Might analysis,synthesis and metabolism of CLA contribute to explain the biological effects of CLA?

Conjugated Linoleic Acids (CLA) are of great interest for analysts since techniques have been developed to determine the dietary occurrence of CLA with a good accuracy. CLA is found in animal products from ruminant sources as the result of biohydrogenation of polyunsaturated fatty acids in the rumen and as the consequence of the delta-9 desaturation of vaccenic acid in animal tissues. CLA can also be obtained in the laboratory by isomerisation of linoleic acid or by total chemical synthesis. While the "natural" isomer is rumenic acid (9c,11t-18:2), synthetic mixtures contain mainly two isomers: the 9c,11t- and the 10t,12c-18:2. Although CLA have been shown to be metabolized into desaturated and chain elongated products, it remains unclear whether these so-formed conjugated metabolites may be involved in the effects of CLA on fatty acid metabolism. Experiments carried out on animal models with CLA have shown different health benefits: anticarcinogenic, antiatherosclerotic effects, modulation of body composition , the "natural" CLA (9c,11t-18:2) being closely related to the protection against cancer and the 10t,12c-18:2 to the reduction of the fat mass. Nevertheless, recent findings have suggested adverse effects in mice. Most of the studies carried out on humans concern the influence of CLA on body composition and its possible inverse association with cancer. Since the results are still controversial and since very few data dealing with the safety of using CLA in long term feeding studies have so far been published, further works are warranted to consider the benefits of CLA for humans.     

Effects of palm oil on cardiovascular risk.

A major public health concern of affluent nations is the excessive consumption of dietary fats which are now closely linked to coronary heart disease. Against this scenario, the tropical oils and palm oil in particular, have been cast as major villains in the U.S.A., despite the fact that palm oil consumption there is negligible. The unsuspecting public may not realise that the call to avoid palm oil is nothing more than a trade ploy since in recent years palm oil has been very competitive and has gained a major share of the world's edible oils and fats market. Many also lose sight of the fact that, palm oil, like other edible oils and fats, is an important component of the diet. The allegation that palm oil consumption leads to raised blood cholesterol levels and is therefore atherogenic is without scientific foundation. Examination of the chemical and fatty acid composition of palm oil or its liquid fraction should convince most nutritionists that the oil has little cholesterol-raising potential. The rationale for these are: it is considered cholesterol free. its major saturated fatty acid, palmitic acid (16:0) has recently been shown to be neutral in its cholesterolaemic effect, particularly in situations where the LDL receptors have not been down-regulated by dietary means or through a genetic effect. palm oil contains negligible amounts (less than 1.5%) of the hypercholesterolemic saturated fatty acids, namely lauric acid (12:0) and myristic acid (14:0). it has moderately rich amounts of the hypocholesterolaemic, monounsaturated oleic acid (18:1, omega-9) and adequate amounts of linoleic acid. (18:2, omega-6). It contains minor components such as the vitamin E tocotrienols which are not only powerful antioxidants but are also natural inhibitors of cholesterol synthesis. Feeding experiments in various animal species and humans also do not support the allegation that palm oil is atherogenic. On the contrary, palm oil consumption reduces blood cholesterol in comparison with the traditional sources of saturated fats such as coconut oil, dairy and animal fats. In addition, palm oil consumption may raise HDL levels and reduce platelet aggregability. As with all nutrients, there is a need to obtain a balance of different fatty acids found in fats in edible oils and other food sources. There is no single ideal source of fat that answers to the recent American Heart Association's call to reflect a 1:1:1 ratio of saturated, monounsaturated and polyunsaturated fats in relation to the recommended dietary fat intake of 30% of calories or less.(ABSTRACT TRUNCATED AT 400 WORDS)     

