Rate of phenylalanine hydroxylation in healthy school-aged children

Hydroxylation of phenylalanine to tyrosine is the first and rate-limiting step in phenylalanine catabolism. Currently, there are data on the rate of phenylalanine hydroxylation in infants and adults but not in healthy children. Thus, the aim of the study reported here was to measure the rate of phenylalanine hydroxylation and oxidation in healthy school-aged children both when receiving diets with and without tyrosine. In addition, hydroxylation rates calculated from the isotopic enrichments of amino acids in plasma and in very LDL apoB-100 were compared. Eight healthy 6- to 10-y-old children were studied while receiving a control and again while receiving a tyrosine-free diet. Phenylalanine flux, hydroxylation, and oxidation were determined by a standard tracer protocol using oral administration of ¹³C-phenylalanine and ²H₂-tyrosine for 6 h. Phenylalanine hydroxylation rate of children fed a diet devoid of tyrosine was greater than that of children fed a diet containing tyrosine (40.25 ± 5.48 versus 29.55 ± 5.35 μmol · kg⁻¹ · h⁻¹; p < 0.01). Phenylalanine oxidation was not different from phenylalanine hydroxylation regardless of dietary tyrosine intake, suggesting that phenylalanine converted to tyrosine was mainly oxidized. In conclusion, healthy children are capable of converting phenylalanine to tyrosine, but the need for tyrosine cannot be met by providing extra phenylalanine.

Direct regulation of myocardial triglyceride metabolism by the cardiomyocyte circadian clock

Maintenance of circadian alignment between an organism and its environment is essential to ensure metabolic homeostasis. Synchrony is achieved by cell autonomous circadian clocks. Despite a growing appreciation of the integral relation between clocks and metabolism, little is known regarding the direct influence of a peripheral clock on cellular responses to fatty acids. To address this important issue, we utilized a genetic model of disrupted clock function specifically in cardiomyocytes in vivo (termed cardiomyocyte clock mutant (CCM)). CCM mice exhibited altered myocardial response to chronic high fat feeding at the levels of the transcriptome and lipidome as well as metabolic fluxes, providing evidence that the cardiomyocyte clock regulates myocardial triglyceride metabolism. Time-of-day-dependent oscillations in myocardial triglyceride levels, net triglyceride synthesis, and lipolysis were markedly attenuated in CCM hearts. Analysis of key proteins influencing triglyceride turnover suggest that the cardiomyocyte clock inactivates hormone-sensitive lipase during the active/awake phase both at transcriptional and post-translational (via AMP-activated protein kinase) levels. Consistent with increased net triglyceride synthesis during the end of the active/awake phase, high fat feeding at this time resulted in marked cardiac steatosis. These data provide evidence for direct regulation of triglyceride turnover by a peripheral clock and reveal a potential mechanistic explanation for accelerated metabolic pathologies after prevalent circadian misalignment in Western society.

Docosahexaenoic acid (DHA) supplementation of orange juice increases plasma phospholipid DHA content of children

The major dietary source of docosahexaenoic acid (DHA) is fish, which is not widely consumed by children. There is concern, therefore, that children may not receive adequate DHA and so might benefit from dietary supplementation. The aim of the present study was to evaluate the effects of providing a supplement of microencapsulated algal DHA in juice. We assessed the effects of two levels of DHA supplementation on the plasma phospholipid DHA content of healthy 4- to 6-year-old and 7- to 12-year-old children who were randomly assigned to consume 180 mL juice containing either 50 mg (lower dose) or 100 mg (higher dose) DHA daily for 6 weeks. Plasma phospholipid DHA content (mole % of total fatty acids) was measured before and after 6 weeks of daily juice consumption. Because there are no data for plasma phospholipid DHA content in healthy children, data were compared to that of breastfed infants. At baseline, plasma phospholipid DHA content was lower in both age groups and dose groups than observed in breastfed infants. It increased significantly in both dose groups, but more so in the higher dose group of both age groups (P<0.05, overall mean+/-standard deviation: 3.72+/-0.66 vs 4.64+/-0.77); reaching levels similar to or greater than content of breastfed infants. Thus, DHA supplementation of juice at either 50 mg/day or 100 mg/day for 6 weeks was effective in increasing plasma phospholipid DHA contents of children.

Circadian rhythms in myocardial metabolism and contractile function: influence of workload and oleate

Multiple extracardiac stimuli, such as workload and circulating nutrients (e.g., fatty acids), known to influence myocardial metabolism and contractile function exhibit marked circadian rhythms. The aim of the present study was to investigate whether the rat heart exhibits circadian rhythms in its responsiveness to changes in workload and/or fatty acid (oleate) availability. Thus, hearts were isolated from male Wistar rats (housed during a 12:12-h light-dark cycle: lights on at 9 AM) at 9 AM, 3 PM, 9 PM, and 3 AM and perfused in the working mode ex vivo with 5 mM glucose plus either 0.4 or 0.8 mM oleate. Following 20-min perfusion at normal workload (i.e., 100 cm H(2)O afterload), hearts were challenged with increased workload (140 cm H(2)O afterload plus 1 microM epinephrine). In the presence of 0.4 mM oleate, myocardial metabolism exhibited a marked circadian rhythm, with decreased rates of glucose oxidation, increased rates of lactate release, decreased glycogenolysis capacity, and increased channeling of oleate into nonoxidative pathways during the light phase. Rat hearts also exhibited a modest circadian rhythm in responsiveness to the workload challenge when perfused in the presence of 0.4 mM oleate, with increased myocardial oxygen consumption at the dark-to-light phase transition. However, rat hearts perfused in the presence of 0.8 mM oleate exhibited a markedly blunted contractile function response to the workload challenge during the light phase. In conclusion, these studies expose marked circadian rhythmicities in myocardial oxidative and nonoxidative metabolism as well as responsiveness of the rat heart to changes in workload and fatty acid availability.

