A novel nonsense mutation in the ß-subunit of the epithelial sodium channel causing Liddle syndrome.

PURPOSE: Liddle syndrome is a hereditary form of arterial hypertension caused by mutations in the genes coding of the epithelial sodium channel - SCNN1A, SCNN1B and SCNN1G. It is characterised by early onset of hypertension and variable biochemical features such as hypokalaemia and low plasma concentrations of renin and aldosterone. Phenotypic variability is large and, therefore, LS is probably underdiagnosed. Our objective was to examine a family suspected from Liddle syndrome including genetic testing and evaluate clinical and biochemical features of affected family members. MATERIALS AND METHODS: Thirteen probands from the Czech family, related by blood, underwent physical examination, laboratory tests, and genetic testing. Alleles of SCNN1B and SCNN1G genes were examined by PCR amplification and Sanger sequencing of amplicons. RESULTS: We identified a novel mutation in the ß-subunit of an epithelial sodium channel coded by the SCNN1B gene, causing the nonsense mutation in the protein sequence p.Tyr604*. This mutation was detected in 7 members of the family. The mutation carriers differed in the severity of hypertension and hypokalaemia which appeared only after diuretics in most of them; low aldosterone level (< 0.12 nmol/l) was, however, present in all. CONCLUSIONS: This finding expands the spectrum of known mutations causing Liddle syndrome. Hypoaldosteronemia was 100% sensitive sign in the mutation carriers. Low levels are observed especially in the Caucasian population reaching 96% sensitivity. Assessment of plasma aldosterone concentration is helpful for differential diagnosis of arterial hypertension. CONDENSED ABSTRACT: Liddle syndrome is a hereditary form of arterial hypertension caused by mutations in the genes encoding the epithelial sodium channel's α-, ß- and γ-subunit. It is usually manifested by early onset of hypertension accompanied by low potassium and aldosterone levels. We performed a physical examination, laboratory tests and genetic screening in 13 members of a Czech family. We found a new mutation of the SCNN1B gene which encodes the ß-subunit of the epithelial sodium channel. We describe the variability of each family member phenotype and point out the relevance of using aldosterone levels as a high sensitivity marker of Liddle syndrome in Caucasians.

The potential of miR-499 plasmatic level as a biomarker of obstructive sleep apnea syndrome.

Background: Obstructive sleep apnea syndrome (OSAS) is one of the most common sleep-related breathing disorders. The aim of this study was to improve diagnostics in OSAS using blood circulating biomarkers. We consider the potential of cardiac-specific miRNAs in the diagnosis and risk assessment of cardiovascular complications. Materials & methods: Plasmatic levels of miR-1-3p, miR-133a-3p and miR-499a-5p were measured by reverse transcription-PCR and compared with the clinical status of OSAS patients and controls. Results: The level of miR-499 was higher (p = 0.0343) in OSAS patients (mean expression: 0.00561) compared with the controls (mean expression: 0.00003), using the multivariate logistic regression. Conclusion: The role of miR-499 in gene expression regulation during hypoxia and our findings indicate that miR-499 could be a new diagnostic biomarker for OSAS.

Synergistic effect of sclerostin and angiotensin II receptor 1 polymorphism on arterial stiffening.

Aim: We aimed to establish the association between sclerostin (a glycoprotein involved in bone metabolism) and development of pulse wave velocity (PWV) in the general population. Methods: A prospective cohort study with a total of 522 subjects. Aortic PWV was measured twice (at baseline and after approximately 8 years of follow-up) and intraindividual change in PWV per year (ΔPWV/year) was calculated. Results: ΔPWV/year increased across the sclerostin quintiles, but generally in a strong age-dependent manner. However, a significant independent positive association between sclerostin and ΔPWV/year was observed exclusively in C allele carriers of rs5186 polymorphism for the angiotensin II receptor 1 (n = 246). Conclusion: Sclerostin concentrations were associated with an accelerated natural course of arterial stiffening, but only in interaction with renin-angiotension system.

The Expression Profile of MicroRNAs in Small and Large Abdominal Aortic Aneurysms.

