Background: 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... Show moreBackground: 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, ANGPTL3, has been causally related to combined hypocholesterolemia. Here, our aim was to elucidate the genetic origin of an unexplained combined hypocholesterolemia inherited in 4 generations of a French family. Methods: Using next-generation sequencing, we identified a novel dominant rare variant in the LIPC gene, encoding for hepatic lipase, which cosegregates with the phenotype. We characterized the impact of this LIPC-E97G variant on circulating lipid and lipoprotein levels in family members using nuclear magnetic resonance-based lipoprotein profiling and lipidomics. To uncover the mechanisms underlying the combined hypocholesterolemia, we used protein homology modeling, measured triglyceride lipase and phospholipase activities in cell culture, and studied the phenotype of APOE*3.Leiden.CETP mice after LIPC-E97G overexpression. Results: Family members carrying the LIPC-E97G variant had very low circulating levels of LDL cholesterol and high-density lipoprotein cholesterol, LDL particle numbers, and phospholipids. The lysophospholipids/phospholipids ratio was increased in plasma of LIPC-E97G carriers, suggestive of an increased lipolytic activity on phospholipids. In vitro and in vivo studies confirmed that the LIPC-E97G variant specifically increases the phospholipase activity of hepatic lipase through modification of an evolutionarily conserved motif that determines substrate access to the hepatic lipase catalytic site. Mice overexpressing human LIPC-E97G recapitulated the combined hypocholesterolemic phenotype of the family and demonstrated that the increased phospholipase activity promotes catabolism of triglyceride-rich lipoproteins by different extrahepatic tissues but not the liver. Conclusions: We identified and characterized a novel rare variant in the LIPC gene in a family who presents with dominant familial combined hypocholesterolemia. This gain-of-function variant makes LIPC the second identified gene, after ANGPTL3, causally involved in familial combined hypocholesterolemia. Our mechanistic data highlight the critical role of hepatic lipase phospholipase activity in LDL cholesterol homeostasis and suggest a new LDL clearance mechanism. Show less
Dijk, W.; Filippo, M. di; Kooijman, S.; Eenige, R. van; Rimbert, A.; Caillaud, A.; ... ; Cariou, B. 2022
Background: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... Show moreBackground: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, ANGPTL3, has been causally related to combined hypocholesterolemia. Here, our aim was to elucidate the genetic origin of an unexplained combined hypocholesterolemia inherited in 4 generations of a French family.Methods:Using next-generation sequencing, we identified a novel dominant rare variant in the LIPC gene, encoding for hepatic lipase, which cosegregates with the phenotype. We characterized the impact of this LIPC-E97G variant on circulating lipid and lipoprotein levels in family members using nuclear magnetic resonance–based lipoprotein profiling and lipidomics. To uncover the mechanisms underlying the combined hypocholesterolemia, we used protein homology modeling, measured triglyceride lipase and phospholipase activities in cell culture, and studied the phenotype of APOE*3.Leiden.CETP mice after LIPC-E97G overexpression.Results:Family members carrying the LIPC-E97G variant had very low circulating levels of LDL cholesterol and high-density lipoprotein cholesterol, LDL particle numbers, and phospholipids. The lysophospholipids/phospholipids ratio was increased in plasma of LIPC-E97G carriers, suggestive of an increased lipolytic activity on phospholipids. In vitro and in vivo studies confirmed that the LIPC-E97G variant specifically increases the phospholipase activity of hepatic lipase through modification of an evolutionarily conserved motif that determines substrate access to the hepatic lipase catalytic site. Mice overexpressing human LIPC-E97G recapitulated the combined hypocholesterolemic phenotype of the family and demonstrated that the increased phospholipase activity promotes catabolism of triglyceride-rich lipoproteins by different extrahepatic tissues but not the liver.Conclusions:We identified and characterized a novel rare variant in the LIPC gene in a family who presents with dominant familial combined hypocholesterolemia. This gain-of-function variant makes LIPC the second identified gene, after ANGPTL3, causally involved in familial combined hypocholesterolemia. Our mechanistic data highlight the critical role of hepatic lipase phospholipase activity in LDL cholesterol homeostasis and suggest a new LDL clearance mechanism. Show less
