Changes in the lipid and fatty acid composition of hemolymph and ovaries during the reproductive cycle of Labidura riparia

Lipid metabolism was investigated during the reproductive cycle of Labidura riparia (Pallas). The lipid classes and their constitutive fatty acids present in hemolymph and ovaries were measured using thin‐layer chromatography and gas‐liquid chromatography. In the hemolymph, total lipids increase steadily from the previtellogenic period to vitellogenic arrest. These lipids are predominantly diacylglycerols and phospholipids. In the ovaries, total lipids increase during vitellogenesis then decrease during the vitellogenesis arrest period. The major lipids are triacylglycerols, followed by phospholipids. In both hemolymph and ovaries, all lipid classes contained variable proportions of seven main fatty acids: the saturated fatty acids myristic acid (14:0), palmetic acid (16:0), and stearic acid (18:0); the monounsaturated fatty acids palmitoleic acid (16:1) and oleic acid (18:1); and the polyunsaturated fatty acids linoleic acid (18:2) and linolenic acid (18:3). Unsaturated fatty acids predominate throughout the reproductive cycle. The percentage compositions of total and triacylglycerol fatty acids do not change markedly during the reproductive cycle in hemolymph nor in ovaries, with 18:2, 18:1 and 16:0 fatty acids being the major components. However, for diacylglycerols and phospholipids, the proportions of fatty acids vary systematically. For phospholipids during the vitellogenesis period, 18:2 increases considerably whereas other fatty acids decrease; for diacylglycerols, these fatty acids vary in the reverse way.     

Cellular fatty acid composition of Leuconostoc oenos

The cellular fatty acid composition of 70 lactic acid bacteria was examined by capillary gas chromatography. Fifty-four Leuconostoc oenos strains, including three reference, type strains from the other Leuconostoc spp., nine Pediococcus spp. and two Lactobacillus spp. were studied. Eighteen fatty acids were determined, of which 10 were identified by gas chromatography-mass spectrometry. The relative percentages of the 18 fatty acids of the Leuconostoc strains were analyzed numerically and grouped using the unweighted pair-group method. Results show that four clusters could be defined at r = 0.920, with five strains unassigned. The major fatty acids of the Leuc. oenos strains were found to be palmitic acid (C16:0), palmitoleic acid (C16:1–9), oleic acid (C18: 1–9), vaccenic acid (C18: 1–11), dihyrosterculic acid (C19-cyclopropane-9) and lactobacillic acid (C19-cyclopropane-11). It was mainly on the basis of the amounts of oleic acid and the C19-cyclopropane fatty acids that the strains of Leuc. oenos could be distinguished from each other. This is the first report of the occurrence of dihydrosterculic acid in lactic acid bacteria. For the majority of Leuc. oenos strains, the result obtained with the cellular fatty acid analysis confirmed the phenotypic relationships.     

Polyphasic taxonomy of symbiotic rhizobia from wild leguminous plants growing in Egypt

About 20 strains of rhizobia from wild legumes were characterized based on numerical analysis of phenotypic characteristics, nodulating ability, fatty acid methyl esters (FAME) and SDS-PAGE profiles of whole cell proteins. FAME analysis revealed that palmitic (16:0), stearic (18:0) and arachidonic (20:0) were detected in most of wild-legume rhizobia, the latter being uncommon in fatty acid profiles of Rhizobium and Sinorhizobium. Numerical analysis of FAME classified strains of wild-legume rhizobia into 9 clusters and one heterogeneous group. There was both agreement and disagreement with the clustering data based on phenotypic analysis and FAME analysis. Four strains were grouped together in the same cluster based on both methods. However, 4 another strains, which were placed in one cluster of phenotypic analysis, were distributed in several clusters after FAME analysis. SDS-PAGE of whole-cell proteins revealed that the rhizobial strains exhibited protein profiles with peptide bands ranging from 5-19 band per profile and showed molar mass of 110-183 kDa. As in the case of FAME analysis, numerical analysis of protein bands was compared with clustering of phenotypic analysis. Agreement of the two methods was obvious when clustering some strains but conflicted in the classification of some other strains. However, integration of the three methods could be the basis of a polyphasic taxonomy. The twenty strains of wild-legume rhizobia were finally classified as follows: 12 strains related to Rhizobium leguminosarum, 5 strains related to Sinorhizobium meliloti and 3 strains to Rhizobium spp. Rhizobia nodulating wild herb legumes are among indigenous strains nodulating crop legumes in cultivated as well as noncultivated lands.     

