Zinc status and growth of children undergoing treatment for phenylketonuria

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 recommendations for pregnant women affected with phenylketonuria]

Prevention of embryopathy due to maternal phenylketonuria is possible thanks to a maternal-specific low-phenylalanine diet, which has to be started before conception and followed during the whole gestation. The setup of this diet implies knowing the recommended dietary allowances for normal pregnant women as well as for women with nutritional deficiencies. Women with phenylketonuria must be considered at risk for nutritional imbalance for two main reasons. First, most adult women with phenylketonuria have been on a vegetarian diet for many years without protein substitutes or medical control. Secondly, the strict diet for pregnant women with phenylketonuria may induce anorexia or nutritional deficits if it is not well tolerated or understood. Protein, iron, calcium, selenium, vitamin B 12 and caloric intakes are the most sensitive parameters. Close cooperation with an experienced medical and dietician team is required.

Immune status of children with phenylketonuria

OBJECTIVE

To determine the effect of differences in plasma phenylalanine (Phe) concentrations (< 363 umol/L, 363 to 605 umol/L, and > 605 umol/L) on hematological and immunological parameters in 22 children with phenylketonuria (PKU).

METHODS

Children with PKU were divided into one of three groups based on fasting plasma Phe levels. Hematologic and immunologic parameters of the children with PKU were compared between the groups and also compared with published values from age-matched children without PKU.

RESULTS

Hematologic and immunologic parameters did not differ among children with different plasma Phe concentrations. Specifically, no significant differences between groups of PKU children with differing plasma Phe levels were found for plasma levels of albumin, hemoglobin, amino acids, IgM, complement C3, interleukins 1 and 2, erythrocyte, leukocyte and differential cell counts, hematocrit, percentages and numbers of CD4+, CD8+, CD3+ and total lymphocytes, or CD4 to CD8 ratio. Mean plasma IgG and IgA concentrations of the PKU children were, however, significantly lower than values from similar aged children. Moreover, positive correlations were obtained between plasma albumin and percentages and numbers of CD3+ and CD4+, between plasma IgG and interleukins 1 and 2, and between intakes of energy, protein, iron and plasma IgG levels. No correlations were found between plasma Phe and immunological parameters.

CONCLUSION

While differences in plasma Phe concentrations up to concentrations of 866 umol/L do not appear to affect selected immune system parameters, further studies are needed to investigate the relationship between dietary nutrient intake, nutritional status, antibody biosynthesis and cytokine production. Assessment of plasma and cell membrane lipids and trace mineral status of PKU children would be helpful to determine if relationships exist between these nutrients and antibody production.

Hair zinc of young children from rural and urban areas in North Rhine-Westphalia, Federal Republic of Germany

Hair zinc levels were estimated by atomic absorption spectrophotometry in 474 children, aged 3-7 years, from 11 kindergartens in a highly industrialized and polluted area (Duisburg) and 8 kindergartens in a rural area of North Rhine-Westphalia. The mean hair zinc level amounted to 118 micrograms/g, increasing between the 4th and 7th year of life. At all ages the values from the urban toddlers were lower than from rural toddlers, and in both regions they were higher in winter than in summer. Children with frequent upper respiratory tract infections (greater than 6 infections/year) showed significantly lower zinc hair values, independent of their age. Low hair zinc values (below 70 micrograms/g) were frequently found, raising the question as to whether this is a normal, age-related phenomenon, or whether it indicates a suboptimal zinc status of young children from North Rhine-Westphalia.

Maternal phenylketonuria (PKU)--a review

This review points out the very high incidence of damage to the fetus in untreated maternal phenylketonuria (PKU). In classical cases, 92% of the offspring are mentally retarded, 73% have microcephaly, 40% are growth retarded at birth, and 12% have congenital anomalies. Less severe types of PKU and its variants and patients treated with a low phenylalanine diet during pregnancy have a much lower incidence of these defects in their offspring. Very promising results have been obtained in a small number of preconception and early first trimester treated patients under very strict dietary control. Nutrition of the mother and fetus is a major concern during the application of this restrictive diet and must be monitored closely to avoid fetal damage from malnutrition. A 7-year collaborative study of maternal PKU began in November 1984 in the US and Canada, but even in this well publicized study, many patients are presenting late for treatment. It is suggested that premarital and/or prenatal screening for maternal PKU should be initiated for the next generation.

