Lipid droplets in the nervous system:involvement in cell metabolic homeostasis

Lipid droplets serve as primary storage organelles for neutral lipids in neurons,glial cells,and other cells in the nervous system.Lipid droplet formation begins with the synthesis of neutral lipids in the endoplasmic reticulum.Previously,lipid droplets were recognized for their role in maintaining lipid metabolism and energy homeostasis;however,recent research has shown that lipid droplets are highly adaptive organelles with diverse functions in the nervous system.In addition to their role in regulating cell metabolism,lipid droplets play a protective role in various cellular stress responses.Furthermore,lipid droplets exhibit specific functions in neurons and glial cells.Dysregulation of lipid droplet formation leads to cellular dysfunction,metabolic abnormalities,and nervous system diseases.This review aims to provide an overview of the role of lipid droplets in the nervous system,covering topics such as biogenesis,cellular specificity,and functions.Additionally,it will explore the association between lipid droplets and neurodegenerative disorders.Understanding the involvement of lipid droplets in cell metabolic homeostasis related to the nervous system is crucial to determine the underlying causes and in exploring potential therapeutic approaches for these diseases.

Porcine enteric alphacoronavirus infection increases lipid droplet accumulation to facilitate the virus replication

Coronaviruses are widely transmissible between humans and animals, causing diseases of varying severity. Porcine enteric alphacoronavirus(PEAV) is a newly-discovered pathogenic porcine enteric coronavirus in recent years, which causes watery diarrhea in newborn piglets. The host inflammatory responses to PEAV and its metabolic regulation mechanisms remain unclear, and no antiviral studies have been reported. Therefore, we investigated the pathogenic mechanism and antiviral drugs of PEAV. The transcriptomic analysis of PEAV-infected host cells revealed that PEAV could upregulate lipid metabolism pathways. In lipid metabolism, steady-state energy processes, which can be mediated by lipid droplets(LDs), are the main functions of organelles. LDs are also important in viral infection and inflammation. In infected cells, PEAV increased LD accumulation, upregulated NF-κB signaling, promoted the production of the inflammatory cytokines IL-1β and IL-8, and induced cell death. Inhibiting LD accumulation with a DGAT-1 inhibitor significantly inhibited PEAV replication, downregulated the NF-κB signaling pathway, reduced the production of IL-1β and IL-8, and inhibited cell death. The NF-κB signaling pathway inhibitor BAY11-7082 significantly inhibited LD accumulation and PEAV replication. Metformin hydrochloride also exerted anti-PEAV effects and significantly inhibited LD accumulation, downregulated the NF-κB signaling pathway, reduced the production of IL-1β and IL-8, and inhibited cell death. LD accumulation in the lipid metabolism pathway therefore plays an important role in the replication and pathogenesis of PEAV, and metformin hydrochloride inhibits LD accumulation and the inflammatory response to exert anti-PEAV activity and reducing pathological injury. These findings contribute new targets for developing treatments for PEAV infections.

Regenerating gene 4 promotes chemoresistance of colorectal cancer by affecting lipid droplet synthesis and assembly