Multivariate approach to evaluating the fatty acid composition of seed oil in a doubled haploid population of winter oilseed rape (Brassica napus L.)

The fatty acid composition of oil of the zero erucic acid commercial Brassica napus L. is typical for this species. It is rich in oleic acid and contains moderate levels of linoleic and linolenic acid. For human nutrition, it is advantageous primarily to obtain the highest possible content of oleic acid and to maintain the 2:1 ratio of linoleic to linolenic acid, while preserving the average total content of saturated acids. Uni- and multivariate analyses of variance were used for evaluation of doubled haploid lines of winter oilseed rape in respect of five fatty acids: palmitic (C16:0), stearic (C18:0) oleic (C18:1), linoleic (C18:2) and linolenic (C18:3). Some proposals of studying doubled haploid (DH) lines with the use of canonical transformation were also given. In MANOVA, the five original variables (individual fatty acids) were replaced by three 'new' variables (combinations of these acids) and used to evaluate DH lines with respect to the requirements concerning the nutritional role of fatty acids. The first variable was the total content of the saturated acids (C16:0 + C18:0), the second (unchanging) was the content of the monounsaturated acid C18:1, and the third was the difference between polyunsaturated acids, i.e. between linoleic acid, and the doubled content of linolenic acid (C18:2 - 2 x C18:3).     

Triacylglycerol and phospholipid fatty acids of the silverleaf whitefly: composition and biosynthesis

The identification and composition of the fatty acids of the major lipid classes (triacylglycerols and phospholipids) within Bemisia argentifolii Bellows and Perring (Homoptera: Aleyrodidae) nymphs were determined. Comparisons were made to fatty acids from the internal lipids of B. argentifolii adults. The fatty acids, as ester derivatives, were analyzed by capillary gas chromatography (CGC) and CGC-mass spectrometry (MS). All lipid classes contained variable distributions of eight fatty acids: the saturated fatty acids, myristic acid (14:0), palmitic acid (16:0), stearic acid (18:0), arachidic acid (20:0); the monounsaturated fatty acids, palmitoleic acid (16:1), oleic acid (18:1); the polyunsaturated fatty acids, linoleic acid (18:2), linolenic acid (18:3). Fourth instar nymphs had 5-10 times the quantities of fatty acids as compared to third instar nymphs and 1-3 times the quantities from adults. The fatty acid quantity differences between fourth and third instar nymphs were related to their size and weight differences. The percentage compositions for fatty acids from each lipid class were the same for the pooled groups of third and fourth instar nymphs. For nymphs and adults, triacylglycerols were the major source of fatty acids, with 18:1 and 16:0 acids as major components and the majority of the polyunsaturated fatty acids, 18:2 and 18:3 were present in the two phospholipid fractions, phosphatidylethanolamine and phosphatidylcholine. Evidence was obtained that whiteflies indeed synthesize linoleic acid and linolenic acid de novo: radiolabel from [2-(14)C] acetate was incorporated into 18:2 and 18:3 fatty acids of B. argentifolii adults and CGC-MS of pyrrolidide derivatives established double bonds in the Delta(9,12) and Delta(9,12,15) positions, respectively.     

