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ObjectiveThis study assessed whether apolipoprotein CIII-lipoprotein(a) complexes (ApoCIII-Lp(a)) associate with progression of calcific aortic valve stenosis (AS).MethodsImmunostaining for ApoC-III was performed in explanted aortic valve leaflets in 68 patients with leaflet pathological grades of 1–4. Assays measuring circulating levels of ApoCIII-Lp(a) complexes were measured in 218 patients with mild–moderate AS from the AS Progression Observation: Measuring Effects of Rosuvastatin (ASTRONOMER) trial. The progression rate of AS, measured as annualised changes in peak aortic jet velocity (Vpeak), and combined rates of aortic valve replacement (AVR) and cardiac death were determined. For further confirmation of the assay data, a proteomic analysis of purified Lp(a) was performed to confirm the presence of apoC-III on Lp(a).ResultsImmunohistochemically detected ApoC-III was prominent in all grades of leaflet lesion severity. Significant interactions were present between ApoCIII-Lp(a) and Lp(a), oxidised phospholipids on apolipoprotein B-100 (OxPL-apoB) or on apolipoprotein (a) (OxPL-apo(a)) with annualised Vpeak (all p<0.05). After multivariable adjustment, patients in the top tertile of both apoCIII-Lp(a) and Lp(a) had significantly higher annualised Vpeak (p<0.001) and risk of AVR/cardiac death (p=0.03). Similar results were noted with OxPL-apoB and OxPL-apo(a). There was no association between autotaxin (ATX) on ApoB and ATX on Lp(a) with faster progression of AS. Proteomic analysis of purified Lp(a) showed that apoC-III was prominently present on Lp(a).ConclusionApoC-III is present on Lp(a) and in aortic valve leaflets. Elevated levels of ApoCIII-Lp(a) complexes in conjunction with Lp(a), OxPL-apoB or OxPL-apo(a) identify patients with pre-existing mild–moderate AS who display rapid progression of AS and higher rates of AVR/cardiac death.Trial registration NCT00800800.

Pyrophosphate is a potent inhibitor of medial vascular calcification where its level is controlled by hydrolysis via a tissue-nonspecific alkaline phosphatase (TNAP). We sought to determine if increased TNAP activity could explain the pyrophosphate deficiency and vascular calcification seen in renal failure. TNAP activity increased twofold in intact aortas and in aortic homogenates from rats made uremic by feeding adenine or by 5/6 nephrectomy. Immunoblotting showed an increase in protein abundance but there was no increase in TNAP mRNA assessed by quantitative polymerase chain reaction. Hydrolysis of pyrophosphate by rat aortic rings was inhibited about half by the nonspecific alkaline phosphatase inhibitor levamisole and was reduced about half in aortas from mice lacking TNAP. Hydrolysis was increased in aortic rings from uremic rats and all of this increase was inhibited by levamisole. An increase in TNAP activity and pyrophosphate hydrolysis also occurred when aortic rings from normal rats were incubated with uremic rat plasma. These results suggest that a circulating factor causes pyrophosphate deficiency by regulating TNAP activity and that vascular calcification in renal failure may result from the action of this factor. If proven by future studies, this mechanism will identify alkaline phosphatase as a potential therapeutic target.

This study aimed to determine if delayed sodium 18F-fluoride (Na18F) PET/CT imaging improves quantification of vascular calcification metabolism. Blood-pool activity can disturb the arterial Na18F signal. With time, blood-pool activity declines. Therefore, delayed imaging can potentially improve quantification of vascular calcification metabolism. Twenty healthy volunteers and 18 patients with chest pain were prospectively assessed by triple time-point PET/CT imaging at approximately 45, 90, and 180 minutes after Na18F administration. For each time point, global uptake of Na18F was determined in the coronary arteries and thoracic aorta by calculating the blood-pool-corrected maximum standardized uptake value (cSUVMAX). A target-to-background ratio (TBR) was calculated to determine the contrast resolution at 45, 90, and 180 minutes. Furthermore, we assessed whether the acquisition time-point affected the relation between cSUVMAX and the estimated 10-year risk for fatal cardiovascular disease (SCORE %). Coronary cSUVMAX (P = .533) and aortic cSUVMAX (P = .654) remained similar with time, whereas the coronary TBR (P < .0001) and aortic TBR (P < .0001) significantly increased with time. Even though the contrast resolution improved with time, positive correlations between SCORE % and coronary cSUVMAX (P < .020) and aortic cSUVMAX (P < .005) were observed at all investigated time points. Delayed Na18F PET/CT imaging does not improve quantification of vascular calcification metabolism. Although contrast resolution improves with time, arterial Na18F avidity is invariant to the time between Na18F administration and PET/CT acquisition. Therefore, the optimal PET/CT acquisition time-point to quantify vascular calcification metabolism is achieved as early as 45 minutes after Na18F administration.

