Renata Cífková

The role of vascular biomarkers for primary and secondary prevention. A position paper from the European Society of Cardiology Working Group on peripheral circulation: Endorsed by the Association for Research into Arterial Structure and Physiology (ARTERY) Society

While risk scores are invaluable tools for adapted preventive strategies, a significant gap exists between predicted and actual event rates. Additional tools to further stratify the risk of patients at an individual level are biomarkers. A surrogate endpoint is a biomarker that is intended as a substitute for a clinical endpoint. In order to be considered as a surrogate endpoint of cardiovascular events, a biomarker should satisfy several criteria, such as proof of concept, prospective validation, incremental value, clinical utility, clinical outcomes, cost-effectiveness, ease of use, methodological consensus, and reference values. We scrutinized the role of peripheral (i.e. not related to coronary circulation) noninvasive vascular biomarkers for primary and secondary cardiovascular disease prevention. Most of the biomarkers examined fit within the concept of early vascular aging. Biomarkers that fulfill most of the criteria and, therefore, are close to being considered a clinical surrogate endpoint are carotid ultrasonography, ankle-brachial index and carotid-femoral pulse wave velocity; biomarkers that fulfill some, but not all of the criteria are brachial ankle pulse wave velocity, central haemodynamics/wave reflections and C-reactive protein; biomarkers that do no not at present fulfill essential criteria are flow-mediated dilation, endothelial peripheral arterial tonometry, oxidized LDL and dysfunctional HDL. Nevertheless, it is still unclear whether a specific vascular biomarker is overly superior. A prospective study in which all vascular biomarkers are measured is still lacking. In selected cases, the combined assessment of more than one biomarker may be required.

Desphospho-uncarboxylated matrix Gla-protein is associated with mortality risk in patients with chronic stable vascular disease

BACKGROUND Vitamin K is the essential co-factor for activation of matrix Gla-protein (MGP), the natural inhibitor of tissue calcification. Biologically inactive, desphospho-uncarboxylated MGP (dp-ucMGP) is a marker of vascular vitamin K status and is described to predict mortality in patients with heart failure and aortic stenosis. We hypothesized that increased dp-ucMGP might be associated with mortality risk in clinically stable patients with chronic vascular disease. MATERIALS AND METHODS We examined 799 patients (mean age 65.1 ± 9.3 years) who suffered from myocardial infarction, coronary revascularization or first ischemic stroke (pooled Czech samples of EUROASPIRE III and EUROASPIRE-stroke surveys), and followed them in a prospective cohort study. To estimate the 5-year all-cause and cardiovascular mortality we ascertained vital status and declared cause of death. Circulating dp-ucMGP and desphospho-carboxylated MGP (dp-cMGP) were measured by ELISA methods (IDS and VitaK). RESULTS During a median follow-up of 2050 days (5.6 years) 159 patients died. In the fully adjusted multivariate Cox proportional hazard model, the patients in the highest quartile of dp-ucMGP (≥ 977 pmol/L) had higher risk of all-cause and cardiovascular 5-year mortality [HRR 1.89 (95% CI, 1.32-2.72) and 1.88 (95% CI, 1.22-2.90)], respectively. Corresponding HRR for dp-cMGP were 1.76 (95% CI, 1.18-2.61) and 1.79 (95% CI, 1.12-2.57). CONCLUSIONS In patients with overt vascular disease, circulating dp-ucMGP and dp-cMGP were independently associated with the risk of all-cause and cardiovascular mortality. Since published results are conflicting regarding the dp-cMGP, we propose only circulating dp-ucMGP as a potential biomarker for assessment of additive cardiovascular risk.

The abnormal status of uncarboxylated matrix Gla protein species represents an additional mortality risk in heart failure patients with vascular disease.

BACKGROUND Matrix Gla protein (MGP) is a natural inhibitor of tissue calcification. In a previous study, we observed the positive association between abnormal concentrations of uncarboxylated MGP species and increased mortality risk in stable vascular patients. We explore whether co-incidence of abnormal status of uncarboxylated MPG and heart failure (HF) affects the mortality risk. METHODS We examined 799 patients (mean age 65.1 years) with stable vascular disease and followed them in a prospective study. Both, desphospho-uncarboxylated and total uncarboxylated MGP (dp-ucMGP or t-ucMGP) were quantified by pre-commercial ELISA assays. RESULTS Elevated (>100 ng/L) circulating brain natriuretic peptide (BNP) and abnormal status of plasma uncarboxylated MGP species (i.e.: dp-ucMGP ≥ 977 pmol/L or t-ucMGP ≤ 2825 nmol/L) were all identified as robust predictors of all-cause 5-year mortality. However, their co-incidence represented a substantial additional risk. We observed the highest mortality risk in patients with elevated BNP plus high dp-ucMGP compared to those with normal BNP plus low dp-ucMGP; fully adjusted HRRs were 4.86 (3.15-7.49). Likewise, the risk was increased when compared with patients with elevated BNP plus low dp-ucMGP; HRR 2.57 (1.60-4.10). Similar result we observed when co-incidence of elevated BNP and low t-ucMGP was analyzed [corresponding HRRs were 4.16 (2.62-6.61) and 1.96 (1.24-3.12)]. CONCLUSIONS The concomitant abnormality of uncarboxylated MGP and mild elevation of BNP leads in chronic patients with vascular disease to about two-fold increase of the relative mortality risk. We hypothesize that abnormal homeostasis of MGP is involved in the pathophysiology of HF.

