Giuliana Fortunato

Refinement of Variant Selection for the LDL Cholesterol Genetic Risk Score in the Diagnosis of the Polygenic Form of Clinical Familial Hypercholesterolemia and Replication in Samples from 6 Countries

BACKGROUND Familial hypercholesterolemia (FH) is an autosomal-dominant disorder caused by mutations in 1 of 3 genes. In the 60% of patients who are mutation negative, we have recently shown that the clinical phenotype can be associated with an accumulation of common small-effect LDL cholesterol (LDL-C)-raising alleles by use of a 12-single nucleotide polymorphism (12-SNP) score. The aims of the study were to improve the selection of SNPs and replicate the results in additional samples. METHODS We used ROC curves to determine the optimum number of LDL-C SNPs. For replication analysis, we genotyped patients with a clinical diagnosis of FH from 6 countries for 6 LDL-C-associated alleles. We compared the weighted SNP score among patients with no confirmed mutation (FH/M-), those with a mutation (FH/M+), and controls from a UK population sample (WHII). RESULTS Increasing the number of SNPs to 33 did not improve the ability of the score to discriminate between FH/M- and controls, whereas sequential removal of SNPs with smaller effects/lower frequency showed that a weighted score of 6 SNPs performed as well as the 12-SNP score. Metaanalysis of the weighted 6-SNP score, on the basis of polymorphisms in CELSR2 (cadherin, EGF LAG 7-pass G-type receptor 2), APOB (apolipoprotein B), ABCG5/8 [ATP-binding cassette, sub-family G (WHITE), member 5/8], LDLR (low density lipoprotein receptor), and APOE (apolipoprotein E) loci, in the independent FH/M- cohorts showed a consistently higher score in comparison to the WHII population (P < 2.2 × 10(-16)). Modeling in individuals with a 6-SNP score in the top three-fourths of the score distribution indicated a >95% likelihood of a polygenic explanation of their increased LDL-C. CONCLUSIONS A 6-SNP LDL-C score consistently distinguishes FH/M- patients from healthy individuals. The hypercholesterolemia in 88% of mutation-negative patients is likely to have a polygenic basis.

A paraoxonase gene polymorphism, PON 1 (55), as an independent risk factor for increased carotid intima-media thickness in middle-aged women.

Paraoxonase (PON) gene polymorphisms have been proposed as genetic markers of risk for cardiovascular disease (CVD). Sporadic results suggest they are correlated with intima-media thickness (IMT), an indicator of preclinical atherosclerotic disease. We have investigated whether polymorphisms PON 1 (M/L) 55, (Q/R) 192, PON 2 (S/C) 311 are related to site-specific carotid plaques in 310 middle-aged women. Subjects were also investigated for physical and biochemical parameters including oxidative markers to evaluate their effect on development of atherosclerotic plaques (IMT>1.2 mm) identified by high resolution B-mode ultrasound. We demonstrate that PON 1 (LL+ML) 55 is associated with plaques both at the bifurcation (OR=2.40; 95% CI 1.00-5.90) and at the common carotid artery (OR=2.75; 95% CI 1.01-7.50), and to the total number of plaques at any site (P<0.05). This polymorphism is an independent parameter with respect to other variables that are significantly associated with plaques, i.e. systolic blood pressure (OR=2.06; 95% CI 1.11-3.81) and oxidized low-density lipoprotein (LDL) antibodies (OR=1.96; 95% CI 1.05-3.69) in cases of common carotid plaques, and lipid peroxides (OR=1.86; 95% CI 1.00-3.50) in cases of bifurcation plaques. In conclusion, PON 1 (LL+ML) 55 but not PON 1 (Q/R) 192 or PON 2 (S/C) 311, appears to be an independent risk factor for increased carotid IMT in middle-aged women.

