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2
*
Research and Development Department, Abbott Laboratories, 18004 Granada, Spain and
Department of Biochemistry and Molecular Biology, University of Granada, 18071 Granada, Spain
2To whom correspondence should be addressed at Abbott Laboratories, Camino de Purchil, 68, 18004 Granada, Spain. E-mail: Maria.Ramirez{at}abbott.com
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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KEY WORDS: • lipoproteins • long-chain polyunsaturated fatty acids • phospholipids • piglets • triacylglycerols
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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). LCP with 20 and 22 carbon atoms,
mainly arachidonic acid (AA) and docosahexaenoic acid (DHA), are
critical components of cellular membranes and are especially enriched
in the developing retina and gray matter of the brain (Bazan et al. 1986
, Clandinin et al. 1980
). Some reports
indicate that LCP status is improved in infants fed LCP-containing
formulas (Clandinin et al. 1992
, Koletzko et al. 1989
). In addition, other studies show that such improvement
could be correlated with improved visual acuity and cognitive
development (Birch et al. 1992a, 1992b and 1998
,
Carlson et al. 1993
and 1996
, Makrides et al. 1995
, Uauy et al. 1990
). Based on these
observations, international committees have recommended that infant
formula, especially for preterm infants, be supplemented with AA and
DHA at levels normally found in human milk (British Foundation 1992
, ESPGAN 1991
, FAO/WHO 1994
,
ISSFAL 1994
). On the other hand, the need to supplement
formulas for term infants with preformed LCP continues to be a matter
of debate (Auestad et al. 1997
, Heird et al. 1997
). Lipid components of infant formulas are obtained from vegetable oils, which contain fatty acids of up to 18 carbon atoms in length. For this reason, LCP supplementation to the diet requires other lipid sources, generally of animal origin. There are several LCP-enriched sources available, such as fish oils, oils from unicellular organisms and egg oil fractions. Fish and unicellular oils are mainly composed of triacylglycerols (TG), and commercial egg oil fractions are rich in phospholipids (PL). Furthermore, these lipid sources also differ in fatty acid composition, presence of other lipid components and the molecular structure of their TG and PL. Because lipid digestion is a complex process involving enzymes, it is possible that these differences between lipid sources affect LCP absorption, distribution and metabolic fate.
Triacylglycerols provide >90% of the total energy of dietary fat;
therefore, TG digestion and absorption have been extensively studied.
On the other hand, little information is available about dietary PL.
Intestinal hydrolysis of TG and PL yields different products:
2-monoacylglycerols and free fatty acids in the case of TG and
1-lysophospholipids and free fatty acids in the case of PL
(Pufal et al. 1995
, Thomson et al. 1988
).
Those products are taken up by enterocytes, reesterified and secreted
into lymph chylomicrons.
A number of studies have focused on TG absorption and metabolism,
mainly on the importance of the sn-2 position
(Christensen et al. 1995
, Jensen et al. 1994
, Pufal et al. 1985). Less attention has
been paid to dietary PL, but there is evidence of impaired TG
absorption when the supply of exogenous PL is insufficient for micelle
formation during fat digestion and absorption (Levy and Roy 1989
). Moreover, clinical trials with premature infants found
that DHA from egg PL was better absorbed than DHA from breast milk and
DHA TG from single-cell oils (Carnielli et al. 1995
). Other studies have also shown a positive effect of
PL-LCP supplementation on fat absorption (Morgan et al. 1998
). PL are also essential for intestinal lipoprotein
formation and for fat distribution outside the enterocytes. Data from
animal studies suggest that the intraduodenal infusion of triolein
results in the formation of chylomicrons, whereas the infusion of egg
phosphatidylcholine favors the formation of intestinal VLDL-size
particles (Tso et al. 1984
).
Based on previous work, we hypothesized that the chemical structure and composition of LCP sources used to supplement infant formula may influence the distribution of these important fatty acids and that therefore LCP sources may not be biologically equivalent. For this purpose, we evaluated the effects of dietary LCP as TG or PL on plasma and plasma lipoproteins in infant piglets. Because small intestine and liver are key organs in the metabolism of lipoproteins, we also determined the lipid composition of jejunum and liver.
