Modifications in postprandial triglyceride-rich lipoprotein composition and size after the intake of pomace olive oil

OBJECTIVE: This study was designed to determine the composition of postprandial triglyceride-rich lipoproteins (TRL) after the intake of pomace olive oil (POO), which is a subproduct of the extraction of virgin olive oil (VOO) and presents a high concentration of minor components with biological activity. METHODS: Meals enriched in POO and refined olive oil (ROO) were administrated to 9 healthy young men and blood was extracted every hour during a postprandial period of 7 hours. Serum and TRL lipid composition were measured by enzymatic and chromatographic methods and apolipoprotein B composition by SDS-PAGE. RESULTS: POO and ROO showed a very similar fatty acid composition but differed in their unsaponifiable fraction. The content of phytosterols, tocopherols, terpenic acids and alcohols and fatty alcohols was much higher in POO than in ROO. Serum lipids were not affected by the administration of the oils but the triglyceride concentration in TRL and the size of the particles (p < 0.05) after POO was higher at time point 2 h and lower at time point 4 h compared with ROO. In contrast, the number of TRL particles was lower after POO, although the rate of clearance was similar. CONCLUSION: We suggest that the unsaponifiable fraction between the two olive oils affect the size and composition of postprandial TRL, which might have a relevant impact on their atherogenicity.     

Dietary oils high in oleic acid but with different unsaponifiable fraction contents have different effects in fatty acid composition and peroxidation in rabbit LDL

OBJECTIVE: We investigated the influence of different edible oils high in oleic acid but with different unsaponifiable fractions on the fatty acid composition and lipid peroxidation in plasma and low-density lipoprotein (LDL) in rabbits. METHODS: Thirty-two rabbits were randomly assigned to four groups of eight animals. For 8 wk each group was fed a semisynthetic isoenergetic diet that differed by lipid source (Picual virgin olive oil, Picual virgin olive oil that had been subjected to an exhaustive process of washing, Arbequina virgin olive oil, and sunflower oil high in oleic acid). We analyzed the fatty acid profile, thiobarbituric acid reactive substances, alpha-tocopherol, coenzyme Q, and retinol in plasma and the fatty acid profile, hydroperoxides, alpha-tocopherol, and coenzyme Q in LDL. RESULTS: The two varieties of virgin olive oil behaved differently from the high-oleic sunflower oil, and the effect of the different ratios of oleic acid to linoleic acid in the lipid sources on fatty acid composition in plasma and LDL was significant. With regard to oxidative stress, LDL in the group that ingested the lipid sources with the greatest amount of phenolic compounds showed the highest level of antioxidants (alpha-tocopherol and coenzyme Q; P < 0.05) and the lowest susceptibility to lipid peroxidation (P < 0.05). CONCLUSION: This study provides evidence in vivo of the considerable antioxidant capacity of the phenolic fraction of virgin olive oil in rabbit LDL and the important role that this unsaponifiable fraction can play in the overall antioxidant benefit attributed to these oils. However, these effects depend on the phenolic content of the oil.     

The unsaponifiable fraction of virgin olive oil in chylomicrons from men improves the balance between vasoprotective and prothrombotic factors released by endothelial cells

Minor components of virgin olive oil (VOO) may play a key role in the beneficial effects of VOO on atherosclerosis. In the present study we evaluated the influence of the unsaponifiable fraction of VOO on the production of eicosanoids and nitric oxide (NO) by endothelial cells (HUVECs). Triglyceride-rich lipoprotein (TRLs) were isolated from human serum after the intake of meals enriched in 3 high-oleic acid oils, i.e., high-oleic sunflower (HOSO), VOO, or enriched-virgin olive (EVO) oils, the last-mentioned containing 2.4% of unsaponifiable matter. HOSO induced a greater accumulation of triglycerides (TGs) in the postprandial serum than VOO or EVO, as measured by calculating the area under the curve. The incubation with TRLs increased NO release by endothelial cells compared with untreated control cells, but the effects of the various TRLs did not differ. EVO-derived TRLs reduced the production of prostaglandin E(2) (PGE(2)) and thromboxane B(2) (TxB(2)) (the stable metabolite of TxA(2)) compared with VOO- or HOSO-derived TRLs. The release of PGI(2) (as 6-keto PGF(1alpha)) was similarly diminished by all TRLs compared with the control. In conclusion, the unsaponifiable fraction of VOO does not affect postprandial triglyceridemia, but it has favorable effects on endothelial function, mainly by reducing proinflammatory and vasoconstrictor eicosanoid synthesis (PGE(2) and TxB(2)).     

