Endogenous surfactant metabolism in critically ill infants measured with stable isotope labeled fatty acids

Little is known about endogenous surfactant metabolism in infants, because radioactive isotopes used for this purpose in animals cannot be used in humans. We developed a novel and safe method to measure the endogenous surfactant kinetics in vivo in humans by using stable isotope labeled fatty acids. We infused albumin-bound [U-13C]palmitic acid (PA) and [U-13C]linoleic acid (LLA) for 24 h in eight critically ill infants (mean+/-SD: weight: 3.7+/-1.3 kg: age: 51.3+/-61.6 d) who required mechanical ventilation. The 13C enrichment of PA and LLA in surfactant phosphatidylcholine (PC), obtained from tracheal aspirates, was measured by gas chromatography combustion interface-isotope ratio mass spectrometry. We measured a significant incorporation of both 13C-PA and 13C-LLA into surfactant PC. PC-PA and PC-LLA became enriched after 8.7+/-4.9 h (range: 3.4-17.3) and 10.0+/-7.2 h (range: 3.0-22.4), respectively; the times at maximum enrichment were 49.2+/-8.9 and 45.6+/-19.3 h, respectively. The fractional synthesis rate of surfactant PC-PA ranged from 0.4 to 3.4% per h, whereas the fractional synthesis rate of PC-LLA ranged from 0.5 to 3.8% per h. The surfactant PC-PA and PC-LLA half-lives ranged from 16.8 to 177.7 and 23.8 to 144.4 h, respectively. This method provides new data on surfactant metabolism in infants requiring mechanical ventilation. We found that synthesis of surfactant from plasma PA and LLA is a slow process and that there were marked differences in PC kinetics among infants. This variability could be related to differences in lung disease and could affect the clinical course of the respiratory failure.

High-linoleate and high-alpha-linolenate diets affect learning ability and natural behavior in SAMR1 mice

Semipurified diets incorporating either perilla oil [high in alpha-linolenate, 18:3(n-3)] or safflower oil [high in linoleate, 18:2(n-6)] were fed to senescence-resistant SAMR1 mouse dams and their pups. Male offspring at 15 mo were examined using behavioral tests. In the open field test, locomotor activity during a 5-min period was significantly higher in the safflower oil group than in the perilla oil group. Observations of the circadian rhythm (48 h) of spontaneous motor activity indicated that the safflower oil group was more active than the perilla oil group during the first and second dark periods. The total number of responses to positive and negative stimuli was higher in the safflower oil group than in the perilla oil group in the light and dark discrimination learning test, but the correct response ratio was lower in the safflower oil group. The difference in the (n-6)/(n-3) ratios of the diets reflected the proportions of (n-6) polyunsaturated fatty acids, rather than those of (n-3) polyunsaturated fatty acids in the brain total fatty acids, and in the proportions of (n-6) and (n-3) polyunsaturated fatty acids in the total polyunsaturated fatty acids of the brain phospholipids. These results suggest that in SAMR1 mice, the dietary alpha-linolenate/linoleate balance affects the (n-6)/(n-3) ratio of brain phospholipids, and this may modify emotional reactivity and learning ability.

Effects of dietary docosahexaenoic acid on surface molecules involved in T cell proliferation

It is known that n-3 polyunsaturated fatty acids (PUFA) such as docosahexaenoic acid (DHA) suppress immunity as compared with n-6 PUFA such as linoleic acid (LA), but the mechanism involved in this phenomenon is still unclear. The present study was designed to assess the effect of dietary DHA on the surface molecules involved in T cell proliferation. Weanling male C57BL/6 mice were divided into four dietary groups that were fed a 10% fat diet for 4 weeks varying in amounts of DHA and LA. As the dietary DHA concentration increased, the surface expression of CD4 and CD8 on splenic T cells decreased, while that of CD28 increased. The surface expression of CD3, however, was invariable in all dietary groups. DNA synthesis of splenic T cells, induced by CD3 crosslinkage with anti-CD3 epsilon monoclonal antibody in the presence of CD28-mediated costimulation, increased as the DHA concentration was elevated. These observations suggest that diets rich in DHA exert some of their immunomodulatory effects by a downregulation of surface expression of CD4 and CD8 and by an upregulation of CD28-mediated costimulatory signal.

