Accumulation Of Lipid Droplets Research Articles

Concurrent inhibition of IR, ITGB1, and CD36 perturbated the interconnected network of energy metabolism and epithelial-to-mesenchymal transition in breast cancer cells.

Altered energy metabolism is an emerging hallmark of cancer and plays a pivotal in cell survival, proliferation, and biosynthesis. In a rapidly proliferating cancer, energy metabolism acts in synergism with epithelial-to-mesenchymal transition (EMT), enabling cancer stemness, dissemination, and metastasis. In this study, an interconnected functional network governing energy metabolism and EMT signaling pathways was targeted through the concurrent inhibition of IR, ITGB1, and CD36 activity. A novel multicomponent MD simulation approach was employed to portray the simultaneous inhibition of IR, ITGB1, and CD36 by a 2:1 combination of Pimozide and Ponatinib. Further, in-vitro studies revealed the synergistic anticancer efficacy of drugs against monolayer as well as tumor spheroids of breast cancer cell lines (MCF-7 and MDA-MB-231). In addition, the combination therapy exerted approximately 40% of the apoptotic population and more than 1.5- to 3-fold reduction in the expression of ITGB1, IR, p-IR, IRS-1, and p-AKT in MCF-7 and MDA-MB-231 cell lines. Moreover, the reduction in fatty acid uptake, lipid droplet accumulation, cancer stemness, and migration properties were also observed. Thus, targeting IR, ITGB1, and CD36 in the interconnected network with the combination of Pimozide and Ponatinib represents a promising therapeutic approach for breast cancer.

A Membrane-Targeting Aggregation-Induced Emission Probe for Monitoring Lipid Droplet Dynamics in Ischemia/Reperfusion-Induced Cardiomyocyte Ferroptosis.

Myocardial ischemia/reperfusion injury (MIRI) is the leading cause of irreversible myocardial damage. A pivotal pathogenic factor is ischemia/reperfusion (I/R)-induced cardiomyocyte ferroptosis, marked by iron overload and lipid peroxidation. However, the impact of lipid droplet (LD) changes on I/R-induced cardiomyocyte ferroptosis is unclear. In this study, an aggregation-induced emission probe, TPABTBP is developed that is used for imaging dynamic changes in LD during myocardial I/R-induced ferroptosis. TPABTBP exhibits excellent LD-specificity, superior capability for monitoring lipophagy, and remarkable photostability. Molecular dynamics (MD) simulation and super-resolution fluorescence imaging demonstrate that the TPABTBP is specifically localized to the phospholipid monolayer membrane of LDs. Imaging LDs in cardiomyocytes and myocardial tissue in model mice with MIRI reveals that the LD accumulation level increase in the early reperfusion stage (0-9h) but decrease in the late reperfusion stage (>24h) via lipophagy. The inhibition of LD breakdown significantly reduces the lipid peroxidation level in cardiomyocytes. Furthermore, it is demonstrated that chloroquine (CQ), an FDA-approved autophagy modulator, can inhibit ferroptosis, thereby attenuating MIRI in mice. This study describes the dynamic changes in LD during myocardial ischemia injury and suggests a potential therapeutic target for early MIRI intervention.

Perilipin1 inhibits Nosema bombycis proliferation by promoting Domeless- and Hop-mediated JAK-STAT pathway activation in Bombyx mori.

Lipid droplets (LDs) are dynamic organelles that participate in the regulation of lipid metabolism and cellular homeostasis inside of cells. LD-associated proteins, also known as perilipins (PLINs), are a family of proteins found on the surface of LDs that regulate lipid metabolism, immunity, and other functions. In silkworms, pébrine disease caused by infection by the microsporidian Nosema bombycis (Nb) is a severe threat to the sericultural industry. Although we found that Nb relies on lipids from silkworms to facilitate its proliferation, the relationship between PLINs and Nb proliferation remains unknown. Here, we found Nb infection caused the accumulation of LDs in the fat bodies of silkworm larvae. The characterized perilipin1 gene (plin1) promotes the accumulation of intracellular LDs and is involved in Nb proliferation. plin1 is similar to perilipin1 in humans and is conserved in all insects. The expression of plin1 was mostly enriched in the fat body rather than in other tissues. Knockdown of plin1 enhanced Nb proliferation, whereas overexpression of plin1 inhibited its proliferation. Furthermore, we confirmed that plin1 increased the expression of the Domeless and Hop in the JAK-STAT immune pathway and inhibited Nb proliferation. Taken together, our current findings demonstrate that plin1 inhibits Nb proliferation by promoting the JAK-STAT pathway through increased expression of Domeless and Hop. This study provides new insights into the complicated connections among microsporidia pathogens, LD surface proteins, and insect immunity.IMPORTANCELipid droplets (LDs) are lipid storage sites in cells and are present in almost all animals. Many studies have found that LDs may play a role in host resistance to pathogens and are closely related to innate immunity. The present study found that a surface protein of insect lipid droplets could not only regulate the morphological changes of lipid droplets but also inhibit the proliferation of a microsporidian pathogen Nosema bombycis (Nb) by activating the JAK-STAT signaling pathway. This is the first discovery of the relationship between microsporidian pathogen and insect lipid surface protein perilipin and insect immunity.

