between different species. Besides its important function in the kidney, Klotho might also be of significance in the liver of NMR. It is suggested that the hepatic extrarenal expression of klotho may function as a further longevity-related factor in supplement to the Klotho in the kidney.

The Vascular Circadian Clock in Chronic Kidney Disease

Chronic kidney disease is associated with extremely high cardiovascular mortality. The circadian rhythms (CR) have an impact on vascular function. The disruption of CR causes serious health problems and contributes to the development of cardiovascular diseases. Uremia may affect the master pacemaker of CR in the hypothalamus. A molecular circadian clock is also expressed in peripheral tissues, including the vasculature, where it regulates the different aspects of both vascular physiology and pathophysiology. Here, we address the impact of CKD on the intrinsic circadian clock in the vasculature. The expression of the core circadian clock genes in the aorta is disrupted in CKD. We propose a novel concept of the disruption of the circadian clock system in the vasculature of importance for the pathology of the uremic vasculopathy.

Sclerostin Downregulation Globally by Naturally Occurring Genetic Variants, or Locally in Atherosclerotic Plaques, Does Not Associate With Cardiovascular Events in Humans

Inhibition of sclerostin increases bone formation and decreases bone resorption, leading to increased bone mass, bone mineral density, and bone strength and reduced fracture risk. In a clinical study of the sclerostin antibody romosozumab versus alendronate in postmenopausal women (ARCH), an imbalance in adjudicated serious cardiovascular (CV) adverse events driven by an increase in myocardial infarction (MI) and stroke was observed. To explore whether there was a potential mechanistic plausibility that sclerostin expression, or its inhibition, in atherosclerotic (AS) plaques may have contributed to this imbalance, sclerostin was immunostained in human plaques to determine whether it was detected in regions relevant to plaque stability in 94 carotid and 50 femoral AS plaques surgically collected from older female patients (mean age 69.6 ± 10.4 years). Sclerostin staining was absent in most plaques (67%), and when detected, it was of reduced intensity compared with normal aorta and was located in deeper regions of the plaque/wall but was not observed in areas considered relevant to plaque stability (fibrous cap and endothelium). Additionally, genetic variants associated with lifelong reduced sclerostin expression were explored for associations with phenotypes including those related to bone physiology and CV risk factors/events in a population-based phenomewide association study (PheWAS). Natural genetic modulation of sclerostin by variants with a significant positive effect on bone physiology showed no association with lifetime risk of MI or stroke. These data do not support a causal association between the presence of sclerostin, or its inhibition, in the vasculature and increased risk of serious cardiovascular events. © 2021 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Cardiovascular Safety and Sclerostin Inhibition

Sclerostin, which is primarily produced by the osteocytes, inhibits the canonical Wnt pathway and thereby the osteoblasts and stimulates RANKL release by the osteocytes and thereby osteoclast recruitment. Inhibition of sclerostin therefore causes stimulation of bone formation and inhibition of resorption. In clinical trials, romosozumab, an antibody against sclerostin, increases bone mineral density and reduces the risk of fractures compared with placebo and alendronate. The cardiovascular safety of romosozumab was adjudicated in 2 large clinical osteoporosis trials in postmenopausal women. Compared with placebo, the incidence of cardiovascular events was similar in the 2 treatment groups. Compared with alendronate, the incidence of serious cardiovascular events was higher in women treated with romosozumab. The incidence of serious cardiovascular adverse events was low and post hoc analyses should therefore be interpreted with caution; however, the relative risk seemed unaffected by preexisting cardiovascular disease or risk factors. Sclerostin is expressed in the vasculature, predominantly in vascular smooth muscle cells in the media. However, preclinical and genetic studies have not demonstrated any increased cardiovascular risk with continuously low sclerostin levels or inhibition of sclerostin. Furthermore, no potential mechanisms for such an effect have been identified. In conclusion, while there is no preclinical or genetic evidence of a harmful effect of sclerostin inhibition on cardiovascular safety, the evidence from the large clinical trials in postmenopausal women is conflicting. Romosozumab should therefore be used for the treatment of postmenopausal women with osteoporosis at high risk of fracture after careful consideration of the cardiovascular risk and the balance between benefits and risks.

Chronic Kidney Disease-Induced Vascular Calcification Impairs Bone Metabolism

An association between lower bone mineral density (BMD) and presence of vascular calcification (VC) has been reported in several studies. Chronic kidney disease (CKD) causes detrimental disturbances in the mineral balance, bone turnover, and development of severe VC. Our group has previously demonstrated expression of Wnt inhibitors in calcified arteries of CKD rats. Therefore, we hypothesized that the CKD-induced VC via this pathway signals to bone and induces bone loss. To address this novel hypothesis, we developed a new animal model using isogenic aorta transplantation (ATx). Severely calcified aortas from uremic rats were transplanted into healthy rats (uremic ATx). Transplantation of normal aortas into healthy rats (normal ATx) and age-matched rats (control) served as control groups. Trabecular tissue mineral density, as measured by μCT, was significantly lower in uremic ATx rats compared with both control groups. Uremic ATx rats showed a significant upregulation of the mineralization inhibitors osteopontin and progressive ankylosis protein homolog in bone. In addition, we found significant changes in bone mRNA levels of several genes related to extracellular matrix, bone turnover, and Wnt signaling in uremic ATx rats, with no difference between normal ATx and control. The bone histomorphometry analysis showed significant lower osteoid area in uremic ATx compared with normal ATx along with a trend toward fewer osteoblasts as well as more osteoclasts in the erosion lacunae. Uremic ATx and normal ATx had similar trabecular number and thickness. The bone formation rate did not differ between the three groups. Plasma biochemistry, including sclerostin, kidney, and mineral parameters, were similar between all three groups. ex vivo cultures of aorta from uremic rats showed high secretion of the Wnt inhibitor sclerostin. In conclusion, the presence of VC lowers BMD, impairs bone metabolism, and affects several pathways in bone. The present results prove the existence of a vasculature to bone tissue cross-talk. © 2020 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Circadian rhythms of mineral metabolism in chronic kidney disease-mineral bone disorder

