A multitrait genetic study of hemostatic factors and hemorrhagic transformation after stroke treatment.

BACKGROUND: Thrombolytic recombinant tissue plasminogen activator (r-tPA) treatment is the only pharmacologic intervention available in the ischemic stroke acute phase. This treatment is associated with an increased risk of intracerebral hemorrhages, known as hemorrhagic transformations (HTs), which worsen the patient's prognosis. OBJECTIVES: To investigate the association between genetically determined natural hemostatic factors' levels and increased risk of HT after r-tPA treatment. METHODS: Using data from genome-wide association studies on the risk of HT after r-tPA treatment and data on 7 hemostatic factors (factor [F]VII, FVIII, von Willebrand factor [VWF], FXI, fibrinogen, plasminogen activator inhibitor-1, and tissue plasminogen activator), we performed local and global genetic correlation estimation multitrait analyses and colocalization and 2-sample Mendelian randomization analyses between hemostatic factors and HT. RESULTS: Local correlations identified a genomic region on chromosome 16 with shared covariance: fibrinogen-HT, P = 2.45 × 10-11. Multitrait analysis between fibrinogen-HT revealed 3 loci that simultaneously regulate circulating levels of fibrinogen and risk of HT: rs56026866 (PLXND1), P = 8.80 × 10-10; rs1421067 (CHD9), P = 1.81 × 10-14; and rs34780449, near ROBO1 gene, P = 1.64 × 10-8. Multitrait analysis between VWF-HT showed a novel common association regulating VWF and risk of HT after r-tPA at rs10942300 (ZNF366), P = 1.81 × 10-14. Mendelian randomization analysis did not find significant causal associations, although a nominal association was observed for FXI-HT (inverse-variance weighted estimate [SE], 0.07 [-0.29 to 0.00]; odds ratio, 0.87; 95% CI, 0.75-1.00; raw P = .05). CONCLUSION: We identified 4 shared loci between hemostatic factors and HT after r-tPA treatment, suggesting common regulatory mechanisms between fibrinogen and VWF levels and HT. Further research to determine a possible mediating effect of fibrinogen on HT risk is needed.

Causal role of lipid metabolome on the risk of ischemic stroke, its etiological subtypes, and long-term outcome: A Mendelian randomization study.

BACKGROUND AND AIMS: The lipid profile is consistently associated with coronary artery disease (CAD) and ischemic stroke (IS). However, the lipoprotein subfractions have not been deeply explored in stroke subtypes, especially in IS outcome. METHODS: We performed two-sample Mendelian randomization (MR) analysis using 92 lipid traits measured by nuclear magnetic resonance in 115,000 subjects from the UK Biobank. Data for genetic associations with IS, its subtypes, and long-term outcome (LTO) were obtained from three cohorts of European ancestry: GIGASTROKE (73,652 cases, 1,234,808 controls), GODS (n = 1791) and GISCOME (n = 6165). Results obtained using CARDIoGRAMPlusC4D were used to identify differences with CAD. RESULTS: Genetically determined low concentration of medium high-density lipoprotein (HDL) particles (odds ratio (OR) = 0.92, 95% CI 0.88-0.96; p = 3.6 × 10-4) and its cholesterol content (OR = 0.92, 95% CI 0.88-0.96; p = 1.9 × 10-4) showed causal associations with an increased risk of stroke. Genetic predisposition to high apolipoprotein (apo)B to apoA-I ratio was causally associated with an increased risk of IS (OR = 1.12, 95% CI 1.06-1.18, p = 1.1 × 10-4), and a highly suggestive association was found between non-esterified cholesterol in low-density lipoprotein (LDL) and increased risk of atherothrombotic stroke (LAS) (OR = 1.35, 95% CI 1.10-1.66; p = 4.0 × 10-3). Low cholesterol in small and medium LDL was suggestively associated with poor LTO. CONCLUSIONS: Our results support that low medium HDL concentration was causally associated with an increased stroke risk, while high levels of non-esterified cholesterol in LDL were suggestively associated with an increased risk of LAS and with a better LTO.

Ischaemic stroke patients present sex differences in gut microbiota.

