Zebrafish models of dyslipidemia: relevance to atherosclerosis and angiogenesis

Impact of distribution of carotid intraplaque neovessels on plaque vulnerability

BACKGROUND AND PURPOSE

Intraplaque neovessels (INVs) are considered important contributors to carotid plaque vulnerability. The purpose of this study was to examine whether differences in INV distribution affect plaque vulnerability.

METHODS

The study cohort comprised 110 patients with significant stenosis of the carotid artery who had undergone carotid endarterectomy. The distribution of INVs within carotid plaques was assessed by immunohistochemical studies using anti-CD-34 antibody as a marker for endothelial cells. First, we divided the patients into M group and S group depending on the numbers of INVs in middle and shoulder region. Next, we categorized carotid plaques into four categories according to the distributions of INVs: Shoulder, Middle, Mixed, and Scarce. We then compared total area of intraplaque hemorrhage, cholesterol, and calcification, width of thinnest fibrous cap, and number of INVs between the four categories of plaque.

RESULTS

The area of intraplaque hemorrhage was significantly larger in the M group than in the S group (P = 0.011). Meanwhile, symptomatic carotid stenosis was significantly more frequently associated with the Middle and Mixed than the Shoulder and Scarce categories (P < 0.01). The area of intraplaque hemorrhage was significantly different between the four groups (P = 0.022). Rupture of the fibrous cap was more frequently detected in the Middle and Mixed than the other categories (P = 0.002).

CONCLUSIONS

INVs in the middle region of carotid plaques are strongly associated with symptomatic carotid stenosis, intraplaque hemorrhage, and rupture of the fibrous cap. Our findings indicate that the distribution of INVs may affect plaque vulnerability.

A high-cholesterol zebrafish diet promotes hypercholesterolemia and fasting-associated liver steatosis

Zebrafish are an ideal model organism to study lipid metabolism and to elucidate the molecular underpinnings of human lipid-associated disorders. Unlike murine models, to which various standardized high lipid diets such as a high-cholesterol diet (HCD) are available, there has yet to be a uniformly adopted zebrasfish HCD protocol. In this study, we have developed an improved HCD protocol and thoroughly tested its impact on zebrafish lipid deposition and lipoprotein regulation in a dose- and time- dependent manner. The diet stability, reproducibility, and fish palatability were also validated. Fish fed HCD developed hypercholesterolemia as indicated by significantly elevated ApoB-containing lipoproteins (ApoB-LP) and increased plasma levels of cholesterol and cholesterol esters. Feeding of the HCD to larvae for 8 days produced hepatic steatosis that become more stable and severer after 1 day of fasting and was associated with an opaque liver phenotype (dark under transmitted light). Unlike larvae, adult fish fed HCD for 14 days followed by a 3 day fast did not develop a stable fatty liver phenotype, though the fish had higher ApoB-LP levels in plasma and an up-regulated lipogenesis gene fasn in adipose tissue. In conclusion, our HCD zebrafish protocol represents an effective and reliable approach for studying the temporal characteristics of the physiological and biochemical responses to high levels of dietary cholesterol and provides insights into the mechanisms that may underlie fatty liver disease.

Identification of Senkyunolide I as a novel modulator of hepatic steatosis and PPARα signaling in zebrafish and hamster models

ETHNOPHARMACOLOGICAL RELEVANCE

Non-alcoholic fatty liver disease (NAFLD) is the leading cause of liver-related morbidity and mortality, with hepatic steatosis being the hallmark symptom. Salvia miltiorrhiza Bunge (Smil, Dan-Shen) and Ligusticum striatum DC (Lstr, Chuan-Xiong) are commonly used to treat cardiovascular diseases and have the potential to regulate lipid metabolism. However, whether Smil/Lstr combo can be used to treat NAFLD and the mechanisms underlying its lipid-regulating properties remain unclear.

PURPOSE

To assess the feasibility and reliability of a short-term high-fat diet (HFD) induced zebrafish model for evaluating hepatic steatosis phenotype and to investigate the liver lipid-lowering effects of Smil/Lstr, as well as its active components.

METHODS

The phenotypic alterations of liver and multiple other organ systems were examined in the HFD zebrafish model using fluorescence imaging and histochemistry. The liver-specific lipid-lowering effects of Smil/Lstr combo were evaluated endogenously. The active molecules and functional mechanisms were further explored in zebrafish, human hepatocytes, and hamster models.

RESULTS

In 5-day HFD zebrafish, significant lipid accumulation was detected in the blood vessels and the liver, as evidenced by increased staining with Oil Red O and fluorescent lipid probes. Hepatic hypertrophy was observed in the model, along with macrovesicular steatosis. Smil/Lstr combo administration effectively restored the lipid profile and alleviated hepatic hypertrophy in the HFD zebrafish. In oleic-acid stimulated hepatocytes, Smil/Lstr combo markedly reduced lipid accumulation and cell damage. Subsequently, based on zebrafish phenotypic screening, the natural phthalide senkyunolide I (SEI) was identified as a major molecule mediating the lipid-lowering activities of Smil/Lstr combo in the liver. Moreover, SEI upregulated the expression of the lipid metabolism regulator PPARα and downregulated fatty acid translocase CD36, while a PPARα antagonist sufficiently blocked the regulatory effect of SEI on hepatic steatosis. Finally, the roles of SEI on hepatic lipid accumulation and PPARα signaling were further verified in the hamster model.

CONCLUSIONS

We proposed a zebrafish-based screening strategy for modulators of hepatic steatosis and discovered the regulatory roles of Smil/Lstr combo and its component SEI on liver lipid accumulation and PPARα signaling, suggesting their potential value as novel candidates for NAFLD treatment.

Comparison of the In Vivo Efficacy of Cuban (Raydel®) and Chinese (BOC Science) Policosanol in Alleviating Dyslipidemia and Inflammation via Safeguarding Major Organs and Reproductive Health in Hyperlipidemic Zebrafish: A Twelve-Week Consumption Study

Policosanol is a blend of long-chain aliphatic alcohols (LCAAs) and is well-known for several health-beneficial activities; however, the functionality of policosanol varied substantially based on the composition of LCAAs. In this study, two distinct policosanols, Raydel® (extracted from Cuban sugarcane wax) and BOC Sciences (extracted from Chinese sugarcane wax), were dietarily supplemented (0.1% w/w) for 12 weeks in hyperlipidemic zebrafish to examine their influence on the blood lipid profile and functionality of the liver, kidney, and reproductive organs. The results demonstrated a noteworthy impact of both policosanols on preventing high-cholesterol diet (HCD, 4% w/w)-induced dyslipidemia by decreasing total cholesterol (TC) and triglyceride (TG) levels in the plasma. However, compared to BOC Sciences, the Raydel® policosanol exhibited a significantly (p < 0.05) higher efficacy in reducing HCD-induced TC and TG levels. A substantial effect was observed exclusively with the Raydel® policosanol in mitigating HCD-impaired low-density-lipoprotein cholesterol (LDL-C) and high-density-lipoprotein cholesterol (HDL-C) levels. Hepatic histology and immunohistochemistry (IHC) analysis revealed the higher efficacy of Raydel® policosanol over BOC Sciences policosanol to prevent HCD-provoked fatty liver changes, cellular senescence, oxidative stress, and interleukin (IL)-6 production. Consistently, a significantly higher effect of Raydel® over BOC Sciences policosanol was observed on the protection of kidney, testis, and ovary morphology hampered by HCD consumption. In addition, Raydel® policosanol exhibited a notably stronger effect (~2-fold, p < 0.05) on the egg-laying ability of the zebrafish compared to policosanol from BOC Sciences. Furthermore, Raydel® policosanol plays a crucial role in improving embryo viability and mitigating developmental defects caused by the intake of an HCD. Conclusively, Raydel® policosanol displayed a substantially higher efficacy over BOC Sciences policosanol to revert HCD-induced dyslipidemia, the functionality of vital organs, and the reproductive health of zebrafish.

