Perilipin Protein Research Articles

Evaluation of Perilipin Expression in Centrifuged Fat Grafts on Different Revolutions Per Minute and Duration Combinations.

Fat graft applications are one of the most frequently used procedures in reconstructive and aesthetic surgery. Fat graft survival rate is variable and depends on many parameters. Those are the features of recipient area, method of obtaining the fat graft, the procedures applied to the harvest to get pure fat graft and the application techniques. In this study, we aimed to find the optimal revolutions per minute(rpm) and duration to be used in the centrifugation technique, which is one of the most frequently used methods in fat grafting. In our study, we used perilipin protein as a survival marker. Liposuction samples were obtained from 10 Caucasian women individuals; whose age range is between 22 and 29 years without any other reported health problem. Fat grafts from all patients were taken by the same surgical team by the same liposuction procedure. The grafts obtained in our study were divided into 6 different groups, these are A1 group (1 minute-1000 rpm) A2 group (3 minutes-1000 rpm) A3 group (5 minutes-1000 rpm) B1 group (1 minute-3000 rpm) B2 group (3 minutes-3000 rpm) and B3 group (5 minutes-3000 rpm). Perilipin expression measurements were made in the sections taken by immunohistochemistry technique. Three minutes-3000 rpm combination (B2 group) was found to be perilipin stained statistically significantly higher than other combinations. This study seeks to make a notable contribution to the literature by demonstrating the relation between frequently used centrifuge combinations and measuring the expression of perilipin. This protein's role in adipocyte regulation is becoming increasingly apparent.Level of Evidence III This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Stress causes lipid droplet accumulation in chondrocytes by impairing microtubules.

Abnormal mechanical stress is intimately coupled with osteoarthritis (OA). Microtubules play a vital role in the regulation of mechanotransduction and intracellular transport. The purpose of the present study was to investigate the impact of stress-induced microtubule impairment on intracellular transport and lipid droplet (LD) accumulation in chondrocytes. Rats were subjected to unilateral anterior crossbite (UAC), which is inducible for degeneration of temporomandibular joint (TMJ) cartilage. Chondrocytes derived from rat TMJ cartilage were subjected to fluid flow shear stress (FFSS) and analyzed via LCMS/MS-based proteomics. The microtubule destabilization agent nocodazole and/or the microtubule stabilizer docetaxel were used in the UAC and FFSS models. In both FFSS- and UAC-treated chondrocytes, decreased acetylated α-Tubulin (ac-Tubulin) expression and LD accumulation were observed. Proteomic data revealed increased levels of the LD-associated protein perilipin 3 (Plin3) and decreased levels of cytoskeleton components in FFSS-treated chondrocytes. Live-cell imaging revealed that the colocalization of LDs with lysosomes was significantly decreased after FFSS treatment. Impairment of microtubules by nocodazole reduced the protein level of ac-Tubulin and disrupted the Hsc70-mediated interaction between Plin3 and Lamp2a, as shown by co-IP assays. In contrast, docetaxel reversed the suppression of ac-Tubulin expression, reduced the accumulation of LDs, and decreased the expression of Plin3 in chondrocytes exposed to FFSS and UAC, and docetaxel ameliorated UAC-induced osteoarthritic lesions in the TMJ cartilage. Microtubule impairment under aberrant stress conditions disrupts intracellular transport and blocks lipophagy, causing LD accumulation in chondrocytes. Microtubule stabilization could be a new approach for treating stress-induced cartilage degeneration.

Lipid droplet protein Perilipin 2 is critical for the regulation of insulin secretion through beta cell lipophagy and glucagon expression in pancreatic islets.

