Size Of Lipid Droplets Research Articles

Impaired suppression of fatty acid release by insulin is a strong predictor of reduced whole-body insulin-mediated glucose uptake and skeletal muscle insulin receptor activation.

To examine factors underlying why most, but not all, adults with obesity exhibit impaired insulin-mediated glucose uptake, we compared: (1) adipose tissue fatty acid (FA) release, (2) skeletal muscle lipid droplet (LD) characteristics, and (3) insulin signalling events, in skeletal muscle of adults with obesity with relatively high versus low insulin-mediated glucose uptake. Seventeen adults with obesity (BMI: 36 ± 3 kg/m2) completed a 2 h hyperinsulinemic-euglycemic clamp with stable isotope tracer infusions to measure glucose rate of disappearance (glucose Rd) and FA rate of appearance (FA Ra). Skeletal muscle biopsies were collected at baseline and 30 min into the insulin infusion. Participants were stratified into HIGH (n = 7) and LOW (n = 10) insulin sensitivity cohorts by their glucose Rd during the hyperinsulinemic clamp (LOW< 400; HIGH >550 nmol/kgFFM/min/[μU/mL]). Insulin-mediated suppression of FA Ra was lower in LOW compared with HIGH (p < 0.01). In skeletal muscle, total intramyocellular lipid content did not differ between cohorts. However, the size of LDs in the subsarcolemmal region (SS) of type II muscle fibres was larger in LOW compared with HIGH (p = 0.01). Additionally, insulin receptor-β (IRβ) interactions with regulatory proteins CD36 and Fyn were lower in LOW versus HIGH (p < 0.01), which aligned with attenuated insulin-mediated Tyr phosphorylation of IRβ and downstream insulin-signalling proteins in LOW. Collectively, reduced ability for insulin to suppress FA mobilization, with accompanying modifications in intramyocellular LD size and distribution, and diminished IRβ interaction with key regulatory proteins may be key contributors to impaired insulin-mediated glucose uptake commonly found in adults with obesity.

Adipose tissue/ heart lipid transport determines cardiac diastolic function

Abstract Introduction Heart failure with preserved ejection fraction (HFpEF) is characterized by diastolic dysfunction and often occurring in obese individuals. Previous research has demonstrated that the modification of lipid metabolism can prevent the onset of diastolic dysfunction. In our project we have investigated how lipid transport influences the onset of diastolic dysfunction utilizing heart- and adipose tissue-specific knockdowns of the fatty acid (FA) transport protein 1 (FatP1) in Drosophila melanogaster. Methods We generated Drosophila with heart-specific (+/+; Hand4.2-GAL4/UAS-FatP1; tdtK/+) (cFatP1-KD) and adipose tissue-specific (+/+; ppl-GAL4/UAS-FatP1; tdtK/+) (atFat-P1-KD) FatP1 knockdowns using the UAS/GAL4 system. The flies' cardiomyocytes endogenously express tdTomato, facilitating fluorescence-based live imaging of the heart by high-resolution video fluorescence microscopy, as previously described. Cardiac morphology and cardiac lipid accumulation was monitored by confocal microscopy. Additionally, mitochondrial function was evaluated using the glycolytic Seahorse assay of whole hearts. Results Blocking FA-uptake into adipose tissue in atFatP1-KD flies resulted in a highly significant reduction in relaxation velocity (p=0.0009, WT vs. atFatP1-KD), indicative of diastolic dysfunction in flies, while contraction velocity and fractional shortening (systolic function) remained unchanged. Diastolic dysfunction was associated with a significant increase of cardiac lipid droplet (LD) quantity and size in flies lacking FatP1 in adipose tissue (p=0.0275 and p&amp;lt;0.0001, respectively, WT vs. atFatP1-KD). Cardiac mitochondrial function was significantly impaired in atFatP1-KD flies compared to WT flies. Reducing cardiac FA uptake in heart-specific FatP1 KD flies led to a decrease in end-diastolic diameter and a significant reduction in relaxation and contraction velocity (p&amp;lt;0.0001 and p=0.0001, respectively, WT vs. cFatP1-KD), suggesting impairment in both diastolic and systolic function. Interestingly, the number of cardiac LDs increased in cFATP1-KD, however their size decreased significantly resulting in an overall unchanged lipid content compared to WT flies (p=0.0475 and p=0.0367, respectively, WT vs. atFatP1-KD). Mitochondrial function showed no significant alterations. Conclusion This study demonstrates that reducing FA-uptake in adipose or cardiac tissue results in cardiac dysfunction in Drosophila melanogaster. Reduction of adipose tissue FA-uptake results exclusively in diastolic dysfunction likely mediated by cardiac lipid overload and subsequent mitochondrial dysfunction. In contrast, blockade of Fatp1-mediated cardiac FA-uptake induces diastolic/ systolic dysfunction which was unrelated to alterations in cardiac lipid content and mitochondrial dysfunction suggesting alternative mechanisms. These study identifies FatP1-mediated FA-uptake in adipose tissue as a potential therapeutic target for the treatment of diastolic dysfunction.

