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PubMed2000

Comparison of wax and glyceride solid lipid nanoparticles (SLN).

The present study compares solid lipid nanoparticles (SLN) formulated with either wax or glyceride bulk material. While most published data deal with glyceride SLN, little knowledge is reported on wax carriers. The two types were compared with respect to drug encapsulation efficacy, particle size distribution after production and storage, and crystal packing. The inclusion of retinol as a model drug was investigated. Retinol is chemically unstable in water and rather stable in lipid phases. Thus, rapid degradation of retinol indicates rapid drug expulsion from the carrier. Good stability indicates an effective drug encapsulation in the lipid phase of the nanoparticles. Particle size distribution was measured by laser diffractometry. Subcell packing and assignment of polymorphic forms was investigated by WAXS measurements. Glyceride SLN showed good drug encapsulation, while physical stability was poor. In contrast, wax SLN possessed good physical stability but lacked sufficient drug encapsulation in the solidified state. These differences were attributed in part to different crystal packing. Less ordered crystal lattices favour successful drug inclusion, as in the case of glyceryl monosterate and glyceryl behenate SLN. The highly ordered crystal packing of wax SLN comprised of beeswax or cetyl palmitate, for instance, leads to drug expulsion, but also to superior physical stability.

Crystallization↗
PubMed1995

Glyceride synthesis catalyzed by cutinase using the monomolecular film technique.

The monomolecular film technique previously used to study the kinetics of lipase hydrolysis was adapted to synthesizing oleoyl glycerides (monoolein, diolein, and triolein). The water subphase was replaced by glycerol, and a film of oleic acid was initially spread on the glycerol surface. In this system a recombinant cutinase from Fusarium solani was able to catalyze oleoyl glyceride synthesis. More than 50% of the oleic acid film was acylated after 7 min of reaction. The surface pressure applied to the monomolecular film acts as a physical selectivity factor since glyceride synthesis can be steered so as to produce either diolein or triolein.

Carboxylic Ester Hydrolases↗
PubMed1966

The biosynthesis of glycerides by mitochondria from rat liver. The requirement for a soluble protein.

1. The synthesis of glycerides from l-3-glycerophosphate and palmitic acid by mitochondrial preparations from rat liver was shown to be stimulated markedly by a soluble factor from the supernatant fraction of the liver. 2. That the soluble factor was a protein was indicated by its inactivation after treatment with papain and after boiling for 3min. at 100 degrees , its precipitation by ammonium sulphate and its behaviour on Sephadex G-200. The soluble factor was purified by ammonium sulphate fractionation and gel filtration. 3. Bovine serum albumin and lipoprotein fractions from rat and human serum also stimulated glyceride biosynthesis but the stimulations were one-twentieth to one-third of that obtained with the soluble factor. 4. The function of the soluble factor could not be explained by assuming a leakage of acyl-CoA synthetase, phosphatidate phosphatase or diglyceride acyltransferase from the mitochondria into the supernatant during preparation of the mitochondrial fraction. 5. Palmitic acid, in the presence of the soluble factor and optimum amounts of ATP and CoA, was a more effective substrate than palmitoyl-CoA or palmitoylcarnitine for the biosynthesis of glycerides by mitochondria.

Acyltransferases↗
PubMed1972

The regulation of glyceride synthesis in isolated white-fat cells. The effects of palmitate and lipolytic agents.

1. 0.5mm-Palmitate stimulated incorporation of [U-(14)C]glucose into glyceride glycerol and fatty acids in normal fat cells in a manner dependent upon the glucose concentration. 2. In the presence of insulin the incorporation of 5mm-glucose into glyceride fatty acids was increased by concentrations of palmitate, adrenaline and 6-N-2'-O-dibutyryladenosine 3':5'-cyclic monophosphate up to 0.5mm, 0.5mum and 0.5mm respectively. Higher concentrations of these agents produced progressive decreases in the rate of glucose incorporation into fatty acids. 3. The effects of palmitate and lipolytic agents upon the measured parameters of glucose utilization were similar, suggesting that the effects of lipolytic agents are mediated through increased concentrations of free fatty acids. 4. In fat cells from 24h-starved rats, maximal stimulation of glucose incorporation into fatty acids was achieved with 0.25mm-palmitate. Higher concentrations of palmitate were inhibitory. In fat cells from 72h-starved rats, palmitate only stimulated glucose incorporation into fatty acids at high concentrations of palmitate (1mm and above). 5. The ability of fat cells to incorporate glucose into glyceride glycerol in the presence of palmitate decreased with increasing periods of starvation. 6. It is suggested that low concentrations of free fatty acids stimulate fatty acid synthesis from glucose by increasing the utilization of ATP and cytoplasmic NADH for esterification of these free fatty acids. When esterification of free fatty acids does not keep pace with their provision, inhibition of fatty acid synthesis occurs. Provision of free fatty acids far in excess of the esterification capacity of the cells leads to uncoupling of oxidative phosphorylation and a secondary stimulation of fatty acid synthesis from glucose.

