Competition of n-3 and n-6 polyunsaturated fatty acids in the isolated perfused rat heart

When perfused with exogenous arachidonic acid (AA) or eicosapentaenoic acid (EPA), the rat heart incorporated these fatty acids into phospholipids, chiefly as phosphatidylcholine. The pattern of fatty acid incorporation at any given concentration of fatty acid in the perfusate was not different between n-3 and n-6 polyenoates. When rat hearts were perfused with the same amounts but different mixtures of EPA and AA, the incorporation of EPA showed a marked increase proportional to the EPA/AA ratio present in the perfusate. Results indicated that cardiac muscle phospholipids incorporate n-3 and n-6 polyenoates equally effectively and hence enrichment of n-3 polyenoate can displace AA in the cardiac phospholipid pool.     

Inhibitory effects of n-3 polyunsaturated fatty acids on sigmoid colon cancer transformants

Various types of polyunsaturated fatty acids (PUFAs) have been suggested to exert different effects on the colon in terms of promotion or inhibition of tumor development. Results of in vitro and in vivo studies are, however, inconsistent and it remains unclear whether or not the cellular effects of PUFAs change along with the malignant transformation of colonic cells. In this study, we used the NIH3T3 cell line and its SIC (sigmoid colon cancer) oncogene transformants to compare the effects of PUFAs on the proliferation of non-malignant and malignant cells. We also determined the cellular utilization of fatty acids in media by a high-performance liquid chromatography method. The addition of exogenous arachidonic acid (ARA, an n-6 fatty acid), eicosapentaenoic acid (EPA, n-3), and docosahexaenoic acid (DHA, n-3) exerted different effects on NIH3T3 cells, and on SIC transformants, in which selective inhibitory effects were observed at media concentrations ranging from 10 to 20 μg/ml. In cells cultured in media supplemented with EPA or DHA at a concentration of 2 μg/ml, which had no effect on cell proliferation, the cellular utilization of linoleic acid (n-6), a precursor of n-3 fatty acids, was inhibited. This inhibition was stronger in SIC transformants than in NIH3T3 cells (P < 0.05). There was no difference in the utilization of fatty acids between the two cell lines cultured in media supplemented with ARA. We conclude that the cellular response to exogenous long-chain PUFAs is modified during the course of malignant transformation, and that EPA and DHA (n-3 PUFAs) appear to have specific inhibitory effects on cancer cells and may thus enhance the host defense against colon cancer. (Received Dec. 10, 1996; accepted July 25, 1997)     

Effects of long-chain polyunsaturated fatty acids on the contraction of neonatal rat cardiac myocytes.

Because of the ability of certain long-chain polyunsaturated fatty acids (PUFAs) to prevent lethal cardiac arrhythmias, we have examined the effects of various long-chain fatty acids on the contraction of spontaneously beating, isolated, neonatal rat cardiac myocytes. The omega 3 PUFA from fish oils, eicosapentaenoic acid [EPA; C20:5 (n-3)] and docosahexaenoic acid [DHA; C22:6 (n-3)], at 2-10 microM profoundly reduced the contraction rate of the cells without a significant change in the amplitude of the contractions. The fatty acid-induced reduction in the beating rate could be readily reversed by cell perfusion with fatty acid-free bovine serum albumin. Addition of either oxygenase inhibitors or antioxidants did not alter the effect of the fatty acids. Arachidonic acid [AA; C20:4 (n-6)] produced two different effects on the beating rate, an increase or a decrease, or it produced no change. In the case of the increased or unchanged beating rate in the presence of AA, addition of AA oxygenase inhibitors subsequently reduced the contraction rate. The nonmetabolizable AA analog eicosatetraynoic acid (ETYA) always reduced the beating rate, as did EPA or DHA. Two other PUFAs, linoleic acid [C18:2 (n-6)] and linolenic acid [C18:3 (n-3)] also exhibited similar but less potent effects compared with EPA or ETYA. In contrast, neither the monounsaturated fatty acid oleic acid [C18:1 (n-9)] nor the saturated fatty acids stearic acid (C18:0), myristic acid (C14:0), and lauric acid (C12:0) affected the contraction rate. The inhibitory effect of these PUFAs on the contraction rate was similar to that produced by the class I antiarrhythmic drug lidocaine. The fatty acids that are able to reduce the beating rate, particularly EPA and DHA, could effectively prevent and terminate lethal tachyarrhythmias (contracture/fibrillation) induced by high extracellular calcium concentrations or ouabain. These results suggest that free PUFAs can suppress the automaticity of cardiac contraction and thereby exert their antiarrhythmic effects.     

