scholarly journals Metabolism of palmitate in perfused rat liver. Computer models of subcellular triacylglycerol metabolism

1979 ◽  
Vol 184 (1) ◽  
pp. 73-81 ◽  
Author(s):  
Jens Kondrup ◽  
Stig E. Damgaard ◽  
Peter Fleron
Keyword(s):  
Fatty Acids ◽  
Endoplasmic Reticulum ◽  
Lipid Droplets ◽  
Preceding Paper ◽  
Computer Models ◽  
The Other ◽  
Triacylglycerol Metabolism ◽  
Cytoplasmic Lipid Droplets ◽  
Hepatic Triacylglycerol ◽  
Hydrolysis Of

1. In the preceding paper [Kondrup (1979) Biochem. J.184, 63–71] the separation of two major fractions of hepatic triacylglycerol was described. One fraction contained triacylglycerol from the endoplasmic reticulum and from the Golgi apparatus. The other fraction contained triacylglycerol from the cytoplasmic lipid droplets. In the present paper possible precursor–product relationships between the two fractions were investigated by means of computer models. 2. The fatty acids present in di- and tri-acylglycerol in the fractions isolated in the time studies were analysed by gas chromatography. From this analysis the relative specific radioactivities, and contents, of palmitate in acylglycerols in the two fractions at the various time points were calculated. 3. A computer was used to predict relative specific radioactivities of pools in defined models of hepatic triacylglycerol metabolism. The acceptability of the models was evaluated by comparing predicted with measured relative specific radioactivities. 4. It is suggested that triacylglycerol in cytoplasmic lipid droplets does not originate (a) directly from triacylglycerol in the endoplasmic reticulum, (b) from a sub-pool of it or (c) directly from non-esterified fatty acids entering the cell. Rather, it is formed from diacylglycerol (and acyl-CoA) in the endoplasmic reticulum. Diacylglycerol, on the other hand, is furnished in part by hydrolysis of triacylglycerol in the endoplasmic reticulum. 5. This suggestion is discussed in relation to previous models of hepatic fatty acid metabolism.

scholarly journals Mdm1 maintains endoplasmic reticulum homeostasis by spatially regulating lipid droplet biogenesis

2019 ◽  
Vol 218 (4) ◽  
pp. 1319-1334 ◽  
Author(s):  
Hanaa Hariri ◽  
Natalie Speer ◽  
Jade Bowerman ◽  
Sean Rogers ◽  
Gang Fu ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Endoplasmic Reticulum ◽  
Lipid Droplet ◽  
Lipid Droplets ◽  
Fatty Acyl ◽  
Nutrient Depletion ◽  
Coenzyme A Ligase ◽  
Response To Stress ◽  
Acyl Coenzyme A ◽  
Er Homeostasis

Lipid droplets (LDs) serve as cytoplasmic reservoirs for energy-rich fatty acids (FAs) stored in the form of triacylglycerides (TAGs). During nutrient stress, yeast LDs cluster adjacent to the vacuole/lysosome, but how this LD accumulation is coordinated remains poorly understood. The ER protein Mdm1 is a molecular tether that plays a role in clustering LDs during nutrient depletion, but its mechanism of function remains unknown. Here, we show that Mdm1 associates with LDs through its hydrophobic N-terminal region, which is sufficient to demarcate sites for LD budding. Mdm1 binds FAs via its Phox-associated domain and coenriches with fatty acyl–coenzyme A ligase Faa1 at LD bud sites. Consistent with this, loss of MDM1 perturbs free FA activation and Dga1-dependent synthesis of TAGs, elevating the cellular FA level, which perturbs ER morphology and sensitizes yeast to FA-induced lipotoxicity. We propose that Mdm1 coordinates FA activation adjacent to the vacuole to promote LD production in response to stress, thus maintaining ER homeostasis.

scholarly journals Spatiotemporal dynamics of triglyceride storage in unilocular adipocytes

