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Journal of the American College of Nutrition, Vol. 26, No. 1, 24-31 (2007)
Published by the American College of Nutrition

Modifications in Postprandial Triglyceride-Rich Lipoprotein Composition and Size after the Intake of Pomace Olive Oil

Rosana Cabello-Moruno, BSc, Javier S. Perona, PhD, Jesus Osada, PhD, Maria Garcia, MD and Valentina Ruiz-Gutierrez, PhD

Nutrición y Metabolismo Lipídico, Instituto de la Grasa (CSIC) (R.C.M., J.S.P., V.R.G.)
Servicio de Análisis, HU Virgen del Rocío (M.G.)
Seville, Dep. Biología Molecular y Celular, Facultad de Veterinaria, Universidad de Zaragoza (J.O.), Zaragoza, SPAIN

Address correspondence to: Valentina Ruiz-Gutierrez, PhD, Nutrición y Metabolismo Lipídico, Instituto de la Grasa (CSIC), Av. Padre García Tejero 4, 41012, Seville, SPAIN. E-mail: valruiz{at}ig.csic.es


   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 CONCLUSION
 ACKNOWLEDGMENTS
 REFERENCES
 
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.

Key words: pomace olive oil, refined olive oil, triglyceride-rich lipoproteins, apolipoprotein B, triglycerides

Abbreviations: POO = pomace olive oil • ROO = refined olive oil • VOO = virgin olive oil • EVO = enriched virgin olive oil • HOSO = high-oleic sunflower oil • TRL = triglyceride-rich lipoprotein • VLDL = very low density lipoproteins • CM = chylomicrons • TG = triglycerides • LPL = lipoprotein lipase • apo = apolipoprotein • MUFA = monounsaturated fatty acids • SFA = saturated fatty acids • LDL = low-density lipoprotein receptor • LRP = low-density-lipoprotein receptor-related protein


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
 RESULTS
 CONCLUSION
 ACKNOWLEDGMENTS
 REFERENCES
 
There is growing agreement that postprandial hypertriglyceridemia is a potential independent cardiovascular risk factor. [1–3]. Triglyceride-rich lipoproteins (TRL) can cross the endothelial barrier and enter into the vascular wall [4] where they can enhance lipid accumulation into macrophages, leading to foam cell formation [5,6]. TRL consist of chylomicrons, which are secreted by the small intestine after a fat load and contain apolipoprotein (apo) B-48 as the structural protein, and very-low-density lipoproteins (VLDL), originated in the liver and containing apo B-100. In addition, TRL also include chylomicron (CM) and VLDL remnant particles, which are partially depleted of triglycerides (TG) and enriched with cholesteryl esters (CE) compared to the parent lipoproteins. The transformation of TRL into remnant particles is dependent upon TG hydrolysis by lipoprotein lipase (LPL), which is attached to the surface of the vascular endothelium [7]. The enzyme can differentiate between substrates and exhibits specificity with respect to fatty acid length chain and unsaturation [7,8]. Therefore, the composition of TRL-TG is decisive for the activity of lipoprotein lipase and the formation of TRL remnants.

The Mediterranean diet, characterized by a high consumption of monounsaturated fatty acids (MUFA), has been proposed as a healthy dietary standard because it is associated with a low rate of cardiovascular mortality [9]. However, there seem to be differences among the effects of diets enriched in MUFA both after acute [10] or long-term intake [11]. We have demonstrated that two MUFA-rich oils (virgin olive oil (VOO) and high-oleic sunflower oil (HOSO) produce different effects on the magnitude and duration of the postprandial triglyceridemia [10]. Therefore, other factors such as TG species composition, minor fatty acids and non-fatty acids constituents (unsaponifiable fraction), rather than the content of oleic acid, might be responsible for the postprandial responses to VOO, and for the effects of the TRL and their remnants formed. In this regard, we have recently reported that the unsaponifiable fraction of VOO, contained in circulating TRL, improves the balance between vasoprotective and pro-thrombotic factors released by endothelial cells [12].

Pomace olive oil (POO) is obtained by chemical processes from the mechanical extraction of VOO. Although this subproduct of VOO is traditionally commercialized in Spain, the nutritional similarities and differences between POO and other olive oils, such as virgin and refined olive oils, have not been studied yet. The new improved procedures for POO extraction allow the presence of a number of unsaponifiable components from the skin of the olive that are present in low concentration in VOO [13]. Thus, the unsaponifiable fraction of POO contains elevated amounts of sterols, tocopherols, waxes and triterpenic acids and alcohols, such as oleanolic acid and erythrodiol, [14–16], with important biological activities [17–19].