BACKGROUND Regenerating gene 4(REG4)has been proved to be carcinogenic in some cancers,but its manifestation and possible carcinogenic mechanisms in colorectal cancer(CRC)have not yet been elucidated.Our previous study found that the drug resistance of CRC cells may be closely linked to their fat metabolism.AIM To explore the role of REG4 in CRC and its association with lipid droplet formation and chemoresistance.METHODS We conducted a meta-analysis and bioinformatics and pathological analyses of REG4 expression in CRC.The effects of REG4 on the phenotypes and related protein expression were also investigated in CRC cells.We detected the impacts of REG4 on the chemoresistance and lipid droplet formation in CRC cells.Finally,we analyzed how REG4 regulated the transcription and proteasomal degradation of lipogenic enzymes in CRC cells.RESULTS Compared to normal mucosa,REG4 mRNA expression was high in CRC(P<0.05)but protein expression was low.An inverse correlation existed between lymph node and distant metastases,tumor-node-metastasis staging or short overall survival and REG4 mRNA overexpression(P<0.05),but vice versa for REG4 protein expression.REG4-related genes included:Chemokine activity;taste receptors;protein-DNA and DNA packing complexes;nucleosomes and chromatin;generation of second messenger molecules;programmed cell death signals;epigenetic regulation and DNA methylation;transcription repression and activation by DNA binding;insulin signaling pathway;sugar metabolism and transfer;and neurotransmitter receptors(P<0.05).REG4 exposure or overexpression promoted proliferation,antiapoptosis,migration,and invasion of DLD-1 cells in an autocrine or paracrine manner by activating the epidermal growth factor receptor-phosphoinositide 3-kinase-Akt-nuclear factor-κB pathway.REG4 was involved in chemoresistance not through de novo lipogenesis,but lipid droplet assembly.REG4 inhibited the transcription of acetyl-CoA carboxylase 1(ACC1)and ATP-citrate lyase(ACLY)by disassociating the complex formation of anti-acetyl(AC)-acetyl-histone 3-AC-histone 4-inhibitor of growth protein-5-si histone deacetylase;-sterol-regulatory element binding protein 1 in their promoters and induced proteasomal degradation of ACC1 or ACLY.CONCLUSION REG4 may be involved in chemoresistance through lipid droplet assembly.REG4 reduces expression of de novo lipid synthesis key enzymes by inhibiting transcription and promoting ubiquitination-mediated proteasomal degradation.

Lipid droplets imaging with three-photon microscopy

Lipid droplets(LDs)participate in many physiological processes,the abnormality of which will cause chronic diseases and pathologies such as diabetes and obesity.It is crucial to monitor the distribution of LDs at high spatial resolution and large depth.Herein,we carried three-photon imaging of LDs in fat liver.Owing to the large three-photon absorption cross-section of the luminogen named NAP-CF_(3)(1:67×10^(-79) cm^(6) s^(2)),three-photon fluorescence fat liver imaging reached the largest depth of 80μm.Fat liver diagnosis was successfully carried out with excellent performance,providing great potential for LDs-associated pathologies research.

Knockout of butyrophilin subfamily 1 member A1(BTN1A1) alters lipid droplet formation and phospholipid composition in bovine mammary epithelial cells

Background: Milk lipids originate from cytoplasmic lipid droplets(LD) that are synthesized and secreted from mammary epithelial cells by a unique membrane-envelopment process. Butyrophilin 1 A1(BTN1 A1) is one of the membrane proteins that surrounds LD, but its role in bovine mammary lipid droplet synthesis and secretion is not well known.Methods: The objective was to knockout BTN1 A1 in bovine mammary epithelial cells(BMEC) via the CRISPR/Cas9 system and evaluate LD formation, abundance of lipogenic enzymes, and content of cell membrane phospholipid(PL) species. Average LD diameter was determined via Oil Red O staining, and profiling of cell membrane phospholipid species via liquid chromatography-tandem mass spectrometry(LC-MS/MS).Results: Lentivirus-mediated infection of the Cas9/sg RNA expression vector into BMEC resulted in production of a homozygous clone BTN1 A1^((-/-)). The LD size and content decreased following BTN1 A1 gene knockout. The m RNA abundance of fatty acid synthase(FASN) and peroxisome proliferator-activated receptor-gamma(PPARG) was downregulated in the BTN1 A1^((-/-))clone. Subcellular analyses indicated that BTN1 A1 and LD were co-localized in the cytoplasm. BTN1 A1 gene knockout increased the percentage of phosphatidylethanolamine(PE) and decreased phosphatidylcholine(PC), which resulted in a lower PC/PE ratio.Conclusions: Results suggest that BTN1 A1 plays an important role in regulating LD synthesis via a mechanism involving membrane phospholipid composition.