HuR-dependent expression of RyR2 contributes to calcium-mediated thermogenesis in brown adipocytes.

Several uncoupling protein 1 (UCP1)-independent thermogenic pathways have been described in thermogenic adipose tissue, including calcium-mediated thermogenesis in beige adipocytes via sarco/endoplasmic reticulum ATPase (SERCA). We have previously shown that adipocyte-specific deletion of the RNA binding protein human antigen R (HuR) results in thermogenic dysfunction independent of UCP1 expression. RNA sequencing revealed the downregulation of several genes involved in calcium ion transport upon HuR deletion. The goal of this work was to define the HuR-dependent mechanisms of calcium driven thermogenesis in brown adipocytes. We generated (BAT)-specific HuR-deletion (BAT-HuR -/- ) mice and show that their body weight, glucose tolerance, brown and white adipose tissue weights, and total lipid droplet size were not significantly different compared to wild-type. Similar to our initial findings in Adipo-HuR -/- mice, mice with BAT-specific HuR deletion are cold intolerant following acute thermal challenge at 4°C, demonstrating specificity of acute HuR-dependent thermogenesis to BAT. We also found decreased expression of ryanodine receptor 2 (RyR2), but no changes in RyR2, SERCA1, SERCA2, or UCP1 expression, in BAT from BAT-HuR -/- mice. Next, we used Fluo-4 calcium indicator dye to show that genetic deletion or pharmacological inhibition of HuR blunts the increase in cytosolic calcium concentration in SVF-derived primary brown adipocytes. Moreover, we saw a similar blunting in β-adrenergic-mediated heat generation, as assessed by ERtherm AC fluorescence, in SVF-derived brown adipocytes following HuR inhibition or deletion. Mechanistically, we show that HuR directly binds and reduces the decay rate of RyR2 mRNA in brown adipocytes, and stabilization of RyR2 via S107 rescues β-adrenergic-mediated cytosolic calcium increase and heat generation in HuR deficient brown adipocytes. In conclusion, our results suggest that HuR-dependent control of RyR2 expression plays a significant role in the thermogenic function of brown adipose tissue through modulation of SR calcium cycling.

Lipid droplet-associated proteins in alcohol-associated fatty liver disease: A proteomic approach.

The earliest manifestation of alcohol-associated liver disease (ALD) is steatosis characterized by deposition of fat in specialized organelles called lipid droplets (LDs). While alcohol administration causes a rise in LD numbers in the hepatocytes, little is known regarding their characteristics that allow their accumulation and size to increase. The aim of the present study is to gain insights into underlying pathophysiological mechanisms by investigating the ethanol-induced changes in hepatic LD proteome as a function of LD size. Adult male Wistar rats (180-200 g BW) were fed with ethanol liquid diet for 6 weeks. At sacrifice, large-, medium-, and small-sized hepatic LD subpopulations (LD1, LD2, and LD3, respectively) were isolated and subjected to morphological and proteomic analyses. Morphological analysis of LD1-LD3 fractions of ethanol-fed rats clearly demonstrated that LD1 contained larger LDs compared with LD2 and LD3 fractions. Our preliminary results from principal component analysis showed that the proteome of different-sized hepatic LD fractions was distinctly different. Proteomic data analysis identified over 2000 proteins in each LD fraction with significant alterations in protein abundance among the three LD fractions. Among the altered proteins, several were related to fat metabolism, including synthesis, incorporation of fatty acid, and lipolysis. Ingenuity pathway analysis revealed increased fatty acid synthesis, fatty acid incorporation, LD fusion, and reduced lipolysis in LD1 compared to LD3. Overall, the proteomic findings indicate that the increased level of protein that facilitates fusion of LDs combined with an increased association of negative regulators of lipolysis dictates the generation of large-sized LDs during the development of alcohol-associated hepatic steatosis. Several significantly altered proteins were identified in different-sized LDs isolated from livers of ethanol-fed rats. Ethanol-induced increases in specific proteins that hinder LD lipid metabolism led to the accumulation and persistence of large-sized LDs in the liver.

