Adult phenylketonuria

Targeting phenylalanine assemblies as a prospective disease-modifying therapy for phenylketonuria

Phenylketonuria is characterized by the accumulation of phenylalanine, resulting in severe cognitive and neurological disorders if not treated by a remarkably strict diet. There are two approved drugs today, yet both provide only a partial solution. We have previously demonstrated the formation of amyloid-like toxic assemblies by aggregation of phenylalanine, suggesting a new therapeutic target to be further pursued. Moreover, we showed that compounds that halt the formation of these assemblies also prevent their resulting toxicity. Here, we performed high-throughput screening, searching for compounds with inhibitory effects on phenylalanine aggregation. Morin hydrate, one of the most promising hits revealed during the screen, was chosen to be tested in vivo using a phenylketonuria mouse model. Morin hydrate significantly improved cognitive and motor function with a reduction in the number of phenylalanine brain deposits. Moreover, while phenylalanine levels remained high, we observed a recovery in dopaminergic, adrenergic, and neuronal markers. To conclude, the ability of Morin hydrate to halt phenylalanine aggregation without reducing phenylalanine levels implies the toxic role of the phenylalanine assemblies in phenylketonuria and opens new avenues for disease-modifying treatment.

How does excess phenylalanine affect the packing density and fluidity of a lipid membrane?

Phenylketonuria (PKU) is an autosomal recessive error of phenylalanine (Phe) metabolism, where untreated Phe becomes cytotoxic. Previous experiments found that excess Phe decreases the packing density and increases the fluidity and permeability of a lipid membrane. It was proposed that Phe forms cytotoxic nanoscopic amyloid-like fibrils. In another study, the Phe fibrils were not visible near the lipid membrane. So, what leads to the deleterious effect of Phe on the lipid membrane? We put forward a molecular mechanism for the observed effect of excess Phe on the lipid membrane using all-atom molecular dynamics simulation. This study suggests that Phe monomers spontaneously intercalate into the membrane and form small hydrogen-bonded clusters, some of which locally perturb the membrane. These local effects result in an overall reduction in the membrane packing density, enhancement of membrane fluidity, and an increase of water permeability, observed in experiments. The present study does not observe any effect of the nanoscopic fibrillar structure of Phe on the membrane. This study, therefore, provides alternative insights into the excess Phe cytotoxicity in PKU disease.

Kinetic and Thermodynamic Driving Factors in the Assembly of Phenylalanine-Based Modules

The formation of ordered protein and peptide assemblies is a phenomenon related to a wide range of human diseases. However, the mechanism of assembly at the molecular level remains largely unknown. Minimal models enable the exploration of the underlying interactions that are at the core of such self-assembly processes. In particular, the ability of phenylalanine, a single aromatic amino acid, to form an amyloid-like structure has challenged the previous dogma viewing a peptide backbone as a prerequisite for assembly. The driving forces controlling the nucleation and assembly in the absence of a peptide backbone remain to be identified. Here, aiming to unravel these forces, we explored the kinetics and thermodynamics of three phenylalanine-containing molecules during their assembly process: the amino acid phenylalanine, which accumulates in phenylketonuria patients, the diphenylalanine core-motif of the amyloid β peptide related to Alzheimer's disease, and the extended triphenylalanine peptide which forms a range of distinct nanostructures in vitro. We found that the aggregation propensity, regarding the critical monomer concentration, strongly increases with size, with triphenylalanine being the most aggregation-prone species under our experimental conditions. In the context of classical nucleation theory, this increase in aggregation propensity can be attributed to the larger free energy decrease upon aggregation of larger peptides and is not due to the presence/absence of a peptide bond per se. Taken together, this work provides insights into the aggregation processes of chemically simple systems and suggests that both backbone-containing peptides and backbone-lacking amino acids assemble through a similar mechanism, thus supporting the classification of amino acids in the continuum of amyloid-forming building blocks.

Phenylalanine Interacts with Oleic Acid-Based Vesicle Membrane. Understanding the Molecular Role of Fibril-Vesicle Interaction under the Context of Phenylketonuria

In the present contribution, on the basis of a spectroscopic and microscopic investigation, the characterization and photophysics of various assemblies of oleic acid/oleate solution at three pH values, namely, 8.28, 9.72, and 11.77, were explored. The variation in the dynamic response of aqua molecules in and around the assemblies has been interrogated by a picoseconds solvation dynamics experiment using a time-correlated single-photon counting setup employing coumarin-153 as a probe. On the one hand, the time-resolved fluorescence anisotropy measurement along with the fluorescence correlation spectroscopy experiment was executed to extract information regarding the comparison of the extent of the internal restricted confinement of these assemblies. On the other hand, an effort to investigate the cross-interaction between the self-assembled architectures of l-phenylalanine (l-Phe), responsible for phenylketonuria (PKU) disorder, and the oleic acid at the vesicle-forming pH established that the l-Phe fibrillar morphologies strongly alter the dynamic properties of the vesicle membrane formed by the oleic acid. Specifically, the interaction of the l-Phe assemblies with the oleic acid vesicle membrane is found to introduce the flexibility of the vesicle membrane and alter the hydration properties of the membrane. To track the fibril-induced alterations of the oleic acid vesicle properties, various spectroscopic and microscopic investigations were performed. The mutual reconciliation of the experimental outputs, therefore, portrays the state of the art, which accounts for the fibril-induced alterations of the properties of the oleic acid vesicle membrane, the mimicking setup of the cellular membrane, thereby informing us that alterations of such a property of the membrane should be taken into active consideration during the rational development of therapeutic modulators against disorders like PKU.

Characterization of an engineered live bacterial therapeutic for the treatment of phenylketonuria in a human gut-on-a-chip

Engineered bacteria (synthetic biotics) represent a new class of therapeutics that leverage the tools of synthetic biology. Translational testing strategies are required to predict synthetic biotic function in the human body. Gut-on-a-chip microfluidics technology presents an opportunity to characterize strain function within a simulated human gastrointestinal tract. Here, we apply a human gut-chip model and a synthetic biotic designed for the treatment of phenylketonuria to demonstrate dose-dependent production of a strain-specific biomarker, to describe human tissue responses to the engineered strain, and to show reduced blood phenylalanine accumulation after administration of the engineered strain. Lastly, we show how in vitro gut-chip models can be used to construct mechanistic models of strain activity and recapitulate the behavior of the engineered strain in a non-human primate model. These data demonstrate that gut-chip models, together with mechanistic models, provide a framework to predict the function of candidate strains in vivo.