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MATERIALS AND METHODS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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Thirty 5-d-old Yorkshire piglets at term gestation (obtained from Ntra. Sra. de las Mercedes Farm, La Guardia, Jaen, Spain) were randomly assigned to each of three dietary groups. Each group of piglets was housed together and freely fed by bottle three times a day for 4 wk. Heating was provided with spot heat lamps attached above each cage. The study was approved by the Animal Care Committee at the University of Granada and conforms to the European Union Regulation of Animal Care for the care and use of animals for research.
Three powdered formulas, identical in all ingredients except for fat
composition, were designed to meet the nutrient requirement of growing
piglets (Miller and Ullrey 1987
). The formulas were
dissolved in warm water at a concentration of 188 g/L. The general
composition of the control formula has been previously reported
(Lopez-Pedrosa et al. 1998
). Control fat was composed of
a blend of olive, soy and coconut oils and milk fat. LCP were added by
supplementation with either tuna and fungal oil (TF-TG diet) or
egg yolk PL (E-PL diet). The final fatty acid composition of the diets
is given in Table 1
. Tuna oil with a low 20:5(n-3)/22:6(n-3) ratio was supplied by Mochida
(Tokyo, Japan), and fungal oil was supplied by Suntory (Tokyo, Japan).
Part of the vegetable fat blend in the control formula (2.7 g/100 g)
was replaced by tuna and fungal oils to reach 0.6 and 0.3 g of AA
and DHA/100 g, respectively. E-PL (Ovothin 160) was supplied by
Lucas Meyer (Hamburg, Germany). For this diet, 13.2 g/100 g of the fat
blend in the control formula was replaced with this source of PL to
reach the same concentration of AA and DHA as in the TF-TG diet.
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Analytical procedures.
After a 4-wk feeding period, piglets were deprived of food overnight and bled to death via jugular vein puncture while under anesthesia. Blood was collected with tripotassium EDTA (2.7 mmol/L) as anticoagulant and centrifuged at 3000 x g for 10 min at 4°C. An aliquot of plasma (10 mL) was collected for lipoprotein isolation; the remaining plasma was frozen in liquid nitrogen and stored at -80°C until analyzed. Livers were excised, washed in cool saline solution and dried with filter paper to remove excess water. Proximal jejunum (60 cm) was removed, rinsed thoroughly with cold saline solution, opened lengthwise and blotted dry. The mucosa was removed by scraping the entire luminal surface with a glass coverslip over an ice-cold Petri dish. The livers and jejunum mucosa were also frozen in liquid nitrogen and stored at -80°C.
Plasma density was adjusted to 1300 kg/L with KBr and overlaid
with NaCl (0.15 mol/L). Lipoproteins were separated through
discontinuous density gradient ultracentrifugation with a Beckman
L8–70M ultracentrifuge equipped with a vertical vTi50 rotor (Beckman
Instruments, Palo Alto, CA) at 240,000 x g for
2 h at 10°C. After centrifugation, bands corresponding to VLDL,
LDL and HDL were collected and frozen at -80°C until analysis. To
determine the different lipid classes of plasma and lipoproteins, these
were extracted using hexane/isopropanol (3:2) according to
Kolarovic and Fournier (1986
) and dried under nitrogen.
Lipid fractions from plasma and lipoprotein extracts were separated by
thin-layer chromatography on Silica Gel 60 plates (0.5 mm; Merck,
Darmstadt, Germany) using hexane/isopropyl ether/acetic acid
(75:25:1.5) according to the method previously described by
Skipski and Barclay (1969
).
