Follow up of phenylketonuria patients

Phenylketonuria from the perspectives of patients in Türkiye

BACKGROUND

The present study aimed to determine the problems, unmet needs and expectations of phenylketonuria (PKU) patients in Türkiye regarding follow-up and treatment in order to provide data for future planning and implementations on PKU.

METHODS

The study included patients diagnosed with PKU and/or their parents. They were informed about the study via phone calls and their verbal consents were obtained. Questions in the data collection forms, which were established separately for pediatric, adolescent, and adult age groups, were applied during the interviews and the answers were recorded.

RESULTS

Among 182 classical PKU patients, 66 (36.3%) were in the pediatric group (0-12 years old), 44 (24.2%) were in the adolescent group (13-19 years old), and 72 (39.5%) were in the adult group (≥ 20 years old). In all patient groups, phenylalanine-restricted diet and medical nutrition products were the main options for treatment. The median of the last measured blood phenylalanine concentration (patient-reported) was 290 µmol/L, 425 µmol/L, and 750 µmol/L in the pediatric, adolescent, and adult groups, respectively. The frequency of blood testing for serum phenylalanine level according to the age groups was appropriate in nearly half of the patients. While the majority of the patients have been visiting the metabolism center they have been diagnosed with PKU for control, considerable proportion of the patients would like to change the center or the doctor they visit for control if they could. It was determined that nearly half of the patients had trouble in accessing the metabolism center. Treatment options' being limited and expensive were the major problems. The main requests of the patients and patient relatives included easier access to the metabolism centers and more options for treatment and diet.

CONCLUSIONS

Access to the services should be easier to improve the patients' follow-up and treatment. There is need for low-cost, easily applicable, and accessible nutrition products and effective novel pharmacological agents. Focusing on these issues in health policies by providing pedagogic/psychological support, establishing support programs also comprising the families, and increasing the awareness activities were the key outcomes.

A Low-Phenylalanine-Containing Whey Protein Hydrolysate Stimulates Osteogenic Activity through the Activation of p38/Runx2 Signaling in Osteoblast Cells

A phenylalanine (Phe)-restricted diet is indispensable for individuals suffering from phenylketonuria (PKU). Our previous study reported a low-Phe-containing whey protein hydrolysate (LPH) prepared from a selected whey protein hydrolysate (TA2H). This study aimed to investigate the osteogenic activity of LPH and TA2H in MC3T3-E1 preosteoblast cells and explore the underlying mechanism. Results showed that the treatment of TA2H and LPH (at the final concentrations of 100–1000 μg/mL) had a stimulatory effect on the proliferation, differentiation, and mineralization of MC3T3-E1 cells. The LPH of 1000 μg/mL significantly increased cell proliferation (2.15- ± 0.11-fold) and alkaline phosphatase activity (1.22- ± 0.07-fold), promoted the protein and mRNA levels of runt-related transcription factor 2 (Runx2, 2.50- ± 0.14-fold and 2.97- ± 0.23-fold, respectively), enhanced the expression of differentiation biomarkers (type-I collagen, osteocalcin, and osteopontin), increased calcium deposition (1.56- ± 0.08-fold), and upregulated the ratio of osteoprotegerin/receptor activator of nuclear factor-κB ligand. The exploration of signaling pathways indicated that the activated p38-dependent Runx2 signaling contributed to the LPH-induced osteogenesis. These results provided evidence, for the first time, that a prepared low-Phe whey protein hydrolysate positively modulated the activity of osteoblasts through the p38/Runx2 pathway, thereby providing a new osteoinductive protein substitute to make functional PKU food.

Development of an mRNA replacement therapy for phenylketonuria

Phenylketonuria (PKU) is an inborn error caused by deficiencies in phenylalanine (Phe) metabolism. Mutations in the phenylalanine hydroxylase (PAH) gene are the main cause of the disease whose signature hallmarks of toxically elevated levels of Phe accumulation in plasma and organs such as the brain, result in irreversible intellectual disability. Here, we present a unique approach to treating PKU deficiency by using an mRNA replacement therapy. A full-length mRNA encoding human PAH (hPAH) is encapsulated in our proprietary lipid nanoparticle LUNAR and delivered to a Pah^enu2 mouse model that carries a missense mutation in the mouse PAH gene. Animals carrying this missense mutation develop hyperphenylalanemia and hypotyrosinemia in plasma, two clinical features commonly observed in the clinical presentation of PKU. We show that intravenous infusion of LUNAR-hPAH mRNA can generate high levels of hPAH protein in hepatocytes and restore the Phe metabolism in the Pah^enu2 mouse model. Together, these data establish a proof of principle of a novel mRNA replacement therapy to treat PKU.

Benchmark Examination of Blood Amino Acids Patterns in Phenylketonuria Neonates and Young Children on Phenylalanine-Restricted Dietary Treatment

Background: Phenylalanine-restricted diets have been the basis of therapy for phenylketonuria; however, little is known how this treatment effects homeostasis of other amino acids. This study aimed to assess blood amino acid alterations in phenylketonuric neonates before and after treatment to identify any residual amino acid alterations with phenylalanine restriction in these treated children. Methods: Concentrations of 11 amino acids were measured using liquid chromatography-tandem mass spectrometry performed on dried blood spots. Results: Elevated blood phenylalanine, arginine, citrulline, valine, methionine concentrations and decreased tyrosine, proline concentrations were observed in phenylketonuria neonates relative to controls, of which phenylalanine, arginine, methionine, tyrosine, and proline levels could be either partially or completely restored with dietary intervention, whereas citrulline and valine were not restored and remained higher. Conclusions: Blood amino acid homeostasis is disrupted in phenylketonuria. Although dietary intervention adjusts amino acid homeostasis in the direction of a healthy equilibrium, complete restoration is not achieved.

