Fatty acid and product selectivities of potato tuber lipid acyl hydrolase in esterification reactions with glycerol in organic media

Fatty acid [FA; butanoic (C₄); octanoic (C₈); tetradecanoic (C₁₄); and cis-9,12-octadecadienoic (C_18:2) acids] reaction selectivity and the corresponding acyl profiles in differentially accumulating acylglycerol (AG) products (mono-, di-, and triacylglycerols; MAG, DAG, TAG, respectively) were evaluated for Celite™-immobilized potato tuber lipid acyl hydrolase (LAH)-mediated esterification reactions in isooctane at 35°C and water activity of 0.19. The ordinal pattern of FA selectivities was C₈>C₁₄>C_18:2>C₄, and the AG products accumulating were α-MAG>DAG>β-MAG>TAG. A dimensionless expression for fatty acid partitioning coefficient (FAPC) was contrived to represent the partitioning patterns of specific FA into specific AG pools on the basis of an equivalent extent of FA reaction. These FAPC values indicated that preferential partitioning of FA was as follows: C₄ was preferentially partitioned into TAG, DAG, and β-MAG; C₈ was preferentially partitioned into DAG; C₁₄ was preferentially partitioned into α,β-MAG; C_18:2 was preferentially partitioned into α,β-MAG and TAG. These findings infer that the tendency for LAH-mediated esterifications to accumulate MAG is based, in part, on a constraint in reactivity of α-MAG of ≥10 acyl carbon groups to serve as acceptors for further esterification events. The general approach taken in this study may assist in identifying the discrete steps in assembling structured glycerides where different biocatalysts exhibit the greatest degree or control of reaction selectivity.     

Selectivity of potato tuber lipid acyl hydrolase toward long-chain unsaturated FA in esterification reactions with glycerol analogs in organic media

FA selectivity of a Celite-immobilized potato lipid acyl hydrolase (LAH) in esterification reactions with long-chain FA, including stearic acid (18∶0), oleic acid (18∶1), linoleic acid (18∶2), α-linolenic acid (18∶3), EPA (20∶5), and DHA (22∶6), and alcohol co-substrates (n-propanol, isopropanol, 1,3-propanediol, and glycerol) was studied in isooctane. Immobilized LAH was selective for FA of greater degrees of unsaturation (18∶3>18∶2>18∶1>18∶0) for all alcohol acceptors evaluated. Selectivity of LAH toward unsaturated C₁₈ FA increased with an increase in water activity (a _w ) from 0.19 to 0.90 for n-propanol, isopropanol, and 1,3-propanediol as alcohol co-substrates. In contrast, with glycerol as the alcohol cosubstrate, selectivity of LAH toward these unsaturated C₁₈ FA increased with a decrease in a _w from 0.90 to 0.19. In addition, immobilized LAH strongly discriminated against EPA and DHA for both 1,3-propanediol and glycerol as alcohol co-substrates.     

Extracting long-chain fatty acids from a fermentation medium

Several solvents were evaluated for extracting free long-chain FA (LCFA) from a fermentation medium. Chloroform, chloroform/methanol (1∶1), hexane, and hexane/methyl tert-butyl ether (MTBE) (1∶1) were evaluated as alternative extraction solvents. Parameters considered for optimizing LCFA recoveries included pH and ionic strength. Maximal LCFA recoveries were obtained by adding 2 mL of the hexane/MTBE (1∶1) solvent mixture, 80 μL of 50% H₂SO₄, and 0.05 g NaCl to 1 mL of the aqueous sample and mixing for 15 min at 200 rpm. This method quantified saturated LCFA [capric acid (C_10∶0) to stearic acid (C_18∶0)] and unsaturated LCFA with 18 carbons [linoleic acid (C_18∶2) and oleic acid (C_18∶1)] with a 98 to 100% recovery. Caproic (C_6∶0) and caprylic (C_8∶0) acids were characterized by 27 and 76% recoveries, respectively.     