BACKGROUND: Gut microbiota plays a role in the pathophysiology of ischaemic stroke (IS) through the bidirectional gut-brain axis. Nevertheless, little is known about sex-specific microbiota signatures in IS occurrence. METHODS: A total of 89 IS patients and 12 healthy controls were enrolled. We studied the taxonomic differences of the gut microbiota between men and women with IS by shotgun metagenomic sequencing. To evaluate the causal effect of several bacteria on IS risk, we performed a two-sample Mendelian randomisation (MR) with inverse-variance weighting (IVW) using genome-wide association analysis (GWAS) summary statistics from two cohorts of 5959 subjects with genetic and microbiota data and 1,296,908 subjects with genetic and IS data, respectively. RESULTS: α-Diversity analysis measured using Observed Species (p = 0.017), Chao1 (p = 0.009) and Abundance-based Coverage Estimator (p = 0.012) indexes revealed that IS men have a higher species richness compared with IS women. Moreover, we found sex-differences in IS patients in relation to the phylum Fusobacteria, class Fusobacteriia, order Fusobacteriales and family Fusobacteriaceae (all Bonferroni-corrected p < 0.001). MR confirmed that increased Fusobacteriaceae levels in the gut are causally associated with an increased risk of IS (IVW p = 0.02, ß = 0.32). CONCLUSIONS: Our study is the first to indicate that there are gut microbiome differences between men and women with IS, identifying high levels of Fusobacteriaceae in women as a specific risk factor for IS. Incorporating sex stratification analysis is important in the design, analysis and interpretation of studies on stroke and the gut microbiota.

Genome-Wide Studies in Ischaemic Stroke: Are Genetics Only Useful for Finding Genes?

Ischaemic stroke is a complex disease with some degree of heritability. This means that heritability factors, such as genetics, could be risk factors for ischaemic stroke. The era of genome-wide studies has revealed some of these heritable risk factors, although the data generated by these studies may also be useful in other disciplines. Analysis of these data can be used to understand the biological mechanisms associated with stroke risk and stroke outcome, to determine the causality between stroke and other diseases without the need for expensive clinical trials, or to find potential drug targets with higher success rates than other strategies. In this review we will discuss several of the most relevant studies regarding the genetics of ischaemic stroke and the potential use of the data generated.

ICA1L Is Associated with Small Vessel Disease: A Proteome-Wide Association Study in Small Vessel Stroke and Intracerebral Haemorrhage.

Small vessel strokes (SVS) and intracerebral haemorrhages (ICH) are acute outcomes of cerebral small vessel disease (SVD). Genetic studies combining both phenotypes have identified three loci associated with both traits. However, the genetic cis-regulation at the protein level associated with SVD has not been studied before. We performed a proteome-wide association study (PWAS) using FUSION to integrate a genome-wide association study (GWAS) and brain proteomic data to discover the common mechanisms regulating both SVS and ICH. Dorsolateral prefrontal cortex (dPFC) brain proteomes from the ROS/MAP study (N = 376 subjects and 1443 proteins) and the summary statistics for the SVS GWAS from the MEGASTROKE study (N = 237,511) and multi-trait analysis of GWAS (MTAG)-ICH−SVS from Chung et al. (N = 240,269) were selected. We performed PWAS and then a co-localization analysis with COLOC. The significant and nominal results were validated using a replication dPFC proteome (N = 152). The replicated results (q-value < 0.05) were further investigated for the causality relationship using summary data-based Mendelian randomization (SMR). One protein (ICA1L) was significantly associated with SVS (z-score = −4.42 and p-value = 9.6 × 10−6) and non-lobar ICH (z-score = −4.8 and p-value = 1.58 × 10−6) in the discovery PWAS, with a high co-localization posterior probability of 4. In the validation PWAS, ICA1L remained significantly associated with both traits. The SMR results for ICA1L indicated a causal association of protein expression levels in the brain with SVS (p-value = 3.66 × 10−5) and non-lobar ICH (p-value = 1.81 × 10−5). Our results show that the association of ICA1L with SVS and non-lobar ICH is conditioned by the cis-regulation of its protein levels in the brain.

