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Disproportional free cholesterol (FC) and cholesterol ester (CE) levels in apoc2 mutant zebrafish (A) Plasma triglyceride (TG) levels in adult wild type (WT) and apoc2 mutant zebrafish; (B) Plasma total cholesterol (TC), FC and CE levels; (C) FC/CE ratio. Results are mean±s.e.m.; n = 3 in each group; ***P<0.001 (Student’s t-test). Graphs in panel A and part of panel B replicate previously reported results [25].
Source publication
Hypertriglyceridemia is an independent risk factor for cardiovascular disease. Apolipoprotein C-II (APOC2) is an obligatory cofactor for lipoprotein lipase (LPL), the major enzyme catalyzing plasma triglyceride hydrolysis. We have created an apoc2 knockout zebrafish model, which mimics the familial chylomicronemia syndrome (FCS) in human patients w...
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Context
Differentiation between familial chylomicronemia syndrome (FCS, type 1 hyperlipoproteinemia), a rare metabolic disorder, and the more common multifactorial severe hypertriglyceridemia (sHTG, type 5 hyperlipoproteinemia) is challenging due to overlapping symptomatology, but important in patient management.
Objective
To assess whether readil...
Citations
... Conversely, we found increased FC levels and FC/CE ratios in these plasma samples from patients with a RINT1 mutation ( Figure 5B). Collectively, these results suggest a potential alteration in cholesterol turnover, as described in other cases of disturbed TG metabolism (39). ...
The Rad50 interacting protein 1 (Rint1) is a key player in vesicular trafficking between the ER and Golgi apparatus. Biallelic variants in RINT1 cause infantile-onset episodic acute liver failure (ALF). Here, we describe 3 individuals from 2 unrelated families with novel biallelic RINT1 loss-of-function variants who presented with early onset spastic paraplegia, ataxia, optic nerve hypoplasia, and dysmorphic features, broadening the previously described phenotype. Our functional and lipidomic analyses provided evidence that pathogenic RINT1 variants induce defective lipid-droplet biogenesis and profound lipid abnormalities in fibroblasts and plasma that impact both neutral lipid and phospholipid metabolism, including decreased triglycerides and diglycerides, phosphatidylcholine/phosphatidylserine ratios, and inhibited Lands cycle. Further, RINT1 mutations induced intracellular ROS production and reduced ATP synthesis, affecting mitochondria with membrane depolarization, aberrant cristae ultrastructure, and increased fission. Altogether, our results highlighted the pivotal role of RINT1 in lipid metabolism and mitochondria function, with a profound effect in central nervous system development.
... Similar to mammals, microsomal triglycerides transfer protein play a critical role in lipid transport in zebrafish [14]. The zebrafish also express cholesteryl ester transfer protein (CETP) and are susceptible to atherosclerosis, making them attractive models for studying this disorder [15]. Apart from these physiological similarities, zebrafish also possess orthologues of critical lipid metabolic genes including microsomal TG transfer protein (mttp), fatty acid transport protein (slc27a), and acyl-CoA synthetase (acsl) gene families, as well as the LDL receptor (ldlr). ...
Nonalcoholic fatty liver disease (NAFLD) is one of the most common liver diseases in adults. NAFLD progresses from benign liver fat accumulation to liver inflammation and cirrhosis, and ultimately leads to liver failure. Although several rodent models have been established for studying NAFLD, they have limitations that include cost, speed of disease development, key dissimilarities, and poor amenability to pharmacological screens. Here, we present a novel 2-hit zebrafish model to replicate aspects of NAFLD pathogenesis. We fed zebrafish larvae a high-fat diet (HFD) to drive liver fat accumulation (first hit). Next, we exacerbated liver-specific inflammation using a transgenic line (fabp10-CETI-PIC3) that induces the expression of proinflammatory cytokines following induction with doxycycline (second hit). These hits promoted fat accumulation and liver inflammation, as demonstrated by the high expression of inflammatory cytokines, macrophage infiltration, stress induction, and hepatic lipid droplet accumulation. Furthermore, zebrafish in this paradigm showed deranged glucose metabolism. To validate a small-molecule screening approach, we treated HFD-fed fish with pioglitazone, a drug shown to be beneficial for NAFLD in humans, and measured a sharp reduction in liver lipid accumulation. These results demonstrate new utility for zebrafish in modeling early NAFLD pathogenesis and demonstrate their feasibility for in vivo screening of new pharmacological interventions.