Natural abundance stable carbon isotope evidence for the routing and <Emphasis Type="Italic">de novo</Emphasis> synthesis of bone FA and cholesterol

This research reported in this paper investigated the relationship between diet and bone FA and cholesterol in rats raised on a variety of isotopically controlled diets comprising 20% C₃ or C₄ protein (casein) and C₃ and/or C₄ nonprotein or energy (sucrose, starch, and oil) macronutrients. Compoundspecific stable carbon isotope analysis (δ¹³C) was performed on the FA (16∶0, 18∶0, 18∶1, and 18∶2) and cholesterol isolated from the diet (n=4) and bone (n=8) of these animals. The dietary signals reflected by the bone lipids were investigated using linear regression analysis. δ¹³C values of bone cholesterol and stearic (18∶0) acid were shown to reflect whole-diet δ¹³C values. whereas the δ¹³C values of bone palmitic (16∶0), oleic (18∶1), and linoleic (18∶2) acids reflected dietary FA δ¹³C values. Dietary signal differences are a result of the balance between direct incorporation (or routing) and de novo synthesis of each of these bone lipids. Estimates of the degree of routing of these bone lipids gleaned from correlations between Δ¹³C _dlipid-wdiet (δ¹³C_{diet lipid}-δ¹³C_{whole diet}) spacings and Δ¹³C _blipid-wdiet (δ¹³C_{bone lipid}-δ¹³C_{whole diet} fractionations demonstrated that the extent of routing, where 18∶2>16∶0>18∶1>18∶0>cholesterol, reflected the relative abundances of these lipids in the diet. These findings provide the basis for more accurate insights into diet when the δ¹³C analysis of bone fatty FA or cholesterol is employed.     

Synthesis of a novel series of 2-methylsulfanyl fatty acids and their toxicity on the human K-562 and U-937 leukemia cell lines

The hitherto unknown 2-methylsulfanyldecanoic acid and 2-methylsulfanyldodecanoic acid were synthesized from methyl decanoate and methyl dodecanoate, respectively, through the reaction of lithium diisopropylamide and dimethyldisulfide in THF followed by saponification with potassium hydroxide in ethanol. Both α-methylsulfanylated FA were cytotoxic to the human chronic myelogenous leukemia K-562 and the human histiocytic lymphoma U-937 cell lines with EC₅₀ values in the 200–300 μM range, which makes them more cytotoxic to these cell lines than decanoic and/or dodecanoic acid. The cytotoxicity of the studied FA toward K-562 followed the order 2-SCH₃-12∶0>2-SCH₃-10∶0>10∶0>12∶0>2-OCH₃-12∶0, whereas toward U-937 the cytotoxicity was 2-SCH₃-10∶0>2-SCH₃-12∶0>12∶0>10∶0>2-OCH₃-12∶0. These results indicate that the α-methylsulfanyl substitution increases the cytotoxicity of the C₁₀ and C₁₂ FA toward the studied leukemia cell lines.     

FA selectivity of lipases in acyl-transfer reactions with acetate esters of polyols in organic media

FA reaction selectivity of Burkholderia cepacia, Rhizomucor miehei, and Candida antarctica fraction B lipases was compared between acyl-transfer and esterification reactions. Multicompetitive reaction mixtures containing a series of n-chain FA (a C₄–C₁₈ series; and a C_18∶x series, where X=0-3 double bonds) and a single acetate ester co-substrate [triacetin, 1,2-propanediol (1,2-PD)diacetate, and 1,3-PD diacetate] were studied in tert-butyl methyl ether at an a _w of 0.69. For B. cepacia lipase, FA optima for C₈, C₁₆, and C_18∶2 were observed in all reactions with 1.0- to 5.9-fold differences in FA selectivity. For R. miehei lipase, an optimum for C₈ FA was observed in all reactions with 1.2- to 6.7-fold differences in FA selectivity. For C. antarctica lipase, FA optima for C₈/C₁₀ were observed in all reactions with 1.0- to 2.8-fold differences in FA selectivity. FA selectivities were broadly modulated upon changing from free polyol to acetate ester co-substrates for B. cepacia and R miehei lipases, whereas FA selectivity modulations were more specific upon this change in reaction configuration for C. antarctica B lipase. For all lipases, reactivity toward unsaturated C_18∶x FA was enhanced in acyl-transfer relative to esterification reactions with these polyol co-substrates.     