Long-chain acyl-CoA synthetase-4 regulates endometrial decidualization through a fatty acid β-oxidation pathway rather than lipid droplet accumulation.

Lipid metabolism plays an important role in early pregnancy, but its effects on decidualization are poorly understood. Fatty acids (FAs) must be esterified by fatty acyl-CoA synthetases to form biologically active acyl-CoA in order to enter the anabolic and/or catabolic pathway. Long-chain acyl-CoA synthetase 4 (ACSL4) is associated with female reproduction. However, whether it is involved in decidualization is unknown. The expression of ACSL4 in human and mouse endometrium was detected by immunohistochemistry. ACSL4 levels were regulated by the overexpression of ACSL4 plasmid or ACSL4 siRNA, and the effects of ACSL4 on decidualization markers and morphology of endometrial stromal cells (ESCs) were clarified. A pregnant mouse model was established to determine the effect of ACSL4 on the implantation efficiency of mouse embryos. Modulation of ACSL4 detects lipid anabolism and catabolism. Through examining the expression level of ACSL4 in human endometrial tissues during proliferative and secretory phases, we found that ACSL4 was highly expressed during the secretory phase. Knockdown of ACSL4 suppressed decidualization and inhibited the mesenchymal-to-epithelial transition induced by MPA and db-cAMP in ESCs. Further, the knockdown of ACSL4 reduced the efficiency of embryo implantation in pregnant mice. Downregulation of ACSL4 inhibited FA β-oxidation and lipid droplet accumulation during decidualization. Interestingly, pharmacological and genetic inhibition of lipid droplet synthesis did not affect FA β-oxidation and decidualization, while the pharmacological and genetic inhibition of FA β-oxidation increased lipid droplet accumulation and inhibited decidualization. In addition, inhibition of β-oxidation was found to attenuate the promotion of decidualization by the upregulation of ACSL4. The decidualization damage caused by ACSL4 knockdown could be reversed by activating β-oxidation. Our findings suggest that ACSL4 promotes endometrial decidualization by activating the β-oxidation pathway. This study provides interesting insights into our understanding of the mechanisms regulating lipid metabolism during decidualization.

Limonoids isolated from Chisocheton ceramicus Miq. and the antiadipogenic mechanism of action of ceramicine B.

Different types of limonoids have been isolated from plants of the Chisocheton genus, notably from the species Chisocheton ceramicus Miq. which is largely distributed in the Indonesian archipelago and Malaysia region. A variety of natural products have been found in the bark of the tree and characterized as antimicrobial and/or antiproliferative agents. The isolated limonoids include chisomicines A-E, proceranolide, and a few other compounds. A focus is made on a large series of limonoids designated ceramicines Ato Z including derivatives with antiparasitic activities, antioxidant, antimelanogenic, and antiproliferative effectsand/or acting as regulators of lipogenesis. The lead compound in the series is ceramicine B functioning as a potent inhibitor of lipid droplet accumulation (LDA). Extracts from Chisocheton ceramicus and ceramicines have shown anti-LDA effects, with little or no cytotoxic effects. Ceramicine B is the most active compound functioning as a regulator of lipid storage in cells and tissues. Ceramicine B is a transcriptional repressor ofperoxisome proliferator-activated receptor γ (PPARγ) and an inhibitor of phosphorylation of the transcription factor FoxO1, acting via an upstream molecular target. Targeting of glycogen synthase kinase-3β is proposed, based on the analogy with structurally related limonoids known to target this enzyme, and supported by a molecular docking analysis. The target and pathway implicated in ceramicine B activity are discussed. The analysis shed light on ceramicine B as a natural product precursor for the design of novel compounds capable of reducing LDA in cells and of potential interest for the treatment of obesity, liver diseases, and other pathologies.