Effect of testicular capsulotomy on lipid droplets in the seminiferous tubules of rats

Aim: In order to reveal the histochemical alteration that might occur during the processes of the spermatogenic dis-ruption induced by testicular capsulotomy, the location and alteration of lipid droplets in the seminiferous tubules wereobserved in the present study. Methods: Osmium tetroxide was used to demonstrate the lipid droplets in the semi-niferous tubules of capsulotomized and sham-operated control testes. Results: In the seminiferous tubules of thesham-operated rat testes, many small lipid droplets were located close to the basement membrane of the seminiferoustubules. But for the capsulotomized testes, the lipid droplets in the seminiferous tubules had increased in size and num-ber, with many lipid droplets migrated towards the lumen of the tubules. Conclusion: The results indicated that aprogressive fatty degeneration occurred in the seminiferous tubules after testicular capsulotomy.

Oleic acid reduces steroidogenesis by changing the lipid type stored in lipid droplets of ovarian granulosa cells

Background:Oleic acid is an abundant free fatty acid present in livestock that are in a negative energy-balance state,and it may have detrimental effects on female reproduction and fertility.Oleic acid induces lipid accumulation in bovine granulosa cells,which leads to a foam cell-like morphology and reduced steroidogenesis.However,why oleic acid increases lipid accumulation but decreases steroidogenesis remains unclear.This study focused on oleic acid’s effects on lipid type and steroidogenesis.Results:Oleic acid increased the lipid accumulation in a concentration-dependent manner and mainly increased the triglyceride level and decreased the cholesterol ester level.Oleic acid also led to a decline in estradiol and progesterone production in porcine granulosa cells in vitro.In addition,oleic acid up-regulated the expression of CD36 and diacylglycerol acyltransferase 2,but down-regulated the expression of 3-hydroxy-3-methylglutarylcoenzyme A reductase,scavenger receptor class B member 1 and acetyl-Coenzyme A acetyltransferase 2,as well as steroidogenesis-related genes,including cytochrome P450 family 11 subfamily A member 1,cytochrome P450family 19 subfamily A member 1 and 3 as well as steroidogenic acute regulatory protein at the mRNA and protein levels.An oleic acid-rich diet also enhanced the triglyceride levels and reduced the cholesterol levels in ovarian tissues of female mice,which resulted in lower estradiol levels than in control-fed mice.Compared with the control,decreases in estrus days and the numbers of antral follicles and corpora lutea,as well as an increase in the numbers of the atretic follicles,were found in the oleic acid-fed female mice.Conclusions:Oleic acid changed the lipid type stored in lipid droplets of ovarian granulosa cells,and led to a decrease in steroidogenesis.These results improve our understanding of fertility decline in livestock that are in a negative energy-balance state.

Lipid droplets as metabolic determinants for stemness and chemoresistance in cancer

Previously regarded as simple fat storage particles,new evidence suggests thatlipid droplets(LDs)are dynamic and functional organelles involved in keycellular processes such as membrane biosynthesis,lipid metabolism,cellsignalling and inflammation.Indeed,an increased LD content is one of the mostapparent features resulting from lipid metabolism reprogramming necessary tosupport the basic functions of cancer cells.LDs have been associated to differentcellular processes involved in cancer progression and aggressiveness,such astumorigenicity,invasion and metastasis,as well as chemoresistance.Interestingly,all of these processes are controlled by a subpopulation of highly aggressivetumoral cells named cancer stem cells(CSCs),suggesting that LDs may befundamental elements for stemness in cancer.Considering the key role of CSCs onchemoresistance and disease relapse,main factors of therapy failure,the design ofnovel therapeutic approaches targeting these cells may be the only chance forlong-term survival in cancer patients.In this sense,their biology and functionalproperties render LDs excellent candidates for target discovery and design ofcombined therapeutic strategies.In this review,we summarise the currentknowledge identifying LDs and CSCs as main contributors to cancer aggressiveness,metastasis and chemoresistance.

