Neuropsychological outcome of subjects participating in the PKU adult collaborative study: a preliminary review

Tackling frontal lobe-related functions in PKU through functional brain imaging: a Stroop task in adult patients

BACKGROUND

Profound mental retardation in phenylketonuria (PKU) can be prevented by a low phenylalanine (Phe) diet. However, even patients treated early have inconsistently shown deficits in several frontal lobe-related neuropsychological tasks such as the widely accepted Stroop task. The goal of this study was to investigate whether adult patients exhibit altered brain activation in Stroop-related locations in comparison to healthy controls and if an acute increase in blood Phe levels in patients has an effect on activation patterns.

METHODS

Seventeen male, early-treated patients with classic PKU (mean ± SD age: 31.0 ± 5.2 years) and 15 male healthy controls (32.1 ± 6.4 years) were compared using a color-word matching Stroop task in a functional magnetic resonance imaging (fMRI) study at 3T. Participants were scanned twice, and an oral Phe load (100 mg/kg body weight) was administered to patients prior to one of the fMRI sessions (placebo-controlled). Activity in brain regions that are known to be involved in Stroop tasks was assessed.

RESULTS

PKU patients exhibited poorer accuracy in incongruent trials. Reaction times were not significantly different. There were no consistent differences in BOLD activations in Stroop-associated brain regions. The oral Phe administration had no significant effect on brain activity.

CONCLUSIONS

Neither a generally slower task performance nor distinctively altered functioning of brain networks involved in a task representing a subset of dopamine-dependent executive functions could be proven. Decreased accuracy and inconsistent findings in posterior areas necessitate further study of frontal-lobe functioning in PKU patients in larger study samples.

Neuroradiological findings of an adolescent with early treated phenylketonuria: is phenylalanine restriction enough?

Phenylketonuria is caused by mutations in the enzyme phenylalanine hydroxylase gene, that can result in abnormal concentrations of phenylalanine on blood, resulting in metabolites that can cause brain damage. The treatment is based on dietary restriction of phenylalanine, and noncompliance with treatment may result in damage of the brain function. Brain abnormalities can be seen on magnetic resonance imaging of these individuals. Studies indicate that the appearance of abnormalities in white matter reflects high levels of phenylalanine on the blood. This case will show the clinical and neuroradiological aspects of a teenager with constant control of phenylalanine levels. Despite the continuous monitoring and early treatment, the magnetic resonance imaging identified impressive abnormalities in the white matter. This leads us to one question: is the restriction of phenylalanine sufficient to prevent changes in the white matter in patients with phenylketonuria?

A cross-sectional study of docosahexaenoic acid status and cognitive outcomes in females of reproductive age with phenylketonuria

Diet therapy for phenylketonuria (PKU) requires restricted phenylalanine (Phe) intake, with the majority of protein and other nutrients coming from synthetic medical food. The fatty acid docosahexaenoic acid (DHA) is important in brain development and function; however, there are reports of low blood DHA concentrations in people treated for PKU. Although the implications of this low blood DHA are unclear, subtle cognitive deficits have been reported in those treated early and continuously for PKU. For this study, we investigated the relationship between DHA status and cognitive performance in 41 females 12 years and older with PKU. Participants were attending the baseline visit of a research-based camp or a supplementation trial. We assessed the domains of verbal ability, processing speed, and executive function using standardized tests, and the proportions of DHA in plasma and red blood cell (RBC) total lipids using gas chromatography/mass spectrometry. Percent plasma and RBC total lipid DHA were significantly lower in the participants compared with laboratory controls (P < .001), and participants consumed no appreciable DHA according to diet records. Plasma and RBC DHA both negatively correlated with plasma Phe (P < .02), and performance on the verbal ability task positively correlated with RBC DHA controlling for plasma Phe (R = .32, P = .03). The relationship between DHA and domains related to verbal ability, such as learning and memory, should be confirmed in a controlled trial. Domains of processing speed and executive function may require a larger sample size to clarify any association with DHA.