Dietary Olive Oil Intake Improves Running Endurance with Intramuscular Triacylglycerol Accumulation in Mice

Olive oil is a functional food shown to have a variety of bioactive effects. Therefore, we expect it to be a novel functional food with an exercise-mimetic effect on skeletal muscles. This study aimed to investigate the effect of olive oil on the endurance capacity and muscle metabolism in mice. Mice fed a 7% (w/w) olive oil diet for eight weeks showed improved treadmill running endurance and increased intramuscular triacylglycerol (IMTG) accumulation in the gastrocnemius muscle compared to soybean oil diet-fed controls. The increase in running endurance with olive oil intake was independent of the muscle fiber type. To elucidate underlying the mechanism of elevated IMTG levels, we examined the expression levels of the genes related to lipid metabolism. We found that the expression of diacylglycerol O-acyltransferase1 (DGAT1) was significantly upregulated in the muscle of olive oil diet-fed mice. In addition, the olive oil diet-fed mice showed no metabolic impairment or differences in growth profiles compared to the controls. These results suggest that dietary olive oil intake affects muscle metabolism and muscle endurance by increasing energy accumulation.     

The role of unsaponifiable components in the lipidemic property of olive oil

Pure olive oil triglycerides (POLO), free from all unsaponifiable matter, were isolated from Virgin Spanish olive oil (COLO) by alumina-charcoal column chromatography. COLO and POLO were used as sources of dietary fat in two animal studies. The responses of serum and liver lipids to the two types of dietary fat were examined. Our results show that animals fed POLO-diet gave somewhat higher serum total and LDL cholesterol levels as compared to those on COLO-diet. The increase in serum cholesterol level is followed by a parallel increase in liver cholesterol content. These results indicate that the hypocholesterolemic effect of olive oil was partly due to the presence of the unsaponifiable matter. Supplement of the POLO-diet separately with a-tocopherol and squalene resulted in serum lipid responses similar to that observed with the COLO-diet. The serum and liver triglyceride levels are not affected by the removal of unsaponifiable components but addition of a--T and squalene to the POLO-diet appeared to lower both the cholesterol and triglyceride levels in the serum but increased only the liver cholesterol content. These results show that the unsaponifiable components modulate the hypocholesterolemic effect of olive oil.     

Differential modulation of hepatic very low-density lipoprotein secretion by triacylglycerol-rich lipoproteins derived from different oleic-acid rich dietary oils

Minor components from dietary oils can modulate the atherogenic response of the TAG-rich lipoproteins (TRL) in which they are transported. In the present study we investigated the influence of TRL isolated from man after the intake of oleic acid-rich oils with different minor component compositions on VLDL secretion by rat primary hepatocytes. TRL were isolated from nine men after the intake of meals enriched with high-oleic sunflower oil (HOSO) or virgin olive oil (VOO) or VOO enriched with minor components (EVO). TRL were incubated with rat primary hepatocytes and the lipid accumulation was analysed in the cells and the secreted VLDL. The expression of genes for proteins related to hepatic lipid metabolism and VLDL production was also measured. Incubation of hepatocytes with TRL derived from HOSO as compared to VOO led to lower intracellular lipid accumulation and VLDL production despite higher mRNA expression for diacylglycerol-acyltransferase, microsomal TAG transfer protein, apoB and PPARalpha. When TRL derived from EVO were used there were no changes in VLDL secretion. These results suggest that incorporation of minor components from dietary high-oleic oils into TRL modulates the effect of these atherogenic particles on VLDL secretion.     

