Specific susceptibility of docosahexaenoic acid and eicosapentaenoic acid to peroxidation in aqueous solution

The peroxidation of different polyunsaturated fatty acids (PUFA) after photoirradiation in aqueous solution was evaluated by measuring fatty acid loss and malonaldehyde production in medium. The oxidation rates of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), two highly unsaturated fatty acids of the n−3 series, were surprisingly lower (14 and 22%, respectively) than the oxidation rates of linoleic, α-linolenic, γ-linolenic, dihomo γ-linolenic, and arachidonic acids (62–90%). The quantities of malonaldehyde (MA) produced were assayed simultaneously by gas chromatography (GC) and high performance liquid chromatography (HPLC). MA production was found to be related to both the degree of unsaturation and the metabolic series of the fatty acid. The maximum value was observed with arachidonic acid (MA production from 2 mM arachidonic acid in aqueous solution was estimated at 44.9±6.0 μM by GC and 46.8 ±4.0 μM by HPLC). Eicosapentaenoic acid and docosahexaenoic acid produced lower MA quantities compared to arachidonic acid (MA production from 2 mM EPA and 2 mM DHA was estimated at 17.9±1.5 μM and 37.9±0.7 μM, respectively, by GC, and 26.3±4.9 μM and 37.3±4.2 μM, respectively, by HPLC). The MA yield, defined as the amount of MA (nmols) produced per 100 nanomoles of oxidized fatty acid, was used to express the susceptibility of individual PUFA to peroxidation. The MA yield correlated well with the degree of unsaturation, but was independent of carbon chain length and metabolic series. The study suggests that adequate assessment of lipid peroxidation cannot be achieved by measuring MA formation alone, but it also requires knowledge of the fatty acid composition of the system studied.     

Species difference of liver cytosolic fatty acid-binding protein in rat,mouse and guinea pig

Binding properties of liver cytosolic protein for oleic acid, palmitoyl-CoA and bromosulphophthalein (BSP) were compared for rat, mouse and guinea pig. Hepatic cytosol of rat, mouse and guinea pig contained proteins with a molecular weight of ca. 12,000 and had an affinity for [1-¹⁴C]-oleic acid. The concentration of fatty acid-binding protein (FABP) was almost the same in livers of the animals of the 3 species and was ca. 50 μg/mg cytosolic protein. Electrophoretic studies revealed that FABP from hepatic cytosol of rat, mouse and guinea pig, purified with affinity chromatography, are distinct from one another in terms of their charge. FABP of rat liver was capable of binding any 3 ligands-oleic acid, palmitoyl-CoA and BSP—at relatively high binding capacity. FABP of mouse liver also bound oleic acid and palmitoyl-CoA to a great extent, but its binding capacity for BSP was only one-third that of rat liver. FABP of guinea pig liver bound less oleic acid and palmitoyl-CoA than rat liver, whereas it had almost the same binding capacity for BSP as rat liver.     

Diffication of high affinity fatty acid receptors in rat myocardial sarcolemmal membranes

High affinity receptors for fatty acid were purified from rat cardiac sarcolemmal membrane using gel filtration, DEAE-cellulose chromatography and affinity chromatography. The purified protein was homogeneous on polyacrylamide gel electrophoresis with the molecular weight of 60 kDa. Binding studies revealed the presence of a single class of high affinity binding sites with an apparent dissociation constant of 1.0 μM and a maximal binding capacity of 12.1 pmol/μg protein.     

Arachidonic acid and eicosapentaenoic acid stimulate type II pneumocyte surfactant secretion

Arachidonic acid and its leukotriene metabolites have been shown to stimulate surfactant secretion by alveolar type II cells. The present study was undertaken to determine the effects of various unsaturated fatty acids, including eicosapentaenoic acid, on surfactant secretion. Surfactant secretion was expressed as the percent of [³H]choline-derived phospholipids released into culture medium by type II pneumocytes of adult rats. Consistent with the earlier findings, arachidonic acid stimulated secretion in a concentration-dependent fashion (3.5–21 μM), doubling baseline secretion at 21 μM. Eicosapentaenoic acid was found to be equally effective as arachidonic acid in stimulating secretion. A comparison with palmitic, oleic and linoleic acids revealed that highly unsaturated fatty acids stimulated secretion to the greatest extent. This was supported by a positive correlation between degree of unsaturation (i.e., 0, 1, 2, 4 and 5 double bonds) and stimulation of surfactant secretion. In the present study, exogenous leukotriene E₄ (10⁻¹³–10⁻⁶) did not stimulate surfactant secretion. Neither nordihydroguaiaretic acid (0.1μM) nor indomethacin (0.1μM) affected arachidonic acid-stimulated secretion. The stimulatory effects of arachidonic acid and eicosapentaenoic acid on surfactant secretion were related to the highly unsaturated nature of the fatty acids and were not mediated by increased levels of cyclic adenosine monophosphate or calcium.     