Follow up of phenylketonuria patients

In recent years our understanding of the follow up policies for PKU has increased substantially. In particular, we now understand the importance of maintaining control of blood phenylalanine (phe) concentrations life-long to achieve the best long-term neuropsychological outcomes. The concordance with the follow up strategy remains a key challenge for the future, especially with respect to adolescents and young adults. The recent therapies could ease the burden of the dietary phe restriction for PKU patients and their families. The time may be right for revisiting the guidelines for follow up of PKU in order to address a number of important issues related to PKU management: promotion of breastfeeding to complementary feeding up to 2 years of age for prevention of early growth retardation and later overweight development, treatment advancements for metabolic control, blood phe and tyr variability, routine screening measures for nutritional biomarkers, neurocognitive and psychological assessments, bone pathology, understanding the challenges of compliance and transitioning into adulthood as an individual with PKU and addressing unmet needs in this population.

Adult phenylketonuria outcome and management

The problem to evaluate treatment outcome in adult PKU (phenylketonuric) patients lies in the heterogeneity of the adult PKU population. This heterogeneity is not only based on the different treatment history of every individual patient but also on the different severity of the underlying defect of the enzyme phenylalanine hydroxylase. Recent, partly double blind studies in adult PKU patients further support recommendation for lifelong treatment. However, it has become evident that dietary treatment is suboptimal and continuation to adulthood often not accepted. Late detected PKU patients (up to 4-6 years of age) benefit from strict dietary treatment and are able to catch up in intellectual performance. Untreated, severely retarded patients with behavioral changes may benefit from introduction of dietary treatment. However, individual decision is necessary and based on the personal situation of the patient. In early and well treated patients a number of studies have demonstrated that cognitive and neurosychologic tests are different from controls. In addition there is evidence that patients with higher blood phenylalanine (phe) levels demonstrate more often psychiatric symptoms like depression and anxiety. Medical problems are more often observed: there are certain risks as impaired growth, decreased bone mineral density and nutrional deficits probably caused by dietary treatment with an artificial protein substitute and/or missing compliance with an unpleasant diet. The long term risk of a strict dietary treatment must be balanced with the risk of higher blood phe (mean blood phenylalanine >600-900 μmol/L) on cognitive and neuropsychological functions and psychiatric symptoms. Further studies should consider the role of blood phe exposure for brain development in childhood and for brain function in all ages. Besides mean blood phe, fluctuation of blood phe over time is important. Fluctuation of blood phe is decreased by sapropterin treatment in responsive patients which would on the long term may have positive effects on cognitive outcome. Further studies also should include adult PKU patients.

Executive strategic processing during verbal fluency performance in children with phenylketonuria

In the current study, we examined a specific aspect of executive abilities, strategic processing, in 32 children with early-treated phenylketonuria (PKU) and 41 typically-developing control children. To do so, clustering and switching were assessed during semantic (animal, food/drink) and phonemic (S, F) fluency tasks. Specifically, number of words generated, number of subcategory clusters, number of words in subcategory clusters, and number of switches between subcategories were analyzed to provide a refined analysis of strategic processing. Compared with controls, children with PKU generated significantly fewer words and made significantly fewer switches between subcategories in the food/drink trial and the phonemic fluency condition. Number of switches was associated with number of words generated in these tasks. In addition, a significant interaction between age and group in number of switches for the food/drink trial reflected a greater increase in number of switches for the control than PKU group as a function of increasing age. These results suggest impairment in frontally-mediated aspects of strategic processing in children with early-treated PKU and indicate that strategic processing should be evaluated carefully as these children age.

