Protective effect of dietary n-3 polyunsaturated fatty acids on myocardial resistance to ischemia-reperfusion injury in rats

Dietary n-3 polyunsaturated fatty acids (PUFA) reduce coronary heart disease (CHD) complications, such as chronic arrhythmia and sudden cardiac death. Improved myocardial resistance to ischemia-reperfusion injury results in smaller myocardial infarction, which is a major factor in the occurrence of CHD complications. We hypothesized that a specific dietary fatty acid profile (low in saturated and n-6 PUFA but high in plant and marine n-3 PUFA) may improve myocardial resistance to ischemia-reperfusion injury and reduce infarct size. To test this assumption, we used a well-defined rat model of myocardial infarction. Based on our results, in comparison to a diet that is high in either saturated or n-6 PUFA but poor in plant and marine n-3 PUFA, a diet that is low in saturated fats and n-6 PUFA but rich in plant and marine n-3 PUFA results in smaller myocardial infarct size (P < .01). The effects of the 3 diets were also examined by analyzing the fatty acid composition of plasma, erythrocyte cell membranes, and the phospholipids of myocardial mitochondria. The results show a great accumulation of n-3 PUFA and a parallel decrease in arachidonic acid, the main n-6 PUFA, in plasma, cell membranes, and cardiac mitochondria (P < .0001). We conclude that improved myocardial resistance to ischemia-reperfusion may be one of the critical factors explaining the protective effects of dietary n-3 PUFA against CHD complications in humans. In addition to increasing n-3 PUFA intake, an optimal dietary pattern aimed at reducing cardiovascular mortality should include a reduction of the intake of both saturated and n-6 PUFA.     

The effects of dietary n-3 polyunsaturated fatty acids on neutrophils

The studies of dietary fish oil supplementation in healthy volunteers demonstrate a significant increase in neutrophil EPA content, a concomitant reduction in neutrophil AA content, and suppression of neutrophil LTB4 synthesis by supplementation with dietary fish oil containing approximately 3-4 g EPA daily for a minimum of 4 weeks. Suppression of neutrophil chemotactic responsiveness to LTB4 and FMLP was observed after dietary n-3 PUFA supplementation at these levels. Dietary EPA is more active than DHA in eliciting these effects in human neutrophils. Dietary n-3 PUFA supplementation inhibits neutrophil chemotaxis to these ligands through the inhibition of the signal transduction pathway between the receptor and phospholipase C, as demonstrated by the inhibition of chemotaxin-stimulated IP3 formation, in the absence of an effect on the number or affinity of the respective chemotaxin receptors. In patients with RA, dietary supplementation with n-3 PUFA resulted in decreased AA content of cellular lipids, with an augmented EPA content and decreased LTB4 generation by neutrophils. Dietary supplementation with n-3 PUFA also resulted in augmentation of depressed neutrophil chemotaxis to LTB4 and FMLP. Preliminary findings suggest that the decreased responsiveness to chemotaxins of neutrophils from RA patients is due to down-regulation of chemotaxin receptor number, resulting in decreased signaling via chemotaxin receptors. Dietary fish oil PUFA partially reversed the down-regulation of the chemotaxin receptor of neutrophils of RA patients, but had a lesser effect on chemotaxin receptor signaling and function, probably due to a post-receptor inhibition induced by fish oil PUFA, as was previously observed in healthy controls. Several small clinical trials have each suggested that dietary supplementation with n-3 PUFA resulted in modest improvements in disease activity. Meta-analysis of these studies confirms statistically significant improvements in tender joint count and morning stiffness after 3 months of dietary fish oil supplementation in patients with RA. Dietary supplementation with gamma-linolenic acid-rich oils also inhibits neutrophil LTB4 formation, has other anti-inflammatory and immunosuppressive effects, and shows promise of therapeutic efficacy in RA.     

Short term effects of dietary medium-chain fatty acids and n-3 long-chain polyunsaturated fatty acids on the fat metabolism of healthy volunteers

Background

The amount and quality of dietary fatty acids can modulate the fat metabolism.