Induction of transforming growth factor-beta 1 (TGF-beta 1), receptor expression and TGF-beta 1 protein production in retinoic acid-treated HL-60 cells: possible TGF-beta 1-mediated autocrine inhibition.

Treatment of HL-60 cells, a human promyelocytic leukemia cell line, with the vitamin A derivative retinoic acid (RA) for 7 days resulted in a dose-dependent decrease in proliferation and increase in granulocytic differentiation. The role of transforming growth factor-beta 1 (TGF-beta 1), a protein with pleiotropic effects on the proliferation and differentiation of various cell types, was examined during RA-induced differentiation of HL-60 cells. Although TGF-beta 1 alone had little effect on proliferation or differentiation of HL-60 cells, addition of TGF-beta 1 to HL-60 cells treated with a suboptimum concentration of RA (1.0 nmol/L) resulted in a marked decrease in proliferation with no effect on granulocytic differentiation. Studies of the mechanism of RA-induced TGF-beta sensitivity showed that although untreated HL-60 cells expressed low levels of TGF-beta 1 binding proteins on the cell surface, the levels were increased in a dose-dependent manner after RA treatment. Maximum induction was achieved after treatment with 10 nmol/L RA and consisted predominantly of the 65-Kd TGF-beta 1 receptor type. Moreover, RA treatment also resulted in a dose-dependent increase in both TGF-beta 1 steady-state mRNA expression and production of active TGF-beta with maximum induction at 10 nmol/LRA. RA treatment of HL-60 cells had no effect on TGF-beta 2 and TGF-beta 3 mRNA expression. These data suggest that the effects of RA may be mediated by a TGF-beta 1-mediated autocrine antiproliferative loop during differentiation of HL-60 cells.     

Retinoic acid receptors in myeloid leukemia: characterization of receptors in retinoic acid-resistant K-562 cells.

Although mRNA for the retinoic acid receptor alpha (RAR-alpha) is expressed in many different myeloid leukemias, most of these leukemia cells exhibit little if any phenotypic response when exposed to retinoic acid (RA). To determine whether such RA resistance is related to altered RA receptor structure or function, we performed a detailed analysis of nuclear RA receptors in RA-resistant K-562 cells. These cells exhibit RA receptors of the same approximate molecular weight and similar kd as those exhibited by the RA-sensitive HL-60 leukemia cell line, but the number of RA receptors in the RA-resistant K-562 cells (80 per cell) is significantly lower than that exhibited by RA-sensitive HL-60 cells (550 per cell). Retroviral-mediated transduction of RAR-alpha cDNA into K-562 significantly increased the number of RA receptors to 2,000 per cell. These RAR-alpha-transduced K-562 cells, when incubated with RA, exhibit diminished cell proliferation associated with decreased c-myc expression and an accumulation of cells in G0/G1. In addition, these RA-treated cells exhibit downregulation of the CD15 surface antigen and a slight increase in hemoglobin production but manifest no other evidence of significant erythroid, megakaryocytic, or myeloid differentiation. These results indicate that an elevated number of nuclear RA receptors can be involved in altering proliferation but not necessarily the differentiation of certain RA-treated myeloid leukemia cells.     