Identifying and elucidating the roles of Y198N and Y204F mutations in the PAH enzyme through molecular dynamic simulations

Phenylketonuria is an autosomal recessive disorder caused by mutations in the phenylalanine hydroxylase gene. In phenylketonuria causes various symptoms including severe mental retardation. PAH gene of a classical Phenylketonuria patient was sequenced, and two novel heterozygous mutations, p.Y198N and p.Y204F, were found. This study aimed to reveal the impacts of these variants on the structural stability of the PAH enzyme. In-silico analyses using prediction tools and molecular dynamics simulations were performed. Mutations were introduced to the wild type catalytic monomer and full length tetramer crystal structures. Variant pathogenicity analyses predicted p.Y198N to be damaging, and p.Y204F to be benign by some prediction tools and damaging by others. Simulations suggested p.Y198N mutation cause significant fluctuations in the spatial organization of two catalytic residues in the temperature accelerated MD simulations with the monomer and increased root-mean-square deviations in the tetramer structure. p.Y204F causes noticeable changes in the spatial positioning of T278 suggesting a possible segregation from the catalytic site in temperature accelerated MD simulations with the monomer. This mutation also leads to increased root-mean-square fluctuations in the regulatory domain which may lead to conformational change resulting in inhibition of dimerization and enzyme activation. Our study reports two novel mutations in the PAH gene and gives insight to their effects on the PAH activity. MD simulations did not yield conclusive results that explains the phenotype but gave plausible insight to possible effects which should be investigated further with in-silico and in-vitro studies to assess the roles of these mutations in etiology of PKU. Communicated by Ramaswamy H. Sarma.

The Adult Phenylketonuria (PKU) Gut Microbiome

Phenylketonuria (PKU) is an inborn error of phenylalanine metabolism primarily treated through a phenylalanine-restrictive diet that is frequently supplemented with an amino acid formula to maintain proper nutrition. Little is known of the effects of these dietary interventions on the gut microbiome of PKU patients, particularly in adults. In this study, we sequenced the V4 region of the 16S rRNA gene from stool samples collected from adults with PKU (n = 11) and non-PKU controls (n = 21). Gut bacterial communities were characterized through measurements of diversity and taxa abundance. Additionally, metabolic imputation was performed based on detected bacteria. Gut community diversity was lower in PKU individuals, though this effect was only statistically suggestive. A total of 65 genera across 5 phyla were statistically differentially abundant between PKU and control samples (p < 0.001). Additionally, we identified six metabolic pathways that differed between groups (p < 0.05), with four enriched in PKU samples and two in controls. While the child PKU gut microbiome has been previously investigated, this is the first study to explore the gut microbiome of adult PKU patients. We find that microbial diversity in PKU children differs from PKU adults and highlights the need for further studies to understand the effects of dietary restrictions.

Occurrence of Inborn Errors of Metabolism in Newborns, Diagnosis and Prophylaxis

Inborn errors of metabolism (IEM) are a heterogeneous group of rare genetic disorders that are generally transmitted as autosomal or X-linked recessive disorders. These defects arise due to mutations associated with specific gene(s), especially the ones associated with key metabolic enzymes. These enzymes or their product(s) are involved in various metabolic pathways, leading to the accumulation of intermediary metabolite(s), reflecting their toxic effects upon mutations. The diagnosis of these metabolic disorders is based on the biochemical analysis of the clinical manifestations produced and their molecular mechanism. Therefore, it is imperative to devise diagnostic tests with high sensitivity and specificity for early detection of IEM. Recent advances in biochemical and polymerase chain reaction-based genetic analysis along with pedigree and prenatal diagnosis can be life-saving in nature. The latest development in exome sequencing for rapid diagnosis and enzyme replacement therapy would facilitate the successful treatment of these metabolic disorders in the future. However, the longterm clinical implications of these genetic manipulations is still a matter of debate among intellectuals and requires further research.

Functional vitamin B12 deficiency in phenylketonuria patients and healthy controls: An evaluation with combined indicator of vitamin B12 status as a biochemical index

BACKGROUND

Vitamin B12 deficiency frequently appears in phenylketonuria patients having a diet poor in natural protein. The aims of this study were to evaluate vitamin B12 status in phenylketonuria patients by using combined indicator of vitamin B12 status (cB12) as well as methylmalonic acid and homocysteine, more specific and sensitive markers, in comparison with healthy controls.

METHODS

Fifty-three children and adolescents with phenylketonuria under dietary treatment and 30 healthy controls were assessed cross-sectionally. Serum vitamin B12 and folate concentrations were analysed by chemiluminescence immunoassay. Plasma methylmalonic acid and total homocysteine concentrations were measured by liquid chromatography-tandem mass spectrometry and liquid chromatography, respectively. cB12 was calculated by using a formula involving blood parameters.

RESULTS

Methylmalonic acid and folate concentrations in phenylketonuria group were higher compared with controls. Methylmalonic acid concentrations were high in 56.5% of the patients and 26.7% of the controls with normal vitamin B12 concentrations. Based on cB12, a significant difference within the normal values was detected between the groups. However, although 24.5% of phenylketonuria patients and 13.3% of controls had decreased vitamin B12 status according to cB12, there was no significant difference.

CONCLUSION

Children and adolescents with phenylketonuria having a strict diet can be at risk of functional vitamin B12 deficiency. This deficiency can be accurately determined by measuring methylmalonic acid concentrations. Calculation of cB12 as a biochemical index did not provide additional information compared with the measurement of methylmalonic acid alone, but may be helpful for classification of some patients with increased methylmalonic acid as having adequate vitamin B12 status.

Genetic variants of the phenylalanine hydroxylase gene in patients with phenylketonuria in the northeast of Iran

Background Phenylketonuria (PKU) is a common metabolic disorder with great burden if left untreated or undiagnosed. Genetic variations in the phenylalanine hydroxylase (PAH) gene may be widely varied across different regions of a country. By knowing the most common mutations, diagnostic work-ups will be offered sooner and with lower costs for patients. The present study defines the most common genetic variations in the PAH gene in Khorasan province of Iran. Methods The present cross-sectional study took place in Khorasan province of Iran within a 6-year period starting from 2012 to 2018. Every patient who had been referred as suspicious PKU cases or referred for prenatal diagnosis was included in the present study. Results A total number of 122 individuals with a mean age of 26.22 years were enrolled in the present study. The most frequent genetic variations in the PAH gene were c.1066-11G > A and c.143 T > C. Exon 7 carried the most genetic variations compared to any single exon. Also, three patients had compound heterozygous status for c.727 C > T/c.1066-11 G > A in exon 7 and 11 of the PAH gene. Conclusions Mutations in the PAH gene are widely varied among different populations, and our results confirmed this fact. Determination of the most prevalent mutations and polymorphisms in each region will reduce the time and cost of diagnosing such preventable diseases and will therefore reduce the disease burden.

Antagonist Effects of l-Phenylalanine and the Enantiomeric Mixture Containing d-Phenylalanine on Phospholipid Vesicle Membrane

One of the congenital flaws of metabolism, phenylketonuria (PKU), is known to be related to the self-assembly of toxic fibrillar aggregates of phenylalanine (Phe) in blood at elevated concentrations. Our experimental findings using l-phenylalanine (l-Phe) at millimolar concentration suggest the formation of fibrillar morphologies in the dry phase, which in the solution phase interact strongly with the model membrane composed of 1,2-diacyl-sn-glycero-phosphocholine (LAPC) lipid, thereby decreasing the rigidity (or increasing the fluidity) of the membrane. The hydrophobic interaction, in addition to the electrostatic attraction of Phe with the model membrane, is found to be responsible for such phenomena. On the contrary, various microscopic observations reveal that such fibrillar morphologies of l-Phe are severely ruptured in the presence of its enantiomer d-phenylalanine (d-Phe), thereby converting the fibrillar morphologies into crushed flakes. Various biophysical studies, including the solvation dynamics experiment, suggest that this l-Phe in the presence of d-Phe, when interacting with the same model membrane, now reverts the rigidity of the membrane, i.e., increases the rigidity of the membrane, which was lost due to interaction with l-Phe exclusively. Fluorescence anisotropy measurements also support this reverse rigid character of the membrane in the presence of an enantiomeric mixture of amino acids. A comprehensive understanding of the interaction of Phe with the model membrane is further pursued at the single-molecular fluorescence detection level using fluorescence correlation spectroscopy (FCS) experiments. Therefore, our experimental conclusion interprets a linear correlation between increased permeability and enhanced fluidity of the membrane in the presence of l-Phe and certifies d-Phe as a therapeutic modulator of l-Phe fibrillar morphologies. Further, the study proposes that the rigidity of the membrane lost due to interaction with l-Phe was reinstated-in fact, increased-in the presence of the enantiomeric mixture containing both d- and l-Phe.

