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PubMed2001

Transmembrane TNF (pro-TNF) is palmitoylated.

Human transmembrane tumor necrosis factor (pro-TNF) was examined for protein acylation. The cDNA encoding pro-TNF was expressed in both COS-1 cells and Sf9 cells and metabolic labeling with [(3)H]myristic or [(3)H]palmitic acid was attempted. The 17 kDa mature TNF secreted from the transfected cells was not labeled, whereas the 26 kDa pro-TNF was specifically labeled with [(3)H]palmitic acid. The [(3)H]palmitic acid labeling of pro-TNF was eliminated by treatment with hydroxylamine, indicating that the labeling was due to palmitoylation of a cysteine residue via a thioester bond. Site-directed mutagenesis of the two cysteine residues residing in the leader sequence of pro-TNF demonstrated that palmitoylation of pro-TNF occurs solely at Cys-47, located at the boundary between the transmembrane and cytoplasmic domains of pro-TNF. Thus, pro-TNF interacts with the plasma membrane via both its proteinaceous transmembrane domain and a lipid anchor.

Acylation↗

PubMed1988

Effect of dietary stearic acid on plasma cholesterol and lipoprotein levels.

We studied the metabolic effects of stearic acid (18:0) on plasma lipoprotein levels in 11 subjects during three dietary periods of three weeks each. The three liquid-formula diets, which were used in random order, were high in palmitic acid (16:0), stearic acid, and oleic acid (18:1), respectively. Caloric intakes were the same during the three periods. As compared with the values observed when the subjects were on the high-palmitic-acid diet, plasma total cholesterol decreased by an average of 14 percent during consumption of the high-stearic-acid diet (P less than 0.005) and by 10 percent during consumption of the high-oleic-acid diet (P less than 0.02). Low-density lipoprotein cholesterol levels fell by 21 percent in subjects on the high-stearic-acid diet (P less than 0.005) and by 15 percent in subjects on the high-oleic-acid diet (P less than 0.005). No significant differences were observed in the plasma levels of triglycerides or high-density lipoprotein cholesterol among the three diets. Measurements of the intestinal absorption of palmitic, stearic, and oleic acids revealed essentially complete absorption of each during the three dietary periods. The oleic acid content of plasma triglycerides and cholesteryl esters increased significantly during the high-stearic-acid period, suggesting that stearic acid is rapidly converted to oleic acid. We conclude that stearic acid appears to be as effective as oleic acid in lowering plasma cholesterol levels when either replaces palmitic acid in the diet.

Cholesterol↗

PubMed1994

Inhibitory effect of fatty acids on glucose and insulin uptake in the perfused rat hindquarter.

To elucidate the effects of fatty acids on the uptake of glucose and insulin in the muscle, the effects of oleic and palmitic acids on the uptake of glucose and insulin were investigated in perfused hind-quarters of rats. In the absence of insulin, glucose uptake in the hindquarter was slightly, but not significantly, decreased by the addition of oleic and palmitic acids. In the presence of 100 or 500 microU/ml insulin, glucose uptake in the hindquarter (243 +/- 58 or 282 +/- 65 mumol/30 min) was significantly decreased by the addition of 1000 microM oleic acid and 500 microM palmitic acid (175 +/- 50 or 207 +/- 47 mumol/30 min). The decrease in insulin uptake rate, although not significant at 500 microU/ml insulin, is of similar magnitude to the decrease in glucose uptake. In the presence of 1000 microU/ml insulin, glucose and insulin uptake was not significantly altered by the addition of fatty acids. These results indicate that fatty acids directly inhibit the muscular glucose uptake via the decrease in muscular insulin uptake at a physiological concentration of insulin.

Adenosine Triphosphate↗

PubMed1992

Lamellar structures formed by stratum corneum lipids in vitro: a deuterium nuclear magnetic resonance (NMR) study.

Hydrated lipid mixtures consisting of stratum corneum ceramides, cholesterol, specifically deuterated palmitic acid, and cholesteryl sulfate were investigated by solid-state 2H NMR spectroscopy at different temperatures. The mole ratio of cholesterol to ceramides was varied from 1 to 0. 2H NMR spectra from these mixtures showed powder patterns with quadrupolar splittings smaller than those obtained from control mixtures containing dipalmitoylphosphatidylcholine (DPPC) instead of the ceramides. This result is attributed to the rigid amide group of the ceramides, with a planar configuration, which could prevent close packing of the alpha-methylenes of the acyl chains. There was a gradual loss of symmetry in the powder pattern as the amount of cholesterol was decreased and the amount of ceramides (or DPPC) was increased concomitantly. The loss was more pronounced in the ceramide-containing samples. This phenomenon is interpreted as a decrease in the axial reorientation rate of the alpha-deuterated palmitic acid in the bilayers, presumably caused by the increased hydrogen bonding resulting from the high amount of hydroxyl-bearing ceramides. Spectra obtained at temperatures above 60 degrees C indicated the formation of a hexagonal phase (HII) by the ceramide-containing mixtures. Spectra of the omega-deuterated palmitic acid in the mixture containing 76 mol% ceramides and no cholesterol indicated phase separation into a more rigid phase and a more mobile phase in the temperature range of 25 to 60 degrees C. The bilayer configuration of lipids at 25 degrees C was confirmed by thin-section electron microscopy.