Deciphering the enigma of the function of alpha-tocopherol as a vitamin

α-Tocopherol (α-T) is a vitamin, but the reasons for the α-T requirement are controversial. Given that α-T deficiency was first identified in embryos, we studied to the premier model of vertebrate embryo development, the zebrafish embryo. We developed an α-T-deficient diet for zebrafish and used fish consuming this diet to produce α-T deficient (E-) embryos. We showed that α-T deficiency causes increased lipid peroxidation, leading to metabolic dysregulation that impacts both biochemical and morphological changes at very early stages in development. These changes occur at an early developmental window, which takes place prior to an analogous time to when a human knows she is pregnant. We found that α-T limits the chain reaction of lipid peroxidation and protects metabolic pathways and integrated gene expression networks that control embryonic development. Importantly, not only is α-T critical during early development, but the neurodevelopmental process is highly dependent on α-T trafficking by the α-T transfer protein (TTPa). Data from both gene expression and evaluation of the metabolome in E- embryos suggest that the activity of the mechanistic Target of Rapamycin (mTOR) signaling pathway is dysregulated-mTOR is a master regulatory mechanism, which controls both metabolism and neurodevelopment. Our findings suggest that TTPa is needed not only for regulation of plasma α-T in adults but is a key regulator during embryogenesis.

Directly Measuring Atherogenic Lipoprotein Kinetics in Zebrafish with the Photoconvertible LipoTimer Reporter

Lipoprotein kinetics are a crucial factor in understanding lipoprotein metabolism since a prolonged time in circulation can contribute to the atherogenic character of apolipoprotein-B (ApoB)-containing lipoproteins (B-lps). Here, we report a method to directly measure lipoprotein kinetics in live developing animals. We developed a zebrafish geneticly encoded reporter, LipoTimer, in which endogenous ApoBb.1 is fused to the photoconvertible fluorophore Dendra2 which shift its emission profile from green to red upon UV exposure. By quantifying the red population of ApoB-Dendra2 over time, we found that B-lp turnover in wild-type larvae becomes faster as development proceeds. Mutants with impaired B-lp uptake or lipolysis present with increased B-lp levels and half-life. In contrast, mutants with impaired B-lp triglyceride loading display slightly fewer and smaller-B-lps, which have a significantly shorter B-lp half-life. Further, we showed that chronic high-cholesterol feeding is associated with a longer B-lp half-life in wild-type juveniles but does not lead to changes in B-lp half-life in lipolysis deficient apoC2 mutants. These data support the hypothesis that B-lp lipolysis is suppressed by the flood of intestinal-derived B-lps that follow a high-fat meal.

Preclinical models of atherosclerosis: An overview

Atherosclerosis is a primary cause of illness and death globally and its mechanism is still unclear. Different animal models have been created to evaluate the progression of atherosclerosis, allowing researchers to carefully control the circumstances of the experiment as well as the nutrition and environmental risk factors. To investigate the negative effects of various interventions, pathophysiological alterations might be generated utilizing genetic or pharmacological methods. These models' molecular and pathophysiological mechanisms have been clarified through experiments, and they have served as platforms for the creation of new drugs. Different models can be employed to address various research problems, each with its own benefits and drawbacks. In the current review study, various species of atherosclerosis models are discussed, along with the viability of using them in experiments.

Consumption of Policosanol (Raydel®) Improves Hepatic, Renal, and Reproductive Functions in Zebrafish: In Vivo Comparison Study among Cuban, Chinese, and American Policosanol

The current study compared three policosanols from Cuba (sugarcane, Raydel®, policosanol (1), China (rice bran, Shaanxi, policosanol (2), and the USA (sugarcane, Lesstanol®, policosanol (3) in the treatment of dyslipidemia and protection of the liver, ovary, and testis in hypercholesterolemic zebrafish. After twelve weeks of supplementation of each policosanol (PCO, final 0.1% in diet, w/w) with a high cholesterol diet (HCD, final 4%, w/w), the Raydel policosanol (PCO1) group showed the highest survivability, approximately 89%. In contrast, Shaanxi policosanol (PCO2) and Lesstanol policosanol (PCO3) produced 73% and 87% survivability, respectively, while the HCD alone group showed 75% survivability. In the 12th week, the PCO1 group demonstrated the most modest increase in body weight along with significantly lower levels of total cholesterol (TC) and triglycerides (TG) in comparison to the HCD control group. Additionally, the PCO1 group exhibited the highest proportion of high-density lipoprotein (HDL)-cholesterol within TC. Notably, the PCO1 group displayed the lowest level of aspartate aminotransferase and alanine aminotransferase, minimal infiltration of inflammatory cells, reduced interleukin (IL)-6 production in the liver, a notable decline in reactive oxygen species (ROS) generation and mitigated fatty liver changes. HCD supplementation induced impairment of kidney morphology with the greatest extent of ROS production and apoptosis. On the other hand, the PCO 1 group showed a remarkably improved morphology with the least ROS generation and apoptosis. Within the ovarian context, the PCO1 group exhibited the most substantial presence of mature vitellogenic oocytes, accompanied by minimal levels of ROS and apoptosis. Similarly, in the testicular domain, the PCO1 group showcased optimal morphology for spermatogenesis, characterized by the least interstitial area and diminished production of ROS in testicular cells. At week 8, the PCO1 group showed the highest egg-laying ability, with around 244 eggs produced per mating. In contrast, the HCD alone, PCO2, and PCO3 groups showed significantly lower egg-laying ability (49, 59, and 86 eggs, respectively). The embryos from the PCO1 group exhibited the highest survivability with the fastest swimming ability and developmental speed. These results suggest that PCO1 consumption significantly enhanced the reproduction system, egg-laying ability, and embryo survivability. In conclusion, among the three policosanols, Cuban (Raydel®) policosanol had the strongest effect on survivability, improving dyslipidemia, liver protection, kidney, ovary, and testis with a restoration of the cell morphology, and the least ROS production and apoptosis-induced by HCD supplementation.

A high-cholesterol zebrafish diet promotes hypercholesterolemia and fasting-associated liver triglycerides accumulation

Zebrafish are an ideal model organism to study lipid metabolism and to elucidate the molecular underpinnings of human lipid-associated disorders. In this study, we provide an improved protocol to assay the impact of a high-cholesterol diet (HCD) on zebrafish lipid deposition and lipoprotein regulation. Fish fed HCD developed hypercholesterolemia as indicated by significantly elevated ApoB-containing lipoproteins (ApoB-LP) and increased plasma levels of cholesterol and cholesterol esters. Feeding of the HCD to larvae (8 days followed by a 1 day fast) and adult female fish (2 weeks, followed by 3 days of fasting) was also associated with a fatty liver phenotype that presented as severe hepatic steatosis. The HCD feeding paradigm doubled the levels of liver triacylglycerol (TG), which was striking because our HCD was only supplemented with cholesterol. The accumulated liver TG was unlikely due to increased de novo lipogenesis or inhibited β-oxidation since no differentially expressed genes in these pathways were found between the livers of fish fed the HCD versus control diets. However, fasted HCD fish had significantly increased lipogenesis gene fasn in adipose tissue and higher free fatty acids (FFA) in plasma. This suggested that elevated dietary cholesterol resulted in lipid accumulation in adipocytes, which supplied more FFA during fasting, promoting hepatic steatosis. In conclusion, our HCD zebrafish protocol represents an effective and reliable approach for studying the temporal characteristics of the physiological and biochemical responses to high levels of dietary cholesterol and provides insights into the mechanisms that may underlie fatty liver disease.

DHCR7 Expression Predicts Poor Outcomes and Mortality From Sepsis

This is a study of lipid metabolic gene expression patterns to discover precision medicine for sepsis.

OBJECTIVES

Sepsis patients experience poor outcomes including chronic critical illness (CCI) or early death (within 14 d). We investigated lipid metabolic gene expression differences by outcome to discover therapeutic targets.