Knockdown (KD) of lipid droplet (LD) protein perilipin 2 (PLIN2) in beta cells impairs glucose-stimulated insulin secretion (GSIS) and mitochondrial function. Here, we addressed a pathway responsible for compromised mitochondrial integrity in PLIN2 KD beta cells. In PLIN2 KD human islets, mitochondria were fragmented in beta cells but not in alpha cells. Glucagon but not insulin level was elevated. While the formation of early LDs followed by fluorescent fatty acids (FA) analog Bodipy C12 (C12) was preserved, C12 accumulated in mitochondria over time in PLIN2 KD INS-1 cells. A lysosomal acid lipase inhibitor Lali2 prevented C12 transfer to mitochondria, mitochondrial fragmentation, and the impairment of GSIS. Direct interactions between LD-lysosome and lysosome-mitochondria were increased in PLIN2 KD INS-1 cells. Thus, FA released from LDs by microlipophagy cause mitochondrial changes and impair GSIS in PLIN2 KD beta cells. Interestingly, glucolipotoxic condition (GLT) caused C12 accumulation and mitochondrial fragmentation similar to PLIN2 KD in beta cells. Moreover, Lali2 reversed mitochondrial fragmentation and improved GSIS in human islets under GLT. In summary, PLIN2 regulates microlipophagy to prevent excess FA flux to mitochondria in beta cells. This pathway also contributes to GSIS impairment when LD pool expands under nutrient load in beta cells.

Optimized 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, Nile Red, LipidTox and LipidSpot, as well as transgenic LD reporters that rely on EGFP fusions of the LD-decorating protein perilipin 2 (PLIN2), demonstrates 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.

R(+) Propranolol decreases lipid accumulation in hemangioma-derived stem cells.

Infantile hemangioma (IH) is a benign vascular tumor that undergoes an initial rapid growth phase followed by spontaneous involution. A fibrofatty residuum remains in many tumors and often necessitates resection. We recently discovered that R(+) propranolol, the non-β blocker enantiomer, inhibits blood vessel formation of IH patient-derived hemangioma stem cells (HemSC) xenografted in mice. HemSC are multipotent cells with the ability to differentiate into endothelial cells, pericytes, and adipocytes. We investigated how R(+) propranolol affects HemSC adipogenic differentiation and lipid accumulation, in vitro and in a preclinical murine model for IH. We conducted a 10-day adipogenesis assay on 4 IH patient-derived HemSCs. Oil Red O (ORO) staining was used to identify the onset and level of lipid accumulation in HemSC while quantitative real-time polymerase chain reaction was conducted to determine the temporal expression of key factors implicated in adipogenesis. 5-20µM R(+) propranolol treatment was added to HemSC induced to undergo adiogenesis for 4 and 8 days, followed by quantification of lipid-stained areas and transcript levels of key adipogenic factors. We immunostained for lipid droplet-associated protein Perilipin 1 (PLIN1) in HemSC-xenograft sections from mice treated with R(+) propranolol and quantified the area using ImageJ. We found that different patient-derived HemSC exhibit a robust and heterogenous adipogenic capacity when induced for adipogenic differentiation in vitro. Consistently across four IH patient-derived HemSC isolates, R(+) propranolol reduced ORO-stained areas and lipoprotein lipase (LPL) transcript levels in HemSC after 4 and 8 days of adipogenic induction. In contrast, R(+) propranolol had no significant inhibitory effect on transcript levels encoding adipogenic transcription factors. In a pre-clinical HemSC xenograft model, PLIN1-positive area was significantly reduced in xenograft sections from mice treated with R(+) propranolol, signifying reduced lipid accumulation. Our findings suggest a novel regulatory role for the R(+) enantiomer of propranolol in modulating lipid accumulation in HemSC. This highlights a novel role of R(+) propranolol in the involuting phase of IH and a strategy to reduce fibrofatty residua in IH. Propranolol is the mainstay treatment for infantile hemangioma (IH), the most common tumor of infancy, but its use can be associated with concerning β-blocker side effects.R(+) propranolol, the enantiomer largely devoid of β-blocker activity, was recently shown to inhibit endothelial differentiation of hemangioma-derived stem cells (HemSC) in vitro and reduce blood vessel formation in a HemSC-derived xenograft murine model of IH. R(+) propranolol inhibits lipid accumulation in HemSC in vitro.R(+) propranolol does not affect mRNA transcript levels of key adipogenic transcription factors in differentiating HemSC in vitro.R(+) propranolol reduces lipid accumulation in a pre-clinical xenograft murine model of IH. The R(+) enantiomer of propranolol could be advantageous in terms of reduction in β-adrenergic side effects and fibrofatty tissue formation in the involuting phase of IH.Less fibrofatty residua might reduce the need for surgical resection.Disfigurement and associated psychosocial impacts might be improved in this young patient cohort.