Inhibition of Lipid Accumulation and Oxidation in Hepatocytes by Bioactive Bean Extracts

During our search for natural resources that can inhibit lipid droplet accumulation (LDA) and potentially prevent metabolic dysfunction-associated fatty liver disease (MAFLD) and its progressive stages, such as metabolic dysfunction-associated steatohepatitis (MASH), eight bean extracts (BE1–BE8) were tested for their ability to inhibit lipid accumulation and oxidation in hepatocytes. Substantial inhibitory effects on LDA with bean extracts (BEs) BE2, BE4, BE5, and BE8 were demonstrated. An advanced lipidomic approach was used to quantify the accumulation and inhibition of intracellular triacylglycerol (TAG) and its oxidized species, TAG hydroperoxide (TGOOH), in hepatocytes under fatty acid-loading conditions. The results show that the antioxidants BE2 and BE8 are potential candidates for regulating TAG and TGOOH accumulation in fatty acid-induced lipid droplets (LDs). This study suggests that bean-based foods inhibit LDs formation by decreasing intracellular lipids and lipid hydroperoxides in the hepatocytes. The metabolic profiling of BEs revealed that BE2 and BE8 contained polyphenolic compounds. These may be potential resources for the development of functional foods and drug discovery targeting MAFLD/MASH.

Unraveling the link between Neuropathy Target Esterase NTE/SWS, lysosomal storage diseases, inflammation, abnormal fatty acid metabolism, and leaky brain barrier.

Mutations in Drosophila Swiss Cheese (SWS) gene or its vertebrate orthologue Neuropathy Target Esterase (NTE) lead to progressive neuronal degeneration in flies and humans. Despite its enzymatic function as a phospholipase is well-established, the molecular mechanism responsible for maintaining nervous system integrity remains unclear. In this study, we found that NTE/SWS is present in surface glia that forms the blood-brain-barrier (BBB) and that NTE/SWS is important to maintain its structure and permeability. Importantly, BBB glia-specific expression of Drosophila NTE/SWS or human NTE in the sws mutant background fully rescues surface glial organization and partially restores BBB integrity, suggesting a conserved function of NTE/SWS. Interestingly, sws mutant glia showed abnormal organization of plasma membrane domains and tight junction rafts accompanied by the accumulation of lipid droplets, lysosomes, and multilamellar bodies. Since the observed cellular phenotypes closely resemble the characteristics described in a group of metabolic disorders known as lysosomal storage diseases (LSDs), our data established a novel connection between NTE/SWS and these conditions. We found that mutants with defective BBB exhibit elevated levels of fatty acids, which are precursors of eicosanoids and are involved in the inflammatory response. Also, as a consequence of a permeable BBB, several innate immunity factors are upregulated in an age-dependent manner, while BBB glia-specific expression of NTE/SWS normalizes inflammatory response. Treatment with anti-inflammatory agents prevents the abnormal architecture of the BBB, suggesting that inflammation contributes to the maintenance of a healthy brain barrier. Considering the link between a malfunctioning BBB and various neurodegenerative diseases, gaining a deeper understanding of the molecular mechanisms causing inflammation due to a defective BBB could help to promote the use of anti-inflammatory therapies for age-related neurodegeneration.

Effects of electroacupuncture of different intensities and durations on PERK/ATF4/CHOP signaling pathway in liver of non-alcoholic fatty liver disease rats.

