The correlation of lipid profile and waist circumference with phenylalanine levels in adult patients with classical phenylketonuria / Correlación del perfil lipídico y el perímetro de cintura con los niveles de fenilalanina en pacientes adultos con fenilcetonuria clásica

Introduction and Objectives Some studies have pointed to a relationship between Phenyketonuria (PKU) and an increased cardiovascular risk (CVR). This study aimed to evaluate the influence of metabolic control on classical CVR factors in adult patients with PKU. Material and methods It was a cross-sectional study conducted in patients older than 18 years with a diagnosis of classical PKU and under strict dietary control. Demographic, epidemiological and laboratory variables related to CVR were collected. The variables of metabolic control were some parameters related to phenylalanine (Phe) plasma levels. Results A total of 47 patients were included with a mean age of 36 ± 10 years of which 30 (64%) were women. Multivariate analysis revealed that range Phe (B = −2.211, P = 0.044, 95%CI: −4.354–(−0.068)) levels were within the model for triglyceride concentrations, while minimum (B = −2.803, P = 0.051, 95%CI: −5.612–0.007) and range (B = −1.515, P = 0.039, 95%CI: −2.945–(−0.084)) Phe levels were within the model for high-density lipoprotein cholesterol concentrations. Median Phe levels showed a stronger correlation with waist circumference (WC) (B = 1.216, P = 0.002, 95%CI: 0.462–1.969) than with body mass index (B = 0.355, P = 0.052, 95%CI: −0.004–0.714). Conclusions High Phe levels and wide Phe fluctuations were related to weight gain, increased WC and lipid profile abnormalities. Systematic CVR assessments and comprehensive monitoring of Phe levels may be desirable to prevent or delay cardiovascular disease in PKU patients (AU)

Introducción y objetivos Algunos estudios señalan una relación entre la fenilcetonuria (PKU) y riesgo cardiovascular (RCV). El objetivo de este estudio fue evaluar la influencia del control metabólico sobre los factores de RCV clásicos en pacientes adultos con PKU. Material y métodos Fue un estudio transversal en pacientes mayores de 18 años con diagnóstico de PKU clásica y bajo control dietético estricto. Se recogieron variables demográficas, epidemiológicas y de laboratorio relacionadas con RCV. Las variables de control metabólico fueron algunos parámetros relacionados con los niveles plasmáticos de fenilalanina (Phe). Resultados Se incluyeron 47 pacientes con una edad media de 36 ± 10 años (64% mujeres). El análisis multivariante reveló que el rango de niveles de Phe (B = −2,211, p = 0,044, IC 95%: −4,354; −0,068) se correlacionó con las concentraciones de triglicéridos, mientras que los niveles mínimos (B = −2,803, p = 0,051, IC 95%: −5,612; 0,007) y el rango (B = −1,515, p = 0,039, IC 95%: −2,945; −0,084) de Phe se correlacionaron con las concentraciones de colesterol ligado a lipoproteínas de alta densidad. La mediana de los niveles de Phe mostró una correlación más fuerte con el perímetro de cintura (B = 1,216, p = 0,002, IC 95%: 0,462; 1,969) que con el índice de masa corporal (B = 0,355, p = 0,052, IC 95%: −0,004; 0,714). Conclusiones Niveles altos y fluctuaciones amplias de Phe se correlacionaron con el aumento de peso corporal, incremento de perímetro de cintura y anomalías del perfil lipídico. La realización de evaluaciones sistemáticas de RCV y un seguimiento exhaustivo de los niveles de Phe podrían ser favorables para prevenir o retrasar la enfermedad cardiovascular en los pacientes con PKU (AU)

PTC923 (sepiapterin) lowers elevated blood phenylalanine in subjects with phenylketonuria: a phase 2 randomized, multi-center, three-period crossover, open-label, active controlled, all-comers study.