2014 ◽  
Vol 25 (25) ◽  
pp. 4096-4105 ◽  
Author(s):  
Michael Chu ◽  
Harini Sampath ◽  
David Y. Cahana ◽  
Christoph A. Kahl ◽  
Romel Somwar ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Endoplasmic Reticulum ◽  
Adipose Tissue ◽  
Free Fatty Acids ◽  
Lipid Droplets ◽  
Ex Vivo ◽  
Spatiotemporal Dynamics ◽  
Biological Features ◽  
Adipocyte Hypertrophy ◽  
Cellular Organelles

The spatiotemporal dynamics of triglyceride (TG) storage in unilocular adipocytes are not well understood. Here we applied ex vivo technology to study trafficking and metabolism of fluorescent fatty acids in adipose tissue explants. Live imaging revealed multiple cytoplasmic nodules surrounding the large central lipid droplet (cLD) of unilocular adipocytes. Each cytoplasmic nodule harbors a series of closely associated cellular organelles, including micro–lipid droplets (mLDs), mitochondria, and the endoplasmic reticulum. Exogenously added free fatty acids are rapidly adsorbed by mLDs and concurrently get esterified to TG. This process is greatly accelerated by insulin. mLDs transfer their content to the cLD, serving as intermediates that mediate packaging of newly synthesized TG in the large interior of a unilocular adipocyte. This study reveals novel cell biological features that may contribute to the mechanism of adipocyte hypertrophy.

scholarly journals Postlipolytic insulin-dependent remodeling of micro lipid droplets in adipocytes

2012 ◽  
Vol 23 (10) ◽  
pp. 1826-1837 ◽  
Author(s):  
Nicholas Ariotti ◽  
Samantha Murphy ◽  
Nicholas A. Hamilton ◽  
Lizhen Wu ◽  
Kathryn Green ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Endoplasmic Reticulum ◽  
Lipid Droplets ◽  
Electron Tomography ◽  
Morphological Changes ◽  
Quantitative Imaging ◽  
The Reformation ◽  
Fundamental Process ◽  
Insulin Dependent ◽  
Fat Pads

Despite the lipolysis–lipogenesis cycle being a fundamental process in adipocyte biology, very little is known about the morphological changes that occur during this process. The remodeling of lipid droplets to form micro lipid droplets (mLDs) is a striking feature of lipolysis in adipocytes, but once lipolysis ceases, the cell must regain its basal morphology. We characterized mLD formation in cultured adipocytes, and in primary adipocytes isolated from mouse epididymal fat pads, in response to acute activation of lipolysis. Using real-time quantitative imaging and electron tomography, we show that formation of mLDs in cultured adipocytes occurs throughout the cell to increase total LD surface area by ∼30% but does not involve detectable fission from large LDs. Peripheral mLDs are monolayered structures with a neutral lipid core and are sites of active lipolysis. Electron tomography reveals preferential association of mLDs with the endoplasmic reticulum. Treatment with insulin and fatty acids results in the reformation of macroLDs and return to the basal state. Insulin-dependent reformation of large LDs involves two distinct processes: microtubule-dependent homotypic fusion of mLDs and expansion of individual mLDs. We identify a physiologically important role for LD fusion that is involved in a reversible lipolytic cycle in adipocytes.

scholarly journals Cerebellar ataxia disease–associated Snx14 promotes lipid droplet growth at ER–droplet contacts

2019 ◽  
Vol 218 (4) ◽  
pp. 1335-1351 ◽  
Author(s):  
Sanchari Datta ◽  
Yang Liu ◽  
Hanaa Hariri ◽  
Jade Bowerman ◽  
W. Mike Henne
Keyword(s):  
Fatty Acids ◽  
Endoplasmic Reticulum ◽  
Cerebellar Ataxia ◽  
Lipid Droplets ◽  
Fatty Acyl ◽  
Droplet Growth ◽  
Sorting Nexin ◽  
Coa Ligase ◽  
In Trans ◽  
Time Point

