Cytoplasmic Lipid Droplets Research Articles

Human Herpesvirus 8 and Host-Cell Interaction: Long-Lasting Physiological Modifications, Inflammation and Related Chronic Diseases.

Oncogenic and latent-persistent viruses belonging to both DNA and RNA groups are known to cause serious metabolism alterations. Among these, the Human Herpesvirus 8 (HHV8) infection induces stable modifications in biochemistry and cellular metabolism, which in turn affect its own pathological properties. HHV8 enhances the expression of insulin receptors, supports the accumulation of neutral lipids in cytoplasmic lipid droplets and induces alterations in both triglycerides and cholesterol metabolism in endothelial cells. In addition, HHV8 is also known to modify immune response and cytokine production with implications for cell oxidative status (i.e., reactive oxygen species activation). This review underlines the recent findings regarding the role of latent and persistent HHV8 viral infection in host physiology and pathogenesis.

Cannabinoid receptor 1 knockout alleviates hepatic steatosis by downregulating perilipin 2

The endocannabinoid (EC) system has been implicated in the pathogenesis of several metabolic diseases, including nonalcoholic fatty liver disease (NAFLD). With the current study we aimed to verify the modulatory effect of endocannabinoid receptor 1 (CB1)-signaling on perilipin 2 (PLIN2)-mediated lipophagy. Here, we demonstrate that a global knockout of the cannabinoid receptor 1 gene (CB1−/−) reduced the expression of the lipid droplet binding protein PLIN2 in the livers of CB1−/− and hepatitis B surface protein (HBs)-transgenic mice, which spontaneously develop hepatic steatosis. In addition, the pharmacologic activation and antagonization of CB1 in cell culture also caused an induction or reduction of PLIN2, respectively. The decreased PLIN2 expression was associated with suppressed lipogenesis and triglyceride (TG) synthesis and enhanced autophagy as shown by increased colocalization of LC3B with lysosomal-associated membrane protein 1 (LAMP1) in HBs/CB1−/− mice. The induction of autophagy was further supported by the increased expression of LAMP1 in CB1−/− and HBs/CB1−/− mice. LAMP1 and PLIN2 were co-localized in HBs/CB1−/− indicating autophagy of cytoplasmic lipid droplets (LDs) i.e., lipophagy. Lipolysis of lipid droplets was additionally indicated by elevated expression of lysosomal acid lipase. In conclusion, these results suggest that loss of CB1 signaling leads to reduced PLIN2 abundance, which triggers lipophagy. Our new findings about the association between CB1 signaling and PLIN2 may stimulate translational studies analyzing new diagnostic and therapeutic options for NAFLD.

Lipid Droplet Composition Varies Based on Medaka Fish Eggs Development as Revealed by NIR-, MIR-, and Raman Imaging.

In fertilized fish eggs, lipids are an energy reservoir for the embryo development and substrate for organogenesis. They occur in the cytoplasmic area and form lipid droplets (LDs), but also the yolk egg is composed of lipids and proteins. Insight on the LD formation and distribution and their interactions with other cellular organelles could provide information about the role based on the egg development. For non-destructive, macro-scale visualization of biochemical components of fish eggs, such as lipids proteins and water, near-infrared (NIR) imaging is the method of choice. Mid-infrared (MIR) and Raman spectroscopy imaging were used to provide details on chemical composition of LDs and other egg organelles. NIR imaging illustrated main compartments of the egg including membrane, LDs, yolk, relative protein, and lipid content in well-localized egg structures and their interactions with water molecules. In the yolk, a co-existence of lipids and proteins with carotenoids and carbohydrates was detected by Raman spectroscopy. Results showed a prominent decrease of unsaturated fatty acids, phospholipids, and triglycerides/cholesteryl esters content in the eggs due to the embryo development. An opposite trend of changes was observed by MIR spectroscopy for the glycogen, suggesting that consumption of lipids occurred with production of this carbohydrate. The comprehensive vibrational spectroscopic analysis based on NIR, MIR, and Raman imaging is a unique tool in studying in situ dynamic biological processes.

Emerging Role of Lymphatics in the Regulation of Intestinal Lipid Mobilization.

