Infant vision and retinal function in studies of dietary long-chain polyunsaturated fatty acids: methods, results, and implications

Dietary Phospholipid-Bound Conjugated Linoleic Acid and Docosahexaenoic Acid Incorporation Into Fetal Liver and Brain Modulates Fatty Acid and N-Acylethanolamine Profiles

We evaluated whether maternal intake of conjugated linoleic acid (CLA) and docosahexaenoic acid (DHA) in the phospholipid (PL) form (CLA-DHA PL) affects maternal and fetal brain and liver fatty acids (FAs) profile and the biosynthesis of FA-derived bioactive lipid mediators N-acylethanolamines (NAEs) involved in several neurophysiological functions. We fed rat dams during the first 2/3 of their pregnancy a CLA-DHA PL diet containing PL-bound 0.5% CLA and 0.2% DHA. FA and NAE profiles were analyzed in maternal and fetal liver and brain by Liquid Chromatography diode array detector (LC-DAD) and MS/MS in line. We found that CLA and DHA crossed the placenta and were readily incorporated into the fetal liver and brain. CLA metabolites were also found abundantly in fetal tissues. Changes in the FA profile induced by the CLA-DHA PL diet influenced the biosynthesis of NAE derived from arachidonic acid (ARA; N-arachidonoylethanolamine, AEA) and from DHA (N-docosahexaenoylethanolamine, DHEA). The latter has been previously shown to promote synaptogenesis and neuritogenesis. The reduced tissue n6/n3 ratio was associated to a significant decrease of AEA levels in the fetal and maternal liver and an increase of DHEA in the fetal and maternal liver and in the fetal brain. Maternal dietary CLA-DHA PL by promptly modifying fetal brain FA metabolism, and thereby, increasing DHEA, might represent an effective nutritional strategy to promote neurite growth and synaptogenesis and protect the offspring from neurological and psychiatric disorders with neuroinflammatory and neurodegenerative basis during the critical prenatal period.

Maternal Fatty Acid Metabolism in Pregnancy and Its Consequences in the Feto-Placental Development

During pregnancy, maternal plasma fatty acids are critically required for cell growth and development, cell signaling, and the development of critical structural and functional aspects of the feto-placental unit. In addition, the fatty acids modulate the early stages of placental development by regulating angiogenesis in the first-trimester human placenta. Preferential transport of maternal plasma long-chain polyunsaturated fatty acids during the third trimester is critical for optimal fetal brain development. Maternal status such as obesity, diabetes, and dietary intakes may affect the functional changes in lipid metabolic processes in maternal-fetal lipid transport and metabolism. Fatty acids traverse the placental membranes via several plasma membrane fatty acid transport/binding proteins (FAT, FATP, p-FABPpm, and FFARs) and cytoplasmic fatty acid-binding proteins (FABPs). This review discusses the maternal metabolism of fatty acids and their effects on early placentation, placental fatty acid transport and metabolism, and their roles in feto-placental growth and development. The review also highlights how maternal fat metabolism modulates lipid processing, including transportation, esterification, and oxidation of fatty acids.

Therapy Approaches for Stargardt Disease

Despite being the most prevalent cause of inherited blindness in children, Stargardt disease is yet to achieve the same clinical trial success as has been achieved for other inherited retinal diseases. With an early age of onset and continual progression of disease over the life course of an individual, Stargardt disease appears to lend itself to therapeutic intervention. However, the aetiology provides issues not encountered with the likes of choroideremia and X-linked retinitis pigmentosa and this has led to a spectrum of treatment strategies that approach the problem from different aspects. These include therapeutics ranging from small molecules and anti-sense oligonucleotides to viral gene supplementation and cell replacement. The advancing development of CRISPR-based molecular tools is also likely to contribute to future therapies by way of genome editing. In this we review, we consider the most recent pre-clinical and clinical trial data relating to the different strategies being applied to the problem of generating a treatment for the large cohort of Stargardt disease patients worldwide.

Parenteral nutrition with fish oil-based lipid emulsion reduces the risk of cholestasis in preterm infants

OBJECTIVE

Preterm infants receive long-term parenteral nutrition (PN) for gastrointestinal immaturity. This study aimed to determine if mixed lipid emulsions containing fish oil decrease the incidence of PN-associated cholestasis by reducing oxidative stress and providing an anti-inflammatory effect.

METHODS

This retrospective cohort study enrolled 399 very low birth weight premature infants (gestational age ≤32 weeks) between January 2009 and November 2017 at a single neonatal intensive care unit. Preterm infants received total PN with either mixed lipid emulsion including fish oil (SMOFlipid®, n = 195) or soybean oil-based lipid emulsion (Lipovenoes®, n = 204) for at least 7 days. We compared the outcomes of PN-associated cholestasis, comorbidities, and mortality between the groups.

RESULTS

The incidence of PN-associated cholestasis was significantly lower in the SMOFlipid group than in the Lipovenoes group. The duration to full feeding days was significantly shorter in the SMOFlipid group compared with the Lipovenoes group. Relevant complications, such as severe retinopathy of prematurity and bronchopulmonary dysplasia, were also significantly reduced in the SMOFlipid group compared with the Lipovenoes group.

CONCLUSION

In premature infants, PN with fish oil-based lipid emulsions is associated with a lower incidence of PN-associated cholestasis compared with soybean oil-based lipid emulsions.

Maternal dietary fatty acids and their roles in human placental development

Fatty acids are essential for feto-placental growth and development. Maternal fatty acids and their metabolites are involved in every stage of pregnancy by supporting cell growth and development, cell signaling, and modulating other critical aspects of structural and functional processes. Early placentation process is critical for placental growth and function. Several fatty acids modulate angiogenesis as observed by increased tube formation and secretion of angiogenic growth factors in first-trimester human placental trophoblasts. Long-chain fatty acids stimulate angiogenesis in these cells via vascular endothelium growth factor (VEGF), angiopoietin-like protein 4 (ANGPTL4), fatty acid-binding proteins (FABPs), or eicosanoids. Inadequate placental angiogenesis and trophoblast invasion of the maternal decidua and uterine spiral arterioles leads to structural and functional deficiency of placenta, which contributes to preeclampsia, pre-term intrauterine growth restriction, and spontaneous abortion and also affects overall fetal growth and development. During the third trimester of pregnancy, placental preferential transport of maternal plasma long-chain polyunsaturated fatty acids is of critical importance for fetal growth and development. Fatty acids cross the placental microvillous and basal membranes by mainly via plasma membrane fatty acid transport system (FAT, FATP, p-FABPpm, & FFARs) and cytoplasmic FABPs. Besides, a member of the major facilitator superfamily-MFSD2a, present in the placenta is involved in the supply of DHA to the fetus. Maternal factors such as diet, obesity, endocrine, inflammation can modulate the expression and activity of the placental fatty acid transport activity and thereby impact feto-placental growth and development. In this review, we discuss the maternal dietary fatty acids, and placental transport and metabolism, and their roles in placental growth and development.