Suboptimal outcomes in patients with PKU treated early with diet alone: revisiting the evidence

BACKGROUND

The National Institute of Health (NIH) published a Consensus Statement on the screening and management of Phenylketonuria (PKU) in 2000. The panel involved in the development of this consensus statement acknowledged the lack of data regarding the potential for more subtle suboptimal outcomes and the need for further research into treatment options. In subsequent years, the approval of new treatment options for PKU and outcome data for patients treated from the newborn period by dietary therapy alone have become available. We hypothesized that a review of the PKU literature since 2000 would provide further evidence related to neurocognitive, psychosocial, and physical outcomes that could serve as a basis for reassessment of the 2000 NIH Consensus Statement.

METHODS

A systematic review of literature residing in PubMed, Scopus and PsychInfo was performed in order to assess the outcome data over the last decade in diet-alone early-treated PKU patients to assess the need for new recommendations and validity of older recommendations in light of new evidence.

RESULTS

The majority of publications (140/150) that contained primary outcome data presented at least one suboptimal outcome compared to control groups or standardized norms/reference values in at least one of the following areas: neurocognitive/psychosocial (N=60; 58 reporting suboptimal outcomes); quality of life (N=6; 4 reporting suboptimal outcomes); brain pathology (N=32; 30 reporting suboptimal outcomes); growth/nutrition (N=34; 29 reporting suboptimal outcomes); bone pathology (N=9; 9 reporting suboptimal outcomes); and/or maternal PKU (N=19; 19 reporting suboptimal outcomes).

CONCLUSIONS

Despite the remarkable success of public health programs that have instituted newborn screening and early introduction of dietary therapy for PKU, there is a growing body of evidence that suggests that neurocognitive, psychosocial, quality of life, growth, nutrition, bone pathology and maternal PKU outcomes are suboptimal. The time may be right for revisiting the 2000 NIH Consensus Statement in order to address a number of important issues related to PKU management, including treatment advancements for metabolic control in PKU, blood Phe variability, neurocognitive and psychological assessments, routine screening measures for nutritional biomarkers, and bone pathology.

Performance of children with phenylketonuria in the Developmental Screening Test--Denver II

BACKGROUND

phenylketonuria is an autosomal recessive disorder resulting from the mutation of a gene located in chromosome 12q22-24.1.

AIM

to describe the performance of children with classic phenylketonuria, who were diagnosed and treated early, in the Development Screening Test Denver - II.

METHOD

participants were 20 children with phenylketonuria, ranging in age from 3 and 6 years, and 10 children with typical language development, paired by gender, age and socioeconomic level to the research group. The plasmatic phenylalanine measure and the neurological, psychological and social information were gathered in the data base of the Neonatal Screening Programs for Metabolic disorder. Assessment consisted on the application of the Development Screening Test Denver II. A descriptive statistical analysis and the Mann Whitney test were used in order to characterize the tested skills. For the measurements of the plasmatic phenylalanine blood levels the values considered for analysis were: below 2 mg/dL, above 4 mg/dL, reference values between 2 and 4 mg/dL, of all exams performed during the participants'lives; maximum and minimum values and values obtained on the day of the screening application.

RESULTS

comparison between the groups indicated statistically significant differences for the personal-social and language areas.

CONCLUSION

children who were diagnosed and treated early for phenylketonuria present deficits in the personal-social and language areas. Also, even when receiving follow-up and undergoing treatment, these children presented difficulties in maintaining normal plasmatic phenylalanine levels.

How individuals with phenylketonuria experience their illness: an age-related qualitative study

BACKGROUND

The aim of the study was to explore the illness experience of individuals affected by phenylketonuria (PKU) and its differences in different patient age groups.

METHODS

A qualitative-interpretative methodology was used through in-depth interviews. Textual data were explored using the principles of grounded theory.

RESULTS

Forty-seven patients participated in the study, aged from 10 to >25 years old. The results suggested the age-related PKU experience: (1) a paradox, either to feel normal but isolated from the social context, or to be different while participating in the convivial aspects of the social being; and (2) the need for education about the disease tailored to the individual and growing needs. Specific themes seem to characterize each age range.

CONCLUSIONS

This study constitutes a first attempt at understanding PKU from a non-medical-biological perspective.

