Lack of Correlation of Plasma HDL With Fecal Cholesterol and Plasma Cholesterol Efflux Capacity Suggests Importance of HDL Functionality in Attenuation of Atherosclerosis

A number of clinical findings suggested HDL-raising as a plausible approach to treat residual risk of CVD. However, lack of CVD risk reduction by elevated HDL cholesterol (HDL-C) through cholesterol ester transfer protein (CETP) inhibition and enhanced risk reduction in apolipoprotein A-I Milano (apoAI-M) individuals with low HDL-C shifted the focus from HDL-C level to HDL function. In the present study, we investigated correlations between HDL-C, HDL function, fecal cholesterol excretion, and ex vivo plasma cholesterol efflux capacity (CEC) in animal models using two HDL modulators, LXR and PPAR-α agonists. In C57Bl mice, LXR agonist, T1317, raised HDL-C by 30%, while PPAR-α agonist, fenofibrate, reduced HDL-C by 30%, but fecal cholesterol showed twofold increase in both cases. CEC showed a 30–40% increase. Combination of LXR and PPAR-α agonists showed no changes in HDL-C, but, interestingly, fecal cholesterol increased by 4.5-fold, and CEC by 40%, suggesting existence of additional pathway for fecal cholesterol excretion. Regression analysis showed a lack of correlation between HDL-C and fecal cholesterol and CEC, while fecal cholesterol showed significant correlation with CEC, a measure of HDL function. ABCA1 and G1, the two important players in RCT showed greater induction with LXR agonist than PPAR-α agonist. HDL-C increased by 40 and 80% in LXR and PPAR-α treated apoA-I transgenic mice, respectively, with 80% increase in fecal cholesterol. A fivefold increase in fecal cholesterol with no correlation with either plasma HDL-C or CEC following co-treatment with LXR and PPAR-α agonists suggested existence of an HDL-independent pathway for body cholesterol elimination. In hyperlipidemic diabetic ob/ob mice also combination of LXR and PPAR-α agonists showed marked increases in fecal cholesterol content (10–20-fold), while HDL-C rise was only 40%, further suggesting HDL-independent elimination of body cholesterol in mice treated with combination of LXR and PPAR-α agonists. Atherosclerosis attenuation by LXR and PPAR-α agonists in LDLr-deficient mice was associated with increased fecal cholesterol, but not HDL-C. However, fecal cholesterol counts showed inverse correlation with aortic cholesteryl ester content. These data suggest: (a) lack of correlation between HDL-C and fecal or aortic cholesterol content; (b) HDL function (CEC) correlated with fecal cholesterol content; (c) association of reduced aortic lipids in LDLr−/− mice with increased fecal cholesterol, but not with HDL-C, and (d) existence of an HDL-independent pathway for fecal cholesterol excretion following co-treatment with LXR and PPAR-α agonists

Exome sequencing in suspected monogenic dyslipidemias

Exome sequencing is a promising tool for gene mapping in Mendelian disorders. We used this technique in an attempt to identify novel genes underlying monogenic dyslipidemias

Exome Sequencing in Suspected Monogenic Dyslipidemias

Abstract BACKGROUND: -Exome sequencing is a promising tool for gene mapping in Mendelian disorders. We utilized this technique in an attempt to identify novel genes underlying monogenic dyslipidemias. METHODS AND RESULTS: -We performed exome sequencing on 213 selected family members from 41 kindreds with suspected Mendelian inheritance of extreme levels of low-density lipoprotein (LDL) cholesterol (after candidate gene sequencing excluded known genetic causes for high LDL cholesterol families) or high-density lipoprotein (HDL) cholesterol. We used standard analytic approaches to identify candidate variants and also assigned a polygenic score to each individual in order to account for their burden of common genetic variants known to influence lipid levels. In nine families, we identified likely pathogenic variants in known lipid genes (ABCA1, APOB, APOE, LDLR, LIPA, and PCSK9); however, we were unable to identify obvious genetic etiologies in the remaining 32 families despite follow-up analyses. We identified three factors that limited novel gene discovery: (1) imperfect sequencing coverage across the exome hid potentially causal variants; (2) large numbers of shared rare alleles within families obfuscated causal variant identification; and (3) individuals from 15% of families carried a significant burden of common lipid-related alleles, suggesting complex inheritance can masquerade as monogenic disease. CONCLUSIONS: -We identified the genetic basis of disease in nine of 41 families; however, none of these represented novel gene discoveries. Our results highlight the promise and limitations of exome sequencing as a discovery technique in suspected monogenic dyslipidemias. Considering the confounders identified may inform the design of future exome sequencing studies