To analyze the effects of electroacupuncture (EA) at "Fenglong" (ST40) and "Zusanli" (ST36) of different intensities and durations on rats with non-alcoholic fatty liver disease (NAFLD) based on the protein kinase R-like endoplasmic reticulum kinase (PERK)-activating transcription factor 4 (ATF4)-C/EBP homologous protein (CHOP) signaling pathway, so as to explore its mechanism underlying improvement of NAFLD. SD rats were randomly divided into normal diet group, high-fat model group, sham EA group, strong stimulation EA (SEA) group, and weak stimulation EA (WEA) group, with 15 rats in each group. Each group was further divided into 2, 3, and 4-week subgroups. NAFLD rat model was established by feeding a high-fat diet. After successful modeling, rats in the SEA and WEA groups received EA at bilateral ST40 and ST36 with dense and sparse waves (4 Hz/20 Hz) at current intensities of 4 mA (SEA group) and 2 mA (WEA group), lasting for 20 minutes, once a day, 5 days a week with 2 days of rest. The sham EA group only had the EA apparatus connected without electricity. Different duration subgroups were intervened for 2, 3, and 4 weeks. After the intervention, the contents of serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) in rats were detected by an automatic biochemical analyzer；liver morphological changes were observed by Oil Red O staining；real-time fluorescence quantitative PCR and Western blot were used to detect the expression of PERK, ATF4, and CHOP mRNAs and proteins in the rat liver tissue. In the high-fat model group, there was a significant accumulation of red lipid droplets in the liver cells, which was reduced significantly in the SEA group at the 4th week. Compared with the normal diet group with the same treatment duration, the contents of serum ALT, AST, and the expression of PERK, ATF4, and CHOP mRNAs and proteins in the liver tissue were elevated (P<0.01) in the high-fat model group . Compared with the high-fat model group with the same treatment duration, the contents of serum ALT, AST, and the expression of PERK, ATF4, CHOP mRNAs and proteins in the liver tissue were decreased (P<0.01, P<0.05) in the SEA and WEA groups. Compared with the sham EA group with the same treatment duration, the contents of serum ALT, AST, and the expression of PERK, ATF4, and CHOP mRNAs were decreased (P<0.01, P<0.05) in the SEA and WEA groups, the expression of PERK, ATF4, and CHOP proteins in the liver tissue was decreased (P<0.01) in the SEA group at the 2nd, 3rd, and 4th week, the expression of PERK and CHOP proteins at the 2nd, 3rd, 4th week and ATF4 protein at 2nd week in the liver tissue were decreased (P<0.01, P<0.05) in the WEA group. Compared with the SEA group with the same treatment duration, the contents of serum ALT, AST, and the expression of PERK, ATF4, and CHOP mRNAs and proteins in the liver tissue were elevated (P<0.05, P<0.01) in the WEA group. Compared with the 2-week time point within the groups, the contents of serum ALT, AST, and the expression of PERK, ATF4, and CHOP mRNAs and PERK proteins in the liver tissue were decreased (P<0.01, P<0.05) in the SEA and WEA groups at 3rd and 4th week, the expression of ATF4 proteins in the liver tissue was decreased (P<0.01) in the SEA group at 3rd and 4th week, and the expression of CHOP proteins in the liver tissue was decreased (P<0.01) in the SEA group at 4th week and in the WEA group at 3rd and 4th week. Compared with the 3-week time point within the groups, the contents of serum ALT, AST, and the expression of PERK, ATF4, and CHOP mRNAs were significantly decreased (P<0.05, P<0.01) in the SEA and WEA groups at 4th week, the expression of PERK and CHOP proteins in the liver tissue was decreased (P<0.01) in the SEA and WEA groups at 4th week, and the expression of ATF4 protein in the liver tissue was decreased (P<0.05) in the SEA group at 4th week. EA at ST40 and ST36 can significantly improve liver function in NAFLD rats, and its mechanism of action may involve inhibiting PERK expression thereby targeting the downstream ATF4/CHOP signaling pathway to suppress endoplasmic reticulum stress, exerting a liver protective effect；the optimal effect was observed with EA intensity of 4 mA for 4 weeks.

Multiparameter Assessment of Foam Cell Formation Progression Using a Dual-Color Switchable Fluorescence Probe.

The assessment of atherosclerosis (AS) progression has emerged as a prominent area of research. Monitoring various pathological features of foam cell (FC) formation is imperative to comprehensively assess AS progression. Herein, a simple benzospiropyran-julolidine-based probe, BSJD, with switchable dual-color imaging ability was developed. This probe can dynamically and reversibly adjust its molecular structure and fluorescent properties in different polar and pH environments. Such a polarity and pH dual-responsive characteristic makes it superior to single-responsive probes in dual-color imaging of lipid droplets (LDs) and lysosomes as well as monitoring their interaction. By simultaneously tracking various pathological features, including LD accumulation and size changes, lysosome dysfunction, and dynamically regulated lipophagy, more comprehensive information can be obtained for multiparameter assessment of FC formation progression. Using BSJD, not only the activation of lipophagy in the early stages and inhibition in the later phases during FC formation are clearly observed but also the important roles of lipophagy in regulating lipid metabolism and alleviating FC formation are demonstrated. Furthermore, BSJD is demonstrated to be capable of rapidly imaging FC plaque sites in AS mice with fast pharmacokinetics. Altogether, BSJD holds great promise as a dual-color organelle-imaging tool for investigating disease-related LD and lysosome changes and their interactions.

