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At least 109 records · Page 6Linked to original sources
PubMed1990

Interleukin-1 stimulates diglyceride accumulation in the absence of protein kinase C activation.

Despite advances in the knowledge of the intracellular signalling in response to extracellular messengers, the mechanism of action of interleukin-1 (IL-1) has remained an enigma. In the present study, we have employed human dermal fibroblasts (Detroit 532 cells) to investigate IL-1 beta-induced changes in intracellular signals. Both recombinant human IL-1 beta and a native preparation purified from human placental tissue were employed. Cyclic AMP levels in cell monolayers were unaltered by IL-1 beta. Also, IL-1 beta did not influence significantly the levels of phosphatidylinositol, phosphatidylinositol 4-monophosphate, and phosphatidylinositol 4,5-bisphosphate in the membrane, nor the water-soluble inositol phosphates, inositol monophosphate, inositol bisphosphate and inositol trisphosphate, in cells prelabelled with myo-[3H]inositol. In addition, intracellular calcium as measured by Quin2 was unaffected by interleukin-1. However, in cells labelled with [3H]glycerol or [3H]arachidonic acid, IL-1 beta caused an immediate rise in diglyceride (DG) accumulation. As the effects of IL-1 beta have been reported to be mimicked by tumour-promoting phorbol esters, this rise in DG suggested the involvement of protein kinase C (PKC). However, repeated experiments failed to reveal any acute effect of IL-1 beta on the activity of this enzyme. Furthermore, IL-1 beta did not cause the translocation of PKC between the membrane and the cytosol as has been found in response to other extracellular signals. Rather, IL-1 beta appeared to increase the synthesis of PKC in both membrane and cytosol preparations, an effect which could be prevented by coincubation with cycloheximide. These findings suggest that the diglyceride formed in response to IL-1 beta does not activate protein kinase C.

Calcium↗
PubMed2004

Formation of phosphatidic acid, ceramide, and diglyceride on radiolysis of lipids: identification by MALDI-TOF mass spectrometry.

By use of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, phosphatidic acid was found to be the main product of gamma radiolysis of cardiolipin, phosphatidylinositol, and phosphatidylglycerol. It has been shown that gamma irradiation of such glycolipids as cerebroside and galactosyl diglyceride leads to formation of ceramide and diglyceride, respectively. These findings, combined with those obtained earlier, allowed an assumption to be made that, owing to radiation-induced free radical fragmentation of lipids in their polar moiety, formation of signaling molecules can occur.

Animals↗
PubMed1997

In vivo and in vitro studies on the stereoselective hydrolysis of tri- and diglycerides by gastric and pancreatic lipases.

The stereoselectivity of dog gastric and dog pancreatic lipases was investigated both in vitro, under simulated physiological conditions, and in vivo, during the digestion of a liquid test meal. In vitro it was observed that although both lipases had a stereopreference for the sn-3 position in triglycerides, it was about three times higher in the case of the gastric lipase. On the other hand, both lipases clearly showed a comparable enantioselectivity for the sn-1 position when a racemic diolein was used as the substrate. In the case of pancreatic lipase, the enantiomeric excess of 1,2-sn-diolein generated in vitro by the hydrolysis of triolein was found to decrease significantly, and even to be slightly reversed, at high rates of hydrolysis (above 50%) due to the further stereoselective hydrolysis of diglycerides into monoglycerides. This finding may explain the low enantiomeric excess of the diglycerides observed in vivo during the early phase of intraduodenal digestion when pancreatic lipase plays a predominant role and the rate of triolein hydrolysis is already high. On the other hand, a large enantiomeric excess of 1,2-sn-diolein generated from triolein was always the fingerprint of the gastric lipase in vitro even at high hydrolysis rates. This fingerprinting of gastric lipase was observed during both the intragastric phase and the late intestinal phase of lipolysis. This feature was therefore taken as an index to determine the respective roles of gastric and pancreatic lipases during in vivo lipolysis. To the best of our knowledge, this is the first time that stereoselectivity has been used as a tool to discriminate between the activities of two enzymes hydrolyzing the same substrate in vivo.