Effect of Heat-Killed Lactobacillus paracasei KW3110 Ingestion on Ocular Disorders Caused by Visual Display Terminal (VDT) Loads: A Randomized, Double-Blind, Placebo-Controlled Parallel-Group Study

BACKGROUND

Visual display terminals (VDTs) emitting blue light can cause ocular disorders including eye fatigue. Some dietary constituents have been reported to be effective in improving ocular disorders while few clinical studies have been performed. We evaluated the effects of heat-killed Lactobacillus paracasei KW 3110 on improving ocular disorders and symptoms of eye fatigue among healthy human subjects with VDT loads.

METHODS

In vitro, the effect of L. paracasei KW3110 on blue light-induced human retinal pigment epithelial (ARPE-19) cell damage. For clinical studies, 62 healthy Japanese volunteers of 35 to 45 years of age who had experienced eye fatigue were randomized into two groups and given a placebo or L. paracasei KW3110-containing supplements for eight weeks. The primary endpoint was changes in VDT load-induced eye fatigue as determined by critical flicker frequency four and eight weeks after the start of supplementation.

RESULTS

In vitro, blue light-induced human retinal cell death was suppressed with the culture supernatants of cells treated with L. paracasei KW3110. In clinical study, the VDT load-induced reduction of critical flicker frequency tended to be milder in the L. paracasei KW3110 group when compared with the placebo group during the fourth week. Subgroup analysis classified by the degree of eye fatigue showed that the VDT load-induced reduction of critical flicker frequency was significantly better in the high-level eye fatigue subjects from the L. paracasei KW3110 group when compared with the placebo group during the fourth week (p = 0.020).

CONCLUSIONS

L. paracasei KW3110 suppressed blue light-induced retinal pigment epithelial cell death. In the clinical study, ingestion of L. paracasei KW3110 had a potential to improve eye fatigue induced by VDT loads especially high levels of eye fatigue. However, further studies should be required to show more dependable clinical efficacy of L. paracasei KW3110.

Phytochemicals in Human Milk and Their Potential Antioxidative Protection

Diets contain secondary plant metabolites commonly referred to as phytochemicals. Many of them are believed to impact human health through various mechanisms, including protection against oxidative stress and inflammation, and decreased risks of developing chronic diseases. For mothers and other people, phytochemical intake occurs through the consumption of foods such as fruits, vegetables, and grains. Research has shown that some these phytochemicals are present in the mother’s milk and can contribute to its oxidative stability. For infants, human milk (HM) represents the primary and preferred source of nutrition because it is a complete food. Studies have reported that the benefit provided by HM goes beyond basic nutrition. It can, for example, reduce oxidative stress in infants, thereby reducing the risk of lung and intestinal diseases in infants. This paper summarizes the phytochemicals present in HM and their potential contribution to infant health.

DHA and ARA addition to infant formula: Current status and future research directions

Docosahexaenoic acid (DHA) and arachidonic acid (ARA) are present in breast milk and play important roles in early infant development. A supply of these fatty acids in infant formula (typically following breast milk as a model with ARA > DHA) is thought to be important since endogenous synthesis is insufficient to maintain tissue levels equivalent to breast-fed infants. Intervention studies assessing the impact of DHA- and ARA-supplemented formulas have resulted in numerous positive developmental outcomes (closer to breast-fed infants) including measures of specific cognition functions, visual acuity, and immune responses. A critical analysis of outcome assessment tools reveals the essentiality of selecting appropriate, focused techniques in order to provide accurate evaluation of DHA- and ARA-supplemented formulas. Future research directions should encompass in-depth assessment of specific cognitive outcomes, immune function, and disease incidence, as well as sources of experimental variability such as the status of fatty acid desaturase polymorphisms.

Comparative analyses of DHA-Phosphatidylcholine and recombination of DHA-Triglyceride with Egg-Phosphatidylcholine or Glycerylphosphorylcholine on DHA repletion in n-3 deficient mice

Background

Docosahexaenoic acid (DHA) is important for optimal neurodevelopment and brain function during the childhood when the brain is still under development.

Methods

The effects of DHA-Phosphatidylcholine (DHA-PC) and the recombination of DHA-Triglyceride with egg PC (DHA-TG + PC) or α-Glycerylphosphorylcholine (DHA-TG + α-GPC) were comparatively analyzed on DHA recovery and the DHA accumulation kinetics in tissues including cerebral cortex, erythrocyte, liver, and testis were evaluated in the weaning n-3 deficient mice.

Results

The concentration of DHA in weaning n-3 deficient mice could be recovered rapidly by dietary DHA supplementation, in which DHA-PC exhibited the better efficacy than the recombination of DHA-Triglyceride with egg PC or α-GPC. Interestingly, DHA-TG + α-GPC exhibited the greater effect on DHA accumulation than DHA-TG + PC in cerebral cortex and erythrocyte (p < 0.05), which was similar to DHA-PC. Meanwhile, DHA-TG + PC showed a similar effect to DHA-PC on DHA repletion in testis, which was better than that of DHA-TG + α-GPC (p < 0.05).

Conclusion

We concluded that different forms of DHA supplements could be applied targetedly based on the DHA recovery in different tissues, although the supplemental effects of the recombination of DHA-Triglyceride with egg PC or α-GPC were not completely equivalent to that of DHA-PC, which could provide some references to develop functional foods to support brain development and function.

Long-chain polyunsaturated fatty acid status in children, adolescents and adults with phenylketonuria

BACKGROUND

Patients with phenylketonuria have been reported to be deficient in long-chain polyunsaturated fatty acids (LCPUFAs). It has been postulated that good compliance with the dietary regimen negatively influences LCPUFA status.

METHODS

In 36 patients with phenylketonuria and 18 age-matched healthy control subjects LCPUFA-levels in plasma phospholipids and cholesteryl esters, erythrocyte phosphatidylcholine and phosphatidylethanolamine were evaluated.

RESULTS

Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) levels did not differ significantly between patients and control subjects in plasma and erythrocyte fractions. There was a significant negative correlation between SDS (standard deviation) scores of DHA-levels in erythrocyte parameters from the respective age-matched control group and patients' concurrent and long-term phenylalanine levels for erythrocyte phosphatidylethanolamine and erythrocyte phosphatidylcholine. Patients with lower (higher) phenylalanine levels had positive (negative) DHA-SDS.

CONCLUSION

In contrast to previous reports we did not find lower LCPUFA-levels in patients with phenylketonuria compared to age-matched healthy control subjects. Good dietary control was associated with better LCPUFA status.

Bilberry extract supplementation for preventing eye fatigue in video display terminal workers

OBJECTIVES

To examine the effect of a dietary supplement containing bilberry extract (BE) on eye fatigue induced by acute video display terminal (VDT) loads.

DESIGN AND SETTING

A prospective, randomized, double-blind, placebo-controlled study was performed from August 2012 to February 2013 in the Medical Corporation Jico-kai Yagi Hospital, and the Shinyokohama Shinoharaguchi Orthopedic Surgery and Dermatology Clinic, in Japan.

