scholarly journals Universal phase behaviors of intracellular lipid droplets

2019 ◽  
Author(s):  
Shunsuke F. Shimobayashi ◽  
Yuki Ohsaki
Keyword(s):  
Phase Transition ◽  
Phase Diagram ◽  
Lipid Droplets ◽  
Neutral Lipids ◽  
Droplet Surface ◽  
Molecular Organization ◽  
Cholesteryl Esters ◽  
Intracellular Lipid

Lipid droplets are cytoplasmic micro-scale organelles involved in energy homeostasis and handling of cellular lipids and proteins. The core structure is mainly composed of two kinds of neutral lipids, triglycerides and cholesteryl esters, which are coated by a phospholipid monolayer and proteins. Despite the liquid crystalline nature of cholesteryl esters, the connection between the lipid composition and physical states is poorly understood. Here, we present the first universal intracellular phase diagram of lipid droplets, semi-quantitatively consistent with the in vitro phase diagram, and reveal that cholesterol esters cause the liquid-liquid crystal phase transition under near-physiological conditions. The internal molecules of the liquid crystallized lipid droplets are aligned radially. We moreover combine in vivo and in vitro studies, together with the theory of confined liquid crystals, to suggest that the radial molecular alignments in intracellular lipid droplets are caused by an anchoring force at the droplet surface. Our findings on the phase transition of lipid droplets and resulting molecular organization contribute to a better understanding of their biological functions and diseases.

scholarly journals Universal phase behaviors of intracellular lipid droplets

2019 ◽  
Vol 116 (51) ◽  
pp. 25440-25445 ◽  
Author(s):  
Shunsuke F. Shimobayashi ◽  
Yuki Ohsaki
Keyword(s):  
Phase Transition ◽  
Phase Diagram ◽  
Lipid Droplets ◽  
Energy Homeostasis ◽  
Neutral Lipids ◽  
Droplet Surface ◽  
Molecular Organization ◽  
Cholesteryl Esters

Lipid droplets are cytoplasmic microscale organelles involved in energy homeostasis and handling of cellular lipids and proteins. The core structure is mainly composed of two kinds of neutral lipids, triglycerides and cholesteryl esters, which are coated by a phospholipid monolayer and proteins. Despite the liquid crystalline nature of cholesteryl esters, the connection between the lipid composition and physical states is poorly understood. Here, we present a universal intracellular phase diagram of lipid droplets, semiquantitatively consistent with the in vitro phase diagram, and reveal that cholesterol esters cause the liquid–liquid crystal phase transition under near-physiological conditions. We moreover combine in vivo and in vitro studies, together with the theory of confined liquid crystals, to suggest that the radial molecular alignments in the liquid crystallized lipid droplets are caused by an anchoring force at the droplet surface. Our findings on the phase transition of lipid droplets and resulting molecular organization contribute to a better understanding of their biological functions and diseases.

Identification of Perilipin-2 as a lipid droplet protein regulated in oocytes during maturation

2010 ◽  
Vol 22 (8) ◽  
pp. 1262 ◽  
Author(s):  
Xing Yang ◽  
Kylie R. Dunning ◽  
Linda L.-Y. Wu ◽  
Theresa E. Hickey ◽  
Robert J. Norman ◽  
...  
Keyword(s):  
Lipid Droplet ◽  
Lipid Content ◽  
Lipid Droplets ◽  
Intracellular Lipids ◽  
Epidermal Growth ◽  
Novel Method ◽  
Perilipin 2 ◽  
Lipid Droplet Protein

