Long-chain polyunsaturated fatty acids in plasma lipids of obese children

Fatty acid composition of plasma phospholipids (PL), triglycerides (TG), and sterol esters (STE) was determined by high-resolution capillary gas-liquid chromatography in 22 obese children (age: 13.7±1.4 y, body weight relative to normal weight for height: 170±24%, mean ±SD) and compared with data obtained in 25 age-matched healthy controls. There were no differences in the levels of linoleic acid (LA, C_18∶2n-6) in any of the plasma fractions from the obese children and the controls. Obese children exhibited significantly higher values of arachidonic acid (AA, C_20∶4n-6) than controls both in PL (12.6 [2.4] vs. 8.3 [1.4], % wt/wt, [median (interquartile range)],P<0.001) and STE (7.3 [1.8] vs. 6.0 [1.1],P<0.05). Similarly, obese children showed higher values than controls for dihomo-γ-linolenic acid (DHGLA, C_20∶3n-6) in PL (4.0 [0.5] vs. 3.0 [0.6],P<0.001), TG (0.4 [0.1] vs. 0.2 [0.1],P<0.001), and STE (0.9 [0.1] vs. 0.7 [0.1],P<0.01), and for γ-linolenic acid (C_18∶3n-6) in STE (1.1 [0.2] vs. 0.8 [0.2],P<0.001). The AA/LA ratios were higher in obese children than in controls in PL (0.68 [0.16] vs. 0.42 [0.09],P<0.0005) and STE (0.16 [0.04] vs. 0.12 [0.02],P<0.05), whereas the AA/DHGLA ratios were lower in TG of obese children than in controls (3.40 [0.64] vs. 5.10 [1.75],P<0.005). Plasma glucose concentrations were inversely related to AA in TG (r=0.53,P<0.05), and plasma TG concentrations were inversely related to AA in PL and STE (r=−0.49,P<0.05 andr=−0.48,P<0.05) and to the AA/DHGLA ratios in PL (r=−0.57,P<0.01),TG (r=−0.56,P<0.01) and STE (r=−0.56,P<0.01). We conclude that the significantly higher values of n-6 long-chain polyunsaturated fatty acids (LCP) in plasma lipids of obese children than in age-matched controls may be caused by an enhanced activity of Δ6-desaturation, and we speculate that elevated fasting immunoreactive insulin seen in obese children (19.4±8.0 μU/mL) may stimulate synthesis of n-6 LCP fatty acids.     

Regulation by carbohydrate and clofibric acid of palmitoyl-CoA chain elongation in the liver of rats

Regulation of palmitoyl-CoA chain elongation (PCE) and its contribution to oleic acid formation were investigated in rat liver in comparison with stearoyl-CoA desaturase (SCD). Hepatic PCE activity was induced by the administration of 20% wt/vol glucose or fructose in the drinking water of normal rats. In streptozotocin-induced diabetic rats, the activities of both PCE and SCD were suppressed, and fructose, but not glucose, feeding caused an increase in the activities of both enzymes. Treatment of normal rats with clofibric acid in combination with carbohydrate further increased PCE, but not SCD, acitivity. FA analysis of hepatic lipids revealed that the proportion of oleic acid (18∶1n−9) increased upon administration of carbohydrate or clofibric acid. The treatment of rats with clofibric acid in combination with carbohydrate greatly increased the proportion of 18∶1n−9. A significant correlation was observed between PCE activity and the hepatic proportion of 18∶1n−9 (r ²=0.874, Po0.01), whereas the relationship between SCD activity and the proportion of 18∶1n−9 was not significant (r ²=0.552, P>0.05). Taken together, these results suggest that carbohydrate induces PCE as well as SCD activity to increase the hepatic 18∶1 content in rat liver, and the increased PCE activity seems to be responsible for the further increase in 18∶1n−9 when carbohydrate is administered in combination with clofibric acid. FA are designated by the number of carbon atoms and double bonds     

A significant inverse relationship between concentrations of plasma homocysteine and phospholipid docosahexaenoic acid in healthy male subjects