PARTICIPANTS

Two hundred eighty-one office workers aged 20-40 years that used VDTs were screened by critical flicker fusion (CFF) and near point accommodation (NPA).

INTERVENTION

The participants were randomized to either a BE (480 mg/day) or placebo (vehicle) group, and took allocated capsule, daily, for 8 weeks.

MEASUREMENTS

The CFF, NPA, contrast visual acuity, functional visual acuity, keratoconjunctival epithelial damage, and fluorescein tear film break-up time were examined, and 18 subjective symptoms of eye fatigue were evaluated by questionnaire. Adverse events were reported via medical interviews. Data were collected both before and after VDT load at baseline, and 4, and 8 weeks after daily supplementation with either BE or placebo.

RESULTS

Of 281 participants screened, 88 having relatively lower levels of CFF and NPA were enrolled in the study. Of these, 37 control and 43 BE group subjects completed the study. The VDT load-induced reduction in CFF was alleviated after 8 weeks of BE supplementation (95% confidence interval, 0.10-1.60; p=0.023), in contrast to placebo supplementation, while NPA variation was not. Of the subjective symptoms of eye fatigue, VDT load-induced ocular fatigue sensation, ocular pain, eye heaviness, uncomfortable sensation, and foreign body sensation were mitigated more in the BE group than in the control group, at week 8 (p<0.05). There were no severe adverse events in either group.

CONCLUSIONS

BE supplementation improved some of the objective and subjective parameters of eye fatigue induced by VDT loads.

Enhanced production of docosahexaenoic acid in mammalian cells

Docosahexaenoic acid (DHA), one of the important polyunsaturated fatty acids (PUFA) with pharmaceutical and nutraceutical effects, may be obtained through diet or synthesized in vivo from dietary a-linolenic acid (ALA). However, the accumulation of DHA in human body or other mammals relies on the intake of high dose of DHA for a certain period of time, and the bioconversion of dietary ALA to DHA is very limited. Therefore the mammalian cells are not rich in DHA. Here, we report a new technology for increased production of DHA in mammalian cells. By using transient transfection method, Siganus canaliculatus Δ4 desaturase was heterologously expressed in chinese hamster ovary (CHO) cells, and simultaneously, mouse Δ6-desaturase and Δ5-desaturase were overexpressed. The results demonstrated that the overexpression of Δ6/Δ5-desaturases significantly enhanced the ability of transfected cells to convert the added ALA to docosapentaenoic acid (DPA) which in turn get converted into DHA directly and efficiently by the heterologously expressed Δ4 desaturase. This technology provides the basis for potential utility of these gene constructs in the creation of transgenic livestock for increased production of DHA/related products to meet the growing demand of this important PUFA.

Coarse-grained molecular dynamics provides insight into the interactions of lipids and cholesterol with rhodopsin

Protein function is a complicated interplay between structure and dynamics, which can be heavily influenced by environmental factors and conditions. This is particularly true in the case of membrane proteins, such as the visual receptor rhodopsin. It has been well documented that lipid headgroups, polyunsaturated tails, and the concentration of cholesterol in membranes all play a role in the function of rhodopsin. Recently, we used all-atom simulations to demonstrate that different lipid species have preferential interactions and possible binding sites on rhodopsin's surface, consistent with experiment. However, the limited timescales of the simulations meant that the statistical uncertainty of these results was substantial. Accordingly, we present here 32 independent 1.6 μs coarse-grained simulations exploring lipids and cholesterols surrounding rhodopsin and opsin, in lipid bilayers mimicking those found naturally. Our results agree with those found experimentally and in previous simulations, but with far better statistical certainty. The results demonstrate the value of combining all-atom and coarse-grained models with experiment to provide a well-rounded view of lipid-protein interactions.

Cloning and in vitro function analysis of codon-optimized FatI gene

Currently, n-3 polyunsaturated fatty acids (n-3 PUFAs) have attracted great attention because of their biological significance to organisms. In addition, PUFAs show an obvious impact on prevention and treatment of various diseases. Because n-3 PUFAs cannot be endogenously synthesized by mammals, mammals have to rely on a dietary supplement for sufficient supply. The finding and application of the fatty acid dehydrogenase I (FatI) gene are expected to change the current situation because it can convert n-6 polyunsaturated fatty acids (n-6 PUFAs) to n-3 PUFAs. Meanwhile, the gradual maturation of transgenic technology makes it possible to produce transgenic animals that can synthesize n-3 PUFAs by themselves. In this study, the DNA coding sequence of FatI was synthesized by a chemical method after codon optimization according to the mammal's codon bias. The synthesized DNA sequence was introduced into Boer goat fetal fibroblasts by the constructed recombinant eukaryotic expression vector pcDNA3.1(+)-FatI. Boer goat fetal fibroblasts were transfected by electroporation, and the stable transfected cell lines were obtained by G418 selection. Genomic DNA PCR and Southern blot were applied to verify that the foreign gene FatI was integrated into the genome of the Boer goat fibroblasts. RT-PCR results showed the expression of FatI gene at the mRNA level. The fatty acid profile of cells carrying the FatI gene revealed an increase in total n-3 PUFAs (from 0.61 to 0.95), but a decrease in n-6 PUFAs (from 10.34 to 9.85), resulting in a remarkable increase in the n-3:n-6 ratio (from 0.059 to 0.096). The n-3:n-6 ratio had a 63.49 percent increase, which is a precursor of the response of n-3 desaturase activity of the FatI gene. The study may provide a practical tool for producing transgenic animals that can produce n-3 PUFAs by themselves, and we hope that the application will lay the foundation for animals producing n-3 PUFAs, which will benefit human nutrition and wellness.

A comparison of 2 intravenous lipid emulsions: interim analysis of a randomized controlled trial

OBJECTIVE

To assess the safety and efficacy of a fish oil-based intravenous fat emulsion (FIFE) in reducing the incidence of cholestasis in neonates compared with the traditional soybean oil-based intravenous fat emulsion (SIFE).

METHODS

A double-blind randomized controlled trial was conducted. Nineteen neonates were enrolled (10 SIFE; 9 FIFE). Nutrition assessments and laboratory studies were serially obtained for the duration of PN support or until 6 months' corrected gestational age. Neurodevelopmental outcomes were assessed at 6 and 24 months' corrected age.

RESULTS

There were no differences between groups in demographic characteristics, with an overall median age of 2 days, gestational age of 36 weeks, and birth weight of 2410 g. There were no differences between groups in baseline laboratory values other than alkaline phosphatase (lower in the FIFE group) or in the duration of parenteral nutrition (PN), amount of enteral intake, or the number of operative procedures. The incidence of cholestasis among enrolled patients was significantly lower than expected, resulting in early study termination and an inability to assess for differences in the incidence of cholestasis. The FIFE was associated with no increased risk of growth impairment, coagulopathy, infectious complications, hypertriglyceridemia, or adverse neurodevelopmental outcomes. No patient developed essential fatty acid deficiency.