Adult patient perspectives on phenylketonuria care: Highlighting the need for dedicated adult management and services

Phenylketonuria (PKU) is an autosomal recessive metabolic disorder characterized by an inability to metabolize the amino acid phenylalanine (Phe). If left untreated, an accumulation of Phe results in neurodevelopmental, neurological and psychological impairments. Advancements in detection and treatment of PKU have improved outcomes and life expectancy for these patients, emphasizing the need for life-long, specialized care. Due to the paucity of adult-focused PKU clinics, patients who are well into adulthood are still being treated in pediatric centers. This retrospective study evaluates the perceived expectations, benefits and challenges of 50 adult PKU patients (mean age 31.3 ± 10.4 years) transitioning from a pediatric to adult care setting using a transition questionnaire administered at the first clinic visit at the adult PKU care center. Patients reported a lack of access to adult resources and adult-specific PKU educational material in their pediatric PKU clinic. In contrast, the established relationships with the pediatric health care team and familiarity with treatment plans were aspects of pediatric care that patients enjoyed. The results from this study will contribute to the optimization of adult PKU patient care, establishment of strategies for transitioning adults with PKU and other metabolic disorders from pediatric to adult care, and support the need to establish adult-only PKU care facilities.

Transition of patients with mucopolysaccharidosis from paediatric to adult care

Mucopolysaccharidoses (MPS) are rare disorders associated with enzyme deficiencies, resulting in glycosaminoglycan (GAG) accumulation in multiple organ systems. As patients increasingly survive to adulthood, the need for a smooth transition into adult care is essential. Using case studies, we outline strategies and highlight the challenges of transition, illustrating practical solutions that may be used to optimise the transition process for patients with MPS disorders.

Seven MPS case studies were provided by four European inherited metabolic disease centres; six of these patients transferred to an adult care setting and the final patient remained under paediatric care. Of the patients who transferred, age at the start of transition ranged between 14 and 18 years (age at transfer ranged from 16 to 19 years).

While there were some shared features of transition strategies, they varied in duration, the healthcare professionals involved and the management of adult patients with MPS. Challenges included complex symptoms, patients' unwillingness to attend appointments with unfamiliar team members and attachment to paediatricians. Challenges were resolved by starting transition at an early age, educating patients and families, and providing regular communication with and reassurance to the patient and family. Sufficient time should be provided to allow patients to understand their responsibilities in the adult care setting while feeling assured of continued support from healthcare professionals. The involvement of a coordinated multidisciplinary team with expertise in MPS is also key. Overall, transition strategies must be comprehensive and individualised to patients' needs.

Seeding of proteins into amyloid structures by metabolite assemblies may clarify certain unexplained epidemiological associations

The accumulation of various metabolites appears to be associated with diverse human diseases. However, the aetiological link between metabolic alteration and the observed diseases is still elusive. This includes the correlation between the abnormally high levels of homocysteine and quinolinic acid in Alzheimer's disease, as well as the accumulation of oncometabolites in malignant processes. Here, we suggest and discuss a possible mechanistic insight into metabolite accumulation in conditions such as neurodegenerative diseases and cancer. Our hypothesis is based on the demonstrated ability of metabolites to form amyloid-like structures in inborn error of metabolism disorders and the potential of such metabolite amyloids to promote protein aggregation. This notion can provide a new paradigm for neurodegeneration and cancer, as both conditions were linked to loss of function due to protein aggregation. Similar to the well-established observation of amyloid formation in many degenerative disorders, the formation of amyloids by tumour-suppressor proteins, including p53, was demonstrated in malignant states. Moreover, this new paradigm could fill the gap in understanding the high occurrence of specific types of cancer among genetic error of metabolism patients. This hypothesis offers a fresh view on the aetiology of some of the most abundant human maladies and may redirect the efforts towards new therapeutic developments.

Phenylalanine intercalation parameters for liquid-disordered phase domains - a membrane model study

BACKGROUND

Propensity of phenylalanine (Phe) for nonpolar environments drives its intercalation into phospholipid membranes, which has been implicated in metabolic and neurological disorders. The knowledge of Phe intercalation parameters can be instrumental in understanding various membrane processes triggered by interactions with Phe, in particular the early events leading to the formation of nucleation/docking sites for the self-assembly of Phe amyloid fibrils at the membrane surface.

RESULTS

In this study, we used monolayers of phosphatidylethanolamine (DPPE) and phosphatidylcholine (DPPC) to mimic the membrane outer leaflet. Its initial interaction with Phe was modeled by injecting Phe into the aqueous phase underneath the monolayer. Constant pressure insertion assays augmented with epifluorescence microscopy imaging were used to monitor Phe intercalation. Our primary goal was to determine the Phe intercalation area, A Phe. Two values were obtained for A Phe, 33 ± 2 and 48 ± 3 Å2.

CONCLUSIONS

Phe appeared to discriminate between DPPE and DPPC packing, and use two modes of intercalation. The area of A Phe 33 ± 2 Å2 is consistent with a Phe monomer intercalating into membrane by inserting the phenyl ring nearly normal to the membrane surface. This mode has been found to operate in DPPE membranes. For DPPC membranes however, the value of A Phe = 48 ± 3 Å2 suggests that, from saline, Phe tends to intercalate as a larger species plausibly dragging along a counterion, Na+, in a Na+(Phe) complex.

Semisynthetic sensor proteins enable metabolic assays at the point of care

Monitoring metabolites at the point of care could improve the diagnosis and management of numerous diseases. Yet for most metabolites, such assays are not available. We introduce semisynthetic, light-emitting sensor proteins for use in paper-based metabolic assays. The metabolite is oxidized by nicotinamide adenine dinucleotide phosphate, and the sensor changes color in the presence of the reduced cofactor, enabling metabolite quantification with the use of a digital camera. The approach makes any metabolite that can be oxidized by the cofactor a candidate for quantitative point-of-care assays, as shown for phenylalanine, glucose, and glutamate. Phenylalanine blood levels of phenylketonuria patients were analyzed at the point of care within minutes with only 0.5 microliters of blood. Results were within 15% of those obtained with standard testing methods.