Fatty acid composition and possible health effects of coconut constituents

The link between excessive consumption of dietary saturated fats and coronary heart disease (CHD) is now well established. Because of its high content of saturated fatty acids, the consumption of foods containing coconut oil may therefore be a risk factor for CHD. While the fatty acid composition of coconut oil is well established, relatively little is known about the other constituents of coconut: the milk, water, cream and meat fractions. In this study, we show that while the water fraction is low in lipid content, the milk contains about 24% of the fat content of oil and the cream and meat fractions about 34%. The other coconut constituents contain significant amounts of medium-chain triglycerides that are formed from fatty acids of chain length 8:0 to 14:0. It is these fatty acids, primarily 14:0, that are thought to be atherogenic. On the other hand, medium-chain triglycerides may be advantageous under some circumstances in that they are absorbed intact and do not undergo degradation and re-esterification processes. As a result, medium-chain triglycerides provide a ready source of energy and may be useful in baby foods or in diet therapy. Nevertheless, the possible negative effects of the saturated fatty acids and the absence of the essential fatty acid linolenic acid from all coconut constituents suggest that the coconut milk, oil and cream should not be used on a regular basis in adults.     

不同脂肪酸对高胆固醇血症小鼠体质量和血脂的影响

目的：比较6种脂肪酸对高胆固醇血症小鼠体质量和血脂的影响。方法建立C57BL/6J小鼠高胆固醇血症模型,分别用含2%的辛酸（C8∶0）、癸酸（C10∶0）、油酸（C18∶1）、α-亚麻酸（C18∶3）、棕榈酸（C16∶0）和硬脂酸（C18∶0）高胆固醇饲料喂养12周,12周时检测血脂及脂蛋白相关指标。结果研究12周后各组小鼠体质量均显著增加,辛酸（C8∶0）、癸酸（C10∶0）、油酸（C18∶1）对控制体质量增加的作用较棕榈酸（C16∶0）和硬脂酸（C18∶0）差异显著（P＜0.05）;6种脂肪酸均显示出不同程度血总胆固醇（total cholesterol,TC）和低密度脂蛋白胆固醇（low density lipoprotein cholesterol, LDL-C）降低,高密度脂蛋白胆固醇（high density lipoprotein cholesterol,HDL-C）与低密度脂蛋白胆固醇比值（HDL-C/LDL-C）增加的作用。辛酸（C8∶0）、癸酸（C10∶0）和α-亚麻酸（C18∶3）降低TC和LDL-C及升高HDL-C/LDL-C比值的作用比油酸、棕榈酸和硬脂酸显著（P＜0.05）。结论中链的饱和脂肪酸（saturated fatty acid,SFA）较长链的SFA降低小鼠体质量和血脂的作用显著。     

不同脂肪酸饮食对大鼠肝脏xbp-1的影响

目的:探讨饱和脂肪酸、单不饱和脂肪酸、多不饱和脂肪酸饮食对大鼠肝脏X盒结合蛋白-1(XBP-1)的影响。方法:48只雄性Wistar大鼠随机分为4组:正常对照组(N组)、饱和脂肪酸饮食组(S组)、单不饱和脂肪酸饮食组(M组)、多不饱和脂肪酸饮食组(P组)。正常对照组给基础饲料(脂肪占10.3%);饱和脂肪酸饮食组的饲料是在基础饲料中添加15%猪油;单不饱和脂肪酸饮食组的饲料是在基础饲料中添加15%茶油;多不饱和脂肪酸饮食组的饲料是在基础饲料中添加15%豆油(脂肪占35.4%)。8周后4组各随机选8只大鼠行高胰岛素-正葡萄糖钳夹试验,同时留取空腹状态血清测定血脂、胰岛素等指标。肝脏XBP-1蛋白表达分别用Western blot法和免疫组化法测定。结果:①实验第8周末,与N组相比,P、M、S组大鼠进食量有所减少(P<0.05)。除外进食量的影响,与N组相比,S组血清总胆固醇(TC)、甘油三酯(TG)升高(P<0.05),M、P组差异无统计学意义(P>0.05);S、P组空腹胰岛素(FINS)、空腹血糖(FBG)升高,葡萄糖输注率(GIR)明显下降(P均<0.05),但S、P两组间无统计学意义(P>0.05);M...     

