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(Investigative Ophthalmology and Visual Science. 2003;44:4559-4566.)
© 2003 by The Association for Research in Vision and Ophthalmology, Inc.
DOI:  10.1167/iovs.03-0478
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Docosahexaenoic and Arachidonic Acid Influence on Preterm Baboon Retinal Composition and Function

Guan-Yeu Diau,1,2 Ellis R. Loew,3 Vasuki Wijendran,1,4 Eszter Sarkadi-Nagy,1,5 Peter W. Nathanielsz,3,6 and J. Thomas Brenna1

1From the Division of Nutritional Sciences and 3College of Veterinary Medicine, Cornell University, Ithaca, New York;


   Abstract
Top
 Abstract
Materials and Methods
 Results
 Discussion
 References
 
PURPOSE. Dietary n-3 polyunsaturated fatty acid deficiency and prematurity are both associated with suboptimal visual function in nonhuman primates and in humans. This study reports measurements of retinal long chain polyunsaturate (LCP) concentrations and electroretinogram (ERG) parameters for term and preterm neonatal baboons consuming clinically relevant diets.

METHODS. ERGs and retinal fatty acid compositions were obtained from baboon neonates in four groups: term-delivered/breast-fed (B), term/formula-fed (T-), preterm/formula-fed (P-), and preterm/formula (P+) supplemented with long chain polyunsaturates. Initial a-wave slope change (ä), a-wave amplitude (aamp) and implicit time (ai), and b-wave amplitude (bamp) and implicit time (bi) were determined and correlations to retinal fatty acid concentrations were evaluated.

RESULTS. The P+ group ä and bamp significantly improved between 0 and 4 weeks’ adjusted age, whereas no P- group parameter improved with age. At four weeks, both aamp and bamp were significantly greater in group B than in all other groups, and ä and ai were greater for P+ than for P-. Concentrations of 22:6n-3, 22:5n-3, and {Sigma}n-3 and the 22:5n-6/22:6n-3 ratio correlated positively with improved retinal response parameters, whereas 22:5n-6, 22:4n-6, 20:4n-6, 20:3n-6, 20:2n-9, 20:1n-9, and 18:1n-9 all correlated negatively (P < 0.05); saturates were uncorrelated. The parameters most linearly related to retinal 22:6n-3 were ä, ai, and aamp. Retinal 20:4n-6 concentrations were not influenced by prematurity or supplementation.

CONCLUSIONS. Breast-feeding optimizes retinal response in 4-week-old baboons. Formula supplemented with 22:6n-3 prevents a decrease in retinal 22:6n-3 and improves preterm ERG parameters compared with unsupplemented formula. Retinal 22:6n-3 status is most closely associated with a-wave parameters.

Retinal docosahexaenoic acid (DHA, or 22:6n-3) concentrations correlates highly with retinal function in rats,1 and severe n-3 deficiency is associated with low 22:6n-3 and impaired visual performance, as assessed by electroretinography (ERG) in several species2 3 4 5 and by preferential looking tests6 in rhesus monkeys. The biochemical n-3 deficiency markers in cerebral cortex and retina, low 22:6n-3 and high 22:5n-6, can be reversed in rhesus monkeys with a few weeks of feeding with fish oil5 7 ; however, the ERG parameters do not become normal. The mechanism by which 22:6n-3 influences retinal function remains unclear.8

The preterm human infant is thought to be particularly vulnerable to dietary n-3 deficiency. Preterm infants of less than 800 g birthweight and 30 weeks’ gestational age routinely survive and until recently were fed formulas devoid of long chain polyunsaturates (LCP, 20 or more carbons). Although it has been established that primate fetuses,9 preterm and term baboon neonates,10 and preterm human infants11 12 synthesize 22:6n-3 from 18:3n-3, it is not known whether preterm infants can synthesize sufficient 22:6n-3 to meet the demands of rapid brain and retinal growth.13 Clinical studies of preterm infants generally agree that supplementation with LCP improves development of the visual system, apparently without risk,14 though the importance of transitory improvements in visual function of healthy term infants fed LCP-free formulas is controversial.15

Ideally, studies relating visual function to biochemical composition would measure a functional outcome, a correlate of function, or some behavioral response and then have access to retinal tissue for analysis in the same animal. Such studies have been reported most extensively using electroretinography in guinea pigs16 17 18 19 ; however, unlike the guinea pig, the primate retina has a high density of cones and a fovea.20 Thus, the most accurate animal models of human retinal function are restricted to higher primates.