Comparison of the validity of direct pediatric developmental evaluation versus developmental screening by parent report

To compare the validity of direct pediatric developmental evaluation with developmental screening by parent report, parents completed a developmental screen (the Child Development Review), a pediatrician performed a direct developmental evaluation (Capute Scales), and a psychologist administered the Bayley Scales of Infant Development to a group of 30-month-old children. The agreement between these instruments was tested. All developmental quotient scores derived from the Capute Scales were more highly correlated with concurrent Bayley Mental Development Index scores than developmental quotient scores derived from the Child Development Review. Differences between developmental quotient scores derived from the Capute Scales and corresponding Bayley Mental Development Index scores were significantly smaller than those derived from the Child Development Review. Thus, direct pediatric developmental evaluation more reliably predicted concurrent Mental Development Index scores at 30 months of age than developmental screening by parent report. Increased emphasis on training of pediatric health care providers in direct developmental evaluation should be considered.

Urinary F2-isoprostanes are poor prognostic indicators for the development of bronchopulmonary dysplasia

OBJECTIVE

Oxygen toxicity is thought to contribute to the development of bronchopulmonary dysplasia (BPD). Oxidant injury leads to formation of F(2)-isoprostanes (F(2)-IsoP). We hypothesized that urinary excretion of the stable metabolite of F(2)-IsoP, 8-iso-PGF(2alpha), would be higher in infants who develop BPD than those who did not.

METHODS

Forty infants <30-weeks gestational age (GA) were enrolled, 24 infants with BPD and 16 without BPD. Urine specimens were collected weekly and stored at -80 degrees C until analyzed. Urinary 8-iso-PGF(2alpha) was measured by gas chromatography/mass spectrometry (GC-MS) and normalized to creatinine excretion.

RESULTS

GA and birth weight (BW) were lower in infants who developed BPD than those who did not. Urinary 8-iso-PGF(2alpha) levels in the first or third weeks of age were not significantly different between the two groups.

CONCLUSION

Urinary excretion of 8-iso-PGF(2alpha) in early postnatal life in preterm infants is not correlated with the development of BPD.

Biochemical homeostasis and body growth are reliable end points in clinical nutrition trials

Studies of biochemical homeostasis and/or body growth have been included as outcome variables in most nutrition trials in paediatric patients. Moreover, these outcome variables have provided important insights into the nutrient requirements of infants and children, and continue to do so. Examples of the value of such studies in improving parenteral nutrition, in defining essential fatty acid metabolism and requirements of infants and in defining the protein and energy needs of low-birth-weight infants are discussed. Data from such studies have helped to define the mechanism of metabolic acidosis and hyperammonaemia associated with the use of early crystalline amino acid mixture and, hence, how to prevent these disorders. Such studies have allowed the development of parenteral amino acid mixtures that circumvent grossly abnormal plasma concentrations of most amino acids and appear to be utilized more efficiently. These studies have also helped define micronutrient requirements, including requirements for several such nutrients that had not been previously recognized as essential (e.g. Cr, Se, Mo, α-linolenic acid). Studies of body growth have been particularly valuable in defining the nutritional requirements of low-birth-weight infants. Finally, studies of metabolic homeostasis coupled with more sophisticated metabolic studies have provided considerable insight into the metabolism of the essential fatty acids, linoleic acid (18:2n-6) and α-linolenic acid (18:3n-3). Although such studies have not defined the amount of the longer-chain PUFA synthesized from each of these essential fatty acids, i.e. arachidonic acid (20:4n-6) and DHA (22:6n-3), they have shown that the rates of conversion are extremely variable from infant to infant, suggesting a possible explanation of why some studies show developmental advantages from intake of these fatty acids while others do not.

Progress in promoting breast-feeding, combating malnutrition, and composition and use of infant formula, 1981-2006

More than 90% of women in developing countries and 50 to 90% of women in industrialized countries now initiate breast-feeding, a marked improvement from 25 y ago. The duration of breast-feeding has lengthened, but fewer than 35% of infants worldwide are still exclusively breast-fed at 4 mo of age. Considerable progress has also been made in combating infant malnutrition. In 1980, 47% of under-5-y-old children in developing countries were stunted. This percentage declined to 29% in 2005. Major advances in formula use and composition include the introduction of formulas tailored to the perceived needs of low-birth-weight infants and the development of fortifiers to overcome the nutritional deficits of human milk for the preterm infant. More recently, postdischarge formulas were introduced and are now being used widely, often in combination with breast-feeding. Formulas for term infants also have undergone a number of changes in the past 25 y to better reproduce the composition of human milk and/or the response of the breast-fed infant. The use of whey-predominant rather than casein-predominant formulas has increased, as has the use of iron-fortified formulas. Cow's milk is introduced into the infant's diet much later than 25 y ago. Despite the progress that has been made in promoting breast-feeding and in the quality of infant formulas, further improvements in the duration of breast-feeding and in the composition of infant formulas are needed.

Body-composition assessment in infancy: air-displacement plethysmography compared with a reference 4-compartment model

BACKGROUND

A better understanding of the associations of early infant nutrition and growth with adult health requires accurate assessment of body composition in infancy.

OBJECTIVE

This study evaluated the performance of an infant-sized air-displacement plethysmograph (PEA POD Infant Body Composition System) for the measurement of body composition in infants.

DESIGN

Healthy infants (n = 49; age: 1.7-23.0 wk; weight: 2.7-7.1 kg) were examined with the PEA POD system. Reference values for percentage body fat (%BF) were obtained from a 4-compartment (4-C) body-composition model, which was based on measurements of total body water, bone mineral content, and total body potassium.

RESULTS

Mean (+/- SD) reproducibility of %BF values obtained with the PEA POD system was 0.4 +/- 1.3%. Mean %BF obtained with the PEA POD system (16.9 +/- 6.5%) did not differ significantly from that obtained with the 4-C model (16.3 +/- 7.2%), and the regression between %BF for the 4-C model and that for the PEA POD system (R2 = 0.73, SEE = 3.7%BF) did not deviate significantly from the line of identity (y = x).