Altered colonic mucosal availability of n-3 and n-6 polyunsaturated fatty acids in ulcerative colitis and the relationship to disease activity

Background and AimsThe polyunsaturated fatty acids (PUFA) arachidonic acid (AA, n-6) and eicosapentaenoic acid (EPA, n-3) are precursors of eicosanoids and other lipid mediators which have critical roles in inflammation. The mediators formed from the different PUFA have different potencies. We hypothesised that metabolic changes associated with colonic mucosal inflammation would modify the bioavailability of the eicosanoid precursors AA and EPA.MethodsColonic mucosa biopsies were obtained from patients with ulcerative colitis and from matched controls. Inflammation was graded endoscopically and histologically. Esterified and non-esterified fatty acids were determined within the biopsies using gas chromatography–mass spectrometry and liquid chromatography–mass spectrometry, respectively.ResultsBiopsy samples were collected from 69 UC patients (54 providing both inflamed and non-inflamed mucosa) and 69 controls. Inflamed mucosa had higher AA (p < 0.001) and lower EPA (p < 0.010) contents and a higher AA:EPA ratio (p < 0.001). Inflamed mucosa also had higher docosapentaenoic acid (DPA) and docosahexaenoic acid (DHA) and lower linoleic acid (LA) and α-linolenic acid (α-LNA) contents (all p < 0.001), compared to non-inflamed and controls. There were significant correlations between severity of inflammation and contents of AA, DPA and DHA (positive correlations) and of LA, α-LNA and EPA (negative correlations).ConclusionsHigher AA, AA:EPA ratio, DPA and DHA and lower LA, α-LNA and EPA are seen in inflamed mucosa in UC and correlate with severity of inflammation. This suggests an alteration in fatty acid metabolism in the inflamed gut mucosa, which may offer novel targets for intervention and should be considered if nutritional strategies are used.     

Recombinant human interferon alpha enhancement of retinoic-acid-induced differentiation of HL-60 cells

We have previously demonstrated that a combination of interferon beta and a differentiation agent, dimethyl sulfoxide (DMSO), is cytotoxic for HL-60 cells, a human promyelocytic leukemic cell line. We now report that a combination of recombinant interferon alpha (Intron; Schering) and retinoic acid is synergistically cytostatic for HL-60 cells. Retinoic acid (RA) induced the differentiation of HL-60 cells into granulocytes. Interferon (IFN) alone at 1-1000 IU/ml had no effect on either differentiation or proliferation of HL-60 cells. The addition of 1000 IU/ml of IFN and 10(-7) M RA at the initiation of culture reduced the number of viable cells to 28% of that observed for cells treated with RA alone. The decreased number of cells was a result of decreased cellular proliferation, rather than of a cytotoxic effect of the combination. IFN-RA-treated cells differentiated more rapidly than cells treated with RA alone. In addition, the final percentage of mature cells was increased at day 7 in IFN-RA-treated cultures, as compared with RA-treated cells. Simultaneous treatment of the cells with IFN and RA decreased the concentration of RA needed to induce differentiation or to exert a cytostatic effect. Significant changes in the nuclear structure of RA-treated HL-60 cells after 24 h have been reported. Cells were pulsed with RA for 24 h, washed, and IFN added. At day 7, cell growth was inhibited to the same extent as that of cells continuously exposed to IFN-RA. However, while 70% of the continuously exposed cell differentiated, cells pulsed with RA and subsequently treated with IFN did not differentiate. The results of this investigation further support our findings that combinations of IFN and inducers of differentiation may be of importance in the treatment of leukemia.     

Effect of polyunsaturated fatty acids of the n-3 and n-6 series on lipid composition and eicosanoid synthesis of platelets and aorta and on immunological induction of atherosclerosis in rabbits

The effect of dietary fish oil (rich in n-3 polyunsaturated fatty acids (PUFA], corn oil (rich in n-6 PUFA) and coconut oil (low in n-3 and n-6 PUFA) on the induction of atherosclerosis by serum sickness in rabbits was investigated over a 12-month period. Dietary fish oil led to a significant increase in the level of eicosapentaenoic acid (EPA) in all platelet phospholipid fractions and to a significant reduction in the level of platelet phosphatidylethanolamine arachidonic acid (AA). In aortic total phospholipids, rabbits given fish oil showed a significant reduction in AA and a significant increase in EPA. Rabbits given fish oil showed significantly lower collagen-induced platelet thromboxane A2 release and aortic production of 6-keto-PGF1 alpha. Serum total immune complex levels and anti-horse serum IgG levels were not influenced by diet. There was a significant reduction in total aortic atherosclerosis in fish oil-fed animals compared with coconut oil fed animals.     