CONCLUSION

The FIFE at 1 g/kg/d was well tolerated in the neonates recruited for this study. Given the necessary early termination of this study, a follow-up trial with revised eligibility criteria is necessary to determine whether the provision of FIFE decreases the incidence of PN-cholestasis compared with the traditional SIFE.

Perturbations in blood phosphatidylcholine and sphingomyelin Fatty Acid composition in a sample population of cigarette smokers

Docosahexaenoic (DHA) and arachidonic acids (AA) are polyunsaturated fatty acids (PUFAs), major components of brain tissue and neural systems, and the precursors of a number of biologically active metabolites with functions in inflammation resolution, neuroprotection and other actions. As PUFAs are highly susceptible to peroxidation, we hypothesised whether cigarette smokers would present altered PUFAs levels in plasma and erythrocyte phospholipids. Adult males from Indian, Sri-Lankan or Bangladeshi genetic backgrounds who reported smoking between 20 and 60 cigarettes per week were recruited. The control group consisted of matched non-smokers. A blood sample was taken, plasma and erythrocyte total lipids were extracted, phospholipids were separated by thin layer chromatography, and the fatty acid content analysed by gas chromatography. In smokers, dihomo-gamma-linolenic acid, the AA precursor, was significantly reduced in plasma and erythrocyte phosphatidylcholine. AA and DHA were significantly reduced in erythrocyte sphingomyelin. Relatively short term smoking has affected the fatty acid composition of plasma and erythrocyte phospholipids with functions in neural tissue composition, cell signalling, cell growth, intracellular trafficking, neuroprotection and inflammation, in a relatively young population. As lipid peroxidation is pivotal in the pathogenesis of atherosclerosis and neurodegenerative diseases such as Alzheimer disease, early effects of smoking may be relevant for the development of such conditions.

The effect of maternal omega-3 (n-3) LCPUFA supplementation during pregnancy on early childhood cognitive and visual development: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Maternal fish consumption during pregnancy has been positively associated with cognitive and visual abilities in the offspring, leading to the hypothesis that maternal omega-3 (n-3) long-chain PUFA (LCPUFA) supplementation improves children's neurologic and visual development.

OBJECTIVE

The objective was to evaluate the effect of maternal omega-3 LCPUFA supplementation in pregnancy on neurologic and visual development in the offspring.

DESIGN

Five electronic databases were searched. Human randomized controlled trials that supplemented the maternal diet with omega-3 LCPUFAs during pregnancy, or pregnancy and lactation, and that assessed either neurologic or visual development of the offspring were included. Trial quality was assessed, and the results of eligible trials were compared in meta-analyses.

RESULTS

Eleven RCTs involving 5272 participants were included in the review. Most trials had methodologic limitations. No differences in standardized psychometric test scores for cognitive, language, or motor development were observed between the LCPUFA-supplemented and control groups, except for cognitive scores in 2-5-y-old children, in whom supplementation resulted in higher Developmental Standard Scores (mean difference: 3.92; 95% CI: 0.77, 7.08; n = 156; P = 0.01). However, this effect was from 2 trials with a high risk of bias. Because of the variety of visual assessments and age ranges, it was not possible to combine studies with visual outcomes in a meta-analysis, although 6 of the 8 assessments in 5 trials reported no difference between the supplemented and control groups.

CONCLUSION

The evidence does not conclusively support or refute that omega-3 LCPUFA supplementation in pregnancy improves cognitive or visual development.

Meta-analysis of LCPUFA supplementation of infant formula and visual acuity

BACKGROUND AND OBJECTIVE

Long-chain polyunsaturated fatty acids (LCPUFAs) are hypothesized to affect visual acuity development in infants. Randomized controlled trials (RCTs) have been conducted to assess whether supplementation of LCPUFAs of infant formulas affects infant visual acuity. This meta-analysis was conducted to evaluate whether LCPUFA supplementation of infant formulas improves infants' visual acuity.

METHODS

PubMed and PsycInfo were searched for RCTs assessing the efficacy of LCPUFA supplementation of infant formulas on infant visual acuity. RCTs assessing the effects of LCPUFA supplementation on visual acuity (by using either visual evoked potential or behavioral methods) in the first year of life were included in this meta-analysis. Our primary outcome was the mean difference in visual resolution acuity (measured in logarithm of minimum angle of resolution [logMAR]) between supplemented and unsupplemented infants. We also conducted secondary subgroup analyses and meta-regression examining the effects of LCPUFA dose and timing, preterm versus term birth status, and trial methodologic quality.

RESULTS

Nineteen studies involving 1949 infants were included. We demonstrated a significant benefit of LCPUFA supplementation on infants' visual acuity at 2, 4, and 12 months of age when visual acuity was assessed by using visual evoked potential and at 2 months of age by using behavioral methods. There was significant heterogeneity between trials but no evidence of publication bias. Secondary analysis failed to show any moderating effects on the association between LCPUFA supplementation and visual acuity.

CONCLUSIONS

Current evidence suggests that LCPUFA supplementation of infant formulas improves infants' visual acuity up to 12 months of age.

Short-term use of parenteral nutrition with a lipid emulsion containing a mixture of soybean oil, olive oil, medium-chain triglycerides, and fish oil: a randomized double-blind study in preterm infants

BACKGROUND

For premature neonates needing parenteral nutrition (PN), a balanced lipid supply is crucial. The authors hypothesized that a lipid emulsion containing medium-chain triglycerides (MCTs) and soybean, olive, and fish oils would be as safe and well tolerated as a soybean emulsion while beneficially influencing the fatty acid profile.

METHODS

Double-blind, controlled study in 53 neonates (<34 weeks' gestation) randomized to receive at least 7 days of PN containing either an emulsion of MCTs and soybean, olive, and fish oils or a soybean oil emulsion. Target lipid dosage was 1.0 g fat/kg body weight [BW]/d on days 1-3, 2 g/kg BW/d on day 4, 3 g/kg BW/d on day 5, and 3.5 g/kg BW/d on days 6-14.

RESULTS

Test emulsion vs control, mean ± SD: baseline triglyceride concentrations were 0.52 ± 0.16 vs 0.54 ± 0.19 mmol/L and increased similarly in both groups to 0.69 ± 0.38 vs 0.67 ± 0.36 on day 8 of treatment (P = .781 for change). A significantly higher decrease in total and direct bilirubin vs baseline was seen in the test group compared with the control group P < .05 between groups). In plasma and red blood cell phospholipids, eicosapentaenoic acid and docosahexaenoic acid were higher, and the n-6/n-3 fatty acid ratio was lower in the test group (P < .05 vs control).

CONCLUSIONS

The lipid emulsion, based on a mixture of MCTs and soybean, olive, and fish oils, was safe and well tolerated by preterm infants while beneficially modulating the fatty acid profile.