CONCLUSIONS

The PEA POD system provided a reliable, accurate, and immediate assessment of %BF in infants. Because of its ease of use, good precision, minimum safety concerns, and bedside accessibility, the PEA POD system is highly suitable for monitoring changes in body composition during infant growth in both the research and clinical settings.

Liver-specific deletion of acetyl-CoA carboxylase 1 reduces hepatic triglyceride accumulation without affecting glucose homeostasis

In animals, liver and white adipose are the main sites for the de novo fatty acid synthesis. Deletion of fatty acid synthase or acetyl-CoA carboxylase (ACC) 1 in mice resulted in embryonic lethality, indicating that the de novo fatty acid synthesis is essential for embryonic development. To understand the importance of de novo fatty acid synthesis and the role of ACC1-produced malonyl-CoA in adult mouse tissues, we generated liver-specific ACC1 knockout (LACC1KO) mice. LACC1KO mice have no obvious health problem under normal feeding conditions. Total ACC activity and malonyl-CoA levels were approximately 70-75% lower in liver of LACC1KO mice compared with that of the WT mice. In addition, the livers of LACC1KO mice accumulated 40-70% less triglycerides. Unexpectedly, when fed fat-free diet for 10 days, there was significant up-regulation of PPARgamma and several enzymes in the lipogenic pathway in the liver of LACC1KO mice compared with the WT mice. Despite the significant up-regulation of the lipogenic enzymes, including a >2-fold increase in fatty acid synthase mRNA, protein, and activity, there was significant decrease in the de novo fatty acid synthesis and triglyceride accumulation in the liver. However, there were no significant changes in blood glucose and fasting ketone body levels. Hence, reducing cytosolic malonyl-CoA and, therefore, the de novo fatty acid synthesis in the liver, does not affect fatty acid oxidation and glucose homeostasis under lipogenic conditions.

Performance on a Visual Sustained Attention and Discrimination Task is Associated with Urinary Excretion of Norepineprhine Metabolite in Children with Attention-Deficit/Hyperactivity Disorder (AD/HD)

The degree of association between performance on a sustained attention task requiring visual discrimination and urinary excretion of catecholamine metabolites was examined in a cohort of 6- to 12-year-old children (n = 31) strictly selected and diagnosed with attention-deficit/hyperactivity disorder (AD/HD) according to DSM-IV and other strict criteria. Sustained visual attention and discrimination were measured using the Test of Variables of Attention (T.O.V.A.). Urinary excretion of dopamine (DA) and norepinephrine (NE) metabolites was measured by reversed high-pressure liquid chromatography (HPLC). Pearson product-moment correlations were used to investigate the relationship between T.O.V.A. errors of omission (OMM), errors of commission (COM), response time (RT), and response time variability (RTV) and catecholamine metabolites of DA and NE. All T.O.V.A. indexes under investigation were significantly correlated with urinary excretion of NE metabolites, but correlations were low-to-moderate in magnitude (.37-.50). In contrast, there were no statistically significant correlations between T.O.V.A. indices and DA metabolites. These findings and their concordance with past research in human adults and animals, as well as theoretical issues associated with the present results, are discussed.

Protection against fatty liver but normal adipogenesis in mice lacking adipose differentiation-related protein

Adipose differentiation-related protein (ADFP; also known as ADRP or adipophilin), is a lipid droplet (LD) protein found in most cells and tissues. ADFP expression is strongly induced in cells with increased lipid load. We have inactivated the Adfp gene in mice to better understand its role in lipid accumulation. The Adfp-deficient mice have unaltered adipose differentiation or lipolysis in vitro or in vivo. Importantly, they display a 60% reduction in hepatic triglyceride (TG) and are resistant to diet-induced fatty liver. To determine the mechanism for the reduced hepatic TG content, we measured hepatic lipogenesis, very-low-density lipoprotein (VLDL) secretion, and lipid uptake and utilization, all of which parameters were shown to be similar between mutant and wild-type mice. The finding of similar VLDL output in the presence of a reduction in total TG in the Adfp-deficient liver is explained by the retention of TG in the microsomes where VLDL is assembled. Given that lipid droplets are thought to form from the outer leaflet of the microsomal membrane, the reduction of TG in the cytosol with concomitant accumulation of TG in the microsome of Adfp-/- cells suggests that ADFP may facilitate the formation of new LDs. In the absence of ADFP, impairment of LD formation is associated with the accumulation of microsomal TG but a reduction in TG in other subcellular compartments.

Current Electrolyte Intakes of Infants and Toddlers

OBJECTIVE

To determine how sodium, chloride, and potassium intakes of today's infants and toddlers compare with the Dietary Reference Intakes (DRIs) of these nutrients established recently by the Food and Nutrition Board of the Institute of Medicine.

STUDY DESIGN

Population estimates of usual intake distributions of sodium, chloride (assumed to be equamolar to sodium), and potassium of 4- to 5-, 6- to 11-, and 12- to 24-month-old infants and toddlers were calculated and compared with DRIs of these nutrients by 0- to 6-month-old, 7- to 12-month-old, and 1- to 3-year-old children.

SUBJECTS

Infants and toddlers (n=3,022) who participated in the 2002 Feeding Infants and Toddlers Study.

STATISTICAL ANALYSES

Means and distributions (percentiles) of the usual intakes of sodium, chloride, and potassium were calculated using Institute of Medicine-recommended procedures and compared with the DRIs (ie, Adequate Intake [AI] and tolerable upper intake level [UL]).