Vascular smooth muscle cells preloaded with eicosapentaenoic acid and docosahexaenoic acid fail to respond to serotonin stimulation

Epidemiological, animal and clinical studies indicate that n-3 fatty acids may benefit individuals with known history of cardiovascular disease or at risk of developing it. Though there is indirect evidence to suggest that the beneficial effects of n-3 fatty acids may be because of their ability to inhibit smooth muscle cell (SMC) proliferation, there are no studies that have examined this hypothesis. In this study, the mitogenic effect of serotonin (5HT) and platelet derived growth factor (PDGF), known mitogens for vascular SMC, on aortic SMCs preloaded with eicosapentaenoic acid (EPA) and/or docosahexaenoic acid (DHA) is examined. 5HT and PDGF could only partially stimulate proliferation of SMC that were preloaded with EPA or DHA as compared to the control cells. gamma-Linolenic acid (LA) and oleic acid (OA) did not block the 5HT or PDGF induced 3[H]thymidine incorporation suggesting that the anti-proliferative effect was specific to n-3 fatty acids only. Further, when EPA and DHA were combined in the ratio they are present in fishoils, there was a synergistic interaction in inhibiting the proliferation of SMC. Further, SMC grown in the presence of EPA or DHA, when stimulated with 5HT, failed to show an increase in 5HT(2) receptor mRNA. One of the potential mechanism by which fish oils may prevent the development of atherosclerosis or restenosis could be inhibition of the mitogen induced SMC proliferation. Combination of EPA with DHA is likely to be more beneficial.     

Modification of the n-6/n-3 fatty acid ratio in the phospholipids of rat ventricular myocytes in culture by the use of synthetic media: functional and biochemical consequences in normoxic and hypoxic conditions

The respective roles of exogenous polyunsaturated fatty acids on the lipid composition, physiological properties and enzyme release was investigated on isolated cardiac muscle cells in normoxia and hypoxia. Rat neonatal ventricular myocytes were grown for 5 days in conventional serum-supplemented medium. Cells were then incubated for 24 h in fully chemically-defined media featuring a balanced fatty acid composition containing either linoleic acid (18:2 n-6) or linolenic acid (18:3 n-3) as sole polyunsaturated fatty acid source. Transmembrane potentials were monitored with microelectrodes and contractions with a photoelectric device. The radio of n-6 to n-3 phospholipid fatty acids increased from 6.3 in control cells to 20.2 in cells exposed to n-6 fatty acids (SM6) and decreased to 1.4 in those exposed to n-3 fatty acids (SM3). These modifications had no influence on the electrical and mechanical activities and on automaticity in normoxic conditions. The action potential depression under hypoxia was less severe in SM6 cells, whereas there was a better electrophysiological recovery upon reoxygenation in SM3 cells. However, the loss of lactate dehydrogenase during sustained hypoxic treatment was not affected by changes in phospholipid fatty acid pattern. These results suggest that the effect of the polyunsaturated fatty acid balance depends on the cellular function under study and on the environmental conditions.     

普伐他汀对红细胞膜n-6、n-3脂肪酸成分影响的研究

目的　观察普伐他汀对原发性高脂血症患者红细胞膜 n3、n6脂肪酸成分的影响。方法　 32例原发性高脂血症患者应用普伐他汀 10 m g qd,采用自身对照的方法分别于治疗前、治疗后 6周及 12周时测定患者血浆脂质成分 ,并用气相色谱法测定红细胞膜脂肪酸成分。结果　本组患者经治疗后胆固醇 (TC)、三酰甘油 (TG)、低密度脂蛋白胆固醇 (L DL- C)、载脂蛋白 B10 0 (apo B10 0 )均明显降低 (P<0 .0 5～ 0 .0 0 1) ;高密度脂蛋白胆固醇 (HDL- C)均升高 (P<0 .0 5～ 0 .0 0 1) ,红细胞膜 n- 6脂肪酸 ,以花生四烯酸为代表 (AA )显著降低 (P<0 .0 1) ,n- 3脂肪酸 ,即廿碳五烯酸 (EPA)和廿二碳六烯酸 (DHA )均显著升高 (P<0 .0 1)。 n- 6 / n- 3比值有降低 ,TC、TG、L DL - C下降与红细胞膜 AA / EPA、AA/ DHA比值降低呈显著正相关 (P<0 .0 1)。结论　普伐他汀在有效调节血脂的同时能调节红细胞膜 n3、n6脂肪酸成分     