Tissue sampling in human infants is generally constrained by ethical guidelines to the sampling of blood a few times during infancy. Fatty acids in blood-borne pools (for example, plasma or red blood cells) are analyzed and used as biochemical indicators of LCP status, and correlations to functional tests are then drawn (e.g., Refs. 21 22 ). A major drawback of this approach is that conclusions are limited to correlations between indirect measures of tissue fatty acid status and function. The detailed relationship between retinal composition and plasma or red blood cell fatty acid concentrations must therefore be inferred. Rigorous direct comparisons are available for retinal function and tissue fatty acid composition in a limited number of animal models,18 23 and the application of these results to humans must be approached with caution.

We report an investigation of the influence of prematurity and dietary LCP on retinal function and tissue fatty acid composition in four randomized groups of baboon neonates: two term groups, breast-fed and formula-fed, and two preterm groups, formula-fed with or without LCP. Lactating females in the breastfed group consumed a standard primate diet that included fish meal containing n-3 LCP (22:6n-3, 22:5n-3, and 20:5n-3), and their milk represents an optimal source of n-3 LCP, thus establishing the best possible control group. Comparison of the unsupplemented groups permits evaluation of prematurity per se. Comparison of the preterm groups permits evaluation of dietary LCP on prematurity.


   Materials and Methods
Top
 Abstract
 Materials and Methods
Results
 Discussion
 References
 
The animals were a subset of animals used in a study of LCP supplementation and prematurity and in part have been reported on elsewhere.24 For reference, we have outlined the study in essential details and re-report summary dietary data.

Animals
The Cornell Institutional Animal Care and Use Committee approved the animal care protocol, and the Association for Assessment and Accreditation of Laboratory Animal Care (AAALAC) approved the facility. Sixteen pregnant baboons (Papio cynocephalus) were transported from a colony at the Southwest Foundation for Biomedical Research (San Antonio, TX) to the College of Veterinary Medicine at Cornell University. Complete veterinary examinations were performed on all baboons on arrival. They were housed individually in cages within sight of one or more baboons and a video showing other baboons. Temperature (24°C), humidity (70%), and a 14:10-hour light–dark cycle were maintained in the primate rooms.

Sixteen female–neonate pairs were randomized to one of four experimental groups (n = 4): B, breastfed; T-, term, fed conventional formula free of LCP; P-, preterm, fed conventional formula; P+, preterm, fed an LCP-supplemented formula. Females in the B and T- groups delivered spontaneously. The T- neonates were removed from the female within 24 hours of birth, admitted to a nursery, and bottle-fed a conventional commercially available human infant formula with no LCP (Enfacare; Mead-Johnson, Evansville, IN) throughout the study.

At approximately 152 days of gestation (normal term gestation, 182 days), a course of antenatal betamethasone, 175 mg/kg body weight per day, was administered to P- and P+ females at 48 and 24 hours before cesarean section. At approximately 154 days gestation, P- and P+ neonates were removed by cesarean section, according to procedures used previously.25 Premature neonates were housed in incubators and provided with intrapulmonary surfactant as clinically necessary. No mechanical ventilation was used. Three P+ neonates received surfactant; no P- neonate needed it. Neither lung nor any other tissue fatty acid composition showed any distinct difference as a result of surfactant administration (data not shown).

P- neonates received the same LCP-free formula as T- neonates. The LCP-free formula Enfacare (Mead-Johnson) contains 47% calories as fat. P+ neonates received the same formula, supplemented with 0.3% energy 22:6n-3 and 0.6% energy 20:4n-6 (arachidonic acid, ARA). The DHA and ARA were supplied as a powdered, encapsulated oil and added directly to the formula powder. Formula and LCP powder were kindly provided by Mead-Johnson Nutritionals.