Objective

This dietary intervention is based on the different metabolic pathways of long-chain saturated fatty acids (LCFA), which are mostly stored in adipocytic triacylglycerols, medium-chain fatty acids (MCFA) which are preferentially available for hepatic mitochondrial β-oxidation and n-3 long-chain polyunsaturated fatty acids (n-3 LCPUFA) suggested to modulate fat oxidation and storage by stimulating the peroxisomal β-oxidation. Combined dietary MCFA and n-3 LCPUFA without LCFA may synergistically stimulate fatty acid oxidation resulting in blood lipid clearance and LCFA release from adipocytes.

Design

In a short term, parallel, randomized, double-blind trial effects on the fatty acid metabolism of 10 healthy volunteers (Body Mass Index 25–30) of a formula containing 72% MCFA and 22% n-3 LCPUFA without LCFA (intake: 1.500 kcal/day; fat: 55.5% of energy) were measured in comparison to an isoenergetic formula with equal fat amount and LCFA dominated lipid profile.

Results

The plasma triacylglycerol (p < 0.1) and cholesterol (p < 0.05) content decreased in the test group. The n-3/n-6 LCPUFA (≥ C 20) ratio increased (p < 0.0001) after 4 days treatment. The LCFA content was similar in both groups despite missing LCFA in the test formula indicating LCFA release from adipocytes into the plasma. Both groups significantly reduced body weight considerably 4 kg (p < 0.01) and fat mass up to 50% of weight loss (p < 0.05).

Conclusion

Combined dietary 72% MCFA and 22% n-3 LCPUFA without LCFA stimulate the fatty acid oxidation and release from adipocytes without affecting any safety parameters measured.

     

A method for assessing dietary intakes of n-3 long-chain polyunsaturated fatty acids and trans fatty acids in an Irish adult population

Abstract

The present study aimed to quantify dietary intakes of eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and trans fatty acids (trans FA) in Irish adults using the North/South Ireland Food Consumption Survey (NSIFCS). To update the NSIFCS database, specific approaches were necessary to select accurate data. Published references were the main data source used to update for EPA and DHA (21.7%), while the UK Nutrient Databank was most frequently used to update for trans FA (46.7%). Total EPA and DHA mean daily intake was 275 mg/day whilst trans FA mean daily intake was 0.72% food energy. Younger adults had significantly lower intakes of EPA and DHA than older adults. The present study shows that dietary EPA and DHA intakes in the Irish adult population are below recommendations, especially among the younger population. Conversely, trans FA intakes are within the recommended value of < 2% food energy.     

n-3 long-chain polyunsaturated fatty acids in type 2 diabetes: a review

Historically, epidemiologic studies have reported a lower prevalence of impaired glucose tolerance and type 2 diabetes in populations consuming large amounts of the n-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFAs) found mainly in fish. Controlled clinical studies have shown that consumption of n-3 LC-PUFAs has cardioprotective effects in persons with type 2 diabetes without adverse effects on glucose control and insulin activity. Benefits include lower risk of primary cardiac arrest; reduced cardiovascular mortality, particularly sudden cardiac death; reduced triglyceride levels; increased high-density lipoprotein levels; improved endothelial function; reduced platelet aggregability; and lower blood pressure. These favorable effects outweigh the modest increase in low-density lipoprotein levels that may result from increased n-3 LC-PUFA intake. Preliminary evidence suggests increased consumption of n-3 LC-PUFAs with reduced intake of saturated fat may reduce the risk of conversion from impaired glucose tolerance to type 2 diabetes in overweight persons. Reported improvements in hemostasis, slower progression of artery narrowing, albuminuria, subclinical inflammation, oxidative stress, and obesity require additional confirmation. Expected health benefits and public health implications of consuming 1 to 2 g/day n-3 LC-PUFA as part of lifestyle modification in insulin resistance and type 2 diabetes are discussed.     

