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PubMed1985

Free fatty-acid uptake by isolated rat hepatocytes.

In isolated rat hepatocytes, the rate of palmitic acid binding and uptake is directly related to the concentration of free fatty acid (FFA) in the medium. After their entry into the cell, FFA are immediately incorporated into cellular phospholipids and triglycerides and no accumulation of free fatty acids can be demonstrated inside the cell. The rate of free fatty-acid uptake remains unchanged after incubation in a 2 mM KCN containing medium, indicating that in the range of fatty-acid concentrations used in this study, this phenomenon does not require energy.

Animals↗
PubMedDate not supplied

Phospholipase activity in human bile.

To investigate the importance of bacterial infection in the formation of free fatty acids found in brown pigment gallstones, free fatty acids and phospholipase activity in hepatic bile, with or without the presence of bacterial infection, were compared. The concentration of free fatty acids in bile with bacterial infection [0.467 +/- 0.447 mg per ml (mean +/- S.D.)] was significantly higher than when bacterial infection was absent (0.073 +/- 0.041 mg per ml; p less than 0.01). However, there was no significant difference in the composition of free fatty acids in hepatic bile when bacterial infection was present. Biliary phospholipase activity was determined by counting [14C] palmitic acid released from [14C]dipalmitoyl phosphatidylcholine that was incubated with native bile. The biliary phospholipase activity was significantly higher when bacterial infection was present. Furthermore, a positive correlation (p less than 0.001) was found between the activity of biliary phospholipases and the concentration of free fatty acids in hepatic bile. Most bacterial strains isolated from bile were shown to have both phospholipase A1 and A2 activity. On the other hand, human pancreatic juice and human gallbladder epithelial cells contained mainly phospholipase A2. Since fatty acids in the gallstone are mainly palmitic acid and must have been cleaved from first position in the biliary phosphatidylcholine molecule, bacterial phospholipase A1 seems to play an important role in the formation of calcium palmitate found in brown pigment gallstones.

Bacterial Infections↗
PubMed1995

Interaction of peptides corresponding to fatty acylation sites in proteins with model membranes.

In recent years, a large number of proteins having covalently linked myristic and palmitic acids have been discovered. It is assumed that fatty acid acylation serves to anchor proteins to membranes. However, it is not clear whether fatty acids modulate orientation of peptide chain in membranes or help in associating hydrophilic segments of peptides with membranes. We have examined the aggregation properties and membrane association of peptides corresponding to myristoylation and palmitoylation regions of proteins by fluorescence spectroscopy. Both acylated and non-acylated peptides were used for investigation. Binding of the peptides to lipid vesicles was assessed by monitoring the fluorescence of tryptophan as well as the quenching of its fluorescence in the presence of quenchers like I- and acrylamide. Our results indicate that in the peptide corresponding to a transmembrane segment, palmitoylation results in a change in the orientation of the peptide chain in the lipid bilayer. In the case of peptides that do not have a hydrophobic segment, acylation with palmitic or myristic acid does not appear to result in increased binding to lipid bilayer. Our results suggest that (i) the primary role of myristoylation may not be an anchor for membrane attachment as assumed, (ii) palmitoylation in the case of proteins having transmembrane segments may serve to realign the transmembrane segment from the normal orientation perpendicular to the bilayer surface, (iii) in the case of proteins where there is no hydrophobic segment, palmitoylation may not serve as a membrane anchor and could be involved in interaction with other membrane-bound proteins.

Acylation↗
PubMed1989

Intestinal absorption of stearic acid after consumption of high fat meals in humans.

