Neutral Lipid Accumulation Research Articles

Delayed First Feeding Chronically Impairs Larval Fish Growth Performance, Hepatic Lipid Metabolism, and Visceral Lipid Deposition at the Mouth-Opening Stage.

During the mouth-opening stage, fish larvae are susceptible to delayed first feeding (DFF). In this study, we explored the effects of DFF for two days on later growth and energy metabolism in larval fish. Results showed that DFF chronically impaired larval growth performance, thereby reducing the efficiency of feed utilization by larvae. In DFF larvae, the mRNA levels of growth inhibitors (i.e., igfbp1a and igfbp1b) were significantly upregulated and consistently maintained at high expression levels, which may be an important attribution of larval growth retardation. Concomitantly, DFF retarded the growth of adipose tissue and reduced lipid deposition in larval viscera, suggesting lipid metabolism is disordered in DFF larvae and generates inefficient lipid reserves. In the liver, we observed that DFF resulted in a significant accumulation of neutral lipids, and this phenotype did not disappear rapidly after DFF larvae received exogenous nutrition. As to the transcript analyses, we found that the expression of genes related to hepatic lipid synthesis (e.g., srebf1, srebf2, dgat1a, dgat1b, fasn, and scdb) in DFF larvae was consistently upregulated, while the expression of genes involved in lipid transport (e.g., apoa2, apoa4b.1, and apoa4b.3) was downregulated. Therefore, it appears that the inefficient lipid reserves in DFF larvae are associated with their hepatic lipid transport dysfunction. Taken together, our findings contribute to understanding the impairments to fish larvae caused by delayed first feeding during the mouth-opening stage and to aiding larval management in the aquaculture industry.

A Zebrafish Model of Dnajc21 Deficiency Identifies Essential Roles in Granulocyte Differentiation and Metabolic Regulation

Shwachman-Diamond syndrome (SDS) is a rare inherited bone marrow failure syndrome (IBMFS) characterized by neutropenia and exocrine pancreatic insufficiency. It is caused by mutations in genes required for ribosome subunit maturation such as SBDS, DNAJC21 and EFL1. The cumulative risk of developing myelodysplastic syndrome and/or acute myeloid leukemia for SDS patients is 36% by 30 years of age. As IBMFS are rare and large numbers of primary human samples are not readily available for mechanistic studies, we employed the zebrafish (Danio rerio), given their highly conserved hematopoietic program and ease of genetic manipulation. In contrast to SBDS, no in vivo models of DNAJC21 mutations have been published to date. Using CRISPR-Cas9 genomic editing, we generated mutations in the zebrafish dnajc21 gene. Homozygous mutant larvae recapitulated key features of SDS such as reduced growth and poor neutrophil counts as assessed by Sudan Black staining. Using whole-mount in situ hybridization, we observed reduced l-plastin+ leukocytes with no changes in upstream myb+/cebpa+ hematopoietic stem and progenitor cells and spi1b+ common myeloid progenitors, suggesting a potential differentiation block. In contrast, Dnajc21 loss did not affect erythrocyte specification. Flow cytometry of mutant whole kidney marrows (WKMs, equivalent to human bone marrow) revealed normal numbers of erythrocytes and lymphocytes but reduced myeloid cells accompanied by a trend towards increased progenitors. Further, we found reduced levels of phosphohistone-H3 (pH3) in the mutant larvae, suggesting hypoproliferation. Bulk RNA sequencing of whole larvae at 48 hours post-fertilization identified xenobiotic metabolism, regulation of endopeptidase activity and immune-related processes as key downregulated pathways in the mutants. Upregulated pathways included platelet-derived growth factor receptor signaling, cell adhesion and lysosomal transport. In addition, several genes involved in carbohydrate metabolism such as g6pd, pck1 and ganc were dysregulated. Further, using Oil Red O staining, we observed a reduced accumulation of neutral lipids in the mutants. Leukemic transformation in SDS is driven by the acquisition of mutations in additional genes, including the tumor suppressor, TP53. To model SDS-AML transformation, we crossed the dnajc21 mutants with a zebrafish line carrying a tp53R217H/R217H gain-of-function mutation that confers anti-apoptotic phenotypes. Embryonic pH3+ cell counts were restored and WKM myeloid cells and hematopoietic progenitors were increased in dnajc21-/-/tp53R217H/R217H fish. Finally, using liquid chromatography-mass spectrometry, we show that Dnajc21 is involved in the regulation of certain metabolite and lipid species including hexosyl-ceramides and sphingomyelins, which may contribute to SDS pathophysiology. Our findings suggest that Dnajc21 is required for normal granulocyte differentiation and cell proliferation. We also identified previously unrecognized roles for Dnajc21 in regulating cellular metabolism. We propose that the zebrafish models described here readily serve as in vivo platforms to identify therapeutic compounds that restore normal hematopoiesis and prevent leukemic transformation in SDS.