Adenosine Triphosphate↗
PubMed1975

Role of glycerol 3-phosphate dehydrogenase in glyceride metabolism. Effect of diet on enzyme activities in chicken liver.

1. The metabolic role of hepatic NAD-linked glycerol 3-phosphate dehydrogenase (EC 1.1.1.8) was investigated vis-a-vis glyceride synthesis, glyceride degradation and the maintainence of the NAD redox state. 2. Five-week-old chickens were placed on five dietary regimes: a control group, a group on an increased-carbohydrate-lowered-fat diet, a group on a high-fat-lowered-carbohydrate diet, a starved group and a starved-refed group. In each group the specific activity (mumol/min per g wet wt. of tissue) of hepatic glycerol 3-phosphate dehydrogenase was compared with the activities of the beta-oxoacyl-(acyl-carrier protein) reductase component of fatty acid synthetase, glycerol kinase (EC 2.7.1.30) and lactate dehydrogenase (EC 1.1.1.27). 3. During starvation, the activities of glycerol 3-phosphate dehydrogenase, glycerol kinase and lactate dehydrogenase rose significantly. After re-feeding these activities returned to near normal. All three activities rose slightly on the high-fat diet. Lactate dehydrogenase activity rose slightly, whereas those of the other two enzymes fell slightly on the increased-carbohydrate-lowered-fat diet. 4. The activity of the beta-oxoacyl-(acyl-carrier protein) reductase component of fatty acid synthetase, a lipid-synthesizing enzyme, contrasted strikingly with the other three enzyme activities. Its activity was slightly elevated on the increased-carbohydrate diet and significantly diminished on the high-fat diet and during starvation. 5. The changes in activity of the chicken liver isoenzyme of glycerol 3-phosphate dehydrogenase in response to dietary stresses suggest that the enzyme has an important metabolic role other than or in addition to glyceride biosynthesis.

Animals↗
PubMed1981

Bacillus licheniformis penicillinase synthesized in Escherichia coli contains covalently linked fatty acid and glyceride.

DNA sequence analysis of the structural gene for Bacillus licheniformis penicillinase has revealed a tetrapeptide sequence of Leu-Ala-Gly-Cys within the NH2-terminal part of the precursor form of penicillinase (penicillin amido-beta-lactamhydrolase, EC 3.5.2.6). The same tetrapeptide occurs in the signal sequence of the prolipoprotein of Escherichia coli, and the cysteine residue in the tetrapeptide of prolipoprotein is modified to form glyceride-cysteine which becomes the NH2 terminus of Braun's lipoprotein. On the basis of labeling, with [2-3H]glycerol, [3H]palmitate, [35S]methionine, and [35S]sulfuric acid, of an E. coli strain lysogenic for a lambda vector containing the penicillinase gene from B. licheniformis and of immunoprecipitation with rabbit antisera against purified B. licheniformis penicillinase, we conclude that B. licheniformis penicillinase synthesized in E. coli contains covalently linked glyceride and fatty acid. These results strongly suggest the operation of a modification system in E. coli, and presumably in other Gram-negative bacteria, which results in the formation of a glyceride-cysteine residue if the proper peptide sequence is present in the signal sequence of membrane proteins.

Bacillus↗
PubMed2001

Assessment of the extrudability of three different mixtures of saturated polyglycolysed glycerides by determination of the "specific work of extrusion" and by capillary rheometry.