Biological Age Acceleration Is Lower in Women With Ischemic Stroke Compared to Men.

BACKGROUND: Stroke onset in women occurs later in life compared with men. The underlying mechanisms of these differences have not been established. Epigenetic clocks, based on DNA methylation (DNAm) profiles, are the most accurate biological age estimate. Epigenetic age acceleration (EAA) measures indicate whether an individual is biologically younger or older than expected. Our aim was to analyze whether sexual dichotomy at age of stroke onset is conditioned by EAA. METHODS: We used 2 DNAm datasets from whole blood samples of case-control genetic studies of ischemic stroke (IS), a discovery cohort of 374 IS patients (N women=163, N men=211), from GRECOS (Genotyping Recurrence Risk of Stroke) and SEDMAN (Dabigatran Study in the Early Phase of Stroke, New Neuroimaging Markers and Biomarkers) studies and a replication cohort of 981 IS patients (N women=411, N men=570) from BASICMAR register. We compared chronological age, 2 DNAm-based biomarkers of aging and intrinsic and extrinsic epigenetic age acceleration EAA (IEAA and extrinsic EAA, respectively), in IS as well as in individual IS etiologic subtypes. Horvath and Hannum epigenetic clocks were used to assess the aging rate. A proteomic study using the SOMAScan multiplex assay was performed on 26 samples analyzing 1305 proteins. RESULTS: Women present lower Hannum-extrinsic EAA values, whereas men have higher Hannum-extrinsic EAA values (women=-0.64, men=1.24, P=1.34×10-2); the same tendency was observed in the second cohort (women=-0.57, men=0.79, P=0.02). These differences seemed to be specific to cardioembolic and undetermined stroke subtypes. Additionally, 42 blood protein levels were associated with Hannum-extrinsic EAA (P<0.05), belonging to the immune effector process (P=1.54×10-6) and platelet degranulation (P<8.74×10-6) pathways. CONCLUSIONS: This study shows that sex-specific underlying biological mechanisms associated with stroke onset could be due to differences in biological age acceleration between men and women.

Polygenic Markers in Patients Diagnosed of Autosomal Dominant Hypercholesterolemia in Catalonia: Distribution of Weighted LDL-c-Raising SNP Scores and Refinement of Variant Selection.

Familial hypercholesterolemia (FH) is associated with mutations in the low-density lipoprotein (LDL) receptor (LDLR), apolipoprotein B (APOB), and proprotein convertase subtilisin/kexin 9 (PCSK9) genes. A pathological variant has not been identified in 30-70% of clinically diagnosed FH patients, and a burden of LDL cholesterol (LDL-c)-raising alleles has been hypothesized as a potential cause of hypercholesterolemia in these patients. Our aim was to study the distribution of weighted LDL-c-raising single-nucleotide polymorphism (SNP) scores (weighted gene scores or wGS) in a population recruited in a clinical setting in Catalonia. The study included 670 consecutive patients with a clinical diagnosis of FH and a prior genetic study involving 250 mutation-positive (FH/M+) and 420 mutation-negative (FH/M-) patients. Three wGSs based on LDL-c-raising variants were calculated to evaluate their distribution among FH patients and compared with 503 European samples from the 1000 Genomes Project. The FH/M- patients had significantly higher wGSs than the FH/M+ and control populations, with sensitivities ranging from 42% to 47%. A wGS based only on the SNPs significantly associated with FH (wGS8) showed a higher area under the receiver operating characteristic curve, and higher diagnostic specificity and sensitivity, with 46.4% of the subjects in the top quartile. wGS8 would allow for the assignment of a genetic cause to 66.4% of the patients if those with polygenic FH are added to the 37.3% of patients with monogenic FH. Our data indicate that a score based on 8 SNPs and the75th percentile cutoff point may identify patients with polygenic FH in Catalonia, although with limited diagnostic sensitivity and specificity.

Molecular analysis of APOB, SAR1B, ANGPTL3, and MTTP in patients with primary hypocholesterolemia in a clinical laboratory setting: Evidence supporting polygenicity in mutation-negative patients.