Comparison of fatty acid composition of cell homogenates and isolated chloroplasts in Acetabularia crenulata (Lamouroux)

Algal preparations from Acetabularia crenulata were analyzed for their fatty acid composition to establish the suitability of this alga as a model to study fatty acid oxidation and oxylipin biosynthesis. The work was based on two goals. The first goal of this study was to determine the contribution of fatty acids from contaminating bacteria and how this influenced the total fatty acid composition of cell homogenates of A. crenulata collected in the wild as compared to specimens cultured in sterile conditions. The major fatty acids detected for both specimens were palmitic (C16:0), palmitoleic (C16:1n-7), oleic (C18:1n-9), linoleic (C18:2n-6), linolenic (C18:3n-3), and octadecatetraenoic acid (C18:4n-3). Significant amounts of odd-chain fatty acids common to bacteria were not detected in either sample. Furthermore, branched-chain fatty acids, typical bacterial biomarkers, were not detected in either sample. Data suggest that bacteria do not greatly contribute to the total fatty acid pool of A. crenulata. The second goal was to compare the fatty acid composition of cell homogenates with that of isolated chloroplasts. Comparatively speaking palmitoleic and octadecatetraenoic acid were found at significantly lower concentrations in the chloroplast whereas oleic and linolenic acid were found at significantly higher amounts in this organelle. Furthermore, the amount of hexadecatrienoic acid (C16:3), a fatty acid commonly esterified to monogalactosyldiacylglycerol (MGDG; lipid present at high concentrations inside the chloroplasts of algae), was present at very low concentrations in these plastids (0.7%). Typically green algal follow the "prokaryotic pathway" for MGDG biosynthesis where C18:3 is esterified at the sn-1 position of the glycerol backbone and C18:3 or C16:3 at the sn-2 position, making C16:3 a major fatty acid inside chloroplasts. Interestingly, our results suggest that chloroplasts of A. crenulata appear to follow the "eukaryotic pathway" for MGDG biosynthesis where C18:3 is both at the sn-1 and sn-2 position of MGDG. Taking into account the exceptions noted, the fatty acid composition for A. crenulata is similar to that reported for most chlorophytes.     

Differentiation of Enterococcus spp. by cell membrane fatty acid methyl ester profiling, biotyping and ribotyping

AIMS: Gas chromatographic analysis of cell membrane fatty acid methyl esters (FAME), biochemical profiling (biotyping) and EcoRI restriction endonuclease profiling of DNA containing ribosomal RNA sequences (ribotyping) were compared for differentiation of Enterococcus spp. METHODS AND RESULTS: FAME profiling, biotype profiling and ribotyping of 41 strains from retail Swiss-type cheeses and five strains from culture collections resulted in 17, 25 and 26 groups, respectively, with only two pairs of strains having the same FAME group, biotype profile and ribogroup. CONCLUSION: Substantial overlap occurred in groupings assigned by the three methods. SIGNIFICANCE AND IMPACT OF THE STUDY: Differentiation of Enterococcus spp. strains increases if multiple methods are used.     

Oleic Acid and Its Positional Isomer,cis-Vaccinic Acid,in the Appendix of Sauromatum guttatum during Anthesis

The fatty acid profiles of various organs of the thermogenic inflorescence of Sauromatum guttatum and of the sporophylls of thermogenic male cones of two cycad species (Encephalartos ferox and Dioon edule var edule and var angustifolium) were determined by gas chromatography. During anthesis, palmitate (16:0), oleate [18:1 (9)], cis-vaccinate [18:1 (11)], and linoleate [18:2 (9, 12)] were the most abundant fatty acids in the Sauromatum appendix. cis-Vaccinic acid, a positional isomer of oleic acid, was identified by comparing its retention time on a gas chromatography column and its mass spectrum to an authentic compound. The percentage of oleic acid from total fatty acids dropped from about 9 in the morning 3 d before heat production to 6 in the morning 2 d before heat production. At this time, the percentage of cis-vaccinic acid increased from 3 to 11%, and then remained at this level until the inflorescence dried and died. Palmitoleic acid [16:1 (9)], the common precursor of cis-vaccinic acid, is a minor component of total fatty acids. In six other organs of the Sauromatum inflorescence including thermogenic organs, such as male flowers and lower spadix, palmitate, oleate, and linoleate were prevalent but cis-vaccinate was not. The thermogenic male cones of the two cycad species were rich in palmitic, oleic, and linolenic acids. The level of cis-vaccinic acid in these organs was less than 0.5%.     