Breast milk was sampled once from the lactating females immediately after neonate necropsy. Studies have shown that total fatty acid concentration in human breast milk decreases with increasing time postpartum, although the concentrations of 22:6n-3 and 20:4n-6, as a percent of fatty acids, are stable.26

Flash Electroretinogram
ERG procedures were performed in accordance with the ARVO Statement for the Use of Animals in Ophthalmic and Vision Research. ERGs were performed on the P- and P+ groups at approximately 28 days of life, corresponding to the postconceptional age of normal term birth. ERGs were performed on all groups at 4 weeks’ corrected age, 3 to 5 days before death, at which time the P- and P+ groups were 7.5 weeks’ birth age. A custom-built, computer-based ERG acquisition system (Windows-based software; Microsoft, Redmond, WA), identical with that used in the electrodiagnostic clinic of the Cornell University veterinary hospital was used for the measurements.

Baboon neonates were held supine in the arms of a caregiver in a quiet darkened room for a minimum of 30 minutes for dark adaptation and mydriasis. Ketamine with/without xylazine was injected intramuscularly at the beginning of the procedure, and isoflurane inhalation anesthesia was used throughout. Subdermal platinum-iridium needle electrodes were placed between the eyes (indifferent) and in an ear flap (ground). A local anesthetic (proparacaine) and a cushioning solution (Murocel; Bausch & Lomb, Tampa, FL) were applied to the cornea before placing the active contact lens electrode (ERG-Jet; LKC Technology, Gaithersburg, MD) on the eye, exposed using a lid speculum.

Each eye was tested separately using 50-ms stimuli from a white-light LED. The highest light intensity used was approximately 1.1 x 104 lux, as measured with a spectroradiometer (model S1000; Ocean Optics, Dunedin, FL), using a photopic conversion utility of the control software with the unit (C-Spec; Ocean Optics). ERGs were obtained at 9 or 10 intensity steps, differing by 0.5 log unit, starting with the lowest intensity. The highest intensity was shown to be above the dark-adapted b-wave saturation level. Figure 1 shows a typical ERG series using this protocol and instrumentation, illustrating responses for the eight highest intensities for this particular series.



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  		FIGURE 1. An ERG series performed on the right eye of a B neonate. The intensity of the stimulus increased in half log unit steps eliciting ERGs starting from the bottom. For all animals, amplitudes, and implicit times of the initial negative-going a- and positive-going b-wave reported in Table 4 were determined for the third most intense flash. The ä parameter is calculated from the top six a-wave slopes only.

 
For all groups, the eighth highest intensity response was chosen as the standard for measurement of a- and b-wave implicit times and amplitudes. The slopes of the ascending limbs of the a-waves were calculated for the six highest intensity responses, and the increase in these slopes with intensity is reported as the parameter ä. In this procedure, a straight line is drawn from the voltage (defined as 0 V) at the time of the flash to the lowest point (highest response intensity) of the a-wave. The slope for each of the six intensities is calculated and plotted against flash intensity, with the lowest intensity set to 1 and the highest set to 6. The resultant straight line is modeled with a linear regression to yield ä as the calculated slope parameter. Slope ä is therefore the increase in initial response with increasing light intensity, similar to a parameter presented by Breton et al.27

At 4 weeks’ corrected age, neonates were anesthetized with halothane and killed by exsanguination. Retinas were immediately collected in ice-cold saline, frozen in liquid nitrogen, and stored at -80°C until analysis, less than 6 weeks later.

Statistics
ERG parameters for the four groups were analyzed by one-way analysis of variance (ANOVA) for measurements taken at 4 weeks’ corrected age. When ANOVA was significant, pair-wise comparisons were performed using the Tukey honest significant difference (HSD) test. ERG parameters were tested for significance by paired t-test for the two measurements of the P- or P+ groups, as indicative of significant improvement over time. Significance was declared at P < 0.05 for all tests.