Evaluation of patients with phenylalanine metabolism disorder: a single center experience

AIM

The aim is to evaluate the clinical, demographic and laboratory data of the patients we followed up with phenylalanine metabolism disorder.

MATERIALS AND METHODS

In this study, patients with phenylalanine metabolism disorder who applied to Bursa Uludag University Faculty of Medicine, Department of Pediatrics, Pediatric Metabolism Department between 2011 and 2021 were retrospectively examined. The files of 397 patients who were followed up in our pediatric metabolism outpatient clinic and were found to have phenylalanine metabolism disorder by plasma phenylalanine level and molecular genetic analysis were evaluated.

RESULTS

According to the highest plasma phenylalanine levels at admission, mild hyperphenylalaninemia phenotype constituted the largest group of 397 patients with 282 cases (71.1%), while the least common phenotype was malignant phenylketonuria (BH4 metabolism disorder) with four patients (1.0%). The number of patients with classical phenylketonuria was 90 (22.6%). 61 (62.8%) of 97 phenylalanine metabolism disorder cases who underwent BH4 loading test had a response. The mean phenylalanine level of the patients was 3.62 ± 1.31 mg/dL in mild hyperphenylalaninemia, 7.98 ± 3.99 mg/dL in mild phenylketonuria and 11.71 ± 4.39 mg/dL in classical phenylketonuria. While 241 (76%) of 317 patients younger than 8 years old were in the well-controlled group, 76 (24%) were in the poorly-controlled group. While 41 (53.9%) of 76 patients older than 8 years of age were in the well-controlled group, 35 (46.1%) were in the poorly-controlled group.

CONCLUSIONS

In our study, the largest patient group consisted of patients with mild hyperphenylalaninemia, and the least common phenotype was mild phenylketonuria.

An enzyme cascade fluorescence-based assay for the quantification of phenylalanine in serum

An enzyme cascade fluorescence assay for phenylalanine quantification was established by the combination of phenylalanine dehydrogenase and nitroreductase.

Long-Term Neurological Outcomes of Adult Patients with Phenylketonuria before and after Newborn Screening in Japan

Japanese newborn screening (NBS) for phenylketonuria (PKU) was initiated in 1977. We surveyed the neurological outcomes of Japanese adult patients with PKU to investigate the long-term effects and of and issues with NBS. Eighty-five patients with PKU aged over 19 years who continued to be treated with a phenylalanine-free amino acid formula were investigated by administering questionnaires regarding clinical characteristics, such as mental ability, education status, and therapeutic condition. Of the 85 subjects, 68 patients were detected by NBS (NBS group), while the other 17 were clinically diagnosed before the initiation of NBS (pre-NBS group). Further, 10 of the 68 NBS patients presented intellectual and/or psychiatric disabilities, 5 of whom had a history of treatment discontinuation; in contrast, 12 of the 17 pre-NBS patients presented with neuropsychiatric symptoms. Regarding social outcomes, almost all patients in the NBS group could live an independent life, while over half of the patients in the pre-NBS group were not employed or lived in nursing-care facilities. Neurological outcomes are obviously improved by NBS in Japan. However, some patients, even those detected by NBS, developed neuropsychiatric symptoms due to treatment disruption. Lifelong and strict management is essential to maintain good neurological and social prognoses for patients with PKU.

Milk proteins and their derived peptides on bone health: Biological functions, mechanisms, and prospects

Bone is a dynamic organ under constant metabolism (or remodeling), where a delicate balance between bone resorption and bone formation is maintained. Disruption of this coordinated bone remodeling results in bone diseases, such as osteoporosis, the most common bone disorder characterized by decreased bone mineral density and microarchitectural deterioration. Epidemiological and clinical evidence support that consumption of dairy products is beneficial for bone health; this benefit is often attributed to the presence of calcium, the physiological contributions of milk proteins on bone metabolism, however, are underestimated. Emerging evidence highlighted that not only milk proteins (including individual milk proteins) but also their derived peptides positively regulate bone remodeling and attenuate bone loss, via the regulation of cellular markers and signaling of osteoblasts and osteoclasts. This article aims to review current knowledge about the roles of milk proteins, with an emphasis on individual milk proteins, bioactive peptides derived from milk proteins, and effect of milk processing in particular fermentation, on bone metabolism, to highlight the potential uses of milk proteins in the prevention and treatment of osteoporosis, and, to discuss the knowledge gap and to recommend future research directions.

Long-Term Metabolic Correction of Phenylketonuria by AAV-Delivered Phenylalanine Amino Lyase

Phenylketonuria (PKU) is an inherited metabolic disorder caused by mutation within phenylalanine hydroxylase (PAH) gene. Loss-of-function of PAH leads to accumulation of phenylalanine in the blood/body of an untreated patient, which damages the developing brain, causing severe mental retardation. Current gene therapy strategies based on adeno-associated vector (AAV) delivery of PAH gene were effective in male animals but had little long-term effects on blood hyperphenylalaninemia in females. Here, we designed a gene therapy strategy using AAV to deliver a human codon-optimized phenylalanine amino lyase in a liver-specific manner. It was shown that PAL was active in lysing phenylalanine when it was expressed in mammalian cells. We produced a recombinant adeno-associated vector serotype 8 (AAV8) viral vector expressing the humanized PAL under the control of human antitrypsin (hAAT) promoter (AAV8-PAL). A single intravenous administration of AAV8-PAL caused long-term correction of hyperphenylalaninemia in both male and female PKU mice (strain Pah^enu2). Besides, no obvious liver injury was observed throughout the treatment process. Thus, our results established that AAV-mediated liver delivery of PAL gene is a promising strategy in the treatment of PKU.