BACKGROUND & AIM: PTC923 (formerly CNSA-001), an oral formulation of sepiapterin, a natural precursor of intracellular tetrahydrobiopterin (BH4), has been shown in humans to induce larger increases in circulating BH4 vs. sapropterin dihydrochloride. Sapropterin reduces blood phenylalanine (Phe) by ≥20-30% in a minority of subjects with PKU. This was a Phase 2 randomized, multicenter, three-period crossover, open-label, active controlled, all-comers [regardless of phenylalanine hydroxylase (PAH) variants] comparison of PTC923 60 mg/kg, PTC923 20 mg/kg and sapropterin 20 mg/kg in 24 adults with phenylketonuria (PKU) and hyperphenylalaninemia. METHODS: Eligible subjects were adult men or women (18-60 y) with PKU. Subjects enrolled received 7 days of once-daily oral treatment with PTC923 20 mg/kg/day, PTC923 60 mg/kg/day and sapropterin dihydrochloride 20 mg/kg/day each in a random order. Treatments were separated by a 7-day washout. Subjects maintained their usual pre-study diet, including consumption of amino acid mixtures. Blood Phe was measured on Day 1 (predose baseline), Day 3, Day 5, and Day 7 of each treatment period. RESULTS: Least squares mean changes (SE) from baseline in blood Phe were: -206.4 (41.8) µmol/L for PTC923 60 mg/kg (p < 0.0001); -146.9 (41.8) µmol/L for PTC923 20 mg/kg (p = 0.0010); and - 91.5 (41.7) µmol/L for sapropterin (p = 0.0339). Effects of PTC923 60 mg/kg on blood Phe vs. sapropterin were significantly larger (p = 0.0098) and faster in onset with a significantly larger mean reduction in blood Phe at day 3 of treatment, p = 0.0135 (20 mg/kg) and p = 0.0007 (60 mg/kg). Only PTC923 60 mg/kg reduced blood Phe in classical PKU subjects (n = 11, p = 0.0287). The mean blood Phe reduction (PTC923 60 mg/kg) in a cofactor responder analysis (n = 8; baseline Phe ≥300 µmol/L and blood Phe reduction ≥30%) was -463.3 µmol/L (SE 51.5) from baseline. Adverse events were mostly mild to moderate, transient, and similar across treatment groups with no serious adverse events or discontinuations. CONCLUSIONS: The substantially significantly better effect of PTC923 60 mg/kg on blood Phe reduction vs. sapropterin supports further clinical development of PTC923 for PKU; ANZCTR number, ACTRN12618001031257.

The effect of casein glycomacropeptide versus free synthetic amino acids for early treatment of phenylketonuria in a mice model.

INTRODUCTION: Management of phenylketonuria (PKU) is mainly achieved through dietary control with limited intake of phenylalanine (Phe) from food, supplemented with low protein (LP) food and a mixture of free synthetic (FS) amino acids (AA) (FSAA). Casein glycomacropeptide (CGMP) is a natural peptide released in whey during cheese making by the action of the enzyme chymosin. Because CGMP in its pure form does not contain Phe, it is nutritionally suitable as a supplement in the diet for PKU when enriched with specific AAs. Lacprodan® CGMP-20 (= CGMP) used in this study contained only trace amounts of Phe due to minor presence of other proteins/peptides. OBJECTIVE: The aims were to address the following questions in a classical PKU mouse model: Study 1, off diet: Can pure CGMP or CGMP supplemented with Large Neutral Amino Acids (LNAA) as a supplement to normal diet significantly lower the content of Phe in the brain compared to a control group on normal diet, and does supplementation of selected LNAA results in significant lower brain Phe level?. Study 2, on diet: Does a combination of CGMP, essential (non-Phe) EAAs and LP diet, provide similar plasma and brain Phe levels, growth and behavioral skills as a formula which alone consist of FSAA, with a similar composition?. MATERIAL AND METHODS: 45 female mice homozygous for the Pahenu2 mutation were treated for 12 weeks in five different groups; G1(N-CGMP), fed on Normal (N) casein diet (75%) in combination with CGMP (25%); G2 (N-CGMP-LNAA), fed on Normal (N) casein diet (75%) in combination with CGMP (19,7%) and selected LNAA (5,3% Leu, Tyr and Trp); G3 (N), fed on normal casein diet (100%); G4 (CGMP-EAA-LP), fed on CGMP (70,4%) in combination with essential AA (19,6%) and LP diet; G5 (FSAA-LP), fed on FSAA (100%) and LP diet. The following parameters were measured during the treatment period: Plasma AA profiles including Phe and Tyr, growth, food and water intake and number of teeth cut. At the end of the treatment period, a body scan (fat and lean body mass) and a behavioral test (Barnes Maze) were performed. Finally, the brains were examined for content of Phe, Tyr, Trp, dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC), serotonin (5-HT) and 5-hydroxyindole-acetic acid (5-HIAA), and the bone density and bone mineral content were determined by dual-energy x-ray absorptiometry. RESULTS: Study 1: Mice off diet supplemented with CGMP (G1 (N-CGMP)) or supplemented with CGMP in combination with LNAA (G2 (N-CGMP-LNAA)) had significantly lower Phe in plasma and in the brain compared to mice fed only casein (G3 (N)). Extra LNAA (Tyr, Trp and Leu) to CGMP did not have any significant impact on Phe levels in the plasma and brain, but an increase in serotonin was measured in the brain of G2 mice compared to G1. Study 2: PKU mice fed with mixture of CGMP and EAA as supplement to LP diet (G4 (CGMP-EAA-LP)) demonstrated lower plasma-Phe levels but similar brain- Phe levels and growth as mice fed on an almost identical combination of FSAA (G5 (FSAA-LP)). CONCLUSION: CGMP can be a relevant supplement for the treatment of PKU.

