The Experts below are selected from a list of 3294 Experts worldwide ranked by ideXlab platform

Michael A. Wells - One of the best experts on this subject based on the ideXlab platform.

  • Role of lipid transfer particle in delivery of diacylglycerol from midgut to lipophorin in larval Manduca sexta.
    Insect biochemistry and molecular biology, 2001
    Co-Authors: Lilián E. Canavoso, Michael A. Wells
    Abstract:

    The present work analyzed the function of lipid transfer particle (LTP) in the process of exporting diacylglycerol from larval Manduca sexta midgut cells to lipophorin. When midgut sacs, which had been prelabeled in vivo with [(3)H]oleic acid, were incubated in vitro with a lipophorin-containing medium, a significant amount of radiolabeled diacylglycerol was transferred to lipophorin. Negligible amounts of diacylglycerol were released into lipophorin-free medium. In contrast, lipid-labeled lipophorin did not transfer diacylglycerol to the midgut sacs. The transfer of diacylglycerol from the midgut sac to lipophorin was blocked by preincubation of midgut sacs with antibody against LTP. Diacylglycerol transfer was restored to control values by the addition of purified LTP to midgut sacs that had been treated with antibody against LTP. Under these conditions the amount of diacylglycerol transferred was a function of the LTP concentration. These are the first results showing that LTP is required to export diacylglycerol from the midgut to lipophorin.

  • adipokinetic hormone induced lipolysis in the fat body of an insect manduca sexta synthesis of sn 1 2 Diacylglycerols
    Journal of Lipid Research, 1997
    Co-Authors: Estela L Arrese, Michael A. Wells
    Abstract:

    The pathway for the adipokinetic hormone-stiniu- lated synthesis of sn-1,2-diacylglyceroIs in the adult Manducu sexta fat body was studied. Adult fat body lipids were labeled by feeding 5th instar larvae either with (9,10(n)-3H)oleic acid or ( 1 (3)-3H)glycerol and after 32 days insects at the adult stage were used. This long-term prelabeling led to labeled fat body acylglycerols in which triacylglycerols comprised the main ra- dioactive lipid component (95.5%), regardless of the radiola- beled compound used. Because the distribution of radioactiv- ity among the lipid classes was very close to the mass distribution of the fat body lipid subspecies, it was concluded that homogeneous labeling of fat body lipids was obtained. After adipokinetic hormone treatment, an accumulation of radioactivity in the sn-1 ,2-diacylglycerol fraction was the only significant change found in the distribution of radioactivity among fat body lipids. The size of diacylglycerol pool in- creased 280% 60 min after adipokinetic hormone stimulation, whereas the fatty acid, monoacylglycerol and phosphatidic acid pool sizees remained constant.m These results support the hypothesis that adipokinetic hormone-stimulated synthe- sis of sn-1 ,2-diacylglycerol in the fat body involves stereospc- cific hydrolysis of the triacylglycerol stores.-Arrese, E. L., and M. A. Wells. Adipokinetic hormone-induced lipolysis in the fat body of an insect, Manducn srxtn: synthesis of .sn-l,2- Diacylglycerols. ,I. Lipad Res. 1997. 38: 68-76.

  • adipokinetic hormone induced lipolysis in the fat body of an insect manduca sexta synthesis of sn 1 2 Diacylglycerols
    Journal of Lipid Research, 1997
    Co-Authors: Estela L Arrese, Michael A. Wells
    Abstract:

    The pathway for the adipokinetic hormone-stimulated synthesis of sn-1,2-Diacylglycerols in the adult Manduca sexta fat body was studied. Adult fat body lipids were labeled by feeding 5th instar larvae either with [9,10(n)-3H]oleic acid or [1(3)-3H] glycerol and after 32 days insects at the adult stage were used. This long-term prelabeling led to labeled fat body acylglycerols in which triacylglycerols comprised the main radioactive lipid component (95.5%), regardless of the radiolabeled compound used. Because the distribution of radioactivity among the lipid classes was very close to the mass distribution of the fat body lipid subspecies, it was concluded that homogeneous labeling of fat body lipids was obtained. After adipokinetic hormone treatment, an accumulation of radioactivity in the sn-1,2-diacylglycerol fraction was the only significant change found in the distribution of radioactivity among fat body lipids. The size of diacylglycerol pool increased 280% 60 min after adipokinetic hormone stimulation, whereas the fatty acid, monoacylglycerol and phosphatidic acid pool sizes remained constant. These results support the hypothesis that adipokinetic hormone-stimulated synthesis of sn-1,2-diacylglycerol in the fat body involves stereospecific hydrolysis of the triacylglycerol stores.