A comprehensive study of phenylalanine hydroxylase gene mutations in the Iranian phenylketonuria patients

Phenylketonuria (PKU) is a metabolic disorder caused by mutations in the phenylalanine hydroxylase (PAH) gene. After thalassemia, PKU is considered as the most common autosomal recessive diseases in the Iranian population. Therefore, an efficient diagnostic strategy is required to identify disease-causing mutations in this population. Following our first report in 2003, here we presented a comprehensive study on the mutation spectrum of the PAH gene in the Iranian population. This study was performed on 280 unrelated chromosomes from 140 Iranian patients with classic PKU. All 13 exons as well as exon-intron boundaries of the PAH gene were analyzed by direct DNA sequencing. Thirty four different mutations were identified by a mutation detection rate of 100%. IVS10-11G > A, p.P281L, R261Q, p.F39del and IVS11+1G > C were the most prevalent mutations with frequencies of 26.07%, 19.3%, 12.86%, 6.07 and 3.93%, respectively. All other mutations represented a relative frequency less than 3.5%. The data from this study provided a comprehensive spectrum of the PAH gene mutations which can facilitate carrier detection and prenatal diagnosis of PKU disease in the Iranian population.

Quinolinic Acid Amyloid-like Fibrillar Assemblies Seed α-Synuclein Aggregation

Quinolinic acid (QA), a downstream neurometabolite in the kynurenine pathway, the biosynthetic pathway of tryptophan, is associated with neurodegenerative diseases pathology. Mutations in genes encoding kynurenine pathway enzymes, which control the level of QA production, are linked with elevated risk of developing Parkinson's disease. Recent findings have revealed the accumulation and deposition of QA in post-mortem samples, as well as in cellular models of Alzheimer's disease and related disorders. Furthermore, intrastriatal inoculation of mice with QA results in increased levels of phosphorylated α-synuclein and neurodegenerative pathological and behavioral characteristics. However, the cellular and molecular mechanisms underlying the involvement of QA accumulation in protein aggregation and neurodegeneration remain elusive. We recently established that self-assembled ordered structures are formed by various metabolites and hypothesized that these "metabolite amyloids" may seed amyloidogenic proteins. Here we demonstrate the formation of QA amyloid-like fibrillar assemblies and seeding of α-synuclein aggregation by these nanostructures both in vitro and in cell culture. Notably, α-synuclein aggregation kinetics was accelerated by an order of magnitude. Additional amyloid-like properties of QA assemblies were demonstrated using thioflavin T assay, powder X-ray diffraction and cell apoptosis analysis. Moreover, fluorescently labeled QA assemblies were internalized by neuronal cells and co-localized with α-synuclein aggregates. In addition, we observed cell-to-cell propagation of fluorescently labeled QA assemblies in a co-culture of treated and untreated cells. Our findings suggest that excess QA levels, due to mutations in the kynurenine pathway, for example, may lead to the formation of metabolite assemblies that seed α-synuclein aggregation, resulting in neuronal toxicity and induction of Parkinson's disease.

A novel compound-primed multiplex ARMS-PCR (CPMAP) for simultaneous detection of common PAH gene mutations

In this study, we introduce a novel compound-primed multiplex ARMS PCR (CPMAP) for simultaneous detection of common PAH gene mutations. This approach was used successfully for simultaneous identification of six most common PAH gene mutations in 137 phenylketonuria patients in the Iranian population. A total of six normal and six mutant allele-specific primers and 4 common primers containing a tag sequence of 12 base pair at the 5'-end were designed and used in two separate optimized multiplex ARMS reactions followed by hot-start PCR. The products were separated and visualized on 3% agarose gel. The CPMAP genotyping data were completely in accordance with the direct sequencing results. The CPMAP suggests a reliable, economical and rapid method for simultaneous detection of PAH point mutations using conventional PCR, which could be applied for diagnosis of other gene mutations.

Investigation of Five Common Mutations on Phenylalanine Hydroxylase Gene of Phenylketonuria Patients from Two Provinces in North of Iran

Background:

There are more than 500 different mutations on phenylalanine hydroxylase (PAH) gene that is responsible for phenylketonuria (PKU) diseases and the spectrum of these mutations is varied in different populations. The main clinical manifestation of untreated patients is severe mental retardation. The PAH gene, that is 90 kb long, is consisted of 13 exons and 12 introns. The aim of the present study was to identify the frequency of five common mutations on PAH gene among patients with PKU in Mazandaran and Golestan provinces including c.1066-11G>A, p. R261Q, p. R252W, p. R261X, and c.1200 + 1G>C.

Methods:

Forty unrelated PKU patients, that 22 of them, were from Mazandaran and 18 of them from Golestan provinces were enrolled in the study. Genomic DNA was extracted from leukocytes using Qiagen DNA extraction kit and polymerase chain reaction - restriction fragment length polymorphism method was applied to detect five common mutations.

Results:

Three out of the 5 investigate mutations were identified among the patients. The c.1066-11G>A mutation has the highest frequency (27.5%) among the patients and the frequency of p. R261Q and p. R261X mutations were 3.75 and 1.25%, respectively. In Golestan province, only c.1066-11G>A mutation was observed in investigated alleles.

Conclusions:

The high frequency of c.1066-11G>A mutation in Golestan province may be related to genetic drift, founder effect, and consanguinity.

The impact of phenylalanine levels on cognitive outcomes in adults with phenylketonuria: Effects across tasks and developmental stages

Objective: Phenylketonuria (PKU) is due to an inability to metabolize the amino acid phenylalanine (Phe), leading to its accumulation in the brain. Phe levels can be controlled following a protein-free diet, but cognitive impairments are still present. A number of questions remain to be answered related to which type of metabolic control is important, the age when it is important, the cognitive functions which are most affected and, the best tests to use to monitor cognitive health. Method: We investigated the impact of metabolic control at different ages on cognitive performance in 37 early treated adults with PKU. Results: (a) Phe variation was as associated to performance as average Phe showing that stable dietary control is as important as strict control; (b) For some tasks, current and adult Phe were stronger predictors of performance than childhood or adolescent Phe, showing the importance of a strict diet even in adulthood; and (c) The relationship between performance and Phe levels varied depending on time and cognitive domain. For some functions (sustained attention, visuomotor coordination), Phe at the time of testing was the best predictor. While for other functions (visual attention, executive functions) there was a diminishing or stable relationship across time. Conclusion: Results show the importance of selecting the right tasks to monitor outcomes across ages, but also that the impact of bio-chemical disruptions is different for different functions, at different ages. We show how inherited metabolic diseases offer us a unique vantage point to inform our understanding of brain development and functioning.