饮食n-3脂肪酸对小鼠脑脂类中多不饱和脂肪酸构成的影响

【目的】观察饮食鱼油n-3多不饱和脂肪酸(n-3 PUFAs)对脑内不同脂类中PUFAs构成的影响。【方法】使用C57BL/6J雌性小鼠,在胎儿期和幼年期分别给予不同种类高脂饲料(18%脂肪,供能比为36%)喂养-高脂豆油饲料、高脂鱼油饲料和高脂豆油:鱼油(5∶1)混合饲料,以正常饲料(6%脂肪来自豆油,供能比为12%)为对照,时间为4个月。采用薄层层析分离脑组织中各主要脂类成份,然后采用甲酯化-气相色谱分析对各脂类成份中的脂肪酸进行测定。【结果】鱼油饲料喂养改变了小鼠脑内主要脂类中PUFAs的构成。在磷脂中,虽然5种PUFAs在各饲料组之间差异均无显著性(P>0.05),但二十二碳六烯酸(DHA)/花生四烯酸(AA)(1.94±0.41)以及n-3/n-6 PUFAs比值(2.31±0.75)在鱼油组较其它三组显著升高(P<0.05);在甘油一和二酯中,与豆油组相比,鱼油组和豆油:鱼油混合组LA含量(0.31±0.09%,0.65±0.58%)降低,而鱼油组DHA/AA(2.60±1.66)以及n-3/n-6 PUFAs比值(2.31±0.75)升高(P<0.05);在甘油三酯中,与豆油组相比,鱼油组和豆油:鱼油混合组AA含量(1.62±0.53%,1.12±0.36%)和EPA含量(0.98±0.58%,1.34±0.31%)显著降低,而DHA/AA比值(1.14±0.21,1.46±0.58)升高(P<0.05),但DHA含量在三组之间无差异(P>0.05);在游离脂肪酸中,5种PUFAs在各饲料组之间无差异(P>0.05)。【结论】饮食鱼油n-3 PUFAs摄入增多虽然不影响脑内DHA的聚积,但改变了DHA/AA以及n-3/n-6PUFAs的比值。甘油酯类可能是脑摄取、聚积DHA的主要直接来源之一。     

不同配比高n-3/n-6多不饱和脂肪酸对大鼠胰岛素抵抗的影响

目的探讨长期摄入高脂不同n-3/n-6多不饱和脂肪酸(PUFAs)构成比的饮食后,大鼠胰岛素敏感性及血清炎症因子表达水平的变化。方法 40只刚断乳雄性SD大鼠适应性喂养7天后,根据体重随机分为4组:空白对照组(基础饲料)、高脂组(猪油)、高脂1∶1组(n-3/n-6为1∶1)和高脂1∶4组(n-3/n-6为1∶4),每组10只。每周记录一次大鼠体重,喂养16周处死动物,检测大鼠血脂、血清胰岛素敏感性和血清炎症因子(IL-6、TNF-α和hs-CRP)表达水平。结果与空白对照组相比,其他3个组体重显著上升(P<0.05);高脂1∶1组胰岛素敏感性与空白对照组比较,差异无显著性,且显著高于高脂组和高脂1∶4组(P<0.05);与高脂组相比,高脂1∶1组血清TNF-α和hs-CRP表达水平显著下降(P<0.05)。结论长期摄取高多不饱和脂肪酸同样具有肥胖风险,提高n-3PUFAs在膳食构成中的比重可以有效抑制炎症因子表达,改善胰岛素敏感性,预防胰岛素抵抗的发生。     

Increased n-6 polyunsaturated fatty acids do not attenuate the effects of long-chain n-3 polyunsaturated fatty acids on insulin sensitivity or triacylglycerol reduction in Indian Asians