Estela L Arrese - One of the best experts on this subject based on the ideXlab platform.

  • adipokinetic hormone induced lipolysis in the fat body of an insect manduca sexta synthesis of sn 1 2 Diacylglycerols
    Journal of Lipid Research, 1997
    Co-Authors: Estela L Arrese, Michael A. Wells
    Abstract:

    The pathway for the adipokinetic hormone-stiniu- lated synthesis of sn-1,2-diacylglyceroIs in the adult Manducu sexta fat body was studied. Adult fat body lipids were labeled by feeding 5th instar larvae either with (9,10(n)-3H)oleic acid or ( 1 (3)-3H)glycerol and after 32 days insects at the adult stage were used. This long-term prelabeling led to labeled fat body acylglycerols in which triacylglycerols comprised the main ra- dioactive lipid component (95.5%), regardless of the radiola- beled compound used. Because the distribution of radioactiv- ity among the lipid classes was very close to the mass distribution of the fat body lipid subspecies, it was concluded that homogeneous labeling of fat body lipids was obtained. After adipokinetic hormone treatment, an accumulation of radioactivity in the sn-1 ,2-diacylglycerol fraction was the only significant change found in the distribution of radioactivity among fat body lipids. The size of diacylglycerol pool in- creased 280% 60 min after adipokinetic hormone stimulation, whereas the fatty acid, monoacylglycerol and phosphatidic acid pool sizees remained constant.m These results support the hypothesis that adipokinetic hormone-stimulated synthe- sis of sn-1 ,2-diacylglycerol in the fat body involves stereospc- cific hydrolysis of the triacylglycerol stores.-Arrese, E. L., and M. A. Wells. Adipokinetic hormone-induced lipolysis in the fat body of an insect, Manducn srxtn: synthesis of .sn-l,2- Diacylglycerols. ,I. Lipad Res. 1997. 38: 68-76.

  • adipokinetic hormone induced lipolysis in the fat body of an insect manduca sexta synthesis of sn 1 2 Diacylglycerols
    Journal of Lipid Research, 1997
    Co-Authors: Estela L Arrese, Michael A. Wells
    Abstract:

    The pathway for the adipokinetic hormone-stimulated synthesis of sn-1,2-Diacylglycerols in the adult Manduca sexta fat body was studied. Adult fat body lipids were labeled by feeding 5th instar larvae either with [9,10(n)-3H]oleic acid or [1(3)-3H] glycerol and after 32 days insects at the adult stage were used. This long-term prelabeling led to labeled fat body acylglycerols in which triacylglycerols comprised the main radioactive lipid component (95.5%), regardless of the radiolabeled compound used. Because the distribution of radioactivity among the lipid classes was very close to the mass distribution of the fat body lipid subspecies, it was concluded that homogeneous labeling of fat body lipids was obtained. After adipokinetic hormone treatment, an accumulation of radioactivity in the sn-1,2-diacylglycerol fraction was the only significant change found in the distribution of radioactivity among fat body lipids. The size of diacylglycerol pool increased 280% 60 min after adipokinetic hormone stimulation, whereas the fatty acid, monoacylglycerol and phosphatidic acid pool sizes remained constant. These results support the hypothesis that adipokinetic hormone-stimulated synthesis of sn-1,2-diacylglycerol in the fat body involves stereospecific hydrolysis of the triacylglycerol stores.

John Browse - One of the best experts on this subject based on the ideXlab platform.

  • acyl editing and headgroup exchange are the major mechanisms that direct polyunsaturated fatty acid flux into triacylglycerols
    Plant Physiology, 2012
    Co-Authors: Philip D Bates, Abdelhak Fatihi, Anna R Snapp, Anders S Carlsson, John Browse
    Abstract:

    Triacylglycerols (TAG) in seeds of Arabidopsis (Arabidopsis thaliana) and many plant species contain large amounts of polyunsaturated fatty acids (PUFA). These PUFA are synthesized on the membrane lipid phosphatidylcholine (PC). However, the exact mechanisms of how fatty acids enter PC and how they are removed from PC after being modified to participate in the TAG assembly are unclear, nor are the identities of the key enzymes/genes that control these fluxes known. By reverse genetics and metabolic labeling experiments, we demonstrate that two genes encoding the lysophosphatidylcholine acyltransferases LPCAT1 and LPCAT2 in Arabidopsis control the previously identified “acyl-editing” process, the main entry of fatty acids into PC. The lpcat1/lpcat2 mutant showed increased contents of very-long-chain fatty acids and decreased PUFA in TAG and the accumulation of small amounts of lysophosphatidylcholine in developing seeds revealed by [14C]acetate-labeling experiments. We also showed that mutations in LPCATs and the PC diacylglycerol cholinephosphotransferase in the reduced oleate desaturation1 (rod1)/lpcat1/lpcat2 mutant resulted in a drastic reduction of PUFA content in seed TAG, accumulating only one-third of the wild-type level. These results indicate that PC acyl editing and phosphocholine headgroup exchange between PC and Diacylglycerols control the majority of acyl fluxes through PC to provide PUFA for TAG synthesis.

  • cholinephosphotransferase and diacylglycerol acyltransferase substrate specificities at a key branch point in seed lipid metabolism
    Plant Physiology, 1996
    Co-Authors: G Vogel, John Browse
    Abstract:

    Many oilseed plants accumulate triacylglycerols that contain unusual fatty acyl structures rather than the common 16- and 18-carbon fatty acids found in membrane lipids of these plants. In vitro experiments demonstrate that triacylglycerols are synthesized via Diacylglycerols in microsomal preparations and that this same sub-cellular fraction is the site for the synthesis of phosphatidylcholine, which in seeds is synthesized from diacylglycerol by CDP-choline: diacylglycerol cholinephosphotransferase. In microsomes from Cuphea lanceolata, a plant that accumulates fatty acids with 10 carbons and no double bonds (10:0) in its oil, the diacylglycerol acyltransferase exhibited 4-fold higher activity with 10:0/10:0 molecular species of diacylglycerol than with molecular species containing 18-carbon fatty acids. In castor bean (Ricinus communis), which accumulates oil containing ricinoleic acid, diricinoleoyldiacylglycerol was the favored substrate for triacylglycerol synthesis. In contrast to these modest specificities of the diacylglycerol acyltransferases, the cholinephosphotransferases from these plants and from safflower (Carthamus tinctorius) and rapeseed (Brassica napus) showed little or no specificity across a range of different diacylglycerol substrates. Consideration of these results and other data suggests that the targeting of unusual fatty acids to triacylglycerol synthesis and their exclusion from membrane lipids are not achieved on the basis of the diacylglycerol substrate specificities of the enzymes involved and may instead require the spatial separation of two different diacylglycerol pools.

Photis Dais - One of the best experts on this subject based on the ideXlab platform.

  • kinetics of diglyceride formation and isomerization in virgin olive oils by employing 31p nmr spectroscopy formulation of a quantitative measure to assess olive oil storage history
    Journal of Agricultural and Food Chemistry, 2004
    Co-Authors: Apostolos Spyros, And Angelos Philippidis, Photis Dais
    Abstract:

    Diacylglycerol isomers and free acidity were determined for five extra virgin olive oils of different initial acidities by employing a facile 31P NMR methodology as a function of storage time and storage conditions. The kinetic treatment of the hydrolysis of triacylglycerols (TGs) and the isomerization of 1,2-Diacylglycerols (1,2-DGs) to 1,3-Diacylglycerols (1,3-DGs) during storage of 18 months at ambient temperature in the dark and light and at 5 °C in the dark showed that the isomerization is strongly dependent on the rate of the TGs hydrolysis, the initial free acidity (H0) of the virgin olive oil samples, and storage conditions. Although the time-evolution of the Diacylglycerols (DGs) depends on the TGs hydrolysis, the ratio D of the concentration of 1,2-DGs to the total amount of DGs was found to be independent of this factor. From the kinetic expression of the ratio D, a quantitative measure was formulated that allows the estimation of the storage time or age of virgin olive oils. Application of thi...