Animals↗
PubMed2000

Application of (31)P NMR spectroscopy in food analysis. 1. Quantitative determination of the mono- and diglyceride composition of olive oils.

This paper introduces a facile method to determine the amount of mono- and diglycerides in virgin olive oils. This method is based on the phosphorylation of the free hydroxyls of the mono- and diglycerides with 2-chloro-4,4,5,5-tetramethyldioxaphospholane and the integration of the appropriate peaks in the (31)P NMR spectrum. Quantitative (31)P NMR spectroscopy can be extended to the quantification of other constituents of olive oils bearing functional groups with labile protons.

Dietary Fats, Unsaturated↗
PubMed1994

Synthesis and in vitro study of a diglyceride prodrug of a peptide.

A diglyceride derivative of a pentapeptide renin inhibitor, the 1,3-dipalmitoyl-[Iva-Phe-Nle-Sta-Ala-Sta-acetyl]-glycerol was synthesized and tested in vitro as a potential prodrug for oral administration. The ability of the diglyceride analog to inhibit the renin activity was equivalent to that of the parent peptide after predigestion with pancreatic lipase. Furthermore, the presence of the palmitoyl groups was found to induce, in vitro, an efficient protection of the peptide from gastric and intestinal hydrolysis. During incubation with intestinal and gastric fluids, and with alpha-chymotrypsin and pancreatic lipase, the glycerolipidic derivative was more stable than the peptide alone. These results support the use of glycerolipidic prodrug for oral administration of peptides.

Amino Acid Sequence↗
PubMed1999

Sequential actions of phospholipase D and phosphatidic acid phosphohydrolase 2b generate diglyceride in mammalian cells.

Phosphatidylcholine (PC) is a major source of lipid-derived second messenger molecules that function as both intracellular and extracellular signals. PC-specific phospholipase D (PLD) and phosphatidic acid phosphohydrolase (PAP) are two pivotal enzymes in this signaling system, and they act in series to generate the biologically active lipids phosphatidic acid (PA) and diglyceride. The identity of the PAP enzyme involved in PLD-mediated signal transduction is unclear. We provide the first evidence for a functional role of a type 2 PAP, PAP2b, in the metabolism of PLD-generated PA. Our data indicate that PAP2b localizes to regions of the cell in which PC hydrolysis by PLD is taking place. Using a newly developed PAP2b-specific antibody, we have characterized the expression, posttranslational modification, and localization of endogenous PAP2b. Glycosylation and localization of PAP2b appear to be cell type and tissue specific. Biochemical fractionation and immunoprecipitation analyses revealed that PAP2b and PLD2 activities are present in caveolin-1-enriched detergent-resistant membrane microdomains. We found that PLD2 and PAP2b act sequentially to generate diglyceride within this specialized membrane compartment. The unique lipid composition of these membranes may provide a selective environment for the regulation and actions of enzymes involved in signaling through PC hydrolysis.

Amino Acid Sequence↗
PubMed1989

Effects of mezerein and diglycerides on the PRL stimulation of cell replication in Nb2 node lymphoma cells.

These studies provide further support for the thesis that the activation of protein kinase C is likely involved in the prolactin (PRL) stimulation of mitogenesis in the Nb2 node lymphoma cell line. The diterpene mezerein is shown to potentiate the mitogenic effect of PRL at a hormone concentration which elicits a less than maximum response. A similar response was observed with two diglycerides, diolein and dicaprin. Neither mezerein nor the diglycerides affected the magnitude of response to a maximum stimulatory concentration of PRL.

Carcinogens↗
PubMed1975

Biosynthesis of digalactosyl diglyceride in Vicia faba leaves.