RESULTS

Mean sodium and chloride intakes of 4- to 5-month-old infants (188 mg/day and 290 mg/day, respectively) were 57% greater than the AIs (120 mg/day and 180 mg/day) and mean potassium intake (730 mg/day) was 83% higher than the AI (400 mg/day). Mean sodium, chloride, and potassium intakes of 6- to 11-month-old infants were 493 mg/day, 761 mg/day, and 1,225 mg/day, respectively-33%, 33%, and 75% higher than the AIs of these nutrients for this age group (sodium, 370 mg/day; chloride, 570 mg/day; potassium, 700 mg/day). Even the 10th percentile of potassium intake of this age group was greater than the AI. The usual mean sodium and chloride intakes of 12- to 24-month-old toddlers (1,638 mg/day and 2,528 mg/day, respectively) were 64% higher than the AIs (1,000 mg/day and 1,540 mg/day, respectively) and the usual mean sodium and chloride intakes of 58% of this age group were above the ULs. In contrast, mean potassium intake of 12- to 24-month-old toddlers (1,971 mg/day) was only 66% of the AI (3,000 mg/day). At all ages, sources of sodium, chloride, and potassium intakes reflected current feeding guidelines, primarily human milk and formula prior to 6 months of age and primarily cow's milk and table foods after 1 year of age.

CONCLUSIONS

Mean sodium and chloride intakes of infants and toddlers who participated in the 2002 Feeding Infants and Toddlers Study exceeded the recently established AIs of these nutrients and the mean intake of 58% of toddlers exceeded the ULs. Mean potassium intake of infants also exceeded the AI of potassium, but the mean potassium intake of toddlers was only 66% of the AI. Whether current intakes of sodium, chloride, and potassium by infants and toddlers are problematical is not clear. Nonetheless, it seems desirable to bring these intakes closer to AIs. This can be accomplished by continuing breast- or formula-feeding and delaying the introduction of cow's milk; limiting the amount of salt added to home-prepared foods; limiting the intake of high-sodium foods, such as processed meats and salty snacks; and increasing the intake of fruits (high potassium and low sodium content) and vegetables (moderate potassium and sodium content).

The role of essential fatty acids in development

The presence of docosahexaenoic acid (DHA) and arachidonic acid (ARA) in human milk but not in infant formula, coupled with lower plasma and brain lipid contents of DHA in formula-fed than in breast-fed infants and reports of higher IQ in individuals who were breast-fed versus formula-fed as infants, suggest that exogenous DHA (and ARA) may be essential for optimal development. Thus, since 1990, several studies have examined the impact of formulas containing DHA or DHA plus ARA on visual function and neurodevelopmental outcome. Some of these studies have shown benefits but others have not. These results leave largely unanswered the question of whether these fatty acids are beneficial for either the term or preterm infant. However, evidence that preterm infants might benefit is somewhat more convincing than that for term infants. Despite the limited evidence for efficacy, formulas supplemented with DHA and ARA are now available and appear to be safe.

Effects of maternal docosahexaenoic acid intake on visual function and neurodevelopment in breastfed term infants

BACKGROUND

Normal brain and visual development is thought to require exogenous docosahexaenoic acid (DHA; 22:6n-3) intake, but the amount needed is debatable. Because the supplementation of breastfeeding mothers with DHA increases the DHA content of their infants' plasma lipids, we hypothesized that it might also improve brain or visual function in the infants.

OBJECTIVE

The objective was to determine the effect of DHA supplementation of breastfeeding mothers on neurodevelopmental status and visual function in the recipient infant.

DESIGN

Breastfeeding women received capsules containing either a high-DHA algal oil ( approximately 200 mg DHA/d) or a vegetable oil (no DHA) for 4 mo after delivery. Outcome variables included the fatty acid pattern of maternal plasma phospholipid and milk lipids 4 mo postpartum, the fatty acid pattern of plasma phospholipids and visual function in infants at 4 and 8 mo of age, and neurodevelopmental indexes of the infants at 12 and 30 mo of age.

RESULTS

Milk lipid and infant plasma phospholipid DHA contents of the supplemented and control groups were approximately 75% and approximately 35% higher, respectively, at 4 mo postpartum. However, neither the neurodevelopmental indexes of the infants at 12 mo of age nor the visual function at 4 or 8 mo of age differed significantly between groups. In contrast, the Bayley Psychomotor Development Index, but not the Mental Development Index, of the supplemented group was higher (P < 0.01) at 30 mo of age.

CONCLUSION

DHA supplementation of breastfeeding mothers results in higher infant plasma phospholipid DHA contents during supplementation and a higher Bayley Psychomotor Development Index at 30 mo of age but results in no other advantages either at or before this age.

Supplementation with aromatic amino acids improves leucine kinetics but not aromatic amino acid kinetics in infants with infection, severe malnutrition, and edema

We investigated whether supplementation with an aromatic amino acid (AAA) cocktail consisting of 0.5 mmol each of phenylalanine, tryptophan, and tyrosine compared with isonitrogenous amounts of alanine (Ala) would improve measures of protein kinetics in 14 (8 with AAA, 6 Ala) children with edematous malnutrition (aged 6-24 mo) during the infected acute malnourished state. Supplementation started immediately after the baseline experiment, 2 d postadmission and continued to the end of the acute phase of treatment. The second (postsupplementation) experiment was done approximately 12 d postadmission. We measured leucine kinetics, phenylalanine and tyrosine fluxes, using an i.g. 8-h prime continuous infusion of (2)H(3)-leucine, and an i.v. 6-h prime continuous infusion of (13)C-leucine, (2)H(2)-tyrosine, and (2)H(5)-phenylalanine in the fed state. Leucine flux tended to be faster (P = 0.06) in the AAA group compared with Ala group after supplementation (mean difference +/- SEM): 22.6 +/- 10.9 micromol/(kg . h). The rate of leucine appearance from protein breakdown [28.1 +/- 9.4 micromol/(kg . h)] and the nonoxidative disposal of leucine [i.e., leucine to protein synthesis; 35.4 +/- 12.9 micromol/(kg . h)] were faster (P < 0.02) in the AAA group than in the Ala group. There was no significant effect of supplementation on leucine splanchnic metabolism, phenylalanine, and tyrosine fluxes. These findings are consistent with the hypothesis that the blunting of the protein catabolic response to infection in children with edematous malnutrition syndrome is due to limited availability of aromatic amino acids.

