Intakes of essential n-6 and n-3 polyunsaturated fatty acids among pregnant Canadian women.
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BACKGROUND: Fetal growth requires n-3 docosahexaenoic acid (DHA), which is derived from the essential n-3 fatty acids in the maternal diet. DHA is accumulated in the developing brain and is critical for normal neural and visual function. Available estimates suggest that 67 mg DHA/d is accumulated by the fetus during the third trimester of gestation. Little is known about n-3 fatty acid intakes in pregnant women, although human milk concentrations of DHA have decreased in recent years. OBJECTIVE: We prospectively determined the n-3 and n-6 fatty acid intakes of 55 pregnant Canadian women. DESIGN: A food-frequency questionnaire was completed at 28 and 35 wk, and plasma n-3 and n-6 fatty acids were measured at 35 wk gestation. The fatty acid composition of approximately 500 foods was analyzed to allow analysis of dietary intakes from specific foods. RESULTS: Intakes, as a percentage of energy, were (macro x +/- SEM) total fat, 28.0 +/- 3.6%; saturated fat, 9.8 +/- 0.3%; monounsaturated fat, 11.2 +/- 0.4%; polyunsaturated fat, 4.7 +/- 0.2%; linoleic acid, 3.9 +/- 0.2%; and alpha-linolenic acid, 0.54 +/- 0.05%. The daily intakes (range) were 160 +/- 20 (24-524) mg DHA/d, 121 +/- 8 (15-301) mg arachidonic acid/d, and 78 +/- 2 (4-125) mg eicosapentaenoic acid/d. The plasma phospholipids had (mg/100 g fatty acid) 5.0 +/- 0.18 DHA, 8.7 +/- 0.18 arachidonic acid, and 0.52 +/- 0.32 eicosapentaenoic acid. CONCLUSION: The low intake of DHA among some pregnant women highlights the need for studies to address the functional significance of maternal fat intakes during pregnancy on fetal development. (+info)
Arachidonic acid and prostacyclin signaling promote adipose tissue development: a human health concern?
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High fat intake is associated with fat mass gain through fatty acid activation of peroxisome proliferator-activated receptors delta and gamma, which promote adipogenesis. We show herein that, compared to a combination of specific agonists to both receptors or to saturated, monounsaturated, and omega-3 polyunsaturated fatty acids, arachidonic acid (C20:4, omega-6) promoted substantially the differentiation of clonal preadipocytes. This effect was blocked by cyclooxygenase inhibitors and mimicked by carbacyclin, suggesting a role for the prostacyclin receptor and activation of the cyclic AMP-dependent pathways that regulate the expression of the CCAAT enhancer binding proteins beta and delta implicated in adipogenesis. During the pregnancy-lactation period, mother mice were fed either a high-fat diet rich in linoleic acid, a precursor of arachidonic acid (LO diet), or the same isocaloric diet enriched in linoleic acid and alpha-linolenic acid (LO/LL diet). Body weight from weaning onwards, fat mass, epididymal fat pad weight, and adipocyte size at 8 weeks of age were higher with LO diet than with LO/LL diet. In contrast, prostacyclin receptor-deficient mice fed either diet were similar in this respect, indicating that the prostacyclin signaling contributes to adipose tissue development. These results raise the issue of the high content of linoleic acid of i) ingested lipids during pregnancy and lactation, and ii) formula milk and infant foods in relation to the epidemic of childhood obesity. (+info)
Rationale and study design of dietary intervention in patients polypectomized for tumors of the colorectum.
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We have implemented a randomized controlled dietary intervention in patients polypectomized for tumors of the colorectum to elucidate potential beneficial effects of n-3 polyunsaturated fatty acids (PUFAs) on the development of colorectal tumors. Those individuals in the experimental group were advised not only to decrease their consumption of fats/oils as a whole and foods supplying n-6 PUFAs but also to increase intake of foods and supplements containing n-3 PUFAs, while those in the comparison group were cautioned to reduce intake of fats/oils as a whole. Patients' compliance/adherence was monitored with a semi-quantitative food frequency questionnaire and by assessment of fatty acid concentrations in plasma, membranes of red blood cells and sigmoid colon samples. As for endpoints to assess tumor suppressive effects of n-3 PUFAs, the number/multiplicity, sizes and incidence rates of colorectal tumors were compared between the experimental and comparison groups after 12 and 24 months of the dietary intervention. On the specified assumption, the number of pairs needed for achieving statistical significance was calculated to be approximately 60-80. A randomized controlled trial is under way to secure enough patients, sustain compliance/adherence and minimize dropouts. (+info)
Differential effects of prostaglandin derived from omega-6 and omega-3 polyunsaturated fatty acids on COX-2 expression and IL-6 secretion.
