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Maurizio Averna

Publications and source records attributed to Maurizio Averna.

16 recordsLinked to original sources
PubMed2006

A novel loss of function mutation of PCSK9 gene in white subjects with low-plasma low-density lipoprotein cholesterol.

OBJECTIVES: The PCSK9 gene, encoding a pro-protein convertase involved in posttranslational degradation of low-density lipoprotein receptor, has emerged as a key regulator of plasma low-density lipoprotein cholesterol. In African-Americans two nonsense mutations resulting in loss of function of PCSK9 are associated with a 30% to 40% reduction of plasma low-density lipoprotein cholesterol. The aim of this study was to assess whether loss of function mutations of PCSK9 were a cause of familial hypobetalipoproteinemia and a determinant of low-plasma low-density lipoprotein cholesterol in whites. METHODS AND RESULTS: We sequenced PCSK9 gene in 18 familial hypobetalipoproteinemia subjects and in 102 hypocholesterolemic blood donors who were negative for APOB gene mutations known to cause familial hypobetalipoproteinemia. The PCSK9 gene variants found in these 2 groups were screened in 42 subjects in the lowest (<5th) percentile, 44 in the highest (>95th) percentile, and 100 with the average plasma cholesterol derived from general population. In one familial hypobetalipoproteinemia kindred and in 2 hypocholesterolemic blood donors we found a novel PCSK9 mutation in exon 1 (c.202delG) resulting in a truncated peptide (Ala68fsLeu82X). Two familial hypobetalipoproteinemia subjects and 4 hypocholesterolemic blood donors were carriers of the R46L substitution previously reported to be associated with reduced low-density lipoprotein cholesterol as well as other rare amino acid changes (T77I, V114A, A522T and P616L) not found in the other groups examined. CONCLUSIONS: We discovered a novel inactivating mutation as well as some rare nonconservative amino acid substitutions of PCSK9 in white hypocholesterolemic individuals.

Adult↗
PubMed2006

The c.43_44insCTG variation in PCSK9 is associated with low plasma LDL-cholesterol in a Caucasian population.

The genetic etiology of familial hypobetalipoproteinemia (FHBL) is unclear in the majority of cases. Mutations in apolipoprotein B (APOB) are the only confirmed causes of FHBL. Recently, loss-of-function mutations of PCSK9 gene have been shown to be associated with the hypocholesterolemia phenotype. Our primary goal was to confirm that mutations in PCSK9 could be another cause of FHBL. Using the sequencing approach, we found that the c.43_44insCTG variation in PCSK9, a common in-frame insertion in both African American and Caucasian populations, is associated with the hypocholesterolemia phenotype in three FHBL families. Then we tested whether this variation could be associated with lower cholesterol levels in the general population. A total of 403 subjects from a Caucasian population, in which hypobetalipoprotein (HBL) and normal groups were classified using standard criteria, were sequenced for this variation. The allele frequency of this variation in the HBL group was 0.186, but was only 0.128 in the normal lipid group. The mean plasma low-density lipoprotein (LDL)-cholesterol level in subjects heterozygous for this variant is significantly lower than that in the normal group (p<0.01). Heterozygous subjects also had higher high-density lipoprotein (HDL)-cholesterol levels (p<0.01). In general, LDL-cholesterol concentration in individuals with PCSK9 c.43_44insCTG variation was approximately 10-15 mg/dL lower than that in normal individuals. We conclude that the c.43_44insCTG variant plays a role in lowering cholesterol in the general population.

Adolescent↗
PubMed2006

Gene expression in mouse spermatogenesis during ontogenesis.

