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PubMed1977

The effects of palmitic acid on skeletal muscle mitochondria of cold and warm acclimated rats.

The effects of palmitic acid on skeletal muscle mitochondria isolated from the hind limb muscle of cold and warm acclimated rats were studied. At higher concentrations of the fatty acid, a greater depression of both ADP/O and RCR (respiratory control ratio) was observed in the cold acclimated group. Initial ADP/O and RCC however, were higher in the cold acclimated group. The enhanced sensitivity of skeletal muscle mitochondria of the cold acclimated rat is discussed.

Acclimatization↗
PubMed1989

Enhanced thermal tolerance in a mutant of Arabidopsis deficient in palmitic Acid unsaturation.

A mutant of Arabidopsis thaliana, deficient in the activity of a chloroplast omega9 fatty acid desaturase, accumulates high amounts of palmitic acid (16:0), and exhibits an overall reduction in the level of unsaturation of chloroplast lipids. Under standard conditions the altered membrane lipid composition had only minor effects on growth rate of the mutant, net photosynthetic CO(2) fixation, photosynthetic electron transport, or chloroplast ultrastructure. Similarly, fluorescence polarization measurements indicated that the fluidity of the membranes was not significantly different in the mutant and the wild type. However, at temperatures above 28 degrees C, the mutant grew more rapidly than the wild type suggesting that the altered fatty acid composition enhanced the thermal tolerance of the mutant. Similarly, the chloroplast membranes of the mutant were more resistant than wild type to thermal inactivation of photosynthetic electron transport. These observations lend support to previous suggestions that chloroplast membrane lipid composition may be an important component of the thermal acclimation response observed in many plant species which are photosynthetically active during periods of seasonally variable temperature extremes.

Journal Article↗
PubMedDate not supplied

Effects of temperature on in vitro palmitic acid uptake by chicken and rat intestinal tissue.

The intestinal absorption of fatty acids proceeds by simple or facilitated diffusion, a mechanism which is affected by temperature. However, most studies in this field have not taken into consideration the fact that birds have higher physiological temperature than mammals, the absorption being studied at 37 degrees C in both cases. The aim of this work has been to find out whether the higher palmitic acid (PA) uptake rate in birds (chickens) compared to mammals (rats) is attributable to the differences between their body temperatures (41.5 degrees C for chickens and 37.5 degrees C for rats). PA-uptake was studied in intestinal (ileal and jejunal) tissue samples of both Hybro broiler chickens (male and female, 4 weeks-old) and Ico:OFA rats (males and females, 8 weeks-old). The intestinal tissue samples were incubated in micellar solution (0.6 mM 14C-PA; 0.3 mM monoolein; 3.4 mM sodium taurodeoxycholate) at 37.5 degrees C and 41.5 degrees C in both cases. Chicken intestinal tissue incorporated PA with higher efficiency at 41.5 degrees C than at 37.5 degrees C. In contrast, increasing the incubation temperature to 41.5 degrees C led to a decrease in PA uptake by female rat intestinal tissue whereas specimens from male rats exhibited the same absorptive efficiency. These results suggest that the incubation temperature determines to some extent the efficiency of fatty acid uptake. However the fact that the temperature caused opposite effects in rats and chickens indicates that the changes in temperature affect the intracellular processing of the fatty acids already taken up rather than the diffusion of fatty acids through the enterocyte brush-border membrane.

Animals↗
PubMed1990

Uptake of palmitic acid by rabbit alveolar type II cells.