Identification and functional characterization of malignant hyperthermia mutation T1354S in the outer pore of the Cavα1S-subunit

To identify the genetic locus responsible for malignant hyperthermia susceptibility (MHS) in an Italian family, we performed linkage analysis to recognized MHS loci. All MHS individuals showed cosegregation of informative markers close to the voltage-dependent Ca(2+) channel (Ca(V)) α(1S)-subunit gene (CACNA1S) with logarithm of odds (LOD)-score values that matched or approached the maximal possible value for this family. This is particularly interesting, because so far MHS was mapped to >178 different positions on the ryanodine receptor (RYR1) gene but only to two on CACNA1S. Sequence analysis of CACNA1S revealed a c.4060A>T transversion resulting in amino acid exchange T1354S in the IVS5-S6 extracellular pore-loop region of Ca(V)α(1S) in all MHS subjects of the family but not in 268 control subjects. To investigate the impact of mutation T1354S on the assembly and function of the excitation-contraction coupling apparatus, we expressed GFP-tagged α(1S)T1354S in dysgenic (α(1S)-null) myotubes. Whole cell patch-clamp analysis revealed that α(1S)T1354S produced significantly faster activation of L-type Ca(2+) currents upon 200-ms depolarizing test pulses compared with wild-type GFP-α(1S) (α(1S)WT). In addition, α(1S)T1354S-expressing myotubes showed a tendency to increased sensitivity for caffeine-induced Ca(2+) release and to larger action-potential-induced intracellular Ca(2+) transients under low (≤ 2 mM) caffeine concentrations compared with α(1S)WT. Thus our data suggest that an additional influx of Ca(2+) due to faster activation of the α(1S)T1354S L-type Ca(2+) current, in concert with higher caffeine sensitivity of Ca(2+) release, leads to elevated muscle contraction under pharmacological trigger, which might be sufficient to explain the MHS phenotype.

Homocysteine levels and sustained virological response to pegylated‐interferon α2b plus ribavirin therapy for chronic hepatitis C: a prospective study

Background: Chronic hepatitis C affects about 3% of the worlds population. Pegylated interferon (IFN) α plus ribavirin is the gold standard treatment. Methylenetetrahydrofolate reductase(MTHFR) is a key enzyme in the metabolism of homocysteine. MTHFR gene polymorphisms and high levels of homocysteine are associated with a high degree of steatosis and fibrosis, conditions associated with a low sustained virological response (SVR) rate.

Multiple Sclerosis and Hepatitis C Virus Infection Are Associated with Single Nucleotide Polymorphisms in Interferon Pathway Genes

We have studied 35 single nucleotide polymorphisms (SNPs) in the interferon (IFN) pathway to determine their contribution to multiple sclerosis (MS) and hepatitis C virus (HCV) infection. A total of 182 patients with MS, 103 patients with chronic hepatitis C, and 118 control subjects were enrolled in the study. Of the 35 SNPs studied, 3 were in IFN-alpha receptor (IFNAR-1), 10 in IFN-alpha/beta receptor (IFNAR-2), 9 in Stat1, 5 in Stat2, and 8 in IFN regulatory factor-1 (IRF-1). Compared to controls, Stat1 gene polymorphisms were significantly more frequent in MS patients (rs# 2066802 OR = 7.46, 95% CI = 2.22-25.10; rs# 1547550 OR = 1.69, 95% CI = 1.01-2.81) and in HCV patients (rs# 2066802 OR = 5.95, 95% CI = 1.55-22.81; rs# 1547550 OR = 2.30, 95% CI = 1.24-4.24). Also one IRF-1 gene SNP was associated with MS (rs# 2070721 OR = 2.05, 95% CI = 1.03-4.09), and four IRF-1 gene SNPs were associated with HCV infection (rs# 2070721 OR = 2.59, 95% CI = 1.23-5.43; rs# 2070723 OR = 4.8, 95% CI = 1.26-18.20; rs# 2070728 OR = 9.81, 95% CI = 1.21-79.4; rs# 2070729 OR = 3.6, 95% CI = 1.23-10.48; rs# 839 OR = 4.67, 95%CI = 1.29-16.87). Characteristic nucleotide combinations on single chromosomes (haplotype) generated block structures, including SNPs, that differed between patients and controls. Using a permutation test to detect differences in haplotype distribution between groups, the CCATTGA and the CCGAA haplotypes in the IRF-1 gene were more frequent in MS (p = 0.03) and in HCV patients (p = 0.001) than in controls. In conclusion, our data show that genetic variants in the IRF-1 and Stat1 genes of the IFN pathway are associated with MS and HCV infection.