A highly accurate mass spectrometry method for the quantification of phenylalanine and tyrosine on dried blood spots: Combination of liquid chromatography, phenylalanine/tyrosine-free blood calibrators and multi-point/dynamic calibration.

BACKGROUND: Measurement of quantitative levels of phenylalanine and tyrosine in blood is an essential test for the diagnosis of and monitoring genetic disorders associated with phenylalanine metabolism, such as phenylketonuria (PKU), tyrosinemia, and defects of tetrahydrobiopterin synthesis and recycling. We developed a highly accurate and fast liquid chromatography with tandem mass spectrometry (LC-MS/MS) method for the quantification of phenylalanine and tyrosine on dried blood spot (DBS). We also designed a performance score system to evaluate various calibration methods in matrix matched material. METHODS: Phenylalanine/tyrosine-free whole blood was used to make accurate and stable DBS calibrators. Six calibrators cover the range of 0-1000 µmol/L. Underivatized phenylalanine and tyrosine were extracted and measured by LC-MS/MS. Precision, accuracy, limit of quantification, recovery and carryover were validated. External quality assurance materials were also used to evaluate performance of multi-point calibrations and single-point calibrations. RESULTS: The run time was 4.5-minute. Accuracy analysis showed good agreement with reference materials. Precision, recovery, and the lower and upper limit of quantification met the criteria. When phenylalanine and tyrosine concentrations were less than 150 µmol/L, the 5-point calibration without the calibrator of 1000 µmol/L had the best performance. When the concentrations were > 250 µmol/L, the single-point calibration of 500 µmol/L had the best performance. CONCLUSION: We developed a simple, fast and highly accurate method for the detection of phenylalanine and tyrosine on DBS, with chromatographic separation and underivatized analysis. Based on the calibration performance, a 6-point calibration method is satisfying for this test. An optional dynamic calibration method, which includes 6-point calibration, 5-point calibration and single-point calibration, can further increase test reliability.

Blood phenylalanine reduction reverses gene expression changes observed in a mouse model of phenylketonuria.

Phenylketonuria (PKU) is a genetic deficiency of phenylalanine hydroxylase (PAH) in liver resulting in blood phenylalanine (Phe) elevation and neurotoxicity. A pegylated phenylalanine ammonia lyase (PEG-PAL) metabolizing Phe into cinnamic acid was recently approved as treatment for PKU patients. A potentially one-time rAAV-based delivery of PAH gene into liver to convert Phe into tyrosine (Tyr), a normal way of Phe metabolism, has now also entered the clinic. To understand differences between these two Phe lowering strategies, we evaluated PAH and PAL expression in livers of PAHenu2 mice on brain and liver functions. Both lowered brain Phe and increased neurotransmitter levels and corrected animal behavior. However, PAL delivery required dose optimization, did not elevate brain Tyr levels and resulted in an immune response. The effect of hyperphenylalanemia on liver functions in PKU mice was assessed by transcriptome and proteomic analyses. We observed an elevation in Cyp4a10/14 proteins involved in lipid metabolism and upregulation of genes involved in cholesterol biosynthesis. Majority of the gene expression changes were corrected by PAH and PAL delivery though the role of these changes in PKU pathology is currently unclear. Taken together, here we show that blood Phe lowering strategy using PAH or PAL corrects both brain pathology as well as previously unknown lipid metabolism associated pathway changes in liver.

Beneficial Effects of Slow-Release Large Neutral Amino Acids after a Phenylalanine Oral Load in Patients with Phenylketonuria.

The mainstay of phenylketonuria treatment is a low protein diet, supplemented with phenylalanine (Phe)-free protein substitutes and micronutrients. Adhering to this diet is challenging, and even patients with good metabolic control who follow the dietary prescriptions in everyday life ignore the recommendations occasionally. The present study explores the ability of slow-release large neutral amino acids (srLNAAs) to prevent Phe increase following a Phe dietary load. Fourteen phenylketonuric patients aged ≥13 years were enrolled in a 6-week protocol. Oral acute Phe loads of 250 and 500 mg were added to the evening meal together with srLNAAs (0.5 gr/kg). Phe and tyrosine were dosed before dinner, 2h-after dinner, and after the overnight fast. After oral Phe loads, mean plasma Phe remained stable and below 600 µmol/L. No Phe peaks were registered. Tyrosine levels significantly increased, and Phe/Tyrosine ratio decreased. No adverse events were registered. In conclusion, a single oral administration of srLNAAs at the dose of 0.5 gr/kg is effective in maintaining stable plasma Phe during acute oral loads with Phe-containing food and may be added to the dietetic scheme in situations in which patients with generally good adherence to diet foresee a higher than prescribed Phe intake due to their commitments.