Comparison of the effects of two low fat diets with different alpha-linolenic:linoleic acid ratios on coagulation and fibrinolysis

Fish oils rich in eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have been demonstrated to alter coagulation and fibrinolysis variables. This study compared the effects of a traditional cholesterol-lowering diet and a similar diet, which had 50% of the linoleic acid (LA) replaced with the 18 carbon n-3 fatty acid, alpha-linolenic acid (ALA), on selected hemostatic variables. After a 2-week run-in diet with 39.5% total energy (en) from fat, 29 healthy male subjects consumed a 31.5% en fat diet with approximately 7% en from polyunsaturated fat and an ALA:LA ratio of either 1:1.2 (ALA-rich, n=15) or 1:21 (LA-rich, n=14) for 6 weeks. Blood was collected at the beginning, middle and end of test diets for analysis of Factor VIIc and VIIIc, fibrinogen, von Willebrand factor, activated protein C resistance (APC resistance), tissue plasminogen activator and plasminogen activator inhibitor type-1 activities and/or protein concentrations and platelet fatty acids. The ALA-rich diet tripled the percentage of platelet EPA, (P < 0.0005) but had little effect on coagulation and fibrinolysis. The APC ratio demonstrated increased anticoagulant activity on the ALA-rich diet (P < 0.001) only. Studies in patients with vascular pathologies are indicated to corroborate the current findings. Greater ratios of ALA:LA, achievable only with greater amounts of polyunsaturated fat, may be necessary to produce the effects demonstrated after feeding fish oils.

Regulation of plasma and liver total cholesterol levels by dietary oleic acid in rats fed a high-cholesterol diet

The effects of diets containing fats and oils or fatty acids on the lipid metabolism were investigated in male rats of the Wistar strain fed hypercholesterolemic diets, especially focusing our attention on the correlation between dietary oleic acid (OLE) contents and the levels of plasma and liver total cholesterol (T-CHOL) or the fatty acid profiles in plasma and liver CHOL-ester. In the rats fed the free (FR)-type fatty acids, the concentrations of plasma and liver T-CHOL were high and the amounts of neutral steroids excreted into the feces were low when compared with those of rats given the triacylglycerol (TG)-type fatty acids, showing that TG-type fatty acids suppress the intestinal CHOL absorption more than the FR-type fatty acids do. The concentrations of plasma T-CHOL were highest in rats fed the oleic acid (OLE)-rich diets, followed in order by rats supplied with the palmitic acid (PAL)-rich diets, the hydrogenated coconut oil (HCO) diet, and the linoleic acid (LIN)-rich diets; the lowest was in rats given tristearin (TSTE) and linseed oil (LIS) diets. A positive correlation was obtained between the dietary OLE contents and the levels of plasma and liver T-CHOL or OLE in the plasma and liver CHOL-ester, and an inverse correlation between dietary OLE contents and the amounts of excreted neutral steroids. These results suggest that the dietary OLE contents regulate the levels of plasma and liver T-CHOL in CHOL-loaded rats.