Unusual minor nonmethylene-interrupted di-, tri-, and tetraenoic fatty acids in limpet gonads

Unusual minor nonmethylene-interrupted (NMI) FA have been identified in the lipids of gonads from the limpets Cellana grata and Collisella dorsuosa by using GC-MS of the combination of their 4,4-dimethyloxazoline derivatives and picolinyl esters. Among 23 NMI unsaturated FA from C₁₈ to C₂₂ and C₂₄ identified in this study, 5,11-nonadecadienoic (5,11-19∶2), 7,16-heneicosadienoic (7,16–21∶2), 9,15-tetracosadienoic (9,15–24∶2), 5,9,15-docosatrienoic (5,9,15–22∶3), and 5,9,15-tetracosatrienoic (5,9,15–24∶3) acids may not have been reported previously from living organisms. The presence of 5,11,14,17-eicosatetraenonoic (5,11,14,17–20∶4) and 7,13,16,19-docosatetraenenoic (7,13,16,19–22∶4) acids as FA components in marine mollusks may be reported here for the first time. In this study, the male and female gonads of both species showed distinct differences in both their composition and proportions of NMI FA. Most NMI FA identified were mainly present in the female gonads of both species, especially in TAG that contained 21 NMI FA.     

Temperature-dependent deacylation of molecular species of phosphatidylcholine by microsomal phospholipase A2 of thermally acclimated rainbow trout,Salmo gairdneri 1

Using the ratios of kinetic parameters, V/Km, the deacylation of different molecular species of 1-palmitoyl,2-acyl phosphatidylcholine via microsomal phospholipase A₂ (PLA₂) was studied in liver tissue of thermally acclimated rainbow trout (Salmo gairdneri). In general, PLA₂ from fish acclimated to cold temperatures showed an order of preference for the acyl moieties of 18∶1>18∶1>18∶2>18∶0. Trout acclimated to warm temperatures generally preferred 18∶0 PC, but the actual order of preference depended on the temperature of the assays and the presence of endogenous lipids in the enzyme preparation. At 5 C, the particulate (microsomal) enzyme preferred 18∶0>18∶2>18∶1, but a lipid-free preparation of the enzyme preferred 18∶2>18∶0>18∶1. At 20 C, particulate enzyme preferred 18∶1>18∶0>18∶2 but purified enzyme preferred 18∶0>18∶2>18∶1. Thus, assay temperature and the presence of microsomal lipids had a greater effect on PLA₂ from fish acclimated to warm temperatures than fish acclimated to cold temperatures. The substrate preference of PLA₂ is discussed with reference to the previously observed changes in membrane fatty acid composition that occur with thermal acclimation in rainbow trout.     

Determination of FA composition and total trans FA of Turkish margarines by capillary GLC

In this research, FA composition and total trans FA contents of 16 different brands of margarine (8 hard-type and 8 soft-type) sold in Turkey were determined by capillary GLC method. According to the results, the contents of saturated FA, monounsaturated FA, and PUFA were within the ranges of 23.9–32.3, 44.0–61.9, and 14.2–24.1%, respectively, in hard-type margarines, and 27.0–39.9, 21.0–40.9, and 32.0–53.7%, respectively, in soft-type margarines. Hard-type margarines contained total trans FA concentrations of 20.1–34.3%, whereas soft-type margarines contained less than 8.9% total trans FA. C_18∶1 trans acid content was within the range of 18.5–29.8% in hard-type margarines, and it was significantly higher than the range in soft margarines (0.7–8.1%). C_18∶1 trans acid was the major trans FA in all margarines, and C_18∶3 trans acid concentrations were less than 0.2%.     