Phenylalanine and COVID-19: Tracking disease severity markers.

BACKGROUND: Although there are several severity predictors for COVID-19, none are specific. Serum levels of phenylalanine were recently associated with increased inflammation, higher SOFA scores, ICU admission, and mortality rates among non-COVID-19 patients. Here, we investigated the relationship between phenylalanine and inflammatory markers in adults with COVID-19. METHODS: We assessed adults with COVID-19 at hospital admission for clinical and laboratory data. Nuclear magnetic resonance spectroscopy measured serum levels of phenylalanine and other amino acids of its metabolomic pathway. Flow Cytometry measured serum levels of IL-2, IL-4, IL-6, Il-10, TNF-α, and IFN-γ. Linear regression models adjusted for potential confounders assessed the relationship between serum levels of phenylalanine and inflammatory cytokines. RESULTS: Phenylalanine and tyrosine were significantly lower in mild disease as compared to moderate and severe groups. Linear regression models showed that phenylalanine is independently and positively associated with disease severity regardless of the cytokine analyzed and after adjustment for potential confounders. In addition, mild cases showed consistently lower serum phenylalanine levels within the first ten days from disease onset to hospital admission. CONCLUSIONS: Phenylalanine is a marker of disease severity. This association is independent of the time between the onset of symptoms and the magnitude of the inflammatory state.

Achieving efficacy in subjects with sustained pegvaliase-neutralizing antibody responses.

Pegvaliase (Palynziq®) is an enzyme substitution therapy using PEGylated recombinant Anabaena variabilis phenylalanine ammonia lyase (PAL) to reduce blood phenylalanine (Phe) levels in adults with phenylketonuria (PKU). In Phase 3 clinical studies, all subjects treated with pegvaliase developed anti-drug antibodies. To specifically evaluate pegvaliase-neutralizing antibodies (NAbs) and assess impact on pegvaliase efficacy, a novel hybrid ligand-binding/tandem mass spectrometry NAb assay was developed. Analysis of Phase 3 study samples revealed that pegvaliase NAb titers developed during early treatment (≤6 months after treatment initiation), and then plateaued and persisted in the majority of subjects during late treatment (>6 months). Subjects with the lowest/undetectable NAb titers had relatively high plasma pegvaliase concentrations and experienced the most rapid decline in blood Phe concentrations at relatively low pegvaliase dose concentrations. In contrast, subjects with higher NAb titers generally had lower plasma pegvaliase concentrations on similar low doses, with little change in blood Phe concentrations. However, with additional time on treatment and individualized dose titration, the majority of subjects achieved substantial and sustained blood Phe reduction, including those with higher NAb titers. Moreover, after maturation of the anti-pegvaliase immune response, NAb titers were stable over time and did not rise in response to dose increases; thus, subjects did not require additional dose increases to maintain reduction in blood Phe.

Natural history of children and adults with phenylketonuria in the NBS-PKU Connect registry.

PURPOSE: Phenylalanine hydroxylase deficiency, or phenylketonuria (PKU), is a rare autosomal recessive metabolic disorder. Early diagnosis via newborn screening (NBS) and initiation of treatment prevent the development of cognitive impairment and other co-morbidities. The purpose of this study is to describe the natural history of PKU in the United States, including prevalence of co-morbidities and predictors of outcomes. METHODS: We analyzed data from a self-report survey in the NBS-PKU Connect online registry. We describe the participants' nutrition management strategies, barriers to management, outcomes of bone disorders, skin, and psychological co-morbidities, and the use of special education or other special services. Predictors of outcomes were identified and assessed, including the impact of sex, age, age at diagnosis, blood phenylalanine concentration, use of sapropterin, use of medical food, adherence to prescribed diet, use of low protein modified foods, whether they had ever been off-diet, and use of tyrosine supplementation. RESULTS: The 219 respondents included individuals with PKU or hyperphenylalanemia (n = 78), or their caregivers (n = 141). Most (84.3%) started treatment before the age of two weeks. About one-third indicated that they had been off-diet at some point in their lives, and 81.4% reported that they currently adhered to their prescribed diet, with adherence to prescribed diet decreasing with age. Blood phenylalanine concentration was under the recommended threshold of 360 µmol/L for 68.5% of participants. One-quarter of respondents reported psychological co-morbidities, with anxiety and ADD/ADHD being the most common. The incidence of psychological co-morbidities increased with age and with ever having been off diet. Special education or other special services were more likely to be reported by individuals who were diagnosed after one week of age. Skin disorders such as acne and eczema were more common in females than males, and a minority of participants reported bone disorders. CONCLUSIONS: Despite recommendations to maintain blood phenylalanine concentrations in the therapeutic range throughout life, it is not uncommon for adults with PKU to discontinue dietary management of their disorder. Early diagnosis was associated with reduced need for special education or other special services, and continuous treatment was associated with decreased psychological co-morbidities.

