Differences in cell morphology, lipid and apo B secretory capacity in caco-2 cells following long term treatment with saturated and monounsaturated fatty acids

The suitability of the caco-2 cell line as a model for studying the long term impact of dietary fatty acids on intestinal lipid handling and chylomicron production was examined. Chronic supplementation of caco-2 cells with palmitic acid (PA) resulted in a lower triacylglycerol secretion than oleic acid (OA). This was coupled with a detrimental effect of PA, but not OA, on transepithelial electrical resistance (TER) measurements, suggesting a loss of structural integrity across the cell monolayer. Addition of OA reversed the adverse effects of PA and stearic acid on TER and increased the ability of cells to synthesise and accumulate lipid, but did not normalise the secretion of lipids by caco-2 cells. Increasing amounts of OA and decreasing amounts of PA in the incubation media markedly improved the ability of cells to synthesise apolipoprotein B and secrete lipids. Real time RT-PCR revealed a down regulation of genes involved in lipoprotein synthesis following PA than OA. Electron microscopy showed adverse effects of PA on cellular morphology consistent with immature enterocytes such as stunted microvilli and poor tight junction formation. In conclusion, previously reported differences in lipoprotein secretion by caco-2 cells supplemented with saturated fatty acids (SFA) and OA may partly reflect early cytotoxic effects of SFA on cellular integrity and function. (C) 2007 Elsevier B.V. All rights reserved.

Preparation of enantiopure long chain threo-2-amino-3-hydroxyesters via chiral morpholinone-derived azomethine ylids

The synthetic approach to threo-2-amino-3-hydroxyesters possessing long alkyl chains outlined herein centres on the generation of chiral azomethine ylids by reaction of (5R)-5-phenyl-morpholin-2-one, (R)-(1), with long chain aldehydes. In the presence of a second equivalent of aldehyde, the azomethine ylid can be trapped to afford a cycloadduct with three new stereodefined centres. Degradation of the cycloadduct allows entry to beta-substituted-alpha-amino acid derivatives, which have potential as building blocks for sphingosine synthesis.

Effects of dietary fat modification on insulin sensitivity and on other risk factors of the metabolic syndrome—LIPGENE: a European randomized dietary intervention study

Background:Excessive energy intake and obesity lead to the metabolic syndrome (MetS). Dietary saturated fatty acids (SFAs) may be particularly detrimental on insulin sensitivity (SI) and on other components of the MetS. Objective:This study determined the relative efficacy of reducing dietary SFA, by isoenergetic alteration of the quality and quantity of dietary fat, on risk factors associated with MetS. Design:A free-living, single-blinded dietary intervention study. Subjects and Methods:MetS subjects (n=417) from eight European countries completed the randomized dietary intervention study with four isoenergetic diets distinct in fat quantity and quality: high-SFA; high-monounsaturated fatty acids and two low-fat, high-complex carbohydrate (LFHCC) diets, supplemented with long chain n-3 polyunsaturated fatty acids (LC n-3 PUFAs) (1.2 g per day) or placebo for 12 weeks. SI estimated from an intravenous glucose tolerance test (IVGTT) was the primary outcome measure. Lipid and inflammatory markers associated with MetS were also determined. Results:In weight-stable subjects, reducing dietary SFA intake had no effect on SI, total and low-density lipoprotein cholesterol concentration, inflammation or blood pressure in the entire cohort. The LFHCC n-3 PUFA diet reduced plasma triacylglycerol (TAG) and non-esterified fatty acid concentrations (P<0.01), particularly in men. Conclusion:There was no effect of reducing SFA on SI in weight-stable obese MetS subjects. LC n-3 PUFA supplementation, in association with a low-fat diet, improved TAG-related MetS risk profiles.

Trans fatty acids and weight gain

Increasing rates of obesity have stimulated research into possible contributing factors, including specific dietary components such as trans fatty acids (TFAs). This review considers the evidence for an association between TFA intake and weight gain. It concludes that there is limited but consistent evidence from epidemiological studies, and from a primate model, that increased TFA consumption may result in a small additional weight gain. Data from a long-term study in a primate model suggest that TFA may have a greater adipogenic effect than cis monounsaturated fatty acids; however, there are currently inadequate mechanistic data to provide a comprehensive and plausible explanation for any such metabolic differences between the types of fatty acids.