Dietary fatty acids and coronary heart disease

Epidemiological studies have confirmed a strong association between fat intake, especially saturated and trans fatty acids, plasma cholesterol levels and rate of coronary heart disease (CHD) mortality. Meanwhile it is clear, that early atherosclerosis is largely preventable by modifying nutritional behaviour and lifestyle. There is clear evidence that a diet moderate in total fat (25-35 % energy) is superior to extremes in dietary fat. Because fat is energy dense moderation in fat intake is also essential for weight control. Saturated fatty acids are very potent in increasing LDL-cholesterol concentration in plasma a dangerous risk factor for early CHD. Unsaturated fatty acids have numerous beneficial health effects. The results of prospective cohort studies fit well to the experimental experience of the antihypercholesterolemic action of Omega-6 fatty acids and the antithrombotic, vasodilatory and antiarrhythmic properties of Omega-3 fatty acids, while the optimistic rating of Omega-9 fatty acids is less supported by epidemiologic studies. The results of prospective cohort studies are confirmed by intervention trials revealing that saturated fatty acids enhance early development of CHD whereas polyunsaturated fatty acids, especially of the Omega-3 type, significantly preserve from CHD. In context with a prudent diet pattern favourable dietary fatty acid composition offers the best chance for a reduced risk of CHD.     

脂肪酸与糖尿病

合理膳食是糖尿病防治的重要基础措施。脂肪酸在糖尿病发生发展中的作用迄今尚无定论,大部分流行病学和膳食干预研究提示饱和脂肪酸、反式脂肪酸是糖尿病的危险因素,而多不饱和脂肪酸特别是长链n-3多不饱和脂肪酸却能改善糖代谢和胰岛素敏感性。脂肪酸对糖尿病的临床意义及其可能机制尚待进一步研究。     

Changing concepts in lipid nutrition in health and disease

Fat remains a hot topic because of concerns over associations between consumption of fats and the incidence of some chronic conditions including coronary artery disease, diabetes, cancer and obesity. Dietary fats serve multiple purposes. The effects of dietary fats generally reflect the collective influences of multiple fatty acids in the diet or food. This presentation highlights some recent developments on the role of dietary fats and oils in health and disease. Debate continues over the role of dietary modification in coronary prevention by lipid lowering. The degree to which a recommended diet will result in health benefits for an individual is difficult to predict, because the outcome will depend on the influence of other factors such as a person's genetic constitution, level of physical activity and total diet composition. There can now be little doubt about the importance of genetic factors in the etiology of cardiovascular disease, diabetes, obesity and cancer. The importance of antioxidant status in the prevention of cardiovascular disease as well as many cancers is being increasingly recognised. It is now evident that not all saturated fatty acids are equally cholesterolemic. Recent accounts evaluating palm oil's effects on blood lipids and lipoproteins suggest that diets incorporating palm oil as the major dietary fat do not raise plasma total and LDL cholesterol levels to the extent expected from its fatty acid composition. Palm oil is endowed with a good mixture of natural antioxidants and together with its balanced composition of the different classes of fatty acids, makes it a safe, stable and versatile edible oil with many positive health and nutritional attributes. In recent times, adverse health concerns from the consumption of trans fatty acids arising from hydrogenation of oils and fats have been the subject of much discussion and controversy. Trans fatty acids when compared with cis fatty acids or unhydrogenated fats have been shown to lower serum HDL cholesterol, raise serum LDL cholesterol and when substituted for saturated fatty acids, increase lipoprotein Lp (a) level, an independent risk factor for the development of coronary heart disease. The idea of which foods, nutrients and supplements are "healthy" is often being amended as new scientific data is presented and then simplified for the consumers. What was once perceived as a healthy diet is often no longer considered as such and vice versa. Dietary recommendations have to change with time and the evidence available. Nutritional recommendations should encourage eating a great variety of nutrient sources within our food supply in moderation. Various lifestyle options to improve health should also be promoted.     

Fatty acid compositions of cholesteryl esters. Different species and their correlation with susceptibility to atherosclerosis]

Fatty acid compositions of serum cholesteryl esters (CE) in human and animals were analysed. Polyunsaturated fatty acids (PUFA) were the predominant fatty acids in CE. A close relation between PUFA to saturated fatty acids (P/S) ratio in CE and susceptibility to atherosclerosis (AS) was observed among different species. Animals with high P/S such as tree shrews and rats (P/S 9.0) were AS-resistant, and those with low P/S such as rabbits (P/S 2.9) were susceptible to AS. The P/S ratio in human serum CE (4.9) was between those in the above two kinds of animals, and similar to those in pigs (4.2) and monkeys (3.7). A great physiological significance of abundant PUFA in CE could be expected. As the main part of low density lipoprotein (LDL), CE might provide PUFA to cells efficiently via LDL receptor. It was assumed that PUFA in CE were closely correlated with the metabolism of cholesterol and the development of AS by regulating LDL receptor activity, platelet function and prostaglandin synthesis, all of which would be affected by PUFA in cells.     