Lipid droplet proteins regulate the storage and utilisation of intracellular lipids. Evidence is emerging that oocyte lipid utilisation impacts embryo development, but lipid droplet proteins have not been studied in oocytes. The aim of the present study was to characterise the size and localisation of lipid droplets in mouse oocytes during the periovulatory period and to identify lipid droplet proteins as potential biomarkers of oocyte lipid content. Oocyte lipid droplets, visualised using a novel method of staining cumulus–oocyte complexes (COCs) with BODIPY 493/503, were small and diffuse in oocytes of preovulatory COCs, but larger and more centrally located after maturation in response to ovulatory human chorionic gonadotrophin (hCG) in vivo, or FSH + epidermal growth factor in vitro. Lipid droplet proteins Perilipin, Perilipin-2, cell death-inducing DNA fragmentation factor 45-like effector (CIDE)-A and CIDE-B were detected in the mouse ovary by immunohistochemistry, but only Perilipin-2 was associated with lipid droplets in the oocyte. In COCs, Perilipin-2 mRNA and protein increased in response to ovulatory hCG. IVM failed to induce Perilipin-2 mRNA, yet oocyte lipid content was increased in this context, indicating that Perilipin-2 is not necessarily reflective of relative oocyte lipid content. Thus, Perilipin-2 is a lipid droplet protein in oocytes and its induction in the COC concurrent with dynamic reorganisation of lipid droplets suggests marked changes in lipid utilisation during oocyte maturation.

scholarly journals Exon 9-deleted CETP inhibits full length-CETP synthesis and promotes cellular triglyceride storage

2020 ◽  
Vol 61 (3) ◽  
pp. 422-431 ◽  
Author(s):  
Lahoucine Izem ◽  
Yan Liu ◽  
Richard E. Morton
Keyword(s):  
Lipid Metabolism ◽  
Lipid Droplets ◽  
Full Length ◽  
Intracellular Lipid ◽  
Transfer Protein ◽  
Lipid Phenotype ◽  
Exon 9 ◽  
And Storage

Cholesteryl ester transfer protein (CETP) exists as full-length (FL) and exon 9 (E9)-deleted isoforms. The function of E9-deleted CETP is poorly understood. Here, we investigated the role of E9-deleted CETP in regulating the secretion of FL-CETP by cells and explored its possible role in intracellular lipid metabolism. CETP overexpression in cells that naturally express CETP confirmed that E9-deleted CETP is not secreted, and showed that cellular FL- and E9-deleted CETP form an isolatable complex. Coexpression of CETP isoforms lowered cellular levels of both proteins and impaired FL-CETP secretion. These effects were due to reduced synthesis of both isoforms; however, the predominate consequence of FL- and E9-deleted CETP coexpression is impaired FL-CETP synthesis. We reported previously that reducing both CETP isoforms or overexpressing FL-CETP impairs cellular triglyceride (TG) storage. To investigate this further, E9-deleted CETP was expressed in SW872 cells that naturally synthesize CETP and in mouse 3T3-L1 cells that do not. E9-deleted CETP overexpression stimulated SW872 triglyceride synthesis and increased stored TG 2-fold. Expression of E9-deleted CETP in mouse 3T3-L1 cells produced a similar lipid phenotype. In vitro, FL-CETP promotes the transfer of TG from ER-enriched membranes to lipid droplets. E9-deleted CETP also promoted this transfer, although less effectively, and it inhibited the transfer driven by FL-CETP. We conclude that FL- and E9-deleted CETP isoforms interact to mutually decrease their intracellular levels and impair FL-CETP secretion by reducing CETP biosynthesis. E9-deleted CETP, like FL-CETP, alters cellular TG metabolism and storage but in a contrary manner.

scholarly journals Dual binding motifs underpin the hierarchical association of perilipins1–3 with lipid droplets

2019 ◽  
Vol 30 (5) ◽  
pp. 703-716 ◽  
Author(s):  
Dalila Ajjaji ◽  
Kalthoum Ben M'barek ◽  
Michael L. Mimmack ◽  
Cheryl England ◽  
Haya Herscovitz ◽  
...  
Keyword(s):  
Lipid Droplets ◽  
Tissue Type ◽  
Binding Motifs ◽  
Amino Terminal ◽  
A Cell ◽  
Oil Water ◽  
Carboxy Terminal ◽  
Hierarchical Manner