The aim of this study was to investigate the possibility of a relationship between plasma homocysteine (Hcy) and phospholipid FA (PUFA) in healthy Australian males. One hundred thirty six healthy male subjects aged 20–55 yr were recruited from the Melbourne metropolitan area. Each volunteer completed a semiquantitative food frequency questionnaire and gave a blood sample. Plasma Hcy concentrations were determined by an established HPLC method; the plasma phospholipid FA were determined by standard methods. Plasma Hcy concentration was significantly negatively correlated with plasma phospholipid concentration of the PUFA 20∶5n−3 (r=−0.226, P=0.009), 22∶5n−3 (r=−0.182, P=0.036), 22∶6n−3 (r=−0.286, P=0.001), total n−3 (r=−0.270, P=0.002) and the ratio n−3/n−6 PUFA (r=−0.265, P=0.002), and significantly positively correlated with 20∶4n−6 (r=0.180, P=0.037). In the partial correlation analysis, after controlling for serum vitamin B₁₂ and folate concentration, plasma Hcy was significantly negatively correlated with the plasma phospholipid concentration of 22∶6n−3 (r=−0.205, P=0.019), total n−3 (r=−0.182, P=0.038) and the ratio n−3/n−6 PUFA (r=−0.174, P=0.048). Evidence indicates that an increased concentration of n−3 PUFA in tissues has a beneficial effect on cardiovascular health. Our findings provide further evidence that increased consumption of dietary n−3 PUFA increases the concentration of n−3 PUFA in plasma phospholipid, which is associated with a protective effect on cardiovascular diseases and lower plasma Hcy levels. The mechanism that might explain the association between plasma 22∶6n−3 and Hcy levels is not clear.     

Genetic diversity for lipid content and fatty acid profile in rice bran

Rice (Oryza sativa L.) bran contains valuable nutritional constituents, which include lipids with health benefits. A germplasm collection consisting of 204 genetically diverse rice accessions was grown under field conditions and evaluated for total oil content and fatty acid (FA) composition. Genotype effects were highly statistically significant for lipid content and FA profile (P<0.001). Environment (year) significantly affected oil content (P<0.05), as well as stearic, oleic, linoleic, and linolenic acids (all with P<0.01 or lower), but not palmitic acid. The oil content in rice bran varied relatively strongly, ranging from 17.3 to 27.4% (w/w). The major FA in bran oil were palmitic, oleic, and linoleic acids, which were in the ranges of 13.9–22.1, 35.9–49.2, and 27.3–41.0%, respectively. The ratio of saturated to unsaturated FA (S/U ratio) was highly related to the palmitic acid content (r ²=0.97). Japonica lines were characterized by a low palmitic acid content and S/U ratio, whereas Indica lines showed a high palmitic acid content and a high S/U ratio. The variation found suggests it is possible to select for both oil content and FA profile in rice bran.     

Lipid,FA, and sterol composition of New Zealand green lipped mussel (<Emphasis Type="Italic">Perna canaliculus</Emphasis>) and tasmanian blue mussel (<Emphasis Type="Italic">Mytilus edulis</Emphasis>)

The lipid, FA, and sterol composition of the New Zealand green lipped mussel (NZGLM, Perna canaliculus) and of the Tasmanian blue mussel (TBM, Mytilus edulis) were compared using TLC-FID and GC-MS. The respective mussel species were obtained from three different sites in both New Zealand (NZ) and Tasmania. Lipid class distribution of both mussel species was characterized by a high proportion of phospholipid (PL, 57–79%) and TG (10–25%), FFA (7–12%), and sterols (ST, 12–18%). The NZGLM had higher proportions of TG, FFA, and ST (P<0.01), whereas the TBM had a higher proportion of PL (P<0.01). There were higher proportions of total PUFA, saturated FA, n−3 FA, and hydroxy and nonmethyleneinterrupted FA (P<0.05) in the TBM compared with the NZGLM. The major FA in the NZGLM were 16∶0 (15–17%), 20∶5n-3 (14–20%), and 22∶6n-3 (11–17%). The same FA dominated lipids in the TBM, although there were significantly higher proportions of 16∶0 (P=0.000) and 22∶6 n−3 (P=0.003) and lower proportions of 20∶5n-3 (P=0.0072) in the TBM. A novel PUFA, 28∶8n-3, was detected in both mussels with higher amounts in the TBM, which probably reflects a greater dietary contribution of dinoflagellates for this species. Cholesterol was the dominant sterol in both mussels. Other major sterols included brassicasterol, 22-methylcholesterol, trans-22-dehydrocholesterol, and desmosterol. There were significant differences (P<0.05) between the NZGLM and TBM for 12 of the 20 sterols measured. Six sterols showed significant site differences for the NZGLM, and 10 for the TBM. The differences in the FA and sterol composition between the two species may be due to the diet of the NZGLM being more diatom-derived and the diet of the TBM having a greater dinoflagellate component.     