BACKGROUND: Abdominal aortic aneurysms (AAA) are relatively frequent in elderly population, and their ruptures are related with high mortality rate. There are no actually used laboratory markers predicting the AAA development, course, and rupture. MicroRNAs are small noncoding molecules involved in posttranscriptional gene expression regulation, influencing processes on cell and tissue levels, and are actually in focus due to their potential to become diagnostic or prognostic markers in various diseases. METHODS: Tissue samples of AAA patients and healthy controls were collected, from which miRNA was isolated. Microarray including the complete panel of 2549 miRNAs was used to find expression miRNA profiles that were analysed in three subgroups: small (N = 10) and large (N = 6) aneurysms and healthy controls (N = 5). Fold changes between expression in aneurysms and normal tissue were calculated including corresponding p values, adjusted to multiple comparisons. RESULTS: Six miRNAs were found to be significantly dysregulated in small aneurysms (miR-7158-5p, miR-658, miR-517-5p, miR-122-5p, miR-326, and miR-3180) and 162 in large aneurysms, in comparison with the healthy control. Ten miRNAs in large aneurysms with more than two-fold significant change in expression were identified: miR-23a-3p, miR-24-3p, miR-27a-3p, miR-27b-3p, miR-30d-5p, miR-193a-3p, miR-203a-3p, miR-365a-3p, miR-4291, and miR-3663-3p and all, but the last one was downregulated in aneurysmal walls. CONCLUSION: We confirmed some previously identified miRNAs (miR-23/27/24 family, miR-193a, and miR-30) as associated with AAA pathogenesis. We have found other, yet in AAA unidentified miRNAs (miR-203a, miR-3663, miR-365a, and miR-4291) for further analyses, to investigate more closely their possible role in pathogenesis of aneurysms. If their role in AAA development is proved significant in future, they can become potential markers or treatment targets.

The low expression of circulating microRNA-19a represents an additional mortality risk in stable patients with vascular disease.

BACKGROUND: Secondary prevention of atherosclerotic vascular diseases represents a cascade of procedures to reduce the risk of future fatal and non-fatal cardiovascular events. We sought to determine whether the expression of selected microRNAs influenced mortality of stable chronic cardiovascular patients. METHODS: The plasma concentrations of five selected microRNAs (miR-1, miR-19, miR-126, miR-133 and miR-223) were quantified in 826 patients (mean age 65.2 years) with stable vascular disease (6-36 months after acute coronary syndrome, coronary revascularization or first-ever ischemic stroke). All-cause and cardiovascular mortality rates were followed during our prospective study. RESULTS: Low expression (bottom quartile) of all five miRNAs was associated with a significant increase in five-year all-cause death, even when adjusted for conventional risk factors, treatment, raised troponin I and brain natriuretic protein levels [hazard risk ratios (HRRs) were as follows: miR-1, 1.65 (95% CI: 1.16-2.35); miR-19a, 2.27 (95% CI: 1.59-3.23); miR-126, 1.64 (95% CI: 1.15-2.33); miR-133a, 1.46 (95% CI: 1.01-2.12) and miR-223, 2.05 (95% CI: 1.45-2.91)]. Nearly similar results were found if using five-year cardiovascular mortality as the outcome. However, if entering all five miRNAs (along with other covariates) into a single regression model, only low miR-19a remained a significant mortality predictor; and only in patients with coronary artery disease [3.00 (95% CI: 1.77-5.08)], but not in post-stroke patients [1.63 (95% CI: 0.94-2.86)]. CONCLUSIONS: In stable chronic coronary artery disease patients, low miR-19a expression was associated with a substantial increase in mortality risk independently of other conventional cardiovascular risk factors.

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 ß 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 (ß coefficient=-5.904; p=0.002) or insulin sensitivity (ß=0.042; p=0.001), but not with ß 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 [ß-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 DRD2/ANKK1 Taq1A polymorphism is associated with smoking cessation failure in patients with coronary heart disease.

AIM: We speculated whether DRD2 or CHRN subunit polymorphisms might be associated with the risk of smoking cessation failure in subjects after coronary heart disease (CHD) manifestation. METHODS: A total of 964 patients with CHD, mean age 64.3 years (standard deviation [SD] 9.0), examined in the EUROASPIRE III and IV surveys were genotyped for rs1800497 (DRD2/ANKK1 Taq1A), rs578776 (CHRNA5-A3-B4), rs16969968 (CHRNA5) and rs1051730 (CHRNA3) SNPs. RESULTS: The presence of DRD2/ANKK1 Taq1A minor T allele was independently associated with increased relative risk of smoking persistence (odds ratio: 1.79; 95% CI: 1.13-4.35). We observed no association between CHRN SNPs and smoking habit. CONCLUSION: DRD2/ANKK1 Taq1A polymorphism is associated with a decreased likelihood of smoking cessation in patients after CHD manifestation.