The role of vitamin K and its related compounds in Mendelian and acquired ectopic mineralization disorders

Ectopic mineralization disorders comprise a broad spectrum of inherited or acquired diseases characterized by aberrant deposition of calcium crystals in multiple organs, such as the skin, eyes, kidneys, and blood vessels. Although the precise mechanisms leading to ectopic calcification are still incompletely known to date, various molecular targets leading to a disturbed balance between pro- and anti-mineralizing pathways have been identified in recent years. Vitamin K and its related compounds, mainly those post-translationally activated by vitamin K-dependent carboxylation, may play an important role in the pathogenesis of ectopic mineralization as has been demonstrated in studies on rare Mendelian diseases, but also on highly prevalent disorders, like vascular calcification. This narrative review compiles and summarizes the current knowledge regarding the role of vitamin K, its metabolism, and associated compounds in the pathophysiology of both monogenic ectopic mineralization disorders, like pseudoxanthoma elasticum or Keutel syndrome, as well as acquired multifactorial diseases, like chronic kidney disease. Clinical and molecular aspects of the various disorders are discussed according to the state-of-the-art, followed by a comprehensive literature review regarding the role of vitamin K in molecular pathophysiology and as a therapeutic target in both human and animal models of ectopic mineralization disorders

Pseudoxanthoma elasticum (PXE) patients and heterozygous carriers have decreased plasma PPi levels which correlate with the (cardio)vascular phenotype.

Introduction Pseudoxanthoma elasticum (PXE) is an autosomal recessive soft tissue calcification disorder caused by biallelic mutations in ABCC6. In patients decreased levels of inorganic pyrophosphate (PPi) have been linked to the formation of ectopic mineralizations. However, no data has been reported on PPi levels in heterozygous carriers. Moreover, it is unknown whether a correlation exists between PPi levels and the ABCC6 genotype or the phenotype of patients. Methods A total of 127 citrated blood samples (91 from 62 PXE patients, 22 from 21 carriers and 14 from 14 controls) was collected and processed. Plasma PPi levels were measured via ATPase luminescence assays and samples were internally calibrated. The ABCC6 gene was screened for variants. The diagnosis of PXE was confirmed by the presence of 2 (likely) pathogenic variants (scored as C3 to C5 according to Verschuere et al. 2020) and/or histopathological changes. PXE phenotypes were assessed using the Phenodex scoring (PS) system at the time the first blood sample was obtained for a patient. Two sets of data were analyzed using SPSS26. First an analysis was performed where all available samples were considered [Bulk]. Concomitantly, a smaller subset (i.e. the samples obtained at Phenodex scoring [Single]) was analyzed. Differences in age, sex and PPi levels between the 3 cohorts were analyzed via ANOVA and T-Test. Correlations between PPi, PS, age and sex were analyzed via Spearman’s correlation analysis. After samples were subdivided based on 3 mutation archetypes: erroneous mRNA transcript (D: deletion, frameshift, splicing), nonsense (N) and missense (M) variants, genotype-PPi correlations were assessed via multiple ANOVA analyses based on more stringent variant selection (C3 - C5, C3 [Subset Likely Pathogenic] - C5, C4 - C5, C5). Results Compared to controls, patients and carriers had respectively ±49% and ±22% less PPi (P<0.001), though overlap in the sample ranges exists between the groups. Interestingly, PPi levels were lower in males compared to females in PXE patients (Bulk: P=0.011; Single: P=0.071), but not in the other cohorts. No significant differences in age between cohorts were observed; however, in the patient cohort PPi levels increased significantly with age (P=0.0015, r=0.279). Moreover, a significant inverse correlation between PPi levels and cardiac PS scores was identified (P=0.041, r=-0.263) as well as a weak inverse association between PPi and vascular PS (P=0.09). No correlation was found with skin or eye symptoms. A significant difference in PPi levels between D+M and N+M clusters was found during bulk, but not single, analysis (P<0.01). Conclusion PPi plasma levels are significantly decreased in patients and carriers and may thus also contribute to the subclinical or partial phenotype seen in the latter. Importantly, there is a region of overlap between both and with controls, suggesting PPi not to be the only relevant pro-mineralization factor in at least a subset of PXE patients. In PXE patients PPi levels appear to be influenced by sex and - to some extent unexpectedly - significantly increase with age. Whether there is a solid correlation with the ABCC6 genotype remains to be confirmed. Though unrelated to skin and eye disease, the PPi levels are inversely correlated with cardio(vascular) burden in PXE patients, making PPi promising as a cardiovascular biomarker in PXE. Reference Verschuere et al. 2020: PMID 3287393