Analysis of fatty acid composition of anaerobic rumen fungi

The fatty acid (FA) composition of fresh mycelia of anaerobic rumen fungi was determined. The fatty acids methyl esters (FAME) of six strains belonging to four genera (Neocallimastix, Caecomyces, Orpinomyces, Anaeromyces) and one unknown strain were analyzed by gas chromatography. All studied fungi possess the same FAs but differences were found in their relative concentrations. The FA profile of anaerobic fungi comprises carbon chains of length ranging from 12 to 24; the most common fatty acids were stearic (C(18:0)), arachidic (C(20:0)), heneicosanoic (C(21:0)), behenic (C(22:0)), tricosanoic (C(23:0)) and lignoceric (C(24:0)) with relative amount representing >4% of total FA. Significant differences were determined for heptadecanoic, oleic, behenic and tricosanoic acids. Rumen anaerobic fungi can contain very long chain fatty acids; we found unsaturated fatty acids including cis-11-eicosenoic (C(20:1)), cis-11,14-eicosadienoic (C(20:2)), erucic (C(22:1n9)), cis-13,16-docosadienoic (C(22:2)) and nervonic (C(24:1)) acids in very small amounts but their presence seems to be unique for anaerobic fungi.     

Acyl-CoA reductase specificity and synthesis of wax esters in mouse preputial gland tumors.

Long-chain alcohols are synthesized in the mouse preputial gland tumor (ESR-586) by NADPH:acyl-CoA oxidoreductase. In this study, a series of labeled acids was tested as substrates for the oxidoreductase in a cell-free system from the tumor, and the distribution of label into alcohols, waxes, and other products was determined. The system contained the labeled acid, an acyl-CoA-generating system, an NADPH-generating system, and tumor homogenate. The highest rates of alcohol synthesis were obtained with palmitic (16:0), heptadecanoic (17:0), stearic (18:0), myristic (14:0), elaidic (18:1 trans), and linoleic (18:2) acids, which yielded, respectively, 151, 124, 102, 76, 65, and 35 pmol alcohol/min per mg protein. Decanoic (10:0), lauric (12:0), oleic (18:1 cis), linolenic (18:3), arachidonic (20:4), and behenic (22:0) acids all gave lower activities. Acyl-CoA formation did not appear to be rate limiting with any of the substrates tested except behenic acid. In addition to the fatty alcohol product, a small amount of fatty aldehyde was formed in the system. Incorporation of the labeled fatty acids into wax esters was examined and the distribution of label between the alcohol and acid components of the waxes was determined. Incubation of [1-(14)C]palmitic acid yielded 3.4% free alcohol, 8.3% alcohol esterified in waxes, and 7.7% palmitoyl groups esterified into waxes, whereas, at the other extreme, [1-(14)C]linolenic acid yielded 0.8%, 0.6%, and 38%, respectively, into the homologous components.-Wykle, R. L., B. Malone, and F. Snyder. Acyl-CoA reductase specificity and synthesis of wax esters in mouse preputial gland tumors.     

Effect of dietary fatty acids on expression of lipogenic enzymes and fatty acid profile in tissues of bulls