Lipid droplet distribution in Atlantic salmon (Salmo salar L.) oocytes is related to the fertilisation and developmental outcome

At present, there is no simple and practical applicable method to determine the quality of Atlantic salmon oocytes upon collection at the fish farm. Investigating oocyte lipid droplet patterns might be a tool for the aquaculture industry to predict oocyte quality in Atlantic salmon. While examining the lipid distribution in oocyte batches from 16 females of Atlantic salmon with a range in fertilisation rate (6–97 %), five categories of lipid droplet patterns were distinguished. In category 1, the lipid droplets were evenly distributed whereas in the remaining categories lipid droplets showed varying degree of coalescence. Categories 2, 3, 4 and 5 were distinguished based on the area of coalesced lipid droplets. The fertilisation rate was observed to be high (≥ 90 %), in females that had more oocytes from category 1, 2 and 3 whereas females with more oocytes from category 4 and 5 showed a low fertilisation rate (<90 %). A similar pattern was revealed between lipid droplet categories and eyed embryo and hatching success. Staining of salmon oocytes further confirmed the observed lipid droplet patterns, and different sizes of lipid droplets were present in almost all oocytes. The study revealed a significant association between lipid droplet category and fertilisation outcome in oocytes of Atlantic salmon that can be a practical tool for predicting oocyte quality.

Optimised methods to image hepatic lipid droplets in zebrafish larvae.

The optical transparency of zebrafish larvae enables visualization of subcellular structures in intact organs, and these vertebrates are widely used to study lipid biology and liver disease. Lipid droplet (LD) presence is a prevalent feature of healthy cells but under conditions such as nutrient excess, toxicant exposure or metabolic imbalance, LD accumulation in hepatocytes can be a harbinger of more severe forms of liver disease. We undertook a comprehensive analysis of approaches useful to investigate LD distribution and dynamics in physiological and pathological conditions in the liver of zebrafish larvae. This comparative analysis of the lipid dyes oil red O (ORO), Nile Red (NR), LipidTox and LipidSpot as well as transgenic LD reporters that rely on EGFP fusions of the LD decorating protein perilipin 2 (PLIN2) demonstrate the strengths and limitations of each approach. These protocols are amenable to detection methods ranging from low resolution stereomicroscopy to confocal imaging, which enables measurements of hepatic LD size, number and dynamics at cellular resolution in live and fixed animals. This resource will benefit investigators studying LD biology in zebrafish disease models.

The mitigating role of lysophospholipids in hepatic lipid metabolism and intestinal immunity in juvenile black seabream (Acanthopagrus schlegelii) fed a high-fat diet

An 8-week feeding experiment investigated the effects of lysophospholipids (LP) on growth performance, hepatic lipid metabolism, intestinal immunity and antioxidation in juvenile black seabream (Acanthopagrus schlegelii) (initial weight 4.60 ± 0.01 g) on a high-fat diet. Five experimental diets were established: normal fat diet (13 %, CON), high-fat diet (18 %, HFD) and HFD with different levels of LP (0.05 %, 0.1 %, and 0.2 %). The results indicated that dietary LP had no impact on the specific growth rate and survival rate of juvenile black seabream (P > 0.05), while 0.2 %LP supplementation reduced the intraperitoneal fat ratio (IPF) (P < 0.05). Dietary 0.1 % and 0.2 %LP supplementation reduced the total lipid content and the size and number of lipid droplets in the liver (P < 0.05). The diets supplemented with LP reduced the contents of TG and LDL-C in the serum (P < 0.05), without affecting T-CHO and HDL-C (P > 0.05). The expression of lipid transport genes including apoa, apob, fatp1, and fatp4, were markedly up-regulated with increased dietary LP supplementation (P < 0.05). Moreover, dietary 0.2 %LP supplementation notably increased mRNA expression levels of scarb1, ffar3, acsl5 and glp-1 in the intestine (P < 0.05). Dietary LP notably down-regulated the mRNA expression of genes related to the lipogenesis pathway including fas, aco and srebp-1c, while up-regulating mRNA expression of lipogenesis-related genes including cpt1α, lpl, and pparα (P < 0.05). Additionally, dietary 0.2 %LP supplementation notably increased total antioxidant capacity in the intestine and up-regulated expression levels of intestinal antioxidant genes, including mn sod, cu-zn sod, gpx, and cat (P < 0.05), fish fed diets with 0.2 %LP down-regulation of pro-inflammatory genes, including tnfα and nf-κb, and up-regulation of anti-inflammatory factors, tgfβ-1, il-10 and tight-junction protein genes including (oclna, cldni, cldn3, and tjp1b) in the intestine (P < 0.05). In conclusion, dietary LP improved intestinal fatty acid transport and liver lipolysis, alleviating intestinal oxidative damage and inflammatory reactions caused by HFD in black seabream.