Decreased Paraoxonase-2 Expression in Human Carotids During the Progression of Atherosclerosis

Objective—Many gene products involved in oxidation and inflammation are implicated in the pathogenesis of atherosclerosis. We investigated paraoxonase 2 (PON2), 5-lipoxygenase (5-LO), and 5-LO activating protein (FLAP) expression and malondialdehyde (MDA) levels in carotid lesions to assess their involvement in plaque formation. Methods and Results—We measured gene expression and MDA levels in atherosclerotic plaques from 59 patients undergoing carotid endarterectomy, and in plaque-adjacent tissue from 41/59 patients. Twenty-three fetal carotids and 6 mammary arteries were also investigated. Real-time polymerase chain reaction and immunohistochemistry revealed decreased PON2 expression in plaques versus adjacent regions (P<0.005, P<0.001, respectively), mammary arteries (P<0.031, P<0.001, respectively), and fetal carotids (both P<0.001). mRNA levels of 5-LO and FLAP were higher (P<0.038, P<0.005, respectively) in lesions versus fetal carotids. MDA was higher in plaques versus plaque-adjacent tissue and fetal carotids. PON2 mRNA was downregulated by oxidative stress in 5 ex vivo experiments, thereby indicating its possible atheroprotection role. Conclusions—We demonstrate that PON2 mRNA and protein are decreased in plaques versus plaque-adjacent tissue, mammary arteries, and fetal carotids. Our data indicate that the protective effect of PON2 could fail during atherosclerosis exacerbation; this was confirmed by the increase of MDA levels. The increase of 5-LO and FLAP mRNA expression confirms their role as inflammatory markers associated to atherosclerosis.

Prevalence and Long-term Course of Macro-Aspartate Aminotransferase in Children

OBJECTIVES To investigate the prevalence, association with clinical conditions, and long-term course of macro-aspartate aminotransferase (macro-AST). STUDY DESIGN Forty-four children with an isolated elevation of serum AST were screened for macro-AST with electrophoresis and % polyethylene glycol (PEG) precipitable activity (PPA). RESULTS All children were healthy, except they had elevated AST values. Seventeen children (38.6%) were macro-AST-positive. They had higher AST values than the 27 children who were macro-AST-negative (P = .001). Values <67.1% PPA and >82.2% PPA were associated with a very low probability of being macro-AST-positive and macro-AST-negative, respectively. Thirty-eight children underwent clinical and laboratory follow-up (mean, 4.7 +/- 3.8; range, 1-16 years). All remained symptom-free. AST levels decreased significantly only in children who were macro-AST-negative (P = .006). Macroenzyme persisted in 6 of the 9 children who were macro-AST-positive after 6.0 +/- 4.1 years. CONCLUSIONS Macro-AST was present in more than one-third of children with an isolated increase of AST levels. The lack of pathological correlates in a long period argues for the benign nature of this phenomenon in childhood. We suggest that our %PPA thresholds can be used as a screening test and that electrophoresis be reserved for confirming positive screen test results and cases in which %PPA levels are of intermediate discriminant accuracy.

Cardiac troponin T and amino-terminal pro-natriuretic peptide concentrations in fetuses in the second trimester and in healthy neonates.

