About: Linoleic acid is a(n) research topic. Over the lifetime, 21503 publication(s) have been published within this topic receiving 651365 citation(s). The topic is also known as: linolic acid & telfairic acid.
01 Apr 2008-Meat Science
TL;DR: It is shown that a major factor is the total amount of fat and that phospholipid, where 18:2n-6 is located, declines as a proportion of muscle lipid and the proportion of neutral lipid, with its higher content of saturated and monounsaturated fatty acids, increases.
Abstract: This paper reviews the factors affecting the fatty acid composition of adipose tissue and muscle in pigs, sheep and cattle and shows that a major factor is the total amount of fat. The effects of fatty acid composition on meat quality are also reviewed. Pigs have high levels of polyunsaturated fatty acids (PUFA), including the long chain (C20-22) PUFA in adipose tissue and muscle. The full range of PUFA are also found in sheep adipose tissue and muscle whereas cattle 'conserve' long chain PUFA in muscle phospholipid. Linoleic acid (18:2n-6) is a major ingredient of feeds for all species. Its incorporation into adipose tissue and muscle in relation to the amount in the diet is greater than for other fatty acids. It is deposited in muscle phospholipid at a high level where it and its long chain products eg aracidonic acid (20:4n-6) compete well for insertion into phospholipid molecules. Its proportion in pig adipose tissue declines as fat deposition proceeds and is an index of fatness. The same inverse relationships are not seen in ruminant adipose tissue but in all species the proportion of 18:2n-6 declines in muscle as fat deposition increases. The main reason is that phospholipid, where 18:2n-6 is located, declines as a proportion of muscle lipid and the proportion of neutral lipid, with its higher content of saturated and monounsaturated fatty acids, increases. Oleic acid (18:1cis-9), formed from stearic acid (18:0) by the enzyme stearoyl Co-A desaturase, is a major component of neutral lipid and in ruminants the same enzyme forms conjugated linoleic acid (CLA), an important nutrient in human nutrition. Like 18:2n-6, α-linolenic acid (18:3n-3) is an essential fatty acid and is important to ruminants since it is the major fatty acid in grass. However it does not compete well for insertion into phospholipid compared with 18:2n-6 and its incorporation into adipose tissue and muscle is less efficient. Greater biohydrogenation of 18:3n-3 and a long rumen transit time for forage diets also limits the amount available for tissue uptake compared with 18:2n-6 from concentrate diets. A positive feature of grass feeding is that levels of the nutritionally important long chain n-3 PUFA are increased ie EPA (20:5n-3) and DHA (22:6n-3). Future research should focus on increasing n-3 PUFA proportions in lean carcasses and the use of biodiverse pastures and conservation processes which retain the benefits of fresh leafy grass offer opportunities to achieve this. The varying fatty acid compositions of adipose tissue and muscle have profound effects on meat quality. Fatty acid composition determines the firmness/oiliness of adipose tissue and the oxidative stability of muscle, which in turn affects flavour and muscle colour. Vitamin E is an essential nutrient, which stabilises PUFA and has a central role in meat quality, particularly in ruminants.
01 Sep 1999-The American Journal of Clinical Nutrition
TL;DR: Alpha-linolenic acid, found in green leafy vegetables, flaxseed, rapeseed, and walnuts, desaturates and elongates in the human body to EPA and DHA and by itself may have beneficial effects in health and in the control of chronic diseases.
Abstract: Human beings evolved consuming a diet that con- tained about equal amounts of n23 and n26 essential fatty acids. Over the past 100-150 y there has been an enormous increase in the consumption of n26 fatty acids due to the increased intake of veg- etable oils from corn, sunflower seeds, safflower seeds, cottonseed, and soybeans. Today, in Western diets, the ratio of n 26 to n23 fatty acids ranges from <20-30:1 instead of the traditional range of 1-2:1. Studies indicate that a high intake of n26 fatty acids shifts the physiologic state to one that is prothrombotic and proaggrega- tory, characterized by increases in blood viscosity, vasospasm, and vasoconstriction and decreases in bleeding time. n 23 Fatty acids, however, have antiinflammatory, antithrombotic, antiarrhythmic, hypolipidemic, and vasodilatory properties. These beneficial effects of n23 fatty acids have been shown in the secondary prevention of coronary heart disease, hypertension, type 2 diabetes, and, in some patients with renal disease, rheumatoid arthritis, ulcerative colitis, Crohn disease, and chronic obstructive pulmonary disease. Most of the studies were carried out with fish oils (eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)). However, a-linolenic acid , found in green leafy vegetables, flaxseed, rapeseed, and walnuts, desaturates and elongates in the human body to EPA and DHA and by itself may have beneficial effects in health and in the control of chronic diseases. Am J Clin Nutr 1999;70(suppl): 560S-9S.
01 Feb 1985-Journal of Lipid Research
TL;DR: Results of this study show that oleic acid is as effective as linoleic acid in lowering LDL-C levels in normo-triglyceridemic patients, and oleoic acid seemingly reduces HDL-C Levels less frequently than does linolesic acid.