In this study, we evaluated the expression of genes probably involved in spermatogenesis in the mouse. We examined cytosolic chaperonin theta subunit (CCTtheta), Ngg1 interacting factor 3 like 1 binding protein 1 (NIF3L1 BP1) and apolipoprotein H (ApoH) expression during mouse onto-geny using RT-PCR. Testicular tissue was obtained from mice 3, 6, 8, 10, 12, 14, 18, 20 and 40 (adult) days after birth. For each mouse, one testis was used for histological examination, whereas RNA was extracted from the controlateral testis for expression analysis. RT-PCR analysis showed that CCTtheta gene expression was low until day 10, but increased drastically afterwards. At this age, spermatocytes started to be present in the mouse testis. Therefore, CCT protein could be involved in chromatin packaging and remodeling during spermiogenesis, as also suggested by other studies. NIF3L1 BP1 expression increased steadily during ontogenesis reaching maximum levels in the adult mouse when all germ cell stages are present. This finding suggests that NIF3L1 BP1 is a gene not expressed by a specific germ cell type. ApoH expression was very low or absent during prepuberal stages, whereas it was detectable in the adult testis when spermatogenesis was completed. This suggests that ApoH may be involved in clearing apoptotic bodies during spermatogenesis since apoptotic events increase during spermatogenesis. This study contributes to understanding the role played by genes important for spermatogenesis.

Animals↗
PubMed2005

Additive effect of mutations in LDLR and PCSK9 genes on the phenotype of familial hypercholesterolemia.

Patients homozygous or compound heterozygous for LDLR mutations or double heterozygous for LDLR and apo B R3500Q mutation have higher LDL-C levels, more extensive xanthomatosis and more severe premature coronary disease (pCAD) than simple heterozygotes for mutations in either these genes or for missense mutations in PCSK9 gene. It is not known whether combined mutations in LDLR and PKCS9 are associated with such a severe phenotype. We sequenced Apo B and PCSK9 genes in two patients with the clinical diagnosis of homozygous FH who were heterozygous for LDLR gene mutations. Proband Z.P. (LDL-C 13.39 mmol/L and pCAD) was heterozygous for an LDLR mutation (p.E228K) inherited from her father (LDL-C 8.07 mmol/L) and a PCSK9 mutation (p.R496W) from her mother (LDL-C 5.58 mmol/L). Proband L.R. and her sister (LDL-C 11.51 and 10.47 mmol/L, xanthomatosis and carotid atherosclerosis) were heterozygous for an LDLR mutation (p.Y419X) inherited from their mother (LDL-C 6.54 mmol/L) and a PCSK9 mutation (p.N425S) probably from their deceased father. The LDL-C levels in double heterozygotes of these two families were 56 and 44% higher than those found in simple heterozygotes for the two LDLR mutations, respectively. The two PCSK9 mutations are novel and were not found in 110 controls and 80 patients with co-dominant hypercholesterolemia. These observations indicate that rare missense mutations of PCSK9 may worsen the clinical phenotype of patients carrying LDLR mutations.

Adult↗
PubMed2005

Mutations in MTP gene in abeta- and hypobeta-lipoproteinemia.

Familial hypobetalipoproteinemia (FHBL) and abetalipoproteinemia (ABL) are inherited disorders of apolipoprotein B (apo B)-containing lipoproteins that result from mutations in apo B and microsomal triglyceride transfer protein (MTP) genes, respectively. Here we report three patients with severe deficiency of plasma low-density lipoprotein (LDL) and apo B. Two of them (probands F.A. and P.E.) had clinical and biochemical phenotype consistent with ABL. Proband F.A. was homozygous for a minute deletion/insertion (c.1228delCCCinsT) in exon 9 of MTP gene predicted to cause a truncated MTP protein of 412 amino acids. Proband P. E. was heterozygous for a mutation in intron 9 (IVS9-1G>A), previously reported in an ABL patient. We failed to find the second pathogenic mutation in MTP gene of this patient. No mutations were found in apo B gene. The third proband (D.F.) had a less severe lipoprotein phenotype which was similar to that of heterozygous FHBL and appeared to be inherited as a co-dominant trait. However, he had no mutations in apo B gene. He was found to be a compound heterozygote for two missense mutations (D384A and G661A), involving highly conserved regions of MTP. Since this proband was also homozygous for varepsilon2 allele of apolipoprotein E (apo E), it is likely that his hypobetalipoproteinemia derives from a combined effect of a mild MTP deficiency and homozygosity for apo E2 isoform.

Abetalipoproteinemia↗
PubMed2005

A novel mutation of the DHCR7 gene in a sicilian compound heterozygote with Smith-Lemli-Opitz Syndrome.