To our knowledge there is no study assessing the effects on lipid postprandial metabolism of POO. Thus, the aim of the present work was to determine the lipid composition of postprandial TRL after the intake of POO in comparison with a refined olive oil (ROO), in order to evaluate its potential impact on cardiovascular disease.


   MATERIALS AND METHODS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
 CONCLUSION
 ACKNOWLEDGMENTS
 REFERENCES
 
Subjects
Nine healthy men aged 26.2 ± 4.3 y with body mass index 23.7 ± 2.0 kg/m2 participated in the study. The subjects were recruited after screening for fasting plasma TG, cholesterol, and glucose concentration, all of which were within normal limits (Table 1). Medical history verified that volunteers did not suffer from any digestive or metabolic disorder. The participants gave written, informed consent to a protocol approved by the Institutional Committee on Human Research (Hospital Universitario Virgen del Rocio, Sevilla).


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  		Table 1. Baseline Data of Normolipidemic Men Participating in the Study1

 
Study Design and Blood Collection
The experiment was carried out over three 1-week periods, as shown in Fig. 1, throughout which each subject consumed 2 test meals on separate occasions. Participants were given 1 L of POO or ROO to substitute their usual dietary oil for the week before the experiment. A 1-week washout period was included between the two periods, during which participants were allowed to return to their normal diet. ROO was administered first and POO was administered after the washout period. POO was compared with ROO because according to the EU legislation (CE2568/91) POO must be refined before commercialization.


Figure 1
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  		Fig. 1. Scheme of the study design. w: week.

 
The day of the experiment a test meal was given to the subjects early in the morning consisting of 1 slice of brown bread (28 g), 100 g of plain pasta (cooked with 200 mL of water), 1 skimmed yogurt (125 g) and 130 g of tomato sauce mixed with 70 g of ROO or POO. The oil contributed with 2587 kJ of energy while the whole meal provided 4523 kJ, of which 32.5% was derived from carbohydrate, 7.6% was from protein, and 59.9% was from fat. ROO and POO were kindly supplied by Oleotejar SA, (El Tejar, Cordoba, Spain). The composition of both oils was provided by the manufacturing company and it was similar with regard to fatty acids but differed in the unsaponifiable fraction (Table 2 and 3).


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  		Table 2. Fatty Acid Composition of Refined Olive Oil (ROO) and Pomace Olive Oil (POO)1

 

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  		Table 3. Unsaponifiable Fraction Composition of Refined Olive Oil (ROO) and Pomace Olive Oil (POO)

 
Participants were asked to abstain from alcohol drinking and smoking for 24 h before each experiment. They were also advised to have a low-fat dinner the evening before. After an overnight fast (12 h), a cubital vein was catheterised and a baseline blood sample was taken immediately before they consumed the test meal. After the intake of the meals, which lasted around 10–15 min, blood samples were collected hourly for a 7-h postprandial period. During the course of the experiment, the subjects were allowed to drink water and/or decaffeinated coffee without sugar ad libitum and to undertake only light activities.

Serum was recovered by centrifugation (1620 x g, 30 min, 4°C). Sodium azide (1 mol/L), phenymehylsulfonyl fluoride (10 mmol/L in isopropanol) and aprotinin (1400 mg/L) were added to the serum to a final concentration of 1 mmol/L, 10 µmol/L, and 28 mg/L, respectively to prevent the proteolytic degradation of the apolipoproteins. Serum cholesterol and triglycerides were determined by an enzymatic colorimetric method on a Roche/Hitachi System analyzer (Roche Diagnostic) (Cholesterol CHOD-PAP and Triglyceride GPO-PAP, Roche Diagnostic, Mannheim, Germany). Serum HDL cholesterol was measured by a direct enzymatic method (HDL-C-plus 2nd generation, Roche Diagnostics, Mannheim, Germany) on a Roche/Hitachi System analyzer (Roche Diagnostic) and LDL cholesterol was estimated by the Friedewald formula [20]. ApoB and apoA-I were determined by automated immunoturbidimetric assays (Tina-quant; Roche Diagnostics, Mannheim, Germany).