Effects of 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) on de novo fatty acid and cholesterol synthesis in the rat

The effects of 1, 5, 10 and 20 μg/kg dosages of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) upon de novo fatty acid and cholesterol synthesis in liver and adipose tissue were determined in pair-fed rats. The incorporation of tritium from³H₂O into tissue lipids was measured. Hepatic and adipose fatty acid synthetic rates (μmoles acetyl units g⁻¹ hr⁻¹ in the control groups were 19.6±4 and 75.7±18.5, respectively, and the liver cholesterol synthetic rate was 2.9±0.5 TCDD (1 μg/kg) inhibited fatty acid synthesis in the liver and adipose tissue, by 44% and 41% respectively, and the liver cholesterol synthesis was inhibited by 37%. The extent of these inhibitions increased with increasing dosages of TCDD. The effect of TCDD on sterol synthesis in adipose tissue could not be determined, because the tritium incorporation into the sterol fraction in this tissue was not detectable.     

Characterization and Immobilization of Marine Algal 11-Lipoxygenase from Ulva fasciata

The lipoxygenase (LOX) of the marine green alga Ulva fasciata was purified and immobilized in order to improve the stability and reusability. The algal LOX was partially purified by fractionation with 35–55% saturation of ammonium sulfate and MacroPrep high Q anion exchange chromatography. The LOX was purified ten times using linoleic acid (C_18:2) or arachidonic acid (C_20:4) as substrate, the Michaelis constant (K _m) of LOX was 117.6, 31.3 μM, and maximum velocity (V _max) was 12.8, 23.3 μmol hydroperoxy fatty acid/min-mg protein, respectively. The algal LOX showed the highest activity towards C_18:4 followed by C_20:4, C_18:2 and methyl ester of C_18:4. LOX activity increased up to 10.5 times with increased concentration of Triton X-100 in the extraction medium reaching an optimum at 0.05%. Calcium chloride, glutathione and phenylmethylsulphonyl fluoride were found effective protectants to LOX during purification. Hydroperoxyeicosatetraenoic acid (HpETE) formed from arachidonic acid catalyzed by this purified algal LOX was reduced and identified as 11-hydroxy-5,8,12,14-eicosatetraenoic acid (11-HETE) by NP-HPLC and GC–MS. This algal 11-LOX was immobilized in alginate beads. The stability was sevenfold greater than that of the unbound lipoxygenase at 4 °C in 0.05 M Tris–HCl buffer (pH 7.5). This is the first report on immobilization of a marine algal lipoxygenase with a view to its potential role in seafood flavor formation.     

Inhibition of lipoxygenase 1 by phosphatidylcholine micelles-bound curcumin

Curcumin (diferuloyl methane) from rhizomes of Curcuma longa L. binds to phosphatidylcholine (PC) micelles. The binding of curcumin with PC micelles was followed by fluorescence measurements. Curcumin emits at 490 nm with an excitation wavelength of 451 nm after binding to PC-mixed micelles stabilized with deoxycholate. Curcumin in aqueous solution does not inhibit dioxygenation of fatty acids by Lipoxygenase 1 (LOX1). But, when bound to PC micelles, it inhibits the oxidation of fatty acids. The present study has shown that 8.6 μM of curcumin bound to the PC micelles is required for 50% inhibition of linoleic acid peroxidation. Lineweaver-Burk plot analysis has indicated that curcumin is a competitive inhibitor of LOX1 with K _l of 1.7 μM for linoleic and 4.3 μM for arachidonic acids, respectively. Based on spectroscopic measurements, we conclude that the inhibition of LOX1 activity by curcumin can be due to binding to active center iron and curcumin after binding to the PC micelles acts as an inhibitor of LOX1.     

