Davide Noto

A novel component of the metabolic syndrome: The oxidative stress

The metabolic syndrome (MS) represents a cluster of cardiovascular (CV) risk factors associated to CV disease and type 2 diabetes. It is still under debate whether MS is a mere aggregation of risk factors or it represents a clinical entity with visceral obesity as underlying pathophysiological trigger. The publication of several diagnostic criteria of MS by scientific associations or experts panels reflects this uncertainty in understanding the real nature of MS. Besides the metabolic disturbances of MS, as visceral obesity, hypertriglyceridemia, low HDL cholesterol, hypertension and hyperglycemia, novel mechanisms of arterial damage have been identified. This paper reviews the evidence showing that MS and MS factors are characterized by increased oxidative stress, a relevant factor contributing to the development of metabolic and cardiovascular complications. In the next future, the measure of plasma oxidative stress may contribute to identify a subset of MS patients at increased CV risk, candidates to more intensive therapies.

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.

Spectrum of mutations and phenotypic expression in patients with autosomal dominant hypercholesterolemia identified in Italy

OBJECTIVE To determine the spectrum of gene mutations and the genotype-phenotype correlations in patients with Autosomal Dominant Hypercholesterolemia (ADH) identified in Italy. METHODS The resequencing of LDLR, PCSK9 genes and a selected region of APOB gene were conducted in 1018 index subjects clinically heterozygous ADH and in 52 patients clinically homozygous ADH. The analysis was also extended to 1008 family members of mutation positive subjects. RESULTS Mutations were detected in 832 individuals: 97.4% with LDLR mutations, 2.2% with APOB mutations and 0.36% with PCSK9 mutations. Among the patients with homozygous ADH, 51 were carriers of LDLR mutations and one was an LDLR/PCSK9 double heterozygote. We identified 237 LDLR mutations (45 not previously reported), 4 APOB and 3 PCSK9 mutations. The phenotypic characterization of 1769 LDLR mutation carriers (ADH-1) revealed that in both sexes independent predictors of the presence of tendon xanthomas were age, the quintiles of LDL cholesterol, the presence of coronary heart disease (CHD) and of receptor negative mutations. Independent predictors of CHD were male gender, age, the presence of arterial hypertension, smoking, tendon xanthomas, the scalar increase of LDL cholesterol and the scalar decrease of HDL cholesterol. We identified 13 LDLR mutation clusters, which allowed us to compare the phenotypic impact of different mutations. The LDL cholesterol raising potential of these mutations was found to vary over a wide range. CONCLUSIONS This study confirms the genetic and allelic heterogeneity of ADH and underscores that the variability in phenotypic expression of ADH-1 is greatly affected by the type of LDLR mutation.

Effect of the -420C/G variant of the resistin gene promoter on metabolic syndrome, obesity, myocardial infarction and kidney dysfunction.

Objective.  Resistin is an adipokine that has been suggested to be correlated with markers of inflammation and to be predictive of coronary atherosclerosis and type II diabetes in humans. A common single nucleotide polymorphism (SNP) (−420C/G) in the promoter of resistin is associated with increased resistin plasma levels and susceptibility to type II diabetes. The aim of this study was to investigate the association of the ‐420C/G polymorphism with metabolic syndrome, obesity, myocardial infarction and kidney disease.

Prevalence of overweight and obesity in a rural southern Italy population and relationships with total and cardiovascular mortality: the Ventimiglia di Sicilia project

OBJECTIVE: We investigated the prevalence of overweight and obesity and their relationships with the main cardiovascular risk factors in the population of Ventimiglia di Sicilia, a rural village in Southern Italy characterized by low cholesterol levels and by a low incidence of early coronary heart disease mortality. We related all deaths to body weight and fat distribution during an 8 y follow-up.DESIGN: Cross-sectional and prospective observational study.SUBJECTS: A total of 835 free-living individuals, 363 males and 472 females, of age between 20 and 69 y.MEASUREMENTS: In all participants body weight, waist-to-hip ratio (WHR), cardiovascular risk factors and plasma lipids were measured. During the follow-up, total and cardiovascular deaths were registered.RESULTS: We found a high overall prevalence of subjects with overweight or obesity (respectively 45.0% and 27.7%), with great differences among classes of age. As expected, body weight and fat distribution were associated with diabetes, hypertension, dyslipidemia and with a worsening of lipid profile. During the follow-up we registered 37 total and 11 cardiovascular deaths. All-cause and cardiovascular mortality risks were, respectively, 1.64 (95% CI 0.65–4.15) and 2.71 (95% CI 0.29–25.26) in subjects with a body mass index (BMI) of 27–29.99 kg/m2 and 2.45 (95% CI 1.03–5.87) and 5.36 (95% CI 1.41–62.01) in subjects with a BMI of≥30 kg/m2 in comparison with participants with a BMI of <27 kg/m2, and 3.48 (95% CI 1.46–8.30) and 4.55 (95% CI 1.12–18.40) in subjects with a WHR higher than the median in comparison with individuals with a WHR lower than the median.CONCLUSION: The Ventimiglia di Sicilia Study highlights the great importance of overweight and obesity as a public health issue in a rural population and indicates that it is necessary to consider the impact of body weight and fat distribution on both total and CHD mortality.