This study investigated the effects of dietary linolenic acid (C18:3n-3) v. linoleic acid (C18:2n-6) on fatty acid composition and protein expression of key lipogenic enzymes, acetyl-CoA carboxylase (ACC), stearoyl-CoA desaturase (SCD) and delta 6 desaturase (Δ6d) in longissimus muscle and subcutaneous adipose tissue of bulls. Supplementation of the diet with C18:3n-3 was accompanied by an increased level of n-3 fatty acids in muscle which resulted in decrease of n-6/n-3 ratio. The diet enriched with n-3 polyunsaturated fatty acids (PUFAs) significantly inhibited SCD protein expression in muscle and subcutaneous adipose tissue, and reduced the Δ6d expression in muscle. There was no significant effect of the diet on ACC protein expression. Inhibition of the Δ6d expression was associated with a decrease in n-6 PUFA level in muscles, whereas repression of SCD protein was related to a lower oleic acid (C18:1 cis-9) content in the adipose tissue. Expression of ACC, SCD and Δ6d proteins was found to be relatively higher in subcutaneous adipose tissue when compared with longissimus muscle. It is suggested that dietary manipulation of fatty acid composition in ruminants is mediated, at least partially, through the regulation of lipogenic enzymes expression and that regulation of the bovine lipogenic enzymes expression is tissue specific.     

Characterization of Phytophthora cinnamomi populations from ornamental plants in South Carolina,USA

Abstract

Fifty-one isolates of Phytophthora cinnamomi isolated from ornamental plants in South Carolina, USA, between 1995 and 2000 were characterized by sporangium morphology, mating type, sensitivity to the fungicide mefenoxam, fatty acid methyl ester (FAME) profile analysis, and amplified fragment length polymorphism (AFLP) analysis. Sporangium shapes were predominantly ovoid to ellipsoid, and size averaged 65.5×40.3 μm (length×breadth) with average length/breadth ratio of 1.6. Forty-nine isolates were the A2 mating type with only two A1 isolates found. This is the first report of the A1 mating type of P. cinnamomi in South Carolina. All isolates were sensitive to mefenoxam and EC₅₀ values for all isolates were less than 0.2 μg ml^?1. FAMEs of each isolate were analysed by gas chromatography and revealed five major fatty acids: myristic (14:0), palmitic (16:0), linoleic (18:2ω6c), oleic (18:1ω9c), and eicosapentaenoic (20:5ω3c) acids. These five fatty acids accounted for more than 80% of FAME profiles. Cluster analysis of FAME profiles showed that individual isolates had unique pattern that could be divided into four major clusters. AFLP analysis based on 200 informative loci also separated isolates into four major clusters. A1 isolates were different from all A2 isolates. The percentage of polymorphic loci (10.5%) and Nei's gene diversity (0.0435) were much higher for the two A1 isolates than for any cluster of A2 isolates even though A2 isolates had more isolates within a cluster. A2 isolates exhibited relatively little genetic variation overall, which suggests that these isolates may have come from a common source.     

Differentiation of Three Varieties of Rhizoctonia circinata; var. circinata, var. oryzae and var. zeae on the Basis of Cellular Fatty Acid Composition

Cellular fatty acid analysis was employed to differentiate three varieties of Rhizoctonia circinata ; var. circinata , var. oryzae and var. zeae . Eight fatty acids including myristic (14 : 0), pentadecanoic (15 : 0), palmitic (16 : 0), palmitoleic (16 : 1  cis 9), stearic (18 : 0), oleic (18 : 1  cis 9), linoleic (18 : 2  cis 9,12) and linolenic (18 : 3  cis 9,12) acids were present in isolates of all three varieties of R. circinata . Heptadecanoic acid (17 : 0) was detected in isolates of R. circinata var. zeae but not in isolates of R. circinata var. circinata or R. circinata var. oryzae . Palmitic, oleic and linoleic acids were the major fatty acids found, comprising 94–98% of the whole-cell fatty acid content. The remaining fatty acids were present in small amounts. Based on the composition (%) of fatty acids, isolates of R. circinata var. circinata , R. circinata var. oryzae and R. circinata var. zeae were clearly differentiated into three groups as shown by principal component and cluster analyses. This finding agrees well with the grouping of R. circinata into three varieties based on differences in colony morphology of the vegetative state. In principal component and cluster analysis, isolates of R. circinata var. circinata from Japan and Alaska were indistinguishable.     

