Polymorphisms of the human matrix gla protein (MGP) gene, vascular calcification, and myocardial infarction

Exercise-induced redox modulation as a mediator of DNA methylation in health maintenance and disease prevention

The evidence for physical activity (PA) as a major public health preventive approach and a potent medical therapy has increased exponentially in the last decades. The biomolecular mechanisms supporting the associations between PA and/or structured exercise training with health maintenance and disease prevention are not completely characterized. However, increasing evidence pointed out the role of epigenetic modifications in exercise adaptation and health-enhancing PA throughout life, DNA methylation being the most intensely studied epigenetic modification induced by acute and chronic exercise. The current data on the modulation of DNA methylation determined by physically active behavior or exercise interventions points out genes related to energy regulation, mitochondrial function, and biosynthesis, as well as muscle regeneration, calcium signaling pathways, and brain plasticity, all consistent with the known exercise-induced redox signaling and/or reactive oxygen species (ROS) unbalance. Thus, the main focus of this review is to discuss the role of ROS and redox-signaling on DNA methylation profile and its impact on exercise-induced health benefits in humans.

Matrix Gla protein polymorphism rs1800802 is associated with atheroma plaque progression and with cardiovascular events in a chronic kidney disease cohort

Background

Chronic kidney disease (CKD) is associated with increased atherosclerotic burden and higher risk for cardiovascular events (CVE). Atherosclerosis has a significant genetic component and, in CKD, it is influenced by mineral metabolism alterations. Therefore, genetic modifications of mineral metabolism-related proteins could affect atherosclerosis in CKD patients. In the present study we investigated the role of single nucleotide polymorphisms (SNPs) of the matrix gamma-carboxy glutamic acid protein (MGP) on atherosclerosis progression and CVE in a CKD cohort.

Methods

A total of 2187 CKD patients from the Observatorio Nacional de Aterosclerosis en Nefrologia (NEFRONA) study were genotyped for SNPs present in the matrix gamma-carboxy glutamic acid (Gla) protein (MGP) gene. Atheromatosis was detected by vascular ultrasound. Progression of atheromatosis, defined as an increase in territories with plaque, was assessed after 24 months. Patients were followed for 48 months for CVE. Association of SNPs with plaque progression was assessed by logistic regression and their capacity to predict CVE by Cox regression.

Results

Three SNPs of the MGP gene were analyzed. No association of the rs4236 or the rs1800801 SNPs was detected with any of the outcomes. However, patients homozygotes for the minor allele of the rs1800802 SNP showed higher adjusted risk for plaque progression [odds ratio 2.3 (95% confidence interval 1.06-4.9)] and higher risk of suffering a CVE [hazard ratio 2.16 (95% confidence interval 1.13-4.12)] compared with the rest of genotypes. No association of the SNP with total or dp-ucMGP levels was found in a subsample.

Conclusions

The rs1800802 polymorphism of MGP is associated with plaque progression and CVE in CKD patients.

Integrated systems biology approach identifies gene targets for endothelial dysfunction

Endothelial dysfunction (ED) is critical in the development and progression of cardiovascular (CV) disorders, yet effective therapeutic targets for ED remain elusive due to limited understanding of its underlying molecular mechanisms. To address this gap, we employed a systems biology approach to identify potential targets for ED. Our study combined multi omics data integration, with siRNA screening, high content imaging and network analysis to prioritise key ED genes and identify a pro- and anti-ED network. We found 26 genes that, upon silencing, exacerbated the ED phenotypes tested, and network propagation identified a pro-ED network enriched in functions associated with inflammatory responses. Conversely, 31 genes ameliorated ED phenotypes, pointing to potential ED targets, and the respective anti-ED network was enriched in hypoxia, angiogenesis and cancer-related processes. An independent screen with 17 drugs found general agreement with the trends from our siRNA screen and further highlighted DUSP1, IL6 and CCL2 as potential candidates for targeting ED. Overall, our results demonstrate the potential of integrated system biology approaches in discovering disease-specific candidate drug targets for endothelial dysfunction.

Single-cell genomics illustrates heterogeneous phenotypes of myocardial fibroblasts under ischemic insults

Myocardial regenerative strategies are promising where the choice of ideal cell population is crucial for successful translational applications. Herein, we explored the regenerative/repair responses of infarct zone cardiac fibroblast(s) (CF) by unveiling their phenotype heterogeneity at single-cell resolution. CF were isolated from the infarct zone of Yucatan miniswine that suffered myocardial infarction, cultured under simulated ischemic and reperfusion, and grouped into control, ischemia, and ischemia/reperfusion. The single-cell RNA sequencing analysis revealed 19 unique cell clusters suggesting distinct subpopulations. The status of gene expression (log2 fold change (log2 FC) > 2 and log2 FC < -2) was used to define the characteristics of each cluster unveiling with diverse features, including the pro-survival/cardioprotective (Clusters 1, 3, 5, 9, and 18), vasculoprotective (Clusters 2 and 5), anti-inflammatory (Clusters 4 and 17), proliferative (Clusters 4 and 5), nonproliferative (Clusters 6, 8, 11, 16, 17, and 18), proinflammatory (Cluster 6), profibrotic/pathologic (Clusters 8 and 19), antihypertrophic (Clusters 8 and 10), extracellular matrix restorative (Clusters 9 and 12), angiogenic (Cluster 16), and normal (Clusters 7 and 15) phenotypes. Further understanding of these unique phenotypes of CF will provide significant translational opportunities for myocardial regeneration and cardiac management.

Urinary matrix Gla protein is associated with mortality risk in Flemish population: A prospective study

Background

Vascular calcification is strongly related to the risk of mortality and cardiovascular (CV) diseases. In vascular calcification, matrix Gla protein (MGP), a small vitamin K-dependent protein, is an important mineralization inhibitor. Recent studies showed that circulating MGP is associated with mortality risk. However, the longitudinal association between urinary excretion of MGP and all-cause mortality was not established.

Materials and methods

Urinary MGP was measured in 776 randomly recruited Flemish population (mean age: 51.2 years; 50.9% women) at baseline (during 2005–2010) using capillary electrophoresis coupled with mass spectrometry. Plasma inactive MGP [desphospho-uncarboxylated MGP (dp-ucMGP)] levels were quantified in 646 individuals by ELISA kits. Mortality status was ascertained through the Belgian Population Registry until 2016. The longitudinal association with mortality was determined by the multivariate-adjusted Cox proportional hazards regression models. The multivariate linear regression models were used to identify determinants of urinary MGP level.

Results

Over the 9.2 years, 47 (6.06%) participants died, including 15 CV deaths. For a doubling of urinary MGP, the hazard ratios (HRs) were 1.31 (95% CI: 1.01–1.69, P = 0.040) for all-cause mortality and 2.05 (95% CI: 1.11–3.79, P = 0.023) for CV mortality with adjustment for covariates, including estimated glomerular filtration rate and urine microalbumin. The addition of urinary MGP to the basic models improved the reclassification as suggested by the increased net reclassification improvement [64.01% (95% CI: 32.64–98.63)] and integrated discrimination improvement [2.33% (95% CI: 0.24–4.71)]. Circulating inactive MGP, total cholesterol, urine microalbumin, and smoking were significantly associated with urinary MGP levels (P ≤ 0.041), independent of sex and age.

Conclusion

Elevated urinary MGP was associated with an increased risk of all-cause mortality and CV mortality and improved the risk reclassification for all-cause mortality. These findings suggested that urinary MGP might be useful in mortality risk assessment in the general population. However, these observations need to be replicated in larger studies with a longer follow-up time.

Matrix Gla Protein Levels Are Associated With Arterial Stiffness and Incident Heart Failure With Preserved Ejection Fraction

OBJECTIVE

Arterial stiffness is a risk factor for cardiovascular disease, including heart failure with preserved ejection fraction (HFpEF). MGP (matrix Gla protein) is implicated in vascular calcification in animal models, and circulating levels of the uncarboxylated, inactive form of MGP (ucMGP) are associated with cardiovascular disease-related and all-cause mortality in human studies. However, the role of MGP in arterial stiffness is uncertain. Approach and Results: We examined the association of ucMGP levels with vascular calcification, arterial stiffness including carotid-femoral pulse wave velocity (PWV), and incident heart failure in community-dwelling adults from the Framingham Heart Study. To further investigate the link between MGP and arterial stiffness, we compared aortic PWV in age- and sex-matched young (4-month-old) and aged (10-month-old) wild-type and Mgp+/- mice. Among 7066 adults, we observed significant associations between higher levels of ucMGP and measures of arterial stiffness, including higher PWV and pulse pressure. Longitudinal analyses demonstrated an association between higher ucMGP levels and future increases in systolic blood pressure and incident HFpEF. Aortic PWV was increased in older, but not young, female Mgp+/- mice compared with wild-type mice, and this augmentation in PWV was associated with increased aortic elastin fiber fragmentation and collagen accumulation.