The intestinal absorption of stearic acid (18:0), relative to other fatty acids, was evaluated in a group of 10 normal volunteers. Subjects were fed two types of high fat meals; one contained a relatively high content of stearic acid and the other a relatively low content. Plasma chylomicrons were isolated at 2, 4, 6 and 8 h after ingestion of the meals. Fatty acid patterns of chylomicron lipids were determined, and relative intestinal absorption rates of each fatty acid were estimated by comparing the fatty acid composition of chylomicron lipids with that of the fat in the meals. Overall, for both meals the fatty acid pattern of chylomicron lipids was very similar to that of ingested fat. Percentages of palmitic acid (16:0) and stearic acid, relative to other fatty acids, were only slightly lower in chylomicron lipids than in the meal fat. These data suggest that intestinal absorbability of stearic acid is similar to that of palmitic acid, and both saturated fatty acids appear to be absorbed almost as well as oleic acid (16:1).

Adult↗
PubMed1983

Abnormal phosphocreatine metabolism in perfused diabetic hearts. A 31P nuclear-magnetic-resonance study.

31P n.m.r. analysis of control and diabetic hearts perfused for 1 h with a glucose buffer showed constant and normal levels of phosphocreatine and ATP. Supplementing the buffer with 0.5, 1.2 or 2.0 mM-palmitic acid had little or no effect on high-energy-phosphate levels in control hearts. In contrast, increases in palmitate concentration produced significant decreases in ATP in diabetic hearts, despite normal and constant levels of phosphocreatine. This 31P n.m.r. study suggests a defect in phosphocreatine metabolism in the perfused diabetic heart that might be related to creatine kinase kinetics.

Adenosine Triphosphate↗
PubMed1990

Chain elongation of fatty acids in rat small intestine: subcellular localization and effects of clofibrate and partially hydrogenated fish oil.

Clofibrate treatment was found to increase by a factor of two the activity of malonyl-CoA-dependent palmitic acid chain elongation in crude 'microsomal' fractions isolated from rat small intestine. A slight stimulation was indicated also after feeding a high fat diet containing partially hydrogenated fish oil (PHFO). This effect was, however, not statistically significant. Subcellular localization of this chain elongation activity was studied by Nycodenz gradient centrifugation. Chain elongation of palmitic acid was observed only in fractions containing high esterase activity, suggesting a microsomal localization. Similar distributions were seen after feeding the peroxisomal proliferators clofibrate and PHFO. Chain-shortening activity was found in the fractions containing high catalase activity, confirming our earlier studies suggesting a peroxisomal localization of this activity also in rat small intestine.

Acetyltransferases↗
PubMed1994

Dietary myristic, palmitic, and linoleic acids modulate cholesterolemia in gerbils.

Previous studies with cebus monkeys and review of published human data indicated that 85% to 90% of the variation in plasma cholesterol (TC) could be explained on the basis of dietary myristic (14:0) and linoleic (18:2) acid intake in the absence of cholesterol, and that 16:0 contributed to cholesterolemia as dietary cholesterol was increased. Because monkeys are a limited resource, a more convenient, sensitive model was sought for investigating these dietary fatty acid and plasma lipid relationships. Accordingly, this report describes the results of multiple regression analysis of the TC response to dietary fatty acids based on 319 young, male Mongolian gerbils fed a total of 59 purified diets supplying about 40% energy as fat from single or blended fat sources. Gerbils (6-16 animals per dietary group) were fed purified diets (21 with 0.01 to 0.08% cholesterol and 38 cholesterol-free) for 4-week periods. When cholesterol-free diets were fed, dietary 14:0 and 18:2 together accounted for 89% of the observed variation in TC. Although 14:0 consumption increased TC in a linear manner, the independent ability of 18:2 to lower cholesterol was nonlinear and exhibited a threshold effect at 5-6% dietary energy, above which further lowering of TC was less remarkable. In gerbils consuming cholesterol-supplemented diets, 87% of the observed variation in TC could be accounted for by a regression equation that included 14:0, palmitic acid (16:0), and a log function of 18:2 plus dietary cholesterol itself. These results demonstrate the applicability of gerbils for such studies and confirm previous observations in monkeys and humans that dietary 14:0 and 18:2 are the main fatty acids modulating plasma cholesterol under normocholesterolemic circumstances (i.e., when consuming low-cholesterol diets and lipoprotein metabolism is normal) whereas 16:0 also appears modestly hypercholesterolemic when LDL receptors are compromised (i.e., when dietary cholesterol or certain metabolic factors have encumbered lipoprotein metabolism).