Nutritional status of patients with phenylketonuria in Japan

Accumulating evidence suggests that hyperphenylalaninemia in phenylketonuria (PKU) can cause neuropsychological and psychosocial problems in diet-off adult patients, and that such symptoms improve after resumption of phenylalanine-restricted diet, indicating the need for lifetime low-phenylalanine diet. While limiting protein intake, dietary therapy should provide adequate daily intake of energy, carbohydrates, fat, vitamins, and microelements. We evaluated nutrient balance in 14 patients with classical PKU aged 4-38 years. Approximately 80-85% of the recommended dietary allowance (RDA) of protein in Japanese was supplied through phenylalanine-free (Phe-free) milk and Phe-free amino acid substitutes. Nutritional evaluation showed that the calorie and protein intakes were equivalent to the RDA. Phenylalanine intake was 9.8 ± 2.2 mg/kg of body weight/day, which maintained normal blood phenylalanine concentration by the 80% Phe-free protein rule. The protein, fat, and carbohydrate ratio was 9.5:23.9:66.6% with relative carbohydrate excess. Phe-free milk and amino acid substitutes provided 33.7% of carbohydrate, 82.1% of protein, and 66.7% of fat intake in all. Selenium and biotin intakes were 25.0% and 18.1% of the RDA and adequate intake (AI) for Japanese, respectively; both were not included in Phe-free milk. PKU patients showed low serum selenium, low urinary biotin, and high urinary 3-hydroxyisovaleric acid in this study. The intakes of magnesium, zinc, and iodine were low (71.5%, 79.5%, and 71.0% of the RDA, respectively) and that of phosphorus was 79.7% of the AI, although they were supplemented in Phe-free milk. PKU patients depend on Phe-free milk and substitutes for daily requirement of microelements and vitamins as well as protein and fat. Development of low-protein food makes it possible to achieve the aimed phenylalanine blood level, but this lowers the intake of microelements and vitamins from natural foods. The dietary habits vary continuously with age and environment in PKU patients. We recommend the addition of selenium and biotin to Phe-free milk in Japan and the need to review the composition of microelements and vitamins in A-1 and MP-11 preparations.

The personal burden for caregivers of children with phenylketonuria: A cross-sectional study investigating time burden and costs in the UK

INTRODUCTION

Management of phenylketonuria (PKU) is mainly achieved through strict dietary control that aims to limit the intake of phenylalanine (Phe). Adherence to this diet is burdensome due to the need for specially prepared low-Phe meals and regular monitoring of Phe concentrations. A UK cross-sectional study was conducted to identify the personal time and monetary burden associated with aspects of the PKU lifestyle for caregivers of children (aged < 18 years) living with PKU.

METHODS

Caregivers of pediatric patients with PKU attending one of four specialist metabolic centers in the UK were invited to participate in a questionnaire-based survey that evaluated different aspects of PKU management that could potentially present out-of-pocket costs (OOPCs) or time burden. Medical clinicians/dieticians provided patient information on PKU severity and an assessment of blood Phe control.

RESULTS

The survey was completed by 114 caregivers of 106 children having mild or moderate (n = 45; 39%) or classical (n = 60; 53%) PKU (severity data missing for n = 1), among whom 8 (8%) and 87 (82%) reported poorly controlled and controlled blood Phe status, respectively; Phe control data were missing for 11 children. Dietary management of PKU incurred a median time burden of > 19 h per week. OOPCs were incurred via attendance at PKU events, PKU-related equipment, and extra holiday expenditure. 21% of caregivers reduced their working hours (median 18.5 h/week) to care for their child, with a further 24% leaving their paid jobs completely.

DISCUSSION AND CONCLUSIONS

Dietary management of PKU is associated with a considerable time burden for caregivers of pediatric patients with PKU. A personal financial burden also arises from OOPCs and lost earnings.

Phenylalanine induces oxidative stress and decreases the viability of rat astrocytes: possible relevance for the pathophysiology of neurodegeneration in phenylketonuria

The aim of this study was to investigate the effects of phenylalanine on oxidative stress and some metabolic parameters in astrocyte cultures from newborn Wistar rats. Astrocytes were cultured under four conditions: control (0.4 mM phenylalanine concentration in the Dulbecco's Modified Eagle Medium (DMEM) solution), Phe addition to achieve 0.5, 1.0 or 1.5 mM final phenylalanine concentrations. After 72 h the astrocytes were separated for the biochemical measurements. Overall measure of mitochondrial function by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and cell viability measured by lactate dehydrogenase (LDH) assays indicated that phenylalanine induced cell damage at the three concentrations tested. The alteration on the various parameters of oxidative stress indicated that phenylalanine was able to induce free radicals production. Therefore, our results strongly suggest that Phe at concentrations usually found in PKU induces oxidative stress and consequently cell death in astrocytes cultures. Considering the importance of the astrocytes for brain function, it is possible that these astrocytes alterations may contribute to the brain damage found in PKU patients.

Genetic and environmental modulation of neurodevelopmental disorders: Translational insights from labs to beds

Neurodevelopmental disorders (NDDs) are a heterogeneous group of prevalent neuropsychiatric illnesses with various degrees of social, cognitive, motor, language and affective deficits. NDDs are caused by aberrant brain development due to genetic and environmental perturbations. Common NDDs include autism spectrum disorder (ASD), intellectual disability, communication/speech disorders, motor/tic disorders and attention deficit hyperactivity disorder. Genetic and epigenetic/environmental factors play a key role in these NDDs with significant societal impact. Given the lack of their efficient therapies, it is important to gain further translational insights into the pathobiology of NDDs. To address these challenges, the International Stress and Behavior Society (ISBS) has established the Strategic Task Force on NDDs. Summarizing the Panel's findings, here we discuss the neurobiological mechanisms of selected common NDDs and a wider NDD+ spectrum of associated neuropsychiatric disorders with developmental trajectories. We also outline the utility of existing preclinical (animal) models for building translational and cross-diagnostic bridges to improve our understanding of various NDDs.

First Case Report of EX3del4765 Mutation in PAH Gene in Asian Population

Introduction:

Phenylketonuria (PKU) is an autosomal recessive inborn error of phenylalanine metabolism, which is caused by mutation in phenylalanine hydroxylase (PAH) gene. Most of the PAH mutations are missense mutations (67%), which are followed by small or large deletions (13%).

Case Presentation:

We reported a patient with classic PKU and his parents harboring a large deletion in exon 3 (EX3del4765) of PAH gene. This is the first case report of EX3del4765 in Asian patients with PKU.

Conclusions:

This finding may help improve early detection, differential diagnosis, genetic counseling, and even treatment of patients with PKU.

Phenylketonuria Pathophysiology: on the Role of Metabolic Alterations

Phenylketonuria (PKU) is an inborn error of phenylalanine (Phe) metabolism caused by the deficiency of phenylalanine hydroxylase. This deficiency leads to the accumulation of Phe and its metabolites in tissues and body fluids of PKU patients. The main signs and symptoms are found in the brain but the pathophysiology of this disease is not well understood. In this context, metabolic alterations such as oxidative stress, mitochondrial dysfunction, and impaired protein and neurotransmitters synthesis have been described both in animal models and patients. This review aims to discuss the main metabolic disturbances reported in PKU and relate them with the pathophysiology of this disease. The elucidation of the pathophysiology of brain damage found in PKU patients will help to develop better therapeutic strategies to improve quality of life of patients affected by this condition.

Fish-Free Diet in Patients with Phenylketonuria Is Not Associated with Early Atherosclerotic Changes and Enhanced Platelet Activation

Background and Purpose

Since patients with phenylketonuria (PKU) have to follow a lifelong restriction of natural protein to lower phenylalanine-intake, they never eat fish. This diet may lead to a chronic deficit of omega-3 and omega-6 fatty acids with the risk of early atherosclerotic changes. The aim of the study was to analyse the fatty acid profile of PKU patients and to correlate the results with surrogate markers of early atherosclerotic changes [enhanced carotid intima media thickness (CIMT) and ß-stiffness index] and platelet activation.