Metabolic Control of Patients with Phenylketonuria in a Portuguese Metabolic Centre Comparing Three Different Recommendations.

Blood phenylalanine (Phe) is used as the primary marker to evaluate metabolic control. Our study aimed to describe the metabolic control of patients with phenylketonuria (PKU) comparing three different treatment recommendations (European guidelines/US guidelines/Portuguese consensus). This was a retrospective, observational, single centre study in patients with PKU collecting data on blood Phe levels from 2017. Nutritional intake data and sapropterin (BH4) prescription were collected at the last appointment of 2017. The final sample studied included 87 patients (48% females) [13 hyperphenylalaninemia; 47 mild PKU; 27 classical PKU] with a median age of 18 y (range: 1-36 y). The median number of blood Phe measurements for patients was 21 (range: 6-89). In patients aged < 12 y, the median blood Phe level was 300 µmol/L (range 168-480) and 474 µmol/L (range 156-1194) for patients ≥ 12 y. Overall, a median of 83% of blood Phe levels were within the European PKU guidelines target range. In patients aged ≥ 12 years, there was a higher median % of blood Phe levels within the European PKU guidelines target range (≥12 y: 84% vs. <12 y: 56%). In children < 12 y with classical PKU (n = 2), only 34% of blood Phe levels were within target range for all 3 guidelines and 49% with mild PKU (n = 11). Girls had better control than boys (89% vs. 66% median Phe levels within European Guidelines). Although it is clear that 50% or more patients were unable to achieve acceptable metabolic control on current treatment options, a globally agreed upper Phe target associated with optimal outcomes for age groups is necessary. More studies need to examine how clinics with dissimilar resources, different therapeutic Phe targets and frequency of monitoring relate to metabolic control.

Casein Glycomacropeptide: An Alternative Protein Substitute in Tyrosinemia Type I.

Tyrosinemia type I (HTI) is treated with nitisinone, a tyrosine (Tyr) and phenylalanine (Phe)-restricted diet, and supplemented with a Tyr/Phe-free protein substitute (PS). Casein glycomacropeptide (CGMP), a bioactive peptide, is an alternative protein source to traditional amino acids (L-AA). CGMP contains residual Tyr and Phe and requires supplementation with tryptophan, histidine, methionine, leucine, cysteine and arginine. AIMS: a 2-part study assessed: (1) the tolerance and acceptability of a low Tyr/Phe CGMP-based PS over 28 days, and (2) its long-term impact on metabolic control and growth over 12 months. METHODS: 11 children with HTI were recruited and given a low Tyr/Phe CGMP to supply all or part of their PS intake. At enrolment, weeks 1 and 4, caregivers completed a questionnaire on gastrointestinal symptoms, acceptability and ease of PS use. In study part 1, blood Tyr and Phe were assessed weekly; in part 2, weekly to fortnightly. In parts 1 and 2, weight and height were assessed at the study start and end. RESULTS: Nine of eleven children (82%), median age 15 years (range 8.6-17.7), took low Tyr/Phe CGMP PS over 28 days; it was continued for 12 months in n = 5 children. It was well accepted by 67% (n = 6/9), tolerated by 100% (n = 9/9) and improved gastrointestinal symptoms in 2 children. The median daily dose of protein equivalent from protein substitute was 60 g/day (range 45-60 g) with a median of 20 g/day (range 15 to 30 g) from natural protein. In part 2 (n = 5), a trend for improved blood Tyr was observed: 12 months pre-study, median Tyr was 490 µmol/L (range 200-600) and Phe 50 µmol/L (range 30-100); in the 12 months taking low Tyr/Phe CGMP PS, median Tyr was 430 µmol/L (range 270-940) and Phe 40 µmol/L (range 20-70). Normal height, weight and BMI z scores were maintained over 12 months. CONCLUSIONS: In HTI children, CGMP was well tolerated, with no deterioration in metabolic control or growth when studied over 12 months. The efficacy of CGMP in HTI needs further investigation to evaluate the longer-term impact on blood Phe concentrations and its potential influence on gut microflora.

Current Practices and Challenges in the Diagnosis and Management of PKU in Latin America: A Multicenter Survey.