Developing and mature leaf tissue from Vicia faba plants were pulse-fed 14-CO2. The lipids were extracted at intervals after exposure to light, and the galactolipids monogalactosyl diglyceride (MGDG) and digalactosyl diglyceride (DGDG) were separated. After methylation and methanolysis, gas-liquid chromatography was used to separate the two galactose units of DGDG and the galactose of MGDG. The specific activities of the galactoses and the changes over the time period of the experiment were determined. The results support the view that DGDG is formed by galactosylation of MGDG. This does not take place by a rapid two-enzyme system reaction but more slowly in two phases: galactosylation of a pool of newly formed MGDG and a more random galactosylation of MGDG. There is no evidence of a high turnover of galactose in these lipids.

Carbon Dioxide↗
PubMed1977

CDP-diglyceride:inositol transferase from rat liver. Purification and properties.

CDP-diglyceride:inositol transferase, which catalyzes the final step of the de novo synthesis of phosphatidylinositol, was solubilized by sodium cholate from microsomes prepared from rat liver and purified by ammonium sulfate fractionation, sucrose density gradient centrifugation, and DEAE-cellulose column chromatography. Addition of phospholipid during the purification and the assay procedures prevented irreversible loss of the enzyme activity to some extent. The resulting preparation was nearly homogeneous as judged by polyacrylamide gel electrophoresis. The recovery of the purified enzyme from the microsomal fraction was 3 to 3.3% with respect to activity and 0.12% with respect to amount of protein. The molecular weight of the enzyme was estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis to be 60,000. The purified enzyme required exogenous phospholipds for its activity. Various phospholipid classes activated the enzyme rather nonspecifically. The Km for myo-inositol was 2.5 X 10(-3) M and that for CDP-diglyceride was 1.7 X 10(-4) M. The pH optimum was 8.6. The enzyme required Mm2+ or Mg2+ for activity. The optimal concentration of Mn2+ for activation was 0.5 mM, while the activity in the presence of Mg2+ increased up to 20 mM. The enzyme was inhibited by thiol-reactive reagents. There was a competition for inositol by inosose-2 but not by scyllitol.

Animals↗
PubMed1990

Complement C5a activation of phospholipase D in human neutrophils. A major route to the production of phosphatidates and diglycerides.

The contribution of phospholipase D (PLD) to the production of phosphatidic acid (PA) and diglyceride (DG) by C5a-stimulated human neutrophils has been studied. Membrane-associated 1-O-alkyl-phosphatidylcholine (alkyl-PC) was double labeled with 3H and 32P by incubating neutrophils with [3H]alkyl-lysoPC and alkyl-[32P]lysoPC. Upon stimulation with recombinant C5a, these labeled neutrophils produce 1-O-alkyl-phosphatidic acid (alkyl-PA) and, in the presence of ethanol, 1-O-alkyl-phosphatidyl-ethanol (alkyl-PEt), containing both 3H and 32P. Formation of radiolabeled alkyl-PEt parallels that of radiolabeled alkyl-PA and requires both extracellular Ca2+ and cytochalasin B. Furthermore, the 3H/32P ratios of alkyl-PA and alkyl-PEt formed during stimulation are very similar to that of th substrate alkyl-PC. These results demonstrate that, in C5a-stimulated neutrophils, alkyl-PA and alkyl-PEt are formed from alkyl-PC almost exclusively by PLD-catalyzed hydrolysis and transphosphatidylation, respectively. Upon C5a stimulation, neutrophils labeled with 3H and 32P also produce 1-O-[3H]alkyl-diglyceride [( 3H]alkyl-DG) and [32P]orthophosphate [( 32P]PO4), but not [32P]phosphocholine. [3H]Alkyl-DG and [32P]PO4 are formed in parallel, although temporally lagging behind alkyl-PA. Propranolol, a PA phosphohydrolase (PPH) inhibitor, decreases the formation of both [3H]alkyl-DG and [32P]PO4, although increasing alkyl-PA accumulation. These data support the conclusion that alkyl-DG is formed from alkyl-PC by the combined activities of PLD and PPH and not by phospholipase C (PLC). Furthermore, by using [3H]acyl-PC-labeled neutrophils, it is demonstrated that, like alkyl-PC, 1-acyl-PC is also degraded sequentially by PLD and PPH to 1-acyl-DG. Propranolol does not inhibit phosphoinositide-specific PLC and yet it causes almost complete inhibition of the total DG mass accumulation in C5a-stimulated neutrophils. We conclude that, in cytochalasin B-treated neutrophils stimulated with C5a, PLD-catalyzed hydrolysis of PC determines the levels of both PA and DG with potentially important ramifications for neutrophil-mediated defense functions.