LDL isolated from Greek subjects on a typical diet or from American subjects on an oleate-supplemented diet induces less monocyte chemotaxis and adhesion when exposed to oxidative stress

The mechanisms underlying the cardiovascular benefits of Mediterranean-style diets are not fully understood. The high content of monounsaturated fatty acids in Mediterranean-style diets derived from oleate-rich olive oil may be beneficial in reducing low density lipoprotein (LDL) oxidation and its subsequent development of atherogenic properties. This study sought to assess the proinflammatory potential of LDL isolated from subjects consuming a diet naturally rich in olive oil. LDL was isolated from 18 Greek, 18 American, and 11 Greek-Americans subjects, all of whom were living in the United States. Fatty acid composition and vitamin E levels of LDL were determined, as was the extent of copper-mediated LDL oxidation. LDL was also mildly oxidized by exposure to fibroblasts overexpressing 15-lipoxygenase and tested in vitro for bioactivity by determining its ability to stimulate monocyte chemotaxis and adhesion to endothelial cells. To confirm that dietary fatty acids influence the proinflammatory properties of mildly oxidized LDL, LDL was also isolated from 13 healthy American subjects after consumption of an 8-week liquid diet supplemented with either oleic (n=6) or linoleic (n=7) acid and tested for bioactivity in a similar fashion. There were no differences in the baseline lipid profiles among the Greeks, Americans, or Greek-Americans. Oleic acid content in LDL was 20% higher in the Greek compared with the American or Greek-American subjects (P<0.001). The extent of in vitro LDL oxidation, measured by conjugated diene formation, was lower in the Greek subjects (P<0.02), but there was no difference in the lag time. Induction of monocyte chemotaxis and adhesion by mildly oxidized LDL was decreased by 42% in the Greek group compared with the American subjects (P<0.001). There was an inverse correlation between the oleic acid content of LDL and stimulation of monocyte chemotaxis (r=-0.64, P<0.001) and a positive correlation between the polyunsaturated fatty acid content of LDL (total linoleate and arachidonic acids levels in LDL) and stimulation of monocyte chemotaxis (r=0.51, P<0.01) in the entire cohort. There were no differences in LDL vitamin E content between the groups. In the liquid-diet groups, the oleic acid-supplemented group had a 113% higher oleic acid content in LDL and a 46% lower linoleic acid content in LDL than the linoleate-supplemented group (P<0.001), whereas the vitamin E content in LDL was equal in both groups. When exposed to oxidative stress, the LDL enriched in oleic acid promoted less monocyte chemotaxis (52% lower) and reduced monocyte adhesion by 77% in comparison with linoleate-enriched LDL (P<0.001). There was a strong, negative correlation between oleic acid LDL content and monocyte adhesion (r=-0.73, P<0.001) and a strong, positive correlation between polyunsaturated fatty acid LDL content and monocyte adhesion (r=0.87, P<0.001). This study demonstrates that dietary enrichment of LDL with oleic acid is realistic and readily achieved by using diets currently in use in Mediterranean countries. In addition, these data suggest that LDL enriched with oleic acid and reduced in polyunsaturated fatty acids may be less easily converted to a proinflammatory, minimally modified LDL.

Research note: effect of duodenal--infused unsaturated fatty acids on dairy milk composition

Investigations were conducted to assess the effect of duodenal infusions of oleic and linoleic acids both on milk composition and fatty acid patterns of milk fat. The investigations were carried out in two trials, I and II, each with 3 cows, fitted with a ruminal and a duodenal cannula. 56 g of oleic acid (Trial I) and 46 g linoleic acid (Trial II) were infused daily into the duodenum over a period of 7 days, while no application of fatty acids acted as a control in each case. An increase in milk fat content was observed in both trials whereas the content of protein and lactose in milk remained unaffected. In both trials the milk oleic acid and linoleic acid concentrations increased. In trial I C18:1 increased from 14.8 to 18.7%. In trial II C18:2 increased from 2.5 to 5.8% of total lipids. It was estimated that 84.8% of the infused C18:1 and 86.5% of C18:2 were transferred into milk fat.

