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At least 955 records · Page 53Linked to original sources
PubMed1989

Decreased incorporation of glucose into lipids and increased lactate production by adipose tissue after long-term treatment of rats with D-fenfluramine.

Male rats were treated with ten daily doses of 10 mg of D-fenfluramine/kg. Body weight decreased after days 1 and 2, but thereafter the weight gain paralleled that of the control rats. After the tenth injection there were decreases in the weights of the epididymal fat pads, their fat content, and the average size of the adipocytes after collaginase digestion. The rate of glucose uptake by incubated pieces of adipose tissue was maintained after D-fenfluramine treatment, and the production of lactate increased. The incorporation of glucose into fatty acids by adipose tissue pieces decreased by 65-74% after treatment with D-fenfluramine. This effect was not reversed by adding insulin or phenylisopropyladenosine to the incubations. D-Fenfluramine also decreased the incorporation of glucose into glyceride-glycerol, but this effect was less pronounced than that for fatty acid synthesis. Direct addition of D-fenfluramine to the incubation inhibited lipid synthesis from [14C]glucose but only at drug concentrations above 1 mM. It is concluded that the treatment of rats with D-fenfluramine modifies the metabolic balance of adipose tissue so as to direct glucose metabolism away from lipid synthesis and towards lactate production. This could be a significant mechanism in the overall loss of adipose tissue mass caused by the administration of D-fenfluramine.

Adipose Tissue↗
PubMed1975

Differential lipid deacylation during brain ischemia in a homeotherm and a poikilotherm. Content and composition of free fatty acids and triacylglycerols.

The free fatty acid (FFA) and triacylglycerol content and composition are compared in the mouse and toad brain during ischemia. Mouse brain FFA are rapidly increased after decapitation, the maximal production rates being attained within the first minutes. Free arachidonic and stearic acids undergo the highest increases, followed by palmitic, oleic and docosahexaenoic. In contrast, toad brain FFA only changes significantly several hours after decapitation. Triacylglycerols remain virtually unmodified in the amphibian brain during ischemia, whereas in the mammal they are partially decreased, reaching a nearly steady level at about 10 min. This triglyceride breakdown may represent a part, but cannot account for all the changes taking place in FFA. Uneven contributions to the FFA are shown for their counterparts in triacylglycerols. Although the neutral glycerides could be the source of free palmitic acid, they are not responsible for the increases in arachidonic and stearic acids. It is suggested that FFA mainly arise from polar lipid deacylation and a relationship is suggested between the slowness of FFA changes and the higher resistance of poikilotherms to oxygen deprivation.

Animals↗
PubMed1987

Effect of di-n-octyl phthalate on fatty acid composition of phosphatidylcholine in Tetrahymena.

We examined the effect of di-n-octyl phthalate (DOP) on fatty acid composition of phosphatidylcholine (PC) in Tetrahymena pyriformis NT-1. When Tetrahymena cells were grown in DOP-containing proteose peptone medium, the cell growth was repressed. This repression was attended by decreases in the PC content of the cells and decreases in oleic (18:1), linoleic (18:2) and linolenic (18:3) acids of PC and an increase in palmitoleic acid (16:1). The ratio of 18:1/stearic acid (18:0) of PC in cells grown in DOP-containing medium was lower than that of control cells, while the ratio of 16:1/palmitic acid (16:0) was higher than that of control. On the other hand, no changes in the ratios of 18:2/18:1 and 18:3/18:2 were observed. The activity of microsomal stearoyl-CoA desaturase from cells grown with DOP (0.63 mumol/ml medium) decreased to 27% of that from control cells, while the microsomal palmitoyl-CoA desaturase activity increased to 210% of the control value. By the addition of dioleoyl glyceride to the DOP-containing medium, the effects of DOP on Tetrahymena cells were completely blocked. These results suggest that the changes in fatty acid composition of PC may be due to the alteration of the substrate specificity of microsomal delta 9-desaturase, and the decrease in stearoyl-CoA desaturase activity may be a cause for the cell growth repression.

Animals↗
PubMed1981

Digestion and absorption of a sulphoxide analogue of triacylglycerol in the rat.