全细胞长链脂肪酸在假丝酵母属分类中的应用初探

本文用气相色谱法测定了35株假丝酵母全细胞长链脂肪酸的组成和含量,并运用主分量分析法处理数据,对菌株进行分类。测定结果表明,这些菌株中共含有38种脂肪酸,其中软脂酸(C_(16:0))、棕榈油酸(C_(16:1))、硬脂酸(C_(18:0))、油酸(C_(18:1))、亚油酸(C_(18:2))和亚麻酸(C_(18:3发))等脂肪酸的含量较高,它们占总含量的90％以上。对脂肪酸的主分量分析将35株假丝酵母分为两个类群,分群结果与表观性状聚类分析的结果相似,根据脂肪酸对一些菌株亲缘关系的测定也有与表观性状分析类似的结果。酵母菌全细胞脂肪酸的分析为探索酵母菌系统分类关系提供了一可行的方法。     

Fatty acid content in wild type and WZSL mutant of Euglena gracilis

The effects of growth conditions on fatty acid profilewere examined in the photosynthetic wild type and inthe spontaneous non-photosynthetic WZSL mutant of theunicellular flagellate Euglena gracilis. Inthe light, the amount of polyunsaturated fatty acids(PUFAs) is higher in the wild type than in the mutant,independent of the carbon source. Among importantPUFAs, linolenic acid (18:3 3) is present inhigh amount only in wild type cells grown in the lightwith any of the tested carbon sources. The content ofother PUFAs, such as arachidonic acid (20:46), EPA (20:5 3) and DHA (22:63), is not correlated with the presence oflight or chloroplasts.The main effect of the dark in both strains is tolower the content of PUFAs and mono-unsaturated fattyacids and to increase the content of saturated fattyacids with all the carbon sources.     

Biosynthesis of gamma-linolenic acid and beta-carotene by Zygomycetes fungi

Due to increasing demand for natural sources of both polyunsaturated fatty acids (PUFAs) and beta-carotene, 28 Zygomycetes fungal soil isolates were screened for their potential to synthesize these biologically active compounds. Although all fungi produced C₁₈ PUFAs, only nine strains also formed beta-carotene. Although Actinomucor elegans CCF 3218 was the best producer of gamma-linolenic acid (GLA) (251 mg/L), Umbelopsis isabellina CCF 2412 was found to be the most valuable fungus because of the dual production of GLA (217 mg/L) and beta-carotene (40.7 mg/L). The calculated ratio of formed PUFAs provided new insight into activities of individual fatty acid desaturases involved in biosynthetic pathways for various types of PUFAs. The maximal activity of delta-9 desaturase was accompanied by high accumulation of storage lipids in fungal cells. On the other hand, maximal activity of delta-15 desaturase was found in strains synthesizing low amounts of oleic acid due to diminished delta-9 desaturase. Activities of delta-6 desaturase showed competition for fatty acids engaged in n3, n6, and n9 biosynthetic pathways. Such knowledge about fatty acid desaturase activities provides new challenges for the regulation of biotechnological production of PUFAs by Zygomycetes fungi.     

Polyunsaturated fatty acids are FXR ligands and differentially regulate expression of FXR targets

Polyunsaturated fatty acids (PUFAs) have been previously reported as agonists of peroxisome proliferatoractivated receptor and antagonists of the liver X receptor. The activities on these two nuclear receptors have been attributed to their beneficial effects such as improvement of dyslipidemia and insulin sensitivity and decrease of hepatic lipogenesis. Here we report that PUFAs are ligands of farnesoid X receptor (FXR), a nuclear receptor for bile acids. In a conventional FXR binding assay, arachidonic acid (AA, 20:4), docosahexaenoic acid (DA, 22:6), and linolenic acid (LA, 18:3) had an affinity of 2.6, 1.5, and 3.5 microM, respectively. In a cell-free coactivator association assay, AA, DA, and LA decreased FXR agonist-induced FXR activation with IC(50)s ranging from 0.9 to 4.7 microM. In HepG2 cells, PUFAs regulated the expression of two FXR targets, BSEP and kininogen, in an opposite fashion, although both genes were transactivated by FXR. All three PUFAs dose-dependently enhanced FXR agonist-induced BSEP expression but decreased FXR agonist-induced human kininogen mRNA. Saturated fatty acids such as stearic acid (SA, 18:0) and palmitic acid (PA, 16:0) did not bind to FXR and did not change BSEP or kininogen expression. The pattern of BSEP and kininogen regulation by PUFAs is closely similar to that of the guggulsterone, previously reported as a selective bile acid receptor modulator. Our results suggest that PUFAs may belong to the same class of FXR ligands as guggulsterone, and that the selective regulation of FXR targets may contribute to the beneficial effects of PUFAs in lipid metabolism.     