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.

Effect of type and amount of modified corn starches on qualitative properties of low-protein biscuits for phenylketonuria

The effect of corn starches (natural, pregelatinized, and cross-linked) in four levels on quality of low-protein biscuit was evaluated. First, the microscopic structure, thermal properties, and low-branched chains content of them were evaluated. Water absorption capacity (WAC) and gelatinization properties of combined starches and physicochemical properties of products were assessed. Cross-linked starch had the highest glass transition temperature (Tg ). The maximum and minimum WAC was observed in samples containing 100% pregelatinized and 100% cross-linked starches, respectively. An increase in the amount of pregelatinized starch was accompanied by a decrease in the maximum viscosity and gelatinization temperature. Pregelatinized starch improved sensory and textural characteristics of samples, while cross-linked starch affected baking properties of the product. The best sample containing 30% of pregelatinized and 70% cross-linked starch with 1.27 g protein and 12 mg phenylalanine in 100 g biscuit is introduced as the low protein and safe product for Phenylketonuria.

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.

Pegvaliase for the treatment of phenylketonuria: Results of a long-term phase 3 clinical trial program (PRISM)

BACKGROUND

Phenylketonuria (PKU) is caused by phenylalanine hydroxylase (PAH) deficiency that results in phenylalanine (Phe) accumulation. Pegvaliase, PEGylated recombinant Anabaena variabilis phenylalanine ammonia lyase (PAL), converts Phe to trans-cinnamic acid and ammonia, and is a potential enzyme substitution therapy to lower blood Phe in adults with PKU.

METHODS

Two Phase 3 studies, PRISM-1 and PRISM-2, evaluated the efficacy and safety of pegvaliase treatment using an induction, titration, and maintenance dosing regimen in adults with PKU. In PRISM-1, pegvaliase-naïve participants with blood Phe >600 μmol/L were randomized 1:1 to a maintenance dose of 20 mg/day or 40 mg/day of pegvaliase. Participants in PRISM-1 continued pegvaliase treatment in PRISM-2, a 4-part clinical trial that includes an ongoing, open-label, long-term extension study of pegvaliase doses of 5 mg/day to 60 mg/day.

RESULTS

Of 261 participants who received pegvaliase treatment, 72.0% and 32.6% reached ≥12 months and ≥ 24 months of study treatment, respectively, and 65% are still actively receiving treatment. Mean (SD) blood Phe was 1232.7 (386.4) μmol/L at baseline, 564.5 (531.2) μmol/L at 12 months, and 311.4 (427) μmol/L at 24 months, a decrease from baseline of 51.1% and 68.7%, respectively. Within 24 months, 68.4% of participants achieved blood Phe ≤600 μmol/L, 60.7% of participants achieved blood Phe ≤360 μmol/L, below the upper limit recommended in the American College of Medical Genetics and Genomics PKU management guidelines, and 51.2% achieved blood Phe ≤120 μmol/L, below the upper limit of normal in the unaffected population. Improvements in neuropsychiatric outcomes were associated with reductions in blood Phe and were sustained with long-term pegvaliase treatment. Adverse events (AEs) were more frequent in the first 6 months of exposure (early treatment phase) than after 6 months of exposure (late treatment phase); 99% of AEs were mild or moderate in severity and 96% resolved without dose interruption or reduction. The most common AEs were arthralgia (70.5%), injection-site reaction (62.1%), injection-site erythema (47.9%), and headache (47.1%). Acute systemic hypersensitivity events consistent with clinical National Institute of Allergy and Infectious Diseases and the Food Allergy and Anaphylaxis Network anaphylaxis criteria were observed in 12 participants (17 events); of these, 6 participants remained on treatment. Acute systemic hypersensitivity events including potential events of anaphylaxis were not associated with immunoglobulin E, and all events resolved without sequelae.

CONCLUSION

Results from the PRISM Phase 3 program support the efficacy of pegvaliase for the treatment of adults with PKU, with a manageable safety profile in most participants. The PRISM-2 extension study will continue to assess the long-term effects of pegvaliase treatment.

Psychological and psychosocial implications for parenting a child with phenylketonuria: a systematic review

INTRODUCTION

Since phenylketonuria (PKU) appears to have specificities that might challenge the parents' adaptation and well-being, the present review aimed to evaluate the impact of parenting a child with PKU on parents' psychological and psychosocial functioning.

EVIDENCE ACQUISITION

A systematic electronic search was conducted using PubMED, Scopus, Embase, PsychInfo, Google Scholar and Cochrane Database to identify studies exploring psychological and psychosocial issues of parents of PKU children. The search retrieved 427 articles to review against inclusion criteria; a total of 17 studies were included in the review. Results were summarized qualitatively.

EVIDENCE SYNTHESIS

Findings revealed a complex pattern of interrelated factors both on parental psychological wellbeing and psychosocial functioning. In particular, crucial for parents' adjustment to child PKU are the diagnosis resolution and the perceived social support; parents showed good coping strategies and quality of life; while, with regard to mental health, the studies reviewed showed inconsistent results, thus pointed out a moderate level of distress. The review examines patterns of results across studies and discusses methodological heterogeneities and problems related to different or inconsistent findings.