Anti-lipid droplets accumulation effect of Annona montana(mountain soursop)leaves extract on differentiation of preadipocytes

The Annona genus is a member of Annonaceae,one of the largest families of plants across tropical and subtropical regions.This family has been used in several ethnomedicinal practices to treat a multitude of human diseases.However,the molecular mechanism underlying its effect on the lipid droplet formation and on the expression of adipogenic markers of this plant remain to be investigated.In this study,we examined whether the extracts from the aerial part of Annona montana affect in vitro differentiation of preadipocytes.For our investigations,both mouse embryo fibroblast 3T3-L1 and normal human primary subcutaneous preadipocytes were incubated with Annona montana extracts(-and its subfractions-)and then analyzed on preadipocyte differentiation,lipid content,lipid droplet size and number,the expression of adipogenic-specific transcriptional factors,as well as cell survival.From our examinations,we found the Annona montana ethyl acetate extract to exhibit a potent inhibitory effect on adipogenesis,without affecting cell survival,in a dose-dependent manner.Such inhibitory effects included a significant decrease in the accumulation of lipid content by both a dramatic reduction of size and number of lipid droplets.This extract strongly attenuated the expression of PPARγand HMGB2.It also inhibited the expression of CEBPα,FAS,and Akt without influencing Erk1/2 activities.Our findings suggest that specifically,the Annona montana ethyl acetate extract has a prominent inhibitory effect in cellular pathways of adipocyte differentiation by modulating specific gene expression,which is known to perform a pivotal role during adipogenesis.

Facile synthesis of ultrabright luminogens with specific lipid droplets targeting feature for in vivo two-photon fluorescence retina imaging

The application of fluorescent probes for in vivo retinal imaging is of great importance,which could provide direct and crucial imaging evidence for a better understanding of common eye diseases.Herein,a group of bright organic luminogens with typical electron-donating(D)and electron-accepting(A)structures(abbreviated as LDs-BDM,LDs-BTM,and LDs-BHM)was synthesized through a simple single-step reaction.They were found to be efficient solid-state emitters with high fluorescence quantum yields of above 70%(e.g.,83.7%for LDs-BTM).Their light-emission properties could be tuned by the modulation ofπ-conjugation effect with methoxy groups at different substituent positions.Their resulting fluorescent nanoparticles(NPs)were demonstrated as specific lipid droplets(LDs)targeting probes with high brightness,good biocompatibility,and satisfactory photostability.LDs-BTM NPs with a large two-photon absorption cross section(σ2=249 GM)were further utilized as ultrabright two-photon fluorescence(2PF)nanoprobes for in vivo retina imaging of live zebrafish by NIR excitation at an ultralow concentration(0.5μmol/L).Integrated histological structures at the tissue level and corresponding fine details at the cellular level of the embryonic retina of live zebrafish were clearly demonstrated.This is the first report of using ultrabright LDs-targeting nanoprobes to accurately measure fine details in the retina with 2PF microscopic technique.These good results are anticipated to open up a new avenue in the development of efficient 2PF emitters for non-invasive bioimaging of living animals.

Golgi-localized MORN1 promotes lipid droplet abundance and enhances tolerance to multiple stresses in Arabidopsis

Lipid droplet(LD)in vegetative tissues has recently been implicated in environmental responses in plants,but its regulation and its function in stress tolerance are not well understood.Here,we identified a Membrane Occupation and Recognition Nexus 1(MORN1)gene as a contributor to natural variations of stress tolerance through genome-wide association study in Arabidopsis thaliana.Characterization of its loss-of-function mutant and natural variants revealed that the MORN1 gene is a positive regulator of plant growth,disease resistance,cold tolerance,and heat tolerance.The MORN1 protein is associated with the Golgi and is also partly associated with LD.Protein truncations that disrupt these associations abolished the biological function of the MORN1 protein.Furthermore,the MORN1 gene is a positive regulator of LD abundance,and its role in LD number regulation and stress tolerance is highly linked.Therefore,this study identifies MORN1 as a positive regulator of LD abundance and a contributor to natural variations of stress tolerance.It implicates a potential involvement of Golgi in LD biogenesis and strongly suggests a contribution of LD to diverse processes of plant growth and stress responses.