Intestinal handling of dietary triglycerides has important implications for health and disease. Following digestion in the intestinal lumen, absorption, and re-esterification of fatty acids and monoacylglycerols in intestinal enterocytes, triglycerides are packaged into lipoprotein particles (chylomicrons) for secretion or into cytoplasmic lipid droplets for transient or more prolonged storage. Despite the recognition of prolonged retention of triglycerides in the post-absorptive phase and subsequent release from the intestine in chylomicron particles, the underlying regulatory mechanisms remain poorly understood. Chylomicron secretion involves multiple steps, including intracellular assembly and post-assembly transport through cellular organelles, the lamina propria, and the mesenteric lymphatics before being released into the circulation. Contrary to the long-held view that the intestinal lymphatic vasculature acts mainly as a passive conduit, it is increasingly recognized to play an active and regulatory role in the rate of chylomicron release into the circulation. Here, we review the latest advances in understanding the role of lymphatics in intestinal lipid handling and chylomicron secretion. We highlight emerging evidence that oral glucose and the gut hormone glucagon-like peptide-2 mobilize retained enteral lipid by differing mechanisms to promote the secretion of chylomicrons via glucose possibly by mobilizing cytoplasmic lipid droplets and via glucagon-like peptide-2 possibly by targeting post-enterocyte secretory mechanisms. We discuss other potential regulatory factors that are the focus of ongoing and future research. Regulation of lymphatic pumping and function is emerging as an area of great interest in our understanding of the integrated absorption of dietary fat and chylomicron secretion and potential implications for whole-body metabolic health.

Steryl Ester Formation and Accumulation in Steroid-Degrading Bacteria.

Steryl esters (SEs) are important storage compounds in many eukaryotes and are often prominent components of intracellular lipid droplets. Here, we demonstrate that selected Actino- and Proteobacteria growing on sterols are also able to synthesize SEs and to sequester them in cytoplasmic lipid droplets. We found cholesteryl ester (CE) formation in members of the actinobacterial genera Rhodococcus, Mycobacterium, and Amycolatopsis, as well as several members of the proteobacterial Cellvibrionales order. CEs maximally accumulated under nitrogen-limiting conditions, suggesting that steryl ester formation plays a crucial role for storing excess energy and carbon under adverse conditions. Rhodococcus jostii RHA1 was able to synthesize phytosteryl and cholesteryl esters, the latter reaching up to 7% of its cellular dry weight and 69% of its lipid droplets. Purified lipid droplets from RHA1 contained CEs, free cholesterol, and triacylglycerols. In addition, we found formation of CEs in Mycobacterium tuberculosis when it was grown with cholesterol plus an additional fatty acid substrate. This study provides a basis for the application of bacterial whole-cell systems in the biotechnological production of SEs for use in functional foods and cosmetics.IMPORTANCE Oleaginous bacteria exhibit great potential for the production of high-value neutral lipids, such as triacylglycerols and wax esters. This study describes the formation of steryl esters (SEs) as neutral lipid storage compounds in sterol-degrading oleaginous bacteria, providing a basis for biotechnological production of SEs using bacterial systems with potential applications in the functional food, nutraceutical, and cosmetic industries. We found cholesteryl ester (CE) formation in several sterol-degrading Actino- and Proteobacteria under nitrogen-limiting conditions, suggesting an important role of this process in storing energy and carbon under adverse conditions. In addition, Mycobacterium tuberculosis grown on cholesterol accumulated CEs in the presence of an additional fatty acid substrate.

Organellar Contacts of Milk Lipid Droplets.