Effect of MEHP on testosterone synthesis via Sirt1/Foxo1/Rab7 signaling pathway inhibition of lipophagy in TM3 cells

Mono-2-ethylhexyl phthalic acid (MEHP) is the most toxic metabolite of the plasticizer di-2-ethylhexyl phthalic acid (DEHP), and studies have shown that MEHP causes serious reproductive effects. However, its exact mechanisms of action remain elusive. In this study, we aimed to investigate the reproductive effects of MEHP and preliminarily explore its underlying molecular mechanisms. We found that TM3 cells gradually secreted less testosterone and intracellular free cholesterol with increasing MEHP exposure. MEHP exposure inhibited lipophagy and the Sirt1/Foxo1/Rab7 signaling pathway in TM3 cells, causing aberrant accumulation of intracellular lipid droplets. Addition of the Sirt1 agonist SRT1720 and Rab7 agonist ML-098 alleviated the inhibition of lipophagy and increased free cholesterol and testosterone contents in TM3 cells. SRT1720 alleviated the inhibitory effect of MEHP on the Sirt1/Foxo1/Rab7 signaling pathway, whereas ML-098 only alleviated the inhibition of Rab7 protein expression by MEHP and had no effect on Sirt1 and Foxo1 protein expression. This suggests that MEHP inhibits lipophagy in TM3 cells by suppressing the Sirt1/Foxo1/Rab7 signaling pathway, ultimately leading to a further decrease in cellular testosterone secretion. This study improves our current understanding of the toxicity and molecular mechanisms of action of MEHP and provides new insights into the reproductive effects of phthalic acid esters.

The fatty liver disease–causing protein PNPLA3-I148M alters lipid droplet–Golgi dynamics

Nonalcoholic fatty liver disease, recently renamed metabolic dysfunction-associated steatotic liver disease (MASLD), is a progressive metabolic disorder that begins with aberrant triglyceride accumulation in the liver and can lead to cirrhosis and cancer. A common variant in the gene PNPLA3, encoding the protein PNPLA3-I148M, is the strongest known genetic risk factor for MASLD. Despite its discovery 20 y ago, the function of PNPLA3, and now the role of PNPLA3-I148M, remain unclear. In this study, we sought to dissect the biogenesis of PNPLA3 and PNPLA3-I148M and characterize changes induced by endogenous expression of the disease-causing variant. Contrary to bioinformatic predictions and prior studies with overexpressed proteins, we demonstrate here that PNPLA3 and PNPLA3-I148M are not endoplasmic reticulum-resident transmembrane proteins. To identify their intracellular associations, we generated a paired set of isogenic human hepatoma cells expressing PNPLA3 and PNPLA3-I148M at endogenous levels. Both proteins were enriched in lipid droplet, Golgi, and endosomal fractions. Purified PNPLA3 and PNPLA3-I148M proteins associated with phosphoinositides commonly found in these compartments. Despite a similar fractionation pattern as the wild-type variant, PNPLA3-I148M induced morphological changes in the Golgi apparatus, including increased lipid droplet-Golgi contact sites, which were also observed in I148M-expressing primary human patient hepatocytes. In addition to lipid droplet accumulation, PNPLA3-I148M expression caused significant proteomic and transcriptomic changes that resembled all stages of liver disease. Cumulatively, we validate an endogenous human cellular system for investigating PNPLA3-I148M biology and identify the Golgi apparatus as a central hub of PNPLA3-I148M-driven cellular change.

Cancer radioresistance is characterized by a differential lipid droplet content along the cell cycle

BackgroundCancer radiation treatments have seen substantial advancements, yet the biomolecular mechanisms underlying cancer cell radioresistance continue to elude full understanding. The effectiveness of radiation on cancer is hindered by various factors, such as oxygen concentrations within tumors, cells’ ability to repair DNA damage and metabolic changes. Moreover, the initial and radiation-induced cell cycle profiles can significantly influence radiotherapy responses as radiation sensitivity fluctuates across different cell cycle stages. Given this evidence and our prior studies establishing a correlation between cancer radiation resistance and an increased number of cytoplasmic Lipid Droplets (LDs), we investigated if LD accumulation was modulated along the cell cycle and if this correlated with differential radioresistance in lung and bladder cell lines.ResultsOur findings identified the S phase as the most radioresistant cell cycle phase being characterized by an increase in LDs. Analysis of the expression of perilipin genes (a family of proteins involved in the LD structure and functions) throughout the cell cycle also uncovered a unique gene cell cycle pattern.ConclusionsIn summary, although these results require further molecular studies about the mechanisms of radioresistance, the findings presented here are the first evidence that LD accumulation could participate in cancer cells’ ability to better survive X-Ray radiation when cells are in the S phase. LDs can represent new players in the radioresistance processes associated with cancer metabolism. This could open new therapeutic avenues in which the use of LD-interfering drugs might enhance cancer sensitivity to radiation.