Female-age-dependent changes in the lipid fingerprint of the mammalian oocytes.

Can oocyte functionality be assessed by observing changes in their intracytoplasmic lipid droplets (LDs) profiles? Lipid profile changes can reliably be detected in human oocytes; lipid changes are linked with maternal age and impaired developmental competence in a mouse model. In all cellular components, lipid damage is the earliest manifestation of oxidative stress (OS), which leads to a cascade of negative consequences for organelles and DNA. Lipid damage is marked by the accumulation of LDs. We hypothesized that impaired oocyte functionality resulting from aging and associated OS could be assessed by changes in LDs profile, hereafter called lipid fingerprint (LF). To investigate if it is possible to detect differences in oocyte LF, we subjected human GV-stage oocytes to spectroscopic examinations. For this, a total of 48 oocytes derived from 26 young healthy women (under 33 years of age) with no history of infertility, enrolled in an oocyte donation program, were analyzed. Furthermore, 30 GV human oocytes from 12 women were analyzed by transmission electron microscopy (TEM). To evaluate the effect of oocytes' lipid profile changes on embryo development, a total of 52 C57BL/6 wild-type mice and 125 Gnpat+/- mice were also used. Human oocytes were assessed by label-free cell imaging via coherent anti-Stokes Raman spectroscopy (CARS). Further confirmation of LF changes was conducted using spontaneous Raman followed by Fourier transform infrared (FTIR) spectroscopies and TEM. Additionally, to evaluate whether LF changes are associated with developmental competence, mouse oocytes and blastocysts were evaluated using TEM and the lipid dyes BODIPY and Nile Red. Mouse embryonic exosomes were evaluated using flow cytometry, FTIR and FT-Raman spectroscopies. Here we demonstrated progressive changes in the LF of oocytes associated with the woman's age consisting of increased LDs size, area, and number. LF variations in oocytes were detectable also within individual donors. This finding makes LF assessment a promising tool to grade oocytes of the same patient, based on their quality. We next demonstrated age-associated changes in oocytes reflected by lipid peroxidation and composition changes; the accumulation of carotenoids; and alterations of structural properties of lipid bilayers. Finally, using a mouse model, we showed that LF changes in oocytes are negatively associated with the secretion of embryonic exosomes prior to implantation. Deficient exosome secretion disrupts communication between the embryo and the uterus and thus may explain recurrent implantation failures in advanced-age patients. Due to differences in lipid content between different species' oocytes, the developmental impact of lipid oxidation and consequent LF changes may differ across mammalian oocytes. Our findings open the possibility to develop an innovative tool for oocyte assessment and highlight likely functional connections between oocyte LDs and embryonic exosome secretion. By recognizing the role of oocyte LF in shaping the embryo's ability to implant, our original work points to future directions of research relevant to developmental biology and reproductive medicine. This research was funded by National Science Centre of Poland, Grants: 2021/41/B/NZ3/03507 and 2019/35/B/NZ4/03547 (to G.E.P.); 2022/44/C/NZ4/00076 (to M.F.H.) and 2019/35/N/NZ3/03213 (to Ł.G.). M.F.H. is a National Agency for Academic Exchange (NAWA) fellow (GA ULM/2019/1/00097/U/00001). K.F. is a Diamond Grant fellow (Ministry of Education and Science GA 0175/DIA/2019/28). The open-access publication of this article was funded by the Priority Research Area BioS under the program "Excellence Initiative - Research University" at the Jagiellonian University in Krakow. The authors declare no competing interest. N/A.

Elongation factor 1A1 inhibition elicits changes in lipid droplet size, the bulk transcriptome, and cell type-associated gene expression in MASLD mouse liver.