Lipid droplets (LDs) in all eukaryotic cells are coated with at least one of the perilipin (Plin) family of proteins. They all regulate key intracellular lipases but do so to significantly different extents. Where more than one Plin is expressed in a cell, they associate with LDs in a hierarchical manner. In vivo, this means that lipid flux control in a particular cell or tissue type is heavily influenced by the specific Plins present on its LDs. Despite their early discovery, exactly how Plins target LDs and why they displace each other in a “hierarchical” manner remains unclear. They all share an amino-terminal 11-mer repeat (11mr) amphipathic region suggested to be involved in LD targeting. Here, we show that, in vivo, this domain functions as a primary highly reversible LD targeting motif in Plin1–3, and, in vitro, we document reversible and competitive binding between a wild-type purified Plin1 11mr peptide and a mutant with reduced binding affinity to both “naked” and phospholipid-coated oil–water interfaces. We also present data suggesting that a second carboxy-terminal 4-helix bundle domain stabilizes LD binding in Plin1 more effectively than in Plin2, whereas it weakens binding in Plin3. These findings suggest that dual amphipathic helical regions mediate LD targeting and underpin the hierarchical binding of Plin1–3 to LDs.

In vitro and in vivo inhibition of renin by fatty acids.

1978 ◽  
Vol 234 (6) ◽  
pp. E593 ◽  
Author(s):  
T A Kotchen ◽  
W J Welch ◽  
R T Talwalkar
Keyword(s):  
Blood Pressure ◽  
Fatty Acids ◽  
Linoleic Acid ◽  
Angiotensin Ii ◽  
Neutral Lipids ◽  
Pressor Response ◽  
Arterial Blood ◽  
Arachidonic Acids

Circulating neutral lipids inhibit the in vitro renin reaction. To identify the inhibitor(s), free fatty acids were added to human renin and homologous substrate. Capric, lauric, palmitoleic, linoleic, and arachidonic acids each inhibited the rate of angiotensin I production in vitro (P less than 0.01). Inhibition by polysaturated fatty acids (linoleic and arachidonic) was less (P less than 0.01) after catalytic hydrogenation of the double bonds. To evaluate an in vivo effect of renin inhibition intra-arterial blood pressure responses to infusions of renin and angiotensin II (5.0 microgram) were measured in anephric rats (n = 6) before and after infusion of linoleic acid (10 mg iv). Mean increase of blood pressure to angiotensin II before (75 mmHg +/- 9) and after (90 +/- 12) linoleic acid did not differ (P greater than 0.05). However, the pressor response to renin after linoleic acid (18 +/- 3) was less (P less than 0.00)) than that before (102 +/- 13). In summary, several fatty acids inhibit the in vitro renin reaction, and in part inhibition is dependent on unsaturation. Linoleic acid also inhibits the in vivo pressor response to renin. These results suggest that fatty acids may modify the measurement of plasma renin activity and may also affect angiotensin production in vivo.

scholarly journals Morphological features of lipid droplet transition during porcine oocyte fertilisation and early embryonic development to blastocyst in vivo and in vitro

Zygote ◽  
2002 ◽  
Vol 10 (4) ◽  
pp. 355-366 ◽  
Author(s):  
Kazuhiro Kikuchi ◽  
Hans Ekwall ◽  
Paisan Tienthai ◽  
Yasuhiro Kawai ◽  
Junko Noguchi ◽  
...  
Keyword(s):  
Embryonic Development ◽  
Oocyte Maturation ◽  
Lipid Droplets ◽  
Early Embryonic Development ◽  
Oocyte Activation ◽  
Energy Status ◽  
Thin Sections ◽  
Porcine Oocyte

