👤 Antoine Rimbert

Familial hypercholesterolaemia (FH) is an inherited disease of high LDL cholesterol (LDL-C) caused by defects in LDLR, APOB, APOE, and PCSK9 genes. A pathogenic variant cannot be found in ∼60% of clinical FH patients. Using whole genome sequencing (WGS), we examined genetic determinants of FH. Whole genome sequencing data generated by the 100 000 Genomes Project (100KGP) included 536 FH patients diagnosed using the FH Simon-Broome criteria. Rare variants in known FH genes were analysed. Genome-wide association study between 443 FH variant-negative unrelated FH cases and 77 275 control participants of the 100KGP was run using high-coverage WGS data. Polygenic risk scores for LDL-C (LDL PRS) and lipoprotein(a) (Lp(a) PRS) were computed. An FH-causing variant was found in 17.4% of FH cases. Genome-wide association study identified the LPA gene locus being significantly associated (P < 1 × 10-8). Familial hypercholesterolaemia variant-negative participants had higher LDL and Lp(a) PRSs in comparison with the controls (P < 1.0 × 10-16 and P < 4.09 × 10-6, respectively). Similar associations were found in the monogenic FH with both LDL and Lp(a) PRSs being higher than in controls (P < 4.03 × 10-4 and P < 3.01 × 10-3, respectively). High LDL PRS was observed in 36.4% of FH variant-negative cases, whereas high Lp(a) PRS in 18.5%, with 7.0% having both high LDL and Lp(a) PRSs. This genome-wide analysis of monogenic and polygenic FH causes confirms a complex and heterogeneous architecture of hypercholesterolaemia, with the LPA gene playing a significant role. Both Lp(a) and LDL-C should be measured for precision FH diagnosis. Specific therapies to lower Lp(a) should be targeted to those who will benefit most. Show less

This study aimed to assess the prevalence of genetic variants responsible for extreme levels of high-density lipoprotein cholesterol (HDL-C) and evaluate the adequacy of current thresholds for genetic testing of HDL-related dyslipidemia. Using data from the Tromsø Study, a population-based cohort in Northern Norway, we identified 210 individuals with HDL-C levels ≤ 0.5 mmol/L or ≥ 3.0 mmol/L. Six HDL-related genes (ABCA1, APOA1, CETP, LCAT, PLTP, SCARB1) were sequenced in these participants. We classified variants according to ACMG guidelines, incorporating functional assays and UK Biobank data for additional phenotype-genotype associations. We identified 38 variants of interest across six HDL-related genes, of which 10 were considered potentially causative, found in 14 individuals. Genetic causes were detected in 33.3% of individuals with low HDL-C and 5.05% of those with high HDL-C. Sex-specific analyses showed that using HDL-C thresholds aligned with population distributions improved detection of individuals with pathogenic variants, particularly among women with high HDL-C and men with low HDL-C. These findings suggest that current uniform thresholds may overlook clinically relevant cases and that incorporating sex-specific HDL-C distributions could enhance the identification of individuals with suspected genetic HDL disorders. Genetic testing for HDL-related dyslipidemia is underutilized, with many individuals not meeting the current extreme HDL-C threshold criteria. Revised sex-specific thresholds for genetic testing will improve the identification of pathogenic variants and provide more accurate diagnoses of HDL-related disorders. Continued research is essential to refine our understanding of HDL genetics and its clinical implications. Show less

Primary hypobetalipoproteinemia (HBL) is mostly due to a polygenic origin or to monogenic disorders including loss of function (LOF) variants in APOB, much less frequently Angiopoietin-like 3 gene (ANGPTL3). A new heterozygous variant of uncertain significance (VUS), p.H343R missense variant in ANGPTL3 cosegregated with HBL in a family. The aim of the present study was to assess in vitro the functionality of this variant and to establish its causality in this family. Targeted next-generation sequencing was performed in the proband to assess monogenic and polygenic origins using an LDL-C-dedicated polygenic risk score (PRS All 8 HBL subjects had PRS This study shows that the novel ANGPTL3-p.H343R variant decreases ANGPTL3 secretion in vitro and can now be considered as a LOF variant. The lipid phenotype in this family results from a synergistic combination of the p.H343R ANGPTL3 variant and a polygenic HBL predisposition. Show less

G-protein coupled receptor 146 (GPR146)-deficient mice exhibit a moderate 21 % reduction in plasma cholesterol. This is associated with decreased phosphorylation of ERK1/2 and reduced SREBP2 activity in the liver, which leads to lower VLDL secretion. Insight into the role of GPR146 in humans is however limited. We therefore set out to study rare genetic variants in GPR146 to improve our understanding of this new player in lipid metabolism. We used whole genome sequencing data from UK Biobank participants to search for rare coding variants in GPR146. We first carried out gene-based burden tests (using SAIGE-GENE-framework) and examined the association of individual variants with plasma cholesterol levels. One of the variants (P62L) was also studied using the Global Lipids Genetics Consortium (GLGC) data set and in a knock-in mouse model. We found that the combination of rare genetic variants identified in GPR146 is significantly associated with plasma cholesterol levels. Three rare variants, i.e. P62L, I129I, and A175T were individually associated with reduced plasma cholesterol. In the GLGC cohort, the P62L variant was associated with reductions in both HDL and LDL cholesterol. Follow-up experiments show lower plasma cholesterol levels in GPR146 This study shows that rare GPR146 gene variants are associated with lower plasma cholesterol levels in humans. One of these variants, P62L is associated with reductions of HDL cholesterol and LDL cholesterol in humans while the ortholog in mice confers a loss of GPR146 function leading to only reduced HDL cholesterol. How GPR146 affects HDL metabolism in humans and mice remains to be resolved. Show less