English

The objective of this work was to analyze the growth of Scenedesmus acutus, Nannochloropsis oculata and Chlorella vulgaris at different temperatures (25, 30 and 38°C) in order to identify changes in lipid content, accumulation of neutral lipids and fatty acids profile. According to the results obtained, the temperature of 30°C does not affect the growth of the microalgae S. acutus, N. oculata and C. vulgaris; however, there is a greater amount of total lipids in S. acutus at 38°C, while for N. oculata and C. vulgaris, temperature variation does not affect the accumulation of total lipids. From the data obtained from the fatty acid profile, we observed a greater accumulation of palmitic acid followed by oleic acid. According to the cetane number, any temperature condition of any evaluated microalgae culture can be used for biodiesel production. The results suggest that a change in temperature during the growth of microalgae could be applied to enhance lipid production and to obtain fatty acids suitable for biodiesel production.    Key words: Chlorella vulgaris, Nannochloropsis oculata, Scenedesmus acutus, fatty acids, lipids, temperature.

Chanarin-Dorfman Syndrome: Exceptional Liver Transplant Indication

• Second Chanarin-Dorfman case published that was treated with a liver transplant. • Liver transplant is an excellent treatment of decompensated cirrhosis in Chanarin-Dorfman syndrome. • There is no evidence of recurrence of the disorder on the graft. We report the second case published about the use of liver transplant in the treatment of a patient with Chanarin-Dorfman syndrome with decompensated cirrhosis who presented excellent results after a 6-month follow-up without recurrence. Chanarin-Dorfman syndrome is an autosomal recessive metabolic disorder caused by a chromosome 3 gene mutation containing α/β-hydrolase 5 domain. It is characterized by the accumulation of neutral lipids in granulocytes of diverse organs, such as muscle, liver, eyes, ear, central nervous system, and bone marrow. The clinical expression consists of ichthyosis and hepatomegaly, followed by bilateral ectropion, cataract, neurosensory deafness, and splenomegaly. About 10% of these patients develop cirrhosis. Even though the management with low-fat diet enriched with medium-chain triglycerides along with ursodeoxycholic acid and vitamin E can normalize liver enzymes, reduce liver size, and minimize cirrhosis; once cirrhosis is established it will determine the patient's prognosis. Liver transplant could be the adequate treatment of a decompensated cirrhosis; in fact, there is no evidence of recurrence on the graft.

ACC1 and ACC2 Genes Expression Microalgae Skletonema costatum On Stress Aeration And fotoperiode In Simultans

Abiotic stresses such as photoperiod, aeration, CO2 concentration, pH, temperature, and salinity can affect and salinity the physiological processes of microalgae. One of the physiological processes that occur is a change in the lipid biosynthetic pathway towards the formation and accumulation of neutral lipids. Neutral lipid accumulation in the form of TAGs. TAGs as one of the defense mechanisms. The regulation of fatty acid biosynthesis is initiated by the ACC1 and ACC2 genes. This study aims to determine the expression of ACC1 and ACC2 genes under conditions of aeration stress and photoperiod simultaneously in microalgae Skeletonema costatum. The method used was the analysis of gene expression in the sample of S. costatum RNA extract using qRT-PCR. Based on the results of the study, it was found that the ACC1 gene was expressed and upregulated in the A2F2 treatment (24-hour aeration and 24:0 photoperiod) with a CT value of 36.85 while the ACC2 gene was expressed and upregulated in the A1F1 treatment (12-hour aeration and 12:12 photoperiod). with the CT value of 36,874.