Virgin olive and fish oils enhance the hepatic antioxidant defence system in atherosclerotic rabbits

BACKGROUND & AIMS: In this study we report the effects of sunflower, virgin olive and fish oils on the lipid profile and antioxidant defence system in liver mitochondria from rabbits with experimental atherosclerosis. METHOD: An atherogenic control group were fed for 50 days on a diet containing 3% lard and 1.3% cholesterol. Four groups were fed for an additional period of 30 days with a diet enriched in different oils: sunflower oil, virgin olive oil, refined olive oil and fish oil. A control group was fed with a standard chow. RESULTS: The atherogenic diet caused important changes in the hepatic mitochondria lipid profile and in the enzymatic and non-enzymatic antioxidant defence system accompanied with an increase in the content of hydroperoxides in liver mitochondria. The administration of virgin olive and fish oils showed a better profile in the antioxidant system as well as decrease in the content of hydroperoxides. CONCLUSIONS: The intake of cholesterol- and lard-enriched diet leads to a high impairment in the hepatic antioxidant defence system. However, the replacement of that diet by other unsaturated fat-enriched diets using virgin olive, sunflower and fish oil enhances hepatic antioxidant defence system, virgin olive and fish oil diet provide the best results.     

Supplementation of diets with the black rice pigment fraction attenuates atherosclerotic plaque formation in apolipoprotein e deficient mice

Apolipoprotein (apo)E-deficient mice were used to study the antiatherogenic effect of black rice pigment fraction (BRF) and the possible mechanisms by which it inhibits atherogenesis. The apoE-deficient mice (n = 45) were randomly divided into three groups and received AIN-93G diet (positive group), AIN-93G with 5 g of black rice pigment fraction/100 g (BRF group) and AIN-93G with 5 g of white rice outer layer fraction/100 g (WRF group) for 16 wk. C57BL/6J mice (n = 15) received AIN-93G and were used as a control group. Blood samples were collected for measurement of lipid concentration, antioxidized LDL antibody and nitric oxide concentration. Livers were extracted for determination of cholesterol concentrations, and aortas were used to determine cholesterol concentrations and inducible nitric oxide synthase protein and mRNA expression. Hearts were used to assess atherosclerotic plaque formation. The apoE-deficient mice fed the black rice pigment fraction diet had 48% (P < 0.01) less atherosclerotic lesion area compared with apoE-deficient mice fed only the AIN-93G diet and 46% (P < 0.01) less lesion area compared with mice fed the white rice outer layer fraction diet. This observation corresponded with significantly (P < 0.05) lower total serum cholesterol, lower liver and aorta cholesterol (P < 0.01) and higher HDL cholesterol (P < 0.05) concentrations and lower (P < 0.05) antioxidized LDL antibody titer in apoE-deficient mice fed the black rice pigment fraction diet compared with positive and WRF groups. Notwithstanding this, mice fed the black rice pigment fraction diet also had lower CD4(+) T lymphocyte expression (P < 0.05) and weaker inducible nitric oxide synthase expression (P < 0.05) compared with mice fed the AIN-93G diet and the white rice outer layer fraction diet, respectively. We concluded that the inhibition of atherosclerotic lesions of the black rice pigment fraction is attributed to the improvement in cholesterol accumulation and reduction in oxidative stress and inflammation.     

Differential effect of high dietary iron on α-tocopherol and retinol levels in the liver and serum of mice fed olive oil– and corn oil–enriched diets

The influence of dietary fats on cellular α-tocopherol and retinol uptake in iron overload is poorly understood. The aim of this study was to investigate the effect of a high-iron diet on the retinol and α-tocopherol levels in mice fed olive oil– and corn oil–enriched diets. Mice were fed for 3 weeks a standard mouse chow (the control group) and diets enriched with 5% by weight of corn oil or olive oil. Diets of the mice fed corn oil and olive oil were additionally supplemented with 1% by weight carbonyl iron. Both dietary oils and iron increased the liver iron uptake. High-iron feeding induced oxidative stress in mice liver, measured as a thiobarbituric acid-reactive substance level. Both fats and iron induced changes in the liver fatty acid composition. Liver retinol and α-tocopherol stores increased with iron supplementation in the olive oil–enriched diet, with a simultaneous decrease in serum. The results suggest that the influx of α-tocopherol and retinol from serum to the liver is induced by high dietary iron. This redistribution appears to be stronger for retinol than for α-tocopherol and is also higher in mice fed olive oil than in mice fed corn oil, suggesting that the composition of dietary lipids is important in the treatment of high-iron tissue conditions. In conclusion, the results of this study suggest that the increase of hepatic α-tocopherol and retinol levels in the olive oil–based diet is a dietary-dependent responsive mechanism that probably is not primarily related to an increased risk of oxidative damage induced by high-iron intake.     