TRL Isolation
TRL were isolated from 4 mL of serum collected 2, 4, and 6 h after the meal intake. Serum was layered under 6 mL of NaCl solution (d = 1.006 kg/L) and TRL were obtained by a single ultracentrifugation spin (39000 rpm, 18 h, 12°C). Ultracentrifugation was performed using a SW 41 Ti rotor in a Beckman L8-70M preparative ultracentrifuge (Beckman Instruments, Palo Alto, CA). Protein content of the TRL fraction was analyzed by the Bradford method [21].

Separation and Identification of Apolipoproteins in the TRL Fraction
Apo B-48 and apo B-100 were quantified after separation by SDS-PAGE. Apolipoproteins were separated by polyacrylamide gel electrophoresis in the presence of SDS on 0.75-mm thick vertical slab gels. Electrophoresis was carried out using the buffer system described by Laemmli [22]. Gels contained a 4–15% acrylamide gradient, 0.1% SDS, and 0.375 M Tris. The acrylamide gradient was poured with the use of a Hoefer SG-50 two-chamber, gravity-flow gradient maker (Hoefer, San Francisco, CA). A stacking gel (5% acrylamide, 0.1% SDS, 2 mM EDTA, 0.11 M Tris-HCl, pH 6.8) was added with a 10-slot wellforming comb. Nondelipidated lipoprotein samples (3 µg of protein) were reduced in SDS sample buffer (3% SDS, EDTA 0.8 mM, 5% mercaptoethanol, 0.004% bromophenol blue, 0.05 M Tris-HCl, 10% glycerol, pH 6.8) for 3 min at 100°C. Gels were run at 60 V for 3 hr. Gels were fixed with a 10% methanol: 7% acetic acid solution for 30 min and stained overnight with SYPRO® Ruby Protein Gel Stain (Molecular Probes) 1/3 diluted in water and under light protection. Destaining was achieved by 1 h wash with the 10% methanol: 7% acetic acid solution. The two molecular weight forms of apo B were clearly separated in this gel system. Apolipoproteins were identified by comparing the distance they migrated into the gels with known molecular weight standards (Sigma Marker, Wide Range (M.W. 6.5–250.0 kDa). The gel was scanned using the Gel Doc 1000 system (Bio-Rad, Richmond, CA) and analyzed with the software Molecular Analyst v.1.6 (Bio-Rad, Richmond, CA). All samples from the same subject were run on the same gel to compare between them after being separated and stained in the same conditions. Considering that apo B-100 and B-48 show the same chromogenicity [23], the relative amounts of the two isoforms were calculated from the staining intensity, and their absolute masses were calculated from the total apo B mass which was determined by immunoturbidimetry (Sigma Diagnostics, St. Louis, MO).

TG Composition of TRL
Total lipids were extracted from 1 mL of TRL following a modification of the method of Folch et al. [24], using 2,6-di-tert-butyl-p-cresol (BHT) as antioxidant. These modifications consisted in the use of 7 mL of chloroform:methanol(2:1, v/v) for every 1.5 mL of TRL and centrifugation at 3000 rpm for 10 minutes to aid the separation of the layers. The extracted lipids were redissolved in 1 mL of choloroform:methanol (2:1, v/v) and preserved at –20°C until used. The TG composition was determined by HPLC as described by Perona and Ruiz-Gutierrez [25].

Statistical Analysis
Results were expressed as means ± SEM (n = 9). Statistically significant differences between different parameters measured after the intake of these two oils at the same time point were evaluated by paired t-test analysis. p values of <0.05 were considered to indicate a significant difference. The data analysis was performed with the GraphPad Prism® statistical package (version 3.0; GraphPad Software Inc., San Diego, CA).


   RESULTS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
CONCLUSION
 ACKNOWLEDGMENTS
 REFERENCES
 
Fatty Acid Composition of ROO and POO
Overall, the fatty acid composition of ROO and POO was very similar. Both oils had a similar amount of MUFA (nearly 80%), with oleic acid (18:1, n-9) accounting for 99% of all MUFA (Table 2). The content in saturated fatty acids (SFA) was very similar as well, although the concentration of stearic acid (18:0) was slightly higher in ROO. In contrast, POO had a higher amount of linoleic acid (18:2, n-6).