PURPOSE OF REVIEW

The circadian rhythms have a systemic impact on all aspects of physiology. Kidney diseases are associated with extremely high-cardiovascular mortality, related to chronic kidney disease-mineral bone disorder (CKD-MBD), involving bone, parathyroids and vascular calcification. Disruption of circadian rhythms may cause serious health problems, contributing to development of cardiovascular diseases, metabolic syndrome, cancer, organ fibrosis, osteopenia and aging. Evidence of disturbed circadian rhythms in CKD-MBD parameters and organs involved is emerging and will be discussed in this review.

RECENT FINDINGS

Kidney injury induces unstable behavioral circadian rhythm. Potentially, uremic toxins may affect the master-pacemaker of circadian rhythm in hypothalamus. In CKD disturbances in the circadian rhythms of CKD-MBD plasma-parameters, activin A, fibroblast growth factor 23, parathyroid hormone, phosphate have been demonstrated. A molecular circadian clock is also expressed in peripheral tissues, involved in CKD-MBD; vasculature, parathyroids and bone. Expression of the core circadian clock genes in the different tissues is disrupted in CKD-MBD.

SUMMARY

Disturbed circadian rhythms is a novel feature of CKD-MBD. There is a need to establish which specific input determines the phase of the local molecular clock and to characterize its regulation and deregulation in tissues involved in CKD-MBD. Finally, it is important to establish what are the implications for treatment including the potential applications for chronotherapy.

Polymorphism rs368234815 of interferon lambda 4 gene and spontaneous clearance of hepatitis C virus in haemodialysis patients: a case-control study

BACKGROUND

In non-uremic subjects, IFNL4 rs368234815 predicts HCV clearance. We investigated whether rs368234815 is associated with spontaneous HCV clearance in haemodialysis patients and whether it is a stronger predictor of HCV resolution than the IFNL polymorphisms already associated with HCV clearance in dialysis subjects. We also evaluated an association of rs368234815 with patients` survival and alterations in transcription factor binding sites (TFBS) caused by IFNL polymorphisms.

METHODS

Among 161 haemodialysis patients with positive anti-HCV antibodies, 68 (42.2%) spontaneously resolved HCV infection, whereas 93 remained HCV RNA positive. Patients were tested for near IFNL3 rs12980275, IFNL3 rs4803217, IFNL4 rs12979860, IFNL4 rs368234815, and near IFNL4 rs8099917. IFNL4 rs368234815 polymorphism (TT/TT, ΔG/TT, ΔG/ΔG) was genotyped by restriction fragment length polymorphism analysis; other IFNL polymorphisms - by high resolution melting curve analysis. We used the Kaplan-Meier method with the log-rank test for survival analysis. In silico analysis included the use of ENCODE TFBS ChIP-seq data, HOCOMOCO, JASPAR CORE, and CIS-BP databases, and FIMO software.

RESULTS

The probability (OR, 95%CI, P) of spontaneous HCV clearance for rs368234815 TT/TT patients was higher than for the ΔG allele carriers (2.63, 1.38-5.04, 0.003). This probability for other major homozygotes varied between 2.80, 1.45-5.43, 0.002 for rs12980275 and 2.44, 1.27-4.69, 0.007 for rs12979860. In the additive model, rs368234815 TT/TT was the strongest predictor of HCV clearance (6.38, 1.69-24.2, 0.003). Survival analysis suggested an association of the ΔG allele with mortality due to neoplasms (log-rank P = 0.005). The rs368234815 ∆G allele caused TFBS removal for PLAGL1.

CONCLUSIONS

In haemodialysis patients, the association of rs368234815 with the spontaneous HCV clearance is better than that documented for other IFNL3/IFNL4 polymorphisms only in the additive mode of inheritance. However, identifying the homozygosity in the variant ∆G allele of rs368234815 means a more potent prediction of persistent HCV infection in haemodialysis subjects that we observe in the case of the variant homozygosity of other tested IFNL3/IFNL4 polymorphisms. Removal of PLAGL1 TFBS in subjects harbouring the rs368234815 ∆G allele may contribute to cancer susceptibility. The association of rs368234815 with cancer-related mortality needs further studies in HCV-exposed subjects.