Accelerated solvent extraction for quantitative measurement of fatty acids in plasma and erythrocytes

Consumption of fish rich in n-3 highly unsaturated FAs (i.e., EPA and DHA) has been suggested to decrease the risk of lifestyle-related diseases such as coronary heart disease, cancer, diabetes, and dementia. Blood eevels of those FA are known appropriate biomarkers of both the corresponding dietary FA intakes and fish consumption. In place of traditional handwork methods for extracting FA, we performed an accelerated solvent extraction (ASE) for at least 13 selected FA in plasma and erythrocytes to measure them by GLC. The FA levels (concentrations and compositions) in 35–50 μL of plasma or erythrocytes were extracted by ASE and measured by GLC. Intra-and interassay coefficients of variation were≤6.0% for both blood materials, except with a minor group of FA (≤1.0% of total FA). When ASE was compared with two traditional handwork methods, FA levels in plasma from 18 healthy subjects were all coincident with very high Pearson's correlation coefficients for the three sets of the sama 18 samples (r≤0.85 to 0.95, P<0.0001), except for 18∶0 (r=0.59, P<0.01). Using ASE and GLC, we have developed a new method for determination the levels of FA in plasma and erythrocytes as biomarkers for dietary intake of fish, fat, and FA. This new method makes it feasible to measure small volumes of samples, automatically, quantitatively, routinely, easily, rapidly and cheaply, with acceptable precision and accuracy.     

Relationship between platelet phospholipid FA and mean platelet volume in healthy men

Increased mean platelet volume (MPV) has been suggested as an independent risk factor for acute myocardial infarction and the increased reactivity of large platelets. The aim of this study was to investigate the correlation between platelet phospholipid (PL) PUFA composition and MPV in 139 free-living healthy men ages 20–55 yr (vegans, n=18; ovolacto vegetarians, n=43; modrerate meat-eaters, n=60; and high meateaters, n=18). Each subject completed a semiquantitative Food Frequency Questionnaire and gave a blood sample. Platelet PL FA composition and MPV were determined by standard methods. MPV was significantly greater in the vegans than in the ovolacto vegetarian, moderate, or high meat-eater groups (P<0.01). Both vegan and ovolacto vegetarian groups had significantly higher platelet PL 18∶2n−6 and 22∶4n−6, and lower 20∶5n−3 and 22∶6n−3 compared with the moderate and high meat-eater groups. The vegans demonstrated a significant reduction in 20∶4n−6 and 22∶5n−3 compared with the ovolacto vegetarian, high meat-eater, and moderate meat-eater groups. Bivariate analysis results showed that MPV was significanly positively correlated with platelet PL 18∶2n−6 (P=0.048) and negatively correlated with 20∶3n−6 (P=0.02), 20∶5n−3 (P=0.005), and 22∶5n−3 (P<0.0001), respectively. In a multiple linear regression analysis, after controlling for potential confounding factors such as dietary group, age exercise, body mass index, and dietary polyunsaturated and saturated fat, cholesterol, carbohydrate, and fiber intake, the MPV was still strongly negatively correlated with platelet PL 20∶3n−6 (P=0.003) and 22∶5n−3 (P=0.001). The present data suggest that 20∶5n−3 and 20∶3n−6 may play a role in the structural function of the platelet membrane.     

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.     

