Vitamin K antagonism aggravates chronic kidney disease-induced neointimal hyperplasia and calcification in arterialized veins: role of vitamin K treatment?

Antiphospholipid Antibodies Associated with Native Arteriovenous Fistula Complications in Hemodialysis Patients: A Comprehensive Review of the Literature

Antiphospholipid antibody (aPL)-persistent positivity is frequent in hemodialysis (HD) patients. Native arteriovenous fistula (AVF) complications such as stenosis and thrombosis are among the most important causes of morbidity and mortality in hemodialysis patients. The association between aPL positivity and AVF thrombosis seems to now be well established. However, whether aPL positivity is associated with other AVF complications, such as maturation failure or stenosis, is not well known. Given the significant impact of AVF failure on patient's prognosis, it is of interest to further investigate this particular point in order to improve prevention, surveillance and treatment, and, ultimately, the patient's outcome. This literature review aims to report the recent literature on aPL-associated native AVF complications.

Randomized Controlled Clinical Trial of the Effect of Treatment with Vitamin K2 on Vascular Calcification in Hemodialysis Patients (Trevasc-HDK)

Introduction

Vitamin K deficiency among patients on hemodialysis (HD) affects the function of matrix GLA protein (MGP), a potent vitamin K-dependent inhibitor of vascular calcification (VC).

Methods

We conducted a single-center randomized controlled trial (RCT) on maintenance HD patients to examine if vitamin K2 supplementation can reduce progression of coronary artery calcification (CAC) over an 18-month study period. Patients were randomized to vitamin K2 group receiving menaquinone-7360 μg 3 times/wk or control group. The primary outcome was CAC scores at the end of the study period. The secondary outcomes were aortic valve calcification (AVC), carotid-femoral pulse wave velocity (cfPWV), aortic augmentation index (AIx), dephosphorylated undercarboxylated MGP (dp-ucMGP) levels, major adverse cardiac events (MACE), and vascular access events.

Results

Of the 178 patients randomized, follow-up was completed for 138 patients. The CAC scores between the 2 groups were not statistically different at the end of 18 months (relative mean difference [RMD] 0.85, 95% CI 0.55-1.31). The secondary outcomes did not differ significantly in AVC (RMD 0.82, 95% CI 0.34-1.98), cfPWV (absolute mean difference [AMD] 0.55, 95% CI -0.50 to 1.60), and AIx (AMD 0.13, 95% CI -3.55 to 3.80). Supplementation with vitamin K2 did reduce dp-ucMGP levels (AMD -86, 95% CI -854 to -117). The composite outcome of MACE and mortality was not statistically different between the 2 groups (Hazard ratio = 0.98, 95% CI 0.50-1.94).

Conclusion

Our study did not demonstrate a beneficial effect of vitamin K2 in reducing progression of VC in this population at the studied dose and duration.

The biological responses of vitamin K2: A comprehensive review

Vitamin K1 (VitK1) and Vitamin K2 (VitK2), two important naturally occurring micronutrients in the VitK family, found, respectively, in green leafy plants and algae (VitK1) and animal and fermented foods (VitK2). The present review explores the multiple biological functions of VitK2 from recently published in vitro and in vivo studies, including promotion of osteogenesis, prevention of calcification, relief of menopausal symptoms, enhancement of mitochondrial energy release, hepato- and neuro-protective effects, and possible use in treatment of coronavirus disease. The mechanisms of action associated with these biological effects are also explored. Overall, the findings presented here suggest that VitK, especially VitK2, is an important nutrient family for the normal functioning of human health. It acts on almost all major body systems and directly or indirectly participates in and regulates hundreds of physiological or pathological processes. However, as biological and clinical data are still inconsistent and conflicting, more in-depth investigations are warranted to elucidate its potential as a therapeutic strategy to prevent and treat a range of disease conditions.

Vitamin K and vascular calcification in chronic kidney disease: An update of current evidence

Vascular calcification, characterized by calcium deposition in the intimal and medial layers of the arterial wall, is frequently encountered in patients with chronic kidney disease (CKD) and leads to an enhanced risk of adverse cardiovascular (CV) outcomes. However, the underlying complex pathophysiology remains incompletely understood. Recently, Vitamin K supplementation aimed at correcting Vitamin K deficiency highly prevalent in CKD holds great promise to mitigate the progression of vascular calcification. This article discusses the functional Vitamin K status in CKD, the pathophysiology linking Vitamin K deficiency and vascular calcification, and reviews current literature from animal models, observational studies, and clinical trials across the different spectrum of CKD. While favorable effects of Vitamin K on vascular calcification and CV outcomes are suggested in animal and observational studies, most recently published clinical trials investigating the effects of Vitamin K on vascular health failed to support the beneficial role of Vitamin K supplementation, despite improving the functional status of Vitamin K. We address the potential reasons for these discrepancies and provide further perspective on Vitamin K research in CKD.