BACKGROUND AND AIMS: Primary hypobetalipoproteinemia is generally considered a heterogenic group of monogenic, inherited lipoprotein disorders characterized by low concentrations of LDL cholesterol and apolipoprotein B in plasma. Lipoprotein disorders include abetalipoproteinemia, familial hypobetalipoproteinemia, chylomicron retention disease, and familial combined hypolipidemia. Our aim was to review and analyze the results of the molecular analysis of hypolipidemic patients studied in our laboratory over the last 15 years. METHODS: The study included 44 patients with clinical and biochemical data. Genomic studies were performed and genetic variants were characterized by bioinformatics analysis. A weighted LDL cholesterol gene score was calculated to evaluate common variants associated with impaired lipid concentrations and their distribution among patients. RESULTS: Twenty-three patients were genetically confirmed as affected by primary hypobetalipoproteinemia. In this group of patients, the most prevalent mutated genes were APOB (in 17 patients, with eight novel mutations identified), SAR1B (in 3 patients, with one novel mutation identified), ANGPTL3 (in 2 patients), and MTTP (in 1 patient). The other 21 patients could not be genetically diagnosed with hypobetalipoproteinemia despite presenting suggestive clinical and biochemical features. In these patients, two APOB genetic variants associated with lower LDL cholesterol were more frequent than in controls. Moreover, the LDL cholesterol gene score, calculated with 11 SNPs, was significantly lower in mutation-negative patients. CONCLUSIONS: Around half of the patients could be genetically diagnosed. The results suggest that, in at least some of the patients without an identified mutation, primary hypobetalipoproteinemia may have a polygenic origin.

Human ApoA-I Overexpression Enhances Macrophage-Specific Reverse Cholesterol Transport but Fails to Prevent Inherited Diabesity in Mice.

Human apolipoprotein A-I (hApoA-I) overexpression improves high-density lipoprotein (HDL) function and the metabolic complications of obesity. We used a mouse model of diabesity, the db/db mouse, to examine the effects of hApoA-I on the two main functional properties of HDL, i.e., macrophage-specific reverse cholesterol transport (m-RCT) in vivo and the antioxidant potential, as well as the phenotypic features of obesity. HApoA-I transgenic (hA-I) mice were bred with nonobese control (db/+) mice to generate hApoA-I-overexpressing db/+ offspring, which were subsequently bred to obtain hA-I-db/db mice. Overexpression of hApoA-I significantly increased weight gain and the incidence of fatty liver in db/db mice. Weight gain was mainly explained by the increased caloric intake of hA-I-db/db mice (>1.2-fold). Overexpression of hApoA-I also produced a mixed type of dyslipidemia in db/db mice. Despite these deleterious effects, the overexpression of hApoA-I partially restored m-RCT in db/db mice to levels similar to nonobese control mice. Moreover, HDL from hA-I-db/db mice also enhanced the protection against low-density lipoprotein (LDL) oxidation compared with HDL from db/db mice. In conclusion, overexpression of hApoA-I in db/db mice enhanced two main anti-atherogenic HDL properties while exacerbating weight gain and the fatty liver phenotype. These adverse metabolic side-effects were also observed in obese mice subjected to long-term HDL-based therapies in independent studies and might raise concerns regarding the use of hApoA-I-mediated therapy in obese humans.

Autosomal dominant hypercholesterolemia in Catalonia: Correspondence between clinical-biochemical and genetic diagnostics in 967 patients studied in a multicenter clinical setting.