CONCLUSIONS

Parenting a child with PKU had direct implications on the diagnosis resolution, the parents mental health and the disease management. Findings could help healthcare professionals to identify situations at risk for psychological maladjustments both in parents and in children, as the unresolved diagnosis or a tendency toward the social isolation. Results highlighted the necessity of a multidisciplinary caring approach for the family, with a particular focus on critical moments such diagnosis or developmental transitions.

Hyperphenylalaninemia Correlated with Global Decrease of Antioxidant Genes Expression in White Blood Cells of Adult Patients with Phenylketonuria

BACKGROUND

Several studies have highlighted disturbance of redox homeostasis in patients with phenylketonuria (PKU) which may be associated with neurological disorders observed in patients, especially during adulthood when phenylalanine restrictive diets are not maintained. The aim of this study was to assess the antioxidant profile in a cohort of PKU patients in comparison to the controls and to evaluate its relation to biochemical parameters especially phenylalaninemia.

METHODS

We measured RNA expression of 22 antioxidant genes and reactive oxygen species (ROS) levels in white blood cells of 10 PKU patients and 10 age- and gender-matched controls. We also assessed plasma amino acids, vitamins, oligo-elements, and urinary organic acids concentrations. Then we evaluated the relationship between redox status and biochemical parameters.

RESULTS

In addition to expected biochemical disturbances, we highlighted a significant global decrease of antioxidant genes expression in PKU patients in comparison to the controls. This global decrease of antioxidant genes expression, including various isoforms of peroxiredoxins, glutaredoxins, glutathione peroxidases, and superoxide dismutases, was significantly correlated to hyperphenylalaninemia.

CONCLUSION

This study is the first to evaluate the expression of 22 antioxidant genes in white blood cells regarding biochemical parameters in PKU. These findings highlight the association of hyperphenylalaninemia with antioxidant genes expression. New experiments to specify the role of oxidative stress in PKU pathogenesis may be useful in suggesting new recommendations in PKU management and new therapeutic trials based on antioxidant defenses.

Table of Phenylalanine Content of Foods: Comparative Analysis of Data Compiled in Food Composition Tables

BACKGROUND

Knowing the phenylalanine (Phe) content of foods is essential for managing the diet of patients with phenylketonuria. Data on the Phe content of foods are scarce and sometimes vary between different Food Composition Tables (FCT). Brazil created its own table of the Phe contents of fruits and vegetables based exclusively on the chemical analysis of protein content, considering that proteins contain 3-4% Phe (TCFA/ANVISA). This study compared the protein and Phe contents of vegetables and fruits provided by the TCFA/ANVISA with those listed in international food composition tables.

METHODS

The Phe content of 71 fruits and vegetables listed in TCFA/ANVISA was classified into four subgroups, and the Wilcoxon nonparametric test compared the Phe and mean protein contents provided by the FCTs. All tests considered the bilateral hypothesis, and the level of significance was set at 5%. The Spearman's correlation coefficient measured the statistical dependence between Phe and protein contents.

RESULTS

The mean Phe content was <50 mg Phe/100 g for 15 fruits; >50 mg/100 g for 11 type-A vegetables; <50 mg/100 g for 8 type-B vegetables; ≤50 mg/100 g for 7 type-C vegetables. The percentage of Phe in protein varied from 3.13 ± 1.03% to 3.74 ± 2.55% in fruits; 3.33 ± 1.41 to 4.82 ± 1.17 in type-A vegetables; 3.46 ± 1.25% to 4.83 ± 2.46 in type-B vegetables; and 3.14% ± 1.49 to 4.62% ± 2.26 in type-C vegetables.

CONCLUSIONS

The Phe and protein contents provided by most FCTs were positively correlated, suggesting that it is possible to estimate the Phe content of fruits by multiplying its protein content by 3%. For type-A, -B, and -C vegetables, 4% may be used.

Modeling correlates of low bone mineral density in patients with phenylalanine hydroxylase deficiency

Phenylalanine hydroxylase (PAH) deficiency is an inherited metabolic disorder requiring life-long restriction of dietary protein and phenylalanine-free medical food. Low bone mineral density (BMD) is reported, but factors associated with BMD Z-score (standard deviations from normal) are unknown. We examined associations between clinical and dietary parameters and total BMD Z-score in PAH deficiency patients, and developed models to predict Z-score. Data collected from patients >4 years of age (n = 88; mean age = 18.8 y; 61 % female) included demographic, clinical, laboratory, and dietary intakes. Adjusted Spearman's correlation coefficients were calculated between parameters and TBMD Z-score, measured by dual energy x-ray absorptiometry (DXA). Parameters approaching significance (p-value < 0.10) were candidate predictors for four linear regression models predicting TBMD Z-score. To validate, model-predicted Z-scores were compared to DXA Z-scores. Mean TBMD Z-score was -0.326; 18 (20.4 %) had Z-score < -1. Z-scores were positively correlated with dietary vitamin D, calcium, and medical food intake and compliance with prescription, and negatively with dietary carbohydrate, sugar, caffeine intake, glycemic load, and prescribed medical food (grams protein/day; p-value < 0.05). The best model included medical food compliance, medical food intake, caffeine intake, and bone-specific alkaline phosphatase (r-square = 0.364). This model predicted Z-score category [normal or low (<-1)] with sensitivity = 66.7 %, likelihood ratio = 14.7, and AUC = 0.83 compared to DXA Z-score. No subjects had low BMD for chronological age (Z-score ≤ -2). Compliance with medical food prescription was the strongest predictor of TBMD Z-score. One model, if validated in a separate sample of patients with more cases of low BMD, showed potential to estimate TBMD Z-score using routine clinical patient parameters.