To analyze the lipid composition, 0.2 g of liver and intestinal
mucosa was homogenized in distilled water and extracted with
hexane/isopropanol (3:2). Lipid extracts were dissolved in chloroform,
aliquots were taken in duplicate for each measurement and the solvent
removed under nitrogen. Isopropanol (100 µL) was added to facilitate
mixing with enzymatic reagents, and total and free cholesterol and
triacylglycerol concentrations were determined through
spectrophotometry with commercial kits (Roche Diagnostic GmbH,
Mannheim, Germany). PL concentrations were determined as inorganic
phosphorous after sample mineralization (Ziversmit et al. 1950
).
Cholesterol and triglycerides in plasma were measured directly with the
commercial kits mentioned and according to the supplier’s
instructions. In lipoproteins, those lipids were measured by the same
method but adapted for a microplate assay. PL in plasma and
lipoproteins were also measured in lipid extracts (Ziversmit et al. 1950
).
Lipid from different plasma fractions and lipoproteins were converted
to fatty acid methyl esters through transmethylation as previously
described by Lepage and Roy (1986
). Fatty acid methyl
esters were separated and quantified by gas-liquid chromatography
with a Hewlett Packard model 5890 gas chromatograph (Palo Alto, CA)
equipped with a flame ionization detector and a 60 m x 0.32 mm
internal diameter SP-2330 capillary column (Supelco, Bellefonte, PA) as
previously described (Amate et al. 1999
).
Statistical analysis.
Diet group differences were investigated by one-way ANOVA with the
7D program of BMDP Statistical Software PC 90 version (Los Angeles, CA)
(Dixon et al. 1990
). The homogeneity of variances was
analyzed by Levene’s test. If variances were not homogeneous, Welch’s
test was used to study group differences. When a significance
difference was found (P < 0.05), Bonferroni’s
test was used to examine individual comparisons. Values in the text are
means ± SEM.
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RESULTS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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The overall mean body weight at the beginning of the study was 2321 ± 46.9 g. Body weight increased exponentially over time. No significant differences were found between groups, with the overall body weight at the end of the study 5848 ± 195.4 g. The daily energy intake was 1239 ± 23 kJ/kg body.
Fatty acid composition of plasma and plasma fractions.
Proportions of AA and DHA in plasma total lipids and its fractions
generally were higher in both LCP-supplemented groups than in the
control group (Table 2
). Oleic acid in plasma and plasma PL and CE were higher in the control
group than in both LCP-supplemented groups, except in PL of piglets
fed TF-TG. Proportions of 18:2(n-6) in plasma PL of control piglets
were also higher than those of the experimental groups.
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Fatty acid composition of lipoproteins.
As in plasma lipids, proportions of DHA were significantly greater in
both LCP-supplemented groups compared with the control group in all
lipoprotein fractions (Table 3
). AA was also greater in HDL lipids of LCP-supplemented groups and
in VLDL and LDL lipids of the E-PL group. On the other hand, the
VLDL and HDL 18:1(n-9) level was lower in the E-PL and TF-TG
groups than in the control group. A lower proportion of 18:2(n-6) was
present in HDL from both LCP-supplemented groups compared with the
control group. Proportions of AA and DHA in HDL-PL were
significantly higher in piglets fed the E-PL diet than in the
control and TF-TG piglets (Fig. 1
). In LDL-PL, the TF-TG group had higher proportions of both AA
and DHA than the E-PL and control groups.
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No significant differences were found between the control and LCP-supplemented groups or between the LCP-supplemented groups in the concentrations of TG, PL and total, free and esterified cholesterol of plasma and lipoproteins (data not shown). Total cholesterol concentrations of liver was significantly lower in both LCP-supplemented groups than in the control group (data not shown). Concentrations of cholesterol, TG and PL in liver did not differ between the E-PL and TF-TG groups. Lipid composition of jejunal mucosa did not differ between the study groups (data not shown).