Animals↗

PubMed1991

Fatty acid composition of adipose tissue in Ethiopian immigrants: a prospective study during their first year in Israel.

We measured the subcutaneous adipose tissue fatty acid composition in 22 male Ethiopian Jews, aged 17-65, shortly after their immigration to Israel. These subjects showed a concentration of linoleic acid (17.8%), which was relatively low compared with Israeli levels, and a high concentration of palmitic acid (28.5%). The linoleic/saturated (P/S) ratio was 0.52. After 5 months, a repeat measurement indicated increases of the linoleic acid content and of the P/S ratio to 20.1% and 0.62, respectively (P less than 0.05). In another sample from the same immigrant group, levels after 1 year in Israel were 20.9% and 25.1% for linoleic and palmitic acid, respectively, and the P/S ratio was 0.67. These results differed significantly (P less than 0.02) from those obtained in the first sample after immigration. Apart from decreasing plasma triglyceride levels, no pattern of lipid changes was discernible in our limited samples. Changes in subcutaneous fatty acid composition reflect changes in diet over months, suggesting a decreased carbohydrate intake and in increased fat intake. It remains to be seen whether changing fatty acid composition in conjunction with changes in blood lipids or other factors, over a prolonged period of time, will affect the cardiovascular risk in the immigrants.

Adipose Tissue↗

PubMed1995

Differential fatty acid accretion in heart, liver and adipose tissues of rats fed beef tallow, fish oil, olive oil and safflower oils at three levels of energy intake.

To examine interactive effects of dietary fatty acid composition and energy restriction on tissue fatty acid accretion, mature rats consumed diets containing beef tallow, fish oil, olive oil or safflower oil with free access or at 85% or 68% of free access energy intakes. Restriction was accomplished by adjustment of dietary carbohydrate level. After 10 wk, animals were killed, and the fatty acid compositions of liver, heart and adipose tissues were examined. Compared with animals given free access to diets, body weight gains were reduced at wk 10 in fish oil- and olive oil-fed groups consuming 85% (P < 0.01) and in all groups consuming 68% (P < 0.005) of free access energy intake. Liver and heart weights were also lower (P < 0.05) in all groups restricted to 68% of free access energy intake. The type of dietary fat and the level of energy restriction influenced fatty acid composition in all three tissues at wk 10. In liver tissue, graded energy restriction increased (P < 0.02) proportions of stearic acid and decreased (P < 0.03) those of palmitic acid. In heart tissue, palmitic acid levels decreased (P < 0.01) with energy restriction. In adipose tissue, significant energy restriction-related changes in fatty acid composition varied with type of fat consumed. These results emphasize the importance of whole-body energy balance in addition to dietary fatty acid supply in utilization of dietary fatty acids for tissue deposition vs. oxidation.

Adipose Tissue↗

PubMed1982

The clearance and placental transfer of free fatty acids and triglycerides in the pregnant guinea-pig.

Bolus injections of [14C]palmitic acid and endogenously prepared very low density lipoprotein (VLDL) were given to 12 guinea-pigs in late gestation in whom the fetal side of the placenta was perfused in situ. Disappearance of [14C] palmitate in the mother was rapid, with a half life of 2.4 min. The [14C] palmitic acid which crossed the placenta into the perfusate disappeared in parallel with the maternal label but with a delay time of 1.6 min. Following injection of [14C] labelled very low density lipoprotein maternal plasma [14C] triglyceride declined rapidly (half life of 0.7 to 9.8 min) and gave rise to [14C] free fatty acids in the plasma. These fatty acids disappeared at a slower rate (half life of 13.5 min) than found following [14C]palmitate bolus. No [14C] triglyceride appeared to cross the placenta, but triglyceride derived free fatty acids did with a delay time of 9.4 min. In experiments performed after 55 days gestation quantities of [14C] free fatty acids were higher in the perfusate than in maternal plasma implying hydrolysis of triglyceride within the placenta. It is concluded that maternal triglyceride may make a considerable contribution to fetal lipids which increases with gestational age.