The stereochemistry of fat digestion and absorption was studied by feeding a triacylglycerol analogue to rats with a thoracic duct cannula. The analogue, rac-1,2-dioleoyl-3-S-tetradecyl-3-thioglycerol-S-oxide was chosen since its enantiomers exhibited high rotation in optical rotary dispersion (ORD) and circular dichroism (CD). In the chyle, triacylglycerol was the major lipid but X-1,2-diacyl-3-S-tetradecyl-3-thioglycerol-S-oxide constituted 8% of lipid weight. It was resolved by thin-layer chromatography (TLC) into two diastereomers. Each of the diastereomers were analyzed for the proportions of 1-thio-sn-glycerol/3-thio-sn-glycerol isomers by ORD and CD. The 1-thio-sn-glycerol isomers dominated for both compounds indicating that they were enriched during the absorption processes, since a racemic compound was fed. The stereospecificities are probably exerted by acyltransferase(s) during chyle lipid synthesis. The methods used will be valuable tools in studies on the metabolism of enantiomeric glycerides and also for characterization of naturally occurring sulphur-containing lipids.

Animals↗
PubMed1975

Biochemical typing of hyperlipoproteinemia. The development of a nomogram.

The accurate biochemical typing of hyperlipoproteinemia would require quantification of lipoprotein fractions. At present, typing is frequently based on the lipoprotein electrophoresis pattern together with serum lipid analyses. Lack of facilities for lipoprotein electrophoresis has however focused the clinical interest for classification of hyperlipoproteinemia into other means of a simple biochemical typing. In the present study a nomogram was developed to allow biochemical typing of hyperlipoproteinemia from serum cholesterol and triglyceride values. Serum cholesterol was determined according to a Liebermann-Burchard reaction by the method of Cramer and Isaksson [1], serum triglycerides by the determination of glyceride glycerol according to Carlson [2], and serum lipoprotein electrophoresis was performed on agarose gel [3]. Cholesterol content [4] of alpha-lipoproteins ("alpha-LP cholesterol") was obtained in serum after the precipitation of very-low-density lipoproteins(VLDL) and low-density lipoproteins(LDL) by manganese chloride and heparin [5]. Preparative ultracentrifugation was performed in a one-step, gradient procedure [6] isolating VLDL, d less than 1.006, LDL, d 1.006--1.063 g/ml and high-density lipoprotein (HDL) including very-high-density lipoproteins, d greater than 1.063 g/ml, or alternatively at d 1.006 g/ml according to the procedure by Gustafson et al. [7].

Cholesterol↗
PubMed1970

Structure des parois cellulaires des nocardia. I-isolement et composition des parois de Nocardia kirovani.

Nocardia kirovani cell walls possess a lipidic fraction, a lipolysaccharidic fraction and a peptidoglycan. The lipidic part is composed of glycerides, C(16) and C(18) free fatty acids, nocardic acids and of a carotenoid pigment. The lipopolysaccharidic part is composed of an arabinogalactan esterified by nocardic acids. The glycan strand consists of alternating 1-->4 linked N-acetylglucosamine and N-glycolylmuramic acid residues substituted by a peptide subunit in which the aminoacids Ala, Glu, meso-Dap are present in the molar proportions 1,7:1,2:1.

Journal Article↗
PubMed1982

Lactate metabolism and cytosolic NADH reducing equivalents in ovine adipocytes.

1. Isolated ovine adipocytes, unlike rat adipose tissue, could utilize lactate at a high rate. 2. When the rate of fatty acid synthesis was attenuated with 5-(tetradecyloxy)-2-furoic acid, a fatty acid synthesis inhibitor, there was a good positive correlation between the rates of lactate oxidation to CO2 and lactate incorporation into fatty acids. 3. Addition of 2,4-dinitrophenol enhanced lactate oxidation to CO2 independent of fatty acid synthesis. Under this condition, estimated cytosolic NADH formation from lactate dehydrogenation exceeded the need of NADH for cytosolic oxaloacetate reduction and for glyceride glycerol formation. 4. Mitochondria isolated from ovine adipocytes oxidized added NADH rapidly in a reconstituted alpha-glycerophosphate shuttle system. 5. It is possible that the ability of ovine adipocytes to utilize lactate may be related to the active alpha-glycerophosphate shuttle for cytosolic NADH reoxidation.

2,4-Dinitrophenol↗
PubMed1984

Direct effect of triiodothyronine on glucose utilization in adipocytes from obese and nonobese Zucker rats.