Reaction selectivity of <Emphasis Type="Italic">rhizomucor miehei</Emphasis> lipase as influenced by monoacylation of <Emphasis Type="Italic">sn</Emphasis>-glycerol

Reaction selectivities were determined in multicompetitive reactions mediated by Rhizomucor miehei (RM) lipase at water activity of 0.19 in hexane. Saturated FA (C4–C18 even chain) and oleic acid (C18∶1) were reacted with a single alcohol, glycerol, or α-or β-MAG containing C4, C10, C16, or C18∶1 individually as alcohol cosubstrate. Similar patterns of broad FA selectivity toward C8–C18 FA were generally observed for esterification into specific acylglycerol (AG) pools with the different α/β-CX-MAG cosubstrates. Exceptions were enrichment of C18 in the MAG pool with α-C16-MAG substrate, and a general suppression of C4/C6 FA reactivity and a specific discrimination toward >C8 FA incorporation into the TAG pool, both for reactions with α-C10- and α-C16-MAG. RM lipase selectivity toward MAG was in descending order: β-C18∶1-MAG>α/β-C4-MAG∼β-C10-MAG∼β-C16-MAG>α-C18∶1-MAG >α-C10-MAG∼α-C16-MAG. Selectivity in channeling CX of the original CX-MAG substrates into higher AG species was in descending order: α-C10-MAG∼α-C16-MAG>β-C10-MAGβ-C16-MAG>α-C18∶1-MAG>β-C18∶1-MAG∼ α/β-C4-MAG. Aside from their characteristic FA selectivity, Burkholderia cepacia (PS-30) and RM lipases behaved similarly in terms of MAG selectivity as well as a general conservation of FA selectivity throughout the sequential steps of TAG assembly from FA and glycerol for processes designed to yield specifically structured TAG.     

The incorporation of fatty acids of different chain length into liver and biliary lipids in the perfused rat liver

In an attempt to correlate the incorporation of fatty acids (FA) of different chain length into liver and biliary lipids’ isolated rat livers were perfused for 2 h with Krebs-Ringer bicarbonate containing 1% albumin and 10 μmol of [1-¹⁴C]-labeled FA: C₂’ C₈’ C₁₀’ C₁₂’ C₁₆’ and C_18∶1. One to 1.36 μmol of medium-chain fatty acids (MCFA’ C₈’ C₁₀’ and C₁₂) and 6.6 μmol of long-chain FA (LCFA) were incorporated into liver lipids’ 40% of the latter into phosphatidylcholine (PC). ¹⁴C-acetate (13 nmol) was incorporated into biliary cholesterol; ¹⁴C-MCFA contributed only 3.2–5 nmol; LCFA did not lead to newly synthesized cholesterol. Newly synthesized liver PC (2.75 to 3.25%) and newly synthesized liver cholesterol (6.5 to 10%) were secreted into bile. The specific radioactivity of biliary PC after infusion of all-saturated FA was 3.8–6.8 times higher than that of liver PC; for C_18∶1 it was only 1.7-fold. The specific radioactivity of biliary cholesterol’ as compared to liver cholesterol’ was 12 times higher for C₂ and five times higher for MCFA. This indicates that a considerable proportion of the newly synthesized lipids was secreted into bile prior to significant mixing with preexisting liver PC and cholesterol pools. liver PC contained 8% of unchanged ¹⁴C−C₁₂; while ¹⁴C−C₁₀ was not detected. Biliary PC’ in contrast’ contained 18% of unchanged ¹⁴C−C₁₂ and 3% ¹⁴C−C₁₀. These results suggest that after prolonged infusion of medium-chain triacylglycerols/longchain triacylglycerols to patients’ biliary PC may become enriched with MCFA. In addition’ the oxidation of these FA may provide C-2 units which increase cholesterol synthesis.     