BACKGROUND: Indian Asians in Western countries have a higher rate of coronary artery disease than do the indigenous white populations, and this higher rate may be influenced by a dietary imbalance of n-6 and n-3 polyunsaturated fatty acids (PUFAs). OBJECTIVE: The objective of the study was to test the hypothesis that a high background dietary intake of n-6 PUFA attenuates the effects of fish-oil supplementation on insulin sensitivity and associated blood lipids of the metabolic syndrome. DESIGN: Twenty-nine Indian Asian men were recruited to participate in a 12-wk dietary intervention trial. Volunteers were randomly assigned to receive either a moderate or a high n-6 PUFA diet featuring modified oils and spreads over a 6-wk period. After this 6-wk period, both groups were supplemented with 4.0 g fish oil/d (2.5 g eicosapentaenoic acid + docosahexaenoic acid) for an additional 6 wk in combination with the dietary treatment. Volunteers participated in a postprandial study and an insulin sensitivity test after the 6-wk dietary intervention and again after the fish-oil supplementation period. RESULTS: There was no significant time x treatment interaction for blood lipids or insulin action after dietary intervention with the moderate or high n-6 PUFA diets in combination with fish oil. After the 6-wk period of fish oil supplementation, fasting and postprandial plasma triacylglycerol concentrations decreased significantly. CONCLUSION: The background dietary n-6 PUFA concentration did not modulate the effect of fish-oil supplementation on blood lipids or measures of insulin sensitivity in this ethnic group.     

Fish, long-chain n-3 polyunsaturated fatty acids, and risk of colorectal cancer in middle-aged Japanese: the JPHC study

Although long-chain n-3 polyunsaturated fatty acids (Ln-3 PUFA), which are abundant in fish, have shown protective effects on colorectal cancer in laboratory studies, epidemiological studies to date have not been consistent. We evaluated the relationship of consumption of fish and Ln-3 PUFA to the colon and rectal cancer risk in the two cohorts of the Japan Public Health Center-based prospective study of 42,525 men and 46,133 women. Dietary and other exposure data were obtained between 1990 and 1994. Through December 1999, 705 cases of colon and rectal cancer were documented. When data from the two cohorts were pooled, multivariable relative risks (RRs) for the highest quartile compared with the lowest quartile of fish consumption were 1.07 (95% confidence interval, CI = 0.77-1.48) for colon cancer and 0.95 (95% CI = 0.63-1.43) for rectal cancer with no dose-risk trend. RRs for the highest quartile compared with the lowest quartile of eicosapentaenoic acid consumption were 1.05 (95% CI = 0.76-1.46) for colon cancer and 0.91 (95% CI = 0.60-1.38) for rectal cancer with no dose-risk trend. This study does not support the role of fish and Ln-3 PUFA in the etiology of colon and rectal cancer in this population whose fish consumption was high and the variation in Ln-3 PUFA consumption was large.     

Impact of foods enriched with n-3 long-chain polyunsaturated fatty acids on erythrocyte n-3 levels and cardiovascular risk factors

Consumption of fish or fish oils rich in the n-3 long chain PUFA EPA and DHA may improve multiple risk factors for CVD. The objective of this study was to determine whether regular consumption of foods enriched with n-3 long-chain PUFA can improve n-3 long-chain PUFA status (erythrocytes) and cardiovascular health. Overweight volunteers with high levels of triacylglycerols (TG; >1.6 mmol/l) were enrolled in a 6-month dietary intervention trial conducted in Adelaide (n 47) and Perth (n 39), and randomised to consume control foods or n-3-enriched foods to achieve an EPA + DHA intake of 1 g/d. Test foods were substituted for equivalent foods in their regular diet. Erythrocyte fatty acids, plasma TG and other CVD risk factors were monitored at 0, 3 and 6 months. There were no significant differences between groups for blood pressure, arterial compliance, glucose, insulin, lipids, C-reactive protein (CRP) or urinary 11-dehydro-thromboxane B2 (TXB2) over 6 months, even though regular consumption of n-3-enriched foods increased EPA + DHA intake from 0.2 to 1.0 g/d. However, the n-3 long-chain PUFA content of erythrocytes increased by 35 and 53 % at 3 and 6 months, respectively, in subjects consuming the n-3-enriched foods. These increases were positively associated with measures of arterial compliance and negatively associated with serum CRP and urinary 11-dehydro-TXB2 excretion. Sustainable increases in dietary intakes and erythrocyte levels of n-3 long-chain PUFA can be achieved through regular consumption of suitably enriched processed foods. Such increases may be associated with reduced CV risk.     