Qualitative and quantitative analysis of lipoxygenase products in bovine corneal epithelium by liquid chromatography-mass spectrometry with an ion trap

Electrospray ionization ion trap mass spectra of 5-, 12-, and 15-hydroperoxyeicosatetraenoic (HPETE), hydroxyeicosatetraenoic (HETE), and ketoeicosatetraenoic (KETE) acids were recorded. The HPETE were partly dehydrated to the corresponding KETE in the heated capillary of the mass spectrometer. 12-HPETE and 15-HPETE were also converted to KETE by collision-induced dissociation (CID) in the ion trap, whereas CID of 5-HPETE yielded little formation of 5-KETE. Subcellular fractions of bovine corneal epithelium were incubated with arachidonic acid (AA) and the metabolites were analyzed. 15-HETE and 12-HETE were consistently formed, whereas significant accumulation of HPETE and KETE was not detected. Biosynthesis of 12- and 15-HETE was quantified with octadeuterated 12-HETE and 15-HETE as internal standards. The average biosynthesis of 15-HETE and 12-HETE from 30μM AA by the cytosol was 38±8 and below 3 ng/mg protein/30 min, respectively, which increased to 78±21 and 10±4 ng/mg protein/30 min in the presence of 1 mM free Ca²⁺. The microsomal biosynthesis was unaffected by Ca²⁺. The microsomes metabolized AA to 15-HETE as the main metabolite at a low protein concentration (0.3 mg/mL), whereas 12-HETE and 15-HETE were formed in a 2∶1 ratio at a combined rate of 0.7±0.2 μg/mg protein/30 min at a high protein concentration (1.8 mg/mL). The level of 12-HETE in corneal epithelial cells was 50±13 pg/mg tissue, whereas the endogenous amount of 15-HETE was low or undetectable (<3 pg/mg tissue). Incubation of corneas for 20 min at 37°C before processing selectively increased the amounts of 12-HETE in the epithelium fourfold to ∼0.2 ng/mg tissue. We conclude that 12-HETE is the main endogenously formed lipoxygenase product of bovine corneal epithelium.     

Isolation and identification of acetyl-CoA carboxylase from rainbow trout (Salmo gairdneri) liver

Acetyl-CoA carboxylase is the pivotal enzyme in the de novo synthesis of fatty acids and is the only carboxylase with a biotin-containing subunit greater than 200,000 daltons. The biotin moiety is covalently linked to the active site and has a high affinity (K_d=10⁻¹⁵ M) for the protein avidin. This relationship has been used in previous studies to identify acetyl-CoA carboxylase isolated from mammalian species. However, acetyl-CoA carboxylase has not been isolated and characterized in a poikilothermic species such as the rainbow trout. The present study describes the isolation and identification of acetyl-CoA carboxylase in the cytosol of rainbow trout (Salmo gairdneri) liver. The enzyme was isolated using two distinct procedures—polyethylene glycol precipitation and avidin-Sepharose affinity chromatography. Identification of the isolated protein as acetyl-CoA carboxylase was made by the following: (1) sodium dodecyl sulfate-polyacrylamide gel electrophoresis; (2) avidin binding; (3) in vivo labeling with [¹⁴C]biotin; and (4) acetyl-CoA carboxylase-specific activity. The subunit molecular weight of the major protein was 230,000 daltons ±3.3%. This protein was shown to bind avidin (M_r=16,600) prior to sodium dodecyl sulfate-polyacrylamide gel electrophoresis, indicating the presence of biotin. In addition, protein isolated from fish that had previously received intraperitoneal injections of [¹⁴C]biotin, showed the majority of radioactivity associated with the 230,000 dalton protein. The polyethylene glycol precipitation yielded 200 μg protein (4.4 μg/g liver), with a specific activity of 5 nmol malonyl-CoA/min/mg protein, whereas avidin affinity chromatography yielded 1.75±1.1 mg protein (9.0 μg/g liver), with a specific activity of 1.37±0.18 μmol malonyl-CoA/min/mg protein. The enzyme was citrate dependent showing maximum activity between 10 and 20 mM. Acetyl-CoA carboxylase-specific activity decreased by 50% in the presence of 0.2 M NaCl. These findings suggest that the major protein (M_r=230,000) purified from rainbow trout liver is acetyl-CoA carboxylase with enzyme characteristics comparable to mammalian acetyl-CoA carboxylase.     