High apolipoprotein B-containing (apoB-containing) low-density lipoproteins (LDLs) and low apoA1-containing high-density lipoproteins (HDLs) are associated with atherosclerotic cardiovascular diseases. In search of a molecular regulator that could simultaneously and reciprocally control both LDL and HDL levels, we screened a microRNA (miR) library using human hepatoma Huh-7 cells. We identified miR-541-3p that both significantly decreases apoB and increases apoA1 expression by inducing mRNA degradation of 2 different transcription factors, Znf101 and Casz1. We found that Znf101 enhances apoB expression, while Casz1 represses apoA1 expression. The hepatic knockdown of Casz1 in mice increased plasma apoA1, HDL, and cholesterol efflux capacity. The hepatic knockdown of Zfp961, an ortholog of Znf101, reduced lipogenesis and production of triglyceride-rich lipoproteins and atherosclerosis, without causing hepatic lipid accumulation. This study identifies hepatic Znf101/Zfp961 and Casz1 as potential therapeutic targets to alter plasma lipoproteins and reduce atherosclerosis without causing liver steatosis. Show less

Dysbetalipoproteinemia (DBL) is a combined dyslipidemia associated with an increased risk of atherosclerotic cardiovascular diseases mostly occurring in ε2ε2 subjects and infrequently in subjects with rare Patients were divided into 3 groups according to their Total cholesterol (TC)/ApoB and NHDLC/ApoB are the best ratios to suspect DBL. In ε2ε2, according to their likelihood ratios (LR), the most clinically efficient algorithms were the HCL, Sniderman and De Graaf's. In APOEmut, Sniderman's algorithm exhibited the lowest negative LR (0.07) whereas the HCL's exhibited the highest positive LR (29). In both cohorts, the HCL algorithm had the best LR. We proposed a powerful algorithm based on ApoB concentration and the routine lipid profile, which performs remarkably well in detecting ε2ε2 or Show less

Plasma lipids are mainly carried in apolipoprotein B (apoB) containing lipoproteins. High levels of these lipoproteins are associated with several metabolic diseases and lowering their plasma levels is associated with reduced incidence of atherosclerotic cardiovascular disease. MicroRNAs (miRs) are small non-coding RNAs that reduce the protein expression of their target mRNAs and are potential therapeutic agents. Here, we identified a novel miR-615-3p that interacts with human 3'-UTR of apoB mRNA, induces post-transcriptional mRNA degradation, and reduces cellular and secreted apoB100 in human hepatoma Huh-7 cells. Reducing cellular miR-615-3p levels by CRISPR-sgRNA increased cellular and secreted apoB100 indicating endogenous miR regulates apoB expression. Overexpression of miR-615-3p along with or without palmitic acid treatment decreased cellular and media apoB and increased cellular triglyceride levels without inducing endoplasmic reticulum stress. These studies have identified miR-615-3p as a negative regulator of apoB expression in human liver-derived cells. It is likely that there are more miRs that regulate apoB-containing lipoprotein assembly and secretion. Discovery of additional miRs may uncover novel mechanisms that control lipoprotein assembly and secretion. Show less

The liver X receptor (LXR) is considered a therapeutic target for atherosclerosis treatment, but synthetic LXR agonists generally also cause hepatic steatosis and hypertriglyceridemia. Desmosterol, a final intermediate in cholesterol biosynthesis, has been identified as a selective LXR ligand that suppresses inflammation without inducing lipogenesis. Δ24-Dehydrocholesterol reductase (DHCR24) converts desmosterol into cholesterol, and we previously showed that the DHCR24 inhibitor SH42 increases desmosterol to activate LXR and attenuate experimental peritonitis and metabolic dysfunction-associated steatotic liver disease. Here, we aimed to evaluate the effect of SH42 on atherosclerosis development in APOE∗3-Leiden.CETP mice and low-density lipoproteins (LDL) receptor knockout mice, models for lipid- and inflammation-driven atherosclerosis, respectively. In both models, SH42 increased desmosterol without affecting plasma lipids. While reducing liver lipids in APOE∗3-Leiden.CETP mice, and regulating populations of circulating monocytes in LDL receptor knockout mice, SH42 did not attenuate atherosclerosis in either model. Show less

Atherosclerotic cardiovascular disease is the main cause of mortality worldwide and is strongly influenced by circulating low-density lipoprotein (LDL) cholesterol levels. Only a few genes causally related to plasma LDL cholesterol levels have been identified so far, and only 1 gene, Using next-generation sequencing, we identified a novel dominant rare variant in the Family members carrying the We identified and characterized a novel rare variant in the Show less