Comparison of the oxidizability of various glycerophospholipids in bilayers by the oxygen uptake method

The aims of this study were twofold: develop a convenient and rapid procedure for assessing the oxidizability of small quantities of glycerophospholipids in bilayers by the oxygen uptake method, and determine and compare the oxidizability of various glycerophospholipids in bilayers. Our purpose was to educidate phospholipid oxidation characteristics in membranes. The quantitative autoxidation kinetics of dilinoleoyl phosphatidylcholine (DLPC) (18∶2/18∶2) was studied in large unilamellar vesicles (LUV) in aqueous dispersions with watersoluble initiator—2,2′-azobis(2-amidinopropane) dihydrochloride—and inhibitor 2-carboxy-2,5,7,8-tetramethyl-6-chromanol. The kinetic data indicated a high efficiency of free radical production, resulting in shortening of measuring time; the very low kinetic chain length, particularly in the induction period, suggested the possibility of including large errors in thekinetics data. Nevertheless, the autoxidation of DLPC obeyed the classic rate law: R _p =k _p [LH]R _i ^1/2 /(2k _t )^1/2 (where R _p -rate of oxygen consumption, k _p =rate constant for chain propagation, [LH]-substrate concentration; R _i ^1/2 -square root of rate of chain initiation, and 2k _t =rate constant for chain termination) in a mixed bilayer system with saturated dimyristoyl PC (14∶0/14∶0), which provided precise and reproducible data. Therefore, the system was used to assess the relative oxidizability of each glycerophospholipid DLPC (18∶2/18∶2), dilinolenoyl PC (18∶3/18∶3), 1-palmitoyl-2-linoleoyl PC (16∶0/18∶2), 1-palmitoyl-2-arachidonoyl PC (16∶0/20∶4), 1-palmitoyl-2-docosahexaenoyl PC (16∶0/22∶6), and dilinoleoyl PE (18∶2/18∶2) in bilayers. The results suggested that the oxidizability of glycerophospholipid in bilayers is substantially influenced by the number of intramolecular oxidizable acyl chains and the content of bis-allylic hydrogen in a structured environment, and showed deviation of the rate law for autoxidation in PC and PE mixed LUV, which possibly was due to nonhomogeneous phospholipid distribution in vesicles.     

The antioxidant effect of natural substances on lipids during irradiation of chicken legs

Entire fresh chicken legs were subjected to three pretreatments (packaged in air; packaged under vacuum; or marinated in natural plant extracts and packaged in air) followed by irradiation (0, 3, or 5 kGy). The control and irradiated chicken legs were stored at 4°C and analyzed for FA composition and sensory quality at predetermined intervals. Irradiation dose had a significant (P<-0.01) effect on FA derived from phospholipid but less than on FA derived from a neutral lipid. In general, levels of unsaturated FA decreased as the radiation dose increased; however, for marinated chicken legs irradiated with 5 kGy, levels of linoleic acid (C_18∶2) and arachidonic acid (C_20∶4) derived from the phospholipid fraction were significanlty (P≤0.05) higher than those irradiated in air or under vacuum. The concentration of FA also decreased significantly (P≤0.05) as storage time increased. For chicken legs packaged in air or marinated and then packaged in air, significant (P≤0.01) inverse correlations existed between high-carbon-number PUFA and lower-carbon-number (≤17) saturated FA; this relationship was not apparent in samples irradiated under vacuum. A processing combination of marinating and vacuum packaging might better control lipid oxidation and degradation in irradiated chicken. Panelists found no significant difference (P>0.05) in the flavor and oder intensity of cooked irradiated chicken legs and their nonirradiated equivalents.     