The pineal gland is a unique organ that synthesizes melatonin as the signaling molecule of natural photoperiodic environment and as a potent neuronal protective antioxidant. An intact and functional pineal gland is necessary for preserving optimal human health. Unfortunately, this gland has the highest calcification rate among all organs and tissues of the human body. Pineal calcification jeopardizes melatonin’s synthetic capacity and is associated with a variety of neuronal diseases. In the current review, we summarized the potential mechanisms of how this process may occur under pathological conditions or during aging. We hypothesized that pineal calcification is an active process and resembles in some respects of bone formation. The mesenchymal stem cells and melatonin participate in this process. Finally, we suggest that preservation of pineal health can be achieved by retarding its premature calcification or even rejuvenating the calcified gland.

Apoptotic cell death is usually a response to the cell’s microenvironment. In the kidney, apoptosis contributes to parenchymal cell loss in the course of acute and chronic renal injury, but does not trigger an inflammatory response. What distinguishes necrosis from apoptosis is the rupture of the plasma membrane, so necrotic cell death is accompanied by the release of unprocessed intracellular content, including cellular organelles, which are highly immunogenic proteins. The relative contribution of apoptosis and necrosis to injury varies, depending on the severity of the insult. Regulated cell death may result from immunologically silent apoptosis or from immunogenic necrosis. Recent advances have enhanced the most revolutionary concept of regulated necrosis. Several modalities of regulated necrosis have been described, such as necroptosis, ferroptosis, pyroptosis, and mitochondrial permeability transition-dependent regulated necrosis. We review the different modalities of apoptosis, necrosis, and regulated necrosis in kidney injury, focusing particularly on evidence implicating cell death in ectopic renal calcification. We also review the evidence for the role of cell death in kidney injury, which may pave the way for new therapeutic opportunities.

Basal ganglia calcifications could be incidental findings up to 20% of asymptomatic patients undergoing CT or MRI scan. The presence of neuropsychiatric symptoms associated with bilateral basal ganglia calcifications (which could occur in other peculiar brain structures, such as dentate nuclei) identifies a clinical picture defined as Fahr’s Disease. This denomination mainly refers to idiopathic forms in which no metabolic or other underlying causes are identified. Recently, mutations in four different genes (SLC20A2, PDGFRB, PDGFB, and XPR1) were identified, together with novel mutations in the Myogenic Regulating Glycosylase gene, causing the occurrence of movement disorders, cognitive decline, and psychiatric symptoms. On the other hand, secondary forms, also identified as Fahr’s syndrome, have been associated with different conditions: endocrine abnormalities of PTH, such as hypoparathyroidism, other genetically determined conditions, brain infections, or toxic exposure. The underlying pathophysiology seems to be related to an abnormal calcium/phosphorus homeostasis and transportation and alteration of the blood-brain barrier.