Involvement of lipid peroxidation in free fatty acid-induced isolated rat pancreatic acinar cell injury

It was reported that free fatty acids degraded from triglycerides by lipase may play a major role in acute necrotizing or hyperlipidemia-induced pancreatitis. We hypothesized that this injury may be related to the peroxidation of cell membrane phospholipids and tested this hypothesis using isolated pancreatic acini. Pancreatic acini were prepared from male Sprague-Dawley rats by collagenase digestion. Linoleic acid was added (0.1-1.0 mM) to the acinar cell suspension to induce cell injury. Acinar cell damage was measured by lactate dehydrogenase release and by trypan blue exclusion. Phosphatidylcholine hydroperoxide and alpha-tocopherol in the acinar cells were measured. Protective effects of alpha-tocopherol (0.5, 5.0 mM) against this type of cell injury were also evaluated. When isolated acinar cells were treated with linoleic acid, a significant decrease in viability was observed in a time- and dose-dependent manner. In addition, the levels of phosphatidylcholine hydroperoxide after treatment of 0.5 mM of linoleic acid were increased and levels of alpha-tocopherol were decreased significantly. alpha-Tocopherol significantly ameliorated both cellular injury (p < 0.01) and increases in phosphatidylcholine hydroperoxide (p < 0.01). These data suggest that lipid peroxidation of the cellular membrane is an important component of the pancreatic cell injury mediated by free fatty acids.

Fatty acid nutriture in hospitalized elderly women

OBJECTIVE

The aim of this study was to measure the fatty acid (FA) dietary intakes and the FA composition of plasma total lipids in a selected group of hospitalized elderly patients.

METHODS

Twenty-three women aged 76 to 99 years were recruited. FA were analyzed in 5-day duplicate portions and in plasma by gas liquid chromatography.

RESULTS

The hospitalized elderly women ingested an average of 5.22 megajoules (MJ) and 45.9 g of lipids per day. Polyunsaturated fatty acids (PUFA) represented 11.0% and saturated fatty acids (SFA) 53.6% of the lipid intake. Minimal recommendations for linoleic acid intake were reached in average, but 32% of the patients ingested less than 3 g of linoleic acid/d. Eighty-six percent received less than 0.5% of energy for alpha-linolenic acid and 64% had low intakes in very long-chain n-3 FA. In parallel, these patients presented several biochemical signs of essential fatty acids (EFA) insufficiency (decrease in linoleic acid, increase in monounsaturated fatty acids (MUFA), in n-7 FA and in indexes of delta-6 and delta-9 desaturase activities).

CONCLUSIONS

Hospitalized elderly patients have low PUFA intakes and show biochemical indices of EFA insufficiency. These patients might benefit from a nutritional supplementation providing both EFA and antioxidant micronutrients to limit the risk of skin troubles, immune system impairment and vascular disease often observed in institutionalized elderly subjects.

Health aspects of fish and n-3 polyunsaturated fatty acids from plant and marine origin

An expert workshop reviewed the health effects of n-3 polyunsaturated fatty acids (PUFA), and came to the following conclusions. 1. Consumption of fish may reduce the risk of coronary heart disease (CHD). People at risk for CHD are therefore advised to eat fish once a week. The n-3 PUFA in fish are probably the active agents. People who do not eat fish should consider obtaining 200 mg of very long chain n-3 PUFA daily from other sources. 2. Marine n-3 PUFA somewhat alleviate the symptoms of rheumatoid arthritis. 3. There is incomplete but growing evidence that consumption of the plant n-3 PUFA, alpha-linolenic acid, reduces the risk of CHD. An intake of 2 g/d or 1% of energy of alpha-linolenic acid appears prudent. 4. The ratio of total n-3 over n-6 PUFA (linoleic acid) is not useful for characterising foods or diets because plant and marine n-3 PUFA show different effects, and because a decrease in n-6 PUFA intake does not produce the same effects as an increase in n-3 PUFA intake. Separate recommendations for alpha-linolenic acid, marine n-3 PUFA and linoleic acid are preferred.