Diverse effects of a Cyperus rotundus extract on glucose uptake in myotubes and adipocytes and its suppression on adipocyte maturation

Cyperus rotundus rhizomes have been used in longevity remedies in Thailand for nourishing good health, which led us to investigate the effect on energy homeostasis, especially glucose utilization in myotubes and adipocytes, and on inhibition of lipogenesis in adipocytes. The results showed that an ethyl acetate extract of C. rotundus rhizomes (ECR) containing 1.61%w/w piceatannol, with a half-maximal concentration of 17.76 ± 0.03 μg/mL in 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay, caused upregulation and cell-membrane translocation of glucose transporters GLUT4 and 1 in L6 myotubes but downregulation and cytoplasmic localization of GLUT4 expression in 3T3-L1 adipocytes and was related to the p-Akt/Akt ratio in both cells, especially at 100 μg/mL. Moreover, ECR (25–100 μg/mL) significantly inhibited lipid accumulation via Adenosine Monophosphate-Activated Protein Kinase (AMPK), Acetyl CoA Carboxylase (ACC), and Glycogen Synthase Kinase (GSK) pathways. Its immunoblot showed increased expression of p-AMPKα/AMPKα and p-ACC/ACC but decreased expression of p-Akt/Akt and p-GSK3β/GSK3β in 3T3-L1 adipocytes. Moreover, the decreased expression of the adipogenic effectors, perilipin1 and lipoprotein lipase, in ECR-incubated adipocytes (50 and 100 μg/mL) indicated reduced de novo lipogenesis. Our study elucidated mechanisms of C. rotundus that help attenuate glucose tolerance in skeletal muscle and inhibit lipid droplet accumulation in adipose tissue.

IL-33 regulates adipogenesis via Wnt/β-catenin/PPAR-γ signaling pathway in preadipocytes

Interleukin-33 (IL-33), an emerging cytokine within the IL-1 family, assumes a pivotal function in the control of obesity. However, the specific mechanism of its regulation of obesity formation remains unclear. In this study, we found that the expression level of IL-33 increased in visceral adipose tissue in mice fed with a high-fat diet (HFD) compared with that in mice fed with a normal diet (ND). In vitro, we also found the expression level of IL-33 was upregulated during the adipogenesis of 3T3-L1 cells. Functional test results showed that knockdown of IL-33 in 3T3-L1 cells differentiation could promote the accumulation of lipid droplets, the content of triglyceride and the expression of adipogenic–related genes (i.e. PPAR-γ, C/EBPα, FABP4, LPL, Adipoq and CD36). In contrast, overexpression of IL-33 inhibits adipogenic differentiation. Meanwhile, the above tests were repeated after over-differentiation of 3T3-L1 cells induced by oleic acid, and the results showed that IL-33 played a more significant role in the regulation of adipogenesis. To explore the mechanism, transcriptome sequencing was performed and results showed that IL-33 regulated the PPAR signaling pathway in 3T3-L1 cells. Further, Western blot and confocal microscopy showed that the inhibition of IL-33 could promote PPAR-γ expression by inhibiting the Wnt/β-catenin signal in 3T3-L1 cells. This study demonstrated that IL-33 was an important regulator of preadipocyte differentiation and inhibited adipogenesis by regulating the Wnt/β-catenin/PPAR-γ signaling pathway, which provided a new insight for further research on IL-33 as a new intervention target for metabolic disorders.

Diurnal expression of Dgat2 induced by time-restricted feeding maintains cardiac health in the Drosophila model of circadian disruption.