Test meals rich in marine long-chain n-3 polyunsaturated fatty acids increase postprandial chylomicron response

Postprandial lipid abnormalities are considered an independent cardiovascular risk factor. Hence, it is important to find nutritional strategies that are able to positively influence these abnormalities. Since the effect of n-3 polyunsaturated fatty acids (PUFA) and polyphenols on postprandial lipids in humans is still under debate, we evaluated the acute response of triglyceride-rich lipoproteins to test meals that are naturally rich in polyphenols and/or marine long-chain (LC) n-3 PUFAs. We hypothesized that LC n-3 PUFA would have a different effect on chylomicron and very low density lipoproteins when compared with polyphenols or their combination. We randomly assigned 78 individuals who were at high cardiometabolic risk to 4 isoenergetic diets. These diets only differed in amount of LC n-3 PUFA and/or polyphenols. Prior to starting the intervention, each subject underwent a test meal similar to the type of diet assigned: low in LC n-3 PUFA and polyphenols (control), rich in LC n-3 PUFA and low in polyphenols, rich in polyphenols and low in LC n-3 PUFA, or rich in both. Blood samples were taken before and up to 6 hours after the test meal in order to evaluate cholesterol and triglycerides (plasma and triglyceride-rich lipoprotein), apolipoprotein B-48 (large very low density lipoprotein), glucagon-like peptide-1, and free fatty acid plasma levels. The levels of chylomicron cholesterol and triglyceride in response to the test meal rich in LC n-3 PUFA were significantly higher than after the control meal (P = .037 and P = .018); there was no difference in the other variables. In conclusion, this study indicates that acute administration of marine LC n-3 PUFA increases postprandial chylomicron response in contrast with their lowering chronic effects. These differences underline the importance of understanding the acute and chronic effects of nutritional, as well as of other types of, interventions.     

Antiarrhythmic effects of n-3 polyunsaturated fatty acids

The n-3 or omega 3 polyunsaturated fatty acids are a promising dietary preventive therapy for cardiovascular disease. The main dietary source of n-3 polyunsaturated fatty acids comes from sea fish. During recent years, the subject of antiarrhythmic role of n-3 polyunsaturated fatty acids has been investigated extensively. A great deal of evidence has shown that the antiarrhythmic effect of n-3 polyunsaturated fatty acids is exerted by altering the electrophysiology of myocytes. This article is intended to review specifically this role of n-3 polyunsaturated fatty acids as demonstrated by both basic and clinical evidence in animal and human studies, including current concepts on the antiarrhythmic mechanism of this class of polyunsaturated fatty acids.     

Synthesis of long-chain polyunsaturated fatty acids in preterm newborns fed formula with long-chain polyunsaturated fatty acids

BACKGROUND: Docosahexaenoic acid (DHA) and arachidonic acid (AA) are long-chain polyunsaturated fatty acids (LCPs) that play pivotal roles in growth and neurodevelopment. OBJECTIVE: We aimed to quantify the synthesis of LCPs in preterm infants fed infant formula containing LCPs. DESIGN: Twenty-two preterm infants were randomly assigned to either the no-LCP group (fed formula without LCPs; n = 11) or the LCP group (fed formula with LCPs; n = 11). Dietary LCPs had higher (13)C content than did the endogenously synthesized LCPs, which were derived from linoleic and alpha-linolenic acids. The (13)C content of major selected plasma fatty acids was measured by using gas chromatography-isotope ratio mass spectrometry at birth and at age 1, 3, and 7 mo. Absolute LCP synthesis and the percentage of LCP synthesis relative to dietary intake were calculated. RESULTS: Percentage AA synthesis was 67.2 +/- 7.8%, 35.9 +/- 9.8%, and 29.0 +/- 10.3%, and that of DHA was 41.7 +/- 14.9%, 10.5 +/- 8.1%, and 7.4 +/- 6.2% at 1, 3, and 7 mo old, respectively. Absolute AA synthesis was 26.7 +/- 4.2, 14.4 +/- 3.9, and 11.6 +/- 4.1 mg x kg(-1) x d(-1) and that of DHA was 12.6 +/- 4.5, 3.2 +/- 2.5, and 2.3 +/- 1.9 mg x kg(-1) . d(-1) at 1, 3, and 7 mo old, respectively. AA and DHA synthesis decreased significantly (P < 0.01) with time, and AA synthesis was significantly (P < 0.01) greater than DHA synthesis. CONCLUSIONS: By this novel approach, we measured endogenous LCP synthesis in infants receiving dietary LCPs over long periods. By age 7 mo, LCP synthesis was dramatically lower in preterm infants fed LCPs.     