Eukaryotic elongation factor 1A1 (EEF1A1), originally identified for its role in protein synthesis, has additional functions in diverse cellular processes. Of note, we previously discovered a role for EEF1A1 in hepatocyte lipotoxicity. We also demonstrated that a 2-wk intervention with the EEF1A1 inhibitor didemnin B (DB) (50 µg/kg) decreased liver steatosis in a mouse model of obesity and metabolic dysfunction-associated steatotic liver disease (MASLD) [129S6/SvEvTac mice fed Western diet (42% fat) for 26 wk]. Here, we further characterized the hepatic changes occurring in these mice by assessing lipid droplet (LD) size, bulk differential expression, and cell type-associated alterations in gene expression. Consistent with the previously demonstrated decrease in hepatic steatosis, we observed decreased median LD size in response to DB. Bulk RNA sequencing (RNA-Seq) followed by gene set enrichment analysis revealed alterations in pathways related to energy metabolism and proteostasis in DB-treated mouse livers. Deconvolution of bulk data identified decreased cell type association scores for cholangiocytes, mononuclear phagocytes, and mesenchymal cells in response to DB. Overrepresentation analyses of bulk data using cell type marker gene sets further identified hepatocytes and cholangiocytes as the primary contributors to bulk differential expression in response to DB. Thus, we show that chemical inhibition of EEF1A1 decreases hepatic LD size and decreases gene expression signatures associated with several liver cell types implicated in MASLD progression. Furthermore, changes in hepatic gene expression were primarily attributable to hepatocytes and cholangiocytes. This work demonstrates that EEF1A1 inhibition may be a viable strategy to target aspects of liver biology implicated in MASLD progression.NEW & NOTEWORTHY Chemical inhibition of EEF1A1 decreases hepatic lipid droplet size and decreases gene expression signatures associated with liver cell types that contribute to MASLD progression. Furthermore, changes in hepatic gene expression are primarily attributable to hepatocytes and cholangiocytes. This work highlights the therapeutic potential of targeting EEF1A1 in the setting of MASLD, and the utility of RNA-Seq deconvolution to reveal valuable information about tissue cell type composition and cell type-associated gene expression from bulk RNA-Seq data.

Glandular cell products in adult cestode: A new tale of tapeworm interaction with fish innate immune response

The caryophyllidean tapeworm Caryophyllaeus brachycollis (Janiszewska, 1953) is indigenous to the Lake Blidinje in the west-central part of Bosnia-Herzegovina where it infects chub Squalius tenellus (Heckel, 1843). Of 22 chubs examined, 45% were infected with C. brachycollis and a total of 912 specimens of this worm were counted. Histopathological and ultrastructural investigations were conducted on interface region between chub intestine and cestode scolex. Different sizes of lipid droplets in cestode tegument, in interface region and in chub enterocytes were observed. C. brachycollis lacks any specialized attachment organs and with an expanded, flattened scolex goes deep in mucosal folds and firmly attaches to them. In the epithelium of fish intestine, near the site of worm attachment, a high number of mucous cells and several rodlet cells were noticed. Indeed, within the intestinal tunica propria-submucosa, beneath the site of scolex attachment, numerous neutrophils and mast cells were encountered. Transmission electron microscopy of the apical part of the scolex of C. brachycollis showed the occurrence of a multicellular, syncytial glandular complex, the scolex produced membrane-bound secretory granules and their fibrillar contents discharged by merocrine and apocrine secretion onto the host-parasite interface. Our results are among the first to provide evidence on the sophisticated relationship between fish intestine and amorphous-undefinable substance produced by scolex glandular complex.

The Impact of Sea Buckthorn (Hippophae rhamnoides L.) and Cornelian Cherry (Cornus mas L.) Plant Extracts on the Physiology of Gastrointestinal Tract Cell In Vitro Model in the Context of Metabolic Diseases

The aim of this study was to evaluate the impact of ethanol extracts from sea buckthorn and Cornelian cherry fruits and leaves on physiology of gastrointestinal tract cells. We used three cell lines relevant to the types of cells, which are exposed to bioactive compounds after oral administration, namely intestinal absorptive cells (Caco-2/HT-29 MTX model), hepatocytes (HepG2 cells) and immunocompetent cells (RAW 264.7 and P388D1 monocytes). The contents of antioxidant and bioactive polyphenols, such as cinnamic, caffeic and p-coumaric acids, rutin, myricetin, resveratrol, quercetin, apigenin and kaempferol, were assessed in the extracts using HPLC chromatography. The application of the extracts to Caco-2/HT-29-MTX cultures increased enterocyte differentiation markers (alkaline phosphatase and villin1 level) and goblet cell markers (mucins) over a fortnight. The extracts reduced lipid droplet size in hepatocytes challenged with hyperglycaemic glucose concentration, insulin and palmitate. Sea buckthorn leaf, fruit and Cornelian cherry leaf extracts blocked oxidative burst in the PMA-stimulated monocytes, while the sea buckthorn leaf and Cornelian cherry fruit extracts downregulated lipopolysaccharide-induced NO and IL-1β, respectively. The results indicate that the tested extracts modulate the behaviour of cells in the gastrointestinal tract in a beneficial way, especially regarding lipid accumulation and innate immunity actions.