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DISCUSSION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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, Foote et al. 1990
) and in infants (Birch et al. 1992a, 1992b and 1998
, Carlson et al. 1993
and 1996
,
Clandinin et al. 1992
, Koletzko et al. 1989
, Makrides et al. 1995
, Uauy et al. 1990
). However, to our knowledge, only two of these studies
compared diets containing LCP from different sources. In one study, a
comparison of LCP absorption in preterm infants fed either breast milk,
infant formula (without LCP), formula with LCP derived from TG or
formula with LCP from PL was reported (Carnielli et al. 1995
); the other study reported the fatty acid composition of
brain cortical areas and non-neural tissues in piglets fed either
sow’s milk, a control formula, formulas enriched with (n-3) fatty
acids or formulas enriched with (n- 3) and (n-6) fatty acids from
either egg yolk or pig brain PL (Goustard-Langelier et al. 1999
). None of them studied lipoprotein composition. In the present study, we report the influence of dietary forms of LCP (either PL or TG) on the lipid and fatty acid composition of plasma and plasma lipoproteins and on the lipid composition of liver and jejunal mucosa in infant piglets.
The direct effect of fatty acids ingested with the diet on plasma and
tissue fatty acid composition has been largely proved (Dougherty et al. 1987
, Hrboticky et al. 1990
).
LCP-supplemented groups had lower proportions of 18:1(n-9) or
18:2(n-6), or both, in some of the plasma fractions (PL and CE) and
lipoproteins (VLDL and HDL) compared with the control group. This
effect was probably caused by the slightly lower proportion of these
fatty acids in the LCP diets (Table 1)
or by the replacement of these
fatty acids to maintain the unsaturation index. As expected, LCP
supplementation resulted in higher proportions of AA and DHA in plasma
and all lipoproteins of piglets fed TF-TG and E-PL diet
compared with the control piglets.
The most important difference found between the piglets fed LCP-PL and those fed LCP-TG was the distribution of AA and DHA in HDL-PL and LDL-PL. In fact, although there were no differences in the fatty acid composition of whole lipoproteins, HDL-PL contained a higher proportion of LCP when those fatty acids were fed as PL. Opposite results were found in LDL-PL, which contained a higher proportion of LCP when those fatty acids were fed as TG. Fatty acid composition of plasma fractions partly reflected this difference; AA was also higher in CE and PL, the main components of HDL, of piglets fed the PL diet than of those fed the TG diet. No effect was found on plasma TG, mainly representative of VLDL TG.
This different distribution of LCP in lipoprotein PL may be explained
if after digestion and absorption, LCP are reesterified to the same
chemical structure in which they were added to the diet (as PL or TG),
being assembled mainly as PL on the chylomicron surface in the case of
the E-PL group and mainly as TG in chylomicron core in the case of
the TF-TG group. Plasma chylomicrons exchange some of their
components with HDL during intravascular catabolism (Posner 1986
); therefore, HDL from piglets fed an E-PL diet would
contain a higher proportion of AA and DHA in HDL-PL, which is
consistent with our observation.
The metabolic fate of LCP from our experimental diets can be determined
taking into account, on one hand, the digestion and absorption process,
and on the other hand, the positional distribution of fatty acids in
the lipid sources used to supplement the experimental diets. We
previously reported that AA and DHA were mainly esterified to the
sn-2 position of E-PL. For example, 50% of DHA acid was
present in the sn-2 position of tuna oil, whereas nearly
80% of AA was esterified to the outer positions of the TG molecule in
fungal oil (Amate et al. 1999
). Therefore, after
digestion, LCP would be released as free fatty acids in case of the
E-PL diet, and DHA mainly as 2-monoacylglycerols and AA mainly as
free fatty acid in the case of the TF-TG diet. 2-Monoacylglycerols
are reestified to newly form TG, which would support in part our
hypothesis that dietary LCP-TG may contribute to chylomicron TG.
However, little information is available concerning lipids released as
free fatty acids in the intestinal lumen (Pufal et al. 1985, Thomson et al. 1988
). The metabolic fate
of LCP from different dietary sources in lymph chylomicrons deserves
further research.