... All major classes of apolipoproteins (ApoA, ApoB, ApoC, and ApoE) are expressed in zebrafish and are highly similar to human apolipoproteins (79). As mentioned above, hypertriglyceridemia is an independent CVD risk factor caused by single mutations in the genes encoding lipoprotein lipase (LPL) or in those encoding LPL cofactors, such as APOC2 (28,55). Liu et al. demonstrated that apoc2 −/− zebrafish exhibit properties of human patients, including dyslipidemia, specifically hypertriglyceridemia as early as 14 dpf, which resulted in type II atherosclerosis. ...
Cardiovascular diseases, such as atherosclerosis, are the leading cause of death worldwide. Although mice are currently the most commonly used model for atherosclerosis, zebrafish are emerging as an alternative, especially for inflammatory and lipid metabolism studies. Here, we review the history of in vivo atherosclerosis models and highlight the potential for future studies on inflammatory responses in lipid deposits in zebrafish, based on known immune reactions in humans and mice, in anticipation of new zebrafish models with more advanced atherosclerotic plaques.
... Recently, deficient cholesterol esterification has been found to occur in an apoC11-deficient zebrafish, which mimics the familial chylomicronemia syndrome in human patients, with a defect in apoC2 or LpL genes. 115 ApoC111 inhibits the delipidation of triglyceride from the particle by inhibiting the action of LpL, thus delaying the clearance of the particle from the circulation. 116 The Bruneck Study 117 was designed to examine the importance of various apolipoproteins in the genesis of cardiovascular events over a 10-year period. ...
Premature atherosclerosis in diabetes accounts for much of the decreased life span. New treatments have reduced this risk considerably. This review explores the relationship among the disturbances in glucose, lipid, and bile salt metabolic pathways that occur in diabetes. In particular, excess nutrient intake and starvation have major metabolic effects, which have allowed us new insights into the disturbance that occurs in diabetes. Metabolic regulators such as the forkhead transcription factors, the farnesyl X transcription factors, and the fibroblast growth factors have become important players in our understanding of the dysregulation of metabolism in diabetes and overnutrition. The disturbed regulation of lipoprotein metabolism in both the intestine and the liver has been more clearly defined over the past few years, and the atherogenicity of the triglyceride-rich lipoproteins, and – in tandem – low levels of high-density lipoproteins, is seen now as very important. New information on the apolipoproteins that control lipoprotein lipase activity has been obtained. This is an exciting time in the battle to defeat diabetic atherosclerosis.
Zebrafish have become a powerful model of mammalian lipoprotein metabolism and lipid cell biology. Most key proteins involved in lipid metabolism, including cholesteryl ester transfer protein, are conserved in zebrafish. Consequently, zebrafish exhibit a human-like lipoprotein profile. Zebrafish with mutations in genes linked to human metabolic diseases often mimic the human phenotype. Zebrafish larvae develop rapidly and externally around the maternally deposited yolk. Recent work revealed that any disturbance of lipoprotein formation leads to the accumulation of cytoplasmic lipid droplets and an opaque yolk, providing a visible phenotype to investigate disturbances of the lipoprotein pathway, already leading to discoveries in microsomal triglyceride transfer protein and ApoB (apolipoprotein B). By 5 days of development, the digestive system is functional, making it possible to study fluorescently labeled lipid uptake in the transparent larvae. These and other approaches enabled the first in vivo description of the STAB (stabilin) receptors, showing lipoprotein uptake in endothelial cells. Various zebrafish models have been developed to mimic human diseases by mutating genes known to influence lipoproteins (eg, ldlra , apoC2 ). This review aims to discuss the most recent research in the zebrafish ApoB-containing lipoprotein and lipid metabolism field. We also summarize new insights into lipid processing within the yolk cell and how changes in lipid flux alter yolk opacity. This curious new finding, coupled with the development of several techniques, can be deployed to identify new players in lipoprotein research directly relevant to human disease.
Dyslipidemia related diseases such as hyperlipidemia and atherosclerosis are the leading cause of death in humans. While cellular and molecular basis on the pathophysiology of dyslipidemia has been extensively investigated over decades, we still lack comprehensive understanding on the etiology of dyslipidemia due to the complexity and the innate multimodality of the diseases. While mouse has been the model organism of choice to investigate the pathophysiology of human dyslipidemia, zebrafish, a small freshwater fish which has traditionally used to study vertebrate development, has recently emerged as an alternative model organism. In this review, we will provide comprehensive perspective on zebrafish as a model organism for human dyslipidemia; we will discuss the attributes of zebrafish as a model, and compare the lipid metabolism in zebrafish and humans. In addition, we will summarize current landscape of zebrafish-based dyslipidemia research.