Dietary long-chain n-3 PUFAs increase LPL gene expression in adipose tissue of subjects with an atherogenic lipoprotein phenotype

We sought to test the hypothesis that dietary long-chain n-3 PUFA (LC n-3 PUFA) in fish oil stimulate the gene expression of lipoprotein lipase (LPL) in human adipose tissue (AT). In a randomized, double blind, placebo-controlled, cross-over study, 51 male subjects expressing an atherogenic lipoprotein phenotype (ALP) had their diets supplemented with fish oil for 6 weeks. As we previously reported for this group, supplementation with LC n-3 PUFA produced a decrease in fasting plasma triglyceride (TG) (−35%, P < 0.05), attenuation of the postprandial TG response (area and incremental area under the curve; AUC and IAUC, P < 0.05), and a decrease in small, dense LDL. The present study extended these observations by showing that these changes were accompanied by a marked increase in the concentration of LPL mRNA in adipose tissue (AT-LPL mRNA, +55%, P = 0.003) and post-heparin LPL activity (PH-LPL, +31%, P = 0.036). There was also evidence of an association between LPL gene expression and polymorphism in the apolipoprotein E gene. We conclude that the favorable influence of dietary n-3 PUFA on the ALP may be mediated, in part, through an increase in the plasma activity and gene expression of lipoprotein lipase in human adipose tissue.

Measurement of apolipoprotein B-48 in the Svedberg flotation rate (Sf) > 400, Sf 60 – 400 and Sf 20 – 60 lipoprotein fractions reveals novel findings with respect to the effects of dietary fatty acids on triacylglycerol-rich lipoproteins in postmenopausal women

The present study was designed to examine whether the type of fat ingested in an initial test meal influences the response and density distribution of dietary-derived lipoproteins in the Svedberg flotation rate (Sf)>400, Sf 60 - 400 and Sf 20 - 60 lipoprotein fractions. A single-blind randomized within-subject crossover design was used to study the effects of palm oil, safflower oil, a mixture of fish and safflower oil, and olive oil on postprandial apolipoprotein (apo) B-48, retinyl ester and triacylglycerol responses in each lipoprotein fraction following an initial test meal containing one of the oils and a second standardized test meal. For all dietary oils, late postprandial (300min) concentrations of triacylglycerol and apo B-48 were significantly higher in the Sf 60 - 400 fraction than in the Sf>400 fraction (P<0.02). Significantly greater apo B-48 incremental areas under the curve (IAUCs) were also observed in the Sf 60 - 400 fraction than in the Sf>400 fraction following palm oil, safflower oil and olive oil (P<0.04), with a similar non-significant trend for fish/safflower oil. Olive oil resulted in a significantly greater apo B-48 IAUC in the Sf>400 fraction (P<0.02) than did any of the other dietary oils, as well as a tendency for a higher IAUC in the Sf 60 - 400 fraction compared with the palm, safflower and fish/safflower oils. In conclusion, we have found that the majority of intestinally derived lipoproteins present in the circulation following meals enriched with saturated, polyunsaturated or monounsaturated fatty acids are of the density and size of small chylomicrons and chylomicron remnants. Olive oil resulted in a greater apo B-48 response compared with the other dietary oils following sequential test meals, suggesting the formation of a greater number of small (Sf 60 - 400) and large (Sf>400) apo B-48-containing lipoproteins in response to this dietary oil.

Effects of n-3 fatty acids on postprandial triacylglycerol and hormone concentrations in normal subjects

The present study reports results from two investigations to determine effects of a 6-week period of moderate n-3 fatty acid supplementation (2.7 g/d) on fasting and on postprandial triacylglycerol and metabolic hormone concentrations in response to standard test meals. In the first study postprandial responses were followed for 210 min after an early morning test meal challenge; in the second study responses to an evening test meal were followed during the evening and overnight for a total period of 12 h. In both studies postprandial triacylglycerol responses to the test meals were significantly reduced after compared with before fish-oil supplementation. In the second study the triacylglycerol peak response seen between 200 and 400 min in subjects studied before supplementation with fish oils was almost completely absent in the same subjects after 6 weeks of n-3 fatty acid supplementation. Analysis of fasting concentrations of metabolites and hormones was carried out on the combined data from the two studies. There were no significant differences in total, low-density-lipoprotein- or high-density-lipoprotein-cholesterol concentrations during fish-oil supplementation, although there was considerable individual variation in cholesterol responses to the supplement. Concentrations of Apo-B and Apo-A1 were unchanged during supplementation with fish oils. Fasting and early morning postprandial GIP concentrations were lower in subjects taking fish oils, possibly due to acute effects of fish-oil capsules taken on the evening before the studies. In both studies fasting insulin and glucose and postprandial insulin concentrations remained unchanged following fish-oil supplementation. The results do not support the view that triacylglycerol-lowering effects of n-3 fatty acids are due to modulation of insulin secretion mediated via the enteroinsular axis. Further studies are required to determine the precise mechanism by which fish oils reduce both fasting and postprandial triacylglycerol concentrations.