CONCLUSIONS

This translational study demonstrates an association between ucMGP levels and arterial stiffness and future HFpEF in a large observational study, findings that are substantiated by experimental studies showing that mice with Mgp heterozygosity develop arterial stiffness. Taken together, these complementary study designs suggest a potential role of therapeutically targeting MGP in HFpEF.

Vitamin K2-a neglected player in cardiovascular health: a narrative review

Vitamin K₂ serves an important role in cardiovascular health through regulation of calcium homeostasis. Its effects on the cardiovascular system are mediated through activation of the anti-calcific protein known as matrix Gla protein. In its inactive form, this protein is associated with various markers of cardiovascular disease including increased arterial stiffness, vascular and valvular calcification, insulin resistance and heart failure indices which ultimately increase cardiovascular mortality. Supplementation of vitamin K₂ has been strongly associated with improved cardiovascular outcomes through its modification of systemic calcification and arterial stiffness. Although its direct effects on delaying the progression of vascular and valvular calcification is currently the subject of multiple randomised clinical trials, prior reports suggest potential improved survival among cardiac patients with vitamin K₂ supplementation. Strengthened by its affordability and Food and Drug Adminstration (FDA)-proven safety, vitamin K₂ supplementation is a viable and promising option to improve cardiovascular outcomes.

Histology and Immunohistochemistry of Radial Arteries Are Suggestive of an Interaction between Calcification and Early Atherosclerotic Lesions in Chronic Kidney Disease

Background and Objectives: recent studies suggest an implication of immune mechanisms in atherosclerotic disease. In this paper, the interaction between inflammation, calcification, and atherosclerosis on the vessel walls of patients with chronic kidney disease (CKD) is described and evaluated. Materials and Methods: patients with stage V CKD, either on pre-dialysis (group A) or on hemodialysis (HD) for at least 2 years (group B), in whom a radiocephalic arteriovenous fistula (RCAVF) was created, were included in the study. The control group included healthy volunteers who received radial artery surgery after an accident. The expressions of inflammatory cells, myofibroblasts, and vascular calcification regulators on the vascular wall were estimated, and, moreover, morphometric analysis was performed. Results: the expressions of CD68(+) cells, matrix carboxyglutamic acid proteins (MGPs), the receptor activator of nuclear factor-kB (RANK) and RANK ligand (RANKL), and osteoprotegerin (OPG), were significantly increased in CKD patients compared to the controls p = 0.02; p = 0.006; p = 0.01; and p = 0.006, respectively. In morphometric analysis, the I/M and L/I ratios had significant differences between CKD patients and the controls 0.3534 ± 0.20 vs. 0.1520 ± 0.865, p = 0.003, and 2.1709 ± 1.568 vs. 4.9958 ± 3.2975, p = 0.03, respectively. The independent variables correlated with the degree of vascular calcification were the intensity of CD34(+), aSMA(+) cells, and OPG, R² = 0.76, p < 0.0001, and, with intima-media thickness (IMT), the severity of RANKL expression R² = 0.3, p < 0.0001. Conclusion: atherosclerosis and vascular calcification in CKD seem to be strongly regulated by an immunological and inflammatory activation on the vascular wall.

SPARC-related modular calcium binding 1 regulates aortic valve calcification by disrupting BMPR-II/p-p38 signalling

Aims

Aortic valve calcification is more prevalent in chronic kidney disease accompanied by hypercalcemia. Secreted protein acidic and rich in cysteine (SPARC)-related modular calcium binding 1 (SMOC1) is a regulator of BMP2 signalling, but the role of SMOC1 in aortic valve calcification under different conditions has not been studied. This study aimed to investigate the roles of SMOC1 in aortic valve calcification under normal and high calcium conditions, focusing on the effects on aortic valve interstitial cells (AVICs).

Methods and results

SMOC1 was expressed by aortic valve endothelial cells and secreted into the extracellular matrix in non-calcific valves and downregulated in calcific aortic valves. In vitro studies demonstrated that HUVEC secreted SMOC1 could enter the cytoplasm of AVICs. Overexpression of SMOC1 attenuated warfarin-induced AVIC calcification but promoted high calcium/phosphate or vitamin D-induced AVIC and aortic valve calcification by regulating BMP2 signalling both in vitro and in vivo. Co-immunoprecipitation revealed that SMOC1 binds to BMP receptor II (BMPR-II) and inhibits BMP2-induced phosphorylation of p38 (p-p38) via amino acids 372–383 of its EF-hand calcium-binding domain. Inhibition of p-p38 by the p38 inhibitor SB203580 blocked the effects of SMOC1 on BMP2 signalling and AVIC calcification induced by high calcium/phosphate medium. In high-calcium-treated AVICs, SMOC1 lost its ability to bind to BMPR-II, but not to caveolin-1, promoting p-p38 and cell apoptosis due to increased expression of BMPR-II and enhanced endocytosis.

Conclusions

These observations support that SMOC1 works as a dual-directional modulator of AVIC calcification by regulating p38-dependent BMP2 signalling transduction according to different extracellular calcium concentrations.

Quantifying dietary vitamin K and its link to cardiovascular health: a narrative review

Cardiovascular disease is the leading cause of death and disability worldwide. Recent work suggests a link between vitamin K insufficiency and deficiency with vascular calcification, a marker of advanced atherosclerosis. Vitamin K refers to a group of fat-soluble vitamins important for blood coagulation, reducing inflammation, regulating blood calcium metabolism, as well as bone metabolism, all of which may play a role in promoting cardiovascular health. Presently, there is a lack of a comprehensive vitamin K database on individual foods, which are required to accurately calculate vitamin K1 and K2 intake for examination in epidemiological studies. This has likely contributed to ambiguity regarding the recommended daily intake of vitamin K, including whether vitamin K1 and K2 may have separate, partly overlapping functions. This review will discuss the presence of: (i) vitamin K1 and K2 in the diet; (ii) the methods of quantitating vitamin K compounds in foods; and (iii) provide an overview of the evidence for the cardiovascular health benefits of vitamin K in observational and clinical trials.

Genome-wide meta-analysis of muscle weakness identifies 15 susceptibility loci in older men and women

Low muscle strength is an important heritable indicator of poor health linked to morbidity and mortality in older people. In a genome-wide association study meta-analysis of 256,523 Europeans aged 60 years and over from 22 cohorts we identify 15 loci associated with muscle weakness (European Working Group on Sarcopenia in Older People definition: n = 48,596 cases, 18.9% of total), including 12 loci not implicated in previous analyses of continuous measures of grip strength. Loci include genes reportedly involved in autoimmune disease (HLA-DQA1 p = 4 × 10-17), arthritis (GDF5 p = 4 × 10-13), cell cycle control and cancer protection, regulation of transcription, and others involved in the development and maintenance of the musculoskeletal system. Using Mendelian randomization we report possible overlapping causal pathways, including diabetes susceptibility, haematological parameters, and the immune system. We conclude that muscle weakness in older adults has distinct mechanisms from continuous strength, including several pathways considered to be hallmarks of ageing.