LCP supplementation to the diet as both PL or TG lowered the hepatic
cholesterol concentration. This result was in agreement with
Ikeda et al. (1994
), who also found less cholesterol in
the livers of rats fed a DHA-containing diet. This effect may be
due to a reduction in hepatic cholesterol synthesis, because (n-3) LCP
inhibits HMG-CoA reductase activity (Choi et al. 1989
). On the other hand, (n-3) LCP have been shown to lower
plasma and liver TG (Harris 1996
, Rustan et al. 1988
). We did not find a lowering effect of (n-3) LCP on liver
TG. However, it should be taken into account that the TG-lowering
effect of (n-3) LCP has been shown in humans and experimental animals
in studies of the prevention or treatment of cardiovascular disease
using high doses of (n-3) LCP, mainly 20:5(n-3) (Rustan et al. 1988
). Both the E-PL and TF-TG diets contained 0.3
g/100 g total fatty acids as DHA with no 20:5(n-3) (E-PL) or <0.05
g/100 g 20:5(n-3) (TF-TG). It is not clear whether DHA has the same
effects as 20:5(n-3) on plasma and tissue lipids (Berge et al. 1999
). Moreover, the presence of AA in our experimental diets
may modulate the TG-lowering effects of (n-3) LCP; in fact, it has
been reported that AA increases circulating levels of TG (Whelan et al. 1995
).
Regarding comparisons between the group fed LCP as PL and the group fed
LCP as TG, there have been two previous studies that showed beneficial
effects of LCP-PL: one by Carlson et al. (1998
) and one
by our research group (Lopez-Pedrosa et al. 1995
and 1999
). Carlson et al. (1998
) reported a lower
incidence of necrotizing enterocolitis in preterm infants fed a formula
with E-PL. The authors justified their finding with one or more
components of E-PL, such as AA and choline.
López-Pedrosa et al. (1995
and 1999
) found that
malnutrition in piglets affects the composition of jejunal mucosa and
liver and plasma lipoproteins. They also reported that dietary
LCP-PL from pig brain improved the recovery of damaged intestine
and normalized the lipid and fatty acid composition of liver and plasma
lipoproteins to the levels of healthy animals of the same age. As in
the study of Carlson et al. (1998
), those results were
explained not only by dietary LCP themselves but also by the form in
which they were esterified or the presence of other components within
the PL source.
The studies by Carlson et al. (1998
) and
López-Pedrosa et al. (1995
and 1999
) pointed out a
positive effect of dietary LCP-PL on some kind of intestinal or
hepatic alterations. However, the results of our study did not show an
effect of LCP-PL on the lipid composition of liver and jejunum in
healthy animals. Some of the effects found in those reports may be
explained by the presence of other components in the LCP-PL
sources, such as cholesterol (Carlson et al. 1998
,
Lopez-Pedrosa et al. 1995
and 1999
). In the present
study, cholesterol was added to the control and TF-TG diets to
match the composition of the E-PL diet to overcome potential
effects of this component.
We found a different distribution of LCP in the PL fraction of HDL and LDL when piglets were fed a diet containing LCP from E-PL or TF-TG. The physiological importance of these results remains to be determined, but on one hand, LCP added as TF-TG or as E-PL are transported in different lipoprotein fractions, which may affect tissue uptake. On the other hand, differences on the composition of HDL and LDL PL may affect particle fluidity of the lipoproteins involved in the transport and removal of cholesterol from tissues, which means that LCP in the form of PL or TG may influence cholesterol metabolism.
In summary, this study showed that the chemical form in which LCP are present in different dietary sources influences their distribution in plasma lipoproteins. This fact should be taken into consideration when LCP sources are selected for infant formula supplementation.
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ACKNOWLEDGMENTS |
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FOOTNOTES |
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3 Abbreviations used: AA, arachidonic acid; DHA, docosahexaenoic acid; LCP, long-chain polyunsaturated fatty acids; PL, phospholipids; TG, triacylglycerols.
Manuscript received July 27, 2000. Initial review completed September 2, 2000. Revision accepted December 14, 2000.