Docosahexaenoic acid (DHA): an ancient nutrient for the modern human brain

Modern humans have evolved with a staple source of preformed docosahexaenoic acid (DHA) in the diet. An important turning point in human evolution was the discovery of high-quality, easily digested nutrients from coastal seafood and inland freshwater sources. Multi-generational exploitation of seafood by shore-based dwellers coincided with the rapid expansion of grey matter in the cerebral cortex, which characterizes the modern human brain. The DHA molecule has unique structural properties that appear to provide optimal conditions for a wide range of cell membrane functions. This has particular implications for grey matter, which is membrane-rich tissue. An important metabolic role for DHA has recently been identified as the precursor for resolvins and protectins. The rudimentary source of DHA is marine algae; therefore it is found concentrated in fish and marine oils. Unlike the photosynthetic cells in algae and higher plants, mammalian cells lack the specific enzymes required for the de novo synthesis of alpha-linolenic acid (ALA), the precursor for all omega-3 fatty acid syntheses. Endogenous synthesis of DHA from ALA in humans is much lower and more limited than previously assumed. The excessive consumption of omega-6 fatty acids in the modern Western diet further displaces DHA from membrane phospholipids. An emerging body of research is exploring a unique role for DHA in neurodevelopment and the prevention of neuropsychiatric and neurodegenerative disorders. DHA is increasingly being added back into the food supply as fish oil or algal oil supplementation.

Altered essential fatty acid metabolism and composition in rat liver, plasma, heart and brain after microalgal DHA addition to the diet

To investigate the effect of docosahexaenoic acid (DHA) without other highly unsaturated fatty acids (HUFA) on n-3 and n-6 essential fatty acid (EFA) metabolism and fatty acid composition in mammals, a stable isotope tracer technique was used in adult rats fed diets with or without 1.3% of algal DHA in a base diet containing 15% of linoleic acid and 3% of alpha-linolenic acid over 8 weeks. The rats were administered orally a mixed oil containing 48 mg/kg body weight of deuterated linoleic and alpha-linolenic acids and euthanized at 4, 8, 24, 96, 168, 240, 360 and 600 h after administration of the isotopes. Fatty acid compositions and the concentrations of deuterated precursors and their respective metabolites were determined in rat liver, plasma, heart and brain as a function of time. DHA, docosapentaenoic acid and eicosapentaenoic acid in the n-3 EFA family were significantly increased in all organs tested in the DHA-fed group, ranging from 5% to 200% greater in comparison with the control group. The accumulation of the metabolites, deuterated-DHA and deuterated-docosapentaenoic acid n-6 was greatly decreased by 1.5- to 2.5-fold in the dietary DHA group. In summary, feeding preformed DHA led to a marked increase in n-3 HUFA content of rat organs at the expense of n-6 HUFA and also prevented the accumulation of newly synthesized deuterated end products. This is the first study which has isolated the effects of DHA on the de novo metabolism on both the n-6 and n-3 EFA pathways.

Safety and efficacy of a lipid emulsion containing a mixture of soybean oil, medium-chain triglycerides, olive oil, and fish oil: a randomised, double-blind clinical trial in premature infants requiring parenteral nutrition

OBJECTIVES

Safety, tolerability, and efficacy of a novel lipid emulsion containing a mixture of soybean oil, medium-chain triglycerides, olive oil, and fish oil (SMOFlipid 20%) with reduced n-6 fatty acids (FA), increased monounsaturated and n-3 FA, and enriched in vitamin E were evaluated in premature infants compared with a soybean oil-based emulsion.

PATIENTS AND METHODS

Sixty (30/30) premature neonates (age 3-7 days, gestational age ≤ 34 weeks, birth weights 1000-2500 g) received parenteral nutrition (PN) with either SMOFlipid 20% (study group) or a conventional lipid emulsion (Intralipid 20%, control group) for a minimum of 7 up to 14 days. Lipid supply started at 0.5 g · kg body weight(-1) · day(-1) on day 1 and increased stepwise (by 0.5 g) up to 2 g · kg body weight(-1) · day(-1) on days 4 to 14. Safety and efficacy parameters were assessed on days 0, 8, and 15 if PN was continued.

RESULTS

Adverse events, serum triglycerides, vital signs, local tolerance, and clinical laboratory did not show noticeable group differences, confirming the safety of study treatment. At study end, γ-glutamyl transferase was lower in the study versus the control group (107.8 ± 81.7 vs 188.8 ± 176.7 IU/L, P < 0.05). The relative increase in body weight (day 8 vs baseline) was 5.0% ± 6.5% versus 5.1% ± 6.6% (study vs control, not significant). In the study group, an increase in n-3 FA in red blood cell phospholipids and n-3:n-6 FA ratio was observed. Plasma α-tocopherol (study vs control) was increased versus baseline on day 8 (26.35 ± 10.03 vs 3.67 ± 8.06 μmol/L, P < 0.05) and at study termination (26.97 ± 18.32 vs 8.73 ± 11.41 μmol/L, P < 0.05).

CONCLUSIONS

Parenteral infusion of SMOFlipid was safe and well tolerated and showed a potential beneficial influence on cholestasis, n-3 FA, and vitamin E status in premature infants requiring PN.

Retailoring docosahexaenoic acid-containing phospholipid species during impaired neurogenesis following omega-3 alpha-linolenic acid deprivation

Diminished levels of docosahexaenoic acid (22:6n-3), the major fatty acid (FA) synthesized from alpha-linolenic acid (18:3n-3), have been implicated in functional impairment in the developing and adult brain. We have now examined the changes in phospholipid (PL) molecular species in the developing postnatal cortex, a region recently shown to be affected by a robust aberration in neuronal cell migration, after maternal diet alpha-linolenic acid deprivation (Yavin et al. (2009)Neuroscience162(4),1011). The frontal cortex PL composition of 1- to 4-week-old rats was analyzed by gas chromatography and electrospray ionization/tandem mass spectrometry. Changes in the cortical PL molecular species profile by dietary means appear very specific as 22:6n-3 was exclusively substituted by docosapentaenoic acid (22:5n-6). However, molecular species were conserved with respect to the combination of specific polar head groups (i.e. ethanolamine and serine) in sn-3 and defined saturated/mono-unsaturated FA in sn-1 position even when the sn-2 FA moiety underwent diet-induced changes. Our results suggest that substitution of docosahexaenoic acid by docosapentaenoic acid is tightly regulated presumably to maintain a proper biophysical characteristic of membrane PL molecular species. The importance of this conservation may underscore the possible biochemical consequences of this substitution in regulating certain functions in the developing brain.