This study aimed to describe the current practices in the diagnosis and dietary management of phenylketonuria (PKU) in Latin America, as well as the main barriers to treatment. We developed a 44-item online survey aimed at health professionals. After a pilot test, the final version was sent to 25 practitioners working with inborn errors of metabolism (IEM) in 14 countries. Our results include 22 centers in 13 countries. Most countries (12/13) screened newborns for PKU. Phenylalanine (Phe) targets at different ages were very heterogeneous among centers, with greater consistency at the 0-1 year age group (14/22 sought 120-240 µmol/L) and the lowest at >12 years (10 targets reported). Most countries had only unflavored powdered amino acid substitutes (10/13) and did not have low-protein foods (8/13). Only 3/13 countries had regional databases of the Phe content of foods, and only 4/22 centers had nutrient analysis software. The perceived obstacles to treatment were: low purchasing power (62%), limited/insufficient availability of low-protein foods (60%), poor adherence, and lack of technical resources to manage the diet (50% each). We observed a heterogeneous scenario in the dietary management of PKU, and most countries experienced a lack of dietary resources for both patients and health professionals.

Cardiac Magnetic Resonance Reveals Incipient Cardiomyopathy Traits in Adult Patients With Phenylketonuria.

Background Phenylketonuria is the most common inborn error of amino acid metabolism, where oxidative stress and collateral metabolic abnormalities are likely to cause cardiac structural and functional modifications. We aim herein to characterize the cardiac phenotype of adult subjects with phenylketonuria using advanced cardiac imaging. Methods and Results Thirty-nine adult patients with phenylketonuria (age, 30.5±8.7 years; 10-year mean phenylalanine concentration, 924±330 µmol/L) and 39 age- and sex-matched healthy controls were investigated. Participants underwent a comprehensive cardiac magnetic resonance and echocardiography examination. Ten-year mean plasma levels of phenylalanine and tyrosine were used to quantify disease activity and adherence to treatment. Patients with phenylketonuria had thinner left ventricular walls (septal end-diastolic thickness, 7.0±17 versus 8.8±1.7 mm [P<0.001]; lateral thickness, 6.1±1.4 versus 6.8±1.2 mm [P=0.004]), more dilated left ventricular cavity (end-diastolic volume, 87±14 versus 80±14 mL/m2 [P=0.0178]; end-systolic volume, 36±9 versus 29±8 mL/m2 [P<0.001]), lower ejection fraction (59±6% versus 64±6% [P<0.001]), reduced systolic deformation (global circumferential strain, -29.9±4.2 % versus -32.2±5.0 % [P=0.027]), and lower left ventricular mass (38.2±7.9 versus 47.8±11.0 g/m2 [P<0.001]). T1 native values were decreased (936±53 versus 996±26 ms [P<0.001]), with particular low values in patients with phenylalanine >1200 µmol/L (909±48 ms). Both mean phenylalanine (P=0.013) and tyrosine (P=0.035) levels were independently correlated with T1; and in a multiple regression model, higher phenylalanine levels and higher left ventricular mass associate with lower T1. Conclusions Cardiac phenotype of adult patients with phenylketonuria reveals some traits of an early-stage cardiomyopathy. Regular cardiology follow-up, tighter therapeutic control, and prophylaxis of cardiovascular risk factors, in particular dyslipidemia, are recommended.

The Impact of the First 2020 COVID-19 Lockdown on the Metabolic Control of Patients with Phenylketonuria.

The present study assessed patients' metabolic control of phenylketonuria (PKU) during the first 2020 COVID-19 lockdown in Poland. Blood (phenylalanine) Phe results of the tests of 535 patients, performed in 2019 and in the first months of 2020, were analysed. The six-week lockdown period was compared to the preceding six-week period as well as to the two corresponding periods of 2019 (three non-lockdown periods). More patients failed to perform Phe tests in the lockdown period (32.7%) than in non-lockdown periods (15.6%, 15.1%, 17.2%; p < 0.001 for all). The median Phe levels for those patients who performed testing in all the four periods did not differ between periods. However, these patients tended to perform only one test during the lockdown (ORs: 1.43 to 1.60; 95% CI: from 1.01-2.04 to 1.11-2.30, p-value 0.02 to 0.005). Patients who did not take blood during the lockdown (46.7%) performed significantly fewer blood tests in the remaining periods (median : 1 <0-1> vs. 2 <1-4>; p < 0.001). In conclusion, direct assessment of patients' compliance based upon Phe levels during the pandemic lockdown was not possible. Pre-pandemic non-compliant patients frequently failed to perform the test during the lockdown, whereas the previously compliant ones were more likely to perform only one test. This strongly suggests that metabolic control might have worsened.

Integrative biology defines novel biomarkers of resistance to strongylid infection in horses.