Lipid droplets (LDs) are nutrient reservoirs used by cells to maintain homeostasis. Nascent droplets form on the endoplasmic reticulum (ER) and grow following an influx of exogenous fatty acids (FAs). The budding of LDs requires extensive ER–LD crosstalk, but how this is regulated remains poorly understood. Here, we show that sorting nexin protein Snx14, an ER-resident protein associated with the cerebellar ataxia SCAR20, localizes to ER–LD contacts following FA treatment, where it promotes LD maturation. Using proximity-based APEX technology and topological dissection, we show that Snx14 accumulates specifically at ER–LD contacts independently of Seipin, where it remains ER-anchored and binds LDs in trans. SNX14KO cells exhibit perturbed LD morphology, whereas Snx14 overexpression promotes LD biogenesis and extends ER–LD contacts. Multi–time point imaging reveals that Snx14 is recruited to ER microdomains containing the fatty acyl-CoA ligase ACSL3, where nascent LDs bud. We propose that Snx14 is a novel marker for ER–LD contacts and regulates FA-stimulated LD growth.

scholarly journals Gonadal macrophage infiltration in congenital lipoid adrenal hyperplasia

2016 ◽  
Vol 175 (2) ◽  
pp. 127-132 ◽  
Author(s):  
Tomohiro Ishii ◽  
Ryuji Fukuzawa ◽  
Takeshi Sato ◽  
Koji Muroya ◽  
Masanori Adachi ◽  
...  
Keyword(s):  
Lipid Droplets ◽  
Immunohistochemical Analysis ◽  
The Other ◽  
Macrophage Infiltration ◽  
Adrenal Hyperplasia ◽  
Theca Cells ◽  
Congenital Lipoid Adrenal Hyperplasia ◽  
Significant Difference ◽  
Cytoplasmic Lipid Droplets ◽  
Steroidogenic Cells

Objective Congenital lipoid adrenal hyperplasia (lipoid CAH) results in impairment of adrenal and gonadal steroidogenesis caused by STAR mutations. Our previous study revealed upregulation of genes associated with inflammatory or immune response and macrophage infiltration in the adrenal cortex of Star-knockout mice. This study aimed at investigating macrophage infiltration in the gonads from human patients with lipoid CAH. Design This study includes seven patients with lipoid CAH who underwent gonadectomy: two XX women (age, 22 and 40 years) and five XY boys (1 year). Two women with ovarian cysts (32 and 40 years) and six boys with autopsy or tumor (1 year) were examined as controls. Immunohistochemical analysis of their gonads was performed to determine steroidogenic cells by NR5A1 or CYP17A1 and macrophages by IBA1 or CD68. Results An increased number of macrophages infiltrated into the ovaries of lipoid CAH and consisted of two subpopulations: one scattered within and around a layer of theca cells of maturing follicles and the other massively aggregated in the stroma. Abundant cytoplasmic lipid droplets were observed not only in the theca cells but also in the stromal macrophages. There was no significant difference in the number of macrophages in the testicular interstitium between lipoid CAH (95% confidence interval (95% CI: 19.3–47.7 per 0.2mm2) and controls (95% CI: 13.3–25.8 per 0.2mm2) (P=0.10). Conclusions These results demonstrate that macrophages infiltrate the ovaries of lipoid CAH, where the theca cells and the stromal macrophages have abundant cytoplasmic lipid droplets.

scholarly journals STRATIFICATION AND SUBSEQUENT BEHAVIOR OF PLANT CELL ORGANELLES

1963 ◽  
Vol 18 (2) ◽  
pp. 441-457 ◽  
Author(s):  
G. Benjamin Bouck
Keyword(s):  
Electron Microscopy ◽  
Endoplasmic Reticulum ◽  
Rough Endoplasmic Reticulum ◽  
Lipid Droplets ◽  
Smooth Endoplasmic Reticulum ◽  
The Other ◽  
Cell Organelles ◽  
Large Unit ◽  
Original Length ◽  
Subsequent Behavior

Living excised roots of pea were centrifuged at 20,000 g for 24 hours, and the behavior of organelles was followed by electron microscopy at various intervals after centrifugation. With these forces, organelles are not perceptibly or irreversibly damaged, nor is the viability of the whole root destroyed. Organelles stratify generally in the order of lipid (centripetal pole), vacuoles, smooth endoplasmic reticulum and dictyosomes, proplastids (without starch), mitochondria, rough endoplasmic reticulum, proplastids with starch. The nucleus distends from the vacuolar region to the extreme centrifugal pole of the cell, while the chromatin and nucleolus seek the centrifugal pole of the nucleus. During the redistribution of organelles the rough endoplasmic reticulum is among the first to reorient, and possible explanations for this are discussed. Mitochondria can be stretched elastically many times their original length, but proplastids seem fairly rigid. Small vacuoles, forced together during centrifugation, apparently may fuse to form a large unit. Lipid droplets, on the other hand, tend to remain separate. Dictyosomes and smooth endoplasmic reticulum layer in the same region of the centrifuged cell, indicating a density similarity between these two organelles.