INTRODUCTION: Smith-Lemli-Opitz syndrome (SLOS) is an autosomal recessive disorder of cholesterol biosynthesis, resulting from deficient 7-dehydrocholesterol reductase (3beta-hydroxysterol Delta7-reductase) activity, the enzyme responsible for conversion of 7-dehydrocholesterol to cholesterol. SLOS is most common among people of European descent, with a reported incidence of 1 per 20,000-60,000 newborns, depending on the diagnostic criteria and the reference population. More than 80 different mutations have been identified in several hundred patients. In Italy, SLOS appears to be a rare condition, probably because of underdiagnosis. METHOD: We analyzed by direct sequencing the 7-dehydrocholesterol reductase gene (DHCR7) in a Sicilian patient with Smith-Lemli-Opitz syndrome and his parents in order to characterize the molecular defect. RESULTS: The molecular analysis of the coding exons and the intron-exon boundaries of the DHCR7 gene demonstrated the presence of two missense mutations: a novel mutation (I251N) and a known mutation (E288K) responsible in a compound heterozygous state for a severe form of SLOS. CONCLUSION: The present study describes a Sicilian patient, a carrier of a novel mutation of the DHCR7 gene (I251N), which is responsible in a compound heterozygous state for a severe form of SLOS.

Heterozygote↗
PubMed2005

Bovine seminal ribonuclease is cytotoxic for both malignant and normal telomerase-positive cells.

Bovine seminal-ribonuclease (BS-RNase) is a member of the 'ribonucleases with special biological actions' family since it possesses specific anti-tumour, anti-spermatogenic and embryotoxic activities and exerts an immunosuppressive effect on T lymphocytes. In previous studies it was demonstrated that BS-RNase induced apoptosis in proliferating, malignant and normal cells and that telomerase activity loss also caused apoptotic death in neoplastic cells. Since an obvious relationship between cell proliferation and telomerase activity exists, the aim of this work was to study if the pro-apoptotic cytotoxic action exerted by BS-RNase on proliferating malignant cells (HT29) and proliferating normal cells (PHA-stimulated lymphocytes) could be linked to a possible BS-RNase effect on telomerase activity. In BS-RNase-treated HT29 cells (Na-butyrate-differentiated or not) and human lymphocytes (proliferating or not), we investigated cell vitality (MTT method) and morphology (SEM), BS-RNase localization (immunofluorescence), telomerase activity (TRAP-ELISA method), hTR mRNA expression (RT-PCR), and hTERT levels (western blot). While no BS-RNase effect was detectable on not proliferating cells, a clear relationship was noticed between the diminished number of vital elements of both proliferating cell populations after treatment (48 h and 72 h for HT29 and PHA-stimulated lymphocytes, respectively) with 50 microg/ml BS-RNase and the decrease of their telomerase activity. At the same time, we found that hTR levels, the RNA subunit of telomerase, in proliferation-inhibited BS-RNase-treated cells were diminished. Moreover, by immunofluorescence technique, we detected BS-RNase in the HT29 cell nucleolus after 3-h treatment. Therefore, as hTR has been recently proven to co-fractionate with nucleoli, we hypothesize that a BS-RNase direct action on the telomerase hTR subunit could be a possible mechanism of action by which BS-RNase exerts its pro-apoptotic effects only on proliferating cells.

Animals↗
PubMed2004

A polymorphism in the cyclooxygenase 2 gene as an inherited protective factor against myocardial infarction and stroke.