Lipid content in mammalian oocytes or embryos differs among species, with bovine and porcine oocytes and embryos showing large cytoplasmic droplets. These droplets are considered to play important roles in energy metabolism during oocyte maturation, fertilisation and early embryonic development, and also in the freezing ability of oocytes or embryos; however, their detailed distribution or function is not well understood. In the present study, changes in the distribution and morphology of porcine lipid droplets during in vivo and in vitro fertilisation, in contrast to parthenogenetic oocyte activation, as well as during their development to blastocyst stage, were evaluated by transmission electron microscopy (TEM). The analysis of semi-thin and ultra-thin sections by TEM showed conspicuous, large, electron-dense lipid droplets, sometimes associated with mitochondrial aggregates in the oocytes, irrespective of whether the oocytes had been matured in vivo or in vitro. Immediately after sperm penetration, the electron density of the lipid droplets was lost in both the in vivo and in vitro oocytes, the reduction being most evident in the oocytes developed in vitro. Density was restored in the pronculear oocytes, fully in the in vivo specimens but only partially in the in vitro ones. The number and size of the droplets seemed, however, to have decreased. At 2- to 4-cell and blastocyst stages, the features of the lipid droplets were almost the same as those of pronuclear oocytes, showing a homogeneous or saturated density in the in vivo embryos but a marbled or partially saturated appearance in the in vitro embryos. In vitro matured oocytes undergoing parthenogenesis had lipid droplets that resembled those of fertilised oocytes until the pronuclear stage. Overall, results indicate variations in both the morphology and amount of cytoplasmic lipid droplets during porcine oocyte maturation, fertilisation and early embryo development as well as differences between in vivo and in vitro development, suggesting both different energy status during preimplantation development in pigs and substantial differences between in vitro and in vivo development.

scholarly journals Dynein-Mediated Cargo Transport in Vivo

2000 ◽  
Vol 148 (5) ◽  
pp. 945-956 ◽  
Author(s):  
Steven P. Gross ◽  
Michael A. Welte ◽  
Steven M. Block ◽  
Eric F. Wieschaus
Keyword(s):  
Lipid Droplets ◽  
Developmental Stages ◽  
Cytoplasmic Dynein ◽  
Chain Gene ◽  
Unit Distance ◽  
Cargo Transport ◽  
Single Droplets ◽  
Drosophila Embryos

Cytoplasmic dynein is a microtubule-based motor with diverse cellular roles. Here, we use mutations in the dynein heavy chain gene to impair the motor's function, and employ biophysical measurements to demonstrate that cytoplasmic dynein is responsible for the minus end motion of bidirectionally moving lipid droplets in early Drosophila embryos. This analysis yields an estimate for the force that a single cytoplasmic dynein exerts in vivo (1.1 pN). It also allows us to quantitate dynein-mediated cargo motion in vivo, providing a framework for investigating how dynein's activity is controlled. We identify three distinct travel states whose general features also characterize plus end motion. These states are preserved in different developmental stages. We had previously provided evidence that for each travel direction, single droplets are moved by multiple motors of the same type (Welte et al. 1998). Droplet travel distances (runs) are much shorter than expected for multiple motors based on in vitro estimates of cytoplasmic dynein processivity. Therefore, we propose the existence of a process that ends runs before the motors fall off the microtubules. We find that this process acts with a constant probability per unit distance, and is typically coupled to a switch in travel direction. A process with similar properties governs plus end motion, and its regulation controls the net direction of transport.

scholarly journals Genetic influence on the reduction in bovine embryo lipid content by L-carnitine

2016 ◽  
Vol 28 (8) ◽  
pp. 1172 ◽  
Author(s):  
Luis Baldoceda ◽  
Dominic Gagné ◽  
Christina Ramires Ferreira ◽  
Claude Robert
Keyword(s):  
Lipid Content ◽  
Culture Medium ◽  
Cell Damage ◽  
Mitochondrial Activity ◽  
Bovine Embryo ◽  
Bovine Embryos ◽  
Intracellular Lipid ◽  
Embryo Culture Medium

The decreased rate of pregnancy obtained in cattle using frozen in vitro embryos compared with in vivo embryos has been associated with over-accumulation of intracellular lipid, which causes cell damage during cryopreservation. It is believed that the higher lipid content of blastomeres of bovine embryos produced in vitro results in darker-coloured cytoplasm, which could be a consequence of impaired mitochondrial function. In this study, l-carnitine was used as a treatment to reduce embryonic lipid content by increasing metabolism in cultured bovine embryos. We have observed previously that in vivo embryos of different dairy breeds collected from cows housed and fed under the same conditions differed in lipid content and metabolism. As such, breed effects between Holstein and Jersey were also examined in terms of general appearance, lipid composition, mitochondrial activity and gene expression. Adding l-carnitine to the embryo culture medium reduced the lipid content in both breeds due to increased mitochondrial activity. The response to l-carnitine was weaker in Jersey than in Holstein embryos. Our results thus show that genetics influence the response of bovine embryos to stimulation of mitochondrial metabolism.