Alveolar type II cells require a source of palmitic acid for synthesis of dipalmitoyl phosphatidylcholine (DPPC), a major constituent of pulmonary surfactant. Previous studies indicated that maximal rates of DPPC synthesis are achieved only if exogenous palmitate is available to the type II cell. Little is known of the mechanisms by which fatty acids enter type II cells. To determine if uptake is mediated by a membrane carrier system, as described in other cell types, we examined the kinetics of palmitate uptake. Using freshly isolated rabbit type II cells, we demonstrated that radiolabeled palmitate uptake was maximal and linear for 45 s; after 1 min the apparent rate of uptake declined. The initial uptake phase was taken as a measure of cellular fatty acid influx because intracellular radiolabeled palmitate remained 80% nonesterified at this time but was 55% esterified by 2 min. Cellular influx of palmitate showed saturation kinetics with increasing concentration of nonalbumin bound palmitate. Michaelis constant was 52.6 nM, and maximum velocity was 152 pmol.10(6) cells-1.min-1. The hypothesis that saturable cellular influx of palmitate is likely linked to the previously identified membrane fatty acid binding protein (MFABP) was supported by Western-blot analysis of rat lung tissue with an antibody to MFABP that demonstrated the presence of this carrier protein in lung tissue. These data suggest that palmitate uptake by type II cells is saturable and may be mediated by a membrane-associated carrier as described in other cell types.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed2002

Anaerobic degradation of oleic acid by suspended and granular sludge: identification of palmitic acid as a key intermediate.

The aim of the present work was to study the maximum potential methane production in batch assays of sludge samples taken along the operation of two EGSB reactors (RI inoculated with granular sludge and RII inoculated with suspended sludge) fed with increasing oleic acid concentrations between 2 and 8 gCOD/l (HRT = 1 day). After removing the residual substrate, the sludge was incubated in batch vials without any added carbon source. A maximum methane production rate of 152+/-21 mlCH4(STP)/gVS.day was obtained for the suspended sludge taken on day 70, when oleate at a concentration of 2 g COD/l was fed with a co-substrate (50% COD). The maximum plateau achieved in the methane production curve was 1145+/-307 mlCH4(STP)/gVS, obtained for the suspended sludge taken on day 162, when oleate was fed as the sole carbon source at 6 g COD/I. The methanization rate of the adsorbed substrate was enhanced under stirring conditions and was inhibited by adding oleic acid. Extraction and GC analysis confirmed that the main adsorbed substrate was palmitate, and not oleate. Accumulated palmitate adsorbed onto the sludge and further beta-oxidation was inhibited when in the presence of oleic acid. If oleic acid was removed from the medium beta-oxidation proceeded with methane production. Suspended sludge was more efficient than granular sludge.

Adsorption↗
PubMedDate not supplied

Activation of palmitic acid by human spermatozoa.

Human spermatozoa were studied to determine if a long chain fatty acid, CoASH ligase (AMP) (E.C. 6.2.1.3), was present. Ligase activity was measured with a radioligand millipore filter technique and was readily detectable in spermatozoa or in the protein fraction extracted with Triton X-100, but was not present in seminal plasma. The assay was optimized for pH, protein concentration, and incubation time. Activity was dependent upon palmitic acid, ATP, coenzyme A, and a divalent cation. Sperm ligase appeared similar to the ligase characterized from other tissues by sharing a common pH optimum (approximately 8.0-8.4), and a preference for magnesium over manganese in the incubation media.

Adenosine Triphosphate↗
PubMed1974

Structure and Biosynthesis of Cuticular Lipids: Hydroxylation of Palmitic Acid and Decarboxylation of C(28), C(30), and C(32) Acids in Vicia faba Flowers.

