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。     

多不饱和脂肪酸不同配比对大鼠血脂影响

目的 研究不同n-3/n-6配比的多不饱和脂肪酸(PUFA)对大鼠血脂影响。方法 将58只SD大鼠根据血清总胆固醇(TC)水平随机分为6组,分别给予基础饲料、高脂饲料和添加n-3/n-6不同配比PUFA的高脂或基础饲料。于第15,30,45 d分别测血脂水平,第45 d取脂肪组织称重并测肝组织中过氧化物酶体增殖物激活受体γ(PPAR-γ)和腺苷酸活化蛋白激酶α2(AMPK-α2)的mRNA表达。结果 摄入添加PUFA膳食的4组大鼠45d后血清甘油三酯(TG)分别为(1.15±0.37),(1.25±0.56),(1.00±0.25),(1.17±0.30)mmol/L,均明显低于高脂组的(1.73±0.33)mmol/L;TC分别为(1.80±0.18),(1.89±0.20),(1.41±0.21),(1.58±0.16)mmol/L,均明显低于高脂组的(2.23±0.19)mmol/L;低密度脂蛋白胆固醇(LDL-C)分别为(1.00±0.23),(1.25±0.18),(1.06±0.13),(1.25±0.14)mmol/L,均明显低于高脂组的(1.53±0.27)mmol/L;其脂体比、PPAR-γmRNA、AMPK-α2mRNA表达量均明显高于高脂组,差异均有统计学意义(P<0.05)。结论 PUFA改善大鼠高血脂并降低脂肪积累,可能与肝组织AMPK和PPAR-γ等脂肪酸氧化基因表达增加有关。     

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。     

The effects of polyunsaturated:saturated fatty acids ratios and peroxidisability index values of dietary fats on serum lipid profiles and hepatic enzyme activities in rats

Raising the dietary PUFA:saturated fatty acids (SFA) ratio has been recommended for the prevention of CVD. However, a high PUFA:SFA (P:S) ratio diet enhances oxidative stress because PUFA are highly susceptible to lipid peroxidation. Thus, we focused on the role of the dietary P:S ratio and peroxidisability index (PI) value on serum and liver tissue and investigated the effects of dietary P:S ratios (0.4, 1.0, and 4.8) with a fixed PI value (81) on serum lipid parameters and hepatic enzyme activities (experiment 1). To elucidate whether those phenomena were unique to the P:S ratio, we examined the effects of dietary PI values (36, 81, 126, and 217) with a constant P:S ratio (1.0) (experiment 2). Female Sprague-Dawley rats weighing 240-280 g were fed experimental diets for 4 weeks. When dietary PI value was maintained at 81, serum HDL-cholesterol (HDL-C) increased with increasing dietary P:S ratio. When the P:S ratio was fixed at 1.0, HDL-C was the lowest with mid-low PI (MLPI) (PI value of 81). In both experiments, serum LDL-cholesterol:HDL-C ratio kept in the range of 0-2. The hepatic superoxide dismutase, catalase, and glutathione peroxidase (GSH-Px) activities and thiobarbituric acid reactive substance (TBARS) concentrations were the highest in the lowest dietary P:S ratio group (experiment 1). GSH-Px, glutathione-S-transferase, and TBARS were the lowest in rats fed the MLPI diet (experiment 2). In conclusion, these results indicate that a P:S ratio of 1.0-1.5 and a PI value of 80-90 in the diet are within a favourable range to reduce the risk of CVD.     

Reversal of the arrhythmogenic effects of long-term saturated fatty acid intake by dietary n-3 and n-6 polyunsaturated fatty acids

This study investigated whether the adverse influences of dietary saturated animal fatty acids (SF) on vulnerability to cardiac arrhythmias in rats could be modified by crossover in maturity to diets rich in polyunsaturated fatty acids (PUFAs). The arrhythmia model was coronary artery occlusion and reperfusion under anesthesia. Animals were fed commercial stock diet (4% fat wt:wt) supplemented (12% wt:wt) with fat (final diets, 35% energy as fat). Of rats fed the SF diet for 9 and 18 mo, ventricular fibrillation (VF) occurred in 71% during occlusion and in 86% on reperfusion. Mortality from VF was 0% after 9 mo on the SF diet but 67% after 18 mo. Dietary crossover to n-3 (tuna-fish oil) or n-6 (sunflower-seed oil) PUFA-supplemented diets at 9 mo reduced arrhythmias (VF incidence less than 30% in occlusion and reperfusion) and mortality (0%). The n-3 PUFAs were most effective. Dietary interventions can be effective even when introduced in mature, high-risk animals and may be of benefit in reducing risk of sudden cardiac death.     