Monounsaturated fatty acid intake by children and adults: temporal trends and demographic differences

Epidemiologic evidence suggests that dietary monounsaturated fatty acids (MUFA) may have a beneficial health effect. Twenty-four-hour dietary intake data collected on 10-year-olds from 1978 to 1994 and on children and adults (ages 0-30 years) were examined for time, age, gender, ethnic, and geographic location differences in MUFA intake. Children's percent energy from MUFA decreased significantly from 1978 (14.1%) to 1994 (11.9%) with intake of oleic acid decreasing from 33.9 g/day (1973) to 25.7 g/day (1994). In 1994-96, percent energy from MUFA was 13% for children and adults aged 12 to 30 years, with 5% from palmitoleic acid and 93% from oleic acid. Males and blacks had significantly higher MUFA intake across all age groups than females and whites. Intakes of MUFA increased from 0 to 11 years of age to young adulthood (12-19 years), with no further increase at 20 to 30 years of age. Intakes of MUFA were lowest in the Northeast and highest in the Midwest. There were differences in food sources of MUFA by age group. For children 0 to 5 years of age, major sources were whole milk, peanut butter, 2% milk, and French fries; for children 6 to 11 years of age, major sources were whole milk, peanut butter, French fries, and 2% milk; for children 12 to 19 years of age, French fries, salt snacks, whole milk, and meat pizza were the major sources; for adults, French fries, whole milk, potato chips, and ground beef were the most common sources of MUFA. U.S. children and adults displayed temporal trends and demographic differences in intakes and food sources of MUFA. The implications of these changes and differences on biologic risk factors for specific chronic diseases warrant further investigation.

Polyunsaturated fatty acids and gene expression

PURPOSE OF REVIEW

This review focuses on the effect(s) of n-3 polyunsaturated fatty acids on gene transcription as determined by data generated using cDNA microarrays. Introduced within the past decade, this methodology allows detection of the expression of thousands of genes simultaneously and, hence, is a potentially powerful tool for studying the regulation of physiological mechanisms that are triggered or inhibited by nutrients.

RECENT FINDINGS

Recent data generated with cDNA microarrays not only confirm the effects of n-3 polyunsaturated fatty acids on regulation of lipolytic and lipogenic gene expression as determined by more traditional methods but also emphasize the tissue specificity of this regulation. cDNA microarray experiments also have expanded our understanding of the role of n-3 polyunsaturated fatty acids in regulation of expression of genes involved in many other pathways. These include: oxidative stress response and antioxidant capacity; cell proliferation; cell growth and apoptosis; cell signaling and cell transduction.

SUMMARY

The cDNA microarray studies published to date show clearly that n-3 polyunsaturated fatty acids, usually provided as fish oil, modulate expression of a number of genes with such broad functions as DNA binding, transcriptional regulation, transport, cell adhesion, cell proliferation, and membrane localization. These effects, in turn, may significantly modify cell function, development and/or maturation.

Plausible mechanisms for effects of long-chain polyunsaturated fatty acids on growth

A few studies conducted over the past decade suggest that formulas supplemented with long-chain polyunsaturated n-3 fatty acids may adversely affect growth of preterm infants. Others suggest that a high intake of alpha-linolenic acid (ALA; 18:3 n-3), the precursor of the long-chain polyunsaturated n-3 fatty acids, also may limit growth. The majority of studies, however, have not shown an effect of either long-chain polyunsaturated n-3 fatty acids or their precursor on growth. Nonetheless, the importance of growth during infancy and the possibility that these fatty acids may inhibit growth under some circumstances makes the issue worthy of further consideration. At the very least, plausible mechanisms for such an effect of n-3 PUFA on growth should be considered. These include (1) altered nutrient intake, absorption, and/or utilization; (2) low plasma and tissue contents of arachidonic acid (ARA;20:4 n-6); (3) an imbalance between n-6 and n-3 LCPUFA eicosanoid precursors and, hence, the eicosanoids produced from each; (4) altered membrane characteristics; and (5) effects on gene expression. Each of these is discussed. It is concluded that any or all are feasible but that none can be specifically implicated. Moreover, since few studies were designed specifically to assess growth, the reported effects of n-3 PUFA on growth could represent chance findings secondary to the suboptimal design. Furthermore, although additional data are needed for a definitive conclusion, the observed effects on growth, regardless of mechanism, does not appear to be biologically significant.

The protein metabolic response to HIV infection in young children

BACKGROUND

Growth failure often precedes secondary infections in HIV-infected infants and children, suggesting that inadequate protein deposition may be an early manifestation of infection by the virus. However, the protein metabolic response elicited by the virus in young children is unknown.

OBJECTIVE

We compared children with HIV infection and age-matched children without HIV infection with regard to whole-body and splanchnic protein kinetics and synthesis of acute phase proteins (APPs).

DESIGN

Whole-body and splanchnic leucine kinetics and fractional and absolute synthesis rates of 2 positive and 4 negative APPs were measured in 6 asymptomatic, HIV-infected children (4 males and 2 females) aged 6-17 mo and 4 uninfected children (3 females and 1 male) aged 7-9 mo who were in the fed state.

RESULTS

Compared with the control children, the HIV-infected children had significantly lower dietary energy and protein intakes and leucine balance and significantly faster leucine flux and fractional splanchnic leucine extraction; there was no significant difference between the groups in leucine oxidation rates. The HIV-infected children also had significantly higher plasma concentrations and absolute synthesis rates of the positive APPs and a significantly higher fractional synthesis rate of fibrinogen. The concentrations of 2 of the 4 negative APPs, albumin and HDL apolipoprotein A-I, were significantly lower in the HIV-infected children but were not associated with slower synthesis rates.

CONCLUSIONS

Children with HIV infection but without secondary infection have reduced protein balance because of an inability to down-regulate protein catabolism. Furthermore, the acute phase protein response elicited by HIV infection is characterized by higher concentrations and synthesis rates of positive APPs without lower concentrations of some negative APPs.