Diet in children with phenylketonuria and risk of cardiovascular disease: A narrative overview

AIMS

The aim of this paper is to review the possible relationship of restricted phenylalanine (Phe) diet, a diet primarily comprising low-protein foods and Phe-free protein substitutes, with major cardiovascular risk factors (overweight/obesity, blood lipid profile, plasma levels of homocysteine, adiponectin and free asymmetric dimethylarginine (ADMA), oxidative stress and blood pressure) in PKU children.

DATA SYNTHESIS

In PKU children compliant with diet, blood total cholesterol, low-density lipoprotein cholesterol (LDL-C), plasma ADMA levels and diastolic pressure were reported to be lower and plasma adiponectin levels to be higher compared to healthy controls. No difference was observed in overweight prevalence and in high-density lipoprotein cholesterol (HDL-C) levels. Inconsistent results were found for plasma homocysteine levels and antioxidant status.

CONCLUSIONS

PKU children compliant with diet seem to display non-different cardiovascular risks compared with the healthy population. Well-designed longitudinal studies are required to clarify the potential underlying mechanisms associated with PKU and cardiovascular risk factors.

Depression and anxiety among parents of phenylketonuria children

Objective:

To investigate the existence of depression and/or anxiety with underlying risk factors among parents of children with classical phenylketonuria (PKU).

Methods:

This cross-sectional study was conducted in the Division of Pediatric Metabolism, Ankara Children’s Hospital, Dokuz Eylul University, Kırıkkale University, and Erzurum Local Research Hospital, Turkey, between January and July 2014. Parents of 61 patients and 36 healthy controls completed the self-report questionnaires. We used Beck Depression Inventory (BDI) to assess the parental depression and State-Trait Anxiety Inventory S-T (STAI S-T) to assess parental anxiety.

Results:

Depression and anxiety scores were significantly higher in the case group (BDI 12.3±9.1; STAI-S: 38.2±9.6; STAI-T: 43.2±6.9) than controls (BDI: 5.4±4.1 p=0.000; STAI-S: 31.8±7.6 p=0.001; STAI-T: 37.0±7.2 p=0.000). Mothers of the patients had higher scores than the other parental groups (BDI: p=0.000, STAI-S: p=0.001 and STAI-T: p=0.000). Logistic regression analysis showed that low educational level of the parent was the only independent factor for depression (OR 9.96, 95% CI: 1.89-52.35, p=0.007) and state anxiety (OR: 6.99, 95% CI: 1.22-40.48, p=0.030) in the case group.

Conclusion:

A subset of parents with PKU patients have an anxiety or depressive disorder. Supportive services dealing with the parents of chronically ill children such as PKU are needed in order to reduce the level of anxiety.

Protective effect of L-carnitine on Phenylalanine-induced DNA damage

The pathogenesis and the progression of phenylketonuria (PKU), an inborn error of phenylalanine (Phe) metabolism, have been associated with oxidative damage. Moreover, it has been increasingly postulated the antioxidant properties of L-Carnitine (LC). The aim of this study was to verify the effect of LC on Phe-induced DNA damage. The in vitro effect of different concentrations of LC (15, 30, 120 and 150 μM) on DNA damage-induced by high phenylalanine levels (1000 and 2500 μM) was examined in white blood cells from normal individuals using the comet assay. Urinary 8-hydroxydeoguanosine (8-OHdG) levels, a biomarker of oxidative DNA damage, and plasmatic sulfhydryl content were measured in eight patients with classical PKU, under therapy with protein restriction and supplemented with a special formula containing LC, and in controls individuals. Both in vitro tested Phe concentrations (1000 and 2500 μM) have resulted in DNA damage index significantly higher than control group. The in vitro co-treatment with Phe and LC reduced significantly DNA damage index when compared to Phe group. The urinary excretion of 8-OHdG and plasmatic sulfhydryl content presented similar levels in both groups analyzed (controls and treated PKU patients). In treated PKU patients, urinary 8-OHdG levels were positively correlated with blood Phe levels and negatively correlated with blood LC concentration and plasmatic sulfhydryl content. The present work yields experimental evidence that LC can reduce the in vitro DNA injury induced by high concentrations of phenylalanine, as well as, allow to hypothesize that LC protect against DNA damage in patients with PKU.

Targeting specific nutrient deficiencies in protein-restricted diets: some practical facts in PKU dietary management

Among aminoacidopathies, phenylketonuria (PKU) is the most prevalent one. Early diagnosis in the neonatal period with a prompt nutritional therapy (low natural-protein and phenylalanine diet, supplemented with phenylalanine-free amino acid mixtures and special low-protein foods) remains the mainstay of the treatment. Data considering nutrient contents of cooked dishes is lacking. In this study, fourteen dishes specifically prepared for PKU individuals were analysed, regarding the lipid profile and iron and zinc contents. These dishes are poor sources of essential nutrients like Fe, Zn or n-3 fatty acids, reinforcing the need for adequate supplementation to cover individual patients' needs. This study can contribute to a more accurate adjustment of PKU diets and supplementation in order to prevent eventual nutritional deficiencies. This study contributes to a better understanding of nutrient intake from PKU patients' meals, showing the need for dietary supplementation.