A multi-omics view of the complex mechanism of vascular calcification

Vascular calcification is a high incidence and high risk disease with increasing morbidity and high mortality, which is considered the consequence of smooth muscle cell transdifferentiation initiating the mechanism of accumulation of hydroxyl calcium phosphate. Vascular calcification is also thought to be strongly associated with poor outcomes in diabetes and chronic kidney disease. Numerous studies have been accomplished; however, the specific mechanism of the disease remains unclear. Development of the genome project enhanced the understanding of life science and has entered the post-genomic era resulting in a variety of omics techniques used in studies and a large amount of available data; thus, a new perspective on data analysis has been revealed. Omics has a broader perspective and is thus advantageous over a single pathway analysis in the study of complex vascular calcification mechanisms. This paper reviews in detail various omics studies including genomics, proteomics, transcriptomics, metabolomics and multiple group studies on vascular calcification. Advances and deficiencies in the use of omics to study vascular calcification are presented in a comprehensive view. We also review the methodology of the omics studies and omics data analysis and processing. In addition, the methodology and data processing presented here can be applied to other areas. An omics landscape perspective across the boundaries between genomics, transcriptomics, proteomics and metabolomics is used to examine the mechanisms of vascular calcification. The perspective combined with various technologies also provides a direction for the subsequent exploration of clinical significance.

2020 Jeffrey M. Hoeg Award Lecture: Calcifying Extracellular Vesicles as Building Blocks of Microcalcifications in Cardiovascular Disorders

Cardiovascular calcification is an insidious form of ectopic tissue mineralization that presents as a frequent comorbidity of atherosclerosis, aortic valve stenosis, diabetes, renal failure, and chronic inflammation. Calcification of the vasculature and heart valves contributes to mortality in these diseases. An inability to clinically image or detect early microcalcification coupled with an utter lack of pharmaceutical therapies capable of inhibiting or regressing entrenched and detectable macrocalcification has led to a prominent and deadly gap in care for a growing portion of our rapidly aging population. Recognition of this mounting concern has arisen over the past decade and led to a series of revolutionary works that has begun to pull back the curtain on the pathogenesis, mechanistic basis, and causative drivers of cardiovascular calcification. Central to this progress is the discovery that calcifying extracellular vesicles act as active precursors of cardiovascular microcalcification in diverse vascular beds. More recently, the omics revolution has resulted in the collection and quantification of vast amounts of molecular-level data. As the field has become poised to leverage these resources for drug discovery, new means of deriving relevant biological insights from these rich and complex datasets have come into focus through the careful application of systems biology and network medicine approaches. As we look onward toward the next decade, we envision a growing need to standardize approaches to study this complex and multifaceted clinical problem and expect that a push to translate mechanistic findings into therapeutics will begin to finally provide relief for those impacted by this disease.

New Aspects of the Kidney in the Regulation of Fibroblast Growth Factor 23 (FGF23) and Mineral Homeostasis

The bone-derived hormone fibroblast growth factor 23 (FGF23) acts in concert with parathyroid hormone (PTH) and the active vitamin D metabolite calcitriol in the regulation of calcium (Ca) and phosphate (P) homeostasis. More factors are being identified to regulate FGF23 levels and the endocrine loops between the three hormones. The present review summarizes the complex regulation of FGF23 and the disturbed FGF23/Klotho system in chronic kidney disease (CKD). In addition to the reduced ability of the injured kidney to regulate plasma levels of FGF23, several CKD-related factors have been shown to stimulate FGF23 production. The high circulating FGF23 levels have detrimental effects on erythropoiesis, the cardio-vascular system and the immune system, all contributing to the disturbed system biology in CKD. Moreover, new factors secreted by the injured kidney and the uremic calcified vasculature play a role in the mineral and bone disorder in CKD and create a vicious pathological crosstalk.

Omics research in vascular calcification

Vascular calcification (VC), the pathological process of hydroxyapatite mineral deposition in the vascular system, is closely associated with aging, atherosclerotic plaque formation, cardiovascular disease (CVD) and diabetes mellitus (DM). Studies have shown that VC is related to cellular phenotypic changes, extracellular vesicles, disordered calcium and phosphate homeostasis, and an imbalance between inducers and inhibitors of VC. Unfortunately, there is currently no effective preventive or targeted treatment for pathologic condition. The rapid evolution of omics technology (genomics, epigenomics, transcriptomics, proteomics and metabolomics) has provided a novel approach for elucidation of pathophysiologic mechanisms in general and those associated with VC specifically. Here, we review articles published over the last twenty years and focus on the current state, challenges, limitations and future of omics in VC research and clinical practice. Highlighting potential targets based on omics technology will improve our understanding of this pathologic condition and assist in the development of potential treatment options for VC related disease.

Omics research in vascular calcification

Vascular calcification (VC), the pathological process of hydroxyapatite mineral deposition in the vascular system, is closely associated with aging, atherosclerotic plaque formation, cardiovascular disease (CVD) and diabetes mellitus (DM). Studies have shown that VC is related to cellular phenotypic changes, extracellular vesicles, disordered calcium phosphate homeostasis and an imbalance between inducers and inhibitors of VC. Unfortunately, there is currently no effective preventive or targeted treatment for this disorder. Recently, the evolution of omics technology (genomics, epigenomics, transcriptomics, proteomics and metabolomics) has paved the way for elucidation of complex biochemical processes and, as such, may provide new insight on VC. Accordingly, we conducted a review of articles published over the last twenty years and herein focus on current and future potential of omics technology in clarifying mechanisms of this disease process. Identification of new biomarkers will provide additional tools in characterizing this pathology and will further assist in the development of potential therapeutic targets.