A study on the causes for the elevated n−3 fatty acids in cows' milk of alpine origin

The influence of grass-only diets either from rye-grass-dominated lowland pastures (400 m above sea level) or botanically diverse alpine pastures (2000 m) on the FA profile of milk was investigated using three groups of six Brown Swiss cows each. Two groups were fed grass-only on pasture (P) or freshly harvested in barn (B), both for two experimental periods in the lowlands and, consecutively, two periods on the alp. Group C served as the control, receiving a silage-concentrate diet and permanently staying in the lowlands. Effects of vegetation stage or pasture vs. barn feeding on milk fat composition were negligible. Compared with the control, α-linoleic acid (18∶3n−3) consumption was elevated in groups P and B (79%, P<0.001) during the lowland periods but decreased on the alp to the level of C owing to feed intake depression and lower 18∶3n−3 concentration in the alpine forage. Average 18∶3n−3 contents of milk fat were higher in groups, P and B than in C by 33% (P<0.01) at low and by 96% (P<0.001) at high altitude, indicating that 18∶3n−3 levels in milk were to some extent independent of 18∶3n−3 consumption. The cis-9,trans-11 CLA content in milk of grass-fed cows was higher compared with C but lower for the alpine vs. lowland periods whereas the trans-11, cis-13 isomer further increased with altitude. Long-chain n−3 FA and phytanic acid increased while arachidonic acid decreased with grass-only feeding, but none of them responded to altitude. Grass-only feeding increased milk α-tocopherol concentration by 86 and 134% at low and high altitude (P<0.001), respectively. Changes in the ruminal ecosystem due to energy shortage or specific secondary plant metabolites are discussed as possible causes for the high 18∶3n−3 concentrations in alpine milk.     

Trans isomeric octadecenoic acids are related inversely to arachidonic acid and DHA and positively related to mead acid in umbilical vessel wall lipids

Long-chain PUFA play an important role in early human neurodevelopment. Significant inverse correlations were reported between values of trans isomeric and long-chain PUFA in plasma lipids of preterm infants and children aged 1–15 yr as well as in venous cord blood lipids of full-term infants. Here we report FA compositional data of cord blood vessel wall lipids in 308 healthy, full-term infants (gestational age: 39.7±1.2 wk, birth weight: 3528±429 g, mean±SD). The median (interquartile range) of the sum of 18-carbon trans FA was 0.22 (0.13)% w/w in umbilical artery and 0.16 (0.10)% w/w in umbilical vein lipids. Nonparametric correlation analysis showed significant inverse correlations between the sum of 18-carbon trans FA and both arachidonic acid and DHA in artery (r=−0.38, P<0.01, and r=−0.20, P<0.01) and vein (r=−0.36, P<0.01, and −0.17, P<0.01) wall lipids. In addition, the sum of 18-carbon trans FA was significantly positively correlated to Mead acid, a general indicator of EFA deficiency, in both artery (r=+0.35, P<0.01) and vein (r=+0.31, P<0.01) wall lipids. The present results obtained in a large group of full-term infants suggest that maternal trans FA intake is inversely associated with long-chain PUFA status of the infant at birth.     

Chylomicron and VLDL TAG structures and postprandial lipid response induced by lard and modified lard

Alterations in chylomicron and VLDL TAG and the magnitude of postprandial lipemia were studied in healthy volunteers after two meals of equal FA composition but different TAG-FA positional distribution. Molecular level information of individual lipoprotein TAG regioisomers was obtained with a tandem MS method. The incremental area under the response curve of VLDL TAG was large (P=0.021) after modified lard than after lard. In plasma TAG, the difference did not quite reach statistical significance (P=0.086). In general, there were less TAG with palmitic acid in the sn-2 position and more TAG with oleic acid in the sn-2 position in chylomicrons than in fat ingested. From 1.5 to 8 h postprandially, the proportion of individual chylomicron TAG was constant or influenced by TAG M.W. VLDL TAG regioisomerism was similar regardless of the positional distribution of fat ingested. Significant alterations were seen in VLDL TAG FA, in M.W. fractions, and in individual regioisomers with respect to time. The TAG sn-14∶0-18∶1-18∶1+sn-18∶1-18∶1-14∶0, sn-16∶0-16∶1-18∶1+sn-18∶1-16∶1-16∶0, and sn-16∶1-18∶1-18∶1+sn-18∶1-18∶1-16∶1 decreased (P<0.05); and sn-16∶0-16∶0-18∶2+sn-18∶2-16∶0-16∶0, sn-16∶0-16∶0-18∶1+sn-18∶1-16∶0-16∶0, sn-16∶0-18∶1-16∶0, and sn-16∶0-18∶1-18∶2+sn-18∶2-18∶1-16∶0 increased (P<0.05) after both meals. In conclusion, positional distribution of TAG FA was found to affect postprandial lipid metabolism in healthy normolipidemic subjects.     