Concurrent and predictive validity of the cognitive adaptive test/clinical linguistic and auditory milestone scale (CAT/CLAMS) and the Mental Developmental Index of the Bayley Scales of Infant Development

The Cognitive Adaptive Test/Clinical Linguistic and Auditory Milestone Scale (CAT/CLAMS) was designed for use by primary pediatric health care providers to identify children with developmental delays. This study assesses the concurrent and predictive validity of CAT/CLAMS developmental quotient (DQ) scores and the Mental Developmental Index (MDI) of the Bayley Scales of Infant Development in healthy children without risk factors for developmental delay. Overall CAT/CLAMS DQ scores correlated significantly with Bayley MDI scores at both 12 (r = 0.393; p = 0.008) and 30 months (r = 0.742; p = 0.0001) of age. Overall CAT/CLAMS DQ scores at 12 months of age also correlated modestly with Bayley MDI scores at 30 months of age (r = 0.181; p = 0.036). Despite its modest predictive validity at 12 months, its satisfactory concurrent validity plus its ease and speed of administration make the CAT/CLAMS a reasonable choice for assessment of early development by primary pediatric health care providers.

Effect of maternal docosahexaenoic acid supplementation on postpartum depression and information processing

OBJECTIVE

The purpose of this study was to determine the effect of docosahexaenoic acid supplementation on plasma phospholipid docosahexaenoic acid content and indices of depression and information processing for women who breast-feed.

STUDY DESIGN

Mothers who planned to breast-feed their infants were assigned randomly in a double-masked fashion to receive either docosahexaenoic acid (approximately 200 mg/d) or placebo for the first 4 months after the delivery. Major outcome variables included plasma phospholipid fatty acid patterns and scores on a self-rating questionnaire of current depression symptoms. A structured clinical interview of depression, scores on another self-rating questionnaire of depression symptoms, and a laboratory measure of information processing were obtained in subgroups of the total population.

RESULTS

Plasma phospholipid contents of docosahexaenoic acid at baseline were 3.15 +/- 0.78 and 3.31 +/- 0.70 (mg/dL of total fatty acids) in the docosahexaenoic acid and placebo groups, respectively. After 4 months, the plasma phospholipid docosahexaenoic acid content of the docosahexaenoic acid group was 8% higher (3.40 +/- 0.97 mg/dL), whereas that of the placebo group was 31% lower (2.27 +/- 0.87 mg/dL). Despite the higher plasma phospholipid docosahexaenoic acid content of the supplemented group after 4 months, there was no difference between groups in either self-rating or diagnostic measures of depression; information processing scores of the two groups also did not differ.

CONCLUSION

Docosahexaenoic acid supplementation ( approximately 200 mg/d) for 4 months after the delivery prevented the usual decline in plasma phospholipid docosahexaenoic acid content of women who breastfeed but did not influence self-ratings of depression, diagnostic measures of depression, or information processing.

Dietary fat has minimal effects on fatty acid metabolism transcript concentrations in pigs

Young, crossbred pigs were fed either a low-fat, corn-based diet; a high-fat, tallow-based diet with a considerable saturated fatty acid (FA) content; or a high-fat, fish oil-based diet with a considerable polyunsaturated FA content, for 14 d. There were six pigs per dietary group (approximately 4-wk-old with a body weight of 6.16 kg). The plasma and adipose tissue FA composition reflected the composition of the diet to a large extent, but also reflected de novo FA synthesis coupled with chain elongation and desaturation. The liver and skeletal muscle FA composition reflected the diet and endogenous synthesis, but the indications for preferential incorporation or exclusion of specific FA were greater in these tissues than in plasma or adipose tissue. An important transcription factor for adipocyte differentiation and other aspects of lipid metabolism is adipocyte determination and differentiation-dependent factor 1 (ADD1). Liver ADD1 messenger RNA (mRNA) tended to be decreased (P = 0.06) in the fish oil-fed group, as well as in the combined high-fat-fed groups (tallow + fish oil) compared to the low-fat-fed group (P = 0.06). The muscle acyl-CoA oxidase mRNA tended to be increased in the tallow-fed group and decreased in fish oil-fed groups (P = 0.06). The muscle carnitine palmitoyltransferase mRNA tended to be elevated in both fat-fed groups (P = 0.07). None of the adipose tissue mRNA were changed by the diet (P > 0.20). The observations suggest there are major differences between rodents and pigs in modulation of transcripts associated with lipid metabolism by the dietary FA composition or concentration. Also, in porcine adipose tissue, as well as in liver and skeletal muscle, these transcripts are rather refractory to modification by dietary FA.

The acute-phase protein response to infection in edematous and nonedematous protein-energy malnutrition

BACKGROUND

Immune structure and function are more compromised in edematous protein-energy malnutrition (PEM) than in nonedematous PEM. Whether the positive acute-phase protein (APP) response to infection is affected remains unknown.

OBJECTIVE

We assessed whether children with edematous PEM can mount a general APP response and compared the kinetic mechanisms of the response in children with edematous PEM with those in children with nonedematous PEM.

DESIGN

Plasma C-reactive protein, alpha(1)-acid glycoprotein, alpha(1)-antitrypsin, haptoglobin, and fibrinogen concentrations and the fractional and absolute synthesis rates of alpha(1)-antitrypsin, haptoglobin, and fibrinogen were measured in 14 children with edematous PEM, aged 11.4 +/- 2 mo, and 9 children with nonedematous PEM, aged 10.1 +/- 1.4 mo, at 3 times: approximately 2 d after hospital admission (period 1), when they were malnourished and infected; approximately 8 d after admission (period 2), when they were malnourished but free of infection; and approximately 54 d after admission (period 3), when they had recovered.

RESULTS

Children with edematous and nonedematous PEM had higher plasma concentrations of 4 of 5 APPs in period 1 than in period 3. The magnitude of the difference in concentration and in the rate of synthesis of the individual APPs was less in the children with edematous PEM than in those with nonedematous PEM. The kinetic data show that the characteristics of the APP response were different in the 2 groups.

