Tissue levels of polyunsaturated fatty acids during early human development

Role of omega-3 fatty acids in brain development and function: potential implications for the pathogenesis and prevention of psychopathology

The principle omega-3 fatty acid in brain, docosahexaenoic acid (DHA), accumulates in the brain during perinatal cortical expansion and maturation. Animal studies have demonstrated that reductions in perinatal brain DHA accrual are associated with deficits in neuronal arborization, multiple indices of synaptic pathology including deficits in serotonin and mesocorticolimbic dopamine neurotransmission, neurocognitive deficits, and elevated behavioral indices of anxiety, aggression, and depression. In primates and humans, preterm delivery is associated with deficits in fetal cortical DHA accrual, and children/adolescents born preterm exhibit deficits in cortical gray matter maturation, neurocognitive deficits particularly in the realm of attention, and increased risk for attention-deficit/hyperactivity disorder (ADHD) and schizophrenia. Individuals diagnosed with ADHD or schizophrenia exhibit deficits in cortical gray matter maturation, and medications found to be efficacious in the treatment of these disorders increase cortical and striatal dopamine neurotransmission. These associations in conjunction with intervention trials showing enhanced cortical visual acuity and cognitive outcomes in preterm and term infants fed DHA, suggest that perinatal deficits in brain DHA accrual may represent a preventable neurodevelopmental risk factor for the subsequent emergence of psychopathology.

A newly discovered member of the fatty acid desaturase gene family: a non-coding, antisense RNA gene to delta5-desaturase

The rate limiting steps in the conversion of 18-carbon unsaturated fatty acids to 20- and 22-carbon products are catalyzed by two desaturase enzymes (Delta5-desaturase and Delta6-desaturase) found within a lipid desaturase gene cluster. Careful examination of this cluster revealed the existence of a conventionally spliced (human) and an intronless (mouse and rat) non-coding RNA gene, reverse Delta5-desaturase, which is transcribed from the opposite strand of the Delta5-desaturase gene. The 654 bp human reverse Delta5-desaturase transcript contains 269 nucleotides that are complementary to exon 1 and intron 1 of the Delta5-desaturase transcript, and the 3'-end of this sequence contains a 143 nucleotide stretch that is 100% complementary to the 5'-end of the Delta5-desaturase. The rat and mouse transcripts are 1355 and 690 bp long and complementary to a portion of the first intron and the entire first exon of their respective Delta5-desaturases. All reverse Delta5-desaturase transcripts contain several stop codons in all frames suggesting that they do not encode a peptide. Reverse Delta5-desaturase RNA was detected in all rat tissues where Delta5-desaturase is expressed, and the transition between fasting and refeeding produced a significant increase in reverse Delta5-desaturase RNA relative to Delta5-desaturase mRNA. Transient expression of reverse Delta5-desaturase in CHO cells stably transformed with Delta5-desaturase produced a modest decrease in Delta5-desaturase mRNA (30%), but lowered Delta5-desaturase enzymatic activity by >70%. More importantly, a diet enriched in fish oil produced a reciprocal increase in reverse Delta5-desaturase mRNA and decrease in Delta5-desaturase mRNA that was accompanied by a 5-6-fold decrease in Delta5-desaturase enzyme activity. These findings support a significant role for reverse Delta5-desaturase as a natural antisense regulator of Delta5-desaturase.

Polyunsaturated fatty acids: biotechnology

Polyunsaturated fatty acids like EPA and DHA have attracted a great attention due to their beneficial effects on human health. At present, fish oil is the major source of EPA and DHA. Various alternative sources are being explored to get these essential fatty acids. Genes encoding enzymes involved in the biosyntheses of PUFAs have been identified, cloned and gene prospecting becomes a novel method for enhanced PUFA production. Desaturase and elongase genes have important biotechnological appeal from genetic engineering point of view. This review highlights the research and results on such enzymes.

Polyunsaturated fatty acid supplementation stimulates differentiation of oligodendroglia cells

Dietary polyunsaturated fatty acids (PUFAs) have been postulated as alternative supportive treatment for multiple sclerosis, since they may promote myelin repair. We set out to study the effect of supplementation with n-3 and n-6 PUFAs on OLN-93 oligodendroglia and rat primary oligodendrocyte differentiation in vitro. It appeared that OLN-93 cells actively incorporate and metabolise the supplemented PUFAs in their cell membrane. The effect of PUFAs on OLN-93 differentiation was further assessed by morphological and Western blot evaluation of markers of oligodendroglia differentiation: 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNP), zonula occludens-1 (ZO-1) and myelin-associated glycoprotein (MAG). Supplementation of the OLN-93 cells with n-3 and n-6 PUFAs increased the degree of differentiation determined by morphological analysis. Moreover, CNP protein expression was significantly increased by gamma-linolenic acid (GLA, 18:3n-6) supplementation. In accordance with the OLN-93 results, studies with rat primary oligodendrocytes, a more advanced model of cell differentiation, showed GLA supplementation to promote oligodendrocyte differentiation. Following GLA supplementation, increased numbers of proteolipid protein (PLP)-positive oligodendrocytes and increased myelin sheet formation was observed during differentiation of primary oligodendrocytes. Moreover, increased CNP, and enhanced PLP and myelin basic protein expression were found after GLA administration. These studies provide support for the dietary supplementation of specific PUFAs to support oligodendrocyte differentiation and function.

Effect of n-3 long-chain polyunsaturated fatty acid supplementation of women with low-risk pregnancies on pregnancy outcomes and growth measures at birth: a meta-analysis of randomized controlled trials

BACKGROUND

It is hypothesized that the intake of long-chain polyunsaturated fatty acids (LC-PUFAs) throughout pregnancy is important to maternal health and fetal and infant development.

OBJECTIVE

The objective was to evaluate systematically the effect of LC-PUFA supplementation of pregnant women's diets on pregnancy outcomes and growth measures at birth.

DESIGN

We searched MEDLINE, EMBASE, CINAHL, and the Cochrane Library through August 2005 and also searched the references in reviewed articles for randomized controlled trials (RCTs) comparing LC-PUFA supplementation with placebo or no supplementation.

RESULTS

Of 6 included RCTs, only 1 was judged to be at low risk of bias. Supplementation with n-3 LC-PUFAs in these 6 RCTs (1278 infants) was associated with a significantly greater length of pregnancy [weighted mean difference (WMD): 1.57 d; 95% CI: 0.35, 2.78 d; findings stable on sensitivity analysis] than in control subjects. We found no evidence that supplementation influenced the percentage of preterm deliveries, the rate of low-birth-weight infants, or the rate of preeclampsia or eclampsia. We found no significant difference in the 6 RCTs (1278 infants) in birth weight (WMD: 54 g; 95% CI: -3.1, 111 g) and no significant difference in 5 RCTs (1262 infants) in birth length (WMD: 0.23 cm; 95% CI: -0.04, 0.5 cm), but, in 4 RCTs (729 infants), there was a significant increase in head circumference (WMD: 0.26 cm; 95% CI: 0.02, 0.49 cm; significance was lost on sensitivity analysis).

CONCLUSIONS

n-3 LC-PUFA supplementation during pregnancy may enhance pregnancy duration and head circumference, but the mean effect size is small. The implications of these findings for later growth and development remain to be elucidated.