Modulation of renal injury in pcy mice by dietary fat containing n−3 fatty acids depends on the level and type of fat

Low-fat diets and diets containing n−3 fatty acids (FA) slow the progression of renal injury in the male Han:Sprague-Dawley (SPRD)-cy rat model of polycystic kidney disease. To determine whether these dietary fat effects are similar in females and in another model of renal cystic disease, in this study we used both male and female pcy mice to examine the effects of fat level and type on disease progression. Adult pcy mice were fed 4, 10, or 20 g soybean oil/100 g diet for 130 d in study 1. In study 2, weanling pcy mice were fed high or low levels of fat rich in 18∶2n−6 (corn oil, CO) 18∶3n−3 (flaxseed oil/CO 4∶1 g/g, FO), or 22∶6n−3 (algal oil/CO 4∶1 g/g, DO) for 8 wk. In adult pcy mice, low-compared with high-fat diets lowered kidney weights (2.4±0.2 vs. 3.1±0.2 g/100 g body weight, P=0.006) and serum urea nitrogen (SUN) (9.6±0.6 vs. 11.9±0.6 mmol/L, P=0.009), whereas in young pcy mice it reduced renal fibrosis volumes (0.44±0.04 vs. 0.62±0.04 mL/kg body weight, P<0.0001). FO feeding in young pcy mice mitigated the detrimental effects of high fat on fibrosis while not altering kidney size, function, and oxidative damage when compared with the CO-fed mice. In contrast, DO-compared with CO-fed mice had higher kidney weights (2.64±0.07 vs. 2.24±0.08 g/100 g body weight, P=0.005), SUN (9.4±0.57 vs. 7.0±0.62 nmol/L, P<0.0001), and cyst volumes (7.9±0.28 vs. 6.2±0.30 mL/kg body weight, P<0.0001) and similar levels of oxidative damage and fibrosis. The FA compositions of the diets were reflected in the kidneys: 18∶2n−6, 18∶3n−3, and 22∶6n−3 were the highest in the CO, FO, and DO diets, respectively. Dietary effects on kidney disease progression were similar in males and females. A low-fat diet slows progression of renal injury in male and female pcy mice, consistent with findings in the male Han:SPRD-cy rat. Dietary fat type also influenced renal injury, with flaxseed oil diets rich in 18∶3n−3 slowing early fibrosis progression compared with diets rich in 18∶2n−6 or in 22∶6n−3.     

Dietary very long chain fatty acids directly influence the ratio of tetracosenoic (24∶1) to tetracosanoic (24∶0) acids of sphingomyelin in rat liver

Twenty-one groups of weanling male Wistar rats were fed semipurified diets containing 5% (w/w) of different dietary fats. After 2 wk, liver sphingomyelin (SM) fatty acid composition was determined. The ratio of 24∶1 to 24∶0 in liver SM varied over a tenfold range in response to dietary fat type. Stepwise multiple regression analysis indicated that dietary 24∶1, 24∶0, and 22∶1 were the most significant factors in predicting the 24∶1/24∶0 ratio of liver SM. The mathematical relation between the dietary fatty acid composition and liver SM 24∶1/24∶0 was y=1.88 (24∶1)−1.49 (24∶0)+0.21 (22∶1)+0.01 (18∶1)+0.26, r ²=0.95, P<0.0001. These results were confirmed by a second experiment in which the rats were fed olive oil-based diets supplemented with various fatty acid ethyl esters.     

Effects of dietary phenolic compounds on tocopherol, cholesterol, and fatty acids in rats

