No abstract

The objective of the present study was to compare hepatic fatty acid deposition, plasma lipid level and expression of cholesterol homeostasis controlling genes in the liver of rats (Wistar Albino; n = 32) and pigs (Large White × Landrace; n = 32) randomly assigned into two groups of 16 animals each and fed 10 weeks the diet with either 2.5% of fish oil (F; source of eicosapentaenoic and docosahexaenoic acid, EPA+DHA) or 2.5% of palm oil (P; high content of saturated fatty acids; control). F-rats deposited in the liver three times less EPA, but 1.3 times more DHA than F-pigs (p < 0.05). Dietary fish oil relative to palm oil increased PPARα and SREBP-2 gene expression much strongly (p < 0.01) in the pig liver in comparison with the rat liver, but expression of Insig-1 and Hmgcr genes in the liver of the F-pigs relative to the expression of these genes in the liver of the P-pigs was substantially lower (p < 0.01 and p < 0.05 respectively) as compared to rats. When plasma lipid concentration in the F-animals was expressed as a ratio of the plasma concentration in the P-counterparts, dietary fish oil decreased HDL cholesterol less (p < 0.01), but LDL cholesterol and triacylglycerols more (p < 0.05 and p < 0.001 respectively) in rats than in pigs: more favourable effect of fish oil on rat plasma lipids in comparison with pigs can therefore be concluded. Concentration of total cholesterol and both its fractions in the rat plasma was negatively correlated (p < 0.01) with hepatic DHA, but also with unsaturated myristic and palmitic acid respectively. It has been concluded that regarding the similarity of the plasma lipid levels to humans, porcine model can be considered superior; however, using this model, dietary fish oil at the tested amount (2.5%) was not able to improve plasma lipid markers in comparison with saturated palm oil.

A hypothesis that eicosapentaenoic acid + docosahexaenoic acid (EPA+DHA) lower plasma cholesterol via increased expression of the Insig-1 gene with ensuing decrease of expression of genes coding for 3-hydroxy-3-methyl-glutaryl-CoA reductase (Hmgcr) and low density lipoprotein receptor (Ldlr) was tested in rats fed a diet with 3% of fish oil (FO). Expression of the Insig-1 gene in the liver of the FO-fed rats was 730% (P < 0.05) of the control. However, contrary to the hypothesis, expression of the Hmgcr gene and Ldlr gene was 165% and 210% of the control (P > 0.05). Nevertheless, FO in the diet decreased (P < 0.05) plasma cholesterol of rats by 10% (from 1.19 to 1.07 mmol/l); it was therefore concluded that the cholesterol-lowering effect of EPA+DHA is at least partly based on mechanisms other than tested in the present experiment.

The purpose of the study was to test the hypothesis that the dietary oils with different content of n-3 polyunsaturated fatty acids (PUFA) eicosapentaenoic acid (EPA) + docosahexaenoic acid (DHA) affect plasma lipid level in rats in a different degree. The diets with 6% of fish oil (FO) and Schizochytrium microalga oil (SchO; EPA+DHA content in the diets 9.5 + 12.3 and 2.6 + 29.5% of the sum of total fatty acids, respectively) were used; the diet with 6% of safflower oil (high content of n-6 PUFA linoleic acid, 65.5%; EPA+DHA content 0.7 + 0.9%) was used as a control. The difference between FO and SchO was established only in the case of plasma triacylglycerol (TAG) level: plasma TAG of the FO-fed rats did not differ from the control rats (p > 0.05), while SchO decreased (p < 0.05) plasma TAG to 46% of the control. On the other hand, FO and SchO decreased (p < 0.05) total plasma cholesterol (TC) in rats in the same extent, to 73% of the control. Regarding the underlying mechanisms for the TC decrease, both SchO and FO up-regulated hepatic Insig-1 gene (181 and 133% of the control; p < 0.05), which tended (p = 0.15 and p = 0.19 respectively) to decrease the amount of hepatic nSREBP-2 protein (61 and 66% of the control). However, neither SchO nor FO influenced hepatic 3-hydroxy-3-methyl-glutaryl-CoA reductase gene expression (p > 0.05); SchO (but not FO) increased (p < 0.05) low-density lipoprotein receptor mRNA in the liver. It was concluded that the decrease of total plasma cholesterol might be caused by an increased cholesterol uptake from plasma into the cells (in the case of SchO), but also by other (in the present study not tested) mechanisms.

The objective of the present study was to evaluate a potential of Schizochytrium microalga oil to alleviate possible negative effects of high-fat-high-energy diets. Forty adult male rats (Wistar Albino) were fed 7 weeks the diet containing beef tallow + evaporated sweetened milk (diet T) intended to cause mild obesity and low-grade systemic inflammation. Consequently, the animals were divided into four groups by 10 animals each and fed either the T-diet (control) or the diet containing 6% of safflower oil (S), 6% of fish oil (F) and 6% of Schizochytrium microalga oil (A), respectively, for another 7 weeks. The A-diet decreased (p < 0.05) live weight to 86% and glycaemia to 85% of control, respectively; an effect of the S- and F-diet on these markers was insignificant (p > 0.05). In comparison with control, higher (p < 0.05) deposition of eicosapentaenoic acid (EPA) + docosahexaenoic acid (DHA) in the epididymal adipose tissue (EAT) of the A-rats correlated with increased (p < 0.05) plasma adiponectin concentration, but it was without the effect (p > 0.05) on cellular adiponectin content in the EAT. Higher (p < 0.05) EPA+DHA deposition in the liver of the A-rats correlated with higher expression (149% of control; p < 0.05) of the gene coding for peroxisome proliferator-activated receptor gamma, and with lower expression (82% and 66%; p < 0.05) of the genes coding for adiponectin receptors AdipoR1 and AdipoR2; no relationship to the expression of receptor GPR120 was found. The A-diet did not affect amount of the nuclear fraction of the nuclear factor kappa B in the liver, but increased plasma level of anti-inflammatory cytokine TGF-β1 (p < 0.05). The presented data agree with results of other in vivo rodent and human studies, but not with literature data regarding in vitro experiments: it can be concluded that the effects of dietary oils on inflammatory markers need further investigation.