Sensitivity of histopathological and histochemical parameters in the digestive gland of the apple snail Pomacea canaliculata exposed to cypermethrin

The aim of this study was to evaluate the toxic effects of the pesticide cypermethrin (CYP) in the digestive gland of the apple snail, Pomacea canaliculata, analysing histological and histochemical alterations. Adult snails were exposed to sublethal CYP concentrations (10, 25, and 100 µg/L) under acute (1 day) and sub-chronic (14 days) conditions. Histological analyses of the morphology of the digestive gland were performed and a histopathological condition index (HI) was calculated. Also, both intracellular accumulation of lipofuscins (LF) and neutral lipids (NL) were evaluated. CYP exposure induced tissue damage to this organ, such as disorganisation of the connective tissue, fibrosis, haemocytic infiltration, atrophy, and necrosis under acute and sub-chronic conditions. These alterations, integrated into a single HI value, revealed notable CYP effects during both acute and sub-chronic exposures. Cell type replacement, measured as VvBAS, was only observed in the sub-chronic treatment. Under acute conditions, the pyrethroid affected NL accumulation at the highest concentration, while in sub-chronic conditions NL accumulation was only observed at the lowest concentrations. P. canaliculata also showed a dose-dependent response of LF under acute CYP exposure conditions. However, under sub-chronic conditions, this parameter was not sensitive to pesticide exposure. All these relevant structural lesions may affect the normal function of the digestive gland, even though the species presented additional mechanisms, as infiltration of hemocyte and basophilic cell hyperplasia, that help it to tolerate the exposure to pollutants. This study showed that some histological and histochemical parameters are sensitive in P. canaliculata at CYP concentrations to which the snail could be exposed in the environments it inhabits.

Minimum nitrogen cell quota for maximal growth rate in cycloturbidostat cultures of Picochlorum oklahomense

Replicate cycloturbidostats cultures of Picochlorum oklahomense were manipulated to quantify the minimum nitrogen cell quota supporting maximum growth rate and to study the effects of nitrogen limitation on cycloturbidostat cultures growing at near-μmax under steady-state, balanced growth conditions. Results show that cyclical diurnal neutral lipid accumulation and ultradian growth are not mutually exclusive, and that cycloturbidostat cultures may be maintained near or at the threshold of N-limitation to control cell composition and modulate biomass and lipid productivity. Using this novel approach, we have identified the threshold of N limitation in P. oklahomense and investigated the effects of N limitation on replicate cycloturbidostat cultures. Mildly N-limited cultures grew rapidly (87 % μmax) and maintained near optimal physiology, while also accumulating neutral lipids during the photoperiod. Flow cytometry revealed differences in temporal patterns between treatments, demonstrating the importance of the cell-based approach in manipulating microalgal cultures. This study highlights the utility of turbidostats in experimental phycology and defines a scantly explored concept in the study of N limitation, the threshold of N cell quota necessary to support μmax below which cells are forced to re-allocate resources and slow growth, denoted QN, T.

Abstract P3032: Liver-directed Mitochondrial Uncoupling Attenuates The Progression Of Early And Late-stage Atherosclerosis In Mice