PURPOSE: Assessment of the extrudability of mixtures of saturated polyglycolysed glycerides used as carriers for poorly soluble drugs. METHODS: Three different mixtures of saturated polyglycolysed glycerides were extruded in a ram extruder at different rates and using different dies. The force applied to the ram and its displacement were recorded and used to determine the "specific work of extrusion" and pursuit rheometric determinations, according to the Bagley's approach. RESULTS: As the melting range of the mixtures, or the length of the dies increased, the higher the "specific work of extrusion" observed. From the rheometric analysis, viscoelastic properties were identified and decomposed into plastic and elastic components. The elastic component contributed more to the total pressure loss, and for the majority of the cases, was higher than the plastic component. From the Bagley plot it was possible to calculate the wall shear stress (sigma w), that increased with the melting range of the materials and the shear rate applied (gamma). The viscosity (eta) decreased as the shear rate increased, reflecting a non-Newtonian behavior of the materials. Finally, materials showing lower viscosities required less work to produce the extrudates. CONCLUSIONS: This study has (a) shown the possibility of preparing extrudates from different mixtures of polyglycolysed glycerides alone in a non-aqueous environment, (b) demonstrated the usefulness of the "specific work of extrusion," and (c) revealed through the rheometric studies the viscoelastic nature of the materials quantifying the contribution of the elastic and the plastic components for the total pressure loss.

Drug Carriers↗
PubMed2002

Glyceride stearic acid content and structure affect the energy available to growing rats.

To better understand the relative absorption of 18:0, specific structured triglycerides (STG) with varied ratios of 18:0 and short-chain organic acids (2:0, 3:0, 4:0) were compared with naturally occurring 18:0 in cocoa butter and to other mono- and diglycerides (DGs) containing 18:0. A bioassay for available fat energy was developed for growing Sprague-Dawley rats fed reduced energy from a control diet containing an American Heart Association (AHA) fat blend to generate 60 or 80% normal growth. The resulting standard growth curve was applied to the test fats, including cocoa butter and six glycerides, which were blended 3:1 with the AHA blend (to ensure EFA sufficiency) and pair-fed to match intake of control rats (AHA diet, 80% normal growth). Available energy from test fats ranged from 30 to 12 kJ/g (7.1 to 2.9 kcal/g) for cocoa butter to 18:0-DG, respectively, with the mean of the four different STG being 22 kJ/g (5.2 kcal/g). Energy available from test fats was negatively related to total 18:0 in the STG (r = -0.90; P < 0.001) and fecal dry weight (r = -0.92; P < 0.001); the effect was greater for monoglyceride (monolong-18:0) than for DG (dilong-18:0) but was not related to fecal 18:0. Compared with monoglyceride-18:0, available energy was increased or decreased when short-chain organic acids (SCOA) were added to form triglycerides, depending on the addition of butyrate or acetate, respectively. The different fat sources altered the available energy without apparent changes in lipoproteins or body composition. Thus, the reduced energy available from a glyceride containing 18:0 is determined by its total 18:0 and reflects the mono- or dilong chain character of the glyceride, its content of SCOA and triglyceride structure or organization per se.

Animals↗
PubMed1977

Glyceride synthesis by four kinds of microbial lipase.

Apart from their usual mechanism of action, lipases from Aspergillus niger and Rhizopus delemar also catalyzed the synthesis of glycerides from oleic acid and glycerol. Lipases from Geotrichum candidum and Penicillium cyclopium were inactivated by oleic acid, but were stable in the presence of casein, albumin or buffer of appropriate pH. Lipases from Aspergillus niger and Rhizopus delemar synthesized glycerides from, not only fatty acid, but dibasic acids and aromatic acids, making ester bonds only at position 1 and 3 of glycerol. In contrast, lipases from Geotricum candidum and Penicillium cyclopium synthesized glycerides only from long chain fatty acids, and made ester bonds at all three available positions of the glycerol molecule.

Aspergillus niger↗
PubMed1982

A re-examination of the fate of glyceride-glycerol in neutral lipid absorption and transport.

Conventional ideas concerning the unidirectional movement of triacylglycerol from intestinal lumen to lymph with sn-2-monoacylglycerol being the major glyceride-glycerol precursor were challenged by our finding that steady state specific activities of radiolabeled triacylglycerol (glyceryl moiety) in the intestinal mucosa and lumen were greatly reduced as compared to the specific activity of intraduodenally infused triacylglycerol. Investigation of the point at which the radiolabel was diluted was performed in mesenteric lymph duct-cannulated rats with a duodenal cannula through which trioleoyl[3H]glycerol was constantly infused. Both within the bowel lumen and in the intestinal mucosa, monoacylglycerol, diacylglycerol, and triacylglycerol specific activities were 31% or less of the specific activity of the infusate; chylomicron triacylglycerol specific activity was 75%. Efflux of neutral lipid from the mucosa into the bowel lumen was directly demonstrated by finding that when 3H glucose was injected intraperitoneally during triolein infusion, luminal triacylglycerol had a higher specific activity than was present in the mucosa. We conclude that there are two pools of mucosal triacylglycerol. One is rapidly transported and derives most of its glyceride-glycerol from luminal monoacylglycerol. The second is slowly transported; it derives its glyceride-glycerol mainly from endogenous sources and may efflux back into the bowel lumen.