Matrix Gla protein polymorphism rs1800801 associates with recurrence of ischemic stroke

The MGP single nucleotide polymorphism (SNP) rs1800801 has previously been associated with recurrent ischemic stroke in a Spanish cohort. Here, we tested for association of this SNP with ischemic stroke recurrence in a North American Caucasian cohort. Acute ischemic stroke patients admitted between 10/2009 and 12/2016 at three hospitals within a large healthcare system in the northeastern United States that were enrolled in a healthcare system-wide exome sequencing program were retrospectively reviewed. Patients with recurrent stroke within 1 year after index event were compared to those without recurrence. Of 9,348 suspected acute ischemic strokes admitted between 10/2009 and 12/2016, 1,727 (18.5%) enrolled in the exome-sequencing program. Among those, 1,068 patients had exome sequencing completed and were eligible for inclusion. Recurrent stroke within the first year of stroke was observed in 79 patients (7.4%). In multivariable analysis, stroke prior to the index stroke (OR 9.694, 95% CI 5.793-16.224, p ≤ 0.001), pro-coagulant status (OR = 3.563, 95% CI 1.504-8.443, p = 0.004) and the AA genotype of SNP rs1800801 (OR = 2.408, 95% CI 1.079-4.389, p = 0.004) were independently associated with recurrent stroke within the first year. The AA genotype of the MGP SNP rs1800801 is associated with recurrence within the first year after ischemic stroke in North American Caucasians. Study of stroke subtypes and additional populations will be required to determine if incorporation of allelic status at this SNP into current risk scores improves prediction of recurrent ischemic stroke.

Arterial Stiffness: A Focus on Vascular Calcification and Its Link to Bone Mineralization

This review focuses on the association between vascular calcification and arterial stiffness, highlighting the important genetic factors, systemic and local microenvironmental signals, and underlying signaling pathways and molecular regulators of vascular calcification. Elevated oxidative stress appears to be a common procalcification factor that induces osteogenic differentiation and calcification of vascular cells in a variety of disease conditions such as atherosclerosis, diabetes mellitus, and chronic kidney disease. Thus, the role of oxidative stress and oxidative stress-regulated signals in vascular smooth muscle cells and their contributions to vascular calcification are highlighted. In relation to diabetes mellitus, the regulation of both hyperglycemia and increased protein glycosylation, by AGEs (advanced glycation end products) and O-linked β-N-acetylglucosamine modification, and its role in enhancing intracellular pathophysiological signaling that promotes osteogenic differentiation and calcification of vascular smooth muscle cells are discussed. In the context of chronic kidney disease, this review details the role of calcium and phosphate homeostasis, parathyroid hormone, and specific calcification inhibitors in regulating vascular calcification. In addition, the impact of the systemic and microenvironmental factors on respective intrinsic signaling pathways that promote osteogenic differentiation and calcification of vascular smooth muscle cells and osteoblasts are compared and contrasted, aiming to dissect the commonalities and distinctions that underlie the paradoxical vascular-bone mineralization disorders in aging and diseases.

Association of Genetic Polymorphisms in the Matrix Gla Protein (MGP) Gene with Coronary Artery Disease and Serum MGP Levels

Matrix Gla protein (MGP) is an important regulatory protein for inhibition of calcification in the vessel wall and cartilage. The MGP gene polymorphisms are suspected to increase the risk of extracellular calcification through altering the related gene expression and serum MGP levels. The goal of this study was to examine the correlation between rs4236 (Thr83-Ala), rs12304 (Glu60-X) and rs1800802 (T138-C) polymorphisms of the MGP gene and coronary artery calcification. Serum MGP levels of 168 subjects who had undergone coronary angiography were analyzed along with genotyping of MGP gene polymorphisms. The results indicated that serum MGP levels were significantly associated with rs4236 and rs1800802 polymorphisms of the MGP gene with the occurrence of coronary artery diseases (CAD). Allelic distributions of MGP gene polymorphisms and serum MGP levels, respectively, were not significantly interconnected with the presence of CAD. Our results revealed that serum MGP levels of CAD patients show association with rs4236 and rs1800802 polymorphisms, but serum MGP levels alone do not directly reflect the risk of CAD. The role of MGP genetic variants on formation and progression of arterial calcification should be regarded in cardiovascular diseases.

Genetic Variants Associated with Chronic Kidney Disease in a Spanish Population

Chronic kidney disease (CKD) patients have many affected physiological pathways. Variations in the genes regulating these pathways might affect the incidence and predisposition to this disease. A total of 722 Spanish adults, including 548 patients and 174 controls, were genotyped to better understand the effects of genetic risk loci on the susceptibility to CKD. We analyzed 38 single nucleotide polymorphisms (SNPs) in candidate genes associated with the inflammatory response (interleukins IL-1A, IL-4, IL-6, IL-10, TNF-α, ICAM-1), fibrogenesis (TGFB1), homocysteine synthesis (MTHFR), DNA repair (OGG1, MUTYH, XRCC1, ERCC2, ERCC4), renin-angiotensin-aldosterone system (CYP11B2, AGT), phase-II metabolism (GSTP1, GSTO1, GSTO2), antioxidant capacity (SOD1, SOD2, CAT, GPX1, GPX3, GPX4), and some other genes previously reported to be associated with CKD (GLO1, SLC7A9, SHROOM3, UMOD, VEGFA, MGP, KL). The results showed associations of GPX1, GSTO1, GSTO2, UMOD, and MGP with CKD. Additionally, associations with CKD related pathologies, such as hypertension (GPX4, CYP11B2, ERCC4), cardiovascular disease, diabetes and cancer predisposition (ERCC2) were also observed. Different genes showed association with biochemical parameters characteristic for CKD, such as creatinine (GPX1, GSTO1, GSTO2, KL, MGP), glomerular filtration rate (GPX1, GSTO1, KL, ICAM-1, MGP), hemoglobin (ERCC2, SHROOM3), resistance index erythropoietin (SOD2, VEGFA, MTHFR, KL), albumin (SOD1, GSTO2, ERCC2, SOD2), phosphorus (IL-4, ERCC4 SOD1, GPX4, GPX1), parathyroid hormone (IL-1A, IL-6, SHROOM3, UMOD, ICAM-1), C-reactive protein (SOD2, TGFB1,GSTP1, XRCC1), and ferritin (SOD2, GSTP1, SLC7A9, GPX4). To our knowledge, this is the second comprehensive study carried out in Spanish patients linking genetic polymorphisms and CKD.

The Role of Matrix Gla Protein (MGP) in Vascular Calcification

Matrix Gla protein (MGP) is a vitamin K-dependent protein, which is synthesized in bone and many other mesenchymal cells, which is also highly expressed by vascular smooth muscle cells (VSMCs) and chondrocytes. Numerous studies have confirmed that MGP acts as a calcification-inhibitor although the mechanism of action is still not fully understood. The modulation of tissue calcification by MGP is potentially regulated in several ways including direct inhibition of calcium-phosphate precipitation, the formation of matrix vesicles (MVs), the formation of apoptotic bodies (ABs), and trans-differentiation of VSMCs. MGP occurs as four species, i.e. fully carboxylated (cMGP), under-carboxylated, i.e. poorly carboxylated (ucMGP), phosphorylated (pMGP), and non-phosphorylated (desphospho, dpMGP). ELISA methods are currently available that can detect the different species of MGP. The expression of the MGP gene can be regulated via various mechanisms that have the potential to become genomic biomarkers for the prediction of vascular calcification (VC) progression. VC is an established risk factor for cardiovascular disease and is particularly prevalent in those with chronic kidney disease (CKD). The specific action of MGP is not yet clearly understood but could be involved with the functional inhibition of BMP-2 and BMP-4, by blocking calcium crystal deposition and shielding the nidus from calcification.

BONE MARKERS IN ARTHROPATHIES

Bone endures a lifelong course of construction and destruction, with bone marker (BM) molecules released during this cycle. The field of measuring BM levels in synovial fluid and peripheral blood is a cardinal part of bone research within modern clinical medicine and has developed extensively in the last years. The purpose of our work was to convey an up-to-date overview on synovial fluid and serum BMs in the most common arthropathies.

Association of the Inactive Circulating Matrix Gla Protein with Vitamin K Intake, Calcification, Mortality, and Cardiovascular Disease: A Review

Matrix Gla Protein (MGP), a small Gla vitamin K-dependent protein, is the most powerful natural occurring inhibitor of calcification in the human body. To become biologically active, MGP must undergo vitamin K-dependent carboxylation and phosphorylation. Vitamin K deficiency leads to the inactive uncarboxylated, dephosphorylated form of MGP (dpucMGP). We aimed to review the existing data on the association between circulating dpucMGP and vascular calcification, renal function, mortality, and cardiovascular disease in distinct populations. Moreover, the association between vitamin K supplementation and serum levels of dpucMGP was also reviewed.