A molecular circadian clock operates in the parathyroid gland and is disturbed in chronic kidney disease associated bone and mineral disorder

Circadian rhythms in metabolism, hormone secretion, cell cycle and locomotor activity are regulated by a molecular circadian clock with the master clock in the suprachiasmatic nucleus of the central nervous system. However, an internal clock is also expressed in several peripheral tissues. Although about 10% of all genes are regulated by clock machinery an internal molecular circadian clock in the parathyroid glands has not previously been investigated. Parathyroid hormone secretion exhibits a diurnal variation and parathyroid hormone gene promoter contains an E-box like element, a known target of circadian clock proteins. Therefore, we examined whether an internal molecular circadian clock is operating in parathyroid glands, whether it is entrained by feeding and how it responds to chronic kidney disease. As uremia is associated with extreme parathyroid growth and since disturbed circadian rhythm is related to abnormal growth, we examined the expression of parathyroid clock and clock-regulated cell cycle genes in parathyroid glands of normal and uremic rats. Circadian clock genes were found to be rhythmically expressed in normal parathyroid glands and this clock was minimally entrained by feeding. Diurnal regulation of parathyroid glands was next examined. Significant rhythmicity of fibroblast-growth-factor-receptor-1, MafB and Gata3 was found. In uremic rats, deregulation of circadian clock genes and the cell cycle regulators, Cyclin D1, c-Myc, Wee1 and p27, which are influenced by the circadian clock, was found in parathyroid glands as well as the aorta. Thus, a circadian clock operates in parathyroid glands and this clock and downstream cell cycle regulators are disturbed in uremia and may contribute to dysregulated parathyroid proliferation in secondary hyperparathyroidism.

Genetic Polymorphisms within Interferon-λ Region and Interferon-λ3 in the Human Pathophysiology: Their Contribution to Outcome, Treatment, and Prevention of Infections with Hepatotropic Viruses

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Genetic polymorphisms within the interferon λ (IFN-λ) chromosomal region, mainly rs12979860 of IFN-λ4 gene (IFNL4), are known as associated with spontaneous hepatitis C virus (HCV) resolution and sustained viral response to therapy with pegylated interferon- α and ribavirin. Strong linkage disequilibrium of IFNL4 rs12979860 with IFNL4 rs368234815, which is casually associated with HCV spontaneous and therapeutical eradication, at least partially explains favorable HCV outcomes attributed to major homozygosity in rs12979860. Effects of IFN-based antiviral treatment are associated with pretreatment expression of the IFN-λ1 receptor, expression of hepatic IFN-stimulated genes, production of IFN- λ4, and preactivation of the JAK-STAT signaling. Nowadays direct-acting antivirals (DAAs) became a potent tool in the treatment of hepatitis C, but IFN-λs are still under investigation as potential antivirals and might be an option in HCV infection (DAA resistance, recurrent viremia, adverse effects).

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Patients with altered immunocompetence are especially prone to infections. In uremic subjects, polymorphisms within the IFN-λ chromosomal region associate with spontaneous HCV clearance, similarly like in the non-uremic population. Circulating IFN-λ3 shows a positive correlation with plasma titers of antibodies to surface antigen of hepatitis B virus (anti-HBs), which are crucial for protection against hepatitis B virus. More efficient anti-HBs production in the presence of higher IFN-λ3 levels might occur due to IFN-λ3-induced regulation of indoleamine 2,3-dioxygenase (IDO) expression. IFN-stimulated response element is a part of IDO gene promoter. It is worth further investigation whether IDO gene, circulating IDO, genetic polymorphisms within the IFN-λ region, and circulating IFN-λ3 act in concordance in immunological response to hepatotropic viruses.

Circadian rhythm of activin A and related parameters of mineral metabolism in normal and uremic rats

Activin A is a new fascinating player in chronic kidney disease-mineral and bone disorder (CKD-MBD), which is implicated in progressive renal disease, vascular calcification, and osteodystrophy. Plasma activin A rises early in the progression of renal disease. Disruption of circadian rhythms is related to increased risk of several diseases and circadian rhythms are observed in mineral homeostasis, bone parameters, and plasma levels of phosphate and PTH. Therefore, we examined the circadian rhythm of activin A and CKD-MBD-related parameters (phosphate, PTH, FGF23, and klotho) in healthy controls and CKD rats (5/6 nephrectomy) on high-, standard- and low-dietary phosphate contents as well as during fasting conditions. Plasma activin A exhibited circadian rhythmicity in healthy control rats with fourfold higher values at acrophase compared with nadir. The rhythm was obliterated in CKD. Activin A was higher in CKD rats compared with controls when measured at daytime but not significantly when measured at evening/nighttime, stressing the importance of time-specific reference intervals when interpreting plasma values. Plasma phosphate, PTH, and FGF23 all showed circadian rhythms in control rats, which were abolished or disrupted in CKD. Plasma klotho did not show circadian rhythm. Thus, the present investigation shows, for the first time, circadian rhythm of plasma activin A. The rhythmicity is severely disturbed by CKD and is associated with disturbed rhythms of phosphate and phosphate-regulating hormones PTH and FGF23, indicating that disturbed circadian rhythmicity is an important feature of CKD-MBD.