Animals↗
PubMed1996

Stereoselectivity of lipases in supercritical carbon dioxide. I. Dependence of the regio- and enantioselectivity of porcine pancreas lipase on the water content during the hydrolysis of triolein and its partial glycerides.

The stereoselectivity of porcine pancreas lipase (PPL) was investigated during the enzymatic hydrolysis of triolein and its partial glycerides in the presence of supercritical carbon dioxide (SCCO2) as reaction medium. The water content of the immobilized lipases was varied. The partial glycerides were separated into mono- and diglycerides by TLC, converted to their 3,5-dinitrophenylurethane derivatives and subsequently resolved into sn-1,2 and sn-2,3 enantiomers (estimation of dioleins) or into sn-1 and sn-3 enantiomers (estimation of monooleins) by HPLC on a chiral stationary phase (Sumichiral OA-4100). In all reactions under the conditions employed, PPL revealed a distinct preference for the sn-3 position of the glycerol. However, the stereoselectivity depends on the reaction time, the substances initially used and the enzyme water content. It seems that the effect of the enzyme water content on the activity and selectivity of porcine pancreas lipase in SCCO2 is based on a modification of the "micro-environment' of the enzyme by the solution of CO2 in water, causing a decrease of the pH value.

Animals↗
PubMedDate not supplied

Turnover of phospholipids and glycerides of spheroplasts of Mycobacterium smegmatis ATCC 14468.

The breakdown and renewal of phospholipids and glycerides from spheroplasts of Mycobacterium smegmatis ATCC 14468 were studied by means of pulse labelling techniques using 1-14C-palmitate. Most of the radioactivity incorporated into total lipids was recovered from phospholipids. Among the phospholipids studied, cardiolipin had the highest radioactivity and specific activity, suggesting its higher pool size as compared to other fractions. The appreciable loss of radioactivity for cardiolipin in pulse chase experiments within growing cells suggests its metabolically active and dynamic nature. Glycerides exhibited no appreciable turnover rates.

Carbon Radioisotopes↗
PubMed2005

The effect of molecular shape on the thermotropic liquid crystal behavior of monolauroylated amino acid glyceride conjugates.

Monoacylglycerol amino acid conjugates constitute a novel class of specific biocompatible surfactants that can be considered analogues to partial glycerides and lysophospholipids. They consist of one aliphatic chain and one polar head, i.e., the amino acid, linked through a glycerol moiety. In a previous work, we synthesized monolauroylated amino acid glyceride conjugates, 1-O-lauroyl-rac-glycero-3-O-(N(alpha)-acetyl-L-amino acid), changing the amino acid headgroup systematically: arginine (compound 2), aspartic acid (compound 3), glutamic acid (compound 4), asparagine (compound 5), glutamine (compound 6), and tyrosine (compound 7), to elucidate the structure-properties relationship governing the occurrence of their polymorphism. The thermotropism of the new compounds was measured with polarizing light microscopy, differential scanning calorimetry, and X-ray diffraction and compared with the classical monoglyceride rac-1-lauroylglycerol (compound 1). The experiments were performed for a sequence of heating, cooling, and reheating scans. The results showed that compounds 1-6 exhibit a thermotropic smectic phase. As a consequence, the substitution of the polar head did not engender any curvature into the system, which might lead to the formation of cubic or columnar phases. Interestingly, liquid crystalline phases were not found in the case of compound 7. Small-angle X-ray diffraction data in the gel phase revealed that the substitution of the polar head by the different amino acid structures did not modify significantly the lamellar repeat distance relative to that of the reference one. The observed area per molecule, however, was larger for the new compounds. Consequently, interdigitation was promoted in compounds 2-7. The diffraction patterns were analyzed in terms of electron density profiles, using a modified Caillé theory plus a Gaussian electron density representation (MCG method) on X-ray diffraction data.

Amino Acids↗
PubMed2002

Fluorimetric analysis of lipase hydrolysis of intermediate- and long-chain glycerides.

