Mobile Element Insertion in the APOB Exon 3 Coding Sequence: A New Challenge in Hypobetalipoproteinemia Diagnosis.

Mobile elements (ME) can transpose by copy-and-paste mechanisms. A heterozygous insertion in APOB exon 3 coding sequence was suspected in a patient with hypobetalipoproteinemia (HBL), by gel electrophoresis of the PCR products. An insertion of a 85 bp fragment flanked by a polyA stretch and a target replication site duplication was identified as a ME insertion (MEI) from the AluYa5 subfamily, NM_000384.

Assessment of three equations to calculate plasma LDL cholesterol concentration in fasting and non-fasting hypertriglyceridemic patients.

Objectives: Low-density lipoprotein cholesterol (LDL-C) concentration was calculated for many years using the Friedewald equation, but those from Sampson and extended-Martin-Hopkins perform differently. Their accuracy in fasting hypertriglyceridemia and non-fasting state were compared and the clinical impact of implementing these equations on risk classification and on the setting of lipid treatment goals was assessed.

Methods: Seven thousand six standard lipid profiles and LDL-C concentrations measured after ultracentrifugation (uLDL-C) were retrospectively included.

Additive Effect of Rare Variants on the Phenotype of Familial Hypercholesterolemia.

Background: Autosomal dominant hypercholesterolemia (ADH) is due to deleterious variants in , , or genes. Double heterozygote for these genes induces a more severe phenotype. More recently, a new causative variant of heterozygous ADH was identified in .

Non-linearity in lipase assays: A multicentric comparison on different analysers.

Objectives: Non-linearity in lipase assays and the ensuing gaps in results distribution have been described on Roche analysers, but have yet to be studied on other analysers.

Design And Methods: Eighteen lithium-heparinized plasma pools of lipase activities decreasing from 1700 to <4 U/L were prepared for multicentric evaluation on several analysers. Non-linearity was modelled as the difference between the polynomial regression of lipase activities depending on relative dilutions over the primary measuring range, and the linear regression of the same variables above the manufacturer's limit of linearity (MLL).

A new 165-SNP low-density lipoprotein cholesterol polygenic risk score based on next generation sequencing outperforms previously published scores in routine diagnostics of familial hypercholesterolemia.

Genetic diagnosis of familial hypercholesterolemia (FH) remains unexplained in 30 to 70% of patients after exclusion of monogenic disease. There is now a growing evidence that a polygenic burden significantly modulates LDL-cholesterol (LDL-c) concentrations. Several LDL-c polygenic risk scores (PRS) have been set up.

Molecular Spectrum in a French Cohort with Primary Dyslipidemia.

Primary hypercholesterolemia is characterized by elevated LDL-cholesterol (LDL-C) levels isolated in autosomal dominant hypercholesterolemia (ADH) or associated with elevated triglyceride levels in familial combined hyperlipidemia (FCHL). Rare variants are known in ADH and FCHL. We explored the molecular spectrum in a French ADH/FCHL cohort of 5743 unrelated probands.

CRISPR-Cas9 Engineering in Hypobetalipoproteinemia: A Promising Tool for Functional Studies of Novel Variants.

Hypobetalipoproteinemia is characterized by LDL-cholesterol and apolipoprotein B (apoB) plasma levels below the fifth percentile for age and sex. Familial hypobetalipoproteinemia (FHBL) is mostly caused by premature termination codons in the gene, a condition associated with fatty liver and steatohepatitis. Nevertheless, many families with a FHBL phenotype carry missense variants of uncertain significance (VUS).

Phenotypic Differences Between Polygenic and Monogenic Hypobetalipoproteinemia.

Objective: Primary hypobetalipoproteinemia is characterized by LDL-C (low-density lipoprotein cholesterol) concentrations below the fifth percentile. Primary hypobetalipoproteinemia mostly results from heterozygous mutations in the (apolipoprotein B) and genes, and a polygenic origin is hypothesized in the remaining cases. Hypobetalipoproteinemia patients present an increased risk of nonalcoholic fatty liver disease and steatohepatitis.

PCSK9 post-transcriptional regulation: Role of a 3'UTR microRNA-binding site variant in linkage disequilibrium with c.1420G.

Background And Aims: Proprotein convertase subtilisin/kexin type 9 (PCSK9) plays a crucial role in cholesterol homeostasis. A common variant, the G allele in position c.1420 (c.

