1,721,098 research outputs found
[alpha]-Linolenic acid metabolism in men and women: nutritional and biological implications
No full textPurpose of review: This review critically evaluates current knowledge of [alpha]-linolenic acid metabolism in adult humans based on the findings of studies using stable isotope tracers and on increased dietary [alpha]-linolenic acid intake. The relative roles of [alpha]-linolenic acid and of longer-chain polyunsaturated fatty acids in cell structure and function are discussed together with an overview of the major metabolic fates of [alpha]-linolenic acid. The extent of partitioning towards [beta]-oxidation and carbon recycling in humans is described. The use and limitations of stable isotope tracers to estimate [alpha]-linolenic acid desaturation and elongation are discussed. A consensus view of the extent of [alpha]-linolenic acid conversion to longer-chain fatty acids in humans is presented. The extent to which increasing dietary [alpha]-linolenic acid intake alters the concentrations of longer-chain n-3 fatty acids is described. The biological and nutritional implications of these findings are discussed.Recent findings: Conversion of [alpha]-linolenic acid to eicosapentaenoic acid is limited in men and further transformation to docosahexaenoic acid is very low. A lower proportion of [alpha]-linolenic acid is used as a substrate for [beta]-oxidation in women compared with men, while the fractional conversion to longer-chain fatty acids is greater, possibly due to the regulatory effects of oestrogen.Summary: Overall, [alpha]-linolenic acid appears to be a limited source of longer-chain n-3 fatty acids in man and so adequate intakes of preformed n-3 polyunsaturated fatty acids, in particular docosahexaenoic acid, may be important for maintaining optimal tissue function. Capacity to upregulate [alpha]-linolenic acid transformation in women may be important for meeting the demands of the fetus and neonate for docosahexaenoic acid
Is essential fatty acid interconversion an important source of PUFA in humans?
No full textHumans can obtain preformed long chain polyunsaturated fatty acids (PUFA) from the diet, but are also able to convert essential fatty acids (EFAs) to longer chain PUFA. The metabolic pathway responsible for EFA interconversion involves alternating desaturation and carbon chain elongation reactions, and carbon chain shortening by peroxisomal β-oxidation. Studies using stable isotope tracers or diets supplemented with EFAs show that capacity for PUFA synthesis is limited in humans such that docosahexaenoic acid (22:6n-3) synthesis in men is negligible. PUFA synthesis is greater in women of reproductive age than men. However, the magnitude of the contribution of hepatic PUFA synthesis to whole body PUFA status remains unclear. A number of extra-hepatic tissues have been shown to synthesise PUFA or to express genes for enzymes involved in this pathway. The precise function of extra-hepatic PUFA synthesis is largely unknown, although in T lymphocytes PUFA synthesis is involved in the regulation of cell activation and proliferation. Local PUFA synthesis may also be important for spermatogenesis and fertility. One possible role of extra-hepatic PUFA synthesis is that it may provide PUFA in a timely manner to facilitate specific cell functions. If so, this may suggest novel insights into the effect of dietary PUFA and / or polymorphisms in genes involved in PUFA synthesis on health and tissue function
<b>𝛼</b><b>-linolenic acid interconversion is sufficient as a source of longer chain ω-3 polyunsaturated fatty acids in humans: An opinion</b> <b/><b/>: An opinion
No full textα-linolenic acid (αLNA) conversion into the functionally important ω-3 polyunsaturated fatty acids (PUFA) eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), has been regarded as inadequate for meeting nutritional requirements for these PUFA. This view is based on findings of small αLNA supplementation trials and stable isotope tracer studies that have been interpreted as indicating human capacity for EPA and, in particular, DHA synthesis is limited. The purpose of this review is to re-evaluate this interpretation. Markedly differing study designs, inconsistent findings and lack of trial replication preclude robust consensus regarding the nutritional adequacy of αLNA as a source of EPC and DHA. The conclusion that αLNA conversion in humans is constrained is inaccurate because it presupposes the existence of an unspecified, higher level of metabolic activity. Since capacity for EPA and DHA synthesis is the product of evolution it may be argued that the levels of EPA and DHA it maintains are nutritionally appropriate. Dietary and supra-dietary EPA plus DHA intakes confer health benefits. Paradoxically, such health benefits are also found amongst vegetarians who do not consume EPA and DHA, and for whom αLNA conversion is the primary source of ω-3 PUFA. Since there are no reported adverse effects on health or cognitive development of diets that exclude EPA and DHA, their synthesis from αLNA appears to be nutritionally adequate. This is consistent with the dietary essentiality of αLNA and has implications for developing sustainable nutritional recommendations for ω-3 PUFA
Introduction to fatty acids and lipids