The structure and composition of the cutin monomers from the flower petals of Vicia faba were determined by hydrogenolysis (LiAlH(4)) or deuterolysis (LiAlD(4)) followed by thin layer chromatography and combined gas-liquid chromatography and mass spectrometry. The major components were 10, 16-dihydroxyhexadecanoic acid (79.8%), 9, 16-dihydroxyhexadecanoic acid (4.2%), 16-hydroxyhexadecanoic acid (4.2%), 18-hydroxyoctadecanoic acid (1.6%), and hexadecanoic acid (2.4%). These results show that flower petal cutin is very similar to leaf cutin of V. faba. Developing petals readily incorporated exogenous [1-(14)C]palmitic acid into cutin. Direct conversion of the exogeneous acid into 16-hydroxyhexadecanoic acid, 10, 16-dihydroxy-, and 9, 16-dihydroxyhexadecanoic acid was demonstrated by radio gas-liquid chromatography of their chemical degradation products. About 1% of the exogenous [1-(14)C]palmitic acid was incorporated into C(27), C(29), and C(31)n-alkanes, which were identified by combined gas-liquid chromatography and mass spectrometry as the major components of the hydrocarbons of V. faba flowers. The radioactivity distribution among these three alkanes (C(27), 15%; C(29), 48%; C(31), 38%) was similar to the per cent composition of the alkanes (C(27), 12%; C(29), 43%; C(31), 44%). [1-(14)C]Stearic acid was also incorporated into C(27), C(29), and C(31)n-alkanes in good yield (3%). Trichloroacetate, which has been postulated to be an inhibitor of fatty acid elongation, inhibited the conversion of [1-(14)C]stearic acid to alkanes, and the inhibition was greatest for the longer alkanes. Developing flower petals also incorporated exogenous C(28), C(30), and C(32) acids into alkanes in 0.5% to 5% yields. [G-(3)H]n-octacosanoic acid (C(28)) was incorporated into C(27), C(29), and C(31)n-alkanes. [G-(3)H]n-triacontanoic acid (C(30)) was incorporated mainly into C(29) and C(31) alkanes, whereas [9, 10, 11-(3)H]n-dotriacontanoic acid (C(32)) was converted mainly to C(31) alkane. Trichloroacetate inhibited the conversion of the exogenous acids into alkanes with carbon chains longer than the exogenous acid, and at the same time increased the amount of the direct decarboxylation product formed. These results clearly demonstrate direct decarboxylation as well as elongation and decarboxylation of exogenous fatty acids, and thus constitute the most direct evidence thus far obtained for an elongation-decarboxylation mechanism for the biosynthesis of alkanes.

Journal Article↗
PubMed2002

Treatment of the rat hepatic stellate cell line, PAV-1, by retinol and palmitic acid leads to a convenient model to study retinoids metabolism.

The main site of vitamin A storage in the liver is the hepatic stellate cells (HSC). Involvement of HSC in vitamin A metabolism has mainly been studied using primary culture, which represents the most physiological model but technically suffers several drawbacks (yield, low reproducibility, etc.). To circumvent these problems, we have previously established and characterised an immortalised rat HSC line named PAV-1. This study aimed to investigate in PAV-1 and in primary HSC (i) the incorporation of retinol and its esterification, (ii) the cellular retinol-binding protein (CRBP) content, (iii) the acid retinyl ester hydrolase activity (aREH), (iv) the thermal susceptibility and (v) the lipid composition of the membranes, which may play a crucial role in retinol transport across cellular membrane. In routine conditions of culture, the rate of retinol esterification in PAV-1 was low (5.2%) compared to that obtained with primary HSC (69.9%). Retinol pre-treatment doubled this esterification rate (10.7%) and the CRBP content in PAV-1. The co-incubation with retinol and palmitic acid enabled PAV-1 to esterify retinol with a rate close to that of primary HSC (66.2% vs. 69.9%) and with similar retinyl ester profiles. aREH activity was higher in primary HSC than in PAV-1. Thermal susceptibility and phospholipid composition of membranes in PAV-1 treated cells were similar to those of primary HSC. In conclusion, our study shows that PAV-1 cells treated with retinol and palmitic acid is a sound and convenient model for studying vitamin A mobilisation, a fundamental physiological event occurring in HSC.

Animals↗
PubMed1985

Studies on the attachment of myristic and palmitic acid to cell proteins in human squamous carcinoma cell lines: evidence for two pathways.

The ability of human keratinocytes and squamous carcinoma cell lines to attach lipid covalently to cell proteins has been examined using both palmitic and myristic acids. SDS-polyacrylamide gel analyses of the proteins labelled with these lipids demonstrated that each labelled a different set of proteins. Covalently protein bound palmitic acid could be removed from the proteins by mild alkali hydrolysis but the bound myristic acid required prolonged acid hydrolysis to release it from the associated proteins. H.p.l.c. analyses of the released lipid confirmed that both lipids were attached to proteins directly and that the labelling was not due to the lipids being catabolised. Cycloheximide could prevent the attachment of myristic acid to cell proteins, but only reduced the levels of palmitic acid incorporation. Pulse chase experiments indicated that there was little turnover of the attached myristic acid whereas this was significant for covalently bound palmitic acid. These observations show for the first time that two different protein populations are labelled by different lipids in eukaryotic cells, and that there appear to be two separate pathways for the acylation of proteins in such cells.