BACKGROUND: Autosomal dominant hypercholesterolemia (ADH) is associated with mutations in the low-density lipoprotein (LDL) receptor (LDLR), apolipoprotein B (APOB), and proprotein convertase subtilisin/kexin 9 (PCSK9) genes, and it is estimated to be greatly underdiagnosed. The most cost-effective strategy for increasing ADH diagnosis is a cascade screening from mutation-positive probands. OBJECTIVE: The objective of this study was to evaluate the results from 2008 to 2016 of ADH genetic analysis performed in our clinical laboratory, serving most lipid units of Catalonia, a Spanish region with approximately 7.5 million inhabitants. METHODS: After the application of the Dutch Lipid Clinic Network (DLCN) clinical diagnostic score for ADH, this information and blood or saliva from 23 different lipid clinic units were investigated in our laboratory. DNA was screened for mutations in LDLR, APOB, and PCSK9, using the DNA-array LIPOchip, the next-generation sequencing SEQPRO LIPO RS platform, and multiplex ligation-dependent probe amplification (MLPA). The Simon Broome Register Group (SBRG) criteria was calculated and analyzed for comparative purposes. RESULTS: A total of 967 unrelated samples were analyzed. From this, 158 pathogenic variants were detected in 356 patients. The main components of the DLCN criteria associated with the presence of mutation were plasma LDL cholesterol (LDLc), age, and the presence of tendinous xanthomata. The contribution of family history to the diagnosis was lower than in other studies. DLCN and SBRG were similarly useful for predicting the presence of mutation. CONCLUSION: In a real clinical practice, multicenter setting in Catalonia, the percentage of positive genetic diagnosis in patients potentially affected by ADH was 38.6%. The DLCN showed a relatively low capacity to predict mutation detection but a higher one for ruling out mutation.

A rare STAP1 mutation incompletely associated with familial hypercholesterolemia.

Autosomal dominant hypercholesterolemia, being referred to as familial hypercholesterolemia (FH), is mainly due to defective LDL receptor (LDLR) function, but is also associated with variants in genes encoding APOB (LDLR ligand) and PCSK9, the catabolic regulator of LDLR. The signal-transducing adaptor family member 1 (STAP1) gene has been recently linked to FH. We describe the case of a 56-year-old male patient found to have hypercholesterolemia at age 34, but who did not continue follow-up nor received treatment with lipid-lowering drugs. At age 55 he suffered a myocardial infarction. A systematic NGS analysis did not show point mutations in the LDLR, APOB, LDLRAP1, or PCSK9 genes, nor large rearrangements of the LDLR gene, but revealed the heterozygous missense variant rs199787258 of STAP1 (c.526C > T; p.Pro176Ser). This variant was also found in heterozygosis in the two siblings of the index case, who also had hypercholesterolemia, but did not cosegregate in his progeny. A bioinformatics analysis and available structural information predicts p.Pro176Ser as the most damaging of all STAP1 missense variants associated with familial hypercholesterolemia. Our findings confirm and extend the linkage between STAP1 variants and FH, and point to an important role of this adaptor protein within a signaling pathway that affects cholesterol homeostasis.

Chylomicrons: Advances in biology, pathology, laboratory testing, and therapeutics.

The adequate absorption of lipids is essential for all mammalian species due to their inability to synthesize some essential fatty acids and fat-soluble vitamins. Chylomicrons (CMs) are large, triglyceride-rich lipoproteins that are produced in intestinal enterocytes in response to fat ingestion, which function to transport the ingested lipids to different tissues. In addition to the contribution of CMs to postprandial lipemia, their remnants, the degradation products following lipolysis by lipoprotein lipase, are linked to cardiovascular disease. In this review, we will focus on the structure-function and metabolism of CMs. Second, we will analyze the impact of gene defects reported to affect CM metabolism and, also, the role of CMs in other pathologies, such as atherothrombotic cardiovascular disease and diabetes mellitus. Third, we will provide an overview of the laboratory tests currently used to study CM disorders, and, finally, we will highlight current treatments in diseases affecting CMs.

Sitosterolemia: diagnosis, investigation, and management.

Sitosterolemia is a rare autosomal recessively inherited disease caused by mutations affecting ABCG5 or ABCG8, which are located on human chromosome band 2p21. Around 100 cases have been reported in the literature. Sitosterolemic patients typically exhibit a 30-fold to 100-fold increase in plasma concentrations of plant sterols. The clinical manifestations include xanthomas, premature atherosclerosis, hemolytic anemia, and macrothrombocytopenia. It is noteworthy that abnormal hematological parameters may be the only clinical feature of sitosterolemic patients, suggesting that sitosterolemia may be more frequent than previously thought. Severe accumulation of plant sterols in mouse models of sitosterolemia induced complex cardiac lesions, anemia, and macrothrombocytopenia, disrupted adrenal and liver cholesterol homeostasis, and caused infertility and hypertriglyceridemia. It remains unclear whether all disease traits are present in sitosterolemic patients. The drug ezetimibe appears to be effective in reducing plasma plant sterol levels, promotes xanthoma regression, and improves the cardiovascular and hematological signs in sitosterolemic patients.