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REFERENCES |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
1. Amate L., Ramírez M., Gil A. Positional analysis of triglycerides and phospholipids rich in long-chain polyunsaturated fatty acids. Lipids 1999;34:865-871[Medline]
2. Arbuckle L. D., Rioux F. M., Mackinnon M. J., Hrboticky N., Innis S. M. Response of n-3 and n-6 fatty acids in piglets brain, liver and plasma to increasing but low, fish oil supplementation of formulas. J. Nutr. 1991;121:1536-1547
3. Auestad N., Montalto M. B., Hall R. T., Fitzgerald K. M., Wheeler R. E., Connor W. E., Neuringer M., Connor S. L., Taylor J. A., Hartman E. E. Visual acuity, erythrocyte fatty acid composition and growth in term infants fed formulas with long-chain polyunsaturated fatty acids for one year. Pediatr. Res. 1997;41:1-10[Medline]
4. Bazan N. G., Reddy T. S., Bazan H. E., Birkle D. L. Metabolism of arachidonic acid and docosahexaenoic acids in the retina. Prog. Lipid Res. 1986;5:595-606
5. Berge R. K., Madsen L., Vaagenes H., Tronstad K. J., Gottlicher M., Rustan A. C. In contrast with docosahexaenoic acid, eicosapentaenoic acid and hypolipidaemic derivatives decrease hepatic synthesis and secretion of triacylglycerol by decreased diacylglycerol acyltransferase activity and stimulation of fatty acid oxidation. Biochem. J. 1999;343:191-197
6.
Birch D. G., Birch E. E., Hoffman D. R., Uauy R. Retinal development in very-low-birth weight infants fed diets differing in 
-3 fatty acids. Invest. Ophthalmol. Vis. Sci. 1992a;33:2365-2376
7.
Birch E. E., Birch D. G., Hoffman D. R., Uauy R. Dietary essential fatty acid supply and visual acuity development. Invest. Ophthalmol. Vis. Sci. 1992b;33:3242-3253
8. Birch E. E., Hoffman D. R., Uauy R., Birch D. G., Prestidge C. Visual acuity and essentiality of docosahexaenoic acid and arachidonic acid in the diet of term infants. Pediatr Res 1998;44:201-209[Medline]
9. British Nutrition Foundation Unsaturated Fatty Acids. Nutritional and Physiological Significance 1992 Chapman Hill London, U.K.
10. Carlson S. E., Montalto M. B., Ponder D. L., Werkman S. H., Korones S. B. Lower incidence of necrotizing enterocolitis in infants fed a preterm formula with egg phospholipids. Pediatr. Res. 1998;44:491-498[Medline]
11. Carlson S. E., Werkman S. H. A randomized trial of visual attention of preterm infants fed docosahexahenoic acid until two months. Lipids 1996;31:85-90[Medline]
12.
Carlson S. E., Werkman S. H., Rhodes P. G., Tolley E. A. Visual-acuity development in healthy preterm infants: effect of marine oil supplementation. Am. J. Clin. Nutr. 1993;58:35-42
13.
Carnielli V. P., Luijendijk I.H.T., Van Goudoever J. B., Sulkers E. J., Boerlage A. A., Degenhart H. J., Sauer P. J. Feeding premature newborn infants palmitic acid in amounts and stereoisomeric position similar to that of human milk: effects on fat and mineral balance. Am. J.Clin. Nutr. 1995;61:1037-1042
14. Clandinin M. T., Chappell J. E., Leong S., Heim T., Swyer P. R., Chance G. W. Extrauterine fatty acid accretion in infant brain: implication for fatty acid requirements. Early Hum. Dev. 1980;4:131-138[Medline]
15. Clandinin M. T., Parrott A., Van Aerde J. E., Hervada A. R., Lien E. Feeding preterm infants a formula containing C20 and C22 fatty acids simulated plasma phospholipid fatty acid composition of infants fed human milk. Early Hum. Dev. 1992;31:41-51[Medline]
16. Choi Y. S., Goto S., Ikeda I., Sugano M. Effect of dietary (n-3) polyunsaturated fatty acids on cholesterol synthesis and degradation in rats of different ages. Lipids 1989;24:45-50[Medline]
17.