Sost Haploinsufficiency Provokes Peracute Lethal Cardiac Tamponade without Rescuing the Osteopenia in a Mouse Model of Excess Glucocorticoids

Glucocorticoid-induced secondary osteoporosis is the most predictable side effect of this anti-inflammatory. One of the main mechanisms by which glucocorticoids achieve such deleterious outcome in bone is by antagonizing Wnt/β-catenin signaling. Sclerostin, encoded by Sost gene, is the main negative regulator of the proformative and antiresorptive role of the Wnt signaling pathway in the skeleton. It was hypothesized that the partial inactivation of sclerostin function by genetic manipulation will rescue the osteopenia induced by high endogenous glucocorticoid levels. Sost-deficient mice were crossed with an established mouse model of excess glucocorticoids, and the effects on bone mass and structure were evaluated. Sost haploinsufficiency did not rescue the low bone mass induced by high glucocorticoids. Intriguingly, the critical manifestation of Sost deficiency combined with glucocorticoid excess was sporadic, sudden, unprovoked, and nonconvulsive death. Detailed histopathologic analysis in a wide range of tissues identified peracute hemopericardium and cardiac tamponade to be the cause. These preclinical studies reveal outcomes with direct relevance to ongoing clinical trials that explore the use of antisclerostin antibodies as a treatment for osteoporosis. They particularly highlight a potential for increased cardiovascular risk and may inform improved stratification of patients who might otherwise benefit from antisclerostin antibody treatment.

Effect of inhibition of CBP-coactivated β-catenin-mediated Wnt signalling in uremic rats with vascular calcifications

Uremic vascular calcification is a regulated cell-mediated process wherein cells in the arterial wall transdifferentiate to actively calcifying cells resulting in a process resembling bone formation. Wnt signalling is established as a major driver for vessel formation and maturation and for embryonic bone formation, and disturbed Wnt signalling might play a role in vascular calcification. ICG-001 is a small molecule Wnt inhibitor that specifically targets the coactivator CREB binding protein (CBP)/β-catenin-mediated signalling. In the present investigation we examined the effect of ICG-001 on vascular calcification in uremic rats. Uremic vascular calcification was induced in adult male rats by 5/6-nephrectomy, high phosphate diet and alfacalcidol. The presence of uremic vascular calcification in the aorta was associated with induction of gene expression of the Wnt target gene and marker of proliferation, cyclinD1; the mediator of canonical Wnt signalling, β-catenin and the matricellular proteins, fibronectin and periostin. Furthermore, genes from fibrosis-related pathways, TGF-β and activin A, as well as factors related to epithelial-mesenchymal transition, snail1 and vimentin were induced. ICG-001 treatment had significant effects on gene expression in kidney and aorta from healthy rats. These effects were however limited in uremic rats, and treatment with ICG-001 did not reduce the Ca-content of the uremic vasculature.

Klotho and activin A in kidney injury: plasma Klotho is maintained in unilateral obstruction despite no upregulation of Klotho biosynthesis in the contralateral kidney

In a new paradigm of etiology related to chronic kidney disease-mineral and bone disorder (CKD-MBD), kidney injury may cause induction of factors in the injured kidney that are released into the circulation and thereby initiate and maintain renal fibrosis and CKD-MBD. Klotho is believed to ameliorate renal fibrosis and CKD-MBD, while activin A might have detrimental effects. The unilateral ureter obstruction (UUO) model is used here to examine this concept by investigating early changes related to renal fibrosis in the obstructed kidney, untouched contralateral kidney, and vasculature which might be affected by secreted factors from the obstructed kidney, and comparing with unilateral nephrectomized controls (UNX). Obstructed kidneys showed early Klotho gene and protein depletion, whereas plasma Klotho increased in both UUO and UNX rats, indicating an altered metabolism of Klotho. Contralateral kidneys had no compensatory upregulation of Klotho and maintained normal expression of the examined fibrosis-related genes, as did remnant UNX kidneys. UUO caused upregulation of transforming growth factor-β and induction of periostin and activin A in obstructed kidneys without changes in the contralateral kidneys. Plasma activin A doubled in UUO rats after 10 days while no changes were seen in UNX rats, suggesting secretion of activin A from the obstructed kidney with potentially systemic effects on CKD-MBD. As such, increased aortic sclerostin was observed in UUO rats compared with UNX and normal controls. The present results are in line with the new paradigm and show very early vascular effects of unilateral kidney fibrosis, supporting the existence of a new kidney-vasculature axis.

Identification of differential gene expression patterns in human arteries from patients with chronic kidney disease