Alkylation↗
PubMed1988

Phorbol myristate acetate (PMA) augments chemoattractant-induced diglyceride generation in human neutrophils but inhibits phosphoinositide hydrolysis. Implications for the mechanism of PMA priming of the respiratory burst.

Pretreatment ("priming") of neutrophils with a non-activating concentration (2 nM) of phorbol myristate acetate (PMA) augments superoxide (O2-) production in response to the chemoattractant formylmethionylleucylphenylalanine (fMLP). We initially examined the effect of sphinganine, an inhibitor of protein kinase C (Ca2+/phospholipid-dependent enzyme), on activation of primed neutrophils. In both primed and unprimed cells activation by fMLP was blocked, and inhibition occurred at identical concentrations, supporting a common inhibited site. PMA also augmented (about 2-fold) fMLP-induced generation of sn-1,2-diglyceride (DG), the level of which correlated with O2- generation. In contrast to its effects on DG, PMA diminished by about 50% the magnitude of the fMLP-stimulated rise in cytosolic Ca2+. Thus, PMA priming dissociates the fMLP-stimulated Ca2+ increase from DG and O2- generation. The effect of PMA on Ca2+ levels appeared to be due in part to lowered levels of inositol trisphosphate. Lowering of inositol phosphate levels correlated with inhibition of fMLP-induced hydrolysis of inositol-containing phospholipids, particularly phosphatidylinositol 4,5-bisphosphate. PMA did not inhibit (and in fact augmented at early time points) formation of [32P] phosphatidic acid in response to fMLP, indicating that the increase in DG was not due to inhibition of cellular diglyceride kinase. Thus, the data suggest that PMA enhances fMLP-stimulated DG generation concomitant with switching the source of DG from phosphatidylinositol 4,5-bisphosphate to an alternative lipid(s). Increased DG and inhibition of activation by sphinganine are consistent with a role for protein kinase C in activation of the respiratory burst in PMA-primed neutrophils.

Diglycerides↗
PubMedDate not supplied

Simple method for derivatization of monoglycerides and diglycerides.

A method has been developed for derivatization of monoglycerides and diglycerides to their propyl esters by using propionic anhydride in the presence of pyridine. The derivatives are volatile and thus can be separated and identified by gas chromatography (GC). Completion of the reaction is monitored by thin-layer chromatography. Monoglyceride propyl esters were positively identified by gas chromatography and by gas chromatography/mass spectrometry. No side products were observed in the derivatization reaction which requires 35 min at 75 degrees C. GC analysis of the mono- and diglyceride propyl esters can be completed in approximately 30 min.

Chemical Phenomena↗
PubMed1981

Gas-liquid chromatographic detection an determination of diacetyl tartaric acid ester of diglyceride in dairy and nondairy coffee cream powders.

Diacetyl tartaric acid ester of diglyceride was directly extracted from dairy or nondairy coffee cream powder under acidic conditions with ethyl acetate; then the extract was saponified with methanolic potash. After acidification with HCl, free fatty acid was removed with ether and the reaction mixture was absorbed on an anion exchange column. Tartaric acid was eluted with 2N HCl-acetone (1+1). An aliquot of the trimethylsilyl (TMS) derivative of the eluate was injected into a gas chromatograph with flame ionization detection, and a 1.5% SE-30 column. Recoveries of diacetyl tartaric acid ester of diglyceride at 50, 200, and 2000 ppm were 85.6-99.5%.

Chromatography, Gas↗
PubMed1994

1-beta-D-Arabinofuranosylcytosine stimulates ceramide and diglyceride formation in HL-60 cells.