The polyunsaturated fatty acid composition of hepatic and plasma lipids differ by both sex and dietary fat intake in rats

In rats and humans, females have higher liver and/or plasma docosahexaenoic acid (DHA) content than males. We hypothesized that the effect of variation in total fat or essential fatty acid intakes on liver and plasma fatty acid composition would differ between sexes. Rats were fed a low-fat soybean oil (LFS), high-fat soybean oil (HFS), or high-fat linseed oil (HFL) diet for 20 d. There were significant sex differences in LFS rats in proportions of (n-3) and (n-6) fatty acids in plasma and liver contingent on lipid class. Significant diet x sex interactions were observed for eicosapentaenoic acid (EPA), DHA, and arachidonic acid (AA) status. HFL females had a higher proportion of EPA in plasma and liver phosphatidylcholine (PC), DHA in liver triacylglycerol (TAG), and AA in plasma PC than HFS and LFS females. These findings show that the effect of varying dietary fat intake on (n-3) and (n-6) long-chain PUFA (LCPUFA) status is modified by sex. Liver phospholipid and TAG fatty acid product:substrate ratios suggested greater Delta6 desaturase (Delta6D) activity in females than in males. The HFL diet induced higher Delta6D mRNA expression compared with the LFS or HFS diets and HFL females had 10% higher expression of Delta6D mRNA than HFL males. Together, these findings show that sex is an important determinant of the effect of variations in fat and fatty acid intake on LCPUFA status, which may have implications for recommendations for fat and fatty acid intake in humans.

Identification of a novel C20-elongase gene from the marine microalgae Pavlova viridis and its expression in Escherichia coli

Pavlova viridis, a species of a unicellular marine microalgae, is rich in the very-long-chain polyunsaturated fatty acids, such as eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3). A new elongase gene (elkj), with high identity with a functionally characterized C20-elongase of Pavlova lutheri, was isolated via reverse transcriptase-polymerase chain reaction using the primers designed from conserved motifs and 5'/3' rapid amplification of cDNA ends. The coding region of 314 amino acids predicted a protein of 34 kDa, which contained seven transmembrane domains with its C-terminal in the cytoplasm and located in the endoplasmic reticulum. The expression of ELKJ in Escherichia coli was carried out by using green fluorescent protein as an indicator, suggesting the correct insertion in cytoplasmic membrane. Functional analysis demonstrated that elkj encoded a C20-elongase that mediated the elongation of EPA into docosapentaenoic acid (22:5n-3), confirming the two-step conversion from EPA to DHA in marine microalga.

Long-chain polyunsaturated fatty acid (LC-PUFA) transfer across the placenta

Fetal long-chain polyunsaturated fatty acid (LC-PUFA) supply during pregnancy is of major importance, particularly with respect to docosahexaenoic acid (DHA) that is an important component of the nervous system cell membranes. Growing evidence points to direct effects of DHA status on visual and cognitive outcomes in the offspring. Furthermore, DHA supply in pregnancy reduces the risk of preterm delivery. Because of limited fetal capacity to synthesize LC-PUFA, the fetus depends on LC-PUFA transfer across the placenta. Molecular mechanisms of placental LC-PUFA uptake and transport are not fully understood, but it has been clearly demonstrated that there is a preferential DHA transfer. Thus, the placenta is of pivotal importance for the selective channeling of DHA from maternal diet and body stores to the fetus. Several studies have associated various fatty acid transport and binding proteins (FATP) with the preferential DHA transfer, but also the importance of the different lipolytic enzymes has been shown. Although the exact mechanisms and the interaction of these factors remains elusive, recent studies have shed more light on the processes involved, and this review summarizes the current understanding of molecular mechanisms of LC-PUFA transport across the placenta and the impact on pregnancy outcome and fetal development.

Effect of dietary docosahexaenoic acid on biosynthesis of docosahexaenoic acid from alpha-linolenic acid in young rats

Docosahexaenoic acid (DHA), a crucial nervous system n-3 PUFA, may be obtained in the diet or synthesized in vivo from dietary alpha-linolenic acid (LNA). We addressed whether DHA synthesis is regulated by the availability of dietary DHA in artificially reared rat pups, during p8 to p28 development. Over 20 days, one group of rat pups was continuously fed deuterium-labeled LNA (d5-LNA) and no other n-3 PUFA (d5-LNA diet), and a second group of rat pups was fed a d5-LNA diet with unlabeled DHA (d5-LNA + DHA diet). The rat pups were then euthanized, and the total amount of deuterium-labeled docosahexaenoic acid (d5-DHA) (synthesized DHA) as well as other n-3 fatty acids present in various body tissues, was quantified. In the d5-LNA + DHA group, the presence of dietary DHA led to a marked decrease (3- to 5-fold) in the total amount of d5-DHA that accumulated in all tissues that we examined, except in adipose. Overall, DHA accretion from d5-DHA was generally diminished by availability of dietary preformed DHA, inasmuch as this was found to be the predominant source of tissue DHA. When preformed DHA was unavailable, d5-DHA and unlabeled DHA were preferentially accreted in some tissues along with a net loss of unlabeled DHA from other organs.

Latitude-of-birth and season-of-birth effects on human color vision in the Arctic

Extreme natural ambient light reduction, in both energy and range of wavelength spectrum, occurs during the winter season at very high latitudes (above the Arctic Circle or 66 degrees 32' North) that in turn results in increased exposure to artificial lighting. In contrast, during the summer months, the sun remains above the horizon and there is no darkness or night. Little is known about these extreme changes in light exposure on human visual perception. Measuring color discriminations with the FM100 Test revealed that Norwegians born above the Arctic Circle were less sensitive to yellow-green, green, and green-blue spectrum differences whereas they were more sensitive to hue variations in the purple range than individuals born below the Arctic Circle. Additionally, it was found that the Norwegian individuals born above the Arctic Circle and during autumn showed an overall decrease in color sensitivity, whereas those born in the summer showed a relative increase. All participants were adults and their color vision was tested in the same location (i.e., in Tromsø at 69.7 degrees North). These findings are consistent with the idea that there is a measurable impact on colour vision as adults of the photic environment that individuals born above the Arctic Circle and in the autumn experienced during infancy, namely a reduction in exposure to direct sunlight and an increase in exposure to twilight and artificial lighting.

Effect of fish oil supplementation on fatty acid status, coordination, and fine motor skills in children with phenylketonuria

OBJECTIVE

To investigate effects of long-chain omega-3 polyunsaturated fatty acids (LC-PUFA) on motor skills in patients with phenylketonuria (PKU).

STUDY DESIGN

Thirty-six patients with PKU (1-11 years of age, good metabolic control: plasma phenylalanine < or = 360 micromol/L for > or = 6 months). We determined plasma phospholipid fatty acids, and in patients > 4 years of age (N = 24) the motometric Rostock-Oseretzky Scale (ROS), before and after supplementation with fish oil for 3 months (15 mg docosahexaenoic acid [DHA]/kg body weight daily). ROS was also assessed in 22 age-matched controls.

RESULTS

Patients had low n-3 LC-PUFA in plasma phospholipids (DHA, 2.37 +/- 0.10%; eicosapentaenoic acid [EPA], 0.4 +/- 0.03%) and poorer ROS performance than controls (motor development index [MQ] 107 +/- 3 vs 117 +/- 3, P = .010). Supplementation increased phospholipid n-3 LC-PUFA (DHA 7.05 +/- 0.24%; EPA 3.31 +/- 0.19%; P < .001), decreased n-6 LC-PUFA (arachidonic acid, 9.26 +/- 0.23% vs 6.76 +/- 0.16%; P < .001) and improved ROS (MQ 115 +/- 3.54, P = .011, paired t test). ROS was unchanged in 11 retested controls (MQ 115 +/- 5.16, P = NS, paired t test multivariate analysis of variance [MANOVA] for time by group, P = .027). Patients tolerated fish oil well. Plasma phenylalanine remained unchanged.