Fatty acid composition of brain glycerophospholipids in peroxisomal disorders

This paper shows for the first time the differential fatty acid composition of ethanolamine plasmalogens (EP) and phosphatidylethanolamine (PE) in the brains of 12 patients with disorders of peroxisomal biogenesis and compares the results to normal values for the age. Other important glycerophospholipids (GPL), such as phosphatidylserine (PS) and phosphatidylcholine (PC), are also included in this study. GPL were separated by two-dimensional thin-layer chromatography, and their fatty acid composition was determined by capillary column gas-liquid chromatography. Total brain GPL were slightly decreased in peroxisomal disorders (27.98±2.95 μmol/g in the patients against 34.5±6.21 μmol/g in age-matched controls, P=0.005), and the distribution of the different GPL classes was much altered. In confirmation of known data, EP were very much decreased (2.18±1.3 μmol/g in the patients against 6.9±2.3 μmol/g in controls) at the expense of PE, which was increased (8.58±2.17 μmol/g in the patients against 5.97±0.58 μmol/g in controls, P<0.005). PS and PC were both significantly decreased (P=0.0001 and P=0.037, respectively). The polyunsaturated fatty acid (PUFA) composition of all the GPL fractions was markedly abnormal. In absolute terms, docosahexaenoic acid (22∶6n−3) was drastically decreased in all GPL classes (always at the P<0.0001 level) while arachidonic acid (20∶4n−6) was increased in PE and PS (P<0.001 in both cases). In the alkenyl acyl form, EP, 22∶6n−3, and 20∶4n−6 were both very significantly decreased (P<0.0001), although the former was always the most affected. The myelin PUFA adrenic acid (22∶4n−6) was decreased in EP (P<0.0001) and slightly increased in PS (P<0.05). The changes found confirm that 22∶6n−3 deficiency is a predominant defect in the brain in peroxisomal disorders.     

Seawater fatty acids and lipid classes in an urban and a rural Nova Scotia inlet

Seawater samples collected in the summer of 1989 in Nova Scotia inlets were analyzed for lipid content to examine water quality. One inlet, the Northwest Arm, is located adjacent to an urban center, while the other, Ship Harbour, is located in an uninhabited area and contains three commercial mollusk farms. Lipids in the dissolved and particulate fractions were measured by Chromarod-Iatroscan thin-layer chromatography with flame ionization detection and by gas chromatography. Samples collected near the urban center had higher levels of particulate hydrocarbons (28±15 μg/L) than those collected in the relatively pristine environment (11±1 μg/L). The urban center samples also had higher levels of particulate free aliphatic alcohols (14±5vs. 8±1 μg/L) and free fatty acids (5±1vs.<0.5 μg/L), suggesting degradation of wax esters and other fatty acid esters. Dissolved and particulate matter fatty acids contained a higher proportion of monounsaturated acids near the urban center (33–35vs. 25–29% of the total fatty acids). The essential fatty acids 20∶5n−3 (eicosapentaenoic acid) and 22∶6n−3 (docosahexaenoic acid), presumably of algal origin, were more prominent in the pristine environment (up to 3.5%), where mollusk aquaculture is practiced. Fatty acid markers of toxic algae were virtually absent (<0.2%) in samples taken from both locations. O.S.C. contribution 173.     

Inhibition of the hormone-sensitive lipase in adipose tissue by long-chain fatty acyl coenzyme A

The effects of free fatty acids and fatty acyl esters of coenzyme A and carnitine on the activity of a hormone-sensitive lipase preparation made from pigeon adipose tissue were determined. Oleic acid (100 μM) resulted in a 40% inhibition of lipase activity A more potent inhibition of lipase activity was seen with long-chain fatty acyl CoA compounds. The concentration required for half-maximal inhibition with oleoyl CoA and palmitoyl CoA was 25–40 μM, whereas palmitoyl carnitine stimulated lipase activity. Activated lipase preparations (preincubated with Mg²⁺, ATP, cyclic AMP and protein kinase) were 4–6 times more sensitive to inhibition by oleoyl CoA than were nonactivated preparations. An increase in cellular levels of fatty acyl coenzyme A could, therefore, contribute to the feedback inhibition of lipolysis in adipose tissue.     