Christensen M. S., Hoy C. E., Becker C. C., Redgrave T. G. Intestinal absorption and lymphatic transport of eicosapentaenoic (EPA), docosahexaenoic (DHA), and decanoic acids: dependence on intramolecular triacylglycerol structure. Am. J. Clin. Nutr. 1995;61:56-61
18. Chung B. H., Wilkinson T., Geer J. C., Segrest J. P. Preparative and quantitative isolation of plasma lipoproteins: rapid, single, discontinuous density gradient ultracentrifugation in a vertical rotor. J. Lipid Res. 1980;21:284-291[Abstract]
19. Dixon W. J., Brown M. B., Engelman L., Jennrich R .I. BMDP Statistical Software Manual 1990 University of California Press Berkeley, CA.
20.
Dougherty R. M., Galli C., Ferro-Luzzi A., Iacono J. M. Lipids and phospholipids fatty acid composition of plasma, red blood cells, and platelets and how they are affected by dietary lipids: a study of normal subjects from Italy, Finland and the USA. Am. J. Clin. Nutr. 1987;45:443-455
21. ESPGHAN Committee on NutritionAggett P. J., Haschke F., Heine W., Hernell O., Koletzko B., Launiala K., Rey J., Rubino A., Schöch G., Senterre J., Tormo R. Comment on the content and composition of lipids in infant formulas. Acta Paediatr. Scand. 1991;80:887-896[Medline]
22. FAO/WHO Expert Committee Fats and Oils in Human Nutrition. Food and Nutrition Paper No. 57 1994 FAO Rome, Italy.
23.
Foote K. D., Hrboticky N., MacKinnon M. J., Innis S. M. Brain synaptosomal, liver, plasma, and red blood cell lipids in piglets fed exclusively on a vegetable-oil-containing formula with and without fish-oil supplements. Am. J. Clin. Nutr. 1990;51:1001-1006
24. Goustard-Langelier B., Guesnet P., Durand G., Antoine J. M., Alessandri J. M. n-3 and n-6 fatty acid enrichment by dietary fish oil and phospholipid sources in brain cortical areas and nonneural tissues of formula-fed piglets. Lipids 1999;34:5-16[Medline]
25. Harris W. S. n-3 fatty acids and lipoproteins: comparison of results from human and animal studies. Lipids 1996;31:243-252[Medline]
26. Heird W. C., Prager T. C., Anderson R. E. Docosahexaenoic acid and the development and function of the infant retina. Curr. Opin. Lipidol. 1997;8:12-16[Medline]
27.
Hrboticky N., MacKinnon M. J., Innis S. M. Effect of a vegetable oil formula rich in linoleic acid on tissue fatty acid accretion in the brain, liver, plasma, and erythrocytes of infant piglets. Am. J. Clin. Nutr. 1990;51:173-182
28.
Ikeda I., Wakamatsu K., Inayoshi A., Imaizumi K., Sugano M., Yazawa K. 
-Linolenic, eicosapentaenoic and docosahexaenoic acids affect lipid metabolism differently in rats. J. Nutr. 1994;124:1989-1906
29. ISSFAL Board of Directors Recommendations for essential fatty acid requirement for infant formulae. ISSFAL Newsletter 1994;1:4-5
30. Jensen R. G., Bitman J., Carlson S. E., Cavel S. C., Hamash M., Newburg D. S. Milk lipids. A. Human milk lipids. Jensen R. G. eds. Handbook of Milk Composition 1995:495-542 Academic Press San Diego, CA.
31. Jensen R. G., deJong F. A., Lambert-Davis L. G., Hamosh M. Fatty acid and positional selectivities of gastric lipase from premature infants: in vitro studies. Lipids 1994;29:433-435[Medline]
32. Kolarovic L., Fournier N. C. A comparison of extraction methods for the isolation of phospholipids from biological sources. Anal. Biochem. 1986;156:244-250[Medline]
33. Koletzko B., Schmidt E., Bremer H. J., Haug H., Hazer G. Effects of dietary long-chain polyunsaturated fatty acids on the essential fatty acid status of premature infants. Eur. J. Pediatr. 1989;148:669-675[Medline]
34. Lepage G., Roy C. C. Direct transesterification of all classes of lipids in a one-step reaction. J. Lipid Res. 1986;27:114-120[Abstract]
35. Levy E., Roy C. C. Developmental aspects of intestinal lipoprotein synthesis and secretion. Lebenthal M. eds. Human Gastrointestinal Development 1989:491-503 Raven Press New York, NY.