A ferrous fluorescence lifetime response probe for monitoring changes in lipid droplets during ferroptosis and imaging in liver disease model

Ferrous ions (Fe2⁺) accumulation and abnormal alterations in lipid droplets (LDs) are closely associated with ferroptosis. In the liver, excessive iron accumulation promotes oxidative stress and exacerbates lipid droplet accumulation, while the disruption of iron homeostasis may also affect the formation and size of lipid droplets, their increased number and size can exacerbate the severity of disease under fatty liver conditions. The leads to hepatocyte damage, further triggering liver inflammation, fibrosis, and ultimately resulting in cirrhosis and hepatocellular carcinoma. Therefore, real-time monitoring of iron ion and lipid droplet changes is crucial for assessing the severity of liver disease, disease progression, and understanding the mechanisms of ferroptosis. We have developed a fluorescent probe, NRFep, for real-time monitoring of iron ion fluctuations and visualization of lipid droplet changes in ferroptosis and liver disease models. NRFep is specific and sensitive to iron ions and exhibits excellent stability in both cells and animal models. In addition, NRFep can be used to monitor changes in iron ions and lipid droplets in mouse liver injury and fatty liver models. Through fluorescence lifetime imaging technology, NRFep can also study the dynamic changes of intracellular iron ion content. NRFep provides a powerful tool for studying ferroptosis and related diseases, and its unique dual-monitoring function opens up new possibilities for developing new diagnostic and therapeutic strategies.

Induction of phospholipase A2 group 4C by hepatitis C virus infection regulates lipid droplet formation

Background & AimsHepatic steatosis, characterized by lipid accumulation in hepatocytes, is a key diagnostic feature in patients with chronic hepatitis C virus (HCV) infection. This study aimed to clarify the involvement of phospholipid metabolic pathways in the pathogenesis of HCV-induced steatosis. MethodsThe expression and distribution of lipid species in the livers of human liver chimeric mice were analyzed using imaging mass spectrometry. Triglyceride accumulation and lipid droplet formation were studied in phospholipase A2 group 4C (PLA2G4C) knockout or overexpressing cells. ResultsImaging mass spectrometry of the infected mouse model revealed increased lysophosphatidylcholine levels and decreased phosphatidylcholine levels in HCV-positive regions of the livers. Among the transcripts associated with phosphatidylcholine biosynthesis, up-regulation of PLA2G4C mRNA was most pronounced following HCV infection. Activation of the transcription factor NF-κB and up-regulation of c-Myc were important for activation of PLA2G4C transcription by HCV infection and expression of the viral proteins Core-NS2. The amount and size of lipid droplets were reduced in PLA2G4C-knockout cells. Inhibition of NF-κB or c-Myc activity suppressed lipid droplet formation in HCV-infected cells. HCV infection promoted the stabilization of lipid droplets, but this stability was reduced in PLA2G4C-knockout cells. Overexpression of PLA2G4C decreased the levels of phosphatidylcholine species in the lipid droplet fraction and led to lower levels of key factors involved in lipolysis (breakdown of triglycerides into glycerol and free fatty acids), such as ATGL, PLIN1 and ABHD5 on the lipid droplets. ConclusionsHCV infection markedly increases PLA2G4C expression. This may alter the phospholipid composition of the lipid droplet membrane, leading to stabilization and enlargement of the droplets.