Animals↗

PubMed1998

Fatty acid alpha-oxidation of tetradecylthioacetic acid and tetradecylthiopropionic acid in cucumber (Cucumis sativus).

Fatty acid alpha-oxidation in cucumber (Cucumis sativus) involves enzymatic conversion of long-chain Cn-fatty acids to the C(n-1)-aldehyde and CO2. However, the mechanism of this process is not well understood. In this study, the alpha-oxidation of the fatty acid analogues tetradecylthioacetic acid (TTA) and tetradecylthiopropionic acid (TTP) with a sulphur atom substituting the methylene group in positions 3 and 4, respectively, was investigated and compared to palmitic acid. Both [1-14C]TTA and [1-14C]TTP could be alpha-oxidised in the cucumber subcellular 150000xgmax fraction. [1-14C]TTP was an even better substrate compared to the natural palmitic acid, while [1-14C]TTA was alpha-oxidised to a lower extent. [2-14C]TTA revealed no 14CO2, indicating that only one cycle of alpha-oxidation occurred. TTA was an inhibitor of the palmitic acid alpha-oxidation, and the inhibitory effects were examined.

Animals↗

PubMed1993

Studies on the effect of fenoprofen on the activation and oxidation of long chain and very long chain fatty acids in hepatocytes and subcellular fractions from rat liver.

We studied the effect of fenoprofen on the activation of palmitic acid (C16:0), lignoceric acid (C24:0) and cerotic acid (C26:0) in microsomal and peroxisomal fractions from rat liver. Fenoprofen was found to inhibit the formation of palmitoyl-CoA in both microsomal and peroxisomal fractions whereas the formation of lignoceroyl-CoA and cerotoyl-CoA was not inhibited at all. In freshly isolated rat hepatocytes palmitic acid beta-oxidation was progressively inhibited at increasing concentrations of fenoprofen, most probably due to its inhibitory effect on palmitoyl-CoA synthetase activity. On the other hand, fenoprofen was also found to inhibit the beta-oxidation of lignoceric acid and cerotic acid in rat hepatocytes. It is shown that the acyl-CoA oxidase activity with lignoceroyl-CoA as substrate was inhibited by fenoprofen whereas the palmitoyl-CoA and pristanoyl-CoA oxidase activities were not inhibited by fenoprofen. This finding provides an explanation for the inhibitory effect of fenoprofen on lignocerate and cerotate beta-oxidation in hepatocytes.

Animals↗

PubMed1987

Deuterium nuclear magnetic resonance studies on the plasmalogens and the glycerol acetals of plasmalogens of Clostridium butyricum and Clostridium beijerinckii.

Deuterium nuclear magnetic resonance was used to investigate the structure of different lipid fractions isolated from the anaerobic bacteria Clostridium butyricum and Clostridium beijerinckii. The fractions isolated from C. butyricum were (1) phosphatidylethanolamine/plasmenylethanolamine and (2) the glycerol acetal of plasmenylethanolamine, and from C. beijerinckii similar fractions containing principally (1) phosphatidyl-N-monomethylethanolamine, along with its plasmalogen, and (2) the glycerol acetal of this plasmalogen were isolated. The third fraction from both species consisted largely of the acidic lipids phosphatidylglycerol and cardiolipin along with plasmalogen forms of these lipids. Palmitic acid with deuterium labels at C-2, C-3, or C-4 or oleic acid with deuterium labels at C-2 and C-9,10 was added to the growth medium and incorporated to various extents in the lipid fractions. Biochemical analysis showed that palmitic acid and oleic acid were preferentially bound to the sn-2 and sn-1 positions, respectively, of the glycerol backbone when both fatty acids were added to the medium. From the 2H NMR spectra, the hydrocarbon chain ordering near the lipid-water interface could be determined and appeared to be similar for all three lipid fractions. The deuterium quadrupole splitting and order parameter were low at the C-2 segment and increased by almost a factor of 2 at positions C-3 and C-4 for cells fed with deuterated palmitic acid along with unlabeled oleic acid. These results agree with previous findings on pure diacyl lipids in which the sn-2 chain was found to adopt a bent conformation at the carbon segment C-2. However, two unusual quadrupole splittings could be detected for the plasmalogens.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetals↗

PubMed1997

Lipid domains and orthorhombic phases in model stratum corneum: evidence from Fourier transform infrared spectroscopy studies.