A fluorescent perilipin 2 knock-in mouse model reveals a high abundance of lipid droplets in the developing and adult brain

Lipid droplets (LDs) are dynamic lipid storage organelles. They are tightly linked to metabolism and can exert protective functions, making them important players in health and disease. Most LD studies in vivo rely on staining methods, providing only a snapshot. We therefore developed a LD-reporter mouse by labelling the endogenous LD coat protein perilipin 2 (PLIN2) with tdTomato, enabling staining-free fluorescent LD visualisation in living and fixed tissues and cells. Here we validate this model under standard and high-fat diet conditions and demonstrate that LDs are highly abundant in various cell types in the healthy brain, including neurons, astrocytes, ependymal cells, neural stem/progenitor cells and microglia. Furthermore, we also show that LDs are abundant during brain development and can be visualized using live imaging of embryonic slices. Taken together, our tdTom-Plin2 mouse serves as a novel tool to study LDs and their dynamics under both physiological and diseased conditions in all tissues expressing Plin2.

Diacylglycerol O-acyltransferase isoforms play a role in peridroplet mitochondrial fatty acid metabolism in bovine liver

Hepatocellular lipid accumulation characterizes fatty liver in dairy cows. Lipid droplets (LD), specialized organelles that store lipids and maintain cellular lipid homeostasis, are responsible for the ectopic storage of lipids associated with several metabolic disorders. In recent years, nonruminant studies have reported that LD-mitochondria interactions play an important role in lipid metabolism. Due to the role of diacylglycerol acyltransferase isoforms (DGAT1 and DGAT2) in LD synthesis, we explored mechanisms of mitochondrial fatty acid transport in ketotic cows using liver biopsies and isolated primary hepatocytes. Compared with healthy cows, cows with fatty liver had massive accumulation of LD and high protein expression of the triglyceride (TAG) synthesis-related enzymes DGAT1 and DGAT2, LD synthesis-related proteins perilipin 2 (PLIN2) and perilipin 5 (PLIN5), and the mitochondrial fragmentation-related proteins dynamin-related protein 1 (DRP1) and fission 1 (FIS1). In contrast, factors associated with fatty acid oxidation, mitochondrial fusion, and mitochondrial electron transport chain complex were lower compared with those in the healthy cows. In addition, transmission electron microscopy revealed significant contacts between LD-mitochondria in liver tissue from cows with fatty liver. Compared with isolated cytoplasmic mitochondria, expression of carnitine palmitoyl transferase 1A (CPT1A) and DRP1 was lower, but mitofusin 2 (MFN2) and mitochondrial electron transport chain complex was greater in isolated peridroplet mitochondria from hepatic tissue of cows with fatty liver. In vitro data indicated that exogenous free fatty acids (FFA) induced hepatocyte LD synthesis and mitochondrial dynamics consistent with in vivo results. Furthermore, DGAT2 inhibitor treatment attenuated the FFA-induced upregulation of PLIN2 and PLIN5 and rescued the impairment of mitochondrial dynamics. Inhibition of DGAT2 also restored mitochondrial membrane potential and reduced hepatocyte reactive oxygen species production. The present in vivo and in vitro results indicated functional differences are present among different types of mitochondria in the liver tissue of dairy cows with ketosis. Activity of DGAT2 may play a key role in maintaining liver mitochondrial function and lipid homeostasis in dairy cows during the transition period.

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.

Unraveling the role of lipid droplets and perilipin 2 in bovine luteal cells.