Primaire ectopische mineralisatieaandoeningen : van (vaat)verkalking tot syndroom

Ectopic mineralization is a pathologic process resulting in inappropriate biomineralization of soft tissues such as the skin and blood vessels. It can be found in frequent western disorders such as chronic kidney disease and diabetes mellitus, though it is also part of a spectrum of primary genetic mineralization disorders such as pseudoxanthoma elasticum (PXE). These heritable disorders are associated with significant morbidity and mortality due to extensive ectopic mineralization in a variety of tissues. Early diagnosis and multidisciplinary treatment and follow-up in a reference center is of the uttermost importance in order to prevent severe or life-threatening complications. In this review, the clinical presentation, diagnosis and management of primary ectopic mineralization disorders is described

The Role of Vitamin K and Its Related Compounds in Mendelian and Acquired Ectopic Mineralization Disorders

Ectopic mineralization disorders comprise a broad spectrum of inherited or acquired diseases characterized by aberrant deposition of calcium crystals in multiple organs, such as the skin, eyes, kidneys, and blood vessels. Although the precise mechanisms leading to ectopic calcification are still incompletely known to date, various molecular targets leading to a disturbed balance between pro- and anti-mineralizing pathways have been identified in recent years. Vitamin K and its related compounds, mainly those post-translationally activated by vitamin K-dependent carboxylation, may play an important role in the pathogenesis of ectopic mineralization as has been demonstrated in studies on rare Mendelian diseases, but also on highly prevalent disorders, like vascular calcification. This narrative review compiles and summarizes the current knowledge regarding the role of vitamin K, its metabolism, and associated compounds in the pathophysiology of both monogenic ectopic mineralization disorders, like pseudoxanthoma elasticum or Keutel syndrome, as well as acquired multifactorial diseases, like chronic kidney disease. Clinical and molecular aspects of the various disorders are discussed according to the state-of-the-art, followed by a comprehensive literature review regarding the role of vitamin K in molecular pathophysiology and as a therapeutic target in both human and animal models of ectopic mineralization disorders

Mitochondrial Dysfunction and Oxidative Stress in Hereditary Ectopic Calcification Diseases

Ectopic calcification (EC) is characterized by an abnormal deposition of calcium phosphate crystals in soft tissues such as blood vessels, skin, and brain parenchyma. EC contributes to significant morbidity and mortality and is considered a major health problem for which no effective treatments currently exist. In recent years, growing emphasis has been placed on the role of mitochondrial dysfunction and oxidative stress in the pathogenesis of EC. Impaired mitochondrial respiration and increased levels of reactive oxygen species can be directly linked to key molecular pathways involved in EC such as adenosine triphosphate homeostasis, DNA damage signaling, and apoptosis. While EC is mainly encountered in common diseases such as diabetes mellitus and chronic kidney disease, studies in rare hereditary EC disorders such as pseudoxanthoma elasticum or Hutchinson&ndash;Gilford progeria syndrome have been instrumental in identifying the precise etiopathogenetic mechanisms leading to EC. In this narrative review, we describe the current state of the art regarding the role of mitochondrial dysfunction and oxidative stress in hereditary EC diseases. In-depth knowledge of aberrant mitochondrial metabolism and its local and systemic consequences will benefit the research into novel therapies for both rare and common EC disorders

Mitochondrial Dysfunction and Oxidative Stress in Hereditary Ectopic Calcification Diseases

Ectopic calcification (EC) is characterized by an abnormal deposition of calcium phosphate crystals in soft tissues such as blood vessels, skin, and brain parenchyma. EC contributes to significant morbidity and mortality and is considered a major health problem for which no effective treatments currently exist. In recent years, growing emphasis has been placed on the role of mitochondrial dysfunction and oxidative stress in the pathogenesis of EC. Impaired mitochondrial respiration and increased levels of reactive oxygen species can be directly linked to key molecular pathways involved in EC such as adenosine triphosphate homeostasis, DNA damage signaling, and apoptosis. While EC is mainly encountered in common diseases such as diabetes mellitus and chronic kidney disease, studies in rare hereditary EC disorders such as pseudoxanthoma elasticum or Hutchinson–Gilford progeria syndrome have been instrumental in identifying the precise etiopathogenetic mechanisms leading to EC. In this narrative review, we describe the current state of the art regarding the role of mitochondrial dysfunction and oxidative stress in hereditary EC diseases. In-depth knowledge of aberrant mitochondrial metabolism and its local and systemic consequences will benefit the research into novel therapies for both rare and common EC disorders