Uremia accelerates atherosclerosis, but little is known about affected pathways in human vasculature. This study aimed to identify differentially expressed arterial transcripts in patients with chronic kidney disease (CKD). Global mRNA expression was estimated by microarray hybridization in iliac arteries ( n = 14) from renal transplant recipients and compared with renal arteries from healthy living kidney donors ( n = 19) in study 1. Study 2 compared nonatherosclerotic internal mammary arteries (IMA) from five patients with elevated plasma creatinine levels and age- and sex-matched controls with normal creatinine levels. Western blotting and immunohistochemistry for selected proteins were performed on a subset of study 1 samples. Fifteen gene transcripts were significantly different between the two groups in study 1 [fold changes (FC) > 1.05 and false discovery rates (FDR) < 0.005]. Most upregulated mRNAs associated with cellular signaling, apoptosis, TNFα/NF-κB signaling, smooth muscle contraction, and 10 other pathways were significantly affected. To focus attention on genes from genuine vascular cells, which dominate in IMA, concordant deregulated genes in studies 1 and 2 were examined and included 23 downregulated and eight upregulated transcripts (settings in study 1: FC > 1.05 and FDR < 0.05; study 2: FC > 1.2 and P < 0.2). Selected deregulated gene products were investigated at the protein level, and whereas HIF3α confirmed mRNA upregulation, vimentin showed upregulation in contrast to the mRNA results. We conclude that arteries from CKD patients display change in relatively few sets of genes. Many were related to differentiated vascular smooth muscle cell phenotype. These identified genes may contribute to understanding the development of arterial injury among patients with CKD.

Rabbit models provide insights into bone formation related biological process in atherosclerotic vascular calcification

Featured as ectopic mineralization along blood vessels, vascular calcification is a major risk factor for a number of prevalent diseases including atherosclerosis. As recent studies identify vascular calcification as a tightly regulated process recapitulating embryonic bone formation, in this study, RNA-seq data generated from rabbit models with inherited or induced hyperlipidemia and atherosclerosis were used, to investigate bone formation related signals and biological processes in atherosclerotic vascular calcification. Evident activation of bone formation was found, together with presence and functioning of bone resorption cell osteoclasts, which were found to possibly also promote bone formation in this disease. Resistance of bone formation and calcification were also found, through down-regulation of pro-ossification regulators and up-regulation of protective inhibitors and Wnt antagonists. Levels of activation and resistance of bone formation differed between the two disease models, suggesting different underlying mechanisms and corresponding treatments. In addition, loss-of-function of protective inhibitors KL and SOST, and possibly crucial role of GPNMB were also highlighted for treatment or further study.

Exogenous BMP7 in aortae of rats with chronic uremia ameliorates expression of profibrotic genes, but does not reverse established vascular calcification

Hyperphosphatemia and vascular calcification are frequent complications of chronic renal failure and bone morphogenetic protein 7 (BMP7) has been shown to protect against development of vascular calcification in uremia. The present investigation examined the potential reversibility of established uremic vascular calcification by treatment of uremic rats with BMP7. A control model of isogenic transplantation of a calcified aorta from uremic rats into healthy littermates examined whether normalization of the uremic environment reversed vascular calcification. Uremia and vascular calcification were induced in rats by 5/6 nephrectomy, high phosphate diet and alfacalcidol treatment. After 14 weeks severe vascular calcification was present and rats were allocated to BMP7, vehicle or aorta transplantation. BMP7 treatment caused a significant decrease of plasma phosphate to 1.56 ± 0.17 mmol/L vs 2.06 ± 0.34 mmol/L in the vehicle group even in the setting of uremia and high phosphate diet. Uremia and alfacalcidol resulted in an increase in aortic expression of genes related to fibrosis, osteogenic transformation and extracellular matrix calcification, and the BMP7 treatment resulted in a decrease in the expression of profibrotic genes. The total Ca-content of the aorta was however unchanged both in the abdominal aorta: 1.9 ± 0.6 μg/mg tissue in the vehicle group vs 2.2 ± 0.6 μg/mg tissue in the BMP7 group and in the thoracic aorta: 71 ± 27 μg/mg tissue in the vehicle group vs 54 ± 18 μg/mg tissue in the BMP7 group. Likewise, normalization of the uremic environment by aorta transplantation had no effect on the Ca-content of the calcified aorta: 16.3 ± 0.6 μg/mg tissue pre-transplantation vs 15.9 ± 2.3 μg/mg tissue post-transplantation. Aortic expression of genes directly linked to extracellular matrix calcification was not affected by BMP7 treatment, which hypothetically might explain persistent high Ca-content in established vascular calcification. The present results highlight the importance of preventing the development of vascular calcification in chronic kidney disease. Once established, vascular calcification persists even in the setting when hyperphosphatemia or the uremic milieu is abolished.

Circulating Interferon-λ3, Responsiveness to HBV Vaccination, and HBV/HCV Infections in Haemodialysis Patients

The IFN-λ3 gene (IFNL3) plays a role in HCV clearance. We investigated circulating IFN-λ3 and IFNL3 SNPs in haemodialysis patients who differed in their response to HBV vaccination and their HBV/HCV infection status. In 201 patients, plasma IFN-λ3 was determined using ELISA. IFNL3 SNPs (rs12979860, rs8099917) were genotyped using HRM analysis. Differences in IFN-λ3 levels were shown between responders and nonresponders to HBV vaccination and between HBsAg-positive patients and those who developed anti-HBs after infection and became HBsAg negative. HBV vaccine responders without HCV resolution revealed lower IFN-λ3 than noninfected responders. HBsAg/HCV RNA-positive subjects showed lower IFN-λ3 than patients positive only for HCV RNA or subjects who resolved both infections. Circulating IFN-λ3 correlated positively with anti-HBs and negatively with positive HCV RNA testing in the adjusted regression analyses. HBV vaccine nonresponders, HBsAg-positive patients, and subjects with replicating HCV composed a group with unfavourable outcomes. Responders to HBV vaccination, subjects who became HBsAg negative, and those who cleared HCV were analysed as having favourable outcomes. The latter showed higher IFN-λ3 but did not differ in distribution of IFNL3 SNPs compared with subjects with unfavourable outcomes. Higher IFN-λ3 concentrations are associated with response to HBV vaccination, self-limited HBV infection, and HCV resolution.