Steroidogenic tissues contain cytosolic lipid droplets that are important for steroidogenesis. Perilipin 2 (PLIN2), a structural coat protein located on the surface of lipid droplets in mammalian cells, plays a crucial role in regulating lipid droplet formation and contributing to various cellular processes such as lipid storage and energy homeostasis. Herein, we examine the role that PLIN2 plays in regulating progesterone synthesis in the bovine corpus luteum. Utilizing gene array databases and Western blotting, we have delineated the expression pattern of PLIN2 throughout the follicular to luteal transition. Our findings reveal the presence of PLIN2 in both ovarian follicular and steroidogenic luteal cells, demonstrating an increase in its levels as follicular cells transition into the luteal phase. Moreover, the depletion of PLIN2 via siRNA enhanced progesterone production in small luteal cells, whereas adenovirus-mediated overexpression of both PLIN2 and Perilipin 3 (PLIN3) induced an increase in cytosolic lipid droplet accumulation and decreased hormone-induced progesterone synthesis in these cells. Lastly, invivo administration of the luteolytic hormone prostaglandin F2α resulted in an upregulation of PLIN2 mRNA and protein expression, accompanied by a decline in serum progesterone. Our findings highlight the pivotal role of PLIN2 in regulating progesterone synthesis in the bovine corpus luteum, as supported by its dynamic expression pattern during the follicular to luteal transition and its responsiveness to luteotropic and luteolytic hormones. We suggest PLIN2 as a potential therapeutic target for modulating luteal function.

The Role of Neutral Sphingomyelinase-2 (NSM2) in the Control of Neutral Lipid Storage in T Cells.

The accumulation of lipid droplets (LDs) and ceramides (Cer) is linked to non-alcoholic fatty liver disease (NAFLD), regularly co-existing with type 2 diabetes and decreased immune function. Chronic inflammation and increased disease severity in viral infections are the hallmarks of the obesity-related immunopathology. The upregulation of neutral sphingomyelinase-2 (NSM2) has shown to be associated with the pathology of obesity in tissues. Nevertheless, the role of sphingolipids and specifically of NSM2 in the regulation of immune cell response to a fatty acid (FA) rich environment is poorly studied. Here, we identified the presence of the LD marker protein perilipin 3 (PLIN3) in the intracellular nano-environment of NSM2 using the ascorbate peroxidase APEX2-catalyzed proximity-dependent biotin labeling method. In line with this, super-resolution structured illumination microscopy (SIM) shows NSM2 and PLIN3 co-localization in LD organelles in the presence of increased extracellular concentrations of oleic acid (OA). Furthermore, the association of enzymatically active NSM2 with isolated LDs correlates with increased Cer levels in these lipid storage organelles. NSM2 enzymatic activity is not required for NSM2 association with LDs, but negatively affects the LD numbers and cellular accumulation of long-chain unsaturated triacylglycerol (TAG) species. Concurrently, NSM2 expression promotes mitochondrial respiration and fatty acid oxidation (FAO) in response to increased OA levels, thereby shifting cells to a high energetic state. Importantly, endogenous NSM2 activity is crucial for primary human CD4+ T cell survival and proliferation in a FA rich environment. To conclude, our study shows a novel NSM2 intracellular localization to LDs and the role of enzymatically active NSM2 in metabolic response to enhanced FA concentrations in T cells.

Knockdown of NEAT1 prevents post-stroke lipid droplet agglomeration in microglia by regulating autophagy

BackgroundLipid droplets (LD), lipid-storing organelles containing neutral lipids like glycerolipids and cholesterol, are increasingly accepted as hallmarks of inflammation. The nuclear paraspeckle assembly transcript 1 (NEAT1), a long non-coding RNA with over 200 nucleotides, exerts an indispensable impact on regulating both LD agglomeration and autophagy in multiple neurological disorders. However, knowledge as to how NEAT1 modulates the formation of LD and associated signaling pathways is limited.MethodsIn this study, primary microglia were isolated from newborn mice and exposed to oxygen-glucose-deprivation/reoxygenation (OGD/R). To further explore NEAT1-dependent mechanisms, an antisense oligonucleotide (ASO) was adopted to silence NEAT1 under in vitro conditions. Studying NEAT1-dependent interactions with regard to autophagy and LD agglomeration under hypoxic conditions, the inhibitor and activator of autophagy 3-methyladenine (3-MA) and rapamycin (RAPA) were used, respectively. In a preclinical stroke model, mice received intraventricular injections of ASO NEAT1 or control vectors in order to yield NEAT1 knockdown. Analysis of readout parameters included qRT-PCR, immunofluorescence, western blot assays, and behavioral tests.ResultsMicroglia exposed to OGD/R displayed a temporal pattern of NEAT1 expression, peaking at four hours of hypoxia followed by six hours of reoxygenation. After effectively silencing NEAT1, LD formation and autophagy-related proteins were significantly repressed in hypoxic microglia. Stimulating autophagy in ASO NEAT1 microglia under OGD/R conditions by means of RAPA reversed the downregulation of LD agglomeration and perilipin 2 (PLIN2) expression. On the contrary, application of 3-MA promoted repression of both LD agglomeration and expression of the LD-associated protein PLIN2. Under in vivo conditions, NEAT1 was significantly increased in mice at 24 h post-stroke. Knockdown of NEAT1 significantly alleviated LD agglomeration and inhibited autophagy, resulting in improved cerebral perfusion, reduced brain injury and increased neurological recovery.ConclusionNEAT1 is a key player of LD agglomeration and autophagy stimulation, and NEAT1 knockdown provides a promising therapeutic value against stroke.Graphical abstract