膳食脂肪酸及n-6/n-3比与血脂及脂质过氧化关系的研究进展

膳食脂肪酸及n-6/n-3比对血脂及脂质过氧化的影响是营养学研究的重要课题,首先叙述膳食脂肪酸对血脂和脂质过氧化的影响及作用机制.然后从预防动脉粥样硬化的角度,提出建立合理的n-6/n-3脂肪酸供给比的重要性.     

不同n-6/n-3多不饱和脂肪酸构成比对高脂饲料喂养大鼠脂联素和糖脂代谢及抗氧化能力的影响

目的探讨高脂饲料喂养条件下,不同n-6/n-3多不饱和脂肪酸(polyunsaturated fatty acid,PUFA)构成比对大鼠脂联素和糖脂代谢及抗氧化能力的影响。方法50只雄性Wistar大鼠按体重随机分为5组:1个普通饲料组(脂肪供能比17%,n-6/n-3PUFA=5∶1)和4个高脂饲料组(脂肪供能比均为42%,n-6/n-3 PUFA构成比分别为1∶1、5∶1、10∶1、20∶1)。喂养12周后检测大鼠血糖和血脂(0、4、8和12周)、血清抗氧化指标(0和12周)以及睾周脂肪组织脂联素mRNA、蛋白表达和血清脂联素水平(12周)。结果大鼠各指标初始值组间差异均无统计学意义(P>0.05)。12周时,n-6/n-3PUFA 10∶1、20∶1组血糖显著高于对照组(P<0.05),4个高脂组血清总胆固醇(total cholesterol,TC)、甘油三酯(triglyceride,TG)显著高于对照组(P<0.01),其中20∶1组TG显著高于其余3组(P<0.01);4个高脂组谷胱甘肽过氧化物酶和超氧化物歧化酶含量显著低于对照组(P<0.05),其中20∶1组下降最明显,丙二醛含量显著高于对照组(P<0.05),其中10∶1组上升最明显;20∶1组脂联素mRNA表达显著低于对照组、1∶1组和5∶1组(P<0.05),5∶1组脂联素蛋白表达水平显著高于其余高脂组(P<0.05),而20∶1组表达水平最低(P<0.05)。结论较低的n-6/n-3 PUFA构成比(1∶1和5∶1),有助于改善高脂饲料条件下大鼠糖脂代谢及抗氧化能力,提高脂联素表达。     

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.     

Effects of dietary n-6/n-3 polyunsaturated fatty acid balance on tissue lipid levels, fatty acid patterns, and eicosanoid production in rats.

The effect of varying n-6/n-3 ratios (0.6-10.2) of dietary fats on various lipid parameters was examined in rats under a constant P/S ratio (1.4-1.5) with sardine oil as the source of n-3 polyunsaturated fatty acid (PUFA) by a combination of palm and safflower oils. The concentration of serum cholesterol tended to increase with n-6/n-3 of up to approximately 2, whereas aortic cholesterol decreased. The proportion of arachidonic acid in liver, heart, and aorta phosphatidylcholine increased linearly with increasing n-6/n-3 whereas that of linoleic acid reached a plateau at this ratio of approximately 4. The proportion of n-3 PUFAs decreased with increasing n-6/n-3 in tissue phosphatidylcholine. Although the production of prostacyclin (PGI2) by the thoracic aorta and thromboxane A2 (TXA2) by platelets increased with increasing n-6/n-3, TXA2/PGI2 was maintained at a low level up to n-6/n-3 of approximately 5. These results indicate that, when fish oil is the source of n-3 PUFAs, n-6/n-3 of 2-5 seems to be desirable for the various lipid parameters related to atherosclerosis and thrombosis.     