Delta6- and delta5-desaturase activities in the human fetal liver: kinetic aspects

Delta6- and delta5-desaturase activities were studied in human fetal liver microsomes obtained after legally approved therapeutic abortion. Enzyme activities were measured by a radiochemical method using reverse-phase high performance liquid chromatography (HPLC). Free and phospholipid fatty acids were assessed in each liver sample by a combination of thin-layer chromatography (TLC) and gas-liquid chromatography (GLC) procedures. The kinetic measurements showed higher delta6-desaturase activity for the n-3 series than for the n-6 series. Apparent Km of 6.5, 3.9, and 24.5 microM and Vm of 7.5, 9.1, and 24.4 pmol x min(-1) x mg(-1) were obtained, respectively, for 18:2n-6 delta6-, 20:3n-6 delta5-, and 18:3n-3 delta6-desaturases. Beyond 30, 20, and 60 microM of 18:2n-6, 20:3n-6, and 18:3n-3 concentration, respectively, the enzyme activity deviated from Michaelis-Menten kinetics, suggesting an inhibition by excess substrate which is unlikely to occur in vivo as endogenous substrate concentration is much lower. We observed a breakdown in linearity between desaturase activity and microsomal protein concentration beyond 4-5 mg microsomal protein, whatever the enzyme or substrate. Both this phenomenon and the inhibition due to excess substrate should be taken into account in the determination of delta6- and delta5-desaturase activities. Comparison of concentrations of the respective endogenous substrates and the kinetic constants of each enzyme suggested that the higher delta6-desaturase activity observed for the n-3 series than for the n-6 series is not physiologically relevant in human fetal liver.

Effects of conjugated linoleic acid on body fat and energy metabolism in the mouse

Conjugated linoleic acid (CLA) is a naturally occurring group of dienoic derivatives of linoleic acid found in the fat of beef and other ruminants. CLA is reported to have effects on both tumor development and body fat in animal models. To further characterize the metabolic effects of CLA, male AKR/J mice were fed a high-fat (45 kcal%) or low-fat (15 kcal%) diet with or without CLA (2.46 mg/kcal; 1.2 and 1.0% by weight in high- and low-fat diets, respectively) for 6 wk. CLA significantly reduced energy intake, growth rate, adipose depot weight, and carcass lipid and protein content independent of diet composition. Overall, the reduction of adipose depot weight ranged from 43 to 88%, with the retroperitoneal depot most sensitive to CLA. CLA significantly increased metabolic rate and decreased the nighttime respiratory quotient. These findings demonstrate that CLA reduces body fat by several mechanisms, including a reduced energy intake, increased metabolic rate, and a shift in the nocturnal fuel mix.

A high linoleic acid diet increases oxidative stress in vivo and affects nitric oxide metabolism in humans

Evidence from in vitro studies shows that increased intake of polyunsaturated fatty acids leads to increased oxidative stress, which may be associated with endothelial damage. We measured the urinary levels of 8-iso-PGF2alpha and nitric oxide metabolites as well as plasma sICAM-1 levels from healthy subjects after strictly controlled diets rich in either linoleic acid (LA, C18:2 n-6) or oleic acid (OA, C18:1 n-9). Thirty-eight volunteers (20 women and 18 men, mean age 27 years) consumed a baseline diet rich in saturated fatty acids (SFA) for 4 weeks and were then switched to either a high LA diet (11.5 en%) or a high OA diet (18.0 en%) also for 4 weeks. During the LA and OA diets, nearly all food was provided for the whole day. A control group of 13 subjects consumed their habitual diet throughout the study. Urinary excretion of 8-iso-PGF2alpha was significantly increased after the LA diet (170 vs 241 ng/mmol creatinine, P=0.04), whereas the urinary concentration of nitric oxide metabolites decreased (4.2 vs 2.6 mg/mmol creatinine, P=0.03). No significant changes were seen in the OA group. Significant differences between the LA and control group were found for both 8-oxo-PGF2alpha (P=0.03) and NO (P=0.02), whereas the OA and LA groups did not differ with respect to any parameter. Also plasma sICAM-1 remained unchanged in both groups throughout the study. In conclusion, the high-LA diet increased oxidative stress and affected endothelial function in a way which may in the long-term predispose to endothelial dysfunction.