Animals↗
PubMed1990

Synthesis of a fluorinated fatty acid, dl-erythro-9,10-[18F]difluoropalmitic acid, and biodistribution studies in rats.

9,10-Difluoropalmitic acid (DFPA) labeled with the cyclotron produced, positron emitting radionuclide 18F has been synthesized as a potential analogue of 9,10-[3H]palmitic acid, a fatty acid which has been used to study lipid metabolism in rat brain and pituitary. [18F]DFPA was prepared by the direct and stereoselective addition of [18F]F2 to the double bond of cis-9,10-palmitoleic acid. The fluorination was carried out in FCCl3 at -70 degrees C using a low concentration of F2 (0.5%) in neon. [18F]DFPA has been obtained in radiochemical yields of 12-16% from end-of-bombardment (EOB) in approx. 2.5 h. Chemical and radiochemical purity exceeded 95%, and specific activities calculated to EOB ranged from 500 to 1000 mCi/mmol. [18F]DFPA crosses the blood-brain barrier and is incorporated into rat brain at about twice the level of that of 9,10-[3H]palmitic acid. The synthesis of [18F]DFPA permits us to study the biological disposition and metabolism of a vicinal-difluoro fatty acid.

Animals↗
PubMed1993

[Chemical constituents of Emilia sonchifolia L. DC].

Five known compounds were obtained from the whole plant of Emilia sonchifolia. By means of chemical and spectral methods, they were identified to be simiral, beta-sitosterol, stigmasterol, palmitic acid and honey acid.

Drugs, Chinese Herbal↗
PubMed2001

Optimization of methods and treatment conditions for studying effects of fatty acids on cell growth.

Antiproliferative properties of molecular regulators of lipid metabolism have been increasingly studied during recent years. Discussion is ongoing concerning optimal treatment conditions and assays used for monitoring proliferation and cytotoxicity. The objective of the present work was to optimize methods and treatment conditions used for studying antiproliferative effects of fatty acids and analogs, represented by palmitic acid (PA) and the beta-oxidation-restricted fatty acid analog tetradecylthioacetic acid (TTA), in rat (BT4Cn) and human (D54Mg and GaMg) glioma cell lines. Changes in [3H]thymidine incorporation preceded changes in cell number in TTA-treated glioma cell cultures, and the growth inhibition was more significantly expressed by [3H]thymidine incorporation than cell number. Addition of bovine serum albumin decreased cellular fatty acid uptake and reduced the effects of TTA and PA on [3H]thymidine incorporation. Determination of the antiproliferative effect of TTA in BT4Cn cells by MTT conversion and [3H]thymidine incorporation yielded concordant results. TTA-mediated reduction in cell number corresponded to reduction in cellular protein and total DNA content in BT4Cn cells. Reduced growth potential in TTA-treated multicellular D54Mg and GaMg spheroids supported the findings from monolayer cultures. In conclusion, cell density, treatment period, fatty acid administration, and methods for growth determination may profoundly influence the outcome of cell growth experiments. Thus, experimental conditions should be carefully controlled when performing cell growth experiments, and effects on cell growth should preferably be confirmed by different methods.

Animals↗
PubMed1995

Palmitoylation of the GluR6 kainate receptor.

The G-protein-coupled metabotropic glutamate receptor mGluR1 alpha and the ionotropic glutamate receptor GluR6 were examined for posttranslational palmitoylation. Recombinant receptors were expressed in baculovirus-infected insect cells or in human embryonic kidney cells and were metabolically labeled with [3H]palmitic acid. The metabotropic mGluR1 alpha receptor was not labeled whereas the GluR6 kainate receptor was labeled after incubation with [3H]palmitate. The [3H]palmitate labeling of GluR6 was eliminated by treatment with hydroxylamine, indicating that the labeling was due to palmitoylation at a cysteine residue via a thioester bond. Site-directed mutagenesis was used to demonstrate that palmitoylation of GluR6 occurs at two cysteine residues, C827 and C840, located in the carboxyl-terminal domain of the molecule. A comparison of the electrophysiological properties of the wild-type and unpalmitoylated mutant receptor (C827A, C840A) showed that the kainate-gated currents produced by the unpalmitoylated mutant receptor were indistinguishable from those of the wild-type GluR6. The unpalmitoylated mutant was a better substrate for protein kinase C than the wild-type GluR6 receptor. These data indicate that palmitoylation may not modulate kainate channel function directly but instead affect function indirectly by regulating the phosphorylation state of the receptor.