Minocycline counteracts ectopic calcification in a murine model of pseudoxanthoma elasticum : a proof-of-concept study

Pseudoxanthoma elasticum (PXE) is an intractable Mendelian disease characterized by ectopic calcification in skin, eyes and blood vessels. Recently, increased activation of the DNA damage response (DDR) was shown to be involved in PXE pathogenesis, while the DDR/PARP1 inhibitor minocycline was found to attenuate aberrant mineralization in PXE cells and zebrafish. In this proof-of-concept study, we evaluated the anticalcifying properties of minocycline in Abcc6−/− mice, an established mammalian PXE model. Abcc6−/− mice received oral minocycline supplementation (40 mg/kg/day) from 12 to 36 weeks of age and were compared to untreated Abcc6−/− and Abcc6+/+ siblings. Ectopic calcification was evaluated using X-ray microtomography with three-dimensional reconstruction of calcium deposits in muzzle skin and Yasue’s calcium staining. Immunohistochemistry for the key DDR marker H2AX was also performed. Following minocycline treatment, ectopic calcification in Abcc6−/− mice was significantly reduced (−43.4%, p &lt; 0.0001) compared to untreated Abcc6−/− littermates. H2AX immunostaining revealed activation of the DDR at sites of aberrant mineralization in untreated Abcc6−/− animals. In conclusion, we validated the anticalcifying effect of minocycline in Abcc6−/− mice for the first time. Considering its favorable safety profile in humans and low cost as a generic drug, minocycline may be a promising therapeutic compound for PXE patients

The Role of Vitamin K and Its Related Compounds in Mendelian and Acquired Ectopic Mineralization Disorders

Ectopic mineralization disorders comprise a broad spectrum of inherited or acquired diseases characterized by aberrant deposition of calcium crystals in multiple organs, such as the skin, eyes, kidneys, and blood vessels. Although the precise mechanisms leading to ectopic calcification are still incompletely known to date, various molecular targets leading to a disturbed balance between pro- and anti-mineralizing pathways have been identified in recent years. Vitamin K and its related compounds, mainly those post-translationally activated by vitamin K-dependent carboxylation, may play an important role in the pathogenesis of ectopic mineralization as has been demonstrated in studies on rare Mendelian diseases, but also on highly prevalent disorders, like vascular calcification. This narrative review compiles and summarizes the current knowledge regarding the role of vitamin K, its metabolism, and associated compounds in the pathophysiology of both monogenic ectopic mineralization disorders, like pseudoxanthoma elasticum or Keutel syndrome, as well as acquired multifactorial diseases, like chronic kidney disease. Clinical and molecular aspects of the various disorders are discussed according to the state-of-the-art, followed by a comprehensive literature review regarding the role of vitamin K in molecular pathophysiology and as a therapeutic target in both human and animal models of ectopic mineralization disorders

From membrane to mineralization : the curious case of the ABCC6 transporter

ATP‐binding cassette subfamily C member 6 gene/protein (ABCC6) is an ATP‐dependent transmembrane transporter predominantly expressed in the liver and the kidney. ABCC6 first came to attention in human medicine when it was discovered in 2000 that mutations in its encoding gene, ABCC6, caused the autosomal recessive multisystemic mineralization disease pseudoxanthoma elasticum (PXE). Since then, the physiological and pathological roles of ABCC6 have been the subject of intense research. In the last 20 years, significant findings have clarified ABCC6 structure as well as its physiological role in mineralization homeostasis in humans and animal models. Yet, several facets of ABCC6 biology remain currently incompletely understood, ranging from the precise nature of its substrate(s) to the increasingly complex molecular genetics. Nonetheless, advances in our understanding of pathophysiological mechanisms causing mineralization lead to several treatment options being suggested or already tested in pilot clinical trials for ABCC6 deficiency. This review highlights current knowledge of ABCC6 and the challenges ahead, particularly the attempts to translate basic science into clinical practice