Vascular Calcification in Chronic Kidney Disease: An Update and Perspective

Chronic kidney disease is a devastating condition resulting from irreversible loss of nephron numbers and function and leading to end-stage renal disease and mineral disorders. Vascular calcification, an ectopic deposition of calcium-phosphate salts in blood vessel walls and heart valves, is an independent risk factor of cardiovascular morbidity and mortality in chronic kidney disease. Moreover, aging and related metabolic disorders are essential risk factors for chronic kidney disease and vascular calcification. Marked progress has been recently made in understanding and treating vascular calcification in chronic kidney disease. However, there is a paucity of systematic reviews summarizing this progress, and investigating unresolved issues is warranted. In this systematic review, we aimed to overview the underlying mechanisms of vascular calcification in chronic kidney diseases and discuss the impact of chronic kidney disease on the pathophysiology of vascular calcification. Additionally, we summarized potential clinical diagnostic biomarkers and therapeutic applications for vascular calcification with chronic kidney disease. This review may offer new insights into the pathogenesis, diagnosis, and therapeutic intervention of vascular calcification.

Role of Vitamin K in Chronic Kidney Disease: A Focus on Bone and Cardiovascular Health

Chronic kidney disease (CKD) is commonly associated with vitamin K deficiency. Some of the serious complications of CKD are represented by cardiovascular disease (CVD) and skeletal fragility with an increased risk of morbidity and mortality. A complex pathogenetic link between hormonal and ionic disturbances, bone tissue and metabolism alterations, and vascular calcification (VC) exists and has been defined as chronic kidney disease–mineral and bone disorder (CKD-MBD). Poor vitamin K status seems to have a key role in the progression of CKD, but also in the onset and advance of both bone and cardiovascular complications. Three forms of vitamin K are currently known: vitamin K1 (phylloquinone), vitamin K2 (menaquinone), and vitamin K3 (menadione). Vitamin K plays different roles, including in activating vitamin K-dependent proteins (VKDPs) and in modulating bone metabolism and contributing to the inhibition of VC. This review focuses on the biochemical and functional characteristics of vitamin K vitamers, suggesting this nutrient as a possible marker of kidney, CV, and bone damage in the CKD population and exploring its potential use for promoting health in this clinical setting. Treatment strategies for CKD-associated osteoporosis and CV disease should include vitamin K supplementation. However, further randomized clinical studies are needed to assess the safety and the adequate dosage to prevent these CKD complications.

Greater Dietary Inflammatory Potential Is Associated With Higher Likelihood of Abdominal Aortic Calcification

Aims: We aimed to assess the association between dietary inflammation index (DII) and abdominal aortic calcification (AAC) in US adults aged ≥40 years. Methods: Data were obtained from the 2013-2014 National Health and Nutrition Examination Survey (NHANES). Participants who were <40 years old and missing the data of DII and AAC were excluded. DII was calculated based on a 24-h dietary recall interview for each participant. AAC score was quantified by assessing lateral spine images and severe AAC was defined as AAC score >6. Weighted multivariable regression analysis and subgroup analysis were preformed to estimate the independent relationship between DII with AAC score and severe AAC. Results: A total of 2,897 participants were included with the mean DII of -0.17 ± 2.80 and the mean AAC score of 1.462 ± 3.290. The prevalence of severe AAC was 7.68% overall, and participants in higher DII quartile tended to have higher rates of severe AAC (Quartile 1: 5.03%, Quartile 2: 7.44%, Quartile 3: 8.38%, Quartile 4: 10.46%, p = 0.0016). A positive association between DII and AAC score was observed (β = 0.055, 95% CI: 0.010, 0.101, p = 0.01649), and higher DII was associated with an increased risk of severe AAC (OR = 1.067, 95% CI: 1.004, 1.134, p = 0.03746). Subgroup analysis indicated that this positive association between DII and AAC was similar in population with differences in gender, age, BMI, hypertension status, and diabetes status and could be appropriate for different population settings. Conclusion: Higher pro-inflammatory diet was associated with higher AAC score and increased risk of severe AAC. Anti-inflammatory dietary management maybe beneficial to reduce the risk of AAC.