This thesis aimed to explore biochemical processes related to migraine outside (interictal) and during upcoming attacks. Chapter 2 describes the biochemical profiling of plasma samples from... Show moreThis thesis aimed to explore biochemical processes related to migraine outside (interictal) and during upcoming attacks. Chapter 2 describes the biochemical profiling of plasma samples from interictal migraine patients and healthy controls from eight Dutch cohorts with a proton nuclear magnetic resonance based metabolomics platform. In Chapter 3 cerebrospinal fluid (CSF) and plasma samples from interictal migraine with and without aura patients and healthy volunteers, were profiled using an ultra-performance liquid chromatography mass spectrometry (UPLC-MS) platform for amine measurements, as multiple amines have been implicated in migraine pathophysiology. Alcoholic beverages are frequently reported migraine triggers. Chapter 4 assessed the potential of various alcohol beverages as a migraine attack trigger using a questionnaire study in a large cohort of migraine patients. In Chapter 5, the frequently used pharmacological migraine trigger glyceryl trinitrate (GTN) was studied in migraine patients and healthy controls to investigate whether previously reported premonitory symptoms are indeed specific to migraine patients. In Chapter 6 glutamate, glutamine, and GABA were assed in the visual cortex of migraine patients before and over the course of a GTN-provoked attack to detect possible involvement of the glutamatergic system in the onset of attacks using proton magnetic resonance spectroscopy. Show less
NAFLD is closely related with the metabolic syndrome (MetS) and increased risk of cardiovascular disease. Liver fat associates with post-prandial hypertriglyceridemia, potentially contributing to... Show moreNAFLD is closely related with the metabolic syndrome (MetS) and increased risk of cardiovascular disease. Liver fat associates with post-prandial hypertriglyceridemia, potentially contributing to triglyceride-enrichment of high-density lipoproteins (HDL-TG), and subsequent HDL dysfunction. We assessed liver fat by MR spectroscopy, and its association with HDL physiochemical properties, and endothelial function, measured as flow-mediated dilation (FMD), before and following three consecutive meals, in 36 men with type 2 diabetes mellitus (T2DM), with the MetS, and controls. Plasma triglycerides increased significantly following the meals (P < .001). Fasting HDL-TG was highest in T2DM, relative to MetS and controls (P = .002), and increased post-prandially in all groups (P < .001). HDL function was negatively associated with HDL-TG following three meals (r = -.32,P<.05). Liver fat associated with HDL-TG after three meals (r = .65,P < .001). HDL-TG was independently associated with FMD following three consecutive meals (r = -.477,P = .003). We conclude liver fat is associated with post-prandial HDL-TG enrichment which was closely related with endothelial and HDL dysfunction. Show less
Trinder, M.; Genga, K.R.; Kong, H.J.; Blauw, L.L.; C. lo; Li, X.; ... ; Brunham, L.R. 2019
Rationale: High-density lipoprotein (HDL) cholesterol (HDL-C) levels decline during sepsis, and lower levels are associated with worse survival. However, the genetic mechanisms underlying changes... Show moreRationale: High-density lipoprotein (HDL) cholesterol (HDL-C) levels decline during sepsis, and lower levels are associated with worse survival. However, the genetic mechanisms underlying changes in HDL-C during sepsis, and whether the relationship with survival is causative, are largely unknown.Objectives: We hypothesized that variation in genes involved in HDL metabolism would contribute to changes in HDL-C levels and clinical outcomes during sepsis.Methods: We performed targeted resequencing of HDL-related genes in 200 patients admitted to an emergency department with sepsis (Early Infection cohort). We examined the association of genetic variants with HDL-C levels, 28-day survival, 90-day survival, organ dysfunction, and need for vasopressor or ventilatory support. Candidate variants were further assessed in the VASST (Vasopressin versus Norepinephrine Infusion in Patients with Septic Shock Trial) cohort (n = 632) and St. Paul's Hospital Intensive Care Unit 2 (SPHICU2) cohort (n = 203).Measurements and Main Results: We