The Pearson correlation coefficient (r) between retinal fatty acids and ERG parameters was calculated for linear least-squares fits for individual animals (n = 16). The correlation coefficient was considered significant if P < 0.05 and |r| > 0.5.


   Results
Top
 Abstract
 Materials and Methods
 Results
Discussion
 References
 
Animal characteristics are presented in Table 1 . There were no significant differences in body weight at death (P > 0.05) among the groups.


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  		TABLE 1. Characteristics of Baboon Neonates

 
Fatty acid compositions of the diets are summarized in Table 2 . Breast milk 22:6n-3, 22:5n-3, and 20:5n-3, were 0.68% ± 0.20%, 0.51% ± 0.15%, and 0.34% ± 0.13% of fatty acids, respectively, and 20:4n-6 and 22:4n-6 were 0.62% ± 0.12% and 0.22% ± 0.06%, respectively. The conventional formula fed to groups T- and P-, as expected, had no LCP. The formula supplemented with LCP and fed to the P+ group had 0.61% ± 0.03 22:6n-3, very low amounts of 22:5n-3 and 20:5n-3, and 1.21% ± 0.09% 20:4n-6. Thus, the 22:6n-3 concentration in the supplemented formula (P+) was comparable to that of breast milk, whereas 20:4n-6 was approximately double. 22:5n-3 and 20:5n-3 concentrations were higher in breast milk than in the P+ formula.


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  		TABLE 2. Fatty Acid Compositions of Various Diets

 
Retina Fatty Acid Composition
The retinal fatty acid composition is presented in Table 3 . The 22:6n-3 concentration in groups consuming nonsupplemented formula (T-, P-) was significantly lower than the B group (19.1% ± 1.4%). LCP supplementation maintained P+ 22:6n-3 levels similar to the B group. Prematurity had no significant effects on 22:6n-3, as judged by the T-/P- comparison. In contrast, neither 20:4n-6 supplementation nor prematurity influenced 20:4n-6 concentration, which remained approximately 10% in retina.


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  		TABLE 3. Retinal Fatty Acid Compositions

 
ERG Parameters
Table 4 presents a summary of the ERG parameters. For the P- and P+ groups, two measurements, performed at two different ages, are presented: (1) 182 days postconceptional age, corresponding to gestational age of normal term birth; and (2) 4 weeks’ adjusted age, corresponding to the same postpartum age at which ERGs were performed on the T- and B groups. Differences between time points within a group (P- or P+) and between the first time points (P- (1) versus P+ (1)) were performed. Statistical tests between groups were also performed on the values for the 4-week adjusted age-matched P- (2), P+ (2), T-, and B neonates.


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  		TABLE 4. ERG Parameters: ä, Implicit Times (ms), and Amplitudes (µV), expressed as Mean ± SD

 
There was no significant difference in preterm groups in any parameter at the first time point (P- (1) versus P+ (1)). For the P+ group, ä and bamp improved with age (äP+(2) > äP+(1); bamp,P+(2) > bamp,P+(1); P < 0.05), but there was no statistically significant improvement detected in any parameter in the P- group.

The B group amplitudes (aamp and bamp) were significantly greater than in all other groups, whereas the P- group was significantly lower than all groups in ä and higher in ai. No significant differences were found between groups in bi.

Pair-wise comparisons reveal that ä and ai were greater in the P+ group than in the P- group at the 4-week time point (P+ (2) versus P- (2), showing improvement due to supplementation. Similarly, the T- group had improved ä and ai compared with the P- group; the catch-up growth in overall body mass of the P- group compared with the T- and B groups, as shown in Table 1 , does not extend to normalization of retinal function. There were no significant differences between the P+ group and the T- group.