Effects of dietary polyunsaturated fatty acid supplementation on fatty acid composition in muscle and subcutaneous adipose tissue of lambs

Lambs (n = 48) were used in a 2 × 2 factorial arrangement of treatments to evaluate effects of inclusion of oil containing PUFA in high-concentrate diets (with or without) and duration of oil supplementation (pre- vs. postweaning) on CLA concentration of muscle and adipose tissue. Lambs were fed preweaning creep diets (with or without oil) corresponding to the dietary lactation treatment diet (with or without oil) of the dam. Dams blocked by lambing date and rearing type were randomly assigned to 1 of 2 lactation dietary treatments with or without oil supplementation. Creep diets contained approximately 70% concentrate and 30% roughage and were provided to lambs for ad libitum intake. At weaning (58.7 ± 2.5 d of age), lambs (n = 48) were randomly assigned within preweaning treatment groups to 1 of 2 postweaning dietary treatments (with or without oil) and 16 pens in a randomized block design, blocked by sex and BW. Postweaning diets were formulated to contain approximately 80% concentrate and 20% roughage and were fed once daily for ad libitum intake. Soybean and linseed oil (2:1, respectively) replaced ground corn and provided 3% additional fat in pre- and postweaning diets. Lambs were slaughtered at 60.3 ± 4.2 kg of BW. A subcutaneous fat (SQ) sample was obtained within 1 h postmortem and a LM sample at the 12th rib was obtained 24 h postmortem, and both were analyzed for fatty acid profile. Feedlot performance and carcass measurements were not affected (P ≥ 0.26) by oil supplementation. Total CLA content of LM and SQ was not affected (P ≥ 0.08) by oil supplementation pre- or postweaning, but trans-10, cis-12 CLA was greater (P = 0.02) in SQ from lambs supplemented with oil postweaning. Total PUFA content in LM was greater (P = 0.02) in lambs supplemented with oil pre- or postweaning as a result of increased concentrations of 18:2cis-9, cis-12 and longer chain PUFA. Conversely, pre- and postweaning oil supplementation resulted in less (P = 0.04) MUFA content in LM. Only postweaning oil supplementation increased (P = 0.001) SQ PUFA content. Feeding oils containing PUFA to lambs pre- and postweaning did not increase CLA content of muscle, whereas postweaning oil supplementation minimally increased CLA concentration of SQ fat. Inclusion of soybean and linseed oil in pre- and postweaning diets increased total PUFA content of SQ fat and muscle tissue without adversely affecting growth performance or carcass characteristics.

Application of the BRAFO-tiered approach for benefit-risk assessment to case studies on natural foods

There is evidence that consumption of fish, especially oily fish, has substantial beneficial effects on health. In particular an inverse relationship of oily fish intake to coronary heart disease incidence has been established. These beneficial effects are ascribed to fish oil components including long chain ω-3 polyunsaturated fatty acids. On the other hand it should be noted that oily fish also contains hazardous substances such as dioxins, PCBs and methylmercury. Soy consumption has been associated with potential beneficial and adverse effects. The claimed benefits include reduced risk of cardiovascular disease; osteoporosis, breast and prostate cancer whereas potential adverse effects include impaired thyroid function, disruption of sex hormone levels, changes in reproductive function and increased breast cancer risk The two cases of natural foods highlight the need to consider both risks and benefits in order to establish the net health impact associated to the consumption of specific food products. Within the Sixth Framework programme of the European Commission, the BRAFO project was funded to develop a framework that allows for the quantitative comparison of human health risks and benefits in relation to foods and food compounds. This paper describes the application of the developed framework to two natural foods, farmed salmon and soy protein. We conclude that the BRAFO methodology is highly applicable to natural foods. It will help the benefit-risk managers in selecting the appropriate dietary recommendations for the population.