Novel action of n-3 polyunsaturated fatty acids: inhibition of arachidonic acid-induced increase in tumor necrosis factor receptor expression on neutrophils and a role for proteases

OBJECTIVE: Neutrophils and tumor necrosis factor (TNF) play important roles in the pathogenesis of rheumatoid arthritis (RA). Modulation of TNF receptors (TNFRs) may contribute to the regulation of tissue damage, and n-6 polyunsaturated fatty acids (PUFAs) such as arachidonic acid (AA) can increase the expression of TNFRI and TNFRII on neutrophils. Because the n-3 PUFAs are antiinflammatory in RA, we examined whether, as a novel mechanism of action, n-3 PUFAs can antagonize the AA-induced increase in TNFR expression. METHODS: Human neutrophils were treated with PUFAs and examined for changes in surface expression of TNFRs by flow cytometry. Translocation of protein kinase C (PKC) and activation of ERK-1/2 MAPK were determined by Western blotting. Intracellular calcium mobilization was measured in Fura 2-loaded cells by luminescence spectrometry. RESULTS: Pretreatment of neutrophils with nanomolar levels of n-3 PUFAs, eicosapentaenoic acid, or docosahexaenoic acid led to a marked inhibition of the AA-induced up-regulation of TNFRs I and II. Such pretreatment, however, did not prevent AA from stimulating the activities of PKC and ERK-1/2, which is required for the actions of AA or its ability to mobilize Ca(2+). Nevertheless, treatment with n-3 PUFAs caused the stimulation of serine proteases that could cleave the TNFRs. CONCLUSION: These findings suggest a mechanism by which the n-3 PUFAs inhibit the inflammatory response in RA, by regulating the ability of AA to increase TNFR expression. These results help fill the gaps in our knowledge regarding the mechanisms of action of n-3 PUFAs, thus allowing us to make specific recommendations for the use of n-3 PUFAs in the regulation of inflammatory diseases.     

脂氧合酶对胰腺癌细胞增殖和凋亡的调节作用

目的观察5-脂氧合酶（LOX）及12-LOX在人胰腺癌中的表达，并初步探讨LOX的作用底物——多不饱和脂肪酸（PUFA）及LOX抑制剂对胰腺癌细胞增殖及凋亡的调节作用。方法用免疫组织（细胞）化学、逆转录聚合酶链反应（RT—PCR）方法研究5-LOX及12-LOX在胰腺癌组织和细胞株SW1990中的表达，用四甲基偶氮唑蓝（MTT）还原法及溴脱氧尿嘧啶（BrdU）标记法研究不饱和脂肪酸包括花生四烯酸（AA）、二十二碳六烯酸（DHA）和二十碳五烯酸（EPA）以及5-LOX抑制剂MK-886和12-LOX抑制剂Baicalein对SW1990细胞增殖的影响；并用末端脱氧核苷酰转移酶介导的d-UTP-生物素缺口末端标记法（TUNEL）及流式细胞术方法研究上述物质对SW1990细胞凋亡的影响。结果5-LOX及12-LOX在胰腺癌组织和SW1990人胰腺癌细胞呈高表达，显著高于人正常胰腺组织对照。AA促进胰腺癌细胞株SW1990的增殖，且呈剂量依赖性；而DHA及EPA抑制SW1990细胞增殖，均呈剂量依赖性，DHA及EPA尚可促进SW1990细胞凋亡。MK-886及Baicalein均能抑制胰腺癌细胞株SW1990的体外增殖，并呈剂量依赖性，两者均可促进SW1990细胞凋亡，作用24h后凋亡细胞比例增高。结论5-LOX及12-LOX在胰腺癌中表达上调，PUFA对胰腺癌细胞增殖与凋亡存在调节作用，并且不同脂肪酸作用存在差异。从促进胰腺癌细胞增殖，而DHA及EPA抑制其增殖，促进其凋亡。LOX抑制剂体外可抑制胰腺癌细胞增殖，并诱导细胞凋亡。LOX可能是胰腺癌生物化学治疗的新靶点。     

