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Leaky beta-oxidation of a trans-fatty acid: incomplete beta-oxidation of elaidic acid is due to the accumulation of 5-trans-tetradecenoyl-CoA and its hydrolysis and conversion to 5-trans-tetradecenoylcarnitine in the matrix of rat mitochondria.

The degradation of elaidic acid (9-trans-octadecenoic acid), oleic acid, and stearic acid by rat mitochondria was studied to determine whether the presence of a trans double bond in place of a cis double bond or no double bond affects beta-oxidation. Rat mitochondria from liver or heart effectively degraded the coenzyme A derivatives of all three fatty acids. However, with elaidoyl-CoA as a substrate, a major metabolite accumulated in the mitochondrial matrix. This metabolite was isolated and identified as 5-trans-tetradecenoyl-CoA. In contrast, little or none of the corresponding metabolites were detected with oleoyl-CoA or stearoyl-CoA as substrates. A kinetic study of long-chain acyl-CoA dehydrogenase (LCAD) and very long-chain acyl-CoA dehydrogenase revealed that 5-trans-tetradecenoyl-CoA is a poorer substrate of LCAD than is 5-cis-tetradecenoyl-CoA, while both unsaturated acyl-CoAs are poor substrates of very long-chain acyl-CoA dehydrogenase when compared with myristoyl-CoA. Tetradecenoic acid and tetradecenoylcarnitine were detected by gas chromatography/mass spectrometry and tandem mass spectrometry, respectively, when rat liver mitochondria were incubated with elaidoyl-CoA but not when oleoyl-CoA was the substrate. These observations support the conclusion that 5-trans-tetradecenoyl-CoA accumulates in the mitochondrial matrix, because it is less efficiently dehydrogenated by LCAD than is its cis isomer and that the accumulation of this beta-oxidation intermediate facilitates its hydrolysis and conversion to 5-trans-tetradecenoylcarnitine thereby permitting a partially degraded fatty acid to escape from mitochondria. Analysis of this compromised but functional process provides insight into the operation of beta-oxidation in intact mitochondria.

Animals↗

Chemical constituents of Selinum cryptotaenium.

A new pyranocoumarin, named secryptotaenin A, determined as 3'(S)-angeloyloxy-3',4'-dihydroseselin, was isolated from the roots of Selinum cryptotaenium, along with thirteen known compounds, umbelliferone, osthol, coumurrayin, (+)-heraclenol, longshengensin A, anomalin, ferulic acid, galactitol, stearic acid, melissic acid, lignoceric acid, beta-sitosterol and daucosterol. Their structures were determined on the basis of spectroscopic methods.

Apiaceae↗

Levoglucosan in PM2.5 at the Fresno supersite.

Ambient air monitoring for PM2.5 has been conducted on a daily basis at the Fresno, CA, supersite since 1999. It has been found that PM2.5 concentrations routinely exceed the National Ambient Air Quality Standards during the winter months. In an effort to determine the effect of biomass burning on PM2.5 concentrations, samples during 2000 were analyzed for levoglucosan, palmitic acid, and stearic acid. The results of this study are presented.

Air Pollutants↗

Patterns of chocolate consumption.

Although consumed in some form since at least 460 AD, cacao (Theobroma cacao) was not used in confectionery until the 19th century when the cocoa press was invented. Per capita consumption of chocolate confectionery in the United States is moderate (approximately 4.6-4.8 kg/y) compared with that of many northern European countries (approximately 7-10 kg/y). Eleven percent of the US population reported consuming chocolate candy on > or = 1 of the 3 d of recorded food intake in the US Department of Agriculture Nationwide Food Consumption Survey 1987-1988; < 1.0% consumed chocolate every day. The Western region of the United States contained the highest proportion of chocolate consumers. More whites than other racial groups were consumers. Chocolate was consumed by more people in the winter than in other seasons and more was consumed at snacks than at meals. The mean amount of chocolate consumed was approximately 30-90 g/d, depending on sex and age group. Chocolate candy was only a minor contributor (0.7-3.4%) to the overall dietary intake of total energy, fat, saturated fatty acids, and stearic acid.

Adolescent↗

Correlation between DNA or protein adducts and benzo[a]pyrene diol epoxide I-triglyceride adduct detected in vitro and in vivo.