Retina Fatty Acid Concentration: ERG Parameter Correlations
Table 5 is a compilation of correlation coefficients calculated from linear regressions of retinal fatty acids concentrations versus ERG parameters. Only those statistically significant correlation coefficients with |r| > 0.5 are presented. The fatty acids 22:6n-3, 22:5n-3, and the sum of the n-3 fatty acids ({Sigma}n-3) were all correlated positively improved retinal response. In contrast, 22:5n-6, 22:4n-6, 20:4n-6, 20:3n-6, 20:1n-9, 20:2n-9, and 18:1n-9 were all negatively correlated with retinal function. Saturates, which do not appear in the table, were all uncorrelated with function. Composite parameters for all the unsaturated fatty acid series are significantly correlated with ERG parameters. In addition to {Sigma}n-3, {Sigma}n-7 correlated positively with function, whereas {Sigma}n-9 and {Sigma}n-6 correlated negatively. The pentene-hexane ratio (22:5n-6/22:6n-3), taken as a 22:6n-3 deficiency index, and the {Sigma}n-6/{Sigma}n-3 ratio, both correlated negatively with retinal function.


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  		TABLE 5. Pearson’s Correlation Coefficient between Retinal Fatty Acids and ERG Parameters at 4 Weeks’ Adjusted Age

 
Figures 2 and 3 are plots of the means of treatment group ERG parameters and 22:6n-3 and the pentene-hexene ratio, respectively. Figure 2 presents plots for 22:6n-3, showing a significant correlation with aamp, ai, and bamp, but not with ä. The functional relationships for a-wave parameters follow a line, whereas the improvement in bamp appears to be independent of retinal 22:6n-3 concentration of the B and P+ groups for the two highest 22:6n-3 levels, around 19%. Figure 3 shows similar results for the pentene/hexene ratio, and bamp confirms this trend.



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  		FIGURE 2. Plots of mean retinal 22:6n-3 versus ERG parameters, including linear regression lines. Regression line omitted for ä because r = 0.48. The B group has the best performance (highest amplitudes and ä, lowest implicit time). The ai and aamp means follow the regression line more closely than bamp, in which the formula groups are nearly invariant with 22:6 concentration. Breast-feeding substantially improves bamp but does not significantly alter 22:6 compared with supplementation in the P+ group.

 


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  		FIGURE 3. Plots of the retinal pentene/hexene ratio (22:5n-6/22:6n-3), a 22:6n-3 insufficiency index, versus ERG parameters, including linear regression lines. Trends mirror those in Figure 2 .

 

   Discussion
Top
 Abstract
 Materials and Methods
 Results
 Discussion
References
 
These data directly support the hypothesis that LCP supplementation affects retinal function in primates through concomitant changes in retinal fatty acid composition. The P- group had significantly poorer retinal function as measured by ä and ai, than the other groups, including the P+ group. This finding, indicating that LCP supplementation improved retinal function, is consistent with functional data from human studies.21 28 29 30 Our fatty acid measurements are direct evidence that this compromised function is at least in part related to a lower retinal 22:6n-3 concentration.5 Previous data show that premature infants can synthesize 22:6n-3 from precursor 18:3n-3,11 12 31 and more recent data demonstrate that fetal baboons can biosynthesize 22:6n-3.9 All data collected to date indicate that late-term primate fetuses and human premature infants, on average, are more efficient in 18:3n-3 to 22:6n-3 conversion than older neonates.9 13 The present data, connecting lower retinal 22:6n-3 concentrations in the P- group with poorer retinal response, are among the first direct data showing that the biosynthetic capability of premature primates is insufficient to support optimal function, at least in the immediate perinatal period.