Apolipoprotein C2 (ApoC2) is an important member of the apolipoprotein C family and functions as a major activator of lipoprotein lipase (LPL). In cardiovascular and cerebrovascular systems, the lipolytic activity of the LPL-ApoC2 complex is critical for the metabolism of triglyceride-rich lipoproteins and contributes to the pathogenesis of ischemic stroke (IS). However, the regulation of ApoC2 in IS development remains unclear. In this study, we first explored potential ApoC2-targeting microRNAs (miRNAs) by bioinformatics tool and compared the miRNA expression profiles in the blood cells of 25 IS patients and 25 control subjects by miRNA microarray. miR-1275 was predicted to bind with the 3' untranslated region of ApoC2, and a significant reduction of blood miR-1275 levels was observed in IS patients. Dual-luciferase reporter assay and quantitative RT-PCR confirmed the regulation of ApoC2 by miR-1275 in THP-1 derived macrophages. miR-1275 also inhibited cellular uptake of ox-LDL and suppressed formation of macrophage foam cell. Furthermore, the whole blood miR-1275 levels were validated in 279 IS patients and 279 control subjects by TaqMan assay. miR-1275 levels were significantly lower in IS cases and logistic regression analysis showed that miR-1275 level was negatively associated with the occurrence of IS (adjusted OR, 0.76; 95% CI, 0.69∼0.85; p<0.001). Addition of miR-1275 to traditional risk factors showed an additive prediction value for IS. Our study shows that blood miR-1275 levels were negatively associated with the occurrence of IS, and miR-1275 might exert an athero-protective role against the development of IS by targeting ApoC2 and blocking the formation of macrophage foam cells.
Insulin and leptin resistance are highly involved in metabolic syndrome and non-alcoholic fatty liver disease (NAFLD). Presently, no approved treatment is available. Actein is isolated from the rthizomes of Cimicifuga foetida, a triterpene glycoside, exhibiting important biological properties, such as anti-inflammatory, anti-cancer, and anti-oxidant activity. However, its effects on metabolic syndrome are poorly understood. The aims of the study were mainly to investigate the molecular mechanisms regulating insulin and leptin resistance, and lipogenic action of actein in high fat diet-fed mice. Our data indicated that actein-treated mice displayed lower body weight, epididymal and subcutaneous fat mass, as well as serum lipid levels. Also, improved insulin and leptin resistance were observed in actein-treated groups. Liver inflammation and fibrosis triggered by high fat diet were decreased for actein administration. Moreover, hepatic lipid accumulation was also reduced by actein along with reductions of hepatic de novo lipogenesis-linked signals in actein-treated rodents with high fat diet. High fat diet-induced activation of insulin receptor substrate 1/Forkhead box protein O1 (IRS1/FOXO1), Janus kinase 2 gene/signal transducer and activator of transcription (JAK2/STAT3) and Protein Kinase B/Glycogen synthase kinase 3 beta (AKT/GSK3β) pathways in liver was inhibited by actein, a potential mechanism by which hyperinsulinemia, hyperleptindemia and dyslipidemia were attenuated. Thus, the findings above might be of nutritional and therapeutic importance for the treatment of NAFLD.
Background and aims:
Familial chylomicronemia syndrome is a rare autosomal recessive disorder leading to severe hypertriglyceridemia (HTG) due to mutations in lipoprotein lipase (LPL)-associated genes. Few data exist on the clinical features of the disorder or on comprehensive genetic approaches to uncover the causative genes and mutations.
Methods:
Eight patients diagnosed with familial hyperchylomicronemia with recessive inheritance were included in this study (two males and six females; median age of onset 23.0 years; mean triglyceride level 3446 mg/dl). We evaluated their clinical features, including coronary artery disease using coronary computed tomography, and performed targeted next-generation sequencing on a panel comprising 4813 genes associated with known clinical phenotypes. After standard filtering for allele frequency <1% and in silico annotation prediction, we used three types of variant filtering to identify causative mutations: homozygous mutations in known familial hyperchylomicronemia-associated genes, homozygous mutations with high damaging scores in novel genes, and deleterious mutations within 37 genes known to be associated with HTG.
Results:
A total of 1810 variants out of the 73,389 identified with 94.3% mean coverage (×20) were rare and nonsynonymous. Among these, our schema detected four pathogenic or likely pathogenic mutations in the LPL gene (p.Ala248LeufsTer4, p.Arg270Cys, p.Ala361Thr, and p.Val227Gly), including one novel mutation and a variant of uncertain significance. Patients harboring LPL gene mutations showed no severe atherosclerotic changes in the coronary arteries, but recurrent pancreatitis with long-term exposure to HTG was observed.
Conclusions:
These results demonstrate that LPL gene plays a major role in extreme HTG associated with hyperchylomicronemia, although the condition may not cause severe atherosclerosis.