Fatty acids and oil content in white lupin seed as affected by production practices

Characteristics of the seed oil of white lupin (Lupinus albus L.), a potential alternative winter crop in the mid-Atlantic region of the United States, are not well established. Replicated experiments were conducted during the 1998–1999 and 1999–2000 growing seasons with a determinate and an indeterminate cultivar to characterize oil and FA in lupin seed in relation to production practices. The experiments were planted in early October, late October, and mid-November using row spacings of 0.3, 0.6, and 0.9 m at each planting time. Seeds from the planting date of early October had significantly (P<0.05) higher oil content than the later plantings (late October and mid-November). A closer row spacing (0.3 m) also had significantly (P<0.05) higher oil content than the wider row spacing (0.9 m). Planting data effects on FA content were significant for some FA, but row spacing did not affect FA contents. Oil content in the seed varied from 7.2 to 8.2% (w/w). The oil from white lupin seed contained FA in the order of 18∶1>18∶2> 18∶3>16∶0>20∶1>22∶1>22∶0>18∶0>24∶0>20∶0. The saturated FA/unsaturated FA ratio in lupin oil was 0.14. White lupin seed contained higher contents of oil and FA than literature values for seed of navy, kidney, and pinto beans.     

Effects of dietary vegetable oil on atlantic salmon hepatocyte fatty acid desaturation and liver fatty acid compositions

Fatty acyl desaturase activities, involved in the conversion of the C₁₈ EFA 18∶2n−6 and 18∶3n−3 to the highly unsaturated fatty acids (HUFA) 20∶4n−6, 20∶5n−3, and 22∶6n−3, are known to be under nutritional regulation. Specifically, the activity of the desaturation/elongation pathway is depressed when animals, including fish, are fed fish oils rich in n−3 HUFA compared to animals fed, vegetable oils rich in C₁₈ FFA. The primary aims of the present study were (i) to establish the relative importance of product inhibition (n−3 HUFA) vs. increased substrate concentration (C₁₈ EFA) and (ii) to determine whether 18∶2n−6 and 18∶3n−3 differ in their effects on the hepatic fatty acyl desaturation/elongation pathway in Atlantic salmon (Salmo salar). Smolts were fed 10 experimental diets containing blends of two vegetable oils, linseed (IO), and rapeseed oil (RO), and fish oil (FO) in a triangular mixture design for 50 wk. Fish were sampled after 32 and 50 wk, lipid and FA composition of liver determined, fatty acyl desaturation/elongation activity estimated in hepatocytes using [1-¹⁴C]18∶3n−3 as substrate, and the data subjected to regression analyses. Dietary 18∶2n−6 was positively correlated, and n−3 HUFA negatively correlated, with lipid content of liver. Dietary 20∶5n−3 and 22∶6n−3 were positively correlated with liver FA with a slope greater than unity suggesting relative retention and deposition of these HUFA. In contrast, dietary 18∶2n−6 and 18∶3n−3 were positively correlated with liver FA with a slope of less than unity suggesting metabolism via β-oxidation and/or desaturation/elongation. Consistent with this, fatty acyl desaturation/elongation in hepatocytes was significantly increased by feeding diets containing vegetable oils. Dietary 20∶5n−3 and 22∶6n−3 levels were negatively correlated with hepatocyte fatty acyl desaturation. At 32 wk, 18∶2n−6 but not 18∶3n−3 was positively correlated with hepatocyte fatty acyl desaturation, wheres the reverse was true at 50 wk. The data indicate that both feedback inhibition through increased n−3 HUFA and decreased C₁₈ fatty acyl substrate concentration are probably important in determining the level of hepatocyte fatty acyl desaturation and that 18∶2n−6 and 18∶3n−3 may differ in their effects on this pathway.     