The direct effects of L-T3 (triiodothyronine) on glucose utilization, 2-deoxyglucose uptake and O2 consumption were evaluated in vitro in isolated adipocytes from 6-week-old obese and nonobese Zucker rats. Adipocytes treated for 30 min with L-T3 had a 20-25% decrease in glucose conversion to CO2, fatty acids and glyceride-glycerol and uptake of 2-deoxyglucose. Incubation of adipocytes with either D-T3 or rT3 (reverse T3) did not decrease utilization of glucose. T3 also decreased the insulin-stimulated fatty acid synthesis from glucose in both obese and nonobese adipocytes. Adipocyte O2 consumption was decreased by T3 in media that contained glucose but not in media that contained either acetate or no exogenous substrate. These data indicate that T3 has a direct, immediate and specific action on adipocyte glucose utilization and may act to modulate adipose lipogenesis and lipolysis.

Adipose Tissue↗
PubMed1985

Glucose infused through the portal vein enhances liver gluconeogenesis and glycogenesis from [3-14C]pyruvate in the starved rat.

After a pulse of [3-14C]pyruvate, 24 hr starved rats were infused through the portal vein with two different doses of glucose (7.8 or 20.8 mg/min) or the medium, and blood was collected from the inferior cava vein at the level of the suprahepatic veins. The highest dose of glucose enhanced the appearance of [14C]glucose in blood from the 2nd to the 20th min after tracer delivery. It also enhanced production of [14C]glycogen and concentration of glycogen in the liver after 5 and 20 min. At 20 min of glucose infusion the appearance of [14C]glyceride glycerol in liver as well as liver lactate concentration and lactate/pyruvate ratio were increased. The low dose of glucose used enhanced liver values of [14C]glycogen, [14C]glycogen specific activity and glycogen concentration. Our results support the hypothesis that in the starved rat glucose is converted into C3 units prior to being deposited as liver glycogen and based on the liver zonation model (Jungermann et al., 1983) it is proposed that glucose stimulated gluconeogenesis by shifting the liver to the cytosolic redox state as a secondary consequence of increased glycolytic activity.

Animals↗
PubMed1993

Cloning and characterization of rabbit pancreatic colipase.

1. Among the digestive enzymes synthesized by pancreas, lipase is the principle lipolytic enzyme which hydrolyses dietary glycerides. 2. For its action it requires a coenzyme, colipase. 3. The molecular mechanisms of the interaction of these two are not fully understood. 4. Further, molecular events that regulate and influence lipid absorption are ill defined. 5. The rabbit is the conventional animal model for the study of lipid absorption. We have undertaken the molecular cloning, and characterization of rabbit pancreatic colipase, the coenzyme for pancreatic lipase. 6. Colipase has been cloned from a gt 11 library of an adult rabbit pancreatic cDNA by probing with an oligonucleotide derived from human colipase sequence. 7. The total reading frame consists of 321 nucleotides coding for 90 amino acids of the functional protein and 17 nucleotides of the leader peptide. 8. Northern blot analysis revealed a distinct band around 0.5 kb. Comparison with other species revealed an over all homology of 75% at the nucleotide level. 9. At the amino acid level highest conservation is observed at the lipase-binding region (AA 53-73). 10. Rabbit enzyme also retained the N-terminal pentapeptide of its preform. 11. The regions of homology and conservation may aid to define the sites of interaction of colipase with lipase.

Amino Acid Sequence↗
PubMed1993

Intracellular transport, organelle biogenesis and establishment of Golgi identity: impact of brefeldin A on the activity of lipid synthesizing enzymes.

1. The effect of brefeldin A (BFA) on generation of transport vesicles, synthesis of phosphoglycerides, sphingosine and ceramides, and utilization of the sphingolipid precursors in the formation of sphingomyelin and glycosphingolipids in Golgi was investigated. 2. In the presence of 5-10 micrograms/ml BFA, the incorporation of [3H]palmitate into glycerides, phosphoglycerides and sphingolipids decreased 45-60%, and the production of endoplasmic reticulum transport vesicles was reduced 30-50%. 3. In Golgi membranes, the presence of 5-10 micrograms/ml BFA in the mixture, assembled to generate Golgi vesicles, evoked inhibitory effect on the synthesis of sphingomyelin, glycosphingolipids and phosphatidylcholine. On average, the synthesis of the sphingolipids and phosphatidylcholine and production of Golgi transport vesicles declined to 30-40%. 4. Addition of 5-10 micrograms/ml BFA to the assay mixture prepared to measure the activity of cytidylyltransferase, phosphocholine diacylglyceroltransferase, and serine palmitoyltransferase, caused up to 50% inhibition of the enzymes involved in the synthesis of phosphatidylcholine and up to 70% inhibition of the enzyme generating 3-ketosphinganine. 5. The results suggest that BFA inhibits the synthesis of phosphoglycerides and sphingolipids. This, at first, is displayed in reduced production of endoplasmic reticulum and Golgi transport vesicles, while the depletion of sphingolipids abrogates the identity of Golgi membranes.