A three component model for the lipid barrier of the stratum corneum (SC) consisting of ceramide III, cholesterol, and perdeuterated palmitic acid, has been characterized by Fourier transform infrared spectroscopy. At physiological temperature the CD2 scissoring mode of the palmitic acid methylenes, and the CH2 rocking mode of the ceramide methylenes, are each split into two components. This indicates that both components exist in separate, conformationally ordered phases, probably with orthorhombic perpendicular subcells. The magnitude of the splitting indicates that the domains are at least 100 chains in size. The thermotropic behavior of the CD2 stretching vibrations demonstrates that conformational disordering of the palmitic acid commences at 42 degrees C with a transition midpoint of 50 degrees C. The CH2 stretching frequency indicates the ceramide chains remain ordered until 50 degrees C then disorder with a midpoint of 67 degrees C. The results provide a molecular characterization for the complex low temperature (10-40 degrees C) dynamic behavior suggested by recent 2H NMR experiments.

Biophysical Phenomena↗

PubMed1977

Fatty acid metabolism in hypoxic rat liver.

Fatty acid metabolism was investigated in adult male albino rats exposed to hypobaric hypoxia at 25,000 ft simulated altitude for 6 h at 32 degrees C. Oxidation and esterification of palmitic acid-1-14C and de novo lipogenesis from acetate-1-14C were studied. Palmitic acid-1-14C oxidation in liver slices was normal while acetoacetate formation was increased. In vivo esterification of palmitic acid-1-14C to form triglycerides was increased while formation of phosphatidylcholine and phosphatidylethanolamine was observed to decrease. Decreased incorporation into plasma phosphatidylcholine with unaltered total activity in plasma triglycerides was observed. The incorporation of acetate-1-14C was observed to remain unaltered in triglycerides and phospholipids of liver with a similar pattern in the plasma indicating unaltered de novo lipogenesis. There appears to be increased esterification of fatty acids with probably impaired release of triglycerides into plasma while fatty acid biosynthesis remains unaffected.

Adrenal Glands↗

PubMed1993

Unique lipids of primate spermatozoa: desmosterol and docosahexaenoic acid.

Spermatozoa represent a tissue readily accessible for study after various exogenous perturbations. To characterize the lipid composition of monkey sperm and to establish a baseline from which dietary or pharmaceutical influences may then be evaluated, we collected semen samples from five rhesus monkeys by electroejaculation and analyzed the sperm for sterols, fatty acid composition, and the molecular species of the ethanolamine glycerophospholipids. Two sterols were identified: cholesterol, 41%, and desmosterol, 59% of total sterols. Desmosterol was found only in the free form. Cholesterol existed in three different forms: free, 60%; esterified, 20%; and sulfated, 20%. Docosahexaenoic acid (22:6, DHA) was almost the only n-3 fatty acid in sperm phospholipids, 24% of the total fatty acids. DHA was present mainly in phosphatidylcholine and phosphatidylethanolamine. Oleic and palmitic acids were the predominant monounsaturated and saturated fatty acids. The ethanolamine glycerophospholipids were separated into three subclasses: diacyl 49%, alkenylacyl 43%, and alkylacyl 8%. Thirteen molecular species were identified and quantified. The sn-1 position of these molecular species contained exclusively 16:0, 18:0, or 18:1. The sn-2 position contained n-3, n-6, and n-9, as well as saturated fatty acids. The molecular species having n-3 fatty acids in the sn-2 position contributed 43, 73, and 100% of the total in the diacyl, alkenylacyl, and alkylacyl subclasses, respectively. The presence of the unusual sterol, desmosterol, a cholesterol precursor not found in measurable quantities in any other tissue suggests an important functional and structural role for desmosterol in spermatozoa. The other unique lipids, cholesterol sulfate and the n-3 docosahexaenoic acid, may also have a significant role in the function of spermatozoa.

Animals↗

PubMed1989

Fatty acid acylation of the 67K envelope glycoprotein of a baculovirus: Autographa californica nuclear polyhedrosis virus.

Modification of Autographa californica multicapsid nuclear polyhedrosis virus extracellular virion polypeptides with fatty acid was investigated. Fatty acid-derived radioactivity was incorporated into gp67, the predominant virion envelope glycoprotein, during metabolic labeling using [3H]palmitic acid or [3H]myristic acid. The acyl moiety resisted extraction with chloroform-methanol but was released by mild alkali or hydroxylamine treatment, features characteristic of an ester-type linkage. Palmitic acid was identified as the fatty acid liberated during acid hydrolysis of purified [3H]palmitic acid and [3H]myristic acid-labeled gp67. Acyl peptides were protected during proteinase K digestion of intact virions but they were larger (Mr 34.3K and 31.8K) than expected on the basis of membrane protection alone. Carbohydrate may have played a role in determining the protease resistance of the observed fragments. Potential acylation sites on gp67 within or adjacent to the C-terminal hydrophobic region are discussed with respect to the predicted amino acid sequence.