Comparison of the effects of dietary fish oils with different n−3 polyunsaturated fatty acid compositions on plasma and liver lipids in rats

The effects of dietary fish oils with different n−3 polyunsaturated fatty acid compositions on plasma lipid profiles in rats have been studied. Forty-eight male rats, previously maintained on a cholesterol-free diet for 15 days, were fed for 60 days with diets supplemented with 10% fat of either marine hilsa fish (Hilsa ilisa, family clupeidae) or fresh-water chital fish (Notopterus chitala, family notopteridae). The diets had similar levels of total saturated (35–41%), monounsaturated (43–47%) and n−3 polyunsaturated (9–10%) fatty acids. Cholesterol contents of the diets were adjusted to 0.85%; γ-linolenic acid (3.3%) in chital oil and eicosapentaenoic acid (4.9%) in hilsa oil diets were the major n−3 contributors. The percentage of eicosapentaenoic acid in the chital oil diet was 0.57 times that of the hilsa oil diet, but the eicosapentaenoic (EPA) to arachidonic acid (AA) ratio in the latter (4.08) was 3.2 times that of the former (1.27). Sixty days of hilsa oil diet feeding decreased the levels of cholesterol (53.3±2.9 to 50.0±1.1 mg/dL), triacylglycerol (75.7±3.8 to 64.3±2.6 mg/dL) and phospholipid (55.8±1.5 to 51.7±3.1 mg/dL) in rat plasma. Similar treatment with chital oil diet elevated the plasma cholesterol level (53.3±2.9 to 62.3±7.6 mg/dL) while triacylglycerol and phospholipid contents remained unaltered. Both the dietary treatments decreased the levels of linoleic and arachidonic acids in liver but only under the hilsa oil diet did the eicosapentaenoic acid percentage increase markedly (0.8±0.06% to 5.5±0.06%) at the expense of arachidonic acid. This study strongly suggests that the hypolipidemic effect depends on the composition of the n−3 polyunsaturated fatty acids rather than on the total n−3 polyunsaturated fatty acid content of the dietary fish oil.     

Vitamin E supplementation increases circulating vitamin E metabolites tenfold in end-stage renal disease patients

Vitamin E supplementation could elevate circulating vitamin E metabolites while modulating oxidative and inflammatory status in end-stage renal failure patients undergoing hemodialysis. Plasma concentrations of carboxyethyl-hydroxychromanols (α-and γ-CEHC), ascorbic acid, α-and γ-tocopherols, E₂-isoprostanes, and inflammatory biomarkers [tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), ferritin, and C-reactive protein (CRP)] were measured in blood samples obtained from patients (n=11) before and after dialysis on two occasions prior to, and at 1 and 2 mon of daily vitamin E supplementation (400 IU RRR-α-tocopherol). Supplementation nearly doubled plasma α-tocopherol concentrations (from 18±0.5 to 31±1.7 μM, P<0.0001), whereas γ-tocopherol concentrations decreased (from 2.8±0.3 to 1.7±0.2 μM, P=0.001). Serum α-CEHC increased 10-fold from 68±3 to 771±175 nM (P<0.0001), and γ-CEHC increased from 837±164 to 1136±230 nM (P=0.008). Vitamin E supplementation also increased postdialysis hematocrits from 38±1% to 41±1% (P<0.001). Dietary antioxidant intakes (vitamins E and C) were low in most subjects; plasma ascorbic acid levels (88±27 μM) decreased significantly with dialysis (33±11 μM, P=0.01). Plasma Il-6, CRP, TNF-α, and free F₂-isoprostane concentrations were elevated throughout the study. There is a complex relationship between chronic inflammation and oxidative stress that is not mitigated by short-term vitamin E supplementation. Importantly, serum vitamin E metabolite concentrations that increased 10-fold within 30 d of supplementation did not increase further, suggesting routes other than urine for removal of metabolites.     