Unsaponifiable Fraction Composition of ROO and POO
More important differences were found among the components of the unsaponifiable fraction (Table 3). The concentration of sterols in POO doubled that of ROO, although the sterol profile was very similar in both oils. The most abundant sterol was ß-sitosterol, accounting for more than 95% in both oils. The content in tocopherols was nearly 5 times higher in POO than in ROO, with {alpha}-tocopherol as the main species, accounting for 94.1 mg/kg in ROO and 80.7 mg/kg in POO. The concentration of the triterpenic alcohols erythrodiol and uvaol (quantified as a single compound) and of waxes (fatty alcohols) was nearly 30 times higher in POO. Finally, the content in squalene was similar in both oils.

Lipid and Apolipoprotein Concentrations in Serum in the Postprandial Period
Lipids were measured in serum after the ingestion of the meals enriched in ROO or POO for 7 h. The highest TG concentration occurred at 2 h after the intake of the oils and the lowest at time point 4 h (Fig. 2A). After that time, there was another increase in TG concentration, up to time point 7 h. No significant differences were found in the TG postprandial response in serum after either of the two dietary oils tested.


Figure 2
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  		Fig. 2. Postprandial serum concentrations of Triglycerides (A), Cholesterol (B) and Apolipoproteins (C) in men during the 7 h after the intake of meals enriched in pomace olive oil (POO) ({blacksquare}) or refined olive oil (ROO) ({Delta}). Results are means ± SEM, n = 9.

 
The total, LDL and HDL-cholesterol concentrations were also measured in serum for 7 h after the intake of ROO and POO (Fig. 2B). No significant variations in the concentrations were observed in the period of time studied and neither ROO nor POO affected those concentrations.

Similarly, we analyzed the total apo A and apo B concentrations but we did not find any variation during the postprandial period or any influence of the dietary oils (Fig. 2C).

TG Composition of Triglyceride-Rich Lipoproteins (TRL)
TG concentrations were analyzed in the TRL at time points 0, 2, 4 and 6 h after the intake of ROO and POO (Fig. 3). The ingestion of both dietary oils increased the TG concentration at time point 2 h, but it was decreased after 4 h. The increase of TG at time point 2 h was higher after POO (p < 0.05) but the decrease was also faster at time point 4 h. Therefore, at time point 4h the TG concentration was significantly lower in the TRL after consumption of POO (p < 0.01).


Figure 3
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  		Fig. 3. Triglyceride (TG) composition of triglyceride-rich lipoproteins (TRL) collected at baseline (0 h), 2, 4, and 6 hours after the intake of pomace olive oil (POO) or refined olive oil (ROO). *: p < 0.05 vs. ROO. Results are means ± SEM, n = 9.

 
Apolipoprotein B-100 and B-48 Concentrations in Triglyceride-Rich Lipoproteins (TRL)
The two isoforms of apo B, apo B-100 and apo B-48, were quantified in the TRL fractions at time points 2, 4 and 6 h (Fig. 4). The concentration of apo B-100 was around twenty times higher (Fig. 4A) than that of apo B-48 (Fig. 4B) but the profiles at the time points studied were similar. The concentrations of both apo B isoforms in TRL obtained after ROO or POO were continuously decreased during the postprandial period. The TG/Apo B ratio in TRL (Fig. 5) was significantly higher (p < 0.05) at time point 2 h after POO but was dramatically reduced at time point 4 h, being significantly lower than after ROO (p < 0.05).


Figure 4
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  		Fig. 4. Apolipoprotein B-100 (A) and Apolipoprotein B-48 (B) concentrations in triglyceride-rich lipoproteins (TRL) collected at 2, 4 and 6 hours after the intake of pomace olive oil (POO) or refined olive oil (ROO). *: p < 0.05, **: p < 0.01, vs. ROO. Results are means ± SEM, n = 9.

 

Figure 5
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  		Fig. 5. Triglyceride to Apolipoprotein B ratio (TG:Apo B) in triglyceride-rich lipoproteins (TRL) collected at 2, 4, and 6 hours after the intake of pomace olive oil (POO) or refined olive oil (ROO). *: p < 0.05 vs. ROO. Results are means ± SEM, n = 9.

 

   DISCUSSION
 
In the present study we investigated the postprandial lipid response of POO in healthy young men and we compared it with ROO. The new improved procedures for POO extraction through centrifugation allow its enrichment with the minor components contained in the unsaponifiable fraction. This fraction contains lipophillic components like sterols, tocopherols, waxes and triterpenic acids and alcohols; all of them with reported biological activities, which hypothetically may influence POO postprandial response.