DESIGN SETTING AND PARTICITPANTS

Secondary analysis of samples from prospectively enrolled sepsis patients (first 24 hr) and a zebrafish endotoxemia model for drug discovery. Patients were enrolled from the emergency department or ICU at an urban teaching hospital. Enrollment samples from sepsis patients were analyzed. Clinical data and cholesterol levels were recorded. Leukocytes were processed for RNA sequencing and reverse transcriptase polymerase chain reaction. A lipopolysaccharide zebrafish endotoxemia model was used for confirmation of human transcriptomic findings and drug discovery.

MAIN OUTCOMES AND MEASURES

The derivation cohort included 96 patients and controls (12 early death, 13 CCI, 51 rapid recovery, and 20 controls) and the validation cohort had 52 patients (6 early death, 8 CCI, and 38 rapid recovery).

RESULTS

The cholesterol metabolism gene 7-dehydrocholesterol reductase (DHCR7) was significantly up-regulated in both derivation and validation cohorts in poor outcome sepsis compared with rapid recovery patients and in 90-day nonsurvivors (validation only) and validated using RT-qPCR analysis. Our zebrafish sepsis model showed up-regulation of dhcr7 and several of the same lipid genes up-regulated in poor outcome human sepsis (dhcr24, sqlea, cyp51, msmo1, and ldlra) compared with controls. We then tested six lipid-based drugs in the zebrafish endotoxemia model. Of these, only the Dhcr7 inhibitor AY9944 completely rescued zebrafish from lipopolysaccharide death in a model with 100% lethality.

CONCLUSIONS

DHCR7, an important cholesterol metabolism gene, was up-regulated in poor outcome sepsis patients warranting external validation. This pathway may serve as a potential therapeutic target to improve sepsis outcomes.

Methylenetetrahydrofolate reductase deficiency and high-dose FA supplementation disrupt embryonic development of energy balance and metabolic homeostasis in zebrafish

Folic acid (synthetic folate, FA) is consumed in excess in North America and may interact with common pathogenic variants in methylenetetrahydrofolate reductase (MTHFR); the most prevalent inborn error of folate metabolism with wide-ranging obesity-related comorbidities. While preclinical murine models have been valuable to inform on diet-gene interactions, a recent Folate Expert panel has encouraged validation of new animal models. In this study, we characterized a novel zebrafish model of mthfr deficiency and evaluated the effects of genetic loss of mthfr function and FA supplementation during embryonic development on energy homeostasis and metabolism. mthfr-deficient zebrafish were generated using CRISPR mutagenesis and supplemented with no FA (control, 0FA) or 100 μm FA (100FA) throughout embryonic development (0-5 days postfertilization). We show that the genetic loss of mthfr function in zebrafish recapitulates key biochemical hallmarks reported in MTHFR deficiency in humans and leads to greater lipid accumulation and aberrant cholesterol metabolism as reported in the Mthfr murine model. In mthfr-deficient zebrafish, energy homeostasis was also impaired as indicated by altered food intake, reduced metabolic rate and lower expression of central energy-regulatory genes. Microglia abundance, involved in healthy neuronal development, was also reduced. FA supplementation to control zebrafish mimicked many of the adverse effects of mthfr deficiency, some of which were also exacerbated in mthfr-deficient zebrafish. Together, these findings support the translatability of the mthfr-deficient zebrafish as a preclinical model in folate research.

From worms to humans: Understanding intestinal lipid metabolism via model organisms

The intestine is responsible for efficient absorption and packaging of dietary lipids before they enter the circulatory system. This review provides a comprehensive overview of how intestinal enterocytes from diverse model organisms absorb dietary lipid and subsequently secrete the largest class of lipoproteins (chylomicrons) to meet the unique needs of each animal. We discuss the putative relationship between diet and metabolic disease progression, specifically Type 2 Diabetes Mellitus. Understanding the molecular response of intestinal cells to dietary lipid has the potential to undercover novel therapies to combat metabolic syndrome.

DHCR7 Expression Predicts Poor Outcomes and Mortality from Sepsis

Objective: Sepsis patients experience poor outcomes including chronic critical illness (CCI) or early death (within 14 days). We investigated lipid metabolic gene expression differences by outcome to discover therapeutic targets. Design: Secondary analysis of samples from prospectively enrolled sepsis patients and a zebrafish sepsis model for drug discovery. Setting: Emergency department or ICU at an urban teaching hospital. Patients: Sepsis patients presenting within 24 hours. Methods: Enrollment samples from sepsis patients were analyzed. Clinical data and cholesterol levels were recorded. Leukocytes were processed for RNA sequencing (RNA-seq) and reverse transcriptase polymerase chain reaction (RT-qPCR). A lipopolysaccharide (LPS) zebrafish sepsis model was used for confirmation of human transcriptomic findings and drug discovery. Measurements and Main Results: There were 96 samples in the derivation (76 sepsis, 20 controls) and 52 in the validation cohort (sepsis only). The cholesterol metabolism gene 7-Dehydrocholesterol Reductase ( DHCR7) was significantly upregulated in both derivation and validation cohorts in poor outcome sepsis compared to rapid recovery patients and in 90-day non-survivors (validation only) and validated using RT-qPCR analysis. Our zebrafish sepsis model showed upregulation of dhcr7 and several of the same lipid genes upregulated in poor outcome human sepsis (dhcr24, sqlea, cyp51, msmo1 , ldlra) compared to controls. We then tested six lipid-based drugs in the zebrafish sepsis model. Of these, only the Dhcr7 inhibitor AY9944 completely rescued zebrafish from LPS death in a model with 100% lethality. Conclusions: DHCR7, an important cholesterol metabolism gene, was upregulated in poor outcome sepsis patients warranting external validation. This pathway may serve as a potential therapeutic target to improve sepsis outcomes.

Establishment of a lipid metabolism disorder model in ApoEb mutant zebrafish

BACKGROUND AND AIMS

ApoEb is a zebrafish homologous to mammalian ApoE, whose deficiency would lead to lipid metabolism disorders (LMDs) like atherosclerosis. We attempted to knock out the zebrafish ApoEb, then establish a zebrafish model with LMD.

METHODS

ApoEb was knocked out using the CRISPR/Cas9 system, and the accumulation of lipids was confirmed by Oil Red O staining, confocal imaging, and lipid measurements. The lipid-lowering effects of simvastatin (SIM), ezetimibe (EZE) and Xuezhikang (XZK), an extract derived from red yeast rice, were evaluated through in vivo imaging in zebrafish larvae.

RESULTS

In the ApoEb mutant, significant vascular lipid deposition occurred, and lipid measurement performed in the whole-body homogenate of larvae and adult plasma showed significantly increased lipid levels. SIM, EZE and XZK apparently relieved hyperlipidemia in ApoEb mutants, and XZK had a significant inhibitory effect on the recruitment of neutrophils and macrophages.

CONCLUSIONS

In this study, an LMD model has been established in ApoEb mutant zebrafish. We suggest that this versatile model could be applied in studying hypercholesterolemia and related vascular pathology in the context of early atherosclerosis, as well as the physiological function of ApoE.

