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.

Effects of early maternal docosahexaenoic acid intake on neuropsychological status and visual acuity at five years of age of breast-fed term infants.

OBJECTIVE: We previously reported better psychomotor development at 30 months of age in infants whose mothers received a docosahexaenoic acid (DHA) (22:6n-3) supplement for the first 4 months of lactation. We now assess neuropsychological and visual function of the same children at 5 years of age. STUDY DESIGN: Breastfeeding women were assigned to receive identical capsules containing either a high-DHA algal oil (∼200 mg/d of DHA) or a vegetable oil (containing no DHA) from delivery until 4 months postpartum. Primary outcome variables at 5 years of age were measures of gross and fine motor function, perceptual/visual-motor function, attention, executive function, verbal skills, and visual function of the recipient children at 5 years of age. RESULTS: There were no differences in visual function as assessed by the Bailey-Lovie acuity chart, transient visual evoked potential or sweep visual evoked potential testing between children whose mothers received DHA versus placebo. Children whose mothers received DHA versus placebo performed significantly better on the Sustained Attention Subscale of the Leiter International Performance Scale (46.5 ± 8.9 vs 41.9 ± 9.3, P < .008) but there were no statistically significant differences between groups on other neuropsychological domains. CONCLUSIONS: Five-year-old children whose mothers received modest DHA supplementation versus placebo for the first 4 months of breastfeeding performed better on a test of sustained attention. This, along with the previously reported better performance of the children of DHA-supplemented mothers on a test of psychomotor development at 30 months of age, suggests that DHA intake during early infancy confers long-term benefits on specific aspects of neurodevelopment.

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.

aP2-Cre-mediated inactivation of acetyl-CoA carboxylase 1 causes growth retardation and reduced lipid accumulation in adipose tissues.

Adipose tissue is one of the major sites for fatty acid synthesis and lipid storage. We generated adipose (fat)-specific ACC1 knockout (FACC1KO) mice using the aP2-Cre/loxP system. FACC1KO mice showed prenatal growth retardation; after weaning, however, their weight gain was comparable to that of wild-type (WT) mice on a normal diet. Under lipogenic conditions of fasting/re-feeding a fat-free diet, lipid accumulation in adipose tissues of FACC1KO mice was significantly decreased; this is consistent with a 50-66% reduction in the ACC activity in these tissues compared with that of WT mice. Surprisingly, FACC1KO mice manifested skeletal growth retardation phenotype accompanied by decreased chondrocyte proliferation in the growth plate and lower trabecular bone density. In addition, there was about a 30% decrease in serum insulin-like growth factor I (IGF1), and while the serum leptin level was decreased by about 50%, it did not counteract the osteopenic effects of IGF1 on the bone. Fatty acid analyses of mutant bone lipids revealed relatively higher levels of C18:2n-6 and C18:3n-3 and lower levels of their elongation C20 homologs than that of WT cohorts, leading to lower levels of C20 homologs and bone development. Moreover, aP2-Cre-mediated ACC1 inactivation in bone tissue led to a decreased number of osteoblasts but not of osteoclasts. The downregulation of ACC1 on osteoblastogenesis may be the cause for the osteopenia phenotype of FACC1KO bone homeostasis.

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.

The Test of Variables of Attention (TOVA): internal consistency (Q1 vs. Q2 and Q3 vs. Q4) in children with attention deficit/hyperactivity disorder (ADHD).

The internal consistency of the Test of Variables of Attention (TOVA) was examined in a cohort of 6- to 12-year-old children (N = 63) strictly diagnosed with ADHD. The internal consistency of errors of omission (OMM), errors of commission (COM), response time (RT), and response time variability (RTV) of different test conditions (stimulus infrequent condition [Q1 vs. Q2] and stimulus frequent condition [Q3 vs. Q4]) was assessed via correlation analyses. All TOVA index scores under investigation assessing its internal consistency exhibited statistically significant correlations. All correlations fell in the moderate-high range.

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.

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.

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.

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).

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, alpha-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 alpha-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.

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.