The effects of the phenolic compounds butylated hydroxytoluene (BHT), sesamin (S), curcumin (CU), and ferulic acid (FA) on plasma, liver, and lung concentrations of α- and γ-tocopherols (T), on plasma and liver cholesterol, and on the fatty acid composition of liver lipids were studied in male Sprague-Dawley rats. Test compounds were given to rats ad libitum for 4 wk at 4 g/kg diet, in a diet low but adequate in vitamin E (36 mg/kg of γ-T and 25 mg/kg of α-T) and containing 2 g/kg of cholesterol. BHT significantly reduced feed intake (P<0.05) and body weight and increased feed conversion ratio; S and BHT caused a significant enlargement of the liver (P<0.001), whereas CU and FA did not affect any of these parameters. The amount of liver lipids was significantly lowered by BHT (P<0.01) while the other substances reduced liver lipid concentrations but not significantly. Regarding effects on tocopherol levels, (i) feeding of BHT resulted in a significant elevation (P<0.001) of α-T in plasma, liver, and lung, while γ-T values remained unchanged; (ii) rats provided with the S diet had substantially higher γ-T levels (P<0.001) in plasma, liver, and lung, whereas α-T levels were not affected; (iii) administration of CU raised the concentration of α-T in the lung (P<0.01) but did not affect the plasma or liver values of any of the tocopherols; and (iv) FA had no effect on the levels of either homolog in the plasma, liver, or lung. The level of an unknown substance in the liver was significantly reduced by dietary BHT (P<0.001). BHT was the only compound that tended to increase total cholesterol (TC) in plasma, due to an elevation of cholesterol in the very low density lipoprotein + low density lipoprotein (VLDL+LDL) fraction. S and FA tended to lower plasma total and VLDL+LDL cholesterol concentrations, but the effect for CU was statistically significant (P<0.05). FA increased plasma high density lipoprotein cholesterol while the other compounds reduced it numerially, but not significantly. BHT, CU, and S reduced cholesterol levels in the liver TC (P<0.001) and percentages of TC in liver lipids (P<0.05). With regard to the fatty acid composition of liver lipids, S increased the n-6/n-3 and the 18∶3/20∶5 polyunsaturated fatty acids (PUFA) ratios, and BHT lowered total monounsaturated fatty acids and increased total PUFA (n−6+n−3). The effects of CU and FA on fatty acids were not highly significant. These results suggest some in vivo interactions between these phenolic compounds and tocopherols that may increase the bioavailability of vitamin E and decrease cholesterol in rats.     

Blood pressure,serum lipids,and fatty acids in populations on a lake-fish diet or on a vegetarian diet in Tanzania

Major risk factors for coronary heart disease were assessed in two populations of Tanzania, one on a fish diet (FD) living along the coast of Lake Nyasa, and the other, mainly on a vegetarian diet (VD), living in a farming area. Lower blood pressure values were found in the FD subjects (n=618) vs. VD (n=618) (systolic blood pressure, SBP, 120±15 vs. 135±20,P<0.01; diastolic blood pressure, DBP, 70±9 vs. 78±11,P<0.01, respectively). In an FD subgroup (n=61), total cholesterol (TC) (122 vs. 136 mg/dL,P<0.01); triglycerides (TG) (82 vs. 105 mg/dL,P<0.01); and lipoprotein (a) [Lp(a)] (19.9±18.4 vs. 32.3±22.4,P<0.001) were lower than in a VD subgroup (n=55). Serum fatty acids (FA) in the FD subgroup were as follows: eicosapentaenoic acid (EPA) (20∶5) 2.48 vs. 0.72%, docosahexaenoic acid (DHA) (22∶6) 5.93 vs. 1.49%, vs. the VD, respectively. Arachidonic acid (AA) (20∶4n-6) also was higher in the FD vs. the VD group (9.85 vs. 8.30%,P<0.05), whereas 18∶2n-6 was about double (23.97 and 14.85%) in VD vs. FD. The peculiar serum FA pattern in FD reflected the FA of dietary fish. In fact, in four main species of lake fish, DHA was 8–19%, higher than EPA (1.8–4.2%), in contrast with the situation in cold-water fish, and AA was 5.8–8%, higher than in cold-water fish. The data, obtained in populations strictly on natural, unprocessed, low-fat diets, show that a diet based on freshwater fish results in lower BP, serum TC, TG, and Lp(a), and suggests that serum AA is not reduced when the major dietary n-3 is DHA rather than EPA.     