The effect of 1-beta-D-arabinofuranosylcytosine (ara-C) on phospholipid metabolism was investigated in HL-60 cells. Treatment of cells with ara-C resulted in a time- and dose-dependent increase in the mass of ceramide and diglyceride. When cells were treated with 10 microM ara-C, an increase in the mass of ceramide and diglyceride was detectable at 5 min and reached a plateau at 30 min with a 2-fold increase compared to control cells. Treatment of cells with 10 microM ara-C resulted in the activation of neutral sphingomyelinase with a peak at 30 min that represented a 2-fold increase in specific activity. ara-C also increased expression of the transcription factor NF-kappa B which is related to the control of monocyte differentiation. These findings suggest that ara-C activates phospholipid hydrolytic pathways to generate second messengers that control gene expression and differentiation in the HL-60 cell line.

Cell Differentiation↗
PubMed1976

Light-independent stoichometry of galactosyl diglyceride and chlorophyll accretion during light-induced chloroplast membrane synthesis in Euglena.

In photobiotic Euglena gracilis, chlorophyll biosynthesis takes place at a rate which is a direct function of light intensity. There is stoichiometry between chlorophyll accumulation and that of galactosyl diglycerides. This stoichiometry remains relatively invariant, regardless of the wide changes in chlorophyll content brought about in response to controlled variation of light intensity. These findings suggest that the formation of chlorophyll-containing photoreceptor membranes may be paced and stabilized by concurrent synthesis of galactosyl diglycerides.

Animals↗
PubMed1990

Synthetic sialyl glycolipids (sialo-cholesterol and sialo-diglyceride) induce granulocytic differentiation of human myelogenous leukemia cell line HL-60.

When HL-60 cells were cultivated with synthetic sialyl glycolipids, sialo-cholesterol and sialo-diglyceride, the cells were found to be differentiated into mature granulocytes on morphological and functional criteria. The differentiation of cells was accompanied by inhibition of cell proliferation. The differentiation-inducing activity of sialo-cholesterol was greater than that of sialo-diglyceride on a molar basis, and the alpha-anomer of each compound was more potent than the beta-anomer, suggesting that the stereospecific structure of the compounds is important for the differentiation-inducing activity.

Cell Transformation, Neoplastic↗
PubMed2004

Prodrugs of HIV protease inhibitors-saquinavir, indinavir and nelfinavir-derived from diglycerides or amino acids: synthesis, stability and anti-HIV activity.

With the aim of improving the pharmacological properties of current protease inhibitors (PIs), the synthesis of various acyl and carbamate amino acid- or diglyceride-containing prodrugs derived from saquinavir, indinavir and nelfinavir, their in vitro stability with respect to hydrolysis and their anti-HIV activity in CEM-SS and MT4 cells have been investigated. l-Leucine (Leu) and l-phenylalanine (Phe) were connected through their carboxyl to the PIs while l-tyrosine (Tyr) was conjugated through its aromatic hydroxyl via various spacer units. Hydrolysis of the prodrug with liberation of the active free drug was crucial for antiviral activity. The Leu- and Phe-PI prodrugs released the active free drug very rapidly (half-lives of hydrolysis in buffer at 37 degree C of 3-4 h). The Tyr-PI conjugates with a -C(O)(CH(2))(4)- linker exhibited half-lives in the 40-70 h range and antiviral activities in the 21-325 nM range (from 2 to 22 nM for the free PIs). The chemically very stable carbamate "peptidomimetic" Tyr-PI prodrugs (no hydrolysis detected after 7 days in buffer) displayed a very low anti-HIV activity or were even inactive (EC(50) from 2300 nM to >10 microM). A very low antiviral activity was measured for the diglyceride-substituted saquinavir and for all of the disubstituted indinavir and nelfinavir prodrugs. All these prodrugs probably released the active parent PI too slowly under the antiviral assay conditions. These results combined with those from transepithelial transport studies (Rouquayrol et al., Pharm. Res., 2002, 19, 1704-1712) indicate that conjugation of amino acids (through their carboxyl) to the PIs constitutes a most appealing alternative which could improve the intestinal absorption of the PIs and reduce their recognition by efflux carriers.

Anti-HIV Agents↗