scholarly journals Glehnia littoralis Root Extract Inhibits Fat Accumulation in 3T3-L1 Cells and High-Fat Diet-Induced Obese Mice by Downregulating Adipogenic Gene Expression

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Heeok Hong ◽  
Joseph F. dela Cruz ◽  
Won Seob Kim ◽  
Kiyeol Yoo ◽  
Seong Gu Hwang
Keyword(s):  
Lipid Accumulation ◽  
High Fat Diet ◽  
Fatty Acid Synthase ◽  
Obese Mice ◽  
Intracellular Lipid ◽  
Glehnia Littoralis ◽  
Intracellular Lipid Accumulation ◽  
Adipogenic Gene

Glehnia littoralis has been reported to have several pharmacological properties but no reports describing the antiadipogenic effect of this plant have been published. This study was conducted to investigate the effects of Glehnia littoralis root hot water extract (GLE) and its underlying mechanism on 3T3-L1 cell adipogenesis and in high-fat diet- (HFD-) induced obese mice. We measured intracellular lipid accumulation using oil red O staining in vitro. For in vivo study, twenty-eight C57BL/6J male mice were randomly divided into four groups, Control, HFD, HFD + 1% GLE, and HFD + 5% GLE, which was performed for eight weeks. We determined the expression levels of the adipogenesis-related proteins by RT-PCR and western blotting in HFD-induced obese mice. The GLE dose-dependently inhibited 3T3-L1 adipocyte differentiation and intracellular lipid accumulation in differentiated adipocytes. Further, body weight gain and fat accumulation were significantly lower in the GLE-treated HFD mice than in the untreated HFD mice. GLE treatment suppressed the expression of adipogenic genes such as peroxisome proliferator-activated receptor (PPAR) γ, CCAAT/enhancer-binding protein (C/EBP) α, fatty acid synthase (aP2), and fatty acid synthase (FAS). These results suggest that the GLE inhibits adipocyte differentiation and intracellular lipid accumulation by downregulating the adipogenic gene expression both in vitro and in vivo.

scholarly journals YPR139c/LOA1encodes a novel lysophosphatidic acid acyltransferase associated with lipid droplets and involved in TAG homeostasis

2012 ◽  
Vol 23 (2) ◽  
pp. 233-246 ◽  
Author(s):  
Sophie Ayciriex ◽  
Marina Le Guédard ◽  
Nadine Camougrand ◽  
Gisèle Velours ◽  
Mario Schoene ◽  
...  
Keyword(s):  
Lysophosphatidic Acid ◽  
Lipid Droplets ◽  
Neutral Lipids ◽  
In Vitro Assays ◽  
Metabolic Labeling ◽  
Lysophosphatidic Acid Acyltransferase ◽  
Escherichia Coli Cells ◽  
Type Strains

For many years, lipid droplets (LDs) were considered to be an inert store of lipids. However, recent data showed that LDs are dynamic organelles playing an important role in storage and mobilization of neutral lipids. In this paper, we report the characterization of LOA1 (alias VPS66, alias YPR139c), a yeast member of the glycerolipid acyltransferase family. LOA1 mutants show abnormalities in LD morphology. As previously reported, cells lacking LOA1 contain more LDs. Conversely, we showed that overexpression results in fewer LDs. We then compared the lipidome of loa1Δ mutant and wild-type strains. Steady-state metabolic labeling of loa1Δ revealed a significant reduction in triacylglycerol content, while phospholipid (PL) composition remained unchanged. Interestingly, lipidomic analysis indicates that both PLs and glycerolipids are qualitatively affected by the mutation, suggesting that Loa1p is a lysophosphatidic acid acyltransferase (LPA AT) with a preference for oleoyl-CoA. This hypothesis was tested by in vitro assays using both membranes of Escherichia coli cells expressing LOA1 and purified proteins as enzyme sources. Our results from purification of subcellular compartments and proteomic studies show that Loa1p is associated with LD and active in this compartment. Loa1p is therefore a novel LPA AT and plays a role in LD formation.

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