scholarly journals Dictyostelium Lipid Droplets Host Novel Proteins

2013 ◽  
Vol 12 (11) ◽  
pp. 1517-1529 ◽  
Author(s):  
Xiaoli Du ◽  
Caroline Barisch ◽  
Peggy Paschke ◽  
Cornelia Herrfurth ◽  
Oliver Bertinetti ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Endoplasmic Reticulum ◽  
Lipid Droplet ◽  
Lipid Droplets ◽  
Unsaturated Fatty Acids ◽  
Neutral Lipids ◽  
Saturated Fatty Acids ◽  
Endoplasmic Reticulum Membrane ◽  
Hydrophobic Core ◽  
Content Type

ABSTRACT Across all kingdoms of life, cells store energy in a specialized organelle, the lipid droplet. In general, it consists of a hydrophobic core of triglycerides and steryl esters surrounded by only one leaflet derived from the endoplasmic reticulum membrane to which a specific set of proteins is bound. We have chosen the unicellular organism Dictyostelium discoideum to establish kinetics of lipid droplet formation and degradation and to further identify the lipid constituents and proteins of lipid droplets. Here, we show that the lipid composition is similar to what is found in mammalian lipid droplets. In addition, phospholipids preferentially consist of mainly saturated fatty acids, whereas neutral lipids are enriched in unsaturated fatty acids. Among the novel protein components are LdpA, a protein specific to Dictyostelium , and Net4, which has strong homologies to mammalian DUF829/Tmem53/NET4 that was previously only known as a constituent of the mammalian nuclear envelope. The proteins analyzed so far appear to move from the endoplasmic reticulum to the lipid droplets, supporting the concept that lipid droplets are formed on this membrane.

scholarly journals Monitoring of the enzymatic activity of intracellular lipases of Ustilago maydis expressed during the growth under nitrogen limitation and its correlation in lipolytic reactions

2019 ◽  
Vol 70 (4) ◽  
pp. 327
Author(s):  
M. G. Araiza-Villanueva ◽  
D. R. Olicón-Hernández ◽  
J. P. Pardo ◽  
H. Vázquez-Meza ◽  
G. Guerra-Sánchez
Keyword(s):  
Fatty Acids ◽  
Polyunsaturated Fatty Acids ◽  
Enzymatic Activity ◽  
Lipase Activity ◽  
Lipid Accumulation ◽  
Lipid Droplets ◽  
Nitrogen Limitation ◽  
Nitrogen Starvation ◽  
Ustilago Maydis ◽  
The Other

Under nitrogen starvation, Ustilago maydis forms lipid droplets (LDs). Although the dynamics of these organelles are known in the literature, the identity of the lipases implicated in their degradation is unknown. We determined lipase activity and identified the intracellular lipases expressed during growth under nitrogen starvation and YPD media by zymograms. The results showed that cytosolic extracts exhibited higher lipase activity when cells were grown in YPD. Under nitrogen starvation, lipase activity was not detected after 24 h of culture, resulting in lipid accumulation in LDs. This suggests that these lipases could be implicated in LD degradation. In the zymogram, two bands, one of 25 and the other of 37 kDa, presented lipase activity. The YPD extracts showed lipase activity in olive and almond oils, which contain triacylglycerols with mono and polyunsaturated fatty acids. This is the first report about U. maydis cytosolic lipases involved in LD degradation.

scholarly journals Metabolism of palmitate in perfused rat liver. Effect of low and high ethanol concentrations at various concentrations of palmitate in the perfusion medium