Abstract We measured the concentrations of cardiac troponin T (cTnT) and amino-terminal pro-natriuretic peptide (NT-proBNP) in umbilical cord blood during the second trimester (20–25weeks of gestation) and at delivery in 109 uncomplicated pregnancies to define reference values. Using the 97.5th percentile, the upper reference limits for cTnT and NT-proBNP were 0.308ng/mL and 5402pg/mL in fetuses in the second trimester, and 0.038ng/mL and 1690pg/mL in healthy neonates, respectively. We also evaluated whether labor and delivery mode affected the concentrations of the two analytes. We found significantly higher (p<0.001) umbilical blood NT-proBNP and cTnT levels at 20–25weeks of gestation than at term. In addition, within the term group, NT-proBNP concentrations were significantly higher in women delivering by elective cesarean section than in women delivering spontaneously (p<0.001), and higher than in women delivering by cesarean section during active labor. This indicates that the decrease in NT-proBNP levels is probably due to labor rather than delivery mode. Finally, we confirmed the at-birth reference values previously established for cTnT and NT-proBNP. Clin Chem Lab Med 2006;44:834–6.

Altered expression of inflammation-related genes in human carotid atherosclerotic plaques

OBJECTIVE Inflammation is a pivotal process in atherosclerosis development and progression, but the underlying molecular mechanisms remain largely obscure. We have conducted an extensive expression study of atherosclerotic plaques to identify the inflammatory pathways involved in atherosclerosis. METHODS We studied 11 human carotid plaques, their respective adjacent regions and 7 control arteries from different subjects. Expression of 92 genes was studied by TaqMan low-density array human inflammation panel. Human aortic endothelial and smooth muscle cells were used for in vitro experiments. RESULTS The mRNA levels of 44/92 genes (48%) differed significantly between the tissues examined (13 up-regulated and 31 down-regulated). Dysregulated genes encode molecules belonging to different functional classes although most of them encode enzymes involved in the eicosanoid synthesis pathway. The expression of PTGIS and PTGIR genes was decreased in human aortic endothelial and smooth muscle cells stimulated with oxLDL and TNF-α. CONCLUSIONS This study not only reveals several dysregulated genes in human lesions but also focuses the role played by the genes involved in the eicosanoid synthesis pathway during atherosclerotic development. The decrease of PTGIS and PTGIR expression after oxLDL treatment mirrors the decreased mRNA levels in atherosclerotic lesions versus control arteries, which suggests that oxidation is important for PTGIS and PTGIR regulation in human vessel cells during atherosclerosis development.

Functional Characterization of Ryanodine Receptor (RYR1) Sequence Variants Using a Metabolic Assay in Immortalized B-Lymphocytes

Mutations in the RYR1 gene are linked to malignant hyperthermia (MH), central core disease and multi‐minicore disease. We screened by DHPLC the RYR1 gene in 24 subjects for mutations, and characterized functional alterations caused by some RYR1 variants. Three novel sequence variants and twenty novel polymorphisms were identified. Immortalized lymphoblastoid cell lines from patients with RYR1 variants and from controls were stimulated with 4‐chloro‐m‐cresol (4‐CmC) and the rate of extracellular acidification was recorded. We demonstrate that the increased acidification rate of lymphoblastoid cells in response to 4‐CmC is mainly due to RYR1 activation. Cells expressing RYR1 variants in the N‐terminal and in the central region of the protein (p.Arg530His, p.Arg2163Pro, p.Asn2342Ser, p.Glu2371Gly and p.Arg2454His) displayed higher activity compared with controls; this could account for the MH‐susceptible phenotype. Cell lines harboring RYR1Cys4664Arg were significantly less activated by 4‐CmC. This result indicates that the p.Cys4664Arg variant causes a leaky channel and depletion of intracellular stores. The functional changes detected corroborate the variants analyzed as disease‐causing alterations and the acidification rate measurements as a means to monitor Ca2+‐induced metabolic changes in cells harboring mutant RYR1 channels.