Methods

In 43 PKU patients and in 58 healthy controls we prospectively examined the fatty acid profile, CIMT, ß-stiffness index and platelet activation (flow cytometric determination of markers of platelet activation). CIMT was measured bilaterally by ultrasound. CIMT _mean was defined as the mean value of the sum of CIMT _left and CIMT _right.

Results

Despite of lower HDL-cholesterol and higher triglyceride concentrations in the PKU group, there was no significant difference in the omega-6 or omega-3 fatty acid profile, CIMT, ß-stiffness index between both groups. Platelet activation was not enhanced in the PKU group.

Conclusions

Fish-free diet does not induce early atherosclerotic changes or enhanced platelet activation in PKU patients.

Adult phenylketonuria presenting with subacute severe neurologic symptoms

We report a 48-year-old Japanese woman with phenylketonuria (PKU) who presented with severe neurological symptoms more than 30 years after discontinuation of dietary treatment. She was diagnosed with PKU at 6-years-old and was treated with a phenylalanine restricted diet until she was 15 years old. When she was 48-years-old she started having difficulty walking. After several months, she presented with severe disturbance of consciousness and was admitted. She was diagnosed as having neurological complications associated with PKU. We observed temporal changes in her laboratory data, brain MRI and single-photon emission computed tomography (SPECT) scan findings. Brain MRI on T2-weighted, fluid-attenuated inversion recovery and diffusion-weighted images revealed high intensity lesions in her bilateral frontal lobes and 123I-IMP SPECT showed marked and diffuse hypoperfusion in the bilateral cerebrum and cerebellum. After the resumption of dietary treatment, serum phenylalanine concentrations immediately decreased to the normal range. However, her neurological symptoms took longer to improve. We also found no clear temporal association between MRI findings and clinical severity. SPECT abnormalities showed marked improvement after treatment. It is well known that PKU patients who discontinue the dietary restriction from their childhood develop minor neurological impairments. However, PKU patients with late-onset severe neurological symptoms are very rare. To our knowledge, this is the first report regarding SPECT findings of PKU patients with late-onset severe neurological deterioration.

Management of adult patients with phenylketonuria: survey results from 24 countries

Phenylketonuria (PKU) is no longer considered merely a pediatric concern; current guidelines recommend life-long treatment. However, information on the adult PKU patient population is scarce. A survey was initiated on behalf of the European PKU Group (EPG) that focused specifically on early-treated adult patients diagnosed by neonatal screening. The online survey was sent via email to 204 healthcare professionals (HCPs) in 33 countries. Eighty-one HCPs from 24 countries responded. The main findings were that the majority of adult patients with PKU in active follow-up are under 30 years of age and are managed in centers that also treat children. Seventy-eight percent of adult PKU patients in follow-up receive treatment, mainly by diet (71 %), with BH4 treatment rarely used in adulthood. Only 26 % of responding HCPs perform routine neurocognitive testing in all their adult patients. There was little consensus regarding target blood phenylalanine (Phe) concentrations, although the majority of respondents reported that their patients achieved blood Phe concentrations below 1200 μmol/l.

CONCLUSION

This survey highlights the need for blood Phe concentration target recommendations and consensus guidelines, more research into adult PKU patient management, and the need to identify those patients lost to follow-up to ensure PKU is managed for life.

Phenylketonuria Scientific Review Conference: state of the science and future research needs

New developments in the treatment and management of phenylketonuria (PKU) as well as advances in molecular testing have emerged since the National Institutes of Health 2000 PKU Consensus Statement was released. An NIH State-of-the-Science Conference was convened in 2012 to address new findings, particularly the use of the medication sapropterin to treat some individuals with PKU, and to develop a research agenda. Prior to the 2012 conference, five working groups of experts and public members met over a 1-year period. The working groups addressed the following: long-term outcomes and management across the lifespan; PKU and pregnancy; diet control and management; pharmacologic interventions; and molecular testing, new technologies, and epidemiologic considerations. In a parallel and independent activity, an Evidence-based Practice Center supported by the Agency for Healthcare Research and Quality conducted a systematic review of adjuvant treatments for PKU; its conclusions were presented at the conference. The conference included the findings of the working groups, panel discussions from industry and international perspectives, and presentations on topics such as emerging treatments for PKU, transitioning to adult care, and the U.S. Food and Drug Administration regulatory perspective. Over 85 experts participated in the conference through information gathering and/or as presenters during the conference, and they reached several important conclusions. The most serious neurological impairments in PKU are preventable with current dietary treatment approaches. However, a variety of more subtle physical, cognitive, and behavioral consequences of even well-controlled PKU are now recognized. The best outcomes in maternal PKU occur when blood phenylalanine (Phe) concentrations are maintained between 120 and 360 μmol/L before and during pregnancy. The dietary management treatment goal for individuals with PKU is a blood Phe concentration between 120 and 360 μmol/L. The use of genotype information in the newborn period may yield valuable insights about the severity of the condition for infants diagnosed before maximal Phe levels are achieved. While emerging and established genotype-phenotype correlations may transform our understanding of PKU, establishing correlations with intellectual outcomes is more challenging. Regarding the use of sapropterin in PKU, there are significant gaps in predicting response to treatment; at least half of those with PKU will have either minimal or no response. A coordinated approach to PKU treatment improves long-term outcomes for those with PKU and facilitates the conduct of research to improve diagnosis and treatment. New drugs that are safe, efficacious, and impact a larger proportion of individuals with PKU are needed. However, it is imperative that treatment guidelines and the decision processes for determining access to treatments be tied to a solid evidence base with rigorous standards for robust and consistent data collection. The process that preceded the PKU State-of-the-Science Conference, the conference itself, and the identification of a research agenda have facilitated the development of clinical practice guidelines by professional organizations and serve as a model for other inborn errors of metabolism.

Antioxidant treatment strategies for hyperphenylalaninemia

Hyperphenylalaninemia (HPA) leads to increased oxidative stress in patients with phenylketonuria (PKU) and in animal models of PKU. Early diagnosis and immediate adherence to a phenylalanine-restricted diet prevents HPA and, consequently, severe brain damage. However, treated adolescent and adult PKU patients have difficulties complying with the diet, leading to an oscillation of phenylalanine levels and associated oxidative stress. The brain is especially susceptible to reactive species, and oxidative stress might add to the impaired cognitive function found in these patients. The restricted PKU diet has a very limited nutrient content from natural foods and almost no animal protein, which reduces the intake of important compounds. These specific compounds can act as scavengers of reactive species and can be co-factors of antioxidant enzymes. Supplementation with nutrients, vitamins, and tetrahydropterin has given quite promising results in patients and animal models. Antioxidant supplementation has been studied in HPA, however there is no consensus about its always beneficial effects. In this way, regular exercise could be a beneficial addition on antioxidant status in PKU patients. A deeper understanding of PKU molecular biochemistry, and genetics, as well as the need for improved targeted treatment options, could lead to the development of new therapeutic strategies.