Fatty acid and lipid compositions of Conidiobolus

The fatty acid composition of the total lipids from two Conidiobolus species was studied by gas—liquid chromatography. The major fatty acids of C. lamprauges were palmitic acid (C_16:0), oleic acid (C_18:1), linolenic acid (C_18:3), and arachidonic acid (C_20:4). For C. eurymitus , myristic acid (C_14:0), C_16:0, and linoleic acid (C_18:2) were the most abundant acids. The fatty acid composition of C. eurymitus was quite different from that of the Conidiobolus species as mentioned in other reports. The lipid composition of the total lipids of C. lamprauges and C. eurymitus was also studied by thinchrography on quartz rods. Triglycerides and phospholipids were the major components in the two Conidiobolus species.     

Beta-oxidation of medium chain (C8-C14) fatty acids studied in isolated liver cells

The beta-oxidation and esterification of medium-chain fatty acids were studied in hepatocytes from fasted, fed and fructose-refed rats. The beta-oxidation of lauric acid (12:0) was less inhibited by fructose refeeding and by (+)-decanoyl-carnitine than the oxidation of oleic acid was, suggesting a peroxisomal beta-oxidation of lauric acid. Little lauric acid was esterified in triacylglycerol fraction, except at high substrate concentrations or in the fructose-refed state. With [1-14C]myristic acid (14:0), [1-14C]lauric acid (12:0), [1-14C]octanoic acid (8:0) and [2-14C]adrenic acid (22:4(n - 6] as substrate for hepatocytes from carbohydrate-refed rats, a large fraction of the 14C-labelled esterified fatty acids consisted of newly synthesized palmitic acid (16:0), stearic acid (18:0) and oleic acid (18:1) while intact [1-14C]oleic acid substrate was esterified directly. With [9,10-3H]myristic acid as the substrate, small amounts of shortened 3H-labelled beta-oxidation intermediates were found. With [U-14C]palmitic acid, no shortened fatty acids were detected. It was concluded that when the mitochondrial fatty acid oxidation is down-regulated such as in the carbohydrate-refed state, medium-chain fatty acids can partly be retailored to long-chain fatty acids by peroxisomal beta-oxidation followed by synthesis of C16 and C16 fatty acids which can then stored as triacylglycerol.     

Effects of fatty acid chain length and saturation on gastric inhibitory polypeptide release in obese hyperglycaemic (ob/ob) mice

Plasma gastric inhibitory polypeptide (GIP) responses to equimolar intragastrically administered emulsions of fatty acids (2.62 mmol/7.5 ml/kg) were examined in 18 h fasted obese hyperglycaemic (ob/ob) mice. Propionic acid (C3:0), a saturated short-chain fatty acid, and capric acid (C10:0), a saturated medium chain fatty acid, did not signilicantly stimulate GIP release. However, the saturated long-chain fatty acid stearic acid (C18:0), and especially the unsaturated long-chain fatty acids oleic (C18:1), linoleic (C18:2) and linolenic (C18:3) acids produced a marked GIP response. The results show that chain length and to a lesser extent the degree of saturation are important determinants of fatty acid-stimulated GIP release. The GIP-release action of long-chain, but not short-chain, fatty acids may be r e l a t e d to differences in their intracellular handling.