The complex single-flash ERG results from the temporal superposition of several monophasic electrical responses differing in polarity, time-course, and phase. The descending limb of the a-wave represents almost exclusively photoreceptor cell activity,32 27 whereas the b-wave is a composite of the responses of bipolar cells and Müller cells.27 33 The ä parameter is related to the amplification factor derived by Breton et al.,27 which is a measure of the time-course of activation for the phosphodiesterase cascade in the rod outer segments. We found a significant improvement in ä in the P+ group compared with the P- group. The decrease in this parameter suggests that the initial amplification induced by photon absorption of rhodopsin is reduced in the P- group compared with the others, though no absolute turnover calculations can be made. Our data cannot distinguish whether this is due to less rhodopsin, less efficient photon absorption, or poorer amplification. However, the generally linear relationship between 22:6n-3 concentrations and ä is consistent with a central and limiting role for 22:6n-3 in initial events in photoreceptor cell transduction. In addition, Table 3 shows that the 22:5n-6/22:6n-3 ratio is greater in the P- group than in the P+ group. Recent biophysical studies demonstrating the preference of rhodopsin for 22:6n-3, along with its pivotal role in signal transduction, suggest that a combination of these factors may be at work.34 35 36

We also found that ai was significantly increased in preterm neonates consuming no LCP (P-) compared with the other groups at 4 weeks’ adjusted age. There was also a nonsignificant increase in ai in the P- group between the first and second measurements. Implicit time of the a-wave normally decreases with maturation37 and these data are further evidence that the retina of these preterm neonates is developmentally delayed.

The b-wave amplitude correlated positively with 22:6n-3, but the interpretation of these data on a physiological level is not straightforward because of two factors: the complex combination of cells that produce the signal and the coupling between the a- and b-wave responses. Although bamp increased with 22:6n-3, we cannot from our data determine whether this is due to improved function of the systems measured exclusively by the b-wave or by improved function of the photoreceptors, which would couple more signal into the b-wave system. Because the generation of the a- and b-waves derives from the transductional step, it is expected that changes in ä should be reflected as changes in the amplitudes and implicit times of the complete ERG. The general linear relationship of aamp to both 22:6n-3 concentration and 22:5n-6/22:6n-3 shown in the bottom right panels of Figures 2 and 3 are consistent with this expectation. However, inspection of the bottom left panel of Figure 2 reveals that bamp in the B group was greater than in the P+ group, even though retinal 22:6n-3 did not significantly increase between these two groups. Further, bamp only slightly responded to increasing retinal 22:6n-3 in the formula (P-, T-, and P+) groups. Figure 3 , showing the 22:5n-6/22:6n-3 ratio, confirms these observations. These data are strong evidence that 22:6n-3 per se is not the limiting factor in development of bamp in formula-fed neonates.

The monounsaturates correlated highly with ERG parameters. The n-7 fatty acids correlated positively with retinal performance, whereas the n-9 fatty acids, including {Sigma}n-9, correlated negatively with retinal performance. This observation is surprising, because there are no known or, to our knowledge, proposed functional relationships between the monounsaturates and retinal function, other than the general observation that monounsaturates are always present at considerable concentrations. Most mammalian tissues synthesize both the monounsaturated fatty acid (MUFA) series (n-9 and n-7) de novo, primarily from acetate-malonate by the action of fatty acid synthase and a {Delta}9-desaturase (e.g., stearoyl CoA desaturases38 ). In addition, it is usually assumed that the physical properties of n-7 versus n-9 MUFAs are sufficiently similar to render them interchangeable for most in vivo physiological processes, although this assumption may not be warranted. Finally, there are no known biochemical roles for MUFA other than as components of structural lipids, as substrates for energy production, or as carbon sources through acetate. Breast milk had a more than five times greater n-7 concentration than the formulas and had lower n-9 (mostly 18:1n-9). Further research is necessary to determine whether the positional isomers of monounsaturates play a specific role in retinal function and, particularly, in the development of bamp.

The bi parameter was uncorrelated to all but one fatty acid, 18:3n-6. The greater breadth of the b-wave compared with the a-wave, makes accurate localization of its extreme value more difficult, and thus decreases our ability to detect differences in bi due to experimental treatments.

Development of monkey fovea39 and retinal vasculature20 occurs earlier in development than in humans. At 4 weeks of life, the monkey fovea is not yet mature and is not adultlike until 12 weeks, whereas the human fovea is adultlike at approximately 1 year of age and continues to develop until 4 to 5 years. Thus, our results establishing an influence of dietary LCP on function apply to the developing, rather than mature, retina, though the stage of development is somewhat later than in the human. A finding of a significant effect in developmental milestones is important even if, as has been noted in human studies,21 differential effects of diet are transient.