CONCLUSIONS

These results suggest that severely malnourished children can mount only a partial APP response to the stress of infection and that the magnitude of this response is less in those with edema.

Response of splanchnic and whole-body leucine kinetics to treatment of children with edematous protein-energy malnutrition accompanied by infection

BACKGROUND

Although the reduction in whole-body protein turnover and net protein loss induced by protein-energy malnutrition (PEM) has been well documented, it is unclear whether the protein-sparing mechanisms elicited by chronically inadequate intakes of dietary protein and energy are affected by the protein catabolic response to infection.

OBJECTIVE

The objective of this study was to determine whether the presence of infection alters the PEM-induced reduction in whole-body protein metabolism.

DESIGN

We determined whole-body leucine kinetics in 4 boys and 3 girls aged 6-15 mo with edematous PEM and infection approximately 3 d after admission (study 1), when they were both infected and malnourished; approximately 11 d after admission (study 2), when infection had resolved but they were still anthropometrically malnourished; and at recovery (study 3), when weight-for-length was at least 90% of that expected.

RESULTS

The children had significantly less leucine flux in both study 1 and study 2 than they had in study 3. There were no significant differences in the amount of leucine released from protein breakdown or used for protein synthesis between study 1 and study 2. There were no significant differences in leucine balance or in either the amount or percentage of enteral leucine extracted by the splanchnic tissues among the 3 studies.

CONCLUSIONS

When subjects are in the fed state, severe PEM induces a marked reduction in whole-body protein synthesis and breakdown rates, and the presence of infection does not alter this adaptation and hence the overall protein balance. A corollary is that children with severe PEM do not mount a protein catabolic response to infection.

Cysteine supplementation improves the erythrocyte glutathione synthesis rate in children with severe edematous malnutrition

BACKGROUND

Children with severe edematous malnutrition have higher than normal oxidant damage and lower concentrations of the antioxidant reduced glutathione (GSH), which are associated with slower synthesis of GSH and with low extra- and intracellular concentrations of the precursor amino acid cysteine.

OBJECTIVE

We tested whether early dietary supplementation with cysteine could restore a normal GSH concentration and synthesis rate in these children.

DESIGN

Erythrocyte cysteine and GSH concentrations and the fractional and absolute synthesis rates of GSH were measured in 2 groups of 16 edematous malnourished children, 10 boys and 6 girls aged 6-18 mo, at 3 times after hospital admission: at approximately 2 d (period 1), when they were malnourished and infected; at approximately 11 d (period 2), when they were malnourished but cleared of infection; and at approximately 50 d (period 3), when they had recovered. Supplementation with either 0.5 mmol. kg(-1). d(-1) N-acetylcysteine (NAC group) or alanine (control group) started immediately after period 1 and continued until recovery.

RESULTS

From period 1 to period 2 the concentration and the absolute synthesis rate of GSH increased significantly (P < 0.05) in the NAC group but not in the control group. The increases in the GSH concentration and synthesis rate were approximately 150% and 510% greater, respectively, in the NAC group than in the control group. The increases in the NAC group were associated with a significant effect of supplement (P < 0.03) on erythrocyte cysteine concentration.

CONCLUSION

These results suggest that the GSH synthesis rate and concentration can be restored during the early phase of treatment if patients are supplemented with cysteine.

The fatty acid profile of buccal cheek cell phospholipids is a noninvasive marker of long-chain polyunsaturated Fatty Acid status in piglets

The fatty acid pattern of cheek cell phospholipids has been proposed as a noninvasive marker of long-chain polyunsaturated fatty acid (PUFA) status. However, the cheek cell phospholipid fatty acid pattern has been compared only with that of plasma and erythrocytes. The objective of this study was to assess the extent to which the fatty acid profile of cheek cell phospholipids reflects that of tissue phospholipids. Piglets (n = 31; 6 d old) were fed five formula diets differing in total fat and fatty acid composition. After 14 d of consuming the assigned diets, cheek cell plasma, erythrocyte, liver, muscle, adipose tissue, retina and brain samples were collected for determination of the phospholipid fatty acid patterns. There were significant correlations between the cheek cell phospholipid content of most PUFA and the content of these fatty acids in tissue phospholipids (r = 0.509-0.951, P < 0.01). The cheek cell phospholipid content of most of the PUFA, except 20:4(n-6), reflected that of other tissue phospholipids as well as, or nearly as well as the contents of plasma and/or erythrocyte phospholipids. The correlations between the 22:6(n-3) contents of cheek cell, plasma, or erythrocyte phospholipids and those of brain and retina phospholipids were relatively poor (r = 0.596-0.737, P < 0.001). We conclude that the fatty acid pattern of cheek cell phospholipid can be used as a noninvasive marker of PUFA status, but it is not a better index than the pattern of plasma or erythrocyte phospholipids, particularly for assessing the fatty acid pattern of organs with slow fatty acid incorporation and/or turnover rates.

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.

Fatty acid regulation of gene expression: a genomic explanation for the benefits of the mediterranean diet

The development of obesity and associated insulin resistance involves a multitude of gene products, including proteins involved in lipid synthesis and oxidation, thermogenesis, and cell differentiation. The genes encoding these proteins are in essence the blueprints that we have inherited from our parents. However, what determines the way in which blueprints are interpreted is largely dictated by a collection of environmental factors. The nutrients we consume are among the most influential of these environmental factors. During the early stages of evolutionary development, nutrients functioned as primitive hormonal signals that allowed the early organisms to turn on pathways of synthesis or storage during periods of nutrient deprivation or excess. As single-cell organisms evolved into complex life forms, nutrients continued to be environmental factors that interacted with hormonal signals to govern the expression of genes encoding proteins involved in energy metabolism, cell differentiation, and cell growth. Nutrients govern the tissue content and activity of different proteins by functioning as regulators of gene transcription, nuclear RNA processing, mRNA degradation, and mRNA translation, as well as functioning as posttranslational modifiers of proteins. One dietary constituent that has a strong influence on cell differentiation, growth, and metabolism is fat. The fatty acid component of dietary lipid not only influences hormonal signaling events by modifying membrane lipid composition, but fatty acids have a very strong direct influence on the molecular events that govern gene expression. In this review, we discuss the influence that (n-9), (n-6), and (n-3) fatty acids exert on gene expression in the liver and skeletal muscle and the impact this has on intra- and interorgan partitioning of metabolic fuels.