The metabolome of Mexican cavefish shows a convergent signature highlighting sugar, antioxidant, and Ageing-Related metabolites

Insights from organisms, which have evolved natural strategies for promoting survivability under extreme environmental pressures, may help guide future research into novel approaches for enhancing human longevity. The cave-adapted Mexican tetra, Astyanax mexicanus, has attracted interest as a model system for metabolic resilience, a term we use to denote the property of maintaining health and longevity under conditions that would be highly deleterious in other organisms (Figure 1). Cave-dwelling populations of Mexican tetra exhibit elevated blood glucose, insulin resistance and hypertrophic visceral adipocytes compared to surface-dwelling counterparts. However, cavefish appear to avoid pathologies typically associated with these conditions, such as accumulation of advanced-glycation-end-products (AGEs) and chronic tissue inflammation. The metabolic strategies underlying the resilience properties of A. mexicanus cavefish, and how they relate to environmental challenges of the cave environment, are poorly understood. Here, we provide an untargeted metabolomics study of long- and short-term fasting in two A. mexicanus cave populations and one surface population. We find that, although the metabolome of cavefish bears many similarities with pathological conditions such as metabolic syndrome, cavefish also exhibit features not commonly associated with a pathological condition, and in some cases considered indicative of an overall robust metabolic condition. These include a reduction in cholesteryl esters and intermediates of protein glycation, and an increase in antioxidants and metabolites associated with hypoxia and longevity. This work suggests that certain metabolic features associated with human pathologies are either not intrinsically harmful, or can be counteracted by reciprocal adaptations. We provide a transparent pipeline for reproducing our analysis and a Shiny app for other researchers to explore and visualize our dataset.

Zebrafish: A New Promise to Study the Impact of Metabolic Disorders on the Brain

Zebrafish has become a popular model to study many physiological and pathophysiological processes in humans. In recent years, it has rapidly emerged in the study of metabolic disorders, namely, obesity and diabetes, as the regulatory mechanisms and metabolic pathways of glucose and lipid homeostasis are highly conserved between fish and mammals. Zebrafish is also widely used in the field of neurosciences to study brain plasticity and regenerative mechanisms due to the high maintenance and activity of neural stem cells during adulthood. Recently, a large body of evidence has established that metabolic disorders can alter brain homeostasis, leading to neuro-inflammation and oxidative stress and causing decreased neurogenesis. To date, these pathological metabolic conditions are also risk factors for the development of cognitive dysfunctions and neurodegenerative diseases. In this review, we first aim to describe the main metabolic models established in zebrafish to demonstrate their similarities with their respective mammalian/human counterparts. Then, in the second part, we report the impact of metabolic disorders (obesity and diabetes) on brain homeostasis with a particular focus on the blood-brain barrier, neuro-inflammation, oxidative stress, cognitive functions and brain plasticity. Finally, we propose interesting signaling pathways and regulatory mechanisms to be explored in order to better understand how metabolic disorders can negatively impact neural stem cell activity.

The zebrafish model system for dyslipidemia and atherosclerosis research: Focus on environmental/exposome factors and genetic mechanisms

Dyslipidemias and atherosclerosis play a pivotal role in cardiovascular risk and disease. Although some pathophysiological mechanisms underlying these conditions have been unveiled, several knowledge gaps still remain. Experimental models, both in vitro and in vivo, have been instrumental to our better understanding of such complex processes. The latter have often been based on rodent species, either wild-type or, in several instances, genetically modified. In this context, the zebrafish may represent an additional very useful in vivo experimental model for dyslipidemia and atherosclerosis. Interestingly, the lipid metabolism of zebrafish shares several features with that present in humans, recapitulating some molecular features and pathophysiological aspects in a better way than that of rodents. The zebrafish model may be of help to address questions related to exposome factors as well as to genetic features, aiming to dissect selected aspects of the more complex scenario observed in humans. Indeed, exposome-related dyslipidemia/atherosclerosis research in zebrafish may target different scientific questions, related to nutrition, microbiota, temperature, light exposure at the larval stage, exposure to chemicals and epigenetic consequences of such external factors. Addressing genetic features related to dyslipidemia/atherosclerosis using the zebrafish model is already a reality and active research is now ongoing in this promising area. Novel technologies (gene and genome editing) may help to identify new candidate genes involved in dyslipidemia and dyslipidemia-related diseases. Based on these considerations, the zebrafish experimental model appears highly suitable for the study of exposome factors, genes and molecules involved in the development of atherosclerosis-related disease as well as for the validation of novel potential treatment options.

Expression and Function of ABC Proteins in Fish Intestine

In fish, the intestine is fundamental for digestion, nutrient absorption, and other functions like osmoregulation, acid-base balance, and excretion of some metabolic products. These functions require a large exchange surface area, which, in turn, favors the absorption of natural and anthropogenic foreign substances (xenobiotics) either dissolved in water or contained in the food. According to their chemical nature, nutrients, ions, and water may cross the intestine epithelium cells' apical and basolateral membranes by passive diffusion or through a wide array of transport proteins and also through endocytosis and exocytosis. In the same way, xenobiotics can cross this barrier by passive diffusion or taking advantage of proteins that transport physiological substrates. The entry of toxic substances is counterbalanced by an active efflux transport mediated by diverse membrane proteins, including the ATP binding cassette (ABC) proteins. Recent advances in structure, molecular properties, and functional studies have shed light on the importance of these proteins in cellular and organismal homeostasis. There is abundant literature on mammalian ABC proteins, while the studies on ABC functions in fish have mainly focused on the liver and, to a minor degree, on the kidney and other organs. Despite their critical importance in normal physiology and as a barrier to prevent xenobiotics incorporation, fish intestine's ABC transporters have received much less attention. All the ABC subfamilies are present in the fish intestine, although their functionality is still scarcely studied. For example, there are few studies of ABC-mediated transport made with polarized intestinal preparations. Thus, only a few works discriminate apical from basolateral transport activity. We briefly describe the main functions of each ABC subfamily reported for mammals and other fish organs to help understand their roles in the fish intestine. Our study considers immunohistochemical, histological, biochemical, molecular, physiological, and toxicological aspects of fish intestinal ABC proteins. We focus on the most extensively studied fish ABC proteins (subfamilies ABCB, ABCC, and ABCG), considering their apical or basolateral location and distribution along the intestine. We also discuss the implication of fish intestinal ABC proteins in the transport of physiological substrates and aquatic pollutants, such as pesticides, cyanotoxins, metals, hydrocarbons, and pharmaceutical products.

Expanding role of vitamin E in protection against metabolic dysregulation: Insights gained from model systems, especially the developing nervous system of zebrafish embryos

This review discusses why the embryo requires vitamin E (VitE) and shows that its lack causes metabolic dysregulation and impacts morphological changes at very early stages in development, which occur prior to when a woman knows she is pregnant. VitE halts the chain reactions of lipid peroxidation (LPO). Metabolomic analyses indicate that thiols become depleted in E- embryos because LPO generates products that require compensation using limited amino acids and methyl donors that are also developmentally relevant. Thus, VitE protects metabolic networks and the integrated gene expression networks that control development. VitE is critical especially for neurodevelopment, which is dependent on trafficking by the α-tocopherol transfer protein (TTPa). VitE-deficient (E-) zebrafish embryos initially appear normal, but by 12 and 24 h post-fertilization (hpf) E- embryos are developmentally abnormal with expression of pax2a and sox10 mis-localized in the midbrain-hindbrain boundary, neural crest cells and throughout the spinal neurons. These patterning defects indicate cells that are especially in need of VitE-protection. They precede obvious morphological abnormalities (cranial-facial malformation, pericardial edema, yolksac edema, skewed body-axis) and impaired behavioral responses to locomotor activity tests. The TTPA gene (ttpa) is expressed at the leading edges of the brain ventricle border. Ttpa knockdown using morpholinos is 100% lethal by 24 hpf, while E- embryo brains are often over- or under-inflated at 24 hpf. Further, E- embryos prior to 24 hpf have increased expression of genes involved in glycolysis and the pentose phosphate pathway, and decreased expression of genes involved in anabolic pathways and transcription. Combined data from both gene expression and the metabolome in E- embryos at 24 hpf suggest that the activity of the mechanistic Target of Rapamycin (mTOR) signaling pathway is decreased, which may impact both metabolism and neurodevelopment. Further evaluation of VitE deficiency in neurogenesis and its subsequent impact on learning and behavior is needed.