No full textThe purpose of this article is to describe the structure, function and metabolism of fatty acids and lipids that are of particular importance in the context of parenteral nutrition. Lipids are a heterogeneous group of molecules that share the common property of hydrophobicity. Lipids range in structure from simple short hydrocarbon chains to more complex molecules, including triacylglycerols, phospholipids and sterols and their esters. Lipids within each class may differ structurally. Fatty acids are common components of complex lipids, and these differ according to chain length and the presence, number and position of double bonds in the hydrocarbon chain. Structural variation among complex lipids and among fatty acids gives rise to functional differences that result in different impacts upon metabolism and upon cell and tissue responses. Fatty acids and complex lipids exhibit a variety of structural variations that influence their metabolism and their functional effects
Biochemical analysis of proteolytic fragments from desmosomal glycoproteins
No full textSIGLEAvailable from British Library Document Supply Centre- DSC:DX79449 / BLDSC - British Library Document Supply CentreGBUnited Kingdo
Long-chain n-3 PUFA in vegetarian women: a metabolic perspective
No full textVegetarian diets have been associated with health benefits, but paradoxically are low in EPA and DHA which are important for development, particularly of the central nervous system, and for health. Humans have limited capacity for synthesis of EPA and DHA from α-linolenic acid, although this is greater in women than men. Oily fish and, to a lesser extent, dairy foods and meat are the primary sources of EPA and DHA in the diet. Exclusion of these foods from the diet by vegetarians is associated consistently with lower EPA and DHA status in vegetarian women compared with omnivores. The purpose of the present review was to assess the impact of low EPA and DHA status in vegetarian pregnancies on the development and health of children. EPA and DHA status was lower in breast milk and in infants of vegetarian mothers than those born to omnivore mothers, which suggests that in the absence of pre-formed dietary EPA and DHA, synthesis from α-linolenic acid is an important process in determining maternal EPA and DHA status in pregnancy. However, there have been no studies that have investigated the effect of low maternal DHA status in vegetarians on cognitive function in children. It is important to address this gap in knowledge in order to be confident that vegetarian and vegan diets during pregnancy are safe in the context of child development
Dietary alpha-linolenic acid and health-related outcomes: a metabolic perspective
No full textalpha-Linolenic acid (alpha LNA; 18 : 3n-3) is essential in the human diet, probably because it is the substrate for the synthesis of longer-chain, more unsaturated n-3 fatty acids, principally EPA (20 : 5n-3) and DHA (22 : 6n-3), which confer important biophysical properties on cell membranes and so are required for tissue function. The extent to which this molecular transformation occurs in man is controversial. The present paper reviews the recent literature on the metabolism of alpha LNA in man, including the use of dietary alpha LNA in beta-oxidation, recycling of carbon by fatty acid synthesis de novo and conversion to longer-chain PUFA. Sex differences in alpha LNA metabolism and the possible biological consequences are discussed. Increased consumption of EPA and DHA in fish oil has a number of well-characterised beneficial effects on health. The present paper also reviews the efficacy of increased alpha LNA consumption in increasing the concentrations of EPA and DHA in blood and cell lipid pools, and the extent to which such dietary interventions might be protective against CVD and inflammation. Although the effects on CVD risk factors and inflammatory markers are variable, where beneficial effects have been reported these are weaker than have been achieved from increasing consumption of EPA+DHA or linoleic acid. Overall, the limited capacity for conversion to longer-chain n-3 fatty acids, and the lack of efficacy in ameliorating CVD risk factors and inflammatory markers in man suggests that increased consumption of alpha LNA may be of little benefit in altering EPA+DHA status or in improving health outcomes compared with other dietary interventions
Fatty acids and epigenetics
No full textPurpose of reviewThe purpose of this review is to assess the findings of recent studies on the effects of fatty acids on epigenetic process and the role of epigenetics in regulating fatty acid metabolism.Recent findingsThe DNA methylation status of the Fads2 promoter was increased in the liver of the offspring of mice fed an ?-linolenic acid-enriched diet during pregnancy. In rats, increasing total maternal fat intake during pregnancy and lactation induced persistent hypermethylation of the Fads2 promoter in the liver and aortae of their offspring. However, increased fish oil intake in adult rats induced transient, reversible hypermethylation of Fads2. High fat feeding in rodents also altered the levels of histone methylation in placentae and in adipose tissue. Dietary docosahexaenoic acid supplementation in pregnant women induced marginal changes in global DNA methylation in cord blood leukocytes. A high fat diet altered the DNA methylation status of specific genes in skeletal muscle in young men.SummaryThere are emerging findings that support the suggestion that fatty acids, in particular polyunsaturated fatty acids, can modify the epigenome. However, there is a need for rigorous investigations that assess directly the effect epigenetic modifications induced by fatty acids on gene function and metabolism
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