The widespread failure of anthelmintic drugs against nematodes of veterinary interest requires novel control strategies. Selective treatment of the most susceptible individuals could reduce drug selection pressure but requires appropriate biomarkers of the intrinsic susceptibility potential. To date, this has been missing in livestock species. Here, we selected Welsh ponies with divergent intrinsic susceptibility (measured by their egg excretion levels) to cyathostomin infection and found that their divergence was sustained across a 10-year time window. Using this unique set of individuals, we monitored variations in their blood cell populations, plasma metabolites and faecal microbiota over a grazing season to isolate core differences between their respective responses under worm-free or natural infection conditions. Our analyses identified the concomitant rise in plasma phenylalanine level and faecal Prevotella abundance and the reduction in circulating monocyte counts as biomarkers of the need for drug treatment (egg excretion above 200 eggs/g). This biological signal was replicated in other independent populations. We also unravelled an immunometabolic network encompassing plasma beta-hydroxybutyrate level, short-chain fatty acid producing bacteria and circulating neutrophils that forms the discriminant baseline between susceptible and resistant individuals. Altogether our observations open new perspectives on the susceptibility of equids to strongylid infection and leave scope for both new biomarkers of infection and nutritional intervention.

Subchronic Tolerance Trials of Graded Oral Supplementation with Phenylalanine or Serine in Healthy Adults.

Phenylalanine and serine are amino acids used in dietary supplements and nutritional products consumed by healthy consumers; however, the safe level of phenylalanine or serine supplementation is unknown. The objective of this study was to conduct two 4-week clinical trials to evaluate the safety and tolerability of graded dosages of oral phenylalanine and oral serine. Healthy male adults (n = 60, 38.2 ± 1.8y) completed graded dosages of either phenylalanine or serine supplement (3, 6, 9 and 12 g/d) for 4 weeks with 2-week wash-out periods in between. Primary outcomes included vitals, a broad spectrum of circulating biochemical analytes, body weight, sleep quality and mental self-assessment. At low dosages, minor changes in serum electrolytes and plasma non-essential amino acids glutamine and aspartic acid concentrations were observed. Serine increased its plasma concentrations at high supplemental dosages (9 and 12 g/day), and phenylalanine increased plasma tyrosine concentrations at 12 g/day, but those changes were not considered toxicologically relevant. No other changes in measured parameters were observed, and study subjects tolerated 4-week-long oral supplementation of phenylalanine or serine without treatment-related adverse events. A clinical, no-observed-adverse-effect-level (NOAEL) of phenylalanine and serine supplementation in healthy adult males was determined to be 12 g/day.

Palynziq clinic: One year and 43 patients later.

Pegvaliase-pqpz (Palynziq) is an enzyme substitution therapy FDA approved May 2018 to treat phenylketonuria in adults with blood phenylalanine levels greater than 600 µmol/L (10 mg/dL). Pegvaliase is administered via subcutaneous injection and carries a high risk of side effects including anaphylaxis. A consensus statement on its use recommends careful education and monitoring of patients. We established a dedicated Palynziq Clinic in October 2018 with detailed protocols to minimize these risks. In the first year, we evaluated 43 patients, initiated Palynziq in 37 and transitioned two trial patients to commercial drug. 13/37 patients (35.1%) have sustained blood phenylalanine levels <360 µmol/L (6 mg/dL) without adjunct sapropterin dihydrochloride treatment or medical food. The timing and dosage needed to achieve a response did not correlate with patient weight, starting phenylalanine level, starting diet, or co-treatment with sapropterin dihydrochloride. Some patients had consistently low phenylalanine levels <30 µmol/L (0.5 mg/dL) and required doses as low as 20 mg weekly. Anaphylactic episodes were reported by 21.6% (8/37 patients) versus 10% seen in the clinical trial. Rates of other side effects were similar to or less than those in the trial. Adverse reactions commonly occurred shortly after dosage increases. We provide a model for safely introducing and managing pegvaliase in adult patients with PKU.

Long-term cognitive and psychosocial outcomes in adults with phenylketonuria.

Previous studies have suggested that cognitive and psychosocial underfunctioning in early-treated adults with phenylketonuria (PKU) may be explained by suboptimal adherence to dietary treatments, however, these studies often employ small samples, with different outcome measures, definitions and cut-offs. Samples have also tended to comprise participants with a limited range of blood phenylalanine concentrations, and often individuals who may not have been treated early enough to avoid neurological damage. In this study, we explore the impact of lifetime dietary control, as indicated by blood phenylalanine concentrations in childhood, adolescence and adulthood, on long-term cognitive and psychosocial outcomes in a large sample of adults with PKU who were diagnosed by neonatal screening and commenced on dietary treatment within the first month of life. One hundred and fifty-four participants underwent cognitive testing, assessing attention, learning, working memory, language, executive functioning and processing speed. One hundred and forty-nine completed measures of psychosocial functioning, documenting educational, occupational, quality of life, emotional and social outcomes which were compared with a group of healthy controls. Many adults with PKU demonstrated cognitive impairments, most frequently affecting processing speed (23%), executive function (20%) and learning (12%). Cognitive outcomes were related to measures of historic metabolic control, but only processing speed was significantly related to phenylalanine concentration at the time of testing after controlling for historic levels. Adults with PKU did not, however, differ from controls in educational, occupational, quality of life or emotional outcomes, or on a measure of family functioning, and showed only minor differences in relationship style. These findings have implications for patient counselling and decisions regarding the management of PKU in adulthood.