Dietary hydroperoxides of linoleic acid decompose to aldehydes in stomach before being absorbed into the body

Our previous study (Biochim. Biophys. Acta 1393 (1998) 336-348, this issue) found that dietary hydroperoxides of trilinoleoylglycerol were broken down, releasing linoleic acid hydroperoxides (LA-OOH) in the stomach without reaching the intestines. The present paper describes the catabolic fate of LA-OOH in rat gastrointestines, in an attempt to elucidate those products which can be absorbed into the body. At an intragastric dose of 6.5 or 18 mumol, LA-OOH was not transported to the intestines as determined by HPLC. At large doses (200 or 800 mumol), much greater than that in the daily diet, there was partial leakage of LA-OOH to the intestines. The periodical fate was analyzed with 17.2 mumol [U-14C]LA-OOH chemically and radiochemically. Exemplifying the product composition at 30 min after treatment (as percentage of dosed amount), 27% unchanged LA-OOH, 9.7% epoxyketones, 3.5% hydroxyls (LA-OH), 2.4% decomposed aldehydes, and 13% unknown products were found in the gastric lumen. Another 25% was incorporated in the gastric tissue, and the other 6.4% occurred in the intestinal lumen and tissue as decomposed aldehyde. The LA-OH further decomposed to aldehydes with time in the stomach. When an aldehyde mixture was prepared and dosed, significant increases in hexanal and 4-hydroxynonenal were detected in the liver 15 h later. These results show that the dietary LA-OOH is decomposed to aldehydes in the stomach and that aldehydes are partly absorbed into the body.

Use of deuterium oxide to measure de novo fatty acid synthesis in normal subjects consuming different dietary fatty acid composition1

The effect of dietary linoleic (C18:2n-6) and palmitic acids (C16:0) on rate of hepatic de novo fatty acid synthesis was assessed in normal subjects. The diet was formulated to provide combinations of high and low levels of C18:2n-6 and C16:0. After 21 days of diet treatment, plasma triacylglycerol level and incorporation of deuterium into the plasma very low density lipoprotein triacylglycerol (VLDL-TG) pool over 24 hours was measured. Plasma triacylglycerol levels were within the normal range. Increasing dietary intake of linoleic acid decreased plasma triacylglycerol level when subjects consumed a low level of dietary palmitic acid. The relative and net amount of de novo synthesized fatty acid in the plasma VLDL-TG pool was not influenced by the diet treatments. A relationship between plasma triacylglycerol level and rate of hepatic de novo fatty acid synthesis was observed.

Linoleic acid intake and cancer risk: a review and meta-analysis

Replacement of saturated fat by the major dietary polyunsaturated fat linoleic acid reduces blood cholesterol concentrations and the risk of coronary artery disease. However, there is concern that long-term consumption of large amounts of linoleic acid might increase cancer risk. We reviewed the epidemiologic and experimental literature on linoleic acid intake and cancer risk and performed additional meta-analyses of risk estimates from case-control and prospective cohort studies. None of the combined estimates from within-population studies indicated a significantly increased risk of cancer with high compared with low intakes of linoleic acid or polyunsaturated fat. For case-control studies, the combined relative risks were 0.84 (95% CI: 0.71, 1.00) for breast, 0.92 (95% CI: 0.85, 1.08) for colorectal, and 1.27 (95% CI: 0.97, 1.66) for prostate cancer. For prospective cohort studies, combined relative risks were 1.05 (95% CI: 0.83, 1.34) for breast, 0.92 (95% CI: 0.70, 1.22) for colon, and 0.83 (95% CI: 0.56, 1.24) for prostate cancer. Ecologic comparisons of populations showed positive associations between cancer rates and per capita use of animal or saturated fat, but less so with per capita use of vegetable oil or polyunsaturated fat. Controlled studies of coronary artery disease in men did not, except for 1 study, show an increased cancer incidence after consumption of diets with a very high linoleic acid content for several years. Animal experiments indicated that a minimum amount of linoleic acid is required to promote growth of artificially induced tumors in rodents; but above this threshold, linoleic acid did not appear to have a specific tumor-promoting effect. Although current evidence cannot exclude a small increase in risk, it seems unlikely that a high intake of linoleic acid substantially raises the risks of breast, colorectal, or prostate cancer in humans.