基于短链脂肪酸防治代谢性疾病的研究进展

短链脂肪酸（SCFAs）是一类含有1~6个碳原子的饱和脂肪酸,主要由肠道内特定菌群通过发酵膳食纤维产生,对维持肠道内环境稳态发挥重要作用。近年来研究表明SCFAs可调节糖脂代谢、调节能量平衡、维持肠道屏障、减轻炎性反应,并通过上述多途径参与2型糖尿病、肥胖、脂代谢紊乱、非酒精性脂肪性肝病等代谢性疾病的发生与发展。本文总结了SCFAs调控代谢的机制及其防治代谢性疾病的研究进展,旨在为代谢性疾病的防治提供更多参考资料。     

新生儿硬肿症患儿白色脂肪与棕色脂肪的脂肪酸组成、血清游离脂肪酸变化及其对血糖的影响

本文应用气相色谱法测定了新生儿患儿白色脂肪及棕色脂肪的脂肪酸百分含量和正常足月儿、早产儿、硬肿症及其它疾病患儿血清游离脂肪酸含量。结果表明白色脂肪中饱和脂肪酸含量高于不饱和脂肪酸,棕色脂肪则相反。棕色脂肪中亚油酸含量明显高于白色脂肪。文中分析了血清游离脂肪酸总量及各组分的变化和它们之间的关系,以及影响因素。还发现血清亚油酸与血糖之间有明显的正相关。     

A systematic review of the impact of n-3 fatty acids in bone health and osteoporosis.

Osteoporosis, especially in postmenopausal women, delineates a major health and economic problem in the world. Regarding the pathogenesis of osteoporosis and the interaction between various cells and mediators, many studies have been conducted to evaluate the benefit of different therapeutic options. Over the past several years evidence has been growing on the effects of dietary fatty acids on bone health. The objective of this paper was to provide a review of the current knowledge of dietary fatty acids and osteoporosis. Medline/Index Medicus and EMBASE/Excerpta Medica were searched for relevant papers regarding the effects of n-3 fatty acids on osteoporosis between 1963 and 2007 using the key words: osteoporosis, bone health, n-3 fatty acids, and PUFA. Bone mineral density and bone markers have been used in several animal studies to evaluate the beneficial effect of n-3 fatty acids on bone health and the prevention of osteoporosis. Generally, animal studies support the beneficial effects of n-3 fatty acids on bone health and osteoporosis; however, the dissimilar lipid metabolism in human and animals, the various study designs, and controversies over the human study outcomes make it difficult to draw a definite conclusion. The authors believe that conclusive findings in humans are still lacking in this area and it needs to be further investigated.     

Long chain fatty acid oxidation defects in children: importance of detection and treatment options

Background  Mitochondrial β oxidation plays a major role in energy production. Long chain fatty acid oxidation defects include deficiency of the trifunctional protein (rare) or more commonly defects of the long chain 3-hydroxy acyl-CoA dehydrogenase enzyme (LCHAD). These long chain defects have variable presentations, they may present in the neonate or infant with sudden death, hepatopathy (Reyes disease), hypoketotic hypoglycaemia, rhabdomyolysis, myopathy, cardiomyopathy and with late complications such as peripheral neuropathy, pigmentary retinopathy, retinal degeneration and progressive visual loss. The correct diagnosis at presentation is not only life saving but also allows for the appropriate dietary and other intervention, which may have major effects on outcome. Aim  Three case reports of patients with long chain fatty acid oxidation defects who have shown significant benefits from treatment are reported. Conclusions  These paediatric presentations illustrate the clinical heterogeneity of long chain fatty acid oxidation defects and opportunities for effective management if correctly diagnosed.     