Lp(a): a genetic cause of clinical FH in children

No abstract availabl

APOC-III: a Gatekeeper in Controlling Triglyceride Metabolism

Purpose of review: Apolipoprotein C-III (ApoC-III) is a widely known player in triglyceride metabolism, and it has been recently recognized as a polyhedric factor which may regulate several pathways beyond lipid metabolism by influencing cardiovascular, metabolic, and neurological disease risk. This review summarizes the different functions of ApoC-III and underlines the recent findings related to its multifaceted pathophysiological role. Recent findings: The role of ApoC-III has been implicated in HDL metabolism and in the development of atherosclerosis, inflammation, and ER stress in endothelial cells. ApoC-III has been recently considered an important player in insulin resistance mechanisms, lipodystrophy, diabetic dyslipidemia, and postprandial hypertriglyceridemia (PPT). The emerging evidence of the involvement of ApoC-III in the in the pathogenesis of Alzheimer's disease open the way to further study if modification of ApoC-III level slows disease progression. Furthermore, ApoC-III is clearly linked to cardiovascular disease (CVD) risk, and progression of coronary artery disease (CAD) as well as the calcification of aortic valve and recent clinical trials has pointed out the inhibition of ApoC-III as a promising approach to manage hypertriglyceridemia and prevent CVD. Several evidences highlight the role of ApoC-III not only in triglyceride metabolism but also in several cardio-metabolic pathways. Results from recent clinical trials underline that the inhibition of ApoC-III is a promising therapeutical strategy for the management of severe hypertriglyceridemia and in CVD prevention

Lipid and Apoprotein Composition of HDL in Partial or Complete CETP Deficiency

Hyperalphalipoproteinemia, as observed in patients who are either homozygous or heterozygous for cholesteryl ester transfer protein (CETP) deficiency, has been shown to be associated with striking changes in apolipoprotein size distribution, namely, of high-density lipoprotein (HDL) and HDL-like particles. We compared the effect of varying degrees of CETP activity on the HDL apolipoprotein profile in Caucasian CETP-deficient subjects and following pharmacological decrease in CETP activity, using Size Exclusion Chromatography followed by Reverse Phase Protein Array (SEC RPA). The main HDL-associated apolipoproteins (Apo), i.e. ApoA-I, ApoA-II, ApoC-I, and ApoC-III, co-eluted with the HDL peak. The presence of a HDL-like peak migrating between the ApoB-LDL and ApoA-I-HDL was identified in a Caucasian patient with homozygosity for a point mutation in exon 2 of the CETP gene (c. 109 C > T) resulting in a premature termination codon (R37X) and complete CETP deficiency. This HDL-like peak was not observed either in healthy volunteers treated with the CETP modulator dalcetrapib, patients heterozygous for the same mutation, or in patients heterozygous with G165X mutations. SEC RPA offers the possibility to investigate the distribution of a large number of apolipoproteins simultaneously under non-denaturing separation in normal and dyslipidemic subjects. This is only limited by the availability of antibodies against specific apolipoproteins to be investigated

Plasma non-cholesterol sterols: a useful diagnostic tool in pediatric hypercholesterolemia.

Current guidelines strongly recommend the identification of genetic forms of hypercholesterolemia (HC) during childhood. The usefulness of non-cholesterol sterols (NCS) in the diagnosis of genetic HC has not been fully explored. Plasma NCS were measured by gas chromatography/mass spectrometry (GC/MS) in 113 children with hypercholesterolemia affected by: autosomal dominant hypercholesterolemia (ADH), familial combined hyperlipidemia (FCHL), polygenic hypercholesterolemia (PHC), and in 79 controls to evaluate: i) plasma NCS profile in different genetic HC and ii) the Usefulness of NCS for the diagnosis of HC beyond current clinical criteria. ADH was characterized by raised lathosterol/total cholesterol (TC) and reduced phytosterols/TC ratios, indicative of increased cholesterol synthesis. FCHL showed a slight increase of lathosterol/TC ratio, whereas PHC showed increased phytosterols/TC ratios, indicative of increased cholesterol absorption. In a post hoc discriminant analysis of patients with HC, lipid values correctly classified the 73% (14 of 19) of ADH, whereas the inclusion of plasma sterols allowed the correct identification of all 19 patients with ADH. FCHL was not differentiated from PHC (62 versus 69%). In conclusion, NCS measurement showed that cholesterol plasma levels are related to the cholesterol synthesis in ADH and to cholesterol absorption in PHC. NCS improve the detection of ADH in pediatric patients, whereas FCHL diagnosis is not improved. (Pediatr Res 67: 200-204, 2010

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

A subgroup analysis of the ODYSSEY APPRISE study: Safety and efficacy of alirocumab in the Italian cohort

ODYSSEY APPRISE trial evaluated efficacy and safety of alirocumab in 994 patients with hypercholesterolemia and high CV risk in a real-life setting. The aim of the present report is to detail on the Italian cohort enrolled and treated in the trial

The C(-260)>T gene polymorphism in the promoter of the CD14 monocyte receptor gene is not associated with acute myocardial infarction

CD surface molecules mediates cell activation and signaling. In particular, CD14 on blood monocytes mediate monocyte/macrophage activation by lipopolysaccharide. Lipopolysaccharide and its receptor, CD14, have been implicated in atherogenesis. It has been recently shown that a C(-260)T polymorphism in the promoter of the CD14 receptor may be a risk factor for coronary artery disease. Recently this association has been questioned because no increased risk was found with the T allele, even in the homozygous state. In the present study we investigated a possible association between the C(-260)T polymorphism in the CD14 promoter and acute myocardial infarction. Two hundred and thrteen patients with and acute myocardial infarction 213 healthy controls were included in the study. Genotype frequencies of the C(-260)T polymorphism in the CD14 promoter were determined by polimerase chain reaction and the amplified product was cleaved with HaeIII. The frequency of the T allele was not significantly different in patients compared with controls. In this study we were not able to detect differences of frequency of the allele T (-260) in the promoter of the CD 14 receptor gene in survivors of myocardial infarction and controls