Linoleic acid and alpha-linolenic acid lightens ultraviolet-induced hyperpigmentation of the skin

This study was conducted to evaluate the effects of unsaturated fatty acids on ultraviolet-induced hyperpigmentation of the skin. An efficient lightening effect was observed following topical application of linoleic acid or alpha-linolenic acid to UV-stimulated hyperpigmented dorsal skin of brownish guinea pigs. The number of melanocytes in the treated skin was similar to the number in the skin of the pigmented control, indicating that the pigment-lightening effect was not due to depletion of melanocytes. In vitro experiments using cultured murine melanoma cells showed that melanin production was inhibited most effectively by alpha-linolenic acid, followed by linoleic acid and then by oleic acid. Furthermore, the turnover of the stratum corneum, which plays an important role in the removal of melanin pigment from the epidermis, was accelerated by linoleic acid and by alpha-linolenic acid. Taken together, the results suggest that the pigment-lightening effects of linoleic acid and alpha-linolenic acid are, at least in part, due to suppression of melanin production by active melanocytes, and to enhanced desquamation of melanin pigment from the epidermis.

Long-chain polyunsaturated fatty acids in plasma and erythrocyte membrane lipids of children with phenylketonuria after controlled linoleic acid intake

It has been reported that children with classical phenylketonuria (PKU) have reduced levels of arachidonic acid (AA, 20:4 n-6) and docosahexaenoic acid (DHA, 22:6 n-3) in plasma and membrane phospholipids compared to controls and may therefore require supplementation. However, it is not established that these changes are specific for PKU. They may as well be attributed to the specific composition of a largely vegetarian diet used for dietary PKU treatment. We therefore investigated the fatty acid composition of plasma phospholipids (PL), plasma cholesterol esters (CE), red blood cell phosphatidylcholine (PC), and red blood cell phosphatidylethanolamine (PE) in two groups of PKU patients including 8 children between 1 and 6 years (group A), 9 adolescents between 11 and 18 years (group B), and 20 age-matched healthy controls. Group A had good dietary control (median plasma phenylalanine 272 mumol/L during the last 6 months before phospholipid analysis) while median phenylalanine in group B was 714 mumol/L (p < 0.001). When compared to age-matched controls, group A showed significantly lower DHA levels in PE (4.21 vs 5.85 weight% (wt%), p < 0.01), in PC (1.02 vs 1.25 wt%, p < 0.05) and in CE (0.25 vs 0.54 wt%, p < 0.05). There was no significant difference of DHA between group B and controls. AA levels were similar in phospholipids of all groups. We conclude that reduced levels of long-chain polyunsaturated fatty acids in PKU patients occur only in those patients with strict dietary therapy with respect to n-3 fatty acids, most probably caused by reduced intake of n-3 fatty acids.

