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It has been demonstrated that in pathological conditions with an increase in the calculated mean melting point (MMP) of phospholipid (PL) fatty acids (FA) there are changes in the composition of the saturated FA (SFA), which partially counteract this effect: shorter-chain SFA with lower melting points are increased, while longer-chain less fluid SFA are suppressed. The aim of this study was to determine whether there are differences in MMP during pregnancy and in the newborn and, if so, whether similar adaptive changes occur in the composition of the SFA The FA composition of plasma PL was determined in healthy women ( n-16) twice during pregnancy (15–24 wk and 29–36 wk) and at delivery and in umbilical venous blood obtained at birth. The MMP of maternal PL was significantly higher at delivery compared to mid-gestation, due to a loss of highly unsaturated FA (HUFA) which were replaced by SFA. In addition, changes in the SFA occurred; 16∶0 with lower melting point was higher while 18∶0 with higher melting point was lower at delivery. MMP of PL FA in umbilical plasma was lower than in maternal plasma at delivery, which was due to higher HUFA content. In contrast to maternal plasma, 16∶0 was lower while 18∶0, 20∶0 and 24∶0 were higher in umbilical plasma resulting in a higher MMP of SFA, tending to raise the overall MMP. It can be concluded that, during pregnancy and in the newborn, the FA composition of SFA changes in a way to counteract changes in MMP induced by reduced and increased HUFA, respectively. [ABSTRACT FROM AUTHOR]

Conclusion We conclude that13C α-linolenic acid is converted into its LCP. The conversion of α-linolenic acid into its LCP appears to be inhibited on diets rich in EPA/DHA, while it appears not to be influenced by age. In addition, oxidation of α-linolenic acid is not dependent on age or dietary α-linolenic acid, but may be slightly increased on diets rich in EPA/DHA. [ABSTRACT FROM AUTHOR]

The effects of a diet rich in alpha-linolenic acid vs. one rich in oleic acid on the oxidation of uniformly labeled 13C-alpha-linolenic acid and its conversion into longer-chain polyunsaturates (LCP) were investigated in vivo in healthy human subjects. Volunteers received a diet rich in oleic acid (n = 5) or a diet rich in alpha-linolenic acid (n = 7; 8.3 g/d) for 6 wk before and during the study. After 6 wk, subjects were given 45 mg of 13C-alpha-linolenic acid dissolved in olive oil. Blood samples were collected at t = 0, 5, 11, 24, 96, and 336 h. Breath was sampled and CO2 production was measured each hour for the first 12 h. The mean (+/- SEM) maximal absolute amount of 13C-eicosapentaenoic acid (EPA) in plasma total lipids was 0.04 +/- 0.01 mg in the alpha-linolenic acid group, which was significantly lower (P = 0.01) than the amount of 0.12 +/- 0.03 mg 13C-EPA in the oleic acid group. Amounts of 13C-docosapentaenoic acid (DPA) and 13C-docosahexaenoic acid (DHA) tended to be lower as well. The mean proportion of labeled alpha-linolenic acid (ALA) recovered as 13CO2 in breath after 12 h was 20.4% in the ALA and 15.7% in the oleic acid group, which was not significantly different (P = 0.12). The cumulative recovery of 13C from 13C-ALA in breath during the first 12 h was negatively correlated with the maximal amounts of plasma 13C-EPA (r = -0.58, P = 0.047) and 13C-DPA (r = -0.63, P = 0.027), but not of 13C-DHA (r = -0.49, P = 0.108). In conclusion, conversion of 13C-ALA into its LCP may be decreased on diets rich in ALA, while oxidation of 13C-ALA is negatively correlated with its conversion into LCP. In a few pilot samples, low 13C enrichments of n-3 LCP were observed in a diet rich in EPA/DHA as compared to oleic acid.

A method is described for the direct and continuous monitoring of lipid peroxidation in an aqueous suspension of sonicated liposomes. By means of ultraviolet difference spectroscopy using tandem cuvettes, the formation of conjugated dienes during liposome peroxidation can be followed. Using this technique, the effect of the fatty acid composition of liposomes on lipid peroxidation can be studied. The results show that both the extent and the time scale of lipid peroxidation are influenced by the fatty acid composition of the phospholipid liposomes. This was confirmed also by other methods, such as measurement of the formation of lipid hydroperoxides and measurement of the decrease in polyunsaturated fatty acids. The advantage of the method described is the direct and continuous monitoring of phospholipid peroxidation in an aqueous environment, without subsampling and extraction of peroxidation products into organic solvents. Using this experimental approach based on difference spectra the contributions from changes in liposome, CuSO4 and H2O2 concentrations are canceled, thus improving sensitivity. The method can be employed for measuring the susceptibility to peroxidation of membrane phospholipids from fatty acid modified endothelial cells.

Wistar rats were fed a control diet containing 5 energy % (en %) sunflowerseed oil or diets containing 50 en % of either palm oil, rich in saturated fatty acids, or sunflowerseed oil, high in linoleic acid, for at least eight weeks. Arterial thrombosis tendency, measured by the aorta loop technique, tended to be lowered by the palm oil diet and was lowered significantly by the sunflowerseed oil diet, compared with the control. Aggregation of platelets in whole blood activated with collagen was not altered by palm oil feeding, but was enhanced in the sunflowerseed oil group, compared with the control. The concomitant formation of thromboxane A2 was decreased by palm oil feeding, although formation of prostacyclin did not change; the ratio of thromboxane/prostacyclin formed was decreased significantly in the palm oil group. Compared with the control diet, platelet membrane fluidity, measured by fluorescence polarization, was not altered in the palm oil group and was significantly increased only by sunflowerseed-oil feeding. Thus, although palm oil contains about 50% saturated fatty acids, it did not increase arterial thrombosis tendency and tended to decrease platelet aggregation, as compared with highly polyunsaturated sunflowerseed oil.