Molecular analysis of chylomicronemia in a clinical laboratory setting: diagnosis of 13 cases of lipoprotein lipase deficiency.

BACKGROUND: Familial chylomicronemia (type I hyperlipidemia) is a rare autosomal recessive disease due mainly to rare variants in the lipoprotein lipase (LPL) gene sequence. Molecular diagnosis of LPL deficiency is now a requirement for the first gene therapy treatment approved in the European Union. Altered coding sequence variants in APOC2, APOA5 or GPIHBP-1 can also cause familial chylomicronemia. Herein, we report the results of our molecular diagnostic activity in this topic, carried out in the setting of a Spanish clinical practice hospital laboratory, which was also extended to some patients who were more likely to have type V hyperlipidemia. METHODS: Samples from twenty-nine unrelated probands with severe hypertriglyceridemia were referred for molecular diagnosis. Samples were first screened for LPL sequence variants by DNA sequencing and, in the absence of alterations, subsequent analysis of APOC2, APOA5, and GPIHBP1 genes was undertaken. Analysis of LPL function in vitro was further studied in two previously uncharacterized LPL sequence variants. RESULTS: Fourteen different, loss-of-function variants were found in the LPL gene: 4 were novel or uncharacterized allelic variants, and of these, 2 were directly shown to affect function. Twenty of 29 probands presented at least one LPL gene allele variant: 8 were homozygous, 9 compound heterozygous and 3 heterozygous. In 13 probands, the finding of two loss-of-function variants supported the diagnosis of LPL deficiency. None of the probands presented sequence variants in the APOC2 gene, whereas 3 presented rare variants within the APOA5 gene. Four of the five patients heterozygous for a common variant in the GPIHBP-1 gene also carried APOA5 sequence variants. CONCLUSIONS: Loss-of-function LPL variants leading to familial chylomicronemia were found in 13 patients, accounting for a significant proportion of the LPL-deficient patients predicted to live in Spain.

Methionine-induced hyperhomocysteinemia impairs the antioxidant ability of high-density lipoproteins without reducing in vivo macrophage-specific reverse cholesterol transport.

SCOPE: High plasma homocysteine concentrations have been associated with increased risk of cardiovascular disease both in humans and experimental animal models, whereas plasma HDL-cholesterol concentration is inversely correlated with such disorders. This work aimed to study the impact of methionine-induced hyperhomocysteinemia (HHcy) on two major antiatherogenic functions of HDL, namely their capacity to prevent LDL oxidation and induce in vivo macrophage-specific reverse cholesterol transport. METHODS AND RESULTS: Methionine-induced HHcy in mice resulted in an approximately 20% decreased concentration of HDL-cholesterol and HDL main protein component, apolipoprotein A-I. The HDL potential to resist oxidation as well as to prevent LDL oxidative modification was impaired in hyperhomocysteinemic mice. Activities of paraoxonase-1 and platelet activation factor acetylhydrolase, two of the main HDL-associated enzymes with antioxidant activity, were reduced. The ability of HDL to efflux cholesterol from macrophages was decreased in hyperhomocysteinemic mice; however, the in vivo macrophage-specific reverse cholesterol transport measured as the output of labeled cholesterol into feces did not significantly differ between groups. CONCLUSION: Our data indicate that the HDL from methionine-induced hyperhomocysteinemic mice was more prone to oxidation and displayed lower capacity to protect LDL against oxidative modification than that of control mice, highlighting a mechanism by which a diet-induced HHcy may facilitate progression of atherosclerosis.

[Basic mechanisms: structure, function and metabolism of plasma lipoproteins]. / Mecanismos básicos: estructura, función y metabolismo de las lipoproteínas plasm.