Romosozumab or Alendronate for Fracture Prevention in Women with Osteoporosis

BACKGROUND

Romosozumab is a monoclonal antibody that binds to and inhibits sclerostin, increases bone formation, and decreases bone resorption.

METHODS

We enrolled 4093 postmenopausal women with osteoporosis and a fragility fracture and randomly assigned them in a 1:1 ratio to receive monthly subcutaneous romosozumab (210 mg) or weekly oral alendronate (70 mg) in a blinded fashion for 12 months, followed by open-label alendronate in both groups. The primary end points were the cumulative incidence of new vertebral fracture at 24 months and the cumulative incidence of clinical fracture (nonvertebral and symptomatic vertebral fracture) at the time of the primary analysis (after clinical fractures had been confirmed in ≥330 patients). Secondary end points included the incidences of nonvertebral and hip fracture at the time of the primary analysis. Serious cardiovascular adverse events, osteonecrosis of the jaw, and atypical femoral fractures were adjudicated.

RESULTS

Over a period of 24 months, a 48% lower risk of new vertebral fractures was observed in the romosozumab-to-alendronate group (6.2% [127 of 2046 patients]) than in the alendronate-to-alendronate group (11.9% [243 of 2047 patients]) (P<0.001). Clinical fractures occurred in 198 of 2046 patients (9.7%) in the romosozumab-to-alendronate group versus 266 of 2047 patients (13.0%) in the alendronate-to-alendronate group, representing a 27% lower risk with romosozumab (P<0.001). The risk of nonvertebral fractures was lower by 19% in the romosozumab-to-alendronate group than in the alendronate-to-alendronate group (178 of 2046 patients [8.7%] vs. 217 of 2047 patients [10.6%]; P=0.04), and the risk of hip fracture was lower by 38% (41 of 2046 patients [2.0%] vs. 66 of 2047 patients [3.2%]; P=0.02). Overall adverse events and serious adverse events were balanced between the two groups. During year 1, positively adjudicated serious cardiovascular adverse events were observed more often with romosozumab than with alendronate (50 of 2040 patients [2.5%] vs. 38 of 2014 patients [1.9%]). During the open-label alendronate period, adjudicated events of osteonecrosis of the jaw (1 event each in the romosozumab-to-alendronate and alendronate-to-alendronate groups) and atypical femoral fracture (2 events and 4 events, respectively) were observed.

CONCLUSIONS

In postmenopausal women with osteoporosis who were at high risk for fracture, romosozumab treatment for 12 months followed by alendronate resulted in a significantly lower risk of fracture than alendronate alone. (Funded by Amgen and others; ARCH ClinicalTrials.gov number, NCT01631214 .).

Tissue expression and source of circulating αKlotho

αKlotho (Klotho), a type I transmembrane protein and a coreceptor for Fibroblast Growth Factor-23, was initially thought to be expressed only in a limited number of tissues, most importantly the kidney, parathyroid gland and choroid plexus. Emerging data may suggest a more ubiquitous Klotho expression pattern which has prompted reevaluation of the restricted Klotho paradigm. Herein we systematically review the evidence for Klotho expression in various tissues and cell types in humans and other mammals, and discuss potential reasons behind existing conflicting data. Based on current literature and tissue expression atlases, we propose a classification of tissues into high, intermediate and low/absent Klotho expression. The functional relevance of Klotho in organs with low expression levels remain uncertain and there is currently limited data on a role for membrane-bound Klotho outside the kidney. Finally, we review the evidence for the tissue source of soluble Klotho, and conclude that the kidney is likely to be the principal source of circulating Klotho in physiology.

Development of a novel chronic kidney disease mouse model to evaluate the progression of hyperphosphatemia and associated mineral bone disease

Medial arterial calcification (MAC) and renal osteodystrophy are complications of mineral bone disease (MBD) associated with chronic kidney disease (CKD). Our aim was to develop a novel mouse model to investigate the clinical course of CKD-MBD. Eight-week-old C57BL/6 J male mice were assigned to the following groups: the control group, fed a standard chow for 6 or 12 weeks; the CKD-normal phosphorus (NP) group, fed a chow containing 0.2% adenine, with normal (0.8%) phosphorus, for 6 or 12 weeks; and the CKD-high phosphorus (HP) group, fed 6 weeks with the 0.2% adenine/0.8% phosphorus diet, followed by a chow with 1.8% phosphorus for 2 weeks, 4 weeks or 6 weeks. Serum phosphorus was significantly increased in the CKD-HP group, and associated with MAC formation; the volume of calcification increased with longer exposure to the high phosphorus feed. MAC was associated with upregulated expression of runt-related transcription factor 2, alkaline phosphatase, and osteopontin, indicative of osteoblastic trans-differentiation of vascular smooth muscle cells. A significant mineral density depletion of cortical bone was observed. We describe the feasibility of developing a model of CKD-MBD and provide findings of a direct association between elevated serum phosphorus and the formation of MAC and renal osteodystrophy.