Minor components of olive oil facilitate the triglyceride clearance from postprandial lipoproteins in a polarity-dependent manner in healthy men

Postprandial triglyceride-rich lipoproteins (TRLs) are recognized as atherogenic particles whose lipid composition and function can be modified by the composition of dietary oils. This study was designed to test the hypothesis that minor components of pomace olive oil (POMACE) can not only change the composition of postprandial TRL but also affect the clearance of triglyceride (TG) molecular species of postprandial TRL. Meals enriched in either POMACE or refined olive oil (OLIVE) were administered to 10 healthy young men. TRL were isolated from serum at 2, 4, and 6 hours postprandially, and their fatty acid and TG molecular species compositions were analyzed by gas chromatography. The apolipoprotein B concentration was determined by immunoturbidimetry. POMACE and OLIVE, differing mainly in their unsaponifiable fraction, led to similar fatty acid and TG molecular species profiles in postprandial TRL. However, POMACE-TRL presented a higher particle size, estimated as TG to apolipoprotein B ratio, which was also found for the main TG molecular species (trioleoyl-glycerol, palmitoyl-dioleoyl-glycerol, palmitoyl-oeloyl-linoleoyl-glycerol, and dioleoyl-linoleoyl-glycerol). TG from POMACE-TRL also showed higher clearance rates. In this regard, apolar TG (with a higher equivalent carbon number) disappeared more rapidly from TRL particles obtained after the ingestion of either POMACE or OLIVE. In conclusion, minor components of POMACE facilitated TG clearance from TRL by modifying their particle size and the hydrolysis of the most apolar species.     

Sterol composition of black cumin (Nigella sativa L.) and Aleppo pine (Pinus halepensis Mill.) seed oils

Oils extracted from Tunisian and Iranian Nigella seeds (TNS and INS, respectively) and Tunisian Aleppo pine seeds were analysed for sterol composition. These components could have many health benefits, especially in lowering LDL-cholesterol and preventing heart disease. The highest level of total unsaponifiable matter was found in Pinus seed oil (17.23 g/kg oil, compared to 15.58 oil and 14.82 g/kg oil in TNS and INS seed oils, respectively). The total sterol content in the three studied oils represented 18.03%, 17.41% and 42.66% of the unsaponifiable matter, respectively. β-Sitosterol was the major sterol in all oils with 44%, 54% and 74% of the total sterols in Tunisian and Iranian Nigella seed oils and Pinus seed oil, respectively. The next major sterol was stigmasterol in both Nigella seed oils studied (16.57–20.92% of total sterols) and campesterol in Pinus seed oil (11.42% of total sterols). TMS 484, Δ7-stigmasterol, Δ7-avenasterol and cholesterol were detected at lower levels. The high level of β-sitosterol in Pinus seed oil could make it the most suitable and effective for lowering blood cholesterol and preventing coronary heart disease.     

Hypocholesterolemic effect of triterpene alcohols with soysterol on plasma cholesterol in rats

To identify the synergistic hypocholesterolemic substance found in soybean oil unsaponifiable matter, rats were fed diets containing various fractions of the unsaponifiable matter prepared by silicic acid column chromatography. The plasma cholesterol level of the group fed the alcohol fraction, which mainly consisted of triterpene alcohols, was significantly lower and the effect was synergistic with soysterol. So the effect of cycloartenol and 24-methylenecycloartanol, which are main constituents of triterpene alcohols in soybean oil unsaponifiable matter, was investigated. Both compounds were prepared from gamma-oryzanol (ferulate) and were added (0.05%) respectively to the experimental diet containing 0.5% cholesterol and 1% soysterol. It was observed that both cycloartenol and 24-methylenecycloartanol in combination with soysterol greatly reduced the plasma cholesterol and enhanced cholesterol excretion. This suggests that the hypocholesterolemic activity of dietary vegetable oils may account for not only their fatty acid compositions and sterol contents but also the synergistic hypocholesterolemic effect of triterpene alcohols.     