CD63+ and MHC Class I+ Subsets of Extracellular Vesicles Produced by Wild-Type and CD47-Deficient Jurkat T Cells Have Divergent Functional Effects on Endothelial Cell Gene Expression

T cells and endothelial cells engage in bidirectional communication that regulates angiogenesis and T cell transmigration. Extracellular vesicles (EVs) mediate intercellular communication by the transfer of bioactive molecules including RNAs. EVs produced by a given cell type are heterogeneous in their RNA content, but it is unclear how specific EV surface markers relate to their functional effects on target cells. Our previous work established that Jurkat T cell EVs bearing CD63, MHC-I, or CD47 surface markers contain distinct noncoding RNA populations. The present study reveals that CD63+ and MHC-I+ EVs from CD47-deficient Jurkat T cells are enriched in small non-coding RNAs relative to EVs from wild-type Jurkat T cells. CD47-deficient Jurkat T cells secrete more CD63+ and MHC-I+ EVs, but MHC-I+ EVs are selectively taken up more by human umbilical vein endothelial cells. Transcriptomics analysis of endothelial cells treated with CD63+ or MHC-I+ EVs showed surface marker- and CD47-dependent changes in gene expression in the target cells. Gene set enrichment analysis identified CD47-dependent, and surface marker-dependent effects of T cell EVs on VEGF and inflammatory signaling, cell cycle, and lipid and cholesterol metabolism. Thus, subsets of T cell EVs differentially regulate endothelial cell metabolism and inflammatory and angiogenic responses.

Glucose inhibits haemostasis and accelerates diet-induced hyperlipidaemia in zebrafish larvae

Hyperglycaemia damages the microvasculature in part through the reduced recruitment of immune cells and interference with platelet signalling, leading to poor wound healing and accelerated lipid deposition in mammals. We investigated the utility of zebrafish larvae to model the effect of exogenous glucose on neutrophil and macrophage recruitment to a tail wound, wound-induced haemostasis, and chicken egg yolk feed challenge-induced hyperlipidaemia by supplementing larvae with exogenous glucose by immersion or injection. Neither method of glucose supplementation affected the recruitment of neutrophils and macrophages following tail transection. Glucose injection reduced thrombocyte retention and fibrin plug formation while only thrombocyte retention was reduced by glucose immersion following tail transection. We observed accelerated lipid accumulation in glucose-injected larvae challenged with high fat chicken egg yolk feeding. Our study identifies conserved and divergent effects of high glucose on inflammation, haemostasis, and hyperlipidaemia in zebrafish larvae compared to mammals.

Embryonic exposure to low concentrations of aflatoxin B1 triggers global transcriptomic changes, defective yolk lipid mobilization, abnormal gastrointestinal tract development and inflammation in zebrafish

Aflatoxin B1-contaminated feeds and foods induce various health problems in domesticated animals and humans, including tumor development and hepatotoxicity. Aflatoxin B1 also has embryotoxic effects in different livestock species and humans. However, it is difficult to distinguish between the indirect, maternally-mediated toxic effects and the direct embryotoxicity of aflatoxin B1 in mammals. In the present study, we investigated the aflatoxin B1-induced direct embryotoxic effects in a zebrafish embryo model system combining toxicological, transcriptomic, immunological, and biochemical approaches. Embryonic exposure to aflatoxin B1 induced significant changes at the transcriptome level resulting in elevated expression of inflammatory gene network and repression of lipid metabolism and gastrointestinal tract development-related gene sets. According to the gene expression changes, massive neutrophil granulocyte influx, elevated nitric oxide production, and yolk lipid accumulation were observed in the abdominal region of aflatoxin B1-exposed larvae. In parallel, aflatoxin B1-induced defective gastrointestinal tract development and reduced L-arginine level were found in our model system. Our results revealed the complex direct embryotoxic effects of aflatoxin B1, including inhibited lipid utilization, defective intestinal development, and inflammation.

Zebrafish mutants provide insights into Apolipoprotein B functions during embryonic development and pathological conditions

Apolipoprotein B (ApoB) is the primary protein of chylomicrons, VLDLs, and LDLs and is essential for their production. Defects in ApoB synthesis and secretion result in several human diseases, including abetalipoproteinemia and familial hypobetalipoproteinemia (FHBL1). In addition, ApoB-related dyslipidemia is linked to nonalcoholic fatty liver disease (NAFLD), a silent pandemic affecting billions globally. Due to the crucial role of APOB in supplying nutrients to the developing embryo, ApoB deletion in mammals is embryonic lethal. Thus, a clear understanding of the roles of this protein during development is lacking. Here, we established zebrafish mutants for 2 apoB genes: apoBa and apoBb.1. Double-mutant embryos displayed hepatic steatosis, a common hallmark of FHBL1 and NAFLD, as well as abnormal liver laterality, decreased numbers of goblet cells in the gut, and impaired angiogenesis. We further used these mutants to identify the domains within ApoB responsible for its functions. By assessing the ability of different truncated forms of human APOB to rescue the mutant phenotypes, we demonstrate the benefits of this model for prospective therapeutic screens. Overall, these zebrafish models uncover what are likely previously undescribed functions of ApoB in organ development and morphogenesis and shed light on the mechanisms underlying hypolipidemia-related diseases.

HDL biodistribution and brain receptors in zebrafish, using HDLs as vectors for targeting endothelial cells and neural progenitors

High density lipoproteins (HDLs) display pleiotropic functions such as anti-inflammatory, antioxidant, anti-protease, and anti-apoptotic properties. These effects are mediated by four main receptors: SCARB1 (SR-BI), ABCA1, ABCG1, and CD36. Recently, HDLs have emerged for their potential involvement in brain functions, considering their epidemiological links with cognition, depression, and brain plasticity. However, their role in the brain is not well understood. Given that the zebrafish is a well-recognized model for studying brain plasticity, metabolic disorders, and apolipoproteins, it could represent a good model for investigating the role of HDLs in brain homeostasis. By analyzing RNA sequencing data sets and performing in situ hybridization, we demonstrated the wide expression of scarb1, abca1a, abca1b, abcg1, and cd36 in the brain of adult zebrafish. Scarb1 gene expression was detected in neural stem cells (NSCs), suggesting a possible role of HDLs in NSC activity. Accordingly, intracerebroventricular injection of HDLs leads to their uptake by NSCs without modulating their proliferation. Next, we studied the biodistribution of HDLs in the zebrafish body. In homeostatic conditions, intraperitoneal injection of HDLs led to their accumulation in the liver, kidneys, and cerebral endothelial cells in zebrafish, similar to that observed in mice. After telencephalic injury, HDLs were diffused within the damaged parenchyma and were taken up by ventricular cells, including NSCs. However, they failed to modulate the recruitment of microglia cells at the injury site and the injury-induced proliferation of NSCs. In conclusion, our results clearly show a functional HDL uptake process involving several receptors that may impact brain homeostasis and suggest the use of HDLs as delivery vectors to target NSCs for drug delivery to boost their neurogenic activity.

Recent Application of Zebrafish Models in Atherosclerosis Research

Atherosclerotic cardiovascular disease is one of the leading causes of death worldwide. Establishing animal models of atherosclerosis is of great benefit for studying its complicated pathogenesis and screening and evaluating related drugs. Although researchers have generated a variety of models for atherosclerosis study in rabbits, mice and rats, the limitations of these models make it difficult to monitor the development of atherosclerosis, and these models are unsuitable for large scale screening of potential therapeutic targets. On the contrast, zebrafish can fulfill these purposes thanks to their fecundity, rapid development ex utero, embryonic transparency, and conserved lipid metabolism process. Thus, zebrafish have become a popular alternative animal model for atherosclerosis research. In this mini review, we summarize different zebrafish models used to study atherosclerosis, focusing on the latest applications of these models to the dynamic monitoring of atherosclerosis progression, mechanistic study of therapeutic intervention and drug screening, and assessment of the impacts of other risk factors.

Zebrafish as an Emerging Model for Dyslipidemia and Associated Diseases

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.