In this study, we demonstrated the in vitro and in vivo formation of carcinogen-lipid adduct and its correlation with DNA or protein adducts. The lipids from serum or hepatocyte membranes of Sprague-Dawley rats, human serum and standard major lipids were in vitro reacted with benzo[a]pyrene (B[a]P) and B[a]P metabolites. 7, 8-Dihydroxy-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene(BPDE-I), an ultimate carcinogenic form of B[a]P, was covalently bound to triglyceride (TG). BPDE-I-TG adducts isolated by thin-layer chromatography (TLC) were further detected by high-performance liquid chromatography. TGs, including triolein, tripalmitin and tristearin, showed positive reactions with BPDE-I. However, cholesterol, phospholipids (phosphatidylcholine, phosphatidyl-ethanolamine, phosphatidyl-inositol and sphingomyelin) and non-esterified fatty acids (palmitic acid, oleic acid, linoleic acid and stearic acid) did not react with BPDE-I. In addition, other B[a]P metabolites (B[a]P-phenols and -diols) did not react with TG. TG appeared to be the most reactive lipid yet studied with respect to its ability to form an adduct with BPDE-I. There was a clear-cut dose-related formation of [1,3-(3)H]BPDE-I-lipid adducts in vitro between TG and [1,3-(3)H]BPDE-I. In an animal study, BPDE-I-TG was also formed in the serum of rats orally treated with B[a]P (25 mg/rat). Also, obvious correlations between [(3)H]B[a]P related-biomolecule adducts (DNA or protein) or lipid damage and the BPDE-I-TG adducts were obtained in various tissues of mice i.p. treated with [(3)H]B[a]P. These data suggest that TG can form an adduct with BPDE-I, as do other macromolecules (DNA, RNA and protein). Therefore, a carcinogen-lipid adduct would be a useful biomarker for chemical carcinogenesis research and cancer risk assessment.

Adult↗

Biosynthesis of triacylglycerol molecular species in an oleaginous fungus, Mortierella ramanniana var. angulispora.

The incorporation of radiolabeled lipid precursors into triacylglycerol (TG) molecular species in Mortierella ramanniana var. angulispora, an oleaginous fungus, was studied to determine the biosynthetic pathways for TG molecular species. Radiolabeled TG molecular species were separated and quantified by reverse-phase high performance liquid chromatography with a radioisotope detector. The major TG molecular species labeled by [1-(14)C]oleic acid at 30 degrees C were OOP, OOO, and OPP (TG molecular species designations represent three constituent acyl groups. G, gamma-linolenic acid; L, linoleic acid; O, oleic acid; S, stearic acid; P, palmitic acid), which were abundant TG molecular species in this fungus. The incorporation of [1-(14)C]oleic acid at 15 degrees C into these molecular species was the same, while that into most other species was decreased, suggesting that biosynthesis of major molecular species such as OOP, OOO, and OPP differs from that of other TG molecular species. [1-(14)C]Linoleic acid incorporation indicated that the major labeled molecular species were LOP and LOO, which may be due to acylation of oleoyl, palmitoyl-glycerol, or dioleoyl-glycerol by exogenous linoleic acid. This is basically the same mechanism as for OOP and OOO biosynthesis from exogenous oleic acid. [(14)C(U)]Glycerol incorporation suggested that TG molecular species containing palmitic acid such as OPP were more readily synthesized through the de novo pathway. Further experiments involving inhibitors such as sodium azide and cerulenin suggested that OOO biosynthesis included a mechanism differing from that in the cases of OOP and OPP. Trifluoperazine, which inhibits the conversion from phosphatidic acid to TG, decreased [1-(14)C]oleic acid incorporation into all molecular species, suggesting that the incorporation into all molecular species included the de novo TG biosynthetic pathway via phosphatidic acid. These results revealed that the biosynthetic pathways for TG molecular species can be classified into several groups, which exhibit different sensitivities to low temperature and inhibitors of lipid metabolism. This implies that the composition of TG molecular species is regulated through different biosynthetic pathways responsible for specific TG molecular species, providing a new insight into the biosynthesis of TG molecular species.

Carbon Radioisotopes↗

Effect of unsaturated fatty acids and Ca2+ on phosphatidylinositol synthesis and breakdown.