Association of n-3 and n-6 long-chain polyunsaturated fatty acids in plasma lipid classes with inflammatory bowel diseases

In order to establish the biochemical basis for dietary interventions, we investigated the fatty acid composition of plasma lipid classes in patients with inactive inflammatory bowel disease. In this cross-sectional study thirty patients with ulcerative colitis (UC), twenty-one with Crohn disease (CD) and twenty-four controls were investigated (mean age: UC, 40.8 (sd 12.1); CD, 37.6 (sd 11.0); control, 31.5 (sd 8.4) years). Fatty acid composition of plasma lipids was determined by high-resolution capillary GLC. In plasma phospholipids, significantly higher values of eicosapentaenoic (20 : 5n-3), docosapentaenoic (22 : 5n-3) and gamma-linolenic (18 : 3n-6) acids were found in control patients and patients with UC as compared to patients with CD [median % (weight by weight), control v. UC v. CD : 20 : 5n-3, 0.09 (interquartile range (IQR) 0.05) v. 0.14 (IQR 0.10) v. 0.16 (IQR 0.10), P < 0.05; 22 : 5n-3, 0.14 (IQR 0.10) v. 0.27 (IQR 0.16) v. 0.31 (IQR 0.10), P < 0.001; 18 : 3n-6, 0.02 (IQR 0.02) v. 0.03 (IQR 0.02) v. 0.05 (IQR 0.03), P < 0.05]. When compared to the control, values of the principal n-3 and n-6 long-chain PUFA, arachidonic acid (20 : 4n-6) and DHA (22 : 6n-3) were significantly higher in patients with UC but not in patients with CD [median % (w/w), UC v. control: 20 : 4n-6, 8.43 (IQR 3.23) v. 6.92 (IQR 2.96), P < 0.05; 22 : 6n-3, 1.22 (IQR 0.56) v. 0.73 (IQR 0.39), P < 0.05]. As seen there are considerable differences between the long-chain PUFA status of patients suffering from UC or CD. The data obtained in the present study do not support the concept of eicosapentaenoic acid or DHA deficiency in patients with either UC or CD.     

Influence of dietary n-3 polyunsaturated fatty acids on plasma lipemic effect of vitamin B6 deficiency.

Since many connections exist between vitamin B6 and lipid metabolism, we aim to investigate the lipemic effect of different dietary intakes of polyunsaturated fatty acids in rats fed a vitamin B6 deficient diet. Diets were either vitamin B6 deficient (-B6) or vitamin B6 sufficient, pair-fed to the deficient group (PF) and ad libitum (N). The diets were combined with normal lipid (LC: soya bean-coconut-palm oils) and fish oil (FO: soya bean-fish oil). The fish oil diet with sufficient vitamin B6 content caused an increase in n-3 long chain polyunsaturated fatty acids and a decrease in arachidonic acid. In the -B6 group fed a normal lipid diet, the arachidonic acid percentage decreased and the linoleic acid percentage increased; in the -B6 group fed fish oil these changes in fatty acid composition, already consequent upon dietary intake of n-3 long chain polyunsaturated fatty acids, did not show further variations. In the dietary condition of vitamin B6 deficiency, plasma cholesterol content increased in rats fed a lipid control diet, whereas no hypocholesterolemic effect was observed in those fed a fish oil diet. Plasma triglyceride contents were not influenced by dietary lipid quality because, in all conditions, the lower food intake of the PF groups caused a decrease and vitamin B6 deficiency caused an elevation in triglyceride contents which reached those of the ad libitum groups. The study highlights the interaction between vitamin B6 and polyunsaturated fatty acids and the opportunity of dietary intake of fish oil to counterbalance some effects of vitamin B6 deficiency.     