Atherosclerotic cardiovascular disease (CVD) remains a leading cause of morbidity and mortality in people with type 2 diabetes (T2D) and new therapies are urgently needed. We recently developed an orally available, liver-directed controlled-release mitochondrial protonophore (CRMP) and showed that this agent safely reverses hypertriglyceridemia, fatty liver, and T2D in rodent and nonhuman primate models of obesity by promoting a subtle sustained increase in hepatic mitochondrial inefficiency. To determine the effect of CRMP on atherogenesis, we performed intervention studies in which 12-week Western-diet fed Ldlr -/- mice with established atherosclerosis were treated with CRMP (30 mg/kg-day) or vehicle control for an additional 12 weeks. CRMP-treated mice displayed a significant reduction in fasting plasma and hepatic triglyceride content, independently of changes in body weight, fasting plasma glucose, insulin or cholesterol levels. Morphometric analysis of the aortic root and brachiocephalic artery revealed that CRMP treatment significantly reduced total plaque area and neutral lipid accumulation. CRMP treatment also decreased markers of plaque vulnerability, as evidenced by a reduction in necrotic core area and increase in fibrous cap area ( P <0.05 vs veh). To determine the mechanisms by which CRMP attenuated atherosclerosis, we performed progression studies in Ldlr -/- mice fed a Western diet containing CRMP or vehicle control for 12 weeks. Similarly to the intervention studies, CRMP significantly reduced aortic root plaque area, neutral lipid accumulation and necrotic core area. These changes were associated with a reduction in plasma triglyceride content and improvement in whole-body insulin sensitivity as assessed by hyperinsulinemic-euglycemic clamps (all P <0.05 vs veh). Single-cell RNA sequencing of whole aortas from CRMP and vehicle-treated Ldlr -/- mice revealed that CRMP reduced the frequency of inflammatory macrophages compared to vehicle (~19% vs ~2%), consistent with an immune-dampening effect of CRMP. Taken together, these data support an anti-atherogenic role for CRMP and suggest the therapeutic potential of liver-directed mitochondrial uncouplers for the treatment of early and late-stage atherosclerosis.

JNK affects on neutral lipids accumulation in the liver of different age insulin resistant rats

Background and Aims : JNK activation is one of the important stages in development of resistance to insulin and could be mediated by oxidative stress and neutral lipids accumulation, the processes which are associated with eldering. The purpose of the experiment was to compare the importance of liver JNK under IR development in young and old rats.

Anthocyanin-Rich Extract of Red Cabbage Attenuates Advanced Alcohol Hepatotoxicity in Rats in Association with Mitochondrial Activity Modulation

Abstract Aim The liver is the main target for alcohol-induced injury. The aims of this work were to carry out further research into the mechanisms of liver damage induced by long-term administration of high-dose ethanol to rats and to evaluate the hepatoprotective potential of red cabbage (Brassica oleracea var. capitata f. rubra) anthocyanins (RCE). Material/Methods Male albino Wistar rats were divided into four groups. Group 1 was the control. Groups 2 through 4 received ethanol (4 g/kg body weight, 8 weeks). Group 3 received 11 mg RCE/kg and Group 4 received 22 mg RCE/kg. Dry lyophilised RCE was prepared from fresh red cabbage and analysed. We then evaluated the liver histology, mitochondrial respiration, and biochemical and immunological parameters in these groups of rats. Results The rat intoxication caused steatohepatitis characterised by macro- and microvesicular steatosis, ballooning and fatty liver dystrophies, lymphocytic infiltration, neutral lipid accumulation, and elevations of the serum activities of the liver injury marker enzymes. The treatment of alcohol-administered rats with RCE (mainly, cyanidin-3-diglucoside-5-glucoside, cyanidin-3-coumaroylrutinoside-5-hexoside, cyanidin-3-feruloylrutinoside-5-hexoside, delphinidin-3-feruloylrutinoside-hexoside) dose-dependently alleviated these pathological changes: The sizes of hepatocyte lipid vacuoles and the inflammatory signs were decreased, and the levels of the rat serum biochemical markers of liver injury, proinflammatory cytokines TNFα and IL-6, and the adipokine leptin (and not TGFβ) were significantly reversed. The RCE administration during intoxication completely recovered the changed liver mitochondria respiration rates and the ADP/O coefficient, as well as the phagocytic index and neutrophil metabolic activity in the blood. In experiments in vitro, RCE (13.6 μg/ml) modulated the respiratory parameters of isolated rat liver mitochondria, dissipated mitochondrial membrane potential, and inhibited the Ca2+-induced mitochondrial permeability transition. Conclusion The red cabbage anthocyanins could be useful for treatment of alcoholic liver injury due to their Ca2+-ionophoric/protonophoric activity, influence on Ca2+ homeostasis, and improving mitochondrial functions and inflammatory status.

Nrf2a dependent and independent effects of early life exposure to 3,3'-dichlorobiphenyl (PCB-11) in zebrafish (Danio rerio).