CDP-diglyceride : inositol transferase was inhibited by unsaturated fatty acids. The inhibitory activity decreased in the following order: arachidonic acid greater than linolenic acid greater than linoleic acid greater than oleic acid greater than or equal to palmitoleic acid. Saturated fatty acids such as myristic acid, palmitic acid, and stearic acid had no effect. Calcium ion also inhibited the activity of CDP-diglyceride : inositol transferase. In rat hepatocytes, arachidonic acid inhibited 32P incorporation into phosphatidylinositol and phosphatidic acid without any significant effect on 32P incorporation into phosphatidylcholine, phosphatidylethanolamine and phosphatidylserine. Ca2+ ionophore A23187 also inhibited 32P incorporation into phosphatidylinositol. However, 32P incorporation into phosphatidic acid was stimulated with Ca2+ ionophore A23187. Phosphatidylinositol-specific phospholipase C was activated by unsaturated fatty acids. Polyunsaturated fatty acids such as arachidonic acid and linolenic acid had a stronger effect than di- and monounsaturated fatty acids. Saturated fatty acids had no effect on the phospholipase C activity. The phospholipase C required Ca2+ for activity. Arachidonic acid and Ca2+ had synergistic effects. These results suggest the reciprocal regulation of phosphatidylinositol synthesis and breakdown by unsaturated fatty acids and Ca2+.

Animals↗

Effects of pH on membrane fluidity of human erythrocytes.

The effects of pH on the membrane fluidity of intact human erythrocytes, ghosts, and their lipid vesicles were studied by spin label techniques in the range of pH 3.0 to 9.1. Two fatty acid spin labels, 5-nitroxide stearic acid (5NS) and 12-nitroxide stearic acid (12NS), and a maleimide spin label were used for the labeling of the membrane lipids and proteins, respectively. The outer hyperfine splitting (T parallel) was measured as a parameter of membrane fluidity. In the case of 5NS, the T parallel values for intact erythrocytes and ghosts remained almost constant over the entire pH range at 22 degrees C but those for their lipid vesicles changed slightly, indicating the vertical displacement of the labels in lipid bilayers. On the other hand, the ESR spectra of 12NS incorporated into intact erythrocytes and ghosts, as compared with their lipid vesicles, showed marked pH dependence. By means of spin labeling of membrane proteins, the conformational changes of the proteins were observed in the pH range mentioned above. These results suggest a possible association between the strong pH dependence of the T parallel values and the conformation changes of membrane proteins. The pH dependence of the membrane fluidity was also investigated in cholesterol-enriched and -depleted erythrocytes. The effects of cholesterol demonstrated that the membrane fluidity was significantly mediated by cholesterol at low pH, but not at high pH.

Cyclic N-Oxides↗

Lipoprotein metabolism and thrombosis.

Recent evidence suggests that long-chain saturated fatty acids (i.e. stearic acid), produced on lipolysis of triglyceride-rich lipoproteins in the interface of circulating remnant particles provide a contact surface that activates the contact system of coagulation and subsequently activates factor VII. Increased level of circulating activated factor VII is probably of little consequence to a healthy individual with minimal expression of tissue factor in the vasculature. However, at a site of an atheromatous plaque or at a vascular injury site where there is tissue factor activity, increased circulating activated factor VII is expected to generate thrombin at a higher rate. Propagation of the prothrombotic environment will be facilitated on expression of additional tissue factor that is induced by the local increased concentration of thrombin. Thrombin with its receptor-mediated interactions with blood and vessel wall cells can signal inflammatory and proliferative responses such as those that occur in atheroma.

Animals↗

Williamsia muralis gen. nov., sp. nov., isolated from the indoor environment of a children's day care centre.