Type 1 diabetes compromises plasma arachidonic and docosahexaenoic acids in newborn babies

The activity of Δ6- and Δ5-desaturase, enzymes required for the synthesis of AA and DHA, are impaired in human and experimental diabetes. We have investigated whether neonates of type 1 diabetic women have compromised plasma AA and DHA at birth. Cord blood was obtained from healthy babies born to mothers with (n=31) and without (n=59) type 1 diabetes. FA composition of plasma choline phosphoglycerides (CPG), TG, and cholesterol esters (CE) was assayed. The neonates of the diabetics had lower levels of AA (20∶4n−6, P<0.0001), adrenic acid (22∶4n−6, P<0.01), Σn−6 metabolites (P<0.0001), docosapentaenoic acid (22∶5n−3, P<0.0001), DHA (22∶6n−3, P<0.0001), Σn−3 (P<0.0001), and Σn−3 metabolites (P<0.0001) in CPG compared with the corresponding babies of the nondiabetic mothers. Similarly, they had lower levels of AA (P<0.05), Σn−6 metabolites (P<0.05), DHA (P<0.0001), and Σn−3 metabolites (P<0.01) in plasma CE. There was also a nonsignificant reduction of AA and DHA in TG in the babies of the diabetic group. The current investigation indicates that healthy neonates born to mothers with type 1 diabetes have highly compromised levels of AA and DHA. These nutrients are of critical importance for neurovisual and vascular system development. In poorly controlled maternal diabetes, it is conceivable that the relative “insufficiency” of AA and DHA may exacerbate speech and reading impairments, behavioral disorders, suboptimal performance on developmental tests, and lower IQ, which have been reported in some children born to mothers with type 1 diabetes mellitus. Further studies are needed to understand the underlying mechanism for this biochemical abnormality and its implications for fetal and infant development.     

In vitro comparison of hepatic metabolism of 9cis-11 trans and 10trans-12cis isomers of CLA in the rat

Hepatic metabolism of the two main isomers of CLA (9cis-11 trans, 10trans-12cisC_18∶2) was compared to that of oleic acid (representative of the main plasma FA) in 16 rats by using the in vitro method of incubated liver slices. Liver tissue samples were incubated at 37°C for 17h under an atmosphere of 95% O₂/5%CO₂ in a medium supplemented with 0.75 mM of FA mixture (representative of circulating nonesterified FA) and with 55 μM [1-¹⁴C]9cis-11 trans C_18∶2, [1-¹⁴C]10trans-12cis C_18∶2, or [1-¹⁴C]oleate. The uptake of CLA by hepatocytes was similar for both isomers (9%) and was three times higher (P<0.01) than for oleate (2.6%). The rate of CLA isomer oxidation was two times higher (49 and 40% of incorporated amounts of 9cis-11 trans and 10trans-12 cis, respectively) than that of oleate (P<0.01). Total oxidation of oleate and CLA isomers into [¹⁴CO₂] was low (2 to 7% of total oxidized FA) compared to the partial oxidation (93 to 98%) leading to the production of [¹⁴C] acid-soluble products. CLA isoemrs escaping from catabolism were both highly desaturated (26.7 and 26.8%) into conjugated 18∶3. Oleate and CLA isomers were mainly esterified into neutral lipids (30%). They were slowly secreted as parts of VLDL particles (<0.4% of FA incorporated into cells), the extent of secretion of oleate and of 10trans-12 cis being 2.2-fold higher than that of 9cis-11 trans (P<0.02). In conclusion, this study clearly showed that both CLA isomers were highly catabolized by hepatocytes, reducing their availability for peripheral tissues. Moreover, more than 25% of CLA escaping from catabolism was converted into conjugated 18∶3, the biological properties of which remain to be elucidated.     

Cardiac and vascular structure and function are related to lipid peroxidation and metabolism

The present study investigated possible relationships between left ventricular mass, intima-media thickness of the carotid artery (IMT), total arterial compliance, and lipid status in a population sample of 58 apparently healthy subjects aged 20 to 69. By stepwise multiple regression analysis, including age, blood pressure, and smoking, left ventricular mass index, measured by M-mode echocardiography, increased by 13.0 g/m² for each 1 standard deviation (SD=0.11 μM, r=0.60, P<0.01) increase in plasma malondialdehyde and 9.50 g/m² per SD increase in plasma 8-iso-prostaglandin F_2α in women only (SD=8.88 ng/L, r=0.44, P=0.01). Each 1-SD (SD=0.27 g/L) increase in apolipoprotein B was associated with a 63 μm increase in IMT (r=0.47, P=0.01) and a 0.27 mL/min/m²/mm Hg (r=−0.60, P<0.01) decrease in stroke index/pulse pressure ratio, reflecting total arterial compliance in women. In men, each 1-SD increase in the proportion of stearic acid (18∶0) in serum cholesterol esters (SD=0.12 percent units) reduced the transmitral E/A ratio, measured by Doppler echocardiography, reflecting left ventricular diastolic function, by 0.10 units (r=−0.29, P<0.05). Thus, important cardiovascular characteristics, such as left ventricular mass, left ventricular diastolic function, carotid IMT, and total arterial compliance, were independently predicted by indices of lipid metabolism and peroxidation in apparently healthy subjects.     