Circadian disruption is associated with an increased risk of cardiometabolic disorders and cardiac diseases. Time-restricted feeding/eating (TRF/TRE), restricting food intake within a consistent window of the day, has shown improvements in heart function from flies and mice to humans. However, whether and how TRF still conveys cardiac benefits in the context of circadian disruption remains unclear. Here, we demonstrate that TRF sustains cardiac performance, myofibrillar organization, and regulates cardiac lipid accumulation in Drosophila when the circadian rhythm is disrupted by constant light. TRF induces oscillations in the expression of genes associated with triglyceride metabolism. In particular, TRF induces diurnal expression of diacylglycerol O-acyltransferase 2 (Dgat2), peaking during the feeding period. Heart-specific manipulation of Dgat2 modulates cardiac function and lipid droplet accumulation. Strikingly, heart-specific overexpression of human Dgat2 at ZT 0-10 significantly improves cardiac performance in flies exposed to constant light. We have demonstrated that TRF effectively attenuates cardiac decline induced by circadian disruption. Moreover, our data suggests that diurnal expression of Dgat2 induced by TRF is beneficial for heart health under circadian disruption. Overall, our findings have underscored the relevance of TRF in preserving heart health under circadian disruptions and provided potential targets, such as Dgat2, and strategies for therapeutic interventions in mitigating cardiac aging, metabolic disorders, and cardiac diseases in humans.

Lycium barbarum polysaccharide ameliorates the accumulation of lipid droplets in adipose tissue via an ATF6/SIRT1-dependent mechanism.

Lipid droplets (LDs) are dynamic organelles that store neutral lipids and are closely linked to obesity. Previous studies have suggested that Lycium barbarum polysaccharide (LBP) supplements can ameliorate obesity, but the underlying mechanisms remain unclear. In this study, we hypothesize that LBP alleviates LD accumulation in adipose tissue (AT) by inhibiting fat-specific protein 27 (Fsp27) through an activating transcription factor-6 (ATF6)/small-molecule sirtuin 1 (SIRT1)-dependent mechanism. LD accumulation in AT is induced in high-fat diet (HFD)-fed mice, and differentiation of 3T3-L1 preadipocytes (PAs) is induced. The ability of LBP to alleviate LD accumulation and the possible underlying mechanism are then investigated both in vivo and in vitro. The influences of LBP on the expressions of LD-associated genes ( ATF6 and Fsp27) are also detected. The results show that HFD and PA differentiation markedly increase LD accumulation in ATs and adipocytes, respectively, and these effects are markedly suppressed by LBP supplementation. Furthermore, LBP significantly activates SIRT1 and decreases ATF6 and Fsp27 expressions. Interestingly, the inhibitory effects of LBP are either abolished or exacerbated when ATF6 is overexpressed or silenced, respectively. Furthermore, SIRT1 level is transcriptionally regulated by LBP through opposite actions mediated by ATF6. Collectively, our findings suggest that LBP supplementation alleviates obesity by ameliorating LD accumulation, which might be partially mediated by an ATF6/SIRT1-dependent mechanism.

Porcine reproductive and respiratory syndrome virus 2 hijacks CMA-mediated lipolysis through upregulation of small GTPase RAB18.

RAB GTPases (RABs) control intracellular membrane trafficking with high precision. In the present study, we carried out a short hairpin RNA (shRNA) screen focused on a library of 62 RABs during infection with porcine reproductive and respiratory syndrome virus 2 (PRRSV-2), a member of the family Arteriviridae. We found that 13 RABs negatively affect the yield of PRRSV-2 progeny virus, whereas 29 RABs have a positive impact on the yield of PRRSV-2 progeny virus. Further analysis revealed that PRRSV-2 infection transcriptionally regulated RAB18 through RIG-I/MAVS-mediated canonical NF-κB activation. Disrupting RAB18 expression led to the accumulation of lipid droplets (LDs), impaired LDs catabolism, and flawed viral replication and assembly. We also discovered that PRRSV-2 co-opts chaperone-mediated autophagy (CMA) for lipolysis via RAB18, as indicated by the enhanced associations between RAB18 and perlipin 2 (PLIN2), CMA-specific lysosomal associated membrane protein 2A (LAMP2A), and heat shock protein family A (Hsp70) member 8 (HSPA8/HSC70) during PRRSV-2 infection. Knockdown of HSPA8 and LAMP2A impacted on the yield of PRRSV-2 progeny virus, implying that the virus utilizes RAB18 to promote CMA-mediated lipolysis. Importantly, we determined that the C-terminal domain (CTD) of HSPA8 could bind to the switch II domain of RAB18, and the CTD of PLIN2 was capable of associating with HSPA8, suggesting that HSPA8 facilitates the interaction between RAB18 and PLIN2 in the CMA process. In summary, our findings elucidate how PRRSV-2 hijacks CMA-mediated lipid metabolism through innate immune activation to enhance the yield of progeny virus, offering novel insights for the development of anti-PRRSV-2 treatments.