Effects of n-3 fatty acids during pregnancy and lactation

n-3 Fatty acids exert important effects on eicosanoid metabolism, membrane properties, and gene expression and therefore are biologically important nutrients. One n-3 fatty acid, docosahexaenoic acid, is an important component of neural and retinal membranes and accumulates rapidly in the brain and retina during the later part of gestation and early postnatal life. It is reasonable to hypothesize that maternal n-3 fatty acid intakes might have significant effects on several pregnancy outcomes as well as on subsequent infant visual function and neurodevelopmental status. Studies, both observational and interventional, assessing the influence of n-3 fatty acids during pregnancy or the early postpartum period on duration of gestation and infant size at birth, preeclampsia, depression, and infant visual function and neurodevelopment have been reported. n-3 Fatty acid intakes (both in terms of absolute amounts of docosahexaenoic acid and eicosapentaenoic acid and the ratio of these 2 fatty acids) varied widely in these studies, however, and no clear consensus exists regarding the effects of n-3 fatty acids on any of these outcomes. The available data suggest a modest effect of these fatty acids on increasing gestational duration and possibly enhancing infant neurodevelopment. Although data from earlier observational studies suggested a potential role of these fatty acids in decreasing the incidence of preeclampsia, this has not been confirmed in randomized, prospective trials. Because of the paucity of data from randomized, prospective, double-blind trials, the effect of n-3 fatty acids on depression during pregnancy or the early postpartum period remains unresolved.

Maternal dietary (n-3) fatty acid deficiency alters neurogenesis in the embryonic rat brain

Docosahexaenoic acid [22:6(n-3)] is enriched in brain membrane phospholipids and essential for brain function. Neurogenesis during embryonic and fetal development requires synthesis of large amounts of membrane phospholipid. We determined whether dietary (n-3) fatty acid deficiency during gestation alters neurogenesis in the embryonic rat brain. Female rats were fed diets with 1.3% energy [(n-3) control] or 0.02% energy [(n-3) deficient], from alpha-linolenic acid [18:3(n-3)], beginning 2 wk before gestation. Morphometric analyses were performed on embryonic day 19 to measure the mean thickness of the neuroepithelial proliferative zones corresponding to the cerebral cortex (ventricular and subventricular zones) and dentate gyrus (primary dentate neuroepithelium), and the thickness of the cortical plate and sectional area of the dentate gyrus. Phospholipids and fatty acids were determined by HPLC and GLC. Docosahexaenoic acid was 55-65% lower and (n-6) docosapentaenoic acid [22:5(n-6)] was 150-225% higher in brain phospholipids at embryonic day 19 in the (n-3) deficient (n = 6 litters) than in the control (n = 5 litters) group. The mean thickness of the cortical plate and mean sectional area of the primordial dentate gyrus were 26 and 48% lower, respectively, and the mean thicknesses of the cortical ventricular zone and the primary dentate neuroepithelium were 110 and 70% higher, respectively, in the (n-3) deficient than in the control embryonic day 19 embryos. These studies demonstrate that (n-3) fatty acid deficiency alters neurogenesis in the embryonic rat brain, which could be explained by delay or inhibition of normal development.

N-3 fatty acids and cognitive and visual acuity development: methodologic and conceptual considerations

Several randomized clinical studies in infants born preterm and at term have explored the effects on visual acuity development of postnatal supplementation with various sources of docosahexaenoic acid (DHA). Higher visual acuity after DHA supplementation is a consistent finding in infants born preterm. For infants born at term, the results are less consistent and are better explained by differences in sensitivity of the visual acuity test (electrophysiologic tests being more sensitive than subjective tests) or by differences in the amount of DHA included in the experimental formula. Differences in the sensitivity of the test may also be relevant in discussions of whether the effects of DHA on visual acuity are transient or persistent. A smaller number of studies have attempted to study the effects of DHA on cognitive development. The major focus of this article is to review the types of methods that have been used to evaluate the effects of DHA on cognition and to provide the rationale for measures that are a better conceptual fit. Research is needed (1) to probe the effects of variable DHA exposure on infant and child development, (2) to measure outcomes that better relate to preschool and school-age cognitive function, and (3) to reinforce, and in some cases demonstrate, links between specific infant and preschool measures of cognitive development. We strongly encourage collaborations with developmental cognitive neuroscientists to facilitate these research goals.

Menhaden fish oil improves spatial memory in rat pups following recurrent pentylenetetrazole-induced seizures

This study investigated the effects of two supplementary dietary oils (fish oil and corn oil) as parts of isocaloric/isoproteic diets on growth, brain fatty acid composition, and behavior in rat pups with recurrent seizures. Recurrent seizures were induced by injecting rat pups with pentylenetetrazole (PTZ) between P10 (10 days of age) and P14. Either menhaden fish oil (FO) or corn oil (CO) was given as supplemental dietary oil throughout the experiment from P3 to P40. We assessed the effects of the two supplemental dietary oils on spatial memory, histomorphology, and fatty acid composition of brain tissue at the end of the study on P40. Rats that received dietary FO performed significantly better in the Morris water maze, a test used to examine spatial performance in rats; the FO group had significantly shorter escape latencies (P=0.041) during the escape test. Compared with the CO group, the FO group stayed a longer time (P=0.015) and swam a longer distance (P=0.033) in the target quadrant in the spatial probe test. The FO group had significantly higher brain docosahexaenoic acid (P0.01) and significantly lower brain C20:3 n-6 and C20:4 n-6 (P<0.01 and P=0.031) levels compared with the CO group, but the two groups did not differ significantly with respect to neuronal cell loss in the histomorphology study. This study demonstrated that, compared with CO, FO is better in improving spatial memory in rats following recurrent PTZ-induced seizures.

Gestational diabetes mellitus enhances arachidonic and docosahexaenoic acids in placental phospholipids

In previous studies, we reported that neonates of women with gestational diabetes mellitus (GDM) have reduced blood levels of arachidonic acid (AA) and docosahexaenoic acid (DHA) that were unrelated to maternal status. Since both AA and DHA are selectively transferred from maternal to fetal circulation by the placenta, we have investigated whether the FA composition of the placenta is altered by GDM. Thirty-six women, 11 with and 25 without GDM, were recruited from Newham General Hospital, London. The women with GDM had higher levels of di-homo-gamma-linolenic (P < 0.05), docosatetraenoic (n-6 DTA; P< 0.0001), docosapentaenoic n-6 (P< 0.005), total n-6 (P < 0.005), docosapentaenoic (n-3 DPA; P < 0.005), and total n-3 (P < 0.01) FA, as well as higher levels of AA (P < 0.05) and DHA (P < 0.01), in placental choline phosphoglycerides (CPG) compared with the healthy women who served as controls. Similarly, the women with GDM had elevated n-6 DTA (P < 0.005), AA, total n-6 metabolites (P < 0.05), DHA, total n-3 metabolites, and total n-3 FA (P < 0.005) in ethanolamine phosphoglycerides (EPG). In contrast to CPG and EPG, the placental TG of the women with GDM had higher linoleic acid (P< 0.05) and lower AA, n-6 metabolites, and n-3 DPA (P < 0.01). The placenta is devoid of desaturase activity, and it is thought to be reliant on maternal circulation for both AA and DHA. Hence, the enhanced levels of the two FA in the placenta of the GDM group suggests that these FA are taken up from the maternal circulation and retained after esterification into phosphoglycerides instead of being transferred to the fetus. Further study is needed to elucidate the mechanism involved and the effect of the phenomenon on postnatal growth and development of the offspring.

Docosahexaenoic acid in red blood cells of term infants receiving two levels of long-chain polyunsaturated fatty acids

OBJECTIVES

A randomized, double-blind, prospective trial assessed effects of different formula levels of polyunsaturated fatty acids on blood phospholipid docosahexaenoic (DHA; 22:6omega3) and arachidonic acids (ARA; 20:4omega6) in term infants at 120 days of age.

METHODS

Healthy, formula-fed term infants (n = 78) were randomized to 1) routine milk-based formula with 8 mg DHA, 21 mg ARA, 110 mg alpha-linolenic (ALA; 18:3omega3), and 1,000 mg linoleic acids (LA; 18:2omega6) per 100 kcal (Lower-long-chain polyunsaturated fatty acids [LCPUFA]; n = 39) or 2) routine milk-based formula with 17 mg DHA, 34 mg ARA, 85 mg ALA, and 860 mg LA per 100 kcal (Higher-LCPUFA; n = 39). Fatty acid methyl esters from red blood cell (RBC) and plasma phospholipid fractions were assessed using capillary column gas chromatography.