Abstract: Twenty patients consumed a liquid diet in which the predominant fatty acids were either saturated (Sat), monounsaturated (Mono), or polyunsaturated (Poly). The fats in these three diets comprised 40% of total calories and consisted of palm oil, high-oleic safflower oil, and high-linoleic safflower oil, respectively. During the third and fourth week of each dietary period, multiple samples of blood were taken and were analyzed for plasma total cholesterol (TC), triglycerides (TG), and cholesterol in lipoprotein fractions (VLDL-C, LDL-C, and HDL-C). Twelve of the patients had normal TG levels; in these patients, both Mono and Poly diets caused statistically significant and equal lowerings of plasma LDL-C, but the Poly diet lowered HDL-C levels more frequently than did the Mono diet. Neither diet changed the level of plasma TG. The proportions of total protein and the various lipid components in isolated fractions (VLDL, IDL, LDL, HDL) were not altered by the two diets. Eight patients had hypertriglyceridemia; these individuals showed considerable variability in response to Mono and Poly diets. Although there was a trend towards reductions in TC and LDL-C levels by both types of unsaturated fats, the changes were inconsistent; furthermore, HDL-C concentrations were low on the Sat diet and were unaffected by either the Mono or the Poly diet. The results of this study show that oleic acid is as effective as linoleic acid in lowering LDL-C levels in normo-triglyceridemic patients, and oleic acid seemingly reduces HDL-C levels less frequently than does linoleic acid. Neither type of unsaturated fat had striking effects on lipoprotein levels of hypertriglyceridemic patients.
01 Jun 1966-Biochemical Journal
TL;DR: Catalysis of peroxidation of unsaturated fatty acids by the mitochondrial and microsomal fractions of liver is inhibited by ascorbic acid at pH7.4 but the activity of the supernatant fraction is enhanced.
Abstract: 1. Homogenates of rat liver, spleen, heart and kidney form lipid peroxides when incubated in vitro and actively catalyse peroxide formation in emulsions of linoleic acid or linolenic acid. 2. In liver, catalytic activity is distributed throughout the nuclear, mitochondrial and microsomal fractions and is present in the 100000g supernatant. Activity is weak in the nuclear fraction. 3. Dilute (0.5%, w/v) homogenates catalyse peroxidation over the range pH5.0-8.0 but concentrated (5%, w/v) homogenates inhibit peroxidation and destroy peroxide if the solution is more alkaline than pH7.0. 4. Ascorbic acid increases the rate of peroxidation of unsaturated fatty acids catalysed by whole homogenates of liver, heart, kidney and spleen at pH6.0 but not at pH7.4. 5. Catalysis of peroxidation of unsaturated fatty acids by the mitochondrial and microsomal fractions of liver is inhibited by ascorbic acid at pH7.4 but the activity of the supernatant fraction is enhanced. 6. Inorganic iron or ferritin are active catalysts in the presence of ascorbic acid. 7. Lipid peroxide formation in linoleic acid or linolenic acid emulsions catalysed by tissue homogenates is partially inhibited by EDTA but stimulated by o-phenanthroline. 8. Cysteine or glutathione (1mm) inhibits peroxide formation catalysed by whole homogenates, mitochondria or haemoprotein. Inhibition increases with increase of pH.
01 Sep 2000-Journal of Nutrition
TL;DR: Results demonstrate that endogenous synthesis of CLA from trans-11 18:1 represented the primary source of CLA in milk fat of lactating cows.
Abstract: Conjugated linoleic acid (CLA) is a naturally occurring anticarcinogen found in milk fat and body fat of ruminants. Although CLA is an intermediate in ruminal biohydrogenation of linoleic acid, we hypothesized that its primary source was from endogenous synthesis. This would involve Delta(9)-desaturase and synthesis from trans-11 18:1, another intermediate in ruminal biohydrogenation. Our first experiment supplied lactating cows (n = 3) with trans-11 18:1 by abomasal infusion and examined the potential for endogenous synthesis by measuring changes in milk fat CLA. By d 3, infusion of trans-11 18:1 resulted in a 31% increase in concentration of cis-9, trans-11 CLA in milk fat, demonstrating that an active pathway for endogenous synthesis of CLA exists. Our second experiment examined the quantitative importance of endogenous synthesis of CLA in lactating cows (n = 3) by abomasally infusing a putative stimulator (retinol palmitate) or an inhibitor (sterculic oil) of Delta(9)-desaturase. Infusion of retinol palmitate had no influence on milk fatty acid desaturation, and yield of CLA in milk fat was not altered. However, sterculic oil infusion decreased the concentration of CLA in milk fat by 45%. Consistent with Delta(9)-desaturase inhibition, the sterculic oil treatment also altered the milk fat concentration of other Delta(9)-desaturase products as indicated by the two- to threefold increase in the ratios of 14:0 to 14:1(,) 16:0 to 16:1 and 18:0 to cis-18:1. Using changes in the ratio of 14:0 to 14:1 as an indication of the extent of Delta(9)-desaturase inhibition with the sterculic oil treatment, an estimated 64% of the CLA in milk fat was of endogenous origin. Overall, results demonstrate that endogenous synthesis of CLA from trans-11 18:1 represented the primary source of CLA in milk fat of lactating cows.