Optimal serum phenylalanine for adult patients with phenylketonuria

High serum phenylalanine in adult patients with phenylketonuria (PKU) causes neuropsychological and psychosocial problems that can be resolved by phenylalanine-restricted diet. Therefore, PKU patients must continue to adhere to phenylalanine-restricted diet for life, although the optimal serum phenylalanine level in later life has yet to be established. The purpose of this review was to establish the optimal serum phenylalanine level in later life of PKU patients. We evaluated oxidative stress status, nitric oxide metabolism, cholesterol-derived oxysterols, vitamin D and bone status, and magnetic resonance imaging (MRI) in adult PKU patients according to serum phenylalanine level. Oxidative stress increased markedly at serum phenylalanine of 700-800 μmol/L. Serum phenylalanine higher than 700-850 μmol/L correlated with the disturbance of nitric oxide regulatory system. Adult PKU patients had poor vitamin D status and exhibited predominance of bone resorption over bone formation. In the brain, the levels of 24S-hydroxycholesterol, a marker of brain cholesterol elimination, were low at serum phenylalanine levels exceeding 650 μmol/L. MRI studies showed high signal intensity in deep white matter on T2-weighted and FLAIR images of PKU patients with serum phenylalanine greater than 500 μmol/L, with decreased apparent diffusion coefficients. Changes in most parameters covering the entire body organs in adult PKU were almost acceptable below 700-800 μmol/L of phenylalanine level. However, the optimal serum phenylalanine level should be 500 μmol/L or less in later life for the brain to be safe.

Delayed diagnosis of phenylketonuria – a case report of two siblings

Phenylketonuria (PKU), is an autosomal recessive condition affecting the amino acid metabolism. The UK National newborn screening programme was commenced in 1969 and PKU is one among the five conditions included in the screening programme. We present the case history of two siblings of a family with a delayed diagnosis of PKU. This case history highlights such an occurrence. PKU should be considered as an important differential in the diagnosis of adult patients with learning difficulties, seizures and behavioural problems. It would be prudent to instigate plasma and urine amino/organic acid analyses in adult patients with unexplained neuropsychological manifestations.

Tetrahydrobiopterin therapy vs phenylalanine-restricted diet: impact on growth in PKU

BACKGROUND

Treatment of phenylketonuria based upon strict vegetarian diets, with very low phenylalanine intake and supplemented by phenylalanine-free formula, has proven to be effective in preventing the development of long-term neurological sequelae due to phenylalanine accumulation. On the other hand, such diets have occasionally been reported to hinder normal development, some individuals presenting with growth retardation. Tetrahydrobiopterin therapy has opened up new treatment options for a significant proportion of phenylketonuric patients, enabling them to eat normal diets and be freed from the need to take synthetic supplements. However, little is known about how this therapy affects their physical development.

METHODS

We conducted a retrospective longitudinal study examining anthropometric characteristics (height, weight, body mass index and growth speed Z-scores) in a cohort of phenylketonuric patients on tetrahydrobiopterin therapy (38 subjects) comparing their characteristics with those of a group of phenylketonuric patients on phenylalanine-restricted diets (76 subjects). Nutritional issues were also considered, to further explore the possibility of higher natural protein intake being associated with better physical development. Data were collected every six months over two different periods of time (two or five years).

RESULTS

No improvement was observed in the aforementioned anthropometric variables in the cohort on tetrahydrobiopterin therapy, from prior to starting treatment to when they had been taking the drug for two or five years. Rather, in almost all cases there was a fall in the mean Z-score for the variables during these periods, although the changes were not significant in any case. Further, we found no statistically differences between the two groups at any considered time point. Growth impairment was also noted in the phenylketonuric patients on low-phenylalanine diets. Individuals on tetrahydrobiopterin therapy increased their natural protein intake and, in some instances, this treatment enabled individuals to eat normal diets, with protein intake meeting RDAs. No association was found, however, between higher protein intake and growth.

CONCLUSION

Our study identified growth impairment in patients with phenylketonuria on tetrahydrobiopterin, despite higher intakes of natural proteins. In fact, individuals undergoing long-term tetrahydrobiopterin treatment seemed to achieve similar developmental outcomes to those attained by individuals on more restricted diets.

Maternal hyperphenylalaninemia: rapid achievement of metabolic control predicts overall control throughout pregnancy

Women with hyperphenylalaninemia are at risk of having offspring affected with the maternal phenylketonuria syndrome. Here we analyze the effect of the intervention of a nutritionist on plasma phenylalanine control in Maternal Hyperphenylalaninemia. We analyzed a retrospective cohort of 35 completed pregnancies in 20 women with Maternal Hyperphenylalaninemia who visited the metabolic nutritionist during the pregnancy to achieve metabolic control. Women who promptly achieved metabolic control had lower plasma phenylalanine concentrations for the remainder of the pregnancy when compared to women who did not achieve prompt control, and this difference reached statistical significance. The achievement of plasma phenylalanine concentrations within the desired target range by the time of the second visit to the nutritionist is a strong predictor of the ability to maintain the desired target range of plasma phenylalanine for the remainder of the pregnancy. Furthermore, we demonstrate that phenylalanine tolerance increases significantly by trimester in women with classical and variant hyperphenylalaninemia.

Dietary treatment in phenylketonuria does not lead to increased risk of obesity or metabolic syndrome

BACKGROUND

Little is known about the consequences of the special energy enriched diet used to treat patients with phenylketonuria (PKU) in terms of obesity and metabolic syndrome (MetSyn) development.

OBJECTIVE

To investigate the prevalence of overweight and obesity, and its consequences in terms of body composition and MetSyn in early treated patients with PKU compared to controls.

DESIGN

A sample of 89 patients with PKU (3-30 y; 14.4±6.6 y) and 79 controls (3-47 y; 16.3±7.9 y) were studied. In the fasted state, anthropometric, body composition, blood pressure and analytical parameters [amino acids, glucose, insulin, total and HDL-cholesterol (HDL-c), triglycerides (TG), high sensitivity c-reactive protein and uric acid] were performed. Data on dietary intake was collected. BMI was classified using WHO criteria, while the definition from International Diabetes Federation (IDF) was used for MetSyn.

RESULTS

Prevalence of overweight and obesity (32.6% vs. 24.1%; p=0.293), body fat percentage (22% vs. 23.1%, p=0.581) and central obesity (36.9% vs. 36.4%, p=0.999) were comparable to controls. Patients revealed a higher TG/HDL-c (p<0.001). The prevalence of MetSyn was 1.5% and 6.1% in patients and controls, respectively. Patients and not controls with central obesity revealed a further significant increase in TG/HDL-c compared with those without central obesity (p=0.023).

CONCLUSION

Patients and controls were similar in terms of overweight and obesity, body composition and MetSyn. However, the dyslipidemia in patients with PKU in relation to overweight and obesity may help us trying to understand the course and the etiology of MetSyn not only in PKU but also in the general population.