RESULTS

Compared with infants fed Lower-LCPUFA formula, the Higher-LCPUFA group had significantly greater percentages of fatty acids as DHA in RBC phosphatidylethanolamine (PE), RBC phosphatidylcholine (PC), total RBC, and plasma phospholipids (P < 0.001). Infants fed Lower-LCPUFA formula had higher percentages of precursor omega6 fatty acids in the desaturation/elongation pathway but lower percentages of ARA (RBC PE, RBC PC, and plasma phospholipid, P < 0.001; total RBC, P = 0.017) compared with the Higher-LCPUFA group.

CONCLUSIONS

Greater amounts of dietary ALA do not produce as great an increase in DHA in blood lipids as preformed dietary DHA. Infants fed DHA at levels similar to human milk had significantly greater percentage of DHAat 120 days of age compared with the Lower-LCPUFA group despite higher precursor levels of ALA.

Variation in [U-13C] alpha linolenic acid absorption, beta-oxidation and conversion to docosahexaenoic acid in the pre-term infant fed a DHA-enriched formula

Docosahexaenoic acid (DHA) is an integral component of neural cell membranes and is critical to the development and function of the CNS. A premature delivery interrupts normal placental supply of DHA such that the infant is dependent on the nature of the nutritional support offered. The most abundant omega-3 fatty acid in pre-term formulas is alpha linolenic acid (ALNA), the precursor of DHA. This project studied the absorption, beta-oxidation and conversion of ALNA to DHA by pre-term infants ranging from 30-37 wk of corrected gestation. [U-(13)C] ALNA was administered emulsified with a pre-term formula to 20 well pre-term infants on full enteral feeds. Enrichment of (13)C in stool and as (13)CO(2) in breath was used to estimate absorption across the gut and partitioning toward beta-oxidation respectively. Excretion of the administered dose of (13)C in stool ranged from 2.0 to 26.2%; excretion decreased with increasing birth gestation. Appearance as (13)CO(2) on breath ranged from 7.6 to 19.0%. All infants synthesised eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA) and DHA with the least mature having the highest cumulative plasma DHA. These results show considerable variation suggesting that the worst absorption of ALNA and the greatest production of DHA occur in infants born at the earliest gestation.

Long-chain polyunsaturated fatty acids in breast milk in La Plata, Argentina: relationship with maternal nutritional status

Milk fat is the major source of energy for breastfed infants; it also supplies polyunsaturated fatty acids (PUFAs) essential for the development of brain, retina, and other organs. Maternal nutritional status is critical for the newborn, and little information exists regarding the PUFA status of vulnerable populations living in Southern regions. We studied the relationship between maternal nourishment and milk fatty acid composition. Mother nutritional status (normal, overweight or obese) was estimated on the body mass index. Milk protein, total lipid, and fatty acid composition were determined. Milk protein was not affected by mother's nutritional status. In obese mothers an increase in lipid content, linoleic acid, total n-6 and total PUFAs was observed comparing to the other groups. Disregarding the nutritional status, the ratio n-6/n-3 fatty acids was very high and the 22:6n-3 content was very low, when compared with those of mothers from other countries. This finding led us to urge Public Health officers to promote changes in the dietary habits of nursing women.

Long-chain (n-3) polyunsaturated fatty acids are more efficient than alpha-linolenic acid in improving electroretinogram responses of puppies exposed during gestation, lactation, and weaning

Long-chain PUFAs (LCPUFAs) are essential for proper neural and retinal development in many mammalian species. We investigated puppies born to dogs fed diets containing varying amounts of vegetable and marine (n-3) fatty acids during gestation/lactation. The fatty acid compositions of dogs' milk and puppy plasma phospholipids were evaluated, and electroretinographic responses of the young dogs were determined after they were weaned to the same diets. Dogs' milk fatty acid composition reflected the diets fed during gestation/lactation. The milk of dogs fed a high alpha-linolenic acid (ALA) diet was enriched in ALA but not docosahexaenoic acid (DHA). Puppies fed this ALA-enriched milk accumulated more plasma phospholipid DHA than the low (n-3) fatty acid group. However, this accumulation was less than that obtained in puppies fed preformed DHA during development and suckling (P < 0.05). Electroretinograms (ERGs) of 12-wk-old puppies revealed significantly improved visual performance in dogs fed the highest amounts of (n-3) LCPUFAs (P < 0.05). These puppies demonstrated improved rod response (improved amplitude and implicit time of the a-wave, P < 0.05). Puppies from the low (n-3) fatty acid group exhibited the poorest ERG responses compared with the high-marine or high-vegetable (n-3) groups. A novel parameter devised in this study, the initial intensity at which the a-wave was detectable (i.e., threshold intensity), also demonstrated that retinal response of puppies consuming the (n-3) LCPUFA-containing diets occurred at lower light intensity, thereby exhibiting greater rod sensitivity, than the other diet groups. These findings indicate that preformed dietary (n-3) LCPUFA is more effective than ALA in enriching plasma DHA during perinatal development and results in improved visual performance in developing dogs.

Is docosahexaenoic acid, an n-3 long-chain polyunsaturated fatty acid, required for development of normal brain function? An overview of evidence from cognitive and behavioral tests in humans and animals

This review is part of a series intended for nonspecialists that will summarize evidence relevant to the question of whether causal relations exist between micronutrient deficiencies and brain function. Here, we focus on experiments that used cognitive or behavioral tests as outcome measures in experimental designs that were known to or were likely to result in altered brain concentrations of the n-3 fatty acid docosahexaenoic acid (DHA) during the perinatal period of "brain growth spurt." Experimental designs reviewed include observational breastfeeding studies and randomized controlled trials in humans and studies in rodents and nonhuman primates. This review is based on a large number of expert reviews and commentaries and on some 50 recent studies in humans and animals that have not yet been included in published reviews. Expert opinion regarding the strengths and weaknesses of the major experimental systems and uncertainties associated with interpreting results is summarized. On the basis of our reading of this literature, we conclude that evidence from several types of studies, particularly studies in animals, suggests that, within the context of specific experimental designs, changes in brain concentrations of DHA are positively associated with changes in cognitive or behavioral performance. Additional experimental information required to conclude that a causal association exists is discussed, as are uncertainties associated with applying results from specific experimental designs to the question of whether infant formula should be supplemented with DHA.

Incomplete replacement of docosahexaenoic acid by n-6 docosapentaenoic acid in the rat retina after an n-3 fatty acid deficient diet

When sources of n-3 fatty acids are not present in the diet, nervous system docosahexaenoic acid (22:6n3) is replaced by docosapentaenoic acid (22:5n6). Dams were fed either an n-3 deficient diet or one containing alpha-linolenic acid (18:3n3) and 22:6n3 throughout pregnancy and lactation. Their male offspring at weaning also received either the n-3 deficient or n-3 adequate diets and were sacrificed at 5, 10, 20, 50 and 91 days of age. Retinal lipids were extracted and analysed by gas chromatography for fatty acyl content. The percentage of retinal 22:6n3 increased continuously over the 13 week course of the experiment but reached its maximal concentration around day 20. Non-reciprocal replacement of 22:6n3 by 22:5n6 was observed at postnatal day 20 and 50 but not at other time points. Complete replacement of 22:6n3 was apparent if elevations in both 22:5n6 and docosatetraenoic acid (22:4n6) were considered. These data indicate that during the rapid period of accretion of retinal 22:6n3 around postnatal day 20, the supply of 22:5n6 to the retina was inadequate to completely replace 22:6n3 in n-3 deficient rats.

Duration of long-chain polyunsaturated fatty acids availability in the diet and visual acuity

BACKGROUND

Little is known about the critical period during which the dietary supply of long-chain polyunsaturated fatty acids (LCPUFAs) may influence the maturation of visual cortical function in term infants.