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.

Determination of nutritional requirements in preterm infants, with special reference to 'catch-up' growth

The usual recommendation for feeding preterm infants is to provide sufficient nutrients to support rates of growth and nutrient accretion equal to intrauterine rates. However, most preterm infants don't tolerate feedings immediately and, therefore, incur significant deficits prior to achieving sufficient intake to support growth. Furthermore, unless they receive nutrient intakes in excess of those usually recommended, they will be smaller than a fetus of the same postmenstrual age at discharge and remain smaller for some time thereafter. The consequences of these early deficits are not known with certainty but there is some evidence that they should be repleted as soon as possible. This requires a redefinition of requirements to include those for both normal growth and catch-up growth. Strategies for doing so include: more aggressive early parenteral nutrition to reduce the magnitude of early losses; greater enteral intakes of protein, and, perhaps, other nutrients once enteral feedings are tolerated; and more attention to nutrition post-discharge. Of these, the latter is somewhat problematic. This is because there seems to be a finite period - perhaps as brief as a few weeks - during which response to increased nutrient intake occurs. Firm data are limited, but those available suggest that current nutritional management of preterm infants can be improved. Whether this will have long-term benefits remains to be determined.

Impaired synthesis of DHA in patients with X-linked retinitis pigmentosa

Many patients with X-linked retinitis pigmentosa (XLRP) have lower than normal blood levels of the long-chain polyunsaturated omega3 fatty acid docosahexaenoic acid (DHA; 22:6omega3). This clinical trial was designed to test whether down-regulation of DHA biosynthesis might be responsible for these reduced DHA levels. DHA biosynthesis was assessed in five severely affected patients with XLRP and in five age-matched controls by quantifying conversion of [U-(13)C]alpha-linolenic acid (alpha-LNA) to [(13)C]DHA. Following oral administration of [U-(13)C]alpha-LNA, blood samples were collected at designated intervals for 21 days and isotopic enrichment of all omega3 fatty acids was determined by gas chromatography/mass spectroscopy. Activity of each metabolic step in the conversion of alpha-LNA to DHA was determined by comparison of the ratios of the integrated concentration of (13)C-product to (13)C-precursor in plasma total lipid fractions. The ratio of [(13)C]DHA to [(13)C]18:3omega3 (the entire pathway) and that of [(13)C]20:5omega3 to [(13)C]20:4omega3 (Delta(5)-desaturase) were significantly lower in patients versus controls (P = 0.03 and 0.05, respectively). The estimated biosynthetic rates of [(13)C]20:5omega3, [(13)C]22:5omega3, [(13)C]24:5omega3, [(13)C]24:6omega3, and [(13)C]22:6omega3 were significantly lower in XLRP patients (42%, 43%, 31%, 18%, and 32% of control values, respectively; P < 0.04), supporting down-regulation of Delta(5)-desaturase in XLRP. The disappearance of (13)C-labeled fatty acids from plasma was not greater in XLRP patients compared with controls, suggesting that XLRP was not associated with increased rates of fatty acid oxidation or other routes of catabolism.Thus, despite individual variation among both patients and controls, the data are consistent with a lower rate of Delta(5)-desaturation, suggesting that decreased biosynthesis of DHA may contribute to lower blood levels of DHA in patients with XLRP.

Internal consistency, temporal stability, and reproducibility of individual index scores of the Test of Variables of Attention in children with attention-deficit/hyperactivity disorder

Psychometric properties of the Test of Variables of Attention (TOVA) were examined in a cohort of children (n=63) strictly diagnosed with attention-deficit/hyperactivity disorder (AD/HD). Internal consistency was assessed via correlational analyses to determine the degree of agreement among various test portions. The temporal stability of errors of omission, errors of commission, response time, and response time variability was evaluated using test-retest reliability. Reproducibility of individual scores for the same indices was assessed using the Bland-Altman procedure. Select TOVA index scores exhibited high internal consistency in this cohort. Although the temporal stability of group scores (test-retest reliability) was satisfactory, individual test scores were less reproducible. Temporal stability and individual test-retest score agreement were greater for response time and response time variability than for errors of omission and errors of commission.

A randomized, double-blind, placebo-controlled trial of docosahexaenoic acid supplementation in children with attention-deficit/hyperactivity disorder

OBJECTIVE

To determine whether docosahexaenoic acid (DHA) supplementation for 4 months decreases the symptoms of attention-deficit/hyperactivity disorder (ADHD).

STUDY DESIGN

Sixty-three 6- to-12-year-old children with ADHD, all receiving effective maintenance therapy with stimulant medication, were assigned randomly, in a double-blind fashion, to receive DHA supplementation (345 mg/d) or placebo for 4 months. Outcome variables included plasma phospholipid fatty acid patterns, scores on laboratory measures of inattention and impulsivity (Test of Variables of Attention, Children's Color Trails test) while not taking stimulant medication, and scores on parental behavioral rating scales (Child Behavior Checklist, Conners' Rating Scale). Differences between groups after 4 months of DHA supplementation or placebo administration were determined by analysis of variance, controlling for age, baseline value of each outcome variable, ethnicity, and ADHD subtype.

RESULTS

Plasma phospholipid DHA content of the DHA-supplemented group was 2.6-fold higher at the end of the study than that of the placebo group (4.85 +/- 1.35 vs 1.86 +/- 0.87 mol % of total fatty acids; P <.001). Despite this, there was no statistically significant improvement in any objective or subjective measure of ADHD symptoms.

CONCLUSION

A 4-month period of DHA supplementation (345 mg/d) does not decrease symptoms of ADHD.