Molecular mechanisms of perilipin protein function in lipid droplet metabolism.

Perilipins are abundant lipid droplet (LD) proteins present in all metazoans and also in Amoebozoa and fungi. Humans express five perilipins, which share a similar domain organization: an amino-terminal PAT domain and an 11-mer repeat region, which can fold into amphipathic helices that interact with LDs, followed by a structured carboxy-terminal domain. Variations of this organization that arose during vertebrate evolution allow for functional specialization between perilipins in relation to the metabolic needs of different tissues. We discuss how different features of perilipins influence their interaction with LDs and their cellular targeting. PLIN1 and PLIN5 play a direct role in lipolysis by regulating the recruitment of lipases to LDs and LD interaction with mitochondria. Other perilipins, particularly PLIN2, appear to protect LDs from lipolysis, but the molecular mechanism is not clear. PLIN4 stands out with its long repetitive region, whereas PLIN3 is most widely expressed and is used as a nascent LD marker. Finally, we discuss the genetic variability in perilipins in connection with metabolic disease, prominent for PLIN1 and PLIN4, underlying the importance of understanding the molecular function of perilipins.

Behavior of intracellular lipid droplets during cell division in HuH7 hepatoma cells

Intracellular lipid droplets (LDs) are ubiquitous organelles found in many cell types. During mitosis, membranous organelles, including mitochondria, are divided into small pieces and transferred to daughter cells; however, the process of LD transfer to daughter cells is not fully elucidated. Herein, we investigated the behavior of LDs during mitosis in HuH7 human hepatoma cells. While fragments of the Golgi apparatus were scattered in the cytosol during mitosis, intracellular LDs retained their size and spherical morphology as they translocated to the two daughter cells. LDs were initially distributed throughout the cell during prophase but positioned outside the spindle in metaphase, aligning at the far sides of the centrioles. A similar distribution of LDs during mitosis was observed in another hepatocarcinoma HepG2 cells. When the spindle was disrupted by nocodazole treatment or never in mitosis gene A-related kinase 2A knockdown, LDs were localized in the area outside the chromosomes, suggesting that spindle formation is not necessary for LD localization at metaphase. The amount of major LD protein perilipin 2 reduced while LDs were enriched in perilipin 3 during mitosis, indicating the potential alteration of LD protein composition. Conclusively, the behavior of LDs during mitosis is distinct from that of other organelles in hepatocytes.

Perilipin1 Expression as a Prognostic Factor in Patients with Squamous Cell Carcinoma of the Lung.

Perilipin (PLIN) is a major structural protein located on the surface of lipid droplets. PLIN plays an important role in human metabolism and is associated with metabolic diseases, such as obesity, diabetes, hypertension, and endocrine disorders. The dysregulation of lipid metabolism is one of the most prominent metabolic changes observed in cancers. Therefore, the PLIN protein family has recently attracted attention owing to its role in lipid metabolism and cancer. To date, no studies have addressed the association between the prognosis of lung cancer and PLIN1 expression. For the first time, we found that high PLIN1 expression was significantly correlated with worse disease-free survival (DFS) in lung squamous cell carcinoma (SCC). We examined PLIN1 expression by the immunohistochemical analysis of surgical lung SCC specimens obtained from 94 patients. We analyzed the correlation between PLIN1 expression, clinicopathological data, and patient survival, using a chi-squared test, Kaplan-Meier analysis with log-rank tests, and the multivariate Cox proportional hazards regression test. High PLIN1 expression was significantly correlated with lower DFS in the Kaplan-Meier analysis and the multivariate Cox proportional hazards regression model. High PLIN1 expression was significantly correlated with worse prognosis in lung SCC.