AIM

To define the relationship between duration of dietary LCPUFA supply and visual acuity at 52 weeks of age.

STUDY DESIGN

Data from 243 infants who participated in four randomized clinical trials of LCPUFA supplementation of infant formula at a single research center were combined. The primary outcome was visual acuity at 52 weeks of age as measured by swept visual evoked potentials (sweep VEP).

RESULTS

Longer duration of LCPUFA supply was associated with better mean acuity at 52 weeks of age (r=-0.878; p<0.001). The relationship between duration of dietary LCPUFA supply and sweep VEP acuity at 52 weeks was similar whether the LCPUFAs were provided via formula containing 0.36% DHA and 0.72% ARA or human milk. Duration of breast-feeding was associated with individual infants' sweep VEP acuity outcomes at 52 weeks (r=-0.286; p<0.005). The duration of LCPUFA supply during infancy has a similar relationship to sweep VEP acuity at 52 weeks in breastfed infants regardless of birth order.

CONCLUSION

A continued benefit from a supply of LCPUFAs is apparent in infants through 52 weeks of age, suggesting that the brain may not have sufficient stores of LCPUFAs from an early postnatal supply to support the optimal maturation of the visual cortex.

n-6 Docosapentaenoic acid is not a predictor of low docosahexaenoic acid status in Canadian preschool children

BACKGROUND

The n-3 fatty acid docosahexaenoic acid (DHA; 22:6n-3) is important for neural and visual functional development. In animals, 22:6n-3 deficiency is accompanied by increased docosapentaenoic acid (DPA; 22:5n-6), which suggests that the ratio of 22:6n-3 to 22:5n-6 could be a useful biochemical marker of low n-3 fatty acid status. The n-3 fatty acid status of preschool children has not been described, and data are lacking on whether low 22:6n-3 is accompanied by high 22:5n-6 in humans.

OBJECTIVE

We determined n-3 fatty acid status and investigated the relation between 22:6n-3 and 22:5n-6 in children.

DESIGN

In Canadian children aged 18-60 mo (n = 84), the n-3 and n-6 fatty acid status of erythrocyte phosphatidylethanolamine was measured, and dietary fat intake was estimated by using a food-frequency questionnaire.

RESULTS

The mean (+/- SEM) 22:6n-3 concentration in erythrocyte phosphatidylethanolamine among children was 3.06 +/- 0.13 g/100 g fatty acids (5th-95th percentiles: 1.43-5.79 g/100 g fatty acids). Concentrations of 22:5n-6 increased with increasing 22:6n-3 concentrations in erythrocyte phosphatidylethanolamine (P < 0.01). Mean intakes of linoleic acid (18:2n-6), linolenic acid (18:3n-3), and trans fatty acids were 3.6 +/- 0.2%, 0.7 +/- 0.5%, and 2.0 +/- 1.3%, respectively. Phosphatidylethanolamine 22:6n-3 and 22:5n-3 concentrations were inversely related to the intakes of 18:2n-6 and trans fatty acids, but not to those of total fat or n-3 fatty acids.

CONCLUSIONS

The concentration of 22:5n-6 is not a useful biochemical marker of low n-3 fatty acid intake or status in the membrane phosphatidylethanolamine of preschool children. High intakes of 18:2n-6 and trans fatty acids could compromise the incorporation of 22:6n-3 into membrane phospholipids.

Fish and shellfish as dietary sources of methylmercury and the omega-3 fatty acids, eicosahexaenoic acid and docosahexaenoic acid: risks and benefits

Fish and shellfish supply the human diet with not only complex nutrients including the omega-3 fatty acids, but also highly toxic chemicals including methylmercury. The dietary essential fatty acids are linoleic and alpha-linolenic acid. Two omega-3 fatty acids with longer carbon chains, eicosahexaenoic acid (EPA) and docosahexaenoic acid (DHA), can be synthesized in humans from alpha-linolenic precursors. Though not required in the diet per se, EPA and DHA have important roles in metabolism. The almost exclusive source of preformed dietary DHA is fish and shellfish. These foods are also an important source of EPA. In marked contrast to the benefits of fish and shellfish as sources of preformed omega-3 fatty acids, fish and shellfish are almost exclusively the dietary source of methylmercury. Fortunately, these chemicals are not uniformly distributed across many species of fish and shellfish. The purpose of this article is to provide information on the comparative distribution of these chemicals and nutrients to help groups formulating dietary recommendations.

Serotoninergic neurotransmission is affected by n-3 polyunsaturated fatty acids in the rat

We explored the effects of chronic alpha-linolenic acid dietary deficiency on serotoninergic neurotransmission. In vivo synaptic serotonin (5-HT) levels were studied in basal and pharmacologically stimulated conditions using intracerebral microdialysis in the hippocampus of awake 2-month-old rats. We also studied the effects of reversion of the deficient diet on fatty acid composition and serotoninergic neurotransmission. A balanced (control) diet was supplied to deficient rats at different stages of development, i.e. from birth, 7, 14 or 21 days of age. We demonstrated that chronic n-3 polyunsaturated fatty acid dietary deficiency induced changes in the synaptic levels of 5-HT both in basal conditions and after pharmacological stimulation with fenfluramine. Higher levels of basal 5-HT release and lower levels of 5-HT-stimulated release were found in deficient than in control rats. These neurochemical modifications were reversed by supply of the balanced diet provided at birth or during the first 2 weeks of life through the maternal milk, whereas they persisted if the balanced diet was given from weaning (at 3 weeks of age). This suggests that provision of essential fatty acids is durably able to affect brain function and that this is related to the developmental stage during which the deficiency occurs.

Type 1 diabetes compromises plasma arachidonic and docosahexaenoic acids in newborn babies

The activity of delta6- and delta5-desaturase, enzymes required for the synthesis of AA and DHA, are impaired in human and experimental diabetes. We have investigated whether neonates of type 1 diabetic women have compromised plasma AA and DHA at birth. Cord blood was obtained from healthy babies born to mothers with (n = 31) and without (n = 59) type 1 diabetes. FA composition of plasma choline phosphoglycerides (CPG), TG, and cholesterol esters (CE) was assayed. The neonates of the diabetics had lower levels of AA (20:4n-6, P< 0.0001), adrenic acid (22:4n-6, P < 0.01), sigman-6 metabolites (P < 0.0001), docosapentaenoic acid (22:5n-3, P < 0.0001), DHA (22:6n-3, P < 0.0001), sigman-3 (P < 0.0001), and sigman-3 metabolites (P< 0.0001) in CPG compared with the corresponding babies of the nondiabetic mothers. Similarly, they had lower levels of AA (P< 0.05), sigman-6 metabolites (P < 0.05), DHA (P< 0.0001), and sigman-3 metabolites (P< 0.01) in plasma CE. There was also a nonsignificant reduction of AA and DHA in TG in the babies of the diabetic group. The current investigation indicates that healthy neonates born to mothers with type 1 diabetes have highly compromised levels of AA and DHA. These nutrients are of critical importance for neurovisual and vascular system development. In poorly controlled maternal diabetes, it is conceivable that the relative "insufficiency" of AA and DHA may exacerbate speech and reading impairments, behavioral disorders, suboptimal performance on developmental tests, and lower IQ, which have been reported in some children born to mothers with type 1 diabetes mellitus. Further studies are needed to understand the underlying mechanism for this biochemical abnormality and its implications for fetal and infant development.