Storage lipid accumulation and acyltransferase action in developing flaxseed

Investigations of storage lipid synthesis in developing flaxseed (Linum usitatissimum) provide useful information for designing strategies to enhance the oil content and nutritional value of this crop. Lipid content and changes in the FA composition during seed development were examined in two cultivars of flax (AC Emerson and Vimy). The oil content on a dry weight basis increased steadily until about 20 d after flowering (DAF). The proportion of α-linolenic acid (α-18∶3, 18∶3cisΔ^{9, 12, 15}) in TAG increased during seed development in both cultivars while the proportions of linoleic acid (18∶2cisΔ^{9, 12}) and saturated FA decreased. The developmental and substrate specificity characteristics of microsomal DAG acyltransferase (DGAT, Ec 2.3.1.20) and lysophosphatidic acid acyltransferase (LPAAT, EC 2.3.1.51) were examined using cultivar AC Emerson. The maximal acyltransferase specific activities occurred in the range of 8–14 DAF, during rapid lipid accumulation on a per seed basis. Acyl-CoA of EPA (20∶5cisΔ^5,8,11,14,17) or DHA (22∶6cis ^{4,7,10,13,16,19}) were included in the specificity studies. DGAT displayed enhanced specificity for α-18∶3-CoA, whereas the preferred substrate of LPAAT was 18∶2-CoA. Both enzymes could use EPA- or DHA-CoA to varying extents. Developing flax embryos were able to take up and incorporate these nutritional FA into TAG and other intermediates in the TAG-formation pathway. This study suggests that if the appropriate acyl-CoA-dependent desaturation/elongation pathways are introduced and efficiently expressed in flax, this may lead to the conversion of α-18∶3-CoA into EPA-CoA, thereby providing an activated substrate for TAG formation.     

Fatty acid profiles and relative mobilization during fasting in adipose tissue depots of the American marten (Martes americana)

The American marten (Martes americana) is a boreal forest marten with low body adiposity but high metabolic rate. The study describes the FA composition in white adipose tissue depots of the species and the influence of food deprivation on them. American marten (n=8) were fasted for 2 d with 7 control animals. Fasting resulted in a 13.4% weight loss, while the relative fat mass was >25% lower in the fasted animals. The FA composition of the fat depots of the trunk was quite similar to other previously studied mustelids with 14∶0, 16∶0, 18∶0, 16∶1n−7, 18∶1n−9, and 18∶2n−6 as the most abundant FA. In the extremities, there were higher proportions of monounsaturated FA (MUFA) and PUFA. Food deprivation decreased the proportions of 16∶0 and 16∶1n−7, while the proportion of long-chain MUFA increased in the trunk. The mobilization of FA was selective, as 16∶1n−7, 18∶1n−9, and particular n−3 PUFA were preferentially mobilized. Relative mobilization correlated negatively with the carbon chain length in saturated FA (SFA) and n−9 MUFA. The Δ9 desaturation of SFA enhanced the mobilization of the corresponding MUFA, but the positional isomerism of the first double bond did not correlate consistently with relative mobilization in MUFA or PUFA. In the marten, the FA composition of the extremities was highly resistant to fasting, and the tail tip and the paws contained more long-chain PUFA to prevent the solidification of lipids and to maintain cell membrane fluidity during cooling.     

Maternal dietary alpine butter intake affects human milk: Fatty acids and conjugated linoleic acid isomers

Consumption of CLA by lactating women affects the composition of their milk, but the pattern of the different CLA isomers is still unknown. We determined the effects of short maternal supplementation with CLA-rich Alpine butter on the occurrence of FA and CLA isomers in human milk. In an open randomized controlled study with a two-period cross-over design, milk FA and CLA isomer concentrations were measured on postpartum days >-20 in two parallel groups of lactating women before, during, and after consumption of defined quantities of Alpine butter or margarine with comparable fat content (10 d of butter followed by 10 d of margarine for one group, and vice versa in the other). In the 16 women who completed the study (8/group), Alpine butter supplementation, increased the C₁₆ and C₁₈ FA, the sum of saturated FA, the 18∶1 trans FA, and the trans FA with CLA. The CLA isomer 18∶2 c9, t11 increased by 19.7%. Significant increases were also found for the isomers t9,t111, t7,c9,t11,c13, and t8,c10 18∶2. The remaining nine of the total 14 detectable isomers showed no changes, and concentrations were <5 mg/100g fat. A breastfeeding mother can therefore modulate the FA/CLA supply of her child by consuming Alpine butter. Further studies will show whether human milk containing this FA and CLA isomer pattern acts as a functional food for newborns.     