Long-term vitamin-K antagonist use and coronary artery calcification

BACKGROUND

The aim of this study was to investigate the impact of vitamin K antagonist (VKA) therapy on coronary artery calcification (CAC) by comparing long-term VKA users with metallic prosthetic valves (MPVs) and VKA-free patients undergoing coronary calcium scoring for cardiovascular (CV) risk stratification.

METHODS

A total of 108 patients (43 VKA users with MPV and 65 gender-, age-, and risk-factor-matched VKA-free patients) were included in the study. CAC was determined via computed tomography (CT) and quantified on the basis of the Agatston score. The VKA group comprised patients who had an MPV for longer than 5 years, which entailed long-term VKA use.

RESULTS

Long-term VKA users had more calcified coronary arteries compared with the control group (178.1 ± 278 vs. 61.1 ± 130.6, p = 0.01). There was no difference between groups in terms of traditional CV risk factors. The mean duration of VKA use was 15 ± 7 years for the patients with MPV. There was no correlation between the duration of VKA use and mean Agatston score (r = 0.2, p = 0.215).

CONCLUSION

With its unique selection of patient groups, our study extends the findings of previous research that long-term VKA use is related to CAC as detected via CT scanning. The longer and more potent VKA regimen required for MPV patients is the primary cause of CAC in this group.

Status of Single Nucleotide Polymorphism of Matrix Gla Protein Gene (rs4236) in Nephrolithiasis: A Preliminary Study in Indian Population

Background:

Urine is a supersaturated solution with solutes in very high concentration. Matrix gla protein (MGP) is one of the proteins involved in inhibition of extracellular calcification. Among the various polymorphisms studied, polymorphism of SNP rs4236 in the MGP gene is found to have association with nephrolithiasis. We evaluated the significance of SNP rs4236 polymorphism in nephrolithiasis among the Indian population.

Materials and Methods:

The study was conducted in 2013 and 2014 among fifty participants. Twenty-five of them were patients with documented symptomatic stone disease and the 25 controls had no history of stone disease and ultrasonogram was normal. Serum creatinine was estimated in all patients. DNA was isolated from the blood sample and amplified by polymerase chain reaction using defined primers. Single strand conformational polymorphism was done to identify abnormal bands and the same was sequenced.

Results:

The patients and controls were matched in age and sex. The serum creatinine levels were similar in both groups. The predominant change in SNP rs4236 in patients was a G to A nucleotide change, resulting in AA homozygous genotype. This was found in 60% of patients. The rest (40%) of patients and all (100%) controls had heterozygous AG genotype. This corresponds to a stone disease with an odds ratio (OR) of 75 (P < 0.003).

Conclusion:

This first study in Indian population shows that genotype AA polymorphism of SNP rs4236 of MGP gene was found to be significant risk factor for renal stone disease. Studies with larger sample size may be needed to confirm this finding and elucidate the exact OR.

No Association of Genetic Markers with Carotid Intimal Medial Thickness in β-Thalassemia Major Patients

Regular transfusion leads to cardiac siderosis resulting in cardiac complications that account for more than 71% of the total mortality in thalassemia patients. We aimed to study the variants of matrix metalloproteinase-9 (MMP9), matrix Gla protein (MGP), and estrogen receptor α(ERα), which might be contributing to atherosclerosis, leading to heart failure in thalassemia major. One hundred and five thalassemia patients on regular transfusion and iron chelation therapy were enrolled for the study. Carotid artery intimal medial thickness (CIMT) measurement was done to check for atherosclerosis. MMP 9 (C1562T), MGP (T138C), and ER α gene ( Pvu II (rs2234693T > C) and Xba I (rs9340799A > G) polymorphism were analyzed using the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method. CIMT values were within the normal range (<0.90 mm) in all patients. There was no difference in mean CIMT values between males and females (0.56 ± 0.11 versus 0.56 ± 0.12, p  = 0.928). There was no correlation of CIMT with age, body surface area, and body mass index as well as with serum ferritin levels. No statistically significant difference in frequency of MMP9, MGP, and ERα genotypes was seen in two dichotomized groups of CIMT (CIMT < 0.56 and CIMT ≥ 0.56). Variants of MMP9 , MGP , and ERα have a reserved influence on cardiac disease pathogenesis, and the disease phenotype in thalassemia patients may be more strongly impacted by other factors.

Vascular calcification is not related to serum fetuin-A and osteopontin levels in hemodialysis patients

INTRODUCTION

Vascular calcification (VC) in hemodialysis (HD) patients is a sign of severe cardiovascular disease and can predict cardiovascular outcomes. Fetuin-A and osteopontin (OPN) inhibit VC. Serum fetuin-A levels are lower in patients with end-stage kidney disease (ESKD) and in those who are on chronic HD therapy. However, there are limited data concerning OPN in patients who are on dialysis. The aim of our study was to determine VC in HD patients, the relationship between VC and 25-OH-vitamin D, fetuin-A, and OPN levels, and independent predictors of VC.

MATERIALS AND METHODS

Ninety-three patients with ESKD on HD therapy were recruited. Among these patients, 44 were male and 49 were female. The patient group was compared with a group of 20 healthy controls of similar age and sex. A plain radiograph of the hand was taken using a mammography machine for the evaluation of VC. Serum fetuin-A, OPN, and 25-OH-vitamin D levels of both patients and controls were measured.

RESULTS

VC was detected in 45 (48.4%) HD patients. When patients were compared with healthy controls, fetuin-A levels (p < 0.029) were significantly lower in patients, whereas OPN (p < 0.000) and VC (p < 0.002) were significantly higher in the patient group. Age [odds ratio (OR) 1.036], the presence of diabetes mellitus (DM) (OR 17.527), and high parathyroid hormone (PTH) levels (OR 1.002) were independent predictors of VC in a logistic regression model including the following factors: age, the presence of DM, HD duration, and serum albumin, phosphate, PTH, 25-OH-vitamin D, fetuin-A, OPN, and calcium levels. No significant correlation was found between patients with VC and patients without VC in terms of fetuin-A, OPN, and 25-OH-vitamin D levels.

CONCLUSIONS

VC is a frequent sign in patients undergoing HD and is not related to serum fetuin-A and osteopontin levels. Age, the presence of DM, and high PTH levels were independent predictors of VC in patients undergoing HD. Further studies are warranted to understand the mechanism underlying and the factors contributing to VC.

Matrix Gla protein T-138C polymorphism is associated with carotid intima media thickness and predicts mortality in patients with diabetic nephropathy

AIMS

We sought to determine the predictive value of Matrix Gla Protein MGP T-138C polymorphism in relation to all-cause mortality, cardiovascular mortality and cardiovascular events in patients with diabetic nephropathy (DN).

METHODS

MGP T-138C polymorphism was assessed in 40 diabetic patients without nephropathy and 118 patients at different stages of DN, including patients on hemodialysis. Measurement of carotid intima-media thickness (cIMT) was performed using real-time B-mode ultrasonography. Plasma levels of dephoshorylated uncarboxylated Matrix Gla Protein (dp-ucMGP) were determined in a subgroup of 67 patients by ELISA. Mortality and cardiovascular events were assessed during a 7year follow-up.

RESULTS

TT homozygotes for the MGP T-138C polymorphism had higher values of cIMT compared to combined TC and CC genotypes (P=0.006) whereas no association was observed between cIMT and dp-ucMGP levels. MGP T-138C polymorphism was a strong independent predictor of cIMT (P<0.0001), after adjustment for several well-known atherosclerosis risk factors. Patients with TT genotype presented a significantly higher all-cause and cardiovascular mortality risk compared to patients with TC and CC genotypes (P=0.01 and P=0.04 respectively), after adjustment for several traditional risk factors.

CONCLUSIONS

MGP T-138C polymorphism is a strong and independent predictor of increased cIMT as well as all-cause and cardiovascular mortality in DN patients.