Tissue and breast milk fatty acid compositions are well-known to be influenced by diet, and the degree of influence depends on the specific fatty acid and tissue. For instance, rat retinal 22:6n-3 is susceptible to manipulation of 18:2n-6 concentration,40 and it is reasonable to hypothesize that diet may have induced the MUFA correlations in the current study. Inspection of Table 2 reveals that breast milk of our baboons was many times richer in 16:1n-7 than in the formula groups, whereas the major n-9 fatty acid and most abundant fatty acid in all neonate diets, 18:1n-9, was approximately 30% lower in breast milk compared with formulas. These differences could explain the relatively subtle changes in the corresponding retinal fatty acid, shown in Table 3 and suggest that the strong correlations with function can be explained as coincident with other factors. Caution is warranted in accepting this hypothesis, because similar arguments about metabolic roles and dietary content apply to saturates, particularly 16:0, and no correlation to retinal function was detected.

This randomized study included a breast-fed group (B), which is not possible for ethical reasons in human studies. The B group, which had the greatest mean 22:6n-3 concentration, had greater aamp and bamp than any of the other groups, including the P+ group, in which the mean retinal 22:6n-3 concentration was not significantly lower than in the B group. None of the other treatments achieved the level of retinal function, as measured by ERG parameters, as the B group. The optimal performance found for breast-fed neonates cannot be uniquely ascribed to the fatty acid composition of breast milk alone. Breast milk contains a myriad of immunologic factors including antibodies and cells that are not present in formula.26 In addition, breast-fed neonates remained with the lactating females for the duration of the study, while formula-fed neonates were separated from maternal contact at birth and hand-fed by humans. The effects of non–fatty-acid milk components, as well as psychosocial aspects of the maternal-neonate pair in breast-feeding cannot be dismissed as irrelevant. However, this study accurately simulated the clinical choice of breast-versus bottle-feeding and in this sense is directly applicable to real-world practice.

In summary, these data are direct evidence that primate retinal response is influenced by retinal fatty acid composition and more specifically by 22:6n-3 concentrations. Retinal 22:6n-3 composition in turn is influenced directly by fatty acid composition of clinically relevant diets, by prematurity, and by breast-feeding. Premature neonates benefited measurably from inclusion of LCP in formula. Two ERG parameters improved between time points in the P+ group, but none improved measurably in the P- group. The parameters ä and ai were improved in the P+ group compared with the P- group, whereas other parameters were not significantly different. These comparisons indicate that there is a delay in retinal development specific to prematurity that is at least partially corrected by LCP supplementation. Finally, the groups investigated are of broad clinical importance, and the results obtained in primates are directly relevant to humans.


   Acknowledgements
 
The authors thank Darlene Campbell for technical assistance and Carolyn Tschanz for capable assistance with the manuscript.


   Footnotes
 
2 Present address: Division of Pediatric Surgery, Department of Surgery, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan; Back

4 Foster Biomedical Laboratory, Brandeis University, Waltham, Massachusetts; Back

5 Department of Nutritional Sciences, University of California, Berkeley, California; and Back

6 New York University Medical Center, New York, New York. Back

Supported by National Institutes of Health Grant EY10208.

Submitted for publication May 17, 2003; revised June 30, 2003; accepted July 5, 2003.

Disclosure: G.-Y. Diau, None; E.R. Loew, None; V. Wijendran, None; E. Sarkadi-Nagy, None; P.W. Nathanielsz, None; J.T. Brenna, Mead-Johnson Nutritionals (C, F, R)

The publication costs of this article were defrayed in part by page charge payment. This article must therefore be marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.

Corresponding author: J. Thomas Brenna, Division of Nutritional Sciences, Cornell University, Savage Hall, Ithaca, NY 14853; jtb4{at}cornell.edu.


   References
Top
 Abstract
 Materials and Methods
 Results
 Discussion
 References
 

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