The macrophage STING-YAP axis controls hepatic steatosis by promoting the autophagic degradation of lipid droplets.

The hallmark of NAFLD or hepatic steatosis is characterized by lipid droplet (LD) accumulation in hepatocytes. Autophagy may have profound effects on lipid metabolism and innate immune response. However, how innate immune activation may regulate the autophagic degradation of intracellular LDs remains elusive. A mouse model of a high-fat diet-induced NASH was used in the myeloid-specific stimulator of interferon genes (STING) knockout or STING/yes-associated protein (YAP) double knockout mice. Liver injury, lipid accumulation, lipid droplet proteins, autophagic genes, chromatin immunoprecipitation coupled with massively parallel sequencing, and RNA-Seq were assessed in vivo and in vitro . We found that high-fat diet-induced oxidative stress activates STING and YAP pathways in hepatic macrophages. The acrophage STING deficiency (myeloid-specific STING knockout) enhances nuclear YAP activity, reduces lipid accumulation, and increases autophagy-related proteins ATG5, ATG7, and light chain 3B but diminishes LD protein perilipin 2 expression. However, disruption of STING and YAP (myeloid STING and YAP double knockout) increases serum alanine aminotransferase and triglyceride levels and reduces β-fatty acid oxidation gene expression but augments perilipin 2 levels, exacerbating high-fat diet-induced lipid deposition. Chromatin immunoprecipitation coupled with massively parallel sequencing reveals that macrophage YAP targets transmembrane protein 205 and activates AMP-activated protein kinase α, which interacts with hepatocyte mitofusin 2 and induces protein disulfide isomerase activation. Protein disulfide isomerase activates hypoxia-inducible factor-1α signaling, increases autophagosome colocalization with LDs, and promotes the degradation of perilipin 2 by interacting with chaperone-mediated autophagy chaperone HSC70. The macrophage STING-YAP axis controls hepatic steatosis by reprogramming lipid metabolism in a transmembrane protein 205/mitofusin 2/protein disulfide isomerase-dependent pathway. These findings highlight the regulatory mechanism of the macrophage STING-driven YAP activity on lipid control.

Omentin-1 induces mechanically activated fibroblasts lipogenic differentiation through pkm2/yap/pparγ pathway to promote lung fibrosis resolution.

Idiopathic pulmonary fibrosis (IPF) is a progressive and fatal lung disease characterized by extensive extracellular matrix (ECM) deposition by activated myofibroblasts, which are specialized hyper-contractile cells that promote ECM remodeling and matrix stiffening. New insights on therapeutic strategies aimed at reversing fibrosis by targeting myofibroblast fate are showing promise in promoting fibrosis resolution. Previously, we showed that a novel adipocytokine, omentin-1, attenuated bleomycin (BLM)-induced lung fibrosis by reducing the number of myofibroblasts. Apoptosis, deactivation, and reprogramming of myofibroblasts are important processes in the resolution of fibrosis. Here we report that omentin-1 reverses established lung fibrosis by promoting mechanically activated myofibroblasts dedifferentiation into lipofibroblasts. Omentin-1 promotes myofibroblasts lipogenic differentiation by inhibiting dimerization and nuclear translocation of glycolytic enzymes pyruvate kinase isoform M2 (PKM2) and activation of the downstream Yes-associated protein (YAP) by increasing the cofactor fructose-1,6-bisphosphate (F1, 6BP, FBP). Moreover, omentin-1 activates proliferator-activated receptor gamma (PPARγ) signaling, the master regulator of lipogenesis, and promotes the upregulation of the lipogenic differentiation-related protein perilipin 2 (PLIN2) by suppressing the PKM2-YAP pathway. Ultimately, omentin-1 facilitates myofibroblasts transformation into the lipofibroblast phenotype, with reduced collagen synthesis and enhanced degradation properties, which are crucial mechanisms to clear the ECM deposition in fibrotic tissue, leading to fibrosis resolution. Our results indicate that omentin-1 targets mechanical signal accelerates fibrosis resolution and reverses established lung fibrosis by promoting myofibroblasts lipogenic differentiation, which is closely associated with ECM clearance in fibrotic tissue. These findings suggest that targeting mechanical force to promote myofibroblast lipogenic differentiation is a promising therapeutic strategy against persistent lung fibrosis.