Installing the neurospora carotenoid pathway in plants enables cytosolic formation of provitamin A and its sequestration in lipid droplets

Vitamin A deficiency remains a severe global health issue,which creates a need to biofortify crops with provitamin A carotenoids(PACs).Expanding plant cell capacity for synthesis and storing of PACs outside the plastids is a promising biofortification strategy that has been little explored.Here,we engineered PAC formation and sequestration in the cytosol of Nicotiana benthamiana leaves,Arabidopsis seeds,and citrus callus cells,using a fungal(Neurospora crassa)carotenoid pathway that consists of only three enzymes converting C5 isopentenyl building blocks formed from mevalonic acid into PACs,including β-carotene.This strategy led to the accumulation of significant amounts of phytoene and γ-and β-carotene,in addition to fungal,health-promoting carotenes with 13 conjugated double bonds,such as the PAC torulene,in the cytosol.Increasing the isopentenyl diphosphate pool by adding a truncated Arabidopsis hydroxymethylglutaryl-coenzyme A reductase substantially increased cytosolic carotene production.Engineered carotenes accumulate in cytosolic lipid droplets(CLDs),which represent a novel sequestering sink for storing these pigments in plant cytosol.Importantly,β-carotene accumulated in the cytosol of citrus callus cells was more light stable compared to compared with plastidialβ-carotene.Moreover,engineering cytosolic carotene formation increased the number of large-sized CLDs and the levels of β-apocarotenoids,including retinal,the aldehyde corresponding to vitamin A.Collectively,our study opens up the possibility of exploiting the high-flux mevalonic acid pathway for PAC biosynthesis and enhancing carotenoid sink capacity in green and non-green plant tissues,especially in lipid-storing seeds,and thus paves the way for further optimization of carotenoid biofortification in crops.

RNA sequencing-based optimization of biological lipid droplets for sonodynamic therapy to reverse tumor hypoxia and elicit robust immune response

Mitochondria-targeted sonodynamic therapy(SDT)is a promising strategy to inhibit tumor growth and activate the anti-tumor immune responses.Identifying the mechanisms underlying mitochondria-targeted SDT,further optimizing its efficacy,developing novel sonosensitizer carriers with good biocompatibility pose major challenges to the clinical practice of SDT.In this study,we investigated the mechanisms of mitochondria-targeted SDT and demonstrated that it suppressed the mitochondrial electron transport chain(ETC)in pancreatic cancer cells through RNA-sequencing analysis.Based on these findings,we constructed the functional lipid droplets(LDs)(CPI-613/IR780@LDs),which combined mitochondria-targeted SDT with the tricarboxylic acid(TCA)cycle inhibitor CPI-613.CPI-613/IR780@LDs synergistically inhibited the TCA cycle and the ETC of mitochondrial aerobic respiration to reduce oxygen consumption and increase reactive oxygen species(ROS)generation at the tumor site,thus enhancing the efficacy of SDT in hypoxic pancreatic cancer.Moreover,the combination of mitochondria-targeted SDT and anti-PD-1 antibody exhibited excellent tumor inhibition and activated anti-tumor immune responses by increasing tumorinfiltrating CD8+T cells and reducing regulatory T cells,synergistically arresting the growth of both primary and metastatic pancreatic tumors.Meanwhile,lipid droplets are cell-derived biological carriers with natural mitochondrial targeting ability and can achieve efficient hydrophobic drug loading through active phagocytosis.Therefore,the functional lipid droplet-based SDT combined with anti-PD-1 antibody holds great potential in the clinical treatment of hypoxic pancreatic cancer.