Milk-secreting epithelial cells of the mammary gland are functionally specialized for the synthesis and secretion of large quantities of neutral lipids, a major macronutrient in milk from most mammals. Milk lipid synthesis and secretion are hormonally regulated and secretion occurs by a unique apocrine mechanism. Neutral lipids are synthesized and packaged into perilipin-2 (PLIN2) coated cytoplasmic lipid droplets within specialized cisternal domains of rough endoplasmic reticulum (ER). Continued lipid synthesis by ER membrane enzymes and lipid droplet fusion contribute to the large size of these cytoplasmic lipid droplets (5–15 μm in diameter). Lipid droplets are directionally trafficked within the epithelial cell to the apical plasma membrane. Upon contact, a molecular docking complex assembles to tether the droplet to the plasma membrane and facilitate its membrane envelopment. This docking complex consists of the transmembrane protein, butyrophilin, the cytoplasmic housekeeping protein, xanthine dehydrogenase/oxidoreductase, the lipid droplet coat proteins, PLIN2, and cell death-inducing DFFA-like effector A. Interactions of mitochondria, Golgi, and secretory vesicles with docked lipid droplets have also been reported and may supply membrane phospholipids, energy, or scaffold cytoskeleton for apocrine secretion of the lipid droplet. Final secretion of lipid droplets into the milk occurs in response to oxytocin-stimulated contraction of myoepithelial cells that surround milk-secreting epithelial cells. The mechanistic details of lipid droplet release are unknown at this time. The final secreted milk fat globule consists of a triglyceride core coated with a phospholipid monolayer and various coat proteins, fully encased in a membrane bilayer.

МОРФОФУНКЦІОНАЛЬНИЙ СТАН ПІДШЛУНКОВОЇ ЗАЛОЗИ ЩУРІВ ПРИ ВВЕДЕННІ МЕЛАТОНІНУ ПІД ЧАС РОЗВИТКУ ОЖИРІННЯ: ХРОНОТЕРАПЕВТИЧНИЙ ПІДХІД

Overweight and obesity often cause some comorbidity like insulin resistance, diabetes type 2, cancer, cardio-vascular pathology etc. Pancreas is the important organ in carbohydrate metabolism and insulin signaling, that under obesity conditions undergo pathologic changes. For diminish adverse effects of obesity in the role of therapeutic agent is considered melatonin – pineal gland pleiotropic multifunctional molecule. In view of development precision medicine, which include processing personalized data of whole genome sequencing, microbiome, individual day/night regime etc., time selection of drug administration for maximize efficacy and minimize side effects to each patient in according of private organism circadian rhythm is the main goal of chronotherapy approach. The aim of our study was to determine morpho-functional state (morphology characteristic of exocrine and endocrine part; morphometric parameters: areas of pancreatic islets, acini and acinar cell nucleus) of pancreas in rats with high-calorie (high fat) diet-induced obesity after melatonin administration in determined time of the day (evening and morning). Melatonin was administered daily by gavage for 7 weeks in dose 30 mg/kg 1 h before lights-off (ZT11, evening) or 1 h after lights-on (ZT01, morning) rats with high-calorie diet (HCD). Rats with HCD had morbid changes in pancreas cells morphology of exocrine and endocrine part, which manifested in presence of macrophage and leukocyte infiltration of islets, vacuolization and lipid droplets in acinocytes cytoplasm, while areas of islets, acini and acinar cell nucleus decreased. Obese rats with melatonin administration demonstrate amelioration of HCD-associated changes in pancreas. Namely, in rats with development obesity melatonin administrations increased area of pancreatic islets in comparison to HCD group, moreover pancreas acini area reach control values. Also were observed difference between time-of-day interventions of melatonin on acinar cell nucleus area parameters: evening administration showed more strong action in increased to control level direction. Together, is suggesting about melatonin ameliorative role on morpho-functional state of pancreas exocrine and endocrine part under HCD-induced obesity conditions, additionally evening administration 1 h before light-off displayed more beneficial influence compared to morning.

Cytoplasm lipids can be modulated through hormone-sensitive lipase and are related to mitochondrial function in porcine IVM oocytes.

Intracellular lipids provide energy for oocyte maturation and development. Triglycerides are the main components of cytoplasm lipid droplets, and hydrolysis of triglycerides requires several lipase-mediated steps. The aim of this study was to determine the effects of the β-adrenoceptor agonist isoproterenol (ISO) and the hormone-sensitive lipase (HSL) inhibitor CAY10499 on the IVM of porcine oocytes. ISO (5mg L-1) and CAY10499 (20mg L-1) had positive and negative effects respectively on invitro oocyte maturation and subsequent embryo development. The rates of polar body extrusion, cleavage and blastocyst formation were significantly higher in the ISO-treated group than the control and CAY10499-treated groups. ISO treatment also upregulated intracellular cAMP levels in comparison with the control group, while CAY10499 significantly increased the triglyceride content of matured oocytes when compared with other groups, consistent with the observed decrease in LIPE (HSL) mRNA levels. Furthermore, the inhibitory effects of CAY10499 included decreases in mitochondrial membrane potential and mitochondrial temperature. These results indicate that ISO has a positive effect on the IVM of porcine oocytes, and that intracellular lipid metabolism can be modulated by CAY10499 through inhibition of HSL and is closely related to mitochondrial function.