New insights in growth of phenylketonuric patients

Treatment of phenylketonuria involves a restriction in the intake of natural proteins. This can lead to growth impairment. Weight, height and body mass index of 109 hyperphenylalaninemic patients (mild hyperphenylalaninemia (HPA) and phenylketonuria (PKU)) were determined from birth until 18 years, every 6 months, and differences to the healthy population, depending on the age, sex and phenotype, were analyzed. Data collection was longitudinal retrospective during 31 years. Statistical analysis of z-score values was performed by advanced statistical tools. Long-term evolution of anthropometric z-scores showed no significant statistical differences between PKU and mild HPA individuals, according to the general population. For PKU individuals, height is slightly lower and weight slightly higher than in the healthy population, but differences are smaller than one standard deviation. Nevertheless, over-time evolutions of female height z-scores are different in each type of pathology, with a crossover between 8 and 12 years (p = 0.0186).

CONCLUSIONS

It is nowadays possible to achieve a long-term normal growth in PKU patients with appropriate dietary treatment. There is however an acceleration of growth up to 8 years old for PKU female patients that leads to a slightly lower final height. Detection of this behaviour was possible by using nonlinear mixed effects models.

Bone health in phenylketonuria: a systematic review and meta-analysis

Patients with Phenylketonuria (PKU) reportedly have decreased bone mineral density (BMD). The primary aim of this study was to perform a systematic review and meta-analysis to determine the extent and significance of low BMD in early treated patients with PKU. Secondary aims were to assess other bone status indicators including bone turnover markers (BTM) and to define areas for future research. Two research teams (Amsterdam, Netherlands and Atlanta, USA) performed literature searches for articles reporting data on BMD, osteopenia and osteoporosis, BTM or other bone indicators in patients with PKU. Included articles were compared between research teams and assessed for quality and risk of bias. A total of 13 unique articles were included; 11/13 articles reported BMD including a total of 360 patients. Ten out of 11 articles found BMD was significantly lower in patients with PKU. Meta-analyses for total BMD (TBMD; 3 studies; n = 133), lumbar spine BMD (LBMD; 7 studies; n = 247), and femoral neck BMD (FBMD; 2 studies; n = 78) Z-scores were performed. Overall effect sizes were: TBMD -0.45 (95% CI -0.61, -0.28); LBMD -0.70 (95% CI -0.82, -0.57); FBMD -0.96 (95% CI -1.42, -0.49). Definitions of osteopenia and osteoporosis were highly heterogeneous between studies and did not align with World Health Organization standards and the International Society for Clinical Densitometry positions on BMD measurement. Despite individual study findings of low BMD indicating higher risk of osteoporosis, pooled available data suggest reduction in BMD is not clinically important when using standard definitions of low BMD. Results from studies evaluating BTM are inconclusive. Phenylalanine concentration, vitamin D, PTH, and nutrient intake do not correlate with BMD or BTM. We recommend forthcoming studies use standard definitions of low BMD to determine clinical implications of BMD Z-scores below 0, explore cause of low BMD in the subset of patients with low BMD for chronological age (Z-score < -2) and assess fracture risk in patients with PKU.

Metabolic syndrome in children and adolescents with phenylketonuria

OBJECTIVE

This study aimed to identify markers of metabolic syndrome (MS) in patients with phenylketonuria (PKU).

METHODS

This was a cross-sectional study consisting of 58 PKU patients (ages of 4-15 years): 29 patients with excess weight, and 29 with normal weight. The biochemical variables assessed were phenylalanine (phe), total cholesterol, HDL-c, triglycerides, glucose, and basal insulin. The patients had Homeostasis Model Assessment (HOMA) and waist circumference assessed.

RESULTS

No inter-group difference was found for phe. Overweight patients had higher levels of triglycerides, basal insulin, and HOMA, but lower concentrations of HDL-cholesterol, when compared to the eutrophic patients. Total cholesterol/HDL-c was significantly higher in the overweight group. A positive correlation between basal insulin level and HOMA with waist circumference was found only in the overweight group.

CONCLUSION

The results of this study suggest that patients with PKU and excess weight are potentially vulnerable to the development of metabolic syndrome. Therefore, it is necessary to conduct clinical and laboratory monitoring, aiming to prevent metabolic changes, as well as excessive weight gain and its consequences, particularly cardiovascular risk.

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: translating research into novel therapies

Phenylketonuria (PKU) is an inborn error of metabolism of the amino acid phenylalanine. It is an autosomal recessive disorder with a rate of incidence of 1 in 10,000 in Caucasian populations. Mutations in the phenylalanine hydroxylase (PAH) gene are the major cause of PKU, due to the loss of the catalytic activity of the enzyme product PAH. Newborn screening for PKU allows early intervention, avoiding irreparable neurological damage and intellectual disability that would arise from untreated PKU. The current primary treatment of PKU is the limitation of dietary protein intake, which in the long term may be associated with poor compliance in some cases and other health problems due to malnutrition. The only alternative therapy currently approved is the supplementation of BH4, the requisite co-factor of PAH, in the orally-available form of sapropterin dihydrochloride. This treatment is not universally available, and is only effective for a proportion (estimated 30%) of PKU patients. Research into novel therapies for PKU has taken many different approaches to address the lack of PAH activity at the core of this disorder: enzyme replacement via virus-mediated gene transfer, transplantation of donor liver and recombinant PAH protein, enzyme substitution using phenylalanine ammonia lyase (PAL) to provide an alternative pathway for the metabolism of phenylalanine, and restoration of native PAH activity using chemical chaperones and nonsense read-through agents. It is hoped that continuing efforts into these studies will translate into a significant improvement in the physical outcome, as well as quality of life, for patients with PKU.

People with intellectual disability: what do we know about adulthood and life expectancy?