Association of Matrix Gla protein gene (rs1800801, rs1800802, rs4236) polymorphism with vascular calcification and atherosclerotic disease: a meta-analysis

Association between the MGP gene rs1800801, rs1800802, rs4236 polymorphisms and vascular calcification and atherosclerotic disease was inconsistent. To clarify precise association, we performed this meta-analysis. Medline, Embase and China Knowledge Resource Integrated Database were systematically searched through December 2016. A total of 23 case-control studies, consisting of 5280 cases and 5773 controls, were included. The overall results suggested that the -7A polymorphism was associated with an increased risk for vascular calcification and atherosclerotic disease in the recessive model (OR = 1.50, 95% CI 1.01-2.24, P = 0.045). Subgroup analyses of Caucasians showed significant associations in the allelic model, recessive model, and homozygote model: allelic model (OR = 1.19, 95% CI 1.06-1.34, P = 0.004), recessive model (OR = 1.60, 95% CI 1.26-2.03, P < 0.001), homozygote model (OR = 1.83, 95% CI 1.18-2.81, P = 0.006). Subgroup analysis of the Asian population did not demonstrate any significant associations in any of the genetic models. No significant association was found in any genetic model amongst the rs1800802 and rs4236 polymorphisms. The findings of this meta-analysis indicate that the MGP gene rs1800801 polymorphism is significantly associated with vascular calcification and atherosclerotic disease, especially in the Caucasian population.

A single gene connects stiffness in glaucoma and the vascular system

Arterial calcification results in arterial stiffness and higher systolic blood pressure. Arterial calcification is prevented by the high expression of the Matrix-Gla gene (MGP) in the vascular smooth muscle cells (VSMC) of the arteries' tunica media. Originally, MGP, a gene highly expressed in cartilage and VSMC, was found to be one of the top expressed genes in the trabecular meshwork. The creation of an Mgp-lacZ Knock-In mouse and the use of mouse genetics revealed that in the eye, Mgp's abundant expression is localized and restricted to glaucoma-associated tissues from the anterior and posterior segments. In particular, it is specifically expressed in the regions of the trabecular meshwork and of the peripapillary sclera that surrounds the optic nerve. Because stiffness in these tissues would significantly alter outflow facility and biomechanical scleral stress in the optic nerve head (ONH), we propose MGP as a strong candidate for the regulation of stiffness in glaucoma. MGP further illustrates the presence of a common function affecting key glaucomatous parameters in the front and back of the eye, and thus offers the possibility for a sole therapeutic target for the disease.

GRECOS Project (Genotyping Recurrence Risk of Stroke): The Use of Genetics to Predict the Vascular Recurrence After Stroke

BACKGROUND AND PURPOSE

Vascular recurrence occurs in 11% of patients during the first year after ischemic stroke (IS) or transient ischemic attack. Clinical scores do not predict the whole vascular recurrence risk; therefore, we aimed to find genetic variants associated with recurrence that might improve the clinical predictive models in IS.

METHODS

We analyzed 256 polymorphisms from 115 candidate genes in 3 patient cohorts comprising 4482 IS or transient ischemic attack patients. The discovery cohort was prospectively recruited and included 1494 patients, 6.2% of them developed a new IS during the first year of follow-up. Replication analysis was performed in 2988 patients using SNPlex or HumanOmni1-Quad technology. We generated a predictive model using Cox regression (GRECOS score [Genotyping Reurrence Risk of Stroke]) and generated risk groups using a classification tree method.

RESULTS

The analyses revealed that rs1800801 in the MGP gene (hazard ratio, 1.33; P=9×10^-03), a gene related to artery calcification, was associated with new IS during the first year of follow-up. This polymorphism was replicated in a Spanish cohort (n=1.305); however, it was not significantly associated in a North American cohort (n=1.683). The GRECOS score predicted new IS (P=3.2×10^-09) and could classify patients, from low risk of stroke recurrence (1.9%) to high risk (12.6%). Moreover, the addition of genetic risk factors to the GRECOS score improves the prediction compared with previous Stroke Prognosis Instrument-II score (P=0.03).

CONCLUSIONS

The use of genetics could be useful to estimate vascular recurrence risk after IS. Genetic variability in the MGP gene was associated with vascular recurrence in the Spanish population.

Matrix-Gla Protein rs4236 [A/G] gene polymorphism and serum and GCF levels of MGP in patients with subgingival dental calculus

AIM

Matrix-Gla Protein (MGP) is one of the major Gla-containing protein associated with calcification process. It also has a high affinity for Ca2+ and hydroxyapatite. In this study we aimed to evaluate the MGP rs4236 [A/G] gene polymorphism in association with subgingival dental calculus. Also a possible relationship between MGP gene polymorphism and serum and GCF levels of MGP were examined.

MATERIAL AND METHODS

MGP rs4236 [A/G] gene polymorphism was investigated in 110 patients with or without subgingival dental calculus, using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) techniques. Additionally, serum and GCF levels of MGP of the patients were compared according to subgingival dental calculus.

RESULTS

Comparison of patients with and without subgingival dental calculus showed no statistically significant difference in MGP rs4236 [A/G] gene polymorphism (p=0.368). MGP concentrations in GCF of patients with subgingival dental calculus were statistically higher than those without subgingival dental calculus (p=0.032). However, a significant association was not observed between the genotypes of AA, AG and GG of the MGP rs4236 gene and the serum and GCF concentrations of MGP in subjects.

CONCLUSION

In this study, it was found that MGP rs4236 [A/G] gene polymorphism was not to be associated with subgingival dental calculus. Also, that GCF MGP levels were detected higher in patients with subgingival dental calculus than those without subgingival dental calculus independently of polymorphism, may be the effect of adaptive mechanism to inhibit calculus formation.

SNP haplotyping technique for evaluation of MGP 5' UTR power in osteoblast cells

Matrix Gla protein (MGP) is involved in calcium trafficking and arterial calcification. The aim of study was to investigate the role of three polymorphisms within the MGP gene promoter region on reporter gene (luciferase) expression level. The fragments containing rs1800799 (C/T), rs1800802 (T/C), and rs1800801 (G/A) sites were constructed and transferred into human G292 osteoblast cells using pGL3-Basic plasmid. The reporter gene expression was calculated for the high and low frequency polymorphic haplotypes (CTG and TCA, respectively). Results showed that the reporter gene expression levels are not statistically different (p > 0.3). We concluded that the investigated polymorphic sites are not able to change the gene expression pattern in human G292 osteoblast cells.

[The matrix-gla protein awakening may lead to the demise of vascular calcification]

Matrix-gla-protein (MGP) is mainly secreted by chondrocytes and smooth vascular muscle cells. This potent inhibitor of vascular calcification need to undergo 2 post-transcriptional steps to be fully active: one phosphorylation of 3 serine residues (on 5) and a carboxylation of 5 glutamate residues (on 9). Like other "Gla" proteins, this carboxylation is vitamin K dependant. Several forms of MGP thus circulate in the plasma, some of them being totally inactive (the unphosphorylated and uncarboxylated MGP), some others being partially or fully active, according to the number of phosphorylated or carboxylated sites. A theoretical link exists between MGP, vitamin K, vascular calcifications and cardiovascular diseases. This link is even more evident in patients suffering from chronic kidney diseases (CKD), and notably hemodialysis patients. If this link has been demonstrated in different experimental studies, clinical studies are mainly observational and their results must be interpreted accordingly. MGP concentrations are definitely not yet a surrogate to estimate the levels of vascular calcification, but could allow the monitoring of vitamin K treatment. Modulation of MGP concentrations may reduce vascular calcification in hemodialyzed patients, if the large ongoing trials show an efficiency of this treatment. In this review, we will summarize the role of MGP in the vascular calcifications process, describe the problems linked to the analytical determination of MGP in plasma and finally describe the different clinical studies on MGP and vascular calcifications in the general population and in CKD patients.