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Omega-6 (omega-6) polyunsaturated fatty acids (PUFA), abundant in the Western diet, are precursors for a number of key mediators of inflammation including the 2-series of prostaglandins (PG). PGE(2), a cyclooxygenase (COX) metabolite of arachidonic acid, a omega-6 PUFA, is a potent mediator of inflammation and cell proliferation. Dietary supplements rich in omega-3 PUFA reduce the concentrations of 2-series PG and increase the synthesis of 3-series PG (e.g., PGE(3)), which are believed to be less inflammatory. However, studies on cellular consequences of increases in 3-series PG in comparison to 2-series PG have not been reported. In this study, we compared the effects of PGE(2) and PGE(3) on (i) cell proliferation in NIH 3T3 fibroblasts, (ii) expression and transcriptional regulation of the COX-2 gene in NIH 3T3 fibroblasts, and (iii) the production of an inflammatory cytokine, IL-6, in RAW 264.7 macrophages. PGE(3), unlike PGE(2), is not mitogenic to NIH 3T3 fibroblasts. PGE(2) and PGE(3) both induce COX-2 mRNA via similar signaling mechanisms; however, compared with PGE(2), PGE(3) is significantly less efficient in inducing COX-2 gene expression. Furthermore, although both PGE(2) and PGE(3) induce IL-6 synthesis in RAW 264.7 macrophages, PGE(3) is substantially less efficient compared with PGE(2). We further show that increasing the omega-3 content of membrane phospholipid results in a decrease in mitogen-induced PGE(2) synthesis. Taken together, our data suggest that successful replacement of omega-6 PUFA with omega-3 PUFA in cell membranes can result in a decreased cellular response to mitogenic and inflammatory stimuli. (+info)
Maternal and umbilical cord erythrocyte omega-3 and omega-6 fatty acids and haemorheology in singleton and twin pregnancies.
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BACKGROUND: Being devoid of both nuclei and mitochondria, mature human erythrocytes provide an opportunity to study membrane structure and function outwith the restrictions of genetic control. With its unique rapid increase in vascularisation, pregnancy is considered the most opportune period in which to investigate blood rheology. METHODS: Maternal and fetal (cord) bloods were retained at delivery from 32 (25 singleton and seven twin) normal pregnancies at two maternity hospitals in the Glasgow area over a nine month period. Erythrocyte fatty acid compositions were assessed by mass spectroscopy, and corresponding membrane deformabilities measured by ultrafiltration through a membrane of 5 micro m diameter pore size, to mimic placental microcirculation. RESULTS: Significant direct correlations (Spearman rank) were found between erythrocyte membrane omega-3 docosahexaenoic acid concentrations and corresponding deformabilities in maternal and cord blood from both singleton and twin pregnancies, whereas greater omega-6 arachidonic acid content was associated with increased maternal membrane rigidity. Membrane concentrations of omega-3 fatty acids only correlated strongly both within and between maternal and cord bloods. Mean cord erythrocyte docosahexaenoic acid concentration was higher than maternal in singletons but lower in twins. When maternal erythrocyte concentrations exceeded about 7% (of total fatty acids), resistance to erythrocyte flow was virtually eliminated. CONCLUSIONS: It may be that a greater maternal intake of docosahexaenoic acid should be encouraged in some pregnancies for optimal tissue perfusion. Fetal demand for docosahexaenoic acid may not be entirely satisfied in multiple pregnancies. (+info)
Effects of beef- and fish-based diets on the kinetics of n-3 fatty acid metabolism in human subjects.
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BACKGROUND: The quantity and type of dietary polyunsaturated fatty acids (PUFAs) can alter essential fatty acid metabolism in humans. Diets rich in 20- and 22-carbon PUFAs may inhibit desaturase expression or activity and decrease the synthesis of long-chain unsaturated fatty acids. OBJECTIVE: It was theorized that the fat content of a fish-based diet would inhibit the kinetics of the in vivo metabolism of n-3 fatty acids compared with a beef-based diet. DESIGN: A compartmental model was used to determine the coefficients of the kinetic rate constants from the plasma concentration time curves of pentadeuterated (d(5)) 18:3n-3, 20:5n-3, 22:5n-3, and 22:6n-3 of 10 subjects who subsisted on 3 diets with different long-chain PUFA contents. For 3 wk, subjects reported their food intake from their usual diets and then consumed a beef-based diet for 3 wk and then a fish-based diet for an additional 3 wk. Subjects consumed 1 g d(5)-18:3n-3 ethyl ester at weeks 3, 6, and 9. Blood was drawn over 168 h and the plasma analyzed for fatty acids. The coefficients of the kinetic constants of n-3 fatty acid metabolism and the percentage utilization of the substrates were determined. RESULTS: Across all diets, < 1% of plasma 18:3n-3 was utilized for long-chain PUFA synthesis. There was a 70% reduction in the value of the rate constant coefficient that regulated transfer of the isotope from the 22:5n-3 compartment to 22:6n-3 when the fish-based diet was compared with the beef-based diet. The turnover rate of plasma d(5)-22:6n-3 also decreased. CONCLUSIONS: The primary effect of a fish-based diet on the kinetics of n-3 metabolism involves processes that inhibit the synthesis of 22:6n-3 from 22:5n-3. These processes may involve a system of feedback control mechanisms responsive to the plasma concentration of 22:6n-3. (+info)
Biomarkers of fat and fatty acid intake.