The role of the anti-ageing protein Klotho in vascular physiology and pathophysiology

Klotho is an anti-ageing protein that functions in many pathways that govern ageing, like regulation of phosphate homeostasis, insulin signaling, and Wnt signaling. Klotho expression levels and levels in blood decline during ageing. The vascular phenotype of Klotho deficiency features medial calcification, intima hyperplasia, endothelial dysfunction, arterial stiffening, hypertension, and impaired angiogenesis and vasculogenesis, with characteristics similar to aged human arteries. Klotho-deficient phenotypes can be prevented and rescued by Klotho gene expression or protein supplementation. High phosphate levels are likely to be directly pathogenic and are a prerequisite for medial calcification, but more important determinants are pathways that regulate cellular senescence, suggesting that deficiency of Klotho renders cells susceptible to phosphate toxicity. Overexpression of Klotho is shown to ameliorate medial calcification, endothelial dysfunction, and hypertension. Endogenous vascular Klotho expression is a controversial subject and, currently, no compelling evidence exists that supports the existence of vascular membrane-bound Klotho expression, as expressed in kidney. In vitro, Klotho has been shown to decrease oxidative stress and apoptosis in both SMCs and ECs, to reduce SMC calcification, to maintain the contractile SMC phenotype, and to prevent μ-calpain overactivation in ECs. Klotho has many protective effects with regard to the vasculature and constitutes a very promising therapeutic target. The purpose of this review is to explore the etiology of the vascular phenotype of Klotho deficiency and the therapeutic potential of Klotho in vascular disease.

Kidney fibroblast growth factor 23 does not contribute to elevation of its circulating levels in uremia

Fibroblast growth factor 23 (FGF23) secreted by osteocytes is a circulating factor essential for phosphate homeostasis. High plasma FGF23 levels are associated with cardiovascular complications and mortality. Increases of plasma FGF23 in uremia antedate high levels of phosphate, suggesting a disrupted feedback regulatory loop or an extra-skeletal source of this phosphatonin. Since induction of FGF23 expression in injured organs has been reported we decided to examine the regulation of FGF23 gene and protein expressions in the kidney and whether kidney-derived FGF23 contributes to the high plasma levels of FGF23 in uremia. FGF23 mRNA was not detected in normal kidneys, but was clearly demonstrated in injured kidneys, already after four hours in obstructive nephropathy and at 8 weeks in the remnant kidney of 5/6 nephrectomized rats. No renal extraction was found in uremic rats in contrast to normal rats. Removal of the remnant kidney had no effect on plasma FGF23 levels. Well-known regulators of FGF23 expression in bone, such as parathyroid hormone, calcitriol, and inhibition of the FGF receptor by PD173074, had no impact on kidney expression of FGF23. Thus, the only direct contribution of the injured kidney to circulating FGF23 levels in uremia appears to be reduced renal extraction of bone-derived FGF23. Kidney-derived FGF23 does not generate high plasma FGF23 levels in uremia and is regulated differently than the corresponding regulation of FGF23 gene expression in bone.

Antibodies to HBV surface antigen in relation to interferon-λ3 in hemodialysis patients

AIM

To investigate circulating IFN-λ3 and IFNL3 polymorphisms in hemodialysis (HD) patients differing in HBV surface antigen antibody (anti-HBs) production.

METHODS

The study included 106 HBV-vaccinated HD patients (88 developed anti-HBs) and 36 HBV-infected HD subjects (27 developed anti-HBs). Plasma IFN-λ3 (enzyme-linked immunosorbent assay) and rs12979860 (C>T) and rs8099917 (T>G) in IFNL3 (high-resolution melting curve analysis) were analyzed with regard to the association with anti-HBs production in response to HBV vaccination or infection. The results were adjusted for gender, age, cause of renal disease, dialysis vintage, dialysis modality, IFN-λ3, and 25(OH)D as appropriate.

RESULTS

HBV vaccine responders had higher circulating IFN-λ3 (ng/L) than non-responders (120, 36-233 vs. 53, 33-109, P<0.000001). Patients who generated anti-HBs after HBV infection also had higher circulating IFN-λ3 levels than those who did not (133, 35-215 vs. 71, 9-229, P=0.043). The IFN-λ3 concentration correlated with the anti-HBs titer in vaccinated (r=0.614, P<0.000001) and infected patients (r=0.589, P=0.0002). Plasma IFN-λ3 was the only significant indicator of responsiveness to HBV vaccination (adjusted P=0.018) and remained the only significant associate for the development of post-infection anti-HBs (adjusted P=0.049). A plasmaIFN-λ3 level of 85.5ng/L was thecut-off value for theprognosis of an anti-HBs titer below vs. equal to or over 10IU/L in the entire group of HD patients (ROC sensitivity 68.7%, specificity 85.2%, and AUC 0.827). Significant associations were not found between IFN-λ3 and IFNL3 rs12979860. Subjects treated with low flux HD that harbored the TT genotype in rs8099917 showed higher IFN-λ3 levels than patients bearing the G allele in rs8099917 (139, 68-233 vs. 103, 9-208, P=0.049).

CONCLUSION

In HD patients, circulating IFN-λ3 strongly correlates with anti-HBs production after HBV vaccination and infection. IFNL3 rs8099917 polymorphisms seem to be associated with IFN-λ3 plasma levels in HD subjects.