Desenvolvimento infantil na fenilcetonúria: atuação fonoaudiológica

TEMA: a fenilcetonúria é manifestada por deficiência parcial ou total da enzima hepática fenilalanina hidroxilase que, em excesso, tem efeito tóxico para as funções do sistema nervoso central, refletindo no desenvolvimento global do indivíduo. OBJETIVO: apresentar as alterações no desenvolvimento verificadas em estudos científicos com indivíduos portadores de fenilcetonúria e refletir sobre as habilidades relacionadas ao desenvolvimento da linguagem. CONCLUSÃO: indivíduos com fenilcetonúria são de risco para alterações nas funções cognitivas, linguísticas, motoras e comportamental-social. Déficits nas funções executivas e habilidades neuropsicolinguísticas são comuns e acarretam defasagens para o desenvolvimento das habilidades de linguagem. Os achados justificam o encaminhamento de proposta para o Ministério da Saúde com vistas à contratação de Fonoaudiólogos nos Programas de Triagem Neonatal credenciados.

5-Hydroxytryptophan rescues serotonin response to stress in prefrontal cortex of hyperphenylalaninaemic mice

Adult early treated hyperphenylalaninaemic patients can show specific deficits of prefrontal cortical functions. The development of additional therapeutic strategies for these patients requires the understanding of the mechanisms involved in phenylalanine-dependent impairment of fronto-cortical functions. We tested the hypothesis of phenylalanine interference with aminergic neurotransmission in the prefrontal cortex by evaluating, in vivo, amine release in adult Pah(enu2) mice, the genetic model of phenylketonuria. Mice of healthy background responded to a psychogenic stressor with the classic time-dependent increase of norepinephrine, dopamine and serotonin release from prefrontal cortical terminals. Neither the dopaminergic nor the serotoninergic responses were observable in the Pah(enu2) mice. Temporary reduction of circulating phenylalanine, by phenylalanine-free diet without amino- acid supplement, promoted recovery of the serotonin response only, demonstrating direct interference with serotonin synthesis in the mature brain. Evaluation of different steps of serotonin synthesis in the prefrontal cortex of hyperphenylalaninaemic mice demonstrated inhibition of cortical tryptophan hydroxylase activity. Finally, systemic administration of 5-hydroxytryptophan, the product of tryptophan hydroxylase activity, allowed frontal cortical serotonin response to stress in hyperphenylalaninaemic mice. Collectively, these results demonstrate that hyperphenylalaninaemia interferes with the ability of the mature prefrontal cortex to respond to psychological challenges, point to serotonin synthesis as the target of phenylalanine interference, and support the use of 5-hydroxytryptophan in lifelong treatment of hyperphenylalaninaemic subjects.

Large neutral amino acids supplementation in phenylketonuric patients

Phenylketonuria is an inborn error of amino acid metabolism that results in severe mental retardation if not treated early and appropriately. The traditional treatment, consisting of a low-phenylalanine diet, is usually difficult to maintain throughout adolescence and adulthood, resulting in undesirable levels of blood phenylalanine and consequent neurotoxicity. The neurotoxicity of phenylalanine is enhanced by its transport mechanism across the blood-brain barrier, which has the highest affinity for phenylalanine compared with the other large neutral amino acids that share the same carrier. The supplementation of large neutral amino acids in phenylketonuric patients has been showing interesting results. Plasma phenylalanine levels can be reduced, which may guarantee important metabolic and clinical benefits to these patients. Although long-term studies are needed to determine the efficacy and safety of large neutral amino acids supplements, the present state of knowledge seems to recommend their prescription to all phenylketonuric adult patients who are non-compliant with the low-phenylalanine diet.