The taxonomic status of an actinomycete (MA 140/96T) isolated from indoor building materials of a children's day care centre was studied using the polyphasic approach. The cell morphology was atypical for an actinomycete, electron microscopy revealed a hairy surface, highly unusual for Gram-positive bacteria. The organisms grew at 10-37 degrees C, no growth was visible at 5 degrees C and 45 degrees C in 5 d. The cell wall contained the diamino acid meso-diaminopimelic acid and the sugars arabinose, galactose, mannose and ribose. The phospholipids phosphatidylethanolamine, phosphatidylinositol, phosphatidylglycerol and diphosphatidylglycerol were detected. The only menaquinone found was MK-9(H2). The fatty acid pattern was composed of palmitic acid (23.6%) palmitoleic acid (16.5%) and another hexadecenoic acid 16:1cis11 (1.4%), oleic acid (29.9%), stearic acid (2.9%) and the 10-methyl-branched tuberculostearic acid (23.3%). A gas-chromatographic analysis of the mycolic acid revealed a carbon-chain length of C50-C56. The G + C was 64.8 mol%. The results of 16S rDNA sequence comparisons revealed that strain MA 140/96T represents a new lineage in the suborder Corynebacterineae of the order Actinomycetales. Therefore, it was concluded that strain MA 140/96T should be assigned to a new genus and species, for which the name Williamsia muralis gen. nov., sp. nov. is proposed. The type strain of the species is MA 140/96T (= DSM 44343T).

Actinomycetales↗

Metabolic Evidence for the Involvement of a [delta]4-Palmitoyl-Acyl Carrier Protein Desaturase in Petroselinic Acid Synthesis in Coriander Endosperm and Transgenic Tobacco Cells.

We have previously demonstrated that the double bond of petroselinic acid (18:1[delta]6cis) in coriander (Coriandrum sativum L.) seed results from the activity of a 36-kD desaturase that is structurally related to the [delta]9-stearoyl-acyl carrier protein (ACP) desaturase (E.B. Cahoon, J. Shanklin, J.B. Ohlrogge [1992] Proc Natl Acad Sci USA 89: 11184-11188). To further characterize the biosynthetic pathway of this unusual fatty acid, 14C-labeling experiments were conducted using developing endosperm of coriander. Studies were also performed using suspension cultures of transgenic tobacco (Nicotiana tabacum L.) that express the coriander 36-kD desaturase, and as a result produce petroselinic acid and [delta]4-hexadecenoic acid. When supplied exogenously to coriander endosperm slices, [1-14C]palmitic acid and stearic acid were incorporated into glycerolipids but were not converted to petroselinic acid. This suggested that petroselinic acid is not formed by the desaturation of a fatty acid bound to a glycerolipid or by reactions involving acyl-coenzyme As (CoA). Instead, evidence was most consistent with an acyl-ACP route of petroselinic acid synthesis. For example, the exogenous feeding of [1-14C]lauric acid and myristic acid to coriander endosperm slices resulted in the incorporation of the radiolabels into long-chain fatty acids, including primarily petroselinic acid, presumably through acyl-ACP-associated reactions. In addition, using an in vitro fatty acid biosynthetic system, homogenates of coriander endosperm incorporated [2-14C]malonyl-CoA into petroselinic acid, of which a portion was detected in a putative acyl-ACP fraction. Furthermore, analysis of transgenic tobacco suspension cultures expressing the coriander 36-kD desaturase revealed significant amounts of petroselinic acid and [delta]4-hexadecenoic acid in the acyl-ACP pool of these cells. Also presented is evidence derived from [U-14C]nonanoic acid labeling of coriander endosperm, which demonstrates that the coriander 36-kD desaturase positions double bonds relative to the carboxyl end of acyl-ACP substrates. The data obtained in these studies are rationalized in terms of a biosynthetic pathway of petroselinic acid involving the [delta]4 desaturation of palmitoyl-ACP by the 36-kD desaturase followed by two-carbon elongation of the resulting [delta]4-hexadecenoyl-ACP.

Journal Article↗

Fat Metabolism in Higher Plants: XLV. Some Factors Regulating Fatty Acid Synthesis by Isolated Spinach Chloroplasts.

In the biosynthesis of fatty acids from 1-(14)C-acetate by intact spinach chloroplasts, ATP and Triton X-100 exert opposing effects on the conversion of palmitic acid to stearic acid; thus, ATP decreases the conversion and Triton X-100 increases the conversion. Changes in the availability of photosynthetically generated reduced nicotinamide adenine dinucleotide phosphate apparently does not markedly affect the C(16)-C(18) ratio. Various H(2)O(2)-generating systems, such as viologen dyes, inhibit oleate synthesis from acetate and cause stearate to accumulate. Catalase partially reverses the effect of these days.