identified a rare missense variant in CETP (cholesteryl ester transfer protein gene; rs1800777A) that was associated with significant reductions in HDL-C levels during sepsis. Carriers of the A allele (n = 10) had decreased survival, more organ failure, and greater need for organ support compared with noncarriers. We replicated this finding in the VASST and SPHICU2 cohorts, in which carriers of rs1800777-A (n = 35 and n = 12, respectively) had significantly reduced 28-day survival. Mendelian randomization was consistent with genetically reduced HDL levels being a causal factor for decreased sepsis survival.Conclusions: Our results identify CETP as a critical regulator of HDL levels and clinical outcomes during sepsis. These data point toward a critical role for HDL in sepsis. Show less
Sluis, R.J. van der; Verwilligen, R.A.F.; Lendvai, Z.; Wever, R.; Hoekstra, M.; Eck, M. van 2018
Although studies in mice have suggested that lesion regression is feasible, the underlying mechanisms remain largely unknown. Here we determined the impact of high-density lipoprotein (HDL) on... Show moreAlthough studies in mice have suggested that lesion regression is feasible, the underlying mechanisms remain largely unknown. Here we determined the impact of high-density lipoprotein (HDL) on atherosclerosis regression outcome.\nAtherosclerotic lesion dynamics were studied upon bone marrow transplantation-mediated re-introduction of apolipoprotein E (Apoe) in Apoe knockout mice. Probucol was used to pharmacologically deplete HDL.\n for controls: p < 0.05).\nWe have shown that probucol-induced HDL deficiency impairs the ability of established lesions to regress in response to reversal of the genetic hypercholesterolemia in Apoe knockout mice. Our studies thus highlight a crucial role for HDL in the process of atherosclerosis regression. Show less
Ouweneel, A.B.; Hoekstra, M.; Wel, E.J. van der; Schaftenaar, F.H.; Snip, O.S.C.; Hassan, J.; ... ; Eck, M. van 2018
Thrombocytopenia in scavenger receptor BI (SR-BI) knockout mice is suggested to result from augmented platelet clearance induced by elevated intracellular unesterified cholesterol (UC) levels. We... Show moreThrombocytopenia in scavenger receptor BI (SR-BI) knockout mice is suggested to result from augmented platelet clearance induced by elevated intracellular unesterified cholesterol (UC) levels. We hypothesize that SR-BI deficiency may also influence platelet production at the level of its precursor cell in the bone marrow, the megakaryocyte.\nIn this study, we compared megakaryopoiesis and platelet production in SR-BI knockout and wild-type mice.\nIn line with our hypothesis, megakaryocytes from SR-BI knockout mice exhibited UC accumulation while no accumulation of UC was detectable in wild-type megakaryocytes. Bone marrow expression of transcription factors involved in megakaryocyte maturation was induced, but megakaryocyte counts were unchanged in bone marrow of SR-BI knockout mice. Interestingly, we did find a striking 62% decrease (p < 0.01) in proplatelet production by SR-BI knockout megakaryocytes. SR-BI knockout mice displayed an impaired increase in circulating platelet concentrations and bone marrow megakaryocyte numbers upon thrombopoietin challenge. Importantly, megakaryocytes from normolipidemic bone marrow-specific SR-BI knockout mice exhibited a normal ability to produce proplatelets. Moreover, bone marrow-specific deletion of SR-BI did not impair the thrombopoietin response or induce thrombocytopenia, confirming that absence of megakaryocyte SR-BI does not underlie the thrombocytopenic phenotype in total body SR-BI knockout mice.\nIn conclusion, the elevation of plasma unesterified cholesterol levels impairs megakaryopoiesis and platelet production in SR-BI knockout mice. Our findings suggest that, in addition to an increased platelet clearance, a decrease in platelet production may also, in part, explain the thrombocytopenic phenotype associated with SR-BI deficiency in mice. Show less
CONCLUSION: TA-8995 dose dependently increased not only total and non-ABCAl-specific CEC but also ABCAl-specific CEC and preBeta-1 HDL particle levels. These findings suggest that TA-8995 not only... Show moreCONCLUSION: TA-8995 dose dependently increased not only total and non-ABCAl-specific CEC but also ABCAl-specific CEC and preBeta-1 HDL particle levels. These findings suggest that TA-8995 not only increases HDL-C levels but also promotes functional properties of HDL particles. This CETP inhibitor driven preBeta-1 HDL increase is an important predictor of both ABCA1 and total CEC increase, independent of HDL-C increase. Whether these changes in HDL particle composition and functionality have a beneficial effect on cardiovascular outcome requires formal testing in a cardiovascular outcome trial. (C) 2016 National Lipid Association. All rights reserved. Show less