Combination of tanshinone IIA and astragaloside IV attenuate atherosclerotic plaque vulnerability in ApoE(-/-) mice by activating PI3K/AKT signaling and suppressing TRL4/NF-κB signaling

Tanshinone IIA (TS IIA) and Astragaloside IV (AS IV) are natural herbal products which exert anti-inflammatory and anti-oxidant effects in order to eliminate unstable plaque in atherosclerosis. However, the combined effect of these two drugs on atherosclerotic plaque vulnerability and its molecular mechanism remains unclear. In the current study, we evaluate the effects of TS IIA and AS IV on atherosclerotic unstable plaque stability, and then further explore the mechanism of TS IIA and AS IV intervention on unstable plaque in vivo and in vitro. Histological characterization of atherosclerotic plaques was measured by Hematoxylin-Eosin (HE), Masson’s Trichrome and Oil Red O staining. Cellular lipid droplet was measured by Oil Red O staining. The size of atherosclerotic lesion areas and content of lipids and collagen in the right common carotid arteries of apoE-/- mice were examined by Hematoxylin-Eosin (HE), Oil-red O, and Masson staining, respectively. The protein expression levels of interleukin (IL)-6, tumor necrosis factor (TNF)-α and C-reactive protein (CRP) in ApoE−/− mice and RAW264.7 cells were determined by enzyme-linked immunosorbent assay. The protein expression levels of matrix metalloproteinase-9 (MMP-9) and endothelial nitric oxide synthase (eNOS) in ApoE−/− mice and RAW264.7 cells were determined by western blotting. In addition, the PI3K/AKT and TRL4/NF-κB signaling were determined by western blotting. Our results revealed that the combination of TS IIA and AS IV significantly decreased lipid areas, increased collagen content and thickened fibrous cap in the right common carotid arteries compared with ApoE (-/-) mice model group. TS IIA and AS IV visibly reduced the cytoplasmic lipid droplet accumulation induced by oxLDL in RAW 264.7 macrophages. The ApoE−/− mice model group and oxLDL -stimulated RAW 264.7 macrophages treated with TS IIA and AS IV showed a downregulation in IL-6, MMP-9, TNF-α and CRP protein expression and upregulation in eNOS protein expression. Furthermore, TSIIA and AS IV may activate PI3K/AKT signaling and suppress TLR4/NF-κB signaling in vivo and in vitro. Additionally, blocking the PI3K/Akt signaling enhanced the translocation of NF-κB to the nucleus, TLR4, IL-6, MMP-9, TNF-α and CRP expression and inhibited eNOS expression in TS IIA and AS IV-treated RAW 264.7 macrophages. Therefore, the present study implicates that TS IIA and AS IV reinforces plaque stability via PI3K/AKT and TLR4/NF-κB signaling. TS IIA and AS IV administration may provide the basis for a potential therapeutic approach for the inhibition of vulnerable atherosclerotic plaques.

Identification of Low-Abundance Lipid Droplet Proteins in Seeds and Seedlings.

The developmental program of seed formation, germination, and early seedling growth requires not only tight regulation of cell division and metabolism, but also concerted control of the structure and function of organelles, which relies on specific changes in their protein composition. Of particular interest is the switch from heterotrophic to photoautotrophic seedling growth, for which cytoplasmic lipid droplets (LDs) play a critical role as depots for energy-rich storage lipids. Here, we present the results of a bottom-up proteomics study analyzing the total protein fractions and LD-enriched fractions in eight different developmental phases during silique (seed) development, seed germination, and seedling establishment in Arabidopsis (Arabidopsis thaliana). The quantitative analysis of the LD proteome using LD-enrichment factors led to the identification of six previously unidentified and comparably low-abundance LD proteins, each of which was confirmed by intracellular localization studies with fluorescent protein fusions. In addition to these advances in LD protein discovery and the potential insights provided to as yet unexplored aspects in plant LD functions, our data set allowed for a comparative analysis of the LD protein composition throughout the various developmental phases examined. Among the most notable of the alterations in the LD proteome were those during seedling establishment, indicating a switch in the physiological function(s) of LDs after greening of the cotyledons. This work highlights LDs as dynamic organelles with functions beyond lipid storage.