Efficacy of sapropterin dihydrochloride in increasing phenylalanine tolerance in children with phenylketonuria: a phase III, randomized, double-blind, placebo-controlled study

OBJECTIVE

To evaluate the ability of sapropterin dihydrochloride (pharmaceutical preparation of tetrahydrobiopterin) to increase phenylalanine (Phe) tolerance while maintaining adequate blood Phe control in 4- to 12-year-old children with phenylketonuria (PKU).

STUDY DESIGN

This international, double-blind, randomized, placebo-controlled study screened for sapropterin response among 90 enrolled subjects in Part 1. In Part 2, 46 responsive subjects with PKU were randomized (3:1) to sapropterin, 20 mg/kg/d, or placebo for 10 weeks while continuing on a Phe-restricted diet. After 3 weeks, a dietary Phe supplement was added every 2 weeks if Phe control was adequate.

RESULTS

The mean (+/-SD) Phe supplement tolerated by the sapropterin group had increased significantly from the pretreatment amount (0 mg/kg/d) to 20.9 (+/-15.4) mg/kg/d (P < .001) at the last visit at which subjects had adequate blood Phe control (<360 micromol/L), up to week 10. Over the 10-week period, the placebo group tolerated only an additional 2.9 (+/-4.0) mg/kg/d Phe supplement; the mean difference from the sapropterin group (+/-SE) was 17.7 +/- 4.5 mg/kg/d (P < .001). No severe or serious related adverse events were observed.

CONCLUSIONS

Sapropterin is effective in increasing Phe tolerance while maintaining blood Phe control and has an acceptable safety profile in this population of children with PKU.

The truth of treating patients with phenylketonuria after childhood: the need for a new guideline

In recent years, an increasing number of national guidelines on the treatment of phenylketonuria (PKU) have emerged. Most of these guidelines are dedicated to the care of children, while less attention is paid to the care of adults, although all guidelines underline the importance of diet for life. This review aims to summarize issues that need to be addressed within a guideline on the treatment of PKU, especially when care for patients beyond childhood is concerned. In this respect, it is of importance that adult patients, both willing and unwilling to be treated, need a guideline for care and follow-up. In PKU there is certainly a need for an improved unified guideline, especially after childhood, although many of the considerations in this article also apply to recommendations for treatment of children. Such a guideline will be a tool to improve treatment in PKU patients but should also include recommendations for collecting data for clinical and research purposes. Guideline development should also focus on nutritional, neuropsychological and psychosocial issues and not only on target plasma phenylalanine concentrations. In addition, guidelines must address not only what has to be done but also how it can be done, thereby improving concordance with the recommendations for treatment and management.

Reduced cerebral fluoro-L-dopamine uptake in adult patients suffering from phenylketonuria

Deficiency of phenylalanine hydroxylase activity in phenylketonuria (PKU) causes an excess of phenylalanine (Phe) throughout the body, predicting impaired synthesis of catecholamines in the brain. To test this hypothesis, we used positron emission tomography (PET) to measure the utilization of 6-[18F]fluoro-L-DOPA [corrected] (FDOPA) in the brain of adult patients suffering from PKU and in healthy controls. Dynamic 2-h long FDOPA emission recordings were obtained in seven adult PKU patients (five females, two males; age: 21 to 27 years) with elevated serum Phe levels, but lacking neurologic deficits. Seven age-matched, healthy volunteers were imaged under identical conditions. The utilization of FDOPA in striatum was calculated by linear graphical analysis (k3S, min(-1)), with cerebellum serving as a nonbinding reference region. The time to peak activity in all brain time-radioactivity curves was substantially delayed in the PKU patients relative to the control group. The mean magnitude of k3S in the striatum of the PKU patients (0.0052+/-0.0004 min(-1)) was significantly lower than in the control group (0.0088+/-0.0009 min(-1)) (P<0.001). There was no significant correlation between individual serum Phe levels and k3S. The unidirectional clearance of FDOPA to brain was impaired in adult patients suffering from PKU, presumably reflecting the competitive inhibition of the large neutral amino acid carrier by Phe. Assuming this competition to be spatially uniform, the relationship between striatum and cerebellum time-activity curves additionally suggests inhibition of DOPA efflux, possibly also due to competition from Phe. The linear graphical analysis shows reduced k3S in striatum, indicating reduced DOPA decarboxylase activity.