Increases in the life expectancy of people with Intellectual Disability have followed similar trends to those found in the general population. With the exception of people with severe and multiple disabilities or Down syndrome, the life expectancy of this group now closely approximates with that of the general population. Middle and old age, which until 30 years ago were not recognized in this population, are now important parts of the life course of these individuals. Older adults with Intellectual Disabilities form a small, but significant and growing proportion of older people in the community. How these persons grow older and how symptoms and complications of the underlying cause of the Intellectual Disability will influence their life expectancy is of the utmost importance.

Altered brain protein expression profiles are associated with molecular neurological dysfunction in the PKU mouse model

Phenylketonuria (PKU), if not detected and treated in newborns, causes severe neurological dysfunction and cognitive and behavioral deficiencies. Despite the biochemical characterization of PKU, the molecular mechanisms underlying PKU-associated brain dysfunction remain poorly understood. The aim of this study was to gain insights into the pathogenesis of this neurological damage by analyzing protein expression profiles in brain tissue of Black and Tan BRachyury-PahEnu2 mice (a mouse model of PKU). We compared the cerebral protein expression of homozygous PKU mice with that of their heterozygous counterparts using two-dimensional difference gel electrophoresis analysis, and identified 21 differentially expressed proteins, four of which were over-expressed and 17 under-expressed. An in silico bioinformatic approach indicated that protein under-expression was related to neuronal differentiation and dendritic growth, and to such neurological disorders as progressive motor neuropathy and movement disorders. Moreover, functional annotation analyses showed that some identified proteins were involved in oxidative metabolism. To further investigate the proteins involved in the neurological damage, we validated two of the proteins that were most strikingly under-expressed, namely, Syn2 and Dpysl2, which are involved in synaptic function and neurotransmission. We found that Glu2/3 and NR1 receptor subunits were over-expressed in PKU mouse brain. Our results indicate that differential expression of these proteins may be associated with the processes underlying PKU brain dysfunction, namely, decreased synaptic plasticity and impaired neurotransmission.

Phenylalanine hydroxylase deficiency: diagnosis and management guideline

Phenylalanine hydroxylase deficiency, traditionally known as phenylketonuria, results in the accumulation of phenylalanine in the blood of affected individuals and was the first inborn error of metabolism to be identified through population screening. Early identification and treatment prevent the most dramatic clinical sequelae of the disorder, but new neurodevelopmental and psychological problems have emerged in individuals treated from birth. The additional unanticipated recognition of a toxic effect of elevated maternal phenylalanine on fetal development has added to a general call in the field for treatment for life. Two major conferences sponsored by the National Institutes of Health held >10 years apart reviewed the state of knowledge in the field of phenylalanine hydroxylase deficiency, but there are no generally accepted recommendations for therapy. The purpose of this guideline is to review the strength of the medical literature relative to the treatment of phenylalanine hydroxylase deficiency and to develop recommendations for diagnosis and therapy of this disorder. Evidence review from the original National Institutes of Health consensus conference and a recent update by the Agency for Healthcare Research and Quality was used to address key questions in the diagnosis and treatment of phenylalanine hydroxylase deficiency by a working group established by the American College of Medical Genetics and Genomics. The group met by phone and in person over the course of a year to review these reports, develop recommendations, and identify key gaps in our knowledge of this disorder. Above all, treatment of phenylalanine hydroxylase deficiency must be life long, with a goal of maintaining blood phenylalanine in the range of 120-360 µmol/l. Treatment has predominantly been dietary manipulation, and use of low protein and phenylalanine medical foods is likely to remain a major component of therapy for the immediate future. Pharmacotherapy for phenylalanine hydroxylase deficiency is in early stages with one approved medication (sapropterin, a derivative of the natural cofactor of phenylalanine hydroxylase) and others under development. Eventually, treatment of phenylalanine hydroxylase deficiency will be individualized with multiple medications and alternative medical foods available to tailor therapy. The primary goal of therapy should be to lower blood phenylalanine, and any interventions, including medications, or combination of therapies that help to achieve that goal in an individual, without other negative consequences, should be considered appropriate therapy. Significant evidence gaps remain in our understanding of the optimum therapies for phenylalanine hydroxylase deficiency, nonphenylalanine effects of these therapies, and long-term sequelae of even well-treated disease in children and adults.

Current situation and prospects of newborn screening and treatment for Phenylketonuria in China - compared with the current situation in the United States, UK and Japan

Phenylketonuria (PKU) is a treat-able and prevent-able inborn error of metabolism which leads to severe mental retardation and neurobehavioral abnormalities. A screening program, especially for early detection, combined with a Phe-restricted therapeutic diet can help to control the process of PKU of most patients. The China government has put more emphasis on newborn screening and treatment against PKU, yet by comparing the situation of newborn screening and treatment against PKU in China and the relatively developed countries - United States, United Kingdom and Japan, the newborn screening and treatment against PKU in China is relatively weak and many deficiencies are found. More studies concerning multi-stage target blood Phe concentration criteria, a policy that requires newborn screening has to be taken, better financial support for newborn screening, publicity for newborn screening, and national guidelines for treatment of PKU may be prospects in China and may provide some support for better development of newborn screening and treatment against PKU in China.

Evaluation of plasma trace element and mineral status in children and adolescents with phenylketonuria using data from inductively-coupled-plasma atomic emission and mass spectrometric analysis

BACKGROUND

Phenylketonuria (PKU) is caused by a severe phenylalanine hydroxylase deficiency; the mainstay of treatment is a low-phenylalanine diet. A diet which is so restrictive is associated with a risk of nutritional deficiencies. We investigated plasma concentrations for 46 elements, including minerals and trace elements.