CONTEXT: Myocardial infarction (MI) and ischemic stroke are thought to be caused by matrix digestion by metalloproteinases (MMPs) leading to rupture of atherosclerotic plaques. Production of macrophage MMP-2 and MMP-9 is induced by cyclooxygenase 2 (COX-2) and prostaglandin E(2) synthesis. Although COX-2 expression may be genetically determined, the relation between COX-2 polymorphisms and the risk of MI and stroke is unclear. OBJECTIVE: To investigate the relationship between the -765G-->C polymorphism of the COX-2 gene and clinically evident plaque rupture. DESIGN, SETTING, AND PARTICIPANTS: Prospective, matched case-control study conducted between March 2002 and October 2003 among 864 patients with first MI or atherothrombotic ischemic stroke and 864 hospitalized controls. The groups were matched for age, sex, body mass index, smoking, hypertension, hypercholesterolemia, and diabetes. The -765G-->C variant of the COX-2 gene was genotyped by restriction endonuclease digestion of polymerase chain reaction products. MAIN OUTCOME MEASURES: Presence of the -765G-->C polymorphism of the COX-2 gene; COX-2, MMP-2, and MMP-9 expression and activity in plaques and in peripheral monocytes; urinary 6-keto PGF1alpha (marker of endothelial prostacyclin); and endothelium-dependent and -independent forearm blood flow vasodilation. RESULTS: The prevalence of -765GC was 2.41 times higher among controls than among cases (43.3% vs 17.9%; P<.001). The prevalence of -765CC homozygosity was 5.81 times higher (6.4% vs 1.1%; P =.04). Among participants carrying the -765GC and -765CC genotypes, the prevalence ratios for MI or stroke were 0.48 (95% CI, 0.36-0.68) and 0.33 (95% CI, 0.24-0.55), respectively. Expression of COX-2 and MMPs was significantly lower in atherosclerotic plaques from participants carrying the -765C allele, while the -765G-->C polymorphism did not affect endothelial prostacyclin biosynthesis or endothelium-dependent vasodilation in vivo. In subgroup analyses (n = 224 cases), serum high-sensitivity C-reactive protein was significantly lower in patients carrying the -765C allele (mean [SD], 0.78 [0.1] vs 2.56 [0.4] mg/L; P =.04). CONCLUSIONS: We found that the -765G-->C polymorphism of the COX-2 gene is associated with a decreased risk of MI and stroke. Detection of this genotype may be useful for predicting genetic risk of MI and stroke.

Arteriosclerosis↗
PubMed2004

Familial HDL deficiency due to ABCA1 gene mutations with or without other genetic lipoprotein disorders.

Mutations in ABCA1 have been shown to be the cause of Tangier disease (TD) and some forms of familial hypoalphalipoproteinemia (HA), two genetic disorders characterized by low plasma HDL levels. Here we report six subjects with low HDL, carrying seven ABCA1 mutations, six of which are previously unreported. Two mutations (R557X and H160FsX173) were predicted to generate short truncated proteins; two mutations (E284K and Y482C) were located in the first extracellular loop and two (R1901S and Q2196H) in the C-terminal cytoplasmic domain of ABCA1. Two subjects found to be compound heterozygotes for ABCA1 mutations did not have overt clinical manifestations of TD. Three subjects, all with premature coronary artery disease (pCAD), had a combination of genetic defects. Besides being heterozygotes for ABCA1 mutations, two of them were also carriers of the R3500Q substitution in apolipoprotein B and the third was a carrier of N291S substitution in lipoprotein lipase. By extending family studies we identified 17 heterozygotes for ABCA1 mutations. Plasma HDL-C and Apo A-I values in these subjects were 38.3 and 36.9% lower than in unaffected family members and similar to the values found in heterozygotes for Apo A-I gene mutations which prevent Apo A-I synthesis. This survey underlines the allelic heterogeneity of ABCA1 mutations and suggests that: (i) TD subjects, if asymptomatic, may be overlooked and (ii) there may be a selection bias in genotyping towards carriers of ABCA1 mutations who have pCAD possibly related to a combination of genetic and environmental cardiovascular risk factors.

ATP Binding Cassette Transporter 1↗
PubMed2004

Genetic polymorphisms affecting the phenotypic expression of familial hypercholesterolemia.

The clinical expression of heterozygous familial hypercholesterolemia (FH) is highly variable even in patients carrying the same LDL receptor (LDL-R) gene mutation. This variability might be due to environmental factors as well as to modifying genes affecting lipoprotein metabolism. We investigated Apo E (2, 3, 4), MTP (-493G/T), Apo B (-516C/T), Apo A-V (-1131T/C), HL (-514C/T and -250G/A), FABP-2 (A54T), LPL (D9N, N291S, S447X) and ABCA1 (R219K) polymorphisms in 221 unrelated FH index cases and 349 FH relatives with defined LDL-R gene mutations. We found a significant and independent effect of the following polymorphisms on: (i) plasma LDL-C (Apo E, MTP and Apo B); (ii) plasma HDL-C (HL, FABP-2 and LPL S447X); (iii) plasma triglycerides (Apo E and Apo A-V). In subjects with coronary artery disease (CAD+), the prevalence of FABP-2 54TT genotype was higher (16.5% versus 5.2%) and that of ABCA1 219RK and KK genotypes lower (33.0% versus 51.5%) than in subjects with no CAD. Independent predictors of increased risk of CAD were male sex, age, arterial hypertension, LDL-C level and FABP-2 54TT genotype, and of decreased risk the 219RK and KK genotypes of ABCA1. These findings show that several common genetic variants influence the lipid phenotype and the CAD risk in FH heterozygotes.