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Unlike other macronutrients such as protein, the amounts and types of fat in the human diet vary tremendously across cultures and over time have changed significantly within Westernized countries. Studies of the effect that fat sources, fat amounts and changes in fat intake have on human disease are extremely difficult to conduct with traditional dietary assessment methods for a number of reasons. These include the hidden nature of many fats, the variation in fatty acids contained in foods and feed and the sensitivity of individuals to questions about fat intake in their diets. For these reasons biomarkers of fat intake are particularly desirable. Fat and fat-soluble substances have the advantages over other nutrients of a long half-life and readily accessible storage depots (in the absence of starvation, undernutrition or eating disorders). Technological advances in quantitative measurements of individual fatty acids, with the help of gas chromatography and mass spectrometry (GCMS)((3)) and high performance liquid chromatography (HPLC), made possible the study of specific isomers of minor fatty acids from small tissue samples. Technological advances also opened the gateways to the study of fats that represent less than 1% of the total fat profiles, such as decosahexanoic acid (DHA), eicosapentanoic acid (EPA) and conjugated linoleic acid (CLA). Biological advances enhanced our appreciation of the differences between fats of differing chain lengths within a family, including the saturated fats. Challenges remain, such as assessing total fat intake, discriminating the contribution of endogenously produced fats, determining how to evaluate the importance of relative versus absolute contributions of fat and accounting for the factors that influence deposition and mobilization of individual fats within and between individuals. Factors that can influence deposition and mobilization include genetic variation, disease status, lifestyle differences (i.e., alcohol consumption and smoking), circulating apolipoprotein levels and the hormonal milieu of the individual and the source tissue. (+info)
Effect of dietary fat sources on systemic and intrauterine synthesis of prostaglandins during early pregnancy in gilts.
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The present experiment was conducted to determine the influence of dietary fatty acids C18:2n-6 and C18:3n-3 on the modulation of intrauterine synthesis of prostaglandin E2 (PGE2) and F2alpha (PGF2alpha) during early pregnancy in pigs. Prostaglandin E2 in uterine fluid has been previously reported to be associated with embryo survival and development. Thirty-two Yorkshire-Landrace nulliparous gilts were randomly allocated to four diets containing 5% supplemental fat. The four dietary treatments were: HT, hydrogenated tallow (26.5% C16:0 and 54.8% C18:0); SO, sunflower oil (61.3% C18:2n-6); LO, linseed oil (50.4% C18:3n-3); and SO(CLA), a mixture of sunflower oil and conjugated linoleic acids to provide 20% CLA. Treatments started 2 d after the first pubertal estrus (d -21) and lasted for 36 d (slaughter), which was 15 d after the second estrus (d 0; insemination). Fatty acids and PGE2 were measured in the peripheral blood plasma on d -19, d -7, d 0, and d 14. Fatty acids in endometrial tissues and PGE2 and PGF2alpha in the uterine fluid collected on d 15 were also measured. Concentrations of fatty acids in the plasma reflected the content of fatty acids in the diet as early as d -7. From d -7, PGE2 concentrations in the plasma were higher in gilts fed SO compared with HT (P < 0.05). Plasma PGE2 concentrations were lower (P < 0.01) on d 14 in gilts fed LO compared with HT. Total PGF2alpha contents in the uterine fluid of gilts fed LO were more than 70% lower (P < 0.05) than for the HT group. A similar trend was observed for total PGE2 content and for the ratio PGF2alpha:PGE2, but the effect (LO vs HT) was less marked (P < 0.07 and P < 0.10, respectively). There was no effect of SO or SO(CLA) on total PGE2 contents in the uterine fluid. Dietary enrichment in C18:2n-6 and/or C18:3n-3 for early pregnant gilts can influence fatty acids in plasma and endometrial tissue and can modulate circulatory and intrauterine prostaglandins. (+info)