The environmental pollutant 3,3'-dichlorobiphenyl (PCB-11) is a lower-chlorinated polychlorinated biphenyl (PCB) congener present in air and water samples. Both PCB-11 and its metabolite, 4-PCB-11-Sulfate, are detected in humans, including in pregnant women. Previous research in zebrafish (Danio rerio) has shown that 0.2μM exposures to 4-PCB-11-Sulfate starting at 1 day post fertilization (dpf) increase hepatic neutral lipid accumulation in larvae at 15 dpf. Here, we explored whether nuclear factor erythroid 2-related factor 2 (Nrf2), known as the master-regulator of the adaptive response to oxidative stress, contributes to metabolic impacts of 4-PCB-11-Sulfate. For this work, embryos were collected from homozygous wildtype or Nrf2a mutant adult zebrafish that also express GFP in pancreatic β-cells, rendering Tg(ins:GFP;nrf2afh318+/+) and Tg(ins:GFP;nrf2afh318-/-) lines. Exposures were conducted from 1-15 dpf to either 0.05% DMSO or DMSO-matched 0.2µM 4-PCB-11-Sulfate, and at 15 dpf subsets of larvae were imaged for overall morphology, primary pancreatic islet area, and collected for fatty acid profiling and RNAseq. At 15 dpf, independent of genotype, fish exposed to 4-PCB-11-Sulfate survived significantly more at 80-85% compared to 65-73% survival for unexposed fish, and had primary pancreatic islets 8% larger compared to unexposed fish. Fish growth at 15 dpf was dependent on genotype, with Nrf2a mutant fish a significant 3-5% shorter than wildtype fish, and an interaction effect was observed where Nrf2a mutant fish exposed to 4-PCB-11-Sulfate experienced a significant 29% decrease in the omega-3 fatty acid DHA compared to unexposed mutant fish. RNAseq revealed 308 differentially expressed genes, most of which were dependent on genotype. These findings suggest that Nrf2a plays an important role in growth as well as for DHA production in the presence of 4-PCB-11-Sulfate. Further research would be beneficial to understand the importance of Nrf2a throughout the lifecourse, especially in the context of toxicant exposures.

Membrane shaping proteins, lipids, and cytoskeleton: Recipe for nascent lipid droplet formation.

Lipid droplets (LDs) are ubiquitous, neutral lipid storage organelles that act as hubs of metabolic processes. LDs are structurally unique with a hydrophobic core that mainly consists of neutral lipids, sterol esters, and triglycerides, enclosed within a phospholipid monolayer. Nascent LD formation begins with the accumulation of neutral lipids in the endoplasmic reticulum (ER) bilayer. The ER membrane proteins such as seipin, LDAF1, FIT, and MCTPs are reported to play an important role in the formation of nascent LDs. As the LDs grow, they unmix from the highly charged ER membrane to form mature LDs. LD biogenesis is an exciting, emerging research area, and herein, we discuss the recent progress in our understanding of the formation of eukaryotic nascent LDs. We focus on the role of ER membrane shaping proteins such as reticulons and reticulon-like proteins, membrane lipids, and cytoskeleton proteins such as septin in the formation of nascent LDs.

Diet-Induced Obesity Disrupts Histamine-Dependent Oleoylethanolamide Signaling in the Mouse Liver

Introduction: Previous work suggests the existence of a paracrine signaling mechanism in which histamine released from visceral mast cells into the portal circulation contributes to fasting-induced ketogenesis by stimulating biosynthesis of the endogenous high-affinity PPAR-α agonist oleoylethanolamide (OEA). Methods: Male C57Bl/6J mice were rendered obese by exposure to a high-fat diet (HFD; 60% fat). We measured histamine, OEA, and other fatty-acid ethanolamides by liquid-chromatography/mass spectrometry, gene transcription by RT-PCR, protein expression by ELISA, neutral lipid accumulation in the liver using Red Oil O and BODIPY staining, and collagen levels using picrosirius red staining. Results: Long-term exposure to HFD suppressed both fasting-induced histamine release into portal blood and histamine-dependent OEA production in the liver. Additionally, subchronic OEA administration reduced lipid accumulation, inflammatory responses, and fibrosis in the liver of HFD-exposed mice. Discussion: The results suggest that disruption of histamine-dependent OEA signaling in the liver might contribute to pathology in obesity-associated liver steatosis.