Comparative responsiveness of HL-60, HL-60R, and HL-60R+ (LRARSN) cells to retinoic acid, calcitriol, 9 cis-retinoic acid, and sodium butyrate

In HL-60 cells, retinoic acid (RA) and 9 cis-RA induce granulocytic differentiation, and calcitriol and sodium butyrate induce monocytic differentiation. To study the role of retinoid resistance on the response to these agents, we investigated their effects in HL-60 cells, retinoid-resistant HL-60R cells, and HL-60R+ cells in which retinoid sensitivity has been restored. In HL-60 cells, cathepsin D (ctsd) mRNA levels are increased by these agents and by cholera toxin after pretreatment with each agent. Calcitriol, 9 cis-RA, and sodium butyrate increase interleukin-8 (IL-8) mRNA expression, and pretreatment with these agents or RA potentiates the stimulation of IL-8 by phorbol ester (TPA). Pretreatment of HL-60 cells with all of the agents confers inducibility of cathepsin L (ctsl) mRNA by TPA in previously unresponsive cells. In HL-60R cells, none of the agents alone or in combination significantly enhances the expression of the ctsd, IL-8, or ctsl mRNAs. Retinoid stimulation (either alone or in combination with the other agents) of the three mRNAs is partially restored in the HL- 60R+ cells. Calcitriol does not alter the expression of any of these mRNAs, and only the stimulation of IL-8 mRNA by sodium butyrate is recovered. Treatment with all of the agents inhibits proliferation and stimulates differentiation of the HL-60 cells. RA and calcitriol are unable to inhibit proliferation of the HL-60R cells, whereas only calcitriol fails to inhibit proliferation of the HL-60R+ cells. None of the agents induces differentiation in either the HL-60R or HL-60R+ cells. Therefore, the mutation of the RA receptor alpha is insufficient to account for the altered responses of the HL-60R cells, and there are likely defects in other signaling pathways in these cells. These cells may prove useful in examining the mechanism of cross-resistance between various differentiating agents.     

Comparative changes in the fatty-acid composition of rat cardiac phospholipids after long-term feeding of sunflower seed oil- or tuna fish oil-supplemented diets

The fatty-acid composition of rat heart phospholipids was examined after long-term, i.e. more than 12 months, feeding of diets supplemented with n-6 fatty acids as sunflower seed oil (SSO), or n-3 fatty acids as tuna fish oil (TFO) which is a particularly rich source of docosahexenoic acid (DHA). Although some small changes occurred in the relative proportions of palmitic and stearic acids and in the ratio of total saturates to total unsaturates, the most important changes were in the relative proportions of 18:2 n-6 and 20:4 n-6 to 20:5 n-3 and 22:6 n-3. In general, the n-6/n-3 ratio of phosphatidylcholine (PC), phosphatidylethanolamine (PE) and diphosphatidyl glycerol (DPG) was altered in favour of the family of fatty acids administered, although the proportions of the individual long-chain polyunsaturated fatty acids which contributed to this ratio varied from one class of phospholipids to another. In cardiac PC and PE, feeding TFO supplements reduced the proportions of arachidonic acid (AA) and significantly elevated (p less than 0.01) the proportions of DHA but produced relatively little change in those of eicosapentenoic acid (EPA). In DPG, feeding TFO led to a significant increase in the proportion of AA as well as an increase in DHA. The level of EPA was relatively low in PC, PE and DPG even after TFO feeding and never reached comparable levels with that of either AA or DHA. Nevertheless the n-6/n-3 ratio in all these classes of major cardiac phospholipids was significantly reduced by feeding TFO compared to the SSO diet or the commercial rat chow (CC) reference group. In contrast to the reports of other workers who have studied the fatty-acid composition of platelet membranes after feeding various fish oil supplements, in the rat heart the major effect of tuna fish oil is an increase in the proportion of DHA rather than EPA in the cardiac phospholipids.     