Journal Article↗

Unsaturated fatty acids induce calcium influx into keratinocytes and cause abnormal differentiation of epidermis.

Abnormal follicular keratinization is involved in comedogenesis in acne vulgaris. We recently demonstrated that calcium influx into epidermal keratinocytes is associated with impaired skin barrier function and epidermal proliferation. Based on these results, we hypothesized that sebum components affect calcium dynamics in the keratinocyte and consequently induce abnormal keratinization. To test this idea, we first observed the effects of topical application of sebum components, triglycerides (triolein), saturated fatty acids (palmitic acid and stearic acid), and unsaturated fatty acids (oleic acid and palmitoleic acid) on hairless mouse skin. Neither triglyceride nor saturated fatty acids affected the skin surface morphology or epidermal proliferation. On the other hand, application of unsaturated fatty acids, oleic acid, and palmitoleic acid induced scaly skin, abnormal keratinization, and epidermal hyperplasia. Application of triglycerides and saturated fatty acids on cultured human keratinocytes did not affect the intracellular calcium concentration ([Ca(2+)](i)), whereas unsaturated fatty acids increased the [Ca(2+)](i) of the keratinocytes. Moreover, application of oleic acid on hairless mouse skin induced an abnormal calcium distribution in the epidermis. These results suggest that unsaturated fatty acids in sebum alter the calcium dynamics in epidermal keratinocytes and induce abnormal follicular keratinization.

Acne Vulgaris↗

Primary structure of human placental 5'-nucleotidase and identification of the glycolipid anchor in the mature form.

A cDNA was cloned coding for human placental 5'-nucleotidase. The 3547-bp cDNA contains an open reading frame that encodes a 574-residue polypeptide with calculated size of 63 375 Da. The NH2-terminal 26 residues comprise a signal peptide, which is followed by the NH2-terminal sequence of the purified protein. four potential N-linked glycosylation sites are found in the molecule, accounting for a larger mass of the mature form (71 kDa). The predicted structure contains a hydrophobic amino acid sequence at the COOH terminus, a possible signal for the post-translational modification by glycophospholipid. To confirm this possibility, we tried to isolate and characterize the membrane-anchoring domain of 5'-nucleotidase. BrCN-cleaved fragments of the protein were extracted with hexane and subjected to HPLC, resulting in purification of a single component of 2.3 kDa. Chemical analyses revealed that the purified fragment contains the tetradecapeptide Lys-Val-Ile-Tyr-Pro-Ala-Val-Glu-Gly-Arg-Ile-Lys-Phe-Ser, ethanolamine, glucosamine, mannose, inositol, palmitic acid, and stearic acid. The peptide sequence determined is identified at positions 510-523 in the primary structure deduced from the cDNA sequence, which predicts a further extension to position 548, containing the hydrophobic amino acid sequence. Thus, it is concluded that the mature 5'-nucleotidase lacks the predicted COOH-terminal peptide extension (524-548), which has been replaced by the glycophospholipid functioning as the membrane anchor of 5'-nucleotidase.

5'-Nucleotidase↗

Effects of long-chain Fatty acids on growth of rumen bacteria.

The effects of low concentrations of long-chain fatty acids (palmitic, stearic, oleic, and vaccenic) on the growth of seven species (13 strains) of rumen bacteria were investigated. Except for Bacteroides ruminicola and several strains of Butyrivibrio fibrisolvens, bacterial growth was not greatly affected by either palmitic or stearic acids. In contrast, growth of Selenomonas ruminantium, B. ruminicola, and one strain of B. fibrisolvens was stimulated by oleic acid, whereas the cellulolytic species were markedly inhibited by this acid. Vaccenic acid (trans Delta11 18:1) had far less inhibitory effect on the cellulolytic species than oleic acid (cis Delta9 18:1). Inclusion of powdered cellulose in the medium appeared to reverse both inhibitory and stimulatory effects of added fatty acids. However, there was little carry-over effect observed when cells were transferred from a medium with fatty acids to one without. Considerable variation in response to added fatty acids was noted among five strains of B. fibrisolvens. In general, exogenous long-chain fatty acids appear to have little, if any, energy-sparing effect on the growth of rumen bacteria.