Alanine↗
PubMed1983

Nature of the Fatty Acid Synthetase Systems in Parenchymal and Epidermal Cells of Allium porrum L. Leaves.

Fatty acid synthesis was compared in cell-free extracts of epidermis and parenchyma of Allium porrum L. leaves. Parenchyma extracts had the major fatty acid synthetase (FAS) activity (70-90%) of the whole leaf; palmitic acid was also the major fatty acid synthesized when acetyl-coenzyme A (CoA) was the primer, but when acetyl-acyl carrier protein (ACP) was employed, C(18:0) and C(16:0) were synthesized in equal proportion. With the epidermal FAS system when either acetyl-CoA or acetyl-ACP was tested in the presence of labeled malonyl-CoA, palmitic acid was the only product synthesized. Specific activities of the FAS enzyme activities were determined in both tissue extracts.The properties of malonyl-CoA:ACP transacylase were examined from the two different tissues. The molecular weights estimated by Sephadex G-200 chromatography were 38,000 for the epidermal enzyme and 45,000 for parenchymal enzyme. The optimal pH was for both enzymes 7.8 to 8.0 and the maximal velocity 0.4 to 0.5 micromoles per milligram protein per minute. These enzymes had different affinities for malonyl-CoA and ACP. For the malonyl-CoA:ACP transacylase of epidermis, the K(m) values were 5.6 and 13.7 micromolar for malonyl-CoA and ACP, respectively, and 4.2 and 21.7 micromolar for the parenchymal enzyme. These results suggest that the FAS system in both tissues are nonassociated, that the malonyl-CoA:ACP transacylases are isozymes, and that both in epidermis and in parenchyma tissue two independent FAS system occur. Evidence would suggest that beta-ketoacyl-ACP synthase II is present in the parenchymal cells but missing in the epidermal cell.

Journal Article↗
PubMed1997

Regulation of osteoclastic bone resorption by glucose.

Osteoclasts degrade bone by pumping molar quantities of HCl to dissolve the calcium salts of bone, an energy intensive process evidently supported by abundant mitochondria. This is the first study to directly examine the ability of various metabolites to serve as potential energy sources for osteoclastic bone resorption. Glucose, and to a lesser extent lactate, supported osteoclastic bone degradation. However, fatty acids (palmitate, myristate and stearate), essential amino acids plus 20 mM alanine, or ketone bodies (acetoacetate, beta-hydroxybutyrate and alpha-ketoglutarate) did not support bone degradation. Resorption declined to 10-30% of glucose controls when fatty acids or ketoacids were substituted for glucose. Resorption was glucose concentration dependent, with maximal activity at approximately 7 mM (K(M) approximately 3 mM). Glucose transport was linear for approximately 15 minutes, specific for D-glucose, and inhibited by cytochalasin B. Osteoclasts cultured on bone transported glucose at almost twice the rate of those off bone (Vmax 23 versus 13 nmols/mg/min, respectively) and medium acid accumulation paralleled glucose uptake, while the K(M) was unchanged. We conclude that glucose is the principal energy source required for bone degradation. Further, characteristics of glucose transport are consistent with the hypothesis that fluctuations in serum glucose concentration are an important component in regulation of osteoclastic bone degradation.

Alanine↗
PubMed1983

Determinants of the plasma protein binding of theophylline in health.