The aim of this work is to present basic information on the lipoprotein physiology. The protein fraction of lipoproteins consists of several apolipoproteins and enzymes whose functions are lipid transport and metabolism. Classification of lipoproteins is based on their density. Chylomicrons, VLDL, IDL, LDL and HDL can be isolated by ultracentrifugation. Both chylomicrons- and VLDL-triglycerides are transported from the intestine and liver, respectively, to the peripheral tissues. The metabolism of VLDL originates IDL and LDL. LDL is the main transporter of cholesterol to extrahepatic tissues. HDL mobilizes cholesterol from peripheral tissues to the liver where it is secreted to bile as free cholesterol or bile salts, a process termed reverse cholesterol transport. Lipoprotein metabolism can be regulated by nuclear receptors that regulate the expression of genes involved in triglyceride and apolipoprotein metabolism.

Mecanismos básicos: estructura, función y metabolismo de las lipoproteínas plasm / No disponible

El objetivo de este capítulo es presentar información básica sobre la fisiología de las lipoproteínas. La fracción proteica de las lipoproteínas consta de varias apolipoproteínas y enzimas cuyas funciones son el transporte y la metabolización de los lípidos. La clasificación de las lipoproteínas se basa en su densidad y se pueden aislar por ultracentrifugación quilomicrones, VLDL, IDL, LDL y HDL. Los quilomicrones y las VLDL transportan los triglicéridos desde el intestino e hígado, respectivamente, hasta los tejidos periféricos. La metabolización de las VLDL origina las IDL y LDL. Las LDL transportan la mayoría del colesterol plasmático a los tejidos extrahepáticos. La HDL moviliza el colesterol de los tejidos periféricos hacia el hígado, donde se elimina en forma de colesterol libre o sales biliares, proceso conocido como transporte reverso de colesterol. El metabolismo de las lipoproteínas puede ser regulado por receptores nucleares que regulan la expresión de genes del metabolismo de triglicéridos y de las apolipoproteínas (AU)

The aim of this work is to present basic information on the lipoprotein physiology. The protein fraction of lipoproteins consists of several apolipoproteins and enzymes whose functions are lipid transport and metabolism. Classification of lipoproteins is based on their density. Chylomicrons, VLDL, IDL, LDL and HDL can be isolated by ultracentrifugation. Both chylomicrons- and VLDL-triglycerides are transported from the intestine and liver, respectively, to the peripheral tissues. The metabolism of VLDL originates IDL and LDL. LDL is the main transporter of cholesterol to extrahepatic tissues. HDL mobilizes cholesterol from peripheral tissues to the liver where it is secreted to bile as free cholesterol or bile salts, a process termed reverse cholesterol transport. Lipoprotein metabolism can be regulated by nuclear receptors that regulate the expression of genes involved in triglyceride and apolipoprotein metabolism (AU)

Structural and functional analysis of APOA5 mutations identified in patients with severe hypertriglyceridemia.

During the diagnosis of three unrelated patients with severe hypertriglyceridemia, three APOA5 mutations [p.(Ser232_Leu235)del, p.Leu253Pro, and p.Asp332ValfsX4] were found without evidence of concomitant LPL, APOC2, or GPIHBP1 mutations. The molecular mechanisms by which APOA5 mutations result in severe hypertriglyceridemia remain poorly understood, and the functional impairment/s induced by these specific mutations was not obvious. Therefore, we performed a thorough structural and functional analysis that included follow-up of patients and their closest relatives, measurement of apoA-V serum concentrations, and sequencing of the APOA5 gene in 200 nonhyperlipidemic controls. Further, we cloned, overexpressed, and purified both wild-type and mutant apoA-V variants and characterized their capacity to activate LPL. The interactions of recombinant wild-type and mutated apoA-V variants with liposomes of different composition, heparin, LRP1, sortilin, and SorLA/LR11 were also analyzed. Finally, to explore the possible structural consequences of these mutations, we developed a three-dimensional model of full-length, lipid-free human apoA-V. A complex, wide array of impairments was found in each of the three mutants, suggesting that the specific residues affected are critical structural determinants for apoA-V function in lipoprotein metabolism and, therefore, that these APOA5 mutations are a direct cause of hypertriglyceridemia.