Nutrition et dysplasie bronchopulmonaire

Bronchopulmonary dysplasia remains a frequent complication of extreme prematurity. In preterm neonates catch-up and pulmonary alveolar growth occur during the first two years of life. However 10 to 25% of preterm infants with bronchopulmonary dysplasia are under-nourished after two years of age, and 30 to 60% of them also suffer from persistent airway obstruction, hyperinflation and bronchial hyperreactivity. Recommendations on nutritional requirements in this population are not yet clearly defined, but an adequate nutritional status in prenatal and early postnatal period can have long-term consequences on brain and lung development. There are a few randomised trial of nutrition for preterm infants with bronchopulmonary dysplasia after discharge. Caloric and protein requirements in this population are probably higher than in full-term infants. Moreover there are potential benefits in using specific nutrients: supplementation with long chain polyunsaturated fatty acids could decrease lung inflammation injuries, glutamine is the main source of energy of pneumocyte, vitamin A is essential for lung development, inositol is necessary for surfactant synthesis, vitamin E and selenium have anti-oxidant effects. Controlled nutritional trial are needed with a long term follow-up in late childhood in order to test their effects on growth and pulmonary status.

Nutrition in the 21st century: what is going wrong

"Things sweet to taste prove in digestion sour" (Shakespeare, Richard II, Act 1, Scene 3, line 236)

Earlier smoking habits are associated with higher serum lipids and lower milk fat and polyunsaturated fatty acid content in the first 6 months of lactation

OBJECTIVE

To investigate the relation between maternal smoking habits, plasma lipids and milk fatty acid (FA) content and composition.

DESIGN

Breastfeeding mothers who gave birth to healthy, full-term infants were recruited. Mothers were interviewed on smoking habits, being defined smokers (S) when usually smoking at least five cigarettes per day before pregnancy.

SETTING

Department of Pediatrics, San Paolo Hospital, Milan, Italy.

SUBJECTS

In total, 92 mothers: 61 non-S (NS) and 31 S.

INTERVENTIONS

Pooled hindmilk was collected at the first raise of milk (colostrum stage), 1, 3 and 6 months, and total lipid (TL) content and fatty acid (FA) composition were evaluated. Maternal dietary habits were assessed by a food-frequency questionnaire. Two subsamples (16 NS, 6 S) were investigated after delivery and at 3 months for serum lipids and FA status. At 6 months after delivery, the number of mothers still breastfeeding decreased to 30. Variables were compared using nonparametric tests.

RESULTS

In smoking mothers serum levels of triglycerides, cholesterol and low-density lipoproteins were higher, while those of high-density lipoproteins were lower. TL content in breast milk was similar in the two groups just after delivery but higher in milk from NS at 1 month. TL content and FA absolute amounts of linoleic, arachidonic, alpha-linolenic and docosahexaenoic (DHA) acid in breast milk were lower in S vs NS 1 month after delivery. Also 3 months after delivery, the breast milk of smoking mothers contained less DHA than the breast milk of nonsmoking mothers.

CONCLUSIONS

Maternal cigarette smoking in early pregnancy is associated with higher plasma lipid levels and lower milk TL and DHA content in the first months of lactation.

Maternal docosahexaenoic acid supplementation during pregnancy and visual evoked potential development in term infants: a double blind, prospective, randomised trial

AIM

To test the hypothesis that maternal docosahexaenoic acid (DHA) supplementation during pregnancy enhances maturation of the visual evoked potential (VEP) in healthy term infants.

METHODS

One hundred women were supplemented with either fish oil capsules rich in DHA (n = 50) or placebo capsules (n = 50) from week 15 of pregnancy until delivery. Total fatty acids in red blood cells and plasma were measured at weeks 15, 28, and 40 of pregnancy and at delivery in umbilical cord blood. Infant visual pathway development was assessed using VEPs recorded to flash stimuli shortly after birth and to both flash and pattern-reversal stimuli at 50 and 66 weeks post-conceptional age (PCA).

RESULTS

Maternal supplementation did not significantly elevate the level of DHA in umbilical cord blood. Moreover, there were no significant differences in any of the VEP measures observed between supplementation groups. However, maturity of the pattern-reversal VEP at 50 and 66 weeks PCA was associated with DHA status of the infants at birth. Infants with higher DHA status, both as a concentration and as a percentage of total fatty acids, showed shorter P100 peak latencies of the pattern-reversal VEP than those with lower DHA status.

CONCLUSIONS

Maternal DHA supplementation during pregnancy did not enhance VEP maturation in healthy term infants. However, these results show an association between the DHA status of infants at term and early postnatal development of the pattern-reversal VEP, suggesting that DHA status itself may influence maturation of the central visual pathways.

Visual, cognitive, and language assessments at 39 months: a follow-up study of children fed formulas containing long-chain polyunsaturated fatty acids to 1 year of age

OBJECTIVE

Docosahexaenoic acid (DHA) and arachidonic acid (ARA) are long-chain polyunsaturated fatty acids found in breast milk and recently added to infant formulas. Their importance in infant nutrition was recognized by the rapid accretion of these fatty acids in the brain during the first postnatal year, reports of enhanced intellectual development in breastfed children, and recognition of the physiologic importance of DHA in visual and neural systems from studies in animal models. These considerations led to clinical trials to evaluate whether infant formulas that are supplemented with DHA or both DHA and ARA would enhance visual and cognitive development or whether conversion of linoleic acid and alpha-linolenic acid, the essential fatty acid precursors of ARA and DHA, respectively, at the levels found in infant formulas is sufficient to support adequately visual and cognitive development. Visual and cognitive development were not different with supplementation in some studies, whereas other studies reported benefits of adding DHA or both DHA and ARA to formula. One of the first trials with term infants that were fed formula supplemented with DHA or both DHA and ARA evaluated growth, visual acuity (Visual Evoked Potential; Acuity Card Procedure), mental and motor development (Bayley Scales of Infant Development), and early language development (MacArthur Communicative Developmental Inventories). Growth, visual acuity, and mental and motor development were not different among the 3 formula groups or between the breastfed and formula-fed infants in the first year of life. At 14 months of age, infants who were fed the formula with DHA but no ARA had lower vocabulary production and comprehension scores than infants who were fed the unsupplemented control formula or who were breastfed, respectively. The present follow-up study evaluated IQ, receptive and expressive vocabulary, visual-motor function, and visual acuity of children from the original trial when they reached 39 months of age.

METHODS

Infants were randomized within 1 week after birth and fed a control formula (n = 65), one containing DHA (n = 65), or one containing both ARA and DHA (n = 66) to 1 year of age. A comparison group (n = 80) was exclusively breastfed for at least 3 months after which the infants continued to be exclusively breastfed or were supplemented with and/or weaned to infant formula. At 39 months, standard tests of IQ (Stanford Binet IQ), receptive vocabulary (Peabody Picture Vocabulary Test-Revised), expressive vocabulary (mean length of utterance), visual-motor function (Beery Visual-Motor Index), and visual acuity (Acuity Card Procedure) were administered. Growth, red blood cell fatty acid levels, and morbidity also were evaluated.

RESULTS

Results were analyzed using analysis of variance or linear regression models. The regression model for IQ, receptive and expressive language, and the visual-motor index controlled for site, birth weight, sex, maternal education, maternal age, and the child's age at testing. The regression model for visual acuity controlled for site only. A variable selection model also identified which of 22 potentially prognostic variables among different categories (feeding groups, the child and family demographics, indicators of illness since birth, and environment) were most influential for IQ and expressive vocabulary. A total of 157 (80%) of the 197 infants studied at 12 months participated in this follow-up study. Characteristics of the families were representative of US families with children up to 5 years of age, and there were no differences in the demographic or family characteristics among the randomized formula groups. As expected, the formula and breastfed groups differed in ethnicity, marital status, parental education, and the prevalence of smoking. Sex, ethnicity, gestational age at birth, and birth weight for those who participated at 39 months did not differ from those who did not. The 12-month Bayley mental and motor scores and 14-month vocabulary scores of the children who participated also were were not different from those who did not. At 39 months, IQ, receptive and expressive language, visual-motor function, and visual acuity were not different among the 3 randomized formula groups or between the breastfed and formula groups. The adjusted means for the control, ARA+DHA, DHA, and breastfed groups were as follows: IQ scores, 104, 101, 100, 106; Peabody Picture Vocabulary Test, 99.2, 97.2, 95.1, 97.4; mean length of utterance, 3.64, 3.75, 3.93, 4.08; the visual-motor index, 2.26, 2.24, 2.05, 2.40; and visual acuity (cycles/degree), 30.4, 27.9, 27.5, 28.6, respectively. IQ was positively associated with female sex and maternal education and negatively associated with the number of siblings and exposure to cigarette smoking in utero and/or postnatally. Expressive language also was positively associated with maternal education and negatively associated with the average hours in child care per week and hospitalizations since birth but only when the breastfed group was included in the analysis. The associations between maternal education and child IQ scores are consistent with previous reports as are the associations between prenatal exposure to cigarette smoke and IQ and early language development. Approximately one third of the variance for IQ was explained by sex, maternal education, the number of siblings, and exposure to cigarette smoke. Growth achievement, red blood cell fatty acid levels, and morbidity did not differ among groups.