For the purpose of deducing the digestive behavior of dietary fat in the digestive organs, a fluorimetric method for the measurement of hydrolysis by porcine pancreatic lipase was performed using intermediate- and long- acyl chain glycerides as substrates. Insoluble glycerides constituted by C10-C16 acyl chains were mechanically dispersed in 100% buffer and hydrolyzed by porcine pancreatic lipase. After the reaction, fatty acid released by the enzyme was extracted and its carboxyl group was fluorescently labeled with 9-bromomethylacridine. The 9-acridinylmethyl derivative of the fatty acid was separated and determined by HPLC. The sensitivity of this method was about 1000 times higher than that of the titrimetric method. Only 0.5 ng of porcine pancreatic lipase was sufficient for one routine assay. This assay method was successfully applied to investigate the enzymatic properties of porcine pancreatic lipase with respect to dietary lipids. The effects of some physiological factors concerned with lipid digestion, such as bile salt and colipase, on the lipase hydrolysis were also examined. The method established in the present study could contribute to a highly sensitive assay of some hydrolases containing lipase with regard to insoluble substrates.

Animals↗
PubMed1971

Evidence for the presence of a pool of glycerides with a rapid rate of turnover in brown fat from newborn rabbits.

1. The specific radioactivity of [(14)C]glycerol released during the incubation of brown fat with [(14)C]glucose is much greater than that of the tissue lipid glycerol. 2. From a study of the release of [(14)C]glycerol from pre-labelled brown fat, it is concluded that the tissue contains a pool of glycerides with a higher rate of turnover than those in the main lipid store. 3. This pool contains newly synthesized glycerides, has a half-life of 25-30min and supplies about 25% of the glycerol liberated by brown fat. 4. Thus, a significant fraction of the total (14)C incorporated from glucose into brown-fat lipids is released as [(14)C]glycerol during an incubation.

Adipose Tissue, Brown↗
PubMed1974

Pathways of glyceride glycerol synthesis.

Isolated rat liver parenchymal cells were incubated for various periods with [U-(14)C,2-(3)H]glycerol and the radioisotopic yields in the major products were determined, as well as the (3)H/(14)C ratios in glyceride glycerol and intracellular glycerol phosphate. Under the conditions used (0.1mm-glycerol+10mm-l-lactate or 10mm-glycerol as substrates), only small differences were found between these (3)H/(14)C ratios. The results suggest a minor role for a pathway of glyceride glycerol synthesis involving reduction of acylated dihydroxyacetone phosphate, under these experimental conditions.

Acetone↗
PubMed1982

alpha-Actinin interacts specifically with model membranes containing glycerides and fatty acids.

A method was developed to identify specific protein-lipid interactions of complex lipid mixtures and to assess their effect upon the arrangement of such complexes in monolayers at an air-water interface. Its application to striated muscle alpha-actinin revealed that just two lipids selectively interact with alpha-actinin. One molecule of glyceride and one molecule of fatty acid were found to be associated in a constant stoichiometry with one molecule of the alpha-actinin dimer. In the presence of both glycerides and fatty acids unexpectedly rigid monolayer areas formed. This lipid specificity could be confirmed by brief protease digestion of alpha-actinin liposome mixtures followed by peptide analysis; the peptide patterns of alpha-actinin depended on the presence or absence of only these two lipids. Possible implications of these findings are discussed in the context of Z-line formation.

Actinin↗
PubMed1966

A radioautographic study of glyceride synthesis in vivo during intestinal absorption of fats and labeled glucose.

Radioautography was used to detect the synthesis of labeled glycerides in intestinal absorptive cells following injections of fatty chyme and glucose-6-H(3) into ligated segments of upper jejunum of fasting rats. Absorption intervals ranged from 2 to 20 min. Labeling is evident throughout the cells in as short a time as 2 min. Most grains are present over droplets of absorbed fat beginning with those in the endoplasmic reticulum immediately subjacent to the terminal web. With longer absorption periods, frequent grains are present over accumulations of fat droplets in the Golgi cisternae and intercellular spaces. A similar pattern of grains is seen following absorption of either linoleic acid or safflower oil. By comparison, considerably less label is present in the cells when the fat is extracted with alcohol prior to radioautographic procedures, or when labeled glucose alone is absorbed. A significant incorporation of glucose label into newly synthesized glycerides is indicated and confirmed by scintillation counts on saponified lipid extracts. The grain distribution implies an involvement of the extreme apical endoplasmic reticulum in this synthesis.

Animals↗