Journal Article↗

Production of Dihomo-gamma-Linolenic Acid by a Delta5-Desaturase-Defective Mutant of Mortierella alpina 1S-4.

A mutant, which has low Delta5-desaturase activity, of an arachidonic acid-producing fungus, Mortierella alpina 1S-4, was shown to be a novel potent producer of dihomo-gamma-linolenic acid (DHGA). On submerged culture under optimal conditions for 6 days at 28 degrees C in a 10-liter fermentor, the mutant produced 3.2 g of DHGA per liter of culture broth (123 mg/g of dry mycelia), which accounted for 23.4% of the total mycelial fatty acids. Mycelial arachidonic acid amounted to only 19 mg/g of dry mycelia (0.5 g/liter of culture broth), which accounted for 3.7% of the total mycelial fatty acids. The other major mycelial fatty acids were palmitic acid (11.0%), stearic acid (12.8%), oleic acid (22.7%), linoleic acid (8.9%), gamma-linolenic acid (6.5%), and lignoceric acid (7.8%). More than 97 mol% of the DHGA produced was found in the triglyceride fraction irrespective of the growth temperature employed (12 to 28 degrees C).

Journal Article↗

A Novel Delta5-Desaturase-Defective Mutant of Mortierella alpina 1S-4 and Its Dihomo-gamma-Linolenic Acid Productivity.

A novel Delta5-desaturase-defective mutant was derived from an arachidonic acid-producing fungus, Mortierella alpina 1S-4, after treating the parental spores with N-methyl-N'-nitro-N-nitrosoguanidine. The mutant produced only a trace (about 1%) amount of arachidonic acid, and the ratio of dihomo-gamma-linolenic acid (DGLA) to total fatty acids in each lipid class was markedly high, accounting for as much as 60% in phosphatidylcholine. Under submerged batch culture conditions, the mutant produced 2.4 g of DGLA per liter (43.3% of total fatty acids) when grown at 28 degrees C for 7 days in a 5-liter jar fermentor. The other major (more that 1%) fatty acids were palmitic acid (21.2%), stearic acid (9.6%), oleic acid (14.3%), linoleic acid (4.4%), and gamma-linolenic acid (5.8%). About 80 mol% of the DGLA produced was found in triacylglycerol.

Journal Article↗

Relationship between structures and biological activities of mycoplasmal diacylated lipopeptides and their recognition by toll-like receptors 2 and 6.

The lipopeptide FSL-1 [S-(2,3-bispalmitoyloxypropyl)-Cys-Gly-Asp-Pro-Lys-His-Pro-Lys-Ser-Phe, Pam(2)CGDPKHPKSF] synthesized on the basis of the N-terminal structure of a Mycoplasma salivarium lipoprotein capable of activating normal human gingival fibroblasts to induce the cell surface expression of ICAM-1 revealed an activity to induce production of monocyte chemoattractant protein 1, interleukin-6 (IL-6), and IL-8. FSL-1 also activated macrophages to produce tumor necrosis factor alpha as the Mycoplasma fermentans-derived lipopeptide MALP-2 (Pam(2)CGNNDESNISFKEK), a potent macrophage-activating lipopeptide, did. The level of the activity of FSL-1 was higher than that of MALP-2. This result suggests that the difference in the amino acid sequence of the peptide portion affects the activity because the framework structure other than the amino acid sequence of the former is the same as that of the latter. To determine minimal structural requirements for the activity of FSL-1, the diacylglyceryl Cys and the peptide portions were examined for this activity. Both portions did not reveal the activity. A single amino acid substitution from Phe to Arg and a fatty acid substitution from palmitic acid to stearic acid drastically reduced the activity. Similar results were obtained in measuring the NF-kappaB reporter activity of FSL-1 to human embryonic kidney 293 cells transfected with Toll-like receptor 2 and 6, together with a NF-kappaB-dependent luciferase reporter plasmid. These results suggest that both the diacylglyceryl and the peptide portions of FSL-1 are indispensable for the expression of biological activities and for the recognition by Toll-like receptors 2 and 6 and that the recognition of FSL-1 by Toll-like receptors 2 and 6 appears to be hydrophobic.

Acylation↗