Effects of various combinations of omega 3 and omega 6 polyunsaturated fats with saturated fat on serum lipid levels and eicosanoid production in rats

The effects of varying the ratio of polyunsaturated/saturated fatty acids (P/S) and omega 3/omega 6 polyunsaturated fatty acids (PUFA) of dietary fats on lipid metabolism were studied in rats using safflower oil (SFO), linseed oil (LSO), palm oil (PLO), and a 1:1 combination of these oils. The hypocholesterolemic and hypotriglyceridemic effects depended on the P/S ratio of dietary fats, LSO (omega 3 PUFA) being more effective than SFO (omega 6 PUFA). A similar pattern of the response was observed on liver cholesterol and triglyceride. The liver cholesterol-lowering effect of LSO, but not SFO, remained even when they were combined with PLO. The activity of liver delta 6-desaturase tended to be higher while that of liver phospholipase A2 was significantly lower in the LSO group than in the SFO or PLO groups. The aortic PGI2 production and the production by platelets of thromboxane A2 were significantly low in rats fed LSO accompanying a distinct reduction of arachidonate in tissue phospholipids. The depressing effect of LSO disappeared when it was combined with SFO but not with PLO. There were no significant differences in enzyme activities and eicosanoid production between SFO and PLO in spite of a large difference in their P/S ratio. Thus, lipid parameters examined were complicatedly regulated by the ratios of omega 3/omega 6 as well as P/S, suggesting an existence of an appropriate ratio for these variables.     

Consumption pattern of dietary fats in Chile: n-6 and n-3 fatty acids

Chile consumes both vegetable and animal fats. Vegetable oils are almost totally imported but animal fats, mainly from marine origin, are locally produced. The country is the second world producer of fish meal and fish oil, and fish oil has been incorporated into the human nutrition through the manufacture of blends of vegetable oil with fractions of deodorized fish oil. Consumption of such oils contributes as a significant source of n-6 and n-3 fatty acids, mainly for the low-income consumers. The use of fish meal and fish oil for animal nutrition is also an additional source of n-3 fatty acids for the Chilean population. Pork, poultry and eggs are important sources of essential fatty acids, especially long-chain n-3 fatty acids. As result of the consumption of these products, milk from low-income Chilean mothers shows significantly higher total n-3 fatty acids relative to mothers from the USA and Germany. Safety concerns about fats consumption in Chile are regulated by a Food Safety Codex recently promulgated which follows FAO/WHO Codex Alimentarius directives.     

Influence of dietary n-6/n-3 polyunsaturated fatty acid balance on the development of tolerance during chronic ethanol intoxication in rats.

The present study addresses the possible interacting effects of dietary n-6/n-3 polyunsaturated fatty acid (PUFA) balance and chronic ethanol intoxication on the synaptic membrane responses to ethanol and the development of tolerance in rats. Wistar rats were fed either a standard lab chow or various semi-synthetic diets: rich in PUFA (from soya oil: SO), deficient in linolenate (from sunflower oil: SFO) or rich in long-chain (n-3) PUFA (cod liver oil: CLO). Male adult rats from the second specially fed generation were submitted to a 3-week alcoholization by daily intubation. Functional tolerance was quantified by the hypothermic response to a challenge dose of ethanol. Synaptic fluidity and sensitivity to ethanol (variations after acute ethanol addition) were assessed by fluorescence polarization (FP) of DPH, TMA-DPH or PROP-DPH. Membrane fatty acid composition was determined by GLC. The fatty acid composition of the synaptic membranes was influenced by the diet, but rearrangements among the lipids occurred, resulting in an apparent stability in brain membrane fluidity parameters. Nevertheless, clear-cut differences were noted in response to ethanol intoxication according to the diet. In the same period of time, rats fed SFO or CLO diets were unable to develop tolerance to ethanol at the membrane level as well as functionally, contrarily to the rats fed SO or standard diets. The structurally specific roles of PUFA are suggested by the negative membrane effects of the alpha-linolenate deficient diet (SFO) and the positive ones of a diet (SO) rich and well balanced in (n-3 + n-6) PUFA. Furthermore, the n-6/n-3 PUFA balance in the synaptic membrane needs to be kept within very narrow limits to allow normal development of the adaptive response to ethanol.     