  • kinetics of diglyceride formation and isomerization in virgin olive oils by employing 31p nmr spectroscopy formulation of a quantitative measure to assess olive oil storage history
    Journal of Agricultural and Food Chemistry, 2004
    Co-Authors: Apostolos Spyros, And Angelos Philippidis, Photis Dais
    Abstract:

    Diacylglycerol isomers and free acidity were determined for five extra virgin olive oils of different initial acidities by employing a facile (31)P NMR methodology as a function of storage time and storage conditions. The kinetic treatment of the hydrolysis of triacylglycerols (TGs) and the isomerization of 1,2-Diacylglycerols (1,2-DGs) to 1,3-Diacylglycerols (1,3-DGs) during storage of 18 months at ambient temperature in the dark and light and at 5 degrees C in the dark showed that the isomerization is strongly dependent on the rate of the TGs hydrolysis, the initial free acidity (H(0)) of the virgin olive oil samples, and storage conditions. Although the time-evolution of the Diacylglycerols (DGs) depends on the TGs hydrolysis, the ratio D of the concentration of 1,2-DGs to the total amount of DGs was found to be independent of this factor. From the kinetic expression of the ratio D, a quantitative measure was formulated that allows the estimation of the storage time or age of virgin olive oils. Application of this quantitative measure to several olive oil samples of known and unknown storage history resulted in a very good agreement with respect to the actual storage time for up to 10-12 months of storage. For a longer storage period, where the isomerization of DGs is close to its equilibrium state, the calculated age index is only indicative.

Varman T Samuel - One of the best experts on this subject based on the ideXlab platform.

  • short term overnutrition induces white adipose tissue insulin resistance through sn 1 2 diacylglycerol pkce insulin receptor thr1160 phosphorylation
    JCI insight, 2021
    Co-Authors: Kun Lyu, Varman T Samuel, Dongyan Zhang, Joongyu D Song, Rachel J Perry, Gerald I Shulman
    Abstract:

    Insulin-mediated suppression of white adipose tissue (WAT) lipolysis is an important anabolic function that is dysregulated in states of overnutrition. However, the mechanism of short-term high-fat diet (HFD)-induced WAT insulin resistance is poorly understood. Based on our recent studies we hypothesize that a short-term HFD causes WAT insulin resistance through increases in plasma membrane (PM) sn-1,2-Diacylglycerols (DAG), which promotes protein kinase C-e (PKCe) activation to impair insulin signaling by phosphorylating insulin receptor (Insr) Thr1160. To test this hypothesis, we assessed WAT insulin action in 7-day HFD-fed versus regular chow diet-fed rats during a hyperinsulinemic-euglycemic clamp. HFD feeding caused WAT insulin resistance, reflected by reductions in both insulin-mediated WAT glucose uptake and suppression of WAT lipolysis. These changes were specifically associated with increased PM sn-1,2-diacylglycerol (DAG) content, increased PKCe activation and impaired insulin-stimulated InsrY1162 phosphorylation. In order to examine the role of InsrT1160 phosphorylation in mediating lipid-induced WAT insulin resistance, we examined these same parameters in short-term HFD-fed InsrT1150A knockin mice (mouse homolog for human Thr1160). Similar to the rat study HFD feeding induced WAT insulin resistance in WT control mice but failed to induce WAT insulin resistance in InsrT1150A mice. Taken together these data demonstrate that the PM sn-1,2-DAG - PKCe - InsrT1160 phosphorylation pathway plays an important role in mediating lipid-induced WAT insulin resistance and represents a potential therapeutic target to improve insulin sensitivity in WAT.

  • hepatic diacylglycerol associated protein kinase ce translocation links hepatic steatosis to hepatic insulin resistance in humans
    Cell Reports, 2017
    Co-Authors: Kasper W Ter Horst, Pim W Gilijamse, Max Nieuwdorp, Ruth I Versteeg, Susanne E La Fleur, Mariëtte T. Ackermans, Dongyan Zhang, Aart J Nederveen, Johannes A. Romijn, Varman T Samuel
    Abstract:

    Summary Hepatic lipid accumulation has been implicated in the development of insulin resistance, but translational evidence in humans is limited. We investigated the relationship between liver fat and tissue-specific insulin sensitivity in 133 obese subjects. Although the presence of hepatic steatosis in obese subjects was associated with hepatic, adipose tissue, and peripheral insulin resistance, we found that intrahepatic triglycerides were not strictly sufficient or essential for hepatic insulin resistance. Thus, to examine the molecular mechanisms that link hepatic steatosis to hepatic insulin resistance, we comprehensively analyzed liver biopsies from a subset of 29 subjects. Here, hepatic cytosolic diacylglycerol content, but not hepatic ceramide content, was increased in subjects with hepatic insulin resistance. Moreover, cytosolic Diacylglycerols were strongly associated with hepatic PKCe activation, as reflected by PKCe translocation to the plasma membrane. These results demonstrate the relevance of hepatic diacylglycerol-induced PKCe activation in the pathogenesis of NAFLD-associated hepatic insulin resistance in humans.