Identification of a novel mutation in the ANGPTL3 gene in two families diagnosed of familial hypobetalipoproteinemia without APOB mutation.

BACKGROUND: Familial hypobetalipoproteinemia (FHBL), characterized by extremely low levels of plasma apolipoprotein (apo) B and cholesterol associated with low-density lipoproteins (LDLc), is considered to be an autosomal co-dominant disorder of heterogeneous origin. The main genetic disorder associated with FHBL consists of mutations in the APOB gene, while other less frequent forms are associated with mutations in NPC1L1, PCSK9, a still unidentified gene in 3p21.1-22 and, more recently, in ANGPTL3. METHODS: We scanned for ANGPTL3 mutations in 4 unrelated Spanish families with FHBL criteria but negative for mutations in APOB. The entire coding region and intron-exon boundaries of the ANGPTL3 gene were amplified and sequenced. RESULTS: Two probands were positive for the same frameshift mutation, a deletion of 5 bp in codon 121 in ANGPTL3, which produces a truncated protein of 122 residues. This mutation in homozygosis was associated in both families with combined hypolipidemia, characterized by low plasma apoB, low total, LDL and HDL cholesterol and low triglycerides. CONCLUSION: We confirm the existence of a new phenotype of FHBL, denominated familial combined hypolipidemia, which consist of a biochemical phenotype of low LDLc, low apoB, low TG and, unlike APOB mutations, low HDL cholesterol, due to a loss-of-function mutation in ANGPTL3.

The antinociceptive effects of JWH-015 in chronic inflammatory pain are produced by nitric oxide-cGMP-PKG-KATP pathway activation mediated by opioids.

BACKGROUND: Cannabinoid 2 receptor (CB2R) agonists attenuate inflammatory pain but the precise mechanism implicated in these effects is not completely elucidated. We investigated if the peripheral nitric oxide-cGMP-protein kinase G (PKG)-ATP-sensitive K(+) (KATP) channels signaling pathway triggered by the neuronal nitric oxide synthase (NOS1) and modulated by opioids, participates in the local antinociceptive effects produced by a CB2R agonist (JWH-015) during chronic inflammatory pain. METHODOLOGY/PRINCIPAL FINDINGS: In wild type (WT) and NOS1 knockout (NOS1-KO) mice, at 10 days after the subplantar administration of complete Freund's adjuvant (CFA), we evaluated the antiallodynic (von Frey filaments) and antihyperalgesic (plantar test) effects produced by the subplantar administration of JWH-015 and the reversion of their effects by the local co-administration with CB2R (AM630), peripheral opioid receptor (naloxone methiodide, NX-ME) or CB1R (AM251) antagonists. Expression of CB2R and NOS1 as well as the antinociceptive effects produced by a high dose of JWH-015 combined with different doses of selective L-guanylate cyclase (ODQ) or PKG (Rp-8-pCPT-cGMPs) inhibitors or a KATP channel blocker (glibenclamide), were also assessed. Results show that the local administration of JWH-015 dose-dependently inhibited the mechanical and thermal hypersensitivity induced by CFA which effects were completely reversed by the local co-administration of AM630 or NX-ME, but not AM251. Inflammatory pain increased the paw expression of CB2R and the dorsal root ganglia transcription of NOS1. Moreover, the antinociceptive effects of JWH-015 were absent in NOS1-KO mice and diminished by their co-administration with ODQ, Rp-8-pCPT-cGMPs or glibenclamide. CONCLUSIONS/SIGNIFICANCE: These data indicate that the peripheral antinociceptive effects of JWH-015 during chronic inflammatory pain are mainly produced by the local activation of the nitric oxide-cGMP-PKG-KATP signaling pathway, triggered by NOS1 and mediated by endogenous opioids. These findings suggest that the activation of this pathway might be an interesting therapeutic target for the treatment of chronic inflammatory pain with cannabinoids.