Effects of dietary saturated,monounsaturated and polyunsaturated fats on plasma lipids and lipoproteins in diabetic rats*

The effects of altering the type of dietary fat on plasma lipid and lipoprotein levels were investigated in streptozotocin‐diabetic rats fed non‐purified diets containing corn oil, olive oil, cod‐liver oil, sheep tallow and lard. After 32 days of experimental feeding, plasma levels of glucose, triglycerides, total cholesterol, low density and high density lipoprotein cholesterol were determined. Body weights and food intake were also measured. In neither animal group did the type of fat in the diet affect significantly the plasma levels of lipids and lipoproteins and their calculated ratios, and plasma glucose, body weight change or accumulative food intakes. In all studied diabetic rats, significant correlations were observed between body weight change and the following plasma variables: total cholesterol level (r = —0.37, P < 0.03), low density lipoprotein cholesterol level (r = —0.38, P<0.03) and triglycéride concentration (r = —0.36, P < 0.04). A significant positive correlation (r = 0.60, P < 0.0003) was also found between plasma levels of glucose and triglycérides. No significant correlations were noticed between accumulative food intakes and any of the studied variables. It is concluded that, in uncontrolled hyperglycemia in diabetes, the type of fat in the diet exerts little or no influence on plasma lipid and lipoprotein concentrations.     

Modulation of liver microsomal monooxygenase system by dietary n-6/n-3 ratios in rat hepatocarcinogenesis

This study was designed to determine the effects of dietary n-3/n-6 fatty acid ratios on preneoplastic foci and the microsomal monooxygenase system in rat hepatocarcinogenesis. Male Sprague-Dawley rats were fed four kinds of diets containing 15% (wt/wt) fat with different n-6/n-3 ratios: low ratio (> or = 1.0) with tuna oil, low ratio (> or = 1.0) with perilla oil, moderate ratio (< or = 4.0), and high ratio (< or = 10.0). Hepatocarcinogenesis was induced by diethylnitrosamine and partial hepatectomy. The moderate ratio diet decreased significantly the area and number of placental glutathione S-transferase-positive foci compared with the high ratio diet and low ratio diet with perilla oil. The fatty acid composition of microsomal membrane varied extensively, reflecting the dietary n-6/n-3 ratios. Liver microsomal lipid peroxidation was significantly decreased in the group fed the low ratio diet with tuna oil compared with the moderate and high ratio groups. Glucose-6-phosphatase activity, which reflects membrane stability, was significantly higher in the low ratio groups than in the high ratio group. The monooxygenase activities were increased significantly in the moderate ratio group compared with the high ratio group. These results suggest that a moderate n-6/n-3 ratio (< or = 4.0) may be the most effective in decreasing preneoplastic foci by elevating the monooxygenase activities and n-3 fatty acids in fish oil may have a protective effect by lowering the lipid peroxidation and stabilizing the microsomal membrane during rat hepatocarcinogenesis.     

The effects of acute and chronic administration of n-6 and n-3 polyunsaturated fatty acids on ethanol-induced gastric haemorrhage in rats.

Female weanling rats in three equal groups (n 12) were given orally by intubation 1 ml micellar solution of taurocholic acid (10 mM) and either arachidonic acid (20:4 n-6), linoleic acid (18:2 n-6) or eicosapentaenoic acid (20:5 n-3) at a concentration of 120 mM. After 1 h the rats were given intragastrically 2 ml absolute ethanol and were killed 1 h later. Rats given oral 20:4 n-6 showed a significant reduction (P less than 0.05) in the extent (%) of gastric mucosal haemorrhage compared with either the rats given 20:5 n-3 or 18:2 n-6 (8.3 (SD 7.3), 23.2 (SD 10.4) and 21.4 (SD 10.4) respectively. In a second experiment, four equal groups (n 12) of female Wistar rats were fed for 5 weeks on either a control diet of standard laboratory rat food, or the same diet enriched with either maize oil or fish oil or butterfat at a level of 100 g/kg. Following a 24 h fast the rats received an intragastric dose of 2 ml ethanol and were killed 1 h later. Examination of the extent (%) of gastric lesion showed a significant reduction (P less than 0.05) with the feeding of either maize oil or fish oil compared with the controls (12.2 (SD 8.2), 15.3 (SD 13.2) and 29.3 (SD 14.0) respectively). The butterfat diet was not significantly different from the control diet (23.8 (SD 8.1)).     