Comparison of transcriptomic changes between zebrafish and mice upon high fat diet reveals evolutionary convergence in lipid metabolism

Hyperlipidemia is an abnormal elevation of lipid level in blood, which affects more than 100 million people in US. Zebrafish has recently emerged as a model to study pathophysiology associated with hyperlipidemia. As a poikilotherm, the innate response toward a high fat diet regimen in zebrafish is likely to be distinct from humans, and therefore, additional caution is warranted to appropriately interpret results obtained from zebrafish model. However, to date, detailed comparative analyses on similarities and dissimilarities between zebrafish and mammals, in particular, at molecular level, have not been reported yet. Here, we identified changes in hepatic specific transcriptomic profiles of zebrafish fed with a high fat diet regimen and comparatively analyzed transcriptomic changes in zebrafish and mice. While a number of previously identified risk factors for human hyperlipidemia has been upregulated in zebrafish fed with a high fat diet regimen, zebrafish hepatic transcriptome does not share high similarity with mice. Despite these differences, KEGG pathway analyses revealed that similar signaling pathways upregulated in zebrafish and mice as a response to a high fat diet. Our data show that these two species may utilize species-specific set of genes to upregulate common signaling pathways, indicating evolutionary convergence between poikilotherm and homeotherm in regulating lipid metabolism and validating the use of zebrafish as a model for human hyperlipidemia and associated diseases.

Studies in Zebrafish Demonstrate That CNNM2 and NT5C2 Are Most Likely the Causal Genes at the Blood Pressure-Associated Locus on Human Chromosome 10q24.32

Background: Globally, high blood pressure (BP) is the most important risk factor for cardiovascular disease. Several genome-wide association studies (GWAS) have identified variants associated with BP traits at more than 535 chromosomal loci with genome-wide significance. The post-GWAS challenge is to annotate the most likely causal gene(s) at each locus. Chromosome 10q24.32 is a locus associated with BP that encompasses five genes: CYP17A1, BORCS7, AS3MT, CNNM2, and NT5C2 and warrants investigation to determine the specific gene or genes responsible for the phenotype. Aim: To identify the most likely causal gene(s) associated with BP at the 10q24.32 locus using zebrafish as an animal model. Results: We report significantly higher blood flow, increased arterial pulse, and elevated linear velocity in zebrafish larvae with cnnm2 and nt5c2 knocked down using gene-specific splice modification transcriptional morpholinos, compared with controls. No differences in blood-flow parameters were observed after as3mt, borcs7, or cyp17a1 knockdown. There was no effect on vessel diameter in animals with any of the four genes knocked down. At the molecular level, expression of hypertension markers (crp and ace) was significantly increased in cnnm2 and nt5c2 knockdown larvae. Further, the results obtained by morpholino knockdown were validated using zebrafish knockout (KO) lines with cnnm2 and nt5c2 deficiency, again resulting in higher blood flow, increased arterial pulse, and elevated linear velocity. Analysis of nt5c2a KO larvae demonstrated that lack of this gene resulted in reduced expression of cnnm2a, with reciprocal downregulation of nt5c2a in cnnm2a KO larvae. Staining of whole-blood smears from nt5c2 mutants revealed that KO of this gene might be associated with an acute lymphoblastic leukemia phenotype, consistent with literature reports. Additional experiments were designed based on previous literature on cnnm2a mutant zebrafish revealed impaired renal function, high levels of renin, and significantly increased expression of the ren gene, leading us to hypothesize that the observed elevated blood-flow parameters may be attributable to triggering of the renin-angiotensin-aldosterone signaling pathway. Conclusion: Our zebrafish data establish CNNM2 and NT5C2 as the most likely causal genes at the 10q24.32 BP locus and indicate that they trigger separate downstream mechanistic pathways.

A Great Catch for Investigating Inborn Errors of Metabolism-Insights Obtained from Zebrafish

Inborn errors of metabolism cause abnormal synthesis, recycling, or breakdown of amino acids, neurotransmitters, and other various metabolites. This aberrant homeostasis commonly causes the accumulation of toxic compounds or depletion of vital metabolites, which has detrimental consequences for the patients. Efficient and rapid intervention is often key to survival. Therefore, it requires useful animal models to understand the pathomechanisms and identify promising therapeutic drug targets. Zebrafish are an effective tool to investigate developmental mechanisms and understanding the pathophysiology of disorders. In the past decades, zebrafish have proven their efficiency for studying genetic disorders owing to the high degree of conservation between human and zebrafish genes. Subsequently, several rare inherited metabolic disorders have been successfully investigated in zebrafish revealing underlying mechanisms and identifying novel therapeutic targets, including methylmalonic acidemia, Gaucher’s disease, maple urine disorder, hyperammonemia, TRAPPC11-CDGs, and others. This review summarizes the recent impact zebrafish have made in the field of inborn errors of metabolism.

Dare to Compare. Development of Atherosclerotic Lesions in Human, Mouse, and Zebrafish

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.

Vascular Damage in Obesity and Diabetes: Highlighting Links Between Endothelial Dysfunction and Metabolic Disease in Zebrafish and Man

Endothelial dysfunction is an initial pathophysiological mechanism of vascular damage and is further recognized as an independent predictor of negative prognosis in diabetes-induced micro- and macrovascular complications. Insight into the capability of zebrafish to model metabolic disease like obesity and type II diabetes has increased and new evidence on the induction of vascular pathologies in zebrafish through metabolic disease is available. Here, we raise the question, if zebrafish can be utilized to study the initial impairments of vascular complications in metabolic disorders. In this review, we focus on the advances made to develop models of obesity and type II diabetes in zebrafish, discuss the key points and characteristics of these models, while highlighting the available information linked to the development of endothelial dysfunction in zebrafish and man. We show that larval and adult zebrafish develop metabolic dysregulation in the settings of obesity and diabetes, exhibiting pathophysiological mechanisms, which mimic the human condition. The most important genes related to endothelial dysfunction are present in zebrafish and further display similar functions as in mammals. Several suggested contributors to endothelial dysfunction found in these models, namely hyperinsulinaemia, hyperglycaemia, hyperlipidaemia and hyperleptinaemia are highlighted and the available data from zebrafish are summarised. Many underlying processes of endothelial dysfunction in obesity and diabetes are fundamentally present in zebrafish and provide ground for the assumption, that zebrafish can develop endothelial dysfunction. Conservation of basic biological mechanisms is established for zebrafish, but focused investigation on the subject is now needed as validation and particularly more research is necessary to understand the differences between zebrafish and man. The available data demonstrate the relevance of zebrafish as a model for metabolic disease and their ability to become a proponent for the investigation of vascular damage in the settings of obesity and diabetes.

A Simple and Rapid Method to Measure Food Intake in Fish Using Brine Shrimp

Food intake is a critical parameter in studies of energy balance, obesity, and metabolic disease, but previous methods to measure food intake in model fish species such as zebrafish (Danio rerio) have been labor intensive or indirect. In this study, we describe a simple and rapid method to measure food intake using freshly hatched brine shrimps as food source, followed by rapid collection using filtration of system water and quantification of collected shrimps using a photometric assay to measure extracted shrimp carotenoid content.

Comorbidities of HIV infection: role of Nef-induced impairment of cholesterol metabolism and lipid raft functionality

Combination antiretroviral therapy has dramatically changed the outcome of HIV infection, turning it from a death sentence to a manageable chronic disease. However, comorbidities accompanying HIV infection, such as metabolic and cardio-vascular diseases, as well as cognitive impairment, persist despite successful virus control by combination antiretroviral therapy and pose considerable challenges to clinical management of people living with HIV. These comorbidities involve a number of pathological processes affecting a variety of different tissues and cells, making it challenging to identify a common cause(s) that would link these different diseases to HIV infection. In this article, we will present evidence that impairment of cellular cholesterol metabolism may be a common factor driving pathogenesis of HIV-associated comorbidities. Potential implications for therapeutic approaches are discussed.