Plasma polyunsaturated fatty acid profile and delta-5 desaturase activity are altered in patients with type 2 diabetes

Objective

The association between imbalance of polyunsaturated fatty acids (PUFAs), especially low plasma n-3 to n-6 PUFA ratio, and risk of cardiovascular diseases is well known. A balance of plasma PUFAs is determined not only by dietary fatty acid intake, but also by the endogenous fatty acid metabolism, which could be dysregulated by diabetes. In this study, we investigated the plasma n-3 and n-6 PUFA profile and fatty acid desaturase activity in patients with type 2 diabetes (T2D).

Materials/Methods

The subjects were 396 patients with T2D and 122 healthy controls. Plasma eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), arachidonic acid (AA), and dihomo-γ-linolenic acid (DGLA) levels were measured by capillary gas chromatography.

Results

Plasma DHA, AA, and DGLA levels were significantly higher, and EPA levels tended to be lower in patients with T2D than in the controls. Patients with T2D also exhibited significantly lower EPA/AA, DHA/AA, and (EPA + DHA)/AA ratios, and a higher AA/DGLA ratio than the controls. Multiple regression analyses, including age, sex, body mass index, and metabolic parameters in the total population, revealed that the presence of T2D was independently associated with elevated plasma DHA, AA, and DGLA levels and decreased EPA/AA, DHA/AA, and (EPA + DHA)/AA ratios. Furthermore, T2D was independently and positively related to the AA/DGLA ratio, which serves as an estimate of delta (Δ)-5 desaturase activity.

Conclusions

Elevated plasma AA levels and decreased n-3 PUFA/AA ratios in T2D are attributable, at least partly, to Δ5 desaturase activation.     

Aspirin-induced decline in prostacyclin production in patients with coronary artery disease is due to decreased endoperoxide shift. Analysis of the effects of a combination of aspirin and n-3 fatty acids on the eicosanoid profile

BACKGROUND. It was the purpose of this study to determine the effects of the combination of aspirin (ASA) and fish oil, which is rich in n-3 polyunsaturated fatty acids, on the eicosanoid profile of patients with coronary artery disease. Specifically, we wanted to determine whether the ASA-induced reduction in prostacyclin production is due to inhibition of endothelial cell cyclooxygenase or to reduced endoperoxide shift from platelets and whether ASA negates the potentially beneficial effects of fish oil on the eicosanoid profile. METHODS AND RESULTS. Fourteen patients with clinically stable but advanced coronary artery disease received 12 g (n = 8) or 16 g (n = 6) of fish oil concentrate containing 6 or 8 g of n-3 fatty acids for 6 weeks. In addition to the fish oil, patients received increasing daily doses of ASA (50 mg, 100 mg, 325 mg, and 1,300 mg; the latter in four divided doses). Each dose was taken for 2 weeks. With fish oil supplementation, red blood cell phospholipid fatty acid content of arachidonic acid (AA) decreased and of eicosapentaenoic acid (EPA) increased so that EPA as a percent of AA increased from 2% to 26%. Serum thromboxane B2, which represents the production of TXA2 by maximally stimulated platelets, was suppressed by 38% on fish oil alone and by 97% or greater on all doses of ASA. Excretion of PGI2-M, the main urinary metabolite of PGI2 (derived from AA), fell from 50 +/- 4 ng/g of creatinine to 42 +/- 2 ng/g on fish oil alone (p = 0.02). On 50 mg of ASA per day, PGI2-M excretion was 26 +/- 2 ng/g of creatinine (p less than 0.001 versus fish oil alone). On 100 mg and 325 mg of ASA per day, PGI2-M was 24 +/- 3 ng/g and 27 +/- 3 ng/g, respectively (p V NS versus value on 50 mg per day). PGI3-M, the main urinary metabolite of PGI3 (derived from EPA), increased from 0.2 +/- 0.1 ng/g of creatinine to 4.9 +/- 0.7 ng/g on fish oil alone (p less than 0.001). In contrast with the marked ASA-induced decline in PGI2-M, PGI3-M excretion was not affected by the addition of ASA, even at the higher doses (4.6 +/- 0.7 ng/g and 4.9 +/- 0.5 ng/g on 325 mg per day and 325 mg four times daily, respectively). CONCLUSIONS. Moderate-dose (325 mg per day or less) ASA taken once daily has no effect on PGI3 production despite significantly reducing PGI2 production. This suggests that endothelial cell cyclooxygenase is minimally inhibited by such doses of ASA and that a large percent of the PGI2 produced in patients with advanced coronary artery disease derives from the transfer of prostaglandin endoperoxides from activated platelets to endothelial cells. The loss of these substrates accounts for the decrease in PGI2 with moderate-dose ASA. Thus, the ASA-induced decrease in PGI2 may in large part be an unavoidable consequence of ASA-induced platelet cyclooxygenase inhibition. ASA does not negate the potentially beneficial effects of n-3 fatty acids on the eicosanoid profile.     