The postprandial serum TG concentration showed a similar response after the intake of both oils, characterized by a biphasic profile with peaks of TG concentration at time points 2 h and 7 h (Fig. 1A). The lowest TG concentration occurred 4 h after the intake of the test meals. Although different responses have been described, the biphasic is the most frequent [10,26]. Previous studies by our group have reported that not all MUFA-rich oils show the same postprandial TG response. Indeed, HOSO caused a higher postprandial TG concentration in serum compared with VOO [10]. We have also compared the postprandial response of VOO and VOO supplemented with the unsaponifiable fraction, finding no effect of this fraction in the serum TG response [12]. Our present work, assessing the effects of POO, containing higher amounts of the minor components from the unsaponifiable fraction than ROO, whilst maintaining an almost equal fatty acid composition, is in agreement with our latter work [12], as postprandial serum TG profiles were not different after consumption of POO or ROO (Fig. 1A). As expected, the other lipid parameters analyzed in serum (total, LDL and HDL-cholesterol, apo A and apo B) were not modified during the postprandial period (7 h) after either POO or ROO (Fig. 1B and 1C).

Even though there were no differences in the lipid profiles in serum, the TG concentration in TRL after POO was higher at time point 2 h and lower at time point 4 h compared with ROO (Fig. 2). The higher TG concentration found 2 hours after POO could be due to a greater increase in the number of circulating particles or to a larger size of the TRL. However, at 4h the TG concentration after the intake of POO became lower compared with that after the intake of ROO. In a previous study, comparing VOO and VOO enriched in its own unsaponifiable fraction (EVO), we found higher TG levels in TRL at 4 hours after the intake of EVO [27]. To explain the discrepancy between these results, we have to point out that there are essential differences among the oils used for the studies: VOO, EVO, ROO and POO, mainly regarding to the content in unsaponifiable fraction. Actually, POO contains some components that are not present in ROO, EVO or VOO, or are present in much lower concentration, such as waxes and terpenoids.

The lower TRL-TG concentration observed at 4 hours after POO suggests a faster TRL clearance. Delay in TRL clearance from the circulation has been found to correlate with the development of atherosclerotic lesions [28,29]. Differential clearance rates could be explained by a different LPL specificity leading to a faster hydrolysis rate after POO, or due to a higher hepatic uptake, removing circulating particles more efficiently.

Quantification of the apo B isoforms, which are synthesized in the liver (apo B-100) and in the intestine (apo B-48), is used as marker of the number of TRL, since these particles contain a single molecule of this protein per particle and it is not exchanged with other lipoproteins [30]. Particularly, apo B-100 is used as marker of the number of VLDL [31] and apo B-48 of CM [31–33]. In the present study, we found that the concentration of apo B-100 was higher than that of apo B-48 in the postprandial period, which is well-known from the studies of Karpe and Björkegren, who reported that the number of CM and their remnants is lower and does not usually account for more than 10% of the number of VLDL [34]. The greater accumulation of VLDL particles was attributed to the continuous secretion by the liver [35] and the unfavorable competition with CM lipolytic pathway [36].

According to Apo B-100 and apo B-48 concentrations, the number of TRL particles during the postprandial period after POO intake was lower than after ROO, although the differences were significant only at 6 hours. The number of TRL particles decreased continuously during the postprandial period, suggesting that CM particles from POO and ROO disappear from circulation at the same rate, probably because there is a similar hepatic uptake.

The size of the particles at the studied postprandial time points was estimated by calculating the ratio of TG to apo B in the TRL fraction (Fig. 4). Different conditions can lead to the formation of TRL with different sizes, which is a relevant factor to take in account in their atherogenicity. It has been previously reported by Karpe et al. [37] that large CMs are cleared from the plasma compartment faster than small VLDL-sized intestinal lipoproteins. This could explain the faster clearance after POO due to the larger size of particles. Results from our study demonstrate differences in the size of TRL particles when comparing the effect of two different MUFA oils, which only differ in the unsaponifiable fraction composition. The significantly higher TG/apo B ratio observed in TRL 2 h after the consumption of the POO enriched meal suggests that newly synthesized TRL contain more TG per particle when this oil is consumed, showing the formation of larger size particles after POO. Likewise, there was an important decrease of the ratio TG/apo B at 4 h, becoming significantly lower after POO than after ROO. This difference in the particle size could be explained by a faster TG hydrolysis, since we did not find a significant difference between the concentrations of both isoforms of apo B after POO or ROO. This suggestion is supported by our previous study [27], showing that the unsaponifiable fraction did not affect TRL incorporation into rat primary hepatocytes, although the mRNA expression of the LDL and LDL-related protein receptors (LDLr and LRP) were enhanced. Therefore, we suggested that the unsaponifiable fraction of VOO might be interfering with the other pathway for TRL clearance from serum, i.e. the hydrolytic pathway.