Acyltransferases↗
PubMed1979

The effect of a putative anti-atherosclerotic agent (S 1204) on lipid metabolism in rabbit aorta.

The effects of the novel fenfluramine derivative, S 1204 (meta-trifluoromethyl phenyl-1 [beta(sulfamyl-3'-chloro-4'-benzoyloxyethyl)]amino-2-propane) were studied on lipid metabolism in rabbit aorta and other tissues. Pretreatment of rabbits with S 1204 (50 mg/kg orally) for 10 days strongly inhibited the aortic incorporation of an intravenous 20 muCi tracer-dose of [4-(14)C]-cholesterol given 24 h earlier. However, incorporation of such cholesterol radioactivity into the liver, intestine, lung or plasma was not affected, in comparison with control animals. One hour after i.v. injection of a 100 muCi tracer-dose of [2-(14)C]acetate, S 1204 significantly reduced the radioactivity of total lipids in the aorta and liver. Such inhibition of acetate incorporation into arterial lipids was observed with all lipid fractions (that is, free fatty acids, esterified cholesterol, especially phospholipids, glycerides and free cholesterol). Incorporation of acetate into intestinal triglyceride fractions was also significantly decreased. The results indicate that S 1204 may have anti-atherogenic properties, which could be valuable in the clinical treatment of atherosclerosis.

Animals↗
PubMedDate not supplied

The effect of local anesthetics on arterial lipid metabolism. Inhibition of sterol esterification in vitro.

The local anesthetics lidocaine, tetracaine, benzocaine and dibucaine were found to inhibit sterol esterification by acylCoA:cholesterol acyltransferase (ACAT, EC 2.3.1.26) in the microsomal fraction isolated from rabbit aortas. In arterial microsomes, the incorporation of [14C]oleoylCoA into [14C]steryl esters was inhibited in a dose-dependent way by the anesthetics over the concentration range 0.25-5.0 mM. The potency of inhibition was dibucaine greater than benzocaine greater than tetracaine greater than lidocaine greater than procaine with inhibition of about 85% occurring with 0.25 mM dibucaine. Sterol esterification to [14C]oleic acid was also inhibited by the anesthetics in intact aortic tissue from the rabbit, dog, and rat. A detailed study of the effects of 5 mM lidocaine on lipid biosynthesis in the rabbit aorta in vitro revealed that lidocaine not only inhibited sterol esterification to [14C]oleate but stimulated [14C]oleate incorporation into glycerides.

Anesthetics↗
PubMed1990

Abnormalities of composition and of in vitro lipolysis products of human small very low density lipoproteins in hypertriglyceridemia.

Small (Sf 20-100) very low density lipoprotein (VLDL) particles were prepared by density gradient ultracentrifugation of plasma from normolipidemic and type IV hypertriglyceridemic post-infarction patients and healthy controls. The small VLDL separated from the plasma of severely hypertriglyceridemic post-infarction patients were found to contain twice the amount of cholesteryl esters per particle, compared with small VLDL from normolipidemic patients and healthy controls. There was a linear increase in the percentage of cholesterol that was esterified in the small VLDL with the serum VLDL triglyceride concentration (r = 0.66). When incubated for two hours with bovine lipoprotein lipase in excess and bovine albumin as a free fatty acid acceptor at one and the same triglyceride concentration in the medium, the end-product isolated by ultracentrifugation varied as a function of the serum VLDL triglyceride level. The amount of glyceride-glycerol recovered after two hours of incubation with lipoprotein lipase was 13.3 +/- 1.3% (mean +/- SEM) of the initial values and did not correlate with the VLDL triglyceride level. With rising serum VLDL triglyceride concentration, the product isolated in the low density lipoprotein (LDL) density region (1.006 less than d less than 1.063 kg/l) contained more total cholesterol and phospholipids. The linear correlation coefficients for these relations were 0.65 and 0.58 for cholesterol and phospholipids respectively. The ratio of total cholesterol to insoluble protein in the LDL density range after lipolysis rose with increasing serum VLDL triglyceride level (r = 0.68). The end-product was further characterized by density gradient ultracentrifugation of the incubate. In vitro LDL derived by lipolysis of normolipidemic small VLDL was denser than in vitro LDL of hypertriglyceridemic small VLDL. A significant relation was found between the percentage of cholesteryl esters of total cholesterol in the substrate and the relative amount of total cholesterol recovered in the LDL density fraction after lipolysis (r = 0.69). We suggest that the enrichment with cholesteryl esters of small VLDL from type IV hypertriglyceridemic patients is caused by lipid transfer from LDL and high density lipoprotein (HDL) and that the change in VLDL particle composition influences the precursor-product relationship to LDL.