Pyruvate and creatine prevent oxidative stress and behavioral alterations caused by phenylalanine administration into hippocampus of rats

Phenylketonuria is characterized by a variable degree of mental retardation and other neurological features whose mechanisms are not fully understood. In the present study we investigated the effect of intrahippocampal administration of phenylalanine, isolated or associated with pyruvate or creatine, on rat behavior and on oxidative stress. Sixty-day-old male Wistar rats were randomly divided into 6 groups: saline; phenylalanine; pyruvate; creatine; phenylalanine + pyruvate; phenylalanine + creatine. Phenylalanine was administered bilaterally in the hippocampus one hour before training; pyruvate, at the same doses, was administered in the hippocampus one hour before phenylalanine; creatine was administered intraperitoneally twice a day for 5 days before training; controls received saline solution at same volumes than the other substances. Parameters of exploratory behavior and of emotionality were assessed in both training and test sessions in the open field task. Rats receiving phenylalanine did not habituate to the open field along the sessions, indicating deficit of learning/memory, but parameters of emotionality were normal, not interfering in the habituation process. Pyruvate or creatine administration prevented the lack of habituation caused by phenylalanine. Pyruvate and creatine also prevented alterations provoked by phenylalanine on lipid peroxidation, total content of sulfhydryls, total radical-trapping antioxidant potential and total antioxidant reactivity. The results suggest that the behavioral alterations provoked by intra-hippocampal administration of phenylalanine may be caused, at least in part, by oxidative stress and/or energy deficit. If this also occurs in PKU, it is possible that pyruvate and creatine supplementation to the phenylalanine-restricted diet might be beneficial to phenylketonuric patients.

Phenylalanine hydroxylase deficiency

Phenylalanine hydroxylase deficiency is an autosomal recessive disorder that results in intolerance to the dietary intake of the essential amino acid phenylalanine. It occurs in approximately 1:15,000 individuals. Deficiency of this enzyme produces a spectrum of disorders including classic phenylketonuria, mild phenylketonuria, and mild hyperphenylalaninemia. Classic phenylketonuria is caused by a complete or near-complete deficiency of phenylalanine hydroxylase activity and without dietary restriction of phenylalanine most children will develop profound and irreversible intellectual disability. Mild phenylketonuria and mild hyperphenylalaninemia are associated with lower risk of impaired cognitive development in the absence of treatment. Phenylalanine hydroxylase deficiency can be diagnosed by newborn screening based on detection of the presence of hyperphenylalaninemia using the Guthrie microbial inhibition assay or other assays on a blood spot obtained from a heel prick. Since the introduction of newborn screening, the major neurologic consequences of hyperphenylalaninemia have been largely eradicated. Affected individuals can lead normal lives. However, recent data suggest that homeostasis is not fully restored with current therapy. Treated individuals have a higher incidence of neuropsychological problems. The mainstay of treatment for hyperphenylalaninemia involves a low-protein diet and use of a phenylalanine-free medical formula. This treatment must commence as soon as possible after birth and should continue for life. Regular monitoring of plasma phenylalanine and tyrosine concentrations is necessary. Targets of plasma phenylalanine of 120-360 μmol/L (2-6 mg/dL) in the first decade of life are essential for optimal outcome. Phenylalanine targets in adolescence and adulthood are less clear. A significant proportion of patients with phenylketonuria may benefit from adjuvant therapy with 6R-tetrahydrobiopterin stereoisomer. Special consideration must be given to adult women with hyperphenylalaninemia because of the teratogenic effects of phenylalanine. Women with phenylalanine hydroxylase deficiency considering pregnancy should follow special guidelines and assure adequate energy intake with the proper proportion of protein, fat, and carbohydrates to minimize risks to the developing fetus. Molecular genetic testing of the phenylalanine hydroxylase gene is available for genetic counseling purposes to determine carrier status of at-risk relatives and for prenatal testing.

Experimental evidence that phenylalanine is strongly associated to oxidative stress in adolescents and adults with phenylketonuria

Few studies have looked at optimal or acceptable serum phenylalanine levels in later life in patients with phenylketonuria (PKU). This study examined the oxidative stress status of adolescents and adults with PKU. Forty PKU patients aged over fifteen years were enrolled, and were compared with thirty age-matched controls. Oxidative stress markers, anti-oxidant enzyme activities in erythrocytes, and blood anti-oxidant levels were examined. Nitric oxide (NO) production was also examined as a measure of oxidative stress. Plasma thiobarbituric acid reactive species and serum malondialdehyde-modified LDL levels were significantly higher in PKU patients than control subjects, and correlated significantly with serum phenylalanine level (P<0.01). Plasma total anti-oxidant reactivity levels were significantly lower in the patient group, and correlated negatively with phenylalanine level (P<0.001). Erythrocyte superoxide dismutase and catalase activities were higher and correlated significantly with phenylalanine level (P<0.01). Glutathione peroxidase activity was lower and correlated negatively with phenylalanine level (P<0.001). The oxidative stress score calculated from these six parameters was significantly higher in patients with serum phenylalanine of 700-800 μmol/l. Plasma anti-oxidant substances, beta-carotene, and coenzyme Q(10) were also lower (P<0.001), although the decreases did not correlate significantly with the phenylalanine level. Serum nitrite/nitrate levels, as stable NO products, were higher together with low serum asymmetric dimethylarginine, as an endogenous NO inhibitor. Oxidative stress status is closely linked with serum phenylalanine levels. Phenylalanine level in should be maintained PKU below 700-800 μmol/l even in adult patients.

Transition of young adults with phenylketonuria from pediatric to adult care

BACKGROUND

Transition from pediatric to adult health care is a particularly vulnerable period for patients with inborn metabolic diseases. Aim of the present study was to evaluate the current transition situation of patients with phenylketonuria (PKU) in Leipzig, Germany, by analysis of the medical care, metabolic control, patients' satisfaction, socio-economic and psychosocial status, in order to identify areas of weakness and potential improvement.

METHODS

Patients who had been transferred from pediatric to adult medical care between 2005 and 2008 were identified. An interview was performed using a questionnaire. Pediatric case notes and the present physician's case notes were analyzed retrospectively. Socio-demographic data were compared to data derived from the annual statistics of the city of Leipzig, Germany in 2008.

RESULTS

seventy two transferred patients were identified and included in the study, 48 patients responded to the questionnaire, the data of 24 non-responders were analysed retrospectively. About 90% of the responding patients with PKU were satisfied with the current transition situation. However, they agreed to several suggestions of improvement. Most specifically an interdisciplinary appointment before the definite transfer to the adult clinics was asked for. At the time of transition, most of the patients were in good metabolic control according to current treatment guidelines (median dried blood phenylalanine concentration 853 μmol/l before versus 690 μmol/l after transition). Of the interviewed patients 92% were still on a low phenylalanine diet in combination with the intake of a phenylalanine free amino acid mixture. Of the interviewees 77% carried a secondary school certificate or a secondary modern school qualification, but only 19% had achieved senior high school diploma (controls 38.2%). Marital status was comparable with the population of Leipzig. However, fewer patients with PKU had children (15% versus 37%).

CONCLUSION

Transition of patients with PKU from pediatric to adult care seems to be successful in Leipzig. Patients were mostly satisfied with the transition situation. Still, some suggestions for improvements appeared to be desirable. During transition medical care and metabolic control were stable. However, with regard to psychosocial and socioeconomic data differences to the control population were detected.

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.