LDAF1 Holds the Key to Seipin Function.

Seipin is an ER protein important for the assembly of cytoplasmic lipid droplets. In this issue of Developmental Cell, Chung etal. (2019) show that a stable seipin-binding protein, LDAF1/promethin, functions with seipin by attracting triacylglycerol and then allowing this lipid to accumulate and partition into nascent droplets.

A novel mutation of ABHD5 gene in a Chanarin Dorfman patient with unusual dermatological findings

BackgroundChanarin Dorfman Syndrome (CDS) is a rare autosomal recessive disorder characterized by the multisytemic accumulation of neutral lipids inside the cytoplasmic lipid droplets. This condition is caused by mutations in the abhydrolase domain containing 5 gene (ABHD5). In CDS the skin involvement is the prevalent and always observed clinical feature, consisting of a non-bullous congenital ichthyosiform erythroderma (NCIE). Moreover, a variable involvement of the liver and neuromuscular system can be also observed. In this report, we aimed to perform the clinical and genetic characterization of a patient affected by CDS with atypical dermatological findings, considering this rare inborn error of neutral lipid metabolism.MethodsGenomic DNA samples obtained from patient and his parents were used to perform the sequencing of the ABHD5 exons and their intron/exon boundaries. Bioinformatic analyses were performed to investigate the possible effect of the identified mutation on protein structure.ResultsHere we present the case of a 29-year-old male patient with CDS, who, for long time, has been misdiagnosed as pityriasis rubra pilaris (PRP). He has a history of increasing hyperlipidemia; hepatomegaly associated with hepatosteatosis was also detected. ABHD5 molecular analysis revealed a novel missense mutation, the c.811G > A (p.G271R). Bioinformatic investigations showed that the variant has a deleterious effect on ABHD5 function, probably causing an incorrect folding of the mutant protein.ConclusionsThese results highlihts the importance of genetic testing for ABHD5 in unresolved cases of patients presenting unusual skin lesions, that resemble PRP, associated with a history of hyperlipidemia and nonalcoholic fatty liver.

DGAT2 partially compensates for lipid-induced ER stress in human DGAT1-deficient intestinal stem cells

Dietary lipids are taken up as FAs by the intestinal epithelium and converted by diacylglycerol acyltransferase (DGAT) enzymes into triglycerides, which are packaged in chylomicrons or stored in cytoplasmic lipid droplets (LDs). DGAT1-deficient patients suffer from vomiting, diarrhea, and protein losing enteropathy, illustrating the importance of this process to intestinal homeostasis. Previously, we have shown that DGAT1 deficiency causes decreased LD formation and resistance to unsaturated FA lipotoxicity in patient-derived intestinal organoids. However, LD formation was not completely abolished in patient-derived organoids, suggesting the presence of an alternative mechanism for LD formation. Here, we show an unexpected role for DGAT2 in lipid metabolism, as DGAT2 partially compensates for LD formation and lipotoxicity in DGAT1-deficient intestinal stem cells. Furthermore, we show that (un)saturated FA-induced lipotoxicity is mediated by ER stress. More importantly, we demonstrate that overexpression of DGAT2 fully compensates for the loss of DGAT1 in organoids, indicating that induced DGAT2 expression in patient cells may serve as a therapeutic target in the future.

Hexokinase is necessary for glucose-mediated photosynthesis repression and lipid accumulation in a green alga

Global primary production is driven largely by oxygenic photosynthesis, with algae as major contributors. The green alga Chromochloris zofingiensis reversibly switches off photosynthesis in the presence of glucose in the light and augments production of biofuel precursors (triacylglycerols) and the high-value antioxidant astaxanthin. Here we used forward genetics to reveal that this photosynthetic and metabolic switch is mediated by the glycolytic enzyme hexokinase (CzHXK1). In contrast to wild-type, glucose-treated hxk1 mutants do not shut off photosynthesis or accumulate astaxanthin, triacylglycerols, or cytoplasmic lipid droplets. We show that CzHXK1 is critical for the regulation of genes related to photosynthesis, ketocarotenoid synthesis and fatty acid biosynthesis. Sugars play fundamental regulatory roles in gene expression, physiology, metabolism, and growth in plants and animals, and we introduce a relatively simple, emerging model system to investigate conserved eukaryotic sugar sensing and signaling at the base of the green lineage.