Issues in the dietary management of phenylketonuria: breast-feeding and trace-metal nutriture

We have reviewed our experience with supplemental breast-feeding of the infant with PKU. Our results indicate no harmful nutritional effects of breast-feeding the child with PKU, in comparison with the traditional approach using formula or cow's milk for supplementation. In addition, breast-feeding may provide a source of emotional support for the mother during this difficult period of initial diagnosis and management. It is hoped that this may improve the family's adjustment to this chronic illness. Our work with breast-feeding led us to a consideration of trace-metal nutriture in children treated with these synthetic and semi-synthetic formulas. The results of these investigations suggest that there is a biochemically significant decrease in the bioavailability of zinc when these artificial formulas are used. While no clinical trace-metal deficiency has been described in treated PKU patients, we suggest that these nutritional deficits may relate to subtle abnormalities exhibited by these patients.

Problems related to diet management of maternal phenylketonuria

Provision of nutritionally complete elemental diets for pregnant women with PKU requires greater knowledge of 'conditionally' essential nutrient requirements than is presently available as well as application of known information. Formulation of elemental products needs to be improved to enhance aroma and taste and to decrease osmolality. Designers of the metal and vitamin components should keep in mind that a major portion (70-80%) of most of these nutrients must be obtained from the elemental products. Thus deletion of suspected essential minerals or vitamins could cause serious deficiencies. On the other hand, knowledge of appropriate ratios that make for improved trace metal absorption should be applied. Clinical nutritionists need to assist patients in selection of foods that are low in binding substances and provide 'conditionally' essential nutrients in adequate amounts. Closer cooperation between clinical nutritionists, nutrition scientists and food technologists should result in improved elemental products for care of pregnant women with PKU.

Biochemical and neuropsychological effects of elevated plasma phenylalanine in patients with treated phenylketonuria. A model for the study of phenylalanine and brain function in man

Phenylketonuria provides a human model for the study of the effect of phenylalanine on brain function. Although irreversible mental retardation is preventable through newborn diagnosis and dietary phenylalanine restriction, controversy exists regarding the effects of increased concentrations of phenylalanine in older patients. We have studied ten older, treated, phenylketonuric patients using a triple-blind, multiple trials, crossover design. Each patient was tested at the end of each of three 1-wk periods of high or low phenylalanine intakes. Tests included a repeatable battery of neuropsychological tests, analysis of plasma amino acids, and measurement of urine amino acids, phenyl organic acids, dopamine, and serotonin. In all 10 patients plasma phenylalanine rose (900-4,000 microM). In 9 of 10 patients there was an inverse relationship between plasma phenylalanine and urine dopamine excretion. When blood phenylalanine was elevated, these patients had prolonged performance times on neuropsychological tests of higher but not lower integrative function. Urinary serotonin fell during phenylalanine loading in six patients. The concentration of phenylacids in the urine was not proportional to the plasma phenylalanine at concentrations below 1.5 mM. In one patient, neither performance time nor dopamine excretion varied as blood phenylalanine rose or fell. We interpret these data as follows: blood phenylalanine above 1.3 mM impairs performance on neuropsychological tests of higher integrative function, this effect is reversible, and one mechanism may involve impaired biogenic amine synthesis.

The effect of treatment on zinc, copper and calcium status in children with phenylketonuria

The trace element status of 25 children receiving a low phenylalanine diet for a treatment of phenylketonuria was studied using hair and serum samples. Hair trace element and calcium concentrations were assayed using X-ray microanalysis and compared with samples from sibling controls. Plasma, zinc and copper levels were compared with unselected hospital attenders. PKU patients were found to have significantly lower hair zinc (P less than 0.001) and calcium (P less than 0.01) concentrations and significantly hair copper (P less than 0.001) concentrations compared with controls. Plasma zinc levels were below the lower limit of normal (9.6 mumol l-1) in 8 of 19 patients (42%) in whom it was measured. The relative zinc deficiency in PKU patients may result from a competitive inhibition of absorption by copper or other metals supplemented in the diet.