Effect of dietary polyunsaturated/saturated fatty acid ratio and dietary vitamin E on lipid peroxidation in the rat

The effects of the dietary ratio of polyunsaturated/saturated fatty acids (P/S) and dietary vitamin E on lipid peroxidation (LP) were examined to determine whether the vitamin E requirement is elevated by increased P/S in ratios comparable to those found in human diets. Twelve groups of male weanling rats (six/group) were fed purified diets containing 20% fat with P/S ratios of 0.38, 0.82 or 2.30. At each P/S level, groups of rats received either 0, 10, 40 or 100 IU vitamin E/kg diet supplied as all-rac-alpha-tocopherol. After the diets were fed for 16 wk, in vivo LP was assessed by measuring pentane in expired breath. Pentane levels were significantly elevated in rats fed 0 IU vitamin E at all P/S levels. Both 40 and 100 IU vitamin E decreased pentane production to minimal levels for all P/S groups. Liver malondialdehyde levels and in vitro spontaneous red blood cell hemolysis results also indicated a significant effect of vitamin E in reducing in vitro LP, but no overall effect of P/S. Testicular and epididymal histology showed no effect of dietary P/S on the vitamin E requirement. These data demonstrated 40 IU vitamin E to be adequate for maximal inhibition of LP at the P/S levels tested and indicated that these levels of dietary P/S had no significant impact on the vitamin E requirement for the growing rat.     

膳食n-6/n-3脂肪酸比值对小鼠淋巴细胞脂肪酸构成和功能的影响

目的观察膳食n6n3脂肪酸比值对淋巴细胞脂肪酸构成及细胞功能的影响。方法BALBc小鼠随机分为5组n6n3比值分别为1(A组)、75(B组)、15(C组)、30(D组)和正常对照组,其中实验组S∶M∶P模拟中国居民膳食脂肪酸摄入的S∶M∶P为1∶15∶1,正常对照组为AIN93G配方的1∶15∶37。基础饲料采用AIN93G配方,脂肪酸构成以食用油脂调配。饲养12周。测定小鼠T淋巴细胞功能,脾淋巴细胞脂肪酸构成、PGE2水平。结果n6n3比值接近1时,小鼠T淋巴细胞增殖活性、CD4+、CD8+T细胞比例、培养上清IL2、PGE2水平显著降低;淋巴细胞C18∶2、C20∶4、n6PUFA含量显著减少;C22∶6、C16∶1、C18∶1、总MUFA含量明显高于其他实验组。淋巴细胞C22∶6含量与淋巴细胞增殖活性显著负相关;C20∶5含量与CD4+T淋巴细胞比例、IL2水平显著负相关;C16∶1含量与CD4+、CD8+T淋巴细胞比例显著负相关。结论小鼠脾淋巴细胞的脂肪酸构成受膳食脂肪酸构成的影响;n6n3比值为1组与比值为30的膳食组相比较,小鼠T淋巴细胞增殖活性受到抑制。     

Influences of dietary polyunsaturated or saturated fats and of concanavalin-a upon proliferation of spleen lymphoid cells from rats

The effects of dietary polyunsaturated and saturated fats upon several metabolic phenomena were studied in rats. These included phospholipid (PL) levels in unstimulated spleen lymphoid cells (SLC) and serum; in vitro proliferation of unstimulated SLC from the two groups of rats; the influence of mitogenic concanavalin-A (Con-A) on in vitro proliferation of SLC from the two groups of rats; and the influence of serum from the two groups of rats on SLC proliferation. Weanling male Long-Evans rats were fed ad libitum either a polyunsaturated fatty acid (PUFA)-adequate (safflower oil, SO) or PUFA-deficient (coconut oil, CNO) diet for 21 days. Growth was significantly less in the CNO group than in the SO group. Food intake was not different for the dietary groups. Unstimulated SLC and serum of CNO rats showed changes in fatty acid composition of PL typical of tissue PL in essential fatty acid-deficient (EFA-D) rats. Unstimulated SLC from the two groups cultured in medium containing serum from the same groups showed equivalent rates of in vitro proliferation. In vitro proliferations of SLC were influenced: by the dietary source of SLC but not by the dietary source of serum, used in the culture medium, when the cells were stimulated by suboptimal doses of Con-A; by the dietary source of serum but not by the dietary source of SLC when the cells were stimulated by the optimal dose of Con-A; and by an interaction between source of SLC and serum, when the cells were stimulated by a supra-optimal dose of Con-A. The present study indicates that in vitro proliferation of SLC from PUFA-adequate and PUFA-deficient rats is influenced by both the dietary source of serum used in the culture medium and the concentration of Con-A used for stimulation of the SLC.     

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.