Polystyrene nanoplastics enhance poxvirus preference for migrasome-mediated transmission

Since the emergence of a global outbreak of mpox in 2022, understanding the transmission pathways and mechanisms of Orthopoxviruses, including vaccinia virus (VACV), has become paramount. Nanoplastic pollution has become a significant global issue due to its widespread presence in the environment and potential adverse effects on human health. These emerging pollutants pose substantial risks to both living organisms and the environment, raising serious health concerns related to their proliferation. Despite this, the effects of nanoparticles on viral transmission dynamics remain unclear. This study explores how polystyrene nanoparticles (PS-NPs) influence the transmission of VACV through migrasomes. We demonstrate that PS-NPs accelerate the formation of migrasomes early in the infection process, facilitating VACV entry as soon as 15 h post-infection (hpi), compared to the usual onset at 36 hpi. Immunofluorescence and transmission electron microscopy (TEM) reveal significant co-localization of VACV with migrasomes induced by PS-NPs by 15 hpi. This interaction coincides with an increase in lipid droplet size, attributed to higher cholesterol levels influenced by PS-NPs. By 36 hpi, migrasomes exposed to both PS-NPs and VACV exhibit distinct features, such as retraction fibers and larger lipid droplets, emphasizing their critical role in cargo transport during viral infections. These results suggest that PS-NPs may act as modulators of viral transmission dynamics through migrasomes, with potential implications for antiviral strategies and environmental health.

Genome-Wide Association Study of Cuticle and Lipid Droplet Properties of Cucumber (Cucumis sativus L.) Fruit.

The fruit surface is a critical first line of defense against environmental stress. Overlaying the fruit epidermis is the cuticle, comprising a matrix of cutin monomers and waxes that provides protection and mechanical support throughout development. The epidermal layer of the cucumber (Cucumis sativus L.) fruit also contains prominent lipid droplets, which have recently been recognized as dynamic organelles involved in lipid storage and metabolism, stress response, and the accumulation of specialized metabolites. Our objective was to genetically characterize natural variations for traits associated with the cuticle and lipid droplets in cucumber fruit. Phenotypic characterization and genome-wide association studies (GWAS) were performed using a resequenced cucumber core collection accounting for >96% of the allelic diversity present in the U.S. National Plant Germplasm System collection. The collection was grown in the field, and fruit were harvested at 16-20 days post-anthesis, an age when the cuticle thickness and the number and size of lipid droplets have stabilized. Fresh fruit tissue sections were prepared to measure cuticle thickness and lipid droplet size and number. The collection showed extensive variation for the measured traits. GWAS identified several QTLs corresponding with genes previously implicated in cuticle or lipid biosynthesis, including the transcription factor SHINE1/WIN1, as well as suggesting new candidate genes, including a potential lipid-transfer domain containing protein found in association with isolated lipid droplets.

RXR nuclear receptor signaling modulates lipid metabolism and triggers lysosomal clearance of alpha-synuclein in neuronal models of synucleinopathy

Disease-modifying strategies for Parkinson disease (PD), the most common synucleinopathy, represent a critical unmet medical need. Accumulation of the neuronal protein alpha-synuclein (αS) and abnormal lipid metabolism have each been implicated in PD pathogenesis. Here, we elucidate how retinoid-X-receptor (RXR) nuclear receptor signaling impacts these two aspects of PD pathogenesis. We find that activated RXR differentially regulates fatty acid desaturases, significantly reducing the transcript levels of the largely brain-specific desaturase SCD5 in human cultured neural cells and PD patient-derived neurons. This was associated with reduced perilipin-2 protein levels in patient neurons, reversal of αS-induced increases in lipid droplet (LD) size, and a reduction of triglyceride levels in human cultured cells. With regard to αS proteostasis, our study reveals that RXR agonism stimulates lysosomal clearance of αS. Our data support the involvement of Polo-like kinase 2 activity and αS S129 phosphorylation in mediating this benefit. The lowering of cellular αS levels was associated with reduced cytotoxicity. Compared to RXR activation, the RXR antagonist HX531 had the opposite effects on LD size, SCD, αS turnover, and cytotoxicity, all supporting pathway specificity. Together, our findings show that RXR-activating ligands can modulate fatty acid metabolism and αS turnover to confer benefit in cellular models of PD, including patient neurons. We offer a new paradigm to investigate nuclear receptor ligands as a promising strategy for PD and related synucleinopathies.

S-acylation of ATGL is required for lipid droplet homoeostasis in hepatocytes.