The present study tested a hypothesis that dietary fish oil (eicosapentaenoic acid+docosahexaenoic acid) in a commonly achievable dose ameliorates a systemic inflammation in pigs. Two groups of pigs of 16 animals each were fed a diet with either 2.5% of fish oil (F) or a control diet with 2.5% of palm oil (P). After 70 days of fattening, eight F and eight P pigs were challenged (F+; P+) i.v. by lipopolysaccharide. After 3 h, all pigs were sacrificed and blood, liver and visceral adipose tissue (VAT) samples were taken. No significant effect (P>0.05) of dietary oil on the feed intake and daily weight gain was found out. Less neutrophils (16.8% v. 28.8%; P0.05) between F+ and P+ pigs in the peroxisome proliferator-activated receptor γ, GPR120, Adipor1 and Adipor2 (adiponectin receptor) gene expression, respectively, was established; plasma adiponectin was the same (21.1 ng/ml) in F+ and P+ pigs. In comparison with the P+ pigs, increased expression of the lipopolysaccharide-binding protein (LBP) gene and intercellular adhesion molecule 1 (ICAM1) gene was found out in the liver of the F+ pigs; expression of the tumor necrosis factor α (TNFα) gene was higher in the liver but lower in the VAT of the F+ pigs (P<0.05). The F+ pigs had higher (P<0.05) plasma concentration of both anti-inflammatory cytokine interleukin-4 (0.46 v. 0.04 ng/ml) and pro-inflammatory TNF-α (13.41 v. 7.72 ng/ml). It was concluded that dietary fish oil at the tested amount had a negligible effect on expression of the evaluated receptor genes and plasma adiponectin, and had an ambiguous effect on expression of cytokine genes and plasma cytokine levels.

Komprda T., Rozíková V., Vícenová M., Procházková N., Ondráčková P., Pešková P., Faldyna M. (2017): Tissue fatty acid deposition, plasma lipid and cytokine profile in pigs fed a diet with fish oil or palm oil. Czech J. Anim. Sci., 62, 482-490.The present study tested a hypothesis concerning a favourable effect of dietary fish oil on the tissue polyunsaturated fatty acid (PUFA) deposition, and on plasma lipid and cytokine profile. Thirty-two pigs divided into two groups of 16 animals each were fed for 70 days a diet with 2.5% of fish oil (F) and palm oil (P), respectively. The content of PUFA n-3 in the liver, muscle (m. quadriceps femoris), and visceral adipose tissue (VAT) of the F-and P-pigs was 530 and 129, 84 and 19, 1365 and 191 mg/100 g of the fresh tissue, respectively (differences between dietary groups were significant at P < 0.01 in all tissues). Dietary fish oil in comparison with palm oil decreased (P < 0.05) total plasma cholesterol, but also desirable high-density lipoprotein cholesterol, and had no effect (P > 0.05) both on low-density lipoprotein cholesterol and triacylglycerols. Moreover, dietary fish oil increased (P < 0.05) expression of the genes coding for not only anti-inflammatory cytokines IL-10 (P < 0.01) and TGF-β1 (P < 0.05), but also for pro-inflammatory cytokines IL-6 (P < 0.01), IL-12, and TNF-α (P < 0.05) in the VAT, and increased (P < 0.05) the expression of the IL6 gene in the liver. On the other hand, no significant differences (P > 0.05) between the F-and P-pigs in plasma levels of any tested cytokine were found out. It was concluded that an effect of dietary fish oil on tissue fatty acid deposition is undeniable, but its effects on plasma markers related to the risk of chronic degenerative diseases require further research.

The objective of the present study was to evaluate in a model organism the effect of different dietary lipids on plasma concentration of total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C) and triacylglycerols (TAG). One hundred adult male rats (Wistar Albino) were divided into 10 groups with 10 animals each and fed for 7 weeks either basic feed mixture (control diet, C) or basic feed mixture with 5% of palm oil (P), safflower oil (SF), salmon oil (S), fish oil (F), Schizochytrium microalga oil (A), and 20% of beef tallow (T; four groups), respectively. The T-groups were fed for another 7 weeks T-, SF-, F-and A-diet, respectively. At the end of both the first and the second 7-week fattening period, plasma lipid concentration and hepatic fatty acid content was determined. Both A and F diets fed for 7 weeks decreased (P < 0.05) plasma TC (0.98 mmol•l ). The highest (P < 0.05) plasma TC was established in rats fed for 7 weeks the SF-diet following the previous 7-week T-treatment (2.15 mmol•l -1 ). A-diet had the most positive (decreasing) effect on TAG concentrations (0.68-0.86 mmol•l -1 compared to 1.22 and 2.88 mmol•l -1 found in the C and T diets, respectively; P < 0.05). Both plasma TC and TAG were in a negative relationship (P < 0.01) with the hepatic eicosapentaenoic acid and docosahexaenoic acid (DHA) contents, respectively. It was concluded that dietary Schizochytrium microalga oil (with high DHA content) may have the potential for decreasing the risk of cardiovascular diseases.