Epidemiological and clinical studies over the past decade have firmly established that elevated plasma concentrations of lipoprotein(a) (Lp(a)) are an important, independent and probably causal risk factor for the development of cardiovascular diseases. Whereas a link between Lp(a) levels and atherosclerotic cardiovascular disease (ASCVD) has been appreciated for decades, the role of Lp(a) in calcific aortic valve disease (CAVD) and aortic stenosis has come into focus only in the past 5 years. ASCVD and CAVD are aetiologically distinct but have several risk factors in common and similar pathological processes at the cellular and molecular levels. Oxidized phospholipids, which modify Lp(a) primarily by covalent binding to its unique apolipoprotein(a) (apo(a)) component, might hold the key to Lp(a) pathogenicity and provide a mechanistic link between ASCVD and CAVD. Oxidized phospholipids colocalize with apo(a)–Lp(a) in arterial and aortic valve lesions and directly participate in the pathogenesis of these disorders by promoting endothelial dysfunction, lipid deposition, inflammation and osteogenic differentiation, leading to calcification. The advent of potent Lp(a)-lowering therapies provides the opportunity to address directly the causality of Lp(a) in ASCVD and CAVD and, more importantly, to provide both a novel approach to reduce the residual risk of ASCVD and a long-sought medical treatment for CAVD.In this Review, Boffa and Koschinsky discuss the role of lipoprotein(a) (Lp(a)) as a risk factor for atherothrombotic cardiovascular disease and calcific aortic valve disease, highlighting the important function of oxidized phospholipid modifications of Lp(a), which elicit harmful signalling processes in the arterial wall and the valve leaflet, in mediating the effects of this lipoprotein on both disorders.

The membrane protein ANKH was known to prevent pathological mineralization of joints and was thought to export pyrophosphate (PPi) from cells. This did not explain, however, the presence of ANKH in tissues, such as brain, blood vessels and muscle. We now report that in cultured cells ANKH exports ATP, rather than PPi, and, unexpectedly, also citrate as a prominent metabolite. The extracellular ATP is rapidly converted into PPi, explaining the role of ANKH in preventing ankylosis. Mice lacking functional Ank (Ankank/ank mice) had plasma citrate concentrations that were 65% lower than those detected in wild type control animals. Consequently, citrate excretion via the urine was substantially reduced in Ankank/ank mice. Citrate was even undetectable in the urine of a human patient lacking functional ANKH. The hydroxyapatite of Ankank/ank mice contained dramatically reduced levels of both, citrate and PPi and displayed diminished strength. Our results show that ANKH is a critical contributor to extracellular citrate and PPi homeostasis and profoundly affects bone matrix composition and, consequently, bone quality.

Vascular calcification is highly associated with cardiovascular disease mortality, particularly in high-risk patients with diabetes and chronic kidney diseases (CKD). In blood vessels, intimal calcification is associated with atherosclerosis, whereas medial calcification is a nonocclusive process which leads to increased vascular stiffness and reduced vascular compliance. In the valves, calcification of the leaflets can change the mechanical properties of the tissue and result in stenosis. For many decades, vascular calcification has been noted as a consequence of aging. Studies now confirm that vascular calcification is an actively regulated process and shares many features with bone development and metabolism. This review provides an update on the mechanisms of vascular calcification including the emerging roles of the RANK/RANKL/OPG triad, osteoclasts, and microRNAs. Potential treatments adapted from osteoporosis and CKD treatments that are under investigation for preventing and/or regressing vascular calcification are also reviewed.

Pseudoxanthoma Elasticum (PXE) is a rare disease caused by loss of function of the ATP-binding cassette C (ABC) member 6 ( Abcc6 ) gene and characterized by ectopic calcification of multiple tissues, but the physiological reasons underlying ectopic calcification in PXE remain unclear. In a murine model of Abcc6 -deficient PXE in which animals developed robust cardiac calcification after heart injury, we show the critical importance of the liver in mediating ectopic cardiac calcification. Tissue-specific deletion of Abcc6 in the liver, but not in the heart, was sufficient to cause post-injury cardiac calcification. Metabolomics and gene expression analysis demonstrated deficiencies in nucleotide metabolism, cellular energetics, and defects in cellular respiration underlying ectopic calcification in PXE. Functional abnormalities in cellular respiration in the injured heart were similar in animals with global or liver-specific Abcc6 deficiency, showing that hepatic Abcc6 expression regulated cellular respiration in the injured heart. We show that ectopic calcification in PXE was primarily dystrophic and that treatment with clodronate or etidronate, which prevent the growth of calcium hydroxyapatite mineralization, was sufficient to rescue the phenotype of ectopic cardiac calcification in Abcc6 -deficient states. Taken together, these observations highlight the role of the liver in regulating target tissue metabolic and mitochondrial function in causing ectopic calcification in Abcc6 -deficient states.