Acylation↗
PubMed2006

Palmitic acid increase levels of pancreatic duodenal homeobox-1 and p38/stress-activated protein kinase in islets from rats maintained on a low protein diet.

A severe reduction in insulin release in response to glucose is consistently noticed in protein-deprived rats and is attributed partly to the chronic exposure to elevated levels of NEFA. Since the pancreatic and duodenal transcription factor homeobox 1 (PDX-1) is important for the maintenance of beta-cell physiology, and since PDX-1 expression is altered in the islets of rats fed a low protein (LP) diet and that rats show high NEFA levels, we assessed PDX-1 and insulin mRNA expression, as well as PDX-1 and p38/stress activated protein kinase 2 (SAPK2) protein expression, in islets from young rats fed low (6%) or normal (17%; control) protein diets and maintained for 48 h in culture medium containing 5.6 mmol/l glucose, with or without 0.6 mmol/l palmitic acid. We also measured glucose-induced insulin secretion and glucose metabolism. Insulin secretion by isolated islets in response to 16.7 mmol/l glucose was reduced in LP compared with control rats. In the presence of NEFA, there was an increase in insulin secretion in both groups. At 2.8 mmol/l glucose, the metabolism of this sugar was reduced in LP islets, regardless of the presence of this fatty acid. However, when challenged with 16.7 mmol/l glucose, LP and control islets showed a severe reduction in glucose oxidation in the presence of NEFA. The PDX-1 and insulin mRNA were significantly higher when NEFA was added to the culture medium in both groups of islets. The effect of palmitic acid on PDX-1 and p38/SAPK2 protein levels was similar in LP and control islets, but the increase was much more evident in LP islets. These results demonstrate the complex interrelationship between nutrients in the control of insulin release and support the view that fatty acids play an important role in glucose homeostasis by affecting molecular mechanisms and stimulus/secretion coupling pathways.

Animals↗
PubMed2001

Bioprospecting for novel hydroxyoxylipins in fungi: presence of 3-hydroxy palmitic acid in Saccharomycopsis malanga.

Electron microscopy studies indicated that the major oxylipin 3-hydroxy palmitic acid (16:0) was associated with aggregating vegetative cells and formed a web-like structure around these cells. Cross sections through this structure showed a hydrophilic outer layer and a more hydrophobic inner layer suggesting that the web-like structure is in fact tube-like micelles. This information sheds more light on the role of these hydroxyoxylipins in fungi.

Cell Wall↗
PubMed1992

Improvement of large intestinal absorption of insulin by chemical modification with palmitic acid in rats.

The intestinal absorption of 125I-labelled palmitoyl insulin was examined following administration into in-situ closed large intestinal loops of rats. When mono- and dipalmitoyl insulins (Palins-1 and Palins-2, respectively) were administered in polyoxyethylene hydrogenated castor oil (HCO 60) micellar system into intestinal loops, a marked increase in plasma radioactivity and a corresponding disappearance of residual radioactivity in the intestinal lumen were observed in the following rank order: Palins-2 greater than Palins-1 greater than native insulin. In addition, the derivatives were more stable than native insulin in the mucosal tissue homogenates of the large intestine. These results suggest that chemical modification of insulin with palmitic acid may not only increase the lipophilicity of insulin but also reduce its degradation, resulting in the increased transfer of insulin across the large intestinal mucous membrane. The linoleic acid-HCO 60 mixed micelles system did not have a significant effect on the large intestinal absorption of radioactivity associated with the lipophilic insulin analogues.