Serum non-esterified very long-chain PUFA are associated with markers of endothelial dysfunction

The objective of this study was to investigate the pattern of serum non-esterified fatty acid (NEFA) fraction in association with atherosclerosis development. We have studied possible relationships between eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and arachidonic acid (AA) in the NEFA fraction and biochemical markers of endothelial activation or dysfunction. The study population consisted of 152 elderly men with high risk for coronary heart disease. The composition of fasting serum NEFA was analysed by gas-liquid chromatography. Endothelial activation was evaluated using biochemical analyses of some markers of endothelial function. A significant inverse linear association was found between serum non-esterified EPA and DHA, and soluble vascular cell adhesion molecule-1 (sVCAM-1) (P=0.02 and 0.001, respectively). An inverse linear association was found between serum non-esterified AA and sVCAM-1 (P=0.001) and von Willebrand Factor (P=0.005). The significant inverse associations for DHA and AA were independent from the serum content of other NEFAs. Taken together, negative associations were found between sVCAM-1 and the serum levels of non-esterified DHA, EPA and AA. The inverse relation between the levels of sVCAM-1 and very long-chain n-3 fatty acids might indicate an anti-inflammatory effect of the latter.     

Reduction of cardiovascular risk factors with longterm fish oil treatment in early rheumatoid arthritis

OBJECTIVE: Rheumatoid arthritis (RA) is associated with increased risk for cardiovascular (CV) events through multiple factors. Fish oil has been shown to reduce symptoms in RA and to reduce CV risk. We assessed the effect of an antiinflammatory dose of fish oil on CV risk factors within a program of combination chemotherapy for patients with early RA. METHODS: Patients who chose not to take fish oil (n = 13) were compared with patients who achieved a sustained elevation of eicosapentaenoic acid (EPA) in plasma phospholipid fatty acids (> 5% total fatty acids) while taking fish oil over a 3-year period (n = 18). We examined cellular content of arachidonic acid (AA), synthesis of thromboxane A2 and prostaglandin E2, use of nonsteroidal antiinflammatory drugs (NSAID), traditional CV lipid risk factors, and disease activity at 3 years. RESULTS: At 3 years, AA (as a proportion of AA plus long-chain n-3 fatty acids that can compete with AA for cyclooxygenase metabolism) was 30% lower in platelets and 40% lower in peripheral blood mononuclear cells in subjects taking fish oil. Serum thromboxane B2 was 35% lower and lipopolysaccharide-stimulated whole-blood prostaglandin E2 was 41% lower with fish oil ingestion compared to no fish oil. NSAID use was reduced by 75% from baseline with fish oil (p < 0.05) and by 37% without fish oil (NS). Favorable changes in fasting blood lipids were seen with, but not without fish oil. Remission at 3 years was more frequent with fish oil use (72%) compared to no fish oil (31%). CONCLUSION: Fish oil reduces cardiovascular risk in patients with RA through multiple mechanisms.