Lipid droplets (LDs) are organelles specialized in the storage of neutral lipids, cholesterol esters and triglycerides, thereby protecting cells from the toxicity of excess lipids while allowing for the mobilization of lipids in times of nutrient deprivation. Defects in LD function are associated with many diseases. S-acylation mediated by zDHHC acyltransferases modifies thousands of proteins, yet the physiological impact of this post-translational modification on individual proteins is poorly understood. Here, we show that zDHHC11 regulates LD catabolism by modifying adipose triacylglyceride lipase (ATGL), the rate-limiting enzyme of lipolysis, both in hepatocyte cultures and in mice. zDHHC11 S-acylates ATGL at cysteine 15. Preventing the S-acylation of ATGL renders it catalytically inactive despite proper localization. Overexpression of zDHHC11 reduces LD size, whereas its elimination enlarges LDs. Mutating ATGL cysteine 15 phenocopies zDHHC11 loss, causing LD accumulation, defective lipolysis and lipophagy. Our results reveal S-acylation as a mode of regulation of ATGL function and LD homoeostasis. Modulating this pathway may offer therapeutic potential for treating diseases linked to defective lipolysis, such as fatty liver disease.

Dynamical modelling of lipid droplet formation suggests a key function of membrane phospholipids.

Cells store triacylglycerol (TAG) within lipid droplets (LDs). A dynamic model describing complete LD formation at the endoplasmic reticulum (ER) membrane does not yet exist. A biochemical-biophysical model of LD synthesis is proposed. It describes the time-dependent accumulation of TAG in the ER membrane as the formation of a potential LD (pLD) bounded by spherical caps of the inner and outer monolayers of the membrane. The expansion rate of the pLD depends on the TAG supply, the elastic properties of the ER membrane, and the recruitment of phospholipids (PLs) to the cap-covering monolayers. Model simulations provided the following insights: (a) Marginal differences in the surface tension of the cap monolayers are sufficient to fully drive the expansion of the pLD towards the cytosol or lumen. (b) Selective reduction of PL supply to the luminal monolayer ensures stable formation of cytosolic LDs, irrespective of variations in the elasto-mechanical properties of the ER membrane. (c) The rate of TAG supply to the cytosolic monolayer has a major effect on the size and maturation time of LDs but has no significant effect on the TAG export per individual LD. The recruitment of additional PLs to the cap monolayers of pLDs critically controls the budding direction, size, and maturation time of LDs. The ability of cells to acquire additional LD initiation sites appears to be key to coping with acutely high levels of potentially toxic free fatty acids.

Effect of four different cooking methods on the fat digestion characteristics of yellow-feathered chicken

The aim of this study was to investigate the effects of four cooking methods (boiling, microwaving, air frying and roasting) on the fat characteristics of chicken. The results showed that cooking significantly exacerbated fat oxidation, with boiling showing significantly lower level of malondialdehyde (MDA) at 0.25 ug/g. Microwaving, air frying and roasting significantly increased the levels of saturated fatty acids (SFA), while boiling decreased the levels to 1137.24 µg/g. In terms of digestive characteristics, in the gastric digestive fluid, the roast group had the largest particles while the boil group had the smallest particles. In the intestinal digestive fluid, boiled and microwaved chicken exhibited significantly smaller particle sizes, which was consistent with the trends in lipid droplet size and number observed by laser confocal. Boiling and microwaving significantly increased digestibility, reaching 51.51% and 54.25%, respectively. In conclusion, boiling could slow fat oxidation and reduce particle size, and promote lipid digestion.

Adaptation of Brown Adipose Tissue in Response to Chronic Exposure to the Environmental Pollutant 1,1-Dichloro-2,2-bis(p-chlorophenyl) Ethylene (DDE) and/or a High-Fat Diet in Male Wistar Rats.

Brown adipose tissue (BAT) participates in thermogenesis and energy homeostasis. Studies on factors capable of influencing BAT function, such as a high-fat diet (HFD) or exposure to environmental pollutants, could be useful for finding metabolic targets for maintaining energy homeostasis. We evaluated the effect of chronic exposure to dichlorodiphenyldichloroethylene (DDE), the major metabolite of dichlorodiphenyltrichloroethane (DDT), and/or a HFD on BAT morphology, mitochondrial mass, dynamics, and oxidative stress in rats. To this end, male Wistar rats were treated for 4 weeks with a standard diet, or a HFD alone, or together with DDE. An increase in paucilocular adipocytes and the lipid droplet size were observed in HFD-treated rats, which was associated with a reduction in mitochondrial mass and in mitochondrial fragmentation, as well as with increased oxidative stress and upregulation of the superoxide dismutase-2. DDE administration mimics most of the effects induced by a HFD on BAT, and it aggravates the increase in the lipid droplet size when administered together with a HFD. Considering the known role of oxidative stress in altering BAT functionality, it could underlie the ability of both DDE and a HFD to induce similar metabolic adaptations in BAT, leading to reduced tissue thermogenesis, which can result in a predisposition to the onset of energy homeostasis disorders.