36.
Lopez-Pedrosa J. M., Ramírez M., Torres M. I., Gil A. Dietary phospholipids rich in long-chain polyunsaturated fatty acid improve the repair of small intestine in malnourished piglets. J. Nutr. 1999;129:1149-1155
37. Lopez-Pedrosa J. M. Contribución de los ácidos grasos polinsaturados de cadena larga de la dieta a la reparación tisular en cerdos malnutridos durante el periodo neonatal (Contribution of dietary long-chain polyunsaturated fatty acids to tissue repair in malnourished piglets) 1995 University of Granada Spain. Doctoral thesis
38.
Lopez-Pedrosa J. M., Torres M. I., Fernandez M. I., Rios A., Gil A. Severe malnutrition alters lipid composition and fatty acid profile of small intestine in newborn piglets. J. Nutr. 1998;128:224-233
39. Makrides M., Neumann M., Simmer K., Pater J., Gibson R. Are long-chain polyunsaturated fatty acids essential nutrients in infancy?. Lancet 1995;345:1463-1468[Medline]
40. Miller E. R., Ullrey D. E. The pig as model for human nutrition. Annu. Rev. Nutr. 1987;:361-382
41. Morgan C., Davies L., Corcoran F., Stammers , Colley J., Spencer S. A., Hull D. Fatty acid balance studies in term infants fed formula milk containing long-chain polyunsaturated fatty acids. Acta Paediatr 1998;87:136-142[Medline]
42. Posner I. Metabolismo de las lipoproteínas. Disliproteinemías (Metabolism of lipoproteins: dyslipoproteinaemia). Herrera E. eds. Bioquímica 1986:523-541 Interamaricana Madrid, Spain.
43. Pufal D. A., Quinlan P. T., Salter A. M. Effect of dietary triacylglycerol structure on lipoprotein metabolism: a comparison of the effects of dioleoylpalmitoylglycerol in which palmitate is esterified to the sn-2 or 1(3)-position of the glycerol. Biochim. Biophys. Acta 1995;1258:41-48[Medline]
44. Rustan A. C., Nossen J. O., Christiansen E. N., Drevon C. A. Eicosapentaenoic acid reduces hepatic synthesis and secretion of triacylglycerol by decreasing the activity of acyl-coenzyme A:1,2-diacylglycerol acyltransferase. J. Lipid Res. 1988;29:1417-1426[Abstract]
45. Skipski V. P., Barclay M. Thin layer chromatography of lipids. Lowenstein J. M. eds. Methods in Enzymology 1969;14:530-598 Academic Press New York, NY.
46. Thomson A. B., Keelan M., Garg M. L., Clandinin M. T. Intestinal aspects of lipid absorption: in review. Can. J. Physiol. Pharmacol. 1988;67:179-191
47. Tso P., Drake D. S., Black D. D., Sabesin S. M. Evidence for separate pathways of chylomicron and very low-density lipoprotein assembly and transport by rat small intestine. Am. J. Physiol. 1984;247:G500-G600
48. Uauy R. D., Birch D. G., Birch E. E., Tyson J. E., Hoffman D. R. Effect of dietary omega-3 fatty acids on retinal function of very-low-birth-weight neonates. Pediatr. Res. 1990;28:485-492[Medline]
49. Whelan J., Surette M. E., Li-Stiles B., Bailey J. W. Evidence that dietary arachidonic acid increases circulating triglycerides. Lipids 1995;30:425-429[Medline]
50. Ziversmit D. B. J. Lab. Clin. Med. 1950;35:155[Medline]
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