Development of a new expanded next-generation sequencing panel for genetic diseases involved in dyslipidemia.

The aim of this study was to provide an efficient tool: reliable, able to increase the molecular diagnosis performance, to facilitate the detection of copy number variants (CNV), to assess genetic risk scores (wGRS) and to offer the opportunity to explore candidate genes. Custom SeqCap EZ libraries, NextSeq500 sequencing and a homemade pipeline enable the analysis of 311 dyslipidemia-related genes. In the training group (48 DNA from patients with a well-established molecular diagnosis), this next-generation sequencing (NGS) workflow showed an analytical sensitivity >99% (n = 532 variants) without any false negative including a partial deletion of one exon.

Involvement of a homozygous exon 6 deletion of LMF1 gene in intermittent severe hypertriglyceridemia.

Severe hypertriglyceridemia (HTG), characterized by triglycerides (TG) permanently over 10 mmol/L, may correspond to familial chylomicronemia syndrome (FCS), a rare disorder. However, hypertriglyceridemic patients more often present multifactorial chylomicronemia syndrome (MCS), characterized by highly variable TG. A few nonsense variants of LMF1 gene were reported in literature in FCS patients.

Normal serum ApoB48 and red cells vitamin E concentrations after supplementation in a novel compound heterozygous case of abetalipoproteinemia.

Background And Aims: Abetalipoproteinemia (ABL) is a rare recessive monogenic disease due to MTTP (microsomal triglyceride transfer protein) mutations leading to the absence of plasma apoB-containing lipoproteins. Here we characterize a new ABL case with usual clinical phenotype, hypocholesterolemia, hypotriglyceridemia but normal serum apolipoprotein B48 (apoB48) and red blood cell vitamin E concentrations.

Methods: Histology and MTP activity measurements were performed on intestinal biopsies.

New rare genetic variants of LMF1 gene identified in severe hypertriglyceridemia.

Background: The LMF1 (lipase maturation factor 1) gene encodes a protein involved in lipoprotein lipase and hepatic lipase maturation. Homozygous mutations in LMF1 leading to severe hypertriglyceridemia (SHTG) are rare in the literature. A few additional rare LMF1 variants have been described with poor functional studies.

Alterations in plasma triglycerides lipolysis in patients with history of multifactorial chylomicronemia.

Background And Aims: The heterogeneity and mechanisms of multifactorial chylomicronemia (MCM) remain poorly understood. To gain new insights, post heparin lipolysis measured at 60 min (PHLA60), in addition to the more commonly used 10 min (PHLA10), was assessed in patients with history of MCM.

Methods: 62 consecutive MCM patients were studied.

Multiple microRNA regulation of lipoprotein lipase gene abolished by 3'UTR polymorphisms in a triglyceride-lowering haplotype harboring p.Ser474Ter.

Background: Lipoprotein lipase (LPL) is a key enzyme in triglyceride (TG) metabolism. LPL gene single nucleotide polymorphisms (SNPs) are associated with TG concentrations however the functionality of many of these SNPs remains poorly understood. MicroRNAs (miR) exert post-transcriptional down-regulation and their target sequence on the 3'UTR may be altered by SNPs.

Post-heparin LPL activity measurement using VLDL as a substrate: a new robust method for routine assessment of plasma triglyceride lipolysis defects.

Background: Determination of lipoprotein lipase (LPL) activity is important for hyperchylomicronemia diagnosis, but remains both unreliable and cumbersome with current methods. Consequently by using human VLDL as substrate we developed a new LPL assay which does not require sonication, radioactive or fluorescent particles.

Methods: Post-heparin plasma was added to the VLDL substrate prepared by ultracentrifugation of heat inactivated normolipidemic human serums, diluted in buffer, pH 8.

Post-heparin LPL activity measurement using VLDL as a substrate: a new robust method for routine assessment of plasma triglyceride lipolysis defects.

Background: Determination of lipoprotein lipase (LPL) activity is important for hyperchylomicronemia diagnosis, but remains both unreliable and cumbersome with current methods. Consequently by using human VLDL as substrate we developed a new LPL assay which does not require sonication, radioactive or fluorescent particles.

Methods: Post-heparin plasma was added to the VLDL substrate prepared by ultracentrifugation of heat inactivated normolipidemic human serums, diluted in buffer, pH 8.