Screening of angiogenesis inhibitors using a 3D vascular microfluidic chip to achieve contraception

Angiogenesis plays a vital role in the process of embryo implantation, as it improves endometrial receptivity and guides embryo implantation, thus creating a favorable environment for subsequent development of the embryo. Hence, a theory of achieving contraception by inhibiting angiogenesis was put forward. Here, we screened the drugs inhibiting angiogenesis using cell scratch wound assay and a 3D biomimetic vascular microfluidic chip, then observed the effect of them on contraception by injecting these drugs into fertilized mice and observing if the embryos were implanted. We preliminarily verify the feasibility of contraception by inhibiting angiogenesis and gives a new direction in the development of contraceptive pills.

Dysfunctional high density lipoprotein failed to rescue the function of oxidized low density lipoprotein-treated endothelial progenitor cells: a novel index for the prediction of HDL functionality

Lipid metabolic disorders play critical roles in atherogenesis. Traditionally, it has been suggested that reduced high density lipoprotein (HDL) levels might be an important morbidity indicator for cardiovascular diseases. Therefore, it has been argued that therapeutically raising HDL levels may reduce atherogenesis in patients with dyslipidemia. However, recent clinical trials to elevate serum HDL levels by pharmacologic approaches failed to demonstrate clinical efficacy. Thus, to investigate the functionality of HDL and to explore the possible clinical relevance as well as to define an effective indicator that can represent HDL function may provide another key and reference to disclose the clinical treatment of dyslipidemia. We analyzed the association between the data of dichlorofluorescein assay (assay the functionality of HDL), the effect of HDL on oxidized low density lipoprotein (oxLDL)-stimulated endothelial progenitor cells (EPCs) in vitro, levels of circulating EPCs, and ex vitro EPC colony forming units of each case, we defined the indicator (relative HDL index (RHDL index) = dichlorofluorescein assay result of each subject/dichlorofluorescein assay reading of our young healthy controls) that may represent functionality of HDL. HDL from healthy adults protected oxLDL-treated EPCs by modulating p38 mitogen-activated protein kinase and Rho activation and by promoting nitric oxide production. HDL from subject with RHDL index ≧2 also failed to restore the functionality of oxLDL-treated EPCs via cell-signaling pathways in vitro. The RHDL index significantly correlated with patients' circulating EPC number or EPC colony forming units ex vivo. In conclusions, we explored the RHDL index as a score to predict a patient's EPC functions in vivo and ex vitro.

Agaricus bisporus-derived β-glucan prevents obesity through PPAR γ downregulation and autophagy induction in zebrafish fed by chicken egg yolk

β-(1,4)-d-Glucan with (1,2) and (1,6)-linked branches (short for β-glucan), extracted from Agaricus bisporus (Lange) Sing, had significant anti-obesity and lowering-fat effect. FITC-β-glucan was absorbed by adipocytes of zebrafish larvae when stained by Nile Red. β-Glucan decreased the adiposity mass, reduced the expression of ppar g, mtp, L-fabp, ifabp in ISH, which was coincident as the results of RT-PCT. β-Glucan lowered the level of C/EBP α, c SREBP1, LXR α, PPAR γ by WB analysis, which were accompanied by an increase level in LC3 II/LC3 I and a decline level in p62 in dose-dependent manner. This study explored the effect and mechanisms of Agaricus bisporus derived-β-glucan to regulate lipid metabolism and prevent lipid deposits, and provided the experimental data for its use in diet food and food addictive.

Novel Anti-Obesity Properties of Palmaria mollis in Zebrafish and Mouse Models

(1) Background: The red seaweed Palmaria mollis (PM), which has a bacon-like taste, is increasingly being included in Western diets. In this study, we evaluate anti-obesity effects of PM using diet-induced obese (DIO) zebrafish and mice models. (2) Methods: We fed PM-containing feed to DIO-zebrafish and mice, and evaluated the anti-obesity effects We also analyzed gene expression changes in their liver and visceral adipose tissues (VAT). (3) Results: PM ameliorated several anti-obesity traits in both animals, including dyslipidaemia, hepatic steatosis, and visceral adiposity. In liver tissues of DIO-zebrafish and mice, PM upregulated gene expressions involved in peroxisome proliferator-activated receptor alpha (PPARA) pathways, and downregulated peroxisome proliferator-activated receptor gamma (PPARG) pathways, suggesting that the lipid-lowering effect of PM might be caused by activation of beta-oxidation and inhibition of lipogenesis. In VAT, PM downregulated genes involved in early and late adipocyte differentiation in zebrafish, but not in mice. (4) Conclusions: We have demonstrated that PM can prevent hepatic steatosis and visceral adiposity for the first time. Dietary supplementation of PM as a functional food may be suitable for obesity prevention and reduction in the prevalence of obesity-related diseases.

NAD(P)HX repair deficiency causes central metabolic perturbations in yeast and human cells

NADHX and NADPHX are hydrated and redox inactive forms of the NADH and NADPH cofactors, known to inhibit several dehydrogenases in vitro. A metabolite repair system that is conserved in all domains of life and that comprises the two enzymes NAD(P)HX dehydratase and NAD(P)HX epimerase, allows reconversion of both the S- and R-epimers of NADHX and NADPHX to the normal cofactors. An inherited deficiency in this system has recently been shown to cause severe neurometabolic disease in children. Although evidence for the presence of NAD(P)HX has been obtained in plant and human cells, little is known about the mechanism of formation of these derivatives in vivo and their potential effects on cell metabolism. Here, we show that NAD(P)HX dehydratase deficiency in yeast leads to an important, temperature-dependent NADHX accumulation in quiescent cells with a concomitant depletion of intracellular NAD⁺ and serine pools. We demonstrate that NADHX potently inhibits the first step of the serine synthesis pathway in yeast. Human cells deficient in the NAD(P)HX dehydratase also accumulated NADHX and showed decreased viability. In addition, those cells consumed more glucose and produced more lactate, potentially indicating impaired mitochondrial function. Our results provide first insights into how NADHX accumulation affects cellular functions and pave the way for a better understanding of the mechanism(s) underlying the rapid and severe neurodegeneration leading to early death in NADHX repair-deficient children.

Genetics of Cardiovascular Disease: Fishing for Causality

Cardiovascular disease (CVD) is still the leading cause of death in all western world countries and genetic predisposition in combination with traditional risk factors frequently mediates their manifestation. Genome-wide association (GWA) studies revealed numerous potentially disease modifying genetic loci often including several SNPs and associated genes. However, pure genetic association does not prove direct or indirect relevance of the modifier region on pathogenesis, nor does it define within the associated region the exact genetic driver of the disease. Therefore, the relevance of the identified genetic disease associations needs to be confirmed either in monogenic traits or in experimental in vivo model system by functional genomic studies. In this review, we focus on the use of functional genomic approaches such as gene knock-down or CRISPR/Cas9-mediated genome editing in the zebrafish model to validate disease-associated genomic loci and to identify novel cardiovascular disease genes. We summarize the benefits of the zebrafish for cardiovascular research and highlight examples demonstrating the successful combination of GWA studies and functional genomics in zebrafish to broaden our knowledge on the genetic and molecular underpinnings of cardiovascular diseases.