Effect of temperature on the incorporation into phospholipid classes and metabolismvia desaturation and elongation of n−3 and n−6 polyunsaturated fatty acids in fish cells in culture

The incorporation of 18∶2n−6, 18∶3n−3, 20∶4n−6 and 20∶5n−3 was greater at 10°C than at 22°C in Atlantic salmon (AS), rainbow trout (RTG-2) and turbot (TF) cells. However, there were generally no significant differences between the amount of incorporation of all four polyunsaturated fatty acids (PUFA) into total lipid within a cell type at either 22°C or 10°C. The distributions of the PUFA between individual phospholipid classes at 22°C was essentially the same in AS and TF cells—with the C₁₈ PUFA the order of incorporation in these cells was phosphatidylcholine (PC) > phosphatidylethanolamine (PE) > phosphatidic acid/cardiolipin (PA/CL); with 20∶4n−6 the order was PE and phosphatidylinositol (PI)>PC; with 20∶5n−3, PE>PC. In RTG-2 cells at 22°C the distributions of the C₁₈ PUFA were similar to the other cell lines, but with 20∶4n−6 the order was PC>PI>PE, and with 20∶5n−3 it was PC>PE. At 10°C the incorporation of C₁₈ PUFA into PC increased and into PE and PA/CL decreased, in general, in all cell lines. Incorporation of 20∶5n−3 into PC and PE was increased and decreased at 10°C, respectively, in AS and TF cells, whereas in RTG-2 cells the changes at 10°C were opposite i.e., increased in PE and decreased in PC. With 20∶4n−6, incorporation into PC at 10°C was increased in all cell lines with decreased incorporation into PI in AS and RTG-2 cells and into PE in AS and TF cells, whereas incorporation of 20∶4n−6 into PE increased in RTG-2 cells. The metabolismvia desaturation and elongation of the n−3 PUFA was greater than that of the equivalent n−6 PUFA in all cell lines, irrespective of temperature. There was less conversion of the C₁₈ PUFA at 10°C than at 22°C in RTG-2 and TF cells, but the conversion of 18∶3n−3 by AS cells was increased at 10°C. Temperature had no effect on the conversion of the C₂₀ PUFA.     

Production and protein kinase C activation of diacylglycerols containing polymethylene-interrupted PUFA

Sciadonic acid (20∶3, Δ-5c,11c,14c) is a polymethylene-interrupted PUFA (PMI-PUFA) that is present in conifer seeds and known to be incorporated into animal cells and to accumulate in membrane PI as a substitute for arachidonate. In this study, we investigated whether PI having sciadonate could serve as source of DAG that could activate protein kinase C (PKC). When Swiss 3T3 cells cultured with sciadonic acid were stimulated with 100 nM of bombesin, 1-stearoyl-2-sciadonoyl-glycerol (G) and 1-stearoyl-2-arachidonoyl-G were produced. The net increments of these two molecular species of DAG reflected the levels of the two molecular species in the PI in the cells. When cells cultured with juniperonic acid (20∶4, Δ-5c,11c,14c,17c) were stimulated 1-stearoyl-2-juniperonoyl-G was produced in proportion to the level of this molecular species in PI in the cells. We also examined PKC activation by synthetic DAG using a partially purified PKC fraction from rat brain and found that both 1-stearoyl-2-sciadonoyl-G and 1-stearoyl-2-juniperonoyl-G could activate PKC comparably to 1-stearoyl-2-arachidonoyl-G. These results indicate that 1-stearoyl-PI having these C₂₀ PMI-PUFA residues can serve as sources of potential signaling molecules.