Formation of Nascent Lipid Droplets at Specialized ER subdomains

Lipid droplets (LDs) are neutral lipid containing organelles enclosed in a single monolayer of phospholipids. LD formation begins with the accumulation of neutral lipids within the bilayer of the endoplasmic reticulum (ER) membrane. It is not known how the sites of formation of nascent LDs in the ER membrane are determined. Here we show that multiple C2 domain–containing transmembrane proteins, MCTP1 and MCTP2, are at sites of LD formation in specialized ER subdomains. We show that the transmembrane domain of these proteins is similar to a reticulon homology domain. Like reticulons, MCTPs tubulate the ER membrane and favor highly curved regions of the ER. Our data indicate that the transmembrane domains (TMD) of MCTP promote LD biogenesis by increasing LD number. MCTPs colocalize with seipin, a protein involved in LD biogenesis, but form more stable microdomains in the ER. The MCTP C2 domains bind charged lipids and regulate LD size, likely by mediating ER–LD contact sites. Together, our data indicate that MCTPs form specialized subdomains within ER tubules that regulate LD biogenesis, size, and ER–LD contacts. Interestingly, MCTP punctae are associated with other organelles as well, suggesting that these proteins may play a more general role in linking tubular ER to organelle contact sites.

Abstract 500: Silencing Apolipoprotein C3 Prevents Diabetic Kidney Disease And Atherosclerosis In A Mouse Model Of Type 2 Diabetes

Diabetes increases the risk of both cardiovascular disease and kidney disease. Notably, most of the excess cardiovascular risk in people with diabetes is in those with kidney disease. Apolipoprotein C3 (APOC3) is a small apolipoprotein that is elevated by insulin-insufficiency and regulates plasma triglyceride levels. To test if APOC3, and the dyslipidemia it represents, play a role in diabetic kidney disease (DKD) and associated atherosclerosis, we treated BTBR wildtype (WT) and leptin-deficient (OB; diabetic) mice with an antisense oligonucleotide (ASO) to APOC3 or a control ASO (cASO), all in the setting of human-like dyslipidemia (accomplished by administration of an ASO targeting the LDLR). APOC3 ASO treatment reduced triglycerides, triglyceride-rich lipoproteins. It prevented diabetes-accelerated atherosclerosis in the aortic sinus, brachiocephalic artery, and aorta (sinus lesion: 67926 ± 8486 μm 2 lesion in cASO-treated OB mice compared to 38589 ± 9507 μm 2 in APOC3 ASO-treated OB mice, p<0.05, n=12-15). The reduction in lesion size with APOC3 treatment was associated with fewer macrophages and reduced perilipin 2 staining (a marker for lipid droplet formation). In the kidney, diabetes resulted in a dramatic increase in glomerular hypertrophy, neutral lipid accumulation, APOC3, and APOE-accumulation, which APOC3 ASO-treatment attenuated. Furthermore, diabetes resulted in monocyte recruitment, macrophage accumulation, and macrophage lipid loading in the glomeruli, all of which was dramatically suppressed in the setting of APOC3 silencing (36% of glomerular macrophages were lipid loaded in OB cASO mice whereas only 9% were lipid loaded in APOC3-ASO treated mice, p<0.0001). The recruitment was driven by increased endothelial cell ICAM1 expression, but monocyte lipid loading may also contribute. Intriguingly, APOC3-ASO treatment reduced diabetes-associated urinary albumin creatinine ratio but did not affect it in non-diabetic mice (WT mice: 374 ± 71 μg albumin/mg creatinine, OB cASO mice: 4648 ± 1021 μg/mg and OB mice with APOC3 ASO: 2341 ± 439 μg/mg, p<0.05, n=12-14). Together, this suggests that targeting APOC3 and diabetic dyslipidemia might be beneficial for both diabetes-accelerated atherosclerosis and kidney disease.

Lack of VMP1 impairs hepatic lipoprotein secretion and promotes non-alcoholic steatohepatitis.