The Australian Calciphylaxis Registry: reporting clinical features and outcomes of patients with calciphylaxis

BACKGROUND

Calciphylaxis is a rare disease, predominantly affecting patients with chronic kidney disease (CKD) and associated with significant morbidity and mortality due to progressive cutaneous calcification, necrotic ulceration and infection. Clinical registries have been established to better understand the risk factors, optimal treatments and disease outcomes of calciphylaxis.

METHODS

We established a prospective, Internet-based clinical registry for the online notification of calciphylaxis cases in Australia. Seven institutions participated, with data recorded on patient characteristics, biochemical parameters, treatments and disease outcomes.

RESULTS

Between 2014 and 2019, 47 cases of calciphylaxis were registered. The mean patient age was 66 ± 11 years and body mass index was 35 ± 9 kg/m2, with a higher proportion of females (51%). Eighty-seven percent of patients had end-stage kidney disease (ESKD), with 61% on hemodialysis or hemodiafiltration, with a median dialysis vintage of 4.8 [interquartile range (IQR) 1.7-7.4)] years. Five patients had CKD not requiring dialysis and two were kidney transplant recipients. Diabetes was present in 76% of patients and the cause of ESKD in 60%; 34% received vitamin K antagonists (VKAs) before diagnosis. The median parathyroid hormone level at diagnosis was 32 (IQR 14-50) pmol/L. The most common site of calciphylaxis was the lower limbs (63%), with 19% of patients having more than one area involved. Ten patients (22%) had a resolution of calciphylaxis and 25 died, with 50% mortality at a median of 1.6 (IQR 0.2-2.5) years from diagnosis.

CONCLUSIONS

The Australian Calciphylaxis Registry highlights risk factors for calciphylaxis, including diabetes, obesity and VKA use. Resolution of calciphylaxis is uncommon despite multimodal therapy and mortality from calciphylaxis in the first year following diagnosis remains high.

Vitamin K for the Treatment of Cardiovascular Disease in End-Stage Renal Disease Patients: Is there Hope?

In Chronic Kidney Disease, vascular calcification (VC) is highly prevalent even at early stages and is gradually enhanced, along with disease progression to End-Stage Renal Disease (ESRD). The calcification pattern in uremia includes all types of mineralization and contributes to the heavy cardiovascular (CV) burden that is common in these patients. Ectopic mineralization is the result of the imbalance between inhibitors and promoters of vascular calcification, with the latter overwhelming the former. The most powerful, natural inhibitor of calcification is Matrix Gla Protein (MGP), a small vitamin K dependent protein, secreted by chondrocytes and vascular smooth muscle cells. In uremia, MGP was reported as the only molecule able to reverse VC by "sweeping" calcium and hydroxyapatite crystals away from the arterial wall. To become biologically active, this protein needs to undergo carboxylation and phosphorylation, reactions highly dependent on vitamin K status. The inactive form of MGP reflects the deficiency of vitamin K and has been associated with CV events and mortality in ESRD patients. During the past decade, vitamin K status has emerged as a novel risk factor for vascular calcification and CV disease in various populations, including dialysis patients. This review presents evidence regarding the association between vitamin K and CV disease in ESRD patients, which are prone to atherosclerosis and atheromatosis.

The Impairment in Kidney Function in the Oral Anticoagulation Era. A Pathophysiological Insight

The need for anticoagulation in patients with atrial fibrillation (AF) is fundamental to prevent thromboembolic events. Direct oral anticoagulants (DOACs) recently demonstrated to be superior, or at least equal, to Warfarin in reducing the risk for stroke/systemic embolism and preventing major bleeding and intracranial hemorrhages. The AF population often suffers from chronic kidney disease (CKD). Indeed, the relationship between AF and renal function is bidirectional: AF can trigger kidney failure, while kidney impairment can promote alterations able to enhance AF. Therefore, there are concerns regarding prescriptions of anticoagulants to patients with AF and CKD. The worsening in kidney function can be effectively due to anticoagulants administration. Warfarin has been recognized to promote acute kidney injury in case of excessive anticoagulation levels. Nevertheless, further mechanisms can induce the chronic worsening of renal function, thus leading to terminal kidney failure as observed in post-hoc analysis from registration trials and dedicated observational studies. By contrast, DOACs seem to protect kidneys from injuries more efficiently than Warfarin, although they still continue to play a role in promoting some kidney lesions. However, the exact mechanisms remain unknown. This narrative review aimed to discuss the influence of oral anticoagulants on renal impairment as well as to overview potential pathophysiological mechanisms related to this clinical complication.