1 The plasma protein binding of theophylline was determined after addition of [14C]-theophylline (15 micrograms/ml) to plasma from 24 healthy drug-free volunteers and equilibrium dialysis for 2 h at 37 degrees C. 2 The percentage of drug unbound was 60.0% +/- 2.2% (s.d.) with very little variation between individuals. The binding ratio of theophylline was not significantly related to the plasma albumin or alpha 1-acid glycoprotein (AAG) concentrations but was significantly, although weakly, negatively related to the logarithm of the non-esterified fatty acid concentration (NEFA) (r = 0.443, P less than 0.05). 3 Intravenous administration of heparin (1000 units) caused a significant rise in plasma NEFA concentration and in the percentage of drug unbound in plasma after equilibrium dialysis. 4 In human serum albumin solutions, the binding ratio of theophylline was significantly related to the albumin concentration and at the albumin concentration seen in the 24 normal subjects, the percentage of drug unbound was almost identical. Addition of AAG in physiological concentrations did not enhance theophylline binding but oleic acid, and to a lesser extent palmitic acid, reduced binding significantly. 5 The percentage of theophylline unbound in plasma varied markedly with pH so that at pH7 the percentage unbound was 52% greater than at pH 8. There was no evidence of concentration dependence of binding up to 140 micrograms/ml theophylline. 6 Theophylline appears to bind almost exclusively to albumin and its plasma protein binding varies little in healthy subjects, showing no concentration-dependence over the therapeutic range of concentrations. The binding is affected by pH and by NEFA concentration, however, and these factors may be of greater importance in disease states. Caution should be employed in the use of heparin in studies of plasma protein binding of theophylline.

Adolescent↗
PubMed2003

Fatty acid esterification in the yolk sac membrane of the avian embryo.

The transfer of lipid from the yolk to the avian embryo is mediated by the yolk sac membrane (YSM). Some, but not all, of the published morphological evidence supports the view that the lipid undergoes a cycle of hydrolysis and re-esterification during translocation across the YSM. The present study aims to test this view by investigating the capacity of the YSM to perform esterification of free fatty acids to form acyl-lipids. YSM pieces (area vasculosa), obtained from the chicken embryo at day 10 of development, were incubated in vitro in medium containing [14C]-palmitic acid. Radioactivity was rapidly incorporated into the tissue lipid indicating a high capacity for esterification. The incorporation was linear with time during the 1-h incubation. Approximately 84% of the incorporated label was recovered in triacylglycerol, 12% was incorporated into phospholipid and less than 1% was detected in cholesteryl ester. [14C]-palmitic acid was incorporated primarily at the sn-1/3 positions in the triacylglycerol molecule and at the sn-1 position of phospholipid. The incorporation of label into tissue pieces obtained from the non-vascularized peripheral region of the YSM (area vitellina) was much more limited than that observed for the area vasculosa. The results support the hypothesis that yolk lipid is hydrolyzed and re-esterified during transfer across the YSM.

Animals↗
PubMed2005

Increased phospholipase activity in Helicobacter pylori strains isolated from patients with gastric carcinoma.