Adult↗
PubMed2004

Beta-2-glycoprotein I is growth regulated and plays a role as survival factor for hepatocytes.

Beta-2-glycoprotein I (beta(2)GPI) is mainly produced by the liver and is found in plasma partially associated to lipoproteins. Although various properties have been attributed to this protein, its physiological role remains still unclear. We investigated its expression in cultured liver cells and in regenerating liver. Expression studies in HepG2 cells demonstrate that beta(2)GPI mRNA is regulated in a cell cycle-dependent manner, with very low expression in low cycling conditions and increasing levels in proliferating cells. p21 WAF-dependent growth arrest, induced by butyrate treatment, down-regulate beta(2)GPI mRNA levels. Immunolocalization in normal rat liver shows a non-homogeneous pattern, being mainly present in the centrolobular area; post-hepatectomy regenerating rat liver is uniformly immunostained and mitotic elements show the highest protein expression. Albumin gene expression, studies as control liver specific product, was not affected by sodium butyrate induced growth arrest. As previously reported for endothelial cells, beta(2)GPI behaves as survival factor for HepG2 cells: when increasing amounts of the protein (10-50 microg) have been added to serum deficient cultured liver cells a progressive reduced cell loss was observed. In conclusion, the present data demonstrate that beta(2)GPI gene expression is strictly related to the proliferative status of hepatic cells and that this protein could play a role in maintaining liver cells vitality when exposed to different stress factors such as regeneration after partial hepatectomy or growth factors depletion.

Albumins↗
PubMed2003

Differential apolipoprotein(a) isoform expression in heterozygosity is an independent contributor to lipoprotein(a) levels variability.

BACKGROUND AND METHODS: Lipoprotein(a) [Lp(a)] levels represent an independent risk factor for cardio- and cerebrovascular diseases. Since lipoprotein(a) levels show a wide variability even in subjects with similar apolipoprotein(a) isoforms, we investigated the contribution of apolipoprotein(a) heterozygosity to lipoprotein(a) variance. Lipoprotein(a) levels, apolipoprotein(a) isoforms identification and expression, and the correlation with other lipo-apolipoprotein parameters have been investigated in 628 subjects >18 years of age. RESULTS: In our study, 246 subjects were found heterozygous for apolipoprotein(a) isoforms. Lipoprotein(a) levels were higher in females. About 40% of the subjects expressed the larger isoform more intensely than the dominant isoform. Lipoprotein(a) was correlated with apolipoprotein(a) dominant isoform size, HDL-cholesterol and smaller apolipoprotein(a) isoform expression rate. Lipoprotein(a) was independently correlated with the smaller apolipoprotein(a) isoform, with its expression rate and with LDL-cholesterol. The inclusion of the smaller apolipoprotein(a) expression rate in a multiple regression model explained at least an additional 4% of the lipoprotein(a) variance after correction for apolipoprotein(a) size. CONCLUSIONS: The smaller isoforms are not always effectively dominant in heterozygosis since 40% of the subjects expressed more the larger isoform. The individual variability of apolipoprotein(a) isoform expression in heterozygosis could explain part of the lipoprotein(a) levels variability.

Adult↗
PubMed2002

Fatty liver in familial hypobetalipoproteinemia: triglyceride assembly into VLDL particles is affected by the extent of hepatic steatosis.