CONCLUSIONS

We reported previously that infants who were fed an unsupplemented formula or one with DHA or with both DHA and ARA through 12 months or were breastfed showed no differences in mental and motor development, but those who were fed DHA without ARA had lower vocabulary scores on a standardized, parent-report instrument at 14 months of age when compared with infants who were fed the unsupplemented formula or who were breastfed. When the infants were reassessed at 39 months using age-appropriate tests of receptive and expressive language as well as IQ, visual-motor function and visual acuity, no differences among the formula groups or between the formula and breastfed groups were found. The 14-month observation thus may have been a transient effect of DHA (without ARA) supplementation on early vocabulary development or may have occurred by chance. The absence of differences in growth achievement adds to the evidence that DHA with or without ARA supports normal growth in full-term infants. In conclusion, adding both DHA and ARA when supplementing infant formulas with long-chain polyunsaturated fatty acids supports visual and cognitive development through 39 months.

Visual function in breast-fed term infants weaned to formula with or without long-chain polyunsaturates at 4 to 6 months: a randomized clinical trial

OBJECTIVE

Breast-fed infants receive docosahexaenoic acid (DHA) and arachidonic acid (ARA) in their diet. Upon weaning, infants lose this dietary source of long-chain polyunsaturates because many commercial formulas do not contain these important constituents for neural membrane biogenesis. We evaluated the benefits of postweaning dietary supplementation of DHA + ARA on visual maturation.

STUDY DESIGN

Healthy term infants (n = 61) were breast-fed to 4 to 6 months, then were randomly assigned to commercial formula or formula supplemented with DHA (0.36%) + ARA (0.72%). Measurements of red blood cell (RBC) fatty acids, visually evoked potential (VEP) acuity, and stereoacuity were done before and after weaning.

RESULTS

At 1 year of age, RBC-DHA in the commercial formula-fed group was reduced by 50% from the weaning level, whereas there was a 24% increase in the DHA + ARA-supplemented group. The primary outcome measure, VEP acuity, was significantly more mature in supplemented infants at 1 year of age. Elevated RBC-DHA levels were associated with more mature VEP acuity. There were no significant diet-related differences in stereoacuity.

CONCLUSIONS

These data extend through the first year of life the critical period in which a dietary supply of DHA and ARA can contribute in optimizing visual development in term infants.

Advances in nutritional modifications of infant formulas

Modifications to infant formulas are continually being made as the components of human milk are characterized and as the nutrient needs of diverse groups of infants are identified. Formulas with long-chain polyunsaturated fatty acids added in amounts similar to those in human milk have recently become available in the United States; infants fed these formulas or human milk have higher tissue concentrations of long-chain polyunsaturated fatty acids and reportedly have better visual acuity than do infants fed nonsupplemented formulas. Selenium, an important antioxidant, is present in higher concentrations in human milk than in non-fortified cow milk-based formula, and the selenium intakes of infants fed nonfortified formulas are reported to be at or below recommended levels. Blood selenium concentrations and plasma glutathione peroxidase activity are higher in infants fed selenium-supplemented formulas or human milk than in infants fed non-fortified formulas. Nucleotides and their related products play key roles in many biological processes. Although nucleotides can be synthesized endogenously, they are considered "conditionally essential." Nucleotide concentrations in human milk are higher than in unsupplemented cow milk-based formulas, and studies in animals and human infants suggest that dietary nucleotides play a role in the development of the gastrointestinal and immune systems. Formulas for preterm infants after hospital discharge are designed to meet the needs of a population in whom growth failure is common. Several studies have shown that preterm infants fed nutrient-enriched formulas after hospital discharge have higher rates of catch-up growth than do infants fed standard term-infant formulas.

Preterm infant formula supplementation with alpha linolenic acid and docosahexaenoic acid

OBJECTIVES

To investigate if supplementation of preterm infant formula with a high docosahexaenoic acid/eicosapentaenoic acid (DHA/EPA) ratio together with alpha-linolenic acid (ALA) was able to maintain plasma and red blood cell DHA levels similar to that obtained with breast milk feeding without altering n-6 fatty acid status.

DESIGN AND SUBJECTS

Preterm infants of mothers who elected not to breast feed (n=13) were assigned to ALA- and DHA-enriched formula (DHA group: DHA/EPA=5/l). Infants fed breast milk (n=25) constituted a reference group (BM group). Anthropometric and fatty acid parameters (plasma phospholipids, cholesterol esters, triglycerides and red blood cell phosphatidylethanolamine, PL, CE, TG, RBC-PE, respectively) were obtained after 2 days (D2) and 15 days (D15) of enteral feeding and at the 37th week (W37) of post-conception age and 1 month later (W37+30) in the DHA group. Mean DHA intake ranged between 16.5+/-1.6 and 17.9+/-2.9 mg/kg/day between D2 and W37+30.

RESULTS

At W37, infant weights, heights, and head circumferences were similar in DHA and BM groups. PL DHA was maintained in the DHA group at the same level as in the BM group and the same for DHA in PE at W37. In RBC-PE and at W37, AA status was the same in both groups. In PL, AA levels remained very stable throughout the study; however, in the DHA group AA levels in PL remained in the range observed with standard formulas.

CONCLUSION

The combined 18:3 n-3 and DHA supplementation of infant formula with DHA/EPA ratio 5/l is compatible with growth and n-3 fatty acid metabolism similar to that of preterm infants fed human milk.

Thyroid hormone induction of the adrenoleukodystrophy-related gene (ABCD2)

X-linked adrenoleukodystrophy (X-ALD) is a demyelinating disorder associated with impaired very-long-chain fatty-acid (VLCFA) beta-oxidation caused by mutations in the ABCD1 (ALD) gene that encodes a peroxisomal membrane ABC transporter. ABCD2 (ALDR) displays partial functional redundancy because when overexpressed, it is able to correct the X-ALD biochemical phenotype. The ABCD2 promoter contains a putative thyroid hormone-response element conserved in rodents and humans. In this report, we demonstrate that the element is capable of binding retinoid X receptor and 3,5,3'-tri-iodothyronine (T3) receptor (TRbeta) as a heterodimer and mediating T3 responsiveness of ABCD2 in its promoter context. After a T3 treatment, an induction of the ABCD2 gene was observed in the liver of normal rats but not that of TRbeta-/- mice. ABCD2 was not induced in the brain of the T3-treated rats. However, we report for the first time that induction of the ABCD2 redundant gene is feasible in myelin-producing cells (differentiated CG4 oligodendrocytes). The induction was specific for this cell type because it did not occur in astrocytes. Furthermore, we observed T3 induction of ABCD2 in human and mouse ABCD1-deficient fibroblasts, which was correlated with normalization of the VLCFA beta-oxidation. Finally, ABCD3 (PMP70), a close homolog of ABCD2, was also induced by T3 in the liver of control rats, but not that of TRbeta-/- mice, and in CG4 oligodendrocytes.