PURPOSE: Phospholipase activity, one of Helicobacter pylori pathogenicity factors, has not been investigated enough, so far, although it may induce a remarkable damage to the gastric mucosa. In the present work, we have compared the whole phospholipase activity of H. pylori strains isolated from patients with gastric carcinoma with that of strains isolated from dyspeptic patients without gastric carcinoma. METHODS: We measured the phospholipase activity of one distinct H. pylori colony isolated from each of 10 patients with gastric carcinoma and 10 controls, dyspeptic patients without endoscopic and histological signs of gastric carcinoma. We also determined the phospholipase activity of 20 additional strains isolated from different areas of neoplastic and non-neoplastic tissue of two patients with gastric carcinoma, the cagA and vacA positive G27 and 328 wild strains and their respective vacA and cagA negative isogenic mutants. The whole phospholipase activity of strains was determined by measuring the release of (14)C-labeled palmitic acid from the radioactive l-3-phosphatidylcholine, 1,2-di[1-(14)C]palmiloyl substrate; results were expressed in pmol of palmitic acid per mg of protein. RESULTS: H. pylori strains isolated from patients with gastric carcinoma had levels of phospholipase activity significantly higher than those of strains isolated from controls (99.37 [S.D. 40.45] versus 34.46 [S.D. 16.46], P<0.001). In patients with gastric carcinoma, the mean phospholipase activity of strains isolated from neoplastic tissue was similar to that of strains isolated from non-neoplastic tissues (123.02 [S.D. 44.36] and 115.77 [S.D. 81.48], respectively. Interruption of cagA gene caused a ca. 20% reduction of phospholipase activity (36.38 versus 45.22 of the wild strain); that of vacA caused no reduction of phospholipase activity (26.53 and 25.37 of the wild strain). CONCLUSIONS: The infection by H. pylori strains that produce high levels of phospholipase may increase the risk of developing gastric carcinoma. We hypothesise that indirect products of phospholipase activity, such as prostaglandins, leukotrienes and lysophospholipids, may mediate carcinogenesis.

Antigens, Bacterial↗
PubMed2002

Effect of diabetes and contractile activity on incorporation of the plasma-borne fatty acids into skeletal muscle lipids.

There are only few data on skeletal muscle lipid metabolism in diabetes. The aim of the present study was to examine effect of streptozotocin diabetes on incorporation of the blood-borne 14C-palmitic acid into different fractions of skeletal muscle lipids at rest and during contractile activity. The experiments were carried out on male Wistar rats. Streptozotocin was administered intravenously. The control rats received saline. Seven days later, the rats were anaesthetized and the calf muscles of one hindleg were made to contract for 1 min by stimulation of the sciatic nerve with tetanic pulses (30 tetani/min). Thereafter, 14C-palmitic acid was administered intravenously and the stimulation was continued for 5 min. The contralateral resting leg served as a control. Samples of the soleus, red and white gastrocnemius were taken. Lipids were extracted with chloroform/methanol and separated into the following fractions by means of thin layer chromatography: phospholipids, mono-, di-, and triacylglycerols, free fatty acids, cholesterol and cholesterol esters. Radioactivity of each fraction was counted. It has been found, that the label was always incorporated mostly into the fraction of triacylglycerols and phospholipids. Diabetes increased radioactivity of each lipid fraction, both at rest and during contractile activity, comparing to the respective values in the control rats. It is concluded that transport of the blood-borne free fatty acids into the myocytes and their incorporation into different lipid fraction increases in acute diabetes.

Animals↗
PubMed1967

Lipid composition and metabolism in testicular and ejaculated ram spermatozoa.

1. Spermatozoa collected directly from the testis of the conscious ram contain 25% more phospholipid than ejaculated spermatozoa. The concentration of lecithin, phosphatidylethanolamine and ethanolamine plasmalogen was greater in testicular spermatozoa; little difference was observed in choline plasmalogen. Both types of spermatozoa had significant amounts of cardiolipin and alkyl ether phospholipid. 2. The fatty acids in the phospholipid extracted from testicular spermatozoa have a very high content of palmitic acid. The phospholipids of ejaculated spermatozoa contained less palmitic acid, but more myristic acid. 3. Ejaculated spermatozoa contained less acyl ester and cholesterol. It is suggested that lipids are a source of substrate for spermatozoa during their passage through the epididymis. 4. Testicular spermatozoa when incubated with [U-(14)C]glucose incorporated more radioactivity into the glycerol part of the phospholipid and neutral lipid fractions than did ejaculated cells. The distribution of radioactivity in the individual phospholipids and neutral lipids was similar for both cell types. No radioactivity was detected in choline plasmalogen, which accounted for approx. 40% of the total phospholipid. 5. Testicular spermatozoa incorporated more radioactivity from glucose into formate than into acetate, whereas a higher proportion of radioactivity was found in acetate in ejaculated cells. 6. The implications of these lipid changes in the process of spermatozoal maturation are discussed.

Animals↗