Chronic free fatty acid infusion in rats results in insulin resistance but no alteration in insulin-responsive glucose transporter levels in skeletal muscle

To investigate the mechanism by which free fatty acids (FFA) affect glucose uptake, we studied the effect of chronic elevation (24 h) of plasma FFA in rats on whole body glucose disposal and glucose utilization index (GUI) in the basal state and under a euglycemic hyperinsulinemic clamp in relation to the amount of insulin-responsive glucose transporter (IRGT, i.e., GLUTU), protein in different muscles (oxidative and glycolytic) and adipose tissue. Infusion of Intralipid in the basal state led to a∼40% increase in whole body glucose uptake and a∼250% increase in GUI in adipose tissue as compared to control rats. There was no change in the amount of IRGT protein in any of the muscle types whereas in fat depots it was either unchanged or decreased. Under moderate or supraphysiological hyperinsulinemia, increment of whole body glucose disposal was significantly lower in Intralipid perfused rats when compared to controls (∼110 μU/mL: 0.7±0.1 vs. 1.3±0.1 mg/min,P<0.02; ∼1000 μU/mL: 3.0±0.2 vs. 3.9±0.4 mg/min,P<0.02). Under moderate hyperinsulinemia stimulation, GUI was significantly reduced in different muscles and adipose tissue as compared to controls. We conclude that peripheral insulin resistance which occurs after elevation of plasma FFA levels does not seem to be explained by changes in the amount of IRGT protein in either oxidative or glycolytic skeletal muscle. Thus fatty acid infusion appears to be associated with a defect in IRGT translocation to the plasma membrane, fusion with the membrane, or intrinsic activity.     

Phospholipid synthesis by chick retinal microsomes: Fatty acid preference and effect of fatty acid binding protein

The acylation of 1-palmitoyl-sn-glycerophosphocholine (1-16∶0-GPC) or 1-palmitoyl-sn-glycerophosphoethanolamine (1-16∶0-GPE) was measured using the microsomal fraction prepared from retinas of 14–15-day-old chick embryos. Rates of incorporation of exogenously supplied fatty acids into diacyl-GPC were generally 5–7 times greater than into diacyl-GPE. Substrate preferences for incorporation into diacyl-GPC and diacyl-GPE were, respectively, 18∶2>18∶3=20∶5>20∶4>18∶1>22∶6=18∶0 and 18∶2>22∶6≽18∶3=18∶0≽20∶4=18∶1>20∶5. The apparent selectivities were not consistent with the reported fatty acid compositions of these lipid classes. The addition of partially purified fatty acid binding protein (FABP) to the reaction had no effect either on overall rates of incorporation or on the substrate preference. When fatty acyl-CoA substrates were used, rates of incorporation of the 18∶0 derivative were much higher than with the fatty acid, while rates with other fatty acyl-CoA were similar to those with the respective fatty acid. Substrate preferences for CoA derivatives incorporated into diacyl-GPC were: 18∶0>20∶4>18∶2≽22∶6, and into diacyl-GPE: 20∶4=22∶6>18∶0>18∶2. Polyunsaturated fatty acyl CoA (PUFA-CoA) were thus favored for incorporation into diacyl-GPE, and to a lesser extent into diacyl-GPC, a result that is consistent with composition data. When purified FABP was added to the reactions, there was an increase in the incorporation of 18∶0-CoA and a decrease or no change in the incorporation of PUFA-CoA. The deacylation/reacylation cycle thus appears to play a role in the modification of phospholipid composition. The data are not consistent, however, with a role for FABP in directing PUFA toward membrane lipid synthesis.     

Brain free fatty acid levels in rats sacrificed by decapitation versus focused microwave irradiation

Values are presented for whole brain free fatty acid levels of rats sacrificed by decapitation vs focused microwave irradiation. Free fatty acids were quantitated by specific colorimetric analysis. Within ca. 1 min of sacrifice by either decapitation or microwave, rat whole brain free fatty acid concentrations ranged from ca. 80–100 μg/g fresh tissue. If the brain remained in the head for a total of 5 min after decapitation, free fatty acid levels increased by over 100%. The free fatty acids at this time were enriched with arachidonic acid. The increase in free fatty acid levels following decapitation was completely absent in rats sacrificed by the microwave irradiation. This microwave technique could be a valuable tool in determining free fatty acid and other heat stable compounds in brain tissue.     