The Impact of Blood Pressure and Visceral Adiposity on the Association of Serum Uric Acid With Albuminuria in Adults Without Full Metabolic Syndrome

BACKGROUND The impact of metabolic phenotypes on the association of uricemia with urinary albumin/creatinine ratio (uACR) remains unresolved. We evaluated the association between serum uric acid and uACR in persons with 0, and 1-2 metabolic syndrome (MetS) components and determined the modification effects of visceral adiposity index (VAI), mean arterial pressure (MAP), and fasting glucose on this association. METHODS Using data from a cross-sectional survey of a representative Czech population aged 25-64 years (n = 3612), we analyzed 1,832 persons without decreased glomerular filtration rate <60ml/min/1.73 m2, diabetes, and MetS. MetS components were defined using the joint statement of the leading societies. RESULTS Of the 1,832 selected participants, 64.1% (n = 1174) presented with 1-2 MetS components (age 46.3±11.2; men 51.7%), whereas 35.9% (n = 658) were free of any component (age 39.4±10.0; men 34.2 %). In fully adjusted multiple linear regression models for uricemia, uACR was an independent factor for increase in uric acid levels only in persons with 1-2 MetS components (standardized beta (Sβ) 0.048; P = 0.024); however, not in those without any component (Sβ 0.030; P = 0.264). Uric acid levels increased by the interaction of uACR with VAI (Sβ 0.06; P = 0.012), and of uACR with MAP (Sβ 0.05; P = 0.009). Finally, the association of uACR with uricemia was confined to persons whose VAI together with MAP were ≥the median of 1.35 and 98mm Hg, respectively (Sβ 0.190; P < 0.001). CONCLUSIONS We demonstrated a strong modification effect of VAI and MAP on the association between uACR and uricemia, which suggests obesity-related hypertension as the underlying mechanism.

The association between uncarboxylated matrix Gla protein and lipoprotein-associated phospholipase A2

BACKGROUND Lipoprotein-associated phospholipase A2 (Lp-PLA2) is independently associated with cardiovascular risk, probably via inflammatory activity in sclerotic plaque. We speculated whether Lp-PLA2 has a role in the aetiology of vascular calcifications, estimated from circulating uncarboxylated matrix Gla protein (MGP) species and whether we could find a potential interaction of Lp-PLA2 and MGP in terms of mortality. MATERIALS AND METHODS We examined 798 patients (mean age 65.1 years) with stable vascular disease and followed them in a prospective study. Both, desphospho-uncarboxylated and total MGP (dp-ucMGP or t-ucMGP) were quantified by pre-commercial ELISA assays, developed by VitaK (Maastricht, The Netherland) RESULTS Lp-PLA2 activity was independently positively associated with desphospho-uncarboxylated MGP (dp-ucMGP) [β coeff = 0.098, p=0.006]. 1SD of Lp-PLA2 activity was associated with 37% increased risk (p=0.001) of elevated dp-ucMGP (≥977 pmol/L, top quartile). In the Cox proportional hazard model adjusted for conventional risk factors, the patients in the highest quartile of dp-ucMGP or lowest quintile of total-uncarboxylated ucMGP (<2660 nmol/L) had higher risk of all-cause mortality [HRR 2.79 (95% CI 1.97-3.94) and HRR 1.69 (95% CI 1.18-2.42), respectively]. We observed no effect of high Lp-PLA2 activity (≥195 nmol/min/mL) on total mortality. CONCLUSIONS We assume that Lp-PLA2 is involved in vascular calcification and that dp-ucMGP is a more appropriate biomarker of residual risk than Lp-PLA2 itself.