Duodenal nutrient infusions differentially affect sham feeding and Fos expression in rat brain stem

Duodenal infusions of macronutrients inhibit sham and normal feeding. Neural substrates of this response were studied by infusing glucose, linoleic acid, an amino acid mixture, saline, or water into the duodenum of unanesthetized rats and then measuring sham feeding of 30% sucrose or Fos expression in the dorsal vagal complex. Linoleic acid and amino acids (both 1.5 kcal) and glucose (4.5 kcal) suppressed sham feeding relative to control infusions, and all three macronutrients triggered Fos expression in the nucleus of the solitary tract and area postrema. Although there were significant quantitative differences, the subnuclear distribution pattern of Fos-expressing neurons was not different for the three macronutrients and was largely localized to the medial, dorsomedial, and commissural subnuclei of the nucleus of the solitary tract and the area postrema. Linoleic acid suppressed intake and stimulated Fos expression similarly to glucose infusions of three times the caloric value. Amino acids strongly suppressed sham feeding but triggered relatively little Fos expression. These results indicate that the intake-suppressing potency of duodenal macronutrients is dependent on nutrient type, rather than simply caloric value, and that amino acids, although potent inducers of satiety, affect ingestion by processes different from those subserving lipids and carbohydrates. Furthermore, the similar patterns of neuronal activation after different duodenal infusions may indicate a large degree of convergence at the level of primary and second-order sensory neurons, whereas the distinctly different pattern obtained earlier with gastric distension indicates partially separate neural pathways for satiety signals generated by duodenal nutrients and gastric mechanoreceptors.

Effect of replacing a high linoleate oil with a low linoleate, high alpha-linolenate oil, as compared with supplementing EPA or DHA, on reducing lipid mediator production in rat polymorphonuclear leukocytes

The fatty acid composition of rat polymorphonuclear leukocytes (PMN) was modified by diets supplemented with a high linoleate (LA) safflower oil (76% LA), mixtures of eicosapentaenoate (EPA) and safflower oil (EPA(20) containing 20% EPA and 61% LA, EPA(40) containing 40% EPA and 46% LA), mixtures of docosahexaenoate (DHA) and safflower oil (DHA(20) containing 20% DHA and 61% LA, DHA(40) containing 40% DHA and 46% LA) or a high alpha-linolenate (alpha-LNA) perilla oil (57% alpha-LNA and 13% LA), and then lipid mediator production in casein-induced peritoneal PMN were compared. EPA and DHA were relatively ineffective in reducing platelet-activating factor (PAF) production; a statistically significant reduction was observed only in the DHA(40) group. In contrast, perilla oil reduced PAF production by 50% as compared with safflower oil. Arachidonate (AA) in the PAF precursor, 1-alkyl-2-acyl-glycerophosphocholine, was roughly correlated with PAF production, but EPA and DHA in the precursor lipid were relatively unrelated. On the other hand, both PGE2 and LTB4 production correlated positively with AA and negatively with EPA and DHA in PMN phospholipids; EPA tended to be somewhat more effective than DHA in reducing PGE2 and LTB4 formation; the activity of perilla oil was no less than EPA(20). Thus, replacing safflower oil with perilla oil was no less effective than supplementing safflower oil with EPA or DHA (at 40% of total fatty acids) in reducing lipid mediator production in rat PMN.

Opposite effects of linoleic acid and conjugated linoleic acid on human prostatic cancer in SCID mice

The relationship between dietary fat intake (level and type) and cancer development is a matter of concern in Western society. The purpose of this study was to determine the effect of three different diets on the local growth and metastatic properties of DU-145 human prostatic carcinoma cells in severe combined immunodeficient (SCID) mice. Animals were fed a standard diet or diets supplemented with 1% LA or 1% CLA for 2 weeks prior to subcutaneous (s.c.) inoculation of DU-145 cells and throughout the study (total of 14 weeks). Mice receiving LA-supplemented diet displayed significantly higher body weight, lower food intake and increased local tumor load as compared to the other two groups of mice. Mice fed the CLA-supplemented diet displayed not only smaller local tumors than the regular diet-fed group, but also a drastic reduction in lung metastases. These results support the view that dietary polyunsaturated fatty acids may influence the prognosis of prostatic cancer patients, thus opening the possibility of new therapeutic options.