Conjugated linoleic acid supplementation in humans: effects on fatty acid and glycerol kinetics

Recent studies with mouse adipocytes have shown that dietary conjugated linoleic acid (CLA) may reduce body fat by increasing lipolysis. The present study examined the effect of CLA supplementation on fatty acid and glycerol kinetics in six healthy, adult women who were participating in a controlled metabolic ward study. These women were fed six CLA capsules per day (3.9 g/d) for 64 d following a baseline period of 30 d. The subjects were confined to a metabolic suite for the entire 94-d study, where diet and activity were controlled and held constant. The rate of appearance (Ra) of glycerol, which indicates lipolytic rates, was similar at baseline and after 4 wk of CLA supplementation at rest (1.87±0.21 and 2.00±0.39 μmol/kg/min, respectively) and during exercise (7.12±0.74 and 6.40±0.99 μmol/kg/min, respectively). Likewise, the Ra of free fatty acids (FFA) was not significantly different after 4 wk of dietary CLA at rest (2.72±0.06 and 2.74±0.12 μmol/kg/min, respectively) or during exercise (6.99±0.40 and 5.88±0.29 μmol/kg/min, respectively). CLA supplementation also had no effect on the percentage of FFA released from lipolysis that were re-esterified. The apparent rate of FFA re-esterification was 65.2±4.2% at rest and 32.1±3.44% during exercise. Four weeks of CLA supplementation had no significant effect on fatty acid or glycerol metabolism in healthy, weight-stable, adult women.     

Lipid content and fatty acid composition of 11 species of Queensiand (Australia) fish

The fatty acid composition of 11 species of fish caught off the northeast coast of Australia was determined. No fatty acid profiles have been previously published for fish from this area nor for nine of these species. Although the percentage of polyunsaturated fatty acid (PUFA) was the same as the calculated average for Australian fish (42.3%), the percentage of n−3 fatty acids was lower (24.4±5.4% vs. 30.7±10.1%) and the n−6 fatty acids higher (16.5±4.5% vs. 11.2±5.9%), P<0.001 in each case. The major n−3 PUFA were docosahexaenoic (15.6 ±6.3%) and eicosapentaenoic acid (4.3±1.1%) while the major n−6 PUFA were arachidonic (8.3±3.2%) and n−6 docosatetraenoic acid (3.1±1.3%). The second-most abundant class of fatty acid was the saturates (31.6±3.5%) while the monounsaturates accounted for 17.4±4.3% of the total fatty acids. The monounsaturate with the highest concentration was octadecenoic acid (11.8±2.6%). There was a positive correlation between the total lipid content and saturated and monounsaturated fatty acids (r=0.675 and 0.567, respectively) and a negative correlation between the total lipid content and PUFA (r=0.774).     

Quantification,characterization and fatty acid composition of lysophosphatidic acid in different rat tissues

The amount and composition of lysophosphatidate present in different rat tissues have been estimated by an internal standard method in which a synthetic unnatural isomer (1-heptadecanoyl-rac-glycerol-3-phosphate) was added to the total lipid extracts, and the fatty acid composition of purified lysophosphatidate was determined. Lipids from tissues were extracted under acidic conditions, and the lysophosphatidate was purified by solvent partitions followed by thin-layer chromatography in multiple solvent systems. The purified lipid was shown to be 1-acyl-sn-glycerol-3-phosphate by chromatographic and chemical analysis, by its resistance to hydrolysis when treated with phospholipase A₂ and also by its complete conversion to 1-acyl-sn-glycerol when treated with alkaline phosphatase. The fatty acid consituents of this lipid were determined by gas-liquid chromatography of the derived methyl esters. The concentrations (nmol/g of tissue) of lysophosphatidate in various tissues were: 86.2±4.2 in brain, 60.3±6.3 in liver, 46.4±6.5 in kidney, 30.6±5.0 in testis, 22.3 in heart and 19.3 in lung. Mostly (80%) saturated fatty acids were found to be present in this lyso lipid. A significantly high level of stearic acid was present in this lipid from all the tissues (50–60% in liver, kidney, brain and testis, and about 40% in heart and lung) compared to plamitic acid (10–15% in liver, kidney and brain and 25–30% in testis, heart and lung). The fatty acid compositions of phosphatidic acid, the putative product of lysophosphatidate acylation, from different tissues were also determined and palmitate was found to be the major saturated fatty acid. These results suggest that tissue lysophosphatidic acid is not only formed byde novo biosynthesis but is also generated via the breakdown of phospholipids such as phosphoinositides.