Conclusion: Impaired HDL functionality in South Asians may be a contributing factor to their high CVD risk. (C) 2016 The Italian Society of Diabetology, the Italian Society for the Study of... Show moreConclusion: Impaired HDL functionality in South Asians may be a contributing factor to their high CVD risk. (C) 2016 The Italian Society of Diabetology, the Italian Society for the Study of Atherosclerosis, the Italian Society of Human Nutrition, and the Department of Clinical Medicine and Surgery, Federico II University. Published by Elsevier B.V. All rights reserved. Show less
OBJECTIVE: The dyslipidemia of type 2 diabetes mellitus has multiple etiologies and impairs lipoprotein functionality, thereby increasing risk for cardiovascular disease. High-density lipoproteins ... Show moreOBJECTIVE: The dyslipidemia of type 2 diabetes mellitus has multiple etiologies and impairs lipoprotein functionality, thereby increasing risk for cardiovascular disease. High-density lipoproteins (HDLs) have several beneficial effects, notably protecting the heart from myocardial ischemia. We hypothesized that glycation of HDL could compromise this cardioprotective effect.APPROACH AND RESULTS: We used in vitro (cardiomyocytes) and ex vivo (whole heart) models subjected to oxidative stress together with HDL isolated from diabetic patients and nondiabetic HDL glycated in vitro (methylglyoxal). Diabetic and in vitro glycated HDL were less effective (P<0.05) than control HDL in protecting from oxidative stress. Protection was significantly, inversely correlated with the degree of in vitro glycation (P<0.001) and the levels of hemoglobin A1c in diabetic patients (P<0.007). The ability to activate protective, intracellular survival pathways involving Akt, Stat3, and Erk1/2 was significantly reduced (P<0.05) using glycated HDL. Glycation reduced the sphingosine-1-phosphate (S1P) content of HDL, whereas the S1P concentrations of diabetic HDL were inversely correlated with hemoglobin A1c (P<0.005). The S1P contents of in vitro glycated and diabetic HDL were significantly, positively correlated (both <0.01) with cardiomyocyte survival during oxidative stress. Adding S1P to diabetic HDL increased its S1P content and restored its cardioprotective function.CONCLUSIONS: Our data demonstrate that glycation can reduce the S1P content of HDL, leading to increased cardiomyocyte cell death because of less effective activation of intracellular survival pathways. It has important implications for the functionality of HDL in diabetes mellitus because HDL-S1P has several beneficial effects on the vasculature. Show less
Excessive accumulation of cholesterol by macrophage-derived foam cells is one of the characteristic features of atherosclerotic lesion development. Macrophages not only play an important role in... Show moreExcessive accumulation of cholesterol by macrophage-derived foam cells is one of the characteristic features of atherosclerotic lesion development. Macrophages not only play an important role in the initiation of the early atherosclerotic lesion, during further progression of the lesions macrophages also contribute to the formation of a necrotic core, thereby affecting the stability of the atherosclerotic plaque. Especially in the initiation of atherosclerosis the balance between cholesterol influx and efflux in macrophages is of prime importance. This balance is maintained by scavenger receptors and ATP-binding cassette (ABC) transporters, which are key mediators for macrophage cholesterol homeostasis as they facilitate the influx and efflux of lipids. Macrophages are incapable of limiting the uptake of cholesterol by scavenger receptors, including scavenger receptor class A (SR-A) and CD36. Therefore, prevention of lipid accumulation in macrophages largely depends on cholesterol efflux pathways, mainly mediated by ABC transporters. Gaining more knowledge on macrophage lipid homeostasis is of prime importance for the development of new therapeutic strategies to prevent atherosclerotic lesion development or induce regression of existing lesions. The aim of the studies described in this thesis was investigation of the role of several ABC transporters and SR-BI in (macrophage) lipid metabolism and atherogenesis. Show less