Background & Aims:Vacuole membrane protein 1 (VMP1) is an endoplasmic reticulum (ER) transmembrane protein that regulates the formation of autophagosomes and lipid droplets. Recent evidence suggests that VMP1 plays a critical role in lipoprotein secretion in zebra fish and cultured cells. However, the pathophysiological roles and mechanisms by which VMP1 regulates lipoprotein secretion and lipid accumulation in non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH) are unknown.Methods:Liver-specific and hepatocyte-specific Vmp1 knockout mice as well as Vmp1 knock-in mice were generated by crossing Vmp1flox or Vmp1KI mice with albumin-Cre mice or by injecting AAV8-TBG-cre, respectively. Lipid and energy metabolism in these mice were characterized by metabolomic and transcriptome analyses. Mice with hepatic overexpression of VMP1 who were fed a NASH diet were also characterized.Results:Hepatocyte-specific deletion of Vmp1 severely impaired VLDL secretion resulting in massive hepatic steatosis, hepatocyte death, inflammation and fibrosis, which are hallmarks of NASH. Mechanistically, loss of Vmp1 led to decreased hepatic levels of phosphatidylcholine and phosphatidylethanolamine as well as to changes in phospholipid composition. Deletion of Vmp1 in mouse liver also led to the accumulation of neutral lipids in the ER bilayer and impaired mitochondrial beta-oxidation. Overexpression of VMP1 ameliorated steatosis in diet-induced NASH by improving VLDL secretion. Importantly, we also showed that decreased liver VMP1 is associated with NAFLD/NASH in humans.Conclusions:Our results provide novel insights on the role of VMP1 in regulating hepatic phospholipid synthesis and lipoprotein secretion in the pathogenesis of NAFLD/NASH.Lay summary:Non-alcoholic fatty liver disease and its more severe form, non-alcoholic steatohepatitis, are associated with a build-up of fat in the liver (steatosis). However, the exact mechanisms that underly steatosis in patients are not completely understood. Herein, the authors identified that the lack of a protein called VMP1 impairs the secretion and metabolism of fats in the liver and could therefore contribute to the development and progression of non-alcoholic fatty liver disease.

Cytochrome P450 2E1-dependent hepatic ethanol metabolism induces fatty acid-binding protein 4 and steatosis.

Hepatic steatosis is an early pathology of alcohol-associated liver disease (ALD). Fatty acid-binding protein-4 (FABP4, a FABP not normally produced in the liver) is secreted by hepatocytes in ALD and stimulates hepatoma proliferation and migration. This study sought to investigate the mechanism[s] by which hepatic ethanol metabolism regulates FABP4 and steatosis. Human hepatoma cells (HepG2/HuH7) and cells stably transfected to express cytochrome P450 2E1 (CYP2E1), were exposed to ethanol in the absence or presence of chlormethiazole (a CYP2E1-inhibitor; CMZ) and/or EX-527 (a sirtuin-1 [SIRT1] inhibitor). The culture medium was analyzed for ethanol metabolism and FABP4 protein abundance. Cells were analyzed for FABP4mRNA expression, SIRT1 protein abundance, and neutral lipid accumulation. In parallel, cells were analyzed for forkhead box O1 [FOXO1], β-catenin, peroxisome proliferator-activated receptor-α [PPARα], and lipin-1α protein abundance in the absence or presence of ethanol and pharmacological inhibitors of the respective target proteins. CYP2E1-dependent ethanol metabolism inhibited the amount of SIRT1 protein detected, concomitant with increased FABP4mRNA expression, FABP4 protein secretion, and neutral lipid accumulation, effects abolished by CMZ. Analysis of pathways associated with lipid oxidation revealed increased FOXO1 nuclear localization and decreased β-catenin, PPARα, and lipin-1α protein levels in CYP2E1-expressing cells in the presence of ethanol. Pharmacological inhibition of SIRT1mimicked the effects of ethanol, while inhibition of FOXO1 abrogated the effect of ethanol on FABP4mRNA expression, FABP4 protein secretion, and neutral lipid accumulation in CYP2E1-expressing cells. Pharmacological inhibition of β-catenin, PPARα, or lipin-1α failed to alter the effects of ethanol on FABP4 or neutral lipid accumulation. CYP2E1-dependent ethanol metabolism inhibits SIRT1-FOXO1signaling, which leads to increased FABP4mRNA expression, FABP4 protein secretion, and neutral lipid accumulation. These data suggest that FABP4 released from steatotic hepatocytes could play a role in promoting tumor cell expansion in the setting of ALD and represents a potential target for therapeutic intervention.