Vitamin K role in mineral and bone disorder of chronic kidney disease

Vitamin K is a key cofactor for the activation of proteins involved in blood coagulation, apoptosis, bone mineralization regulation, and vessel health. Scientific evidence shows an important role of activated osteocalcin and matrix-Gla protein in bone and vessels, markedly affected along the course of chronic kidney disease (CKD). In fact, CKD corresponds to an unique condition of vitamin K deficiency caused by dietary restriction, intestinal dysfunction, and impaired vitamin K recycling. Clinical data suggest that vitamin K status can be modulated and this prompts us to speculate whether patients with CKD might benefit from vitamin K supplementation. However, as important as whether the improvement in vitamin K status would be able to result in better bone quality, less vascular calcification, and lower mortality rates, several issues need to be clarified. These include better standardized methods for measuring vitamin K levels, and definition of the optimal concentration range for supplementation in different subgroups. Here, we review the literature data concerning the impact of vitamin K deficiency and supplementation on CKD-associated mineral and bone disorders (CKD-MBD). We present and discuss the available evidence from basic science and clinical studies, and highlight perspectives for further research.

Vitamin K1 Inhibition of Renal Crystal Formation through Matrix Gla Protein in the Kidney

BACKGROUND AND OBJECTIVES

Vitamin K (VK) plays a major role in modifying the binding of calcium in bones and blood vessels. Understanding the effect of VK on crystal formation in the kidney would contribute to advancing the treatment and prevention of kidney stones.

METHODS

Rats were treated with vitamin K1 (VK1) for 8 weeks. VK1 levels were detected and crystal formation were observed. HK2 cells were exposed to calcium oxalate monohydrate crystals. Apoptosis and cell viability were detected. Crystal deposition was analyzed using atomic absorption assay. The adenovirus vectors expressing matrix Gla protein (MGP) and siMGP were constructed to elucidate the effect and mechanism of VK1 on crystal formation. MGP expression in vivo and in vitro was analyzed by Western blot. The mRNA levels of monocyte chemoattractant protein-1 (MCP-1) and collagen I was measured by semiquantitative RT-PCR.

RESULTS

The concentrations of VK1 in whole blood and kidney tissues rose under treatment with VK1. Crystal formation was inhibited from the second to the 6th week, the frequency and quality of crystal formation decreased significantly, and the location of crystal formation was limited to a greater extent in the rats treated by VK1 compared to the control group. Warfarin treatment in the crystals-exposed HK2 cells significantly increased the number of crystals adhering to cells and the number of apoptotic cells and reduced cell viability. VK1 treatment reversed warfarin's above influence. VK1 inhibited the upregulations of MCP-1 and collagen I in kidney tissues under crystal load. VK1 treatment increased MGP expression in vivo and in vitro, and MGP is necessary for VK1 to play a role in crystal deposition in cells.

CONCLUSIONS

VK1 treatment can inhibit the formation of renal crystals in vivo. VK1 increases MGP expression and functions through MGP to reduce crystal deposition in cells and provide cell protection. Our findings suggest that VK1 treatment could be a potential strategy for the treatment and prevention of nephrolithiasis.

Vitamin K in Chronic Kidney Disease

Vitamin K is a composite term referring to a group of fat-soluble vitamins that function as a cofactor for the enzyme γ-glutamyl carboxylase (GGCX), which activates a number of vitamin K-dependent proteins (VKDPs) involved in haemostasis and vascular and bone health. Accumulating evidence demonstrates that chronic kidney disease (CKD) patients suffer from subclinical vitamin K deficiency, suggesting that this represents a population at risk for the biological consequences of poor vitamin K status. This deficiency might be caused by exhaustion of vitamin K due to its high requirements by vitamin K-dependent proteins to inhibit calcification.

Emerging Role of Vitamins D and K in Modulating Uremic Vascular Calcification: The Aspect of Passive Calcification

Vascular calcification is a critical complication in patients with chronic kidney disease (CKD) because it is predictive of cardiovascular events and mortality. In addition to the traditional mechanisms associated with endothelial dysfunction and the osteoblastic transformation of vascular smooth muscle cells (VSMCs), the regulation of calcification inhibitors, such as calciprotein particles (CPPs) and matrix vesicles plays a vital role in uremic vascular calcification in CKD patients because of the high prevalence of vitamin K deficiency. Vitamin K governs the gamma-carboxylation of matrix Gla protein (MGP) for inhibiting vascular calcification, and the vitamin D binding protein receptor is related to vitamin K gene expression. For patients with chronic kidney disease, adequate use of vitamin D supplements may play a role in vascular calcification through modulation of the calciprotein particles and matrix vesicles (MVs).