Analysis of the Expression of Genes Related to Lipidic and Glycogenic Metabolism in Pleomorphic Adenomas and Carcinomas Ex Pleomorphic Adenomas

Abstract Introduction The carcinoma ex pleomorphic adenoma (CXPA) arises from a pleomorphic adenoma (PA) and is supposed to gain lipogenesis and glycogenesis during its malignant transformation. Increased lipogenesis is a characteristic of cancer cells, consisting of increased fatty acid synthesis by the enzyme fatty acid synthase (FASN) and by the accumulation of cytoplasmic lipid droplets, which express adipophilin. The increase in glycolytic metabolism has been associated with the activity of glycolytic enzymes and glucose transporters (GLUTs), whose expression is induced by HIF-1 (inducing factor of hypoxia 1). Objectives To analyze the gene expression of FASN, adipophilin, HIF-1α, and GLUT-1 in PA and CXPA samples. Methodology Gene expression analysis of the FASN, adipophilin, HIF1-α, and GLUT-1 genes was performed by the real-time PCR (qPCR) method. Fourteen cases of PA and 14 cases of CXAP were evaluated. Results FASN, adipophilin, HIF-1α, and GLUT-1 were more expressed in CXAP than in AP, although there was no significant difference between levels of adipophilin expression in CXPA and PA. Conclusion Increased expression of FASN, HIF1-α, and GLUT-1 in CXAP may be associated with malignant transformation of PA, while additional studies are needed to understand the role of adipophilin in PA carcinogenesis. Moreover, this is the first study to investigate the role of these genes in the malignant transformation of PA.

A modified in vitro tool for isolation and characterization of rat quiescent islet stellate cells

BackgroundIslet stellate cells (ISCs) play a critical role in islet fibrosis, contributing to the progression of pancreatic diseases. Previous studies have focused on fibrosis-associated activated ISCs obtained by standard islet explant techniques. However, in vitro models of quiescent ISCs (qISCs) are lacking. This study aims to develop a method to isolate qISCs and analyze their phenotype during activation. MethodsImmunofluorescence staining was applied to localize ISCs in normal human, rat, and mouse islets. qISCs were isolated from rat islets using density gradient centrifugation (DGC) method. qRT-PCR, immunoblotting, proliferation, and migration assays were employed for their characterization. ResultsDesmin-positive ISCs were detected in normal human, rat, and mouse islets. Freshly isolated qISCs, obtained by density gradient centrifugation, displayed a polygonal appearance with refringent cytoplasmic lipid droplets and expressed transcriptional markers indicating a low activation/quiescent state. With increasing culture time, the marker expression pattern changed, reflecting ISC activation. qISCs contained more lipid droplets and exhibited lower proliferation and migration abilities compared to spindle-shaped ISCs obtained by traditional explant techniques. ConclusionsThis study describes a new method for efficient isolation of qISCs from rat islets, representing a useful in vitro tool to study the biology of ISCs in more physiological conditions.

Role of Lipid Droplets in the Development of Oocytes and Preimplantation Embryos in Mammals

Lipids are one of the most common and important cell components. Particularly, cytoplasmic lipid droplets (LDs) play a crucial role in cellular energy metabolism. The consideration of the methods for studying intracellular lipids and their composition and role during the oocyte maturation and early embryonic development are the main directions of this review. Recent studies demonstrate that LDs in oocytes and embryos are not only repositories of the energy substrate but also active intracellular structures that perform many other functions.

Expression and significance of urinary microRNA in patients with chronic hepatitis B.