Maximize microalgal carbon dioxide utilization and lipid productivity by using toxic flue gas compounds as nutrient source

NOx and SOx present in flue gas inhibit microalgal based CO2 mitigation process. In this work, 13 microalgal strains were screened to evaluate their gradual acclimation capacity to toxic flue gas compounds, by testing their growth capability and photosynthetic ability in dissolved flue gas compounds. Six strains out of them were evaluated for their acclimation to bicarbonate and 15% CO2 as sole carbon sources. Two strains, Micractinium pusillum KMC8 and Scenedesmus acutus NCIM5584 were found to accumulate nitrite as fixed nitrogen and showed improved growth performance in photobioreactor upon stepwise acclimation to bisulphite/sulphite. Notably, the strain KMC8 showed a high tolerance and rapidly acclimated dissolved flue gas compounds with higher biomass yield (1.32 g L−1) and neutral lipid accumulation (32%), enhanced CO2 utilization efficiency (3.07%) and CO2 fixation rate (136.79 mg L−1 d−1) post acclimation. KMC8 sustained its stability in biomass and lipid productivity while simultaneously bio-mitigated CO2 under semi-continuous mode.

Endoplasmic reticulum stress is involved in lipid accumulation induced by oleic acid in adipocytes of grass carp (Ctenopharyngodon idella): focusing on the transcriptional level.

It has been extensively claimed that endoplasmic reticulum stress (ER stress) is related to lipid accumulation in mammals, but little is known in fish. This study aims at elucidating the role of ER stress in mediating lipid accumulation induced by monounsaturated oleic acid (OA) with a focus on the transcriptional level. We treated the adipocytes of grass carp with 200μM and 400μM OA, respectively, while the control group was treated with 2% bovine serum albumin (BSA). The results showed that cell viability was significantly improved, while 400μM OA treatment promoted neutral lipid accumulation along with stimulating ER stress more obviously. Although lipolysis and fatty acid β-oxidation were activated simultaneously, the primary effect of OA seems to be promotion of lipid accumulation. To further explore whether ER stress affects lipid accumulation, 4-phenyl butyric acid (4-PBA), an effective inhibitor of ER stress, was used to pretreat the cells for 4h. Unsurprisingly, it was found that the mRNA expressions of genes linked with ER stress were decreased. Intracellular triglyceride (TG) content was also decreased, which was in accordance with the mRNA expressions of adipogenic and lipogenic transcription factors as well as their target genes. Collectively, our data shows that ER stress may take part in OA-induced lipid accumulation in adipocytes via activating adipogenesis and lipogenesis. Based on this, strategies for protecting ER could be used to alleviate excessive accumulation of lipid in grass carp adipose tissue.

PHLPP1 promotes neutral lipid accumulation through AMPK/ChREBP-dependent lipid uptake and fatty acid synthesis pathways

SummaryInfiltration of arterial intima by foamy macrophages is a hallmark of early atherosclerotic lesions. Here, we investigated the potential role of Ser/Thr phosphatase PHLPP1 in foam cell development. PHLPP1 levels were elevated in OxLDL-exposed macrophages and high-fat diet (HFD)-fed zebrafish larvae. Using overexpression and knockdown approaches, we show that PHLPP1 promotes the accumulation of neutral lipids, and augments cellular total cholesterol and free fatty acid (FFA) levels. RNA-Seq analysis uncovered PHLPP1 role in lipid metabolism pathways. PHLPP1 interacted with and modestly increased ChREBP recruitment to Fasn promoter. PHLPP1-mediated lipid accumulation was attenuated by AMPK activation. Pharmacological inhibition or CRISPR/Cas9-mediated disruption of PHLPP1 resulted in lower lipid accumulation in the intersegmental vessels of HFD-fed zebrafish larvae along with a reduction in total cholesterol and triglyceride levels. Deficiency of phlp-2, C. elegans PHLPP1/2 ortholog, abolished lipid accumulation in high cholesterol-fed worms. We conclude that PHLPP1 exerts a significant effect on lipid buildup.