1979 ◽  
Vol 184 (1) ◽  
pp. 83-88 ◽  
Author(s):  
Jens Kondrup ◽  
Frank Lundquist ◽  
Stig E. Damgaard
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Rat Liver ◽  
Lipid Droplets ◽  
Fatty Acid Uptake ◽  
Acid Uptake ◽  
Acute Fatty Liver ◽  
Cytoplasmic Lipid Droplets ◽  
Ethanol Ethanol ◽  
High Ethanol

1. The effect of ethanol on the metabolism of [1-14C]palmitate in rat liver was investigated in a single-pass perfusion system at concentrations of 10mm- or 80mm-ethanol and 0.2mm- or 1mm-palmitate. 2. After the perfusion the hepatic lipid was isolated in subcellular fractions. The two major fractions contained triacylglycerol from cytoplasmic lipid droplets and from endoplasmic reticulum plus Golgi apparatus respectively. 3. In experiments with 0.2mm-palmitate perfusion with 10mm- or 80mm-ethanol did not measurably increase the esterification, and the oxidation was markedly decreased and the fatty acid uptake was not affected. 4. Perfusion with ethanol, at 1mm-palmitate, increased the fatty acid uptake, increased esterification and decreased oxidation. The effects of 10mm- and 80mm-ethanol were similar. The incorporation of [1-14C]palmitate into triacylglycerol in cytoplasmic lipid droplets was not affected statistically significantly by ethanol. Ethanol increased the incorporation of [1-14C]palmitate into di- and tri-acylglycerol in the membranous fraction. Estimated chemically, the contents of di- and tri-acylglycerol were only slightly affected by ethanol. These results suggest that the effect of ethanol was to increase the turnover of fatty acids in triacylglycerol rather than to increase its accumulation. 5. The results indicate that an increased concentration of fatty acids is more important for the formation of acute fatty liver in fed rats than are the direct effects of ethanol on hepatic fatty acid metabolism.

scholarly journals Metabolism of palmitate in perfused rat liver. Effect of ethanol in livers from rats fed on a high-fat diet with or without ethanol

1979 ◽  
Vol 184 (1) ◽  
pp. 89-95 ◽  
Author(s):  
Jens Kondrup ◽  
Frank Lundquist ◽  
Stig E. Damgaard
Keyword(s):  
Fatty Liver ◽  
High Fat Diet ◽  
Lipid Droplets ◽  
Energy Content ◽  
Chow Diet ◽  
Perfused Rat Liver ◽  
High Fat ◽  
Cytoplasmic Lipid Droplets ◽  
Hepatic Triacylglycerol ◽  
Palmitate Metabolism

1. Rats were treated for 4 weeks with liquid diets that contained, on the basis of energy content, 35% fat, 18% protein and 47% carbohydrate (high-fat diet) or 35% fat, 18% protein, 11% carbohydrate and 36% ethanol (high-fat/ethanol diet). 2. The livers were perfused with 1mm-[1-14C]palmitate and with 0, 10mm- or 80mm-ethanol. The oxidation and esterification of palmitate was measured. Two subcellular pools of triacylglycerol were separated; one contained triacylglycerol from cytoplasmic lipid droplets and the other contained triacylglycerol from the endoplasmic reticulum and Golgi apparatus. 3. In the presence of ethanol, liver from rats fed on the high-fat diet esterified about 70% of the [1-14C]palmitate taken up compared with 90% in liver from rats fed chow (containing 11% fat on the basis of energy content). Compared with chow diet the high-fat diet did not potentiate the effect of ethanol on storage of [1-14C]palmitate in hepatic triacylglycerol. The relation between the fat content of the diet and the degree of fatty liver induced by by ethanol [Lieber & DeCarli (1970) Am. J. Clin. Nutr.23, 474–478] is discussed. 4. The ethanol-containing diet increased the hepatic content of triacylglycerol 4-fold and the increase was exclusively found in the fraction suggested to contain lipid from cytoplasmic lipid droplets. The ethanol-induced fatty liver, perfused with ethanol, esterified and oxidized palmitate at rates that were quite similar to the rates found in high-fat control livers perfused without ethanol. This suggests that the fatty liver had adapted to the presence of ethanol with respect to palmitate metabolism. 5. O2 and ethanol uptake by the livers were not affected by the ethanol-containing diet.

Sign in / Sign up

Export Citation Format

Share Document