Phenylketonuria: outcomes and treatment

Phenylketonuria (PKU) is an inborn error of metabolism affecting approximately one in every 10,000 infants born in Europe and the USA. Unless treated with a phenylalanine-restricted diet beginning in infancy, PKU can be associated with mental retardation, seizures, eczema and other symptoms. Treatment prevents the most severe consequences of PKU, but compliance with the strict dietary regimen is poor, especially in adolescents and adults. Despite the decline in IQ and increased emotional problems associated with poor adherence to the diet, few novel advances in treatments for PKU have occurred since 1963, when it became the first condition for which newborn screening was available. Sparked in part by acceptance of the policy of lifelong dietary treatment, alternative therapies are being investigated. These include innovations in production of low-protein foods, psychosocial interventions, new medications, enzyme therapy and perhaps even gene therapy in the future.

Phenylketonuria: questioning the gospel

Phenylketonuria (PKU) was first described over 70 years ago, treatment was developed 50 years ago and universal newborn PKU screening was introduced 40 years ago. Phenylalanine-restricted dietary treatment has prevented mental retardation in thousands of individuals worldwide. We acknowledge, however, that there is still much to learn in the field. The incidence of mental retardation in untreated PKU is likely to be considerably less than the original estimates. Since dietary control is suboptimal in late childhood, adolescence and adulthood, alternative methods of treatment are being explored. These include large neutral amino acids, phenylalanine ammonia lyase, tetrahydrobiopterin and gene replacement. Evidence has surfaced that the semisynthetic, low-protein diet used to treat PKU may be deficient in certain important nutrients. Maternal PKU treatment may be successful even if initiated as late as 8-10 weeks into pregnancy. A plea is made for the immediate establishment of adult treatment centers for PKU (and other inherited metabolic diseases) for long-term treatment, follow-up and research.

Epilepsy in Phenylketonuria: A Complex Dependence on Serum Phenylalanine Levels

PURPOSE

Phenylketonuria (PKU) is a disorder of phenylalanine (Phe) metabolism that frequently results in epilepsy if a low Phe diet was not implemented at birth. The mechanisms by which Phe affects the brain are poorly understood.

METHODS

Audiogenic seizures (AGS) were studied in female homozygous Pah(enu2) BTBR (PKU) mice.

RESULTS

Adult PKU mice, 18-20 weeks of age, in contrast to wild-type and heterozygous counterparts, exhibited a full range of AGS. Younger PKU mice, 5-7 weeks of age, had higher serum Phe levels (2.22 +/- 0.20 mM) in comparison with the adult animals (1.72 +/- 0.05 mM) and were not susceptible to AGS. Among adult mice, animals susceptible to AGS had significantly lower serum Phe levels (1.62 +/- 0.06 mM) in comparison with those resistant to AGS (1.86 +/- 0.07 mM). Susceptibility to AGS tended to increase in the afternoon when serum Phe concentration decreased in comparison to evening and morning. Normalization of serum Phe level by instituting a low Phe diet generally prevented susceptibility to AGS within 12 h. Although return to a standard diet raised Phe levels to hyperphenylalaninemic within 12 h in animals treated with a low Phe diet for 2 weeks, more than 7 weeks were needed for a complete resumption of AGS.

CONCLUSIONS

Transient decrease in Phe levels within hyperphenylalaninemic range may be a necessary condition for PKU-related seizures to occur. A low Phe diet prevents susceptibility to seizures, which can resume with the significant delay after termination of dietary treatment.