n-3及n-6多不饱和脂肪酸与乳腺癌关系的Meta分析

目的 系统评价n-3多不饱和脂肪酸(n-3PUFAs)、n-6多不饱和脂肪酸(n-6PUFAs)及其比例与乳腺癌发病风险的关系。方法 系统检索Pubmed、Embase、Web of Science、知网、万方等数据库截止至2022年1月1日有关n-3及n-6多不饱和脂肪酸与乳腺癌关系的研究,对最终纳入的文献进行数据提取与质量评价,采用Stata 15.1软件进行Meta分析。结果 共纳入33项针对n-3及n-6PUFAs和乳腺癌发病风险关联的观察性流行病学研究,其中队列研究14项,病例对照研究20项,共纳入研究对象1 077 178例,患者19 207例。Meta分析结果显示:n-3多不饱和脂肪酸(OR=0.933,95%CI:0.858～1.014)、n-6多不饱和脂肪酸(OR=1.018,95%CI:0.914～1.133)与乳腺癌发病风险无统计学关联(P>0.05),而较高的n-6/n-3PUFAs比值会显著增加乳腺癌的发病风险(OR=1.166,95%CI:1.047～1.299,P=0.005)。结论 n-6/n-3多不饱和脂肪酸的比值与乳腺癌的发病风险呈正相关,提示合理的膳食脂肪摄入比可能会降低乳腺癌的患病风险。而n-3及n-6多不饱和脂肪酸与乳腺癌发病风险的单独效应关系尚不明确,仍需更多前瞻性实验流行病学证据进行支持。     

n-3 polyunsaturated fatty acids and immune function

n-3 PUFA have been shown to reduce the risk of cardiovascular and inflammatory diseases. However, they have also been shown to suppress T-cell-mediated immune function, an undesirable effect, especially in immuno-suppressed individuals. Studies have thus far suggested that this immuno-suppression may be in part attributable to increased lipid peroxidation and decreased antioxidant (especially vitamin E) levels, which can be prevented by appropriate vitamin E supplementation. Further well-designed human studies are needed to determine the appropriate levels of n-3 PUFA and vitamin E supplementation to optimize the beneficial anti-inflammatory effect of n-3 PUFA and minimize their suppressive effect on T-cell function.     

不同n-3/n-6多不饱和脂肪酸构成比对大鼠脂代谢和食欲的影响

目的研究不同n-3/n-6配比脂肪酸对大鼠食欲影响及其与腺苷酸活化蛋白激酶(AMPK)基因表达的关系。方法58只SD大鼠适应性喂养7天后,尾静脉取血。根据血清总胆固醇(TC)水平随机分为6组:空白组(基础饲料),高脂组(高脂饲料),高脂1∶1组(高脂饲料+n-3/n-6=1∶1油),高脂1∶5组(高脂饲料+n-3/n-6=1∶5油),低脂1∶1组(脱脂基础饲料+n-3/n-6=1∶1油),低脂1∶5组(脱脂基础饲料+n-3/n-6=1∶5油),喂养45天,观察大鼠摄食与体重增长,并于实验第0、15、30和45天测定血清总胆固醇(TC)和甘油三酯(TG)含量。于45天处死动物,取下丘脑,用RT-PCR分别测下丘脑组织中NPY、AMPK-α2 mRNA表达。结果添加PUFA的四个组血清TC、TG、摄食量、体重及NPY、AMPK-α2mRNA表达均比高脂组大鼠明显降低(P<0.05)。结论PUFA改善血脂可能是通过影响AMPK表达,从而抑制下丘脑食欲相关基因表达,进而影响血脂代谢。