Novel LMF1 Nonsense Mutation in a Patient with Severe Hypertriglyceridemia

CONTEXT Lipase maturation factor 1 (LMF1) gene is a novel candidate gene in severe hypertriglyceridemia. Lmf1 is involved in the maturation of lipoprotein lipase (LPL) and hepatic lipase in endoplasmic reticulum. To date only one patient with severe hypertriglyceridemia and related disorders was found to be homozygous for a nonsense mutation in LMF1 gene (Y439X). OBJECTIVE The objective of the study was to investigate LMF1 gene in hypertriglyceridemic patients in whom mutations in LPL, APOC2, and APOA5 genes had been excluded. RESULTS The resequencing of LMF1 gene led to the discovery of a novel homozygous nonsense mutation in one patient with severe hypertriglyceridemia and recurrent episodes of pancreatitis. The mutation causes a G>A substitution in exon 9 (c.1395G>A), leading to a premature stop codon (W464X). LPL activity and mass were reduced by 76 and 50%, respectively, compared with normolipidemic controls. The proband over the years has shown a good response to treatment. The probands son, heterozygous for the W464X, shows normal plasma triglyceride levels. CONCLUSIONS We identified the second novel pathogenic mutation in LMF1 gene in a patient with severe hypertriglyceridemia. LPL deficiency in our patient was milder than in the carrier of the Y439X previously described.

Low‐density‐lipoprotein peak particle size in a Mediterranean population

Background The predominance of small, dense low‐density lipoprotein (LDL) particles (‘LDL phenotype B’) has been associated with a three‐fold increased risk of myocardial infarction, but the feasibility of the identification of small, dense LDL as independent predictors of coronary artery disease risk in population studies remains questioned.

Prevalence of ANGPTL3 and APOB Gene Mutations in Subjects With Combined Hypolipidemia

Objective—Mutations of the ANGPTL3 gene have been associated with a novel form of primary hypobetalipoproteinemia, the combined hypolipidemia (cHLP), characterized by low total cholesterol and low HDL-cholesterol levels. The aim of this work is to define the role of ANGPTL3 gene as determinant of the combined hypolipidemia phenotype in 2 large cohorts of 913 among American and Italian subjects with primary hypobetalipoproteinemia (total cholesterol <5th percentile). Methods and Results—The combined hypolipidemia cut-offs were chosen according to total cholesterol and HDL-cholesterol levels reported in the ANGPTL3 kindred described to date: total cholesterol levels, <2nd percentile and HDL-cholesterol, levels <2nd decile. Seventy-eight subjects with combined hypolipidemia were analyzed for ANGPTL3 and APOB genes. We identified nonsense and/or missense mutations in ANGPTL3 gene in 8 subjects; no mutations of the APOB gene were found. Mutated ANGPTL3 homozygous/compound heterozygous subjects showed a more severe biochemical phenotype compared to heterozygous or ANGPTL3 negative subjects, although ANGPTL3 heterozygotes did not differ from ANGPTL3 negative subjects. Conclusion—These results demonstrated that in a cohort of subjects with severe primary hypobetalipoproteinemia the prevalence of ANGPTL3 gene mutations responsible for a combined hypolipidemia phenotype is about 10%, whereas mutations of APOB gene are absent.

FragClust and TestClust, two informatics tools for chemical structure hierarchical clustering analysis applied to lipidomics. The example of Alzheimer's disease.

AbstractLipidomic analysis is able to measure simultaneously thousands of compounds belonging to a few lipid classes. In each lipid class, compounds differ only by the acyl radical, ranging between C10:0 (capric acid) and C24:0 (lignoceric acid). Although some metabolites have a peculiar pathological role, more often compounds belonging to a single lipid class exert the same biological effect. Here, we present a lipidomics workflow that extracts the tandem mass spectrometry data from individual files and uses them to group compounds into structurally homogeneous clusters by chemical structure hierarchical clustering analysis (CHCA). The case-to-control peak area ratios of the metabolites are then analyzed within clusters. We created two freely available applications to assist the workflow: FragClust to generate the tables to be subjected to CHCA, and TestClust to perform statistical analysis on clustered data. We used the lipidomics data from the plasma of Alzheimers disease (AD) patients in comparison with healthy controls to test the workflow. To date, the search for plasma biomarkers in AD has not provided reliable results. This article shows that the workflow is helpful to understand the behavior of whole lipid classes in plasma of AD patients. Graphical AbstractChemical Hierarchical Cluster Analysis applied to Lipidomics. Software assisted workflow.

A Novel APOB Mutation Identified by Exome Sequencing Cosegregates With Steatosis, Liver Cancer, and Hypocholesterolemia

Objective—In familial hypobetalipoproteinemia, fatty liver is a characteristic feature, and there are several reports of associated cirrhosis and hepatocarcinoma. We investigated a large kindred in which low-density lipoprotein cholesterol, fatty liver, and hepatocarcinoma displayed an autosomal dominant pattern of inheritance. Approach and Results—The proband was a 25-year-old female with low plasma cholesterol and hepatic steatosis. Low plasma levels of total cholesterol and fatty liver were observed in 10 more family members; 1 member was affected by liver cirrhosis, and 4 more subjects died of either hepatocarcinoma or carcinoma on cirrhosis. To identify the causal mutation in this family, we performed exome sequencing in 2 participants with hypocholesterolemia and fatty liver. Approximately 22 400 single nucleotide variants were identified in each sample. After variant filtering, 300 novel shared variants remained. A nonsense variant, p.K2240X, attributable to an A>T mutation in exon 26 of APOB (c.6718A>T) was identified, and this variant was confirmed by Sanger sequencing. The gentotypic analysis of 16 family members in total showed that this mutation segregated with the low cholesterol trait. In addition, genotyping of the PNPLA3 p.I148M did not show significant frequency differences between carriers and noncarriers of the c.6718A>T APOB gene mutation. Conclusions—We used exome sequencing to discover a novel nonsense mutation in exon 26 of APOB (p.K2240X) responsible for low cholesterol and fatty liver in a large kindred. This mutation may also be responsible for cirrhosis and liver cancer in this family.