Adult↗
PubMed1992

Determination of the triglyceride composition of avocado oil by high-performance liquid chromatography using a light-scattering detector.

The triglyceride composition of avocado oil was determined by high-performance liquid chromatography using a light-scattering detector. Two avocado varieties, Fuerte and Hass, were analysed, and the qualitative composition of each was found to be similar, though quantitative differences were detected. The triglyceride composition was predicted using a system of equations based on the relationship between log k' and the molecular variables equivalent carbon number, chain length and number of double bonds for each of the fatty acids in the glycerides. A total of 24 molecular species of triglycerides were identified. The chromatographic system used successfully separated the critical pairs OOO-LOS, PaPaO-LnPP and PaOO-LOP (O = olein; L = linolein; S = stearin; Pa = palmitolein; Ln = linolenin; P = palmitin). Detector response was found to have a linear relationship with the amount of sample injected over the injection range 10-70 micrograms.

Chromatography, High Pressure Liquid↗
PubMed1985

Glucose metabolism in isolated adipocytes from lean and obese Zucker rats following treatment with dehydroepiandrosterone.

Previous work has demonstrated that chronic administration of dehydroepiandrosterone (DHEA) to obese Zucker rats reduces the severity of hyperinsulinemia that is usually present. There were also significant decreases in body weight, fat depot weight, and adipose tissue cellularity. It was hypothesized that the decreased serum insulin was a reflection of improved tissue responsiveness to insulin. The purpose of the present study was to evaluate this hypothesis by examining the insulin response in isolated adipocytes of DHEA-treated rats. Glucose incorporation into CO2, fatty acids, and glyceride-glycerol was measured in isolated parametrial and retroperitoneal adipocytes. Cells from control and DHEA-treated lean rats and control and DHEA-treated obese rats were used, as well as cells from a group of obese rats pair-fed to the DHEA-obese rats. Increased basal and insulin-stimulated rates of incorporation of glucose into CO2 and fatty acids were found in adipocytes from DHEA-lean rats compared to control, lean rats. In contrast, cells from DHEA-treated obese rats tended to incorporate less glucose into CO2 and fatty acids than either the control or pair-fed obese rats. These data indicate that the decrease in serum insulin levels seen in DHEA-treated obese rats is not due to an improvement of adipose tissue responsiveness.

Adipose Tissue↗
PubMed1983

Epitaxial crystallization of alkane chain lipids for electron diffraction analysis.

Thin microcrystals of a wide variety of polymethylene chain materials, including n-alkanes, linear waxes, glycerides, a detergent, phospholipids and phospholipid analogs based on cyclopentane-1,2,3-triol, are epitaxially grown on naphthalene to give an orientation with long chain axes parallel to the best developed crystal face. These crystals, which represent a different orientation than those grown from solution, facilitate ab initio quantitative crystal structure analysis from electron diffraction intensity data from the projection yielding the most crystallographic information.

Alkanes↗
PubMed1980

Lipids of stages in the life-cycle of the cestode Spirometra mansonoides.

The kinds and amounts of the lipids of each stage (egg, coracidium, procercoid, plerocercoid, adult) in the life-cycle of the cestode Spirometra mansonoides, and of environmental lipids, have been examined by combinations of TEAE-cellulose and silicic acid column, silica gel thin-layer and SCOT column gas-liquid chromatography. Major lipids of all stages were triacylglycerols, cholesterol, diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylserine, phosphatidylinositol, and phosphatidylcholine. Minor lipids were sterol esters, fatty acids, benzoquinones, partial glycerides phosphatidic acid, sphingolipids and lysolipids. Triacylglycerols decreased and cholesterol and phospholipids, particularly diphosphatidylglycerol and phosphatidylcholine, increased during embryogenesis (egg to coracidium). Neutral and phosphoglycerides had characteristic fatty acyl group patterns irrespective of life-cycle stage, except for procercoid lipids, which were unique in their content of branched and odd-numbered forms. The patterns seen in the total lipids of the various life-cycle stages were qualitatively similar to those of the environments of those stages, but were often quantitatively dissimilar.

Animals↗