CONCLUSION

In patients with PKU, fish oil supplementation enhances n-3 LC-PUFA levels and improves motor skills.

Dietary omega-3 fatty acids for women

This review details the specific needs of women for omega-3 fatty acids, including alpha linoleic acid (ALA) and the very long chain fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Omega-3 fatty acid (dietary or in capsules) ensures that a woman's adipose tissue contains a reserve of these fatty acids for the developing fetus and the breast-fed newborn infant. This ensures the optimal cerebral and cognitive development of the infant. The presence of large quantities of EPA and DHA in the diet slightly lengthens pregnancy, and improves its quality. Human milk contains both ALA and DHA, unlike that of other mammals. Conditions such as diabetes can alter the fatty acid profile of mother's milk, while certain diets, like those of vegetarians, vegans, or even macrobiotic diets, can have the same effect, if they do not include seafood. ALA, DHA and EPA, are important for preventing ischemic cardiovascular disease in women of all ages. Omega-3 fatty acids can help to prevent the development of certain cancers, particularly those of the breast and colon, and possibly of the uterus and the skin, and are likely to reduce the risk of postpartum depression, manic-depressive psychosis, dementias (Alzheimer's disease and others), hypertension, toxemia, diabetes and, to a certain extend, age-related macular degeneration. Omega-3 fatty acids could play a positive role in the prevention of menstrual syndrome and postmenopausal hot flushes. The normal western diet contains little ALA (less than 50% of the RDA). The only adequate sources are rapeseed oil (canola), walnuts and so-called "omega-3" eggs (similar to wild-type or Cretan eggs). The amounts of EPA and DHA in the diet vary greatly from person to person. The only good sources are fish and seafood, together with "omega-3" eggs.

A docosahexaenoic acid-functional food during pregnancy benefits infant visual acuity at four but not six months of age

Within the visual system, docosahexaenoic acid (DHA, 22:6n-3) is an important structural component for retinal photoreceptors and cortical gray matter. There is a marked decrease in neural DHA accumulation in the face of DHA deficiency. DHA is accumulated at an accelerated rate during pregnancy, especially in the third trimester. However, pregnant women in the US and Canada have dietary DHA intakes that are significantly below the optimal level. The main objective of this study was to determine whether a DHA-functional food during pregnancy would benefit infant visual acuity at four and six months of age measured behaviorally using the acuity card procedure (ACP). In a randomized, longitudinal, double-blinded, and placebo-controlled trial, 30 pregnant women received either the DHA-functional food (n = 16) or the placebo (n = 14). There were significant main effects for visual acuity at four months of age (P = 0.018). The mean acuity scores were 3.8 +/- 1.1 cycles/degree in the DHA group versus 3.2 +/- 0.7 cycles/degree in the placebo group. At six months there were no group differences. Based on our results, we conclude that DHA supplemented during pregnancy plays a role in the maturation of the visual system.

Prenatal methylmercury exposure affects spatial vision in adult monkeys

Decades of research have demonstrated that exposure to methylmercury (MeHg), a ubiquitous environmental pollutant, can have both early and long-term neurobehavioral consequences in exposed offspring. The present study assessed visual functioning in adult macaque monkeys (Macaca fascicularis) exposed in utero to 0, 50, 70, or 90 microg/kg/day of MeHg hydroxide. Twenty-one full-term, normal birth weight offspring (9 controls, 12 exposed) were tested at approximately 11-14.5 years of age on a visual contrast sensitivity task. A forced-choice tracking procedure was utilized with spatial frequencies of 1, 4, 10, and 20 cycles per degree of visual angle. On each test session, a single spatial frequency was presented across five levels of contrast, each differing by 3 dB. Methylmercury-exposed monkeys exhibited reduced contrast sensitivity thresholds, particularly at the higher spatial frequencies. The degree of visual impairment was not related to MeHg body burden or clearance and almost half of the exposed animals were unimpaired. The results from this study demonstrate that chronic in utero MeHg exposure, at subclinical levels, is associated with permanent adverse effects on spatial vision in adult monkeys.

Isolation and functional characterization of fatty acid delta5-elongase gene from the liverwort Marchantia polymorpha L

Bryophyte Marchantia polymorpha L. produces C22 very-long-chain polyunsaturated fatty acid (VLCPUFA). Thus far, no enzyme that mediates elongation of C20 VLCPUFAs has been identified in land plants. Here, we report the isolation and characterization of the gene MpELO2, which encodes an ELO-like fatty acid elongase in M. polymorpha. Heterologous expression in yeast demonstrated that MpELO2 encodes delta5-elongase, which mediates elongation of arachidonic (20:4) and eicosapentaenoic acids (20:5). Phylogenetic and gene structural analysis indicated that the MpELO2 gene is closely related to bryophyte Delta6-elongase genes for C18 fatty acid elongation and diverged from them by local gene duplication.

Can prenatal N-3 fatty acid deficiency be completely reversed after birth? Effects on retinal and brain biochemistry and visual function in rhesus monkeys

Our previous studies of rhesus monkeys showed that combined prenatal and postnatal n-3 fatty acid deficiency resulted in reduced visual acuity, abnormal retinal function, and low retina and brain docosahexaenoic acid content. We now report effects of n-3 fatty acid deficiency during intrauterine development only. Rhesus infants, born to mothers fed an n-3 fatty acid deficient diet throughout pregnancy, were repleted with a diet high in alpha-linolenic acid from birth to 3 y. Fatty acid composition was determined for plasma and erythrocytes at several time points, for prefrontal cerebral cortex biopsies at 15, 30, 45, and 60 wk, and for cerebral cortex and retina at 3 y. Visual acuity was determined behaviorally at 4, 8, and 12 postnatal weeks, and the electroretinogram was recorded at 3-4 mo. Total n-3 fatty acids were reduced by 70-90% in plasma, erythrocytes, and tissues at birth but recovered to control values within 4 wk in plasma, 8 wk in erythrocytes, and 15 wk in cerebral cortex. At 3 y, fatty acid composition was normal in brain phospholipids, but in the retina DHA recovery was incomplete (84% of controls). Visual acuity thresholds did not differ from those of control infants from mothers fed a high linolenic acid diet. However, the repleted group had lower amplitudes of cone and rod ERG a-waves. These data suggest that restriction of n-3 fatty acid intake during the prenatal period may have long-term effects on retinal fatty acid composition and function.

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.