The role of carbonic anhydrase in the pathogenesis of vascular calcification in humans

Carbonic anhydrases are a group of isoenzymes that catalyze the reversible conversion of carbon dioxide into bicarbonate. They participate in a constellation of physiological processes in humans, including respiration, bone metabolism, and the formation of body fluids, including urine, bile, pancreatic juice, gastric secretion, saliva, aqueous humor, cerebrospinal fluid, and sweat. In addition, carbonic anhydrase may provide carbon dioxide/bicarbonate to carboxylation reactions that incorporate carbon dioxide to substrates. Several isoforms of carbonic anhydrase have been identified in humans, but their precise physiological role and the consequences of their dysfunction are mostly unknown. Carbonic anhydrase isoenzymes are involved in calcification processes in a number of biological systems, including the formation of calcareous spicules from sponges, the formation of shell in some animals, and the precipitation of calcium salts induced by several microorganisms, particularly urease-producing bacteria. In human tissues, carbonic anhydrase is implicated in calcification processes either directly by facilitating calcium carbonate deposition which in turn serves to facilitate calcium phosphate mineralization, or indirectly via its action upon γ-glutamyl-carboxylase, a carboxylase that enables the biological activation of proteins involved in calcification, such as matrix Gla protein, bone Gla protein, and Gla-rich protein. Carbonic anhydrase is implicated in calcification of human tissues, including bone and soft-tissue calcification in rheumatological disorders such as ankylosing spondylitis and dermatomyositis. Carbonic anhydrase may be also involved in bile and kidney stone formation and carcinoma-associated microcalcifications. The aim of this review is to evaluate the possible association between carbonic anhydrase isoenzymes and vascular calcification in humans.

Wnt16 attenuates TGFβ-induced chondrogenic transformation in vascular smooth muscle

OBJECTIVE

Phenotypic plasticity of vascular smooth muscle cells (VSMCs) contributes to cardiovascular disease. Chondrocyte-like transformation of VSMCs associates with vascular calcification and underlies the formation of aortic cartilaginous metaplasia induced in mice by genetic loss of matrix Gla protein (MGP). Previous microarray analysis identified a dramatic downregulation of Wnt16 in calcified MGP-null aortae, suggesting an antagonistic role for Wnt16 in the chondrogenic transformation of VSMCs.

APPROACH AND RESULTS

Wnt16 is significantly downregulated in MGP-null aortae, before the histological appearance of cartilaginous metaplasia, and in primary MGP-null VSMCs. In contrast, intrinsic TGFβ is activated in MGP-null VSMCs and is necessary for spontaneous chondrogenesis of these cells in high-density micromass cultures. TGFβ3-induced chondrogenic transformation in wild-type VSMCs associates with Smad2/3-dependent Wnt16 downregulation, but Wnt16 does not suppress TGFβ3-induced Smad activation. In addition, TGFβ3 inhibits Notch signaling in wild-type VSMCs, and this pathway is downregulated in MGP-null aortae. Exogenous Wnt16 stimulates Notch activity and attenuates TGFβ3-induced downregulation of Notch in wild-type VSMCs, prevents chondrogenesis in MGP-null and TGFβ3-treated wild-type VSMCs, and stabilizes expression of contractile markers of differentiated VSMCs.

CONCLUSIONS

We describe a novel TGFβ-Wnt16-Notch signaling conduit in the chondrocyte-like transformation of VSMCs and identify endogenous TGFβ activity in MGP-null VSMCs as a critical mediator of chondrogenesis. Our proposed model suggests that the activated TGFβ pathway inhibits expression of Wnt16, which is a positive regulator of Notch signaling and a stabilizer of VSMC phenotype. These data advance the comprehensive mechanistic understanding of VSMC transformation and may identify a novel potential therapeutic target in vascular calcification.

[Association of allelic polymorphisms of genes matrix Gla-protein system with ischemic atherothrombotic stroke]

There are results of the determination of 10 polymorphisms of matrix Gla-protein system (gene MGP-T(-138)-->C (rs1800802), G(-7)-->A (rs1800801), Thr83-->Ala (rs4236), gene VDR-FokI (rs2228570), BsmI (rs1544410), ApaI (rs7975232), TaqI (rs731236), gene GGCX-Arg325-->Gln (rs699664), gene VKORS1-T(2255)-->C (rs2359612), gene BMP-2-Ser37-->Ala (rs2273073)) into 170 patients with ischemic atherothrombotic stroke (IATS) and 124 healthy individual is (control group). It is established that there is a connection between the IATS and polymorphic variants of genes MGP (G(-7)-->A) and VKORC1 (T(2255)-->C). The risk of IATS in carriers of minor allele A/A (G(-7)-->A polymorphism) in 2.6 times higher than in carriers of the major allele (G/A + G/G), and C/C genotype (T(2255)-->C polymorphism) in 2.2 times higher than the homozygotes of major allele. The coincidence of patients T/C and G/G, C/C and G/A genotypes, and A/A genotype (G(-7)-->A polymorphism) with any genotype T(2255)-->C polymorphism are increases the risk of IATS.

Unified theory on the pathogenesis of Randall's plaques and plugs

Kidney stones develop attached to sub-epithelial plaques of calcium phosphate (CaP) crystals (termed Randall's plaque) and/or form as a result of occlusion of the openings of the Ducts of Bellini by stone-forming crystals (Randall's plugs). These plaques and plugs eventually extrude into the urinary space, acting as a nidus for crystal overgrowth and stone formation. To better understand these regulatory mechanisms and the pathophysiology of idiopathic calcium stone disease, this review provides in-depth descriptions of the morphology and potential origins of these plaques and plugs, summarizes existing animal models of renal papillary interstitial deposits, and describes factors that are believed to regulate plaque formation and calcium overgrowth. Based on evidence provided within this review and from the vascular calcification literature, we propose a "unified" theory of plaque formation-one similar to pathological biomineralization observed elsewhere in the body. Abnormal urinary conditions (hypercalciuria, hyperoxaluria, and hypocitraturia), renal stress or trauma, and perhaps even the normal aging process lead to transformation of renal epithelial cells into an osteoblastic phenotype. With this de-differentiation comes an increased production of bone-specific proteins (i.e., osteopontin), a reduction in crystallization inhibitors (such as fetuin and matrix Gla protein), and creation of matrix vesicles, which support nucleation of CaP crystals. These small deposits promote aggregation and calcification of surrounding collagen. Mineralization continues by calcification of membranous cellular degradation products and other fibers until the plaque reaches the papillary epithelium. Through the activity of matrix metalloproteinases or perhaps by brute physical force produced by the large sub-epithelial crystalline mass, the surface is breached and further stone growth occurs by organic matrix-associated nucleation of CaOx or by the transformation of the outer layer of CaP crystals into CaOx crystals. Should this theory hold true, developing an understanding of the cellular mechanisms involved in progression of a small, basic interstitial plaque to that of an expanding, penetrating plaque could assist in the development of new therapies for stone prevention.

Association of matrix Gla protein gene functional polymorphisms with loss of bone mineral density and progression of aortic calcification

Two matrix Gla protein (MGP) polymorphisms were associated with progression of aortic calcification and femoral neck bone loss in men. All these findings were also functionally corroborated in two vascular and bone in vitro systems indicating that MGP genetic variations can be partly responsible of higher risk of bone loss and vascular calcification.

INTRODUCTION

MGP plays an important role in bone and vascular mineralization as confirmed by MGP-deficient murine model. We therefore aimed to find a genetic association among -138T>C, -7G>A, and Thr83Ala MGP single-nucleotide polymorphisms (SNPs), bone loss, and progression of aortic calcification in a randomly selected general population of 296 individuals who participated in the European Vertebral Osteoporosis Study.

METHODS

To evaluate the rate of change in bone mineral density (BMD) and the progression of aortic calcification, dual X-ray absorptiometry and lateral spine X-rays were performed at baseline and after 4 years of follow-up. Genotyping for the three polymorphisms was carried out using polymerase chain reaction and restriction fragment length analysis. In addition, functional studies of MGP-7G>A and Thr83Ala SNPs were performed on transiently transfected osteoblast-like UMR-106 and vascular smooth muscle A7r5 cells.

RESULTS

The proportion of men who had lost BMD in the femoral neck was higher among homozygous -7AA and 83Ala-Ala (p = 0.039 and p = 0.009, respectively), and also featured a higher risk of progression of aortic calcifications (OR = 5.6, 95% CI = 1.2-27.8 and OR = 6.8, 95% CI = 1.4-32.3, respectively). No effect was observed in women. The MGP-7A allele produced a reduction in luciferase activity compared to MGP-7G: 47% less in vascular cells and 34% less in bone cells (p = 0.001 and 0.012, respectively). In vascular cells under calcifying conditions, the MGP 83Thr allele showed a slightly higher, although not significant, inhibition than the MGP 83 Ala allele in calcium content suggesting functional differences between both variants.

CONCLUSION

These results suggest that MGP genetic variations could predict a higher risk of bone loss and progression of vascular calcification in men.