A neuropsychological profile of off-diet adults with phenylketonuria

The metabolic disorder phenylketonuria (PKU) is treated early by a low-phenylalanine diet. While this prevents global cognitive impairment, some patients still experience cognitive and neurophysiological abnormalities. Neuropsychological testing of early treated, currently off-diet, PKU patients attending an adult PKU clinic showed a reduction in the Perceptual Organization Index (POI), Processing Speed Index (PSI) from the Wechsler Adult Intelligence Scale Third Edition (WAIS-III), and Part A of the Trail Making Test for the PKU group relative to controls. Taken together, these results supported a profile of reduced information-processing speed.

The effects of large neutral amino acid supplements in PKU: an MRS and neuropsychological study

OBJECTIVE

To determine the effects of large neutral amino acid (LNAA) supplements on brain and plasma phenylalanine (Phe) levels and other metabolites in early treated subjects with classical phenylketonuria (PKU), and to investigate the relationship between these metabolites and neuropsychological performance.

METHODS

This was a prospective, double blind, cross over study consisting of four two-week phases with a 4 week washout period. Sixteen subjects (7 males), with classical PKU were recruited into the study and completed all 4 phases. Each phase consisted of either the LNAA supplement or placebo, and either the patient's usual medical product or not. Subjects were instructed to follow their usual Phe restricted diet, maintain energy intake and complete a 3-day food record during each phase. At the end of each phase, brain Phe and other metabolites were measured by proton magnetic resonance spectroscopy (MRS), and plasma amino acids quantified. A detailed neuropsychological assessment was performed on the same day as the MRS and plasma collection.

RESULTS

There was no correlation between plasma and brain Phe, but few of the plasma Phe readings were over 1200 micromol/L. Plasma Phe decreased with LNAA supplementation when patients were not taking their medical formula. LNAA supplementation had a specific impact on executive functions particularly in verbal generativity and cognitive flexibility. Measures of attention were better on medical product, with or without LNAA supplements.

CONCLUSIONS

LNAA supplementation was associated with a trend to a lowering of plasma Phe levels. LNAA supplementation had a specific impact on executive functions particularly in verbal generativity and flexibility. For individuals already complying with diet and PKU medical product, additional supplementation with LNAA is of limited value. LNAA supplementation may be of benefit to those unable to comply with PKU medical product by reducing plasma Phe, perhaps by competing with Phe at the level of transport across the gut.

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.

Meta-Analysis of Neuropsychological Symptoms of Adolescents and Adults with PKU

Phenylketonuria (PKU; OMIM 261600) is an autosomal recessive inborn error of phenylanaline metabolism. PKU is characterized by deficient or defective phenylalanine hydroxylase activity and persistantly increased levels of the essential amino acid phenylalanine in the circulation. The present article examines current understanding of the etiology of PKU, along with a meta-analysis examining neuropsychological and intellectual presentations in continuously treated adolescents and adults. Patients with PKU differed significantly from controls on Full-Scale IQ, processing speed, attention, inhibition, and motor control. Future research utilizing an integrative approach and detailed analysis of specific cognitive domains will assist both the scientist and clinician, and ultimately the patient.

Consensus national sur la prise en charge des enfants dépistés avec une hyperphénylalaninémie

Phenylketonuria (PKU) is an inherited metabolic disease affecting about one birth out of 15 000. From 1978, a national systematic neonatal screening was set up in France with a regional organisation. French rational and guidelines have been established by the national PKU group with the collaboration of all the physicians responsible for the regional centres. These guidelines specify the minimal diagnosis procedures leading to an optimal treatment of all patients. A low-phenylalanine diet must be started as soon as possible in the neonatal period for all newborns whose phenylalanine levels are above 10 mg/dl. The dietary control must keep the phenylalanine plasma levels between 2 and 5 mg/dl until 10 years of age. After this age, several data argue for a progressive and controlled relaxation of the diet, keeping the phenylalanine level below 15 mg/dl until the end of the adolescence and below 20 to 25 mg/dl in adulthood. All PKU patients must be followed up for life, in order to screen those who may not bear the diet relaxation and in order to strictly prevent maternal PKU deleterious consequences.