Animals↗
PubMed1992

Beta-oxidation of [1-14C]palmitic acid by mouse astrocytes in primary culture: effects of agents implicated in the encephalopathy of Reye's syndrome.

beta-Oxidation of [1-14C]palmitic acid was examined in homogenates of astrocytes cultured from neonatal mouse brain. Under optimal reaction conditions (< or = 50 micrograms protein, 10 min at 37 degrees C), oxidation increased as a function of palmitate concentration (15 microM to 2 mM) and reached a maximum rate of 1.98 +/- 0.29 nmol/min/mg protein (mean +/- SEM) at 0.2 mM substrate. Eadie-Hofstee analysis of data from four experiments yielded apparent values for Vmax of 1.87 nmol/min/mg protein, and for Km, 35-40 microM. There were no dramatic changes in the oxidation rate in cells between 10 and 36 days in culture. During the 10-min assays, less than 0.05% of the radioactivity was converted to 14CO2 by the astrocytes; water-soluble products accounted for 1-2% of the total substrate added. Studies with KCN indicated that 60-70% of the total activity occurred in the mitochondria. We have been studying the structural and functional changes associated with the cerebral encephalopathy of Reye's syndrome (RS). Three-week-old astrocytes exposed to serum from RS children for the final 7 days of culture exhibited minor mitochondrial pleomorphism and had increased numbers of other intracellular organelles. Examination of the effects of agents implicated in RS indicated that oxidation of [1-14C]palmitate was not altered by Na+ salicylate (1-3 mM), but was inhibited by the industrial surfactant, Toximul MP-8 (> or = 10 micrograms/ml), 4-pentenoic acid (> or = 0.1 microM), or with 4 days' exposure to ammonia (10 nM). The latter treatment also resulted in an increase in protein synthesis, cell volume, and malondialdehyde formation. These results suggest that some of the "toxins" implicated in RS inhibit fatty-acid oxidation in the astrocytes and produce other lipid-related abnormalities that could be related to encephalopathy.

Ammonia↗
PubMed1973

Metabolism of palmitic acid in the subcellular fractions of mouse brain.

After an intracerebral injection of [(14)C]palmitic acid to C57BL/10J mice, the radioactivity in the brains decreased rapidly with time. The incorporated radioactivity was primarily in the 16:0 acyl groups of the diacyl phosphoglycerides at 1 and 3 days after injection. At longer times, increasing proportions of the radioactivity were found in cerebrosides, alkenyl groups, and other acyl groups. The specific radioactivities of the phosphoglycerides were highest in the microsomal fraction at 1 day after injection. The exchange of the diacyl glycerophosphorylcholines and diacyl glycerophosphorylethanolamines between the microsomes and the myelin required 8-14 days. When calculated on the basis of the radioactivity in the 16:0 acyl groups, the half-lives for both of these phosphoglycerides were 6-8 days in all subcellular fractions during the period from 14 to 30 days after injection. The radioactivity in the total lipids from the purified myelin fraction did not decline until more than 14 days after injection because of the reutilization of labeled 16:0 acyl groups for lipid biosynthesis. Recycling of the acyl groups explains the long half-lives reported for myelin phosphoglycerides after injection of [(14)C]acetic acid. Lipids with a relatively high specific radioactivity were lost from the myelin fraction during the purification procedure. The most likely source of these lipids is the most recently formed myelin that is not consolidated into the myelin sheath.

Acylation↗
PubMed1979

The effect of DL-2-bromopalmitate on the utilization of palmitic acid by rat granular pneumocytes.

The effect of DL-2-bromopalmitate (BrPA), an analogue of palmitic acid (PA), on the utilization of this fatty acid by rat lungs was investigated by a combination of anatomic and biochemical methods. The experiments were performed in vitro on two types of preparations, isolated perfused lungs and lung slices. In the isolated lung preparation the substrate reached the lung via the capillaries, in lung slices via the alveolar epithelium. Electron microscope autoradiography showed that BrPA depressed uptake of PA by granular pneumocytes. Radioactivity recovered by tissue analysis and capture of CO2 established that PA oxidation and incorporation into phospholipids and triglycerides was depressed by BrPA. A close correlation was found between the reduction in radioactivity in phospholipids and the grain density over lamellar bodies. The study shows that BrPA reversibly interferes with the uptake and utilization of long chain fatty by granular pneumocytes. BrPA appears as a useful tool to study palmitate metabolism and surfactant production by the lung.

Animals↗