Dysregulated Phenylalanine Catabolism Plays a Key Role in the Trajectory of Cardiac Aging.

BACKGROUND: Aging myocardium undergoes progressive cardiac hypertrophy and interstitial fibrosis with diastolic and systolic dysfunction. Recent metabolomics studies shed light on amino acids in aging. The present study aimed to dissect how aging leads to elevated plasma levels of the essential amino acid phenylalanine and how it may promote age-related cardiac dysfunction. METHODS: We studied cardiac structure and function, together with phenylalanine catabolism in wild-type (WT) and p21-/- mice (male; 2-24 months), with the latter known to be protected from cellular senescence. To explore phenylalanine's effects on cellular senescence and ectopic phenylalanine catabolism, we treated cardiomyocytes (primary adult rat or human AC-16) with phenylalanine. To establish a role for phenylalanine in driving cardiac aging, WT male mice were treated twice a day with phenylalanine (200 mg/kg) for a month. We also treated aged WT mice with tetrahydrobiopterin (10 mg/kg), the essential cofactor for the phenylalanine-degrading enzyme PAH (phenylalanine hydroxylase), or restricted dietary phenylalanine intake. The impact of senescence on hepatic phenylalanine catabolism was explored in vitro in AML12 hepatocytes treated with Nutlin3a (a p53 activator), with or without p21-targeting small interfering RNA or tetrahydrobiopterin, with quantification of PAH and tyrosine levels. RESULTS: Natural aging is associated with a progressive increase in plasma phenylalanine levels concomitant with cardiac dysfunction, whereas p21 deletion delayed these changes. Phenylalanine treatment induced premature cardiac deterioration in young WT mice, strikingly akin to that occurring with aging, while triggering cellular senescence, redox, and epigenetic changes. Pharmacological restoration of phenylalanine catabolism with tetrahydrobiopterin administration or dietary phenylalanine restriction abrogated the rise in plasma phenylalanine and reversed cardiac senescent alterations in aged WT mice. Observations from aged mice and human samples implicated age-related decline in hepatic phenylalanine catabolism as a key driver of elevated plasma phenylalanine levels and showed increased myocardial PAH-mediated phenylalanine catabolism, a novel signature of cardiac aging. CONCLUSIONS: Our findings establish a pathogenic role for increased phenylalanine levels in cardiac aging, linking plasma phenylalanine levels to cardiac senescence via dysregulated phenylalanine catabolism along a hepatic-cardiac axis. They highlight phenylalanine/PAH modulation as a potential therapeutic strategy for age-associated cardiac impairment.

Nutrition status of adults with phenylketonuria treated with pegvaliase.

BACKGROUND: Pegvaliase is an enzyme substitution therapy that reduces blood phenylalanine (Phe) in adults with phenylketonuria (PKU), and often allows normalization of protein intake (≥0.8 g protein/kg). Here we examine the nutrition status of adults with PKU consuming a normal protein intake without medical food after being treated with pegvaliase for ≥1 year. METHODS: A cross-sectional study evaluating nutritional intake (3-day food record and food frequency questionnaire), anthropometrics, laboratory indices of protein, micronutrient, and essential fatty acid (EFA) status, and questionnaires evaluating food neophobia and Epicurean eating pleasure. RESULTS: Participants (n = 18, 61% female) started pegvaliase 4.9 ± 2.1 years prior to enrollment and were aged 38.2 ± 8.8 years with a mean BMI of 29.2 ± 4.1 kg/m2. Participants consumed a mean of 73.2 ± 17.6 g protein/d (1.0 ± 0.3 g/kg/d). Eleven participants had low blood Phe (<30 µmol/L) with adequate protein intake and normal indices of protein status. Micronutrient and EFA concentrations were normal except for mildly low vitamin D (<30 ng/mL, n = 12). Intakes of sodium, saturated fat, and added sugars exceeded recommendations for healthy adults, though mean diet quality was comparable to a US adult reference population. Lower food neophobia scores correlated with an increased aesthetic appreciation of food. However, 53% of participants self-reported having moderate (n = 6) to high (n = 3) food neophobia. DISCUSSION: Participants treated with pegvaliase consumed an unrestricted diet with adequate dietary protein and, overall, had normal protein, micronutrient, and fatty acid status. Despite low blood Phe, protein nutriture was not compromised. While nutritional deficiencies were not identified, diet quality was suboptimal and some participants reported food neophobia. Nutrition education remains an important component of care as patients adapt to a normal diet.