The only study available on the effect of minor components of VOO on TRL clearance was focused on the structure of phytosterols. Mortimer et al. [38], demonstrated that the structure of the sterol molecules regulate the clearance of CM-like particles. These authors showed that additional hydroxyl groups delays CM-like particle uptake by rat liver, whereas side chain variations such as campesterol, ß-sitosterol, stigmasterol were cleared similarly to emulsions containing cholesterol. The greatest difference between POO composition and the rest of olive oils (VOO and ROO) is the concentration of the wax fraction. In fact, this parameter is used to detect adulteration of VOO with POO (EU Regulation CE2568/91). Waxes are long-chain aliphatic alcohols of C20 to C28 carbon atoms that are esterified with fatty acids. Policosanol is a mixture of aliphatic alcohols containing mainly octacosanol, which has demonstrated hypocholesterolemic effects. Although the mechanism of action is presently unknown [39], there is evidence of effective absorption of its constituting aliphatic alcohols and conversion to long-chain fatty acids in the liver, including esterification to TG and CE [40].

Few works have studied the effects of the intake of very-long-fatty alcohols other than policosanol. It was initially reported that policosanol did not affect plasma TG levels [39], but recent studies have indicated that doses of 5 mg/day for 2 years reduced TG by 16% in elderly patients with Type-2 diabetes [41]. In fact, Kato et al., [42] had already showed that octacosanol supplementation (10 g/kg diet) decreased serum TG levels in rats fed a high-fat diet, which was concomitant with a higher activity of LPL. Since LPL exhibits specificity with respect to fatty acid length chain and unsaturation [7,8] it is plausible that the metabolism of TRL, including the hydrolysis of TG, is affected by the incorporation of very-long-chain fatty alcohols and acids into the particles. POO in the present study contained around 3.5 g of waxes pre kg of oil. Therefore the administrated dose (for 70 g of oil) was 245 mg, which is much higher than the dose reported by Mas et al. [41] and Kato et al. [42] in rats.


   CONCLUSION
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 CONCLUSION
ACKNOWLEDGMENTS
 REFERENCES
 
Our study shows for the first time the serum postprandial lipid response to a meal enriched in POO. We conclude that, compared with ROO, consumption of POO leads to the formation of a lower number of TRL particles but containing a higher TG concentration, i.e. a higher particle size. Although TRL particles were removed from serum at a similar rate regardless of the oil consumed, particles formed after POO were depleted of TG much more rapidly, probably through enhanced hydrolysis by LPL, rather than through hepatic uptake. Since ROO and POO differ basically in their unsaponifiable fraction composition, we suggest that a component of this fraction may be responsible of these effects. We consider that fatty alcohols (waxes), present in very relevant concentration in POO and almost absent in ROO, might be plausible candidates in these regard.


   ACKNOWLEDGMENTS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 CONCLUSION
 ACKNOWLEDGMENTS
REFERENCES
 
This work was supported by funds from Comision Interministerial de Ciencia y Tecnologia (CYCIT, AGL2002-00195 and AGL2005-00572), a FPI fellowship (Ministerio de Educación y Ciencia) to RCM and a Juan de la Cierva contract to JSP.

Received February 15, 2006. Accepted June 1, 2006.


   REFERENCES
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 CONCLUSION
 ACKNOWLEDGMENTS
 REFERENCES
 

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J. Martinez-Gonzalez, R. Rodriguez-Rodriguez, M. Gonzalez-Diez, C. Rodriguez, M. D. Herrera, V. Ruiz-Gutierrez, and L. Badimon
Oleanolic Acid Induces Prostacyclin Release in Human Vascular Smooth Muscle Cells through a Cyclooxygenase-2-Dependent Mechanism
J. Nutr., March 1, 2008; 138(3): 443 - 448.
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