Effect of an acute long-duration exercise bout on skeletal muscle lipid droplet morphology, GLUT 4 protein, and perilipin protein expression.

Smaller lipid droplet morphology and GLUT 4 protein expression have been associated with greater muscle oxidative capacity and glucose uptake, respectively. The main purpose of this study was to determine the effect of an acute long-duration exercise bout on skeletal muscle lipid droplet morphology, GLUT4, perilipin 3, and perilipin 5 expressions. Twenty healthy men (age 24.0 ± 1.0 years, BMI 23.6 ± 0.4 kg/m2) were recruited for the study. The participants were subjected to an acute bout of exercise on a cycle ergometer at 50% VO2max until they reached a total energy expenditure of 650kcal. The study was conducted after an overnight fast. Vastus lateralis muscle biopsies were obtained before and immediately after exercise for immunohistochemical analysis to determine lipid, perilipin 3, perilipin 5, and GLUT4 protein contents while GLUT 4 mRNA was quantified using RT-qPCR. Lipid droplet size decreased whereas total intramyocellular lipid content tended to reduce (p=0.07) after an acute bout of endurance exercise. The density of smaller lipid droplets in the peripheral sarcoplasmic region significantly increased (0.584 ± 0.04 to 0.638 ± 0.08 AU; p=0.01) while larger lipid droplets significantly decreased (p<0.05). GLUT4 mRNA tended to increase (p=0.05). There were no significant changes in GLUT 4, perilipin 3, and perilipin 5 protein levels. The study demonstrates that exercise may impact metabolism by enhancing the quantity of smaller lipid droplets over larger lipid droplets.

Oleic acid abomasal infusion limits lipolysis and improves insulin sensitivity in adipose tissue from periparturient dairy cows

Excessive adipose tissue (AT) lipolysis around parturition in dairy cows is associated with impaired AT insulin sensitivity and increased incidence of metabolic diseases. Supplementing cows with oleic acid (OA) reduces circulating biomarkers of lipolysis and improves energy balance. Nevertheless, it is unclear if OA alters lipid trafficking in AT. In the liver and skeletal muscle, OA improves mitochondrial function and promotes lipid droplet formation by activating perilipin 5 (PLIN5) and peroxisome proliferator-activated receptor α (PPARα). However, it is unknown if this mechanism occurs in AT. The objective of this study was to determine the effect of OA on AT lipolysis, systemic and AT insulin sensitivity, and AT mitochondrial function in periparturient dairy cows. Twelve rumen-cannulated Holstein cows were infused abomasally following parturition with ethanol (CON) or OA (60 g/d) for 14 d. Subcutaneous AT samples were collected at 11 ± 3.6 d before calving (-12 d), and 6 ± 1.0 d (7 d) and 13 ± 1.4 d (14 d) after parturition. An intravenous glucose tolerance test was performed on d 14. Adipocyte morphometry was performed on hematoxylin and eosin-stained AT sections. The antilipolytic effect of insulin (1 μg/L) was evaluated using an ex vivo explant culture following lipolysis stimulation. PLIN5 and PPARα transcription and translation were determined by real-time quantitative PCR and capillary electrophoresis, respectively. RNA sequencing was used to evaluate the transcriptomic profile of mitochondrial gene networks. In CON cows, postpartum lipolysis increased the percentage of smaller (<3,000 µm2) adipocytes at 14 d compared with -12 d. However, OA limited adipocyte size reduction at 14 d. Likewise, OA decreased lipolysis plasma markers nonesterified free fatty acids and β-hydroxybutyrate at 5 and 7 d. Over the 14-d period, compared with CON, OA increased the concentration of plasma insulin and decreased plasma glucose. During the glucose tolerance test, OA decreased circulating glucose concentration (at 10, 20, 30, 40 min) and the glucose clearance rate. Moreover, OA increased insulin at 10 and 20 min and tended to increase it at 30 min. Following lipolysis stimulation, OA improved the antilipolytic effect of insulin in the AT at 14 d. PLIN5 and PPARA gene expression decreased postpartum regardless of treatment. However, OA increased PLIN5 protein expression at 14 d and increased PPARA at 7 and 14 d. Immunohistochemical analysis of AT and RNA sequencing data showed that OA increased the number of mitochondria and improved mitochondrial function. However, OA had no effect on production and digestibility. Our results demonstrate that OA limits AT lipolysis, improves systemic and AT insulin sensitivity, and is associated with markers of mitochondrial function supporting a shift to lipogenesis in AT of periparturient dairy cows.