Regulation of human delta-6 desaturase gene transcription: identification of a functional direct repeat-1 element

The rate-limiting step in 20:4(n-6) and 22:6(n-3) synthesis is the desaturation of 18:2(n-6) and 18:3(n-3) by Delta-6 desaturase. In this report, we demonstrate that n-6 and n-3 PUFAs suppressed the hepatic expression of rodent Delta-6 desaturase by inhibiting the rate of Delta-6 desaturase gene transcription. In contrast, consumption of the peroxisome proliferator-activated receptor (PPAR)alpha activator WY 14,643 significantly enhanced the transcription of hepatic Delta-6 desaturase by more than 500%. Transfection reporter assays with HepG2 cells revealed that the PUFA response region for the human Delta-6 desaturase gene involved the proximal promoter region of -283/+1 human Delta-6 desaturase gene, while the WY 14,643 response element (RE) was identified as an imperfect direct repeat (DR-1) located at -385/-373. The WY 14,643 induction of the human Delta-6 desaturase promoter activity was dependent upon the expression of PPARalpha. Electrophoretic mobility shift assays revealed that nuclear proteins extracted from HepG2 cells expressing PPARalpha specifically interacted with the -385/-373 DR-1 sequence of the human Delta-6 desaturase gene. The interaction was eliminated by the unlabeled PPARalpha RE of the rat acyl-CoA oxidase gene, and the protein-DNA complex was super-shifted by treatment with anti-PPARalpha. The -385/-373 sequence also interacted with a mixture of in vitro translated PPARalpha-retinoic acid receptor X (RXR)alpha, but by themselves neither PPARalpha nor RXRalpha could bind to the Delta-6 desaturase DR-1. These data indicate that the 5'-flanking region of the human Delta-6 desaturase gene contains a DR-1 that functions in the regulation of human Delta-6 desaturase gene transcription, and thereby plays a role in the synthesis of 20- and 22-carbon polyenoic fatty acids.

Effect of supplementation of preterm formula with long chain polyunsaturated Fatty acids on mineral balance in preterm infants

BACKGROUND

Incorporation of long chain polyunsaturated fatty acids (LCP) into formulas may interfere with mineral metabolism. We investigate mineral balance in preterm infants who were fed a formula with LCP.

METHODS

Infants were randomized in a double-blind manner, 20 infants in each group, to receive a formula with LCP (F+LCP) or without LCP (F) for 30 days. Plasma levels (at the beginning and after 30 days) and nutritional balance (after 1 week) for Ca, P, Mg, Zn, and Cu were obtained for all infants.

RESULTS

Groups were similar regarding birth weight, gestational age, weight, and corrected age at study start. During the 30-day study period, the groups had comparable milk intake and reached similar and satisfactory weight gains and longitudinal growth. Within each group, there was no change in plasma mineral concentrations over the course of the study, and there were no differences at each time point between groups. All values were within the normal range for age. No differences in mineral balance were detected between the F and F+LCP groups, with both groups demonstrating comparable intake, net retention, and fecal losses of each mineral.

CONCLUSIONS

Adding a content of LCP blend similar to that of human milk to a preterm formula caused no disturbance in Ca, P, Mg, Zn, or Cu nutritional balance.

Visual acuity and retinal function in infant monkeys fed long-chain PUFA

Previous randomized clinical trials suggest that supplementation of the human infant diet with up to 0.35% DHA may benefit visual development. The aim of the current study was to assess the impact of including arachidonic acid (AA) and a higher level of DHA in the postnatal monkey diet on visual development. Infant rhesus monkeys were fed either a control diet (2.0% alpha-linolenic acid as the sole n-3 FA) or a supplemented diet (1.0% DHA and 1.0% AA) from birth. Visual evoked potential acuity was measured at 3 mon of age. Rod and cone function were assessed in terms of parameters describing phototransduction. Electroretinogram (ERG) amplitudes and implicit times were recorded over a wide intensity range (-2.2 to 4.0 log scot td-sec) and assessed in terms of intensity response functions. Plasma DHA and AA were significantly increased (P < 0.001) in the diet-supplemented monkeys compared with the control monkeys. There was an approximately equal effect of diet for the rod phototransduction parameters, sensitivity, and capacitance but in the opposite directions. Diet-supplemented monkeys had significantly shorter b-wave implicit times at low retinal illuminances (<-0.6 log scot td-sec). There were no significant effects of diet for visual acuity or the other 23 ERG parameters measured. The results suggest that supplementation of the infant monkey diet with 1.0% DHA and 1.0% AA neither harms nor provides substantial benefit to the development of visual acuity or retinal function in the first four postnatal months.

Cognitive and visual development: influence of differences in breast and formula fed infants

Several recent studies document a beneficial effect of breast-feeding on later neurodevelopmental outcomes. The mechanisms involved are still in need of elucidation, but evidence is accruing that the fatty acid (FA) composition of human milk plays a role. The composition of body fats, from circulating erythrocyte lipids to brain phospholipids, is linked in infants to the early feeding mode and which FA predominates among circulating lipids influences visual and neurodevelopmental performance test scores. In these studies, greater differences were found between breast-fed and standard formula-fed infants, the latter showing low tissue long-chain polyunsaturated fatty acids (LCPUFA: arachidonic acid, AA, 20:4n-6; eicosapentaenoic acid, EPA, 20:5n-3; docosahexaenoic acid, DHA, 22:6n-3) accretion and lower visual and neurodevelopmental test scores. Human milk contains LCPUFA, while most available formulas, especially those intended for full-term infants, do not. With the progressive introduction of solid foods, the question arises whether a specific or "ideal" dietary lipid mixture can be found to meet growth requirements and ensure a lipid balance adequate for the early and effective preventive purposes. These complementary aspects are challenges for the paediatric nutrition researcher today.

The lipids that matter from infant nutrition to insulin resistance

Breast-fed infants showed decreased incidence of obesity, hypertension, diabetes mellitus, and coronary heart disease in later life and higher cognitive function. Breast milk is rich in long-chain polyunsaturated fatty acids (LCPUFAs) and brain preferentially accumulates LCPUFAs during the last trimester of pregnancy and the first few months of life. Breast-fed infants showed significantly lower plasma glucose levels and higher percentage of docosahexaenoic acid and total percentages of LCPUFAs in their skeletal muscle biopsies compared with formula fed. LCPUFAs suppress the production of pro-inflammatory cytokines, regulate the function of several neurotransmitters, enhance the number of insulin receptors in the brain and other tissues, and decrease insulin resistance. LCPUFAs may enhance the production of bone morphogenetic proteins (BMPs), which participate in neurogenesis. It is proposed that the beneficial effects of breast feeding in later life can be attributed to its rich LCPUFA content. It is likely that inadequate breast feeding results in marginal deficiency of LCPUFAs during the critical stages of development, which can lead to insulin resistance. Hence, promoting prolonged breast feeding and/or supplementing LCPUFAs during the critical stages of development may be beneficial in preventing insulin resistance.

Recent studies on interactions between n-3 and n-6 polyunsaturated fatty acids in brain and other tissues

Recent literature provides a basis for understanding the behavioral, functional, and structural consequences of nutritional deprivation or disease-related abnormalities of n-3 polyunsaturated fatty acids. The literature suggests that these effects are mediated through competition between n-3 and n-6 polyunsaturated fatty acids at certain enzymatic steps, particularly those involving polyunsaturated fatty acid elongation and desaturation. One critical enzymatic site is a delta6-desaturase. On the other hand, an in-vivo method in rats, applied following chronic n-3 nutritional deprivation or chronic administration of lithium, indicates that the cycles of de-esterification/re-esterification of docosahexaenoic acid (22:6n-3) and arachidonic acid (20:4n-6) within brain phospholipids operate independently of each other, and thus that the enzymes regulating each of these cycles are not likely sites of n-3/n-6 competition.