Serum Vitamin D Status, Vitamin D Receptor Polymorphism, and Glucose Homeostasis in Healthy Subjects

Low vitamin D status has been frequently associated with impaired glucose metabolism. We examined associations between 25-hydroxyvitamin D (25-OH-D) and several parameters of glucose homeostasis in virtually healthy subjects, and explored possible interaction with vitamin D receptor (VDR) polymorphism. Nondiabetic subjects without chronic medication or any known significant manifest disease were selected from large general-population based population survey. Insulin sensitivity and β cell secretion were calculated by homeostasis model assessment (HOMA) and soluble isoform of receptor for advanced glycation end-products (sRAGE) using commercial ELISA. Subjects were also genotyped for rs2228570 polymorphism of VDR. After adjustment for potential confounders, we observed a significant relationship between 25-OH-D and fasting glycemia (β coefficient=-5.904; p=0.002) or insulin sensitivity (β=0.042; p=0.001), but not with β cell secretion or sRAGE. We found also an interaction with VDR polymorphism. Subjects with low 25-OH-D and AA genotype had significantly lower insulin sensitivity than those with GG genotype plus highest 25-OH-D concentrations (107.3% vs. 183.9%, p=0.021). In conclusion, low vitamin D status was in virtually healthy subjects associated with decreased insulin sensitivity, namely in those with GG genotype of rs2228570 VDR polymorphism.

Synergistic effect of low K and D vitamin status on arterial stiffness in a general population

Both vitamins K and D are nutrients with pleiotropic functions in human tissues. The metabolic role of these vitamins overlaps considerably in calcium homeostasis. We analyzed their potential synergetic effect on arterial stiffness. In a cross-sectional study, we analyzed aortic pulse wave velocity (aPWV) in 1023 subjects from the Czech post-MONICA study. Desphospho-uncarboxylated matrix γ-carboxyglutamate protein (dp-ucMGP), a biomarker of vitamin K status, was measured by sandwich ELISA and 25-hydroxyvitamin D3 (25-OH-D3) by a commercial immunochemical assay. In a subsample of 431 subjects without chronic disease or pharmacotherapy, we detected rs2228570 polymorphism for the vitamin D receptor. After adjustment for confounders, aPWV was independently associated with both factors: dp-ucMGP [β-coefficient(S.E.M.)=13.91(4.87); P=.004] and 25-OH-D3 [0.624(0.28); P=.027]. In a further analysis, we divided subjects according to dp-ucMGP and 25-OH-D3 quartiles, resulting in 16 subgroups. The highest aPWV had subjects in the top quartile of dp-ucMGP plus bottom quartile of 25-OH-D3 (i.e., in those with insufficient status of both vitamin K and vitamin D), while the lowest aPVW had subjects in the bottom quartile of dp-ucMGP plus top quartile of 25-OH-D3 [9.8 (SD2.6) versus 6.6 (SD1.6) m/s; P<.0001]. When we compared these extreme groups of vitamin K and D status, the adjusted odds ratio for aPWV≥9.3 m/s was 6.83 (95% CI:1.95-20.9). The aPWV was also significantly higher among subjects bearing the GG genotype of rs2228570, but only in those with a concomitantly poor vitamin K status. In conclusion, we confirmed substantial interaction of insufficient K and D vitamin status in terms of increased aortic stiffness.

The predictive potential of asymptomatic mild elevation of cardiac troponin I on mortality risk of stable patients with vascular disease.

OBJECTIVES Due to improved analytical performance of the newest generation of troponin assays, several patients have mild elevations of this parameter. Nevertheless, they do not show any signs of acute coronary syndrome. We speculated whether non-acute cardiac troponin I (cTnI) concentrations may improve prediction of residual mortality risk in clinically stable outpatients with chronic vascular disease. DESIGN AND METHODS We followed 830 patients (mean age 65.2years) after myocardial infarction, coronary revascularization or first ischemic stroke (pooled Czech samples of EUROASPIRE III and EUROASPIRE-stroke surveys, interviewed in 2006/2007) in a prospective cohort study. In addition to standard protocol, troponin I and brain natriuretic peptide (BNP) was estimated from frozen samples. Vital status and declared cause of death from death certificates was registered to ascertain a 5-year all-cause and cardiovascular mortality. RESULTS During a median follow up of 2050days (5.6years) 168 patients died. In the multivariate Cox proportional hazard model, cTnI≥0.03ng/mL independently predicted an all-cause 5-year mortality with HRR 1.76 (95% CI: 1.09-2.83). In the Cox model, the better predictor of mortality was BNP >150ng/L [HRR 3.47 (95% CI: 2.23-5.41)]. However, the combination of BNP with cTnI did not substantially improve its sensitivity or predictive power. CONCLUSION We cannot confirm the utility of asymptomatic mild cTnI elevation as a tool to detect residual risk of stable patients with vascular disease. On the other hand, BNP seems to be more appropriate for this purpose.