Cardiac Plin5 interacts with SERCA2 and promotes calcium handling and cardiomyocyte contractility.

The adult heart develops hypertrophy to reduce ventricular wall stress and maintain cardiac function in response to an increased workload. Although pathological hypertrophy generally progresses to heart failure, physiological hypertrophy may be cardioprotective. Cardiac-specific overexpression of the lipid-droplet protein perilipin 5 (Plin5) promotes cardiac hypertrophy, but it is unclear whether this response is beneficial. We analyzed RNA-sequencing data from human left ventricle and showed that cardiac PLIN5 expression correlates with up-regulation of cardiac contraction-related processes. To investigate how elevated cardiac Plin5 levels affect cardiac contractility, we generated mice with cardiac-specific overexpression of Plin5 (MHC-Plin5 mice). These mice displayed increased left ventricular mass and cardiomyocyte size but preserved heart function. Quantitative proteomics identified sarcoplasmic/endoplasmic reticulum Ca2+ ATPase 2 (SERCA2) as a Plin5-interacting protein. In situ proximity ligation assay further confirmed the Plin5/SERCA2 interaction. Live imaging showed increases in intracellular Ca2+ release during contraction, Ca2+ removal during relaxation, and SERCA2 function in MHC-Plin5 versus WT cardiomyocytes. These results identify a role of Plin5 in improving cardiac contractility through enhanced Ca2+ signaling.

Aflatoxin B1 exposure triggers hepatic lipotoxicity via p53 and perilipin 2 interaction-mediated mitochondria-lipid droplet contacts: An in vitro and in vivo assessment

Aflatoxin B1 (AFB1) is one of the most toxic mycotoxins widely found in food contaminants, and its target organ is the liver. It poses a major food security and public health threat worldwide. However, the lipotoxicity mechanism of AFB1 exposure-induced liver injury remains unclear and requires further elucidation. Herein, we investigated the potential hepatic lipotoxicity of AFB1 exposure using in vitro and in vivo models to assess the public health hazards of high dietary AFB1 exposure. We demonstrated that low-dose of AFB1 (1.25 μM for 48 h, about one-fifth of the IC50 in HepG2 and HepaRG cells, IC50 are 5.995 μM and 5.266 μM, respectively) exposure significantly induced hepatic lipotoxicity, including abnormal lipid droplets (LDs) growth, mitochondria-LDs contacts increase, lipophagy disruption, and lipid accumulation. Mechanistically, we showed that AFB1 exposure promoted the mitochondrial p53 (mito-p53) and LDs-associated protein perilipin 2 (PLIN2) interaction-mediated mitochondria-LDs contacts, resulting in lipid accumulation in hepatocytes. Mito-p53-targeted inhibition, knockdown of PLIN2, and rapamycin application efficiently promoted the lysosome-dependent lipophagy and alleviated the hepatic lipotoxicity and liver injury induced by AFB1 exposure. Overall, our study found that mito-p53 and PLIN2 interaction mediates three organelles-mitochondria, LDs, and lysosomal networks to regulate lipid homeostasis in AFB1 exposure-induced hepatotoxicity, revealing how this unique trio of organelles works together and provides a novel insight into the targeted intervention in inter-organelle lipid sensing and trafficking for alleviating hazardous materials-induced hepatic lipotoxicity.