Lipids with an emphasis on long-chain polyunsaturated fatty acids

In addition to their role as a source of energy, several fatty acids are important components of cell membranes and/or precursors of biologically important eicosanoids. The long-chain polyunsaturated fatty acids, docosahexaenoic acid (DHA) and arachidonic acid (AA), are important for optimal visual function and neurodevelopment. These fatty acids are present in human milk but, until recently, have not been included in formulas marketed in the United States. Although the results of clinical trials assessing the effect of DHA and AA intakes on visual and cognitive development have been inconsistent, some studies suggest benefits. Adequate intake of these fatty acids may be especially important for the preterm infant.

Nutrient requirements for preterm infant formulas

Achieving appropriate growth and nutrient accretion of preterm and low birth weight (LBW) infants is often difficult during hospitalization because of metabolic and gastrointestinal immaturity and other complicating medical conditions. Advances in the care of preterm-LBW infants, including improved nutrition, have reduced mortality rates for these infants from 9.6 to 6.2% from 1983 to 1997. The Food and Drug Administration (FDA) has responsibility for ensuring the safety and nutritional quality of infant formulas based on current scientific knowledge. Consequently, under FDA contract, an ad hoc Expert Panel was convened by the Life Sciences Research Office of the American Society for Nutritional Sciences to make recommendations for the nutrient content of formulas for preterm-LBW infants based on current scientific knowledge and expert opinion. Recommendations were developed from different criteria than that used for recommendations for term infant formula. To ensure nutrient adequacy, the Panel considered intrauterine accretion rate, organ development, factorial estimates of requirements, nutrient interactions and supplemental feeding studies. Consideration was also given to long-term developmental outcome. Some recommendations were based on current use in domestic preterm formula. Included were recommendations for nutrients not required in formula for term infants such as lactose and arginine. Recommendations, examples, and sample calculations were based on a 1000 g preterm infant consuming 120 kcal/kg and 150 mL/d of an 810 kcal/L formula. A summary of recommendations for energy and 45 nutrient components of enteral formulas for preterm-LBW infants are presented. Recommendations for five nutrient:nutrient ratios are also presented. In addition, critical areas for future research on the nutritional requirements specific for preterm-LBW infants are identified.

Estimated biological variation of the mature human milk fatty acid composition

We estimated the biological variation (CV(biol)) of 28 fatty acids (FA) in 465 mature human milk samples from The Netherlands, Caribbean, Jerusalem, Tanzania and Pakistan, by using data from the observed variation (CV(obs)) and analytical variation (CV(anal)). CV(biol) of the various regions was remarkably similar. The average CV(biol) of 455 samples, Pakistan excluded, ranged from 12.7% for 16:0 and 18.9% for 18:1 omega 9 to 68% for 22:6 omega 3 and about 100% for 20:5 omega 3. Those of 20:4 omega 6, 18:2 omega 6 and 18:3 omega 3 were 28.0, 33.0 and 37.3%, respectively. Because of the large CV(biol) and the many dietary changes in recent history, it seems impossible to consider the present human milk FA composition as the 'gold standard' for infant formula. Optimal human milk FA composition should rather derive from populations that consume traditional diets or from the scientific data that show the function of the individual FAs in neonatal development.

Relationship between omega3 long-chain polyunsaturated fatty acid status during early infancy and neurodevelopmental status at 1 year of age

OBJECTIVE

To determine the influence of alpha-linolenic acid (ALA; 18 : 3omega3) intake and, hence, the influence of plasma and/or erythrocyte phospholipid content of docosahexaenoic acid (DHA; 22 : 6omega3) during early infancy on neurodevelopmental outcome of term infants.

METHODS

The Bayley Scales of Infant Development (second edition), the Clinical Adaptive Test/Clinical Linguistic and Auditory Milestone Scale (CAT/CLAMS) and the Gross Motor Scale of the Revised Gesell Developmental Inventory were administered at a mean age of 12.26 +/- 0.94 months to 44 normal term infants enrolled in a study evaluating the effects of infant formulas differing only in ALA content (0.4, 1.0, 1.7 and 3.2% of total fatty acids).

RESULTS

As reported previously [Jensen et al., Lipids 13 (1996) 107; J. Pediatr. 131 (1997) 200], the group fed the formula with the lowest ALA content had the lowest mean plasma and erythrocyte phospholipid DHA contents at 4 months of age. This group also had the lowest mean score on every neurodevelopmental measure. The difference in mean gross motor developmental quotient of this group versus the group fed the formula with 1.0% ALA but not of the other groups was statistically significant (P < 0.05). Across the groups, motor indices correlated positively with each other and with the plasma phospholipid DHA content at 4 months of age (P=0.02-0.03). The CLAMS developmental quotient correlated with the erythrocyte phospholipid content of 20 : 5omega3 (P < 0.01) but not with DHA.

CONCLUSIONS

These statistically significant correlations suggest that the omega3 fatty acid status during early infancy may be important with respect to neurodevelopmental status at 1 year of age and highlight the need for further studies of this possibility.

Decrease in neuron size in docosahexaenoic acid-deficient brain

Docosahexaenoic acid is an important fatty acid for neuronal function because its deficiency leads to many behavioral and functional deficits. In a previous study, we reported that docosahexaenoic acid deficiency caused a reduction in the size of neurons of the CA1 region in the hippocampus. To extend these results to other regions of the brain, the present study entailed a morphologic analysis of neuronal size in hippocampus, hypothalamus, piriform cortex, and parietal cortex in rats that were raised on docosahexaenoic acid-deficient and supplemented diets for three generations. Neuron size in these regions was measured both at weaning (21 days) and maturity (68 days), and docosahexaenoic acid content in the brain was measured on a separate set of sibling rats using fatty acid analysis. Neuron size in hippocampus, hypothalamus, and parietal cortex decreased in weanling and in piriform cortex in mature rats raised on the docosahexaenoic acid-deficient diet. The brains of these rats exhibited a nearly 90% decrease of docosahexaenoic acid. Decrease of neuron size has been linked to a loss of optimal function in neurons. In the United States, human infant-milk formulas use vegetable oils as fat sources that lack docosahexaenoic acid. If docosahexaenoic acid deficiency reduces neuron size, then human infants raised on these formulas may also have smaller neurons relative to breast-fed infants.

Efficacy of dietary arachidonic acid provided as triglyceride or phospholipid as substrates for brain arachidonic acid accretion in baboon neonates

Arachidonic acid (AA) is a long-chain polyunsaturate (LCP) present in human breast milk as both triglyceride (TG) and as phospholipid (PL). There has been little attention to the metabolic consequences of lipid form of AA in infant formulas. Our objective was to investigate the efficacy of dietary TG and PL as carriers of AA for accretion in the brain and associated organs of term baboon neonates consuming a formula with LCP composition typical of human milk. TG and phosphatidylcholine (PC) with [U-(13)C]-AA in the sn-2 position and with unlabeled 16:0 in the remaining positions (TG-AA* or PL-AA*, respectively) were used as tracers to study the tissue AA* incorporation. Baboon neonates received a single oral dose of either TG-AA* (n = 3) or PL-AA* (n = 4) at 18-19 d of life. Tissues were obtained 10 d later (28-29 d of life) and isotopic enrichment was measured. In the brain, 4.5% of the PL-AA* dose and 2.1% of the TG-AA* dose were recovered as brain AA*, respectively, indicating that PL was about 2.1-fold more effective than TG as a substrate for brain AA accretion. Preferential incorporation of PL-derived AA* over TG source of AA* was also observed in the liver, lung, plasma, and erythrocytes. Because of the quantitative predominance of TG-AA in formula, total brain AA accretion, expressed as absolute weight, was 5.0-fold greater from TG-AA than from PL-AA. We estimate that about half of postnatal brain AA accretion is derived from dietary preformed AA in term baboon neonates consuming a formula with lipid composition similar to that of human milk.