不同类型脂肪酸对SD大鼠血清脂肪酸及胰岛素抵抗的影响

目的分析中链饱和脂肪酸(MC-SFA,MCF组)、长链饱和脂肪酸(LC-SFA,LCF组)、n-6多不饱和脂肪酸(n-6 PUFA,SUF组)和n-3多不饱和脂肪酸(n-3 PUFA,TUF组)四种脂肪酸对大鼠血清脂肪酸及胰岛素抵抗的影响。方法雄性SD大鼠40只随机分为5组,对照组给予普通日粮,高脂组给予脂肪热量比相同的高脂日粮。喂养10周,每18 d测定空腹血糖(GLU)、血清脂肪酸、血清胰岛素水平,根据胰岛素敏感性指数(ISI)=ln1/(FPG×FINS)评定大鼠的胰岛素敏感性。结果10周后,LCF组和SUF组大鼠体重显著高于对照组和其它高脂组;LCF组血清胰岛素显著高于对照组(P﹤0.05);LCF组、TUF组ISI显著低于对照组(P﹤0.05);各组间血糖无明显差异(P0.05)。SUF组、TUF组血清LC-SFA浓度显著低于LCF组(P﹤0.05);TUF组血清(n-3 PUFA)显著高于对照组和其它高脂组(P﹤0.05)。结论不同类型脂肪酸的高脂饲料对SD大鼠的血清脂肪酸组成和含量有显著的影响,SD大鼠脂肪沉积及胰岛素抵抗程度随血清脂肪酸代谢作用的不同而变化。     

Prevention of coronary heart disease: the role of essential fatty acids.

There are 2 classes of essential fatty acids (EFA), the linoleic (n-6) and linolenic (n-3). They are required for the glycerophosphatides (phospholipids) of cellular membranes; the transport and oxidation of cholesterol; the formation of prostaglandins. In deficiency of EFA, cellular membranes are imperfectly formed which causes increased susceptibility to various insults and increased permeability. Low-density lipoproteins (LDL) transport cholesterol mainly as cholesteryl linoleate and supply EFA to tissue. A relative deficiency of EFA (i.e. a high ratio in the body of non-EFA such as long-chain saturated fatty acids to EFA) causes an increase in plasma cholesterol. EFAs cause decreased aggregation of platelets. Atherosclerosis is not caused by increased aggregation of platelets, and can be prevalent in a population in which coronary thrombosis is rare.     

Coconut fats

In many areas of Sri Lanka the coconut tree and its products have for centuries been an integral part of life, and it has come to be called the "Tree of life". However, in the last few decades, the relationship between coconut fats and health has been the subject of much debate and misinformation. Coconut fats account for 80% of the fat intake among Sri Lankans. Around 92% of these fats are saturated fats. This has lead to the belief that coconut fats are 'bad for health', particularly in relation to ischaemic heart disease. Yet most of the saturated fats in coconut are medium chain fatty acids whose properties and metabolism are different to those of animal origin. Medium chain fatty acids do not undergo degradation and re-esterification processes and are directly used in the body to produce energy. They are not as 'bad for health' as saturated fats. There is the need to clarify issues relating to intake of coconut fats and health, more particularly for populations that still depend on coconut fats for much of their fat intake. This paper describes the metabolism of coconut fats and its potential benefits, and attempts to highlight its benefits to remove certain misconceptions regarding its use.     

Physical exercise and the prevention of atherosclerosis and cholesterol gall stones

There is accumulating evidence in man and experimental animals that even mild exercise, if regularly repeated, may alter the metabolism of lipids. Exercise has been reported as decreasing peripheral tissue cholesterol in red blood cells, working muscle, lungs and the liver. During physical activity, the output of cholesterol and bile acids into the bile increases. This probably leads to higher faecal losses of sterols which may lead to lower cholesterol levels in the peripheral tissues and in the bile, when exercise is repeated regularly. Preferential release of unsaturated fatty acids from the adipose tissue during exercise and the linoleic acid-dependent LCAT enzyme (transporting plasma cholesterol) may be partly responsible for this effect of exercise. The experimental data reviewed provide supportive basis for epidemiological studies reporting on the beneficial effect of regular exercise.     