The aim of this study was to investigate the alterations of urinary microRNA (miRNA) expression and explore its clinical significance in patients with chronic hepatitis B (CHB).The expression levels of urinary miRNA were detected by miRNA microarray and quantitative reverse transcription polymerase chain reaction (qRT-PCR) from 106 CHB and 40 healthy controls (Ctrl) subjects. The correlation between the levels of miRNA expression and clinical characteristics were analyzed. Receiver-operator characteristic (ROC) curves were generated to determine the specificity and sensitivity of each individual miRNA. MiRNAs expression were further measured by PCR from exosomes, which were isolated from urine samples. LX2 cells were transfected with miRNA inhibitor and accumulation of cytoplasmic lipid droplets was analyzed by Oil Red O staining.miRNA expression profile analysis showed that 22 miRNAs were upregulated and 55 miRNAs were downregulated in CHB patients compared with Ctrl subjects (fold-change>1.5 and P < .05). miR-92b-3p, miR-770-5p, miR-5196-5p, and miR-7855-5p were significantly higher (P < .0001) in CHB subjects than in Ctrl subjects. ROC curve analysis showed that these four miRNAs were sensitive and specific enough to distinguish CHB and Ctrl subjects. The levels of miR-92b-3p expression were negatively correlated with total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), and APOA-1. Moreover, in vitro experiments indicated that inhibition of miR-92b-3p increased lipid droplet formation in LX2 cells.Aberrant expression of miRNAs has been observed in urine of CHB patients. Our findings may provide novel insights into the pathogenesis of CHB and may assist in the diagnosis of patients with CHB.

HADHA overexpression disrupts lipid metabolism and inhibits tumor growth in clear cell renal cell carcinoma

Hydroxyacyl-CoA dehydrogenase alpha subunit (HADHA) is a key lipid metabolic enzyme with a novel role in carcinogenesis. We previously reported that HADHA, a prognostic marker, was downregulated in clear cell renal cell carcinoma (ccRCC). Herein, the tumor inhibitory role of HADHA overexpression in ccRCC was investigated further. The quantitative proteomic analysis displayed that a total of 1293 and 1293 proteins were identified in HADHA overexpressed 786-O-hadha and vector-transfected control 786-O-vc cells, respectively, and 206 proteins were found to be up- or downregulated. PANTHER, OmicsNet, STRING, and DAVID tools were utilized on the dysregulated proteins in order to elucidate multiple metabolic pathways (especial lipid metabolism) and lipid metabolism-related proteins (e.g. ACAT1, ACLY). The dysregulation of the lipid metabolic enzymes, ACAT1, ACLY, CYB5R3 and FASN, were confirmed by Western blotting. Further assays demonstrated that HADHA overexpression significantly inhibited cell growth, induced cell apoptosis, and decreased the formation of cytoplasmic lipid droplets (LDs); moreover, it also inhibited tumor growth and lessened the formation of LDs in xenografted mouse. Collectively, these data revealed that HADHA overexpression disrupted lipid metabolism and inhibited tumor growth, which shed light on HADHA as a potential therapeutic target for clinical intervention of ccRCC.

Neutral Lipids Are Not a Source of Arachidonic Acid for Lipid Mediator Signaling in Human Foamy Monocytes

Human monocytes exposed to free arachidonic acid (AA), a secretory product of endothelial cells, acquire a foamy phenotype which is due to the accumulation of cytoplasmic lipid droplets with high AA content. Recruitment of foamy monocytes to the inflamed endothelium contributes to the development of atherosclerotic lesions. In this work, we investigated the potential role of AA stored in the neutral lipids of foamy monocytes to be cleaved by lipases and contribute to lipid mediator signaling. To this end, we used mass spectrometry-based lipidomic approaches combined with strategies to generate monocytes with different concentrations of AA. Results from our experiments indicate that the phospholipid AA pool in monocytes is stable and does not change upon exposure of the cells to the external AA. On the contrary, the AA pool in triacylglycerol is expandable and can accommodate relatively large amounts of fatty acid. Stimulation of the cells with opsonized zymosan results in the expected decreases of cellular AA. Under all conditions examined, all of the AA decreases observed in stimulated cells were accounted for by decreases in the phospholipid pool; we failed to detect any contribution of the triacylglycerol pool to the response. Experiments utilizing selective inhibitors of phospholipid or triacylglyerol hydrolysis confirmed that the phospholipid pool is the sole contributor of the AA liberated by stimulated cells. Thus, the AA in the triacylglycerol is not a source of free AA for the lipid mediator signaling during stimulation of human foamy monocytes and may be used for other cellular functions.