Bisphenol S induces obesogenic effects through deregulating lipid metabolism in zebrafish (Danio rerio) larvae

It has been suggested that dramatic increase in obesity may be caused by growing exposure to environmental chemicals. In vitro data has suggested bisphenol S (BPS), a compound widely used in polycarbonate plastic production, can induce lipid accumulation in preadipocytes. However, the mechanisms responsible for BPS-induced obesity in vivo remain unclear. In this study, we used translucent zebrafish (Danio rerio) larvae as a model to investigate the effect of environmentally relevant BPS exposure (1, 10, and 100 μg/L from 2 h to 15 d post fertilization) on lipid accumulation, triacylglycerol (TAG) and lipoproteins content, and mRNA expression of genes involved in the regulation of lipid synthesis, transport, degradation, and storage. We also analyzed activities of two enzymes critical to TAG metabolism: lipoprotein lipase and diglyceride acyltransferase. Overfed, obese larvae were used as positive control. The results indicated that BPS-treated and overfed larvae had much higher TAG levels and visceral fat accumulation compared with control. BPS exhibited obesogenic effects by interfering with lipid metabolism as evidenced by (a) upregulation of the mRNA expression of fasn, acc1, and agpat4 genes encoding enzymes involved in the de novo synthesis of TAG in the liver, (b) downregulation of apolipoprotein expression, which should reduce TAG transport from the liver, and (c) increase in rxrα expression, which should promote visceral fat accumulation. Our study is the first to demonstrate that the obesogenic effects of BPS in zebrafish are related to the disruption of TAG metabolism.

Lipoprotein lipase regulates hematopoietic stem progenitor cell maintenance through DHA supply

Lipoprotein lipase (LPL) mediates hydrolysis of triglycerides (TGs) to supply free fatty acids (FFAs) to tissues. Here, we show that LPL activity is also required for hematopoietic stem progenitor cell (HSPC) maintenance. Knockout of Lpl or its obligatory cofactor Apoc2 results in significantly reduced HSPC expansion during definitive hematopoiesis in zebrafish. A human APOC2 mimetic peptide or the human very low-density lipoprotein, which carries APOC2, rescues the phenotype in apoc2 but not in lpl mutant zebrafish. Creating parabiotic apoc2 and lpl mutant zebrafish rescues the hematopoietic defect in both. Docosahexaenoic acid (DHA) is identified as an important factor in HSPC expansion. FFA-DHA, but not TG-DHA, rescues the HSPC defects in apoc2 and lpl mutant zebrafish. Reduced blood cell counts are also observed in Apoc2 mutant mice at the time of weaning. These results indicate that LPL-mediated release of the essential fatty acid DHA regulates HSPC expansion and definitive hematopoiesis.

Steroid Transport, Local Synthesis, and Signaling within the Brain: Roles in Neurogenesis, Neuroprotection, and Sexual Behaviors

Sex steroid hormones are synthesized from cholesterol and exert pleiotropic effects notably in the central nervous system. Pioneering studies from Baulieu and colleagues have suggested that steroids are also locally-synthesized in the brain. Such steroids, called neurosteroids, can rapidly modulate neuronal excitability and functions, brain plasticity, and behavior. Accumulating data obtained on a wide variety of species demonstrate that neurosteroidogenesis is an evolutionary conserved feature across fish, birds, and mammals. In this review, we will first document neurosteroidogenesis and steroid signaling for estrogens, progestagens, and androgens in the brain of teleost fish, birds, and mammals. We will next consider the effects of sex steroids in homeostatic and regenerative neurogenesis, in neuroprotection, and in sexual behaviors. In a last part, we will discuss the transport of steroids and lipoproteins from the periphery within the brain (and vice-versa) and document their effects on the blood-brain barrier (BBB) permeability and on neuroprotection. We will emphasize the potential interaction between lipoproteins and sex steroids, addressing the beneficial effects of steroids and lipoproteins, particularly HDL-cholesterol, against the breakdown of the BBB reported to occur during brain ischemic stroke. We will consequently highlight the potential anti-inflammatory, anti-oxidant, and neuroprotective properties of sex steroid and lipoproteins, these latest improving cholesterol and steroid ester transport within the brain after insults.

Anti-hypercholesterolemic Effect of Berbamine Isolated from Rhizoma Coptidis in Hypercholesterolemic Zebrafish Induced by High-Cholesterol Diet

The anti-hypercholesterolemic effect of berbamine (BBM) isolated from Rhizoma Coptidis (RC) was investigated in hypercholesterolemic zebrafish model induced by high-cholesterol (HC) diet. Zebrafish embryo assay revealed no significant difference in morphology and cell death with the treatment of BBM less than 20 μg/mL. In zebrafish larvae, the fluorescently labeled cholesterol in caudal artery was reduced dose-dependently after BBM treatment. For adult zebrafish, administration of 0.2% BBM exhibited a significant decrease in plasma total cholesterol (TC), triglyceride (TG) and low-density lipoprotein cholesterol (LDL-c) levels by 37%, 38% and 28%, respectively, along with a fall in lipid content in liver. Further investigation suggested that the mRNA expression of 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR) and microsomal triglyceride transfer protein (MTP) in liver were down-regulated and the transcription levels of liver gene low-density lipoprotein receptor (LDLR) and cytochrome P450 polypeptide 1a of subfamily A of family 7 (CYP7A1a) were significantly up-regulated with BBM treatment. Histological study showed that BBM can alleviate hepatic steatosis induced by HC diet. These data suggested that BBM has anti-hypercholesterolemic and hepatoprotective effects. The mechanism probably related to the up-regulation of cholesterol transport and bile acid synthesis as well as inhibition of cholesterol synthesis and lipoprotein assembly or secretion.

Role of lipids and intraplaque hypoxia in the formation of neovascularization in atherosclerosis

According to the current paradigm, chronic vascular inflammation plays a central role in the pathogenesis of atherosclerosis. The plaque progression is typically completed with rupture and subsequent acute cardiovascular complications. Previously, the role of adventitial vasa vasorum in atherogenesis was underestimated. However, investigators then revealed that vasa vasorum neovascularization can be observed when no clinical manifestation of atherosclerosis is present. Vasa vasorum is involved in various proatherogenic processes such as intimal accumulation of inflammatory leukocytes, intimal thickening, necrotic core formation, intraplaque haemorrhage, lesion rupture and atherothrombosis. Due to the destabilizing action of the intraplaque microenvironment, lesional vasa vasorum neovessels experience serious defects and abnormalities during development that leads to their immaturity, fragility and leakage. Indeed, intraplaque neovessels are a main cause of intraplaque haemorrhage. Visualization techniques showed that presence of neovascularization/haemorrhage can serve as a good indicator of lesion instability and higher risk of rupture. Vasa vasorum density is a strong predictor of acute cardiovascular events such as sudden death, myocardial infarction and stroke. At present, arterial vasa vasorum neovascularization is under intensive investigation along with development of therapeutic tools focused on the control of formation of vasa vasorum neovessels in order to prevent plaque haemorrhage/rupture and thromboembolism. KEY MESSAGE Neovascularization plays an important role in atherosclerosis, being involved in unstable plaque formation. Presence of neovascularization and haemorrhage indicates plaque instability and risk of rupture. Various imaging techniques are available to study neovascularization.

Modeling hypercholesterolemia and vascular lipid accumulation in LDL receptor mutant zebrafish

Elevated plasma LDL cholesterol is the dominant risk factor for the development of atherosclerosis and cardiovascular disease. Deficiency in the LDL receptor (LDLR) is a major cause of familial hypercholesterolemia in humans, and the LDLR knockout mouse is a major animal model of atherosclerosis. Here we report the generation and characterization of an ldlr mutant zebrafish as a new animal model to study hypercholesterolemia and vascular lipid accumulation, an early event in the development of human atherosclerosis. The ldlr mutant zebrafish were characterized by activated SREBP-2 pathway and developed moderate hypercholesterolemia when fed a normal diet. However, a short-term, 5-day feeding of ldlr mutant larvae with a high-cholesterol diet (HCD) resulted in exacerbated hypercholesterolemia and accumulation of vascular lipid deposits. Lomitapide, an inhibitor of apoB lipoprotein secretion, but not the antioxidant probucol, significantly reduced accumulation of vascular lipid deposits in HCD-fed ldlr mutant larvae. Furthermore, ldlr mutants were defective in hepatic clearance of lipopolysaccharides, resulting in reduced survival. Taken together, our data suggest that the ldlr knockout zebra-fish is a versatile model for studying the function of the LDL receptor, hypercholesterolemia, and related vascular pathology in the context of early atherosclerosis.