METHODS

We enrolled 20 children and adolescents with PKU and 20 matched controls. Multi-elementary quantification was carried out by solution-based inductively coupled plasma atomic emission spectroscopy (ICP-AES) and ICP mass spectrometry (ICP-MS).

RESULTS

With the exception of manganese and aluminium, no significant differences were found for element levels between PKU patients and controls. As a trend, manganese levels were lower in PKU patients than in control subjects (p < 0.05) but were within the reference range. There was a positive linear relationship between manganese and tyrosine levels in subjects with PKU (r(2) = 0.2295, p < 0.05). If detectable, potentially toxic elements were only identified in ultra-trace quantities in plasma samples of either group; aluminium levels were found to be slightly higher in PKU subjects than in controls (p < 0.01).

CONCLUSION

The combination of ICP-AES and ICP-MS data is a useful diagnostic tool for element quantification at a high analytical rate and for monitoring bio-element status, e.g. in patients on a restrictive diet.

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.

Nutrition education tools used in phenylketonuria: clinician, parent and patient perspectives from three international surveys

BACKGROUND

Three international surveys were developed aiming to identify the current nutrition educational tools used in the management of phenylketonuria (PKU) and the perceived effectiveness of these tools by clinicians, parents and patients.

METHODS

The first two surveys were distributed through the Metabolic Dietitians ListServe (pno-metabl@listserv.cc.emory.edu), and the third survey was distributed by international clinics and the National PKU Alliance website (www.npkua.org). A total of 888 responses (S1, n = 88; S2, n = 81; S3, n = 719) were collected from all three surveys. The surveys represent participants from 17 countries, in Europe; North America (USA and Canada); Mexico; Argentina; Turkey; Australia; and Africa (Tunisia).

RESULTS

A consistent decline in 'parents as role models' as an educational tool was observed starting at age 10 years. Patients responded they feel their families are the most effective form of education, whereas handouts were selected as the least effective educational tool by patients. Parents responded they feel the most effective educational tool is one-on-one counselling. Patients and parents show a desirable trend in wanting to attend group clinic, even in centres where this type of educational tool is not offered.

CONCLUSIONS

There was a discrepancy between clinicians and patient views regarding the perceived effectiveness of the nutrition education tools. Future research is needed surrounding the impact nutrition education may have on improved dietary compliance in patients with PKU.

A Systematic Review of BH4 (Sapropterin) for the Adjuvant Treatment of Phenylketonuria

CONTEXT

Dietary management is the mainstay of effective treatment in PKU, but dietary restriction is difficult and additional treatment options are needed.

OBJECTIVE

To systematically review evidence regarding sapropterin (BH4) use as an adjunct to dietary restriction in individuals with PKU.

DATA SOURCES

Five databases including MEDLINE up to August 2011.

STUDY SELECTION

Two reviewers independently assessed studies against predetermined inclusion/exclusion criteria.

DATA EXTRACTION

Two reviewers independently extracted data regarding participant and intervention characteristics and outcomes and assigned overall quality and strength of evidence ratings based on predetermined criteria.

RESULTS

BH4 research includes two randomized controlled trials (RCTs) and three uncontrolled open-label trials. Phenylalanine (Phe) levels were reduced by at least 30 % in up to half of treated participants (32-50 %). In one RCT comparing placebo on likelihood of a 30 % reduction in Phe, 9 % of those on placebo achieved this effect, compared with 44 % of the treated group after 6 weeks. Phe tolerance and variability were improved in treated participants in studies assessing those outcomes. No comparative studies assessed long-term outcomes including cognitive effects, nutritional status, or quality of life.

CONCLUSIONS

Adjuvant pharmacologic therapy has the potential to support individuals in achieving optimal Phe levels. BH4 has been shown to reduce Phe levels in some individuals, with significantly greater reductions seen in treated versus placebo groups. The strength of the evidence is moderate for short-term effects on reducing Phe in a subset of initially BH4-responsive individuals, moderate for a lack of significant harms, low for longer-term effects on cognition, and insufficient for all other outcomes.

Phenylalanine hydroxylase misfolding and pharmacological chaperones

Phenylketonuria (PKU) is a loss-of-function inborn error of metabolism. As many other inherited diseases the main pathologic mechanism in PKU is an enhanced tendency of the mutant phenylalanine hydroxylase (PAH) to misfold and undergo ubiquitin-dependent degradation. Recent alternative approaches with therapeutic potential for PKU aim at correcting the PAH misfolding, and in this respect pharmacological chaperones are the focus of increasing interest. These compounds, which often resemble the natural ligands and show mild competitive inhibition, can rescue the misfolded proteins by stimulating their renaturation in vivo. For PKU, a few studies have proven the stabilization of PKU-mutants in vitro, in cells, and in mice by pharmacological chaperones, which have been found either by using the tetrahydrobiopterin (BH(4)) cofactor as query structure for shape-focused virtual screening or by high-throughput screening of small compound libraries. Both approaches have revealed a number of compounds, most of which bind at the iron-binding site, competitively with respect to BH(4). Furthermore, PAH shares a number of ligands, such as BH(4), amino acid substrates and inhibitors, with the other aromatic amino acid hydroxylases: the neuronal/neuroendocrine enzymes tyrosine hydroxylase (TH) and the tryptophan hydroxylases (TPHs). Recent results indicate that the PAH-targeted pharmacological chaperones should also be tested on TH and the TPHs, and eventually be derivatized to avoid unwanted interactions with these other enzymes. After derivatization and validation in animal models, the PAH-chaperoning compounds represent novel possibilities in the treatment of PKU.