Familial hypobetalipoproteinemia (FHBL) subjects may develop fatty liver. Liver fat was assessed in 21 FHBL with six different apolipoprotein B (apoB) truncations (apoB-4 to apoB-89) and 14 controls by magnetic resonance spectroscopy (MRS). Liver fat percentages were 16.7 +/- 11.5 and 3.3 +/- 2.9 (mean +/- SD) (P = 0.001). Liver fat percentage was positively correlated with body mass index, waist circumference, and areas under the insulin curves of 2 h glucose tolerance tests, suggesting that obesity may affect the severity of liver fat accumulation in both groups. Despite 5-fold differences in liver fat percentage, mean values for obesity and insulin indexes were similar. Thus, for similar degrees of obesity, FHBL subjects have more hepatic fat. VLDL-triglyceride (TG)-fatty acids arise from plasma and nonplasma sources (liver and splanchnic tissues). To assess the relative contributions of each, [2H2]palmitate was infused over 12 h in 13 FHBL subjects and 11 controls. Isotopic enrichment of plasma free palmitate and VLDL-TG-palmitate was determined by mass spectrometry. Non-plasma sources contributed 51 +/- 15% in FHBL and 37 +/- 13% in controls (P = 0.02). Correlations of liver fat percentage and percent VLDL-TG-palmitate from liver were r = 0.89 (P = 0.0001) for FHBL subjects and r = 0.69 (P = 0.01) for controls. Thus, apoB truncation-producing mutations result in fatty liver and in altered assembly of VLDL-TG.

Adult↗
PubMed2002

Replication of linkage of familial hypobetalipoproteinemia to chromosome 3p in six kindreds.

Familial hypobetalipoproteinemia (FHBL) is a genetically heterogeneous condition characterized by very low apolipoprotein B (apoB) concentrations in plasma and/or low levels of LDL-cholesterol (LDL-C) with a propensity to developing fatty liver. In a minority of cases, truncation-specifying mutations of the apoB gene (APOB) are etiologic, but the genetic basis of most cases is unknown. We previously reported linkage of FHBL to a 10 cM region on 3p21.1-22 in one kindred. The objectives of the current study were to identify other FHBL families with linkage to 3p and to narrow the FHBL susceptibility region on 3p. Six additional FHBL kindreds unlinked to the APOB region on chromosome 2 were genotyped with polymorphic markers spanning a region of approximately 13 cM on chromosome 3. Quantitative linkage analyses indicated that the FHBL in these families was linked to 3p21.1-22. Haplotype analysis identified several meiotic crossover events, allowing us to narrow the critical region from 10 cM to 2.0 cM, between markers D3S2407 and D3S1767.

Adult↗
PubMedDate not supplied

Association between HFE mutations and acute myocardial infarction: a study in patients from Northern and Southern Italy.

There is interest in the role of iron in age-related diseases such as atherosclerosis. Tissue iron deposition could be harmful, because Fe(2+) can react with H(2)O(2) to form OH(-) radicals and Fe(2+) can react with O(2) to form reactive oxygen species. Free radicals react with cell membranes and cell organelles and could lead to the development of atherosclerosis by initiating lipid peroxidation. Hereditary hemochromatosis provides an opportunity for studying the effects of iron on cardiovascular disease. Some studies have shown that individuals who carried HFE mutations may be at greater risk of developing coronary heart disease than those without the mutations. In contrast, a large number of studies have reported no association between HFE mutations and coronary heart disease. These studies have possible confounding factors, such as the homogeneity of the population in term of geographical origin among others. We studied the relation between HFE mutations and acute myocardial infarction in two case-control studies involving two sets of subjects representing different age groups from different geographic regions in Italy. The first one was composed of 172 older patients (139 males and 33 females; mean age 67) and 207 healthy controls (91 males and 116 females; mean age 46) from Emilia-Romagna. The second one was composed of younger 77 patients (75 males and 2 females; mean age 41) and 172 healthy controls (75 males and 97 females, mean age: 38) from Sicily. All patients were genotyped for ApoE alleles, since the ApoE- epsilon 4 allele is considered a risk factor for cardiovascular diseases and can interfere with other genetic and environmental factors by modifying susceptibility to this disease. DNA typing for C282Y and H63D HFE alleles was performed also. There were no significant differences in frequencies of the different HFE alleles between acute myocardial infarction patients and controls in cohorts of both old and young patients. Also taking into account the presence or absence of the ApoE- epsilon 4 allele, no significant differences in H63D allele frequencies were observed. Thus, our study, performed in two samples of genetically homogeneous patients and controls, does not support the suggestion that HFE mutations may be associated with acute myocardial infarction in susceptible individuals.

Adult↗