Mineral and bone disorders in conventional hemodialysis: Challenges and solutions

Despite the advent of cinacalcet and noncalcium-containing phosphate binders, controlling the progression of vascular calcification (VC) is still challenging. Recent reports demonstrate that carbamylation driven by high urea concentration aggravates VC, suggesting the importance of adequate dialysis in retarding its progression. Theoretically, other promising measures include the use of iron-based phosphate binders, vitamin K, and magnesium supplements, which should be investigated in future randomized controlled trials (RCTs), ideally with hard outcomes. While incidence of hip fracture in patients on dialysis is decreasing in the United States and Japan (possibly owing to better control of PTH levels by cinacalcet) it remains much higher than that in the general population. Many drugs used in the treatment of osteoporosis, including bisphosphonate, raloxifene, denosumab, and teriparatide can, under specific conditions, increase bone mineral density (BMD), which is associated with a lower fracture rate. However, the efficacy of these drugs in reducing the fracture rate remains to be proven in hemodialysis (HD) patients, given their adverse effects such as severe hypocalcemia and resultant worsening of secondary hyperparathyroidism. Some clinical studies have shown that cinacalcet, lanthanum carbonate, and sevelamer reduce mortality in elderly patients on HD, suggesting the benefits of reducing PTH and serum phosphate levels. However, the target ranges of PTH and phosphate levels are based solely on observational studies. This is also the case when treating low PTH levels by decreasing vitamin D or calcium load. RCTs with hard clinical endpoints comparing different targets are necessary in the future.

Current and potential therapeutic strategies for the management of vascular calcification in patients with chronic kidney disease including those on dialysis

Patients with CKD have accelerated vascular stiffening contributing significantly to excess cardiovascular morbidity and mortality. Much of the arterial stiffening is thought to involve vascular calcification (VC), but the pathogenesis of this phenomenon is complex, resulting from a disruption of the balance between promoters and inhibitors of calcification in a uremic milieu, along with derangements in calcium and phosphate metabolic pathways. Management of traditional cardiovascular risk factors to reduce VC may be influential but has not been shown to significantly improve mortality. Control of mineral metabolism may potentially reduce the burden of VC, although using conventional approaches of restricting dietary phosphate, administering phosphate binders, and use of active vitamin D and calcimimetics, remains controversial because recommended biochemical targets are hard to achieve and clinical relevance hard to define. Increasing time on dialysis is perhaps another therapy with potential effectiveness in this area. Despite current treatments, cardiovascular morbidity and mortality remain high in this group. Novel therapies for addressing VC include magnesium and vitamin K supplementation, which are currently being investigated in large randomized control trials. Other therapeutic targets include crystallization inhibitors, ligand trap for activin receptors and BMP-7. This review summarizes current treatment strategies and therapeutic targets for the future management of VC in patients with CKD.

Association between Dietary Intake and Coronary Artery Calcification in Non-Dialysis Chronic Kidney Disease: The PROGREDIR Study

Coronary artery calcification (CAC) is a widespread condition in chronic kidney disease (CKD). Diet may play an important role in CAC, but this role is not clear. This study evaluated the association between macro-and micronutrient intakes and CAC in non-dialysis CKD patients. We analyzed the baseline data from 454 participants of the PROGREDIR study. Dietary intake was evaluated by a food frequency questionnaire. CAC was measured by computed tomography. After exclusion of participants with a coronary stent, 373 people remained for the analyses. The highest tertile of CAC was directly associated with the intake of phosphorus, calcium and magnesium. There was a higher intake of pantothenic acid and potassium in the second tertile. After adjustments for confounding variables, the intake of pantothenic acid, phosphorus, calcium and potassium remained associated with CAC in the generalized linear mixed models. In order to handle the collinearity between these nutrients, we used the LASSO (least absolute shrinkage and selection operator) regression to evaluate the nutrients associated with CAC variability. In this approach, the nutrients that most explained the variance of CAC were phosphorus, calcium and potassium. Prospective studies are needed to confirm these findings and assess the role of interventions regarding these micronutrients on CAC prevention and progression.