Matrix Gla protein (MGP) promoter polymorphic variants and its serum level in stenosis of coronary artery

Although the role of matrix Gla protein (MGP) is not completely known but, its expression within subendothelial macrophages and vascular smooth muscle cells is suggested to be involved in vascular calcification. In this study, we investigated the associations between the serum MGP levels and the MGP promoter high minor allele frequency (MAF) variants with the development of stenosis in coronary arteries. Moreover, we evaluated the allele changes within predicted transcription factor elements with bioinformatics tools. 182 subjects were recruited from who underwent coronary angiography. The MGP promoter rs1800801, rs1800802 and rs1800799 genotypes and haplotypes were detected by ARMS-RFLP PCR techniques. The serum MGP concentration was measured using ELISA method. Jaspar profiles were used for scoring the polymorphic variations within the transcription factor elements. The genotype and two-allelic haplotype distributions were not significant between the patient and control groups (P > 0.05). The serum MGP levels had not significant differences between the genotypes (P > 0.1) and haplotypes (P > 0.4). Based on the prediction studies, we did not observe significant differences between the polymorphic scores in the predicted elements (P > 0.05). We concluded that the genotype and haplotype distributions of the MGP promoter high-MAF polymorphisms, as confirmed in the prediction studies and the serum MGP level are not significantly associated with the coronary artery disease. Based on the study results, the MGP protein did not play an important role in the development of stenosis of coronary arteries.

Calcium oxalate nephrolithiasis and expression of matrix GLA protein in the kidneys

OBJECTIVES

Polymorphism of the gene for matrix GLA protein (MGP), a calcification inhibitor, is associated with nephrolithiasis. However, experimental investigations of MGP role in stone pathogenesis are limited. We determined the effect of renal epithelial exposure to oxalate (Ox), calcium oxalate (CaOx) monohydrate (COM) or hydroxyapatite (HA) crystal on the expression of MGP.

METHODS

MDCK cells in culture were exposed to 0.3, 0.5 or 1 mM Ox and 33, 66 or 133-150 μg/cm(2) of COM/HA for 3-72 h. MGP expression and production were determined by Western blotting and densitometric analysis. Enzyme-linked immunosorbent assay was performed to determine MGP release into the medium. Hyperoxaluria was induced in male Sprague-Dawley rats by feeding hydroxyl-L-proline. Immunohistochemistry was performed to detect renal MGP expression.

RESULTS

Exposure to Ox and crystals led to time- and concentration-dependent increase in expression of MGP in MDCK cells. Cellular response was quicker to crystal exposure than to the Ox, expression being significantly higher after 3-h exposure to COM or HA crystals and more than 6 h of exposure to Ox. MGP expression was increased in kidneys of hyperoxaluric rats particularly in renal peritubular vessels.

CONCLUSION

We demonstrate increased expression of MGP in renal tubular epithelial cells exposed to Ox or CaOx crystals as well as the HA crystals. The most significant finding of this study is the increased staining seen in renal peritubular vessels of the hyperoxaluric rats, indicating involvement of renal endothelial cells in the synthesis of MGP.

Polymorphism in the human matrix Gla protein gene is associated with the progression of vascular calcification in maintenance hemodialysis patients

BACKGROUND

Matrix Gla protein (MGP) is one of the important proteins inhibiting vascular calcification (VC). Single nucleotide polymorphisms (SNPs) located in the promoter and coding regions of the MGP gene affect the transcriptional activity. In this study, we investigated the relationship between the SNPs and progression of VC in patients undergoing maintenance hemodialysis (MHD).

METHODS

This was a retrospective, longitudinal cohort study of 134 MHD patients whose VC could be followed by multi-detector computed tomography (MDCT) examinations. MGP-SNPs (T-138C, rs1800802 and G-7A, rs1800801) were determined. The progression speed of VC was examined by plotting the abdominal aortic calcium volume scores.

RESULTS

The progression speed of VC of patients with the CC genotype of T-138C was significantly slower than that of patients with the CT or TT genotype. Multiple regression analysis showed that CT/TT genotype, greater age at the beginning of MHD, male sex, high levels of calcium × phosphate, low levels of high-density lipoprotein cholesterol, high levels of low-density lipoprotein cholesterol, low levels of ferritin and non-use of angiotensin II receptor blockers were significantly associated with progression of VC.

CONCLUSIONS

The MGP-138CC genotype may be associated with slower progression of VC in MHD patients. The genotype of the MGP gene will be a genomic biomarker that is predictive of VC progression.

Two sides of MGP null arterial disease: chondrogenic lesions dependent on transglutaminase 2 and elastin fragmentation associated with induction of adipsin

Mutations in matrix Gla protein (MGP) have been correlated with vascular calcification. In the mouse model, MGP null vascular disease presents as calcifying cartilaginous lesions and mineral deposition along elastin lamellae (elastocalcinosis). Here we examined the mechanisms underlying both of these manifestations. Genetic ablation of enzyme transglutaminase 2 (TG2) in Mgp(-/-) mice dramatically reduced the size of cartilaginous lesions in the aortic media, attenuated calcium accrual more than 2-fold, and doubled longevity as compared with control Mgp(-/-) animals. Nonetheless, the Mgp(-/-);Tgm2(-/-) mice still died prematurely as compared with wild-type and retained the elastocalcinosis phenotype. This pathology in Mgp(-/-) animals was developmentally preceded by extensive fragmentation of elastic lamellae and associated with elevated serine elastase activity in aortic tissue and vascular smooth muscle cells. Systematic gene expression analysis followed by an immunoprecipitation study identified adipsin as the major elastase that is induced in the Mgp(-/-) vascular smooth muscle even in the TG2 null background. These results reveal a central role for TG2 in chondrogenic transformation of vascular smooth muscle and implicate adipsin in elastin fragmentation and ensuing elastocalcinosis. The importance of elastin calcification in MGP null vascular disease is highlighted by significant residual vascular calcification and mortality in Mgp(-/-);Tgm2(-/-) mice with reduced cartilaginous lesions. Our studies identify two potential therapeutic targets in vascular calcification associated with MGP dysfunction and emphasize the need for a comprehensive approach to this multifaceted disorder.

Attenuation of chondrogenic transformation in vascular smooth muscle by dietary quercetin in the MGP-deficient mouse model

RATIONALE

Cartilaginous metaplasia of vascular smooth muscle (VSM) is characteristic for arterial calcification in diabetes and uremia and in the background of genetic alterations in matrix Gla protein (MGP). A better understanding of the molecular details of this process is critical for the development of novel therapeutic approaches to VSM transformation and arterial calcification.

OBJECTIVE

This study aimed to identify the effects of bioflavonoid quercetin on chondrogenic transformation and calcification of VSM in the MGP-null mouse model and upon TGF-β3 stimulation in vitro, and to characterize the associated alterations in cell signaling.

METHODS AND RESULTS

Molecular analysis revealed activation of β-catenin signaling in cartilaginous metaplasia in Mgp-/- aortae in vivo and during chondrogenic transformation of VSMCs in vitro. Quercetin intercepted chondrogenic transformation of VSM and blocked activation of β-catenin both in vivo and in vitro. Although dietary quercetin drastically attenuated calcifying cartilaginous metaplasia in Mgp-/- animals, approximately one-half of total vascular calcium mineral remained as depositions along elastic lamellae.

CONCLUSION

Quercetin is potent in preventing VSM chondrogenic transformation caused by diverse stimuli. Combined with the demonstrated efficiency of dietary quercetin in preventing ectopic chondrogenesis in the MGP-null vasculature, these findings indicate a potentially broad therapeutic applicability of this safe for human consumption bioflavonoid in the therapy of cardiovascular conditions linked to cartilaginous metaplasia of VSM. Elastocalcinosis is a major component of MGP-null vascular disease and is controlled by a mechanism different from chondrogenic transformation of VSM and not sensitive to quercetin.

No association between MGP rs1800802 polymorphism and stenosis of the coronary artery

BACKGROUND AND OBJECTIVES

Matrix Gla protein (MGP) was originally isolated from bone but it is known to be expressed in several tissues including kidney, lung, heart, cartilage and vascular smooth muscle cells (VSMC) of the blood vessel wall. Since it inhibits calcification in subendothelial space of vessels thus, we evaluated the association of rs1800802(T > C) polymorphism and stenosis of the coronary artery.