Identification of two novel microalgal enzymes involved in the conversion of the omega3-fatty acid, eicosapentaenoic acid, into docosahexaenoic acid

Marine microalgae such as Pavlova and Isochrysis produce abundant amounts of the omega3-PUFAs (polyunsaturated fatty acids), EPA (eicosapentaenoic acid, 20:5n-3) and DHA (docosahexaenoic acid, 22:6n-3). The pathway leading to the conversion of EPA into DHA in these lower eukaryotes is not well established although it is predicted to involve an elongation step, catalysed by an elongating enzyme complex, leading to the conversion of EPA into omega3-DPA (omega-3-docosapentaenoic acid, 22:5n-3); followed by a desaturation step, catalysed by a Delta4-desaturase, which results in the conversion of DPA into DHA. To date, the enzymes involved in the elongation of EPA have not been identified from any lower eukaryote. In the present study, we describe the identification of microalgal genes involved in the two-step conversion of EPA into DHA. By expressed sequence tag analysis, a gene (pavELO) encoding a novel elongase was identified from Pavlova, which catalysed the conversion of EPA into omega3-DPA in yeast. Unlike any previously identified elongase from higher or lower eukaryotes, this enzyme displayed unique substrate specificity for both n-6 and n-3 C20-PUFA substrates, with no activity towards any C18- or C22-PUFA substrates. In addition, a novel Delta4-desaturase gene (IgD4) was isolated from Isochrysis, which was capable of converting omega3-DPA into DHA, as well as adrenic acid (22:4n-6) into omega6-DPA. Yeast co-expression studies, with pavELO and IgD4, revealed that these genes were capable of functioning together to carry out the two-step conversion of EPA into DHA.

Effects of alcohol intake during pregnancy on docosahexaenoic acid and arachidonic acid in umbilical cord vessels of black women

OBJECTIVE

Alcohol influences the intake and metabolism of several nutrients including long-chain polyunsaturated fatty acids (LC-PUFAs). The LC-PUFAs docosahexaenoic acid (DHA) and arachidonic acid (AA) are particularly crucial for intrauterine growth and brain development. We hypothesized that alcohol consumption adversely affects LC-PUFA levels in pregnant women and their newborn infants.

METHODS

Pregnant black women (N = 208) presenting at a core city antenatal clinic were screened and recruited. Shortly before delivery, maternal plasma was collected. After delivery, umbilical arteries and veins were dissected from the cords, total lipids were extracted from the vessel tissues and maternal plasma, and fatty acid levels were assayed by gas chromatography. For statistical analysis, subjects were categorized according to absolute alcohol intake per day (AAD) and absolute alcohol intake per drinking day (AADD) around the time of conception, with smoking and other potential confounders included in the analyses.

RESULTS

Significant differences in fatty acid composition of total lipid extracts were detected in umbilical cord vessels among the AADD groups: abstainers (AADD = 0), moderate drinkers (AADD < 130 g), and heavy drinkers (AADD > or = 130 g). DHA and AA content in the arterial umbilical vessel wall was approximately 14% and approximately 10% higher in the moderate (n = 127) and heavy (n = 32) alcohol groups, respectively, than in abstainers (n = 49). A small, nonsignificant increase ( approximately 3%) was seen in the umbilical vein for AA but not for DHA. Alcohol intake was positively correlated to both DHA and AA concentrations in the arterial vessel wall but to neither in the venous wall nor maternal plasma. Maternal plasma DHA was positively correlated with both umbilical arteries and vein DHA, but there were no significant correlations for AA between maternal plasma and either umbilical vessel.

CONCLUSIONS

Our findings indicate that alcohol intake during pregnancy is associated with altered DHA and AA status in fetal tissues. Although differences may be due to either metabolism and/or distribution, it is most likely a result of a direct influence of alcohol on fetal metabolism.

Packing and Viscoelasticity of Polyunsaturated ω-3 and ω-6 Lipid Bilayers as Seen by2H NMR and X-ray Diffraction

Polyunsaturated phospholipids of the omega-3 and omega-6 classes play key roles in cellular functions, yet their mechanisms of biological action are still a matter of debate. Using deuterium ((2)H) NMR spectroscopy and small-angle X-ray diffraction, we show how membrane properties are modified by docosahexaenoic (DHA; 22:6) and arachidonic (AA; 20:4) acyl chains of the omega-3 and the omega-6 families, respectively. Structural and dynamical differences due to polyunsaturation are evident in both the ordered and disordered phases of mixed-chain (16:0)(22:6)PC and (16:0)(20:4)PC bilayers. Due to the lower chain melting temperature, the omega-6 AA bilayer is more disordered in the fluid (L(alpha)) state than the omega-3 DHA bilayer; it is thinner with a larger area per lipid. The thermal hysteresis observed for the DHA bilayer may represent the influences of angle-iron conformers in the gel state and back-bended, hairpinlike conformers in the fluid state, consistent with molecular dynamics studies. Interpretation of the (2)H NMR order profiles of (16:0-d(31))(22:6)PC and (16:0-d(31))(20:4)PC together with X-ray electron density profiles reveals an uneven distribution of mass; i.e., the sn-1 saturated chain is displaced toward the membrane center, whereas the sn-2 polyunsaturated chain is shifted toward the bilayer aqueous interface. Moreover, the (2)H NMR relaxation rates are increased by the presence of omega-6 AA chains compared to omega-3 DHA chains. When evaluated at the same amplitude of motion, relaxation parameters give a naturally calibrated scale for comparison of fluid lipid bilayers. Within this framework, polyunsaturated bilayers are relatively soft to bending and area fluctuations on the mesoscale approaching molecular dimensions. Significant differences are evident in the viscoelastic properties of the omega-3 and omega-6 bilayers, a possibly biologically relevant feature that distinguishes between the two phospholipid classes.

Half-lives of docosahexaenoic acid in rat brain phospholipids are prolonged by 15 weeks of nutritional deprivation of n-3 polyunsaturated fatty acids

Male rat pups (21 days old) were placed on a diet deficient in n-3 polyunsaturated fatty acids (PUFAs) or on an n-3 PUFA adequate diet containing alpha-linolenic acid (alpha-LNA; 18 : 3n-3). After 15 weeks on a diet, [4,5-3H]docosahexaenoic acid (DHA; 22 : 6n-3) was injected into the right lateral cerebral ventricle, and the rats were killed at fixed times over a period of 60 days. Compared with the adequate diet, 15 weeks of n-3 PUFA deprivation reduced plasma DHA by 89% and brain DHA by 37%; these DHA concentrations did not change thereafter. In the n-3 PUFA adequate rats, DHA loss half-lives, calculated by plotting log10 (DHA radioactivity) against time after tracer injection, equaled 33 days in total brain phospholipid, 23 days in phosphatidylcholine, 32 days in phosphatidylethanolamine, 24 days in phosphatidylinositol and 58 days in phosphatidylserine; all had a decay slope significantly greater than 0 (p < 0.05). In the n-3 PUFA deprived rats, these half-lives were prolonged twofold or greater, and calculated rates of DHA loss from brain, Jout, were reduced. Mechanisms must exist in the adult rat brain to minimize DHA metabolic loss, and to do so even more effectively in the face of reduced n-3 PUFA availability for only 15 weeks.