Highly lipophilic coumarin fluorophore with excimer-monomer transition property for lipid droplet imaging

Lipid droplet(LD) fluorescent imaging plays an important role in the detection of lipid-related diseases.Due to their poor photostability and low hydrophobicity of currently available LD imaging fluorophores,LD imaging is limited by its short imaging period and low imaging contrast. Herein, we reasonably designed a highly lipophilic compound Cou-Flu with excellent photostability and excimer-monomer transition property. It exhibited weak excimer emission in cytoplasm, but strong monomer emission in LDs,enabling high contrast LD imaging and LD movement tracing in cells. Zebrafish imaging study demonstrated that Cou-Flu was also suitable for in vivo LD detection with excellent sensitivity. We anticipate that Cou-Flu could be widely applied to understand LD-related intracellular activities and even LD-related diseases in the future.

Hydrogen-bond locked purine chromophores with high photostability for lipid droplets imaging in cells and tissues

Recently, hydrogen-bonding has attracted extensive attention in the design of chromophores. Here, a new class of hydrogen-bond locked purine chromophores(HOPs) were reported by introducing a hydroxyphenyl group into the C(6) position of purine. The intramolecular hydrogen bond plays a dominant role to light up these probes. As a bonus, HOPs show high photostability. Moreover, HOPs exhibit remarkable capability for the specific lipid droplets imaging in living cells with excellent biocompatibility and are also potential for diagnosing fatty liver diseases. These results bring important new insights into the photophysics of the purine-based chromophores and provide a new scaffold with high photostability for bioimaging.

Manifesting viscosity changes in lipid droplets during iodined CT contrast media treatment by the real-time and in situ fluorescence imaging

Computed tomography(CT) is one of the most commonly used non-invasive clinical imaging modalities to predict, diagnose and treat the disease. Iodinated contrast media(ICM) is a form of intravenous radiocontrast agent containing iodine, which enhances the visibility of hollow tissue structures in medical CT imaging. ICM may cause allergic reactions, contrast-induced nephropathy, hyperthyroidism and possibly metformin accumulation. It is significant to find out the risk factors, pathogenesis, diagnosis, prevention, and treatment of adverse reactions caused by ICM. Revealing the changes of the lipid droplets(LDs)viscosity in pathophysiological processes such as cancer and iodined contrast media induced adverse reaction is not only important for monitoring the occurrence and development of some pathophysiological processes but also vital for the deep insight of the biological effects of LDs in these pathophysiological processes. A lipid droplets targeted fluorescent probe DN-1 was devised to sense cellular viscosity alteration with high selectivity and sensitivity, which was applied to distinguish cancer cells and normal cells and reveal viscosity changes during iodined CT contrast media treatment.

Constructing D-π-A-π dye to obtain red-emission fluorescent probe for structured illumination microscopy imaging of lipid droplet dynamics

Lipid droplets(LDs)are dynamic organelles interacting with a variety of intracellular organelles.Tracking intracellular LD dynamics employing synthetic small molecules is crucial for biological studies.Fluorescence imaging in the red and near infrared(NIR)region is more suitable for biological imaging due to its low phototoxicity and high signal-to-noise ratio.However,available LD-dyes in the red region with remarkable environmental sensitivity,selectivity for LDs staining are limited.Here,we constructed a red-emission D-π-A-π type LDdye LD 688P with higher environmental sensitivity and suitable“calculated log P”(Clog P)for LDs dynamic imaging.LD 688P was proved to be highly selective and photostable for tracing LD fusion including multiple consecutive fusions and fusions in a centrosymmetric manner by super-resolution microscopy.We believe that the D-π-A-π skeleton would be an efficient strategy to construct red and even NIR-emission dyes.