Lymph chylomicron composition and size are modified by level of intestinally infused cholesterol and triglyceride source in rats.

Mesenteric lymph chylomicrons were characterized following acute continuous intestinal infusion of triglyceride emulsions in rats. Emulsions were prepared using corn, olive or butter oils with graded doses of cholesterol (0, 3, 10, 20, 30, 60, 100 mg/g triglyceride) added to each. Chylomicron cholesterol content varied directly with dose of cholesterol infused, ranging from approximately 1.5% (by weight) with no added cholesterol to 5-10% at 100 mg cholesterol/g triglyceride. Minimum effective dose for increasing chylomicron cholesterol content (about twofold) was 20 mg/g triglyceride regardless of the triglyceride source. Esterified cholesterol accounted for most of the increase in chylomicron total cholesterol with corn oil infusion, whereas increases in the unesterified fraction accounted for 10-30% of the increase in total cholesterol during infusion of olive or butter oils. The effect of infused cholesterol on chylomicron lipid composition was dependent on triglyceride source: no effect on phospholipid:triglyceride ratio with corn and butter oils, but increased phospholipid:triglyceride ratio with olive oil at cholesterol doses greater than 20 mg/g triglyceride. Infusion of butter emulsions produced smaller chylomicrons than those produced during infusion of corn or olive oil emulsions.     

A wax ester and astaxanthin-rich extract from the marine copepod Calanus finmarchicus attenuates atherogenesis in female apolipoprotein E-deficient mice

The aim of this study was to investigate the effect of dietary supplementation with an oil extracted from the zooplankton copepod Calanus finmarchicus [calanus oil (CO)] on atherosclerosis in apoE-deficient (apoE(-/-)) mice. Thirty 6-wk-old female apoE(-/-) mice (n = 10/group) were fed: 1) a Western-type, high-fat diet (HFD); 2) HFD supplemented with 1% (wt:wt) CO; or 3) HFD supplemented with 0.88% (wt:wt) corn oil + 0.12% (wt:wt) EPA+DHA ethyl esters (EPA+DHA) for 13 wk. Dietary CO supplementation lowered total aorta atherogenesis by 36.5% compared to the HFD (P < 0.01), whereas the reduction in the lesion prone aortic arch was 34.8% (P < 0.01). The degree of aortic atherogenesis was intermediate in mice fed EPA+DHA compared to those fed HFD and CO. The effect on atherogenesis was paralleled by reduced expression of hepatic genes for the proinflammatory cytokines, Ccl2, Icam1, Il1b, and Nfkb1, in mice fed CO compared to those fed HFD. For mice fed EPA+DHA, gene expression did not differ compared to those fed CO or HFD. Plasma concentrations of total cholesterol, TG, and cytokines did not differ between the groups at the end of the study. However, mice fed CO gained more weight compared to those fed HFD but not compared to those fed EPA+DHA. In conclusion, dietary CO supplementation attenuated atherosclerotic lesion formation in female apoE(-/-) mice and may be an effective and safe dietary intervention to reduce the development of atherosclerosis. However, further studies are warranted to elucidate the underlying physiological and molecular mechanisms.     

Hypothalamic Renin–Angiotensin System and Lipid Metabolism: Effects of Virgin Olive Oil versus Butter in the Diet

The brain renin–angiotensin system (RAS) has been recently involved in the homeostatic regulation of energy. Our goal was to analyse the influence of a diet rich in saturated fatty acids (butter) against one enriched in monounsaturated fatty acids (olive oil) on hypothalamic RAS, and their relationship with the metabolism of fatty acids. Increases in body weight and visceral fat, together with an increase in aminopeptidase A expression and reductions in AngII and AngIV were observed in the hypothalamus of animals fed with the butter diet. In this group, a marked reduction in the expression of genes related to lipid metabolism (LPL, CD36, and CPT-1) was observed in liver and muscle. No changes were found in terms of body weight, total visceral fat and the expression of hepatic genes related to fatty acid metabolism in the olive oil diet. The expressions of LPL and CD36 were reduced in the muscles, although the decrease was lower than in the butter diet. At the same time, the fasting levels of leptin were reduced, no changes were observed in the hypothalamic expression of aminopeptidase A and decreases were noted in the levels of AngII, AngIV and AngIII. These results support that the type of dietary fat is able to modify the hypothalamic profile of RAS and the body energy balance, related to changes in lipid metabolism.     