DESIGN AND SETTING

Cross-sectional case-control.

SUBJECTS AND METHODS

One hundred eighty two subjects recruited on the basis of study protocol from who underwent coronary angiography. The controls (n=70) had normal coronary arteries (up to 5% stenosis). The patients (n=112) subdivided into three subgroups; single-vessel disease (SVD), two-vessel disease (2VD) and three-vessel disease (3VD) based on the number of stenosed coronary vessels (at least 50% stenosis). rs1800802 (T > C) polymorphism was determined by PCR-RFLP technique.

RESULTS

Genotype distribution was not significant between control and patient groups. In addition, there were no significant differences between rs1800802 (T > C) frequency and gender (P=.092), and also patient subgroups (one-, two- and three vessel disease) (P=.840).

CONCLUSION

We concluded that rs1800802 (T > C) polymorphism within the MGP promoter is not related to stenosis of the coronary artery.

Matrix gla protein gene polymorphism is associated with increased coronary artery calcification progression

OBJECTIVE

Matrix gla protein (MGP) inhibits arterial and cartilaginous calcification. A threonine to alanine (Thr83Ala) polymorphism (codon 83) in MGP is associated with myocardial infarction and femoral artery calcification. We examined the association of the MGP Thr83Ala polymorphism with quantity and progression of coronary artery calcification (CAC), a noninvasive measure of subclinical coronary atherosclerosis.

METHODS AND RESULTS

In 605 participants of the Epidemiology of Coronary Artery Calcification Study, generalized linear mixed models were fit to determine the association of MGP Thr83Ala with CAC quantity and progression. There was a significant additive relation between MGP Thr83Ala and CAC progression (P=0.001). In the fully adjusted model, every 1 Ala83 allele increase was associated with an estimated 1.9% (95% confidence interval, 0.7%-3.0%) per year since baseline larger increase in CAC quantity. A proxy single nucleotide polymorphism for MGP Thr83Ala (rs6488724) was similarly associated with CAC progression in an independent cohort from the Genetic Epidemiology Network of Arteriopathy (GENOA) study.

CONCLUSIONS

Increased risk of myocardial infarction associated with MGP ThrAla83 genotype observed elsewhere may be related to faster progression of subclinical coronary atherosclerosis. MGP genotype could be a potential candidate for identifying individuals at increased risk of atherosclerotic disease who would benefit from aggressive primary prevention strategies.

Matrix Gla protein reinforces angiogenic resolution

Matrix Gla Protein (MGP) is an ECM molecule commonly associated with dysfunctions of large blood vessels such as arteriosclerosis and atherosclerosis. However, the exact role of MGP in the microvasculature is not clear. Utilizing a mouse MGP knockout model we found that MGP suppresses angiogenic sprouting from mouse aorta restricts microvascular density in cardiac and skeletal muscle, and is an endogenous inhibitor of tumor angiogenesis. Similarly, morpholino based knockdown of MGP in zebrafish embryos caused a progressive loss of luminal structures in intersegmental vessels, a phenotype reminiscent of Dll4/Notch inhibition. Accordingly, MGP suppressed Notch-dependent Hes-1 promoter activity and expression of Jagged1 mRNA relative to Dll4 mRNA. However, inhibition of BMP but not Notch or VEGF signaling reversed the excessive angiogenic sprouting phenotype of MGP knockout aortic rings suggesting that MGP may normally suppress angiogenic sprouting by blocking BMP signaling. Collectively, these results suggest that MGP is a multi-functional inhibitor of normal and abnormal angiogenesis that may function by coordinating with both Notch and BMP signaling pathways.

Serum phosphate and hip bone mineral density as additional factors for high vascular calcification scores in a community-dwelling: the São Paulo Ageing & Health Study (SPAH)

OBJECTIVE

To analyze the association between abdominal aortic calcification scores (AACS) and bone metabolism parameters in a well-characterized general population of older adults.

BACKGROUND

Several studies suggest a link between bone mineral metabolism disorders and vascular calcification; although only few of them analyze bone mineral density(BMD), laboratory bone markers and cardiovascular parameters at the same time and none were done in a miscegenated population.

METHODS

This cross-sectional study included 815 subjects ≥ 65 years old. The risk factors for osteoporosis and cardiovascular disease as well as a wide array of demographic and lifestyle characteristics were collected using a standardized questionnaire. BMD was measured by DXA. Kauppila's method was used to quantify the AAC score (AACS) by spine X-rays. Laboratory analyses were also performed.

RESULTS

AAC was observed in 63.2% of subjects with a median AACS of 2 (IQR: 0-7). AACS were categorized in quartiles and the highest quartile of AACS (>7) were compared with the three lower quartiles of AACS (≤ 7). Logistic regression analysis was performed using parameters with statistical significance in the univariate analysis. The best logistic regression model revealed that AACS>7 was negatively associated with femoral neck BMD and positively associated with phosphorus, adjusted by age, current smoking, LDL, and arterial hypertension in the elderly community-dwelling population.

CONCLUSIONS

We identified that higher serum phosphate levels and lower hip BMD are independent bone variables that are associated with elevated vascular calcification scores, supporting the search for effective prevention and treatment strategies that may simultaneously reduce these modifiable risk factors in older subjects.

A polymorphism of matrix Gla protein gene is associated with kidney stone in the Chinese Han population

PURPOSE

Matrix Gla protein (MGP) is a molecular determinant regulating the extracellular matrix calcification. To further confirm whether the MGP genetic polymorphism was universally associated with the risk of kidney stone, we investigated the association of genetic polymorphisms of MGP with kidney stone in the Chinese Han population.

MATERIALS AND METHODS

728 subjects were recruited for the study. We firstly re-sequenced the human genomic MGP gene including the 1500 bp promoter, 5'-UTR, 4 exons and 3'-untranslated regions, identified single nucleotide polymorphisms (SNPs) in MGP, and performed an association analysis with kidney stones in 54 subjects of the Chinese Han population. A candidate tag SNP was genotyped in total subjects using an allele specific PCR, and further analyzed the association with kidney stone.

RESULTS

We identified 18 polymorphisms including four tag SNPs. A tag SNPrs4236 was associated with kidney stones. The G allele carrier had a 1.373-fold reduced kidney stone risk compared with A allele carriers in SNPrs4236 (odds ratios (OR)=1.373; 95%CI, 1.051-1.793; p=0.019). However, we did not find an association between the polymorphism and clinical characteristics of kidney stones.

CONCLUSIONS

Our findings showed that SNPrs4236 of the MGP gene is associated with kidney stones in the Chinese Han population, and influences the genetic susceptibility to kidney stones. In the future, functional assays of the polymorphism should permit a better understanding of the role of MGP genetic variants and kidney stones.

Association of VKORC1 -1639 G>A polymorphism with carotid intima-media thickness in type 2 diabetes mellitus

AIMS

Media calcification is a predictor of cardiovascular mortality in type 2 diabetes mellitus (T2DM). Undercarboxylation of some vitamin K-dependent proteins, due to genetic polymorphisms of VKORC1, can lead to calcification. We examined a potential association between VKORC1 -1639 G>A polymorphism and T2DM and, also, the association of this polymorphism with carotid intima-media thickness (cIMT).

METHODS

VKORC1 -1639 G>A polymorphism was determined in 299 T2DM patients and 328 controls of Caucasian origin using PCR-RFLP. cIMT was measured in a subgroup of 118 T2DM patients.

RESULTS

The frequency of VKORC1 genotypes between diabetic and nondiabetic subjects differed significantly (p=0.01). VKORC1 genotype was associated with T2DM in an adjusted model (OR 1.36, p=0.009). A statistically significant difference was observed in the maximum value of cIMT among different genotypes. VKORC1 -1639 G>A polymorphism was an independent predictor of cIMT (p=0.029) after adjusting for established risk factors.

CONCLUSIONS

The association between VKORC1 -1639 G>A polymorphism and risk of T2DM could be due to the higher prevalence of calcification in T2DM patients. This is supported by the independent association between VKORC1 -1639 G>A polymorphism and maximum cIMT in T2DM patients which is likely due to atherosclerosis characterized by increased calcification.