Autophagic Clearance of Lipid Droplets Alters Metabolic Phenotypes in a Genetic Obesity–Diabetes Mouse Model

Lipid droplets(LDs)are intracellular organelles that store neutral lipids,and their aberrant accumulation is associated with many diseases including metabolic disorders such as obesity and diabetes.Meanwhile,the potential pathological contribu-tions of LDs in these diseases are unclear,likely due to a lack of chemical biology tools to clear LDs.We recently developed LD-clearance small molecule compounds,Lipid Droplets·AuTophagy TEthering Compounds(LD·ATTECs),that are able to induce autophagic clearance of LDs in cells and in the liver of db/db(C57BL/6J Leprdb/Leprdb)mouse model,which is a widely used genetic model for obesity–diabetes.Meanwhile,the potential effects on the metabolic phenotype remain to be elucidated.Here,using the metabolic cage assay and the blood glucose assay,we performed phenotypic characteriza-tion of the effects of the autophagic degradation of LDs by LD·ATTECs in the db/db mouse model.The study reveals that LD·ATTECs increased the oxygen uptake of mice and the release of carbon dioxide,enhanced the heat production of animals,partially enhanced the exercise during the dark phase,decreased the blood glucose level and improved insulin sensitivity.Collectively,the study characterized the metabolic phenotypes induced by LD·ATTECs in an obesity–diabetes mouse model,revealing novel functional impacts of autophagic clearance of LDs and providing insights into LD biology and obesity–dia-betes pathogenesis from the phenotypic perspective.

miR-29a Promotes Lipid Droplet and Triglyceride Formation in HCV Infection by Inducing Expression of SREBP-1c and CAV1

Aims:To examine the regulation of SREBP-1c and CAV1 by microRNA-29a (miR-29a) in cells infected with hepatitis C virus (HCV) in an attempt to control HCV-induced nonalcoholic fatty liver disease.Methods:In order to examine the manipulation of SREBP-1c and CAV1 by miR-29a,oleic acid (OA)-treated JFH-I-infected Huh-7 cells were used.OA was added 24 h post-transfection and gene expression was investigated by qRT-PCR at 48 h post treatment.The functional impact of the observed alteration in SREBP-1c and CAV1 expression was analyzed by examining lipid droplet (LD) and triglyceride (TG) content at 72 h post-OA treatment using light microscopy and spectrophotometry,respectively.Viral load was quantified by qRT-PCR at 72 h post-transfection.Results:OA treatment induced the expression of miR-29a and SREBP-1c,as compared to untreated cells.Forced miR-29a expression led to a significant up-regulation of SREBP-1c as well as CAV1 compared to mock untransfected cells.Ectopic expression of miR-29a resulted in a marked increase in LDs and their respective TGs,while miR-29a antagomirs decreased both the LD and TG content compared to mock untransfected cells.Moreover,forcing the expression of miR-29a in JFH-1 HCV-infected Huh-7 cells resulted in 53% reduction in viral titers compared to mock untransfected Huh-7 cells.Conclusion:Inducing miR-29a expression significantly induces SREBP-1c and CAV1 expression,thereby increasing LDs as well as their respective TGs.Nonetheless,forcing the expression of miR-29a resulted in reduction of HCV RNA levels in Huh-7 cells.

A Lipid Droplet-Associated GFP Reporter-Based Screen Identifies New Fat Storage Regulators in C.elegans

Fat storage disorders including obesity are pandemic human health problems. As a genetically amenable model organism, Caeno- rhabditis elegans has often been used to explore the molecular mechanisms of fat storage regulation. Dye staining of fixed animals and stimulated Raman scattering （SRS） microscopy methods have been used successfully to study fat storage, but a genetic screening system that takes full advantage of C. elegans transparency to perform live imaging of fluorescent protein reporters has not yet been reported. Here, we investigated the tissue-specific expression of the GFP fusion of Perilipin 1 （PLIN1）, a Drosophila lipid droplet-associated protein, in C. elegans. Our results indicate that PLINI：：GFP labels lipid droplets and can be used as a fat storage indicator in live worms. Through an RNAi screen, we further identified several previously uncharacterized new fat storage regulators.