Trans fatty acids,HDL-cholesterol,and cardiovascular disease. Effects of dietary changes on vascular reactivity

A high consumption of trans fatty acids increases the risk of cardiovascular disease (CVD). We investigated whether this increase in risk was due to the decrease in serum HDL-cholesterol by trans fatty acids, because low concentrations of serum HDL-cholesterol also increase risk of CVD. Flow-mediated vasodilation (FMD) was used as an endpoint in dietary interventions that were designed to change the concentration of serum HDL-cholesterol within 4 weeks in healthy volunteers. Replacement of 10% of energy from saturated by trans fatty acids decreased serum HDL-cholesterol by 21 % and impaired FMD. However, a replacement of monounsaturated fats by carbohydrates did not impair FMD, although it decreased serum HDL-cholesterol by 13%. Acute postprandial impairments of FMD by either trans fats or saturated fats were not found, suggesting that long-term effects are responsible for the detrimental effect of trans fats on health. However, the role of serum HDL-cholesterol appears to be less than we expected.     

Protective effect of Arthrospira maxima on fatty acid composition in fatty liver

BACKGROUND: Arthrospira maxima has been widely used for nutritional purposes. Additionally, A. maxima has shown immunomodulator, antiviral, antioxidant, vasomotor and hypolipidemic effects in laboratory and animal studies. A. maxima prevents fatty liver induced by either carbon tetrachloride (CCl4) or fructose-rich diet; however, the liver lipid composition in these models is not clearly known yet. The aim of this study was to evaluate the effects of A. maxima on the liver lipid profile in CCl4-induced steatohepatitis. METHODS: A single sublethal, intraperitoneal dose of CCl4 was administered to male Wistar rats fed a diet with or without 5% A. maxima. Liver lipids: total lipids, triacylglycerols, total cholesterol, free fatty acids, and thiobarbituric acid reactive substances were assessed 24 and 48 h after injury with CCl4. Additionally, triacylglycerols, total cholesterol and aspartate aminotransferase were evaluated in blood. RESULTS: Forty eight hours after CCl4 treatment, rats fed a diet without A. maxima had serum aspartate aminotransferase and liver triacylglycerols values that were, respectively, 2.2 and 1.4 times higher than those of animals receiving 5% A. maxima in their diet. The same pattern was observed for liver free fatty acids and thiobarbituric acid reactive substances. The groups fed a diet with A. maxima and treated with CCl4 showed a higher saturated fatty acid liver content than the groups without A. maxima in their diet. The percentage of unsaturated fatty acids increased 48 h after CCl4 treatment, but its value was 0.5 times lower in the group receiving A. maxima than in the group fed without A. maxima. In the liver, all animals receiving A. maxima showed a trend towards a lower percentage of unsaturated fatty acids, despite the mentioned increase 48 h after CCl4 treatment. CONCLUSIONS: The results suggest that, in the fatty liver induced by CCl4, the hepatoprotective effect of A. maxima involves (a) an antioxidant mechanism and (b) a lower unsaturation of the liver fatty acids. The preventive effect of A. maxima on the liver lipid changes induced by CCl4 could be partially explained by its antioxidant action and the ability to increase the synthesis/release of nitric oxide, but not by its soluble dietary fiber.     

N-花生四烯酰乙醇胺及其类似物的神经保护作用

N-花生四烯酰乙醇胺(anandamide, AEA)属于内源性大麻素类长链脂肪酸衍生物,可通过大麻素受体（CB1/CB2）和(或)非CB1/CB2受体途径发挥神经保护作用。AEA类似物包括脂氨基酸类、脂肪酰乙醇胺类和甲基氟膦酸酯类化合物等。AEA类似物在生物活性及化学结构上与AEA相似,但作用靶点及作用机制并不完全相同,非CB1/CB2受体途径介导的神经保护活性及对脂肪酸酰胺水解酶活性的调节作用为该类化合物的重要特征。由于AEA作用于多靶点所致的许多副作用,给其临床试验和应用带来一定困难,而AEA类似物可能既具备AEA的神经保护活性又避免其毒副作用,因此研究AEA类似物的神经保护作用具有重要的理论意义和应用价值。本文主要对AEA及其类似物的神经保护活性和其作用机制进行综述。