Assessment of dietary and genetic factors influencing serum and adipose fatty acid composition in obese female identical twins

Fourteen pairs of obese female monozygotic twins were recruited for a study of genetic influences on serum and adipose fatty acid (FA) composition. Following 1 wk of inpatient stabilization, fasting serum and adipose tissue obtained by surgical excision were analyzed by thin-layer and gas chromatography. Intrapair resemblances (IPR) for individual FA were assessed by Spearman rank correlation and by analysis of variance and were found in serum cholesteryl esters (CE), triglycerides (TG), and adipose TG. With two exceptions (CE linoleate and adipose eicosapentaenoate), these IPR were limited to the nonessential FA. Palmitate had significant IPR in four lipid fractions; in serum CE and adipose TG palmitate was strongly correlated with multiple measures of adiposity. In contrast to other lipid fractions, serum phosphatidylcholine (PC) FA had 12 IPR, of which 6 were essential FA including arachidonate (r=0.76, P<0.0005), eicosapentaenoate (r=0.78, P<0.0005), and docosahexaenoate (r=0.86, P<0.0001). The PC IPR could not be explained by analysis of preadmission 7-d food records. After dividing the pairs into two groups differing and nondiffering according to fat intake of individuals in the pair, there was no evidence of a gene-environment interaction between fat intake and FA composition. The IPR for nonessential FA indicate that there is active genetic control of either food choices or postabsorptive metabolic processing. The high level of IPR in the PC fraction in contrast to the other lipid fractions suggests strong genetic influence over selection of specific FA for this membrane fraction independent of diet.     

Use of α-tocopherol acetate to improve fresh pig meat quality of full-fat rapeseed-fed pigs

Thirty-two pigs were allocated to one of four diets, FFRD0 and FFRD200, containing full-fat rapeseed (FFR), 150 g/kg [25–50 kg liveweight (LW)], and 250 g/kg (50–90 kg LW), or CD0 and CD200, containing equivalent quantities of rapeseed meal and 34 g/kg (25–50 kg LW) or 59.2 g/kg (50–90 kg LW) coconut oil and lard (0.5:0.5, w/w). Diets FFRD200 and CD200 were supplemented with 200 mg/kg α-tocopherol acetate (ATA). ATA supplementation significantly (P<0.001) reduced muscle drip loss. The melting point (°C) of subcutaneous fat was significantly lowered by FFR (P<0.001) but increased by ATA supplementation (P<0.05). Tissue α-tocopherol (AT) concentrations were significantly increased by ATA supplementation. Longissimus dorsi AT concentration was positively correlated with AT concentration in subcutaneous fat (r=0.86) and in plasma at 35 (r=0.65) and 77 (r=0.85) days of feeding (P<0.001). In both L. dorsi and subcutaneous adipose tissue lipids, FFRD caused a significant (P<0.001) decrease in the ratio of n-6 to n-3 fatty acids and a significant (P<0.001) increase in the ratio of polyunsaturated to saturated fatty acids. AT supplementation significantly reduced the susceptibility of L. dorsi and subcutaneous fat to lipid oxidation during storage at 4°C for up to 16 d. For all dietary treatments and storage times, lipid oxidation [mg malondialdehyde (MDA)/kg muscle] was greater in the surface layer (0–2.5 mm) of L. dorsi than below the surface (2.5–5 mm). Oxidative stability of L. dorsi lipids to iron-induced lipid peroxidation was significantly improved (P<0.001) by AT supplementation. Meat from pigs fed FFRD diets was significantly less stable to iron-induced oxidation (nmoles MDA/mg protein) at the longer incubation periods (100 and 200 min). The susceptibility of L. dorsi to iron-induced lipid oxidation decreased as the ratio of the tissue concentration of AT to unsaturated fatty acid increased.