Vegetable oils affect the composition of lipoproteins in sea bream (Sparus aurata)

The aim of the present study was to determine the influence of the dietary fatty acid profile on the lipoprotein composition in sea bream fed different vegetable oils. Six experimental diets were formulated combining fish oil with three vegetable oils (soybean, rapeseed, linseed) in order to obtain 60-80 % (w/w) fish-oil replacement. VLDL, LDL and HDL in plasma samples were obtained by sequential centrifugal flotation. The lipid class, protein content and fatty acid composition of each lipoprotein fraction were analysed. HDL was the predominant lipoprotein in sea bream plasma containing the highest proportion of protein (34 %) and phosphatidylcholine. LDL presented a high content of cholesterol, whereas triacylglycerol comprised a larger proportion of VLDL. The lipid class of the lipoprotein fractions was affected by the dietary vegetable oils. Thus, a high dietary inclusion of soyabean and linseed oil (80 %) increased the cholesterol in HDL and LDL in comparison to fish oil. Similarly, the triacylglycerol concentration of VLDL was increased in fish fed 80 % soyabean and linseed oils owing to the low n-3 highly unsaturated fatty acid content of these diets. Lipoprotein fatty acid composition easily responded to dietary fatty acid composition. VLDL was the fraction more affected by dietary fatty acid, followed by LDL and HDL. The n-3 highly unsaturated fatty acid content increased in the order VLDL less than LDL and less than HDL, regardless of dietary vegetable oils.     

Polyunsaturated fats attenuate the dietary phytol-induced increase in hepatic fatty acid oxidation in mice

The effects of dietary phytol and the type of dietary fat on hepatic fatty acid oxidation were examined in male ICR mice. Mice were fed diets containing 0 or 5 g/kg phytol and 100 g/kg palm, safflower, or fish oil for 21 d. Among the groups fed phytol-free diets, the activities and mRNA abundance of various enzymes involved in fatty acid oxidation were greater in mice fed fish oil than in those fed palm or safflower oil. Dietary phytol profoundly increased the activities and mRNA abundance of hepatic fatty acid oxidation enzymes in mice fed palm oil. However, safflower and fish oils, especially the latter, greatly attenuated the phytol-dependent increase in hepatic fatty acid oxidation. The hepatic concentration of phytanic acid, a metabolite of phytol that is the ligand and activator of retinoid X receptors and peroxisome proliferator-activated receptors, was higher in mice fed fish oil than safflower or palm oil, and in those administered safflower oil than palm oil. The hepatic mRNA abundance of sterol carrier protein-2, a lipid-binding protein involved in phytol metabolism, was inversely correlated with the hepatic concentration of phytanic acid. We demonstrated that polyunsaturated fats attenuate the enhancing effect of dietary phytol on hepatic fatty acid oxidation. Dietary fat-dependent changes in the hepatic phytanic acid concentration cannot account for this phenomenon.     

Naturally occurring vitamin D3 in fish products analysed by HPLC, using vitamin D2 as an international standard.

A chemical method for the analysis of naturally occurring vitamin D is proposed. The unsaponifiable matter of oils and tissues is prepared, cholesterol is partly removed by double precipitation at low temperature in methanol. The vitamin D fraction is collected on an adsorption column by high performance liquid chromatography. The fraction is further purified and the vitamins D2 and D3 are separated on a partition column (reverse phase) by HPLC. Recovery was 89 to 93%, standard deviation 3%. The only vitamin D analogue found in fish oils, livers and fillets, was cholecalciferol (D3). Hence, ergocalciferol (D2) could be used as an internal standard. The provitamins ergosterol and 7-dehydrocholesterol, as well as the previtamins, were separated from the vitamin D-fraction on the adsorption column. Results in the range 0.050 to 134 microgram D3 per gram (2 to 5360 I.U. per gram) are given. One cod liver oil was analysed in a rat bioassay, giving supporting results.