Acylation↗

PubMed1975

Effect of micelle formation on the absorption of neutral fat and fatty acids by the chicken.

Experiments were conducted to determine the absorption of various dietary fatty acids and glycerides singly and in mixtures. Chickens with or without cannulated bile ducts or ligated pancreatic ducts were used to evaluate the absorption of fatty acids or mixtures of fatty acids and the absorption patterns of several classes of lipids and their effect on the absorption of palmitic acid under in vivo conditions. In spite of wide melting point differences, isomers of various monoglycerides or 18-carbon unsaturated fatty acids exhibited identical absorption and solubility patterns. A homologous series of saturated monoglycerides showed a maximum absorption value for the monoglycerides with fatty acids of 12 and 14 carbons. Absorption decreased with increasing chain lengths of the fatty acid in the monoglyceride. Conversely, the absorption of palmitic acid when fed with the various monoglycerides progressively increased to a maximum in the mixture containing monomyristin and then decreased when fed with monopalmitin or monostearin.

Animal Nutritional Physiological Phenomena↗

PubMed1981

The effects of cerulenin on lipid metabolism in vitro in cellular preparations from the rat.

The effects of the fatty acid-like antibiotic, cerulenin, on fatty acid biosynthesis in preparations of rat adipocytes and mammary cells in vitro have been investigated. Synthesis of palmitic acid was most strongly inhibited, although the magnitude of the effect was dependent on the nature of the tissue, and was especially diminished in the larger adipocytes from older rats. Cerulenin had no effect on the chain-elongation of preformed fatty acids in any of the tissues studied. Some inhibition of the esterification of preformed palmitic acid was also observed, but this appeared to be due to disruption of the cells rather than direct inhibition of the acyltransferases. It is concluded that cerulenin is a valuable experimental tool in studies of lipogenesis in preparations of intact mammalian cells in vitro.

Adipose Tissue↗

PubMed1991

Lipolytic response to metabolic stress in critically ill patients.

OBJECTIVE: To measure whole-body lipolysis and fatty acid re-esterification in critically ill patients. DESIGN: The rates of appearance of glycerol and palmitic acid in blood plasma were measured by infusing stable isotope tracers [2H5]glycerol and [1-13C]palmitic acid, respectively. Energy expenditure was measured by indirect calorimetry. SETTING: Medical ICU of The University of Texas Medical Branch Hospital, a university-based referral center. PATIENTS: Five uninjured critically ill patients. Four patients were hospitalized because of respiratory insufficiency and one because of myocardial infarction. Three patients died during their hospitalization. INTERVENTIONS: Metabolic studies were performed in each patient after an overnight (12-hr) fast. MEASUREMENTS AND MAIN RESULTS: Mean +/- SE glycerol and fatty acid rates of appearance were 4.5 +/- 1.0 and 11.5 +/- 0.8 mumol/kg.min, respectively. The ratio of fatty acid to glycerol rate of appearance was 2.9 +/- 0.5. Resting energy expenditure was 132 +/- 6% of predicted. CONCLUSIONS: An accelerated rate of lipolysis is part of the metabolic response to severe stress, regardless of its etiology. Because the rate of fatty acid release far exceeded energy requirements, fatty acids that were not oxidized as fuel were re-esterified to triglyceride, presumably in the liver.

Acute Disease↗

PubMed1992

Research note: eggshell quality in Japanese quail fed different fatty acids.

The purpose of the present study was to determine the effects of diets containing 3% palmitic acid (Diet PA), oleic acid (Diet OA), or linoleic acid (Diet LA) on the shell quality of eggs of Japanese quail. Each diet was fed to 10 hens maintained individually in wire quail laying cages. There was no difference (P greater than .05) in feed consumption between hens fed Diets OA and LA, but hens of both groups consumed less (P less than .05) feed than those fed Diet PA. Egg weight, shell weight, and thickness of shell plus membrane were not influenced by dietary treatment (P greater than .05). However, specific gravity of eggs from hens fed Diet OA was significantly higher (P less than .05) than that of eggs from those fed either Diet PA or Diet LA. Comparison of these data with hatchability data obtained in a previous experiment conducted under similar conditions suggests that the differences in hatchability would not be explained by differences in eggshell quality.

Animals↗