Hepatokine ITIH3 protects against hepatic steatosis by downregulating mitochondrial bioenergetics and de novo lipogenesis

Recent studies demonstrate that liver secretory proteins, also known as hepatokines, regulate normal development, obesity, and simple steatosis to non-alcoholic steatohepatitis (NASH) progression. Using a panel of ∼100 diverse inbred strains of mice and a cohort of bariatric surgery patients, we found that one such hepatokine, inter-trypsin inhibitor heavy chain 3 (ITIH3), was progressively lower in severe non-alcoholic fatty liver disease (NAFLD) disease states highlighting an inverse relationship between Itih3/ITIH3 expression and NAFLD severity. Follow-up animal and cell culture models demonstrated that hepatic ITIH3 overexpression lowered liver triglyceride and lipid droplet accumulation, respectively. Conversely, ITIH3 knockdown in mice increased the liver triglyceride in two independent NAFLD models. Mechanistically, ITIH3 reduced mitochondrial respiration and this, in turn, reduced liver triglycerides, via downregulated de novo lipogenesis. This was accompanied by increased STAT1 signaling and Stat3 expression, both of which are known to protect against NAFLD/NASH. Our findings indicate hepatokine ITIH3 as a potential biomarker and/or treatment for NAFLD.

MiR-103-5p deficiency suppresses lipid accumulation via upregulating PLSCR4 and its host gene PANK3 in goat mammary epithelial cells

Lipids are intimately related to the unique flavor and nutritional values of goat milk. MicroRNAs (miRNA) participate in the regulation of various biological functions, including the synthesis and degradation of lipids. Several studies have shown that miR-103 is involved in the regulation of lipid metabolism, however, the molecular mechanism by which miR-103 regulates lipid metabolism in goat mammary gland is poorly understood. In this study, miR-103 was knocked out in goat mammary epithelial cells (GMECs) by CRISPR/Cas9, and the accumulation of lipid droplets, triglycerides, and cholesterol in the cells was suppressed subsequently. Overexpression or knockdown of miR-103-5p and miR-103-3p in GMECs revealed that it was miR-103-5p that promoted lipid accumulation but not miR-103-3p. In addition, Pantothenate Kinase 3 (PANK3), the host gene of miR-103, and Phospholipid Scramblase 4 (PLSCR4) were identified as the target genes of miR-103-5p by dual fluorescein and miRNA pulldown. Furthermore, we identified that cellular lipid levels were negatively regulated by PANK3 and PLSCR4. Lastly, in miR-103 knockout GMECs, the knockdown of PANK and PLSCR4 rescued the lipid accumulation. These findings suggest that miR-103-5p promotes lipid accumulation by targeting PLSCR4 and the host gene PANK3 in GMECs, providing new insights for the regulation of goat milk lipids via miRNAs.

Potential role of lipophagy impairment for anticancer effects of glycolysis-suppressed pancreatic ductal adenocarcinoma cells

Although increased aerobic glycolysis is common in various cancers, pancreatic ductal adenocarcinoma (PDAC) cells can survive a state of glycolysis suppression. We aimed to identify potential therapeutic targets in glycolysis-suppressed PDAC cells. By screening anticancer metabolic compounds, we identified SP-2509, an inhibitor of lysine-specific histone demethylase 1A (LSD1), which dramatically decreased the growth of PDAC PANC-1 cells and showed an anti-tumoral effect in tumor-bearing mice. The growth of glycolysis-suppressed PANC-1 cells was also inhibited by another LSD1 inhibitor, OG-L002. Similarly, the other two PDAC cells (PK-1 and KLM-1) with suppressed glycolysis exhibited anticancer effects against SP-2509. However, the anticancer effects on PDAC cells were unrelated to LSD1. To investigate how PDAC cells survive in a glycolysis-suppressed condition, we conducted proteomic analyses. These results combined with our previous findings suggested that glucose-starvation causes PDAC cells to enhance mitochondrial oxidative phosphorylation. In particular, mitochondrial fatty acid metabolism was identified as a key factor contributing to the survival of PDAC cells under glycolysis suppression. We further demonstrated that SP-2509 and OG-L002 disturbed fatty acid metabolism and induced lipid droplet accumulation through the impairment of lipophagy, but not bulk autophagy. These findings indicate a significant potential association of lipophagy and anticancer effects in glycolysis-suppressed PDAC cells, offering ideas for new therapeutic strategies for PDAC by dual inhibition of glycolysis and fatty acids metabolism.